Water vapor transport in liquid crystalline and non-liquid crystalline epoxies

This paper presents a comparison of moisture permeation in liquid crystalline and non-liquid crystalline epoxy systems. The permeability is obtained using a dynamic method. It is found that diffusion in both epoxy systems is Fickian. The liquid crystalline epoxy network exhibits higher barrier properties to moisture transport than the conventional epoxy network. The efficient chain packing of the smectic mesophase of the liquid crystalline epoxy is the main factor for this difference. The stoichiometry has a large effect on the moisture permeation. The diffusion coefficient decreases monotonically with increasing amine/epoxide functional ratio. The permeability (P) and solubility coefficient (S) reach a minimum for a functional ratio of one. The results are described on the basis of hydrogen bonding of water to the epoxy network and the two phase morphology of cured epoxies.     

Overt Anger in Response to Victimization: Attributional Style and Organizational Norms as Moderators.

Prior theory and research suggests a positive relation between perceived victimization and overt anger. The authors proposed and tested a theoretical extension of this link by investigating possible moderating effects of individual and contextual variables. A sample of 158 employees of a municipality was used to test hypotheses that the relationship between perceived victimization and overt anger is moderated by hostile attributional style and perceptions of organizational norms. The results showed that the relation between perceptions of direct victimization and overt anger was stronger when the employee had a more rather than less hostile attributional style and when the employee perceived the organizational norms as more rather than less oppositional. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Analyzing Nonindependent Outcomes in Couple Therapy Using the Actor-Partner Interdependence Model.

The nonindependent components of couple data require data-analytic strategies tailored to the interpersonal processes occurring between relationship partners. This article examines the benefits of a specifically dyadic analytic method, the actor-partner interdependence model (APIM), for evaluating interpartner influence across time. Both conceptual and methodological features of the APIM are exemplified by applying this model to observations of negative and positive affect and global distress in spouses participating in a randomized trial of couple therapy. In addition to elucidating specific advantages of the APIM relative to alternative data-analytic strategies, the current results shed new light on previous findings from a comparative treatment outcome study evaluating behavioral and insight-oriented approaches to couple therapy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neurocognitive signs in prodromal Huntington disease.

Objective: PREDICT-HD is a large-scale international study of people with the Huntington disease (HD) CAG-repeat expansion who are not yet diagnosed with HD. The objective of this study was to determine the stage in the HD prodrome at which cognitive differences from CAG-normal controls can be reliably detected. Method: For each of 738 HD CAG-expanded participants, we computed estimated years to clinical diagnosis and probability of diagnosis in 5 years based on age and CAG-repeat expansion number (Langbehn, Brinkman, Falush, Paulsen, & Hayden, 2004). We then stratified the sample into groups: NEAR, estimated to be ≤9 years; MID, between 9 and 15 years; and FAR, ≥15 years. The control sample included 168 CAG-normal participants. Nineteen cognitive tasks were used to assess attention, working memory, psychomotor functions, episodic memory, language, recognition of facial emotion, sensory–perceptual functions, and executive functions. Results: Compared with the controls, the NEAR group showed significantly poorer performance on nearly all of the cognitive tests and the MID group on about half of the cognitive tests (p = .05, Cohen's d NEAR as large as ?1.17, MID as large as ?0.61). One test even revealed significantly poorer performance in the FAR group (Cohen's d = ?0.26). Individual tasks accounted for 0.2% to 9.7% of the variance in estimated proximity to diagnosis. Overall, the cognitive battery accounted for 34% of the variance; in comparison, the Unified Huntington's Disease Rating Scale motor score accounted for 11.7%. Conclusions: Neurocognitive tests are robust clinical indicators of the disease process prior to reaching criteria for motor diagnosis of HD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Strong, low density, hexylene- and phenylene-bridged polysilsesquioxane aerogel–polycyanoacrylate composites

