Ice/metal interfaces: fracture energy and fractography

Results are presented of the fracture tests of ice/metal interfaces in an attempt to utilize fracture mechanics to characterize the failure of ice/solid adhesion. The four-point bending delamination specimen was used to measure the fracture energy of ice/aluminium and ice/steel joints at — 15 °C. The interfacial fracture energy was found to be dependent on ice type and formation procedure of the ice/metal composites. Crack growth was in a manner of asymmetrical bursting, and both cohesive and adhesive failure mechanisms were observed. Although the fracture of ice/metal interfaces was brittle in nature, the evidence of dislocation slip in ice crystals, as revealed by etching and replicating, suggests that microplastic deformations occur in the ice component.     

Peptide amidating activity in human bronchoalveolar lavage fluid

Monitoring respiratory epithelial biology may reveal individuals with incipient lung cancer. The expression of neuroendocrine (NE) markers in pulmonary epithelium is thought to be central to lung development, repair of injury and may contribute to carcinogenesis. In this study, we evaluate several candidate NE markers to determine the feasibility of prospective analysis of clinical specimens. The potential NE markers include the enzyme L-DOPA decarboxylase (DDC), the neuropeptide gastrin releasing peptide (GRP), and peptidyl-glycine alpha-amidating monooxygenase (PAM), the bifunctional enzyme responsible for the final bioactivation step of many neuropeptides. A comparison of PAM activity and DDC levels in 30 lung cancer cell lines indicated that peptide amidating activity may be an indicator of NE status. Bronchoalveolar lavage (BAL) fluid from subjects at risk of developing second primary lung cancer and from volunteers was obtained. The activity of the first PAM enzyme, peptidylglycine alpha-hydroxylating monooxygenase (PHM), ranged from not detectable to 507 pmol/h/mg protein in 57 specimens. The second PAM enzyme, peptidylamidoglycolate lyase (PAL), ranged from not detectable to 414 pmol/h/mg protein in 56 specimens. Using cluster analysis by the average linkage method, a group of enzyme values with PHM greater than 230 pmol/h/mg protein was determined. Long-term follow-up of these patients for new second primary lung cancers may help to determine the potential predictive value of PAM detected in the BAL fluid.     

Beneficial effects of S-adenosyl-L-methionine on blood-brain barrier breakdown and neuronal survival after transient cerebral ischemia in gerbils

In the present study, the effect of bradykinin on basal and precontracted mouse-isolated trachea was investigated. In basal conditions mouse-isolated tracheal rings do not respond to bradykinin. However, when the tracheal rings were precontracted with carbachol (10(-7) M) a relaxation with bradykinin (3 x 10(-9)-3 x 10(-7)) was found. The maximal response amounted 69.7+/-4.1% (n=15) with a pD2 value of 7.2+/-0.21. The selective bradykinin B2 receptor antagonist HOE 140 (10(-10)-10(-8) M) antagonized the bradykinin-induced relaxation, while the bradykinin B1 receptor antagonist des-Arg9-Leu8-bradykinin (10(-6) M) had no influence. The selective bradykinin B1 receptor agonist des-Arg9-bradykinin (10(-6) M) caused a small relaxation (8.4+/-2.5%, n=6), which could be antagonized completely by the selective bradykinin B1 receptor antagonist des-Arg9-Leu8-bradykinin (10(-6) M) while addition of the selective bradykinin B2 receptor antagonist HOE 140 (10(-8) M) was without effect. In the presence of indomethacin (10(-6) M) the relaxation of bradykinin was completely abolished. Pretreatment of the tracheal rings with capsaicin, or the presence of the selective NK1 receptor antagonist RP 67851 (10(-6) M) or the presence of the nitric oxide synthase inhibitor L-NAME (3 x 10(-4) M) had no effect on the bradykinin-induced relaxation. In conclusion, these results demonstrate that the mouse-isolated tracheal is a preparation in which bradykinin exerts a relaxant response via stimulation of bradykinin B2 receptors. This response is probably mediated by prostaglandins.     

Sleep-induced breathing instability. University of Wisconsin-Madison Sleep and respiration Research Group

We present a view of the neuromechanical regulation of breathing and causes of breathing instability during sleep. First, we would expect transient increases in upper airway resistance to be a major cause of transient hypopnea. This occurs in sleep because a hypotonic upper airway is more susceptible to narrowing and because the immediate excitatory increase in respiratory motor output in response to increased loads is absent in non-REM sleep. Secondly, sleep predisposes to an increased occurrence of ventilatory "overshoots", in part because abruptly changing sleep states cause transient changes in upper airway resistance and in the gain of the respiratory controller. Following these ventilatory overshoots, breathing stability will be maintained if excitatory short-term potentiation is the prevailing influence. On the other hand, apnea and hypopnea will occur if inhibitory mechanisms dominate following the ventilatory overshoot. These inhibitory mechanisms include: a) hypocapnia-if transient, will inhibit carotid chemoreceptors and cause hypopnea, but if prolonged will inhibit medullary chemoreceptors and cause apnea; b) a persistent inhibitory effect from lung stretch; c) baroreceptor stimulation, from a transient rise in systemic blood pressure immediately following termination of apnea or hypopnea may partially suppress the accompanying hyperpnea; d) depression of central respiratory motor output via prolonged brain hypoxia. Once apneas are initiated, reinitiation of inspiration is delayed even though excitatory stimuli have risen well above their apneic thresholds, and these prolonged apneas are commonly accompanied by tonic EMG activation of expiratory muscles of the chest wall and upper airway.     

