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  • 1
    Digitale Medien
    Digitale Medien
    s.l. : American Chemical Society
    Analytical chemistry 64 (1992), S. 2821-2825 
    ISSN: 1520-6882
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 8019-8036 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The frequency dispersion of χ(3) of conjugated polyenes is calculated using equations of motion which provide an anharmonic (exciton) oscillator picture. Quantum confinement of the relative electron–hole motion is shown to play an important role in determining the magnitude of χ(3). The nature of the two-photon resonance observed in two-photon absorption and third harmonic generation is discussed, and the electroabsorption spectrum is calculated for a broad range of polyene sizes with up to 160 double bonds.
    Materialart: Digitale Medien
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  • 3
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The thermal stability of spin valve films with synthetic antiferromagnet (SAF) pinned by antiferromagnetic IrMn, NiO, and NiMn layers were studied. The SAF layer enhances the thermal stability in general; however, the blocking temperature (and the blocking temperature distribution) of the antiferromagnet is still important for the magnetic rigidity of the pinned layer. Once the temperature reaches the blocking temperature the SAF layer can go into either the spin flip or flop state, depending upon the magnetic moment ratio of the reference layer and pinned layers. The GMR linear head response can be distorted for nonlinearity. The NiMn pinned SAF structure shows magnetic and thermal stability which makes it practical for the real products. A high GMR of 11% can be obtained in both bottom and top NiMn SAF spin valves by advanced processes. Recording heads were built using such stacks which demonstrated recording areal density of 20 Gbit/in.2 and beyond. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 5729-5731 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: In this paper we report on magnetization reversal processes of pinned layers in different ferromagnetic and anti-ferromagnetic bilayer and spin-valve structures by observing hysteresis, switching field distribution (SFD), and time-dependent effects. The fact that time-dependent coercivity Hc tendency is more pronounced in ordered AF materials than that of disordered AF materials implies a spin reversal of some AF grains with locally low pinning field and low blocking temperature. We propose a simple qualitative model to explain our results in terms of a distribution of the pinning reversal field and temperature in AF layer, which may be due to a grain size distribution in the AF layer and an incomplete and inhomogeneous phase transformation in some ordered AF materials. High resolution electron microscopy (HREM) results reveal that lattice spacing does change from place to place in AF region of some ordered AF materials. The evidence indicates an incomplete and inhomogeneous phase transformation in the ordered AF systems, supporting the results of the magnetization reversal process study. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 4267-4272 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: In this work, low-temperature photoluminescence (PL) is used for the investigation of beryllium (Be) dopant outdiffusion in AlGaAs/GaAs single-heterojunction bipolar transistors (HBTs). Near the typical emission peak at ∼1.92 eV which is due to the band-to-band transition from AlGaAs emitter, an additional emission peak is found in the PL spectrum. This peak is found to be caused by the Be-related transition from AlGaAs emitter due to the Be outdiffusion from the GaAs base to the AlGaAs emitter. The concentration of Be outdiffused into the emitter can be estimated from the energy separation between these two emission peaks in AlGaAs range based on the band gap narrowing effect. The measured dc current gain and the emitter-base turn-on voltage of the HBTs fabricated on different wafers with different growth conditions were found to correlate well with the PL results. Our results demonstrate that low temperature PL technique is an efficient method in identifying Be outdiffusion in HBTs and is useful in HBT growth and device structure optimization. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 6468-6473 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: AlGaAs/GaAs single heterojunction bipolar transistor (HBT) structures with Be- and C-doped bases have been annealed at different temperatures using rapid thermal processing (RTP). Both electrical and low-temperature photoluminescence measurements were used to investigate their thermal stability. We found that the conventional AlGaAs/GaAs abrupt HBT structures could undergo significant degradation at temperatures commonly encountered in typical RTP for device fabrication. The decrease of current gain was observed in both molecular beam epitaxy-grown HBTs with a Be-doped base and metalorganic chemical vapor deposition-grown HBTs with a C-doped base after RTP at temperatures greater than 600 °C. Our studies show that high-temperature RTP could induce undesirable degradation in AlGaAs/GaAs HBTs. Different degradation mechanisms, which are similar to those for the degradation of the Be- and C-doped base HBTs under current-induced stress, are responsible for the degradation of the Be- and C-doped HBTs subjected to RTP. The degradation of Be-doped HBTs is believed to be due to the outdiffusion of Be from the highly doped base, whereas the decrease of current gain for C-doped HBTs is closely related to the unintentionally incorporated hydrogen during material growth. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
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  • 7
    ISSN: 1523-5378
