地基非均匀沉降下天然气管道应力分析

湿陷性黄土在受水浸湿后产生了严重的地基非均匀沉降现象,对管道产生了附加应力,产生了肉眼可见的位移偏量,严重影响天然气管道的运输安全。针对志丹压气站天然气输气管道的复杂铺设结构进行了应力计算与分析,结合现场监测数据与数值模拟分析,给出关键点的应力和位移,验证了模型合理性,对输气管道应力状态进行预测分析,得到了对工程设计与改进具有重要意义的结论,为天然气管道的应力预测提供了理论依据。

Characterization of hippocampal Cajal-Retzius cells during development in a mouse model of Alzheimer's disease(Tg2576)

Cajal-Retzius cells are reelin-secreting neurons in the marginal zone of the neocortex and hippocampus. The aim of this study was to investigate Cajal-Retzius cells in Alzheimer＇s disease pathology. Results revealed that the number of Cajal-Retzius cells markedly reduced with age in both wild type and in mice over-expressing the Swedish double mutant form of amyloid precursor protein 695 （transgenic （Tg） 2576 mice）. Numerous reelin-positive neurons were positive for activated caspase 3 in Tg2576 mice, suggesting that Cajal-Retzius neuronal loss occurred via apoptosis in this Alzheimer＇s disease model. Compared with wild type, the number of Cajal-Retzius cells was significantly lower in Tg2576 mice. Western blot analysis confirmed that reelin levels were markedly lower in Tg2576 mice than in wild-type mice. The decline in Cajal-Retzius cells in Tg2576 mice was found to occur concomitantly with the onset of Alzheimer＇s disease amyloid pathology and related behavioral deficits. Overall, these data indicated that Cajal-Retzius cell loss occurred with the onset and development of Alzheimer＇s disease.

Subdiaphragmatic vagotomy reduces intake of sweet-tasting solutions in rats

Studies have shown that there are strong interactions between gustatory and visceral sensations the central nervous system when rats ingest sweet foods or solutions. To investigate the role of th subdiaphragmatic vagi in transmitting general visceral information during the process of drinking sweet-tasting solutions, we examined the effects of subdiaphragmatic vagotomy on the intake of 0.5 mol/L sucrose, 0.005 mol/L saccharin or distilled water over the course of 1 hour in rats depriv~ of water. Results showed no significant difference in consumption of these three solutions in vagotomized rats. However, rats in the sham-surgery group drank more saccharin solution than sucrose solution or distilled water. Moreover, the intake of distilled water was similar between vagotomized rats and sham-surgery group rats, but significantly less sucrose and saccharin were consumed by vagotomized rats compared with rats in the sham-surgery group. These findings indicate that subdiaphragmatic vagotomy reduces intake of sweet-tasting solution in rats, and suggest that vagal and extravagal inputs play a balanced role in the control of the intake of sweet-tasting solutions. They also suggest that subdiaphragmatic vagotomy eliminates the difference in hedonic perception induced by sweet-tasting solutions compared with distilled water II E

Development of the cerebellar cortex in the mouse

The cerebellum is a highly conserved structure in the central nervous system of vertebrates, and is involved in the coordination of voluntary motor behavior. Supporting this function, the cerebellar cortex presents a layered structure which requires precise spatial and temporal coordination of proliferation, migration, differentiation, and apoptosis events. The formation of the layered structure in the developing cerebellum remains unclear. The present study investigated the development of the cerebellar cortex. The results demonstrate that the primordium of the cerebellum comprises the ependymal, mantle, and marginal layers at embryonic day 12 （E12）. Subsequently, the laminated cerebellar cortex undergoes cell proliferation, differentiation, and migration, and at about postnatal day 0 （P0）, the cerebellar cortex presents an external granular layer, a molecular layer, a Purkinje layer, and an internal granular layer. The external granular layer is thickest at P6/7 and disappears at P20. From P0 to P30, the internal granular cells and the Purkinje cells gradually differentiate and develop until maturity. Apoptotic neurons are evident in the layered structure in the developing cerebellar cortex. The external granular layer disappears gradually because of cell migration and apoptosis. The cells of the other layers primarily undergo differentiation, development, and apoptosis.

Asymmetric breakup of a droplet in an axisymmetric extensional flow

The asymmetric breakups of a droplet in an axisymmetric cross-like microfluidic device are investigated by using a three-dimensional volume of fluid(VOF) multiphase numerical model. Two kinds of asymmetries(droplet location deviation from the symmetric geometry center and different flow rates at two symmetric outlets) generate asymmetric flow fields near the droplet, which results in the asymmetric breakup of the latter. Four typical breakup regimes(no breakup, one-side breakup, retraction breakup and direct breakup) have been observed.Two regime maps are plotted to describe the transition from one regime to another for the two types of different asymmetries, respectively. A power law model, which is based on the three critical factors(the capillary number,the asymmetry of flow fields and the initial volume ratio), is employed to predict the volume ratio of the two unequal daughter droplets generated in the direct breakup. The influences of capillary numbers and the asymmetries have been studied systematically in this paper. The larger the asymmetry is, the bigger the oneside breakup zone is. The larger the capillary number is, the more possible the breakup is in the direct breakup zone. When the radius of the initial droplet is 20 μm, the critical capillary numbers are 0.122, 0.128, 0.145,0.165, 0.192 and 0.226 for flow asymmetry factor AS= 0.05, 0.1, 0.2, 0.3, 0.4 and 0.5, respectively, in the flow system whose asymmetry is generated by location deviations. In the flow system whose asymmetry is generated by two different flow rates at two outlets, the critical capillary numbers are 0.121, 0.133, 0.145, 0.156 and 0.167 for AS= 1/21, 3/23, 1/5, 7/27 and 9/29, respectively.

Characterizing the influence of gut microbiota on host tryptophan metabolism with germ-free pigs

Intestinal microbes are closely associated with host health,depending on metabolic crosstalk between the microbiota and host.Tryptophan metabolism is one of the best examples of metabolic crosstalk between intestinal microbiota and host;however,our understanding about the influence of intestinal microbiota on host tryptophan metabolism is limited.Thus,we established germ-free(GF)pig models to systemically explore the influence of intestinal microbiota on tryptophan metabolism.Five GF pigs were kept in GF conditions throughout the experiment(GF group).Six GF pigs were transplanted with fecal microbiota from donor sows to act as control pigs.Compared with control pigs,the GF pigs had remarkable alterations in tryptophan metabolism.The differential metabolites(P<0.05)were mainly found in the liver,circulation system and large intestine.Notably,the alteration of metabolites in tryptophan metabolism varied among organs,especially for the serotonin pathway.In GF pigs,tryptophan and kynurenine in the large intestine and 5-hydroxytryptophan in most organs were increased(P<0.05),while metabolites in the indole pathway in most organs were decreased(P<0.05).Collectively,our study reveals changes in tryptophan metabolism in GF pigs,highlighting the critical role of gut microbes in shaping host tryptophan metabolism.