1,290 research outputs found
Analytic results for particles with interaction in two dimensions and an external magnetic field
The -dimensional quantum problem of particles (e.g. electrons) with
interaction in a two-dimensional parabolic potential
(e.g. quantum dot) and magnetic field , reduces exactly to solving a
-dimensional problem which is independent of and . An
exact, infinite set of relative mode excitations are obtained for any . The
problem reduces to that of a ficticious particle in a two-dimensional,
non-linear potential of strength , subject to a ficticious magnetic
field , the relative angular momentum.Comment: To appear in Physical Review Letters (in press). RevTeX file. Two
figures available from [email protected] or
[email protected]
Two and three electrons in a quantum dot: 1/|J| - expansion
We consider systems of two and three electrons in a two-dimensional parabolic
quantum dot. A magnetic field is applied perpendicularly to the electron plane
of motion. We show that the energy levels corresponding to states with high
angular momentum, J, and a low number of vibrational quanta may be
systematically computed as power series in 1/|J|. These states are relevant in
the high-B limit.Comment: LaTeX, 15 pages,6 postscript figure
Microscopic analytical theory of a correlated, two-dimensional N-electron gas in a magnetic field
We present a microscopic, analytical theory describing a confined N-electron
gas in two dimensions subject to an external magnetic field. The number of
electrons N and strength of the electron-electron interaction can be
arbitrarily large, and all Landau levels are included implicitly. A possible
connection with the Integer and Fractional Quantum Hall Effects is proposed.Comment: The revised version contains minor changes to text. To be published
in J. Phys: Condens. Mat
Entangled Electronic States in Multiple Quantum-Dot Systems
We present an analytically solvable model of colinear, two-dimensional
quantum dots, each containing two electrons. Inter-dot coupling via the
electron-electron interaction gives rise to sets of entangled ground states.
These ground states have crystal-like inter-plane correlations and arise
discontinously with increasing magnetic field. Their ranges and stabilities are
found to depend on dot size ratios, and to increase with .Comment: To appear in Physical Review B (in press). RevTeX file. Figures
available from [email protected]
Stable ring vortex solitons in Bessel optical lattices
Stable ring vortex solitons, featuring a bright-shape, appear to be very rare
in nature. However, here we show that they exist and can be made dynamically
stable in defocusing cubic nonlinear media with an imprinted Bessel optical
lattice. We find the families of vortex lattice solitons and reveal their
salient properties, including the conditions required for their stability. We
show that the higher the soliton topological charge, the deeper the lattice
modulation necessary for stabilization.Comment: 14 pages, 4 figures, submitted to Physical Review Letter
The cirrhotic liver is depleted of docosahexaenoic acid (DHA), a key modulator of NF-ÎșB and TGFÎČ pathways in hepatic stellate cells
Liver cirrhosis results from chronic hepatic damage and is characterized by derangement of the organ architecture
with increased liver fibrogenesis and defective hepatocellular function. It frequently evolves into progressive hepatic
insufficiency associated with high mortality unless liver transplantation is performed. We have hypothesized that the
deficiency of critical nutrients such as essential omega-3 fatty acids might play a role in the progression of liver
cirrhosis. Here we evaluated by LC-MS/MS the liver content of omega-3 docosahexaenoic fatty acid (DHA) in cirrhotic
patients and investigated the effect of DHA in a murine model of liver injury and in the response of hepatic stellate
cells (HSCs) (the main producers of collagen in the liver) to pro-fibrogenic stimuli. We found that cirrhotic livers exhibit
a marked depletion of DHA and that this alteration correlates with the progression of the disease. Administration of
DHA exerts potent anti-fibrogenic effects in an acute model of liver damage. Studies with HSCs show that DHA inhibits
fibrogenesis more intensely than other omega-3 fatty acids. Data from expression arrays revealed that DHA blocks
TGFÎČ and NF-ÎșB pathways. Mechanistically, DHA decreases late, but not early, SMAD3 nuclear accumulation and
inhibits p65/RelA-S536 phosphorylation, which is required for HSC survival. Notably, DHA increases ADRP expression,
leading to the formation of typical quiescence-associated perinuclear lipid droplets. In conclusion, a marked depletion
of DHA is present in the liver of patients with advanced cirrhosis. DHA displays anti-fibrogenic activities on HSCs
