鼠笼式搅拌磨的流体场建模及计算机仿真

搅拌磨机在工业与研究领域是一种效率高的超细粉磨设备。为了优化设计参数，提高鼠笼式搅拌磨机的粉碎效果，需要对磨机研磨室内的流体场作深入的研究。利用Ansys有限元软件对鼠 式搅拌磨机研磨室的圆截面内的流体场进行仿真分析。通过对仿真结果的分析可知，在该流体场内存在着2个速度梯度较高的区域。在这2个区域中，粉碎作用明显。为了得到最佳的粉碎效果，应该使磨球尽可能地通过这2个区域。     

Necrotizing enterocolitis

Advances in neonatal care have resulted in an enlarging population of vulnerable premature newborns at risk for necrotizing enterocolitis (NEC). This article presents data supporting a unifying hypothesis for the initiation of NEC based on bacteria as the inciting agent(s), and the preterm baby as the vulnerable host. Facts and controversies concerning the pathology, microbiology, clinical presentation, management and outcome of infants afflicted with NEC are presented.     

Fetal and maternal lipoprotein metabolism in human pregnancy complicated by type I diabetes mellitus

Serum lipid, apolipoprotein concentration, and lipoprotein composition were determined in maternal and umbilical venous cord blood at delivery by elective Cesarean section (CS) in 10 singleton, full-term pregnancies with maternal insulin-dependent diabetes mellitus (type I DM), which predated pregnancy, and in 22 nondiabetic pregnancies. The objectives of the study were to determine the influence of maternal type I DM, and hence potential fetal overnutrition on fetal lipid metabolism. There were no significant differences in gestational age, fetal weight, or fetal serum insulin concentration between the type I DM group and those with nondiabetic pregnancies, although fetal venous cord blood glucose was 3.4 mmol/L (3.0-4.5 mmol/L) (median and 25th-75th percentiles) and 2.9 mmol/L (2.0-3.4 mmol/L), respectively, and maternal Hemoglobin A1c [9.6% (8.2-10.7%) and 6.8% (6.3-7.8%), respectively], was significantly greater in the type I DM subjects (P < 0.02 and 0.002 respectively). Plasma nonesterified fatty acid (NEFA) concentrations were lower in the type I DM mothers [0.85 mmol/L (0.56-2.31 mmol/L) compared with 1.14 mmol/L (0.88-1.24 mmol/L] in nondiabetic pregnancies; P < 0.0001). Serum high-density lipoprotein phospholipids (HDL-PL) were increased in type I DM mothers because of elevated HDL2 phospholipid [0.39 mmol/L (0.27-0.48 mmol/L) compared with 0.12 mmol/L (0.06-0.21 mmol/L), respectively, P < 0.01). The maternal HDL cholesterol (C) concentration was not significantly different in the uncomplicated and type I DM pregnancies. However, in the umbilical venous cord blood, serum levels of NEFA [0.49 mmol/L (0.33-1.29 mmol/L) in type I DM compared with 0.13 mmol/L (0.06-0.33 mmol/L) in nondiabetics; P < 0.02)], total cholesterol (TC) [2.87 mmol/L (1.65-4.86 mmol/L) in type I DM compared with 1.65 mmol/L (1.46-1.87 mmol/L) in nondiabetics; P < 0.02]; free cholesterol (FC) [0.97 mmol/L (0.60-1.26 mmol/L) in type I DM compared with 0.62 mmol/L (0.37-0.75 mmol/L) in nondiabetics; P < 0.05), and cholesteryl ester (CE) [1.90 mmol/L (1.44-3.33 mmol/L) in type I DM compared with 1.01 mmol/L (0.83-1.24 mmol/L) in nondiabetics; P < 0.02), triglyceride (TG) (1.06 [0.50-1.91) mmol/L in type I DM compared with 0.29 [0.25-0.36] mmol/l in nondiabetics; P < 0.001), phospholipid (PL) (2.52 [1.73-3.03) mmol/L in type I DM compared with 1.34 [1.27-1.48] mmol/L in nondiabetics; P < 0.01], and the apolipoproteins A-I and B had significantly higher concentrations in type I DM. In umbilical venous cord blood, ratios of HDL-TC and HDL-PL to apo AI, reflecting the lipid content of HDL, were reduced when the mother had type I DM during pregnancy (P < 0.02 and P < 0.0001, respectively). These results indicate that maternal type I DM may lead to a fetal serum lipoprotein composition more closely resembling that seen in the adult. In type I DM, maternal TG and PL and fetal TC, TG, PL, CE, and FC were correlated to NEFA levels (P < 0.05), but not to glucose, insulin secretion, or maternal control of type I DM. These data suggest that the enhanced supply of NEFA to the fetus in type I DM pregnancies may drive the synthesis of cholesterol as well as TGs and PLs.     

Brain mapping in animals and humans

The discovery of the Mothers against dpp (Mad) gene in Drosophila has opened a window on an entirely unique signalling pathway that functions to mediate responses to the tumour growth factor beta (TGF beta) superfamily. This pathway, which is comprised of a family of proteins related to Mad, acts to convey signals directly from TGF beta receptors to the nucleus and is implicated in the pathogenesis of human diseases.     

