4,259 research outputs found
Timber type separability in Southeastern United States on LANDSAT-1 MSS data
A quantitative, computer-aided study was made on the spectral separability of timber types and condition classes in the Southeastern United States, using LANDSAT-1 multispectral scanner data. It was concluded that LANDSAT-1 could be used effectively to discriminate the gross forest features of softwood, hardwood, and regeneration. The only significant detectable age difference would be between an established forest versus a young (or denuded) forest. The red or near infrared bands would be better for discrimination; phenological early and late spring data would be better than winter. And a temporal analysis would be superior to single-season analysis. Lastly, two spectral bands would be most cost effective for computer analysis. The study site was Sam Houston National Forest of East Texas, a typical forest in the Flatwoods Zone, Southern Region, U. S. Forest Service
Kondo Effect in Fermi Systems with a Gap: A Renormalization Group Study
We present the results of a Wilson Renormalization Group study of the
single-impurity Kondo and Anderson models in a system with a gap in the
conduction electron spectrum. The behavior of the impurity susceptibility and
the zero-frequency response function, are discussed in the
cases with and without particle-hole symmetry. In addition, for the asymmetric
Anderson model the correlation functions, , are computed.Comment: 10 pages, 10 figure
Data resolution versus forestry classification
There are no author-identified significant results in this report
Phase Coexistence Near a Morphotropic Phase Boundary in Sm-doped BiFeO3 Films
We have investigated heteroepitaxial films of Sm-doped BiFeO3 with a
Sm-concentration near a morphotropic phase boundary. Our high-resolution
synchrotron X-ray diffraction, carried out in a temperature range of 25C to
700C, reveals substantial phase coexistence as one changes temperature to
crossover from a low-temperature PbZrO3-like phase to a high-temperature
orthorhombic phase. We also examine changes due to strain for films greater or
less than the critical thickness for misfit dislocation formation.
Particularly, we note that thicker films exhibit a substantial volume collapse
associated with the structural transition that is suppressed in strained thin
films
Theories for multiple resonances
Two microscopic theories for multiple resonances in nuclei are compared,
n-particle-hole RPA and quantized Time-Dependent Hartree-Fock (TDHF). The
Lipkin-Meshkov-Glick model is used as test case. We find that quantized TDHF is
superior in many respects, except for very small systems.Comment: 14 Pages, 3 figures available upon request
Genetic screening of 202 individuals with congenital limb malformations and requiring reconstructive surgery
BACKGROUND: Congenital limb malformations (CLMs) are common and present to a variety of specialties, notably plastic and orthopaedic surgeons, and clinical geneticists. The authors aimed to characterise causative mutations in an unselected cohort of patients with CLMs requiring reconstructive surgery. METHODS: 202 patients presenting with CLM were recruited. The authors obtained G-banded karyotypes and screened EN1, GLI3, HAND2, HOXD13, ROR2, SALL1, SALL4, ZRS of SHH, SPRY4, TBX5, TWIST1 and WNT7A for point mutations using denaturing high performance liquid chromatography (DHPLC) and direct sequencing. Multiplex ligation dependent probe amplification (MLPA) kits were developed and used to measure copy number in GLI3, HOXD13, ROR2, SALL1, SALL4, TBX5 and the ZRS of SHH. RESULTS: Within the cohort, causative genetic alterations were identified in 23 patients (11%): mutations in GLI3 (n = 5), HOXD13 (n = 5), the ZRS of SHH (n = 4), and chromosome abnormalities (n = 4) were the most common lesions found. Clinical features that predicted the discovery of a genetic cause included a bilateral malformation, positive family history, and having increasing numbers of limbs affected (all p<0.01). Additionally, specific patterns of malformation predicted mutations in specific genes. CONCLUSIONS: Based on higher mutation prevalence the authors propose that GLI3, HOXD13 and the ZRS of SHH should be prioritised for introduction into molecular genetic testing programmes for CLM. The authors have developed simple criteria that can refine the selection of patients by surgeons for referral to clinical geneticists. The cohort also represents an excellent resource to test for mutations in novel candidate genes
Role of the employment status and education of mothers in the prevalence of intestinal parasitic infections in Mexican rural schoolchildren
