Numerical analysis of the manipulated high performance catalyst layer design for polymer electrolyte membrane fuel cell

A two‐dimensional, multiphase, non‐isothermal numerical model was used to investigate the effect of the high performance catalyst layer (CL) design. Microstructure‐related parameters were studied on the basis of the agglomerate model assumption. A conventional CL design (uniform Pt/C composition, e.g., 40 wt%) was modified into two sub‐layers with two different Pt/C compositions (in this study, 40 and 80 wt%). The performance of sub‐layers with different CL designs is shown to be different. Simulation results show that substituting part of the Pt/C 40 wt% with Pt/C 80 wt% increases the cell performance. It was found that factors including proton conductivity, open circuit voltage, and sub‐layer thickness have a significant impact on overall cell performance. Different water distribution for different membrane electrode assembly designs was also observed in the simulation results. More liquid water accumulation inside the membrane electrode assembly is seen when the Pt/C 80 wt% sub‐layer is next to the gas diffusion layer. Finally, several key design parameters for the proposed high performance CL design including agglomerate radius, Nafion thin film thickness, and the Nafion volume fraction within the agglomerate in terms of CL fabrication were identified on the basis of our simulation results. Copyright © 2014 John Wiley & Sons, Ltd.     

Processing and characterization of recycled poly(ethylene terephthalate) blends with chain extenders,thermoplastic elastomer,and/or poly(butylene adipate‐co‐terephthalate)

Poly(ethylene terephthalate) (PET) resin is one of the most widely used thermoplastics, especially in packaging. Because thermal and hydrolytic degradations, recycled PET (RPET) exhibits poor mechanical properties and lacks moldability. The effects of adding elastomeric modifiers, chain extenders (CE), and poly(butylene adipate‐co‐terephthalate), PBAT, as a toughener to RPET on its moldability and mechanical property were investigated. Melt blending of RPET with CE, thermoplastic elastomer (TPE), and/or PBAT was performed in a thermokinetic mixer (K‐mixer). The blended materials were then injection molded to produce tensile specimens. Various techniques were used to study the mechanical properties, rheological properties, compatibility, and crystallization behavior of the RPET blends. By melt blending with proper additives, recycled PET regained its moldability, thereby enabling the recycling of RPET. Furthermore, the addition of CE greatly enhanced the mechanical properties of RPET. While the RPET and TPE blends also showed improved mechanical properties, the improvement was less significant and the blends were often immiscible due to the difference in polarities between RPET and TPE. Finally, it was found that the mechanical properties of RPET blends depended on the prior thermal history of the material and could be improved with an extra annealing step that increased the degree of crystallinity. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Development of a rheo‐dielectric sensor for online shear stress measurement during the injection molding process

This study presents the development of a novel rheo‐dielectric sensing technique, based on dielectrostriction measurement, for online injection molding process monitoring. Dielectrostriction, defined as a variation of dielectric properties of material under deformation, detects evolution of molecular orientation during injection molding and enables online shear stress measurement. The dielectrostriction effect resembles the well‐known birefringence phenomenon. As birefringence in polymers is described by the stress‐optical relationship (Fuller, Optical Rheometry of Complex Fluids, Oxford University Press, New York (1995); Janeschitz‐Kriegl, Polymer Melt Rheology and Flow Birefringence, Springer, Berlin (1983); Saiz and Rainde, Dipole Moments and Birefringence of Polymers, Prentice‐Hall, New Jersey (1992)), a stress‐dielectric relationship exists for and is applicable to dielectrostriction. In addition,dielectrostriction measurements can be performed on both transparent and opaque materials with a much simpler data acquisition technique. To demonstrate the feasibility of the dieletrostriction measurement, a planar capacitor sensor rosette has been developed and attached to the surface of an injection mold to obtain the dielectrostriction signal under various processing conditions. The calculated shear stresses of polymer melts based on dielectrostriction signals were validated by agreement with simulation predictions. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Thoracic manifestations of Beh?et syndrome: radiographic and CT findings in nine patients

PURPOSE: To evaluate the radiographic and computed tomographic (CT) findings of patients with thoracic Beh?et syndrome. MATERIALS AND METHODS: Chest radiographs and CT scans of nine patients with thoracic Beh?et syndrome were retrospectively reviewed. Findings were compared. RESULTS: Radiographs of the nine patients showed mediastinal widening in five (56%), air-space consolidation in five (56%), and lung mass in three (33%). CT scans of the nine patients showed that mediastinal widening was due to thrombosis in four (44%) or narrowing of the superior vena cava in one [11%], which caused mediastinal edema; that air-space consolidation (seen on both radiographs and CT scans) was due to pulmonary hemorrhage or infarction in five (56%); and that lung mass was due to aneurysm of the right or left pulmonary artery in three (33%). In addition, CT scans showed hyperinflation in one patient. CONCLUSION: Chest radiographic findings of thoracic Beh?et syndrome are variable and nonspecific. CT can be helpful in the assessment of the syndrome by showing thrombosis of the superior vena cava and characteristic aneurysms of the pulmonary arteries.     

