1,366 research outputs found
Hydration of Heavy Alkaline-Earth Cations Studied by Molecular Dynamics Simulations and X-ray Absorption Spectroscopy
The physicochemical properties of the three heaviest alkaline-earth cations, Sr2+, Ba2+, and Ra2+ in water have been studied by means of classical molecular dynamics (MD) simulations. A specific set of cation-water intermolecular potentials based on ab initio potential energy surfaces has been built on the basis of the hydrated ion concept. The polarizable and flexible model of water MCDHO2 was adopted. The theoretical-experimental comparison of structural, dynamical, energetic, and spectroscopical properties of Sr2+ and Ba2+ aqueous solutions is satisfactory, which supports the methodology developed. This good behavior allows a reasonable reliability for the predicted Ra2+ physicochemical data not experimentally determined yet. Simulated extended X-ray absorption fine-structure (EXAFS) and X-ray absorption near-edge spectroscopy spectra have been computed from the snapshots of the MD simulations and compared with the experimental information available for Sr2+ and Ba2+. For the Ra2+ case, the Ra L3-edge EXAFS spectrum is proposed. Structural and dynamical properties of the aqua ions for the three cations have been obtained and analyzed. Along the [M(H2O)n]m+ series, the M-O distance for the first-hydration shell is 2.57, 2.81, and 2.93 Å for Sr2+, Ba2+, and Ra2+, respectively. The hydration number also increases when one is going down along the group: 8.1, 9.4, and 9.8 for Sr2+, Ba2+, and Ra2+, respectively. Whereas [Sr(H2O)8]2+ is a typical aqua ion with a well-defined structure, the Ba2+ and Ra2+ hydration provides a picture exhibiting an average between the ennea- and the deca-hydration. These results show a similar chemical behavior of Ba2+ and Ra2+ aqueous solutions and support experimental studies on the removal of Ra-226 of aquifers by different techniques, where Ra2+ is replaced by Ba2+. A comparison of the heavy alkaline ions, Rb+ and Cs+, with the heavy alkaline-earth ions is made.Universidad de Sevilla US-126447
Revisiting the cobalt(II) hydration from molecular dynamics and X-ray absorption spectroscopy
Solution chemistry of Co(II) is receiving a renewal attention due to the high interest for knowing the speciation in seawater of its (Formula presented.) Co radioactive isotope which appeared in the Japan sea as a consequence of the Fukushima-Daichii nuclear power plant accident. Experimental EXAFS and XANES spectra of a dilute Co(II) aqueous solution have been recorded and structural data derived from their analysis. Based on QM calculations, an ab-initio intermolecular potential has been generated for the Co(II)–H (Formula presented.) O interaction using the hydrated ion model that uses a polarisable and flexible solvent description through the MCDHO2 model. Classical molecular dynamics simulations of Co(II) in water have been performed and X-ray Absorption spectra have been simulated and compared with the experimental ones. Energetic, structural, dynamical and spectroscopical properties of the cobalt cation in solution have been computed and compared with previous experimental and theoretical data. These comparisons have assessed the good performance of the developed intermolecular potential.Ministerio de Ciencia, Innovación y Universidades PGC2018-099366-B-I0
Retrieval validation during the European Aqua Thermodynamic Experiment
Atmospheric and surface thermodynamic parameters retrieved with advanced hyperspectral remote sensors
aboard Earth observing satellites are critical to weather prediction and scientific research. The retrieval algorithms and
retrieved parameters from satellite sounders must be validated to demonstrate the capability and accuracy of both observation
and data processing systems. The European Aqua Thermodynamic Experiment (EAQUATE) was conducted not only for
validation of the Atmospheric InfraRed Sounder on the Aqua satellite, but also for assessment of validation systems of both
ground-based and aircraft-based instruments that will be used for other satellite systems, such as the Infrared Atmospheric
Sounding Interferometer on the European MetOp satellite, the Cross-track Infrared Sounder from the National Polar-orbiting
Operational Environmental Satellite System (NPOESS) Preparatory Project and the continuing series of NPOESS satellites.
Detailed intercomparisons were conducted and presented using different retrieval methodologies: measurements from
airborne ultraspectral Fourier transform spectrometers, aircraft in situ instruments, dedicated dropsondes and radiosondes,
ground-based Raman lidar, as well as the European Centre for Medium-range Weather Forecasting modelled thermal
structures. The results of this study not only illustrate the quality of the measurements and retrieval products, but also
demonstrate the capability of the validation systems put in place to validate current and future hyperspectral sounding
instruments and their scientific products
Left ventricular assist device implants in patients on extracorporeal membrane oxygenation:Do we need cardiopulmonary bypass?
Impact of a surgical approach for implantation of durable left ventricular assist devices in patients on extracorporeal life support
Background The aim of this study was to evaluate the impact of the surgical approach on the postoperative outcome in patients who underwent left ventricular assist device (LVAD) implantation after having received veno-arterial extracorporeal life support (va-ECLS) using data from a European registry (ECLS-VAD). Five hundred and thirty-one patients were included. Methods A propensity score-adjusted outcome analysis was performed, resulting in 324 patients in the full sternotomy (FS) group and 39 in the less invasive surgery (LIS) group. Results The surgery lasted in median 236 min in the FS group versus 263 min in the LIS group (p = 0.289). The median chest tube output during the first 24 h was similar in both groups. Patients who underwent implantation with an FS required more blood products during the first 24 postoperative hours (median 16 vs. 12, p = 0.033). The incidence of revision due to bleeding was also higher (35.5 vs. 15.4%, p = 0.016). A temporary postoperative right ventricular assist device was necessary in 45.1 (FS) versus 23.1% (LIS) of patients, respectively (p = 0.067). No stroke occurred in the LIS group during the first 30 days after surgery (7.4% in the FS group). The incidence of stroke and of renal, hepatic, and respiratory failure during the follow-up was similar in both groups. The 30-day and one-year survival were similar in both groups. Conclusion LIS for implantation of a durable LVAD in patients on va-ECLS implanted for cardiogenic shock is associated with less revision due to bleeding, less administration of blood products and absence of perioperative stroke, with no impact on survival
The DESI Sky Continuum Monitor System
The Dark Energy Spectroscopic Instrument (DESI) is an ongoing spectroscopic
survey to measure the dark energy equation of state to unprecedented precision.
