Mechanisms of Breakaway Oxidation and Application to a Chromia-Forming Steel

Breakaway oxidation or chemical failure has beendescribed in this paper in terms of two possiblemechanisms and applied to the behavior of achromia-forming 20Cr-25Ni austenitic steel. Bothmechanisms relate to the depletion of chromium arisingfrom its selective oxidation and quantitative modelingof the depletion profile is used to identify thedominant chemical-failure mechanism as a function oftemperature. Intrinsic Chemical Failure (InCF) develops whenthe chromium concentration within the alloy at theoxide-metal interface is less than that in equilibriumwith chromia. This occurs at high temperatures, typically above 1390 K, but the temperature atwhich the alloy becomes susceptible to this form offailure increases as the alloy grain size decreases. Atlower temperatures, chemical failure is associated with the general depletion of chromium acrossthe specimen section to a level below which reformationof a healing chromia layer will not occur, should thesurface layer become damaged. In this regime, failure is termed Mechanically Induced ChemicalFailure (MICF).     

The influence of sulfide on solid-phase mercury bioavailability for methylation by pure cultures of Desulfobulbus propionicus (1pr3)

To help understand the mechanism and control of Hg uptake in Hg-methylating bacteria, we investigated the effect of sulfide on Hg methylation by pure cultures of the sulfate-reducing bacterium Desulfobulbus propionicus (1pr3). Our previous research in natural sediments has suggested that Hg methylation occurs most rapidly when sulfide concentrations favor formation of neutral dissolved Hg-S species. In this study, the chemical speciation of Hg in culture media was manipulated by growing D. propionicus across a range of sulfide concentrations, with inorganic Hg (HgI) added in the form of ground ores. A solid-phase, rather than a dissolved source of Hg, was used to simulate the controls on Hg partitioning between solid and aqueous phases found in natural sediments. Methylmercury (MeHg) production by cultures was not related to the absolute solid-phase concentration of Hg in the ores, and it was only weakly related to the dissolved HgI concentration in the medium. However, MeHg production was linearly related to the calculated concentration of the dominant neutral complex in solution, HgS degrees. Furthermore, the diffusive membrane permeability of HgS degrees, as estimated from its octanol-water partitioning coefficient, was found to be sufficient to support MeHg production by cells. The present paper expands on our previous work by providing experimental support of our hypothesis that sulfide influences methylation by affecting the speciation of dissolved HgI and its uptake via passive diffusion.     

DIFFERENTIATION OF YEASTS BY ELECTROPHORETIC METHODS

An examination of the esterase isoenzymes reacting with α-naphthyl acetate indicated five types of electrophoretic pattern in 94 strains of 54 species of 15 yeast genera. Groups classified according to esterase patterns agreed with accepted taxonomic groups, but there were no differences of obvious value for routine identification of separate species of yeasts. Strictly aerobic yeasts produced up to four bands of esterase activity; facultative anaerobes produced two lines or only one. Proteins detected by staining with trifalgic acid after electrophoresis formed identical patterns from all yeasts tested.     

Altered alveolar macrophage function in calorie-restricted rats

The capacity of four chicken lines (Y11, L2, B13, PA12) to control Salmonella enteritidis (SE) phage type 4 (PT4) systemic colonization was investigated. Thirteen-week-old chickens were intravenously inoculated with 10(6) SE colony-forming units, and the levels of SE colonization were determined at various time intervals after inoculation in liver, spleen, genital organs, and ceca. The course of SE infection showed a rapid contamination of liver, spleen, and genital organs, whereas the ceca were infected later. A significant (P < 0.001) effect of the chicken line on levels of SE was detected on day 3 postinoculation (PI) in liver and ceca, on day 10 PI in ceca, and on day 15 PI in spleen. Because an early control of systemic Salmonella infection by the Ity/Nramp1 gene has been demonstrated in mice, we aimed to study the early resistance of chickens to SE. As a consequence, we then focused our study on the between- and within-line variabilities of SE levels on day 3 PI. According to the SE levels in liver on day 3 PI, the chicken lines could be classified as susceptible (Y11 and L2) or resistant (PA12 and B13). This early variability was explored in resistant B13 and susceptible L2 lines. Differences between these two lines were confirmed in liver but not in ceca. A large within-line variability was observed in all organs of these two lines. The genetic origin of this variability will have to be determined as a prerequisite to an eventual selection.     

