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  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 5433-5441 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The output characteristics and the optical efficiency of SrS:Ce and ZnS:Mn thin-film electroluminescent devices are studied by measuring and evaluating light either directly emitted from the active area or indirectly emitted from its surroundings, including substrate edge. A special preparation of the devices allows access to edge emission and emission between pixel area and sample edge caused by scattering. The measuring method is optimized for registration of the entire output into the far field, exploiting the azimuthal symmetry of the pixel emission. In this study the optical efficiency is defined as the ratio of the directly emitted luminous flux to the total flux emitted from the segment within the sandwiched phosphor layer, which is activated. Optical efficiencies ranging from 0.16 for a smooth ZnS:Mn to 0.26 for a rougher SrS:Ce specimen are found. Theoretical limitations of the measuring method are discussed. A new quantity called scattering gain is introduced for characterizing the coupling of the output into the front hemisphere. Differential scattering gains ranging from a few percent to nearly 20% are observed. The optical characterization of SrS:Ce and ZnS:Mn samples also allows for an estimate of the optical efficiency of future inverted electroluminescent structures. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    [s.l.] : Macmillan Magazines Ltd.
    Nature 391 (1998), S. 261-263 
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] Carbon-rich ‘carbonaceous’ meteorites contain several types of dust grains with an isotopic signature that identifies them as being of pre-solar origin. Of these grains, diamonds are of particular interest: such grains are by far the most abundant, and they host an isotopically ...
    Materialart: Digitale Medien
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  • 3
    ISSN: 1530-0358
    Schlagwort(e): Colonoscopy ; Crohn's disease ; Inflammation ; Leukocyte scanning ; Ulcerative colitis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract AIM: This study was undertaken to evaluate technetium 99m (Tc 99m) hexamethyl propylenamine oxime (HMPAO)-labeled leukocyte scintigraphy for assessment of disease extent and activity in acute colitis. PATIENTS AND METHODS: Twenty-seven patients, hospitalized because of acute watery and/or bloody diarrhea, were investigated using both total colonoscopy and Tc 99m HMPAO-labeled leukocyte scintigraphy within 48 hours after admittance. RESULTS: Final diagnoses were ulcerative colitis in 14 patients, Crohn's disease in 7 patients, and infectious colitis in 6 patients. Using colonoscopy as the reference method, the maximum extent of colitis was correctly assessed by the leukocyte scan in 18 patients (67 percent), although rectal engagement was not visualized in 5 (19 percent). In six additional patients, there was almost complete agreement between the two methods. One other patient, with left-sided ulcerative colitis, was erroneously assessed as having total extent. Two other patients (one with Crohn's colitis and one with infectious colitis) had different segments incorrectly assessed. Sensitivity, specificity, and diagnostic accuracy of scintigraphy in detecting active inflammatory segments were 0.85, 0.83, and 0.85, respectively. Intensity of inflammatory activity assessed by the leukocyte scan correlated significantly with colonoscopic assessment (r=0.719;P 〈0.0001). CONCLUSION: Information regarding extent, localization, and disease activity in patients with acute colitis of inflammatory or infectious origin may be satisfactorily obtained using Tc 99m HMPAO-labeled leukocyte scanning. The noninvasive nature of the method makes it an attractive early alternative to other investigational procedures such as total colonoscopy or barium examination, particularly in cases with an established diagnosis of inflammatory bowel disease.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Der Ophthalmologe 95 (1998), S. 784-787 
    ISSN: 1433-0423
    Schlagwort(e): Key words Behçet's disease • Uveitis • Hypopyon • Immunosuppressive therapy • Vasculitis ; Schlüsselwörter Morbus Behçet • Uveitis • Hypopyoniritis -immunsuppressive Therapie • Vaskulitis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Hintergrund: Der Morbus Adamantiades-Behçet ist eine seltene systemische Vaskulitis unklarer Ätiologie, zu deren typischen Symptomen neben rezidivierenden oralen und genitalen Aphthen die rezidivierende Iridozyklitis (historisch Hypopyoniritis) zählt. Das Manifestationsalter hat sich mit durchschnittlich 25 Jahren in Deutschland in den letzten Jahren nach unten verlagert, auch Manifestationen im Kindes- und Jugendalter nehmen zu. Eine okuläre Beteiligung gilt als ungünstiger prognostischer Parameter und bei 15–25 % dieser Patienten ist ein vollständiger Visusverlust zu erwarten. Patienten: Wir berichten über eine 19-jährige, weibliche Patientin, deutscher Abstammung, mit seit dem 16. Lebensjahr rezidivierenden Uveitiden beidseits. Ergebnisse: Nach fast 3-jährigem Verlauf der Augensymptomatik konnte anhand der Anamnese, der histologischen Untersuchung der Hauteffloreszenzen und des ophthalmologischen Befundes die Diagnose eines Morbus Behçet (entsprechend den Kriterien der „International Study Group for Behçet's Disease“) gestellt werden. Der Restvisus konnte unter der eingeleiteten immunsuppressiven Behandlung bis jetzt stabil gehalten werden, obwohl die Erkrankung bisher nicht in Remission gebracht wurde und sich zusätzlich eine zerebrale Vaskulitis manifestiert hat. Schlußfolgerung: Das Krankheitsbild des Morbus Behçet sollte auch dem Ophthalmologen vertraut sein und insbesondere bei rezidivierenden Uveitiden in die Differentialdiagnose einbezogen werden, da einer frühzeitigen Diagnose und adäquaten Therapie entscheidende prognostische Bedeutung zukommt, um irreversible Veränderungen an Retina und Glaskörper zu verhindern und den Visus zu erhalten.