<p><b>Background:</b> Intestinal parasitic infections are a public health problem in developing countries such as Mexico. As a result, two governmental programmes have been implemented: a) "National Deworming Campaign" and b) "Opportunities" aimed at maternal care. However, both programmes are developed separately and their impact is still unknown. We independently investigated whether a variety of socio-economic factors, including maternal education and employment levels, were associated with intestinal parasite infection in rural school children.</p>
<p><b>Methods:</b> This cross-sectional study was conducted in 12 rural communities in two Mexican states. The study sites and populations were selected on the basis of the following traits: a) presence of activities by the national administration of albendazole, b) high rates of intestinal parasitism, c) little access to medical examination, and d) a population having less than 2,500 inhabitants. A total of 507 schoolchildren (mean age 8.2 years) were recruited and 1,521 stool samples collected (3 per child). Socio-economic information was obtained by an oral questionnaire. Regression modelling was used to determine the association of socio-economic indicators and intestinal parasitism.</p>
<p><b>Results:</b> More than half of the schoolchildren showed poliparasitism (52%) and protozoan infections (65%). The prevalence of helminth infections was higher in children from Oaxaca (53%) than in those from Sinaloa (33%) (p < 0.0001). Giardia duodenalis and Hymenolepis nana showed a high prevalence in both states. Ascaris lumbricoides, Trichuris trichiura and Entamoeba hystolitica/dispar showed low prevalence. Children from lower-income families and with unemployed and less educated mothers showed higher risk of intestinal parasitism (odds ratio (OR) 6.0, 95% confidence interval (CI) 1.6–22.6; OR 4.5, 95% CI 2.5–8.2; OR 3.3, 95% CI 1.5–7.4 respectively). Defecation in open areas was also a high risk factor for infection (OR 2.4, 95% CI 2.0–3.0).</p>
<p><b>Conclusion:</b> Intestinal parasitism remains an important public health problem in Sinaloa (north-western Mexico) and Oaxaca (south-eastern Mexico). Lower income, defecation in open areas, employment status and a lower education level of mothers were the significant factors related to these infections. We conclude that mothers should be involved in health initiatives to control intestinal parasitism in Mexico.</p>
Four problems regarding representable functors
Let , be two rings, an -coring and the
category of left -comodules. The category of all representable functors is shown to be equivalent to the opposite of the
category . For an -bimodule we give
necessary and sufficient conditions for the induction functor to be: a representable functor, an
equivalence of categories, a separable or a Frobenius functor. The latter
results generalize and unify the classical theorems of Morita for categories of
modules over rings and the more recent theorems obtained by Brezinski,
Caenepeel et al. for categories of comodules over corings.Comment: 16 pages, the second versio
Appearance of Flat Bands and Edge States in Boron-Carbon-Nitride Nanoribbons
Presence of flat bands and edge states at the Fermi level in graphene
nanoribbons with zigzag edges is one of the most interesting and attracting
properties of nanocarbon materials but it is believed that they are quite
fragile states and disappear when B and N atoms are doped at around the edges.
In this paper, we theoretically investigate electronic and magnetic properties
of boron-carbon-nitride (BCN) nanoribbons with zigzag edges where the outermost
C atoms on the edges are alternately replaced with B and N atoms using the
first principles calculations. We show that BCN nanoribbons have the flat bands
and edge states at the Fermi level in both H_2 rich and poor environments. The
flat bands are similar to those at graphene nanoribbons with zigzag edges, but
the distributions of charge and spin densities are different between them. A
tight binding model and the Hubbard model analysis show that the difference in
the distribution of charge and spin densities is caused by the different site
energies of B and N atoms compared with C atoms.Comment: 5 pages; 3 figure
Plasma-Induced Frequency Chirp of Intense Femtosecond Lasers and Its Role in Shaping High-Order Harmonic Spectral Lines
We investigate the self-phase modulation of intense femtosecond laser pulses
propagating in an ionizing gas and its effects on collective properties of
high-order harmonics generated in the medium. Plasmas produced in the medium
are shown to induce a positive frequency chirp on the leading edge of the
propagating laser pulse, which subsequently drives high harmonics to become
positively chirped. In certain parameter regimes, the plasma-induced positive
chirp can help to generate sharply peaked high harmonics, by compensating for
the dynamically-induced negative chirp that is caused by the steep intensity
profile of intense short laser pulses.Comment: 5 pages, 5 figure
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