Geographic distribution and clinical description of leishmaniasis cases in Peru

Asymmetric acetylcholinesterase (AChE) is anchored to the basal lamina (BL) of cholinergic synapses via its collagenic tail, yet the complement of matrix receptors involved in its attachment remains unknown. The development of a novel overlay technique has allowed us to identify two Torpedo BL components that bind asymmetric AChE: a polypeptide of approximately 140 kDa and a doublet of 195-215 kDa. These were found to stain metachromatically with Coomassie blue R-250, were solubilized by acetic acid, and were sensitive to collagenase treatment. Upon sequence analysis, the 140 kDa polypeptide yielded a characteristic collagenous motif. Another AChE-binding BL constituent, identified by overlay, corresponded to a heparan sulfate proteoglycan. Lastly, we established that this proteoglycan, but not the collagenous proteins, interacted with at least one heparin binding domain of the collagenic tail of AChE. Our results indicate that at least two BL receptors are likely to exist for asymmetric AChE in Torpedo electric organ.     

Patterns of expression for the mRNA corresponding to the four isoforms of phospholipase Cbeta in mouse brain

Ligand binding to neurotransmitter and hormone receptors which couple to the Gq subclass of GTP-binding protein leads to the activation of phospholipase Cbeta (PLCbeta) which hydrolyses phosphatidyl-inositol 4,5-bisphosphate, yielding a pair of second messengers, diacylglycerol and inositol 1,4,5-trisphosphate (IP3). The expression of PLCbeta1-4 mRNAs was comparatively examined by in situ hybridization in the mouse brain. In adults, PLCbeta1 mRNA was expressed predominantly in the telencephalon, including the cerebral cortex, hippocampus, amygdala, lateral septum and olfactory bulb, with little expression in most thalamic nuclei. PLCbeta2 mRNA was distributed in the white matter, suggesting its expression in non-neuronal cells, most likely oligodendrocytes. PLCbeta3 mRNA was specifically expressed in cerebellar Purkinje cells. The highest levels of PLCbeta4 mRNA were detected in Purkinje cells. High levels of PLCbeta4 mRNA were also found in the thalamus and medial septum, whereas weak signals were detected in most telencephalic regions, thus showing an expression pattern almost reciprocal to that of PLCbeta1 mRNA. During development, such characteristic regional expression of PLCbeta1 and PLCbeta4 were observed starting in late foetal stages, while specific expression of PLCbeta2 and PLCbeta3 appeared in early postnatal stages. We conclude that despite the existence of four PLCbeta isoforms, only one or two of them is expressed in individual neurons and glial cells. The distinct expression of PLCbetas provides a molecular basis for analysing the nature of the specific signal transduction pathway leading to the production of diacylglycerol and IP3 in distinct cell types and in different regions of the brain.     

RP-HPLC binding domains of proteins

Procedures have been developed to identify the chromatographic binding domains of horse heart cytochrome c (Cyt c) and bovine growth hormone (bGH) during their interaction with reversed-phase sorbent materials. The procedure involves adsorption of the protein solute to the chromatographic sorbent, followed by proteolytic cleavage. Comparison of the proteolytic map obtained for Cyt c and bGH in free solution with the corresponding map obtained when these proteins are adsorbed to the chromatographic sorbent revealed significant differences in the digestion pattern. Following characterization of the peptides generated in both maps, the results indicated that specific regions on the surface of both Cyt c and bGH are inaccessible to tryptic cleavage when adsorbed to the hydrophobic surface of both a C-4 and a C-18 sorbent. Based on the assumption that the region of the protein surface that is in contact with the sorbent remains intact and bound to the sorbent during the digestion step, while the protein surface that is exposed to the solvent is accessible to proteolysis, the regions that were inaccessible to tryptic digestion were found to correspond to hydrophobic domains on the protein surface. These results also suggest that the three-dimensional structures of these proteins remain largely intact upon adsorption to the hydrophobic surface.     

Non-transferrin iron uptake by trophoblast cells in culture. Significance of a NADH-dependent ferrireductase

BACKGROUND: Glucocorticoids have been linked to self-administration of a wide range of drugs in animals and are increased endogenously by chronic nicotine intake. Corticosteroids have also been shown to regulate nicotine receptor sensitivity and to be involved in behavioral sensitization to nicotine. METHODS: Cortisol levels and cortisol suppression in response to dexamethasone were measured in a sample of smokers participating in a smoking cessation treatment trial. RESULTS: Cortisol levels dropped significantly during the early quitting process (2 weeks post-quit) and returned to a level below baseline 1 month post-quit. The magnitude of the initial drop in cortisol was strongly related to post-quit distress and marginally predictive of abstinence. Neither baseline nor post-quit changes in percent cortisol suppression after dexamethasone were related to abstinence success or withdrawal distress. CONCLUSIONS: Withdrawal from cigarette smoking is marked by a reduction in cortisol levels that appears to be related to the degree of distress experienced during the early quitting period. Further work is needed to determine whether withdrawal-related cortisol changes or distress are predictive of abstinence success.     

Radiation doses in the population of the coastal area of the Kakhovsk Water Reservoir

Central and cerebral hemodynamics was studied using echocardiography and transcranial dopplerography in 200 poststroke patients over 60 in the course of 5-year follow-up. It was established that cardiac hypodynamic syndrome, i.e. continuous or paroxysmal fall of minute blood volume below 3 l, is the most significant contributing factor in the onset of cerebral ischemia. Drugs are recommended for prevention of ischemic stroke. Those lowering cardiac hemodynamic reserve should be excluded in patients at high risk of acute failure of cerebral circulation.