66 research outputs found
Algebraic symmetries of generic dimensional periodic Costas arrays
In this work we present two generators for the group of symmetries of the
generic dimensional periodic Costas arrays over elementary abelian
groups: one that is defined by multiplication on
dimensions and the other by shear (addition) on dimensions. Through
exhaustive search we observe that these two generators characterize the group
of symmetries for the examples we were able to compute. Following the results,
we conjecture that these generators characterize the group of symmetries of the
generic dimensional periodic Costas arrays over elementary abelian
groups
On The Existence of Roton Excitations in Bose Einstein Condensates: Signature of Proximity to a Mott Insulating Phase
Within the last decade, artificially engineered Bose Einstein Condensation
has been achieved in atomic systems. Bose Einstein Condensates are superfluids
just like bosonic Helium is and all interacting bosonic fluids are expected to
be at low enough temperatures. One difference between the two systems is that
superfluid Helium exhibits roton excitations while Bose Einstein Condensates
have never been observed to have such excitations. The reason for the roton
minimum in Helium is its proximity to a solid phase. The roton minimum is a
consequence of enhanced density fluctuations at the reciprocal lattice vector
of the stillborn solid. Bose Einstein Condensates in atomic traps are not near
a solid phase and therefore do not exhibit roton minimum. We conclude that if
Bose Einstein Condensates in an optical lattice are tuned near a transition to
a Mott insulating phase, a roton minimum will develop at a reciprocal lattice
vector of the lattice. Equivalently, a peak in the structure factor will appear
at such a wavevector. The smallness of the roton gap or the largeness of the
structure factor peak are experimental signatures of the proximity to the Mott
transition.Comment: 4 pages, 5 figure
Nonlinear effects in tunnelling escape in N-body quantum systems
We consider the problem of tunneling escape of particles from a multiparticle
system confined within a potential trap. The process is nonlinear due to the
interparticle interaction. Using the hydrodynamic representation for the
quantum equations of the multiparticle system we find the tunneling rate and
time evolutions of the number of trapped particles for different nonlinearity
values.Comment: 10 pages, 3 figure
Non-Abelian hydrodynamics and the flow of spin in spin-orbit coupled substances
Motivated by heavy ion collision experiments, we study the hydrodynamic
properties of non-Abelian systems. These issues arise in condensed matter
physics in the context of transport of spins in the presence of spin orbit
coupling: the Pauli Hamiltonian governing the leading relativistic corrections
in condensed matter systems can be rewritten in a language of SU(2) covariant
derivatives, where the role of the non-Abelian gauge fields is taken by the
physical electromagnetic fields. Taking a similar perspective as Jackiw and
coworkers, we show that non-abelian hydrodynamical currents can be factored in
a non-coherent 'classical' part, and a coherent part requiring macroscopic
non-abelian quantum entanglement. Non-abelian flow being thus a much richer
affair than familiar hydrodynamics, permits us to classify the various spin
transport phenomena in in condensed matter physics in a unifying framework.In
semiconductor spintronics, the absence of hydrodynamics is well known, but in
our formulation it is directly associated with the fact that non-abelian
currents are only covariantly conserved.We analyze the quantum mechanical
single particle currents of relevance to mesoscopic transport with as highlight
the Aharonov-Casher effect, where we demonstrate that the non-abelian transport
structure renders it much more fragile than its abelian counterpart, the
Aharonov-Bohm effect. We subsequently focus on spin flows protected by order
parameters, of which the spin-spiral magnets and the spin superfluids are
important examples. The surprising bonus is that the presence of an order
parameter, being single-valued, restores hydrodynamics. We demonstrate a new
effect: the trapping of electrical line charge, being the 'fixed frame'
non-Abelian analogue of the familiar magnetic flux trapping by superconductors.Comment: 23 pages, 7 figure
Site-Specific Reduction-Induced Hydrogenation of a Helical Bilayer Nanographene with K and Rb Metals: Electron Multiaddition and Selective Rb+ Complexation
Transcriptional responses of ecologically diverse drosophila species to larval diets differing in relative sugar and protein ratios
We utilized three ecologically diverse Drosophila species to explore the influence of ecological adaptation on transcriptomic responses to isocaloric diets differing in their relative proportions of protein to sugar. Drosophila melanogaster, a cosmopolitan species that breeds in decaying fruit, exemplifies individuals long exposed to a Western diet higher in sugar, while the natural diet of the cactophilic D. mojavensis, is much lower in carbohydrates. Drosophila arizonae, the sister species of D. mojavensis, is largely cactophilic, but also utilizes rotting fruits that are higher in sugars than cacti. We exposed third instar larvae for 24 hours to diets either (1) high in protein relative to sugar, (2) diets with equal amounts of protein and sugar, and (3) diets low in protein but high in sugar. As we predicted, based upon earlier interspecific studies of development and metabolism, the most extreme differences in gene expression under different dietary conditions were found in D. mojavensis followed by D. arizonae. No differential expression among diets was observed for D. melanogaster, a species that survives well under all three conditions, with little impact on its metabolism. We suggest that these three species together provide a model to examine individual and population differences in vulnerability to lifestyle-associated health problems such as metabolic syndrome and diabetes
