3,052 research outputs found
Electronic structure and optical properties of lightweight metal hydrides
We study the electronic structures and dielectric functions of the simple
hydrides LiH, NaH, MgH2 and AlH3, and the complex hydrides Li3AlH6, Na3AlH6,
LiAlH4, NaAlH4 and Mg(AlH4)2, using first principles density functional theory
and GW calculations. All these compounds are large gap insulators with GW
single particle band gaps varying from 3.5 eV in AlH3 to 6.5 eV in the MAlH4
compounds. The valence bands are dominated by the hydrogen atoms, whereas the
conduction bands have mixed contributions from the hydrogens and the metal
cations. The electronic structure of the aluminium compounds is determined
mainly by aluminium hydride complexes and their mutual interactions. Despite
considerable differences between the band structures and the band gaps of the
various compounds, their optical responses are qualitatively similar. In most
of the spectra the optical absorption rises sharply above 6 eV and has a strong
peak around 8 eV. The quantitative differences in the optical spectra are
interpreted in terms of the structure and the electronic structure of the
compounds.Comment: 13 pages, 10 figure
Acute-on-chronic liver failure in cirrhosis
The definition of acute-on-chronic liver failure (ACLF) remains contested. In Europe and North America, the term is generally applied according to the European Association for the Study of the Liver-Chronic Liver Failure (EASL-CLIF) Consortium guidelines, which defines this condition as a syndrome that develops in patients with cirrhosis and is characterized by acute decompensation, organ failure and high short-term mortality. One-third of patients who are hospitalized for acute decompensation present with ACLF at admission or develop the syndrome during hospitalization. ACLF frequently occurs in a closed temporal relationship to a precipitating event, such as bacterial infection or acute alcoholic, drug-induced or viral hepatitis. However, no precipitating event can be identified in approximately 40% of patients. The mechanisms of ACLF involve systemic inflammation due to infections, acute liver damage and, in cases without precipitating events, probably intestinal translocation of bacteria or bacterial products. ACLF is graded into three stages (ACLF grades 1–3) on the basis of the number of organ failures, with higher grades associated with increased mortality. Liver and renal failures are the most common organ failures, followed by coagulation, brain, circulatory and respiratory failure. The 28-day mortality rate associated with ACLF is 30%. Depending on the grade, ACLF can be reversed using standard therapy in only 16–51% of patients, leaving a considerable proportion of patients with ACLF that remains steady or progresses. Liver transplantation in selected patients with ACLF grade 2 and ACLF grade 3 increases the 6-month survival from 10% to 80%
An Accurate Data Preparation Approach for the Prediction of Mortality in ACLF Patients using the CANONIC Dataset
The incidence of chronic liver disease has increased in Europe and can lead to Acute on Chronic Liver Failure (ACLF) which is associated with high levels of mortality due to multisystem organ failure. The characteristics of the ACLF patients can change very rapidly within a short period of time. Continuous assessment of their recovery status is critical for clinicians to adjust and deliver effective treatment. The aim of this paper is to validate the usefulness of a data preparation approach by combining different criteria to replace missing values, balance target-class variables, select useful patient characteristics and optimise hyperparameters of machine learning models for the prediction of ACLF associated mortality rates. A key step in the data preparation is a feature selection Mutual Information (MI) based multivariate approach to build smaller, and yet equally and in some cases more informative, subsets of patient characteristics than those frequently proposed for the prediction of mortality, from patients with ACLF in the CANONIC dataset. The usefulness of the data preparation approach proposed to predict mortality was evaluated by training the XGBoost and Logistic Regression models with the prepared data. Evaluations of the models trained using a test set provided evidence of an overall high accuracy in the prediction of the mortality rates of patients for days after their diagnosis, and in some cases even higher when reduced and more informative subsets of patient characteristics were found
Proposal for the numerical solution of planar QCD
Using quenched reduction, we propose a method for the numerical calculation
of meson correlation functions in the planar limit of QCD. General features of
the approach are outlined, and an example is given in the context of
two-dimensional QCD.Comment: 31 pages, 10 figures, uses axodraw.sty, To appear in Physical Review
Acute-on-Chronic Liver Failure: Definition, Diagnosis, and Clinical Characteristics
Acute-on-chronic liver failure (ACLF) is a recently recognized syndrome in cirrhosis characterized by acute decompensation (AD), organ failure(s), and high short-term mortality. Organ failure(s) is defined by the Chronic Liver Failure-Sequential Organ Failure (CLIF-SOFA) score or by its simplified version Chronic Liver Failure-Organ Failure Assessment (CLIF-OF) score. They include six types of organ failure: liver, renal, coagulation, cerebral, respiratory, and circulatory. One third of patients hospitalized with AD present with ACLF at admission or develop ACLF during hospitalization. Acute-on-chronic liver failure frequently occurs in a closed relationship to a precipitating event. According to the number of organ failures, ACLF is graded into three stages: ACLF-1 = single renal failure or single nonrenal organ failure if associated with renal dysfunction and/or cerebral dysfunction; ACLF-2 = two organ failures; and ACLF-3 = three to six organ failures, with increasing 28-day mortality rate (from 23%–74%). Acute-on-chronic liver failure may develop at any phase during the clinical course of the disease. Patients without prior AD develop a severe form of ACLF
