230 research outputs found
Static quarks with improved statistical precision
We present a numerical study for different discretisations of the static
action, concerning cut-off effects and the growth of statistical errors with
Euclidean time. An error reduction by an order of magnitude can be obtained
with respect to the Eichten-Hill action, for time separations beyond 1.3 fm,
keeping discretization errors small. The best actions lead to a big improvement
on the precision of the quark mass Mb and F_Bs in the static approximation.Comment: 3 pages, 4 figures, Lattice2003(heavy
Towards a precision computation of f_Bs in quenched QCD
We present a computation of the decay constant f_Bs in quenched QCD. Our
strategy is to combine new precise data from the static approximation with an
interpolation of the decay constant around the charm quark mass region. This
computation is the first step in demonstrating the feasability of a strategy
for f_B in full QCD. The continuum limits in the static theory and at finite
mass are taken separately and will be further improved.Comment: Lattice2003(heavy), 3 pages, 2 figure
Can electron distribution functions be derived through the Sunyaev-Zel'dovich effect?
Measurements of the Sunyaev-Zel'dovich (hereafter SZ) effect distortion of
the cosmic microwave background provide methods to derive the gas pressure and
temperature of galaxy clusters. Here we study the ability of SZ effect
observations to derive the electron distribution function (DF) in massive
galaxy clusters.
Our calculations of the SZ effect include relativistic corrections considered
within the framework of the Wright formalism and use a decomposition technique
of electron DFs into Fourier series. Using multi-frequency measurements of the
SZ effect, we find the solution of a linear system of equations that is used to
derive the Fourier coefficients; we further analyze different frequency samples
to decrease uncertainties in Fourier coefficient estimations.
We propose a method to derive DFs of electrons using SZ multi-frequency
observations of massive galaxy clusters. We found that the best frequency
sample to derive an electron DF includes high frequencies =375, 600, 700,
857 GHz. We show that it is possible to distinguish a Juttner DF from a
Maxwell-Bolzman DF as well as from a Juttner DF with the second electron
population by means of SZ observations for the best frequency sample if the
precision of SZ intensity measurements is less than 0.1%. We demonstrate by
means of 3D hydrodynamic numerical simulations of a hot merging galaxy cluster
that the morphologies of SZ intensity maps are different for frequencies
=375, 600, 700, 857 GHz. We stress that measurements of SZ intensities at
these frequencies are a promising tool for studying electron distribution
functions in galaxy clusters.Comment: 11 pages, 12 figures, published in Astronomy and Astrophysic
Stringing Spins and Spinning Strings
We apply recently developed integrable spin chain and dilatation operator
techniques in order to compute the planar one-loop anomalous dimensions for
certain operators containing a large number of scalar fields in N =4 Super
Yang-Mills. The first set of operators, belonging to the SO(6) representations
[J,L-2J,J], interpolate smoothly between the BMN case of two impurities (J=2)
and the extreme case where the number of impurities equals half the total
number of fields (J=L/2). The result for this particular [J,0,J] operator is
smaller than the anomalous dimension derived by Frolov and Tseytlin
[hep-th/0304255] for a semiclassical string configuration which is the dual of
a gauge invariant operator in the same representation. We then identify a
second set of operators which also belong to [J,L-2J,J] representations, but
which do not have a BMN limit. In this case the anomalous dimension of the
[J,0,J] operator does match the Frolov-Tseytlin prediction. We also show that
the fluctuation spectra for this [J,0,J] operator is consistent with the string
prediction.Comment: 27 pages, 4 figures, LaTex; v2 reference added, typos fixe
Efficient transduction and optogenetic stimulation of retinal bipolar cells by a synthetic adeno-associated virus capsid and promoter
