Toward efficient binders for Li-ion battery Si-based anodes: polyacrylic acid

Si-based Li-ion battery anodes offer specific capacity an order of magnitude beyond that of conventional graphite. However, the formation of stable Si anodes is a challenge because of significant volume changes occurring during their electrochemical alloying and dealloying with Li. Binder selection and optimization may allow significant improvements in the stability of Si-based anodes. Most studies of Si anodes have involved the use of carboxymethylcellulose (CMC) and poly(vinylidene fluoride) (PVDF) binders. Herein, we show for the first time that pure poly(acrylic acid) (PAA), possessing certain mechanical properties comparable to those of CMC but containing a higher concentration of carboxylic functional groups, may offer superior performance as a binder for Si anodes. We further show the positive impact of carbon coating on the stability of the anode. The carbon-coated Si nanopowder anodes, tested between 0.01 and 1 V vs Li/Li+ and containing as little as 15 wt % of PAA, showed excellent stability during the first hundred cycles. The results obtained open new avenues to explore a novel series of binders from the polyvinyl acids (PVA) family.     

Following the trail of the focus in time-limited psychotherapy.

Studied 47 short-term psychotherapy cases (aged 18–33 yrs) from a college counseling center that followed the evolution of the focus from the patient's presenting problem, through the formulation of the focus during the consultation, to the stated focus at termination. Findings suggest that the presenting complaint was not the same as the consultation or the termination focus and that the consultation focus was not the same as the termination focus. The longer the time-limited therapy progressed, the more likely it was that the focus was revised between the time of the initial consultation and termination. Clinical examples of these findings are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Issues in the delivery of psychological services in rural school settings.

Presents an overview of the barriers associated with the effective delivery of school psychological services in rural areas, including transportation and accessibility, social-cultural, and professional problems. Based on a review of the relevant literature in special education and community, clinical, and school psychology, strategies for overcoming each of these barriers are offered. Some of the advantages of practicing school psychology in a rural setting are discussed. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Electromagnetically coupled microstrip dipoles

A new class of printed circuit radiator consisting of a microstrip dipole electromagnetically coupled to a microstrip feed line is described. Several configurations which differ in bandwidth, efficiency, and construction simplicity are presented. A geometry which has been found to be optimum for many applications is noted. Radiation characteristics of both isolated elements and arrays of elements are examined. Experimental and theoretical results are presented.     

An improved element for use in array antennas

An antenna element consisting of a slot plus two parasitically excited wires has been found to exhibit many properties useful in array applications. The introduction of the wires provides a means of controlling both theE- andH-plane element radiation patterns. Specifically, the principal plane radiation patterns can be equalized and the directivity increased. If desired, the element pattern can closely approximate acos thetapattern in both planes. A 14-dB reduction in interelement mutual coupling is also achievable with this source as compared to a slot alone. A comparison of the characteristics of a four-quadrant 60-slot monopulse array with and without the wire elements indicates a 0.6-dB increase in gain and a significant reduction in back radiation for the former.     

Application of finite element methods to thermohydrodynamic lubrication

A finite element formulation is presented for the equations governing the steady thermohydrodynamic behaviour of liquid lubricated bearings. This formulation permits application of the iterative solution scheme to bearings of arbitrary geometry. A generalized Reynolds equation resulting from the combination of the mass and momentum conservation equations is cast into variational form and used to derive general finite element equations. The method of weighted residuals with Galerkin's criterion is used to generate finite element matrix equations for the thermal energy equation. In addition to the finite element formulation, a discussion of appropriate finite difference techniques is also given for problems without complex geometry. As an example, the formulations are applied to obtain numerical solutions for a three-dimensional sector thrust bearing operating in the thermohydrodynamic regime. Pressure, velocity and temperature distributions are give, and the thermohydrodynamic solutions are compared with the results of classical isothermal theory.     

The effects of HIV-related thought suppression on risk behavior: Cognitive escape in men who have sex with men.

This study investigated the relationship between suppressing thoughts about HIV risk and several outcomes related to HIV risk, including sexual risk behavior and HIV prevention service use, in men who have sex with men (MSM). Synthesizing the ironic processing theory (D. M. Wegner, 1994) with a cognitive escape paradigm (D. J. McKiman, D. G. Ostrow, & B. Hope, 1996), it was hypothesized that thought suppression might increase risk by leading MSM to "escape" from sexual safety norms and engage in risky sex behaviors and, via a paradoxical process, increase future use of community prevention services. Results from a sample of MSM (N = 709) indicated that thought suppression was positively related to concurrent sexual risk behavior and to future use of prevention services. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Highly Textured BaTiO3 via Templated Grain Growth and Resulting Polarization Reversal Dynamics

Samples of bulk textured polycrystalline BaTiO₃ ceramics were fabricated using a templated grain growth (TGG) approach in order to investigate effects of polycrystallinity and texture related to ferroelectric domain reversal under high‐power drive conditions. Barium titanate platelets were formed via two‐step topochemical conversion of bismuth titanate platelets grown via molten salt synthesis, then aligned via tape casting within a matrix of fine BaTiO₃ powder. The coarse‐grained parts showed a high degree of crystallographic texture after sintering. Combined with ceramics of similar density and polycrystallinity, but random orientation and commercial single‐crystal specimens, this sample set enabled direct isolation of crystallographic texture and polycrystallinity as the primary variables for high‐power polarization reversal studies. These studies have also demonstrated a link between grain size and polarization reversal time that strongly suggests that grain boundaries serve effectively as nucleation sites during the ferroelectric switching process.     

Composite PTCR thermistors utilizing conducting borides,silicides, and carbide powders

Ceramic-polymer composite thermistors using conducting boride, silicide, and carbide powders that include TiB₂, ZrB₂, NbB₂, NbSi₂, WSi₂, MoSi₂, and TiC have been fabricated. Percolation and subsequent PTCR effects were observed for all the powders in both semi-crystalline (polyethylene) and amorphous (epoxy) polymer matrix materials, however, as found for carbon black and metal fillers, both niobate powders did not exhibit a PTCR effect in the amorphous polymer. Results indicate that percolation and PTCR behaviour are related to the powder characteristics (size/distribution), composite microstructure and ceramic-polymer interface.Composite thermistors with room temperature resistivities as low as 1 cm and a nine-order of magnitude change () at 1 kHz (12 at d.c.) were achieved.     

Opsonophagocytic assay as a potentially useful tool for assessing safety of enterococcal preparations

Enterococci are commonly used in foods and food additives. A number of putative virulence factors are usually evaluated to assure that the strains used are not harmful. We propose an additional test to assess the safety of these bacteria by testing the susceptibility to opsonophagocytic killing. One probiotic Enterococcus faecalis strain was compared to a collection of 27 clinical isolates and our results indicate that 89% of the clinical strains were less susceptible to killing mediated by normal rabbit sera. Opsonophagocytic killing is the best in vitro surrogate for a protective immune response against bacteria, and the susceptibility of bacteria against normal rabbit sera indicates that these strains may not be able to survive in the bloodstream of the host. Further studies comparing a larger collection of pathogenic strains with commensal isolates are necessary to confirm these findings.