280 research outputs found
Effects of rehydration nutrients on H2S metabolism and formation of volatile sulfur compounds by the wine yeast VL3
In winemaking, nutrient supplementation is a common practice for optimising fermentation and producing quality wine. Nutritionally suboptimal grape juices are often enriched with nutrients in order to manipulate the production of yeast aroma compounds. Nutrients are also added to active dry yeast (ADY) rehydration media to enhance subsequent fermentation performance. In this study we demonstrate that nutrient supplementation at rehydration also has a significant effect on the formation of volatile sulfur compounds during wine fermentations. The concentration of the 'fruity' aroma compounds, the polyfunctional thiols 3-mercaptohexan-1-ol (3MH) and 3-mercaptohexyl acetate (3MHA), was increased while the concentration of the 'rotten egg' aroma compound, hydrogen sulfide (H2S), was decreased. Nutrient supplementation of the rehydration media also changed the kinetics of H2S production during fermentation by advancing onset of H2S production. Microarray analysis revealed that this was not due to expression changes within the sulfate assimilation pathway, which is known to be a major contributor to H2S production. To gain insight into possible mechanisms responsible for this effect, a component of the rehydration nutrient mix, the tri-peptide glutathione (GSH) was added at rehydration and studied for its subsequent effects on H2S formation. GSH was found to be taken up during rehydration and to act as a source for H2S during the following fermentation. These findings represent a potential approach for managing sulfur aroma production through the use of rehydration nutrients
Absence of hepatitis delta infection in a large rural HIV cohort in Tanzania
OBJECTIVES: The epidemiological and clinical determinants of
hepatitis delta virus (HDV) infection in Sub-Saharan Africa are
ill-defined. The prevalence of HDV infection was determined in
HIV/hepatitis B virus (HBV) co-infected individuals in rural
Tanzania. METHODS: All hepatitis B virus (HBV)-infected adults
under active follow-up in the Kilombero and Ulanga
Antiretroviral Cohort (KIULARCO) were screened for anti-HDV
antibodies. For positive samples, a second serological test and
nucleic acid amplification were performed. Demographic and
clinical characteristics at initiation of antiretroviral therapy
(ART) were compared between anti-HDV-negative and positive
patients. RESULTS: Among 222 HIV/HBV co-infected patients on
ART, 219 (98.6%) had a stored serum sample available and were
included in the study. Median age was 37 years, 55% were female,
46% had World Health Organization stage III/IV HIV disease, and
the median CD4 count was 179 cells/mul. The prevalence of
anti-HDV positivity was 5.0% (95% confidence interval 2.8-8.9%).
There was no significant predictor of anti-HDV positivity. HDV
could not be amplified in any of the anti-HDV-positive patients
and the second serological test was negative in all of them.
CONCLUSIONS: No confirmed case of HDV infection was found among
over 200 HIV/HBV co-infected patients in Tanzania. As
false-positive serology results are common, screening results
should be confirmed with a second test
Spectral Diversity and Regulation of Coral Fluorescence in a Mesophotic Reef Habitat in the Red Sea
The phenomenon of coral fluorescence in mesophotic reefs, although well described for shallow waters, remains largely unstudied. We found that representatives of many scleractinian species are brightly fluorescent at depths of 50â60 m at the Interuniversity Institute for Marine Sciences (IUI) reef in Eilat, Israel. Some of these fluorescent species have distribution maxima at mesophotic depths (40â100 m). Several individuals from these depths displayed yellow or orange-red fluorescence, the latter being essentially absent in corals from the shallowest parts of this reef. We demonstrate experimentally that in some cases the production of fluorescent pigments is independent of the exposure to light; while in others, the fluorescence signature is altered or lost when the animals are kept in darkness. Furthermore, we show that green-to-red photoconversion of fluorescent pigments mediated by short-wavelength light can occur also at depths where ultraviolet wavelengths are absent from the underwater light field. Intraspecific colour polymorphisms regarding the colour of the tissue fluorescence, common among shallow water corals, were also observed for mesophotic species. Our results suggest that fluorescent pigments in mesophotic reefs fulfil a distinct biological function and offer promising application potential for coral-reef monitoring and biomedical imaging
J/psi suppression at forward rapidity in Au+Au collisions at sqrt(s_NN)=39 and 62.4 GeV
We present measurements of the J/psi invariant yields in sqrt(s_NN)=39 and
62.4 GeV Au+Au collisions at forward rapidity (1.2<|y|<2.2). Invariant yields
are presented as a function of both collision centrality and transverse
momentum. Nuclear modifications are obtained for central relative to peripheral
Au+Au collisions (R_CP) and for various centrality selections in Au+Au relative
to scaled p+p cross sections obtained from other measurements (R_AA). The
observed suppression patterns at 39 and 62.4 GeV are quite similar to those
previously measured at 200 GeV. This similar suppression presents a challenge
to theoretical models that contain various competing mechanisms with different
energy dependencies, some of which cause suppression and others enhancement.Comment: 365 authors, 10 pages, 11 figures, 4 tables. Submitted to Phys. Rev.
