288 research outputs found
On a class of nonlocal elliptic problems via Galerkin method
AbstractIn this paper we study existence and uniqueness of solutions to some cases of the following nonlocal elliptic problem: −Δu=(g(x,u))α(∫Ωf(x,u))β with zero Dirichlet boundary conditions on a bounded and smooth domain of RN and also when Ω=RN, where α and β are real constants
A utilização de alumino-silicatos como agentes protetores contra a aflatoxicose na alimentação de frangos de corte
This experiment was conducted to evaluate the efficiency of two alumino-silicates against deleterious effects of a toxin on growth performance and blood parameters of male broilers. The products did not counteract the negative effects on growth performance. Total protein and gtotamic-oxalacetic transaminase in blood from birds fed contaminated and non contaminated rations, were negatively affected (PO experimento foi conduzido para testar a eficiência de dois alumino-silicatos, no controle da aflatoxicose em frangos de corte (machos). Foram efetuadas análises de sangue para verificação da influência da aflatoxina no perfil sanguíneo das aves. Os resultados mostraram efeito negativo (
Normal-state conductivity in underdoped La_{2-x}Sr_xCuO_4 thin films: Search for nonlinear effects related to collective stripe motion
We report a detailed study of the electric-field dependence of the
normal-state conductivity in La_{2-x}Sr_xCuO_4 thin films for two
concentrations of doped holes, x=0.01 and 0.06, where formation of diagonal and
vertical charged stripes was recently suggested. In order to elucidate whether
high electric fields are capable of depinning the charged stripes and inducing
their collective motion, we have measured current-voltage characteristics for
various orientations of the electric field with respect to the crystallographic
axes. However, even for the highest possible fields (~1000 V/cm for x=0.01 and
\~300 V/cm for x=0.06) we observed no non-linear-conductivity features except
for those related to the conventional Joule heating of the films. Our analysis
indicates that Joule heating, rather than collective electron motion, may also
be responsible for the non-linear conductivity observed in some other 2D
transition-metal oxides as well. We discuss that a possible reason why moderate
electric fields fail to induce a collective stripe motion in layered oxides is
that fairly flexible and compressible charged stripes can adjust themselves to
the crystal lattice and individual impurities, which makes their pinning much
stronger than in the case of conventional rigid charge-density waves.Comment: 10 pages, 10 figures, accepted for publication in Phys. Rev.
Competition between quantum-liquid and electron-solid phases in intermediate Landau levels
On the basis of energy calculations we investigate the competition between
quantum-liquid and electron-solid phases in the Landau levels n=1,2, and 3 as a
function of their partial filling factor. Whereas the quantum-liquid phases are
stable only in the vicinity of quantized values 1/(2s+1) of the partial filling
factor, an electron solid in the form of a triangular lattice of clusters with
a few number of electrons (bubble phase) is energetically favorable between
these fillings. This alternation of electron-solid phases, which are insulating
because they are pinned by the residual impurities in the sample, and quantum
liquids displaying the fractional quantum Hall effect explains a recently
observed reentrance of the integral quantum Hall effect in the Landau levels
n=1 and 2. Around half-filling of the last Landau level, a uni-directional
charge density wave (stripe phase) has a lower energy than the bubble phase.Comment: 12 pages, 9 figures; calculation of exact exchange potential for
n=1,2,3 included, energies of electron-solid phases now calculated with the
help of the exact potential, and discussion of approximation include
Stripes and holes in a two-dimensional model of spinless fermions and hardcore bosons
We consider a Hubbard-like model of strongly-interacting spinless fermions
and hardcore bosons on a square lattice, such that nearest neighbor occupation
is forbidden. Stripes (lines of holes across the lattice forming antiphase
walls between ordered domains) are a favorable way to dope this system below
half-filling. The problem of a single stripe can be mapped to a spin-1/2 chain,
which allows understanding of its elementary excitations and calculation of the
stripe's effective mass for transverse vibrations. Using Lanczos exact
diagonalization, we investigate the excitation gap and dispersion of a hole on
a stripe, and the interaction of two holes. We also study the interaction of
two, three, and four stripes, finding that they repel, and the interaction
