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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 4894-4896 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dielectric function of thin-film hydrogenated amorphous silicon (a-Si:H) grown on fused silica at different substrate temperatures has been investigated by spectroscopic ellipsometry. An improved interpretation of the ellipsometric data is based on a tetrahedron model that takes into account the influence of hydrogen incorporation in the amorphous network. It is shown that the film density can be derived from an accurate data interpretation, whereas the maximum value of the imaginary part of the dielectric function ε2max and the void volume fraction are not proportional to the density of a-Si:H films.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of pineal research 14 (1993), S. 0 
    ISSN: 1600-079X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The effect of exogenous melatonin on the adrenocortical axis was studied by determining serum corticosteroid and adrenocorticotrophic hormone (ACTH) levels under basal and stressed conditions in intact, pinealectomized, and adrenalectomized mature male rats. A direct interrelationship between pineal/melatonin and the adrenal cortex, dissociated from the hypothalamic-pituitary axis, was established. Intraperitoneal injection of 100 μg melatonin brought about an elevated adrenocortical response recorded in the serum corticosteroid levels 15 hr afterwards. This effect could be demonstrated only at the beginning of the photophase, when physiological levels of corticosteroids and ACTH are at their lowest daily levels. The pattern of this reaction is different from those caused by stressors such as ether or hypoglycemic reagents, and did not occur in pinealectomized animals although the daily rhythm of corticosteroids and ACTH persisted. No effect on ACTH was evident in intact or adrenalectomized rats, where the serum levels remained unchanged. Moreover, the corticotrophin releasing factor (CRF) content of the median eminence was not affected by melatonin.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1435-1463
    Keywords: Melatonin ; oxazepam ; pinealectomy ; circadian ; diurnal ; brain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Sham-operated and pinealectomized male rats were maintained at 14h light: 10 h dark cycles (lights-on 5.00 h) and injected daily, for 14 days, with oxazepam or vehicle.125I-melatonin binding was recorded in synaptosomes prepared at 10.00, 18.00, and 24.00 h from the hypothalamus, hippocampus and medulla-pons of the rats. In the sham-operated, vehicle treated rats, specific125I-melatonin binding in all brain areas studied was higher at 18.00 h, whereas in the oxazepam-treated animals, binding was higher at 24.00 h than at the other times tested. In the pinealectomized, vehicle-treated rats, the binding recorded at 18.00 h in all three brain areas, was lower than at the other times of day tested. Oxazepam treatment decreased125I-melatonin binding at 24.00 h in the hippocampus and medulla-pons of the pinealectomized rats and did not significantly affect the binding in the hypothalamus. These results indicate the ability of oxazepam, pinealectomy and their combination, to manipulate the diurnal variations in125I-melatonin binding sites in the rat brain.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1440
    Keywords: Heart failure ; Idiopathic dilated cardiomyopathy ; Human myocardium ; Positive inotropic agents ; Force-frequency relationship ; Calcium homeostasis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In isolated papillary muscle strips from nonfailing donor hearts (NF) and from the hearts of patients with dilated cardiomyopathy with severe heart failure (NYHA IV), the force-frequency relationship was studied. Experiments were performed under basal conditions and in the presence of 0.01 μM or 0.1 μM isoprenaline and 0.02 μM ouabain. In NF, there was a positive inotropic effect following an increase of the stimulating frequency, whereas in NYHA IV, the force gradually declined under these conditions. Low concentrations (0.01) μM of isoprenaline prevented the negative inotropic effect in NYHA IV, whereas at 0.1 μM the mechanical function deteriorated in NF and NYHA IV. Ouabain had no effect on the force-frequency relationship compared to basal conditions. It is concluded that a reduction of high frequencies does improve the contractility in the failing myocardium. It is not unreasonable to speculate that this mechanism might be involved in the beneficial effects of drugs which reduce the heart rate, such as β-adrenoceptor antagonists and cardiac glycosides, in the condition of congestive heart failure in which the sympathetic tone is high.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Naturwissenschaften 77 (1990), S. 292-294 
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Intensive care medicine 20 (1994), S. 278-281 
    ISSN: 1432-1238
    Keywords: Blood brain barrier ; Urapidil ; Serotonin-(5HT1A) ; Receptors ; Cerebrospinal fluid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Objective To determine the plasma and cerebrospinal fluid (CSF) levels of urapidil after i.v. administration and the effect on CSF serotonin and 5-hydroxyindoleacetic acid (5-HIAA) concentrations. Design Open, single-dose study. Setting Post-surgery following neurosurgical removal of the hypophysis (n=5) or aneurysm clipping (n=1). Patients 6 patients, aged 32–71 years, with intact bloodbrain barrier (BBB); 1 patient was studied twice. Interventions Single dose of 25 mg urapidil i.v. as prophylaxis of BP increase during extubation or as treatment of hypertensive episodes. Measurements and results Urapidil, serotonin and 5-HIAA were measured by HPLC in CSF during 8 h after urapidil administration. Urapidil was detected in CSF as soon as 5 min after injection in 3 patients. The concentration ratio of plasma/CSF after the distribution phase was about 5∶1. No significant effect on serotonin and 5-HIAA in CSF was seen. Conclusion After administration of a therapeutic dose, urapidil permeates the BBB and may interact with central 5-HT1A-receptors.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Experiments in fluids 15 (1993), S. 200-208 
