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  • 1
    Digitale Medien
    Digitale Medien
    Neutron diffraction and transmission electron microscopy study of hydrogen-induced phase transformations in Zr3Al (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 1312-1319 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Hydrogen-induced phase transformations of the equilibrium intermetallic compound Zr3 Al have been studied by in situ elastic neutron scattering, x-ray diffraction, and transmission electron microscopy (TEM). TEM observations reveal two distinct modes of amorphous phase formation in Zr3 Al upon hydrogenation, namely, heterogeneous nucleation at preexisting grain boundaries, and homogeneous nucleation within single-crystal grains. In situ neutron diffraction reveals a phase separation between a hydrogen (deuterium) poor and a hydrogen (deuterium) rich crystalline phase. Rietveld profile refinement of the neutron diffraction data indicates predominant hydrogen (deuterium) occupation of the octahedral interstitial sites in the crystalline matrix that have only Zr nearest-neighbor atoms. The two different modes of amorphous phase nucleation are directly related to the degree of hydrogen dissolution in the host crystalline matrix.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.345683
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  • 2
    Digitale Medien
    Digitale Medien
    Design study of a time-of-flight small-angle diffractometer for a pulsed neutron source (1978)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 11 (1978), S. 464-465 
    Details
    ISSN: 1600-5767
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Geologie und Paläontologie , Physik
    Notizen: A design study was made of a neutron small-angle scattering (SAS) instrument for use at Argonne National Laboratory's proposed Intense Pulsed Neutron Source, IPNS-II (Carpenter & Werner, 1976; Werner, 1977; Carpenter, 1977). The instrument design incorporates several features: a converging-slit collimator, wavelength band-limiting choppers, capacity for large samples, and a two-dimensional detector. Machine design-dependent parameters are considered in a Monte-Carlo code that produces estimates of the instrumental resolution function and available flux at the sample. It was found that the calculated flux on sample exceeds that at steady-state reactor instruments of comparable resolution.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S002188987801359X
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  • 3
    Digitale Medien
    Digitale Medien
    A plea for hyphens (1977)
    [s.l.] : Nature Publishing Group
    Nature 267 (1977), S. 202-202 
    Details
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] SIR,-At the risk of sounding pedantic I want to make a plea for a return to the sound practice of writing a hyphen in compound words used adjectivally. Today's general practice of omitting the hyphen in such adjectives as 'hormone-induced' and 'temperature-sensitive' is sheer sloppiness and, more ...
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1038/267202d0
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  • 4
    Digitale Medien
    Digitale Medien
    X-ray diffraction study of Zr(Ca,Y)O2−x. I. The average structure (1979)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 35 (1979), S. 789-795 
    Details
    ISSN: 1600-5724
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Notizen: Integrated X-ray intensities of Bragg peaks were observed from single crystals of Zr0.866Ca0.134Ol.866 and Zr0.786Y0.214O1.893 in the disordered state. There are displacements of oxygen ions (characterized by Δ/a ̃0.05) from the ideal positions of the fluorite structure along (100) directions similar to those that occur on ordering below 1273 K and related to the cubic to tetragonal transition in pure ZrO2. These displacements are not related to anharmonicity, at least to fourth-order terms. In addition, there are small displacements of the cations (Δ/a ̃0.015) in (111) directions in the yttria-stabilized zirconia.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1107/S0567739479001807
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  • 5
    Digitale Medien
    Digitale Medien
    Positional information in the amphibian limb (1976)
    Springer
    Acta biotheoretica 25 (1976), S. 44-65 
    Details
    ISSN: 1572-8358
