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  • Artikel: DFG Deutsche Nationallizenzen  (6.874)
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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Journal of ornithology 141 (2000), S. 263-274 
    ISSN: 1439-0361
    Schlagwort(e): Systematics ; evolution ; anagenesis ; genealogy ; reference system
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Verglichen mit anderen Tiergruppen, scheint die artliche Bestandsaufnahme der rezenten Vögel nahezu abgeschlossen zu sein. Doch ist das System der Vögel weiterhin umstritten und mit vielen Neuerungen konfrontiert. Die Gründe dafür liegen hauptsächlich in neuen, vor allem molekularbiologischen Methoden und in den unerwartet reichen Fossilfunden der jüngsten Zeit. Als Beispiele werden Altgaumenvögel, Kranichvögel, Ibisse, Flamingos, Mausvögel, Hopfe und Sperlingsvögel kurz behandelt. Die hier erzielten Fortschritte lassen die Befürchtung Stresemanns, die Großsystematik der Vögel sei mit den vorhandenen Methoden phylogenetisch nicht interpretierbar, zunächst als unbergründet erscheinen. Doch erwachsen einer solchen Interpretation andere Hindernisse, deren Bedeutung bisher zu wenig beachtet wurde, nämlich Parallelentwicklungen, die viel verbreiteter sind als gemeinhin angenommen. Ihre Häufigkeit lässt sich sogar mit evolutionsbiologischen Argumenten begründen. Es ist deshalb nicht zu erwarten, dass die Diskussionen um das „richtige“ System bald verstummen. Um dennoch die Eindeutigkeit der Information in nicht-systematischen Veröffentlichungen zu wahren, wird empfohlen ein etabliertes Referenzsystem auf Zeit zu wählen.
    Notizen: Summary Unlike in most animal classes the inventory of extant species of the class Aves seems to be almost complete. Nevertheless avian systematics is challenged by many novelties and seems far from being settled. This is caused mainly by the application of novel methods of molecular analysis to phylogenetic problems and by the unexpectedly rich fossil record collected within the last 10–20 years. Examples from the Palaeognathae, Gruiformes, Threskiornithidae, Phoenicopteridae, Coliiformes, Upupiformes and Passeriformes are briefly treated. The progress in the field seems to disprove Stresemann's pessimistic view that the phylogeny of higher categories (orders) cannot be reconstructed by the available methods. However, phylogenetic interpretations are impeded by obstacles not considered by Stresemann and highly underestimated in most cases, namely by multiple independent developments leading to identical features. Frequent parallel developments are to be expected for theoretical evolutionary reasons. The diagnosis of such homoplasies can be extremely difficult or even impossible. Therefore we cannot expect the discussion about the “best” system of birds to end in the near future. Considering this dynamic situation in systematics, it is recommended to maintain unambiguousness of information in not strictly systematic publications by refering to a well established system as a temporally limited reference.
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Acta biotheoretica 48 (2000), S. 137-147 
    ISSN: 1572-8358
    Schlagwort(e): Sex ; sexual selection ; mate selection ; evolution ; ploidy ; assortative mating ; recombination
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Using computer simulations I studied the simultaneous effect of variable environments, mutation rates, ploidy, number of loci subject to evolution and random and assortative mating on various reproductive systems. The simulations showed that mutants for sex and recombination are evolutionarily stable, displacing alleles for monosexuality in diploid populations mating assortatively under variable selection pressure. Assortative mating reduced excessive allelic variance induced by recombination and sex, especially among diploids. Results suggest a novel adaptive value for sex and recombination. They show that the adaptive value of diploidy and that of the segregation of sexes is different to that of sex and recombination. The results suggest that the emergence of sex had to be preceded by the emergence of diploid monosexual organisms and provide an explanation for the emergence and maintenance of sex among diploids and for the scarcity of sex among haploid organisms.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Entomologia experimentalis et applicata 97 (2000), S. 237-249 
    ISSN: 1570-7458
    Schlagwort(e): herbivores ; predators ; parasitoids ; mutualism ; induced defence ; behaviour ; ecology ; evolution ; sensory physiology ; plant fitness ; pathogens
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Herbivorous and carnivorous arthropods use plant volatiles when foraging for food. In response to herbivory, plants emit a blend that may be quantitatively and qualitatively different from the blend emitted when intact. This induced volatile blend alters the interactions of the plant with its environment. We review recent developments regarding the induction mechanism as well as the ecological consequences in a multitrophic and evolutionary context. It has been well established that carnivores (predators and parasitoids) are attracted by the volatiles induced by their herbivorous victims. This concerns an active plant response. In the case of attraction of predators, this is likely to result in a fitness benefit to the plant, because through consumption a predator removes the herbivores from the plant. However, the benefit to the plant is less clear when parasitoids are attracted, because parasitisation does usually not result in an instantaneous or in a complete termination of consumption by the herbivore. Recently, empirical evidence has been obtained that shows that the plant's response can increase plant fitness, in terms of seed production, due to a reduced consumption rate of parasitized herbivores. However, apart from a benefit from attracting carnivores, the induced volatiles can have a serious cost because there is an increasing number of studies that show that herbivores can be attracted. However, this does not necessarily result in settlement of the herbivores on the emitting plant. The presence of cues from herbivores and/or carnivores that indicate that the plant is a competitor- and/or enemy-dense space, may lead to an avoidance response. Thus, the benefit of emission of induced volatiles is likely to depend on the prevailing faunal composition. Whether plants can adjust their response and influence the emission of the induced volatiles, taking the prevalent environmental conditions into account, is an interesting question that needs to be addressed. The induced volatiles may also affect interactions of the emitting plant with its neighbours, e.g., through altered competitive ability or by the neighbour exploiting the emitted information. Major questions to be addressed in this research field comprise mechanistic aspects, such as the identification of the minimally effective blend of volatiles that explains the attraction of carnivores to herbivore-infested plants, and evolutionary aspects such as the fitness consequences of induced volatiles. The elucidation of mechanistic aspects is important for addressing ecological and evolutionary questions. For instance, an important tool to address ecological and evolutionary aspects would be to have plant pairs that differ in only a single trait. Such plants are likely to become available in the near future as a result of mechanistic studies on signal-transduction pathways and an increased interest in molecular genetics.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Entomologia experimentalis et applicata 95 (2000), S. 141-149 
    ISSN: 1570-7458
    Schlagwort(e): ecology ; reproductive success ; fecundity ; intraspecific competition ; evolution ; pest outbreaks ; pest control ; chemical control ; economic threshold ; oilseed rape ; turnip rape
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Populations of the rapeseed pollen beetle Meligethes aeneus F. (Col., Nitidulidae) from areas with 0–16 years of history of intensive rapeseed growing were compared for key ecological characters. During the first 16 years of rapeseed cultivation the reproductive success of M. aeneus increased 200–300% over that of the beetles living on the natural host plants, cruciferous weeds. The increase was linear over time and statistically highly significant, and it did not appear to be related to food quality or to the size of the beetles. During the same period the tolerance to intraspecific competition decreased, possibly due to the relative absence of such competition on the new crop. Furthermore, the optimum population density for M. aeneus to maximize the size of its next generation on summer turnip rape was determined to be 0.5–1.0 beetles/plant, which is slightly below the economic threshold for chemical control (1 beetle/plant). Therefore the practical protection of the rapeseed yield also ensures the highest possible pest population size for the next year. These mechanisms may in part explain the particular noxiousness of the species as a pest all over Europe. In general these data show that after the introduction of a new crop plant into a region, significant changes during the recruitment process in a pestiferous insect may take place, contributing to the future pest status of the insect. It is suggested that such genetic and ecological changes in insects may be a more common mechanism than previously thought in initiating and sustaining pest outbreaks, and that conventional pest management methods may enhance that effect.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Journal of insect behavior 13 (2000), S. 71-86 
    ISSN: 1572-8889
    Schlagwort(e): copulatory courtship ; behavioral interactions ; songs ; evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract D. birchii and D. serrata, two endemic Australian Drosophila species, have a copulatory courtship. The males of these species begin to court the female after mounting her and often go on with the courtship after the copulation is over. In the present paper we have described behavioral interactions between the male and the female and analyzed acoustic signals produced by the flies during courtship. Species differences were more pronounced in female than in male behavior. Variation within the species was obvious in the relative proportions of time the flies spent in different behaviors. Even though courtship took place nearly solely during copulation, some remains of precopulatory courtship were observed in both species. It is suggested that copulatory courtship exhibited by D. birchii and D. serrata flies is a derived rather than a primitive character.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Adsorption 6 (2000), S. 137-147 
    ISSN: 1572-8757
    Schlagwort(e): adsorption ; kinetics ; linear driving force model ; process design
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract The Linear Driving Force (LDF) model for gas adsorption kinetics is frequently and successfully used for analysis of adsorption column dynamic data and for adsorptive process designs because it is simple, analytic, and physically consistent. Yet, there is a substantial difference in the characteristics of isothermal batch uptake curves on adsorbent particles by the LDF and the more rigorous Fickian Diffusion (FD) model. It is demonstrated by using simple model systems that the characteristics of the adsorption kinetics at the single pore or the adsorbent particle level are lost in (a) evaluating overall uptake on a heterogeneous porous solid, (b) calculating breakthrough curves from a packed adsorbent column, and (c) establishing the efficiency of separation by an adsorptive process due to repeated averaging of the base kinetic property. That is why the LDF model works in practice.
    Materialart: Digitale Medien
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  • 7
    ISSN: 1572-879X
    Schlagwort(e): ammonia synthesis ; kinetics ; ruthenium catalysts ; promotional effect
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The kinetics of NH3 synthesis over carbon-based ruthenium catalysts promoted with barium or alkali was studied. Both the ammonia partial pressure dependencies of the reaction rates (T = 400°C, p = 63 bar, H2 : N2 = 3 : 1) and the pressure variations of the activity (T = 370°C, p= 4–63 bar, H2 : NN2 = 3 : 1) were found to be different for Ba and for the alkali (K, Cs). Ba–Ru/C proved to be more sensitive to the NH3 content and to the total pressure. The rate of synthesis over the alkali-promoted catalysts is, in turn, much stronger influenced by the ruthenium dispersion. TOFs of NH3 synthesis for the promoted samples at 370°C and 4 bar (Ba 0.085 1/s, Cs 0.05 1/s, K 0.035 1/s) are significantly higher than that for the Ru(0001) basal plane (0.0085 1/s results from the literature data at 370°C, 2 bar). The most active Ru/C samples (Ba or Cs) exceed significantly the fused iron catalyst, especially at high conversions.
    Materialart: Digitale Medien
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  • 8
    ISSN: 1572-9028
    Schlagwort(e): rutile supported V2O5–WO3 catalyst ; evolution ; NO reduction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract This paper concerns the relation between surface structure of crystalline vanadia-like active species on vanadia–tungsta catalyst and their activity in the selective reduction of NO by ammonia to nitrogen. The investigations were performed for Ti–Sn-rutile-supported isopropoxy-derived catalyst. The SCR activity and surface species structure were determined for the freshly prepared catalyst, for the catalyst previously used in NO reduction by ammonia (320 ppm NO, 335 ppm NH3 and 2.35 vol% O2) at 573 K as well as for the catalyst previously annealed at 573 K in helium stream containing 2.35 vol% O2. The crystalline islands, exposing main V2O5 surface, with some tungsten atoms substituted for V-ones, were found, with XPS and FT Raman spectroscopy, to be present at the surface of the freshly prepared catalyst. A profound evolution of the active species during the catalyst use at 573 K was observed. Dissociative water adsorption on V5+OW6+ sites is discussed as mainly responsible for the catalyst activity at 473 K and that on both V5+OW6+ and V4+OW6+ sites as determining the activity at 523 K.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Topics in catalysis 11-12 (2000), S. 327-333 
    ISSN: 1572-9028
    Schlagwort(e): hydrodenitrogenation ; toluidine ; methylcyclohexylamine ; kinetics ; nickel-promoted molybdenum sulphide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The hydrodenitrogenation (HDN) of o-toluidine and its reaction intermediates was studied over a NiMo/γ-Al2O3 catalyst. The kinetics of the HDN of methylcyclohexylamine and of the hydrogenation of cyclohexene were also studied. Hydrogenation of o-toluidine alone produces methylcyclohexene and methylcyclohexane. When a sufficient quantity of cyclohexene is added during the HDN of toluidine, methylcyclohexylamine, the first intermediate in the hydrogenation of toluidine, becomes detectable. Because of its strong adsorption constant and high rate constant for reacting further to methylcyclohexene and methylcyclohexane, methylcyclohexylamine is not observed in the HDN of toluidine. Adding cyclohexene decreases the adsorption of methylcyclohexylamine, thus enabling its detection. The rate and adsorption constants of methylcyclohexylamine and cyclohexene in the HDN of methylcyclohexylamine were calculated by fitting the kinetic data to a Langmuir–Hinshelwood equation. A two-site model was used to describe the surface reactions, with one site for the methylcyclohexylamine reactions and the other for the cyclohexene reaction.
    Materialart: Digitale Medien
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  • 10
    ISSN: 1129-2377
    Schlagwort(e): Key words Cluster headache ; Familial occurrence ; Genetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract A Danish genetic study showed increased risk of cluster headache (CH) among relatives of CH patients. We studied the families of 191 CH patients (118 males, 73 females; mean age 45.9 years) attending the Milan Headache Center. Information on 3589 relatives was collected by direct interview of the probands (n = 118) or by mailed questionnaire (n = 73). The diagnostic criteria of the IHS were used. A positive family history was found in 19% (37 of 191) of the families. A total of 32 first-degree (32 of 1036, 3.1%) and 15 second-degree (15 of 2553, 0.6%) relatives were affected. The relative risk of CH was 26.89 (95% CI, 17.57–36.21) in the first-degree relatives and 4.35 (95% CI, 2.13–5.21) in second-degree relatives. This study shows increased familial risk of cluster headache in an Italian population and confirms that cluster headache is, in some families, and inherited disorder.
