High thermal conductivity of spark plasma sintered silicon carbide ceramics with yttria and scandia

A fully dense SiC ceramic with a room‐temperature thermal conductivity of 262 W·(m·K)^?1 was obtained via spark plasma sintering β‐SiC powder containing 0.79 vol% Y₂O₃‐Sc₂O₃. High‐resolution transmission electron microscopy revealed two different SiC‐SiC boundaries, that is, amorphous and clean boundaries, in addition to a fully crystallized junction phase. A high thermal conductivity was attributed to a low lattice oxygen content and the presence of clean SiC‐SiC boundaries.     

Effect of Ganglioside GM3 Synthase Gene Knockout on the Glycoprotein N‐Glycan Profile of Mouse Embryonic Fibroblast

The structural and clinical significance of cellular glycoproteins and glycosphingolipids (GSLs) are often separately discussed. Considering the biosynthetic pathway of glycoconjugates, glycans of cell‐surface glycoproteins and GSLs might partially share functions in maintaining cellular homeostatis. The purpose of this study is to establish a general and comprehensive glycomics protocol for cellular GSLs and N‐glycans of glycoproteins. To test the feasibility of a glycoblotting‐based protocol, whole glycans released both from GSLs and glycoproteins were profiled concurrently by using GM3 synthase‐deficient mouse embryonic fibroblast GM3(?/?). GM3(?/?) cells did not synthesize GM3 or any downstream product of GM3 synthase. Instead, expression levels of o‐series gangliosides involving GM1‐b and GD1‐α increased dramatically, whereas a‐/b‐series gangliosides were predominantly detected in wild‐type (WT) cells. We also discovered that glycoprotein N‐glycan profiles of GM3(?/?) cells are significantly altered as compared to WT cells, although GM3 synthase is responsible only for GSLs synthesis and is not associated with glycoprotein N‐glycan biosynthesis. The present approach allows for high‐throughput profiling of cellular glycomes enriched by different classes of glycoconjugates, and our results demonstrated that gene knockout of the enzymes responsible for GSL biosynthesis significantly influences the N‐glycans of glycoproteins.     

An Engineered Biocatalyst for the Synthesis of Glycoconjugates: Utilization of β1,3‐N‐Acetyl‐D‐glucosaminyltransferase from Streptococcus agalactiae Type Ia Expressed in Escherichia coli as a Fusion with Maltose‐Binding Protein

A fusion protein composed of β1,3‐N‐acetyl‐D ‐glucosaminyltransferase (β1,3‐GlcNAcT) from Streptococcus agalactiae type Ia and maltose‐binding protein (MBP) was produced in Escherichia coli as a soluble and highly active form. Although this fusion protein (MBP‐β1,3‐GlcNAcT) did not show any sugar‐elongation activity to some simple low‐molecular weight acceptor substrates such as galactose, Galβ(1→4)Glc (lactose), Galβ(1→4)GlcNAc (N‐acetyllactosamine), Galβ(1→4)GlcNAcβ(1→3)Galβ(1→4)Glc (lacto‐N‐tetraose), and Galβ(1→4)GlcβCer (lactosylceramide, LacCer), the multivalent glycopolymer having LacCer‐mimic branches (LacCer mimic polymer, LacCer primer) was found to be an excellent acceptor substrate for the introduction of a β‐GlcNAc residue at the O‐3 position of the non‐reducing galactose moiety by this engineered enzyme. Subsequently, the polymer having GlcNAcβ(1→3)Galβ(1→4)Glc was subjected to further enzymatic modifications by using recombinant β1,4‐D ‐galactosyltransferase (β1,4‐GalT), α2,3‐sialyltransferase (α2,3‐SiaT), α1,3‐L ‐fucosyltransferase (α1,3‐FucT), and ceramide glycanase (CGase) to afford a biologically important ganglioside; Neu5Aα(2→3)Galβ(1→4)[Fucα(1→3)]GlcNAcβ(1→3)Galβ(1→4)GlcCerα(IV3Neu5Acα,III3Fucα‐nLc4Cer) in 40% yield (4 steps). Interestingly, it was suggested that MBP‐β1,3‐GlcNAcT could also catalyze a glycosylation reaction of the LacCer mimic polymer with N‐acetyl‐D ‐galactosamine served from UDP‐GalNAc to afford a polymer carrying trisaccharide branches, GalNAcβ(1→3)Galβ(1→4)Glc. The versatility of the MBP‐β1,3‐GlcNAcT in the practical synthesis was preliminarily demonstrated by applying this fusion protein as an immobilized biocatalyst displayed on the amylose resin which is known as a solid support showing potent binding‐affinity with MBP.     

Fracture behavior of core‐shell rubber–modified clay‐epoxy nanocomposites

Morphology and fracture mechanisms in two nanoclay‐filled epoxy systems were investigated using both microscopy and spectroscopy tools. Clay exfoliation was achieved using a series of sample preparation steps, and confirmed using wide angle X‐ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. Significant improvement in modulus was obtained when clay exfoliation was achieved. Incorporation of core‐shell rubber (CSR) in both caly‐filled epoxy systems leads to greatly enhanced fracture toughness. Optical microscopy and TEM observations of the CSR‐modified nanocomposites suggest that CSR cavitation. shear yielding of the matrix, clay layer delamination. CSR bridging, crack bifurcation. and crack deflection are among the operative toughening mechanisms observed, depending on the nature of the epoxy matrix utilized.     

