A search for X-rays from UV Ceti flare stars

A search of MIT/OSO-7 data was made for evidence of X-ray emission from flares of UV Ceti flare stars. Observations from McDonald Observatory were used to identify the times of optical flares. The only instance of coincident coverage occurred on 1974 January 21 UT at 03:43:26 GMT for delta m(u)=0.86 flare of YZ CMi. No radio coverage of this particular event was obtained. Upper limits (3 sigma) of 0.8, 1.0, and 0.7 photons/sq cm-sec on the observed X-ray flux were set for the energy ranges greater than or approximately equal to 15, greater than or approximately equal to 3, and 1-10 keV, respectively

The oxygen-independent metabolism of cyclic monoterpenes in Castellaniella defragrans 65Phen

BACKGROUND: The facultatively anaerobic betaproteobacterium Castellaniella defragrans 65Phen utilizes acyclic, monocyclic and bicyclic monoterpenes as sole carbon source under oxic as well as anoxic conditions. A biotransformation pathway of the acyclic β-myrcene required linalool dehydratase-isomerase as initial enzyme acting on the hydrocarbon. An in-frame deletion mutant did not use myrcene, but was able to grow on monocyclic monoterpenes. The genome sequence and a comparative proteome analysis together with a random transposon mutagenesis were conducted to identify genes involved in the monocyclic monoterpene metabolism. Metabolites accumulating in cultures of transposon and in-frame deletion mutants disclosed the degradation pathway. RESULTS: Castellaniella defragrans 65Phen oxidizes the monocyclic monoterpene limonene at the primary methyl group forming perillyl alcohol. The genome of 3.95 Mb contained a 70 kb genome island coding for over 50 proteins involved in the monoterpene metabolism. This island showed higher homology to genes of another monoterpene-mineralizing betaproteobacterium, Thauera terpenica 58Eu(T), than to genomes of the family Alcaligenaceae, which harbors the genus Castellaniella. A collection of 72 transposon mutants unable to grow on limonene contained 17 inactivated genes, with 46 mutants located in the two genes ctmAB (cyclic terpene metabolism). CtmA and ctmB were annotated as FAD-dependent oxidoreductases and clustered together with ctmE, a 2Fe-2S ferredoxin gene, and ctmF, coding for a NADH:ferredoxin oxidoreductase. Transposon mutants of ctmA, B or E did not grow aerobically or anaerobically on limonene, but on perillyl alcohol. The next steps in the pathway are catalyzed by the geraniol dehydrogenase GeoA and the geranial dehydrogenase GeoB, yielding perillic acid. Two transposon mutants had inactivated genes of the monoterpene ring cleavage (mrc) pathway. 2-Methylcitrate synthase and 2-methylcitrate dehydratase were also essential for the monoterpene metabolism but not for growth on acetate. CONCLUSIONS: The genome of Castellaniella defragrans 65Phen is related to other genomes of Alcaligenaceae, but contains a genomic island with genes of the monoterpene metabolism. Castellaniella defragrans 65Phen degrades limonene via a limonene dehydrogenase and the oxidation of perillyl alcohol. The initial oxidation at the primary methyl group is independent of molecular oxygen

Resonance production in heavy ion collisions

Recent results of resonance production from RHIC at $\sqrt{s_{\rm NN}} =$ 200 GeV and SPS at $\sqrt{s_{\rm NN}} =$ 17 GeV are presented and discussed in terms of the evolution and freeze-out conditions of a hot and dense fireball medium. Yields and spectra are compared with thermal model predictions at chemical freeze-out. Deviations in the low transverse momentum region of the resonance spectrum of the hadronic decay channel, suggest a strongly interaction hadronic phase between chemical and kinetic freeze-out. Microscopic models including resonance rescattering and regeneration are able to describe the trend of the data. The magnitude of the regeneration cross sections for different inverse decay channels are discussed. Model calculations which include elastic hadronic interactions between chemical freeze-out and thermal freeze-out based on the K(892)/K and $\Lambda$(1520)/$\Lambda$ ratios suggest a time between two freeze-outs surfaces of $\Delta \tau>$ 4 fm/c. The difference in momentum distributions and yields for the $\phi$(1020) resonance reconstructed from the leptonic and hadronic decay channels at SPS energy are discussed taking into account the impact of a hadronic phase and possible medium modifications.Comment: 8 pages, 4 figures, conference proceedings (SQM2004

What do we learn from Resonance Production in Heavy Ion Collisions?

