11,166 research outputs found
Electron correlations in a C fullerene cluster: A lattice density-functional study of the Hubbard model
The ground-state properties of C fullerene clusters are determined in
the framework of the Hubbard model by using lattice density-functional theory
(LDFT) and scaling approximations to the interaction-energy functional. Results
are given for the ground-state energy, kinetic and Coulomb energies, local
magnetic moments, and charge-excitation gap, as a function of the Coulomb
repulsion and for electron or hole doping close half-band
filling (). The role of electron correlations is analyzed by
comparing the LDFT results with fully unrestricted Hartree-Fock (UHF)
calculations which take into account possible noncollinear arrangements of the
local spin-polarizations. The consequences of the spin-density-wave symmetry
breaking, often found in UHF, and the implications of this study for more
complex fullerene structures are discussed.Comment: 18 pages, 7 figures, Submitted to PR
The Characterization of Effective Electromagnetic Fields on the Safety and Quality of Low-Moisture Foods (EFFS) - Prototype Device Development
Contamination of low-moisture foods including flour, wheat grain, baby formula, and more, have increasingly become a concern due to sanitizing challenges. While industrial food processors have long used RF heating to sanitize mass quantities, an equivalent consumer device is absent from the market today. The Characterization of Effective Electromagnetic Fields on the Safety and Quality of Low-Moisture Foods (EEFS) project is an interdisciplinary effort to develop an RF heating consumer device to sanitize low-moisture foods.
A prototype device was designed to sanitize low-moisture food items using RF heating acceptable for commercial or consumer applications
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Damages caused by cotton rat, Sigmodon hispidus zanjonensis, on sugar cane in San Pedrosula, Honduras
Technical assistance was given to CompañĂa Azucarera Hondureña, S.A. (Agro-Industrial Co.), Honduras, Central America, to determine if a campaign against noxious rodents to agriculture crops was needed. Several trappings were carried out at different places using snap traps to determine the population structure of rodents associated with the crop, and live traps to determine the index or density of the Sigmodon hispidus rat population, which was identified as being responsible for the damage to sugarcane. Results were 43.24% adult males, 14.86% young males, 31.41% adult females, and 10.47% young females. Of the adult females captured, 54.83% were pregnant with an average of 3 to 4 embryos per rat. A control demonstration combat was carried out at one of the experimental stations with a bait prepared with 2% zinc phosphide in a place where it had been previously determined there was a population of 39 rats per hectare. After such control, the population was reduced to 18 rats per hectare, which represents an efficiency of 53.85%. An evaluation of damages was also measured at different places to determine the degree of loss caused by the rats, which proved to be 22.79% damage. The size of the sample was estimated in 3 samples per hectare, with a level of confidence of 95%
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Electronic properties of SnO2-based ceramics with double function of varistor and humidity sensor
This is the post-print version of the article. The official published version can be obtained from the link below - Copyright @ 2010 AD-Tech.Tin dioxide based varistor ceramics SnO2-Co3O4-Nb2O5-Cr2O3-xCuO (x=0; 0.05; 0.1 and 0.5) were made and their electrical properties were studied. The highest nonlinearity coefficient and electric field (at current density 10-3 A cm-2) were obtained for 0.1 mol.% CuO addition. It was observed that low-field electrical conductivity is increased with relative humidity, therefore, materials obtained exhibit double function of varistor and humidity sensor. The highest humidity sensitivity coefficient is found for SnO2-Co3O4-Nb2O5-Cr2O3 ceramics (without CuO). Observed varistor and humidity-sensitive properties are explained in the frames of grain-boundary double Schottky barrier concept as a decrease of the barrier height with electric field or relative humidity. Using suggested simple theory and data obtained on isothermal capacitance relaxation, the energy of the grain-boundary monoenergetic trapping states were estimated. These values are less than found for activation energy of electrical conduction (as a measure of the barrier height). These observations confirm the barrier concept.This work is funded by the Royal Society, United Kingdom (2007R1/R26999)
Scintillation observations at Ancon and Jicamarca Observatories
Satellite scintillation and diffraction pattern scale size distribution from ionospheric irregularitie
Characterization of Ascaris from Ecuador and Zanzibar
To shed light on the epidemiology of ascariasis in Ecuador and Zanzibar, 177 adult worms retrieved by chemo-expulsion from either people or pigs were collected, measured and subjected to polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of the ribosomal internal transcribed spacer (ITS) region. Upon double digestion with RsaI and HaeIII, PCR-RFLP analysis revealed the presence of A. lumbricoides in people and A. suum in pigs in Ecuador. In contrast, while there are no pigs on Zanzibar, of the 56 worms obtained from people, one was genotyped as A. suum. No additional genetic variation was detected upon further PCR-RFLP analysis with several other restriction enzymes. Upon measurement, worm mass and length differed by location and by species, A. suum being lighter and longer. While there is no evidence to suggest zoonotic transmission in Ecuador, an enduring historical signature of previous zoonotic transmission remains on Zanzibar
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