Entropy of glass transition and polymorphism

An analysis is made of the change in entropy in the glass transition process. It is shown that although the entropy of glass transition is less than that of melting, it is no more than two orders of magnitude smaller. The main results are obtained without using the conditions of local equilibrium, which are not satisfied for the glassy state. Pis’ma Zh. Tekh. Fiz. 24, 12–17 (February 12, 1998)     

Andreev and normal reflections at normal metal—Superconductor boundaries: Limitations of the semiclassical approximation

We study the scattering of quasiparticles at a normal metal—superconductor interface using Bogoliubov-de Gennes equations, taking the motion parallel to the interface fully into account. We show that while the Andreev reflection is the dominant scattering process in case of nearly perpendicular impacts (as predicted by the semiclassical theory), the normal reflection becomes increasingly important for quasiparticles with large momenta parallel to the interface, and the semiclassical approximation becomes progressively inadequate. We work out consequence of this feature for spectra of bound states in superconductor—normal metal—superconductor junctions.     

An Overlooked Hepcidin–Cadmium Connection

Hepcidin (DTHFPICIFCCGCCHRSKCGMCCKT), an iron-regulatory hormone, is a 25-amino-acid peptide with four intramolecular disulfide bonds circulating in blood. Its hormonal activity is indirect and consists of marking ferroportin-1 (an iron exporter) for degradation. Hepcidin biosynthesis involves the N-terminally extended precursors prepro-hepcidin and pro-hepcidin, processed by peptidases to the final 25-peptide form. A sequence-specific formation of disulfide bonds and export of the oxidized peptide to the bloodstream follows. In this study we considered the fact that prior to export, reduced hepcidin may function as an octathiol ligand bearing some resemblance to the N-terminal part of the α-domain of metallothioneins. Consequently, we studied its ability to bind Zn(II) and Cd(II) ions using the original peptide and a model for prohepcidin extended N-terminally with a stretch of five arginine residues (5R-hepcidin). We found that both form equivalent mononuclear complexes with two Zn(II) or Cd(II) ions saturating all eight Cys residues. The average affinity at pH 7.4, determined from pH-metric spectroscopic titrations, is 10^10.1 M⁻¹ for Zn(II) ions; Cd(II) ions bind with affinities of 10^15.2 M⁻¹ and 10^14.1 M⁻¹. Using mass spectrometry and 5R-hepcidin we demonstrated that hepcidin can compete for Cd(II) ions with metallothionein-2, a cellular cadmium target. This study enabled us to conclude that hepcidin binds Zn(II) and Cd(II) sufficiently strongly to participate in zinc physiology and cadmium toxicity under intracellular conditions.     

Mechanochemical synthesis of ternary chalcogenide chalcostibite CuSbS2 and its characterization

Journal of Materials Science: Materials in Electronics - In this work, the very rapid one-step mechanochemical synthesis of nanocrystalline ternary chalcogenide chalcostibite CuSbS2 prepared from...     

Microbial community changes with decaying chloramine residuals in a lab-scale system

When chloramine is used as a disinfectant, managing an acceptable “residual” throughout the water distribution systems particularly once nitrification has set in is challenging. Managing chloramine decay prior to the onset of nitrification through effective control strategies is important and to-date the strategies developed around nitrification has been ineffective. This study aimed at developing a more holistic knowledge on how decaying chloramine and nitrification metabolites impact microbial communities in chloraminated systems. Five lab-scale reactors (connected in series) were operated to simulate a full-scale chloraminated distribution system. Culture independent techniques (cloning and qPCR) were used to characterise and quantify the mixed microbial communities in reactors maintaining a residual of high to low (2.18–0.03 mg/L). The study for the first time associates chloramine residuals and nitrification metabolites to different microbial communities. Bacterial classes Solibacteres, Nitrospira, Sphingobacteria and Betaproteobacteria dominated at low chloramine residuals whereas Actinobacteria and Gammaproteobacteria dominated at higher chloramine residuals. Prior to the onset of nitrification bacterial genera Pseudomonas, Methylobacterium and Sphingomonas were found to be dominant and Sphingomonas in particular increased with the onset of nitrification. Nitrosomonas urea, oligotropha, and two other novel ammonia-oxidizing bacteria were detected once the chloramine residuals had dropped below 0.65 mg/L. Additionally nitrification alone failed to explain chloramine decay rates observed in these reactors. The finding of this study is expected to re-direct the focus from nitrifiers to heterotrophic bacteria, which the authors believe could hold the key towards developing a control strategy that would enable better management of chloramine residuals.     

