Damage evolution in polymer due to exposure to high-pressure hydrogen gas

The use of hydrogen as a fuel is increasing exponentially, and the most economical way to store and transport hydrogen for fuel use is as a high-pressure gas. Polymers are widely used for hydrogen distribution and storage systems because they are chemically inert towards hydrogen. However, when exposed to high-pressure hydrogen, some hydrogen diffuses through polymers and occupies the preexisting cavities inside the material. Upon depressurization, the hydrogen trapped inside polymer cavities can cause blistering or cracking by expanding these cavities. A continuum mechanics–based deformation model was deployed to predict the stress distribution and damage propagation while the polymer undergoes depressurization after high-pressure hydrogen exposure. The effects of cavity size, cavity location, and pressure inside the cavity on damage initiation and evolution inside the polymer were studied. The stress and damage evolution in the presence of multiple cavities was also studied, because interaction among cavities alters the damage and stress field. It was found that all these factors significantly change the stress state in the polymer, resulting in different paths for damage propagation. The effect of adding carbon black filler particles and plasticizer on the damage was also studied. It was found that damage tolerance of the polymer increases drastically with the addition of carbon black fillers, but decreases with the addition of the plasticizer.     

Goodwin House, a place for healing

The following report is excerpted from a senior thesis project prepared by Kirstin Shank. For her thesis, Shank produced an exceptionally thorough and thoughtful proposal for a home for people living with AIDS and HIV. The specifics of her plan may not be easily translated for all such centers, but her holistic approach to designing a therapeutic environment can indeed serve as a models for designers across the country grappling with similar challenges.     

Inspection time and attention-deficit/hyperactivity disorder symptoms in children with cerebral palsy.

Objective: To examine between-groups differences in the associations between aspects of processing speed assessed with an inspection time task and attention-deficit/hyperactivity disorder (ADHD) symptoms. Research Design: Two groups comprising 34 children with cerebral palsy (CP) and 70 nonaffected peers (control), ages 8–16 years, participated in a prospective correlational study. Measures included a visual inspection time task and the Conners' Parent Rating Scale—Revised: Long Version. Results: Children with CP exhibited significantly slower processing speed and more symptoms of inattention and hyperactivity than controls. Significant associations between inspection time and ADHD symptoms were found only in the control group. Conclusions: Findings have implications for clinical assessment and understanding of attentional risks associated with CP. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

S-adenosylmethionine metabolism and DNA methylation in hydrazine-treated rats

The treatment of rats with hepatotoxic doses of hydrazine (NH2-NH2) induces the rapid formation of 7-methylguanine and O6-methylguanine in liver DNA. The methyl moiety in these reactions might be derived from the cellular S-adenosylmethionine pool because radioactivity administered to these rats as methionine rapidly appears in the DNA as methylated guanine. An increased incorporation of radioactivity into 5-methylcytosine was previously reported followed by subsequent suppression. This increased radiolabeling of 5-methylcytosine coincided with time of maximal DNA guanine methylation. To determine the nature of S-adenosylmethionine metabolism during the period of DNA methylation induced by hydrazine treatment, and to determine if the increased radiolabeling of 5-methylcytosine at this time reflected an actual increase in 5-methylcytosine synthesis, liver DNA synthesis and S-adenosylmethionine levels and turnover were assayed. Liver S-adenosylmethionine concentrations varied slightly between control rats and hydrazinetreated rats during the first five hours after hydrazine administration, and no difference was detectable in the incorporation of administered [3H]methionine into S-adenosylmethionine. Because S-adenosylmethionine specific radioactivity in hydrazine-treated rats was not different from control rats, the previously observed increased radiolabeling of 5-methylcytosine appeared to represent an actual increase in synthesis. This conclusion was supported by finding that incorporation of radioactive thymidine into DNA was also accelerated immediately following hydrazine administration, again followed by a decrease. 5-Methylcytosine sythesis, therefore, appears to follow DNA synthesis during hydrazine toxicity, and formation of 7-methylguanine and O6-methylguanine in liver DNA of hydrazine-treated rats occurs during a short period of increased DNA sythesis and 5-methylcytosine formation very early in hydrazine toxicity.     

