3,343 research outputs found
Improved variables for measuring the polarization
We discuss a few possible strategies for measuring the polarization of the
baryons produced in -annihilation at the
resonance through their inclusive semileptonic decays. After
reviewing the existing methods, a new method is proposed, based on the ratio of
the averages of the squared electron and neutrino energy, including both
perturbative and nonperturbative corrections. This variable minimizes the
statistical error on the polarization, while keeping the
systematic theoretical errors at the level of 1-2%. A number of other
polarization-sensitive variables are also discussed, such as averages of ratios
of the electron and neutrino energy and the distribution in the difference of
the electron and neutrino rapidities.Comment: 23 pages, 4 uuencoded figures, REVTe
Broken-Symmetry Unrestricted Hybrid Density Functional Calculations on Nickel Dimer and Nickel Hydride
In the present work we investigate the adequacy of broken-symmetry
unrestricted density functional theory (DFT) for constructing the potential
energy curve of nickel dimer and nickel hydride, as a model for larger bare and
hydrogenated nickel cluster calculations. We use three hybrid functionals: the
popular B3LYP, Becke's newest optimized functional Becke98, and the simple
FSLYP functional (50% Hartree-Fock and 50% Slater exchange and LYP
gradient-corrected correlation functional) with two basis sets: all-electron
(AE) Wachters+f basis set and Stuttgart RSC effective core potential (ECP) and
basis set.
We find that, overall, the best agreement with experiment, comparable to that
of the high-level CASPT2, is obtained with B3LYP/AE, closely followed by
Becke98/AE and Becke98/ECP. FSLYP/AE and B3LYP/ECP give slightly worse
agreement with experiment, and FSLYP/ECP is the only method among the ones we
studied that gives an unaceptably large error, underestimating the dissociation
energy of nickel dimer by 28%, and being in the largest disagreement with the
experiment and the other theoretical predictions.Comment: 17 pages, 7 tables, 7 figures; submitted to J. Chem. Phys.;
Revtex4/LaTeX2e. v2 (8/5/04): New (and better) ECP results, without charge
density fitting (which was found to give large errors). Subtracted the
relativistic corrections from all experimental value
Pelvic floor disorders in gynecological malignancies. An overlooked problem?
Cervical, endometrial, ovarian, vulvar, and vaginal cancers affect women of a broad age spectrum. Many of these women are still sexually active when their cancer is diagnosed. Treatment options for gynecological malignancies, such as gynecological surgery, radiation, and chemotherapy, are proven risk factors for pelvic floor dysfunction. The prevalence of urinary incontinence, fecal incontinence, and sexual dysfunction before cancer treatment is still unclear. Hypotheses have been raised in the literature that these manifestations could represent early symptoms of pelvic cancers, but most remain overlooked even in cancer surviving patients.
The primary focus of therapy is always cancer eradication, but as oncological and surgical treatment options become more successful, the number of cancer survivors increases. The quality of life of patients with gynecological cancers often remains an underrated subject. Pelvic floor disorders are not consistently reported by patients and are frequently overlooked by many clinicians. In this brief review we discuss the importance of pelvic floor dysfunction in patients with gynecological malignant tumors
Weyl group multiple Dirichlet series constructed from quadratic characters
We construct multiple Dirichlet series in several complex variables whose
coefficients involve quadratic residue symbols. The series are shown to have an
analytic continuation and satisfy a certain group of functional equations.
These are the first examples of an infinite collection of unstable Weyl group
multiple Dirichlet series in greater than two variables.Comment: incorporated referee's comment
Accurate Hartree-Fock energy of extended systems using large Gaussian basis sets
Calculating highly accurate thermochemical properties of condensed matter via
wave function-based approaches (such as e.g. Hartree-Fock or hybrid
functionals) has recently attracted much interest. We here present two
strategies providing accurate Hartree-Fock energies for solid LiH in a large
Gaussian basis set and applying periodic boundary conditions. The total
energies were obtained using two different approaches, namely a supercell
evaluation of Hartree-Fock exchange using a truncated Coulomb operator and an
extrapolation toward the full-range Hartree-Fock limit of a Pad\'e fit to a
series of short-range screened Hartree-Fock calculations. These two techniques
agreed to significant precision. We also present the Hartree-Fock cohesive
energy of LiH (converged to within sub-meV) at the experimental equilibrium
volume as well as the Hartree-Fock equilibrium lattice constant and bulk
modulus.Comment: 7.5 pages, 2 figures, submitted to Phys. Rev. B; v2: typos removed,
References adde
Mott Transition of MnO under Pressure: Comparison of Correlated Band Theories
The electronic structure, magnetic moment, and volume collapse of MnO under
pressure are obtained from four different correlated band theory methods; local
density approximation + Hubbard U (LDA+U), pseudopotential self-interaction
correction (pseudo-SIC), the hybrid functional (combined local exchange plus
Hartree-Fock exchange), and the local spin density SIC (SIC-LSD) method. Each
method treats correlation among the five Mn 3d orbitals (per spin), including
their hybridization with three O orbitals in the valence bands and their
changes with pressure. The focus is on comparison of the methods for rocksalt
MnO (neglecting the observed transition to the NiAs structure in the 90-100 GPa
range). Each method predicts a first-order volume collapse, but with variation
in the predicted volume and critical pressure. Accompanying the volume collapse
is a moment collapse, which for all methods is from high-spin to low-spin (5/2
to 1/2), not to nonmagnetic as the simplest scenario would have. The specific
manner in which the transition occurs varies considerably among the methods:
pseudo-SIC and SIC-LSD give insulator-to-metal, while LDA+U gives
insulator-to-insulator and the hybrid method gives an insulator-to-semimetal
transition. Projected densities of states above and below the transition are
presented for each of the methods and used to analyze the character of each
transition. In some cases the rhombohedral symmetry of the
antiferromagnetically ordered phase clearly influences the character of the
transition.Comment: 14 pages, 9 figures. A 7 institute collaboration, Updated versio
Bioremediation of Cr(VI) polluted wastewaters by sorption on heat inactivated Saccharomyces cerevisiae biomass
The potential of heat inactivated Saccharomyces cerevisiae in the bioremoval and reduction of
Cr (VI) ions from wastewaters was evaluated in terms of metal uptake in time and at equilibrium, and
biosorption efficiency, by varying pH, biosorbent doses, contact time and temperature, in batch mode. During the sorption process, the heat inactivated biomass of the yeast Saccharomyces cerevisiae is capable of reducing Cr(VI) to Cr(III). Different kinetic models based on adsorption and reduction are used to represent the kinetic data of Cr(VI) bioremoval by S. cerevisiae, in explaining the biosorption mechanism of heavy metals and potential rate-controlling steps, in the perspective of full-scale process design. The results indicated some potential differences in the Cr(VI) removal mechanism at different experimental conditions. FTIR and SEM analysis were performed as well as to elucidate the mechanism of metal bioremoval by S. cerevisiae. FTIR spectra indicate that heavy metal bioremoval process doesn’t imply in this case the formation of stable covalent bonds, but it is predominantly based on chemical interactions, ion-exchange type. The SEM micrographs of Cr-loaded yeast, indicates that the surface morphology doesn’t change much after chromium ions were uptaken. This leads to the conclusion that Cr(VI) reduction occurs at the interface of the adsorbent.This paper was elaborated with the support of BRAIN project Doctoral scholarships as an investment in intelligence - ID 6681, financed by the European Social Found and Romanian Government and with the support of a grant of the Romanian National Authority for Scientific Research, CNCS - UEFISCDI, project number PN-II-ID-PCE-2011-3-0559", Contract 265/2011
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