1,241 research outputs found
Physiological Responses of Switchgrass (Panicum virgatum L.) to Organic and Inorganic Amended Heavy-Metal Contaminated Chat Tailings
Study plots established at the Galena subsite of the Cherokee County Superfund Site in southeastern Kansas by the U.S. Bureau of Mines in 1990 were examined during the summer of 1996 to determine whether physiological criteria could be used to determine suitability of switchgrass for remediation of heavy-metal contaminated substrates. Switchgrass was chosen because it was the most frequently encountered species on these plots. Treatment plots included a treatment control, an organic residue treatment of 89.6 Mg ha-1 composted cattle manure, and two inorganic fertilizer treatments recommended for either native grass or grass/legume mixtures. Plant response variables were photosynthetic rate, leaf conductance to water vapor, internal concentration of carbon dioxide in leaves, foliar transpiration rate, leaf water-use efficiency, predawn leaf xylem water potential, and midday leaf xylem water potential. Predawn and midday xylem water potentials were higher for grass/legume inorganic treatment than for the other inorganic treatments. Leaf conductances were lower for organically treated plots than those plots not organically amended and both photosynthesis and transpiration were lower for organically treated plots. Leaf conductances and transpiration were higher for grass/legume treated plots than for plots lacking inorganic treatment. Water-use-efficiency was higher for native grass-treated plots than for other inorganic treatments. Grass/legume inorganic treatment in absence of organic treatment increased predawn and midday xylem water potential, leaf conductance, photosynthesis, and transpiration. Organic amendment in absence of inorganic amendment increased predawn and midday xylem water potential
Day Care Experienced Vs. Non-Day Care Experienced Children: A Comparison of Maturity and Achievement in Grade School
While a considerable amount of evaluative research has been performed in the area of day care, the overwhelming majority of these studies have dealt only with experimental programs aimed at lower class children. The present study was conceived as an evaluation of established day care and preschool programs available to the general community. The study was performed in an Upper Midwest community with a total population of 35*000.
Three groups of fifth-grade students were selected and matched on the bases of age, sex, and family income. Members of Group 1 had no day care experience, Group 2 had 20- 120 total days of day care experience, and Group 3 had from 121-360 total days of day care experience.
The groups were compared with each other on the basis of three criteria: academic achievement, intelligence, and social maturity* Academic achievement was measured by each subjects final, grades for reading (language arts) and mathematics as recorded for the 1st, 3rd, and 5th grades in school* Intelligence was measured by the subject\u27s Iowa Test of Basic Skills national percentile, as achieved on an administration of that test six months prior to the present study. Social maturity was measured by the Vine- land Social Maturity Scale, which was administered by the author to each subject\u27s parents, and by parents\u27 and teachers\u27 ratings of each subject\u27s maturity on a scale from 1 through 10.
Data were treated in the following manner: reading and mathematics scores were each analyzed by means of a 3 by 3 analysis of variance. Iowa Basic Test percentiles, Vine- land Age score, Parents\u27 Ratings and Teachers\u27 Ratings were subjected to one-way analysis of variance. Miscellaneous correlation coefficients exploring the possible influence of partially-controlled extraneous variables were also performed.
It was found that scores for most measures tended to increase in value as amount of day care increased. However, only Reading scores were found to differ significantly between groups with Group 3 being highest achievers and Group 1 being lowest. The influence of a major extraneous variable was ruled out by the lack of significant correlation between amount of days spent in day care and family income for this sample.
The significant P for Reading was regarded as the major observation of the study, since this effect was the only statistically significant difference between the day care and non-day care groups and one of the few effects known to have endured beyond the third grade in any study of this type* It was also noted that the effect of differing sets of teachers can be an important extraneous variable in studies involving school achievement score
Consequences of the partial restoration of chiral symmetry in AdS/QCD
Chiral symmetry is an essential concept in understanding QCD at low energy.
We treat the chiral condensate, which measures the spontaneous breaking of
chiral symmetry, as a free parameter to investigate the effect of partially
restored chiral symmetry on the physical quantities in the frame work of an
AdS/QCD model. We observe an interesting scaling behavior among the nucleon
mass, pion decay constant and chiral condensate. We propose a phenomenological
way to introduce the temperature dependence of a physical quantity in the
AdS/QCD model with the thermal AdS metric.Comment: 11 pages, 6 figure
Heavy quarkonium in a holographic QCD model
Encouraged by recent developments in AdS/QCD models for light quark system,
we study heavy quarkonium in the framework of the AdS/QCD models. We calculate
the masses of vector meson states using the AdS/QCD models at zero
and at finite temperature. Among the models adopted in this work, we find that
the soft wall model describes the low-lying heavy quark meson states at zero
temperature relatively well. At finite temperature, we observe that once the
bound state is above , its mass will increase with temperature until it
dissociates at a temperature of around . It is shown that the
dissociation temperature is fixed by the infrared cutoff of the models. The
present model serves as a unified non perturbative model to investigate the
properties of bound quarkonium states above .Comment: 9 pages, 1 figure, minor revision, to appear in phys. Rev.
