Synthesis of dysprosium oxide by homogeneous precipitation

Nanocrystals of uniform dysprosium oxide (Dy₂O₃) particles have been prepared by homogeneous precipitation technique. The particles were produced by aging DyCl₃solution in presence of urea at elevated temperature. The particles were characterized with respect to their size, shape, and thermal decomposition behavior. It was found that the precipitated particles were spherical, uniform in size, and amorphous in nature. Upon heating in air, these particles decomposed into oxide and no change in morphology was observed. The dysprosium ion concentration was found to have significant effect on the particle size and its distribution.     

Effects of increased physician–patient communication on patient anxiety.

50 medical patients completed the State–Trait Anxiety Inventory before and after a physical examination, during which they were encouraged or not encouraged to discuss their health concerns. Results suggest that encouraging patients to disclose their underlying concerns and then confirming or discrediting these concerns are effective ways to reduce anxiety. Findings also indicate that many medical patients overestimate the severity of their physical ailments. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Thermodynamic Modeling of Equilibrium Subsolidus Phase Relations in the Ag–Pd–O2 System

From literature values of the thermodynamic activity of Pd in Ag/Pd solid solutions and the Gibbs free energy of formation of PdO as a function of temperature, subsolidus equilibrium phase relations in the Pd–Ag–O₂ system have been calculated and compared to results from high-temperature XRD analyses. The developed model takes into account the nonideal activity of Pd in Ag/Pd solid solutions and confirms that increasing the Ag/Pd ratio or decreasing the oxygen activity decreases the temperature at which PdO reduces. It also accurately predicts that the temperature range over which the PdO reduces is broad for Ag-rich compositions, and narrow for Pd-rich compositions.     

Effect of the solvent on the particle morphology of spray dried PMMA

The effect of various solvents on the morphology of polymethyl methacrylate (PMMA) particles synthesized by spray drying is examined. It is concluded that the product PMMA particles, derived from the PMMA-acetone dilute solution, have a smaller particle size than those from the PMMA-THF dilute solution. This is due to the stronger PMMA-acetone interaction, since acetone is a good solvent for PMMA, while THF is a poor solvent for PMMA. By controlling the temperature of each section of the tube furnace, the heating rate was adjusted so that both solid and hollow particles could be obtained. When water was added to these dilute solutions, porous or honeycomb particles were produced due to the different evaporation rates of solvent and water. This was a result of a large difference in the solubility parameter values between PMMA and solvent. The strong interaction between PMMA and acetone results in the formation of porous particles while the weak interaction between THF and PMMA produced honeycomb structure particles.     

Monitoring a reaction at submillisecond resolution in picoliter volumes

Well-established rapid mixing techniques such as stopped-flow have been used to push the dead time for kinetic experiments down to a few milliseconds. However, very fast reactions are difficult to resolve below this limit. We now outline an approach that provides access to ultrafast kinetics but does not rely on active mixing at all. Here, the reagents are compartmentalized into water-in-oil emulsion microdroplets (diameter ～50 μm) that are statically arrayed in pairs, resting side-by-side in a well feature of a poly(dimethylsiloxane) (PDMS) device. A reaction between the contents of two droplets arrayed in such a holding trap is initiated by droplet fusion that is brought about by electrocoalescence and known to occur on a time scale of about 100 μs. A reaction between the reactants (Fe(3+) and SCN(-)) is monitored by image analysis measuring the product formation in the newly merged drop in both space and time, by use of a fast camera. A comparison of the concentration field of the reaction product with the output of a reaction-diffusion system of equations yields a rate constant k ～ 3 × 10(4) M(-3)·s(-1). Since reaction and diffusion are formally included in the mathematical model, measurements can proceed immediately after the drop fusion, removing the need to allow time for mixing. This approach is different from existing methodologies, for example, experiments in a conventional stopped-flow apparatus but also electrofusion of moving droplets where contents are mixed by chaotic advection before a reaction is monitored. Our analysis makes kinetics accessible that are several times faster than techniques that have to allow time for mixing.     

A review of life satisfaction research with children and adolescents.

An important construct in positive psychology is life satisfaction (LS). Although its importance has been recognized by some school psychologists, research findings have remained unsynthesized. In this article, theory, measurement, and correlates of LS among children and youth are reviewed. Following this review, interrelationships among LS research, positive psychology, and school psychology are discussed. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Instability of tuberculin and Candida skin test reactivity in HIV-infected Ugandans. The Uganda-Case Western Reserve University Research Collaboration

Anergy testing has been used as an adjunct to tuberculin testing for assessing M. tuberculosis (MTB) infection and indications for isoniazid preventive therapy in HIV-infected persons. We examined factors associated with the stability of skin test responses to purified protein derivative (PPD) and candida antigens in a cohort of HIV-infected adults followed prospectively in a tuberculosis preventive therapy trial in Uganda. PPD-positive and anergic subjects in the placebo arms of the preventive therapy study underwent repeat skin testing and immunologic testing including measurement of MTB culture filtrate (CF)-stimulated interferon gamma (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha) levels in whole-blood culture supernatants. Anergy was present in 27% of 4,058 HIV-infected subjects screened for the tuberculosis preventive therapy trial compared with 10% of 682 HIV-non-infected persons. On follow-up testing of enrolled subjects, 42% of 139 initially anergic subjects were no longer anergic; two thirds of these had PPD reactions >= 5 mm. Stability of anergy was associated with intercurrent opportunistic infections and AIDS-associated dermatitis at baseline. Thirty-five percent of 313 subjects with an initial positive PPD had a negative PPD test at follow-up, 26% of whom had a positive candida skin test at the same time as the negative PPD test. Baseline MTBCF-stimulated IFN-gamma levels were significantly higher among PPD-positive subjects who remained PPD-positive than in those who were falsely negative. We conclude first that anergy is unstable and second that anergy testing is unreliable in identifying HIV-infected adults who are not infected with MTB and should not be used routinely for this purpose in assessing indications for isoniazid preventive therapy.     

Silver-Palladium Thick-Film Conductors

The trends in integrated circuit packaging technology are toward high speed, high density, reliability, and low cost. These demand the improvement of material formulations and processing technology. Among the thick-film materials systems, conductor materials generally represent an important and the most expensive element. Therefore, attention has been centered on the performance of the fired metal film and its cost. Silver and palladium (Ag/Pd) conductors are important components of thick-film paste technology. Thick-film Ag/Pd conductors find applications in many aspects of electronics and electronic packaging, such as hybrid microcircuits, multichip modules, packaging for integrated microcircuits, and in passive electronic components such as multilayer capacitors, varistors, and inductors. In this paper, the performance and properties of fired Ag/Pd films are discussed through their physical and chemical aspects. The final film properties are correlated to a number of factors, including thermodynamics and kinetics of Pd oxidation during burnout and firing; chemical and physical reaction of the Ag/Pd with the ceramic substrate, organic vehicle, and solder; Ag diffusion and migration; inorganic and organic additives; powders characteristics; and paste properties.     

Pulse scattering from a sphere coated with an inhomogeneous sheath

The backscattered waveform produced by a short electromagnetic pulse incident upon a metallic sphere clad with a radially stratified dielectric is considered. Typical results are presented which demonstrate the dependence of the specular and creeping wave returns on the permittivity gradient and thickness of the sheath.