Extracytoplasmic function (ECF) sigma factor sigma(F) is involved in Caulobacter crescentus response to heavy metal stress

Background: The alpha-proteobacterium Caulobacter crescentus inhabits low-nutrient environments and can tolerate certain levels of heavy metals in these sites. It has been reported that C. crescentus responds to exposure to various heavy metals by altering the expression of a large number of genes. Results: In this work, we show that the ECF sigma factor sigma(F) is one of the regulatory proteins involved in the control of the transcriptional response to chromium and cadmium. Microarray experiments indicate that sigma(F) controls eight genes during chromium stress, most of which were previously described as induced by heavy metals. Surprisingly, sigma(F) itself is not strongly auto-regulated under metal stress conditions. Interestingly, sigma(F)-dependent genes are not induced in the presence of agents that generate reactive oxygen species. Promoter analyses revealed that a conserved sigma(F)-dependent sequence is located upstream of all genes of the sigma(F) regulon. In addition, we show that the second gene in the sigF operon acts as a negative regulator of sigma(F) function, and the encoded protein has been named NrsF (Negative regulator of sigma F). Substitution of two conserved cysteine residues (C131 and C181) in NrsF affects its ability to maintain the expression of sigma(F)-dependent genes at basal levels. Furthermore, we show that sigma(F) is released into the cytoplasm during chromium stress and in cells carrying point mutations in both conserved cysteines of the protein NrsF. Conclusion: A possible mechanism for induction of the sigma(F)-dependent genes by chromium and cadmium is the inactivation of the putative anti-sigma factor NrsF, leading to the release of sigma(F) to bind RNA polymerase core and drive transcription of its regulon.

Mechanistic changes observed in heavy water for nitrate reduction reaction on palladium-modified Pt(hkl) electrodes

Reduction of nitrate on palladium-modified platinum single-crystal electrodes has been investigated both voltammetrically and spectroscopically in acidic media (pH = 1). Results obtained in H2O and D2O solvents are compared for the three crystallographic orientations. FTIR and differential electrochemical mass spectrometry (DEMS) results clearly indicate that the isotopic substitution of the solvent has a large effect in the mechanism of the reaction, changing the nature of the detected products. For Pt(111)/Pd and Pt(100)/Pd, N2O is detected as the main product of nitrate reduction when D2O is used as solvent, while no N2O is detected when the reaction is performed in H2O. For Pt(110)/Pd, N2O is detected in both solvents, although the use of D2O clearly favours the preferential formation of this product. The magnitude of voltammetric currents is also affected by the nature of the solvent. This has been analysed considering, in addition to the different product distribution, the existence of different transport numbers and optical constants of the solvent.

Water-assisted Flow of Heavy Oil in a Vertical Pipe: Pilot-scale Experiments

The use of the core-annular flow pattern, where a thin fluid surrounds a very viscous one, has been suggested as an attractive artificial-lift method for heavy oils in the current Brazilian ultra-deepwater production scenario. This paper reports the pressure drop measurements and the core-annular flow observed in a 2 7/8-inch and 300 meter deep pilot-scale well conveying a mixture of heavy crude oil (2000 mPa.s and 950 kg/m3 at 35 C) and water at several combinations of the individual flow rates. The two-phase pressure drop data are compared with those of single-phase oil flow to assess the gains due to water injection. Another issue is the handling of the core-annular flow once it has been established. High-frequency pressure-gradient signals were collected and a treatment based on the Gabor transform together with neural networks is proposed as a promising solution for monitoring and control. The preliminary results are encouraging. The pilot-scale tests, including long-term experiments, were conducted in order to investigate the applicability of using water to transport heavy oils in actual wells. It represents an important step towards the full scale application of the proposed artificial-lift technology. The registered improvements in terms of oil production rate and pressure drop reductions are remarkable.

Origin of the heavy elements in HD 140283 Measurement of europium abundance

Context. HD 140283 is a nearby (V = 7.7) subgiant metal-poor star, extensively analysed in the literature. Although many spectra have been obtained for this star, none showed a signal-to-noise (S/N) ratio high enough to enable a very accurate derivation of abundances from weak lines. Aims. The detection of europium proves that the neutron-capture elements in this star originate in the r-process, and not in the s-process, as recently claimed in the literature. Methods. Based on the OSMARCS 1D LTE atmospheric model and with a consistent approach based on the spectrum synthesis code Turbospectrum, we measured the europium lines at 4129 angstrom and 4205 angstrom, taking into account the hyperfine structure of the transitions. The spectrum, obtained with a long exposure time of seven hours at the Canada-France-Hawaii Telescope (CFHT), has a resolving power of 81 000 and a S/N ratio of 800 at 4100 angstrom. Results. We were able to determine the abundance A(Eu) = -2.35 +/- 0.07 dex, compatible with the value predicted for the europium from the r-process. The abundance ratio [Eu/Ba] = +0.58 +/- 0.15 dex agrees with the trend observed in metal-poor stars and is also compatible with a strong r-process contribution to the origin of the neutron-capture elements in HD 140283.

