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  • 1
    Electronic Resource
    Electronic Resource
    Positron-trap centers in neutron-irradiated silicon containing hydrogen (1995)
    Springer
    Applied physics 60 (1995), S. 81-85 
    Details
    ISSN: 1432-0630
    Keywords: PACS: 61.72–y; 61.80.Hg; 78.70.Bj
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. The defect evolution as a function of the annealing temperature has been studied in monocrystalline silicon grown in a hydrogen atmosphere and irradiated with 3.6×1017 neutrons/cm2. Positron lifetime spectroscopy has been used and the results compared with infrared absorption measurements. Vacancy-H, vacancy-2H, vacancy-O-H and divacancy complexes with m hydrogen atoms (m〈6) have been identified for the first time as possible positron traps.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01577618
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  • 2
    Electronic Resource
    Electronic Resource
    Positron mobility in polyethylene in the 60–400 K temperature range (1995)
    Springer
    Applied physics 60 (1995), S. 447-453 
    Details
    ISSN: 1432-0630
    Keywords: 78.70.Bj ; 36.10.Dr ; 61.41.+e
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract We have determined the positron mobility (μ+) in polyethylene samples (67.2% crystalline, glass transition temperatureT g=151 K) in the 64–400 K temperature range by Doppler shift measurements. A method based on the simulataneous observation of two γ lines from133Ba and137Cs radioactive sources together with the positron annihilation γ line, was employed to measure the Doppler shift of the 511 keV γ line as a function of the electric field applied to the samples. With this method we were able to measure at the same time the drift velocity of positrons and theS parameter. This parameter is very important in the interpretation of the mobility trend in samples where the positron states change with temperature. The positron mobility was corrected for positronium formation. μ+ at 64 K is 31.7±0.8 cm2 V−1 s−1 then decreases up to 123 K, increases at 148 K and decreases again up to 170 K (μ+=26.9±0.8 cm2 V−s−). This sharp change in mobility is centred around the glass transition temperature of our samples. Then the mobility remains almost constant up to 230 K. From 250 K to 377 K, μ+ increases and reaches the value of 38.4±1.0 cm2 V−1s−1. The corrected experimental data were well fitted by a simple model taking into account scattering and a thermally activated process (hopping mechanism).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01538768
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  • 3
    Electronic Resource
    Electronic Resource
    Pharmacokinetics and bioavailability of intravenous and oral chlordesmethyldiazepam in humans (1988)
    Springer
    European journal of clinical pharmacology 34 (1988), S. 109-112 
    Details
    ISSN: 1432-1041
    Keywords: chlordesmethyldiazepam ; lorazepam ; pharmacokinetics ; i.v./p.o. administration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Six healthy, fasting volunteers were given single doses of chlordesmethyldiazepam by 1 mg i. v., or as drops or tablets. Chlordesmethyldiazepam and its metabolite, lorazepam, in multiple plasma samples and in urine collected for 120 h after each dose were determined by electron-capture GLC. Mean kinetic variables for intravenous chlordesmethyldiazepam were: volume of distribution, 1.71 l · kg−1; elimination half-life, 113 h; total clearance, 0.21 ml · min−1 · kg−1; cumulative excretion of lorazepam glucuronide 24.2% of the dose. Following a lag time of 15.5 min (tablets) and 4.2 min (drops), which were significantly different, the absorption of oral chlordesmethyldiazepam was a first order process, with apparent absorption half-life values averaging 1.5 h (tablets) and 1.1 h (drops). Bioavailability was 77% for tablets and 79% for drops.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01061430
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  • 4
    Electronic Resource
    Electronic Resource
    Pharmacokinetics of pirprofen and its pyrrol metabolite in elderly patients (1988)
    Springer
    European journal of clinical pharmacology 35 (1988), S. 379-383 
    Details
    ISSN: 1432-1041
    Keywords: pirprofen ; pharmacokinetics ; old age
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Plasma concentrations of pirprofen and of its pyrrol metabolite were assessed in 9 elderly patients (3 males, 6 females; mean age 76 years) suffering from chronic degenerative disease. Pirprofen 400 mg in 4 ml was administered i.m. and the pharmacokinetic profile of the drug and the metabolite was calculated. The AUC, Cmax and t1/2 of pirprofen were similar to those found in previous studies, and, as expected, those parameters for the pyrrol metabolite were lower (Cmax=2.8 µg/ml−1; tmax=6.4 h; AUC(0–32)=56.5 µg · h · ml−1). One patient (n=8) showed different pharmacokinetic behaviour, which is discussed. The data suggest that age has little influence on the pharmacokinetic of pirprofen, although unpredictable responses should always be considered in clinical practice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00561368
