Gas tungsten arc welding process for surfacing of aluminium alloys with Al‐Cu cored wire 2nd report: Surfacing of aluminium alloy

Abstract

In alloy steels, ferrite is formed during the solidification of the metal. Structure of the steel changes depending on the content of austenite (nickel, carbon, nitrogen, manganese, copper and cobalt) – and ferrite-forming (chromium, molybdenum, silicon, tungsten, vanadium, aluminium, titanium and niobium) elements.¹ According to the current state of knowledge, the structure of the weld at ambient temperature depends on the content of ferrite which existed at very high temperatures (below the liquidus curve), i.e. it depends on the ratio of the austenite–ferrite forming elements. Welds in 18–10 grade steels, after cooling to ambient temperatures, have austenitic–ferritic structures.     

Cultivation-independent identification of candidate dehalorespiring bacteria in tetrachloroethylene degradation

Tetrachloroethylene (PCE) is one of the major pollutants and is degraded by dissimilation by dehalorespiring bacteria. The dehalorespiring bacteria are anaerobic, and most cannot be cultured by conventional agar plating methods. Therefore, to identify the dehalorespiring bacteria that dissimilatively degrade PCE, a cultivation-independent method is required. To achieve accurate and detailed analysis of the bacteria, we developed a novel stable isotope probing (SIP) method. This technique involves 2 steps, namely, a labeling step, in which a labeled carbon source is incorporated into the sample's DNA, and an analysis step, in which the DNA is isolated, fractionated, and analyzed by polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE). Subsequently, 16S rRNA sequencing and phylogenetic analysis were performed to identify the bacteria. Initially, we examined the effectiveness of this method by using Dehalococcoides ethenogenes 195 consortium as a defined model system. The result indicated the method was able to correctly identify the dehalorespiring bacteria D. ethenogenes 195 from the consortium. Moreover, in an artificially contaminated microcosm experiment, we confirmed that the method was able to identify the indigenous dehalorespiring bacteria Dehalobacter sp. Thus, we concluded that this novel method was a feasible tool to identify dehalorespiring bacteria in natural environments.     

Case study of the relationship between fungi and bacteria associated with high-molecular-weight polycyclic aromatic hydrocarbon degradation

Although bacteria play dominant roles in microbial bioremediation, few of them have been reported that were capable of utilizing high-molecular-weight (HMW) organic pollutants as their sole sources of carbon and energy. However, many soil fungi can metabolize those of pollutants, although they rarely complete mineralization. In this paper, we investigated the dynamic relationship between fungi and bacteria associated with degradation of HMW-polycyclic aromatic hydrocarbons (PAHs). Artificial fungal-bacterial mixed cultures were constructed to simulate the environment of actual polluted sites. Four bacterial strains and seven fungal strains were isolated that related to the removal of phenanthrene, fluoranthene and pyrene in the soil. Furthermore, these strains were used to create mixed culture of bacteria (Bact-mix), mixed culture of fungi (Fung-mix), fungal-bacterial co-cultures (Fung-Bact), respectively. The maximal pyrene removal rate (67%, 28days) was observed in the Fung-Bact, compared with cultures of Fung-mix (39%) and Bact-mix (56%). The same tendency was also indicated in the degradation of phenanthrene and fluoranthene. In addition, a dynamic relationship during the degradation process between fungi and bacteria was monitored through using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) method.     

Analysis of Largest Sulfide Inclusions in Low Carbon Steel by Using Statistics of Extreme Values

The statistics of extreme values was applied for the determination of the largest sulfide inclusions with different morphology in low carbon steel samples by using both two‐dimensional (2D) observations on the polished cross section and three‐dimensional (3D) observations on a surface of a film filter after electrolytic extraction of the samples. It was found that the globular, rod‐like and dendritic sulfides in the molten steel sample as well as the elongated sulfides in the rolled steel sample can be successfully extracted from the both samples, and analyzed precisely by using extreme value analysis in 3D. Based on the geometrical considerations of the probability for measurement of the true length of rod‐like and elongated inclusions on a cross section, it was found that this probability for inclusions decreases dramatically with an increasing real aspect ratio value of them. Particularly for the determination of the true length for elongated inclusions in the rolled steel sample by 2D investigations on a metal cross section, it is required to be cut investigating section of steel sample within ± 1 degree against rolling direction. Therefore, a 3D observation is considered to be more preferable and accurate than the conventional cross sectional observation in 2D, due to the possibility for the measurements of the real size of them.     