Production of Muons from Heavy Flavor Decays at Forward Rapidity in pp and Pb-Pb Collisions at root s(NN)=2.76 TeV

The ALICE Collaboration has measured the inclusive production of muons from heavy-flavor decays at forward rapidity, 2.5 < y < 4, in pp and Pb-Pb collisions at root s(NN) = 2.76 TeV. The p(t)-differential inclusive cross section of muons from heavy-flavor decays in pp collisions is compared to perturbative QCD calculations. The nuclear modification factor is studied as a function of p(t) and collision centrality. A weak suppression is measured in peripheral collisions. In the most central collisions, a suppression of a factor of about 3-4 is observed in 6 < p(t) < 10 GeV/c. The suppression shows no significant p(t) dependence.

1(--) and 0(++) heavy four-quark and molecule states in QCD

We estimate the masses of the 1(--) heavy four-quark and molecule states by combining exponential Laplace (LSR) and finite energy (FESR) sum rules known perturbatively to lowest order (LO) in alpha(s) but including non-perturbative terms up to the complete dimension-six condensate contributions. This approach allows to fix more precisely the value of the QCD continuum threshold (often taken ad hoc) at which the optimal result is extracted. We use double ratio of sum rules (DRSR) for determining the SU(3) breakings terms. We also study the effects of the heavy quark mass definitions on these LO results. The SU(3) mass-splittings of about (50-110) MeV and the ones of about (250-300) MeV between the lowest ground states and their 1st radial excitations are (almost) heavy-flavor independent. The mass predictions summarized in Table 4 are compared with the ones in the literature (when available) and with the three Y-c(4260, 4360, 4660) and Y-b(10890) 1(--) experimental candidates. We conclude (to this order approximation) that the lowest observed state cannot be a pure 1(--) four-quark nor a pure molecule but may result from their mixings. We extend the above analyzes to the 0(++) four-quark and molecule states which are about (0.5-1) GeV heavier than the corresponding 1(--) states, while the splittings between the 0(++) lowest ground state and the 1st radial excitation is about (300-500) MeV. We complete the analysis by estimating the decay constants of the 1(--) and 0(++) four-quark states which are tiny and which exhibit a 1/M-Q behavior. Our predictions can be further tested using some alternative non-perturbative approaches or/and at LHCb and some other hadron factories. (c) 2012 Elsevier B.V. All rights reserved.

Staining of the Internal Limiting Membrane with the Use of Heavy Brilliant Blue G

Background: Brilliant blue G (BBG) is frequently used in chromovitrectomy to facilitate internal limiting membrane (ILM) peeling. A study was initiated to evaluate if heavy BBG is safe and effective in staining the ILM. Methods: We studied 30 eyes, 23 with idiopathic macular holes and 7 of patients with diabetic macular edema. Removal of the ILMs was assisted by heavy BBG staining. In cases with histopathological correlation the ILMs were evaluated with hematoxylin and eosin, Masson's trichrome, periodic acid-Schiff and glial fibrillary acidic protein staining. In addition, immunohistochemistry was also performed using specific antibodies for vimentin, neuron-specific enolase, factor VIII and CD68. Using the Image-Pro Plus software of Media Cybernetics Co. we found an average thickness in ILMs. Results: Of the ILM specimens sent, 19/30(63.33%) could not be processed properly because of the limited sample material, recognizing only fragments of dispersed fibrillar material. In macular hole ILMs we found an average thickness of 1.3 +/- 0.65 mu m, and in diabetic macular edema ILMs an average thickness of 6.2 +/- 1.4 mu m. Conclusions: In heavy BBG-assisted ILM peeling we observed no intraoperative or postoperative complications after a mean follow-up of 12 months. Heavy BBG could be an effective and safe vehicle for staining the ILM. Copyright (C) 2012 S. Karger AG, Basel

Energy and system-size dependence of two- and four-particle nu(2) measurements in heavy-ion collisions at root S-NN=62.4 and 200 GeV and their implications on flow fluctuations and nonflow

We present STAR measurements of azimuthal anisotropy by means of the two- and four-particle cumulants nu(2) (nu(2){2} and nu(2){4}) for Au + Au and Cu + Cu collisions at center-of-mass energies root S-NN = 62.4 and 200 GeV. The difference between nu(2){2}(2) and nu(2){4}(2) is related to nu(2) fluctuations (sigma(nu 2)) and nonflow (delta(2)). We present an upper limit to sigma(nu 2)/nu 2. Following the assumption that eccentricity fluctuations sigma(epsilon) dominate nu(2) fluctuations nu(2)/sigma nu(2) approximate to epsilon/sigma epsilon we deduce the nonflow implied for several models of eccentricity fluctuations that would be required for consistency with nu(2){2} and nu(2){4}. We also present results on the ratio of nu(2) to eccentricity.

