Low-Temperature Synthesis of Aluminum Silicon Carbide Using Ultrafine Aluminum Carbide and Silicon Carbide Powders

The conditions for preparing α-aluminum silicon carbide (α-Al₄SiC₄) were examined by heating stoichiometric mixtures of ultrafine A1₄C₃ and SiC powders with sizes of <0.1 μm at and below 1600°C. The starting A1₄C₃ powder was obtained by the pyrolysis of trimiethylaluminum; the starting SiC powders were obtained by the pyrolyses of triethylsilane (3ES), tetraethylsilane (4ES), and hexamethyldisilane (6MDS). The reactivity of SiC with Al₄C₃ to form α-Al₄SiC₄ varies according to the kind of starting alkylsilane: 3ES > 4ES > 6MDS. The reaction of 3ES-derived SiC with A1₄C₃ produced α-Al₄SiC₄ at temperatures as low as 1400°C for 240 min, regardless of the presence of A1₄C₃ (trace). Only α-Al₄SiC₄ was formed at and above 1500°C for 60 min; the crystal growth was appreciable.     

Monitoring the microbial population dynamics at the start-up stage of wastewater treatment reactor by terminal restriction fragment length polymorphism analysis based on 16S rDNA and rRNA gene sequences

The microbial population dynamics at the start-up stage of a wastewater treatment reactor was investigated using terminal restriction fragment length polymorphism (T-RFLP) analysis based on 16S rDNA and rRNA gene sequences. The results of fragment peaks suggested that the number and activity of nitrifying bacteria increased in association with the start of nitrification, and the relative ratios of 16S rRNA of these bacteria changed prior to those of the 16S rDNA. Furthermore, multidimensional scaling (MDS) analysis revealed that the 16S rRNA exhibited wider dispersion than the 16S rDNA at the start-up stage, indicating that the diversity of 16S rRNA in the microbial communities was strongly affected by environmental changes.     

Scalable resource management for high‐performance Web servers

Although many research efforts have been devoted to network congestion in the face of an increase in the Internet traffic, there is little recent discussion on performance improvements for endhosts. In this paper, we propose a new architecture, called scalable socket buffer tuning (SSBT), to provide high‐performance and fair service for many TCP connections at Internet endhosts. SSBT has two major features. One is to reduce the number of memory accesses at the sender host by using some new system calls, called Simple Memory‐copy Reduction (SMR) scheme. The other is equation‐based automatic TCP buffer tuning (E‐ATBT), where the sender host estimates ‘expected’ throughput of the TCP connections through a simple mathematical equation, and assigns a send socket buffer to them according to the estimated throughput. If the socket buffer is short, max–min fairness policy is used. We confirm the effectiveness of our proposed algorithm through both simulation technique and an experimental system. From the experimental results, we have found that our SSBT can achieve up to a 30% gain for Web server throughput, and a fair and effective usage of the sender socket buffer can be achieved. Copyright © 2004 John Wiley & Sons, Ltd.     

Csk controls antigen receptor-mediated development and selection of T-lineage cells

The development and function of alphabetaT lymphocytes depend on signals derived from pre-T and alphabetaT cell receptors (preTCR and alphabetaTCR) (reviewed in refs 1, 2). The engagement of these receptors leads to the activation of Lck and Fyn, which are protein tyrosine kinases (PTKs) of the Src family. It remains unclear to what extent the activation of Src-family PTKs can direct the differentiation steps triggered by preTCR and alphabetaTCR. Here we show that the inactivation of the negative regulator of Src-family PTKs, carboxy-terminal Src kinase (Csk), in immature thymocytes abrogates the requirement for preTCR, alphabetaTCR and major histocompatibility complex (MHC) class II for the development of CD4+ 8+ double-positive and CD4+ single-positive thymocytes as well as peripheral CD4 alphabetaT-lineage cells. These data show that Csk and its substrates are required to establish preTCR/alphabetaTCR-mediated control over the development of alphabetaT cells.     

Photo-induced absorption changes in selenium-based chalcogenide glass films

The random network model for amorphous alloys proposed by White has been developed for some selenium-based amorphous semiconductors (GeSe and AsSe) annealed or irradiated with light. The model suggests that the photo-bleaching and the photo-darkening observed in these systems may be due to changes in the numbers of bonds.     

