375 research outputs found
Economic Fluctuations and Diffusion
Stock price changes occur through transactions, just as diffusion in physical
systems occurs through molecular collisions. We systematically explore this
analogy and quantify the relation between trading activity - measured by the
number of transactions - and the price change ,
for a given stock, over a time interval . To this end, we
analyze a database documenting every transaction for 1000 US stocks over the
two-year period 1994-1995. We find that price movements are equivalent to a
complex variant of diffusion, where the diffusion coefficient fluctuates
drastically in time. We relate the analog of the diffusion coefficient to two
microscopic quantities: (i) the number of transactions in
, which is the analog of the number of collisions and (ii) the local
variance of the price changes for all transactions in , which is the analog of the local mean square displacement between
collisions. We study the distributions of both and , and find that they display power-law tails. Further, we find that
displays long-range power-law correlations in time, whereas
does not. Our results are consistent with the interpretation
that the pronounced tails of the distribution of w_{\Delta t}|
G_{\Delta t} |N_{\Delta t}$.Comment: RevTex 2 column format. 6 pages, 36 references, 15 eps figure
Nutritional status of Lusitano broodmares on extensive feeding systems: body condition, live weight and metabolic indicators
Articles in International JournalsThe present research aimed to evaluate the
effects of foaling season and feeding management in extensive systems on the nutritional status of Lusitano broodmares throughout the gestation/lactation cycle, by assessment of body condition (BC), body weight (BW), and some blood metabolic indicators. Four groups of Lusitano
broodmares (A, B, C, D) were monitored during
four years, in a total of 119 gestation/lactation
cycles. All mares were kept on pasture, and A and B mares were daily supplemented. Monthly, mares were weighed and BC evaluated. Suckling foals from these mares were also monitored for BW and withers height. Glucose, non-esterified fatty acids, urea and albumin concentrations were determined in blood. BW changes were
influenced by reproductive stage and foaling season (P<0.001), reflecting also pasture availability.
Changes on BC were observed (P<0.05),
although with small amplitudes within each
group. Higher scores were reached at the end of spring, decreasing 0.25 point until late summer.
Early foaling had also a marked effect, hindering the recovery of BC along the cycle. Glucose values decreased from late gestation to early lactation (P<0.05) and lower levels were recorded during
the summer months. Uremia was mainly influenced by the reproductive stage (P<0.05). Under nutrition was not detected. Foals born in February-March had higher average daily gain than those born in April-May (P<0.05), probably reflecting differences in milk production of the
mares. BC and BW changes and, particularly,
blood indicators showed an overall balanced
nutritional status, reflecting an adaptation to feed availability and climate.Portuguese Foundation for Science and
Technolog
Shrinking a large dataset to identify variables associated with increased risk of Plasmodium falciparum infection in Western Kenya
Large datasets are often not amenable to analysis using traditional single-step approaches. Here, our general objective was to apply imputation techniques, principal component analysis (PCA), elastic net and generalized linear models to a large dataset in a systematic approach to extract the most meaningful predictors for a health outcome. We extracted predictors for Plasmodium falciparum infection, from a large covariate dataset while facing limited numbers of observations, using data from the People, Animals, and their Zoonoses (PAZ) project to demonstrate these techniques: data collected from 415 homesteads in western Kenya, contained over 1500 variables that describe the health, environment, and social factors of the humans, livestock, and the homesteads in which they reside. The wide, sparse dataset was simplified to 42 predictors of P. falciparum malaria infection and wealth rankings were produced for all homesteads. The 42 predictors make biological sense and are supported by previous studies. This systematic data-mining approach we used would make many large datasets more manageable and informative for decision-making processes and health policy prioritization
Global Search for New Physics with 2.0/fb at CDF
Data collected in Run II of the Fermilab Tevatron are searched for
indications of new electroweak-scale physics. Rather than focusing on
particular new physics scenarios, CDF data are analyzed for discrepancies with
the standard model prediction. A model-independent approach (Vista) considers
gross features of the data, and is sensitive to new large cross-section
physics. Further sensitivity to new physics is provided by two additional
algorithms: a Bump Hunter searches invariant mass distributions for "bumps"
that could indicate resonant production of new particles; and the Sleuth
procedure scans for data excesses at large summed transverse momentum. This
combined global search for new physics in 2.0/fb of ppbar collisions at
sqrt(s)=1.96 TeV reveals no indication of physics beyond the standard model.Comment: 8 pages, 7 figures. Final version which appeared in Physical Review D
Rapid Communication
Observation of Orbitally Excited B_s Mesons
We report the first observation of two narrow resonances consistent with
states of orbitally excited (L=1) B_s mesons using 1 fb^{-1} of ppbar
collisions at sqrt{s} = 1.96 TeV collected with the CDF II detector at the
Fermilab Tevatron. We use two-body decays into K^- and B^+ mesons reconstructed
as B^+ \to J/\psi K^+, J/\psi \to \mu^+ \mu^- or B^+ \to \bar{D}^0 \pi^+,
\bar{D}^0 \to K^+ \pi^-. We deduce the masses of the two states to be m(B_{s1})
= 5829.4 +- 0.7 MeV/c^2 and m(B_{s2}^*) = 5839.7 +- 0.7 MeV/c^2.Comment: Version accepted and published by Phys. Rev. Let
Measurement of the Bottom-Strange Meson Mixing Phase in the Full CDF Data Set
We report a measurement of the bottom-strange meson mixing phase \beta_s
using the time evolution of B0_s -> J/\psi (->\mu+\mu-) \phi (-> K+ K-) decays
in which the quark-flavor content of the bottom-strange meson is identified at
production. This measurement uses the full data set of proton-antiproton
collisions at sqrt(s)= 1.96 TeV collected by the Collider Detector experiment
at the Fermilab Tevatron, corresponding to 9.6 fb-1 of integrated luminosity.
We report confidence regions in the two-dimensional space of \beta_s and the
B0_s decay-width difference \Delta\Gamma_s, and measure \beta_s in [-\pi/2,
-1.51] U [-0.06, 0.30] U [1.26, \pi/2] at the 68% confidence level, in
agreement with the standard model expectation. Assuming the standard model
value of \beta_s, we also determine \Delta\Gamma_s = 0.068 +- 0.026 (stat) +-
0.009 (syst) ps-1 and the mean B0_s lifetime, \tau_s = 1.528 +- 0.019 (stat) +-
0.009 (syst) ps, which are consistent and competitive with determinations by
other experiments.Comment: 8 pages, 2 figures, Phys. Rev. Lett 109, 171802 (2012
Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in âs = 7 TeV pp collisions with the ATLAS detector
A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fbâ1 of protonâproton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results
Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC
Measurements of inclusive jet suppression in heavy ion collisions at the LHC
provide direct sensitivity to the physics of jet quenching. In a sample of
lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated
luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with
a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the
transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the
anti-kt algorithm with values for the distance parameter that determines the
nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of
the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp.
Jet production is found to be suppressed by approximately a factor of two in
the 10% most central collisions relative to peripheral collisions. Rcp varies
smoothly with centrality as characterized by the number of participating
nucleons. The observed suppression is only weakly dependent on jet radius and
transverse momentum. These results provide the first direct measurement of
inclusive jet suppression in heavy ion collisions and complement previous
measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables,
submitted to Physics Letters B. All figures including auxiliary figures are
available at
http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02
Influence of chromium supplementation on energy metabolism in horses used in policing activity
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