    Notizen: Background: Behçet's disease is a rare systemic vasculitis of unknown etiology. The typical symptoms includ recurrent oral and/or genital aphthous lesions, iridocyclitis (historically with hypopyon) and various skin lesions. The number of young adults and children which are diagnosed with Behçet-syndrome is increasing in recent years and the mean age of manifestation has decreased to 25 years in German patients. The disease is generally diagnosed later in German (48.5 months) than in Turkish patients (25.5 months). Ocular manifestation has been confirmed as a marker of severe prognosis. In 15–25 % of affected patients it leads to blindness. Patient: We describe a 19-year-old Caucasian woman who has suffered from the typical symptoms (oral aphthous lesions, recurrent uveitis posterior, various skin lesions) since the 16th year of age. Results: After three years the patient was finally be diagnosed with Behçet's disease (using the criteria of the “International Study Group for Behçet's Disease”). Visual acuity was stabilized with an immunosuppressive therapy, although there was no complete remission in disease activity. In additon a cerebral vasculitis was manifested. Conclusions: Ophthalmologists should be familiar with Behçet's disease. In cases of recurrent uveitis Behçet's disease should be included in the differential diagnosis because timely immunosuppressive therapy can prevent irrevocable changes in the corpus vitreum and retina and preserve complete visual acuity.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Journal of statistical physics 82 (1996), S. 963-998 
    ISSN: 1572-9613
    Schlagwort(e): Cellular automata ; interacting particle systems ; quantum spin systems ; approach to equilibrium ; oscillation norm
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We define a class of dynamical maps on the quasi-local algebra of a quantum spin system, which are quantum analoges of probabilistic cellular automata. We develop criteria for such a system to be ergodic, i.e., to posses a unique invariant state. Intuitively, ergodicity obtains if the local transition operators exhibit sufficiently large disorder. The ergodicity criteria also imply bounds for the exponential decay of correlations in the unique invariant state. The main technical tool is a quantum version of oscillation norms, defined in the classical case as the sum over all sites of the variations of an observable with respect to local spin flips.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Fresenius' journal of analytical chemistry 364 (1999), S. 478-481 
    ISSN: 1432-1130
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A new technique for accurate Mg isotope ratio measurements has been developed with MgF2 as sample compound. With the help of a fluorinating agent negatively charged MgF3 molecular ions were formed in the ion source of a thermal ionisation mass spectrometer. An evaporation study has been performed and the results clearly show that Mg is evaporated from the filament as MgF2 molecules. The MgF2 technique has been applied in the certification of a candidate 26Mg-enriched Spike Isotope Reference Material. The result from this new technique has been compared with results obtained for the same material using ICP-MS.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Fresenius' journal of analytical chemistry 365 (1999), S. 221-226 
    ISSN: 1432-1130
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The chemical microanalysis of semiconductor heterostructures by electron probe x-ray microanalysis (EPMA) is presented. The great advantage of EPMA is the sensitive detection and accurate quantification of partial mass coverage down to about 0.01 μg/cm2. To improve depth resolution of EPMA the surface was sputtered by inert gas ions and x-ray intensities were measured with increasing sputter depth. These intensity-sputter profiles represent a convolution of the structure of the material by the excitation characteristics of the incident electrons. They were interpreted and evaluated with respect to the chemical composition and thickness of each layer. For this purpose a Monte-Carlo-Simulation program package was developed, which can calculate realistic x-ray intensities versus sputter depth for a given material. Additionally, it can reconstruct the structure of the material assuming a laterally homogeneous multilayered system with sharp interfaces and constant composition inside each layer. The results of the reconstruction could be quantified with an accuracy of less than 5% rel.. In spite of the large information depth of x-rays a depth resolution of about 1–3 nm could be determined.
