528 research outputs found
Photoemission "experiments" on holographic superconductors
We study the effects of a superconducting condensate on holographic Fermi
surfaces. With a suitable coupling between the fermion and the condensate,
there are stable quasiparticles with a gap. We find some similarities with the
phenomenology of the cuprates: in systems whose normal state is a non-Fermi
liquid with no stable quasiparticles, a stable quasiparticle peak appears in
the condensed phase.Comment: 14 pages, 13 figures; v2: typos corrected and some clarification
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An optically stimulated superconducting-like phase in K3C60 far above equilibrium Tc
The control of non-equilibrium phenomena in complex solids is an important
research frontier, encompassing new effects like light induced
superconductivity. Here, we show that coherent optical excitation of molecular
vibrations in the organic conductor K3C60 can induce a non-equilibrium state
with the optical properties of a superconductor. A transient gap in the real
part of the optical conductivity and a low-frequency divergence of the
imaginary part are measured for base temperatures far above equilibrium Tc=20
K. These findings underscore the role of coherent light fields in inducing
emergent order.Comment: 40 pages, 23 figure
Proximity of Iron Pnictide Superconductors to a Quantum Tricritical Point
We determine the nature of the magnetic quantum critical point in the doped
LaFeAsO using a set of constrained density functional calculations that provide
ab initio coefficients for a Landau order parameter analysis. The system turns
out to be remarkably close to a quantum tricritical point, where the nature of
the phase transition changes from first to second order. We compare with the
effective field theory and discuss the experimental consequences.Comment: 4 pages, 4 figure
Analysis of optimal phenotypic space using elementary modes as applied to Corynebacterium glutamicum
BACKGROUND: Quantification of the metabolic network of an organism offers insights into possible ways of developing mutant strain for better productivity of an extracellular metabolite. The first step in this quantification is the enumeration of stoichiometries of all reactions occurring in a metabolic network. The structural details of the network in combination with experimentally observed accumulation rates of external metabolites can yield flux distribution at steady state. One such methodology for quantification is the use of elementary modes, which are minimal set of enzymes connecting external metabolites. Here, we have used a linear objective function subject to elementary modes as constraint to determine the fluxes in the metabolic network of Corynebacterium glutamicum. The feasible phenotypic space was evaluated at various combinations of oxygen and ammonia uptake rates. RESULTS: Quantification of the fluxes of the elementary modes in the metabolism of C. glutamicum was formulated as linear programming. The analysis demonstrated that the solution was dependent on the criteria of objective function when less than four accumulation rates of the external metabolites were considered. The analysis yielded feasible ranges of fluxes of elementary modes that satisfy the experimental accumulation rates. In C. glutamicum, the elementary modes relating to biomass synthesis through glycolysis and TCA cycle were predominantly operational in the initial growth phase. At a later time, the elementary modes contributing to lysine synthesis became active. The oxygen and ammonia uptake rates were shown to be bounded in the phenotypic space due to the stoichiometric constraint of the elementary modes. CONCLUSION: We have demonstrated the use of elementary modes and the linear programming to quantify a metabolic network. We have used the methodology to quantify the network of C. glutamicum, which evaluates the set of operational elementary modes at different phases of fermentation. The methodology was also used to determine the feasible solution space for a given set of substrate uptake rates under specific optimization criteria. Such an approach can be used to determine the optimality of the accumulation rates of any metabolite in a given network
Comparison of long-term mortality risk following normal exercise vs adenosine myocardial perfusion SPECT
A higher frequency of clinical events has been observed in patients undergoing pharmacological vs exercise myocardial perfusion single-photon emission computed tomography (SPECT). While this difference is attributed to greater age and co-morbidities, it is not known whether these tests also differ in prognostic ability among patients with similar clinical profiles.
We assessed all-cause mortality rates in 6,069 patients, followed for 10.2 ± 1.7 years after undergoing exercise or adenosine SPECT. We employed propensity analysis to match exercise and adenosine subgroups by age, gender, symptoms, and coronary risk factors. Within our propensity-matched cohorts, adenosine patients had an annualized mortality rate event rates that was more than twice that of exercise patients (3.9% vs 1.6%, P < .0001). Differences in mortality persisted among age groups, including those <55 years old. In the exercise cohort, mortality was inversely related to exercise duration, with comparable mortality noted for patients exercising <3 min and those undergoing adenosine testing.
Among patients with normal stress SPECT tests, those undergoing adenosine testing manifest a mortality rate that is substantially higher than that observed among adequately exercising patients, but comparable to that observed among very poorly exercising patients. This elevated risk underscores an important challenge for managing patients undergoing pharmacological stress testing
Azimuthal anisotropy and correlations at large transverse momenta in and Au+Au collisions at = 200 GeV
Results on high transverse momentum charged particle emission with respect to
the reaction plane are presented for Au+Au collisions at =
200 GeV. Two- and four-particle correlations results are presented as well as a
comparison of azimuthal correlations in Au+Au collisions to those in at
the same energy. Elliptic anisotropy, , is found to reach its maximum at
GeV/c, then decrease slowly and remain significant up to
-- 10 GeV/c. Stronger suppression is found in the back-to-back
high- particle correlations for particles emitted out-of-plane compared to
those emitted in-plane. The centrality dependence of at intermediate
is compared to simple models based on jet quenching.Comment: 4 figures. Published version as PRL 93, 252301 (2004
Azimuthal anisotropy in Au+Au collisions at sqrtsNN = 200 GeV
The results from the STAR Collaboration on directed flow (v_1), elliptic flow
(v_2), and the fourth harmonic (v_4) in the anisotropic azimuthal distribution
of particles from Au+Au collisions at sqrtsNN = 200 GeV are summarized and
compared with results from other experiments and theoretical models. Results
for identified particles are presented and fit with a Blast Wave model.