Cold-Nuclear-Matter Effects on Heavy-Quark Production in d+Au Collisions at root S-NN=200 GeV

The PHENIX experiment has measured electrons and positrons at midrapidity from the decays of hadrons containing charm and bottom quarks produced in d + Au and p + p collisions at root S-NN = 200 GeV in the transverse-momentum range 0.85 <= p(T)(e) <= 8.5 GeV/c. In central d + Au collisions, the nuclear modification factor R-dA at 1.5 < p(T) < 5 GeV/c displays evidence of enhancement of these electrons, relative to those produced in p + p collisions, and shows that the mass-dependent Cronin enhancement observed at the Relativistic Heavy Ion Collider extends to the heavy D meson family. A comparison with the neutral-pion data suggests that the difference in cold-nuclear-matter effects on light- and heavy-flavor mesons could contribute to the observed differences between the pi(0) and heavy-flavor-electron nuclear modification factors R-AA. DOI: 10.1103/PhysRevLett.109.242301

Mapping the hydrodynamic response to the initial geometry in heavy-ion collisions

We investigate how the initial geometry of a heavy-ion collision is transformed into final flow observables by solving event-by-event ideal hydrodynamics with realistic fluctuating initial conditions. We study quantitatively to what extent anisotropic flow (nu(n)) is determined by the initial eccentricity epsilon(n) for a set of realistic simulations, and we discuss which definition of epsilon(n) gives the best estimator of nu(n). We find that the common practice of using an r(2) weight in the definition of epsilon(n) in general results in a poorer predictor of nu(n) than when using r(n) weight, for n > 2. We similarly study the importance of additional properties of the initial state. For example, we show that in order to correctly predict nu(4) and nu(5) for noncentral collisions, one must take into account nonlinear terms proportional to epsilon(2)(2) and epsilon(2)epsilon(3), respectively. We find that it makes no difference whether one calculates the eccentricities over a range of rapidity or in a single slice at z = 0, nor is it important whether one uses an energy or entropy density weight. This knowledge will be important for making a more direct link between experimental observables and hydrodynamic initial conditions, the latter being poorly constrained at present.

Extracytoplasmic function (ECF) sigma factor σF is involved in Caulobacter crescentus response to heavy metal stress

Background The α-proteobacterium Caulobacter crescentus inhabits low-nutrient environments and can tolerate certain levels of heavy metals in these sites. It has been reported that C. crescentus responds to exposure to various heavy metals by altering the expression of a large number of genes. Results In this work, we show that the ECF sigma factor σF is one of the regulatory proteins involved in the control of the transcriptional response to chromium and cadmium. Microarray experiments indicate that σF controls eight genes during chromium stress, most of which were previously described as induced by heavy metals. Surprisingly, σF itself is not strongly auto-regulated under metal stress conditions. Interestingly, σF-dependent genes are not induced in the presence of agents that generate reactive oxygen species. Promoter analyses revealed that a conserved σF-dependent sequence is located upstream of all genes of the σF regulon. In addition, we show that the second gene in the sigF operon acts as a negative regulator of σF function, and the encoded protein has been named NrsF (Negative regulator of sigma F). Substitution of two conserved cysteine residues (C131 and C181) in NrsF affects its ability to maintain the expression of σF-dependent genes at basal levels. Furthermore, we show that σF is released into the cytoplasm during chromium stress and in cells carrying point mutations in both conserved cysteines of the protein NrsF. Conclusion A possible mechanism for induction of the σF-dependent genes by chromium and cadmium is the inactivation of the putative anti-sigma factor NrsF, leading to the release of σF to bind RNA polymerase core and drive transcription of its regulon.