Are computers good or bad for business? How mediated customer–computer interaction alters emotions,impressions, and patronage toward organizations

Are computers good or bad for business? Although computers are social actors research finds that people react to computers and humans with similar tendencies, little research directly compares human–computer interaction to human–human interaction. I ask how mediated transactions with a company’s human or computer representatives alter customers’ reactions toward that company. I conduct an experiment where subjects in the role of customers received products (low or high quality) from a representative (human or computer). I measure the customer’s emotions, impressions, and patronage toward both the representative and the organization. The data indicate few differences in reactions toward the representative and the organization, however, customers perceive the organization as more responsible and in control when they have employed human, not computer, representatives. A hypothesized statistical interaction effect (a moderation effect) on several emotions indicates that computer representatives decrease the strength of the relationship between receiving low or high quality products and customer’s emotions. Although many customer reactions indicate no human/computer differences, I discuss how the statistical moderation effect of computer identity on several emotions may relate to computers are social actors and other research.     

Development of a Risk-Ranking Framework to Evaluate Potential High-Threat Microorganisms, Toxins, and Chemicals in Food

ABSTRACT:  Through a cooperative agreement with the U.S. Food and Drug Administration, the Institute of Food Technologists developed a risk-ranking framework prototype to enable comparison of microbiological and chemical hazards in foods and to assist policy makers, risk managers, risk analysts, and others in determining the relative public health impact of specific hazard–food combinations. The prototype is a bottom-up system based on assumptions that incorporate expert opinion/insight with a number of exposure and hazard-related risk criteria variables, which are propagated forward with food intake data to produce risk-ranking determinations. The prototype produces a semi-quantitative comparative assessment of food safety hazards and the impacts of hazard control measures. For a specific hazard–food combination the prototype can produce a single metric: a final risk value expressed as annual pseudo-disability adjusted life years (pDALY). The pDALY is a harmonization of the very different dose–response relationships observed for chemicals and microbes. The prototype was developed on 2 platforms, a web-based user interface and an Analytica® model (Lumina Decision Systems, Los Gatos, Calif., U.S.A.). Comprising visual basic language, the web-based platform facilitates data input and allows use concurrently from multiple locations. The Analytica model facilitates visualization of the logic flow, interrelationship of input and output variables, and calculations/algorithms comprising the prototype. A variety of sortable risk-ranking reports and summary information can be generated for hazard–food pairs, showing hazard and dose–response assumptions and data, per capita consumption by population group, and annual p-DALY.     

Nanocrystalline Hf and Ta containing FeCo based alloys for high frequency applications

FeCo based nanocrystalline materials have excellent soft magnetic properties even at high temperature, but are limited to low frequency applications due to their relatively low electrical resistivities, ρ_e, resulting in high eddy current losses. Amorphous alloys of (Fe₈₁Co₁₉)₈₄M₉B₇ where M = (Hf, HfTa, Ta) were prepared by meltspinning and annealed for increasing times at their respective crystallization temperatures. The nanocrystalline alloys had coercivities less than 0.4 Oe and saturation inductions greater than 1 T. The electrical resistivities of the amorphous ribbons were all similar with values of ρ_e ? 180 μΩ cm. After annealing at the crystallization temperature, the M = Ta alloy had the largest ρ_e of 140 ± 3 μΩ cm. The Ta alloy also had the best high frequency properties, with an initial permeability of 822 at 1 MHz.     

Interaction of relativistic electrons with ultrashort laser pulses:generation of femtosecond X-rays and microprobing of electron beams

The interaction of relativistic electrons with terawatt femtosecond laser pulses is reviewed with emphasis on how the scattering process can be used as a source of ultrashort X-ray pulses and as a time-resolved diagnostic for measuring transverse and longitudinal phase space distributions of an electron beam with microns spatial and subpicosecond temporal resolution. Recent experimental results are presented in which 90° Thomson scattering was utilized to generate 300 fs duration pulses of X-rays with peak energy of 30 keV. It is shown that, through analysis of the scattered X-ray beam properties, transverse and longitudinal distributions of the electron beam can be obtained