Influence of clays on the rheology of cement pastes

The fresh state of concrete is becoming increasingly important in furthering the types of applications of today's construction world. Processing techniques have resulted in technologies such as self-consolidating concrete and depend on the microstructural changes that take place during and immediately after mixing and placing. These changes to the microstructure reflect the flocculation behavior between the particles in suspension. The ability to modify this behavior allows control over the balance among flowability and shape-stability of concrete. This study investigates how clay admixtures affect the microstructure of cement pastes from a rheological stand point. Shear and compressive rheology techniques are used to measure how the solids volume fraction of suspensions with different admixtures evolves with stress. Based on these relationships, the effectiveness of clays on the balance between flowability and shape-stability is measured. Results are consistent with green strength tests performed on concrete mixes derived from the cement paste mixes.     

实验用纳米纤维的电纺丝装置

近些年来,纳米工艺技术领域取得了飞速发展。纳米纤维已被广泛地应用于许多领域,例如,超细物料的过滤介质、保健与保护织物和生物医学等。     

Longitudinal predictors of reading and math trajectories through middle school for African American versus Caucasian students across two samples.

This study's primary purpose was to examine the relative contribution of social-behavioral predictors to reading and math skills. The study expands on Duncan et al.'s (2007) work by using longitudinal methodology from the National Institute of Child Health and Human Development's Study of Child Care and Youth Development (SECCYD) and the Early Childhood Longitudinal Study, Kindergarten Class of 1998–1999 (ECLS-K) databases, and by focusing on potential differences in patterns of early predictors of later reading and math trajectories for African American versus Caucasian students. Predictor measures were selected at kindergarten, and the outcomes included standardized reading and math scores obtained from Grades 1, 3, 5, and 9 for the SECCYD sample, and Grades 3, 5, and 8 for the ECLS-K sample. Consistent with Duncan et al.'s findings, results reflect the relative contributions of early reading and math skills to later functioning in these respective academic domains for both samples, and there are indications for the importance of early expressive language skills to both reading and math in the SECCYD sample. Findings related to the power of social-behavioral predictors, however, are not consistent across samples. Although the SECCYD sample evidenced no such predictors, several interactions in the ECLS-K sample suggested the moderating effects of early ratings of aggressive behaviors and internalizing behaviors on later reading and math for African American students. The moderating effects of early teacher ratings of attention and internalizing behaviors for African American students as compared with Caucasian students in later math growth also were noted. The importance of early social-behavioral functions as related to later academic skills remains an important area of inquiry. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Jurors’ discussions of a defendant’s history of child abuse and alcohol abuse in capital sentencing deliberations.

We tested a novel theoretical model explaining the psychological processes underlying jurors’ discussions about a defendant’s history of child abuse and alcohol abuse in a capital case. We coded the extent to which jurors used child abuse and alcohol abuse as mitigating factors, as aggravating factors, or argued that they should be ignored. Relying on attribution theory, we coded the extent to which jurors rendered controllable or uncontrollable and stable or unstable attributions regarding the defendant’s history of child abuse and alcohol abuse. Jurors were more likely to argue that child abuse and alcohol abuse should not be used as mitigators or to even use them against the defendant as aggravators than they were to use them as mitigators. Jurors made more controllable than uncontrollable attributions regarding child abuse and more stable than unstable attributions regarding both child abuse and alcohol abuse. The more jurors supported the death penalty, the more they argued to discount child abuse and alcohol abuse as mitigators or use them as aggravators and the more controllable and stable attributions they made. Political orientation predicted discussions and attributions about alcohol abuse, but not child abuse. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparisons of organizational constraints and their relations to strains in China and the United States.

Organizational constraints is an important source of job stress. To study the relations between organizational constraints and four indices of job strains in cross-cultural work settings, both self-report and coworker-report data were collected from university employees in two culturally dissimilar countries: China and the United States. As predicted, U.S. university employees reported more interpersonal constraints than did their Chinese counterparts. No country difference was found for job context constraints. Both self-report and coworker-report data revealed significant correlations between organizational constraints and job strains in both countries. Country moderated the relations between interpersonal constraints and negative emotions/job satisfaction/voluntary lateness, with stronger correlations in the United States than in China. Country also moderated the relations between job context constraints and all four indicators of job strains, indicating that U.S. university employees were more sensitive to workplace constraints than were their Chinese counterparts. Suggestions are provided for future research and practice applications. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evaluating worker vibration exposures using self-reported and direct observation estimates of exposure duration