In this report, we describe the development of a modified adeno-associated virus (AAV) capsid and promoter for transduction of retinal ON-bipolar cells. The bipolar cells, which are post-synaptic to the photoreceptors, are important retinal targets for both basic and preclinical research. In particular, a therapeutic strategy under investigation for advanced forms of blindness involves using optogenetic molecules to render ON-bipolar cells light-sensitive. Currently, delivery of adequate levels of gene expression is a limiting step for this approach. The synthetic AAV capsid and promoter described here achieves high level of optogenetic transgene expression in ON-bipolar cells. This evokes high-frequency (âź100 Hz) spiking responses in ganglion cells of previously blind, rd1, mice. Our vector is a promising vehicle for further development toward potential clinical use
Mol Vis
PURPOSE: To analyze in vivo the function of chicken acidic leucine-rich epidermal growth factor-like domain containing brain protein/Neuroglycan C (gene symbol: Cspg5) during retinal degeneration in the Rpe65(-)/(-) mouse model of Leber congenital amaurosis. METHODS: We resorted to mice with targeted deletions in the Cspg5 and retinal pigment epithelium protein of 65 kDa (Rpe65) genes (Cspg5(-)/(-)/Rpe65(-)/(-)). Cone degeneration was assessed with cone-specific peanut agglutinin staining. Transcriptional expression of rhodopsin (Rho), S-opsin (Opn1sw), M-opsin (Opn1mw), rod transducin alpha subunit (Gnat1), and cone transducin alpha subunit (Gnat2) genes was assessed with quantitative PCR from 2 weeks to 12 months. The retinal pigment epithelium (RPE) was analyzed at P14 with immunodetection of the retinol-binding protein membrane receptor Stra6. RESULTS: No differences in the progression of retinal degeneration were observed between the Rpe65(-)/(-) and Cspg5(-)/(-)/Rpe65(-)/(-) mice. No retinal phenotype was detected in the late postnatal and adult Cspg5(-)/(-) mice, when compared to the wild-type mice. CONCLUSIONS: Despite the previously reported upregulation of Cspg5 during retinal degeneration in Rpe65(-)/(-) mice, no protective effect or any involvement of Cspg5 in disease progression was identified
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A pilot randomised controlled trial using prophylactic dressings to minimise sacral pressure injuries in high risk hospitalised patients
This pilot randomised controlled trial examined the effect of prophylactic dressings to minimise sacral pressure injuries in high-risk hospitalised patients and assessed feasibility criteria to inform a larger study. Eighty patients were recruited at admission points (the Emergency Department and Surgical Care Unit) or directly from participating wards in the general medical surgical setting following assessment of high risk for sacral pressure injury. Participants were randomised into either the routine care or routine care and silicone foam border dressing group. Outcome assessment comprised digital photographs of each participantâs sacrum every 72 hours for evaluation by a blind-to-intervention assessor. Sixty-seven participants had at least one sacral photograph taken and assessed by a blind-to-intervention assessor. Three participants were assessed as having a Stage I pressure injury. While the use of photography was effective, feasibility criteria identified challenges related to bias, blinding, weight assessment, preparation of nursing staff and sample size estimation
The Cyanobacterial Hepatotoxin Microcystin Binds to Proteins and Increases the Fitness of Microcystis under Oxidative Stress Conditions
Microcystins are cyanobacterial toxins that represent a serious threat to drinking water and recreational lakes worldwide. Here, we show that microcystin fulfils an important function within cells of its natural producer Microcystis. The microcystin deficient mutant ÎmcyB showed significant changes in the accumulation of proteins, including several enzymes of the Calvin cycle, phycobiliproteins and two NADPH-dependent reductases. We have discovered that microcystin binds to a number of these proteins in vivo and that the binding is strongly enhanced under high light and oxidative stress conditions. The nature of this binding was studied using extracts of a microcystin-deficient mutant in vitro. The data obtained provided clear evidence for a covalent interaction of the toxin with cysteine residues of proteins. A detailed investigation of one of the binding partners, the large subunit of RubisCO showed a lower susceptibility to proteases in the presence of microcystin in the wild type. Finally, the mutant defective in microcystin production exhibited a clearly increased sensitivity under high light conditions and after hydrogen peroxide treatment. Taken together, our data suggest a protein-modulating role for microcystin within the producing cell, which represents a new addition to the catalogue of functions that have been discussed for microbial secondary metabolites
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