1,184 research outputs found
Balanced Allocation on Graphs: A Random Walk Approach
In this paper we propose algorithms for allocating sequential balls into
bins that are interconnected as a -regular -vertex graph , where
can be any integer.Let be a given positive integer. In each round
, , ball picks a node of uniformly at random and
performs a non-backtracking random walk of length from the chosen node.Then
it allocates itself on one of the visited nodes with minimum load (ties are
broken uniformly at random). Suppose that has a sufficiently large girth
and . Then we establish an upper bound for the maximum number
of balls at any bin after allocating balls by the algorithm, called {\it
maximum load}, in terms of with high probability. We also show that the
upper bound is at most an factor above the lower bound that is
proved for the algorithm. In particular, we show that if we set , for every constant , and
has girth at least , then the maximum load attained by the
algorithm is bounded by with high probability.Finally, we
slightly modify the algorithm to have similar results for balanced allocation
on -regular graph with and sufficiently large girth
Corporate political activity and firm outcomes: A meta-analysis
Using meta-analytic methods on a sample of 74 studies, we explore the links between CPA and public policy outcomes, and between CPA and firm outcomes. We find that CPA has at best a weak effect and that it appears to be better at maintaining public policy than changing them
Scaling property of the critical hopping parameters for the Bose-Hubbard model
Recently precise results for the boundary between the Mott insulator phase
and the superfluid phase of the homogeneous Bose-Hubbard model have become
available for arbitrary integer filling factor g and any lattice dimension d >
1. We use these data for demonstrating that the critical hopping parameters
obey a scaling relationship which allows one to map results for different g
onto each other. Unexpectedly, the mean-field result captures the dependence of
the exact critical parameters on the filling factor almost fully. We also
present an approximation formula which describes the critical parameters for d
> 1 and any g with high accuracy.Comment: 5 pages, 5 figures. to appear in EPJ
GP attitudes and self-reported behaviour in primary care consultations for low back pain
Background. The implementation of guideline recommendations in primary care has become widespread. The treatment of low back pain (LBP) has followed suite. Research shows that the use of LBP guidelines is influenced by the believability of the underlying evidence, the GPs consultation style and uncertainties surrounding diagnosis and treatment
Gravity-induced Wannier-Stark ladder in an optical lattice
We discuss the dynamics of ultracold atoms in an optical potential
accelerated by gravity. The positions and widths of the Wannier-Stark ladder of
resonances are obtained as metastable states. The metastable Wannier-Bloch
states oscillate in a single band with the Bloch period. The width of the
resonance gives the rate transition to the continuum.Comment: 5 pages + 8 eps figures, submitted to Phys. Rev.
Periodically-dressed Bose-Einstein condensates: a superfluid with an anisotropic and variable critical velocity
Two intersecting laser beams can produce a spatially-periodic coupling
between two components of an atomic gas and thereby modify the dispersion
relation of the gas according to a dressed-state formalism. Properties of a
Bose-Einstein condensate of such a gas are strongly affected by this
modification. A Bogoliubov transformation is presented which accounts for
interparticle interactions to obtain the quasiparticle excitation spectrum in
such a condensate. The Landau critical velocity is found to be anisotropic and
can be widely tuned by varying properties of the dressing laser beams.Comment: 5 pages, 4 figure
Towards the More Efficient Use of Water and Nutrients in Food Legume Cropping
Nutrient imbalance and soil moisture stress are the major abiotic constraints limiting productivity of cool season food legumes. These constraints are more pronounced in the semi-arid tropics and sub-tropics which are the principal production zones of chickpea, lentil and faba bean. The legumes are generally grown on residual moisture as a mono crop and consequently face drought especially during the reproductive phase. In recent years, chickpea, lentil, peas and faba bean have been grown in some areas with an irrigated/assured water supply under intensive cropping to sustain cereal based systems. An increased water supply favourably influences productivity in dry environments. Faba bean, French beans and peas show a relatively better response to irrigation. The pod initiation stage is considered most critical with respect to moisture stress. Excessive moisture often has a negative effect on podding and seed yield. Eighty to ninety percent of the nitrogen requirements of leguminous crops is met from N2 fixation hence a dose of 15â25 kg N ha-1 has been recommended. However, in new cropping systems like rice-chickpea, higher doses of 30â40 kg N ha-1 are beneficial. Phosphorus deficiency is wide spread and good responses occur to 20 to 80 kg P2O5 ha-1, depending on the nutrient status of soil, cropping systems and moisture availability. Response to potassium application is localized. The use of 20â30 kg S ha-1 and some of the micronutrients such as Zn, B, Mo and Fe have improved productivity. Band placement of phosphatic fertilizers and use of bio-fertilizers has enhanced the efficiency of applied as well as native P. Foliar applications of some micronutrients have been effective in correcting deficiencies. Water use efficiency has been improved with some management practices such as changed sowing time, balanced nutrition, mulching and tillage
Pfsec13 is an unusual chromatin-associated nucleoporin of plasmodium falciparum that is essential for parasite proliferation in human erythrocytes
In Plasmodium falciparum, the deadliest form of human malaria, the nuclear periphery has drawn much attention due to its role as a subnuclear compartment involved in virulence gene expression. Recent data have implicated components of the nuclear envelope in regulating gene expression in several eukaryotes. Special attention has been given to nucleoporins that compose the nuclear pore complex (NPC). However, very little is known about components of the nuclear envelope in Plasmodium parasites. Here we characterize PfSec13, an unusual nucleoporin of P. falciparum, which shows unique structural similarities suggesting that it is a fusion between Sec13 and Nup145C of yeast. Using super resolution fluorescence microscopy (3D-SIM) and in vivo imaging, we show that the dynamiclocalization of PfSec13 during parasites' intra-erythrocytic development corresponds with that of the NPCs and that these dynamics are associated with microtubules rather than with F-actin. In addition, PfSec13 does not co-localize with the heterochormatin markers HP1 and H3K9me3, suggesting euchromatic location of the NPCs. The proteins associated with PfSec13 indicate that this unusual Nup is involved in several cellular processes. Indeed, ultrastructural and chromatin immunoprecipitation analyses revealed that, in addition to the NPCs, PfSec13 is found in the nucleoplasm where it is associated with chromatin. Finally, we used peptide nucleic acids (PNA) to downregulate PfSec13 and show that it is essential for parasite proliferation in human erythrocytes. © 2013. Published by The Company of Biologists Ltd
A mapping approach to synchronization in the "Zajfman trap": stability conditions and the synchronization mechanism
We present a two particle model to explain the mechanism that stabilizes a
bunch of positively charged ions in an "ion trap resonator" [Pedersen etal,
Phys. Rev. Lett. 87 (2001) 055001]. The model decomposes the motion of the two
ions into two mappings for the free motion in different parts of the trap and
one for a compressing momentum kick. The ions' interaction is modelled by a
time delay, which then changes the balance between adjacent momentum kicks.
Through these mappings we identify the microscopic process that is responsible
for synchronization and give the conditions for that regime.Comment: 12 pages, 9 figures; submitted to Phys Rev
Effect of spinal anesthesia-induced deafferentation on pain processing in healthy male volunteers: a task-related fMRI study
Stress and Psychopatholog
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