PCR-based identification of pathogenic Candida species using primer mixes specific to Candida DNA topoisomerase II genes

For rapid identification of Candida to the species level, degenerated primers and specific primers based on the genomic sequences of DNA topoisomerase II of C. albicans, C. dubliniensis, C. tropicalis (genotypes I and II), C. parapsilosis (genotypes I and II), C. krusei, C. kefyr, C. guilliermondii, C. glabrata, C. lusitaniae and Y. lipolytica were designed and their specificities tested in PCR-based identifications. Each of the specific primers selectively and exclusively amplified its own DNA fragment, not only from the corresponding genomic DNA of the Candida sp. but also from DNA mixtures containing other DNAs from several fungal species. For a simpler PCR-based identification, the specific primers were divided into three groups (PsI, PsII and PsIII), each of which contained four specific primer pairs. PCR with the primer mixes yielded four different sizes of PCR product, corresponding to each Candida sp. in the sample DNA. To obtain higher sensitivity of PCR amplification, sample DNAs were preamplified by the degenerated primer pair (CDF28/CDR148), followed by the main amplification using the primer mixes. By including this nested PCR step, 40 fg yeast genomic DNA was detected in the sample. Furthermore, we applied this nested PCR to a clinical diagnosis, using splenic tissues from experimentally infected mice and several clinical materials from patients. In all cases, the nested PCR amplifications detected proper DNA fragments of Candida spp., which were also identified by the standard identification tests. These results suggest that nested PCR, using primer mixes of the Candida DNA topoisomerase II genes, is simple and feasible for the rapid detection/identification of Candida to species level in clinical materials.     

Design Considerations and Performance Evaluation of a Compact Aerosol Particle Mass Analyzer

A compact aerosol particle mass analyzer (APM) of which the size of the classifier was significantly reduced than that of the first commercial model (Kanomax Model 3600) was developed. Firstly, requirements for desired performance in classifying particle mass were set forth. Secondly, a theoretical framework for the design parameters of an APM that satisfies the requirements was formulated. Thirdly, the design parameters were determined that satisfies the requirements while reducing the instrument size. The requirements include the condition that the classification range covers from 0.001 to 1000 fg (approximately 12 to 1200 nm in size for spherical particles having the density of 1 g/cm³), and the condition that both the classification resolution and particle penetration in this mass range are higher than certain specified values. A prototype having the design parameters determined according to this theoretical framework was constructed, and its performance was evaluated experimentally. The external dimensions of the electrodes of the compact APM are approximately 140 mm in length and 60 mm in diameter. It was confirmed that the performance of the compact APM operated at the aerosol flow rate of 0.3 L/min was comparable to that of the Model 3600 APM operated at 1 L/min. Because of the reduced size and of the resultant improved portability, it is expected that the compact APM is readily applicable to field measurements.

Copyright 2013 American Association for Aerosol Research     

Diffusion-controlled size-selective chloride ion sensing in the presence of bromide ion using a thin, nanoporous, plasma-polymerized coating on an Ag/AgCl electrode

We have developed a diffusion-controlled size-selective method for sensing chloride ion in the presence of bromide ion, based on a thin, nanoporous, plasma-polymerized coating of hexamethyldisiloxane on an Ag/AgCl electrode. Sub-nanometer-sized pores responsible for a highly cross-linked polymer network in the plasma-polymerized coating allowed diffusion-controlled permeation of chloride ion while blocking the larger bromide ion. An electrode coating of thickness greater than 70 nm enabled chloride detection in the concentration range 1-10 mM in the presence of 0.63 mM bromide ion. Advantages of this approach are: (1) simple design compared with ionophore-based strategies and (2) compatibility with microfabrication and mass production processes.     