Two RND proteins involved in heavy metal efflux in Caulobacter crescentus belong to separate clusters within proteobacteria

Abstract Background Heavy metal Resistance-Nodulation-Division (HME-RND) efflux systems help Gram-negative bacteria to keep the intracellular homeostasis under high metal concentrations. These proteins constitute the cytoplasmic membrane channel of the tripartite RND transport systems. Caulobacter crescentus NA1000 possess two HME-RND proteins, and the aim of this work was to determine their involvement in the response to cadmium, zinc, cobalt and nickel, and to analyze the phylogenetic distribution and characteristic signatures of orthologs of these two proteins. Results Expression assays of the czrCBA operon showed significant induction in the presence of cadmium and zinc, and moderate induction by cobalt and nickel. The nczCBA operon is highly induced in the presence of nickel and cobalt, moderately induced by zinc and not induced by cadmium. Analysis of the resistance phenotype of mutant strains showed that the ΔczrA strain is highly sensitive to cadmium, zinc and cobalt, but resistant to nickel. The ΔnczA strain and the double mutant strain showed reduced growth in the presence of all metals tested. Phylogenetic analysis of the C. crescentus HME-RND proteins showed that CzrA-like proteins, in contrast to those similar to NczA, are almost exclusively found in the Alphaproteobacteria group, and the characteristic protein signatures of each group were highlighted. Conclusions The czrCBA efflux system is involved mainly in response to cadmium and zinc with a secondary role in response to cobalt. The nczCBA efflux system is involved mainly in response to nickel and cobalt, with a secondary role in response to cadmium and zinc. CzrA belongs to the HME2 subfamily, which is almost exclusively found in the Alphaproteobacteria group, as shown by phylogenetic analysis. NczA belongs to the HME1 subfamily which is more widespread among diverse Proteobacteria groups. Each of these subfamilies present distinctive amino acid signatures.

Availability of heavy metals in contaminated soil evidenced by chemical extractants

Heavy metals have been accumulating in Brazilian soils, due to natural processes, such as atmospheric deposition, or human industrial activities. For certain heavy metals, when in high concentrations in the soil, there is no specific extractant to determine the availability of these elements in the soil. The objective of the present study was to evaluate the availability of Cd, Cu, Fe, Mn, Pb and Zn for rice and soybeans, using different chemical extractants. In this study we used seven soil samples with different levels of contamination, in completely randomized experimental design with four replications. We determined the available concentrations of Cd, Cu, Fe, Mn, Pb and Zn extracted by Mehlich-1, HCl 0.1 mol L-1, DTPA, and organic acid extractants and the contents in rice and soybeans, which extracts were analyzed by ICP-OES. It was observed that Mehlich-1, HCl 0.1 mol L-1 and DTPA extractants were effective to assess the availability of Cd, Cu, Pb and Zn for rice and soybeans. However, the same was not observed for the organic acid extractant.

Treatment of gingival recessions in heavy smokers using two surgical techniques: a controlled clinical trial

Smokers have small root coverage which is associated with bad vascularity of periodontal tissues. This study evaluated a technique that can increase the blood supply to the periodontal tissues compared with a traditional technique. Twenty heavy smokers (10 males and 10 females) with two bilateral Miller class I gingival recessions received coronally positioned flaps in one side (Control group)and extended flap technique in the other side (Test group). Clinical measurements (probing pocket depth, clinical attachment level, bleeding on probing, gingival recession height, gingival recession width, amount of keratinized tissue, and width and height of the papillae adjacent to the recession) were determined at baseline, 3 and 6 months postoperatively. Salivary cotinina samples were taken as an indicator of the nicotine exposure level. No statistically significant differences (p>0.05) were detected for the clinical measurements or smoke exposure. Both techniques promoted low root coverage (Control group: 43.18% and Test group: 44.52%). In conclusion, no difference was found in root coverage between the techniques. Root coverage is possible and uneventful even, if rather low, in heavy smoker patients with low plaque and bleeding indices.

Origin of the heavy elements in HD 140283: measurement of europium abundance

Context. HD140283 is a nearby (V = 7:7) subgiant metal-poor star, extensively analysed in the literature. Although many spectra have been obtained for this star, none showed a signal-to-noise (S/N) ratio high enough to enable a very accurate derivation of abundances from weak lines. Aims. The detection of europium proves that the neutron-capture elements in this star originate in the r-process, and not in the s-process, as recently claimed in the literature. Methods. Based on the OSMARCS 1D LTE atmospheric model and with a consistent approach based on the spectrum synthesis code Turbospectrum, we measured the europium lines at 4129 Å and 4205 Å, taking into account the hyperfine structure of the transitions. The spectrum, obtained with a long exposure time of seven hours at the Canada-France-Hawaii Telescope (CFHT), has a resolving power of 81 000 and a S/N ratio of 800 at 4100 Å. Results. We were able to determine the abundance A(Eu) =