Cross-sectional investigation of task demands and musculoskeletal discomfort among restaurant wait staff

A cross-sectional study of task demands and musculoskeletal discomfort among a sample of 100 wait staff in ten casual dining restaurants was conducted. In addition to answering a questionnaire about musculoskeletal discomfort and symptoms experienced in the past 12 months and attributed to work, subjects were asked about various aspects of their jobs, such as shift length, number of shifts per week and safety training. The managers of the restaurants were also interviewed to gather basic information on factors such as work hours, alternative duty availability and safety practices. When asked to rank the three most important causes of injuries, the responses of both managers and wait staff were congruent with Bureau of Labor Statistics (USA) data for 1999 on the nature of injuries and attributed exposures, with slips and falls, musculoskeletal disorders and acute injuries (e.g. burns, cuts) highlighted. Of the 100 subjects, 42% reported experiencing musculoskeletal symptoms in the past year, with the lower back area (18%) and shoulder (11%) with the most frequent symptoms reported in the responses. Although many of the materials handling tasks were not excessive, the heavier tray lifts and carries are a cause for concern. There are also slip and fall issues that influence the risks of these tasks. Future research needs, including addressing the mismatch between more common materials handling assessment tools and the nature of food serving tasks, are discussed.     

On the evolution of task-based analysis of manual materials handling, and its applicability in contemporary ergonomics

The industrial revolution significantly changed the way work was organized and analyzed by the introduction and widespread implementation of the division of labor philosophy. This philosophy has continued to dominate work design, and has evolved beyond the factory to include many facets of service industries, and even professional occupations. The analysis of manual work, particularly materials handling tasks, remains an active domain of ergonomics research and practice. Many of the task-analytic tools used for workplace analysis are rooted in the philosophy of dividing work into elements, analyzing the individual elements, and synthesizing the results into conclusions about the entire job, including the risk of contracting musculoskeletal disorders (MSDs). The authors discuss the notion that the nature of modern work, which is characterized by multiple tasks in a complex time pattern, and the complex nature of MSDs, which are influenced by biomechanical as well as psychological, political, and economic factors, may limit the effectiveness of classical task analytic techniques in preventing MSDs.     

Analysis of Site-Specific Phosphorylation of PTEN by Using Enzyme-Catalyzed Expressed Protein Ligation

The activity and localization of PTEN, a tumor suppressor lipid phosphatase that converts the phospholipid PIP3 to PIP2, is governed in part by phosphorylation on a cluster of four Ser and Thr residues near the C terminus. Prior enzymatic characterization of the four monophosphorylated (1p) PTENs by using classical expressed protein ligation (EPL) was complicated by the inclusion of a non-native Cys at the ligation junction (aa379), which may alter the properties of the semisynthetic protein. Here, we apply subtiligase-mediated EPL to create wt 1p-PTENs. These PTENs are more autoinhibited than previously appreciated, consistent with the role of Tyr379 in driving autoinhibition. Alkaline phosphatase sensitivity analysis revealed that these autoinhibited 1p conformations are kinetically labile. In contrast to the Cys mutant 1p-PTENs, which are poorly recognized by an anti-phospho-PTEN antibody, three of the four wt 1p-PTENs are recognized by a commonly used anti-phospho-PTEN antibody.     

Arsenic removal by iron-modified activated carbon

Iron-impregnated activated carbons have been found to be very effective in arsenic removal. Oxyanionic arsenic species such as arsenate and arsenite adsorb at the iron oxyhydroxide surface by forming complexes with the surface sites. Our goal has been to load as much iron within the carbon pores as possible while also rendering as much of the iron to be available for sorbing arsenic. Surface oxidation of carbon by HNO3/H2SO4 or by HNO3/KMnO4 increased the amount of iron that could be loaded to 7.6-8.0%; arsenic stayed below 10 ppb until 12,000 bed volumes during rapid small-scale tests (RSSCTs) using Rutland, MA groundwater (40-60 ppb arsenic, and pH of 7.6-8.0). Boehm titrations showed that surface oxidation greatly increased the concentration of carboxylic and phenolic surface groups. Iron impregnation by precipitation or iron salt evaporation was also evaluated. Iron content was increased to 9-17% with internal iron-loading, and to 33.6% with both internal and external iron loading. These iron-tailored carbons reached 25,000-34,000 bed volumes to 10 ppb arsenic breakthrough during RSSCTs. With the 33.6% iron loading, some iron peeled off.