17,357 research outputs found
Effective Low-Energy Model for f-Electron Delocalization
We consider a Periodic Anderson Model (PAM) with a momentum-dependent
inter-band hybridization that is strongly suppressed near the Fermi level.
Under these conditions, we reduce the PAM to an effective low-energy
Hamiltonian, , by expanding in the small parameter (
is the maximum inter-band hybridization amplitude and is the hopping
integral of the broad band). The resulting model consists of a t-J f-band
coupled via the Kondo exchange to the electrons in the broad band. allows for studying the f-electron delocalization transition. The result
is a doping-induced Mott transition for the f-electron delocalization, which we
demonstrate by density-matrix renormalization group (DMRG) calculations
In vitro Culture of Several Rice Cultivars
Tissue culture methods have been established to regenerate certain rice (Oryza sativa L) cultivars, but regeneration of the rice cultivars widely grown in Arkansas has not been reported. This study has established an in vitroculture for the rice cultivars \u27Nortai\u27, \u27Starbonnet\u27, \u27Mars\u27, Tebonnet\u27, \u27Newbonnet\u27, and \u27Lemont\u27. Callus was induced in the dark at either 20 or 28 C from dehusked seeds cultured on Murashige and Skoog (MS) medium (Murashige and Skoog, 1962) containing 40 g L^-1 sucrose, 10 g L^1 agar, 0.5, 1.0, or 2.0 mg L^-1 1 2,4-dichlorophenoxyacetic acid (2,4-D) and adjusted to pH 5.7. After four weeks the calli were weighed, transferred onto MS medium containing no 2,4-D, and maintained in a 1 2-h photoperiod (65 uE m^-2 s^-1) at 25 ± 2 C to induce plant regeneration. Callus production was best when cultured on a medium containing 1.0 mg L^-1 2,4-D and incubated at 28 C. Plant regeneration was observed two to four weeks later. The percentage of calli regenerating platlets varied with the cultivar and the callus induction treatment. Callus induction at 20 C on a medium with a 2,4-D level less than 2.0 mg L^-1 enhanced the regenerability of most cultivars. Regenerates were transplanted to soil and grow normally to maturity. This system can be helpful in improving rice cultivars with tissue culture techniques such as somaclonal variant selection and somatic hybridization
Modelling of water transport through mixed-ion conducting dense ceramics
WOS: 000434365200020This study develops and demonstrates a model that characterizes defect transports, responsible for water transport within dense ceramics, and calculates the diffusion coefficients for those defects. The multi-species mass transfer processes within yttrium doped barium cerates are modelled by applying the Nernst-Planck equation to the system. The Nernst-Planck equation with suitable boundary conditions is adopted to compute defect diffusion coefficients in COMSOL Multiphysics. All related equations, based on charge and defect conservation, are solved numerically and validated experimentally. The model also predicts the concentration distribution of the defects and potential profiles throughout the membranes. The results provided convenient insights about the water transport and charge distribution as a function of membrane thickness.Ministry of National Education TurkeyMinistry of National Education - TurkeyThe authors would like to acknowledge the Ministry of National Education Turkey for funding. Also, we would like to thank Prof. Ian Metcalfe for the useful discussions and School of Chemical Engineering, Newcastle University, UK for the university"s resources
On Using Magnetic and optical methods to determine the size and characteristics of nanoparticles embedded in oxide semiconductors
Films of oxides doped with transition metals are frequently believed to have
magnetic inclusions. Magnetic methods to determine the amount of nanophases and
their magnetic characteristics are described. The amount of the sample that is
paramagnetic may also be measured. Optical methods are described and shown to
be very powerful to determine which defects are also magnetic.Comment: Manuscript of poster to be presented at MMM-Intermag 2010. Accepted
for publication in Magnetic Trans of IEE
Heavy fermions and two loop electroweak corrections to
Applying effective Lagrangian method and on-shell scheme, we analyze the
electroweak corrections to the rare decay from some
special two loop diagrams in which a closed heavy fermion loop is attached to
the virtual charged gauge bosons or Higgs. At the decoupling limit where the
virtual fermions in inner loop are much heavier than the electroweak scale, we
verify the final results satisfying the decoupling theorem explicitly when the
interactions among Higgs and heavy fermions do not contain the nondecoupling
couplings. Adopting the universal assumptions on the relevant couplings and
mass spectrum of new physics, we find that the relative corrections from those
two loop diagrams to the SM theoretical prediction on the branching ratio of
can reach 5% as the energy scale of new physics
GeV.Comment: 30 pages,4 figure
Optimum Cone Collection Period in Arkansas for Establishing In vitro Cultures of Loblolly Pine (Pinus Taeda L.)
This study was conducted to determine the optimum period to collect loblolly pine (Pinus taeda L.) cones that contain embryos with the greatest capacity to produce embryogenic callus for establishing somatic embryogenesis. Cones were collected from trees at the University of Arkansas Agricultural Experiment Station, Fayetteville, in 1991 during four consecutive months: May, June, July, and August. Seeds were extracted and disinfected in 70% ethanol for 1 min, 50% Clorox for 20 min, followed by four water rinses. Seed coats were removed, and embryos were cultured on DCR medium adjusted to pH 5.7 and supplemented with 3 mg/L 2,4-D, 0.5 mg/L 6-BAP, 30 g/L sucrose, and 6 g/L agar. Callus was induced and maintained in the dark at 20 ± 5 C. Embryos collected in May failed to proliferate; however, 55%, 88%, and 66% of the embryos cultured produced callus from June, July, and August collections, respectively. Suspension cultures were initiated from pine callus and maintained for over 6 months in MSG medium for subsequent investigation of the conversion of embryogenic complexes into mature embryos and eventually into plantlets. Evidence for embryogenesis was observed with double-staining techniques
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