1,213 research outputs found
Nonlinear Volatility of River Flux Fluctuations
We study the spectral properties of the magnitudes of river flux increments,
the volatility. The volatility series exhibits (i) strong seasonal periodicity
and (ii) strongly power-law correlations for time scales less than one year. We
test the nonlinear properties of the river flux increment series by randomizing
its Fourier phases and find that the surrogate volatility series (i) has almost
no seasonal periodicity and (ii) is weakly correlated for time scales less than
one year. We quantify the degree of nonlinearity by measuring (i) the amplitude
of the power spectrum at the seasonal peak and (ii) the correlation power-law
exponent of the volatility series.Comment: 5 revtex pages, 6 page
Mechanism of Fluoride Uptake by Hydroxyapatite from Acidic Fluoride Solutions: I. Theoretical Considerations
A mathematical model for the mechanism of calcium fluoride formation on hydroxyapatite in buffered fluoride solutions is proposed. It takes into account the physical and chemical processes that occur during the reaction. With the model it is possible to evaluate a priori the fluoride uptake potential of fluoride solutions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67263/2/10.1177_00220345700490066601.pd
Oxygen Moment Formation and Canting in Li2CuO2
The possibilities of oxygen moment formation and canting in the quasi-1D
cuprate Li2CuO2 are investigated using single crystal neutron diffraction at 2
K. The observed magnetic intensities could not be explained without the
inclusion of a large ordered oxygen moment of 0.11(1) Bohr magnetons.
Least-squares refinement of the magnetic structure of Li2CuO2 in combination
with a spin-density Patterson analysis shows that the magnetization densities
of the Cu and O atoms are highly aspherical, forming quasi-1D ribbons of
localised Cu and O moments. Magnetic structure refinements and low-field
magnetization measurements both suggest that the magnetic structure of Li2CuO2
at 2 K may be canted. A possible model for the canted configuration is
proposed.Comment: 10 pages, 8 figures (screen resolution
Catalytically inactive carbonic anhydrase-related proteins enhance transport of lactate by MCT1
Carbonic anhydrases (CA) catalyze the reversible hydration of CO2 to protons and bicarbonate and thereby play a fundamental role in the epithelial acid/base transport mechanisms serving fluid secretion and absorption for whole-body acid/base regulation. The three carbonic anhydrase-related proteins (CARPs) VIII, X, and XI, however, are catalytically inactive. Previous work has shown that some CA isoforms noncatalytically enhance lactate transport through various monocarboxylate transporters (MCT). Therefore, we examined whether the catalytically inactive CARPs play a role in lactate transport. Here, we report that CARP VIII, X, and XI enhance transport activity of the MCT MCT1 when coexpressed in Xenopus oocytes, as evidenced by the rate of rise in intracellular H+ concentration detected using ion-sensitive microelectrodes. Based on previous studies, we suggest that CARPs may function as a 'proton antenna' for MCT1, to drive proton-coupled lactate transport across the cell membrane
Neutron charge form factor at large
The neutron charge form factor is determined from an analysis of
the deuteron quadrupole form factor data. Recent calculations, based
on a variety of different model interactions and currents, indicate that the
contributions associated with the uncertain two-body operators of shorter range
are relatively small for , even at large momentum transfer . Hence,
can be extracted from at large without undue
systematic uncertainties from theory.Comment: 8 pages, 3 figure
Evidence of Final-State Suppression of High-p_T Hadrons in Au + Au Collisions Using d + Au Measurements at RHIC
Transverse momentum spectra of charged hadrons with 6 GeV/c have
been measured near mid-rapidity (0.2 1.4) by the PHOBOS experiment
at RHIC in Au + Au and d + Au collisions at . The spectra for different collision centralities are compared to collisions at the same energy. The resulting nuclear modification
factor for central Au + Au collisions shows evidence of strong suppression of
charged hadrons in the high- region ( GeV/c). In contrast, the d +
Au nuclear modification factor exhibits no suppression of the high-
yields. These measurements suggest a large energy loss of the high-
particles in the highly interacting medium created in the central Au + Au
collisions. The lack of suppression in d + Au collisions suggests that it is
unlikely that initial state effects can explain the suppression in the central
Au + Au collisions.Comment: 3 pages, 4 figures, International Europhysics Conference on High