    Materialart: Digitale Medien
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  • 11
    Digitale Medien
    Digitale Medien
    Springer
    The journal of headache and pain 1 (2000), S. S135 
    ISSN: 1129-2377
    Schlagwort(e): Key words Migraine ; Headache ; Genetics ; Serotonin ; Dopamine ; Mitochondria
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Migraine carries a significant hereditary determination. Familial hemiplegic migraine (FHM) has been recently linked to mutations in the CACNA1A gene on chromosome 19. CACNA1A codes for a subunit of a neural calcium channel. Other linkage loci on chromosome 1q21-23 and 1q31 have been reported. Several linkage and association studies have been performed to determine the role of the CACNA1A gene, and of other candidate genes implicated in the metabolism of serotonin and dopamine, in the more common types of migraine. Co-morbidity of migraine with vascular events has been analysed versus genetic prothrombotic factors and mitochondrial DNA, and genes involved in the inflammatory cascade have been explored. Though no definite conclusions have emerged from these studies as yet, molecular genetics of migraine can be expected to unravel the complex aetiologies of these fascinating diseases.
    Materialart: Digitale Medien
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  • 12
    Digitale Medien
    Digitale Medien
    Springer
    The journal of headache and pain 1 (2000), S. S147 
    ISSN: 1129-2377
    Schlagwort(e): Key words Dopamine ; Migraine ; Genetics ; DRD2
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Molecular genetics offers a novel approach to the understanding and management of migraine since the disorder is known to have a strong genetic component. In recent studies, polymorphisms in the genes for dopamine receptors have been evaluated. Both positive and negative association studies have been reported. In particular, these data suggest that activation of the DRD2 receptor plays a modifying role in the pathophysiology of migraine. As a result, existing data provide a molecular rationale for the documented efficacy of dopamine D2 receptor antagonists in the treatment of migraine. Therefore, at the present time, molecular genetic data provide support for the hypothesis that susceptibility to migraine may be modified, in part, by variations in dopamine DRD2 receptor function.
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  • 13
    Digitale Medien
    Digitale Medien
    Springer
    The journal of headache and pain 1 (2000), S. S157 
    ISSN: 1129-2377
    Schlagwort(e): Key words Migraine ; Chronic tension type headache ; Genetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Pathophysiological studies have dominated migraine research for several years. However, these studies are difficult to interpret because it is difficult to decide whether the observed phenomena are primary or secondary to the migraine attack. For that reason it is important that future migraine research focus on studies that concern migrain etiology. Migraine is a paroxysmal disorder. It is most likely and ion-channel disorder like familial hemiplegic migraine. The present paper focuses on genetic factors in migraine and chronic tension-type headache.
    Materialart: Digitale Medien
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  • 14
    ISSN: 1437-2320
    Schlagwort(e): Key words Von Hippel-Lindau disease ; Hemangioblastoma ; Endolymphatic sac tumor ; Angiogenesis ; Genetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract  Von Hippel-Lindau disease (VHL) is a hereditary cancer syndrome caused by germline mutations of the VHL tumor suppressor gene. Major progress has been made in the last decade in both clinical and fundamental aspects of VHL. The VHL gene product, pVHL, has major and multiple functions: pVHL regulates not only first angiogenesis but also extracellular matrix formation and the cell cycle. A molecular diagnosis of VHL is now available, leading to a transformation in clinical management of patients and their families. Diagnosis of VHL has to be suspected in patients with a VHL-related tumor without familial history and especially in case of hemangioblastoma or endolymphatic sac tumors. Such patients should be systematically investigated for clinical and molecular evidence of VHL disease. Treatment of symptomatic hemangioblastomas remains mainly neurosurgical, often in emergency, but stereotactic radiosurgery is emerging as an alternative therapeutic procedure. In the future, antiangiogenic drugs could represent a potential medical treatment of CNS hemangioblastomas in view of their highly vascular structure. Lastly, visceral manifestations of VHL disease are also of critical importance and require early detection for effective treatment.
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  • 15
    Digitale Medien
    Digitale Medien
    Springer
    Adsorption 6 (2000), S. 349-357 
    ISSN: 1572-8757
    Schlagwort(e): sulfadiazene ; adsorption ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract To investigate the nature of interactive forces between sulfadiazene molecules and alumina surface the experiments were performed for the adsorption of sulfadiazene (SD) from its aqueous sulution onto the alumina surfaces at 25 ± 0.2°C and the influence of factors such as increasing concentration of SD (4.0–20.0 × 10−3 mol cm−3), the time required for adsorption equilibrium, pH (2.0–12.0) and temperature (5–45°C) of the adsorption medium, the presence of ions like Cl−, SO2− 4 and PO3− 4 (0.01–0.30 M) and organic solvents (5% v/v) were observed on the course of adsorption of SD. Various adsorption and kinetic parameters such as adsorption coefficient, the rate constants for adsorption and desorption were also evaluated. The results of the above cited studies facilitated to formulate the mechanisms of interaction between SD and alumina surfaces. From application view point the present work may be a potential tool for an effective chromatographic separation of sulfa drugs from industrial effluents.
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  • 16
    Digitale Medien
    Digitale Medien
    Springer
    Catalysis letters 64 (2000), S. 65-75 
    ISSN: 1572-879X
    Schlagwort(e): NO reduction ; CH3OH ; La2O3 ; methyl nitrite ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Nitric oxide (NO) reduction by methanol was studied over La2O3 in the presence and absence of oxygen. In the absence of O2, CH3OH reduced NO to both N2O and N2, with selectivity to dinitrogen formation decreasing from around 85% at 623 K to 50–70% at 723 K. With 1% O2 in the feed, rates were 4–8 times higher, but the selectivity to N2 dropped from 50% at 623 K to 10% at 723 K. The specific activities with La2O3 for this reaction were higher than those for other reductants; for example, at 773 K with hydrogen a specific activity of 35 μmol NO/s m2 was obtained whereas that for methanol was 600 μmol NO/s m2. The Arrhenius plots were linear under differential reaction conditions, and the apparent activation energy was consistently near 14 kcal/mol with CH3OH. Linear partial pressure dependencies based on a power rate law were obtained and showed a near‐zero order in CH3OH and a near‐first order in H2. In the absence of O2, a Langmuir–Hinshelwood type model assuming a surface reaction between adsorbed CH3OH and adsorbed NO as the slow step satisfactorily fitted the data, and the model invoking two types of sites provided the best fit and gave thermodynamically consistent rate constants. In the presence of O2 a homogeneous gas‐phase reaction between O2, NO, and CH3OH occurred to yield methyl nitrite. This reaction converted more than 30% of the methanol at 300 K and continued to occur up to temperatures where methanol was fully oxidized. Quantitative kinetic studies of the heterogeneous reaction with O2 present were significantly complicated by this homogeneous reaction.
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  • 17
    Digitale Medien
    Digitale Medien
    Springer
    Foundations of science 5 (2000), S. 429-456 
    ISSN: 1572-8471
    Schlagwort(e): awareness ; reflexive awareness and consciousness ; evolution ; experience and pattern matching ; symbolic language
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Allgemeine Naturwissenschaft
    Notizen: Abstract An evolutionary point of view is proposed to make more appropriate distinctions between experience, awareness and consciousness. Experience can be defined as a characteristic linked closely to specific pattern matching, a characteristic already apparent at the molecular level at least. Awareness can be regarded as the special experience of one or more central, final modules in the animal neuronal brain. Awareness is what experience is to animals. Finally, consciousness could be defined as reflexive awareness. The ability for reflexive awareness is distinctly different from animal and human awareness and depends upon the availability of a separate frame of reference, as provided by symbolic language. As such, words have made reflexive awareness – a specific and infrequent form of awareness – possible. Conciousness might be defined as the experience evoked by considering, i.e. thinking about experiences themselves. If there is a hard problem of explaining consciousness, than this actually must be considered as the hard problem already met when trying to explain basic experience, since its nature remains elusive.
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  • 18
    Digitale Medien
    Digitale Medien
    Springer
    Catalysis letters 69 (2000), S. 103-107 
    ISSN: 1572-879X
    Schlagwort(e): dicyclopentadiene ; Wacker oxidation ; Pd(AcO)2 ; benzoquinone ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The oxidation of dicyclopentadiene catalyzed by palladium(II) acetate and benzoquinone in the presence of perchloric acid was studied. Tricyclodecenone in high selectivity (85–98%) at a conversion of dicyclopentadiene up to 76% was obtained. The kinetic model assumed the significant inhibition complexation between dicyclopentadiene and tricyclodecenone with the catalytic species.
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  • 19
    Digitale Medien
    Digitale Medien
    Springer
    Journal for general philosophy of science 31 (2000), S. 57-73 
    ISSN: 1572-8587
    Schlagwort(e): complex systems ; evolution ; nonlinearity ; pre-determination ; self-organization ; soft management ; structure-attractors ; synergetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Philosophie , Wissenschaftskunde und Wissenschaftsorganisation, Hochschul- und Universitätswesen, Museumswissenschaft
    Notizen: Abstract The philosophical consequences of synergetics, the interdisciplinary theory of evolution and self-organization of complex systems, are being drawn in the paper. The idea of discreteness of evolutionary paths is in the focus of attention. Although the future is open, and there are many alternative evolutionary paths for complex systems, not any arbitrary (either conceivable or desirable) evolutionary path is feasible in a given system. There are discrete spectra of possible evolutionary paths which are determined exclusively by inner properties of the corresponding systems. Synergetics allows us to reveal general laws of self-organization and, therefore, certain limits of arbitrariness of nature in choosing possible paths of evolution as well as in constructing of a complex evolutionary whole. A comparative analysis between the modern synergetic notions and a few ideas of the Western philosophy (F. Nietzsche, N. Hartmann, M. Heidegger) and of the Eastern teachings (Taoism, Buddhism) is made.
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  • 20
    Digitale Medien
    Digitale Medien
    Springer
    International journal of value-based management 13 (2000), S. 297-308 
    ISSN: 1572-8528
    Schlagwort(e): morality ; moral systems ; behavior ; evolution ; adaptation ; natural selection ; altruism ; reciprocal altruism ; fitness ; reciprocity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Wirtschaftswissenschaften
    Notizen: Abstract The ethical and moral behavior of Homo sapiens is no longer the exclusive domain of religion and philosophy because we recognize that such behavior affects the reproductive success of individuals within the species. We are a social species and therefore our survival is influenced by our capacity for cooperation and our willingness to take risks for kin. Emotions, some of which are found in other species, help to mediate our altruistic behavior. The reproductive benefits of helping kin, especially offspring, are readily seen. Helping non-kin can be beneficial if individuals can differentiate between ‘reciprocators’ and ‘non-reciprocators’ and direct altruistic behavior toward reciprocators. Also, if third parties are favorably impressed by observing altruistic behavior, the rewards need not come from the recipient of the altruistic behavior.
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  • 21
    Digitale Medien
    Digitale Medien
    Springer
    Conservation genetics 1 (2000), S. 341-355 
    ISSN: 1572-9737
    Schlagwort(e): conservation genetics ; Equus ; evolution ; mitochondrial DNA control region ; mitochondrial 12S rRNA
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The evolution, taxonomy and conservation of the genus Equuswere investigated by examining the mitochondrial DNA sequences of thecontrol region and 12S rRNA gene. The phylogenetic analysis of thesesequences provides further evidence that the deepest node in thephylogeny of the extant species is a divergence between twolineages; one leading to the ancestor of modern horses (E.ferus, domestic and przewalskii) and the other to thezebra and ass ancestor, with the later speciation events of the zebrasand asses occurring either as one or more rapid radiations, or withextensive secondary contact after speciation. Examination of the geneticdiversity within species suggested that two of the E. hemionussubspecies (E. h. onager and E. h. kulan) onlyrecently diverged, and perhaps, are insufficiently different to beclassified as separate subspecies. The genetic divergence betweendomestic and wild forms of E. ferus (horse) and E.africanus (African ass) was no greater than expected within anequid species. In E. burchelli (plains zebra) there was anindication of mtDNA divergence between populations increasing withdistance. The implications of these results for equid conservation arediscussed and recommendations are made for conservation action.
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  • 22
    Digitale Medien
    Digitale Medien
    Springer
    Journal of the history of biology 33 (2000), S. 457-491 
    ISSN: 1573-0387
    Schlagwort(e): J. B. S. Haldane ; biology ; politics ; genetics ; evolution ; population genetics ; physiology ; Darwinism ; experimental biology ; eugenics ; Britain ; Russia ; India ; Soviet ; Communism ; socialism ; philosophy ; vision ; literature ; popularization ; religion ; human experimentation ; bioethics ; Venus ; Mars ; science fiction ; technocracy ; futurology ; H. G. Wells ; Julian Huxley ; Olaf Stapledon ; C. S. Lewis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geschichte
    Notizen: Abstract This paper seeks to reinterpret the life and work of J. B. S. Haldane by focusing on an illuminating but largely ignored essay he published in1927, “The Last Judgment” – the sequel to his better known work, Daedalus (1924). This astonishing essay expresses a vision of the human future over the next 40,000,000 years, one that revises and updates Wellsian futurism with the long range implications of the “new biology” for human destiny. That vision served as a kind of lifelong credo, one that infused and informed his diverse scientific work, political activities, and popular writing, and that gave unity and coherence to his remarkable career.
