Tensile testing and fracture mechanism analysis of polyvinyl alcohol nanofibrous webs

A tensile properties testing study was conducted to understand the influence of thickness, cross-head speed (speed of testing), gauge length (GL; specimen test length), and sample shape on important tensile properties of polyvinyl alcohol (PVA) nanofiber webs. The effects of each testing parameter on load at break, extension at break, Young's modulus, and tensile stress–strain curve of PVA nanofiber webs are analyzed. The Welch two sample t-tests show the significant difference among tested data. Using interaction plots, two-way analysis of variance, and margin mean plots, the interaction effects among testing parameters have been analyzed. Of all the factors, cross-head speed, the interaction among GL, and sample thickness (GL: Thickness) and the interaction among GL, testing speed and sample thickness (GL: Speed: Thickness) have significant influence on the tensile properties of PVA nanofiber webs. Moreover, the hypothesized model of mechanism of tensile strain–stress curve of PVA nanofiber webs has been proposed. Based on the model, the tensile strain–stress curve can be split into three stages: linear elastic, partial break up, and complete breakage. This study will provide a better understanding of tensile testing parameters' effects and their interaction effects on the tensile properties of nanowebs.     

Analysis of multilayered dielectric waveguides: variationaltreatment

A fast and near exact modal analysis is presented to obtain the propagation constants and electric field profiles for dielectric multilayered channel (rib) waveguides. Calculations are performed for a particular channel configuration and found to be in excellent agreement with those obtained using the finite difference method     

Perceived consequences of risky behaviors: Adults and adolescents.

Adult and adolescent Ss were asked to list possible consequences of either accepting or declining opportunities to engage in various potentially risky behaviors (e.g., drinking and driving, skipping school to go to a mall). Response patterns were quite similar for these adults and adolescents, indicating shared beliefs about the possibilities. Although taking and avoiding a risk are logically complementary actions, they did not prove to be psychologically complementary. Other comparisons showed systematic differences in the consequences produced for 1-time and regular (or repeated) versions of the same behaviors, as well as open-ended and closed-ended response modes. These results are discussed in terms of their methodological implications for studying risk perceptions, their practical implications for influencing adolescents' risk behaviors, and their theoretical implications for understanding intellectual development. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparing the effectiveness of process-experiential with cognitive-behavioral psychotherapy in the treatment of depression.

This study compared process-experiential and cognitive-behavioral psychotherapy in the treatment of major depression in a researcher allegiance-balanced randomized clinical trial. Sixty-six clients participated in weekly sessions of psychotherapy for 16 weeks. Clients' level of depression, self-esteem, general symptom distress, and dysfunctional attitudes significantly improved in both therapy groups. Clients in both groups showed significantly lower levels of reactive and suppressive coping strategies and higher reflective coping at the end of treatment. Although outcomes were generally equivalent for the 2 treatments, there was a significantly greater decrease in clients' self-reports of their interpersonal problems in process-experiential than cognitive-behavioral therapy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Lipoprotein(a) as a risk predictor for cardiac mortality in patients with acute coronary syndromes

AIMS: Raised lipoprotein(a) concentrations are considered to be a risk factor for atherothrombotic diseases. We examined whether baseline concentrations were a risk factor for an adverse outcome in patients admitted with acute coronary syndromes. METHODS AND RESULTS: Five hundred and nineteen patients admitted with suspected acute coronary syndromes were studied and followed prospectively for a median of 3 years. The prognostic significance of a baseline lipoprotein(a) concentration of > or = 30 mg x dl(-1) or lower for subsequent cardiac death was assessed in patients with myocardial infarction (266) and unstable angina (197) and compared with other variables in regression models. In patients with myocardial infarction, a baseline lipoprotein(a) concentration of > or =30 mg x dl(-1) was associated with a 62% increase in subsequent cardiac death compared to the lower concentration group (29.8% vs 18.6%, Log rank P=0.04). In a multivariate regression model a baseline lipoprotein(a) concentration of > or = 30 mg x dl(-1) retained its significance as an independent predictor of cardiac death (P=0.037). In patients with unstable angina, baseline concentrations of > or = 7.9 mg x dl(-1) were found to be significant predictors of cardiac death in univariate (P=0.021) and multivariate (P=0.035) regression models. CONCLUSION: Baseline lipoprotein(a) concentrations in patients admitted with acute coronary syndromes are associated with an increased risk of cardiac death. For patients with myocardial infarction a concentration of > or = 30 mg x dl(-1) appears appropriate as a risk discriminator; for patients admitted with unstable angina, however, much lower concentrations of lipoprotein(a) appear to be prognostically important.     