Energy Physics EPS (July 17th-23rd 2003) in Aachen, German
Learedius learedi Price 1934 (Digenea, Spirorchiidae) in Chelonia mydas Linnaeus 1758 (Testudines, Chelonidae) in Brazil: case report
Oscillation enhanced search for new interaction with neutrinos
We discuss the measurement of new physics in long baseline neutrino
oscillation experiments. Through the neutrino oscillation, the probability to
detect the new physics effects such as flavor violation is enhanced by the
interference with the weak interaction. We carefully explain the situations
that the interference can take place. Assuming a neutrino factory and an
upgraded conventional beam, we estimate the feasibility to observe new physics
numerically and point out that we can search new interactions using some
channels, for example , in these experiments. We also
discuss several models which induce the effective interactions interfering with
the weak interaction, and show that some new physics effects are large enough
to be observed in the oscillation enhanced way.Comment: 25 pages, 20 figure
Monte Carlo Methods for Estimating Interfacial Free Energies and Line Tensions
Excess contributions to the free energy due to interfaces occur for many
problems encountered in the statistical physics of condensed matter when
coexistence between different phases is possible (e.g. wetting phenomena,
nucleation, crystal growth, etc.). This article reviews two methods to estimate
both interfacial free energies and line tensions by Monte Carlo simulations of
simple models, (e.g. the Ising model, a symmetrical binary Lennard-Jones fluid
exhibiting a miscibility gap, and a simple Lennard-Jones fluid). One method is
based on thermodynamic integration. This method is useful to study flat and
inclined interfaces for Ising lattices, allowing also the estimation of line
tensions of three-phase contact lines, when the interfaces meet walls (where
"surface fields" may act). A generalization to off-lattice systems is described
as well.
The second method is based on the sampling of the order parameter
distribution of the system throughout the two-phase coexistence region of the
model. Both the interface free energies of flat interfaces and of (spherical or
cylindrical) droplets (or bubbles) can be estimated, including also systems
with walls, where sphere-cap shaped wall-attached droplets occur. The
curvature-dependence of the interfacial free energy is discussed, and estimates
for the line tensions are compared to results from the thermodynamic
integration method. Basic limitations of all these methods are critically
discussed, and an outlook on other approaches is given
Risk factors for fluoroquinolone-resistant Escherichia coli in adults with community-onset febrile urinary tract infection
Objectives To assess risk factors for fluoroquinolone resistance in community-onset febrile Escherichia coli urinary tract infection (UTI). Methods A nested case-control study within a cohort of consecutive adults with febrile UTI presenting at primary healthcare centres or emergency departments during January 2004 through December 2009. Resistance was defined using EUCAST criteria (ciprofloxacin MIC >1.0 mg/L). Cases were subjects with fluoroquinolone-resistant E. coli, and controls those with fluoroquinolone-susceptible isolates. Multivariable logistic regression analysis was used to identify potential risk factors for fluoroquinolone resistance. Results Of 787 consecutive patients, 420 had E. coli-positive urine cultures. Of these, 51 (12%) were fluoroquinolone resistant. Independent risk factors for fluoroquinolone resistance were urinary catheter [odds ratio (OR) 3.1; 95% confidence interval (CI) 0.9-11.6], recent hospitalization (OR 2.0; 95% CI 1.0-4.3) and fluoroquinolone use in the past 6 months (OR 17.5; 95% CI 6.0-50.7). Environmental factors (e.g. contact with animals or hospitalized household members) were not associated with fluoroquinolone resistance. Of fluoroquinolone-resistant strains, 33% were resistant to amoxicillin/clavulanate and 65% to trimethoprim/sulfamethoxazole; 14% were extended-spectrum β-lactamase (ESBL) positive compared with <1% of fluoroquinolone-susceptible isolates. Conclusions Recent hospitalization, urinary catheter and fluoroquinolone use in the past 6 months were independent risk factors for fluoroquinolone resistance in community-onset febrile E. coli UTI. Contact with animals or hospitalized household members was not associated with fluoroquinolone resistance. Fluoroquinolone resistance may be a marker of broader resistance, including ESBL positivity.Immunogenetics and cellular immunology of bacterial infectious disease
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