Identification of a new porin, RafY, encoded by raffinose plasmid pRSD2 of Escherichia coli

The conjugative plasmid pRSD2 carries a raf operon that encodes a peripheral raffinose metabolic pathway in enterobacteria. In addition to the previously known raf genes, we identified another gene, rafY, which in Escherichia coli codes for an outer membrane protein (molecular mass, 53 kDa) similar in function to the known glycoporins LamB (maltoporin) and ScrY (sucrose porin). Sequence comparisons with LamB and ScrY revealed no significant similarities; however, both lamB and scrY mutants are functionally complemented by RafY. Expressed from the tac promoter, RafY significantly increases the uptake rates for maltose, sucrose, and raffinose at low substrate concentrations; in particular it shifts the apparent K(m) for raffinose transport from 2 mM to 130 microM. Moreover, RafY permits diffusion of the tetrasaccharide stachyose and of maltodextrins up to maltoheptaose through the outer membrane of E. coli. A comparison of all three glycoporins in regard to their substrate selectivity revealed that both ScrY and RafY have a broad substrate range which includes alpha-galactosides while LamB seems to be restricted to malto-oligosaccharides. It supports growth only on maltodextrins but not, like the others, on raffinose and stachyose.     

X-ray techniques using synchrotron radiation in materials analysis

The extraordinary properties of SR have opened up new horizons for all techniques which use vacuum ultraviolet light and X-rays. In this article, some applications of SR in materials science have been discussed. X-ray absorption spectroscopy is a local, atom specific probe of the geometrical and electronic structure of the absorbing species. As an example, the lattice site location and the valence of Co in a doped high-T_c, superconductor YBa₂Cu_2–5Co_0–5O_7–4 has been discussed.     

Focusing high-energy x rays by compound refractive lenses

Compound lenses made from low-Z materials (e.g., Be, B, C, and Al) set up as a linear array of refractive lenses are proposed for submicrometer focusing of high-energy x rays (>5 keV) in one or two dimensions. A theory of focusing based on Maxwell's equation and the Fresnel-Kirchhoff approach is presented. Compound refractive lenses were manufactured by drilling into an Al block a linear array of 200 closely spaced holes 0.5 mm in diameter for linear focusing and two crossed arrays of 100 holes each for point focusing. Focal spots of 3.7 mum and 8 mum x 18 mum were obtained at 30 keV for linear and two-dimensional lenses, respectively. Different technologies of manufacturing and possible applications of the proposed lenses are discussed.     

rf superconductivity: expectations and achievements

Since 1962 a great effort has been made in rf superconductivity, mainly aimed at possible applications for particle accelerators. Most of the studies have been concentrated on niobium-cavities in the frequency range between 100 MHz and 10 GHz. It was possible to reach even in large and complicated cavities, surface resistances around 10^?8 ohm, satisfying the most demanding requirements for accelerators. It has been demonstrated that the surface treatments developed since then made it possible to reach in small and simple cavaties field levels of the order of the critical dc magnetic field for the material used. However, one is not yet able to reproduce such high field levels in a reliable and reproducible way in the large multicell cavities needed for accelerators. The explanations for these field limitations are numerous and for their elimination a much better understanding of real superconducting surfaces will be needed. rf superconductivity has pushed forward the first large cooling systems working at temperatures below 2 K and using He-II as a coolant. The application of new Type II superconductors may make it possible to overcome some of the field limitations and may render operating temperatures around 4.2 K possible.     

High-resolution X-ray fluorescence microtomography of homogeneoussamples

First experimental results of fluorescence microtomography with 6 μm resolution obtained at ESRF, Grenoble, France, are described. The setup comprises high-quality optics (monochromator, mirror, focusing lenses) coupled to the high-energy/brilliance/coherence of the ID 22 undulator beamline. The tomographic setup allows precise measurements in the “pencil-beam” geometry. The image reconstruction is based on a modification of the algebraic reconstruction method but includes simplifications of the model. The quality and precision of the two-dimensional reconstructed elemental images of a phantom sample are encouraging. The method will be further refined and applied for the analysis of more complex inhomogeneous samples     

Language bias in randomised controlled trials published in English and German

BACKGROUND: Some randomised controlled trials (RCTs) done in German-speaking Europe are published in international English-language journals and others in national German-language journals. We assessed whether authors are more likely to report trials with statistically significant results in English than in German. METHODS: We studied pairs of RCT reports, matched for first author and time of publication, with one report published in German and the other in English. Pairs were identified from reports round in a manual search of five leading German-language journals and from reports published by the same authors in English found on Medline. Quality of methods and reporting were assessed with two different scales by two investigators who were unaware of authors' identities, affiliations, and other characteristics of trial reports. Main study endpoints were selected by two investigators who were unaware of trial results. Our main outcome was the number of pairs of studies in which the levels of significance (shown by p values) were discordant. FINDINGS: 62 eligible pairs of reports were identified but 19 (31%) were excluded because they were duplicate publications. A further three pairs (5%) were excluded because no p values were given. The remaining 40 pairs were analysed. Design characteristics and quality features were similar for reports in both languages. Only 35% of German-language articles, compared with 62% of English-language articles, reported significant (p < 0.05) differences in the main endpoint between study and control groups (p = 0.002 by McNemar's test). Logistic regression showed that the only characteristic that predicted publication in an English-language journal was a significant result. The odds ratio for publication of trials with significant results in English was 3.75 (95% CI 1.25-11.3). INTERPRETATION: Authors were more likely to publish RCTs in an English-language journal if the results were statistically significant. English language bias may, therefore, be introduced in reviews and meta-analyses if they include only trials reported in English. The effort of the Cochrane Collaboration to identify as many controlled trials as possible, through the manual search of many medical journals published in different languages will help to reduce such bias.     

The distribution of Schistosoma haematobium in the Isoka district, Zambia; and a possible strategy for its control

The distribution of schools prevalent for Schistosoma haematobium in the Isoka district, Zambia was estimated by examining haematuria in the urine of the pupils found in Grades Three, Four or Five using reagent sticks. Thirty three (57 pc) schools had prevalence rates of 25 pc or more. The distribution of S. haematobium was patchy with significant differences in prevalence rates between some areas only short distances apart. A sociological study in the same schools showed that 68 (97 pc) head/senior teachers associated the disease with blood in urine and agreed to perform a reagent stick test on their pupils' urine. Thirty five (50 pc) of these respondents considered S. haematobium infection as a major problem and 66 (94 pc) of them were ready to administer a diagnostic questionnaire to their pupils in a study to identify high risk schools for S. haematobium. We conclude that the identification of high risk schools in the Isoka district, Zambia, using a diagnostic questionnaire and reagent stick testing by teachers, should proceed as a step to controlling S. haematobium infection in the district.     

Quantum simulations of an ultrashort channel single-gated n-MOSFETon SOI

We present quantum mechanical simulations of a single-gated ultrashort channel MOSFET on silicon-on-insulator (SOI). Ballistic transport is assumed, in order to investigate ideal device performance. In particular, the electrical characteristics and the dependence on the SOI body thickness variation and doping of source and drain is elaborated. The results show that excellent performance can be achieved for devices with channel lengths down to 15 nm for a single-gated device layout. The influence of the SOI-film roughness is investigated with an SOI body thickness down to 2.5 nm. Extremely high transconductances far in excess of today's state-of-the-art devices can be expected if the doping level in source and drain is chosen appropriately. We give the relevant design rules for the fabrication of such devices