Optimization of a Nanoparticle Suspension for Freeze Casting

Poly(acrylic acid) (PAA) dispersant concentration, suspension pH, and Al₂O₃ solids loading effects on PAA adsorption onto Al₂O₃ nanoparticles were studied; the stability and rheology of the Al₂O₃ nanoparticle suspensions were examined. The most desirable suspension conditions were 7.5–9.5 for pH and 2.00–2.25 wt% of Al₂O₃ for the PAA concentration. Electrical double-layer thickness and PAA adsorption layer thickness comparison showed that electrosteric stabilization was dominant. 45.0 vol% Al₂O₃ solids loading can be achieved for freeze casting. The maximum solids loading was predicted to be 50.7 vol%. The freeze-cast sample showed that pre-rest before freezing was critical for achieving desirable microstructures.     

Crossing the line from physical discipline to child abuse: how much is too much?

OBJECTIVE: The aim of this paper was to better differentiate physical discipline, corporal punishment, and physical child abuse based on samples drawn from the United States. METHODOLOGY: The American literature was examined to differentiate these three constructs, first on such dimensions as severity, intention, and child effects; and second on key contextual or environmental factors empirically associated with higher rates of violent behavior in families. Third, normative data on parental spanking frequencies were summarized to better operationalize patterns of physical discipline among abusive and nonabusive parents. RESULTS: Five articles that met selection criteria revealed that abusive parents spanked their children more often than did nonabusive parents. Aggregated data from nonabusive parents were used to compute a continuum or "normal range" of daily spanking frequencies from 0 to 5.73 (M = 2.5) times in 24 hours. CONCLUSION: While further research is needed to address spanking intensity, severity, and context, results of the research suggest that "relative exposure" to spanking may be an additional risk marker for abuse when considered with other known indicators or risk factors.     

Effects of task interdependence on the relationship between helping behavior and group performance.

The authors examine whether task interdependence moderates the relationship between the helping form of organizational citizenship behavior (OCB) and group performance. In a laboratory study, 62 groups with 3 members each completed a card-sequencing activity in which the level of task interdependence among group members was manipulated. Independent evaluators assessed helping by viewing videotapes of the groups' interactions during the sequencing activities. Performance was measured as a combined function of group speed and accuracy. Two prior field studies reported contradictory results regarding the impact of helping on group performance. Results from this study suggest that task interdependence may explain these results, and that the relationship between helping and group performance depends on the level of task interdependence required of group members. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attention training for generalized social anxiety disorder.

Attentional bias toward negative social cues is thought to serve an etiological and/or maintaining role in social anxiety disorder (SAD). The current study tested whether training patients to disengage from negative social cues may ameliorate social anxiety in patients (N = 36) with a primary diagnosis of generalized SAD. Patients were randomly assigned to either an attention training condition (n = 18), in which patients completed a modified dot-probe task designed to facilitate attentional disengagement from disgusted faces, or a control dot-probe task condition (n = 18). As predicted, patients in the attention training condition exhibited significantly greater reductions in social anxiety and trait anxiety, compared with patients in the control condition. At termination, 72% of patients in the active treatment condition, relative to 11% of patients in the control condition, no longer met Diagnostic and Statistical Manual of Mental Disorders (4th ed.) criteria for SAD. At 4-month follow-up, patients in the attention training condition continued to maintain their clinical improvement, and diagnostic differences across conditions were also maintained. Results support attention-based models of anxiety and suggest that attention training is a promising alternative or complementary intervention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of polymer coatings on proton transverse relaxivities of aqueous suspensions of magnetic nanoparticles

Iron oxide magnetic nanoparticles are good candidates for magnetic resonance imaging (MRI) contrast agents due to their high magnetic susceptibilities. Here we investigate 19 polyether-coated magnetite nanoparticle systems comprising three series. All systems were synthesized from the same batch of magnetite nanoparticles. A different polyether was used for each series. Each series comprised systems with systematically varied polyether loadings per particle. A highly significant (p < 0.0001) linear correlation (r = 0.956) was found between the proton relaxivity and the intensity-weighted average diameter measured by dynamic light scattering in the 19 particle systems studied. The intensity-weighted average diameter measured by dynamic light scattering is sensitive to small number fractions of larger particles/aggregates. We conclude that the primary effect leading to differences in proton relaxivity between systems arises from the small degree of aggregation within the samples, which appears to be determined by the nature of the polymer and, for one system, the degree of polymer loading of the particles. For the polyether coatings used in this study, any changes in relaxivity from differences in water exclusion or diffusion rates caused by the polymer are minor in comparison with the changes in relaxivity resulting from variations in the degree of aggregation.     