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Background. Bismuth triple therapy provides consistently good results in Helicobacter pylori eradication worldwide, whereas quadruple therapy using a combination of omeprazole and bismuth triple regimen has produced cure rates in excess of 90%. The prevalence of metronidazole-resistant strains was 26.8% in our area. Colloidal bismuth pectin (CBP) is a new, lower-priced bismuth salt made in China. The purpose of this study was to investigate the efficacy and safety of CBP triple and quadruple regimens in the treatment of H. pylori–positive duodenal ulcer.Materials and Methods. In this prospective trial, 205 patients with H. pylori–positive duodenal ulcer were allocated randomly to receive one of four regimens: metronidazole, 200 mg; amoxicillin, 250 mg; and colloidal bismuth subcitrate (CBS), 120 mg (group 1), or CBP, 100 mg qid (group 2) for 2 weeks, then continued CBS, 240 mg, or CBP, 200 mg bid for a further 2 weeks. A quadruple regimen using a combination of omeprazole, 20 mg bid, and CBS triple therapy (group 3) or CBP triple therapy (group 4), respectively, was given to patients for 1 week, followed by omeprazole, 20 mg once daily for a further 3 weeks. Further endoscopy was performed at least 4 weeks after cessation of the treatment. H. pylori status was determined by histology, a 14C urea breath test, and a urease test.Results. The per-protocol H. pylori cure rates were 85% (22 of 26 patients), 90% (35 of 39), 96% (46 of 48), and 95% (75 of 79) for groups 1 through 4. In the intention-to-treat analysis, cure rates were 79% (22 of 28), 83% (35 of 42), 90% (46 of 51), and 89% (75 of 84), respectively. The cure rates of quadruple therapy were higher than those of triple therapy; an 8.2% difference was not statistically significant (95% confidence interval [CI], 2.3–18.7%). The ulcer-healing rates were 88%, 87%, 98%, and 97%, respectively, for groups 1 through 4. The ulcer pain was relieved more rapidly in quadruple- than in triple-therapy regimens. Two patients discontinued treatment prematurely owing to drug-related side effects.Conclusion. One-week quadruple therapy is highly effective and safe in H. pylori eradication in Chinese patients. CBP is as effective as CBS.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 62 (1994), S. 0 
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: We have examined the induction of nitric oxide syhthase (NOS) activity in the rat astrocyte-derived C6 glioma cell line. In contrast to the previous results with primary astrocyte cultures, incubation of C6 cells with bacterial endotoxin lipopolysaccharide (LPS; 1 μg/ml for 24 h) did not stimulate NO2 production. However, addition of either tumor necrosis factor-a (TNF-α) or interferon-γ (IFN-γ), cytokines that by themselves had no effect on NOS activity, imparted LPS responsiveness onto these cells in a dose-dependent manner (EC50 values of 39 ng/ml of TNF-α and 9.4 U/ml of IFN-γ), and the effect of TNF-α could be further potentiated (twofold) by the presence of interleukin-1β. The simultaneous presence of TNF-α and IFN-γ yielded a greater response than either cytokine alone; however, the respective EC50 values were not affected. A cytoplasmic extract from induced C6 cells catalyzed the Ca2+-independent conversion of l-arginine to l- citrulline, with an apparent Km of 51.2 nM, and this activity could be blocked by l-arginine analogues in the potency order amino 〉 methyl 〉 nitroarginine. Immunoblot analysis revealed an apparent molecular mass of 125 kDa for the NOS protein induced in C6 cells. These results indicate that the combination of LPS plus cytokines can induce NOS activity in C6 glioma cells with properties similar to those of the enzyme expressed in primary astrocyte cultures.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 56 (1991), S. 0 
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: Previous work in this laboratory has shown that adrenal medullary transplants into the spinal cord subarachnoid space can reduce pain sensitivity. This analgesia most likely results from the release of neuroactive substances, particularly catecholamines and opioid peptides, from the transplanted cells into the CSF of the spinal cord, since it can be attenuated or blocked by α-adrenergic or opiate antagonists. The purpose of the present study was to more directly measure the release of catecholamines from adrenal medullary transplants in the spinal cord CSF using a spinal superfusion technique. CSF samples from rats with 6-month-old transplants were assayed for catecholamines using HPLC with electrochemical detection. Results indicated that norepinephrine levels were increased threefold, and epinephrine levels nearly 100-fold, in animals with adrenal medullary transplants compared with control transplanted animals. There was no apparent increase in dopamine levels. Furthermore, the increased levels of total catecholamines were correlated with decreased pain sensitivity. Results of this study indicate that adrenal medullary transplants can survive for long periods in the rat spinal CSF and continue to release high levels of catecholamines. Together, the release of catecholamines and opioid peptides from adrenal medullary transplants may provide the ideal combination for the reduction of pain.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiac surgery 17 (2001), S. 0 
    ISSN: 1540-8191
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract  Cardiac remodeling by chronic L-thyroxine medication causes exaggerated cardiac arrhythmias in relation to ion channelopathies that involve multichannels. The matrix of lipid membrane is likely the key site where channel lesions, possibly will develop and be benefitted by drug intervention. Cardiac remodeling in rats and guinea pigs was developed by L-thyroxine 0.5 mg/kg SC for 10 days. Propranolol was instituted on days 8–10. Whole cell holding was applied to measure ion currents. An increase in HR, dispersion of QTc, mitochondrial Na+/K+ ATPase, Ca2+/Mg2+ ATPase, and LPO production were found in the model. T3 and T4 levels in plasma were high. Propranolol was effective in regressing cardiac remodeling, together with lowering all the parameters and the enhanced lCa L, IKS, and IKR currents, but T3 and T4 remained basically unchanged. The changes in ion channels are likely the consequence of the cardiac remodeling that is formed by oxidative stress and increased energy consumption provoked by L-thyroxine. The benefit of propranolol on the disordered ion channels is mediated by its ability to ameliorate lesions of the matrix.
    Materialart: Digitale Medien
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