1,270 research outputs found
Hot Electron Capture Dissociation Distinguishes Leucine from Isoleucine in a Novel Hemoglobin Variant, Hb Askew, β54(D5)Val→Ile
Population migration has led to the global dispersion of human hemoglobinopathies and has precipitated a need for their identification. An effective mass spectrometry-based procedure involves analysis of the intact α- and β-globin chains to determine their mass, followed by location of the variant amino acid residue by direct analysis of the enzymatically digested chains and low-energy collision induced dissociation of the variant peptide. Using this procedure, a variant was identified as either β54Val→Leu or β54Val→Ile, since the amino acids leucine and isoleucine cannot be distinguished using low-energy collisions. Here, we describe how hot electron capture dissociation on a Fourier transform-ion cyclotron resonance mass spectrometer was used to distinguish isoleucine from leucine and identify the mutation as β54(D5)Val→Ile. This is a novel variant, and we have named it Hb Askew
Complete genome sequence of Desulfocapsa sulfexigens, a marine deltaproteobacterium specialized in disproportionating inorganic sulfur compounds
Desulfocapsa sulfexigens SB164P1 (DSM 10523) belongs to the deltaproteobacterial family Desulfobulbaceae and is one of two validly described members of its genus. This strain was selected for genome sequencing, because it is the first marine bacterium reported to thrive on the disproportionation of elemental sulfur, a process with a unresolved enzymatic pathway in which elemental sulfur serves both as electron donor and electron acceptor. Furthermore, in contrast to its phylogenetically closest relatives, which are dissimilatory sulfate-reducers, D. sulfexigens is unable to grow by sulfate reduction and appears metabolically specialized in growing by disproportionating elemental sulfur, sulfite or thiosulfate with CO2 as the sole carbon source. The genome of D. sulfexigens contains the set of genes that is required for nitrogen fixation. In an acetylene assay it could be shown that the strain reduces acetylene to ethylene, which is indicative for N-fixation. The circular chromosome of D. sulfexigens SB164P1 comprises 3,986,761 bp and harbors 3,551 protein-coding genes of which 78% have a predicted function based on auto-annotation. The chromosome furthermore encodes 46 tRNA genes and 3 rRNA operons
Masked hypertension in type 2 diabetes: never take normotension for granted and always assess out-of-office blood pressure.
Spectroscopy of the roAp star Alpha-Cir -- II. The bisector and equivalent-width of the H-alpha line
We present bisector measurements of the H-alpha line of the rapidly
oscillating Ap (roAp) star, Alpha-Cir, obtained from dual-site observations
with medium-dispersion spectrographs. The velocity amplitude and phase of the
principal pulsation mode vary significantly, depending on the height in the
H-alpha line, including a phase reversal between the core and the wings of the
line. This supports the theory, suggested in Paper I, of a radial pulsational
node in the atmosphere of the star. Blending with metal lines partially affects
the H-alpha bisector results but probably not enough to explain the phase
reversal.
We have also detected changes in the equivalent-width of the line during the
pulsation, and measured the oscillatory signal as a function of wavelength
across the H-alpha region.Comment: 13 pages, 14 figures, accepted by MNRA
Highlights of the 2023 European Society of Hypertension Guidelines: what has changed in the management of hypertension in patients with cardiac diseases?
Modeling Kepler Observations of Solar-like Oscillations in the Red-giant Star HD 186355
We have analysed oscillations of the red giant star HD 186355 observed by the
NASA Kepler satellite. The data consist of the first five quarters of science
operations of Kepler, which cover about 13 months. The high-precision
time-series data allow us to accurately extract the oscillation frequencies
from the power spectrum. We find the frequency of the maximum oscillation
power, {\nu}_max, and the mean large frequency separation, {\Delta}{\nu}, are
around 106 and 9.4 {\mu}Hz respectively. A regular pattern of radial and
non-radial oscillation modes is identified by stacking the power spectra in an
echelle diagram. We use the scaling relations of {\Delta}{\nu} and {\nu}_max to
estimate the preliminary asteroseismic mass, which is confirmed with the
modelling result (M = 1.45 \pm 0.05 M_sun) using the Yale Rotating stellar
Evolution Code (YREC7). In addition, we constrain the effective temperature,
luminosity and radius from comparisons between observational constraints and
models. A number of mixed l = 1 modes are also detected and taken into account
in our model comparisons. We find a mean observational period spacing for these
mixed modes of about 58 s, suggesting that this red giant branch star is in the
shell hydrogen-burning phase.Comment: 26 pages, 5 figures and 2 table
Oscillation frequencies and mode lifetimes in alpha Centauri A
We analyse our recently-published velocity measurements of alpha Cen A
(Butler et al. 2004). After adjusting the weights on a night-by-night basis in
order to optimize the window function to minimize sidelobes, we extract 42
oscillation frequencies with l=0 to 3 and measure the large and small frequency
separations. We give fitted relations to these frequencies that can be compared
with theoretical models and conclude that the observed scatter about these fits
is due to the finite lifetimes of the oscillation modes. We estimate the mode
lifetimes to be 1-2 d, substantially shorter than in the Sun.Comment: Accepted by Ap
Oscillations in the Sun with SONG: Setting the scale for asteroseismic investigations
Context. We present the first high-cadence multi-wavelength radial-velocity
observations of the Sun-as-a-star, carried out during 57 consecutive days using
the stellar \'echelle spectrograph at the Hertzsprung SONG Telescope operating
at the Teide Observatory. Aims. The aim was to produce a high-quality data set
and reference values for the global helioseismic parameters {\nu_{max}}, and
{\Delta \nu} of the solar p-modes using the SONG instrument. The obtained data
set or the inferred values should then be used when the scaling relations are
applied to other stars showing solar-like oscillations which are observed with
SONG or similar instruments. Methods. We used different approaches to analyse
the power spectrum of the time series to determine {\nu_{max}}; simple Gaussian
fitting and heavy smoothing of the power spectrum. {\Delta\nu} was determined
using the method of autocorrelation of the power spectrum. The amplitude per
radial mode was determined using the method described in Kjeldsen et al.
(2008). Results. We found the following values for the solar oscillations using
the SONG spectrograph: {\nu_{max}} = 3141 {\pm} 12 {\mu}Hz, {\Delta\nu} =
134.98 {\pm} 0.04 {\mu}Hz and an average amplitude of the strongest radial
modes of 16.6 {\pm} 0.4 cm/s. These values are consistent with previous
measurements with other techniques.Comment: 5 pages, 5 figures, letter accepted for A&
Stochastic excitation of acoustic modes in stars
For more than ten years, solar-like oscillations have been detected and
frequencies measured for a growing number of stars with various characteristics
(e.g. different evolutionary stages, effective temperatures, gravities, metal
abundances ...).
Excitation of such oscillations is attributed to turbulent convection and
takes place in the uppermost part of the convective envelope. Since the
pioneering work of Goldreich & Keely (1977), more sophisticated theoretical
models of stochastic excitation were developed, which differ from each other
both by the way turbulent convection is modeled and by the assumed sources of
excitation. We review here these different models and their underlying
approximations and assumptions.
We emphasize how the computed mode excitation rates crucially depend on the
way turbulent convection is described but also on the stratification and the
metal abundance of the upper layers of the star. In turn we will show how the
seismic measurements collected so far allow us to infer properties of turbulent
convection in stars.Comment: Notes associated with a lecture given during the fall school
organized by the CNRS and held in St-Flour (France) 20-24 October 2008 ; 39
pages ; 11 figure
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