Stereoselective reductase-catalysed deoxygenation of sulfoxides in aerobic and anaerobic bacteria

Direct and indirect evidence, Of unexpected stereoselective reductase-catalysed deoxygenations of sulfoxides, was found. The deoxygenations proceeded simultaneously, with the expected dioxygenase-catalysed asymmetric sulfoxidation of sulfides, during some biotransformations with the aerobic bacterium Pseudomonas putida UV4. Stereoselective reductase-catalysed asymmetric deoxygenation of racemic alkylaryl, dialkyl and phenolic sulfoxides was observed, without evidence of the reverse sulfoxidation reaction, using anaerobic bacterial strains. A purified dimethyl sulfoxide reductase, obtained from the intact cells of the anaerobic bacterium Citrobacter braakii DMSO 11, yielded, from the corresponding racemates, enantiopure alkylaryl sulfoxide and thiosulfinate samples.

Crossing the threshold: exile and literature in "El Canto del peregrino" (1999) by Angelina Muñiz-Huberman

This paper analyses the relation between exile and literature in Angelina Muñiz-Huberman’s work El canto del peregrino. In this collection of essays, the Spanish-Mexican writer, member of the second generation of Spanish Republican exiles in Mexico, outlines a poetics of exile. From the outset, the relation between exile and literature is presented in terms of identity: while defining exile as “literary form”, the book tends to prefer a metaphorical concept of exile over ‘merely’ historical or referential approaches to it. More in particular, this paper will examine how the author constructs an identity of ‘exiled writer’ based on the close association between exile and literature on the one hand, and on the view of exile as ‘home’ or ‘dwelling’, on the other hand. A second point of interest concerns the discursive impact of this literary and metaphorical concept of exile and the author’s personal experience. A brief analysis of the essayist’s discursive voice and her writing practice shows how Muñiz-Huberman gives shape to an intrinsically complex and paradoxical view on exile.

Appearance of the frequency-doubling stimulus at threshold.

PURPOSE. It has been argued that the threshold for detecting frequency-doubling (FD) technology perimeter stimuli differs from the threshold for perceiving spatial structure (pattern) in the same targets. Thresholds for perceiving spatial structure have typically been assessed using orientation-identification experiments. The authors investigated the influence of orientation, edge profile, and psychophysical method on the origin of the reported differences in detection and orientation-identification thresholds for FD gratings.

METHODS. Detection and orientation-identification thresholds were determined in 12 observers with the use of FD stimuli (0.25 cyc/deg, 25 Hz) presented centrally and at 15° eccentricity. Edge profile (square- and Gaussian-windowed) and orientation (horizontal, vertical, and oblique) were independently modified. Detection thresholds were also measured for spatially uniform flickering targets (25 Hz). Orientation-identification thresholds using a two-alternative forced choice (2-AFC) and a two-interval forced choice (2-IFC) method were also compared in five experienced observers.

RESULTS. Orientation-identification and detection thresholds did not significantly differ under any condition tested. Orientation-identification thresholds obtained with 2-AFC were not significantly different from those obtained with 2-IFC. Thresholds for spatially uniform flicker were significantly lower than for FD stimuli.

CONCLUSIONS. The authors found that orientation-identification and detection thresholds for FD gratings did not differ and argue that recent findings to the contrary arise from the inappropriate use of spatially uniform flicker targets as alternatives in 2-IFC experiments.

Effect of a finite energy spread of the positron beam on the threshold behaviour of the positron annihilation cross section

In a recent paper [Phys. Rev. Lett. 88, 163202 (2002)] we established the threshold behavior of the cross section of positron-atom annihilation into two gamma quanta near the positronium (Ps)-formation threshold. Here, the near-threshold behavior of the positron 3 gamma annihilation cross section and its relation to the ortho-Ps-formation cross section are determined. We also analyze the feasibility of observing these effects by examining the effect of the ?nite-energy resolution of a positron beam on the threshold behavior.

Double-Electron Above-Threshold Ionization Resonances as Interference Phenomena

We report calculations of double ionization energy spectra and momentum distributions of laser-driven helium due to few-cycle pulses of wavelength 195 nm. The results are obtained from full-dimensional numerical integration of the two electron time-dependent Schr¨odinger equation. A momentum-space analysis of doubly ionizing wavepackets shows that the concentric-ring structure of above-threshold double ionization, together with the associated structure of peaks in the total kinetic energy spectrum, may be attributed to wavepacket interference effects, where at least two doubly-ionizing wavepackets from different recollision events populate the same spatial hemisphere.