The objective of this study was to compare objective and subjective methods of collecting exposure time data for hand arm vibration (HAV) and whole-body vibration (WBV), and to evaluate the impact of inaccurate exposure times’ on the calculation of the average vibration exposure over an 8 h working day A(8).The study was carried out in the engineering services and maintenance departments of a construction and property management company. Worker exposure time data was collected using three methods, questionnaire surveys, daily worker interviews and 8 h direct workplace observations. Vibration magnitudes (m/s²) were measured for a range of hand tools and vehicles, and daily vibration exposure estimates A(8) were calculated using exposure times observed, reported in interview and self reported in the questionnaire.Results from the study showed that self-reported exposure time estimates from the questionnaire survey were a factor of 9.0 (median value) times greater for HAV and a factor of 6.0 (median value) times greater for WBV when compared with direct observation estimates. Exposure times reported in interview were higher, than those observed, but more reliable than those self reported in the questionnaire; a factor of 2.1 (median value) times greater for HAV and a factor of 1.4 (median value) times greater for WBV. A(8) values calculated using questionnaire exposure times were up to 66% and 75% greater for sources of HAV and WBV respectively when compared to A(8) values calculated using observed exposure times.For the purposes of carrying out a reliable risk assessment, results from this study indicate that direct measurements of worker exposure time are not recommended over questionnaires especially where work is highly variable for example in construction and property management. Worker interviews or direct workplace observation methods were found to be reliable alternative methods for collecting exposure time.     

BRAF Gene and Melanoma: Back to the Future

As widely acknowledged, 40–50% of all melanoma patients harbour an activating BRAF mutation (mostly BRAF V600E). The identification of the RAS–RAF–MEK–ERK (MAP kinase) signalling pathway and its targeting has represented a valuable milestone for the advanced and, more recently, for the completely resected stage III and IV melanoma therapy management. However, despite progress in BRAF-mutant melanoma treatment, the two different approaches approved so far for metastatic disease, immunotherapy and BRAF+MEK inhibitors, allow a 5-year survival of no more than 60%, and most patients relapse during treatment due to acquired mechanisms of resistance. Deep insight into BRAF gene biology is fundamental to describe the acquired resistance mechanisms (primary and secondary) and to understand the molecular pathways that are now being investigated in preclinical and clinical studies with the aim of improving outcomes in BRAF-mutant patients.     

Effects of ultrahigh speed twin screw extrusion on the thermal and mechanical degradation of polystyrene

This article characterizes a novel twin screw extrusion (TSE) process with the capability of rotating at speeds up to 4500 rpm. The resulting extreme high shear rate is expected to result in molecular weight changes due to thermomechanical degradation of the polymeric materials being extruded, polystyrene (PS) in this case. In order to differentiate between mechanical and thermal factors affecting degradation of PS running at ultrahigh speeds and also to evaluate the relative importance of the two mechanisms, PS has been extruded at different screw speeds and different barrel temperatures with corresponding melt temperatures. Viscosity measurements and size exclusion chromatography measurements show the extent of degradation due to mechanical stress as a result of high screw rotational speeds. Furthermore, through analyzing the kinetics of PS depolymerization, the reaction rate and hypothetical apparent temperatures at each screw speed have been calculated. All results support the idea that the mechanical shear stress can be considered as the controlling factor of polymer degradation in ultrahigh speed TSE. POLYM. ENG. SCI., 56:743–751, 2016. © 2016 Society of Plastics Engineers     

Differential Effects of Estrogen and Progestin on Apolipoprotein B100 and B48 Kinetics in Postmenopausal Women

The distinct effects of the estrogen and progestin components of hormonal therapy on the metabolism of apolipoprotein (apo) B‐containing lipoproteins have not been studied. We enrolled eight healthy postmenopausal women in a placebo‐controlled, randomized, double‐blind crossover study. Each subject received placebo, conjugated equine estrogen (CEE, 0.625 mg/day) and CEE plus medroxyprogesterone acetate (MPA, 2.5 mg/day) for 8 weeks in a randomized order, with a 4‐week washout between phases. Main outcomes were the fractional catabolic rate (FCR) and production rate (PR) of apo B100 in triglyceride‐rich lipoproteins (TRL), intermediate‐density lipoproteins (IDL) and low ‐density lipoprotein (LDL) and of apo B48 in TRL. Compared to placebo, CEE increased TRL apo B100 PR (p = 0.04). CEE also increased LDL apo B100 FCR (p = 0.02), but this effect was offset by a significant increase in LDL apo B100 PR (p = 0.04). Adding MPA to CEE negated the CEE effects resulting in no significant changes in TRL apo B100 PR and LDL apo B100 FCR and PR relative to placebo. Relative to placebo, during CEE there was a trend toward a reduction in plasma apo B48 concentrations and PR (p = 0.07 and p = 0.12, respectively). Compared with CEE, CEE + MPA significantly increased TRL apo B48 FCR (p = 0.02) as well as apo B48 PR (p = 0.01), resulting in no significant changes in apo B48 concentration. Estrogen and progestin have independent and opposing effects on the metabolism of the atherogenic apo B100‐ and apo B48‐containing lipoproteins.     

The design process and the ‘crisis’ in the UK information technology industry

The competitive position of UK information technology (IT) manufacturers in the expanding markets for IT equipment is declining. A recent report published by the National Economic Development Council (NEDC)¹ describes the situation facing the UK IT industry as one of ‘crisis’.This paper reports some of the findings of an investigation, conducted by the Design Innovation Group at the Open University, into the role of design in the competitiveness of manufacturers of IT equipment. The approach to design and development of four UK companies is examined in detail. It is argued that the supplier's lack of attention to design for user needs contributes to the ‘crisis’ situation expressed by the NEDC.