Resonances with their short life time and strong coupling to the dense and hot medium are suggested as a signature of the early stage of the fireball created in a heavy ion collision \cite{rap00,lut01,lut02}. The comparison of resonances with different lifetimes and quark contents may give information about time evolution and density and temperature of during the expanding of fireball medium. Resonances in elementary reactions have been measured since 1960. Resonance production in elementary collisions compared with heavy ion collisions where we expect to create a hot and dense medium may show the direct of influence of the medium on the resonances. This paper shows a selection of the recent resonance measurements from SPS and RHIC heavy ion colliders.Comment: 10 pages, 8 figures, HotQuarks 2004 conference proceeding

Linalool isomerase, a membrane-anchored enzyme in the anaerobic monoterpene degradation in Thauera linaloolentis 47Lol

Background: Thauera linaloolentis 47Lol uses the tertiary monoterpene alcohol (R,S)-linalool as sole carbon and energy source under denitrifying conditions. The conversion of linalool to geraniol had been observed in carbon-excess cultures, suggesting the presence of a 3,1-hydroxyl-Delta(1)-Delta(2)-mutase (linalool isomerase) as responsible enzyme. To date, only a single enzyme catalyzing such a reaction is described: the linalool dehydratase/isomerase (Ldi) from Castellaniella defragrans 65Phen acting only on (S)-linalool. Results: The linalool isomerase activity was located in the inner membrane. It was enriched by subcellular fractionation and sucrose gradient centrifugation. MALDI-ToF MS analysis of the enriched protein identified the corresponding gene named lis that codes for the protein in the strain with the highest similarity to the Ldi. Linalool isomerase is predicted to have four transmembrane helices at the N-terminal domain and a cytosolic domain. Enzyme activity required a reductant for activation. A specific activity of 3.42 +/- 0.28 nkat mg * protein(-1) and a k(M) value of 455 +/- 124 mu M were determined for the thermodynamically favored isomerization of geraniol to both linalool isomers at optimal conditions of pH 8 and 35 degrees C. Conclusion: The linalool isomerase from T. linaloolentis 47Lol represents a second member of the enzyme class 5.4.4.4, next to the linalool dehydratase/isomerase from C. defragrans 65Phen. Besides considerable amino acid sequence similarity both enzymes share common characteristics with respect to substrate affinity, pH and temperature optima, but differ in the dehydratase activity and the turnover of linalool isomers

Effect of Hydrostatic Pressure on the Superconductivity in NaxCoO2.yH2O

The effect of hydrostatic pressure on the superconducting transition temperature of Na{0.35}CoO{2}.yH{2}O was investigated by ac susceptibility measurements up to 1.6 GPa. The pressure coefficient of T{c} is negative and the dependence T{c}(p) is nonlinear over the pressure range investigated. The magnitude of the average dlnT{c}/dp=-0.07 GPa^{-1} is comparable to the pressure coefficient of electron-doped high-T{c} copper oxide superconductors with a similar value of T{c}. Our results provide support to the assumption of two-dimensional superconductivity in Na{0.35}CoO{2}.yH{2}O, which is similar to the cuprate systems, and suggest that intercalation of larger molecules may lead to an enhancement of T{c}.Comment: Revised Manuscrip

Splenic B1 B Cells Acquire a Proliferative and Anti-Inflamatory Profile During Pregnancy in Mice

B cells are a heterogeneous cell population with differential ontogeny, anatomical location, and functions. B1 B cells are a distinct subpopulation characterized by their unique capacity of self-renewal, the production of large quantities of IL-10, and the ability to secrete protective, anti-inflammatory natural antibodies (NAbs), presumably upon down-regulation of CD1d expression. Although natural antibodies are thought to be protective, due to their polyreactivity, their participation in certain autoimmune diseases has been suggested. In the context of pregnancy, the role of B1 B cells has been discussed controversially. While in human pregnancies B1 B cells and natural/polyreactive antibodies they produce are involved in the development of preeclampsia, in mice they promote healthy gestation and fetal protection. In this work, we aimed to functionally characterize the splenic B1 B cell population during pregnancy in mice. Functional enrichment analysis using only up-regulated transcripts from a transcriptomic profile performed on total splenic B cells from pregnant compared to non-pregnant mice showed augmented cell cycle and DNA replication pathways. Proliferation studies by flow cytometry showed augmented Ki-67 proliferation marker expression and percentages of B1 B cells. Furthermore, B1 B cells produced higher levels of IL-10 and lower levels of TNF-α leading to an increased IL-10/TNF-α ratio and showing an immunoregulatory phenotype. Finally, we observed lower expression of CD1d on B1 B cells, suggesting a higher capacity to produce NAbs in the context of pregnancy. In summary, our results showed not only an expanded and proliferative splenic B1 B cell population during pregnancy but also the acquisition of immunomodulatory capacities suggesting its critical role in the intricate process of pregnancy tolerance