Glucose lowers the threshold for human aortic vascular smooth muscle cell migration: inhibition by protein phosphatase-2A

AIMS/HYPOTHESIS: Atherosclerosis, which occurs prematurely in individuals with diabetes, incorporates vascular smooth muscle cell (VSMC) chemotaxis. Glucose, through protein kinase C-beta(II) signalling, increases chemotaxis to low concentrations of platelet-derived growth factor (PDGF)-BB. In VSMC, a biphasic response in PDGF-beta receptor (PDGF-betaR) level occurs as PDGF-BB concentrations increase. The purpose of this study was to determine whether increased concentrations of PDGF-BB and raised glucose level had a modulatory effect on the mitogen-activated protein kinase/extracellular-regulated protein kinase pathway, control of PDGF-betaR level and chemotaxis.

METHODS: Cultured aortic VSMC, exposed to normal glucose (NG) (5 mmol/l) or high glucose (HG) (25 mmol/l) in the presence of PDGF-BB, were assessed for migration (chemotaxis chamber) or else extracted and immunoblotted.

RESULTS: At concentrations of PDGF-BB <540 pmol/l, HG caused an increase in the level of PDGF-betaR in VSMC (immunoblotting) versus NG, an effect that was abrogated by inhibition of aldose reductase or protein kinase C-beta(II). At higher concentrations of PDGF-BB (>540 pmol/l) in HG, receptor level was reduced but in the presence of aldose reductase or protein kinase C-beta(II) inhibitors the receptor levels increased. It is known that phosphatases may be activated at high concentrations of growth factors. At high concentrations of PDGF-BB, the protein phosphatase (PP)2A inhibitor, endothall, caused an increase in PDGF-betaR levels and a loss of biphasicity in receptor levels in HG. At higher concentrations of PDGF-BB in HG, the chemoattractant effect of PDGF-BB was lost (chemotaxis chamber). Under these conditions inhibition of PP2A was associated with a restoration of chemotaxis to high concentrations of PDGF-BB.

CONCLUSION/INTERPRETATION: The biphasic response in PDGF-betaR level and in chemotaxis to PDGF-BB in HG is due to PP2A activation.

Threshold In School – As Event And Place For The Autism Spectrum Disorder Pupil

As architects and designers we have a responsibility to provide an inclusive built environment. For the Autistic Spectrum Disorder (ASD) sufferer however, the built environment can be a frightening and confusing place, difficult to negotiate and tolerate. The challenge of integrating more fully into society is denied by an alienating built environment. This barrier can be magnified for ASD pupils in a poorly designed school, where their environment can further distance them from learning. Instead, if more at ease in their surroundings, in an ASD friendly environment, the ASD pupil stands a greater chance of doing better.

Whilst researchers have looked at the classroomenvironment, the transition of classroom to corridor andbeyond has so far been largely ignored. However, theneed for a well-considered threshold between class andcorridor needs to be considered. In this regard, threshold is much more than a doorway, but instead an event that demands a carefully considered place. The following paper firstly outlines why threshold as place andevent for the ASD pupil should be given consideration. It then goes onto highlight, through case studies in anIrish context, the opportunities for aiding the ASD pupil integrating in a mainstream school environment throughsensitive use of threshold. Finally it highlights inconclusion, some of the benefits for an enriched school environment for all pupils, if considering threshold as design generator.The objective is straightforward. By increasing awareness of the relationship between the ASD child and the built environment it will hopefully facilitate greater inclusion of the ASD pupil into mainstream education and society at large.

Threshold effects in the Teaching Space Allocation Problem with Splitting

Universities aim for good “Space Management” so as to use the teaching space efficiently. Part of this task is to assign rooms and time-slots to teaching activities with limited numbers and capacities of lecture theaters, seminar rooms, etc. It is also common that some teaching activities require splitting into multiple events. For example, lectures can be too large to fit in one room or good teaching practice requires that seminars/tutorials are taught in small groups. Then, space management involves decisions on splitting as well as the assignments to rooms and time-slots. These decisions must be made whilst satisfying the pedagogic requirements of the institution and constraints on space resources. The efficiency of such management can be measured by the “utilisation”: the percentage of available seat-hours actually used. In many institutions, the observed utilisation is unacceptably low, and this provides our underlying motivation: to study the factors that affect teaching space utilisation, with the goal of improving it. We give a brief introduction to our work in this area, and then introduce a specific model for splitting. We present experimental results that show threshold phenomena and associated easy-hard-easy patterns of computational difficulty. We discuss why such behaviour is of importance for space management.

