Dielectric effect on electric fields in the vicinity of the metal-vacuum-dielectric junction.

The dielectric effect was theoretically investigated in order to describe the electric field in the vicinity of a junction of a metal, dielectric, and vacuum. The assumption of two-dimensional symmetry of the junction leads to a simple analytic form and to a systematic numerical calculation for the field. The electric field obtained for the triple junction was found to be enhanced or reduced according to a certain criterion determined by the contact angles and dielectric constant. Further numerical calculations of the dielectric effect show that an electric field can experience a larger enhancement or reduction for a quadruple junction than that achieved for the triple junction. It was also found that even though it changes slowly in comparison with the shape effect, the dielectric effect was noticeably large over the entire range of the shape change.

Simulations of infrared and optical rectification by geometrically asymmetric metal-vacuum-metal junctions for applications in energy conversion devices.

We use a transfer-matrix methodology to simulate the rectification of infrared and optical radiation by geometrically asymmetric metal-vacuum-metal junctions in which one of the metals is flat while the other is extended by a tip. We determine in particular the power this junction could provide to an external load and the efficiency with which the energy of incident radiations is converted. We consider first situations in which the external radiation is monochromatic, with typical frequencies in the infrared and optical domains. We then consider situations in which the external radiation consists of a full range of frequencies, with amplitudes that are representative of a focused beam of solar radiation. We investigate in particular how the efficiency of the rectification is affected by the aspect ratio of the tip, the work function of the metallic elements and the occurrence of polarization resonances. Our results demonstrate that the rectification of infrared and optical radiation is possible using devices of the type considered in this work. They finally provide a quantitative analysis of the efficiency of this rectification.

Nitric oxide produced by a novel nitric oxide synthase isoform is necessary for gonadotropin-releasing hormone-induced growth hormone secretion via a cGMP-dependent mechanism.

The involvement of nitric oxide (NO) in the regulation of goldfish growth hormone (GH) secretion was further characterized using primary cultures of dispersed goldfish pituitary cells. Western blots revealed the presence of an inducible nitric oxide synthase (iNOS)-like protein of approximately 120 kDa in cytosol/plasma membrane extracts. By contrast, brain NOS-immunoreactive proteins of approximately 120-140 kDa were occasionally detected in a cytoskeleton/organelle fraction but were absent from cytosol/plasma membrane extracts. The NO donor sodium nitroprusside (SNP) acutely increased GH secretion but this response was not observed in the presence of either a NO scavenger (PTIO) or a soluble guanylate cyclase inhibitor (ODQ). SNP also significantly increased the levels of cyclic (c)GMP in somatotrope-enriched cell populations. Treatments with 1400W (iNOS inhibitor), PTIO and rutin hydrate (NO scavengers) and ODQ abolished the acute GH-release response to two endogenous gonadotropin-releasing hormones (GnRH). 1400W, rutin hydrate, PTIO and ODQ alone did not significantly alter basal GH secretion. Together, these results establish that an iNOS-like peptide is constitutively present in the pituitary of the goldfish. Furthermore, these data suggest that NO, most likely through the generation of cGMP, is a necessary signal transduction component of GnRH-induced GH secretion.

The relationship between 'critical weight' and 20-hydroxyecdysone in the female ixodid tick, Amblyomma hebraeum.

THE FEEDING CYCLE OF ADULT FEMALE TICKS (ACARI: Ixodidae) is divided into preparatory, slow and rapid feeding phases. At the transition from slow to rapid feeding, Amblyomma hebraeum (Koch) females reach a 'critical weight' (CW; approx. 10x the unfed weight) that is characterized by several behavioural and physiological changes. Five of these changes were used as criteria to establish a more precise estimate of CW than we have to date. The CW as defined by re-attachment to the host was 9x the unfed weight, while for haemolymph ecdysteroid titre, salivary gland degeneration, ovary weight, oocyte length and oocyte vitellin content the CW was 10x, 10x, 12x, 12x and 13x, respectively. CW thus varies depending on the parameter measured. Although previous studies have established the influence of ecdysteroids on salivary gland degeneration and vitellogenesis, here we demonstrate a further effect of ecdysteroids: inhibiting re-attachment to the host.

A placebo-controlled multicenter trial of Limbitrol versus its components (amitriptyline and chlordiazepoxide) in the symptomatic treatment of depressive illness.

In a multicenter, placebo-controlled, clinical trial, the efficacy of Limbitrol was compared with that of its components, amitriptyline and chlordiazepoxide. All patients had a diagnosis of primary depression. Data from 279 patients were evaluated using the Hamilton depression scale, the Beck depression inventory, and physician and patient global change measures. Statistically significant differences favoring Limbitrol occurred after 1 week of treatment, and a trend in favor of Limbitrol continued throughout the remaining 3 weeks. In most efficacy comparisons, the combination was as good as, or better than, amitriptyline alone. It was superior to chlordiazepoxide alone after 2 and 4 weeks of treatment. Each component produced an independent contribution to the total therapeutic effect: the chlordiazepoxide effect was more prominent in the first 2 weeks and the amitriptyline effect in the latter 2 weeks. A trend favoring amitriptyline over chlordiazepoxide was evident by week 4. The overall incidence of side effects was comparable in both Limbitrol- and amitriptyline-treated groups. Limbitrol-treated patients exhibited more sedation, but significantly fewer Limbitrol patients discontinued treatment prematurely because of side effects.

The measurement of psychological states by use of factors derived from a combination of items from mood and symptom checklists.

The similarities in structure and usage of two widely used adjective checklists, the Profile of Mood States (POMS) and Symptom Checklist (SCL), suggested the feasibility of pooling the items from the two scales into a single factor analysis. This procedure was clinically appealing, statistically sound, and provided an efficient method to reduce and refine assessments of psychopathology. Data from 413 Miami Symptomatic Volunteers were used in this factor analysis. Nine factor dimensions were found to meet the dual criteria of statistical salience and clinical meaningfulness. The results demonstrated the factorial stability of the SCL and the POMS and identified the dimensions of psychopathology in which items from the two scales tended to complement each other in factor structure. Some factors were found to be unique to each scale. In addition, it was found that pooling the items from both scales yielded two new factor dimensions that were not previously available from either of the individual scales.

The clinical research ward as a therapeutic community: incompatibilities.

The authors discuss the numerous incompatibilities between the clinical research ward, with its emphasis on the collection of baseline and treatment data, and the therapeutic milieu environment, with its emphasis on an open door, team orientation, and nonauthoritarianism. They posit that the two orientations may be mutually destructive and that the therapeutic milieu may not be the best treatment setting for patients with schizophrenic or certain affective disorders. Two case histories illustrating these ideas are included.

Sleep disturbance in schizophrenia. A revisit.

Rapid eye movement (REM) sleep mechanisms may play a role in the pathophysiology of schizophrenia, but results have been inconclusive and studies of sleep in schizophrena have been deficient in identifying, comparing, and differentiating between subcategories of schizophrenia. Twenty-nine hospitalized, drug-free schizophrenics were divided into three subgroupsacute, latent, and schizoaffective. The REM intensity measures and REM latency were found to differentiate significantly the schizoaffective group. Sleep-continuity indexes separated the latent and acute groups. Seven patients who later required treatment with tricyclic an tidepressants had base line REM latencies significantly lower and hospitalizations significantly more prolonged than the patients who did not require antidepressants. Sleep measurements may thus identify diagnostic subgroups of schizophrenia as well as predict which schizophrenic depressive syndrome or a concurrent affective syndrome.