Field effect on the impact ionization rate in semiconductors

Impact ionization plays a crucial role for electron transport in semiconductors at high electric fields. We derive appropriate quantum kinetic equations for electron transport in semiconductors within linear response theory. The field-dependent collision integral is evaluated for the process of impact ionization. A known, essentially analytical result is reproduced within the parabolic band approximation [W. Quade , Phys. Rev. B 50, 7398 (1994)]. Based on the numerical results for zero field strengths but realistic band structures, a fit formula is proposed for the respective field-dependent impact ionization rate. Explicit results are given for GaAs, Si, GaN, ZnS, and SrS. (C) 2000 American Institute of Physics. [S0021-8979(00)03002-4].87278178

Emerging pharmacotherapy of tinnitus

Tinnitus, the perception of sound in the absence of an auditory stimulus, is perceived by about 1 in 10 adults, and for at least 1 in 100, tinnitus severely affects their quality of life. Because tinnitus is frequently associated with irritability, agitation, stress, insomnia, anxiety and depression, the social and economic burdens of tinnitus can be enormous. No curative treatments are available. However, tinnitus symptoms can be alleviated to some extent. The most widespread management therapies consist of auditory stimulation and cognitive behavioral treatment, aiming at improving habituation and coping strategies. Available clinical trials vary in methodological rigor and have been performed for a considerable number of different drugs. None of the investigated drugs have demonstrated providing replicable long-term reduction of tinnitus impact in the majority of patients in excess of placebo effects. Accordingly, there are no FDA or European Medicines Agency approved drugs for the treatment of tinnitus. However, in spite of the lack of evidence, a large variety of different compounds are prescribed off-label. Therefore, more effective pharmacotherapies for this huge and still growing market are desperately needed and even a drug that produces only a small but significant effect would have an enormous therapeutic impact. This review describes current and emerging pharmacotherapies with current difficulties and limitations. In addition, it provides an estimate of the tinnitus market. Finally, it describes recent advances in the tinnitus field which may help overcome obstacles faced in the pharmacological treatment of tinnitus. These include incomplete knowledge of tinnitus pathophysiology, lack of well-established animal models, heterogeneity of different forms of tinnitus, difficulties in tinnitus assessment and outcome measurement and variability in clinical trial methodology. © 2009 Informa UK Ltd.Fil: Langguth, Berthold. Universitat Regensburg; AlemaniaFil: Salvi, Richard. State University of New York; Estados UnidosFil: Elgoyhen, Ana Belen. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; Argentin

The opposite effects of fluvoxamine and sertraline in the treatment of psychotic major depression: a case report

<p>Abstract</p> <p>Background</p> <p>Psychotic major depression is a clinical subtype of major depressive disorder. A number of clinical studies have demonstrated the efficacy of the combination of an antidepressant (for example, a tricyclic antidepressant or selective serotonin reuptake inhibitor (SSRI)) and an atypical antipsychotic or electroconvulsive therapy (ECT) in treating psychotic major depression. In several studies, monotherapy of SSRIs such as fluvoxamine has been shown to be effective in the treatment of psychotic major depression.</p> <p>Methods</p> <p>We report on a 36-year-old Japanese woman in whom fluvoxamine (a SSRI with sigma-1 receptor agonist) and sertraline (a SSRI with sigma-1 receptor antagonist) showed the opposite effects on psychotic symptoms in the treatment of psychotic major depression.</p> <p>Results</p> <p>Symptoms of depression and psychosis in the patient who was non-respondent to antipsychotic drugs improved after fluvoxamine monotherapy. At 3 years later, a switch to sertraline from fluvoxamine dramatically worsened the psychotic symptoms in the patient. Then, a switch back to fluvoxamine from sertraline improved these symptoms 1 week after fluvoxamine treatment.</p> <p>Conclusion</p> <p>Doctors should consider the monotherapy of sigma-1 receptor agonist fluvoxamine as an alternative approach to treating psychotic major depression.</p

Nitric oxide production and monoamine oxidase activity in cancer patients during interferon-α therapy

Both increased and decreased nitric oxide (NO) synthesis have been reported in patients treated with interferon-α (IFN-α). Animal studies showed that IFN-α administration results in increased levels of biogenic amines, subsequent activation of monoamine oxidases (MAOs), and finally in a change in NO production due to the H2O2 generated by MAOs. We examined the potential relationship between NO production in plasma and MAO-B activity in platelets of 43 cancer patients during 8 weeks of treatment with IFN-α. NO synthesis was quantitated by measuring both the ratio of citrulline and arginine (CIT/ARG-ratio) and total nitrite/nitrate (NOx) levels. Compared to baseline, MAO activity and NOx increased, while the CIT/ARG-ratio decreased. No associations were found between NOx, MAO and CIT/ARG-ratio. Only few associations were observed between changes in the biochemical parameters and changes in psychopathology induced by IFN-α, of which the association between changes in CIT and lassitude was the most consistent. The results suggest that peripheral NO production and MAO activity are unrelated to each other, and that peripheral changes in these biochemical parameters induced by IFN-α are unlikely to contribute to definite psychiatric disturbance

MICROSCOPIC CALCULATION OF THE ELECTRON OPTICAL-PHONON INTERACTION IN ULTRATHIN GAAS/ALXGA1-XAS ALLOY QUANTUM-WELL SYSTEMS

MICROSCOPIC CALCULATION OF THE ELECTRON OPTICAL-PHONON INTERACTION IN ULTRATHIN GAAS/ALXGA1-XAS ALLOY QUANTUM-WELL SYSTEM