238 research outputs found
Pairing in a three component Fermi gas
We consider pairing in a three-component gas of degenerate fermions. In
particular, we solve the finite temperature mean-field theory of an interacting
gas for a system where both interaction strengths and fermion masses can be
unequal. At zero temperature we find a a possibility of a quantum phase
transition between states associated with pairing between different pairs of
fermions. On the other hand, finite temperature behavior of the three-component
system reveals some qualitative differences from the two-component gas: for a
range of parameters it is possible to have two different critical temperatures.
The lower one corresponds to a transition between different pairing channels,
while the higher one corresponds to the usual superfluid-normal transition. We
discuss how these phase transitions could be observed in ultracold gases of
fermionic atoms.Comment: 10 pages, 3 figure
On the Maximal Excess Charge of the Chandrasekhar-Coulomb Hamiltonian in Two Dimensions
We show that for the straightforward quantized relativistic Coulomb
Hamiltonian of a two-dimensional atom -- or the corresponding magnetic quantum
dot -- the maximal number of electrons does not exceed twice the nuclear
charge. It result is then generalized to the presence of external magnetic
fields and atomic Hamiltonians. This is based on the positivity of |\bx|
T(\bp) + T(\bp) |\bx| which -- in two dimensions -- is false for the
non-relativistic case T(\bp) = \bp^2, but is proven in this paper for T(\bp)
= |\bp|, i.e., the ultra-relativistic kinetic energy
Noise correlations of the ultra-cold Fermi gas in an optical lattice
In this paper we study the density noise correlations of the two component
Fermi gas in optical lattices. Three different type of phases, the BCS-state
(Bardeen, Cooper, and Schieffer), the FFLO-state (Fulde, Ferrel, Larkin, and
Ovchinnikov), and BP (breach pair) state, are considered. We show how these
states differ in their noise correlations. The noise correlations are
calculated not only at zero temperature, but also at non-zero temperatures
paying particular attention to how much the finite temperature effects might
complicate the detection of different phases. Since one-dimensional systems
have been shown to be very promising candidates to observe FFLO states, we
apply our results also to the computation of correlation signals in a
one-dimensional lattice. We find that the density noise correlations reveal
important information about the structure of the underlying order parameter as
well as about the quasiparticle dispersions.Comment: 25 pages, 11 figures. Some figures are updated and text has been
modifie
Interband physics in an ultra-cold Fermi gas in an optical lattice
We study a gas of strongly polarized cold fermions in an optical lattice when
the excited p-bands are populated. We derive the relevant Hamiltonian and
discuss the expected phase diagram for both repulsive and attractive
interactions. In the parameter regime covered here, checkerboard
anti-ferromagnetic ordering is found to be possible for repulsive interactions
while for attractive interactions, transitions between different types of
paired phases are predicted.Comment: 5 pages, 2 figure
Superfluid phases of the three-species fermion gas
We discuss the zero temperature phase diagram of a dilute gas with three
fermionic species. We make use of solvable limits to conjecture the behavior of
the system in the "unitary" regions. The physics of the Thomas-Efimov effect
plays a role in these considerations. We find a rich phase diagram with
superfluid, gapless superfluid and inhomogeneous phases with different symmetry
breaking patterns. We then discuss one particular possible experimental
implementation in a system of ^6Li atoms and the possible phases arising in
this system as an external magnetic field is varied across three overlaping
Feshbach resonances. We also suggest how to experimentally distinguish the
different phases.Comment: 4 pages, 1 figure, typos corrected and references adde
Characterization of seedling and adult-plant resistance to stem rust race Ug99 in Iranian bread wheat landraces
The full-length infectious cDNA clone was constructed and sequenced from the strain DM of echovirus 9, which was recently isolated from a 6-week-old child at the clinical onset of type 1 diabetes. Parallel with the isolate DM, the full-length infectious cDNA clone of the prototype strain echovirus 9 Barty (Barty-INF), was constructed and sequenced. Genetic relationships of the sequenced echo 9 viruses to the other members of the human enterovirus type B species were studied by phylogenetic analyses. Comparison of capsid protein sequences showed that the isolate DM was closely related to both prototype strains: Hill and Barty-INF. The only exception was the inner capsid protein VP4 where serotype specificity was not evident and the isolate DM clustered with the strain Hill and the strain Barty-INF with echovirus 30 Bastianni. Likewise, the nonstructural protein coding region, P2P3, of isolate DM was more similar to strain Hill than to strain Barty-INF. However, like echovirus 9 Barty, the isolate DM contained the RGD-motif in the carboxy terminus of capsid protein VP1. By blocking experiments using an RGD-containing peptide and a polyclonal rabbit antiserum to the alpha(v)beta(3)-integrin, it was shown that this molecule works as a cellular receptor for isolate DM. By using primary human islets, it was shown that the isolate DM is capable of infecting insulin-producing beta-cells like the corresponding prototype strains did. However, only isolate DM was clearly cytolytic for beta-cells. The infectious clones that were made allow further investigations of the molecular features responsible for the diabetogenicity of the isolate DM
3D reflection seismic investigation for mine planning and exploration in the Kevitsa Ni-Cu-PGE deposit, Northern Finland
A 3D reflection seismic survey was conducted over an area of about 9 km2 at the Kevitsa Ni-Cu-PGE (platinum group elements) deposit, Northern Finland. The principal objective of the survey was to image major fault and fracture zones at depth. Understanding the geometry of these zones is important for designing a steep open-pit for mining. Initial processing results suggest that the 3D seismic survey has been successful in imaging both gently dipping and steeply dipping reflections as shallow as 50 ms (or about 150 m), many of which correlate with fault systems and lithological contacts observed at the surface. Several new target areas can be identified in the seismic data that require further investigations for their mineralization potential
FORG3D: Force-directed 3D graph editor for visualization of integrated genome scale data
<p>Abstract</p> <p>Background</p> <p>Genomics research produces vast amounts of experimental data that needs to be integrated in order to understand, model, and interpret the underlying biological phenomena. Interpreting these large and complex data sets is challenging and different visualization methods are needed to help produce knowledge from the data.</p> <p>Results</p> <p>To help researchers to visualize and interpret integrated genomics data, we present a novel visualization method and bioinformatics software tool called FORG3D that is based on real-time three-dimensional force-directed graphs. FORG3D can be used to visualize integrated networks of genome scale data such as interactions between genes or gene products, signaling transduction, metabolic pathways, functional interactions and evolutionary relationships. Furthermore, we demonstrate its utility by exploring gene network relationships using integrated data sets from a <it>Caenorhabditis elegans </it>Parkinson's disease model.</p> <p>Conclusion</p> <p>We have created an open source software tool called FORG3D that can be used for visualizing and exploring integrated genome scale data.</p
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