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  • 23
    Digitale Medien
    Digitale Medien
    Springer
    Journal of the history of biology 33 (2000), S. 221-246 
    ISSN: 1573-0387
    Schlagwort(e): August Weismann ; ciliates ; Clifford Dobell ; cytology ; death ; Emile Maupas ; evolution ; Herbert Spencer Jennings ; Otto Bütschli ; Paramecium ; rejuvenescence ; sex
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geschichte
    Notizen: Abstract In the period 1875–1920, a debate about the generality and applicability of evolutionary theory to all organisms was motivated by work on unicellular ciliates like Paramecium because of their peculiar nuclear dualism and life cycles. The French cytologist Emile Maupas and the German zoologist August Weismann argued in the 1880s about the evolutionary origins and functions of sex (which in the ciliates is not linked to reproduction), and death (which appeared to be the inevitable fate of lineages denied sexual conjugation), an argument rooted in the question of whether the ciliates and their processes where homologous to other cellular organisms. In the beginning of the twentieth century, this question of homology came to be less important as the ciliates were used by the British protozoologist Clifford Dobell and the American zoologist Herbert Spencer Jennings to study evolutionary processes in general rather than problems of development and cytology. For them, homology mattered less than analogy. This story illustrates two partially distinct problems in evolutionary biology: first, the question of whether all living things have common features and origins; and second, whether their history and current nature can be described by identical mechanisms. Where Maupas (contra Weismann) made the ciliates qualitatively the same as all other organisms in order to create a cohesive evolutionary theory for biology, Jennings and Dobell made them qualitatively different in order to achieve the same end.
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  • 24
    Digitale Medien
    Digitale Medien
    Springer
    Anatomy and embryology 202 (2000), S. 281-290 
    ISSN: 1432-0568
    Schlagwort(e): Key words Extracellular matrix ; cartilage ; bone ; evolution ; lamprey ; agnathan
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract  Previous evidence from our laboratories showed that collagen is not the major matrix protein of the cartilaginous endoskeleton of the lamprey (Petromyzon marinus). Here we have characterized the cartilage matrix proteins of the only other extant agnathan, the hagfish (Myxine glutinosa). Using morphological, immunochemical and biochemical methods, we show that the structural proteins of the cartilaginous endoskeleton of the hagfish are also non-collagenous in nature. Although these hagfish cartilage proteins share properties both with each other and with lamprey cartilage proteins, including resistance to solubilization with cyanogen bromide and an usual amino acid composition rich in glycine and non-polar amino acids, it is clear that at least two and probably more hagfish cartilage proteins can be distinguished, with distinct distributions in different cartilage structures. Furthermore, in spite of their similarities, matrix proteins from hagfish cartilage are not identical to the proteins we have previously characterized in lamprey cartilage. These results suggest the existence of a larger family of similar but not identical proteins that form the major structural elements of cartilage tissues of agnathans. These data also support our previous conclusion that type II collagen became the predominant structural protein of cartilage only after the divergence of the agnathans from the ancestral line of the vertebrates.
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  • 25
    Digitale Medien
    Digitale Medien
    Springer
    The journal of headache and pain 1 (2000), S. S153 
    ISSN: 1129-2377
    Schlagwort(e): Key words Migraine ; Genetics ; Dopamine ; Hypersensitivity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Migraine is a common chronic disorder with an etiology still mostly unknown. Several neurotransmitters such as dopamine and serotonin are considered to be involved in the pathogenesis of the disease and the study of their systems is crucial in the understanding of migraine. Dopaminergic receptors are variously represented in human CNS and periphery. The hypothesis that a hypersensitivity of the dopaminergic system may have a role in migraine is based on clinical and genetic data. Genetic data are represented by association studies using dopaminergic genes as candidate genes which show that the D2 receptor gene appears to be involved in the pathogenesis of migraine.
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  • 26
    Digitale Medien
    Digitale Medien
    Springer
    The journal of headache and pain 1 (2000), S. S141 
    ISSN: 1129-2377
    Schlagwort(e): Key words Migraine ; Genetics ; Human leukocyte antigens ; Heredity ; Susceptibility
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Human leukocyte Antigens (HLA) are encoded by genes located on chromosome 6p21. Genes important in migraine are being recognized in two basic ways: association studies and linkage analysis. One of the strongest associations is with the HLA region. Actually, genome scan studies suggest that multiple genes are involved in both migraine without aura (MWoA) and migraine with aura (MWA). However, both MWoA and MWA are disorders in which multiple factors, including environmental and genetic factors, confer disease susceptibility. Linkage analysis is identifying new candidate genes that will help to explain the etiology of migraine. In this review previous studies regarding genetic susceptibility to migraine are analyzed, particularly those related to the HLA region. I discuss evidence that HLA shared-hyplotypes in MWoA-affected pairs in different than that expected, that HLA-DR2 antigen provides additional basis for the proposed genetic heterogeneity between MWoA and MWA, and lastly that TNFB gene studies seem to play an important role in the susceptibility to MWoA. In the past years, major advances hae been made in understanding the genetic foundation of MWoA and MWA. Our reported genome-scan studies support the concept that MWoA/MWA are coinherited with a particular HLA region. However, the examination of candidate genes (Ca2+ channel, vascular, CNS, etc.) in a large migraine population seems to be the correct direction in which we have to move. More MWoA/MWa gene studies are needed to test this developing hypothesis and to further establish the complete genetic scenario of migraine.
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  • 27
    ISSN: 1364-6753
    Schlagwort(e): Key words Parkinson's disease ; Familial Parkinson's disease ; Synuclein ; Parkin ; Genetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: ABSTRACT¶Parkinson's disease (PD) is a neurodegenerative disease with clinical features resulting from deficiency of dopamine in the nigrostriatal system. Most PD cases are sporadic and the primary cause of the disease is still unknown. Recently, familial PD and parkinsonism have received much attention because these forms of the disease might provide clues to the genetic risk factors involved in the pathogenesis of idiopathic PD. To date, two causative genes, α-synuclein and the parkin gene, have been identified. α-Synuclein is involved in the pathogenesis of an autosomal dominant form of PD and constitutes a major component of the Lewy body, which is a pathological hallmark of idiopathic PD. In addition, mutations in the parkin gene have been identified as the cause of autosomal recessive juvenile parkinsonism (AR-JP). AR-JP manifests itself as a highly selective degeneration of the substantia nigra and the locus coeruleus, but without Lewy body formation. In addition to these two genes, four chromosomal loci have been linked to other forms of familial PD. Furthermore, there are a number of other pedigrees of familial PD in which linkage to known genetic loci has been excluded. Molecular cloning of these disease genes and elucidation of the function of their gene products will greatly contribute to our understanding of the pathogenesis of idiopathic PD.
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  • 28
    Digitale Medien
    Digitale Medien
    Springer
    Accreditation and quality assurance 5 (2000), S. 409-413 
    ISSN: 1432-0517
    Schlagwort(e): Key words Metrology ; Comparisons ; Chemistry ; Standards
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract  After stressing the importance in the modern world of accurate and reproducible measurements, the actions taken by the Bureau International des Poids et Mesures to set up, together with the regional metrology organizations, a series of key comparisons are described. They are the technical foundation of a mutual recognition of national measurement standards arrangement prepared in conjunction with the National Metrology Institutes (NMIs). This arrangement also includes the recognition of calibration and measurement certificates issued by these institutes. Then, the consequences of this arrangement for trade are described. The case of chemical analysis is illustrated by the application of the Kyoto protocol on the reduction of greenhouse gases. But the global workload to be taken up by the International Committee of Weights and Measures, its Consultative Committee for Amount of Substance and the NMIs is huge.
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  • 29
    ISSN: 1432-1211
    Schlagwort(e): Key words Skin ; Genetics ; TNFA ; ¶Inflammation ; PCR-RFLP
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract  Mechanisms underlying susceptibility to skin irritants are not clearly understood. Cytokines play a key role in inflammation, and functional polymorphisms in cytokine genes may affect responses to irritants. We investigated the relationship between polymorphism in the tumor necrosis factor (TNF) α-chain gene and responses to irritants. Volunteers (n=221) tested with sodium dodecyl sulfate (SDS) and benzalkonium chloride (BKC) were divided into responders and nonresponders and high and low irritant-threshold groups. DNA was assayed for the TNF-308 polymorphism by a polymerase chain reaction-restriction fragment length polymorphism method. There was a significant increase in the A allele (P=0.030) and AA genotype (P=0.023) in both the SDS low irritant-threshold group and in SDS responders (A allele P=0.022, AA genotype P=0.048). In the BKC low irritant-threshold group, we found a significant increase in the A allele (P=0.002) and AA genotype (P=0.016). Individuals with a low threshold to both irritants demonstrated a significant increase (P=0.002) in the A allele. This is the first description of a nonatopic genetic marker for irritant susceptibility in normal individuals. Genotyping for theTNF-308 polymorphism may thus contribute to screening of individuals deemed at risk of developing irritant contact dermatitis.
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  • 30
    Digitale Medien
    Digitale Medien
    Springer
    Intensive care medicine 26 (2000), S. S057 
    ISSN: 1432-1238
    Schlagwort(e): Key words Critical illness ; Intensive care ; Severity of illness ; Scoring systems ; Genetics ; Susceptibility ; Education
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Risk of critical illness is determined both by genetic and environmental influences, particularly those relating to infectious and cardiovascular diseases. Physiologically-based scoring systems cannot measure prior risk because they do not quantify physiological reserve independently of the acute illness. Genetic profiling could be useful for risk assessment. Early detection of critical illness involves identifying physiological ’triggers' for referral; this requires the education of nursing and medical staff in their significance. Analysis of the relationship between risk factors and interventions may need complex modelling techniques. Therapeutic strategies depend on the nature of the underlying problem: the most useful are likely to be those which enhance tissue oxygen delivery and resistance to infection.
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  • 31
    ISSN: 1432-198X
    Schlagwort(e): Key words Glomerulocystic kidney disease ; Oligohydramnion ; Renal failure-neonate ; Genetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract  Two newborns with glomerulocystic kidney disease manifesting as late onset oligohydramnion and neonatal anuria, yet without severe respiratory distress, are presented. They had a similar perinatal course and associated clinical manifestations. No associated congenital or inherited malformation syndrome could be defined. Both infants’ parents were first degree cousins and belonged to the same small Bedouin tribe, and neither they nor the infants’ siblings had polycystic kidneys or renal insufficiency, pointing to either a possible genetic etiology or a common external toxic exposure.
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  • 32
    Digitale Medien
    Digitale Medien
    Springer
    European journal of pediatrics 159 (2000), S. S183 
    ISSN: 1432-1076
    Schlagwort(e): Key words Database ; Genetics ; Information services ; Internet ; Mutation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Thanks to the World Wide Web, most results of research in genetics are made available in public databases. At the present time there are resources on genetic diseases, genes and their location, mutations of already cloned genes and on laboratories performing the mutation analysis. The main resources on phenotypes are On-line Mendelian Inheritance in Man (OMIM), Pedbase, GeneClinics, London Dysmorphology Database (LDDB) and Orphanet. The main resources on human genes are, in addition to OMIM, the Genome Database, Genatlas and Genecard. There are also two major sequence databases. All of them can be queried using the OMIM number of the disease. Central databases of mutations, as well as locus specific databases have been created. Their list is maintained at the Human Genome Organisation mutation database initiative website. Several initiative have been taken to integrate all these data and help the clinician to find out quickly what he/she needs. The website of the National Center for Biotechnology Information is the best example of such an effort with sections on diseases, a genome guide, and locus links. Several databases of genetic testing resources have been established. GeneTests is an on-line genetics resource that contains a directory of North American laboratories providing testing for heritable disorders. Orphanet is a similar database on French services which is in the process of becoming a European database. Conclusion Even if clinicians do not have as many services at their disposal as the molecular geneticists, various useful databases already exist and should no longer be ignored in practice.
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  • 33
    Digitale Medien
    Digitale Medien
    Springer
    European journal of pediatrics 159 (2000), S. S208 
    ISSN: 1432-1076
    Schlagwort(e): Key words Cardiovascular disease ; Cystathionine β-synthase ; Genetics ; Methylenetetrahydrofolate reductase ; Mild hyperhomocysteinaemia
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Over the last decade mild hyperhomocysteinaemia has widely been recognised as a new risk factor for arteriosclerosis and thrombosis. Main regulating enzymes of homocysteine (Hcy) metabolism are cystathionine β-synthase (CBS), methionine synthase and methylenetetrahydrofolate reductase (MTHFR). Early studies on patients with vascular disease described elevated Hcy concentrations after methionine loading and decreased CBS activity, resembling heterozygotes for CBS deficiency. Therefore, heterozygosity for CBS deficiency was proposed as the main cause of mild hyperhomocysteinaemia. However, more recent enzymatic and molecular genetic studies have demonstrated that heterozygosity for CBS deficiency is not or only a very minor cause of mild hyperhomocysteinaemia in vascular disease. We discovered two common genetic causes of mild hyperhomocysteinaemia, the 677C 〉 T and the 1298A 〉 C mutations in the coding region of MTHFR. The 677C 〉 T mutation causes reduced enzyme activity with thermolabile protein properties, elevated Hcy and low-normal or decreased plasma folate levels. The 1298A 〉 C mutation relates also to decreased enzyme activity, but not to thermolabile protein, and Hcy and folate levels are not influenced. However, compound heterozygosity for these two mutations, i.e. individuals with the 677CT/1298AC genotype, have elevated Hcy and decreased plasma folate levels. Gene-enviroment interactions between 677C 〉 T and folate is demonstrated in individuals with the 677TT genotype. Those with low-normal folate have elevated Hcy, whereas those with high-normal folate have normal Hcy concentrations. The elevated Hcy levels due to these mutations can be normalised by administration of folate, but whether folate reduces the risk of cardiovascular disease remains to be established. Conclusion Heterozygosity for cystathionine β-synthase deficiency is a minor cause of hyperhomocysteinaemia. The current data on mutations in the methylenetetrahydrofolate reductase gene do not tell us whether elevated plasma homocysteine plays a causal role in vascular disease. Low cellular vitamin status may be a possible cause and homocysteine may just be a marker for this situation.