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  • 5
    Electronic Resource
    Electronic Resource
    The diffusion of pirprofen into the cerebrospinal fluid in man (1988)
    Springer
    European journal of clinical pharmacology 35 (1988), S. 81-83 
    Details
    ISSN: 1432-1041
    Keywords: pirprofen ; pharmacokinetics ; cerebrospinal fluid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary We have measured the concentrations of pirprofen at various times in plasma and cerebrospinal fluid (CSF) samples, drawn during diagnostic myelography from 28 patients affected by sciatica. After intramuscular injection of 400 mg plasma concentrations of pirprofen reached a peak in 60 min then fell slowly. In contrast, the CSF concentration rose until 12 h and then fell. Pirprofen rapidly crossed the blood-brain barrier and was detectable in CSF at 15–30 min after injection. These results support the suggested hypothesis of a central analgesic action of pirprofen along with the known peripheral one. A new sensitive HPLC method was developed for measuring the concentration of pirprofen in the CSF.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00555512
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  • 6
    Electronic Resource
    Electronic Resource
    Pharmacodynamics and pharmacokinetics of eptastigmine in elderly subjects (1993)
    Springer
    European journal of clinical pharmacology 45 (1993), S. 373-376 
    Details
    ISSN: 1432-1041
    Keywords: Eptastigmine ; Cholinesterase inhibition ; Elderly subjects ; adverse effects ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Eptastigmine is a new cholinesterase inhibitor, which may be potentially useful for the symptomatic treatment of Alzheimer's disease. A preliminary evaluation of its pharmacodynamic and pharmacokinetic profiles in the elderly has now been made in 6 healthy subjects (63–84 years of age) given 30 mg eptastigmine as a single oral dose. Blood was collected prior to and 1, 2, 3, 4, 6, 8, and 12 h after eptastigmine administration for measurement of cholinesterase inhibition in plasma and red blood cells and the plasma drug concentrations. The maximum plasma cholinesterase inhibition was 17%, which was reached 2.7 h after treatment. In red cells the maximum inhibition of the enzyme was 29% after 3.8 h. The estimated half-time of cholinesterase recovery was 12.4 h in plasma and 13.6 h in red blood cells. The peak plasma concentration of eptastigmine of 0.86 ng·ml−1 was reached after 1.4 h. Following absorption the drug was rapidly distributed into tissues (t1/2α = 0.44 h) and then eliminated with a half-life of 12.1 h. The drug was well tolerated in all but one subject, who showed bradycardia with hypertension and nausea for about 2 h after the dose. The results indicate that oral administration of eptastigmine to elderly subjects produces long lasting inhibition of cholinesterase activity in plasma and in red blood cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00265958
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  • 7
    Electronic Resource
    Electronic Resource
    Observation of carbon segregation and evolution of vacancy defects in a surface layer of iron exposed to a low-energy high-current electron beam (1998)
    Springer
    Technical physics letters 24 (1998), S. 334-337 
    Details
    ISSN: 1090-6533
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract For the first time, Rutherford backscattering (RBS) and proton-induced x-ray emission (PIXE) using a proton microbeam and a slow positron beam were used to analyze (scan) the surface and near-surface layers of α-Fe after exposure to a low-energy high-current electron beam. Grain-boundary segregation of carbon and the formation of impurity complexes were observed. Proton microbeam scanning revealed regions of reduced local density which are sources of crater formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1262112
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  • 8
    Electronic Resource
    Electronic Resource
    Elastic and vibrational excitation cross-sections in the Ps-H2 scattering: a perturbative approach (1983)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 2 (1983), S. 1347-1375 
    Details
    ISSN: 0392-6737
    Keywords: Elastic scattering of atoms and molecules ; Inelastic scattering of atoms and molecules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Si dà un resoconto particolareggiato di un calcolo perturbativo della sezione d'urto elastica e di eccitazione vibrazionale per la collisione positronio su molecola d'idrogeno. Il problema è studiato nel contesto della teoria dello scattering a molti canali per sistemi di particelle identiche; sono calcolate l'ampiezza di scambio al primo ordine e l'ampiezza diretta al secondo ordine per energie da zero alla soglia di eccitazione del positronio. È anche valutata l'approssimante di Padé piú bassa e questo suggerisce la comparsa di una forte esaltazione della sezione d'urto vibrazionale e della perdita di energia nella materia attorno alla soglia di eccitazione del positronio. Rispetto ad un breve resoconto preliminare presentato in precedenza si sono apportati diversi miglioramenti sia nelle approssimazioni di carattere fisico che nelle valutazioni numeriche.
