Plasma etching treatment for surface modification of boron-doped diamond electrodes

Boron-doped diamond (BDD) thin film surfaces were modified by brief plasma treatment using various source gases such as Cl₂, CF₄, Ar and CH₄, and the electrochemical properties of the surfaces were subsequently investigated. From X-ray photoelectron spectroscopy analysis, Cl and F atoms were detected on the BDD surfaces after 3 min of Cl₂ and CF₄ plasma treatments, respectively. From the results of cyclic voltammetry and electrochemical AC impedance measurements, the electron-transfer rate for Fe(CN)₆^3−/4− and Fe^2+/3+ at the BDD electrodes was found to decrease after Cl₂ and CF₄ plasma treatments. However, the electron-transfer rate for Ru(NH₃)₆^2+/3+ showed almost no change after these treatments. This may have been related to the specific interactions of surface halogen (C-Cl and C-F) moieties with the redox species because no electrical passivation was observed after the treatments. In addition, Raman spectroscopy showed that CH₄ plasma treatment of diamond surfaces formed an insulating diamond-like carbon thin layer on the surfaces. Thus, by an appropriate choice of plasma source, short-duration plasma treatments can be an effective way to functionalize diamond surfaces in various ways while maintaining a wide potential window and a low background current.     

Deformability enhancement in ultra-fine grained, Ar-contained W compacts by TiC additions up to 1.1%

Nano-sized Ar bubbles give negative influence on the fracture resistance and occurrence of superplasticity in ultra-fine grained (UFG) W–TiC compacts. In order to enhance deformability in UFG, Ar-contained W–TiC compacts, effects of TiC addition on the high-temperature deformation behavior were examined. W–TiC compacts with TiC additions of 0, 0.25, 0.5, 0.8 and 1.1 wt% were fabricated by mechanical alloying in a purified Ar atmosphere and hot isostatic pressing. Tensile tests were conducted at 1673–1973 K (0.45–0.54 T_m, T_m: melting point of W) at initial strain rates from 5 × 10⁻⁵ to 5 × 10⁻³ s⁻¹. It is found that as TiC addition increases, the elongation to fracture significantly increases, e.g., from 3 to 7% for W–0 and 0.25TiC/Ar to above 160% for W–1.1TiC/Ar when tested at 1873 and 1973 K at 5 × 10⁻⁴ s⁻¹. The flow stress takes a peak at 0.25%TiC and decreases to a nearly constant level at 0.5–1.1%TiC. The ranges of the strain rate sensitivity of flow stress, m, and the activation energy for deformation, Q, with TiC additions are 0.17–0.30 and 310–600 kJ/mol, respectively. The observed effects of the TiC additions on the tensile properties are discussed.     

Algorithm for the surgical treatment of malignant lesions of the proximal tibia

Complications are common among patients treated for malignant lesions of the proximal tibia and can be difficult to manage. This investigation was a retrospective review of 40 patients treated with total knee replacements after proximal tibial resections. Various reconstructive methods were used to fix the prosthetic stems, reestablish the extensor mechanism, and provide soft tissue coverage. Thirty-one patients had adequate followup to allow for review of prosthetic outcome (means, 78 months; range, 25-193 months). Seven patients died with less than 2 years followup, and two patients had postoperative acute infections treated by early amputation to allow chemotherapy to resume promptly. The overall 5-, 8-, and 12-year event free prostheses survival rates were 62%, 33%, and 16%, respectively. Prognostic factors for prosthetic survival were analyzed (age, gender, type of excision, type of prosthesis, type of fixation, and percent of bone resected). None were statistically significant. Patients with less than 40% of the tibia resected had better prosthetic survival at 5 years. The durability of uncemented stem fixation exceeded that of cemented stems. Expected survival of prostheses after revision was 52% at 8 years. The major cause of limb loss was infection. Failure to reconstruct soft tissues satisfactorily caused most failures. Aggressive multistage management of infection is needed. Prosthetic knee replacement is most suitable for patients with cancers that require chemotherapy and for those patients who have short potential survival.     

Outer-loop control of target SIR for fast transmit power control inturbo-coded W-CDMA mobile radio

A technique for obtaining outer-loop control of the target SIR for closed-loop fast transmit power control (TPC) is presented for turbo-coded wideband DS-CDMA (W-CDMA) mobile radio systems. The frame error rate (FER) of an intermediate decoding output in the turbo-decoder. i.e. before the final iteration stage is reached, is measured to control the target SIR. The bit error rate (BER) after the final decoding iteration can be maintained accurately at the prescribed BER value, e.g. BER=10^-6, without losing the tracking ability in the presence of slowly changing propagation channel conditions. Computer simulation results supporting this ability are reported     

