Evaluation and prediction of the effects of melt‐processing conditions on the degree of mixing in alumina/poly(ethylene terephthalate) nanocomposites

Alumina/poly(ethylene terephthalate) nanocomposites were prepared by melt compounding with a twin‐screw extruder. The melt temperature, screw rotation speed, and feed rate were selected as important processing parameters, and their effects on the degree of mixing were studied with full‐factorial, two‐level experimental design. To quantitatively assess the effects of the processing parameters, the degree of mixing of the nanocomposites was evaluated by the skewness of the quadrat method based on the number of particles in transmission electron microscopy images. The screw speed was found to be the most important processing parameter controlling the degree of mixing under the conditions in this investigation. The specific energy input (SEI), related to the shear intensity, was found to correlate closely to the degree of mixing. The degree of mixing improved with increased SEI up to a limiting value, termed the critical SEI, indicating that there may be a critical value required for the optimum dispersion of a given system. A modeling approach was proposed to determine the critical SEI needed for complete mixing. Initial results showed that the critical SEI predicted by this model was within a factor of 3.5 of that obtained experimentally, demonstrating the utility of this approach for the dispersion of nanofillers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Theoretical Assessment of Increased Tensile Strength of Fibrous Soil Undergoing Desiccation

Soil reinforcement with discrete fibers is a viable technique to reduce desiccation cracking in compacted clay soils. The reduction in cracking is attributed to an increase in the tensile strength of the fiber-soil composite. A theoretical model is developed to describe the mechanism of the increased tensile strength due to fiber inclusion of soil undergoing desiccation. The model includes a distinctive effective stress combination acting on the fiber strings due to the generated matric suction by desiccation. Model formulation makes use of Mohr-Coulomb failure criterion at the interface area between fibers and the surrounding soil. The desiccation process of the soil generates matric suction within the soil mass, under given stress condition. The basic elements used in the model formulation include soil-water characteristic curve, Mohr-Coulomb parameters, and unsaturated soil parameters. Fiber inclusion increases significantly the tensile strength of the fiber-soil composite. This increase in tensile strength is expressed as a function of fiber content and soil-water content in this paper. Comparisons are made to published data regarding changes in tensile strength with variable water content.     

The differentiation of semantic dementia and frontal lobe dementia (temporal and frontal variants of frontotemporal dementia) from early Alzheimer's disease: A comparative neuropsychological study.

The authors compared age-matched groups of patients with the frontal and temporal lobe variants of frontotemporal dementia (FTD; dementia of frontal type [DFT] and semantic dementia), early Alzheimer's disease (AD), and normal controls (n?=?9 per group) on a comprehensive neuropsychological battery. A distinct profile emerged for each group: Those with AD showed a severe deficit in episodic memory with more subtle, but significant, impairments in semantic memory and visuospatial skills; patients with semantic dementia showed the previously documented picture of isolated, but profound, semantic memory breakdown with anomia and surface dyslexia but were indistinguishable from the AD group on a test of story recall; and the DFT group were the least impaired and showed mild deficits in episodic memory and verbal fluency but normal semantic memory. The frontal and temporal presentations of FTD are clearly separable from each other and from early AD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Developing A Motivational Freshman Course In Using The Principle Of Attached Learning*

This paper describes the development of a new, team-taught, interdisciplinary, design-oriented, introduction to engineering course that plays a role in the retention efforts of the engineering programs at our university. While the primary purpose of the new course has not changed from its original purpose, i.e., to introduce students to engineering as a field of study, the goals have been expanded to include motivating experiences to increase student retention. We discuss the rationale for the new course, the topics selected for the syllabus, the “attached learning” strategy that was developed for the selection of course materials, the teaching strategies selected for the course, the results of the assessment of student satisfaction, and the impact of the course on the curriculum and on minority and under represented groups.     

Friction‐induced two‐dimensional solid films from lubricant additives

Tribochemical interactions between some lubricant additives, namely zinc dithiophosphate (ZnDTP), an antiwear additive, molybdenum dithiocarbamate (MoDTC), a friction modifier, and overbased calcium borate (OCaB) detergent, have been investigated. The nature of the tribofilms formed was studied by combining high‐resolution transmission electron microscopy of wear fragments and inside wear scars with micro‐spot X‐ray photoelectron spectroscopy at the same location of the wear track (‘dual’ analysis). The OCaB/ZnDTP/MoDTC ternary system provides both a low wear rate and ultralow friction, while adding detergent and anti‐corrosion properties to the formulation. The analytical data indicate that such a synergistic effect can be attributed to an outstanding feature of the tribofilm nanostructure: it is composed of perfectly oriented MoS₂ single sheets embedded in a single‐phase calcium and zinc borophosphate glass. Compared to phosphate alone, MoS₂ sheets are oriented by the borophosphate phase. This could be related to a template effect of friction‐aligned planar molecules of the glassy borate polymer.     

Acylierung von Heterocyclen mit Kohlensäurederivaten. II. Endo- und exo-Carbamoylierung von 2-Amino-benzimidazol-Derivaten mit Isocyanaten. Mechanismus der Acylgruppenwanderung

Acylation of Heterocycles with Carbonic Acid Derivatives. II. Endo and Exo Carbamoylation of 2-Amino-benzimidazole Derivatives with Isocyanates. Mechanism of the Acyl Group Migration 2-Amino-benzimidazoles react with isocyanates with good yields to give 2-amino-1-carbamoyl-aminobenzimidazoles 1 at −30°C and the corresponding 2-carbamoyl isomeres 2 at room temperature, respectively. The isomerization mechanism was studied by crossover experiments and kinetic measurements and has been found to consist of inter- and monomolecular acyl transfer.     

Red meats: Time for a paradigm shift in dietary advice

Recent evidence suggests dietary advice to limit red meat is unnecessarily restrictive and may have unintended health consequences. As nutrient-rich high quality protein foods, red meats can play an important role in helping people meet their essential nutrient needs. Yet dietary advice to limit red meat remains standard in many developed countries, even though red meat intakes appear to be within current guidelines. Meanwhile, energy intakes from processed foods have increased dramatically at the expense of nutrient-rich foods, such as red meat. Research suggests these food trends are associated with the growing burden of obesity and associated diseases in recent decades. It is time for dietary advice that emphasizes the value of unprocessed red meat as part of a healthy balanced diet.     

Safe babies: a qualitative analysis of the determinants of postpartum smoke-free and relapse states

This qualitative study explores smoking cessation during pregnancy and the factors that contribute to remaining smoke-free and relapsing. Ninety-four women attending prenatal clinics in central North Carolina who had quit smoking before 30 weeks gestation were enrolled in an observational study that included a face-to-face interview at 4 months postpartum. Results were analyzed for common themes in the two groups: those who remained smoke-free and those who had relapsed. Fetal health motivated pregnant women to quit smoking, while stress, socializing with smokers, cravings, and easy access to cigarettes tempted women to smoke. Women who remained smoke-free postpartum overcame temptations by continuing to acknowledge the health benefits of not smoking and having a strong internal belief system, significant social support, negative experiences with renewed exposure to cigarettes, and concrete strategies for dealing with temptations. For women who relapsed postpartum, factors having the greatest influence on relapse included easy access to cigarettes, lack of social and financial support, insufficient resources for coping with the challenges of childrearing, physical addiction, reliance on cigarettes as a primary form of stress management, and feelings of regret, shame, or low self-esteem. Recommendations for relapse prevention include assessing women who quit during pregnancy for low or high risk of relapse and offering comprehensive interventions and case management for those at higher risk to address the physical, mental, behavioral, and social contexts leading to relapse.