    Materialart: Digitale Medien
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  • 8
    ISSN: 1432-2242
    Schlagwort(e): Embryo rescue ; Glycine spp. ; Intersubgeneric hybrids ; Soybean ; Wide hybridization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Employing a different culture strategy, we obtained a greatly improved frequency of embryo rescue in intersubgeneric soybean hybrids. Successful crosses were obtained in 31 different genotype combinations between nine Brazilian soybean lines as the female parents and 12 accessions from Glycine canescens, G. microphylla, G. tabacina and G. tomentella. The hybrid pod retention rate dropped to about 10% during the first 8 days after pollination and stayed largely unchanged up to the 20th day. Immature harvested seeds fell into three size groups: Group 1, smaller than 1.3 mm (mostly empty seed coats); Group 2, 1.9–5.0 mm; Group 3, larger than 5 mm (from selfing). A total of 90 putative hybrid embryos were rescued using a highly enriched B5 medium to nourish the newly dissected embryos. The growing embryos were then placed in a high osmotic, modified B5 medium to induce maturation and dormancy. Schenk and Hildebrandt medium was used to germinate the dormant, partially dehydrated, physiologically mature embryos. Approximately 37% of the rescued embryos developed into plantlets in vitro, and approximately 8% grew into mature plants in the greenhouse. Morphological, cytological and isoenzyme patterns confirmed the hybrid status of all seven mature plants, all of which were generated using G. tomentella G 9943 as the paternal parent. It was observed that all soybean lines crossed with G 9943 were capable of producing mature hybrid plants. There was no correlation between the initial size of Group 2 seeds and plant survival rate. The hybrids were cloned by grafting and treated with colchicine. One of the treated plants displayed chromosome doubling.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Molecular genetics and genomics 257 (1998), S. 534-541 
    ISSN: 1617-4623
    Schlagwort(e): Key words Biotinylated fusion proteins ; DNA binding domain ; gor ; oriC ; Replication initiation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract In order to study DNA replication control elements in cyanobacteria we cloned and sequenced the dnaA gene from the marine cyanobacterium Prochlorococcus marinus. The dnaA gene is ubiquitous among bacteria and encodes the DNA replication initiation factor DnaA. The deduced amino acid sequence of the P. marinus DnaA protein shows highest similarity to the DnaA protein from the freshwater cyanobacterium Synechocystis sp. PCC6803. Using a solid-phase DNA binding assay we demonstrated that both cyanobacterial DnaA proteins specifically recognize chromosomal origins, oriC, of Escherichia coli and Bacillus subtilis in vitro. The genetic environment of dnaA is not conserved between the two cyanobacteria. Upstream of the P. marinusdnaA gene we identified a gene encoding a putative ATP-binding cassette (ABC) transport protein. The gor gene encoding glutathione reductase lies downstream of dnaA. Comparison of the genetic structure of dnaA regions from 15 representative bacteria shows that the pattern of genes flanking dnaA is not universally conserved among them.
    Materialart: Digitale Medien
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  • 10
    ISSN: 1573-0832
    Schlagwort(e): API YeastIdent ; Enzyme ; Nocardia asteroides ; Proteolysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Glucose represses production of ammonium in many clinical isolates ofNocardia asteroides growing on bromcresolpurple casein glucose agar. Strains exhibiting this property are designated as group A, while group B represents isolates showing a high degree of proteolytic activity and a resulting rapid increase in pH. Twenty isolates ofN. asteroides were characterized as group A or B. Enzymatic profiles obtained using the API YeastIdent system showed significant enzymatic variation between 12 group B and 8 group A isolates. Proteolytic enzymes which most varied in activity between groups were glycine aminopeptidase, histidine aminopeptidase and leucyl glycine aminopeptidase. As some of theN. asteroides isolates were isolated from asymptomatic patients, it is of interest to consider the possibility of one group being of low virulence while the other is more strongly associated with infection.
    Materialart: Digitale Medien
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