A criterion for the nature of the superconducting transition in strongly interacting field theories : Holographic approach
It is beyond the present techniques based on perturbation theory to reveal
the nature of phase transitions in strongly interacting field theories.
Recently, the holographic approach has provided us with an effective dual
description, mapping strongly coupled conformal field theories to classical
gravity theories. Resorting to the holographic superconductor model, we propose
a general criterion for the nature of the superconducting phase transition
based on effective interactions between vortices. We find "tricritical" points
in terms of the chemical potential for U(1) charges and an effective
Ginzburg-Landau parameter, where vortices do not interact to separate the
second order (repulsive) from the first order (attractive) transitions. We
interpret the first order transition as the Coleman-Weinberg mechanism, arguing
that it is relevant to superconducting instabilities around quantum
criticality.Comment: 7 pages, 7 figure
Network Structures and the Properties of Na-Ca-Sr-Borophosphate Glasses
Borophosphate glasses were prepared with the nominal molar compositions 16Na2O-(24-y)CaO-ySrO-xB2O3-(60-x)P2O5 (mol%), where 0≤x≤60 and y=0, 12, and 24. Information about the compositional dependence of borate and phosphate site speciation and next nearest neighbor linkages was obtained by 11B and 31P MAS NMR and Raman spectroscopies, and by high pressure liquid chromatography (HPLC). With the initial replacement of P2O5 by B2O3, tetrahedral borate sites linked to four phosphate anions, B(ØP)4, are created in the glass structure, and the average phosphate anion becomes smaller as bridging PØP bonds are replaced by bridging PØB bonds. With further increases in the B2O3 content, borate units, including B-triangles, replace phosphate units linked to the B-tetrahedra. Compositional trends for the glass transition temperature (Tg) and molar volume are explained by considering the number and types of bridging oxygens per glass former, consistent with topological models reported elsewhere
Mesons and nucleons from holographic QCD in a unified approach
We investigate masses and coupling constants of mesons and nucleons within a
hard wall model of holographic QCD in a unified approach. We first examine an
appropriate form of fermionic solutions by restricting the mass coupling for
the five dimensional bulk fermions and bosons. We then derive approximated
analytic solutions for the nucleons and the corresponding masses in a small
mass coupling region. In order to treat meson and nucleon properties on the
same footing, we introduce the same infrared (IR) cut in such a way that the
meson-nucleon coupling constants, i.e., g_{pi NN} and g_{rho NN} are uniquely
determined. The first order approximation with respect to a dimensionless
expansion parameter, which is valid in the small mass coupling region,
explicitly shows difficulties to avoid the IR scale problem of the hard wall
model. We discuss possible ways of circumventing these problems.Comment: 15 pages, No figure. Several typos have been remove
Lorentz gauge theory as a model of emergent gravity
We consider a class of Lorentz gauge gravity theories within Riemann-Cartan
geometry which admits a topological phase in the gravitational sector. The
dynamic content of such theories is determined only by the contortion part of
the Lorentz gauge connection. We demonstrate that there is a unique Lagrangian
that admits propagating spin one mode in correspondence with gauge theories of
other fundamental interactions. Remarkably, despite the R^2 type of the
Lagrangian and non-compact structure of the Lorentz gauge group, the model
possesses rather a positive-definite Hamiltonian. This has been proved in the
lowest order of perturbation theory. This implies further consistent
quantization and leads to renormalizable quantum theory. It is assumed that the
proposed model describes possible mechanism of emergent Einstein gravity at
very early stages of the Universe due to quantum dynamics of contortion.Comment: 11 pages, final version, minor correction
Micro-Auger Electron Spectroscopy Studies of Chemical and Electronic Effects at GaN-Sapphire Interfaces
We have used cross-sectional micro-Auger electron spectroscopy (AES), coupled with micro-cathodoluminescence (CLS) spectroscopy, in a UHV scanning electron microscope to probe the chemical and related electronic features of hydride vapor phase epitaxy GaN/sapphire interfaces on a nanometer scale. AES images reveal dramatic evidence for micron-scale diffusion of O from Al2O3 into GaN. Conversely, plateau concentrations of N can extend microns into the sapphire, corresponding spatially to a 3.8 eV defect emission and Auger chemical shifts attributed to Al-N-O complexes. Interface Al Auger signals extending into GaN indicates AlGaN alloy formation, consistent with a blue-shifted CLS local interface emission. The widths of such interface transition regions range from ≪100 nm to ∼1 μm, depending on surface pretreatment and growth conditions. Secondary ion mass spectroscopy depth profiles confirm the elemental character and spatial extent of diffusion revealed by micro-AES, showing that cross-sectional AES is a useful approach to probe interdiffusion and electronic properties at buried interfaces
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