Modified spontaneous emission in oligo (p-phenylene vinylene) planar microcavities

This paper reports on the photoluminescence properties of phenylene vinylene oligomers films (OPV) the emission of which was modified by microcavity effect. Films with 4 and 6 vinyl groups (respectively denoted OPV-4 and OPV-6) were investigated. A strong blue luminescence at 470 nm is observed for OPV-4. OPV-6 shows an emission spectrum quite similar to that of poly phenylene vinylene (PPV). Photoluminescence excitation measurements (PLE) give similar behaviors for the two samples and do not show any change in the shape of the spectra. Ageing under UV irradiation (380 nm) of the unencapsulated OPV-4 layers was evidenced by an exponential decrease of the photoluminescence intensity of about 40% after 3 h a continuous illumination. OPV-6 samples, aged on shelf, for weeks does only show a small decrease (15%) of the PL level over more than 7 h under continuous UV irradiation. Microcavity related effects were observed by inserting the films between two mirrors. These are generally a TiO₂/SiO₂ distributed Bragg reflectors (DBR) as bottom mirror and a Ag film as top mirror. However best results were obtained with two dielectric DBR. As expected, a strong enhancement of the emission at the cavity resonance and pronounced angular effects (emission peaking in the direction normal to the surface of the device) were observed. The importance of the position of the emitting material within the microcavity is evidenced with a thin tris(8-hydroxy) quinoline aluminum (Alq) embedded in SiO₂ with various cavity configurations.     

WorkSpace and the study of Chagas' disease

Chagas' disease afflicts more than 18 million people throughout South and Central America. Some areas of North America have also seen an increased incidence in recent years. The Trypanosoma cruzi (T. cruzi) parasite, which causes the disease, is most often transmitted by Triatomid bugs living in close proximity to humans. The T. cruzi parasite depends heavily on a small molecule called trypanothione to protect itself against damage from free radicals produced during normal metabolism. The concentration of trypanothione in the cell is carefully maintained by an enzyme called trypanothione reductase (TR). Drugs that inhibit TR should cause the parasite to die. Human cells have a similar enzyme-substrate pair: glutathione and glutathione reductase (GR). Fortunately, the enzyme GR differs electrostatically from TR, so there is hope of developing a drug that will be safe for human cells. The molecular structures of both TR and GR are known from ongoing X-ray crystallography studies. Both enzymes are dimers, that is, they consist of two equivalent domains, each having its own active site (the place where glutathione or trypanothione binds). One surprising feature of this system is a long tunnel passing through the center of the dimer and connecting the active sites of the two domains. While this is a naturally interesting feature to explore in a VR environment, the goal of the research is to evaluate the binding ability of particular drugs. For purposes of early testing, we chose chlorpromazine, an antidepressant drug. Large doses of the drug are known to kill the parasite, but are also toxic to the human host. It is possible that minor structural changes to this molecule would improve the selectivity and potency of the drug. For purposes of testing our VR environment, we present only a token calculation on chlorpromazine     

Localization of corticotropin-releasing factor in primary and secondary lymphoid organs of the rat

Cells of the immune system produce a variety of neuropeptides or peptide hormones, either constitutively or upon induction, and possess specific neuropeptide receptors that display ligand-receptor interactions similar to those described in the central nervous system (CNS). These findings suggest that specific subsets of lymphoid cells can produce and respond to peptides previously thought to be principally neural mediators. Recently, corticotropin releasing factor (CRF) mRNA was detected in the rat thymus and spleen, although the cells that synthesize CRF were not identified. We examined the localization of CRF and its mRNA in the rat spleen, thymus, and mesenteric lymph nodes using immunocytochemistry (ICC) and in situ hybridization (ISH), respectively. Immunoreactive CRF was present in cells in the marginal zone and red pulp of the spleen, in connective tissue septa and the subcapsular region of the thymus, and in the medullary cords and sinuses of the mesenteric lymph nodes. Dual ICC/ISH for CRF and its mRNA, respectively, demonstrated CRF mRNA over CRF-immunoreactive cells, suggesting CRF synthesis. Double-label ICC for CRF and markers for specific immunocyte subsets suggest that CRF+ cells in the spleen and thymus are macrophages. CRF+ cells in primary and secondary lymphoid organs reside in compartments that are innervated by sympathetic nerves, and some cells appears to be contacted by noradrenergic sympathetic nerve fibers, suggesting that CRF release may be influenced by the sympathetic nervous system, as it is in the hypothalamo-pituitary-adrenal axis. The presence of CRF in organs of the immune system suggests that this neuropeptide may modulate immune functions after paracrine release.     

