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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 4174-4176 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This article concerns a novel negative-conductance device consisting of a series of N laterally indented barriers which exhibits resonant tunneling under one bias polarity and simple tunneling under the opposite one, thus acting as a rectifier. Electrons undergo resonant tunneling when the bias creates a band profile with N triangular wells which can each contain a resonant state. From 1 to N the addition of each indentation can be used to increase the current density and the rectification ratio, calculated at the current-peak bias at resonance, provided that at a given bias all the states in the triangular wells align each other with the emitter Fermi energy in order to form a resonance along the structure. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Langmuir 11 (1995), S. 3337-3346 
    ISSN: 1520-5827
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 2675-2677 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We analyze the current density-voltage characteristics of double-barrier tunneling diodes, with different spacer layers, within the framework of a Poisson solver together with a coherent tunneling approximation for transmission probabilities. We show that varying the spacer layer thickness, together with barrier heights, changes dramatically the current density-voltage characteristics line shape, which is revealed to be an important qualitative signature of the tunneling paths involved in the double-barrier diodes under operation. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 810-812 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on photoluminescence (PL) and photoluminescence-excitation measurements in GaAs/In0.1Ga0.9As/AlAs double-barrier tunneling structures as a function of bias voltage and temperature. We have observed a splitting in the quantum well photoluminescence due to island formation in the quantum well. We have a good correlation between the variation of integrated PL intensity, linewidth, and tunnel current bias for both lines. The temperature dependence of photoluminescence spectra shows that transfer of carrier between islands can be tuned by the applied bias and that states in different islands are populated by electrons in the resonant tunneling process. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of pineal research 19 (1995), S. 0 
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Differences and similarities in the temporal organization of hormone secretion in plasma reflect the activity of CNS pacemakers. One aspect of this activity, the temporal synchronization of the secretion of different hormones is still poorly understood. We report the analysis of melatonin and testosterone plasma concentrations during two nights in 6 normal healthy young men. Blood was collected every 20 min between 2040 and 0640. Plasma testosterone concentrations increased by 1.5- to 2-fold during the second part of the night, and melatonin by 2.5- to 4-fold. In each subject, the individual temporal pattern of melatonin was quite stable over the two nights of sampling, while testosterone profiles showed fluctuations. There was a high degree of parallelism in these two hormones nocturnal secretion. These results, together with previous studies, suggest that melatonin might entrain the nocturnal secretion of testosterone.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Physical Chemistry 30 (1979), S. 379-409 
    ISSN: 0066-426X
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Journal of neuroendocrinology 9 (1997), S. 0 
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Brain metabolites of progesterone such as tetrahydroprogesterone (THP) act on GABAA receptors and have anxiolytic properties. The formation of THP and its 5α-reduced precursor, dihydroprogestrone (DHP) was measured in vitro in various microdissected brain areas obtained from males of two psychogenetically selected rat lines, i.e. the Roman High-(RHA/Verh) and Low-(RLA/Verh) Avoidance rats, which are known to differ in emotional reactivity and/or anxiety. The behavioural and neuroendocrine responses of these rats were also measured following exposure to a novel environment in two different test situations. The formation of DHP and THP was found to be significantly higher in the frontal cortex (FCX), and DHP in the bed nucleus of the stria terminalis (BST), of the hypoemotional RHA/Verh rats. In addition, enzymatic activity in the FCX was found to be inversely correlated with behavioural measures of anxiety. These results suggest that individual, possibly genetically-determined differences in brain production of endogenous anxiolytics derived from progesterone may account at least in part for the behavioural differences characterizing these two lines, and provide further evidence that neurosteroids acting on the GABAergic system may play an important role in modulating physiological and/or behavioural responses to environmental stressors.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-2145