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  • 34
    Digitale Medien
    Digitale Medien
    Springer
    European journal of pediatrics 159 (2000), S. S35 
    ISSN: 1432-1076
    Schlagwort(e): Key words Obesity ; Genetics ; Child ; Nutrient balance ; Energy balance ; Environment
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The epidemic diffusion of obesity in industrialised countries has promoted research on the aetiopathogenesis of this disorder. The purpose of this review is to focus mainly on the contribution that European research has made to this field. Available evidence suggests that obesity results from multiple interactions between genes and environment. Parents obesity is the most important risk factor for childhood obesity. Twin, adoption, and family studies indicated that inheritance is able to account for 25% to 40% of inter-individual difference in adiposity. Single gene defects leading to obesity have been discovered in animals and, in some cases, confirmed in humans as congenital leptin deficiency or congenital leptin receptor deficiency. However, in most cases, genes involved in weight gain do not directly cause obesity but they increase the susceptibility to fat gain in subjects exposed to a specific environment. Both genetic and environmental factors promote a positive energy balance which cause obesity. The relative inefficiency of self-adapting energy intake to energy requirements is responsible for fat gain in predisposed individuals. The role of the environment in the development of obesity is suggested by the rapid increase of the prevalence of obesity accompanying the rapid changes in the lifestyle of the population in the second half of this century. Early experiences with food, feeding practices and family food choices affect children's nutritional habits. In particular, the parents are responsible for food availability and accessibility in the home and they affect food preferences of their children. Diet composition, in particular fat intake, influences the development of obesity. The high energy density and palatability of fatty foods as well as their less satiating properties promotes food consumption. TV viewing, an inactivity and food intake promoter, was identified as a relevant risk factor for obesity in children. Sedentarity, i.e. a low physical activity level, is accompanied by a low fat oxidation rate in muscle and a low fat oxidation rate is a risk factor of fat gain or fat re-gain after weight loss. Conclusion Further research is needed to identify new risk factors of childhood obesity, both in the genetic and environmental areas, which may help to develop more effective strategies for the prevention and treatment of obesity.
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  • 35
    ISSN: 1432-1459
    Schlagwort(e): Key words Amyotrophic lateral sclerosis ; Genetics ; Presenilin-1 intron 8 polymorphism ; Apoptosis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The mechanisms underlying motor neuron degeneration in amyotrophic lateral sclerosis are not fully understood. Recent studies suggest that apoptosis is involved in the abnormal neural death that occurs in this devastating disease. Presenilin-1, a transmembrane protein, seems to be implicated in apoptosis. To determine whether presenilin-1 intron 8 polymorphism has an influence in the course of amyotrophic lateral sclerosis, we examined this polymorphism genotypes in a large group of patients (n=72) with amyotrophic lateral sclerosis and in a random sample of 213 healthy individuals. The results showed a significant difference in genotype (P 〈 0.04) and allele (P 〈 0.03) distribution between patients and controls. These results suggest a possible intervention of presenilin-1 in the pathogenesis of amyotrophic lateral sclerosis.
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  • 36
    Digitale Medien
    Digitale Medien
    Springer
    Journal of neurology 247 (2000), S. 81-87 
    ISSN: 1432-1459
    Schlagwort(e): Key words Dementia ; Vascular ¶dementia ; Alzheimer’s disease ; Risk factors, stroke ; Genetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract This review describes differing profiles of vascular risk factors in different types of dementia. Although vascular risk factors are related to various types of strokes, their independent effect on the occurrence of poststroke dementia appears to be small. Various risk factors have been identified for microangiopathy-related cerebral abnormalities, such as white matter changes and lacunae, which are the core lesions for the development of a vascular dementia syndrome without stroke symptoms. Most consistently, arterial hypertension and diabetes mellitus have been found to be associated with such brain abnormalities. Diastolic blood pressure seems to be of particular importance as recent investigations demonstrate that this factor is related to the course of multiple lacunar strokes and the progression of white matter disease. Epidemiological studies report that various vascular risk factors including arterial hypertension, diabetes mellitus, and atrial fibrillation may also be associated with Alzheimer’s disease. There is also evidence of a direct relationship between Alzheimer’s disease and general atherosclerosis. Further investigations are needed to determine whether these associations are due to the weakness of diagnostic criteria, or whether vascular risk factors indeed modulate the clinical expression of primary degenerative dementia. Common susceptibility genes leading to shared risk factors may be one of the reasons for a higher coincidence of Alzheimer’s disease and vascular dementia than can be expected by chance. A modulatory effect of vascular risk factors in the development of primary degenerative dementia may extend treatment options.
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  • 37
    ISSN: 1432-1459
    Schlagwort(e): Key words Parkinson’s disease ; Monoamine oxidase B ; Genetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Monoamine oxidase B (MAOB) metabolises dopamine and activates neurotoxins known to induce parkinsonism in humans and primates. Therefore the MAOB gene (MAOB; Xp15.21–4) is a candidate gene for Parkinson’s disease (PD). Longer length dinucleotide repeat sequences in a highly polymorphic GT repeat region of intron 2 of this gene showed an association with PD in an Australian cohort. We repeated this allele-association study in a population of 176 Chinese PD patients ¶(90 men, 86 women) and 203 age-matched controls (99 men, 104 women). Genomic DNA was extracted from venous blood and the polymerase chain reaction was used to amplify the appropriate regions of the MAOB gene. The length of each (GT) repeat sequence was determined by 5% polyacrylamide denaturing gel electrophoresis. There was no significant difference in allele frequencies of the (GT) repeat allelic variation between patients and controls (χ2 = 2.48; df = 5, P 〈 0.75). Therefore the longer length GT repeat alleles are not associated with PD in this Chinese population. Possible reasons for the discrepancy between Chinese and Australian populations include a different interaction between this genetic factor and environmental factors in the two populations and the possibility that the long length GT repeat alleles may represent a marker mutation, genetically linked to another susceptibility allele in whites but not in Chinese. Methodological differences in the ascertainment of cases and controls in this cohort could also explain the observed differences. Further study is required to determine whether the longer length GT repeat alleles are true susceptibility alleles in PD.
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  • 38
    ISSN: 1432-1459
    Schlagwort(e): Key words Progressive ¶supranuclear palsy ; Genetics ; Clinical characteristics ; Parkinsonism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Genetic studies have detected an association between the presence of the τ gene A0 allele and patients with progressive supranuclear palsy (PSP). This study examined whether patients with this polymorphism exhibit distinct demographic or clinical characteristics. We studied 26 patients who fulfilled clinical criteria for the diagnosis of PSP, 20 who had the A0/A0 genotype and 6 who had other genotypes. A questionnaire on demographic data, past medical history, familial history, and initial symptoms was completed as part of the consultation. A complete neurological examination was performed and PSP symptoms were quantified following Golbe’s PSP disability scale. We found a significant difference in the age at onset of PSP symptoms, which was 65.9 ± 5.3 years in the A0/A0 group and 71.2 ± 5.6 in the non-A0/A0 group (P = 0.016). There were no significant differences in the years from disease onset between the two groups. Symptom severity did not differ significantly in patients with the different A0/A0 genotypes. The detection of significantly lower age at onset with the A0/A0 alleles is consistent with the known association of this genotype as a risk factor for PSP. No significant differences were detected in symptom severity between the two groups of patients.
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  • 39
    ISSN: 1432-1459
    Schlagwort(e): Key words Multiple sclerosis ; Siblings ; Genetics ; Oligoclonal bands ; Measles
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract We found that 19% (9/47) of healthy siblings of patients with clinically definite multiple sclerosis had an intrathecal immunological reaction with two or more 2 CSF-enriched oligoclonal bands (OCBs), in contrast to (4%) (2/50) unrelated healthy controls. Furthermore, in this group of nine healthy sibs the measles CSF IgG antibody titers were higher than that of the other sibs and that of controls. There were also differences in the serum titers for measles IgG antibody, which were higher in the group of all healthy sibs than in healthy volunteers, and (as with CSF titers) higher in the subgroup of healthy sibs with two or more 2 CSF-enriched OCBs than the other sibs. Thus a significant proportion of healthy siblings to MS patients have a partially hyperimmune condition similar to that occurring in MS, which in 19% manifested itself as an OCB reaction, in 9% as increased CSF measles IgG antibody titers, and in 21% as increased serum measles IgG antibody titers, these phenomena tending to occur in the same individuals. This condition is characterized by CSF-enriched OCBs with undefined specificity, although some increased antiviral reactivity is found both in the serum and CSF. While it needs further characterization, a genetic trait interacting with common infections is suggested. The recurrence risk of this condition is approximately five times higher than the 3–4% recurrence risk for manifest MS reported for sibs.
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  • 40
    Digitale Medien
    Digitale Medien
    Springer
    Child's nervous system 16 (2000), S. 809-820 
    ISSN: 1433-0350
    Schlagwort(e): Keywords Pediatric neurosurgery ; Molecular biology ; Genetics ; Novel therapeutics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract  The new millennium beckons for novel advances in the diagnosis and treatment of pediatric neurosurgical conditions. Almost every aspect of pediatric neurosurgery has changed over the last decade. Undoubtedly with the application of knowledge in molecular biology to human disease many aspects of neurosurgery, especially neuro-oncology and the field of neuro-developmental anomalies, will change appreciably over the next decade. Overall, the trend in surgery in general and neurosurgery in particular is toward less invasive procedures and possibly non-surgical interventions. This review will briefly cover many of the important areas of pediatric neurosurgery. We will describe the state-of-the-art of our subspecialty and discuss possible future directions.
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  • 41
    Digitale Medien
    Digitale Medien
    Springer
    Theoretical and applied genetics 101 (2000), S. 234-240 
    ISSN: 1432-2242
    Schlagwort(e): Key words Cherry ; Genetics ; Compatibility ; Incompatibility ; Isoelectric focusing ; Prunus avium ; Ribonuclease
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  The (in)compatibility genotypes of two self-compatible sweet cherry selections, JI 2420 and JI 2434, originating from the John Innes Institute were re-examined. The selections and seedlings derived from them were analysed for stylar ribonucleases, which are known to correlate with S alleles, and the outcome of test crosses was recorded. JI 2420, which had been reported previously as S 3 S 4 ", where " indicates loss of pollen activity, was deduced to have the genotype S 4 S 4 ’. For JI 2434, which had been reported previously as S 3 S 4 0 , S 3 S 3 0 or S 3 S 3 ", where 0 indicates loss of pollen and stylar activity, two different clones were identified. One, at East Malling, was deduced to be S 3 "S 4 ; the other, at Ahrensburg, appeared to be S 3 S 3 " or S 3 S 3 0 .
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  • 42
    ISSN: 1432-2242
    Schlagwort(e): Key words Avicennia marina ; Microsatellite ; Mangrove ; Genetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  An enriched microsatellite library of the mangrove species Avicennia marina was constructed, in which 85.8% of the clones contained microsatellite sequences. Of the microsatellite repeat sequences isolated, 55.0% were di-nucleotides, 34.2% were tri-nucleotides, 50.0% were perfect, 24.2% were imperfect, and 15.0% were compound. Four different di-nucleotide repeats were isolated with repeat lengths ranging from 5 to 33; ten different tri-nucleotide repeats were isolated with repeat lengths ranging from 3 to 25. The most common di-nucleotide was the AC/TG repeat; the most common tri-nucleotide was the CCG/GGC repeat. Sixteen microsatellite sequences were selected for primer design, and 6 primers were selected to investigate the polymorphism detected among 15 individuals of A. marina from three natural populations in Australia. A total of 40 alleles were detected at 6 microsatellite loci. The number of alleles per microsatellite locus ranged from 5 to 13. On average, 7 alleles were detected per locus. All microsatellite loci showed high levels of gene diversity (heterozygosity), with values ranging from 0.53 to 0.88; the mean value of gene diversity was 0.70. Microsatellite loci were also tested for conservation across Avicennia species. There was a decline in amplification success with increasing divergence between Avicennia species. The results indicate that microsatellites are abundant in the Avicennia genome and can be valuable genetic markers for assessing the effects of deforestation and forest fragmentation in mangrove communities, which is an important issue for mangrove conservation and afforestation schemes.
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  • 43
    ISSN: 1433-8491
    Schlagwort(e): Key words Pharmacogenetics ; Genetics ; Risk factor ; Choreoathetotic movements
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract In the search for genetic factors contributing to tardive dyskinesia, dopamine receptor genes are considered major candidates. The dopamine D3 receptor is of primary interest as dopamine D3 receptor knock-out mice show locomotor hyperactivation resembling extrapyramidal side-effects of neuroleptic treatment. Furthermore, Steen and colleagues (1997) recently reported an association between tardive dyskinesia and a dopamine D3 receptor gene variant. In the present study we tried to replicate this finding. We investigated 157 patients with schizophrenia or schizoaffective disorder receiving long-term neuroleptic medication who never or persistently displayed tardive dyskinesia. As advanced age is a main risk factor for tardive dyskinesia, we also compared older patients with a long duration of schizophrenia not displaying tardive dyskinesia to younger patients with a shorter duration of the illness displaying tardive dyskinesia. However, we found no evidence that the dopamine D3 receptor gene is likely to confer susceptibility to the development of tardive dyskinesia.