Isolation of the uterotonic principle from Leonurus artemisia, the Chinese motherwort

A search in ancient Chinese medicinal literature and modern phytochemical references indicates that the therapeutic value of Leonurus artemisia (I-mu ts'ao, the Chinese motherwort) might reside in a uterotonic principle present in leaves. Leonurine (4-guanidino-n-butyl syringate) was isolated from fresh and dry leaves of Leonurus artemisia. The uterotonic effect of leonurine was demonstrated in rat uterus in vitro. Results from this study suggest that functional phytochemistry based on ethnobotanical experience could lead to development of new and effective drugs from Chinese medicine.     

A case of abdominal cocoon

Abdominal cocoon is a rare disease of the peritoneum and almost invariably presents as an acute or subacute intestinal obstruction with or without a mass. The etiology of this disease is largely unknown and abdominal cocoon of unknown etiology has been limited to the tropical and subtropical zones and primarily affects young adolescent females. In the temperate zone, only one case has been reported from the United Kingdom, but the patient was also born in Pakistan. No case of abdominal cocoon purely developed in the temperate zone has been reported. Recently, we experienced a case of abdominal cocoon in a 34-year-old female patient(Korean) who had never been abroad. The diagnosis was made postoperatively by reviewing the literature. We herein report this rare condition developed in an unusual geographical location with a brief review of the literature.     

First-trimester fetal chromosomal diagnosis using endocervical lavage: a negative evaluation

A report in the literature indicated that fetal cells could be obtained by endocervical lavage during the first trimester of pregnancy and successfully cultured. This would allow prenatal diagnosis earlier in pregnancy than is currently possible with second-trimester amniocentesis. Therefore, we attempted to confirm these findings. Our results indicated that the cultural cells were maternal in origin. We disagree with interpretations of the data given in the initial report and conclude that first-trimester prenatal diagnosis is not feasible at this time.     

Switching nucleotide specificity of Ha-Ras p21 by a single amino acid substitution at aspartate 119

We examined c-Ha-Ras harboring an aspartate to asparagine substitution at position 119 (mutation D119N). The Asp-119 is part of the conserved NKXD motif shared by members of the regulatory GTPase family. This asparagine residue has been proposed to participate in direct bonding to the guanine ring and to determine the guanine-nucleotide binding specificity. The D119N mutation was found to alter nucleotide specificity of Ha-Ras from guanine to xanthine, an observation that directly supports the essential role of hydrogen bonding between the side chain of the aspartic acid residue and the guanine ring in nucleotide binding specificity. Besides nucleotide binding specificity, the D119N mutation has little or no effect on the interaction of Ha-Ras with SDC25C, SOS1, GAP, or Raf. Neither does it affect the hydrolysis of nucleotide triphosphate. Like xanthine-nucleotide-specific EF-Tu, xanthine-nucleotide-specific Ras and related proteins will be useful tools for elucidating cellular systems containing multiple regulatory GTPases.     

B cells are anergic in transgenic mice that express IgM anti-DNA antibodies

B lymphocytes in individuals with systemic lupus erythematosus (SLE) secrete pathogenic autoantibodies to DNA which cause clinical nephritis. (NZB X NZW) F1 (BW) female mice also secrete pathogenic anti-DNA autoantibodies, and therefore are considered to be an animal model of SLE. The rearranged immunoglobulin (Ig) genes that encode an anti-DNA antibody from a diseased BW mouse have been cloned, and transgenic (Tg) mice have been created by microinjection of these constructs into fertilized eggs from normal mice. As we reported previously, when the construct contains the C gamma 2a heavy chain constant (CH) region, the mice spontaneously secrete anti-DNA IgG and they develop mild nephritis. This demonstrated that the Ig encoded by the transgene is pathogenic. In contrast, here we report that when the construct contains the same anti-DNA Ig variable (V) regions used previously, along with the C mu region, the autoreactive B cells are rendered tolerant. Most B cells in the Tg mice express the mu transgene product on their surface, and rearrangement of endogenous light chain genes is partially suppressed. Furthermore, most hybridomas made from Tg B cells secrete IgM anti-DNA. Despite this, the Tg mice have reduced levels of total serum Ig and they do not secrete anti-DNA IgM either spontaneously or following immunization with DNA. We conclude that most B cells in the Tg mice have been rendered anergic. Anergy is however reversible in vitro; lipopolysaccharide stimulation of Tg B cells leads to the production of a significant amount of IgM anti-DNA antibody. The studies demonstrate that in this line of Tg mice on a normal mouse genetic background potentially pathogenic B cells that express a high-affinity Ig specific for a natural autoantigen are subject to tolerance by induction of anergy.     

Vaginal douching and the risk of ectopic pregnancy among black women

OBJECTIVE: Our goal was to determine whether vaginal douching was associated with ectopic pregnancy among black women and whether specific douching behaviors were associated with differences in risk. STUDY DESIGN: We analyzed data from a case-control study of ectopic pregnancy conducted between October 1988 and August 1990 at a major public hospital in Atlanta, Georgia. Case subjects were 197 black women with surgically confirmed ectopic pregnancies; the control group included 882 black women who were delivered of live or stillborn infants and 237 black women who were seeking to terminate a pregnancy. RESULTS: The adjusted odds ratio for ectopic pregnancy associated with ever having douched was 3.8 (95% confidence interval 1.6 to 8.9). The risk increased with increasing number of years of douching at least once per month. No douching behavior was found to be without risk; even women who douched for routine cleanliness were at increased risk of ectopic pregnancy. CONCLUSIONS: Vaginal douching is a modifiable behavior that may greatly increase a woman's risk of ectopic pregnancy.