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  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 4885-4893 
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Comparative electron polarization measurement with a helium electron polarimeter and a high-precision Mott detector are presented. For these measurements the helium electron polarimeter was calibrated according to theory, whereas the Mott detector was calibrated independently with an improved auxiliary-target method. The comparison of the experimental results reveals various problems inherent in helium electron polarimetry, such as poor efficiency and problems occurring in precise light polarization measurements. At present, a high-precision Mott detector is therefore clearly superior to a helium polarimeter with respect to efficiency and accuracy. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 777 (1996), S. 0 
    ISSN: 1749-6632
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Allgemeine Naturwissenschaft
    Notizen: Patients with probable Alzheimer's disease were either stimulated with a continuous visual recognition task (n = 18) or with a continuous auditory recognition task during PET measurement with 18 FDG. The PET scanner was a Siemens CTI, ECAT EXACT with 5 mm transaxial and 6 mm axial resolution. The global stimulation effects were nearly identical in both groups and increased of 4.17 ± 8.14% in the auditory stimulated group and of 4.03 ± 11.78% in the visual stimulated group. Beyond regional stimulation effects in both groups a common cerebellar stimulation effect was measured. It is concluded that the cerebellar stimulation effect reflects a modality independent cognitive process and that the only small enhancement of global glucose metabolism indicates disturbed stimuli processes and finally explained the patient's failure in memory tasks.
    Materialart: Digitale Medien
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  • 3
    ISSN: 1432-1920
    Schlagwort(e): Brain, MR ; Positron imaging ; Dementia ; Metabolism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract We compared the correlation of PET and MRI with neuropsychological tests in 26 patients with probable Alzheimer's disease (AD). The width of the temporal horns and the third ventricle, regional metabolic rates of glucose (rCMRGlu) and the proportion of cerebrospinal fluid space in mesial temporal and temporoparietal cortical regions were measured with three-dimensionally coregistered PET and MRI in two planes perpendicular to the Sylvian fissure. Highly significant correlations between rCMRGlu and neuropsychological tests were found mainly in the temporoparietal cortex, with and without correction for atrophy. Correlations of similar magnitude were seen also between most tests and the width of the temporal horns and third ventricle. Changes in the third ventricle and mesial temporal lobe were best seen with MRI, whereas PET most clearly depicted alterations in neocortical association areas. These two aspects of the disease correlated with the severity of dementia to a similar degree.
    Materialart: Digitale Medien
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  • 4
    ISSN: 1432-1920
    Schlagwort(e): Key words Brain ; MR ; Positron imaging ; Dementia ; Metabolism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract We compared the correlation of PET and MRI with neuropsychological tests in 26 patients with probable Alzheimer's disease (AD). The width of the temporal horns and the third ventricle, regional metabolic rates of glucose (rCMRGlu) and the proportion of cerebrospinal fluid space in mesial temporal and temporoparietal cortical regions were measured with three-dimensionally coregistered PET and MRI in two planes perpendicular to the Sylvian fissure. Highly significant correlations between rCMRGlu and neuropsychological tests were found mainly in the temporoparietal cortex, with and without correction for atrophy. Correlations of similar magnitude were seen also between most tests and the width of the temporal horns and third ventricle. Changes in the third ventricle and mesial temporal lobe were best seen with MRI, whereas PET most clearly depicted alterations in neocortical association areas. These two aspects of the disease correlated with the severity of dementia to a similar degree.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 55 (1999), S. 0-0 
    ISSN: 1600-5759
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Materialart: Digitale Medien
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  • 6
    ISSN: 1432-0533
    Schlagwort(e): Key words Alzheimer's disease ; Regional cerebral ; glucose metabolism ; Semiquantitative neuropathology ; Neurofibrillary tangles ; Senile plaques
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract In four patients with an antemortem diagnosis of probable Alzheimer's disease (AD) regional cerebral glucose metabolism (rCMRGl) was studied prospectively by positron emission tomography (PET) and compared with postmortem semiquantitative neuropathology. The interval between the last PET study and autopsy was 1.3±0.8 years. In comparison with age-matched controls, the AD patients showed predominant temporoparietal hypometabolism spreading to other cortical and subcortical regions during serial PET scans. All patients had neuropathological findings typical for AD. There was a significant relationship between rCMRGl and density of senile plaques (SP) in one patient (τb = –0.86, P 〈 0.05). SP were distributed quite homogeneously in all regions examined. Neurofibrillary tangles (NFT) were concentrated focally in the hippocampus-amygdala-entorhinal complex. In the context of widespread developing cortical hypometabolism, the predilection of NFT for involvement in limbic areas suggests a disruption of projection neurons as the pathogenetic process of cortical dysfunction.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Bulletin of mathematical biology 57 (1995), S. 299-344 
    ISSN: 1522-9602
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Mathematik