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The motion of the speckle pattern in the far field limit is uniquely determined by the velocity gradient of the light scattering medium. This is the basic physical effect of a non-invasive method that allows the measurement of velocity gradients with high spatial and temporal resolution down to 75 μm and 1 ms, respectively. We present three different measurement schemes for the analysis of the scattered light. The experimental results refer to mean gradients obtained from measurements on turbulent channel flows.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 168 (1991), S. 45-51 
    ISSN: 1432-1351
    Keywords: Hearing ; Chiroptera ; Desmodus Inferior colliculus ; Tonotopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 1. Within the tonotopic organization of the inferior colliculus two frequency ranges are well represented: a frequency range within that of the echolocation signals from 50 to 100 kHz, and a frequency band below that of the echolocation sounds, from 10 to 35 kHz. The frequency range between these two bands, from about 40 to 50 kHz is distinctly underrepresented (Fig. 3B). 2. Units with BFs in the lower frequency range (10–25 kHz) were most sensitive with thresholds of -5 to -11 dB SPL, and units with BFs within the frequency range of the echolocation signals had minimal thresholds around 0 dB SPL (Fig. 1). 3. In the medial part of the rostral inferior colliculus units were encountered which preferentially or exclusively responded to noise stimuli. — Seven neurons were found which were only excited by human breathing noises and not by pure tones, frequency modulated signals or various noise bands. These neurons were considered as a subspeciality of the larger sample of noise-sensitive neurons. — The maximal auditory sensitivity in the frequency range below that of echolocation, and the conspicuous existence of noise and breathing-noise sensitive units in the inferior colliculus are discussed in context with the foraging behavior of vampire bats.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' Zeitschrift für analytische Chemie 341 (1991), S. 260-264 
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The application of plasma-based SNMS to salt samples was examined to reveal the analytical features of this technique for the analysis of environmental material, which is frequently composed of ionic compounds. 1016 s−1 cm−2 argon ions of 300–500 eV energy were used to sputter halides, sulfates, nitrates and carbonates. The mass spectra are dominated by atomic signals of all elements of the salt and contain additional minor signals of binary homo- and heteroelemental clusters. The latter, such as salt monomers of alkali halides, are useful for compound identification. In sputter equilibrium the atomic mass signals can be used for elemental quantitation with a matrix dependence of about ±30% for the detection factors of most elements. As the average elemental detection factors are shown to be governed by atomic ionization probabilities the erosion flux from salts comprises mainly atoms. Results indicate that thermal release of atoms as well as emission of clusters are the main cause of the matrix dependence. The relative yield of the clusters was found to be strongly enhanced with increasing mass difference of the combined ions. The sputter yield of NaCl was determined to be 3.3 atoms/projectile at 490 eV argon ion energy which results in a depth propagation of ≈5 nm/s for the given sputter conditions.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 19 (1963), S. 315-323 
    ISSN: 1573-5036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The organic matter and nitrogen contents of soils from cultivated lands were compared with those from adjacent veld sites at 0–30, 30–60, and 60–90 cm depths. At 0–30 cm depth the veld and adjacent cultivated soils did not differ much in organic matter and nitrogen contents. The largest differences were found at 60–90 cm depth, where the soils under cultivated lands contained considerably less organic matter and nitrogen than the veld soils. This was particularly evident in two sites at the Glen College of Agriculture and to a lesser degree in two sites in the Theunissen district where the soil was more sandy. The soil from the cultivated lands showed a marked decrease in organic matter and nitrogen contents and a distinct narrowing of the C : N ratio with increasing depth whereas the C- and N-contents and the C : N ratios of veld soils differed much less between depths. These results were explained by the soil moisture conditions prevailing under veld and cultivated lands during the course of the year. Judging from the decreases in organic matter and nitrogen contents since cultivation commenced, Central Orange Free State soils may vay considerably in the amounts of mineral nitrogen liberated following cultivation.
    Type of Medium: Electronic Resource
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