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  • 44
    ISSN: 1433-8491
    Schlagwort(e): Key words Dopamine receptor D4 ; Genetics ; Personality inventory ; Polymorphism ; Excitement-Seeking
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract An association between long alleles of a variable number tandem repeat (VNTR) polymorphism in the dopamine receptor D4 gene and the extraversion related personality traits Excitement and Novelty Seeking has been reported in healthy subjects. In an attempt to replicate the previous findings, 256 healthy Caucasian volunteers were analysed for a potential relationship between the dopamine receptor D4 exon III VNTR polymorphism and Extraversion as assessed by the Revised Neo Personality Inventory (NEO PI-R). The present study did not yield evidence for an association between Extraversion and the dopamine receptor D4 polymorphism.
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  • 45
    Digitale Medien
    Digitale Medien
    Springer
    Pflügers Archiv 440 (2000), S. r200 
    ISSN: 1432-2013
    Schlagwort(e): Key words oxygen uptake ; kinetics ; threshold
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The linear relationship between oxygen consumption (Vo2) and exercise intensity is a well established phenomenon observed during incremental exercise. Recently, a non-linear increase in Vo2 has been reported by Zoladz et al., who used a relatively complicated method to describe the phenomenon. In this study, we tried to ascertain whether the same phenomenon, which we named the oxygen uptake threshold (OUT), could be described by a simple method, using the two best fitting lines adopted for the less and more steep parts of the Vo2 increase. Our hypothesis was that the non-linear Vo2 increase was the result of a continuous Vo2 increase (oxygen drift) occurring during the more intense steps only. Therefore, we analysed the Vo2 time course during each step. Six cyclists performed an incremental exercise test on a cyclo - ergometer. The lactate threshold (LT) was calculated by using the intersection point of the two best fitting lines in the diagram of log LA (lactate concentration) dependence on log P (Power). The time course of Vo2 during each step was analysed by an exponential rise to the maximum model. The results showed that OUT could be determined in five of the six subjects, whereas LT could be determined in all six subjects. The power output determined by OUT (168 ± 13 W) was similar to that determined by LT (180 ± 25 W). The Vo2 time course during each step showed steady values during low intensity exercise. At intensities above LT and OUT, however, Vo2 increased continuously, showing oxygen drift. It may be concluded that OUT is a realistic phenomenon, which is based on oxygen drift.
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  • 46
    ISSN: 1432-1459
    Schlagwort(e): Key words Multiple sclerosis ; Genetics ; ICAM-1 gene
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract An increased amount of the intercellular adhesion molecule (ICAM) 1 molecule has been found in the blood of actively relapsing multiple sclerosis (MS) patients, but is unclear whether this enhanced expression is partially causative of the MS process, or whether it is merely an epiphenomenon of the inflammatory-immunological reaction. Using the transmission disequilibrium test (TDT), we studied exon 4 and exon 6 polymorphism of the ICAM-1 gene from 157 families with both parents, one affected and one healthy sib coming from Sardinia, an Italian island having a high incidence and prevalence of MS. TDT did not show variation in the expected 50:50 frequency in transmission in either healthy or affected sibs, using phenotypic or genotypic analysis. Moreover, independence from the predisposing HLA-DRB1-DQA1-DQB1 haplotype was confirmed by TDT analysis performed on the patients stratified according to the presence or absence of the HLA-DRB1, DQA1, DQB1 Sardinian predisposing haplotypes. Our data suggest that the increased expression of the ICAM-1 molecule observed in both blood and periplaque microvessels may be considered a consequence of the inflammatory process rather than the result of a genetic variation.
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  • 47
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 633-642 
    ISSN: 1572-8943
    Schlagwort(e): cadmium ; dialkyldithiocarbamate ; kinetics ; thermal decomposition ; thermogravimetry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The thermal decomposition kinetics of the solid complexes Cd(S2 CNR2 )2 , where R =C2 H5 , n -C3 H7 , n -C4 H9 or iso -C4 H9 , was studied by using isothermal and non-isothermal thermogravimetry. The superimposed TG/DTG/DSC curves revealed that thermal decomposition reactions occur in the liquid phase. The kinetic model that best fitted the experimental isothermal TG data was the one-dimensional phase-boundary reaction-controlled process R1 . The thermal analysis data suggested the thermal stability sequence Cd(S2 CNBun 2 )2 〉Cd(S2 CNPrn 2 )2 〉Cd(S2 CNBui 2 )2 〉Cd(S2 CNEt2 )2 , which accords with the sequence of stability of the apparent activation energies.
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  • 48
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 807-814 
    ISSN: 1572-8943
    Schlagwort(e): facial and meridional Co(III) complexes ; kinetics ; thermodynamics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Thermal properties of facial and meridional uns-cis-[Co(eddp)gly]0.5H2O complexes were investigated by means of DSC and TG techniques. It wasshown that the processes of thermal decomposition of these complexes are multi-stepdegradation processes, which can also be well separated into individual steps, depending onthe molecular symmetry. Thus, the process of thermal degradation of the meridional isomerof the above complex consists of 4 well-separated steps in the temperature interval from 100to 500°C. The corresponding kinetic and thermodynamic parameters of this process weredetermined, and a possible mechanism is discussed.
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  • 49
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 955-965 
    ISSN: 1572-8943
    Schlagwort(e): kinetics ; metal complexes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Thermogravimetry (TG) and differential thermal analysis (DTA) were performed on the complexes with general formula (M(DEBT)n (where M =Fe, Co, Ni, Cu or Ru; n =2, or 3 and DEBT=N,N-diethyl-N'-benzoylthiourea). Derivative thermogravimetric (DTG) curves were also recorded in order to obtain decomposition data on the complexes. The complexes of Fe(III), Co(II), Ni(II), Cu(II) and Ru(III) displayed two- or three-stage decomposition patterns when heated in a dynamic nitrogen atmosphere. Mass loss considerations relating to the decomposition stages indicated the conversion of the complexes to the sulfides or to the corresponding metal alone (Cu, Ru, NiS, CoS or FeS). Mathematical analysis of the TG and DTG data showed that the order of reaction varied between 0.395 and 0.973. Kinetic parameters such as the decomposition energy, the entropy of activation and the pre-exponential factor are reported.
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  • 50
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 62 (2000), S. 429-433 
    ISSN: 1572-8943
    Schlagwort(e): adsorption ; fast measurement ; gravimetry ; kinetics ; sorption ; kw6
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Jäntti introduced a method to reduce the time required for the stepwise measurement of adsorption isotherms. After each pressure change he measured the adsorbed mass three times and calculated its equilibrium value at the new pressure. In the present paper, we discuss the applicability of this method in a broader scope without starting from a given combination of sorptive and adsorbent and the influence of measuring inaccuracies. The method is applied to detect whether the adsorption process is based on more than one adsorption mechanism or not.
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  • 51
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 63 (2000), S. 375-386 
    ISSN: 1572-8943
    Schlagwort(e): activation energy ; ammonium perchlorate ; decompositon ; isothermal ; kinetics ; thermogravimetry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The kinetics of the thermal decomposition of ammonium perchlorate at temperatures between 215 and 260°C is studied, in this work, by measuring the sample mass loss as a function of time applying the isothermal thermogravimetric method. From the maximum decomposition rate – temperature dependence two different decomposition stages, corresponding to two different structural phases of ammonium perchlorate, are identified. For the first region (215–235°C), corresponding to the orthorhombic phase, the mean value of the activation energy of 146.3 kJ mol–1, and the pre-exponential factor of 3.43⋅1014 min–1 are obtained, whereas for the second region (240–260°C), corresponding to the cubic phase, the mean value of the activation energy of153.3 kJ mol–1, and the pre-exponential factor of 4.11⋅1014 min–1 are obtained.
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  • 52
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 35-43 
    ISSN: 1572-8943
    Schlagwort(e): kinetics ; 10-methylacridinium halides ; thermodynamics ; thermogravimetric investigations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract 10-Methylacridinium chloride, bromide and iodide were prepared in crystalline forms (the first two salts as monohydrates) and subjected to thermogravimetric investigations. Decomposition of the compounds is initially accompanied by the liberation of water (in case of monohydrates), halomethanes and acridine molecules. As decomposition proceeds, side reactions occur which are reflected in a complex pattern of thermogravimetric curves. TG traces corresponding to the initial decomposition stage were used to determine the kinetic characteristics of the thermal dissociation of the salts. MNDO/d, AM1 and PM3 methods were employed independently to examine reaction pathways and to predict thermodynamic and kinetic barriers for the thermal decomposition of the compounds. These data were subsequently supplemented with theoretically determined crystal lattice energies, which enabled the relevant characteristics for the decomposition of crystalline phases to be predicted. The theoretically predicted characteristics are qualitatively comparable with those originating from thermogravimetric investigations, which allows one to believe that both are valid.
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  • 53
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 103-110 
    ISSN: 1572-8943
    Schlagwort(e): cyanazine ; DSC ; kinetics ; thermal stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Cyanazine was taken as an example for investigations under the influence of different conditions on thermal decomposition of triazine herbicides. DSC measurements were carried out under atmospheric pressure and hermetically closed, under pressure 1.3 kPa. The influence of the pressure on the constant reaction rate of decomposition of cyanazine was discussed. It was also proved that the predicted reaction constant rates from isothermal and non-isothermal measurements are consistent.
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  • 54
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 247-255 
    ISSN: 1572-8943
    Schlagwort(e): desulfuration ; gas atmosphere ; kinetics ; thermal decomposition ; titanium dioxide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The studies were devoted to determination of the effect of gas atmosphere and its pressure on the second step of decomposition of hydrated titanium dioxide (HTD) promoted by sulfate groups. It has been found that thermal decomposition of HTD at temperatures above 300°C consists of a number of processes such as dehydroxylation, desulfuration, recrystallization and sintering of solid grains, photochemical processes (if the decomposition proceeds in the presence of light) and adsorption of gas phase components (in the presence of air or SO2). Kinetic parameters characterizing this step of decomposition have been determined for processes carried out in vacuum and in argon or air atmospheres (at a pressure of 13.33hPa). The kinetic curves of decomposition carried out in the presence of gases capable of being adsorbed on the surface of partly dehydrated HTD are featured by local extrema due to simultaneous processes of decomposition and adsorption of gas components.
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  • 55
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 9-15 
    ISSN: 1572-8943
    Schlagwort(e): coordination compounds ; kinetics ; thermal dissociation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Physicalo-chemical importance of the quantitative study of kineticliability of coordination compounds in thermal dissociation processes is considered. Muchattention is given to the proof of the physicalo-chemical meaning and validity of kineticparameters calculated from thermoanalytical data. Experimental data (thermal dissociation ofcoordination compounds and clathrates with such a matrix) are discussed.
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  • 56
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 401-407 
    ISSN: 1572-8943
    Schlagwort(e): cross-linking ; isothermal crystallization ; kinetics ; modification ; polypropylene ; silica
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The effect of addition of silica on the parameters of isothermal crystallization of polypropylene has been investigated. It was found that the covering of the silica surface by a layer of low-density polyethylene leads to a deactivation of the filler regarding the positive effect on the polypropylene crystallization rate parameters. Cross-linking of the surface polyethylene layer results in a stronger attachment of the modifying polymer to the filler surface and the deactivation effect of the silica surface modification is more pronounced.
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  • 57
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 541-547 
    ISSN: 1572-8943
    Schlagwort(e): Cr(II) ; chromium trioxide ; kinetics ; reduction ; thermal analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The thermal behaviour of CrO3 on heating up to 600°C in dynamic atmospheres of air, N2 and H2 was examined by thermogravimetry (TG), differential thermal analysis (DTA), IR spectroscopy and diffuse reflectance spectroscopy (DRS). The results revealed three major thermal events, depending to different extents on the surrounding atmosphere: (i) melting of CrO3 near 215°C (independent of the atmosphere), (ii) decomposition into Cr2(CrO4)3 at 340–360°C (insignificantly dependent), and (iii) decomposition of the chromate into Cr2O3 at 415–490°C (significantly dependent). The decomposition CrO3 → Cr2(CrO4)3 is largely thermal and involves exothermic deoxygenation and polymerization reactions, whereas the decomposition Cr2(CrO4)3 → Cr2O3 involves endothermic reductive deoxygenation reactions in air (or N2) which are greatly accelerated and rendered exothermic in the presence of H2. TG measurements as a function of heating rate (2–50°C min−1) demonstrated the acceleratory role of H2, which extended to the formation of Cr(II) species. This could sustain a mechanism whereby H2 molecules are considered to chemisorb dissociatively, and then spillover to induce the reduction. DTA measurements as a function of the heating rate (2–50°C min−1) helped in the derivation of non-isothermal kinetic parameters strongly supportive of the mechanism envisaged.
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  • 58
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 667-674 
    ISSN: 1572-8943
    Schlagwort(e): accommodation function ; crystal growth ; glass-ceramics ; kinetics ; number of nuclei ; thermal history
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Kinetic modeling of the crystal growth from pre-existing nuclei was reexamined to obtain a fundamental information about the controlled crystallization of glasses during formation of advanced inorganic glass-ceramics. Methods of kinetic analysis were reviewed by taking account of thermal history of the sample within the temperature range of nucleation. An accommodation function depending on the thermal history was introduced in the kinetic equation. The role of the accommodation function was reinvestigated when determining the activation energy from a series of kinetic curves. The kinetic description of the crystal growth in the samples with different thermal history was generalized by extrapolating the rate behavior to infinite temperature.