Platelet activation and turnover in the primary antiphospholipid syndrome

Recent advances in glaucoma genetics hold potential for dramatically changing the clinical care of glaucoma patients. To date, 5 primary open-angle glaucoma genes and 2 congenital glaucoma genes have been mapped. As more glaucoma genes are identified, earlier diagnosis for glaucoma should become more readily available. Progress in molecular genetics holds considerable promise for both current and future therapy of glaucoma. Glaucoma classification will be tailored to each individual based upon that person's family history, i.e. family glaucoma genotype. In the future, the optimum treatment for a specific glaucoma patient might rely on the knowledge of the phenotype of that person's causal gene, without having to resort to 'trial and error'. At this time, glaucoma treatment is restricted to lowering intraocular pressure. In the near future, with the knowledge of the pathophysiology caused by the defective glaucoma gene, more traditional drug treatments may be used to bypass the gene defect. Ultimately, gene therapy would replace the mutant gene with a normal one before visual loss has occurred as has been done with a model for retinitis pigmentosa, the retinal degeneration mouse.     

Nonlinear dynamic modeling and social contagion: Reply to Stoolmiller (1998).

M. Stoolmiller's (1998) comments about the authors' epidemic models of the onset of social activities (EMOSA models) and about nonlinear modeling in general further stimulate the developmental community to give more attention to this class of methods. The authors review and comment on Stoolmiller's criticisms. Following, they discuss the idea of social contagion as a general theoretical tool. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Testing the Interactivity Principle: Effects of Mediation, Propinquity, and Verbal and Nonverbal Modalities in Interpersonal Interaction

Early channel reliance research compared different modes of communication to assess relationships among nonverbal and verbal cues. Emerging communication technologies represent a new venue for gaining insights into the same relationships. In this article, the authors advance a principle of interactivity as a framework for decomposing some of those relationships and report an experiment in which physical proximity—whether actors are in the same place ("co-located") or interacting at a distance ("distributed")—and the availability of other nonverbal environmental, auditory, and visual information in distributed modes is varied. Results indicate that both proximity and availability of nonverbal cues affect communication processes, social judgments participants make about each other, and task performance. The authors discuss implications about gains and losses due to presence of nonverbal features.     

Gender and smoking cessation: A factor structure comparison of processes of change.

This study examined gender differences in the pattern of process use for smoking cessation using the Processes of Change Questionnaire (J. O. Prochaska et al; see record 1989-03620-001). The goals were (a) to determine the degree to which the covariance structure of the Processes of Change Questionnaire is invariant across gender, (b) to test the existence of the theoretical 2-factor process model using confirmatory factor analysis, and (c) to explore mean differences, if found, in the use of the 10 processes of change across 4 stages of change (precontemplation, contemplation, preparation, and action). The sample (N?=?516) had an equal distribution of men and women across the stages of change. Results demonstrated that the structure of the measure for men and women was invariant at the level of the variance–covariance matrices and that the hypothesized 2-factor model fit the data. Only stage of change predicted the experiential and behavioral process factors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Solid-state Reactions and Phase Relations in the Ti-Si-O System at 1373 K

Reactions between Ti and SiO₂ were studied at 1373 K (1100°C) under vacuum conditions using planar diffusion couples. A method to correct for the presence of surface oxide was developed which led to improved oxygen measurements with the electron probe microanalyzer. An isothermal section through the Ti-Si-O phase diagram at 1373 K was determined using measured diffusion paths and phase compositions in equilibrated alloys. The experimentally determined isothermal section was compared to isothermal sections calculated using thermodynamic data. In addition the sequence of reaction layers formed in the diffusion couples is discussed in terms of thermodynamic activity diagrams.