伞

大学是人类最纯净的精神家园,它们除了有一个象牙塔的统一标识外,每所大学还有各自所代表的建筑景观,被人们津津乐道,就像剑桥的国王礼拜堂,麻省理工的无尽长廊,北大一塔湖图的博雅塔,清华的二校门??那些耳熟能详的建筑之所以能被推崇为标志,是因为它们是历史     

Chemical characterization of the oligosaccharides in Bactrian camel (Camelus bactrianus) milk and colostrum

Bactrian camel milk and colostrum are commonly used as foods in Mongolia, whose people believe that these products promote human health. It has been hypothesized that milk oligosaccharides are biologically significant components of human milk, acting as receptor analogs that inhibit the attachment of pathogenic microorganisms to the colonic mucosa, and as prebiotics, which stimulate the growth of bifidobacteria within the infant colon. To evaluate their biological significance, we studied the oligosaccharides present in samples of Bactrian camel milk and colostrum. Using ¹H-nuclear magnetic resonance spectroscopy, we identified and characterized the following oligosaccharides of camel colostrum: Gal(β1–4)[Fuc(α1–3)]Glc (3-fucosyllactose), Gal(β1–3)Gal(β1–4)Glc (3′-galactosyllactose), Gal(β1–6)Gal(β1–4)Glc (6′-galactosyllactose), Neu5Ac(α2–3)Gal(β1–4)Glc (3′-sialyllactose), Neu5Ac(α2–6)Gal(β1–4)Glc (6′-sialyllactose), Neu5Ac(α2–3)Gal(β1–3)Gal(β1–4)Glc (sialyl-3′-galactosyllactose), Neu5Ac(α2–6)Gal(β1–4)GlcNAc(β1–3)Gal(β1–4)Glc (sialyllacto-N-tetraose c), Neu5Ac(α2–3)Gal(β1–3)[Gal(β1–4)GlcNAc(β1–6)]Gal(β1–4)Glc (sialyllacto-N-novopentaose a), Gal(β1–3)[Neu5Ac(α2–6)Gal(β1–4)GlcNAc(β1–6)]Gal(β1–4)Glc (sialyllacto-N-novopentaose b); and Neu5Ac(α2–6)Gal(β1–4)GlcNAc(β1–3)[Gal(β1–4)GlcNAc(β1–6)]Gal(β1–4)Glc (monosialyllacto-N-neohexaose). The oligosaccharides in the mature camel milk were characterized as 3′-galactosyllactose, Gal(β1–3)[Gal(β1–4)GlcNAc(β1–6)]Gal(β1–4)Glc (lacto-N-novopentaose I), and 3′-sialyllactose.     

Large eddy simulation of turbulent flow past a square cylinder confined in a channel

Turbulent flow past a square cylinder confined in a channel is numerically investigated by large eddy simulation (LES). The main objectives of this study are to extensively verify the experimental results of Nakagawa et al. [Exp. Fluids 27(3) (1999) 284] by LES and to identify the features of flows past a square cylinder confined in a channel in comparison with the conventional one in an infinite domain. The LES results obtained are in excellent agreement with the experiment both qualitatively and quantitatively. The well-known Kármán vortex shedding is observed. However, the vortices shed from the cylinder are significantly affected by the presence of the plates; mean drag and fluctuation of lift force increase significantly. Furthermore, periodic and alternating vortex-rollups are observed in the vicinity of the plates. The rolled-up vortex is convected downstream together with the corresponding Kármán vortex; they form a counter-rotating vortex pair. It is also revealed that the cylinder greatly enhances mixing process of the flow.     

Glucosylceramide Changes Bacterial Metabolism and Increases Gram-Positive Bacteria through Tolerance to Secondary Bile Acids In Vitro

Glucosylceramide is present in many foods, such as crops and fermented foods. Most glucosylceramides are not degraded or absorbed in the small intestine and pass through the large intestine. Glucosylceramide exerts versatile effects on colon tumorigenesis, skin moisture, cholesterol metabolism and improvement of intestinal microbes in vivo. However, the mechanism of action has not yet been fully elucidated. To gain insight into the effect of glucosylceramide on intestinal microbes, glucosylceramide was anaerobically incubated with the dominant intestinal microbe, Blautia coccoides, and model intestinal microbes. The metabolites of the cultured broth supplemented with glucosylceramide were significantly different from those of broth not treated with glucosylceramide. The number of Gram-positive bacteria was significantly increased upon the addition of glucosylceramide compared to that in the control. Glucosylceramide endows intestinal microbes with tolerance to secondary bile acid. These results first demonstrated that glucosylceramide plays a role in the modification of intestinal microbes.     

Hill Plot Focusing on Ce Compounds with High Magnetic Ordering Temperatures and Consequent Study of Ce<Subscript>2</Subscript>AuP<Subscript>3</Subscript>

The Hill plot is a well-known criterion of the f-electron element interatomic threshold distance separating the nonmagnetic state from the magnetic state in actinides and lanthanides. We have reinvestigated the Hill plot of Ce compounds using the commercial crystallographic database CRYSTMET, focusing on a relationship between the Ce-Ce distance and the magnetic ordering temperature because a Ce compound with no other magnetic elements rarely has a magnetic ordering temperature that is higher than 20 K. The Hill plot of approximately 730 compounds has revealed that a Ce compound, particularly a ferromagnet, showing a high magnetic ordering temperature would require a short Ce-Ce distance with a suppression of the valence instability of the Ce ion. From the study, we developed interest in Ce₂AuP₃ with a Curie temperature of 31 K. The ferromagnetic nature of this material has been examined in terms of a doping effect, which suggests a possible increase in magnetic anisotropy energy.