Numerical analysis of ice-induced stresses in the membrane electrode assembly of a PEM fuel cell under sub-freezing operating conditions

In this work, we report on numerical investigation on the behavior of a polymer electrolyte membrane fuel cell (PEMFC) during a non-optimized start-up procedure from (?20 °C) with a two-dimensional model that couple transport, electrochemical reaction, ice formation and accumulation and mechanical stress induced by ice. The results indicate that the regions with maximum values of ice saturation and von Mises stress are all located in the cathode catalyst layer (CL) and the micro pore layer (MPL) under the land; assuming a 5% ice expansion rate, predicts ice saturation of 0.95 in the cathode CL 240 s, and von Mises stress of 2.8 MPa in the membrane which is below the critical value for damage. However, in the CL the von Mises stress exceeds 15 MPa. Tensile stresses in particular are found to attain sufficiently high values to cause after only 150 s to potentially cause delamination and/or dislocation of particles resulting in higher bulk and interfacial resistance. The simulations indicate that ice-induced degradation may be prevented with measures that reduce the cold start time to under 75 s.     

Correspondence of Interactive Voice Response (IVR) reports of nicotine withdrawal, craving, and negative mood with questionnaire ratings.

This study focuses on comparing reports of nicotine withdrawal, craving, and depressive symptoms obtained using an Interactive Voice Response (IVR) system and several questionnaires. As part of a smoking cessation trial, daily reports of withdrawal, craving, and negative mood were collected using an IVR system for 7 days after participants attempted to quit smoking, and several pencil and paper questionnaires (i.e., the Minnesota Nicotine Withdrawal Scale, the Questionnaire on Smoking Urges, and the Center for Epidemiological Studies-Depression) were completed a week after the target quit date. The sample was composed of 378 daily smokers. Moderate to high correlations were found between the research questionnaires obtained at the end of the week and the corresponding daily IVR reports of nicotine withdrawal, craving, and depressive symptoms. However, the sample size decreased on each day of IVR reporting due to attrition. Thus, an appealing aspect of daily assessment using an IVR system is that it can provide additional data that are not obtained with paper and pencil assessments given once per week, but it will be important for future studies to concentrate on improving adherence with the IVR system in this population.     

Photoperiod-dependent modulation of anti-Müllerian hormone in female Siberian hamsters, Phodopus sungorus

Fertility and fecundity decline with advancing age in female mammals, but reproductive aging was decelerated in Siberian hamsters (Phodopus sungorus) raised in a short-day (SD) photoperiod. Litter success was significantly improved in older hamsters when reared in SD and the number of primordial follicles was twice that of females held in long days (LD). Because anti-Müllerian hormone (AMH) appears to inhibit the recruitment of primordial follicles in mice, we sought to determine whether the expression patterns of AMH differ in the ovaries and serum of hamsters raised in SD versus LD. Ovaries of SD female hamsters are characterized by a paucity of follicular development beyond the secondary stage and are endowed with an abundance of large eosinophilic cells, which may derive from granulosa cells of oocyte-depleted follicles. In ovaries from 10-week-old SD hamsters, we found that the so-called 'hypertrophied granulosa cells' were immunoreactive for AMH, as were granulosa cells within healthy-appearing primary and secondary follicles. Conversely, ovaries from age-matched LD animals lack the highly eosinophilic cells present in SD ovaries. Therefore, AMH staining in LD was limited to primary and secondary follicles that are comparable in number to those found in SD ovaries. The substantially greater AMH expression in SD ovaries probably reflects the abundance of hypertrophied granulosa cells in SD ovaries and their relative absence in LD ovaries. The modulation of ovarian AMH by day length is a strong mechanistic candidate for the preservation of primordial follicles in female hamsters raised in a SD photoperiod.     

Coping skills and treatment outcomes in cognitive-behavioral and interactional group therapy for alcoholism.

In the present study 128 alcohol dependent men and women received 26 weeks of group treatment in one of two modalities: Cognitive-behavioral treatment (CBT) intended specifically to develop coping skills or interactional therapy intended to examine interpersonal relationships. Coping skills and drinking were assessed prior to and after treatment and up to 18 months after intake. Results indicated that both treatments yielded very good drinking outcomes throughout the follow-up period. Increased coping skills was a significant predictor of outcome. However, neither treatment effected greater increases in coping than the other. Specific coping-skills training was not essential for increasing the use of coping skills. The results raise questions about the efficacy of specific treatment elements of CBT in treatment of alcohol dependence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of fine precipitate particles on the creep behaviour of ferritic model steels – III. Model calculations

With the findings of the preceding part II a model is established which considers dislocation and diffusion creep and which is used to simulate the creep behaviour of alloys with grain and particle coarsening during creep. It is found that the structure changes during creep give rise to a complex stress – strain rate dependence and to additional transition fields in the corresponding deformation maps which is of importance for the interpretation of practical long-term creep results.     

