Listening to Radiation Damage In Situ: Passive and Active Acoustic Techniques

JOM - Knowing when, why, and how materials evolve, degrade, or fail in radiation environments is pivotal to a wide range of fields from semiconductor processing to advanced nuclear reactor design....     

Non‐natural Peptide Triazole Antagonists of HIV‐1 Envelope gp120

We investigated the derivation of non‐natural peptide triazole dual receptor site antagonists of HIV‐1 Env gp120 to establish a pathway for developing peptidomimetic antiviral agents. Previously we found that the peptide triazole HNG‐156 [R‐I‐N‐N‐I‐X‐W‐S‐E‐A‐M‐M‐CONH₂, in which X=ferrocenyltriazole‐Pro (FtP)] has nanomolar binding affinity to gp120, inhibits gp120 binding to CD4 and the co‐receptor surrogate mAb 17b, and has potent antiviral activity in cell infection assays. Furthermore, truncated variants of HNG‐156, typified by UM‐24 (Cit‐N‐N‐I‐X‐W‐S‐CONH₂) and containing the critical central stereospecific ^LX‐^LW cluster, retain the functional characteristics of the parent peptide triazole. In the current work, we examined the possibility of replacing natural with unnatural residue components in UM‐24 to the greatest extent possible. The analogue with the critical “hot spot” residue Trp 6 replaced with L ‐3‐benzothienylalanine (Bta) (KR‐41), as well as a completely non‐natural analogue containing D ‐amino acid substitutions outside the central cluster (KR‐42, ^DCit‐^DN‐^DN‐^DI‐X‐Bta‐^DS‐CONH₂), retained the dual receptor site antagonism/antiviral activity signature. The results define differential functional roles of subdomains within the peptide triazole and provide a structural basis for the design of metabolically stable peptidomimetic inhibitors of HIV‐1 Env gp120.     

Dynamic assessment of algebraic learning in predicting third graders' development of mathematical problem solving.

Dynamic assessment (DA) involves helping students learn a task and indexing responsiveness to that instruction as a measure of learning potential. The purpose of this study was to explore the utility of a DA of algebraic learning in predicting third graders' development of mathematics problem solving. In the fall, 122 third-grade students were assessed on language, nonverbal reasoning, attentive behavior, calculations, word-problem skill, and DA. On the basis of random assignment, students received 16 weeks of validated instruction on word problems or received 16 weeks of conventional instruction on word problems. Then, students were assessed on word-problem measures proximal and distal to instruction. Structural equation measurement models showed that DA measured a distinct dimension of pretreatment ability and that proximal and distal word-problem measures were needed to account for outcome. Structural equation modeling showed that instruction (conventional vs. validated) and pretreatment calculation skills were sufficient to account for math word-problem outcome proximal to instruction; by contrast, language, pretreatment word-problem skill, and DA were needed to forecast learning on word-problem outcomes more distal to instruction. Findings are discussed in terms of responsiveness-to-intervention models for preventing and identifying learning disabilities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The structure of individual differences in batteries of rapid acquisition tasks in mice.

Two experiments examined the structure of individual differences in mice by means of tasks that produced significant acquisition within 1 session. In Experiment 1, 5 cognitive tasks-detour, winshift, olfactory discrimination, fear conditioning, and operant acquisition-were used in conjunction with two control procedures: an open field and a light- dark test. In Experiment 2, some modifications were made to the tasks used in the 1st experiment, and 3 new tasks were used in conjunction with the same control procedures. The battery consisted of 5 learning tasks: detour, Hebb-Williams, radial maze, olfactory foraging, and fear conditioning. Results of both experiments indicate that when cognitive tasks and control procedures were included in principal-components analyses most of the variance attached principally to individual tasks rather than to a general component as is found typically in human cognitive batteries. When control procedures were eliminated, there was better evidence for the presence of a general cognitive factor, particularly in Experiment 2. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evaluating pedestrian crashes in areas with high low-income or minority populations