Biomimetic Ca-P coatings Incorporating bisphosphonates produced on starch-based degradable biomaterials
In this study, sodium clodronate, a well-known therapeutic agent from the family
of bisphosphonates (BPs), is incorporated in a biomimetic calcium phosphate (CaP) coating,
previously formed on the surface of a starch-based biomaterial by a sodium silicate
methodology, as a strategy to develop a site-specific drug delivery system for bone tissue
regeneration applications. The effects on the resulting CaP coatings were evaluated in terms of
morphology, chemistry, and structure. The dissolution of Ca and P from the coating and the
release profiles of sodium clodronate was also assessed. As a preliminary approach, this first
study also aimed at evaluating the effects of this BP on the viability of a human osteoblastic
cell line since there is still little information available on the interaction between BPs and this
type of cells. Sodium clodronate was successfully incorporated, at different doses, in the
structure of a biomimetic CaP layer previously formed by a sodium silicate process. This
type of BPs had a stimulatory effect on osteoblastic activity, particularly at the specific
concentration of 0.32 mg/mL. It is foreseen that these coatings can, for instances, be
produced on the surface of degradable polymers and then used for regulating the
equilibrium on osteoblastic/osteoclastic activity, leading to a controlled regenerative effect
at the interface between the biomaterial and bone
Computing Yukawa Couplings from Magnetized Extra Dimensions
We compute Yukawa couplings involving chiral matter fields in toroidal
compactifications of higher dimensional super-Yang-Mills theory with magnetic
fluxes. Specifically we focus on toroidal compactifications of D=10
super-Yang-Mills theory, which may be obtained as the low-energy limit of Type
I, Type II or Heterotic strings. Chirality is obtained by turning on constant
magnetic fluxes in each of the 2-tori. Our results are general and may as well
be applied to lower D=6,8 dimensional field theories. We solve Dirac and
Laplace equations to find out the explicit form of wavefunctions in extra
dimensions. The Yukawa couplings are computed as overlap integrals of two Weyl
fermions and one complex scalar over the compact dimensions. In the case of
Type IIB (or Type I) string theories, the models are T-dual to (orientifolded)
Type IIA with D6-branes intersecting at angles. These theories may have
phenomenological relevance since particular models with SM group and three
quark-lepton generations have been recently constructed. We find that the
Yukawa couplings so obtained are described by Riemann theta-functions, which
depend on the complex structure and Wilson line backgrounds. Different patterns
of Yukawa textures are possible depending on the values of these backgrounds.
We discuss the matching of these results with the analogous computation in
models with intersecting D6-branes. Whereas in the latter case a string
computation is required, in our case only field theory is needed.Comment: 73 pages, 9 figures. Using JHEP3.cls. Typos and other minor
corrections fixed. References adde
A new test for random number generators: Schwinger-Dyson equations for the Ising model
We use a set of Schwinger-Dyson equations for the Ising Model to check
several random number generators. For the model in two and three dimensions, it
is shown that the equations are sensitive tests of bias originated by the
random numbers. The method is almost costless in computer time when added to
any simulation.Comment: 6 pages, 3 figure
Length of hospital stay for elective electrophysiological procedures: a survey from the European Heart Rhythm Association
AIMS: Electrophysiological (EP) operations that have traditionally involved long hospital lengths of stay (LOS) are now being undertaken as day case procedures. The coronavirus disease-19 pandemic served as an impetus for many centres to shorten LOS for EP procedures. This survey explores LOS for elective EP procedures in the modern era. METHODS AND RESULTS: An online survey consisting of 27 multiple-choice questions was completed by 245 respondents from 35 countries. With respect to de novo cardiac implantable electronic device (CIED) implantations, day case procedures were reported for 79.5% of implantable loop recorders, 13.3% of pacemakers (PMs), 10.4% of implantable cardioverter defibrillators (ICDs), and 10.2% of cardiac resynchronization therapy (CRT) devices. With respect to CIED generator replacements, day case procedures were reported for 61.7% of PMs, 49.2% of ICDs, and 48.2% of CRT devices. With regard to ablations, day case procedures were reported for 5.7% of atrial fibrillation (AF) ablations, 10.7% of left-sided ablations, and 17.5% of right-sided ablations. A LOS ≥ 2 days for CIED implantation was reported for 47.7% of PM, 54.5% of ICDs, and 56.9% of CRT devices and for 54.5% of AF ablations, 42.2% of right-sided ablations, and 46.1% of left-sided ablations. Reimbursement (43-56%) and bed availability (20-47%) were reported to have no consistent impact on the organization of elective procedures. CONCLUSION: There is a wide variation in the LOS for elective EP procedures. The LOS for some procedures appears disproportionate to their complexity. Neither reimbursement nor bed availability consistently influenced LOS
A High Statistics Search for Electron-Neutrino --> Tau-Neutrino Oscillations
We present new limits on nu_e to nu_tau and nu_e to nu_sterile oscillations
by searching for electron neutrino dissappearance in the high-energy wide-band
CCFR neutrino beam. Sensitivity to nu_tau appearance comes from tau decay modes
in which a large fraction of the energy deposited is electromagnetic. The beam
is composed primarily of muon neutrinos but this analysis uses the 2.3%
electron neutrino component of the beam. Electron neutrino energies range from
30 to 600 GeV and flight lengths vary from 0.9 to 1.4 km. This limit improves
the sensitivity of existing limits and obtains a lowest 90% confidence upper
limit in sin**2(2*alpha) of 9.9 x 10**(-2) at delta-m**2 of 125 eV**2.Comment: submitted to Phys. Rev. D. Rapid Com
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