targeting NF-ÎșB and TGFÎČ pathways and inducing ADPR expression and quiescence in these cells
Universal quantum gates based on both geometric and dynamic phases in quantum dots
A large-scalable quantum computer model, whose qubits are represented by the
subspace subtended by the ground state and the single exciton state on
semiconductor quantum dots, is proposed. A universal set of quantum gates in
this system may be achieved by a mixed approach, composed of dynamic evolution
and nonadibatic geometric phase.Comment: 4 pages, to appear in Chin. Phys. Let
Quantum-Information Processing with Semiconductor Macroatoms
An all optical implementation of quantum information processing with
semiconductor macroatoms is proposed. Our quantum hardware consists of an array
of semiconductor quantum dots and the computational degrees of freedom are
energy-selected interband optical transitions. The proposed quantum-computing
strategy exploits exciton-exciton interactions driven by ultrafast sequences of
multi-color laser pulses. Contrary to existing proposals based on charge
excitations, the present all-optical implementation does not require the
application of time-dependent electric fields, thus allowing for a
sub-picosecond, i.e. decoherence-free, operation time-scale in realistic
state-of-the-art semiconductor nanostructures.Comment: 11 pages, 5 figures, to be published in Phys. Rev. Lett., significant
changes in the text and new simulations (figure 3
Gaps between calcium recommendations to prevent pre-eclampsia and current intakes in one hospital in Argentina
Background: Hypertensive disorders are a major cause of maternal mortality. In Latin America and the Caribbean, pre-eclampsia accounts for approximately one in every four maternal deaths. The World Health Organization recommends calcium supplementation during pregnancy for the prevention and treatment of pre-eclampsia and eclampsia in locations where dietary calcium intake is low. Calcium intake in Argentina is reported to be below WHO recommended levels; however, calcium intake from supplements and water has not been fully evaluated.The objective of this study was to evaluate calcium intake from supplements and water in a group of pregnant women.
Methods: This cross-sectional study was conducted at a maternity hospital in the city of Buenos Aires, Argentina. Questionnaires were verbally administered to women attending a routine antenatal care visit. Participants were 18 years of age or older and in their third trimester of pregnancy. Participants were first interviewed to evaluate nutritional supplement consumption and a subgroup was invited to undergo a 24-hour dietary recall.
Results: 137 women meeting inclusion criteria consented to participate.The average participant age was 27 years (SD ± 5.9), and all resided in an urban setting. None of the subjects took calcium supplements specifically, although 24 (17%) recalled taking supplements or antacids which contributed to their calcium intake. Mean calcium intake was 663mg SD ±389 for those women completing the 24-hour dietary recall,. This value increased to 706 mg SD ±387 upon considering water intake and measuring chemical composition of water from the areas where women lived at the time of the interview and was further increased to 719 mg (SD ±392) when calcium from supplements was taken into consideration.
Conclusions: None of the subjects were consuming calcium supplements. Taking into account the low calcium intake in this population, diverse strategies would be required to comply with recommendations.Facultad de Ciencias ExactasFacultad de IngenierĂ
Medium-modified evolution of multiparticle production in jets in heavy-ion collisions
The energy evolution of medium-modified average multiplicities and
multiplicity fluctuations in quark and gluon jets produced in heavy-ion
collisions is investigated from a toy QCD-inspired model. In this model, we use
modified splitting functions accounting for medium-enhanced radiation of gluons
by a fast parton which propagates through the quark gluon plasma. The leading
contribution of the standard production of soft hadrons is found to be enhanced
by the factor while next-to-leading order (NLO) corrections are
suppressed by , where the nuclear parameter accounts for
the induced-soft gluons in the hot medium. The role of next-to-next-to-leading
order corrections (NNLO) is studied and the large amount of medium-induced soft
gluons is found to drastically affect the convergence of the perturbative
series. Our results for such global observables are cross-checked and compared
with their limits in the vacuum and a new method for solving the second
multiplicity correlator evolution equations is proposed.Comment: 21 pages and 8 figures, typo corrections, references adde
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