Nanocomposite aerogels were prepared by chemical vapor deposition and polymerization of cyanoacrylate on the surface of bridged polysilsesquioxane aerogels. Phenylene- and hexylene-bridged aerogels were prepared by sol–gel polymerizations and supercritical carbon dioxide drying. Hydrophobic organic bridging groups in the polysilsesquioxane aerogels reduced the amount of adsorbed water available for initiating polymerizations and led to higher molecular weight polycyanoacrylate than was observed with silica aerogels. Densities increased as much as 65% due to the addition of the organic polymer, but the nanocomposite aerogels remained highly porous with surface areas between 440 and 750 m²/g. Polycyanoacrylate–phenylene-bridged aerogel composites were the strongest with flexural strengths up to 780 kPa or 16-fold stronger than the untreated phenylene-bridged aerogels and fivefold stronger than a silica aerogel of the same density. The strongest polycyanoacrylate–hexylene-bridged aerogel composites had flexural strength of 285 kPa or ninefold stronger than the untreated hexylene-bridged aerogels and twice as strong as a silica aerogel of comparable density. The greater strength of the new composites is, in part, due to the greater strength of the bridged aerogels. However, higher molecular weight polycyanoacrylate, due to less surface water on the hydrophobic bridged aerogels, also contributes to the greater nanocomposite strengths.     

Thermal management of power electronics modules packaged by a stacked-plate technique

The research presented in this paper is part of a multidisciplinary research program of the Center for Power Electronics Systems at Virginia Tech. The program supported by the Office of Naval Research focuses on the development of innovative technologies for packaging power electronics building blocks. The primary objective of this research is to improve package performance and reliability through thermal management, i.e., reducing device temperatures for a given power level. The task of thermal management involves considering trade-offs in the electrical design, package layout and geometry, materials selection and processing, manufacturing feasibility, and production cost. Based on the electrical design of a simple building block, samples of packaged modules, rated at 600 V and 3.3 kW, were fabricated using a stacked-plate technique, termed metal posts interconnected parallel plate structure (MPIPPS). The MPIPPS technique allows the power devices to be interconnected between two direct-bond copper substrates via the use of metal posts. Thermal modeling results on the MPIPPS packaged modules indicate that the new packaging technique offers a superior thermal management means for packaging power electronics modules.     

Computer focused communication: changes and challenges for the contemporary organization

Many changes in organizations are based on communication developments, the most prevalent of which currently is the expanding nature of electronic communication media. The use of electronic communications leads to changes in other areas. Manager and employee relationships rely on organizational structure, type of technology, group work and task, and employee empowerment and organizational attitude. This paper explores the communication changes by comparing components of the traditional, hierarchical organization with the modern, spherical or flat organization. A synthesis of the literature concerning this topic is presented. From this, a survey instrument was developed, and a pretest was run. The information presented here gives managers certain insights about the impact of new communication technologies on the evolving modern organization. ©     

A FLAVOUR MODEL FOR BEER FERMENTATION

A new beer fermentation model is developed based upon fundamental knowledge of biochemical pathways. The model can be subdivided into a growth model, an amino acid model, and a flavour/aroma model. Experimentation allowed for accurate model parameter identification. The results demonstrate the capability to accurately describe batch beer fermentation dynamics.     

A generalist herbivore in a specialist mode Metabolic,sequestrative, and defensive consequences

Adults of a generalist herbivore, the lubber grasshopper,Romalea guttata, can be converted to functional specialists by feeding them exclusively on catnip,Nepeta cataria. No obvious adverse effects on adult development resulted from this enforced monophagy. Notwithstanding the fact thatR. guttata has had no coevolutionary relationship with this Eurasian mint, it readily sequesters compounds that are identical to or derived from the terpenoid lactones that are characteristic ofN. cataria. R. guttata appears to both biomagnify minor allelochemicals and to sequester metabolites of theNepeta terpenes in its paired defensive glands. The levels of autogenously produced phenolics are not affected by feeding onN. cataria and the defensive secretions of catnip-fed grasshoppers are more repellent to ants than those of wild-fed acridids. Metabolites of theN. cataria monoterpenes are sequestered in the defensive glands when catnip is added to the natural diet ofR. guttata. The ability of a generalist,R. guttata, to facilely bioaccumulate a potpourri of foreign allelochemicals when feeding in a specialist mode is analyzed in terms of its biochemical, physiological, and functional significance. Sequestration is examined as a response to the enteric effronteries represented by the phytochemicals that can be characteristic of the overload in a monophagous diet.