1,843 research outputs found
Coulomb effects in artificial molecules
We study the capacitance spectra of artificial molecules consisting of two
and three coupled quantum dots from an extended Hubbard Hamiltonian model that
takes into account quantum confinement, intra- and inter-dot Coulomb
interaction and tunneling coupling between all single particle states in
nearest neighbor dots. We find that, for weak coupling, the interdot Coulomb
interaction dominates the formation of a collective molecular state. We also
calculate the effects of correlations on the tunneling probability through the
evaluation of the spectral weights, and corroborate the importance of selection
rules for understanding experimental conductance spectra.Comment: dvi file and 4 postscript figures, all included in uu file. To appear
in Superlatt. and Microstr. Also available at
http://www.phy.ohiou.edu/~ulloa/ulloa.htm
Bipolar spin filter in a quantum dot molecule
We show that the tunable hybridization between two lateral quantum dots
connected to non-magnetic current leads in a `hanging-dot' configuration that
can be used to implement a bipolar spin filter. The competition between Zeeman,
exchange interaction, and interdot tunneling (molecular hybridization) yields a
singlet-triplet transition of the double dot {\it ground state} that allows
spin filtering in Coulomb blockade experiments. Its generic nature should make
it broadly useful as a robust bidirectional spin polarizer.Comment: 5 pages, 3 figures (to appear in Appl. Phys. Lett.
Anisotropic electron g-factor in quantum dots with spin-orbit interaction
g-factor tuning of electrons in quantum dots is studied as function of
in-plane and perpendicular magnetic fields for different confinements. Rashba
and Dresselhaus effects are considered, and comparison is made between wide-
and narrow-gap materials. The interplay between magnetic fields and intrinsic
spin-orbit coupling is analyzed, with two distinct phases found in the spectrum
for GaAs in perpendicular field. The anisotropy of the g-factor is reported,
and good agreement with available experimental findings is obtained.Comment: 5 pages, 4 figs. (higher resol. figs. under request
Zebrafish as animal model for aquaculture nutrition research.
The aquaculture industry continues to promote the diversification of ingredients used in aquafeed in order to achieve a more sustainable aquaculture production system. The evaluation of large numbers of diets in aquaculture species is costly and requires time-consuming trials in some species. In contrast, zebrafish (Danio rerio) can solve these drawbacks as an experimental model, and represents an ideal organism to carry out preliminary evaluation of diets. In addition, zebrafish has a sequenced genome allowing the efficient utilization of new technologies, such as RNA-sequencing and genotyping platforms to study the molecular mechanisms that underlie the organism's response to nutrients. Also, biotechnological tools like transgenic lines with fluorescently labeled neutrophils that allow the evaluation of the immune response in vivo, are readily available in this species. Thus, zebrafish provides an attractive platform for testing many ingredients to select those with the highest potential of success in aquaculture. In this perspective article aspects related to diet evaluation in which zebrafish can make important contributions to nutritional genomics and nutritional immunity are discussed
Spatial correlations in chaotic nanoscale systems with spin-orbit coupling
We investigate the statistical properties of wave functions in chaotic
nanostructures with spin-orbit coupling (SOC), focussing in particular on
spatial correlations of eigenfunctions. Numerical results from a microscopic
model are compared with results from random matrix theory in the crossover from
the gaussian orthogonal to the gaussian symplectic ensembles (with increasing
SOC); one- and two-point distribution functions were computed to understand the
properties of eigenfunctions in this crossover. It is found that correlations
of wave function amplitudes are suppressed with SOC; nevertheless,
eigenfunction correlations play a more important role in the two-point
distribution function(s), compared to the case with vanishing SOC. Experimental
consequences of our results are discussed.Comment: Submitted to PR
Picophytoplankton biomass distribution in the global ocean
The smallest marine phytoplankton, collectively termed picophytoplankton, have been routinely enumerated by flow cytometry since the late 1980s during cruises throughout most of the world ocean. We compiled a database of 40 946 data points, with separate abundance entries for Prochlorococcus, Synechococcus and picoeukaryotes. We use average conversion factors for each of the three groups to convert the abundance data to carbon biomass. After gridding with 1? spacing, the database covers 2.4% of the ocean surface area, with the best data coverage in the North Atlantic, the South Pacific and North Indian basins, and at least some data in all other basins. The average picophytoplankton biomass is 12 ± 22 µg Cl-1 or 1.9 g Cm-2. We estimate a total global picophytoplankton biomass of 0.53–1.32 Pg C (17–39% Prochlorococcus, 12–15% Synechococcus and 49–69% picoeukaryotes), with an intermediate/best estimate of 0.74 Pg C. Future efforts in this area of research should focus on reporting calibrated cell size and collecting data in undersampled regions
Lactoferrin Decreases the Intestinal Inflammation Triggered by a Soybean Meal-Based Diet in Zebrafish
Indexación: Web of ScienceIntestinal inflammation is a harmful condition in fish that can be triggered by the ingestion of soybean meal. Due to the positive costs-benefits ratio of including soybean meal in farmed fish diets, identifying additives with intestinal anti-inflammatory effects could contribute to solving the issues caused by this plant protein. This study evaluated the effect of incorporating lactoferrin (LF) into a soybean meal-based diet on intestinal inflammation in zebrafish. Larvae were fed with diets containing 50% soybean meal (50SBM) or 50SBM supplemented with LF to 0.5, 1, 1.5 g/kg (50SBM+LF0.5; 50SBM+LF1.0; 50SBM+LF1.5). The 50SBM+LF1.5 diet was the most efficient and larvae had a reduced number of neutrophils in the intestine compared with 50SBM larvae and an indistinguishable number compared with control larvae. Likewise, the transcription of genes involved in neutrophil migration and intestinal mucosal barrier functions (mmp9, muc2.2, and beta-def-1) were increased in 50SBM larvae but were normally expressed in 50SBM+LF1.5 larvae. To determine the influence of intestinal inflammation on the general immune response, larvae were challenged with Edwardsiella tarda. Larvae with intestinal inflammation had increased mortality rate compared to control larvae. Importantly, 50SBM+LF1.5 larvae had a mortality rate lower than control larvae. These results demonstrate that LF displays a dual effect in zebrafish, acting as an intestinal anti-inflammatory agent and improving performance against bacterial infection.http://www.hindawi.com/journals/jir/2016/1639720
Coherent control of indirect excitonic qubits in optically driven quantum dot molecules
We propose an optoelectronic scheme to define and manipulate an indirect
neutral exciton qubit within a quantum dot molecule. We demonstrate coherent
dynamics of indirect excitons resilient against decoherence effects, including
direct exciton spontaneous recombination. For molecules with large interdot
separation, the exciton dressed spectrum yields an often overlooked avoided
crossing between spatially indirect exciton states. Effective two level system
Hamiltonians are extracted by Feshbach projection over the multilevel exciton
configurations. An adiabatic manipulation of the qubit states is devised using
time dependent electric field sweeps. The exciton dynamics yields the necessary
conditions for qubit initialization and near unitary rotations in the
picosecond time scale, driven by the system internal dynamics. Despite the
strong influence of laser excitation, charge tunneling, and interdot
dipole-dipole interactions, the effective relaxation time of indirect excitons
is much longer than the direct exciton spontaneous recombination time,
rendering indirect excitons as potential elemental qubits in more complex
schemes.Comment: Submitted to PRB, 11 pages and 6 figure
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