Different anisotropic flow analysis methods are compared and nonflow effects
are extracted from the data. For v_2, scaling with the number of constituent
quarks and parton coalescence is discussed. For v_4, scaling with v_2^2 and
quark coalescence is discussed.Comment: 26 pages. As accepted by Phys. Rev. C. Text rearranged, figures
modified, but data the same. However, in Fig. 35 the hydro calculations are
corrected in this version. The data tables are available at
http://www.star.bnl.gov/central/publications/ by searching for "flow" and
then this pape
Isolation and analysis of high quality nuclear DNA with reduced organellar DNA for plant genome sequencing and resequencing
<p>Abstract</p> <p>Background</p> <p>High throughput sequencing (HTS) technologies have revolutionized the field of genomics by drastically reducing the cost of sequencing, making it feasible for individual labs to sequence or resequence plant genomes. Obtaining high quality, high molecular weight DNA from plants poses significant challenges due to the high copy number of chloroplast and mitochondrial DNA, as well as high levels of phenolic compounds and polysaccharides. Multiple methods have been used to isolate DNA from plants; the CTAB method is commonly used to isolate total cellular DNA from plants that contain nuclear DNA, as well as chloroplast and mitochondrial DNA. Alternatively, DNA can be isolated from nuclei to minimize chloroplast and mitochondrial DNA contamination.</p> <p>Results</p> <p>We describe optimized protocols for isolation of nuclear DNA from eight different plant species encompassing both monocot and eudicot species. These protocols use nuclei isolation to minimize chloroplast and mitochondrial DNA contamination. We also developed a protocol to determine the number of chloroplast and mitochondrial DNA copies relative to the nuclear DNA using quantitative real time PCR (qPCR). We compared DNA isolated from nuclei to total cellular DNA isolated with the CTAB method. As expected, DNA isolated from nuclei consistently yielded nuclear DNA with fewer chloroplast and mitochondrial DNA copies, as compared to the total cellular DNA prepared with the CTAB method. This protocol will allow for analysis of the quality and quantity of nuclear DNA before starting a plant whole genome sequencing or resequencing experiment.</p> <p>Conclusions</p> <p>Extracting high quality, high molecular weight nuclear DNA in plants has the potential to be a bottleneck in the era of whole genome sequencing and resequencing. The methods that are described here provide a framework for researchers to extract and quantify nuclear DNA in multiple types of plants.</p
Effective Rheology of Bubbles Moving in a Capillary Tube
We calculate the average volumetric flux versus pressure drop of bubbles
moving in a single capillary tube with varying diameter, finding a square-root
relation from mapping the flow equations onto that of a driven overdamped
pendulum. The calculation is based on a derivation of the equation of motion of
a bubble train from considering the capillary forces and the entropy production
associated with the viscous flow. We also calculate the configurational
probability of the positions of the bubbles.Comment: 4 pages, 1 figur
Chronic kidney disease increases cardiovascular unfavourable outcomes in outpatients with heart failure
<p>Abstract</p> <p>Background</p> <p>Chronic heart failure (CHF) has a high morbidity and mortality. Chronic kidney disease (CKD) has consistently been found to be an independent risk factor for unfavorable cardiovascular (CV) outcomes. Early intervention on CKD reduces the progression of CHF, hospitalizations and mortality, yet there are very few studies about CKD as a risk factor in the early stages of CHF. The aims of our study were to assess the prevalence and the prognostic importance of CKD in patients with systolic CHF stages B and C.</p> <p>Methods</p> <p>This is a prospective cohort study, dealing with prognostic markers for CV endpoints in patients with systolic CHF (ejection fraction ≤ 45%).</p> <p>Results</p> <p>CKD was defined as estimated glomerular filtration rate <60 mL/min/1.73 m<sup>2 </sup>and CV endpoints as death or hospitalization due to CHF, in 12 months follow-up. Eighty three patients were studied, the mean age was 62.7 ± 12 years, and 56.6% were female. CKD was diagnosed in 49.4% of the patients, 33% of patients with CHF stage B and 67% in the stage C. Cardiovascular endpoints were observed in 26.5% of the patients. When the sample was stratified into stages B and C of CHF, the occurrence of CKD was associated with 100% and 64.7%, respectively, of unfavorable CV outcomes. After adjustments for all other prognostic factors at baseline, it was observed that the diagnosis of CKD increased in 3.6 times the possibility of CV outcomes (CI 95% 1.04-12.67, p = 0.04), whereas higher ejection fraction (R = 0.925, IC 95% 0.862-0.942, p = 0.03) and serum sodium (R = 0.807, IC 95% 0.862-0.992, p = 0.03) were protective.</p> <p>Conclusion</p> <p>In this cohort of patients with CHF stages B and C, CKD was prevalent and independently associated with increased risk of hospitalization and death secondary to cardiac decompensation, especially in asymptomatic patients.</p
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