    Notizen: Abstract When a suspension of bacterial cells of the speciesBacillus subtilis is placed in a chamber with its upper surface open to the atmosphere complex bioconvection patterns are observed. These arise because the cells: (1) are denser than water; and (2) usually swim upwards, so that the density of an initially uniform suspension becomes greater at the top than the bottom. When the vertical density gradient becomes large enough, an overturning instability occurs which ultimately evolves into the observed patterns. The reason that the cells swim upwards is that they are aerotactic, i.e. they swim up gradients of oxygen, and they consume oxygen. These properties are incorporated in conservation equations for the cell (N) and oxygen (C) concentrations, and these are solved in the pre-instability phase of development whenN andC depend only on the vertical coordinate and time. Numerical results are obtained for both shallow- and deep-layer chambers, which are intrinsically different and require different mathematical and numerical treatments. It is found that, for both shallow and deep chambers, a thin boundary layer, densely packed with cells, forms near the surface. Beneath this layer the suspension becomes severely depleted of cells. Furthermore, in the deep chamber cases, a discontinuity in the cell concentration arises between this cell-depleted region and a cell-rich region further below, where no significant oxygen concentration gradients develop before the oxygen is fully consumed. The results obtained from the model are in good qualitative agreement with the experimental observations.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Bulletin of mathematical biology 58 (1996), S. 391-407 
    ISSN: 1522-9602
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Mathematik
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Agroforestry systems 33 (1996), S. 87-98 
    ISSN: 1572-9680
    Schlagwort(e): indigenous knowledge ; parkland system ; Sahel ; semiarid regions ; tree management
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Beschreibung / Inhaltsverzeichnis: Résumé Cette étude sur la taille du néré (Parkia biglobosa) a été faite par des observations détaillées de 80 nérés et les entretiens avec leurs propriétaires dans 21 villages au Plateau Central du Burkina Faso. La taille du néré n'est pas générale, mais révèle diverses motivations et techniques. La plupart des motivations est orientée vers une gestion consciente de l'arbre en vue d'une amélioration de la production furitière, et rerament en vue d'une reduction de l'influence de l'arbre sur les cultures. Les caracteristiques des techniques de taille (fréquence, intensité, période de taille) et les motivations impliquées paraissent s'adapter à la dégradation de l'environnement et al détérioration de la viabilité des arbres. Les résultats montrent la durabilité des pratiques concernant la gestion des arbres.
    Notizen: Abstract This study of the pruning of néré (Parking biglobosa) trees in central Burkina Faso included detailed surveys of 83 trees and their owners in 21 villages. Pruning is not widespread, but appears to be a practice with various motives and techniques. The motives are mainly aimed at deliberate management of the trees, in order to enhance their fruit production, and are rarely aimed at reducing tree impact on crop productivity. The characteristics of tree pruning techniques (e.g., frequency, intensity and seasonality) and their corresponding motives appear to change as an adaptation to land degradation processes and the deterioration of tree condition. The results demonstrate that indigenous silvicultural management techniques contribute to a sustainable use of tree resources.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Der Nervenarzt 69 (1998), S. 991-998 
    ISSN: 1433-0407
    Schlagwort(e): Schlüsselwörter Alzheimer-Erkrankung ; Visuokonstruktive Störung ; Zeichnen ; Demenzausprägung ; Key words Alzheimer’s disease ; Visuo-constructive impairment ; Drawing ; Severity of dementia
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Summary In this study we assessed the drawing abilities in 37 patients with probable Alzheimer’s disease according to NINCDS-ADRDA criteria. Drawing abilities (drawing: house, flower, clock; Rey-Osterrieth figure; copying: MMST-figure; Rey-Osterrieth figure) were quantified with different rating schemes and related to other neuropsychological assessments. All patients underwent a positron emission tomography with 18-FDG. Drawing performance was highly correlated with severity of dementia – expressed in MMST scores (r=0.78; p〈0.0001) – with visuo-spatial short-term memory (r=–0.69; p=0.001), and writing abilities (r=–0.77; p〈0.0001). The summarized drawing score showed a statistically significant correlation with the rate of temporoparietal glucose metabolism measured with positron emission tomography and 18-FDG (r=0.39; p=0.017). In the drawings of AD patients omittings and simplifications were typical, whereas perseverations rarely occured. In severely demented patients closing-in phenomenons could be de- scribed, too. A subgroup of AD patients with visuo-constructive impairment as the leading symptom could not be identified.
    Notizen: Zusammenfassung Bei 37 Patienten mit der wahrscheinlichen Alzheimer-Erkrankung (AD) nach NINCDS-ADRDA-Kriterien wurden die Zeichenleistungen (freies Zeichnen: Haus, Blume, Uhr; Rey-Osterrieth-Figur; Abzeichnen: MMST-Figur; Rey-Osterrieth Figur) untersucht und mit anderen neuropsychologischen Tests verglichen. Bei allen Patienten wurde weiterhin eine Positronen-Emissions-Tomographie mit 18-FDG durchgeführt. Die Zeichenleistungen der Patienten waren hoch mit der Demenzausprägung, ausgedrückt in MMST-Werten, korreliert (r=0,78; p〈0,0001) und wiesen einen engen Zusammenhang zur visuospatialen Kurzzeitgedächtnisspanne (r=–0,69; p=0,001) und zur Schreibleistung (r=–0,77; p〈0,0001) auf. Der summierte Zeichenscore wies einen statistisch signifikanten Zusammenhang mit der temporoparietalen Stoffwechselrate – gemessen mit PET und FDG – auf (r=0,39; p=0,017). Bei den Zeichnungen der AD-Patienten zeigten sich v.a. Auslassungen und Vereinfachungen. Perseverationen kamen selten vor. Bei schwer dementen Patienten ließen sich auch Closing-in-Phänomene beobachten. Eine Subgruppe von AD-Patienten, bei denen visuokonstruktive Störungen die Leitsymptomatik ihrer Demenz waren, ließ sich nicht identifizieren.
    Materialart: Digitale Medien
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