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary (1) The concept of positional information is applied to a large amount of data obtained previously in experiments on developing and regenerating amphibian limbs. Only the proximo-distal axis of the limb is considered. It is shown that the concept provides a simple, unitary hypothesis which satisfactorily accounts for the experimental data, and may moreover suggest meaningful new approaches. (2) It is suggested that the boundaries of the bipolar limb system lie in the girdle skeleton and at the distal end of the limb, respectively, and that it is the apical epidermis of the growing or regenerating limb which defines the distal boundary conditions. A relatively stable gradient of positional information is assumed to be set up in the mesoderm (or mesenchyme). It is further shown that the differentiated limb retains its positional information and upon amputation imparts it to the base of the blastema. (3) To explain an apparent discrepancy between the developing and the regenerating limb, it is proposed that dedifferentiation of mesodermal limb tissues upon amputation entails a change of positional value in the mesenchyme. Consequently, the amputation level does not once and for all specify the positional value at the proximal end of a mass of blastemal mesenchyme, particularly when the mesenchyme is transplanted in such a way that its linear size decreases (regression) or increases (fusion of several blastemas).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02113740
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  • 6
    Digitale Medien
    Digitale Medien
    Shape: Its development and regulation capacity during embryogenesis (1978)
    Springer
    Acta biotheoretica 27 (1978), S. 185-200 
    Details
    ISSN: 1572-8358
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Although several theoretical approaches consider general methods for dealing with shape, recent observations and experimental data show that embryos exhibit marked changes in the properties of the biological material involved in shape development and shape regulation capacity. In vivo experiments have shown that the amphibian embryo gradually develops from a situation in which it is not able to maintain its shape to one in which it can not only maintain its shape but also possesses a maximal tolerance towards deformation together with a maximal shape regulation capacity. So far two especially clear conclusions have emerged: (i) the form of the embryo appears to be determined by cell activities intrinsic to each stage, and (ii) the morphogenetic programme can be executed normally within wide limits notwithstanding dramatic deformations of the embryo during quite a long period. Thus the hypothesis may be advanced that shape and morphogenesis to some extent become independent phenomena during embryonic development.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00115833
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  • 7
    Digitale Medien
    Digitale Medien
    Failure mechanisms of ceramic membrane reactors in partial oxidation of methane to synthesis gas (1994)
    Springer
    Catalysis letters 30 (1994), S. 201-212 
    Details
    ISSN: 1572-879X
    Schlagwort(e): synthesis gas ; methane ; perovskite ; oxygen permeable membrane
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract In the course of generating synthesis gas (H2, CO) from methane, we have observed two types of fractures occurring on the Sr(Co, Fe)Ox-type oxygen membrane reactors. The first type occurred shortly after the reaction started and the second type often occurred days after the reaction. To determine the causes of these fractures, we have examined the starting material and fractured membranes using a combination of X-ray diffraction and thermogravimetric analyses. We found that the first type of fracture was the consequence of an oxygen gradient in the membrane, pointing from the reaction side to the air side. This causes a lattice mismatch inside the membrane, leading to fracture. The second type of fracture, however, was the result of a chemical decomposition. We found that the Sr(Co, Fe)Ox-type membrane had been reduced to SrCO3, and elemental Co and Fe by the synthesis gas generated in the reaction. The decomposition causes enormous expansion leading to a large crack along the axis of tube.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00813686
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  • 8
    Digitale Medien
    Digitale Medien
    Re-investigation of titanium silicalite by X-ray absorption spectroscopy: Are the novel titanium sites real? (1993)
    Springer
    Catalysis letters 21 (1993), S. 333-344 
    Details
    ISSN: 1572-879X
    Schlagwort(e): EXAFS ; zeolite ; titanium silicalite
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract EXAFS studies have been carried out on titanium silicalite-1 (TS-1). The titanium atom is coordinated to four oxygen atoms at the distance of 1.80(1) Å. There is no evidence for the presence of 5- and 6-coordinated titanium species or the novel 4-coordinated titanium species involving [TiO x ] units sharing edges with [SiO4] units. The EXAFS spectrum of TS-1 appears to be consistent with the model that titanium resides at the tetrahedral sites of the framework.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00769485
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  • 9
    Digitale Medien
    Digitale Medien