We describe the DESI Sky Continuum Monitor System, which tracks the night sky
brightness as part of a system that dynamically adjusts the spectroscopic
exposure time to produce more uniform data quality and to maximize observing
efficiency. The DESI dynamic exposure time calculator (ETC) will combine sky
brightness measurements from the Sky Monitor with data from the guider system
to calculate the exposure time to achieve uniform signal-to-noise ratio (SNR)
in the spectra under various observing conditions. The DESI design includes 20
sky fibers, and these are split between two identical Sky Monitor units to
provide redundancy. Each Sky Monitor unit uses an SBIG STXL-6303e CCD camera
and supports an eight-position filter wheel. Both units have been completed and
delivered to the Mayall Telescope at the Kitt Peak National Observatory.
Commissioning results show that the Sky Monitor delivers the required
performance necessary for the ETC.Comment: 9 pages, 7 figures, 1 tabl
A comparison of forward and backward pp pair knockout in 3He(e,e'pp)n
Measuring nucleon-nucleon Short Range Correlations (SRC) has been a goal of
the nuclear physics community for many years. They are an important part of the
nuclear wavefunction, accounting for almost all of the high-momentum strength.
They are closely related to the EMC effect. While their overall probability has
been measured, measuring their momentum distributions is more difficult. In
order to determine the best configuration for studying SRC momentum
distributions, we measured the He reaction, looking at events
with high momentum protons ( GeV/c) and a low momentum neutron
( GeV/c). We examined two angular configurations: either both protons
emitted forward or one proton emitted forward and one backward (with respect to
the momentum transfer, ). The measured relative momentum distribution
of the events with one forward and one backward proton was much closer to the
calculated initial-state relative momentum distribution, indicating that
this is the preferred configuration for measuring SRC.Comment: 8 pages, 9 figures, submitted to Phys Rev C. Version 2 incorporates
minor corrections in response to referee comment
Measurement of the nuclear multiplicity ratio for hadronization at CLAS
The influence of cold nuclear matter on lepto-production of hadrons in
semi-inclusive deep inelastic scattering is measured using the CLAS detector in
Hall B at Jefferson Lab and a 5.014 GeV electron beam. We report the
multiplicity ratios for targets of C, Fe, and Pb relative to deuterium as a
function of the fractional virtual photon energy transferred to the
and the transverse momentum squared of the . We find that the
multiplicity ratios for are reduced in the nuclear medium at high
and low , with a trend for the transverse momentum to be
broadened in the nucleus for large .Comment: Submitted to Phys. Lett.
Outcome Prediction in Patients with Severe COVID-19 Requiring Extracorporeal Membrane Oxygenation—A Retrospective International Multicenter Study
The role of veno-venous extracorporeal membrane oxygenation therapy (V-V ECMO) in
severe COVID-19 acute respiratory distress syndrome (ARDS) is still under debate and conclusive
data from large cohorts are scarce. Furthermore, criteria for the selection of patients that benefit most
from this highly invasive and resource-demanding therapy are yet to be defined. In this study, we
assess survival in an international multicenter cohort of COVID-19 patients treated with V-V ECMO
and evaluate the performance of several clinical scores to predict 30-day survival. Methods: This is
an investigator-initiated retrospective non-interventional international multicenter registry study
(NCT04405973, first registered 28 May 2020). In 127 patients treated with V-V ECMO at 15 centers in
Germany, Switzerland, Italy, Belgium, and the United States, we calculated the Sequential Organ
Failure Assessment (SOFA) Score, Simplified Acute Physiology Score II (SAPS II), Acute Physiology And Chronic Health Evaluation II (APACHE II) Score, Respiratory Extracorporeal Membrane
Oxygenation Survival Prediction (RESP) Score, Predicting Death for Severe ARDS on V-V ECMO
(PRESERVE) Score, and 30-day survival. Results: In our study cohort which enrolled 127 patients,
overall 30-day survival was 54%. Median SOFA, SAPS II, APACHE II, RESP, and PRESERVE were 9,
36, 17, 1, and 4, respectively. The prognostic accuracy for all these scores (area under the receiver
operating characteristic—AUROC) ranged between 0.548 and 0.605. Conclusions: The use of scores
for the prediction of mortality cannot be recommended for treatment decisions in severe COVID-19
ARDS undergoing V-V ECMO; nevertheless, scoring results below or above a specific cut-off value
may be considered as an additional tool in the evaluation of prognosis. Survival rates in this cohort of
COVID-19 patients treated with V-V ECMO were slightly lower than those reported in non-COVID-19
ARDS patients treated with V-V ECMO
BRAIN ABSCESS DUE TO Staphylococcus aureus OF CRYPTOGENIC SOURCE IN AN HIV-1 INFECTED PATIENT IN USE OF ANTIRETROVIRAL THERAPY
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