In this paper, we present an analysis of the relationship between pedestrian–vehicle crashes and characteristics of areas with high low-income and minority populations in the Chicago metropolitan area (also called environmental justice or EJ areas in the United States). While related research has indicated that pedestrian crashes occur more frequently in these areas than in non-EJ areas, this paper attempts to relate the incidence to environmental characteristics and behavioral factors through a better understanding of the contributing factors present in crash occurrences in EJ versus non-EJ areas. Specially constructed small-area factors from a Spatial Decision Support System (SDSS) are used to explain pedestrian–vehicle crashes.Using a Poisson model that corrects for underreporting, we find that pedestrian crash incidents in EJ areas are related to variables of exposure (including the suitability of the area for walking and transit accessibility), crime rates, transit availability, and general population demographics such as income and presence of children. Results suggest that it may be necessary to better incorporate a safety perspective or measures of safety improvements in pedestrian and transit improvements and expansion programs within EJ areas.     

Non-programmers identifying functionality in unfamiliar code: strategies and barriers

Source code on the web is a widely available and potentially rich learning resource for non-programmers. However, unfamiliar code can be daunting to end-users without programming experience. This paper describes the results of an exploratory study in which we asked non-programmers to find and modify the code responsible for specific functionality within unfamiliar programs. We present two interacting models of how non-programmers approach this problem: the Task Process Model and the Landmark-Mapping model. Using these models, we describe code search strategies non-programmers employed and the barriers they encountered. Finally, we propose guidelines for future programming environments that support non-programmers in finding functionality in unfamiliar programs.     

Organosulfates as Tracers for Secondary Organic Aerosol (SOA) Formation from 2-Methyl-3-Buten-2-ol (MBO) in the Atmosphere

2-Methyl-3-buten-2-ol (MBO) is an important biogenic volatile organic compound (BVOC) emitted by pine trees and a potential precursor of atmospheric secondary organic aerosol (SOA) in forested regions. In the present study, hydroxyl radical (OH)-initiated oxidation of MBO was examined in smog chambers under varied initial nitric oxide (NO) and aerosol acidity levels. Results indicate measurable SOA from MBO under low-NO conditions. Moreover, increasing aerosol acidity was found to enhance MBO SOA. Chemical characterization of laboratory-generated MBO SOA reveals that an organosulfate species (C(5)H(12)O(6)S, MW 200) formed and was substantially enhanced with elevated aerosol acidity. Ambient fine aerosol (PM(2.5)) samples collected from the BEARPEX campaign during 2007 and 2009, as well as from the BEACHON-RoMBAS campaign during 2011, were also analyzed. The MBO-derived organosulfate characterized from laboratory-generated aerosol was observed in PM(2.5) collected from these campaigns, demonstrating that it is a molecular tracer for MBO-initiated SOA in the atmosphere. Furthermore, mass concentrations of the MBO-derived organosulfate are well correlated with MBO mixing ratio, temperature, and acidity in the field campaigns. Importantly, this compound accounted for an average of 0.25% and as high as 1% of the total organic aerosol mass during BEARPEX 2009. An epoxide intermediate generated under low-NO conditions is tentatively proposed to produce MBO SOA.     

Water in exoplanets

Exoplanets--planets orbiting around stars other than our own Sun--appear to be common. Significant research effort is now focused on the observation and characterization of exoplanet atmospheres. Species such as water vapour, methane, carbon monoxide and carbon dioxide have been observed in a handful of hot, giant, gaseous planets, but cooler, smaller planets such as Gliese 1214b are now analysable with current telescopes. Water is the key chemical dictating habitability. The current observations of water in exoplanets from both space and the ground are reviewed. Controversies surrounding the interpretation of these observations are discussed. Detailed consideration of available radiative transfer models and linelists are used to analyse these differences in interpretation. Models suggest that there is a clear need for data on the pressure broadening of water transitions by H(2) at high temperatures. The reported detections of water appear to be robust, although final confirmation will have to await the better quality observational data provided by currently planned dedicated space missions.