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  • 59
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 333-343 
    ISSN: 1572-8943
    Schlagwort(e): base line ; DSC ; kinetics ; modeling ; thermodynamics ; TMDSC
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The application of non-linear heating program to a heat-flux DSC apparatus has attracted much attention. From thermodynamics viewpoint, it is shown that the variation of enthalpy of a sample changing with temperature change is due, to both the true heat capacity of the sample and the enthalpy of some transformations occurring in the sample, characterized by its degree of advance. Using the simple assumption that the rate of the transformation is proportional to the distance from the thermodynamic equilibrium, an electrical model of the thermal event is given. Using the coupled cell model of the DSC apparatus, we show how to obtain the rate of transformation of the sample and heat capacity, which is directly related to the base line of the experiment.
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  • 60
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 759-778 
    ISSN: 1572-8943
    Schlagwort(e): decomposition temperature ; error sources ; gas-flow and vapor control ; kinetics ; thermogravimetry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The well-known divergence between the present ‘state of the art’ of thermogravimetry and industrial requirements is discussed. Sources of errors are analyzed and the optimization of measuring conditions is discussed regarding the problems associated with static and dynamic (flow) atmospheres, and interactions between materials and gases or vapors. Recommendations for gas-flow control systems and vapor sources are given. Thermal stability and the kinetics of gas-evolving, reversible, thermal decompositions of solids are discussed. The scope of TG-derived kinetics for practical use is examined. Some new characteristic points of TG curves are proposed and defined, e.g. ‘procedure-independent decomposition temperature’ and ‘augmented decomposition temperature’ (obtained at pseudo-equilibrium conditions).
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  • 61
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 879-886 
    ISSN: 1572-8943
    Schlagwort(e): driving force ; kinetics ; rate equation ; reversible reactions
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract This paper outlines the different ways of taking the distance from thermodynamic equilibrium into account in kinetic studies based on thermoanalytical experiments. The three main approaches are: (i) avoiding or neglecting the effect of the reverse reaction, (ii) describing the influence of distance from equilibrium on apparent kinetic parameters, and (iii) incorporating a driving force factor in the rate equation. Finally, the contradiction of the microscopic nature of the processes and the macroscopic character of the usual rate equation are briefly discussed.
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  • 62
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 943-954 
    ISSN: 1572-8943
    Schlagwort(e): CRTA ; kinetics ; self-generated atmospheric conditions ; synthetic malachite ; thermal decomposition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The kinetic behavior of the thermal decomposition of synthetic malachite was investigated by means of CRTA under different conditions of reduced pressure, flowing gases and quasi-isobaric atmospheres. The thermal decomposition was found to proceed at lower temperatures under the influence of the self-generated gases, CO2 and H2O. From a viewpoint of chemical equilibrium, the normal and opposite effects on the overall kinetics were observed for the self-generated CO2 and H2O, respectively. The complexity of the present reaction is also reflected by the variations of the apparent kinetic parameters which depend on the applied and self-generated atmospheric conditions. The practical usefulness of CRTA when applied to a complicated thermal decomposition is discussed as exemplified by the kinetic approaches to the present reaction.
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  • 63
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 151-156 
    ISSN: 1572-8943
    Schlagwort(e): complexes ; kinetics ; TG-DTA
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Thermal behaviour of a few lanthanide complexes of the type ML3(I) [M=Eu,Gd; HL=4,4,4-trifluoro- 1-(2-napthyl)-1,3-butanedione and EuL30.5dmm dmm=2,6-dimethylmorpholine(II)], has been investigated. From thermogravimetric(TG) curves, the decomposition pattern of the compounds has been analysed on the basis of mass loss data. The order and activation energy of the thermal decomposition reactions have been elucidated. From differential thermal analysis (DTA) studies, the heat of reaction and rate of thermal decomposition reaction have been enumerated.
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  • 64
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 239-242 
    ISSN: 1572-8943
    Schlagwort(e): kinetics ; Mannich compounds ; thermal decomposition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The authors present data concerning the evaluation of kinetic parameters of the decomposition of a Mannich compound by using the classical method of constant heating rate thermal analysis and the new one of controlled rate thermal analysis (CRTA). The data processed using the CRTA method allow to obtain more reliable kinetic parameters according to the proposed reaction mechanism.
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  • 65
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 437-450 
    ISSN: 1572-8943
    Schlagwort(e): crystallization ; EPDM ; kinetics ; morphology ; PP ; rubber
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The effect of the incorporation of an amorphous immiscible polymer (ethylene-propylene-diene- terpolymer) on the PP crystallization kinetics and thermodynamics is investigated by thermal analysis. The results of the investigation have shown that EPDM acts as a nucleant agent. A marked decrease of the half time of PP crystallization, τ1/2 , as well as a sensible increase of the overall crystallization rate, K n , has been observed in the presence of EPDM. Moreover, at any crystallization temperature, a minimum of τ1/2 , is obtained at 25% EPDM content in the blend. The Avrami model has been successfully applied to describe the crystallization kinetics of the blend. The kinetic curves obtained under non-isothermal conditions confirm the results obtained under isothermal conditions and demonstrate the nucleant action of the EPDM phase on the PP crystallization.
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  • 66
    Digitale Medien
    Digitale Medien
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    Journal of thermal analysis and calorimetry 62 (2000), S. 721-727 
    ISSN: 1572-8943
    Schlagwort(e): kinetics ; metal exchange ; thermaldehydration ; zeolite
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Zeolite-4A is a hydrated aluminosilicate which becomes more hydrated when exchanged with transition metals. In this work, the dehydration kinetics of cobalt, nickel and copper(II)-exchanged zeolite-4A were studied by means of TG and DTA over the temperature range from 20 to 500°C, and the numbers of water molecules in the metal-exchanged zeolite samples were calculated. It was observed that, as the ionic radius of the hydrated metal increased, the number of water molecules also increased. The loss of water from the zeolite samples generally occurred in the temperature range 100–300°C and was manifested in the DTA graphs by an extended endothermic effect. The DTA curves demonstrated that the peak position shifted towards lower temperatures as the metal concentration increased or, in other words, the water of hydration increased. The kinetic parameters (order of reaction and activation energy) were calculated via the Coats and Redfern method. The process of dehydration was found to follow first-order kinetics.
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  • 67
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 63 (2000), S. 359-374 
    ISSN: 1572-8943
    Schlagwort(e): KEKAM equation ; kinetics ; thermal dissociation of solids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Relationships have been established between the average conversion degree and the dissociation time for polydisperse granular material, taking its grain size distribution into account. It has been checked in which cases the kinetic curves obtained by a numerical solution can be described in terms of KEKAM equation.
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  • 68
    ISSN: 1572-8943
    Schlagwort(e): isoconversional methods ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract An analysis is presented of the consequences of the use of a one term equation containing apparent activation parameters, instead of the true rate equation to describe two successive decomposition reactions undergone by a solid compound. It is demonstrated that the apparent activation energy, obtained by means of isoconversional differential and integral methods, varies with the conversion degree for a relatively narrow temperature range and with temperature at a given value of the conversion degree. The activation energy values obtained with the isoconversional differential method are higher than the corresponding values obtained with the isoconversional integral method.
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  • 69
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 869-875 
    ISSN: 1572-8943
    Schlagwort(e): decomposition ; kinetics ; plumbo-jarosite
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract An investigation was carried out on the kinetics of thermal decomposition of plumbo-jarosite. The kinetic models of dissociation of the compounds in the ore were identified. The results of the kinetic studies and the mechanism of the process are discussed. The thermal decomposition of plumbo-jarosite occurs in three stages: the first up to 763, the second up to 1023 and the third up to 1223 K, the corresponding activation energy values being 62.2, 60.3 and 98.0 kJ mol–1 , respectively.
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  • 70
    Digitale Medien
    Digitale Medien
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    Journal of thermal analysis and calorimetry 61 (2000), S. 805-818 
    ISSN: 1572-8943
    Schlagwort(e): aluminium ; ARC ; DSC ; kinetics ; nanometric size ; SDT ; TG
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The thermal properties of Alex, a nanosized Al powder, were determined using various techniques, including DSC, TG, simultaneous TG-DTA (SDT) and accelerating rate calorimetry (ARC). The results demonstrate that the specific heat capacities of nano and micron size Al powders are similar between 30 and 400°C. Dynamic and isothermal methods were used to determine the kinetic parameters for the oxidation reaction of Alex, which was detected at an onset temperature of 481°C. The results obtained were in good agreement with each other. From the ARC experiments, exotherms were detected near 340 and 260°C for experiments started at ambient pressure and at 0.72 MPa, respectively.
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  • 71
    Digitale Medien
    Digitale Medien
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    Journal of thermal analysis and calorimetry 61 (2000), S. 861-871 
    ISSN: 1572-8943
    Schlagwort(e): DAGN ; kinetics ; mechanism and IR spectroscopy ; TAGN ; thermal decomposition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Diaminoguanidine nitrate (DAGN) and triaminoguanidine nitrate (TAGN),potential energetic materials in emerging propulsion technology with high mass impetus at low isochoric flame temperature have been studied as regards kinetics and mechanism of thermal decomposition using thermogravimetry (TG), differential thermal analysis (DTA),infrared spectroscopy (IR) and hot stage microscopy. Kinetics of thermolysis has been followed by isothermal TG and IR. For the initial stage of thermolysis of DAGN the best linearity with a correlation coefficient of 0.9976 was obtained for the Avrami-Erofe'evequation, n=2, by isothermal TG. The activation energy was found to be 130 kJ mol–1 and logA=11.4. The initial stage of thermolysis of TAGN also obeyed the Avrami-Erofe'ev equation, n=2, with a correlation coefficient of 0.9975by isothermal TG and the kinetic parameters are E=160.0 kJ mol–1 and logA=16.0. High temperature IR spectra showed exquisite preferential loss in intensity of the NH2, NH, N–N stretching and CNN bending. Spectroscopic and other results favour deamination reaction involving the rupture of the N–N bond as the primary step in the thermal decomposition.
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  • 72
    Digitale Medien
    Digitale Medien
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    Journal of thermal analysis and calorimetry 61 (2000), S. 979-984 
    ISSN: 1572-8943
    Schlagwort(e): kinetics ; nucleation-growth
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The author presents some applications of the fractal geometry in the kinetics of heterogeneous decomposition of solids.
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  • 73
    Digitale Medien
    Digitale Medien
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    Journal of thermal analysis and calorimetry 59 (2000), S. 935-942 
    ISSN: 1572-8943
    Schlagwort(e): CoSO46H2O ; kinetics ; thermal decomposition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Thermogravimetry (TG-DTG), and differential thermal analysis (DTA) were used in the study of the kinetics of decomposition of cobalt sulphate hexahydrate under an air atmosphere. The kinetics of the particular stages of CoSO4 6H2 O decomposition were evaluated from the dynamic mass loss data. The values of the kinetic parameters for each stage of the thermal decomposition were calculated from the α(T) data by using the integral method, applying the Coats-Redfern approximation.
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  • 74
    Digitale Medien
    Digitale Medien
    Springer
    Journal of thermal analysis and calorimetry 62 (2000), S. 681-685 
    ISSN: 1572-8943
    Schlagwort(e): coal-burning additive ; combustion ; graphite ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The catalytic and accelerating effects of three coal-burning additives (CBA) on the burning of graphite were studied with the help of thermogravimetric (TG) analysis. The kinetic study on the catalytic oxidation of the graphite doped with CBA was carried out and the results were presented. The results show that the CBA can change the carbon oxidation/combustion course by catalytic action and change the activation energy, thus improving the combustion efficiency.
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  • 75
    Digitale Medien
    Digitale Medien
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    Journal of thermal analysis and calorimetry 63 (2000), S. 457-463 
    ISSN: 1572-8943
    Schlagwort(e): isoconversional methods ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract It is demonstrated that, if the activation energy depends on the degree of conversion, its values obtained by isoconversional differential and integral methods are different.
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  • 76
    Digitale Medien
    Digitale Medien
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    Journal of materials synthesis and processing 8 (2000), S. 139-144 
    ISSN: 1573-4870
    Schlagwort(e): TiO2 ; phase transformations ; mechanical alloying ; kinetics ; modeling
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract A high-pressure and high-temperature phase of TiO2 : TiO2 II is formed transiently during room-temperature high-energy ball milling of anatase TiO2 : TiO2 anatase → TiO2 II → TiO2 rutile. Rutile is the only phase present after prolonged ball milling. The present paper focuses on the influences of physical and chemical processing conditions on the transformation kinetics. The effects of two milling parameters on the kinetics of phase transformation of anatase TiO2 were investigated: the nature of milling tools and the powder-to-ball weight ratio R. Granulometric characterizations and TEM observations have demonstrated that the transformation of TiO2 anatase into TiO2 II occurs without fracturing of particles and that TiO2 II nanograins form at the surface of anatase particles. The parameter R affects only the transformation rate. For a given R, the transformation rate is the largest with alumina grinding tools, intermediate with zirconia tools, and the smallest with steel tools. The parameters involved in current models of the mechanical alloying process do not suffice to explain the differences in transformation rates observed here. A parameter, which takes into account the influence of the mechanical properties of grinding materials, is considered.
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  • 77
    Digitale Medien
    Digitale Medien
    Springer
    Journal of materials synthesis and processing 8 (2000), S. 271-277 
    ISSN: 1573-4870
    Schlagwort(e): Comminution ; kinetics ; mechanical alloying ; phase transformation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract It has been shown that structural evolution occurring in powder mixtures subjected to mechanical treatment by milling follow well-defined conversion trends as a function of milling time. Sigmoidal curves were observed in the case of the mechanical alloying of transition metal mixtures, whereas a simpler kinetic course with a progressively decreasing transformation rate was found to characterize the disordering process of intermetallic equilibrium compounds by mechanical milling. Under the stipulation that collisions are the dominant energy transfer events, a kinetic model is developed to relate the observed macrokinetic features to the discrete powder fractions, which transform at each impact. Because of its intrinsic qualities, the milling process was regarded as discrete processing. A statistical approach was followed to work out a set of differential equations, solutions of which provide a sound description of the transformation kinetics in terms of conventional rate expressions. The model allows one to reproduce the different kinetic behaviors by means of a single, unifying mathematical formalism. Furthermore, quantifying the structural evolution rate by suitable kinetic constants permits the exploration of the reactive behavior of a system treated under different milling regimes or to compare, on an absolute basis, different systems processed under similar conditions.