Identification and Characterization of Ixodes scapularis Antigens That Elicit Tick Immunity Using Yeast Surface Display
Repeated exposure of rabbits and other animals to ticks results in acquired resistance or immunity to subsequent tick bites and is partially elicited by antibodies directed against tick antigens. In this study we demonstrate the utility of a yeast surface display approach to identify tick salivary antigens that react with tick-immune serum. We constructed an Ixodes scapularis nymphal salivary gland yeast surface display library and screened the library with nymph-immune rabbit sera and identified five salivary antigens. Four of these proteins, designated P8, P19, P23 and P32, had a predicted signal sequence. We generated recombinant (r) P8, P19 and P23 in a Drosophila expression system for functional and immunization studies. rP8 showed anti-complement activity and rP23 demonstrated anti-coagulant activity. Ixodes scapularis feeding was significantly impaired when nymphs were fed on rabbits immunized with a cocktail of rP8, rP19 and rP23, a hall mark of tick-immunity. These studies also suggest that these antigens may serve as potential vaccine candidates to thwart tick feeding
Canagliflozin and Renal Outcomes in Type 2 Diabetes and Nephropathy
BACKGROUND Type 2 diabetes mellitus is the leading cause of kidney failure worldwide, but few effective long-term treatments are available. In cardiovascular trials of inhibitors of sodium–glucose cotransporter 2 (SGLT2), exploratory results have suggested that such drugs may improve renal outcomes in patients with type 2 diabetes. METHODS In this double-blind, randomized trial, we assigned patients with type 2 diabetes and albuminuric chronic kidney disease to receive canagliflozin, an oral SGLT2 inhibitor, at a dose of 100 mg daily or placebo. All the patients had an estimated glomerular filtration rate (GFR) of 30 to 300 to 5000) and were treated with renin–angiotensin system blockade. The primary outcome was a composite of end-stage kidney disease (dialysis, transplantation, or a sustained estimated GFR of <15 ml per minute per 1.73 m 2), a doubling of the serum creatinine level, or death from renal or cardiovascular causes. Prespecified secondary outcomes were tested hierarchically. RESULTS The trial was stopped early after a planned interim analysis on the recommendation of the data and safety monitoring committee. At that time, 4401 patients had undergone randomization, with a median follow-up of 2.62 years. The relative risk of the primary outcome was 30% lower in the canagliflozin group than in the placebo group, with event rates of 43.2 and 61.2 per 1000 patient-years, respectively (hazard ratio, 0.70; 95% confidence interval [CI], 0.59 to 0.82; P=0.00001). The relative risk of the renal-specific composite of end-stage kidney disease, a doubling of the creatinine level, or death from renal causes was lower by 34% (hazard ratio, 0.66; 95% CI, 0.53 to 0.81; P<0.001), and the relative risk of end-stage kidney disease was lower by 32% (hazard ratio, 0.68; 95% CI, 0.54 to 0.86; P=0.002). The canagliflozin group also had a lower risk of cardiovascular death, myocardial infarction, or stroke (hazard ratio, 0.80; 95% CI, 0.67 to 0.95; P=0.01) and hospitalization for heart failure (hazard ratio, 0.61; 95% CI, 0.47 to 0.80; P<0.001). There were no significant differences in rates of amputation or fracture. CONCLUSIONS In patients with type 2 diabetes and kidney disease, the risk of kidney failure and cardiovascular events was lower in the canagliflozin group than in the placebo group at a median follow-up of 2.62 years
Understanding Factors Associated With Psychomotor Subtypes of Delirium in Older Inpatients With Dementia
Scaling for faster macroparticle simulation in longitudinal multiparticle dynamics
Macroparticle tracking is a direct and attractive approach to following the evolution of a longitudinal phase space distribution. When the particles interact through short-range wake fields or when the interparticle force is included, calculations of this kind require a large number of macroparticles. However, it is possible to reduce both the number of macroparticles required and the number of tracking steps per unit simulated time by employing a simple scaling. It is demonstrated that the Vlasov equation is unchanged by introduction of the scaled quantities. It is further shown that under rather general conditions the speed of calculation improves with the fourth power of the scaling constant. Two examples comparing scaled and original cases illustrate the effectiveness of the approach. Limitations to the amount of rescaling are discussed
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