17,970 research outputs found
Mixing of Xi_c and Xi_c' Baryons
The mixing angle between the Xi_c and Xi_c' baryons is shown to be small,
with a negligible shift in the Xi_c masses.Comment: One missprint corrected. The numerator of Eq. (12) should read
{2[(Sigma_c^{*++}-Sigma_c^{++})-(Xi_c^{*+}-Xi_c^{'+})]} The correct equation
was used in the calculation so no other change is mad
Sum rules for charmed baryon masses
The measured masses of the three charge states of the charmed
baryon are found to be in disagreement with a sum rule based on the quark
model, but relying on no detailed assumptions about the form of the
interaction. This poses a significant problem for the charmed baryon sector of
the quark model. Other relations among charmed baryon masses are also
discussed.Comment: 5 pages, latex, no figure
Local Density Approximation Description of Electronic Properties of Wurtzite Cadmium Sulfide (w-CdS)
We present calculated, electronic and related properties of wurtzite cadmium
sulfide (w-CdS). Our ab-initio, non-relativistic calculations employed a local
density functional approximation (LDA) potential and the linear combination of
atomic orbitals (LCAO). Following the Bagayoko, Zhao, and Williams (BZW)
method, we solved self-consistently both the Kohn-Sham equation and the
equation giving the ground state density in terms of the wave functions of the
occupied states. Our calculated, direct band gap of 2.47 eV, at the point, is
in excellent agreement with experiment. So are the calculated density of states
and the electron effective mass. In particular, our results reproduce the peaks
in the conduction band density of states, within the experimental
uncertainties.Comment: 22 Pages 4 Figure
FOCIS: A forest classification and inventory system using LANDSAT and digital terrain data
Accurate, cost-effective stratification of forest vegetation and timber inventory is the primary goal of a Forest Classification and Inventory System (FOCIS). Conventional timber stratification using photointerpretation can be time-consuming, costly, and inconsistent from analyst to analyst. FOCIS was designed to overcome these problems by using machine processing techniques to extract and process tonal, textural, and terrain information from registered LANDSAT multispectral and digital terrain data. Comparison of samples from timber strata identified by conventional procedures showed that both have about the same potential to reduce the variance of timber volume estimates over simple random sampling
To Stay at Home: Analysis of Rights and Recommendations on Procedures for Persons Receiving Mental Health Services in the Community
Before the pendulum swings back to the use of institutions as the primary treatment modality for persons with severe mental illness, there should be a re-examination of the alternatives available to community care providers to ensure compliance with treatment outside of the hospital. This article will focus on the alternatives available in the Ohio mental health system, which is fundamentally oriented towards community-based treatment, and the effects of this orientation
Appearance Potentials and Kinetic Energies of Ions from N2, CO, and NO
This is the publisher's version, also available electronically from http://scitation.aip.org/content/aip/journal/jcp/47/9/10.1063/1.1712367A recently developed method has permitted the measurement of excess translational energy of ions formed in a time‐of‐flight mass spectrometer. The method, in conjunction with the RPD technique for determining appearance potentials, has been applied to the electron‐impact study of nitrogen, carbon monoxide, and nitric oxide. A total of 31 different ionization processes have been observed and identified, several of which had not been previously reported in the literature
Identification of senescence and death in Emiliania huxleyi and Thalassiosira pseudonana: Cell staining, chlorophyll alterations, and dimethylsulfoniopropionate (DMSP) metabolism
We measured membrane permeability, hydrolytic enzyme, and caspase-like activities using fluorescent cell stains to document changes caused by nutrient exhaustion in the coccolithophore Emiliania huxleyi and the diatom Thalassiosira pseudonana, during batch-culture nutrient limitation. We related these changes to cell death, pigment alteration, and concentrations of dimethylsulfide (DMS) and dimethylsulfoniopropionate (DMSP) to assess the transformation of these compounds as cell physiological condition changes. E. huxleyi persisted for 1 month in stationary phase; in contrast, T. pseudonana cells rapidly declined within 10 d of nutrient depletion. T. pseudonana progressively lost membrane integrity and the ability to metabolize 5-chloromethylfluorescein diacetate (CMFDA; hydrolytic activity), whereas E. huxleyi developed two distinct CMFDA populations and retained membrane integrity (SYTOX Green). Caspase-like activity appeared higher in E. huxleyi than in T. pseudonana during the post-growth phase, despite a lack of apparent mortality and cell lysis. Photosynthetic pigment degradation and transformation occurred in both species after growth; chlorophyll a (Chl a) degradation was characterized by an increase in the ratio of methoxy Chl a : Chl a in T. pseudonana but not in E. huxleyi, and the increase in this ratio preceded loss of membrane integrity. Total DMSP declined in T. pseudonana during cell death and DMS increased. In contrast, and in the absence of cell death, total DMSP and DMS increased in E. huxleyi. Our data show a novel chlorophyll alteration product associated with T. pseudonana death, suggesting a promising approach to discriminate nonviable cells in nature
Orientation isotope effect in ion–molecule reactions
This is the publisher's version, also available electronically from http://scitation.aip.org/content/aip/journal/jcp/67/10/10.1063/1.434632.A simple kinematicmodel is proposed to account for the kinetic isotope effect (KIE) upon the reactions of simple ions X+ with HD. This model is based upon (1) the fact that the displacement of the center of polarizability from the center of mass in the HD molecule will affect the alignment of the reactants, (2) the fact that, for many ions X+, reaction must occur by a surface crossing mechanism, and (3) the assumption that the ratio XH+/(XH++XD+) equals the fraction of intimate collisions in which the H end of HD is oriented towards the ion at the moment the reactants pass over the centrifugal barrier in the effective radial potential (or cross over to the X–HD+ surface if the crossing occurs before the centrifugal barrier is reached). Use of the ion–induced dipole potential for the reactants permits the derivation of an analytic expression for the KIE. With no adjustable parameters, this model accounts quantitatively for the very different KIE’s observed in the reactions of Ar+ and Kr+ with HD at low collision energies
Radio-frequency discharges in Oxygen. Part 1: Modeling
In this series of three papers we present results from a combined
experimental and theoretical effort to quantitatively describe capacitively
coupled radio-frequency discharges in oxygen. The particle-in-cell Monte-Carlo
model on which the theoretical description is based will be described in the
present paper. It treats space charge fields and transport processes on an
equal footing with the most important plasma-chemical reactions. For given
external voltage and pressure, the model determines the electric potential
within the discharge and the distribution functions for electrons, negatively
charged atomic oxygen, and positively charged molecular oxygen. Previously used
scattering and reaction cross section data are critically assessed and in some
cases modified. To validate our model, we compare the densities in the bulk of
the discharge with experimental data and find good agreement, indicating that
essential aspects of an oxygen discharge are captured.Comment: 11 pages, 10 figure
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