23,251 research outputs found
Research notes: Response of four soybean varieties to foliar zinc fertilizer
Zinc deficiency symptoms are commonly encountered in irrigated soybean crops grown on grey self-mulching clay soils in Northern N.S.W . These experiments aimed to (1) quantify the yield loss due to zinc deficiency at different sites and (2) examine the differences in genotypic sensitivity to zinc deficiency among commercially grown soybean cultivars. Materials and Methods : Experiments were conducted at (1) Narrabri Agricultural Research Station, (2) Breeza Substation and (3) Trangie Agricultural Research Station
Relativistic theory of the double photoionization of helium-like atoms
A fully relativistic calculation of the double photoionization of helium-like
atoms is presented. The approach is based on the partial-wave representation of
the Dirac continuum states and accounts for the retardation in the
electron-electron interaction as well as the higher-order multipoles of the
absorbed photon. The electron-electron interaction is taken into account to the
leading order of perturbation theory. The relativistic effects are shown to
become prominent already for the medium-Z ions, changing the shape and the
asymptotic behaviour of the photon energy dependence of the ratio of the
double-to-single photoionization cross section
The Operator form of 3H (3He) and its Spin Structure
An operator form of the 3N bound state is proposed. It consists of eight
operators formed out of scalar products in relative momentum and spin vectors,
which are applied on a pure 3N spin 1/2 state. Each of the operators is
associated with a scalar function depending only on the magnitudes of the two
relative momenta and the angle between them. The connection between the
standard partial wave decomposition of the 3N bound state and the operator form
is established, and the decomposition of these scalar function in terms of
partial wave components and analytically known auxiliary functions is given.
That newly established operator form of the 3N bound state exhibits the
dominant angular and spin dependence analytically. The scalar functions are
tabulated and can be downloaded. As an application the spin dependent nucleon
momentum distribution in a polarized 3N bound state is calculated to illustrate
the use of the new form of the 3N bound state.Comment: 21 pages, 1 table, 8 figures, revtex
GOES imagery fills gaps in Montserrat volcanic cloud observations
GOES satellite imagery offers great potential to lessen the risk of volcanic ash clouds to aviation, and the situation at Montserrat in the Caribbean is providing the proof. Many transatlantic, commercial, and private aircraft use airspace around Montserrat, where the Soufriere Hills Volcano has been erupting since 1995.
Worldwide over the last 15 years, more than 80 airplanes have reported encountering volcanic ash along flight paths. Encounters cannot be avoided because onboard radar cannot detect fine-grained ash particles—those with a radius of 15 microns or less. In recent years volcanic cloud encounters are estimated to have caused hundreds of millions of dollars worth of damage and in a few cases have caused in-flight engine failure [Casadevall et al., 1996]
Research notes: Resistance to Heliothis armigera and Heliothis punctigera in three soybean lines
Multiple insect resistance has been detected in the soybean lines PI 171,451, PI 227,687 and PI 229,358 (Van Duyn et al., 1971; Clark et al., 1972; Hatchett et al., 1976). In particular Hatchett et al. (1976) demonstrated resistance to Heliothis zea and Heliothis virescens in all three lines. On the basis of percentage larval mortality, PI 171,451 and PI 229,358 were more resistant to H. zea than H. virescens, while PI 227,687 was equally resistant to both species and also showed superior levels of resistance
Virtual light-by-light scattering and the g factor of a bound electron
The contribution of the light-by-light diagram to the g factor of electron
and muon bound in Coulomb field is obtained. For electron in a ground state,
our results are in good agreement with the results of other authors obtained
numerically for large Z. For relatively small Z our results have essentially
higher accuracy as compared to the previous ones. For muonic atoms, the
contribution is obtained for the first time with the high accuracy in whole
region of Z.Comment: 10 pages, 3 figures, RevTe
Relative Effectiveness of Inquiry and Expository Methods of Teaching Social Studies on Academic Performance of Secondary Students in Akwa Ibom State, Nigeria
The aim of this work was to find out the relative effectiveness of inquiry and expository methods of teaching social studies on the academic achievement of secondary school students in Akwa Ibom State. Related literature was reviewed. The research design was pretest-post-test experimental design. Two hypotheses were raised to guide the study. The independent t-test statistical instrument was used in analyzing the data at .05 level of significance. The sample of the study was made up of 300 randomly sampled students from six public secondary schools in the state. The result revealed that students taught with the expository method. Based on this finding, it was recommended that inquiry method of teaching social studies be encouraged in the secondary school setting. Keywords: Inquiry, Expository, Social Studies, Performance
A Library of Integrated Spectra of Galactic Globular Clusters
We present a new library of integrated spectra of 40 Galactic globular
clusters, obtained with the Blanco 4-m telescope and the R-C spectrograph at
the Cerro Tololo Interamerican Observatory. The spectra cover the range ~ 3350
-- 6430 A with ~ 3.1 A (FWHM) resolution. The spectroscopic observations and
data reduction were designed to integrate the full projected area within the
cluster core radii in order to properly sample the light from stars in all
relevant evolutionary stages. The S/N values of the flux-calibrated spectra
range from 50 to 240/A at 4000 A and from 125 to 500/A at 5000 A. The selected
targets span a wide range of cluster parameters, including metallicity,
horizontal-branch morphology, Galactic coordinates, Galactocentric distance,
and concentration. The total sample is thus fairly representative of the entire
Galactic globular cluster population and should be valuable for comparison with
similar integrated spectra of unresolved stellar populations in remote systems.
For most of the library clusters, our spectra can be coupled with deep
color-magnitude diagrams and reliable metal abundances from the literature to
enable the calibration of stellar population synthesis models. In this paper we
present a detailed account of the observations and data reduction. The spectral
library is publicly available in electronic format from the National Optical
Astronomical Observatory website.Comment: 39 Pages, including 2 tables and 15 Figures. To appear in the
Astrophysical Journal, Supplement Serie
Dirac Hamiltonian with superstrong Coulomb field
We consider the quantum-mechanical problem of a relativistic Dirac particle
moving in the Coulomb field of a point charge . In the literature, it is
often declared that a quantum-mechanical description of such a system does not
exist for charge values exceeding the so-called critical charge with based on the fact that the standard expression for the
lower bound state energy yields complex values at overcritical charges. We show
that from the mathematical standpoint, there is no problem in defining a
self-adjoint Hamiltonian for any value of charge. What is more, the transition
through the critical charge does not lead to any qualitative changes in the
mathematical description of the system. A specific feature of overcritical
charges is a non uniqueness of the self-adjoint Hamiltonian, but this non
uniqueness is also characteristic for charge values less than the critical one
(and larger than the subcritical charge with ). We present the spectra and (generalized) eigenfunctions for all
self-adjoint Hamiltonians. The methods used are the methods of the theory of
self-adjoint extensions of symmetric operators and the Krein method of guiding
functionals. The relation of the constructed one-particle quantum mechanics to
the real physics of electrons in superstrong Coulomb fields where multiparticle
effects may be of crucial importance is an open question.Comment: 44 pages, LaTex file, to be published in Teor.Mat.Fiz.
(Theor.Math.Phys.
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