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  • 78
    Digitale Medien
    Digitale Medien
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    Oxidation of metals 53 (2000), S. 351-360 
    ISSN: 1573-4889
    Schlagwort(e): Co-base superalloy ; high-temperature oxidation ; kinetics ; structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The oxidation behavior of the Co-base superalloy DZ40M was studied in air at900–1100°C for times of up to 2000 hr. The results indicated thatthis alloy can grow a protective oxide scale at 900 and 1000°C duringisothermal oxidation, but not at 1100°C because of serious cracking andspalling of the oxide scales. Moreover, an internal-precipitate zone formedin the subsurface region of the alloy at all temperatures and times. Theprecipitates were rich in Cr in the vicinity of the alloy–scaleinterface and rich in Al deep in the alloy. The internal-precipitatemorphology changed from a granular to needlelike shape with increasingoxidation temperature.
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  • 79
    Digitale Medien
    Digitale Medien
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    The environmentalist 20 (2000), S. 257-271 
    ISSN: 1573-2991
    Schlagwort(e): evolution ; tides ; sea level ; time series
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Energietechnik
    Notizen: Abstract The increasing use of computers since the 1960s, has implied the digitization of observations in meteorology, oceanography and other observational sciences. Enough data has been accumulated to suggest that some patterns of evolution in the world may be discernable. The present article deals with what appears as changing tides around Canada.
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  • 80
    ISSN: 1573-4943
    Schlagwort(e): Aluminum ; yeast hexokinase ; preferential interactions ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The aluminum and yeast hexokinase interaction was studied. Structural changes were correlated with variations in protein functionality. Results show two different behaviors: At low metal concentrations preferential adsorption of metal (and water exclusion) induces aggregate formation. No significant changes in the protein structure occur, but there is a continuous loss of activity (from the first concentration). At large salt concentrations a monomerization process and a conformational change in the secondary structure as well as in the three-dimensional structure take place. This change reduces the percentage of α-helix conformation, gives thermal stability to the protein, and allows the exposure of some tryptophan residue and hydrophobic regions. The protein inhibition increases. Conformational change and monomerization may allow access of the metal to the substrate site, mainly the ATP site. The inhibition in any case is of mixed type with a competitive component.
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  • 81
    ISSN: 1573-4927
    Schlagwort(e): ancient endogenous provirus ; evolution ; retrotransposition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract A new family of murine endogenous proviruses (VL6.0) is described here. The intact provirus is near 6 kb in length and shows a genomic organization of 5" LTR, gag, pol, env, and 3" LTR. The primer binding site (PBS) is that of a tRNAgly. The lack of functional open reading frames and occurrence of significant gaps in most, if not all, members of this group show it to be ancient. Our estimate of copy number per haploid genome is 30+. Members of this group have been isolated from Mus musculus domesticus, M. m. casteneus, M. m. hortulanus, M. caroli, and M. spretus. The occurrence of these sequences throughout such diverse members of the genus Mus may indicate that the date of the original infection predated the divergence of the extant Mus lineages at around 2.5 million years ago. Analysis of gap (deletion/insertion) patterns indicates that these sequences may have proliferated within the Mus genome by a mechanism of reverse transcriptase-mediated transposition. As yet, there are no closely related murine retroviruses described. The closest mammalian retrovirus based on sequence similarity is from the miniature swine (Sus scrofa).
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  • 82
    ISSN: 1573-4943
    Schlagwort(e): Creatine kinase ; human ; expression ; brain ; muscle ; purification ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract We report the expression of the human muscle (CK-MM) and brain (CK-BB) creatine kinases in Escherichia coli. The proteins have been purified to apparent homogeneity and several of their physical and kinetic properties investigated. In the process, we have conclusively verified the correct DNA sequence of the genes encoding the respective isozymes, and determined the correct primary structure and mass of the gene products. Alignment of the primary sequences of these two enzymes shows 81% sequence identity with each other, and no obvious gross structural differences. However, Western blot analyses demonstrated the general lack of antigenic cross-reactivity between these isozymes. Preliminary kinetic analyses show the K m and k cat values for the creatine and MgATP substrates are similar to values reported for other isozymes from various tissues and organisms. The human muscle and brain CKs do not, however, exhibit the synergism of substrate binding that is observed, for example, in rabbit muscle creatine kinase.
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  • 83
    Digitale Medien
    Digitale Medien
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    Theoretical and applied genetics 100 (2000), S. 401-408 
    ISSN: 1432-2242
    Schlagwort(e): Key words Complementary genes ; Extreme virus resistance ; Genetics ; Necrotic tubers ; Restricted virus distribution ; Solanum tuberosum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  The potato cultivar ’Shepody’ is susceptible to a number of potato viruses including potato virus Y (PVY, potyvirus) but was found to possess extreme resistance to another potyvirus, potato virus A (PVA). ’Shepody’ plants were resistant to PVA infection in manual and graft inoculations. PVA replication was not detected in any of the inoculated plants by ELISA, an infectivity assay and RT-PCR. However, ’Shepody’ plants grafted with shoots containing PVA developed a novel symptomology which resembled a virus infection in appearance and in rate of translocation to the entire plant. Efforts to transmit the symptom-inducing agent manually failed. Graft-inoculation to potato virus indicator plants and PVA-susceptible potato plants showed that the symptom inducer was PVA at an extremely low concentration, detected using RT-PCR followed by Southern blot assay. Tubers from grafted but resistant ’Shepody’ plants had necrotic surfaces and internal spots. PVA was detected from necrotic areas but not from the non-necrotic ones. However, plants resulting from necrotic tubers were free from aerial leaf symptoms observed in grafted plants and produced non-necrotic normal tubers. A trace-back of the parental lineage of ’Shepody’ indicated that the resistance had been introgressed from the cultivar ’Bake King’. Analysis of progeny of a cross of resistant ’Shepody’ to the susceptible ’Goldrus’ indicated that this resistance is controlled by two independent dominant complementary genes in contrast to monogenic resistance reported for other potato viruses.
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  • 84
    Digitale Medien
    Digitale Medien
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    Russian chemical bulletin 49 (2000), S. 1974-1976 
    ISSN: 1573-9171
    Schlagwort(e): ammonium dinitramide ; thermal decomposition ; kinetics ; stabilization ; isotope composition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The kinetics of accumulation of the main products of thermal decomposition of ammonium dinitramide in the melt was investigated. The isotope composition of nitrogen-containing gases evolved by the decomposition of 15NH4N(NO2)2 and NH4 15N(NO2)2 was found. Easily oxidized salts, amines, amides, iodides, and other compounds soluble in the melt interfere with the liquid-phase decomposition of ammonium dinitramide.
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  • 85
    ISSN: 1573-9171
    Schlagwort(e): 2-alkylthiopropenals ; Diels–Alder reaction ; kinetics ; reaction mechanism ; 2,5-dialkylthio-3,4-dihydro-2H-pyran-2-carbaldehyde ; IR spectroscopy ; ab initio calculations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The kinetics of 2-alkylthiopropenals cyclodimerization was studied in the temperature range from -7 to +42 °C in heptane and at 20 °C in various solvents. The rate constants for cyclodimerization of 2-alkylthiopropenals are four orders of magnitude higher than those for dimerization of the oxygen-containing analogs, 2-alkoxypropenals, and are independent of the solvent polarity and substituent steric constant. The activation parameters for 2-butylthiopropenal cyclodimerization were estimated. The distribution of electron density in the 2-methoxy- and 2-methylthiopropenals molecules was calculated by the ab initio method. From comparison of the HOMO and LUMO energies for these aldehydes it was concluded that the ratio between the cyclodimerization rates for 2-alkylthio-, 2-ethoxypropenals, and propenal is determined by the HOMO–LUMO gap.
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  • 86
    ISSN: 1608-3245
    Schlagwort(e): DNA ; kinetics ; oligonucleotide derivatives ; photomodification ; sensitization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Quantitative characteristics of thermodynamic and kinetic cooperativity arising in the process of photomodification of a single-stranded DNA fragment with binary systems of oligonucleotide conjugates forming an active site on the target were studied. Oligonucleotides of the binary system were complementary to adjacent segments of the DNA target, and contained arylazide (X) and perylene (S) residues covalently attached to their terminal phosphates. Upon irradiation at the perylene absorption wavelength, the target was modified by the arylazide residue, which was activated owing to the contiguity with the sensitizing perylene group in the tandem complex. Basing on the kinetic data, the constants of association of both derivatives of oligonucleotides with the target were determined: K x = 1.13 · 106 M–1, K s = 1.49 · 104 M–1. It was determined that association of both oligonucleotides with the target proceeded with a positive cooperativity characterized by parameter α = 45. The kinetic cooperativity parameter β was found to be approximately equal to 200; this characterized the acceleration of target modification in complex with the binary reagent versus that in the absence of sensitizer.
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  • 87
    ISSN: 1618-2545
    Schlagwort(e): biogeography ; calmodulin ; DNA sequence ; elongation factor EF-1α ; evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Phylogenetic relationships within theGibberella fujikuroi species complex were extended to newly discovered strains using nucleotide characters obtained by sequencing polymerase chain reaction (PCR) amplified DNA from 4 loci used in a previous study [nuclear large subunit 28S rDNA, nuclear ribosomal internal transcribed spacer (ITS) region, mitochondriaal small subunit (mtSSU) ribosomal DNA, and β-tubulin] together with two newly sampled protein-encoding nuclear genes, translation elongation factor EF-1α and calmodulin. Sequences from the ribosomal ITS region were analyzed separately and found to contain of two highly divergent, nonorthologous ITS2 types. Phylogenetic analysis of the individual and combined datasets identified 10 new phylogenetically distinct species distributed among the following three areas: 2 within Asia and 4 within both Africa and South America. Hypotheses of the monophyly ofFusarium subglutinans and its two formae speciales, f. sp.pini and f. sp.ananas, were strongly rejected by a likelihood analysis. Maximum parsimony results further indicate that the protein-encoding nuclear genes provide considerably more phylogenetic signal that the ribosomal genes sequenced. Relative apparent synapomorphy analysis was used to detect long-branch attraction taxa and to obtain a statistical measure of phylogenetic signal in the individual and combined datasets.
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  • 88
    ISSN: 1618-2545
    Schlagwort(e): Ascomycota ; evolution ; pyrenomycetes ; systematics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract To investigate the systematic position of the unitunicate pyremomycetePapulosa amerospora, we performed phylogenetic analyses of SSU rDNA sequences from 37 ascomycetes. Among these sequences were some new ones from taxa that might be related toPapulosa: Hyponectriaceae (Hyponectria buxi, Monographella nivalis), Phyllachorales (Phyllachora graminis), and Xylariales (Barrmaelia melanotes, Poronia punctata). Our results showed 100% bootstrap support for a clade of all unitunicate pyrenomycetes, the class Sordariomycetes. We also found strong support for recognizing the subclasses Hypocreomycetidae and Xylariomycetidae. The remaining taxa, belonging to subclass Sordariomycetidae, appeared as a polyphyletic group in one analysis, but was monophyletic when shorter SSU sequences were used.Barrmaelia melanotes, Poronia punctata, Hyponectria buxi, andMonographella nivalis are members of Xylariomycetidae, but we could not determine whetherMonographella should be included in Hyponectriaceae. The new family Papulosaceae is erected forPapulosa on molecular and morphological bases, but the exact systematic position ofPapulosa within subclass Sordariomycetidae is still uncertain, since the genus did not cluster consistently with any of the included taxa. Phyllachorales are not closely related to Diaporthales, as previously suggested.
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  • 89
    ISSN: 1608-3407
    Schlagwort(e): Dunaliella salina ; lactate dehydrogenase ; kinetics ; glycerol synthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The dependence of the catalytic properties of lactate dehydrogenase (LDH, EC 1.1.1.27) from a halophilic alga Dunaliella salina, a glycophilic alga Chlamydomonas reinhardtii, and from porcine muscle on glycerol concentration, medium pH, and temperature was investigated. Several chemical properties of the enzyme from D. salina differentiated it from the LDH preparation obtained from C. reinhardtii and any homologous enzymes of plant, animal, and bacterial origin. (1) V max of pyruvate reduction manifested low sensitivity to the major intracellular osmolyte, glycerol. (2) The affinity of LDH for its coenzyme NADH dropped in the physiological pH region of 6–8. Above pH 8, NADH virtually did not bind to LDH, while the enzyme affinity for pyruvate did not change considerably. (3) The enzyme thermostability was extremely low: LDH was completely inactivated at room temperature within 30 min. The optimum temperature for pyruvate reduction (32°C) was considerably lower than with the enzyme preparations from C. reinhardtii (52°C) and porcine muscle (61°C). (4) NADH greatly stabilized LDH: the ratio of LDH inactivation constants in the absence of the coenzyme and after NADH addition at the optimum temperature in the preparation from D. salina exceeded the corresponding indices of LDH preparations from C. reinhardtii twelve times and from porcine muscle eight times. The authors believe that these LDH properties match the specific metabolism of D. salina which is set at rapid glycerol synthesis under hyperosmotic stress conditions. The increase of cytoplasmic pH value produced in D. salina by the hyperosmotic shock can switch off the terminal reaction of the glycolytic pathway and thus provide for the most efficient utilization of NADH in the cycle of glycerol synthesis. As LDH is destabilized in the absence of NADH, this reaction is also switched off. In the course of alga adaptation to the hyperosmotic shock, glycerol accumulation and the neutralization of intracellular pH stabilize LDH, thus creating the conditions for restoring the complete glycolytic cycle.
