Fabrication and evaluation of nanostructure Al-SiCp composite by accumulative roll-bonding

A nanostructured Al/SiCp composite was fabricated by accumulative roll bonding (ARB) process. The amount of SiC particles introduced into aluminum sheet by one cycle ARB was 0.22 mg/cm2. Increment of the number of ARB cycles increased the amount of SiC particles and enhanced the homogeneity of the distribution of SiC particles. Microstructural change in aluminum matrix with proceeding of the ARB was very similar to that of the ARB-processed unreinforced aluminum; showing a dislocation cell and/or sub-grain structure in samples of lower ARB cycles and ultrafine grained structure in samples of higher ARB cycles. The variation of tensile strength with the ARB was also very similar to that of unreinforced aluminum. However, the effect of strengthening by the ARB was higher in the Al/SiCp composite than in unreinforced aluminum due to an existence of the SiC particles and the formation of finer grains.     

Influence of side chain length on fluorescence intensity of ROMP-based polymeric nanoparticles and their tumor specificity in in-vivo tumor imaging

In this study, amphiphilic brush-like copolymers conjugated with short alkyl or long polymeric chains of various lengths are synthesized using ring-opening metathesis polymerization (ROMP) of substituted norbornadiene monomers followed by chemical transformations. These amphiphilic copolymers form spherical self-assemblies in aqueous media with diameters of 132-244 nm. The low critical aggregation concentration of these assemblies (2.5 × 10(-3) -1.4 × 10(-5) g/L) indicates that they are quite stable in dilute conditions. An appropriate length of polymer side chain that conjugates the polymer backbone with a hydrophobic ICG (indocyanine green) moiety enhanced the fluorescence intensities of these self-assemblies in aqueous solution as well as in tumor-bearing mice. A longer side chain conjugated with tumor targeting agents could significantly affect the tumor specificity of self-assemblies to a greater extent. The self-assemblies bearing hydrophilic tumor targeting agents, such as a glucosamine molecule and a cyclic RGD (arginine-glycine-asparatic acid) peptide, accumulated in tumor tissues with high selectivity, while those having a hydrophobic targeting agent, such as folate moieties, accumulated in tumor sites with low selectivity. The results demonstrated here unambiguously indicate that the fluorescence intensity and tumor specificity of self-assemblies are strongly affected by the length of side chains that conjugate with dyes and targeting agents.     

Structural advantages of rectangular-like channel cross-section on electrical characteristics of silicon nanowire field-effect transistors

We have experimentally demonstrated structural advantages due to rounded corners of rectangular-like cross-section of silicon nanowire (SiNW) field-effect transistors (FETs) on on-current (I_ON), inversion charge density normalized by a peripheral length of channel cross-section (Q_inv) and effective carrier mobility (μ_eff). The I_ON was evaluated at the overdrive voltage (V_OV) of 1.0 V, which is the difference between gate voltage (V_g) and the threshold voltage (V_th), and at the drain voltage of 1.0 V. The SiNW nFETs have revealed high I_ON of 1600 μA/μm of the channel width (w_NW) of 19 nm and height (h_NW) of 12 nm with the gate length (L_g) of 65 nm. We have separated the amount of on-current per wire at V_OV = 1.0 V to a corner component and a flat surface component, and the contribution of the corners was nearly 60% of the total I_ON of the SiNW nFET with L_g of 65 nm. Higher Q_inv at V_OV = 1.0 V evaluated by advanced split-CV method was obtained with narrower SiNW FET, and it has been revealed the amount of inversion charge near corners occupied 50% of all the amount of inversion charge of the SiNW FET (w_NW = 19 nm and h_NW = 12 nm). We also obtained high μ_eff of the SiNW FETs compared with that of SOI planar nFETs. The μ_eff at the corners of SiNW FET has been calculated with the separated amount of inversion charge and drain conductance. Higher μ_eff around corners is obtained than the original μ_eff of the SiNW nFETs. The higher μ_eff and the large fractions of I_ON and Q_inv around the corners indicate that the rounded corners of rectangular-like cross-sections play important roles on the enhancement of the electrical performance of the SiNW nFETs.     

Effective passivation of defects in Ge-rich SiGe-on-insulator substrates by Al2O3 deposition and subsequent post-annealing

A method of Al₂O₃ deposition and subsequent post-deposition annealing (Al₂O₃-PDA) was proposed to passivate electrically active defects in Ge-rich SiGe-on-insulator (SGOI) substrates, which were fabricated using Ge condensation by dry oxidation. The effect of Al₂O₃-PDA on defect passivation was clarified by surface analysis and electrical evaluation. It was found that Al₂O₃-PDA could not only suppress the surface reaction during Al-PDA in our previous work [Yang H, Wang D, Nakashima H, Hirayama K, Kojima S, Ikeura S. Defect control by Al-deposition and the subsequent post-annealing for SiGe-on-insulator substrates with different Ge fractions. Thin Solid Films 2010; 518: 2342-5.], but could also effectively passivate p-type defects generated during Ge condensation. The concentration in the range of 10¹⁶-10¹⁸ cm⁻³ for defect-induced acceptors and holes in Ge-rich SGOI drastically decreased after Al₂O₃-PDA. As a result of defect passivation, the electrical characteristics of both back-gate p-channel and n-channel metal-oxide-semiconductor field-effect transistors fabricated on Ge-rich SGOI were greatly improved after Al₂O₃-PDA.     