    Keywords: Wheat pollen ; Chemical hybridizing agents ; Male sterility ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Phenylcinnoline carboxylate compounds SC-1058 and SC-1271 cause complete male sterility in wheat when applied at suitable dosages at the pre-meiotic stage of anther development. Anthers from treated and untreated plants were compared using light and electron microscopy from the pre-meiotic stage through the formation of nearly mature pollen. Overall anther development is gradually slowed in treated plants and pollen development is generally arrested in the late prevacuolate or early vacuolate microspore stage, although the first pollen mitosis does sometimes occur. The sporopollenin-containing exine walls are thinner, and show abnormally developed foot and tectum layers with sparse connecting baculi. Microspore cytoplasm degenerates and the cells eventually collapse. At the early, prevacuolate, free microspore stage treated tapetal cells hypertrophy, expanding into the locule. They contain abnormally large vacuoles that appear to form from the fusion of secretory vesicles, and some vacuoles contain electrondense deposits. The sporopollenin-containing orbicular wall and Ubisch bodies are retarded in their development and are structurally deformed. Acetolysis of whole anthers and of thick sections shows that the sporopollen-in-containing structures of treated materials are greatly reduced in thickness and are less rigid than in the control. We conclude that application of these compounds causes interference with the secretory function of tapetal cells which supplies sporopollenin cell-wall polymers to the exine of the microspores and to the tapetal orbicular wall and associated Ubisch bodies. Interference with the tapetal secretion of other nutrients required for microspore development is strongly suggested.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    European journal of pediatrics 125 (1977), S. 45-57 
    ISSN: 1432-1076
    Keywords: New chromosome deletion syndrome ; Partial monosomy 8p ; Conggenital heart anomalies ; Slow growth ; Mental retardation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammefassung Es wird der Fall eines geistig retardierten 8jährigen Knaben mit einer de novo Defizienz des kurzen Arms eines Chromosoms 8 beschrieben. Mit Hilfe einer G-Banden-Methode wurde in Lymphocyten und Fibroblasten der Karyotyp 46,XY,del(8) (pter p21:) festgestellt. Die Chromosomenbefunde der phänotypisch unauffälligen Mutter, Vater und Schwester waren normal. Veröffentlichungen über 4 ähnliche Patienten weisen auf das Vorliegen eines neuen Syndroms der partiellen Monosomie des kurzen Arms des Chromosoms 8 hin, das durch folgende Stigmata charakterisiert ist: geistige Retardierung, langsames Wachstum, hohe Stirn, breiter Brustkorb, weiter Mamillenabstand, Pulmonalstenose, Atrium- und/oder Ventrikulum-Septumdefekt, Hypoplasie der Genitalia, dermatoglyphische Stigmata.
    Notes: Abstract A mentally retarded 8-year-old boy with a de novo partial monosomy for the short arm of the No. 8 chromosome is described. Based on G-banding analysis, the patient's karyotype was identified in lymphocytes and skin fibroblasts as 46,XY,del(8) (pter→p21:). No chromosomal abnormalities were found in the phenotypically normal mother, father and sister of the propositus. Four further cases described in the literature indicate that partial monosomy of the short arm of the No. 8 chromosome might be associated with a syndrome characterized by the following stigmata: mental retardation, slow growth, high forehead, broad chest, wide-set nipples, pulmonary stenosis with atrial and/or ventricular septal defect, hypoplasia of the genitalia, dermatoglyphic stigmata.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1435-1536
    Keywords: Monomersdistribution ; micellarphase ; emulsioncopolymerization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The location and distribution of acrylic acid and styrene in emulsions made with a cationic surfactant, cetyltrimethylammonium bromide (CTAB), or an anionic surfactant, sodium dodecylsulfate (SDS), were determined with ultra-violet spectroscopy, conductivity, and potentiometry. In these systems, the acrylic acid remains in the aqueous phase near the micelle surface, whereas the styrene is located in the micelles or in emulsified droplets. In the absence of acrylic acid, some of the styrene is solubilized in the micelle interior and some is adsorbed at the micelle inner surface. Upon addition of acrylic acid, all the styrene is displaced to the center of the micelles. The interaction between acrylic acid and CTAB micelles is stronger than that between acrylic acid and SDS micelles. With CTAB, acrylic acid is adsorbed at the micelle surface, whereas with SDS, acrylic acid remains in the intermicellar solution. These differences can account for the differences reported in the emulsion copolymerization of acrylic acid and styrene using CTAB or SDS.
    Type of Medium: Electronic Resource
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