Plastic deformation of single crystals of Pt_3Al with the L1_2 structure

The plastic deformation behaviour of single crystals of Pt3Al with the L12 structure having an off-stoichiometric composition of Pt–27 at% Al has been investigated in compression from 77 to 1073 K. The L12 structure is not stable below around 220 K, transforming into either a D0c or D0c′ structure. Slip occurs along 1 1 0 both on (001) and on (111) with slip on (001) being the primary slip system, which operates for most crystal orientations except for near [0 01], accompanied by a considerably lower CRSS (critical resolved shear stress). The CRSS tends to decrease gradually with increasing temperature for both slip in the temperature range where the L12 phase is stable, except for a moderate increase in CRSS observed above 673 K for slip on (001). Dislocations with b  = [1‾01] dissociate into two collinear superpartials with b  = 1/2[1‾01] separated by an APB on the corresponding slip plane for both slip on (001) and (111). For slip on (111), dislocations tend to align along their screw orientation at room temperature, suggesting the high Peierls stress for their motion. The possibility of showing the normal (large negative) temperature dependence of CRSS at low temperatures as well as the reason for the absence of the anomalous (positive) temperature dependence of CRSS for slip on (111) at high temperatures is discussed

Woody debris production and deposition during floods at extreme rainfall period 2012-2013 in Yabe and Tsuwano River Basin, Japan

The behavior of woody debris has become a critical issue in river dynamics. It is still not widely understood, particularly during a flood event. Field investigations were performed to investigate the characteristics of woody debris production and deposition during the 2012 and 2013 floods in Yabe and Tsuwano River Basin, Japan. Ground-level photos, aerial photos, and direct measurements were used to measure the length and diameter of woody debris,   characteristics of obstacles (length. width, diameter, and shape). These investigations revealed that woody debris deposition was divided into two types: the rest of individual woody debris pieces on the riverside slope or floodplain and the formation of a woody debris jam at obstacles such as bridges, riparian trees, houses, and irregular topographic relief. Individual woody debris pieces at the production sites are around two times longer than those at the deposition sites. However, the variation coefficient of piece length at the production sites is smaller than that at the deposition site. Our results also show that the most extended piece in the jam and horizontal scale of the obstacle are two essential factors in jam formation. An empirical equation for predicting the apparent volume of jam at an obstacle is also proposed

Developmental switching of perisomatic innervation from climbing fibers to basket cell fibers in cerebellar Purkinje cells.

In early postnatal development, perisomatic innervation of cerebellar Purkinje cells (PCs) switches from glutamatergic climbing fibers (CFs) to GABAergic basket cell fibers (BFs). Here we examined the switching process in C57BL/6 mice. At postnatal day 7 (P7), most perisomatic synapses were formed by CFs on to somatic spines. The density of CF-spine synapses peaked at P9, when pericellular nest around PCs by CFs was most developed, and CF-spine synapses constituted 88% of the total perisomatic synapses. Thereafter, CF-spine synapses dropped to 63% at P12, 6% at P15, and <1% at P20, whereas BF synapses increased reciprocally. During the switching period, a substantial number of BF synapses existed as BF-spine synapses (37% of the total perisomatic synapses at P15), and free spines surrounded by BFs or Bergmann glia also emerged. By P20, BF-spine synapses and free spines virtually disappeared, and BF-soma synapses became predominant (88%), thus attaining the adult pattern of perisomatic innervation. Parallel with the presynaptic switching, postsynaptic receptor phenotype also switched from glutamatergic to GABAergic. In the active switching period, particularly at P12, fragmental clusters of AMPA-type glutamate receptor were juxtaposed with those of GABA(A) receptor. When examined with serial ultrathin sections, immunogold labeling for glutamate and GABA(A) receptors was often clustered beneath single BF terminals. These results suggest that a considerable fraction of somatic spines is succeeded from CFs to BFs and Bergmann glia in the early postnatal period, and that the switching of postsynaptic receptor phenotypes mainly proceeds under the coverage of BF terminals

The Human Gut Microbe <i>Bacteroides thetaiotaomicron</i> Suppresses Toxin Release from <i>Clostridium difficile</i> by Inhibiting Autolysis

Disruption of the human gut microbiota by antibiotics can lead to Clostridium difficile (CD)-associated diarrhea. CD overgrowth and elevated CD toxins result in gut inflammation. Herein, we report that a gut symbiont, Bacteroides thetaiotaomicron (BT), suppressed CD toxin production. The suppressive components are present in BT culture supernatant and are both heat- and proteinase K-resistant. Transposon-based mutagenesis indicated that the polysaccharide metabolism of BT is involved in the inhibitory effect. Among the genes identified, we focus on the methylerythritol 4-phosphate pathway gene gcpE, which supplies the isoprenoid backbone to produce the undecaprenyl phosphate lipid carrier that transports oligosaccharides across the membrane. Polysaccharide fractions prepared from the BT culture suppressed CD toxin production in vitro; the inhibitory effect of polysaccharide fractions was reduced in the gcpE mutant (ΔgcpE). The inhibitory effect of BT-derived polysaccharide fraction was abrogated by lysozyme treatment, indicating that cellwall-associated glycans are attributable to the inhibitory effect. BT-derived polysaccharide fraction did not affect CD toxin gene expression or intracellular toxin levels. An autolysis assay showed that CD cell autolysis was suppressed by BT-derived polysaccharide fraction, but the effect was reduced with that of ΔgcpE. These results indicate that cell wall-associated glycans of BT suppress CD toxin release by inhibiting cell autolysis