热扩散塔分离甲烷和氢的实验研究

引言用甲烷直接合成C_2以上的碳氢化合物非常困难,例如,由甲烷脱氢合成乙烯,按热力学计算在1000K下甲烷的平衡转化率只有4.8％,所以至今甲烷仍主要用作燃料．为了充分利用这一化工基础原料,作者利用热扩散塔进行了甲烷的催化脱氢反应,使反应与分离同时进行,大幅度提高了甲烷的转化率．为考察热扩散的分离效果,本文用甲烷脱氢反应的主要成分甲烷和氢混合物为原料,在热扩散塔中分别进行了空塔和填料塔的热扩散分离实验,考察了一些操作参数对分离效果的影响,以期对反应操作条件提供必要的参考．l原理所谓热扩散现象,就是在温度场…     

Separation–permeation performance of porous Si3N4 ceramics composed of columnar β-Si3N4 grains as membrane filters for microfiltration

The separation–permeation performance of porous silicon nitride (Si₃N₄) ceramics (consisting of columnar grains connected at random in three dimensions) as membrane filters was evaluated, and compared with commercial Al₂O₃ membranes having a three-layer structure. Si₃N₄ membranes separate particles with diameters much less than their pore diameters. The permeability of Si₃N₄ membranes with separability values the same as those of the Al₂O₃ membranes was about 1.3–2.4 times as large as the Al₂O₃ membranes. Dead-end filtration examination, using Al₂O₃ particles with a particle size distribution, indicated that the Si₃N₄ membrane filtration mechanism obeyed the cake filtration mechanism although the particle size was smaller than the pore size of the Si₃N₄ membranes.     

Effect of ethyl alcohol on growth and intracellular alanine racemase of psychrotrophs

The psychrotrophic alanine racemase from Pseudomonas fluorescens, a typical psychrotroph, is less resistant to organic solvents than the enzymes from thermophilic and mesophilic bacteria (Okubo et al., J. Home Econ. Jpn., 46: 1135-1140, 1995). To further elucidate this difference, we examined the effect of ethyl alcohol on the growth and intracellular alanine racemase activity of three typical psychrotrophs-P. fluorescens, Bacillus psychrosaccharolyticus and B. psychrophilus-in comparison with two mesophiles, Escherichia coli and B. subtilis. Although all the bacteria grew to the early stationary phase when cultivated at 22 degrees C for 36 h in the absence of ethyl alcohol, the growth of the psychrotrophs was more effectively suppressed by the addition of 3 and 5% ethyl alcohol to the medium than that of the mesophiles. The intracellular alanine racemase activity of the psychrotrophs was also more markedly reduced in the presence of ethyl alcohol than that of the mesophiles. When bacterial cells of each strain grown at 22 degrees C for 36 h in the absence of alcohol were suspended in 0-5 % ethyl alcohol solution and incubated at 30 degrees C for 1 h, both the survival ratio and intracellular alanine racemase activity of the psychrotrophs were lower than those of the mesophiles. Thus, ethyl alcohol effectively reduced both the growth of the psychrotrophs and their intracellular alanine racemase activity. Low concentrations of various other alcohols also repressed the growth of the psychrotrophs at 10 degrees C.     

Enzymatic and genetic bases on assimilation, depolymerization, and transport of heteropolysaccharides in bacteria

When microorganisms utilize macromolecules for their growth, they commonly produce extracellular depolymerization enzymes and then incorporate the depolymerized low-molecular-weight products. Assimilation of heteropolysaccharides (gellan and xanthan) by Bacillus sp. GL1 depends on this generally accepted mechanism. On the other hand, Sphingomonas sp. A1 represents an unexplored specific and interesting system for macromolecule assimilation. In the presence of heteropolysaccharide (alginate), the bacterium forms a mouthlike pit on its cell surface and directly incorporates the macromolecule using a novel ATP-binding cassette transporter (ABC transporter). In this review, we discuss enzymatic and genetic bases on the depolymerization and assimilation routes of heteropolysaccharides in bacteria, with particular emphasis on the novel incorporation system for macromolecules, characteristic post-translational modification processes of polysaccharide lyases and on the mouthlike pit structure on the bacterial cell surface.     

Ytterbium-decreasing Streptomyces sp. and its naphthoquinone-pigment production in the presence of rare-earth elements

We screened for oligotrophic microorganisms capable of decreasing the concentration of ytterbium (Yb), a representative of the heavy rare-earth elements, in a culture medium. From 476 strains of oligotrophic microorganisms (grown on 1/100 diluted nutrient agar) isolated from soil and river water samples, 5 strains capable of reducing the concentration of Yb in diluted nutrient broth containing 5 ppm Yb were selected. Among them, a strain capable of reducing the concentration of all rare-earth elements to a great extent was identified as Streptomyces sp. (strain YB-1). This strain produced redish-purple pigment(s) only in the presence of rare earths, but not in that of other metals. The pigment was extracted with ethyl acetate and purified by a series of column chromatography steps. From the results of structural analysis using ultraviolet or infrared absorption spectrometry and 13C-NMR, the pigment was determined to be a kind of naphthoquinone similar to nanaomycin produced by a Streptomyces sp. These results suggested that rare earths might affect the physiological activity of this strain.