Scientific Challenges,Opportunities and Priorities for the U.S. Fusion Energy Sciences Program

In October 2003, Dr. Raymond Orbach, Director of the Department of Energy’s Office of Science, issued a charge to the Fusion Energy Sciences Advisory Committee (FESAC) “to identify the major science and technology issues that need to be addressed, recommend how to organize campaigns to address these issues, and recommend the priority order for these campaigns.” The sections in this report document the results of the Panel’s work. The first two sections describe the concepts of the overarching themes, topical scientific questions, and campaigns. The next six sections (Sections 3–8) describe in detail the six scientific campaigns. Section 9 describes some important enabling research activities necessary for the campaigns. Sections 10–12 describe the overarching themes, which provide a crosscutting perspective of the activities in the six campaigns. Finally, the Panel’s recommendations are set forth in Section 13. The charge letter to the panel is provided as Appendix A; the FESAC response letter is provided as Appendix D.     

Iron‐Rich Iron‐Aluminium‐Molybdenum Alloys with Strengthening Intermetallic μ phase and R phase Precipitates

Single‐phase and two‐phase ternary Fe‐Al‐Mo alloys with Al contents of usually 10 ‐16 at.% and Mo contents up to 42 at.% have been studied with respect to hardness at room temperature, yield stress and fracture strain at room temperature and higher temperatures up to 1000 °C and oxidation at temperatures of 400 ‐ 1000 °C. Thse alloys are strengthened by precipitation of the metastable R phase and/or the stable m phase depending on composition and heat treatment; both are hard and brittle intermetallic phases. The yield stress as well as the brittle‐to‐ductile transition temperature increases with increasing Mo content to reach yield stresses above 1400 MPa with, however, fracture strains below 1 % at temperatures below 800 °C. The observed short‐term oxidation is similar to that of other Fe‐Al alloys.     

Distribution of radiocaesium (137Cs) and radiopotassium (40K) during the cheese production

Distribution of radionuclides depends on various factors, and milk processing into cheese is recommended as one of the significant measures of radiation protection during radioactive contamination of the environment. A total of 16 milk and 16 cheese (soft and hard) samples were examined using HPGe gamma-ray spectrometry to obtain ¹³⁷Cs and ⁴⁰K activity concentrations. The Pearson's correlation coefficients between ¹³⁷Cs and ⁴⁰K were determined (0.73, 0.68, 0.19, −0.23), followed by determination of distribution of ¹³⁷Cs and ⁴⁰K from cow milk to two types of cheeses using food processing retention factors (0.07–0.34). Transfer of ¹³⁷Cs obtained could serve a great purpose for predicting its distribution during cheesemaking.     

Separation and identification of phospholipid peroxidation products

The molecular species in mixtures of phospholipid hydroperoxides are difficult to separate and identify by typical chromatographic and mass spectrometric techniques. As reported by Havrilla and coworkers, silver ion coordination ionspray mass spectrometry (CIS-MS) has proven to be a powerful technique for the identification of mixtures of hydroperoxides. This ionization technique, which involves the formation of Ag⁺ adducts of the hydroperoxides, provides valuable, unambiguous structural information about the hydroperoxides. Herein, we report a method for the analysis and identification of phospholipid hydroperoxides using CIS-MS. We also report an improved method for the separation of phospholipid hydroperoxides by reversed-phase high-performance liquid chromatography (RP-HPLC), which, for the first time, separates some of the hydroperoxide isomers. CIS-MS can be coupled with this RP-HPLC method by the addition of AgBF₄ to the mobile phase or to the HPLC effluent postcolumn, thus allowing powerful HPLC-MS techniques to be used to identify complex mixtures of phospholipid hydroperoxides.     

Structural changes in a commercial lithium-ion battery during electrochemical cycling: An in situ neutron diffraction study

The structural response to electrochemical cycling of the components within a commercial Li-ion battery (LiCoO₂ cathode, graphite anode) is shown through in situ neutron diffraction. Lithuim insertion and extraction is observed in both the cathode and anode. In particular, reversible Li incorporation into both layered and spinel-type LiCoO₂ phases that comprise the cathode is shown and each of these components features several phase transitions attributed to Li content and correlated with the state-of-charge of the battery. At the anode, a constant cell voltage correlates with a stable lithiated graphite phase. Transformation to de-lithiated graphite at the discharged state is characterised by a sharp decrease in both structural cell parameters and cell voltage. In the charged state, a two-phase region exists and is composed of the lithiated graphite phase and about 64% LiC₆. It is postulated that trapping Li in the solid|electrolyte interface layer results in minimal structural changes to the lithiated graphite anode across the constant cell voltage regions of the electrochemical cycle.