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.     

Biohydrogen Production from Organic Waste – A Review

Hydrogen fuel is a promising alternative to fossil fuels because of its energy content, clean nature, and fuel efficiency. However, it is not readily available. Most current producion processes are very energy intensive and emit carbon dioxide. Therefore, this article reviews technological options for hydrogen production that are eco-friendly and generate clean hydrogen fuel. Biological methods, such different fermentation processes and photolysis are discussed together with the required substrates and the process efficiency.     

Length of maternity leave and quality of mother-infant interactions

The aim of this study was to assess the association between the length of maternity leave and the quality of mother-infant interactions; 198 employed mothers of 4-month-old infants were interviewed and videotaped in their homes during a feeding time. Hierarchical multiple regression analyses indicated a direct association between shorter length of leave and more negative affect and behavior in maternal interactions with their infants. Infant and mother stressor/protective variables added significantly in predicting the quality of the mother-infant relationship. There were also significant interaction effects between the length of leave and these variables. Mothers who either reported more depressive symptoms or who perceived their infant as having a more difficult temperament and who had shorter leaves, compared with mothers who had longer leaves, were observed to express less positive affect, sensitivity, and responsiveness in interactions with their infants. The public policy implications of the relation between length of maternity leave, maternal and infant individual differences, and the quality of mother-infant interactions are discussed.     

Traumatic vertebral arterial dissection and vertebrobasilar arterial thrombosis successfully treated with endovascular thrombolysis and stenting

A case of traumatic extracranial vertebral arterial dissection leading to vertebrobasilar thrombosis and respiratory compromise requiring mechanical ventilation was managed with intraarterial thrombolysis and stenting of the vertebral intimal dissection. In contrast to similar, previously reported cases, this critically ill patient made a full recovery, returning to his job as a secondary school teacher.     

Animal models of bacterial gastritis: the role of host, bacterial species and duration of infection on severity of gastritis

Gastric bacteria from cheetahs with gastritis were used to inoculate specific-pathogen free kittens and conventional mice. Helicobacter sp. and Gastrospirillum sp. colonized kittens, while only Gastrospirillum sp. colonized mice. In kittens, both bacterial species induced mild lymphofolliclar gastritis which did not change over the course of the 11 months observation period. In mice, Gastrospirillum sp. induced lymphoplasmacytic and follicular gastritis which increased in severity over 6 months and persisted for the 12 month observation period. Gastric ulcers and gastric mucosal hypertrophy were present in chronically infected mice. These results indicate that host but not bacterial factors influence the severity of gastritis, and that in mice, bacterial gastritis increases in severity with time and may lead to gastric ulceration in some individuals.     

Frequency of molecular alterations in heterozygous beta-thalassemia in southern Spain and their relation to the hematologic phenotype

INTRODUCTION: Heterozygous beta-thalassemia manifests hematologically with microcytosis, reduced red blood cell hemoglobin concentration and high hemoglobin A2 levels. Almost all molecular alterations are due to point mutations. We attempt to determinate the frequency of that mutations in the Oriental Andalusia Area, and its relationship with the hematological phenotype. PATIENTS AND METHODS: We have studied 45 heterozygous patients. DNA samples were amplified by PCR, using the printers CD7 and HI1. A 16 Kb fragment corresponding to beta globin gene was obtained and analyzed by Dot Blot assay and hybridized with allelic specific oligonucleotide (ASO) probes to detect the 6 more frequent mutations found in the South of Spain. RESULTS: Codon 39 nonsense mutation (31.1%) was the most frequent finding followed by IVS-1 NT 110 (26.7%). The relationship between hematological parameters and molecular mutations concluded that IVS-I NT 6 mutation developed a minimal anemia. DISCUSSION: From the practical point of view, this study indicates that we were able to detect more than 90% of heterozygous beta-tal. with 5 out of 6 ASO probes used in this work. Thus, our data also provides a further implication in prenatal diagnosis.     

Embryonic stem cells and hematopoietic stem cell biology

Two advances in murine embryonic stem (ES) cell technology and their applications for the study of hematopoietic stem cells (HSCs) are discussed in this article. First, ES cells induced to differentiate in vitro form hematopoietic lineages in a fashion that recapitulates the ontogeny of blood formation in the embryo. This system offers a unique opportunity to isolate, examine, and manipulate the most primitive hematopoietic progenitors. Second, targeted gene ablation (knockout) studies in ES cells have identified several genes that are required for normal hematopoiesis and may function in the formation, maintenance, and differentiation of HSCs. Insights into murine hematopoiesis gained through the study of ES cells generally should be applicable to other vertebrates, including humans.     

Thoracic epidural anesthesia as the last option for treating angina in a patient before coronary artery bypass surgery

Robertsonian translocations, although relatively common as a constitutional genetic aberration, are rarely encountered in leukaemia. We report a case of acute myeloid leukaemia which showed an acquired Robertsonian translocation in the form of der(14;21) by cytogenetic analysis of leukaemic cells. This was confirmed by the PHA-stimulated culture of peripheral blood lymphocytes. A review of the literature identifies only eight reported cases of acquired Robertsonian translocations in leukaemia. In the majority of cases the Robertsonian translocation occurs as a secondary change in a complex abnormal clone, whereas in two out of nine patients reported, including ours, it is found as a sole karyotypic abnormality.