    Abstract: Резюме Проводится пертурбационное вычисление поперечных сечений упругого рассеяния и вибрационного возбуждения в процессе рассеяния позитрония на молекуле H2. Рассматриваемая проблема исследуется в связи с теорией многоканального рассеяния тождественных частиц. Вычисляются обменная амплитуда первого порядка и прямая амплитуда второго порядка в области энергий от нуля до порога возбуждения позитрония. Также определяется низший порядка Падэ приближения, предполагая наличие сильного увеличения в вибрационном поперечном сечении и в энергетических потерях в веществе на пороге возбуждения позитрония. По сравнению с существующими подходами, предлагаются различные улучшения в физических приблизениях и в численных расчетах.
    Notes: Summary A detailed account is reported of a perturbative calculation of the elastic and vibrational excitation cross-sections for the positronium-H2 molecule scattering. The problem is studied in the context of the multichannel scattering theory for identical particles; the first-order exchange amplitude and the second-order direct amplitude are evaluated for energy from zero to the positronium excitation threshold. The lowest-order Padé approximant is also constructed and this suggests the occurrence of a strong enhancement in the vibrational cross-section and in the related energy loss in matter at the positronium excitation threshold. In comparison with a short preliminary account presented elsewhere, various improvements are introduced both in the physical approximations and in the numerical calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02460219
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  • 9
    Electronic Resource
    Electronic Resource
    On the Ps-H2 scattering (1985)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 6 (1985), S. 105-123 
    Details
    ISSN: 0392-6737
    Keywords: Elastic scattering of atoms and molecules ; Inelastic scattering of atoms and molecules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Si presenta un calcolo perturbativo della sezione d'urto elastica, di prima e seconda eccitazione vibrazionale per la collisione di positronio su molecola d'idrogeno per energie da zero alla soglia di prima eccitazione del positronio. Si calcola il rapporto tra la perdita di energia vibrazionale ed elastica del positronio nella materia. Rispetto ad un analogo calcolo fatto precedentemente si tiene conto del contributo del continuo del positronio all'ampiezza diretta al second'ordine e si valuta la sezione d'urto di seconda eccitazione vibrazionale.
    Abstract: Резюме В рамках теории возмущений вычисляются поперечное сечение упругого рассеяния и поперечное сечение первого и второго колебательных возбуждений при соударении позитрония с молекулой водорода при энергиях в диапазоне от нуля до порога возбуждения позитрония. Мы также вычисляем отношение между потерями энергии на колебательные возбуждения и упругими потерями энергии позитрония в веществе. По сравнению с предыдущими вычислениями мы учитываем вклад непрерывного спектра позитрония в прямую амплитуду во втором борновском приближении. Мы также оцениваем поперечное сечение второго колебательного возбуждения.
    Notes: Summary We perform a perturbative calculation of the elastic, first and second vibrational excitation cross-sections for the positronium-H2 molecule scattering for an energy from zero to the positronium excitation threshold. We calculate also the ratio between the averaged vibration threshold. We calculate also the ratio between the averaged vibrational-and elastic-energy loss of the positronium in matter. In comparison with a previous similar calculation, we take now into account the contribution of the continuum of the positronium to the second Born approximation to the direct amplitude and we add the calculation of the second vibrational excitation cross-section.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02450674
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  • 10
    Electronic Resource
    Electronic Resource
    Defects in TCIRG1 subunit of the vacuolar proton pump are responsible for a subset of human autosomal recessive osteopetrosis (2000)
    [s.l.] : Nature America Inc.
    Nature genetics 25 (2000), S. 343-346 
    Details
    ISSN: 1546-1718
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] Osteopetrosis includes a group of inherited diseases in which inadequate bone resorption is caused by osteoclast dysfunction. Although molecular defects have been described for many animal models of osteopetrosis, the gene responsible for most cases of the severe human form of the disease ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/77131
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