C. Plain text data tables for the points plotted in figures for this and
previous PHENIX publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
L\'evy-stable two-pion Bose-Einstein correlations in GeV AuAu collisions
We present a detailed measurement of charged two-pion correlation functions
in 0%-30% centrality GeV AuAu collisions by the
PHENIX experiment at the Relativistic Heavy Ion Collider. The data are well
described by Bose-Einstein correlation functions stemming from L\'evy-stable
source distributions. Using a fine transverse momentum binning, we extract the
correlation strength parameter , the L\'evy index of stability
and the L\'evy length scale parameter as a function of average
transverse mass of the pair . We find that the positively and the
negatively charged pion pairs yield consistent results, and their correlation
functions are represented, within uncertainties, by the same L\'evy-stable
source functions. The measurements indicate a decrease of the
strength of the correlations at low . The L\'evy length scale parameter
decreases with increasing , following a hydrodynamically
predicted type of scaling behavior. The values of the L\'evy index of stability
are found to be significantly lower than the Gaussian case of
, but also significantly larger than the conjectured value that may
characterize the critical point of a second-order quark-hadron phase
transition.Comment: 448 authors, 25 pages, 11 figures, 4 tables, 2010 data. v2 is version
accepted for publication in Phys. Rev. C. Plain text data tables for the
points plotted in figures for this and previous PHENIX publications are (or
will be) publicly available at http://www.phenix.bnl.gov/papers.htm
meson production in Au collisions at GeV
The PHENIX experiment has measured meson production in Au
collisions at GeV using the dimuon and dielectron decay
channels. The meson is measured in the forward (backward) -going
(Au-going) direction, () in the transverse-momentum
() range from 1--7 GeV/, and at midrapidity in the
range below 7 GeV/. The meson invariant yields and
nuclear-modification factors as a function of , rapidity, and centrality
are reported. An enhancement of meson production is observed in the
Au-going direction, while suppression is seen in the -going direction, and
no modification is observed at midrapidity relative to the yield in
collisions scaled by the number of binary collisions. Similar behavior was
previously observed for inclusive charged hadrons and open heavy flavor
indicating similar cold-nuclear-matter effects.Comment: 484 authors, 16 pages, 12 figures, 6 tables. v1 is the version
accepted for publication in Phys. Rev. C. Data tables for the points plotted
in the figures are given in the paper itsel
Single electron yields from semileptonic charm and bottom hadron decays in AuAu collisions at GeV
The PHENIX Collaboration at the Relativistic Heavy Ion Collider has measured
open heavy-flavor production in minimum bias AuAu collisions at
GeV via the yields of electrons from semileptonic decays
of charm and bottom hadrons. Previous heavy-flavor electron measurements
indicated substantial modification in the momentum distribution of the parent
heavy quarks due to the quark-gluon plasma created in these collisions. For the
first time, using the PHENIX silicon vertex detector to measure precision
displaced tracking, the relative contributions from charm and bottom hadrons to
these electrons as a function of transverse momentum are measured in AuAu
collisions. We compare the fraction of electrons from bottom hadrons to
previously published results extracted from electron-hadron correlations in
collisions at GeV and find the fractions to be
similar within the large uncertainties on both measurements for
GeV/. We use the bottom electron fractions in AuAu and along
with the previously measured heavy flavor electron to calculate the
for electrons from charm and bottom hadron decays separately. We find
that electrons from bottom hadron decays are less suppressed than those from
charm for the region GeV/.Comment: 432 authors, 33 pages, 23 figures, 2 tables, 2011 data. v2 is version
accepted for publication by Phys. Rev. C. Plain text data tables for the
points plotted in figures for this and previous PHENIX publications are (or
will be) publicly available at http://www.phenix.bnl.gov/papers.htm
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