The effect of slurry storage and anaerobic-digestion on survival of pathogenic bacteria

The decline in viable numbers of Salmonella typhimurium, Yersinia enterocolitica and Listeria monocytogenes in beef cattle slurry is temperature-dependent; they decline more rapidly at 17-degrees-C than at 4-degrees-C. Mesophilic anaerobic digestion caused an initial rapid decline in the viable numbers of Escherichia coli, Salm. typhimurium, Y. enterocolitica and L. monocytogenes. This was followed by a period in which the viable numbers were not reduced by 90%. The T90 values of E. coli, Salm. typhimurium and Y. enterocolitica ranged from 0.7 to 0.9 d during batch digestion and 1.1 to 2-5 d during semi-continuous digestion. Listeria monocytogenes had a significantly higher mean T90 value during semi-continuous digestion (35.7 d) than batch digestion (12.3 d). Anaerobic digestion had little effect in reducing the viable numbers of Campylobacter jejuni.

Survival of pathogenic bacteria during mesophilic anaerobic-digestion of animal waste

The survival of pathogenic bacteria was investigated during the operation of a full-scale anaerobic digester which was fed daily and operated at 28-degrees-C. The digester had a mean hydraulic retention time of 24 d. The viable numbers of Escherichia coli, Salmonella typhimurium, Yersinia enterocolitica, Listeria monocytogenes and Campylobacter jejuni were reduced during mesophilic anaerobic digestion. Escherichia coli had the smallest mean viable numbers at each stage of the digestion process. Its mean T90 value was 76-9 d. Yersinia enterocolitica was the least resistant to the anaerobic digester environment; its mean T90 value was 18.2 d. Campylobacter jejuni was the most resistant bacterium; its mean T90 value was 438.6 d. Regression analysis showed that there were no direct relationships between the slurry input and performance of the digester and the decline of pathogen numbers during the 140 d experimental period.

Metabolic-activity of pathogenic bacteria during semicontinuous anaerobic-digestion

In natural environments such as anaerobic digesters, bacteria are frequently subjected to the stress of nutrient fluxes because of the continual changes in the flow of nutrients, and to survive, they must be capable of adapting readily to nutrient changes. In this study, the metabolic activities of Escherichia coli, Salmonella typhimurium, Yersinia enterocolitica, Listeria monocytogenes, and Campylobacter jejuni were studied within culture bags (Versapor-200 filters, 0.22-mu m pore size) in laboratory anaerobic digesters. The metabolic activity of these bacteria was indicated by their adenylate energy charge (EC) ratios and their ability to incorporate [H-3]thymidine, which was related to the respective changes in viable numbers within the culture bags during anaerobic digestion. Fluctuations in the adenylate EC ratios, the uptake of [H-3]thymidine, and the viable numbers of E. coli, S. typhimurium, Y. enterocolitica, and L. monocytogenes cells were probably due to constant changes in the amount of available nutrients within the anaerobic digesters. The viability of S. typhimurium increased quickly after a fresh supply of nutrients was added to the system as indicated by the uptake of [H-3]thymidine and an increase in the adenylate EC ratios. The viable numbers of E. coli, S. typhimurium, Y. enterocolitica, and L. monocytogenes organisms declined rapidly from 10(7) to 10(8) CFU/ml to 10(3) to 10(4) CFU/ml and remained at this level for an indefinite period. The decimal reduction time calculated during the period of exponential decline ranged from 0.8 to 1.2 days for these bacteria. C. jejuni had the greatest mean decimal reduction time value (3.6 days). This bacterium had adenylate EC ratios of less than 0.5 during anaerobic digestion, although the adenylate nucleotide concentrations in the cells were much greater than those in the other enteric cells. The results show that the enteric bacteria investigated probably exist in transient states between different stages of growth because of fluctuating nutrient levels during anaerobic digestion.