Three-dimensional large-strain tensile deformation of neat and calcium carbonate-filled high-density polyethylene

The large-strain tensile deformation of high-density polyethylene and high-density polyethylene filled with two volume fractions (f) of calcium carbonate particles is studied via an optical method. Digital image correlation is used to determine the local displacement gradients and full-field displacements during uniaxial tension tests on specimens of rectangular cross-section. A novel technique measures simultaneously, with a single camera, the deformation in all three dimensions. Full-field strain contours, macroscopic true stress-true strain behavior, and local volumetric strains are reduced from the raw test data. The true stress-true strain data shows an increase in modulus, but a decrease in yield stress and subsequent strain hardening, with increasing f. These results are strong evidence of particle debonding and are corroborated by an increase in volumetric strain with increasing f.     

The nuclear freeze resolution: A question of empowerment.

The American Psychological Association has done little to empower the nuclear freeze resolution (NFR) adopted in 1982. The general debate on the issues of advocacy, competency, and ethics should be suspended so that the issues associated specifically with the NFR can be resolved. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social Media and Political Change: Capacity,Constraint, and Consequence

This introductory essay highlights the key findings, methodological tool kit, and production process of this Special Issue. We argue that communication researchers are uniquely positioned to analyze the relationships between social media and political change in careful and nuanced ways, in terms of both causes and consequences. Finally, we offer a working definition of social media, based on the diverse and considered uses of the term by the contributors to the collection. Social media consists of (a) the information infrastructure and tools used to produce and distribute content that has individual value but reflects shared values; (b) the content that takes the digital form of personal messages, news, ideas, that becomes cultural products; and (c) the people, organizations, and industries that produce and consume both the tools and the content.     

A candidate recombination modifier gene for Zea mays L

Maize meiotic mutant desynaptic (dy) was tested as a candidate recombination modifier gene because its effect is manifested in prophase I. Recombination rates for desynaptic (dy) and its wild type were compared in two ways: (1) segregation analysis using six linked molecular markers on chromosome 1L and (2) cytogenetic analysis using fluorescence in situ hybridization (FISH)-aided meiotic configurations observed in metaphase I. Chromosome 1L map lengths among the six linked markers were 45-63 cM for five F2 dy/dy plants, significantly lower than the wild-type F2 map distance of 72 cM. Chromosomes 2 and 6 were marked with rDNA FISH probes, and their map lengths were estimated from FISH-adorned meiotic configurations using the expectation-maximization algorithm. Chiasma frequencies for dy/dy plants were significantly reduced for both arms of chromosome 2, for chromosome arm 6L, and for eight unidentified chromosomes. There was a notable exception for the nucleolus-organizing region-bearing arm chromosome arm 6S, where dy increased chiasma frequency. Maize meiotic mutant desynaptic is a recombination modifier gene based on cytogenetic and segregation analyses.     

A gene for autosomal recessive symmetrical spastic cerebral palsy maps to chromosome 2q24-25

Cerebral palsy has an incidence of approximately 1/500 births, although this varies between different ethnic groups. Genetic forms of the disease account for approximately 1%-2% of cases in most countries but contribute a larger proportion in populations with extensive inbreeding. We have clinically characterized consanguineous families with multiple children affected by symmetrical spastic cerebral palsy, to locate recessive genes responsible for this condition. The eight families studied were identified from databases of patients in different regions of the United Kingdom. After ascertainment and clinical assessment, we performed a genomewide search for linkage, using 290 polymorphic DNA markers. In three families, a region of homozygosity at chromosome 2q24-q25 was identified between the markers D2S124 and D2S148. The largest family gave a maximum LOD score of 3.0, by multipoint analysis (HOMOZ). The maximum combined multipoint LOD score for the three families was 5.75. The minimum region of homozygosity is approximately 5 cM between the markers D2S124 and D2S2284. We have shown that a proportion of autosomal recessive symmetrical spastic cerebral palsy maps to chromosome 2q24-25. The identification of genes involved in the etiology of cerebral palsy may lead to improved management of this clinically intractable condition.     

A physical approach to reduce nonspecific adhesion in molecular recognition atomic force microscopy

Atomic force microscopy is one of the few techniques that allow analysis of biological recognition processes at the single-molecule level. A major limitation of this approach is the nonspecific interaction between the force sensor and substrate. We have modeled the nonspecific interaction by looking at the interaction potential between a conical Si3N4 tip with a spherical end face and a mica surface in solution, using DLVO (Derjaguin, Landau, Verwey, Overbeek) theory and numerical calculations. Insertion of the tip-sample potential in a simulation of an approach-retract cycle of the cantilever gives the well-known force-distance curve. Simulating a force-distance curve at low salt concentration predicts a discrete hopping of the tip, caused by thermal fluctuations. This hopping behavior was observed experimentally and gave rise to a novel approach to making measurements in adhesion mode that essentially works in the repulsive regime. The distance between tip and sample will still be small enough to allow spacer-involved specific interactions, and the percentage of nonspecific interactions of the bare tip with the mica is minimized. We have validated this physical model by imaging intercellular adhesion molecule 1 (ICAM-1) antigen with a tip functionalized with anti-ICAM-1 antibody. The measurement demonstrated that a significant decrease in the number of nonspecific interactions was realized, and the topographical image quality and the specific bonding capability of the tip were not affected.     

Characterization of binding properties to human P-glycoprotein: development of a [3H]verapamil radioligand-binding assay

Interaction with the exsorptive transporter P-glycoprotein (P-gp) is a possible source of peculiarities in drug pharmacokinetics, including dose-dependent absorption, drug-drug interactions, intestinal secretion, and limited permeability of the blood-brain barrier. Among the established in vitro methods of the analysis of drug interactions with P-gp, none directly quantifies the affinity of ligands with P-gp. Instead, they measure the result of a membrane permeation and a receptor-binding process; this may lead to difficulties in the interpretation of results. An assay for quantification of drug affinity to the transporter is presented on the basis of the radioligand-binding assay principle. This has the advantage of directly quantifying the interaction between drugs and P-gp. Because of the reversible and competitive interaction of numerous substrates with P-gp, a radioligand-binding assay was developed by taking [3H]verapamil and [3H]vinblastine as radioligands and the human intestinal Caco-2 cells, overexpressed with P-gp by culturing in the presence of vinblastine or transfecting with multidrug resistance gene MDR-1 as receptor preparation. The assay was performed in 96-well plates and has the potential to be used as a high-throughput method. A clear induction of the expression of P-gp was demonstrated in the Caco-2 cells grown in the presence of vinblastine, as well as in the transfected cells, although to a lesser extent. Both radioligands were shown to bind to P-gp. Verapamil was the radioligand of choice for further investigations due to its lower nonspecific binding to the transporter preparation. Kinetics as well as specificity of the binding of verapamil to the P-gp preparation were demonstrated. A two-affinity model was found to adequately describe the data derived from saturation as well as from competition experiments, in accordance with previous findings on two exsorption sites for P-gp. The binding properties of [3H]verapamil and [3H]vinblastine to a P-gp preparation derived from induced Caco-2 cells are described. The concentration-dependent displacement of the radioligand by nonlabeled substrates for P-gp should be a suitable principle for the determination of drug affinity to the respective binding sites at the human intestinal multidrug transporter P-gp.     

Caries and fluorosis prevalence in communities with different concentrations of fluoride in the water

The need to defluoridate and fluoridate the water supplies in areas with drinking water naturally containing above-optimal (>/=2.5 mg/l) and suboptimal (相似文献