    Sequence analysis of the cystic fibrosis gene in patients with disseminated bronchiectatic lung disease (1991)
    Springer
    Journal of molecular medicine 69 (1991), S. 657-663 
    Details
    ISSN: 1432-1440
    Schlagwort(e): Polymerase chain reaction ; Direct genomic DNA sequencing ; Automated DNA sequencing ; Cystic fibrosis gene ; Bronchiectatic lung disease
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The diagnosis of classical cystic fibrosis (CF) is easily made by clinical assessment alone, but may be missed or delayed in cases with an atypical clinical course. In a recent major study the age at diagnosis varied between 2 months and 47 years. For diagnostic purposes we have investigated the cystic fibrosis transmembrane regulator (CFTR) gene in 10 adult patients (age 18 to 45 years) with chronic obstructive pulmonary disease since childhood or adolescence and bronchiectases disseminated through both lungs. Only one subject (a 29-year-old male) had exocrine pancreatic insufficiency (PI); all others were pancreatic-sufficient (PS). The first nucleotide (ATP)-binding fold of the CFTR was analyzed by direct sequencing of polymerase chain reaction (PCR)-amplified genomic DNA in these cases. Two patients with different phenotypes (one PI, one PS) were found to be homozygous for the common ΔF508 mutation of the CFTR gene, which proved the diagnosis of cystic fibrosis in their cases and allowed genetic counselling. The PS patient had normal sweat tests and had not previously been recognized as having CF. Four other patients were heterozygous for ΔF508, with no other mutation in exons 10 or 11 of the gene, and four patients had normal sequences of these exons. Because only about 70% of all CF chromosomes carry ΔF508, the unexpectedly high frequency (4/8=50%) of heterozygosity for ΔF508 among the non-ΔF508/ΔF508 patients with bronchiectases suggests that some of these might also have unrecognized CF with rare genotypes and mutations in any of the 22 exons not sequenced. About 90 different mutations have already been detected in coding regions of the CFTR gene and a very broad and so far not fully recognized spectrum of clinical phenotypes may be caused by mutations of this gene. Screening for the most frequent CFTR gene mutations, which is practicable using recent technology, may provide significant new diagnostic information in patients with CF-like pulmonary phenotypes, especially if they have normal or borderline sweat tests and no pancreatic insufficiency.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01649427
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  • 10
    Digitale Medien
    Digitale Medien
    Highly variable clinical course in severeα 1-antitrypsin deficiency — Use of polymerase chain reaction for the detection of rare deficiency alleles (1990)
    Springer
    Journal of molecular medicine 68 (1990), S. 857-863 
    Details
    ISSN: 1432-1440
    Schlagwort(e): Polymerase chain reaction ; Direct DNA sequencing ; α1AT deficiency alleles Pi QO, Pi Z ; Chronic obstructive lung disease ; Lung function
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Among 20 individuals with severeα 1 antitrypsin (α1AT) deficiency we observed extremely variable clinical phenotypes ranging from rapidly progressive lung disease fatal at the age of 42 years to an asymptomatic individual with normal lung function at the age of 50 years. Eighteen subjects, including the asymptomatic one, carried the deficient Pi ZZ phenotype as determined by isoelectric focusing (IEF). Their meanα1AT serum level was 36.7±7.7 mg/dl. DNA restriction analysis showed that all of them had the classical Pi Z-allele-associated DNA haplotype, thus confirming the IEF data. Obviously not all Pi ZZ individuals will have clinical sequelae caused by this genotype. The important differences in clinical course observed could not be explained by smoking habits alone. Probably additional factors are pertinent to the pathogenesis of the lung disease associated withα1AT deficiency (defects in other genes, environmental influences other than smoking). In two patients with very lowα1AT serum levels definitive phenotyping by IEF was not possible. Therefore we investigated the molecular basis of their deficiency using polymerase chain reaction (PCR) amplification of the coding exons of theirα1AT genes and direct sequencing of the amplification products. Sequence data analysis showed that one of these patients, who had initially been phenotyped as Pi ZZ by IEF, had in fact the genotype Pi QObellinghamZ, thus explaining her lowα1AT serum level of 20 mg/dl. The other patient (α1AT serum level 3.7 mg/dl) exhibited the rare genotype Pi MheerlenQOgranite falls. Despite his nearly completeα1AT deficiency, he suffered from only moderately severe pulmonary disease at the age of 42 years.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01662782
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