Interaction of cation-exchange membrane with polycation I. Poly(N-methyl-4-vinylpyridinium chloride)

We elucidated the effect of the molecular weight of poly(N-methyl-4-vinylpyridinium chloride) (PMVP) on its adsorbed or ion-exchanged amount on the cation-exchange membrane and the preferntial permselectivity of the membrane for sodium ion to calcium ion. The amount of the adsorbed or ion-exchanged PMVP increases with time and then attains to a definite value at a definite concentration. Also, the ultimate value increases with increasing the concentration of PMVP. When the molecular weight of PMVP is 3090, the ratio of the pyridinium groups of PMVP ion-exchanged with the sulfonic acid groups on the membrane surface to the total pyridinium groups of the cohered PMVP is in the range of 70–80%. The relative transport number of calcium ions to sodium ions(P_Na^Ca) decreases with increasing the amount of adsorbed or ion-exchanged PMVP and the numbe rof non-ion-exchanged pyridinium groups of PMVP and the number of non-ion-exchanged pyridinium groups of PMVP on the membrane surface. The smaller the molecular weight of PMVP, the more the adsorbed or ion-exchanged amount and the more preferable the permselectivity for sodium ion.     

Adrenomedullin augments inducible nitric oxide synthase expression in cytokine-stimulated cardiac myocytes

BACKGROUND: Plasma levels of adrenomedullin are increased in patients with congestive heart failure, but there has been no report concerning the effects of adrenomedullin on the heart. We investigated the effects of adrenomedullin on NO synthase activity in cardiac myocytes. METHODS AND RESULTS: We measured the production of nitrite, a stable metabolite of NO, in cultured neonatal rat cardiac myocytes with the Griess reagent. Inducible NO synthase mRNA and protein expression were assayed by Northern and Western blotting, respectively. Incubation of the cultures with interleukin-1 beta (10 ng/mL) for 24 hours caused a significant increase in nitrite accumulation. Adrenomedullin significantly augmented nitrite production by interleukin-1 beta-stimulated but not by unstimulated cardiac myocytes in a dose-dependent manner (10(-10) to 10(-6) mol/L). The adrenomedullin-induced nitrite production by interleukin-1 beta-stimulated cells was accompanied by increased inducible NO synthase mRNA and protein expression. In the presence of dibutyryl cAMP, the interleukin-1 beta-induced nitrite accumulation was increased further, but the stimulatory effect of adrenomedullin on nitrite production was abolished. Adrenomedullin dose-dependently increased intracellular cAMP levels in cardiac myocytes. Addition of the calcitonin gene-related peptide (CGRP) receptor antagonist CGRP[8-37] to the culture dose-dependently inhibited both cAMP and NO generation stimulated by adrenomedullin. CONCLUSIONS: These results indicate that adrenomedullin acts on cardiac myocytes and augments NO synthesis in these cells under cytokine-stimulated conditions, at least partially through a cAMP-dependent pathway.     

New empirical relation for MOSFET noise unified over linear and saturation regions

This paper proposes an empirical relation, which represents noise bias condition dependence for a silicon N-channel MOSFET. No matter whether the MOSFET is operated in linear or saturation region, bias condition dependence is found to be well described by a power function of voltage gain. By introducing a device's intrinsic noise emf v_nc(ƒ), which is independent from bias condition, and empirical parameter β, input-referred noise voltage v_ni(ƒ) is clarified to be a function of v_nc(ƒ), β, and voltage gain , i.e. . This relation implies that noise voltage depends implicitly on bias condition through voltage gain, because transconductance g_m and drain-source differential conductance g_DS depend on bias condition. If β − 1 value is negligible, v_ni(ƒ) = v_nc(ƒ) is almost independent from bias condition, whereas, if β − 1 value is not negligible, bias condition dependence for v_ni(ƒ) appears to be observed. The β deviation from unity, which characterizes bias condition dependence, measures the difference between signal amplification and noise amplification.