A comparison of two paradigms for distributed shared memory

Two paradigms for distributed shared memory on loosely-coupled computing systems are compared: the shared data-object model as used in Orca, a programming language specially designed for loosely-coupled computing systems, and the shared virtual memory model. For both paradigms two systems are described, one using only point-to-point messages, the other using broadcasting as well. The two paradigms and their implementations are described briefly. Their performances are compared on four applications: the travelling-salesman problem, alpha-beta search, matrix multiplication and the all-pairs shortest-paths problem. Measurements were obtained on a system consisting of 10 MC68020 processors connected by an Ethernet. For comparison purposes, the applications have also been run on a system with physical shared memory. In addition, the paper gives measurements for the first two applications above when remote procedure call is used as the communication mechanism. The measurements show that both paradigms can be used efficiently for programming large-grain parallel applications, with significant speed-ups. The structured shared data-object model achieves the highest speed-ups and is easiest to program and to debug.     

Glutathione-binding proteins of Setaria digitata: antibody responses in human infected with Wuchereria bancrofti

Glutathione-s-transferase activity was determined in filarial parasites. The activity was detected in adult stages of cattle parasite Setaria digitata. It was absent in other stages of Setaria and also in infective larval stages of Wuchereria bancrofti and Brugia malayi. The activity was enhanced about twenty five fold following purification of adult setaria extracts on glutathione agarose column. Antibody (IgG and IgM) levels to the affinity purified proteins (SdGBP) were detected predominantly (90%) in Wuchereria bancrofti infected individuals compared with normal residents of endemic regions. IgA and IgE responses could not be detected. Filarial sera in contrast to non-filarial caused reduction in the enzymatic activities of Sd GBP. Microfilaraemic sera after diethylcarbamazine treatment resulted in enhanced reduction of enzymatic activity.     

What stops synchronized thalamocortical oscillations?

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) suppresses B lymphocyte proliferation and immunoglobulin production. We previously reported that the aryl hydrocarbon receptor (AhR) complex, composed of the AhR ligand binding subunit and the Ah receptor nuclear translocator (ARNT), was constitutively present in nuclear extracts from two human B lymphocyte cell lines (Biochem. Biophys. Res. Commun. 212, 27-34, 1995). The present study compared the AhR complex in the IM-9 and PJS-91 human B lymphocyte and HepG2 human hepatoma cell lines. AhR mRNA levels in the two lymphocyte cell lines were substantially lower than those in HepG2 cells, as was immunoreactive AhR protein. In contrast, ARNT mRNA and protein were expressed at a high level in all three cell lines. TCDD induction of cytochrome P450 1A1 mRNA and protein was detected in only the PJS-91 lymphocyte cell line, and at a markedly lower level than that in HepG2 cells. In gel shift assays, the cytosolic DNA-binding AhR complex in IM-9 and PJS-91 cells was indistinguishable from that in HepG2 cells. In contrast, the nuclear DNA-binding AhR complex in IM-9 and PJS-91 cells consisted of several closely migrating species, one being recognized by an AhR antibody, while an ARNT antibody reacted with all species. Protein:DNA cross-linking analysis revealed the presence of a novel Mr 100,000 DNA-binding protein in nuclear extracts from IM-9 and PJS-91, but not HepG2, cells that was not recognized by either AhR or ARNT antibodies. These results show that IM-9 and PJS-91 human B cells constitutively express a distinct nuclear DNA-binding form of the AhR complex that may result from the presence of an additional protein or a structural variant of the AhR.     

Periprosthetic femoral osteolysis around an uncemented nonmodular Moore prosthesis

alpha-Amylase and hemicellulase, derived from culture of Aspergillus species, are commonly added to flour as improvers during baking. Two cases of women occupationally sensitized to alpha-amylase who developed allergic symptoms after eating baked bread have been reported. With a randomized, controlled study design, we have investigated whether similar responses occur in those sensitized to Aspergillus species. Seventeen subjects with positive skin prick tests to Aspergillus fumigatus were studied. Symptomatic and physiologic responses after ingestion of bread baked with alpha-amylase and hemicellulase were compared, in a crossover fashion, with those after ingestion of bread baked without enzymes. No increase in respiratory or other symptoms, lung function, or nonspecific bronchial hyperreactivity was reported after ingestion of the enzyme-containing bread. We conclude that important clinical reactions to alpha-amylase and hemicellulase in baked bread do not frequently occur in those sensitized to Aspergillus species.