Mating Communication Systems of Four Plusiinae Species Distributed in Japan: Identification of the Sex Pheromones and Field Evaluation

The sex pheromones of four Plusiinae species in the family Noctuidae, Ctenoplusia albostriata (CA), Macdunnoughia purissima (MP), Syngrapha ain (SA), and Diachrysia stenochrysis (DS) were identified by GC-EAD and GC-MS analyses. These were subsequently evaluated by a series of field trials in different ecological habitats. CA females produced (Z)-5-decenyl acetate (I), (Z)-7-dodecenyl acetate (II), and (Z)-7-dodecen-1-ol (III) in a ratio of 2:100:13. While the antennae of CA males responded to all three components, neither I nor III was essential to capture males. The MP females produced II, III, and (Z)-5-dodecenyl acetate (IV) in a ratio of 100:80:20, and this blend captured the most MP males. Compounds II and III were also identified from SA females, and mixtures ranging from 4:1 to 2:3 were equally attractive to males. DS females only produced one active compound, (Z)-7-decenyl acetate (V), and DS is the first Plusiinae species identified as using only the ω3-compound and none of ω5-compounds, such as II and III, which are common components of Plusiinae pheromones. Using previously published chemical and biosynthetic data, together with the finding from this study, we propose a classification of the Plusiinae sex pheromones.     

On the stress corrosion cracking and hydrogen embrittlement of sensitized austenitic stainless steels in boiling saturated magnesium chloride solutions: Effect of applied stress

Stress corrosion cracking (SCC) and hydrogen embrittlement (HE) of sensitized stainless steels of types 304, 310 and 316 were investigated as a function of applied stress at different test temperatures in boiling saturated magnesium chloride (MgCl₂) solutions under a constant applied stress condition. The stress dependence of fracture appearance and three parameters of time to failure (t_f), steady-state elongation rate (l_ss) and transition time to time to failure ratio suggests that types 304 and 310 suffered SCC, while type 316 suffered only HE. It was also found that the applied stress dependence of three parameters for the sensitized types 304 and 310 was almost similar to that of the solution-annealed stainless steels, whereas that of type 316 showed a clear difference between sensitized and solution-annealed specimens. The relationships between the logarithms of the time to failure and the steady-state elongation rate became a straight line for all stainless steels. However, its slope depended upon the fracture mode: −2.0 for SCC and −1.5 for HE. This showed that the steady-state elongation rate was a good parameter for predicting the time to failure for the stainless steels in the MgCl₂ solutions. The results obtained were explained in terms of martensite transformation, hydrogen entry site, and sensitization.     

Ingestion of gelatinized potato starch containing a high level of phosphorus decreases serum and liver lipids in rats

Potato starch is known to have a higher concentration of phosphate than other starches. The presence of phosphate groups in amylopectin results in resistance to digestion by amylase. Therefore, there is a possibility that potato starch is slowly digested, inducing a physiological effect similar to that of resistant starch and indigestible oligosaccharides. The amount of phosphate group in starch differs with potato cultivar. In the present study, we investigated the effects of gelatinized potato starch containing a high level of phosphorus on lipid metabolism in rats. For this purpose, we determined lipid levels in the serum and liver in rats fed two kinds of gelatinized potato starches with different phosphorus contents. Four groups of male Sprague-Dawley rats were fed a 60% sucrose diet (control) or one of three diets containing cornstarch (CS), Benimaru (BM) potato starch or Hokkaikogane (HK) potato starch. Fat pad weight was slightly decreased in the HK diet group compared with that in the other groups. Free fatty acids in serum were significantly lowered by dietary HK starch compared with control, and serum triglyceride in rats fed the HK diet was also decreased. In the BM and HK diet groups, triglyceride levels in the liver were decreased compared with that in the control and CS groups. As for hepatic total cholesterol level, there were no significant differences among three starch diet groups. Fecal bile acid excretion was greater in the two potato starch groups than in the control group. On the other hand, there were no significant differences in cecal short-chain fatty acid content or pH. Thus, we conclude that dietary gelatinized potato starch reduces free fatty acid and triglyceride in serum and hepatic triglyceride, but does not affect cecal fermentation.     

Measurement of self-diffusion coefficients in Li ionic conductors by using the short-lived radiotracer of 8Li

For the effective use of short-lived radioactive beams, soon to be available at the Tokai Radioactive Ion Accelerator Complex, the authors have developed a radiotracer method for diffusion studies in solids. The experimental test was performed by the measurement of the diffusion coefficients of Li in a sample of the compound βLiAl using an α-emitting radiotracer of ⁸Li (T_1/2=0.84 s). It was found that the time-dependent yields of the α particles from the diffusing ⁸Li that was initially implanted in the sample could be used as a measure of the diffusivity of the tracer in a nondestructive way. The method was applied to measure the self-diffusion coefficients of Li in βLiGa, and for investigating how the Li diffusion in the Li ionic conductors is affected by the concentration of atomic defects (i.e., the existence of the atomic vacancies of Li and the defects in Ga sites that are replaced by Li).     

The effects of air pollution and climatic factors on atmospheric corrosion of marble under field exposure

The atmospheric corrosion of marble was evaluated in terms of SO₂ concentration as air pollution and climatic factors such as rainfall, relative humidity, temperature and so on under the field exposure. Marble of calcite type (CaCO₃) was exposed to outdoor atmospheric environment with and without a rain shelter at four test sites in the southern part of Vietnam for 3-month, 1- and 2-year periods from July 2001 to September 2003. The thickness loss of marble was investigated gravimetrically. X-ray diffraction and X-ray fluorescent methods were applied to study corrosion products on marble. The corrosion product of marble was only gypsum (CaSO₄ · 2H₂O) and was washed out by rain under the unsheltered exposure condition. It was found that the most substantial factors influencing the corrosion of marble were rainfall, SO₂ concentration in the air and relative humidity. Based on the results obtained, we estimated the dose-response functions for the atmospheric corrosion of marble in the southern part of Vietnam.