1,458 research outputs found
The Orienteering Problem under Uncertainty Stochastic Programming and Robust Optimization compared
The Orienteering Problem (OP) is a generalization of the well-known traveling salesman problem and has many interesting applications in logistics, tourism and defense. To reflect real-life situations, we focus on an uncertain variant of the OP. Two main approaches that deal with optimization under uncertainty are stochastic programming and robust optimization. We will explore the potentialities and bottlenecks of these two approaches applied to the uncertain OP. We will compare the known robust approach for the uncertain OP (the robust orienteering problem) to the new stochastic programming counterpart (the two-stage orienteering problem). The application of both approaches will be explored in terms of their suitability in practice
The acceleration and storage of radioactive ions for a neutrino factory
The term beta-beam has been coined for the production of a pure beam of
electron neutrinos or their antiparticles through the decay of radioactive ions
circulating in a storage ring. This concept requires radioactive ions to be
accelerated to a Lorentz gamma of 150 for 6He and 60 for 18Ne. The neutrino
source itself consists of a storage ring for this energy range, with long
straight sections in line with the experiment(s). Such a decay ring does not
exist at CERN today, nor does a high-intensity proton source for the production
of the radioactive ions. Nevertheless, the existing CERN accelerator
infrastructure could be used as this would still represent an important saving
for a beta-beam facility. This paper outlines the first study, while some of
the more speculative ideas will need further investigations.Comment: Accepted for publication in proceedings of Nufact02, London, 200
An analysis of blood pressure screening of 21 112 participants in Armenia: May Measurement Month 2018.
Elevated blood pressure (BP) is a growing burden worldwide and is the leading cause of mortality and disability-adjusted life years all over the world. May Measurement Month (MMM) is a global initiative aimed to raise awareness of high BP and to act as a temporary solution to the lack of screening programmes worldwide. An opportunistic cross-sectional survey of volunteers aged ≥18 was carried out in May to July 2018. Blood pressure measurement, the definition of hypertension (HTN) and statistical analysis followed the standard MMM protocol. The study was conducted in public areas (17 sites in Yerevan and 22 in regions), both indoor and outdoor, as well as in 78 primary care centres. A total of 21 112 individuals were screened during MMM18, of which 20 732 had three BP measurements available. The mean age of screened individuals was 46.2 ± 17.3 years, 57.8% were female. At the time of screening, 26.1% were on antihypertensive medication. After imputation, the percentage of participants with HTN was 38.7%, and 76.7% of them were aware of their high BP. Of participants receiving treatment, 47.1% had a controlled BP. MMM18 was the largest BP screening campaign undertaken in Armenia. We found that the proportion of HTN is substantial in Armenia, which may be a vital contributor to the growing burden of non-communicable diseases. Our results also suggest that untreated HTN is common and when treated still not adequately controlled in Armenia. The current situation, with an insufficient control rate of HTN, must be changed as soon as possible
The characteristics, dynamics and risk of death in COVID-19 positive dialysis patients in London, UK
Background: Dialysis patients, with frequent co-morbidities, advanced age and frailty, visiting treatment facilities frequently are perhaps more prone to SARS-Cov-2 infection and related death - the risk-factors and dynamics of which are unknown. The aim of this study was to investigate the hospital outcomes in SARS-CoV-2 infected dialysis patients. Methods: Data on 224 hemodialysis patients between 02/29/2020 and 05/15/2020 with confirmed SARS-CoV-2 were analyzed for outcomes and potential risk factors for death, using competing risk regression model assessed by sub-distribution hazards ratio (SHR). Results: Crude data analyses suggest an overall case fatality ratio of 22.7(95%CI(17.3-28.3)%) overall but that varies across age groups from 11.4(95%CI(0.9-9.2)) in 80 years; with 60% of deaths occurring in the first 15 days and 80% within 21 days indicating a rapid deterioration towards death after admission. Almost 90% of surviving patients were discharged within 28 days. Death was more likely than hospital discharge in more frail (WHO performance status 3-4) [SHR=2.16(1.25-3.74);p=0.006)], ischemic heart disease [SHR=2.28(1.32-3.94),p=0.003], cerebrovascular disease [SHR=2.11(1.20-3.72),p=0.010], smoking history [SHR=2.69(1.33-5.45),p=0.006], and (completely or partially) hospitalized patients [SHR=10.26.