energy decays with stripe separation as if they are hardcore particles moving
in one (transverse) direction. To determine the stability of an array of
stripes against phase separation into particle-rich phase and hole-rich liquid,
we evaluate the liquid's equation of state, finding the stripe-array is not
stable for bosons but is possibly stable for fermions.Comment: 24 pages, 18 figure
Recommended from our members
Cytochrome P450 isoforms 1A1, 1B1 AND 2W1 as targets for therapeutic intervention in head and neck cancer
YesEpidemiological studies have shown that head and neck cancer (HNC) is a complex multistage process that in part involves exposure to a combination of carcinogens and the capacity of certain drug-metabolising enzymes including cytochrome P450 (CYP) to detoxify or activate such carcinogens. In this study, CYP1A1, CYP1B1 and CYP2W1 expression in HNC was correlated with potential as target for duocarmycin prodrug activation and selective therapy. In the HNC cell lines, elevated expression was shown at the gene level for CYP1A1 and CYP1B1 whereas CYP2W1 was hardly detected. However, CYP2W1 was expressed in FaDu and Detroit-562 xenografts and in a cohort of human HNC samples. Functional activity was measured in Fadu and Detroit-562 cells using P450-Glo™ assay. Antiproliferative results of duocarmycin prodrugs ICT2700 and ICT2706 revealed FaDu and Detroit-562 as the most sensitive HNC cell lines. Administration of ICT2700 in vivo using a single dose of ICT2700 (150 mg/kg) showed preferential inhibition of small tumour growth (mean size of 60 mm3) in mice bearing FaDu xenografts. Significantly, our findings suggest a potential targeted therapeutic approach to manage HNCs by exploiting intratumoural CYP expression for metabolic activation of duocarmycin-based prodrugs such as ICT2700.The authors would like to thank Bradford Institute for Health Research for funding a PhD studentship to DP through a competitive scheme and Yorkshire Cancer Research programme Grant (B381PA) for supporting our cytochrome P450-focused drug discovery research
The Effect of Chemical Information on the Spatial Distribution of Fruit Flies: I Model Results
Animal aggregation is a general phenomenon in ecological systems. Aggregations are generally considered as an evolutionary advantageous state in which members derive the benefits of protection and mate choice, balanced by the costs of limiting resources and competition. In insects, chemical information conveyance plays an important role in finding conspecifics and forming aggregations. In this study, we describe a spatio-temporal simulation model designed to explore and quantify the effects of these infochemicals, i.e., food odors and an aggregation pheromone, on the spatial distribution of a fruit fly (Drosophila melanogaster) population, where the lower and upper limit of local population size are controlled by an Allee effect and competition. We found that during the spatial expansion and strong growth of the population, the use of infochemicals had a positive effect on population size. The positive effects of reduced mortality at low population numbers outweighed the negative effects of increased mortality due to competition. At low resource densities, attraction toward infochemicals also had a positive effect on population size during recolonization of an area after a local population crash, by decreasing the mortality due to the Allee effect. However, when the whole area was colonized and the population was large, the negative effects of competition on population size were larger than the positive effects of the reduction in mortality due to the Allee effect. The use of infochemicals thus has mainly positive effects on population size and population persistence when the population is small and during the colonization of an area
Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS
We present the results of a search for new, heavy particles that decay at a
significant distance from their production point into a final state containing
charged hadrons in association with a high-momentum muon. The search is
conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV
and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS
detector operating at the Large Hadron Collider. Production of such particles
is expected in various scenarios of physics beyond the standard model. We
observe no signal and place limits on the production cross-section of
supersymmetric particles in an R-parity-violating scenario as a function of the
neutralino lifetime. Limits are presented for different squark and neutralino
masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final
version to appear in Physics Letters
- …