Control of valence states by a codoping method in CuInS2

We deviate the valence and conduction band energies of stoichiometric CuInS₂ crystals based on ab initio electronic band structure calculations using the augmented spherical wave (ASW) method and discuss that at low doping levels, the Madelung energy is a good intrinsic parameter for stabilization of p- or n-type doped CuInS₂ crystals. We find that P and Sb atoms are eminently suitable dopants substituted for S atoms for p-type doped CuInS₂ crystals with lower resistivity from both the character of electronic states around E_F and the Madelung energy. A closer study of the nature of chemical bonds of CuInS₂ crystals using first-principles band structure calculation method reveals that In with polyvalence codoping for p-type CuInS₂ doped with P results in a decrease of the Madelung energy compared with CuInS₂: P, to be an effective method for stabilizing of its ionic charge distributions.     

Estimation of mechanochemical dechlorination rate of poly(vinyl chlorde)

Poly(vinyl chloride) (PVC) was ground in air with CaO in the presence of quartz powder as a grinding aid by a small-scale planetary ball mill to investigate the relation of the dechlorination rate of PVC with the impact energy of the balls calculated from a computer simulation based on the Discrete Element Method under various conditions. Mechanochemical dechlorination proceeds as the grinding progresses and is improved with an increase in both the mill speed and the amount of balls introduced into the mill. The same trend can be seen in the relation between the specific normal impact energy of the balls and the rotational speed. The relationship between the observed dechlorination rate and the computed normal impact energy of the balls is linear, with a correlation coefficient of 0.965. This relationship can be used to estimate the dechlorination rate of PVC in a large-scale planetary ball mill.     

Amino Acid Absorption in Portal Blood After Duodenal Infusions of a Soy Protein Hydrolysate Prepared by a Novel Soybean Protease D3

ABSTRACT:  The intestinal absorption of amino acids from decapeptide was investigated in rats under unrestrained conditions. The soy protein hydrolysate utilized in the experiment was produced by a novel soybean protease D3. The enzymatic features of protease D3 showed high homology with cathepsin L and cathepsin K and the average molecular weight of D3 hydrolysate is approximately 1200. We compared the intestinal absorption of D3 hydrolysate in portal blood with that of an amino acids mixture and soy protein with the same amino acid composition by determining the concentration of individual amino acids after a single administration of a nitrogen source. The absorptive velocity and intensity of each amino acid were calculated from its rate of elevation in the portal blood. And in most cases, these were higher in the D3 hydrolysate than in amino acids mixture and protein. The proportion of the amount of each amino acid absorbed in portal blood from D3 hydrolysate was much more like the composition of the administrated amino acids than like that from the amino acids mixture. The result of in vitro digestion assay indicated that D3 hydrolysate was hydrolyzed easier than the hydrolysates produced by microbial proteases. This is the first report to demonstrate that the D3 hydrolysate, which contains decapeptide as a dominant fraction, was more rapidly utilized than the amino acids mixture and protein as is the case with di-, tripeptides. This suggested that this hydrolysate could be available for nutraceutical use as well as use in nutritious foods for athletes and patients.     

Effect of pressure at primary drying of freeze-drying mouse sperm reproduction ability and preservation potential

Freeze-dried spermatozoa are capable of participating in normal embryonic development after injection into oocytes and thus useful for the maintenance of genetic materials. We recently reported that long-term preservation of freeze-dried mouse spermatozoa by conventional methods requires temperatures lower than -80 degrees C. Successful permanent preservation of mouse spermatozoa at much higher temperatures requires thorough investigation of the freeze-drying procedure. Thus, we examined the relationship between the pressure at primary drying and the preservation potential of freeze-dried mouse spermatozoa. Three different primary drying pressures were applied to evaluate the effect of pressure on freeze-dried spermatozoa under varying storage conditions and the rate of development measured. The developmental rate of embryos to the blastocyst stage from intracytoplasmic sperm injection by freeze-dried spermatozoa at pressures of 0.04, 0.37, and 1.03 mbar without storage were 59% (337/576), 71% (132/187), and 33% (99/302) respectively. When stored at 4 degrees C for 6 months, the rate was 13% (48/367), 50% (73/145), and 36% (66/182) respectively. These results show that primary drying pressure is an influential factor in the long-term preservation of freeze-dried mouse spermatozoa.     

Metabolic engineering--integrating methodologies of molecular breeding and bioprocess systems engineering

Metabolic engineering is an integrating methodology of analysis and synthesis for the improvement of flux distribution of metabolic pathways in complicated bioprocesses, which are highly multi-hierarchical systems to extend from macroscopic to microscopic levels. Recent progress in metabolic engineering methodologies to improve metabolic pathways in microorganisms was reviewed with many studies in this paper. Metabolic flux distribution was analyzed under different environmental conditions, using a metabolic reaction model. The physiological states of microorganisms were understood by interpreting metabolic flux analysis (MFA). This analysis was also used for development of process operation and control strategy. Cell capability to form a targeted product was analyzed with a metabolic reaction model and linear programming (LP). The use of a 13C-enriched carbon source and nuclear magnetic resonance (NMR) and gas chromatography-mass spectrometry (GCMS) analyses of intracellular and extracellular metabolites enabled determination of a metabolic flux distribution more accurately than the flux distribution determined only by the metabolic reaction model, which involves not only metabolite balances but also energy and redox balances. The comparison of metabolic flux distributions between before and after genetic modification of cells yielded information on the mechanism of regulation of metabolic flux in microorganisms. Finally, integration of bioinformatics and metabolic engineering is discussed, and cyclic modification of the complex bionetwork and process development were emphasized.