Optimization of SiGe HBTs for operation at high current densities

A comprehensive investigation of the impact of Ge profile shape as well as the scaling of collector and base doping profiles on high-injection heterojunction barrier effects in SiGe HBTs has been conducted over the -73-85°C temperature range. The onset of Kirk effect at high current densities is shown to expose the Si/SiGe heterojunction in the collector-base space charge region, thereby inducing a conduction band barrier which negatively impacts the collector and base currents as well as the dynamic response, leading to a premature roll-off in both β and f_T. In light of this, careful profile optimization is critical for emerging SiGe HBT circuit applications, since they typically operate at high current densities to realize maximum performance. We first explore the experimental consequences and electrical signature of these barrier effects over the 200-358 K temperature range for a variety of Ge profiles from an advanced UHV/CVD SiGe HBT technology. We then use extensive simulations which were calibrated to measured results to explore the sensitivity of these barrier effects to both the Ge profile shape and collector profile design, and hence investigate the optimum profile design points as a function of vertical scaling     

简单MP3播放器

曾几何时,MP3播放器似乎需要一个软件工程专业的博士才能进行简单的歌曲下载和播放。然而,目前MP3播放器市场出现了一个新的趋势——外形小巧、功能简单的MP3正大行其道。这些播放器具有播放、暂停、跳过、重复、保持以及音量控制等操作功能。这些简单的MP3播放器绝大多数采用的是闪存芯片,而不是复杂播放器内使用的微型硬盘。本文中提到的设计是以Microchip的8位单片机(MCU)—PIC18F4550为核心进行的。该MCU具有一个集成的USB2.0接口,32KB的程序存储器和一个灵活的振荡器。该振荡器可以使MP3播放器平时工作在低速、低电流的模式…     

The incremental validity of the MMPI-2: When does therapist access not enhance treatment outcome?

The present study examined whether therapist access to the Minnesota Multiphasic Personality Inventory (MMPI-2) predicted favorable treatment outcome, above and beyond other assessment measures. A manipulated assessment design was used, in which patients were randomly assigned either to a group in which therapists had access to their MMPI-2 data or to a group without therapist access to such information. Illness severity, improvement ratings, number of sessions attended, and premature termination were indicators of therapy outcome. Results indicated that therapist access to the MMPI-2 data did not add to the prediction of positive treatment outcome beyond that predicted by other measures in this setting. Findings from this initial study suggest that, compared with other resources, perhaps in clinical settings with an emphasis on diagnosis-based and evidence-based treatment, the MMPI-2 may not provide incrementally valid information. However, these effects warrant replication across different settings and samples. Guidelines for future studies are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of arbitration program characteristics on applicants' intentions toward potential employers.

The authors examined intentions toward prospective employers with different alternative dispute resolution (ADR) policies and no ADR policy. In Study 1, students (N?=?124) were randomly assigned to 1 of 4 conditions in which 2 variables, arbitration policy presence or absence and firm desirability, were manipulated. The presence of a voluntary, nonbinding arbitration policy had no impact on intentions and did not interact with firm desirability. In Study 2, students (N?=?273) were randomly assigned to 1 of 8 conditions (mandatory vs. voluntary arbitration, binding vs. nonbinding arbitration, and highly desirable vs. less desirable employer). Both mandatory and binding arbitration policies were related to less favorable intentions toward firms. Predictions regarding the interaction of ADR policy and firm desirability were partially supported. Some support was found for the interaction between ADR policy and ethnicity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)