Nuclear but not cytoplasmic phospholipase C beta 1 inhibits differentiation of erythroleukemia cells

A body of evidence has shown the existence of a nuclear phosphoinositide cycle in different cell types. The cycle is endowed with kinases as well as phosphatases and phospholipase C (PLC). Among the PLC isozymes, the beta family is characterized by a long COOH-terminal tail that contains a cluster of lysine residues responsible for nuclear localization. Indeed, PLC beta 1 is the major isoform that has been detected in the nucleus of several cells. This isoform is activated by insulin-like growth factor I, and when this isoform is lacking, as a result of gene ablation, the onset of DNA synthesis induced by this hormone is abolished. On the contrary, PLC beta 1 is down-regulated during the erythroid differentiation of Friend erythroleukemia cells. A key question is how PLC beta 1 signaling at the nucleus fits into the erythroid differentiation program of Friend erythroleukemia cells, and whether PLC beta 1 signaling activity is directly responsible for the maintenance of the undifferentiated state of erythroleukemia cells. Here we present evidence that nuclear PLC beta 1 but not the isoform located at the plasma membrane is directly involved in maintaining the undifferentiated state of Friend erythroleukemia cells. Indeed, when wild-type PLC beta 1 is overexpressed in these cells, differentiation in response to DMSO is inhibited in that the expression of beta-globin is almost completely abolished, whereas when a mutant lacking the ability to localize to the nucleus is expressed, the cells differentiate, and the expression of beta-globin is the same as in wild-type cells.     

Development of lithographic techniques for metallisation of organic substrates

A wide range of applications which involve organic crystalline materials require the metallisation of low-molecular-weight compounds. Conventional lithographic techniques used in silicon fabrication technology use high-temperature processing methods which are unsuitable for organic materials. Gold/titanium bilayer and shadow-masking techniques were found to provide suitable solutions to the problem of metallisation of these materials and allowed fabrication of a surface acoustic wave (SAW) device with (–)-2-α-methylbenzylamino-5-nitropyridine (MBANP) as substrate.     

The MAP kinase pathway controls differentiation from double-negative to double-positive thymocyte

T cell development is regulated at two major control points where maturation, proliferation, and antigen receptor gene rearrangement are coordinated. Progression through these developmental control points is dependent upon the expression of different forms of the T cell receptor. Here we show that the MAP kinase cascade is a regulator of the differentiation of immature thymocytes from double-negative to double-positive cell, most probably acting as a transducer of pre-T cell receptor signaling. Furthermore, this study demonstrates the use of retrovirus-mediated gene transfer in fetal thymic organ culture in the analysis of thymic development in mutant mice, an alternative to transgenesis by oocyte injection.     

Factors influencing exfiltration processes in sewers.

Exfiltration from sewers is widespread and emerging legislation may require water service providers to identify, and rectify, its sources in sewerage systems. This paper describes exfiltration test apparatus and a series of experiments undertaken using sewage to gain a better understanding of the influence of sewage solids and sediments on leakage rates. An overview of the results obtained is given, which demonstrates that most previous estimates of exfiltration leakage rates were too high due to a lack of appreciation of the "self-repairing" action of sewage and sewage associated solids. Exfiltration rates of 0.1% of the sewer flow or 0.001 I/s have been recorded for defects up to 6 mm wide.     

Dissolved organic matter enhances microbial mercury methylation under sulfidic conditions

Dissolved organic matter (DOM) is generally thought to lower metal bioavailability in aquatic systems due to the formation of metal-DOM complexes that reduce free metal ion concentrations. However, this model may not be pertinent for metal nanoparticles, which are now understood to be ubiquitous, sometimes dominant, metal species in the environment. The influence of DOM on Hg bioavailability to microorganisms was examined under conditions (0.5-5.0 nM Hg and 2-10 μM sulfide) that favor the formation of β-HgS(s) (metacinnabar) nanoparticles. We used the methylation of stable-isotope enriched (201)HgCl(2) by Desulfovibrio desulfuricans ND132 in short-term washed cell assays as a sensitive, environmentally significant proxy for Hg uptake. Suwannee River humic acid (SRHA) and Williams Lake hydrophobic acid (WLHPoA) substantially enhanced (2- to 38-fold) the bioavailability of Hg to ND132 over a wide range of Hg/DOM ratios (9.4 pmol/mg DOM to 9.4 nmol/mg DOM), including environmentally relevant ratios. Methylmercury (MeHg) production by ND132 increased linearly with either SRHA or WLHPoA concentration, but SRHA, a terrestrially derived DOM, was far more effective at enhancing Hg-methylation than WLHPoA, an aquatic DOM dominated by autochthonous sources. No DOM-dependent enhancement in Hg methylation was observed in Hg-DOM-sulfide solutions amended with sufficient l-cysteine to prevent β-HgS(s) formation. We hypothesize that small HgS particles, stabilized against aggregation by DOM, are bioavailable to Hg-methylating bacteria. Our laboratory experiments provide a mechanism for the positive correlations between DOC and MeHg production observed in many aquatic sediments and wetland soils.     

How to select tools for microcontroller software

The factors that determine the choice of tools are identified. Symbolic versus source-level debugging, programming language tradeoffs, and assembler features are examined. The use of CASE (computer-aided software engineering) tools is briefly considered