(3.10-33.94),p<.001]; and in patients with high CRP [SHR=1.35(1.10-1.67)] and high neutrophil:lymphocyte ratio [SHR=1.03(1.01-1.04),p<0.001]. Our data did not support differences in the risk of death associated with gender, ethnicity, dialysis vintage or other comorbidities. However, comparison with the entire dialysis population attending these hospitals, and 12.9% being affected, revealed that non-Caucasians (62% vs. 52% in all patients, p=0.001) and diabetic patients (54% vs. 22%, p<0.001) were disproportionately affected. Conclusion: This report discusses the outcomes of a large cohort of dialysis patients with SARS-CoV-2, infection affecting more diabetics and non-Caucasians; with a high case fatality ratio, which increased significantly with age, frailty, smoking, increasing CRP and neutrophil:lymphocyte ratio at presentation
Azimuthal Angle Correlations for Rapidity Separated Hadron Pairs in d+Au Collisions at sqrt(s_NN) = 200 GeV
We report on two-particle azimuthal angle correlations between charged
hadrons at forward/backward (deuteron/gold going direction) rapidity and
charged hadrons at mid-rapidity in deuteron-gold (d+Au) and proton-proton (p+p)
collisions at sqrt(s_NN) = 200 GeV. Jet structures are observed in the
correlations which we quantify in terms of the conditional yield and angular
width of away side partners. The kinematic region studied here samples partons
in the gold nucleus carrying nucleon momentum fraction x~0.1 to x~0.01. Within
this range, we find no x dependence of the jet structure in d+Au collisions.Comment: 330 authors, 6 pages text, 4 figures, no tables. Submitted to Phys.
Rev. Lett. Plain text data tables for the points plotted in figures for this
and previous PHENIX publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
Centrality dependence of charged hadron production in deuteron+gold and nucleon+gold collisions at sqrt(s_NN)=200 GeV
We present transverse momentum (p_T) spectra of charged hadrons measured in
deuteron-gold and nucleon-gold collisions at \sqrts = 200 GeV for four
centrality classes. Nucleon-gold collisions were selected by tagging events in
which a spectator nucleon was observed in one of two forward rapidity
detectors. The spectra and yields were investigated as a function of the number
of binary nucleon-nucleon collisions, \nu, suffered by deuteron nucleons. A
comparison of charged particle yields to those in p+p collisions show that the
yield per nucleon-nucleon collision saturates with \nu for high momentum
particles. We also present the charged hadron to neutral pion ratios as a
function of p_T.Comment: 330 authors, 15 pages text, 16 figures, 3 tables. Submitted to Phys.
Rev. Lett. v2 has minor changes to reflect revisions during review process.
Plain text data tables for the points plotted in figures for this and
previous PHENIX publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
Deuteron and antideuteron production in Au+Au collisions at sqrt(s_NN)=200 GeV
The production of deuterons and antideuterons in the transverse momentum
range 1.1 < p_T < 4.3 GeV/c at mid-rapidity in Au + Au collisions at
sqrt(s_NN)=200 GeV has been studied by the PHENIX experiment at RHIC. A
coalescence analysis comparing the deuteron and antideuteron spectra with those
of protons and antiprotons, has been performed. The coalescence probability is
equal for both deuterons and antideuterons and increases as a function of p_T,
which is consistent with an expanding collision zone. Comparing (anti)proton
yields p_bar/p = 0.73 +/- 0.01, with (anti)deuteron yields: d_bar/d = 0.47 +/-
0.03, we estimate that n_bar/n = 0.64 +/- 0.04.Comment: 326 authors, 6 pages text, 5 figures, 1 Table. Submitted to PRL.
Plain text data tables for the points plotted in figures for this and
previous PHENIX publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
Event-by-event fluctuations in Mean and Mean in sqrt(s_NN) = 130 GeV Au+Au Collisions
Distributions of event-by-event fluctuations of the mean transverse momentum
and mean transverse energy near mid-rapidity have been measured in Au+Au
collisions at sqrt(s_NN) = 130 GeV at RHIC. By comparing the distributions to
what is expected for statistically independent particle emission, the magnitude
of non-statistical fluctuations in mean transverse momentum is determined to be
consistent with zero. Also, no significant non-random fluctuations in mean
transverse energy are observed. By constructing a fluctuation model with two
event classes that preserve the mean and variance of the semi-inclusive p_T or
e_T spectra, we exclude a region of fluctuations in sqrt(s_NN) = 130 GeV Au+Au
collisions.Comment: 10 pages, RevTeX 3, 7 figures, 4 tables, 307 authors, submitted to
Phys. Rev. C on 22 March 2002. Plain text data tables for the points plotted
in figures for this and previous PHENIX publications are (will be made)
publicly available at
http://www.phenix.bnl.gov/phenix/WWW/run/phenix/papers.htm
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