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  • 90
    ISSN: 1573-4986
    Schlagwort(e): β-glycosidase ; temperature dependence ; kinetics ; glucose ; transglycosylation ; (Thermus thermophilus)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A β-glycosidase of a thermophile, Thermus thermophilus, belonging to the glycoside hydrolase family 1, was cloned and overexpressed in Escherichia coli. The purified enzyme (Ttβgly) has a broad substrate specificity towards β-D-glucoside, β-D-galactoside and β-D-fucoside derivatives. The thermostability of Ttβgly was exploited to study its kinetic properties within the range 25–80[emsp4 ]°C. Whatever the temperature, except around 60[emsp4 ]°C, the enzyme displayed non-Michaelian kinetic behavior. Ttβgly was inhibited by high concentrations of substrate below 60[emsp4 ]°C and was activated by high concentrations of substrate above 60[emsp4 ]°C. The apparent kinetic parameters (k cat and K m ) were calculated at different temperatures. Both k cat and K m increased with an increase in temperature, but up to 75[emsp4 ]°C the values of k cat increased much more rapidly than the values of K m . The observed kinetics might be due to a combination of factors including inhibition by excess substrate and stimulation due to transglycosylation reactions. Our results show that the substrate could act not only as a glycosyl donor but also as a glycosyl acceptor. In addition, when the glucose was added to reaction mixtures, inhibition or activation was observed depending on both substrate concentration and temperature. A reaction model is proposed to explain the kinetic behavior of Ttβgly. The scheme integrates the inhibition observed at high concentrations of substrate and the activation due to transglycosylation reactions implicating the existence of a transfer subsite.
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  • 91
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    Glycoconjugate journal 17 (2000), S. 465-483 
    ISSN: 1573-4986
    Schlagwort(e): N-acetylglucosaminyltransferases ; glycosylation ; glycoproteins ; Golgi complex ; evolution ; development
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract This review covers discoveries made over the past 30–35 years that were important to our understanding of the synthetic pathway required for initiation of the antennae or branches on complex N-glycans and O-glycans. The review deals primarily with the author's contributions but the relevant work of other laboratories is also discussed. The focus of the review is almost entirely on the glycosyltransferases involved in the process. The following topics are discussed. (1) The localization of the synthesis of complex N-glycan antennae to the Golgi apparatus. (2) The “evolutionary boundary” at the stage in N-glycan processing where there is a change from oligomannose to complex N-glycans; this switch correlates with the appearance of multicellular organisms. (3) The discovery of the three enzymes which play a key role in this switch, N-acetylglucosaminyltransferases I and II and mannosidase II. (4) The “yellow brick road” which leads from oligomannose to highly branched complex N-glycans with emphasis on the enzymes involved in the process and the factors which control the routes of synthesis. (5) A short discussion of the characteristics of the enzymes involved and of the genes that encode them. (6) The role of complex N-glycans in mammalian and Caenorhabditis elegans development. (7) The crystal structure of N-acetylglucosaminyltransferase I. (8) The discovery of the enzymes which synthesize O-glycan cores 1, 2, 3 and 4 and their elongation.
    Materialart: Digitale Medien
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  • 92
    Digitale Medien
    Digitale Medien
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    Journal of bioeconomics 2 (2000), S. 9-23 
    ISSN: 1573-6989
    Schlagwort(e): evolution ; altruism ; morality ; utilitarianism ; Marxism ; Rawls ; fairness
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Wirtschaftswissenschaften
    Notizen: Abstract Several evolutionary mechanisms have been identified in the literature that would generate altruism in humans. The most powerful (except for kin selection) and most controversial is group selection, as recently analyzed by Sober & D.S. Wilson. I do not take a stand on the issue of the existence of group selection. Instead, I examine the level of human altruism that could exist if group selection were an engine of human evolution. For the Sober & Wilson mechanism to work, groups practicing altruism must grow faster than other groups. I call altruistic behavior that would lead to faster growth ‘efficient altruism’. This often consists of cooperation in a prisoner's dilemma. ltruistic acts such as helping a temporarily hungry or injured person would qualify as efficient altruism. Efficient altruism would also require monitoring recipients to avoid shirking. Utilitarianism would be an ethical system consistent with efficient altruism, but Marxism or the Rawlsian system would not. Discussions of efficient altruism also help understand intuitions about fairness. We perceive those behaviors as ‘fair’ that are consistent with efficient altruism. It is important to understand that, even if humans are selected to be altruistic, the forms of altruism that might exist must be carefully considered and ircumscribed.
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  • 93
    Digitale Medien
    Digitale Medien
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    Biology and philosophy 15 (2000), S. 443-463 
    ISSN: 1572-8404
    Schlagwort(e): David Hull ; evolution ; selection
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Philosophie
    Notizen: Abstract One of the principal difficulties in assessing Science as aProcess (Hull 1988) is determining the relationship between the various elements of Hull's theory. In particular, it is hard to understand precisely how conceptual selection is related to Hull's account of the social dynamics of science. This essay aims to clarify the relation between these aspects of his theory by examining his discussion of the``demic structure'' of science. I conclude that the social account cando significant explanatory work independently of the selectionistaccount. Further, I maintain that Hull's treatment of the demicstructure of science points us toward an important set of issues insocial epistemology. If my reading of Science as a Process iscorrect, then most of Hull's critics (e.g., those who focus solelyon his account of conceptual selection) have ignored promisingaspects of his theory.
    Materialart: Digitale Medien
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  • 94
    Digitale Medien
    Digitale Medien
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    Biology and philosophy 15 (2000), S. 493-508 
    ISSN: 1572-8404
    Schlagwort(e): complexity ; entropy balance ; environment independence ; evolution ; information fundamental identity ; uncertainty
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Philosophie
    Notizen: Abstract Some real objects show a very particular tendency: that of becomingindependent with regard to the uncertainty of their surroundings. This isachieved by the exchange of three quantities: matter, energy andinformation. A conceptual framework, based on both Non-equilibriumThermodynamic and the Mathematical Theory of Communication is proposedin order to review the concept of change in living individuals. Three mainsituations are discussed in this context: passive independence inconnection with resistant living forms (such as seeds, spores, hibernation,...), active independence in connection with the life span of aliving individual (whether an ant or an ant farm), and the newindependence in connection with the general debate of biological evolution.
    Materialart: Digitale Medien
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  • 95
    Digitale Medien
    Digitale Medien
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    Biology and philosophy 15 (2000), S. 641-668 
    ISSN: 1572-8404
    Schlagwort(e): complexity ; evolution ; function ; modularity ; parts
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Philosophie
    Notizen: Abstract The functional complexity, or the number of functions, of organisms hasfigured prominently in certain theoretical and empirical work inevolutionary biology. Large-scale trends in functional complexity andcorrelations between functional complexity and other variables, such assize, have been proposed. However, the notion of number of functions hasalso been operationally intractable, in that no method has been developedfor counting functions in an organism in a systematic and reliable way.Thus, studies have had to rely on the largely unsupported assumption thatnumber of functions can be measured indirectly, by using number ofmorphological, physiological, and behavioral “parts” as a proxy. Here, amodel is developed that supports this assumption. Specifically, the modelpredicts that few parts will have many functions overlapping in them, andtherefore the variance in number of functions per part will be low. If so,then number of parts is expected to be well correlated with number offunctions, and we can use part counts as proxies for function counts incomparative studies of organisms, even when part counts are low. Alsodiscussed briefly is a strategy for identifying certain kinds of parts inorganisms in a systematic way.
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  • 96
    Digitale Medien
    Digitale Medien
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    Biology and philosophy 15 (2000), S. 713-732 
    ISSN: 1572-8404
    Schlagwort(e): Darwin ; error theory ; ethics ; evolution ; evolutionary ethics ; Mackie ; naturalistic fallacy ; Ruse
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Philosophie
    Notizen: Abstract Suppose that the human tendency to think of certain actions andomissions as morally required – a notion that surely lies at the heart of moral discourse – is a trait that has been naturallyselected for. Many have thought that from this premise we canjustify or vindicate moral concepts. I argue that this is mistaken, and defend Michael Ruse's view that the moreplausible implication is an error theory – the idea thatmorality is an illusion foisted upon us by evolution. Thenaturalistic fallacy is a red herring in this debate,since there is really nothing that counts as a ‘fallacy’ at all. If morality is an illusion, it appears to followthat we should, upon discovering this, abolish moraldiscourse on pain of irrationality. I argue that thisconclusion is too hasty, and that we may be able usefullyto employ a moral discourse, warts and all, withoutbelieving in it.
    Materialart: Digitale Medien
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  • 97
    ISSN: 1618-2545
    Schlagwort(e): Ascomycota ; evolution ; molecular clock ; plant pathogen ; powdery mildew
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Phylogenetic relationships of Erysiphales within Ascomycota were inferred from the newly determined sequences of the 18S rDNA and partial sequences of the 28S rDNA including the D1 and D2 regions of 10 Erysiphales taxa. Phylogenetic analyses revealed that the Erysiphales form a distinct clade among ascomycetous fungi suggesting that the Erysiphales diverged from a single ancestral taxon. The Myxotrichaceae of the Onygenales was distantly related to the other onygenalean families and was the sister group to the Erysiphales calde, with which it combined to form a clade. The Erysiphales/Myxotrichaceae clade was also closely related to some discomycetous fungi (Leotiales, Cyttariales and Thelebolaceae) including taxa that form cleistothecial ascomata. The present molecular analyses as well as previously reported morphological observations suggest the possible existence of a novel evolutionary pathway from cleistothecial discomycetous fungi to Erysiphales and Myxotrichaceae. However, since most of these fungi, except for the Erysiphales, are saprophytic on dung and/or plant materials, the questions of how and why an obligate biotroph like the Erysiphales radiated from the saprophytic fungi remain to be addressed. We also estimated the radiation time of the Erysiphales using the 18S rDNA sequences and the two molecular clockes that have been previously reported. The calculation showed that the Erysiphales split from the Myxotrichaceae 190–127 myr ago. Since the radiation time of the Erysiphales does not exceed 230 myr ago, even when allowance is made for the uncertainty of the molecular clocks, it is possible to consider that the Erysiphales evolved after the radiation of angiosperms. The results of our calculation also showed that the first radiation within the Erysiphales (138–92 myr ago) coincided with the date of a major diversification of angiosperms (130–90 myr ago). These results may support our early assumption that the radiation of the Erysiphales coincided with the evolution of angiosperm plants.
    Materialart: Digitale Medien
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  • 98
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    International journal of historical archaeology 4 (2000), S. 71-112 
    ISSN: 1573-7748
    Schlagwort(e): evolution ; archaeology ; natural selection ; classification ; style ; function
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Klassische Archäologie
    Notizen: Abstract Over the past decade or so, an increasing number of archaeologists have begun to show interest in employing Darwinian evolutionary theory to explain variations in the material record. Epistemological and methodological issues surrounding the implementation of Darwinian evolutionism in archaeology are numerous, the most basic of which is that Darwinism embodies a materialist perspective, whereas archaeology traditionally has maintained an essentialist outlook. Stemming from this dichotomy are fundamental differences in such things as how units are created and how they are used to measure change. As archaeologists grapple with these issues, specific examples of how Darwinian evolutionism can be used to build historical narratives and create historical explanations are appearing with more frequency, but with few exceptions, proponents have focused specifically on the prehistoric record. This gives the impression that Darwinian evolutionism is not applicable to the more-recent material record, which is decidedly not the case. The kind of evolutionism proposed here transcends the age of the record under investigation.
    Materialart: Digitale Medien
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  • 99
    Digitale Medien
    Digitale Medien
    Springer
    Journal of happiness studies 1 (2000), S. 323-349 
    ISSN: 1573-7780
    Schlagwort(e): progress ; quality of life ; happiness ; optimism ; pessimism ; social indicators ; forecasting ; world view ; evolution ; development.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Psychologie
    Notizen: Abstract This paper argues that both the relativist and the pessimist critiques of the idea of progress are inadequate. Progress is defined as increase in global quality of life (QOL). Such QOL is intrinsically subjective, but not relative. It can be reliably measured through “life satisfaction”-type questions. The “World Database of Happiness” provides extensive data on social, economic and psychological factors that correlate with overall QOL. They include wealth, health, security, knowledge, freedom and equality. Various statistical data suggest that all these QOL indicators have undergone significant improvements during the last half century, in most of the world. This gives strong support to the thesis that progress objectively occurs.
    Materialart: Digitale Medien
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  • 100
    Digitale Medien
    Digitale Medien
    Springer
    Journal of happiness studies 1 (2000), S. 351-374 
    ISSN: 1573-7780
    Schlagwort(e): progress ; quality of life ; optimism ; pessimism ; social indicators ; world view ; evolution ; development ; global change ; information overload.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Psychologie
    Notizen: Abstract This paper attempts to update the 18th century concept of progress by an evolutionary theoretical framework, while replying to some of the contemporary critiques. Progress, understood as increase in fitness (or its proxy, quality of life) necessarily accompanies evolution by natural selection. In socio-cultural evolution, this mechanism is reinforced by growth of knowledge and virtuous cycles, but can be accompanied by negative side-effects such as overshooting and parasitism. The most pressing of the contemporary side-effects, such as pollution and the increased pace of life, are discussed, but it is concluded that they can be tackled without really endangering global progress. The anxiety that they engender is unfortunately amplified by a “bad news” bias in the media, leading to an inappropriately pessimistic view of the situation by the public.
    Materialart: Digitale Medien
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