1,174 research outputs found
Jamming of multiple persistent random walkers in arbitrary spatial dimension
We consider the persistent exclusion process in which a set of persistent
random walkers interact via hard-core exclusion on a hypercubic lattice in
dimensions. We work within the ballistic regime whereby particles continue to
hop in the same direction over many lattice sites before reorienting. In the
case of two particles, we find the mean first-passage time to a jammed state
where the particles occupy adjacent sites and face each other. This is achieved
within an approximation that amounts to embedding the one-dimensional system in
a higher-dimensional reservoir. Numerical results demonstrate the validity of
this approximation, even for small lattices. The results admit a
straightforward generalisation to dilute systems comprising more than two
particles. A self-consistency condition on the validity of these results
suggest that clusters may form at arbitrarily low densities in the ballistic
regime, in contrast to what has been found in the diffusive limit.Comment: Version to appear in JSTAT (18 pages; 10 figures
From a microscopic solution to a continuum description of active particles with a recoil interaction in one dimension
We consider a model system of persistent random walkers that can jam, pass
through each other or jump apart (recoil) on contact. In a continuum limit,
where particle motion between stochastic changes in direction becomes
deterministic, we find that the stationary inter-particle distribution
functions are governed by an inhomogeneous fourth-order differential equation.
Our main focus is on determining the boundary conditions that these
distribution functions should satisfy. We find that these do not arise
naturally from physical considerations, but need to be carefully matched to
functional forms that arise from the analysis of an underlying discrete
process. The inter-particle distribution functions, or their first derivatives,
are generically found to be discontinuous at the boundaries.Comment: 16 pages; 5 figures; published in PR
Global Opportunities to Increase Agricultural Independence Through Phosphorus Recycling
Food production hinges largely upon access to phosphorus (P) fertilizer. Most fertilizer P used in the global agricultural system comes from mining of nonrenewable phosphate rock deposits located within few countries. However, P contained in livestock manure or urban wastes represents a recyclable source of P. To inform development of P recycling technologies and policies, we examined subnational, national, and global spatial patterns for two intersections of land use affording high P recycling potential: (a) manureârich cultivated areas and (b) populous cultivated areas. In turn, we examined overlap between P recycling potential and nationâlevel P fertilizer import dependency. Populous cultivated areas were less abundant globally than manureârich cultivated areas, reflecting greater segregation between crops and people compared to crops and livestock, especially in the Americas. Based on a global hexagonal grid (290âkm2 grid cell area), disproportionately large shares of subnational âhot spotsâ for P recycling potential occurred in India, China, Southeast Asia, Europe, and parts of Africa. Outside of China, most of the remaining manureârich or populous cultivated areas occurred within nations that had relatively high imports of P fertilizer (net P import:consumption ratios âĽ0.4) or substantial increases in fertilizer demand between the 2000s (2002â2006) and 2010s (2010â2014). Manureârich cultivated grid cells (those above the 75th percentiles for both manure and cropland extent) represented 12% of the global grid after excluding cropless cells. Annually, the global sum of animal manure P was at least 5 times that contained in human excreta, and among cultivated cells the ratio was frequently higher (median = 8.9). The abundance of potential P recycling hot spots within nations that have depended on fertilizer imports or experienced rising fertilizer demand could prove useful for developing local P sources and maintaining agricultural independence
Sphenopalatine-sphenopalatine anastomosis: a unique cause of intractable epistaxis, safely treated with microcatheter embolization: a case report
Epistaxis is the most common emergency presenting to the ENT surgeon. Here we present a case of epistaxis arising from the sphenopalatine artery in a patient who had previously had the ipsilateral external carotid artery ligated due to previous epistaxis. On investigation the epistaxis was determined to arise from an anastamosis with the contralateral sphenopalatine artery. The anatomy was demonstrated with angiography and the epistaxis treated using microcatheter embolization. Anatomical variation can be a cause for failure of ligation as a permanent treatment for epistaxis. Embolization is used less frequently for epistaxis control due to concerns about the risks involved, but it can be a valuable treatment option in intractable epistaxis following a failure of arterial ligation
An Analysis on the Impact of Export Rebate to Export Structure in China
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ĺľčżčĄĺŽć§ĺćďźçśĺĺć šćŽ...It has been proved that export rebate policy plays an important role in promoting the international trade of a country,particularly the development of the export. Under the principle of tax neutrality, adopting different export rebate rate in different conditions makes positive effect on optimization of export structure and industry structure. Since 1985, China has repeatedly adjusted the export r...ĺŚä˝ďźçťćľĺŚçĄĺŁŤé˘çłťä¸ä¸ďźçťćľĺŚé˘č´˘ćżçłť_č´˘ćżĺŚ(ĺŤç¨ćśĺŚ)ĺŚĺˇďź1552007115009
Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV
A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay
channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7
TeV is presented. The data were collected at the LHC, with the CMS detector,
and correspond to an integrated luminosity of 4.6 inverse femtobarns. No
significant excess is observed above the background expectation, and upper
limits are set on the Higgs boson production cross section. The presence of the
standard model Higgs boson with a mass in the 270-440 GeV range is excluded at
95% confidence level.Comment: Submitted to JHE
Measurement of the t t-bar production cross section in the dilepton channel in pp collisions at sqrt(s) = 7 TeV
The t t-bar production cross section (sigma[t t-bar]) is measured in
proton-proton collisions at sqrt(s) = 7 TeV in data collected by the CMS
experiment, corresponding to an integrated luminosity of 2.3 inverse
femtobarns. The measurement is performed in events with two leptons (electrons
or muons) in the final state, at least two jets identified as jets originating
from b quarks, and the presence of an imbalance in transverse momentum. The
measured value of sigma[t t-bar] for a top-quark mass of 172.5 GeV is 161.9 +/-
2.5 (stat.) +5.1/-5.0 (syst.) +/- 3.6(lumi.) pb, consistent with the prediction
of the standard model.Comment: Replaced with published version. Included journal reference and DO
Combined search for the quarks of a sequential fourth generation
Results are presented from a search for a fourth generation of quarks
produced singly or in pairs in a data set corresponding to an integrated
luminosity of 5 inverse femtobarns recorded by the CMS experiment at the LHC in
2011. A novel strategy has been developed for a combined search for quarks of
the up and down type in decay channels with at least one isolated muon or
electron. Limits on the mass of the fourth-generation quarks and the relevant
Cabibbo-Kobayashi-Maskawa matrix elements are derived in the context of a
simple extension of the standard model with a sequential fourth generation of
fermions. The existence of mass-degenerate fourth-generation quarks with masses
below 685 GeV is excluded at 95% confidence level for minimal off-diagonal
mixing between the third- and the fourth-generation quarks. With a mass
difference of 25 GeV between the quark masses, the obtained limit on the masses
of the fourth-generation quarks shifts by about +/- 20 GeV. These results
significantly reduce the allowed parameter space for a fourth generation of
fermions.Comment: Replaced with published version. Added journal reference and DO
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