Fabrication and characterization of β−FeSi2 thin films prepared by PLD method using Nd:YAG laser

β?FeSi₂ thin films were grown on Si(111) substrates by pulsed laser deposition (PLD) method using a Nd:YAG laser (λ=1064nm, laser energy=50mJ, laser energy density=1.65J/cm², repetition frequency=10Hz). In the fabrication process, three targets of (a) Fe(5N), (b) FeSi₂(3N), and (c) Fe(5N)+FeSi₂(3N) were used. The β?FeSi₂ thin films having the best properties of crystallinity were obtained in the case of (c), in which the first layer as the template was formed with the target of Fe(5N) and then, on top of that, the second layer was deposited with the target of FeSi₂(3N). At this time, it was found that by XRD measurement, the degree of crystallinity of the films of case (c) in which the first layer was introduced as the template improved 1.4 times as much compared with case (a), and that by SEM and AFM observations, surface morphologies also improved. Moreover, it was found that by TEM observation, the β?FeSi₂ thin films grew uniformly along the direction of (220) or (202) from the interface of the Si substrate and the film to the free surface and that by EDS analysis, the compositions of Fe and Si were uniformly distributed. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(2): 39–45, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/ eej.20238     

Cytotoxic lymphocytes in the peripheral blood of patients with B cell lymphomas

In order to analyze systemic immune surveillance in patients with B cell non-Hodgkin's lymphomas (B-NHL), we investigated circulating lymphocytes using two-color flow cytometry. The proportions of CD3-CD56+ natural killer (NK) cells and CD8++(bright) S6F1++ killer-effector T cells corresponding to activated cytotoxic T lymphocytes (aCTL) were studied in the peripheral blood of 26 patients with indolent lymphoma (IL) and 24 with aggressive lymphoma (AL). The AL patients with both limited disease and advanced disease had an increased proportion of NK cells. However, this feature was not evident in IL patients with either limited or advanced disease. In contrast, an increased proportion of aCTL was observed only in IL patients with advanced disease. These findings indicate that IL may differ from AL in terms of immune surveillance against neoplastic B cells.     

Novel inhibitors for multidrug resistance: 1,3,5-triazacycloheptanes

1,3,5-Triazacycloheptanes were synthesized and examined for reversal of the multidrug resistance dependent on P-glycoprotein. Most of these compounds increased the intracellular uptake of vinblastine in multidrug-resistant mouse leukemia P388/ADR cells without influence upon the vinblastine accumulation in P388/S cells. The efficacy of 1,5-dibenzyl-1,3,5-triazacycloheptanes in increasing the vinblastine accumulation was in the order of 2,4-dithioxo (5) > 2-oxo-4-thioxo (4) approximately 4-(methylthio)-2-oxo (6) > 2,4-dioxo (2). The efficacy was further increased when the benzyl group was converted to a chlorobenzyl group. Among these compounds, 6c [1,5-bis(4-chlorobenzyl)-1,5,6,7-terahydro-4-(methylthio)-2H-1,3,5 - triazepin-2-one] potentiated the in vitro cell growth-inhibitory effect of vinblastine, adriamycin, and mitomycin C on P388/ADR cells and prolonged the life span of P388/ADR-bearing mice in combined therapy with vinblastine more than vinblastine alone.     

Production and characterization of recombinant tachycitin, the Cys-rich chitin-binding protein

Tachycitin is an invertebrate chitin-binding protein with anamidated C-terminus, and possesses antimicrobial activity againstboth fungi and bacteria. The ¹H-NMR-based tertiary structureof tachycitin was recently determined [Suetake et al. (2000)J. Biol. Chem., 275, 17929–17932]. In order to examinethe structural and functional features of tachycitin more closely,we performed for the first time, gene expression, refolding,¹⁵N-NMR-based characterizations, and antimicrobial activitymeasurements of a recombinant tachycitin (rTcn) that does nothave the amide group at the C-terminus. The NMR analysis indicatedthat rTcn possesses the same structural construction as thenative tachycitin. The backbone ¹⁵N relaxation measurementsshowed that the molecular motional correlation time of rTcnincreases as its concentration increases, indicating that tachycitinshave a tendency to aggregate with each other. rTcn exhibitsantimicrobial activity against fungi but not against bacteria.The cell surface of fungi contains chitin as an essential constituent,but that of bacteria does not. These results suggest that notonly the chitin-binding region but also the C-terminal amidegroup of tachycitin plays a significant role in its antimicrobialproperties.