Empirically supported psychological therapies.

This article introduces the special section of the Journal of Consulting and Clinical Psychology on empirically supported psychological therapies. After a discussion of the rationale for the selection of the specific terms in the label, several justifications are considered for conducting and learning from empirical evaluations of psychological therapies. Finally, the process that guided the special section is described. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Secondary Metabolic Profile as a Tool for Distinction and Characterization of Cultivars of Black Pepper (Piper nigrum L.) Cultivated in Pará State,Brazil

This study evaluated the chemical compositions of the leaves and fruits of eight black pepper cultivars cultivated in Pará State (Amazon, Brazil). Hydrodistillation and gas chromatography–mass spectrometry were employed to extract and analyze the volatile compounds, respectively. Sesquiterpene hydrocarbons were predominant (58.5–90.9%) in the cultivars “Cingapura”, “Equador”, “Guajarina”, “Iaçará”, and “Kottanadan”, and “Bragantina”, “Clonada”, and “Uthirankota” displayed oxygenated sesquiterpenoids (50.6–75.0%). The multivariate statistical analysis applied using volatile composition grouped the samples into four groups: γ-Elemene, curzerene, and δ-elemene (“Equador”/“Guajarina”, I); δ-elemene (“Iaçará”/“Kottanadan”/“Cingapura”, II); elemol (“Clonada”/“Uthirankota”, III) and α-muurolol, bicyclogermacrene, and cubebol (“Bragantina”, IV). The major compounds in all fruit samples were monoterpene hydrocarbons such as α-pinene, β-pinene, and limonene. Among the cultivar leaves, phenolics content (44.75–140.53 mg GAE·g⁻¹ FW), the enzymatic activity of phenylalanine-ammonia lyase (20.19–57.22 µU·mL⁻¹), and carotenoids (0.21–2.31 µg·mL⁻¹) displayed significant variations. Due to black pepper’s susceptibility to Fusarium infection, a molecular docking analysis was carried out on Fusarium protein targets using each cultivar’s volatile components. F. oxysporum endoglucanase was identified as the preferential protein target of the compounds. These results can be used to identify chemical markers related to the susceptibility degree of black pepper cultivars to plant diseases prevalent in Pará State.     

Aliphatic heterocyclic polymers

Aliphatic polybenzoxazoles, polybenzothiazoles, and polybenzimidazoles have been prepared by three methods: in poly(phosphoric acid), by the polyamide precursor, and by melt polymerization. The melt polymerization method was found to be the most satisfactory. All of the aliphatic heterocyclic polymers had excellent thermal stability, resistance to alkaline hydrolysis, high glass transition temperatures, and a high degree of flexibility. The only class of polymer found having any degree of solubility, however, was the polybenzimidazoles. Aliphatic polybenzimidazole films were prepared by solution casting. These films were found to be extremely flexible at ambient and cryogenic temperatures. The films were unaffected by alkaline hydrolysis, even in an oxidizing medium. A molding prepared from the aliphatic polybenzimidazole had excellent physical properties at both cryogenic and room temperature.     

On tool wear and its effect on machined surface integrity

This paper presents the results of an investigation of induced residual stress, induced strain, and induced subsurface energy in machined surfaces due to the machining process. The influence of tool wear on residual stress, strain, and energy is also reported. The exact elasticity solution for a split ring was extended and used to calculate the residual stress in the machined surface by using ring dimension changes caused by the electrochemical removal of a thin layer of residually stressed surface. The strain distribution beneath the machined surface was determined by using the grid technique. The subsurface energy stored in the machined surface was then obtained from the data of residual stress and strain. For the materials studied, this investigation showed that such energy could not be neglected when establishing the total energy needed for machining a unit volume of material. Tool coatings having different surface roughness and tools having various magnitudes of flank wear were investigated. The experimental results show that tool wear is a dominant factor affecting the values of induced residual stress, strain, subsurface energy, and the quality of the machined surface. The increase of tool wear caused an increase of residual stress and strain beneath the machined surface. It was also found that the overall energy stored in the machined subsurface increases as the tool wear increases and as the tool surface gets rougher. When the cutting tool is severely worn, the machined surface not only becomes very rough, but also contains many partially fractured laps or cracks. This makes tool wear a key factor in controlling the quality of the machined surface.