508 research outputs found
An Actor-Based Model of Social Network Influence on Adolescent Body Size, Screen Time, and Playing Sports
Recent studies suggest that obesity may be “contagious” between individuals in social networks. Social contagion (influence), however, may not be identifiable using traditional statistical approaches because they cannot distinguish contagion from homophily (the propensity for individuals to select friends who are similar to themselves) or from shared environmental influences. In this paper, we apply the stochastic actor-based model (SABM) framework developed by Snijders and colleagues to data on adolescent body mass index (BMI), screen time, and playing active sports. Our primary hypothesis was that social influences on adolescent body size and related behaviors are independent of friend selection. Employing the SABM, we simultaneously modeled network dynamics (friendship selection based on homophily and structural characteristics of the network) and social influence. We focused on the 2 largest schools in the National Longitudinal Study of Adolescent Health (Add Health) and held the school environment constant by examining the 2 school networks separately (N = 624 and 1151). Results show support in both schools for homophily on BMI, but also for social influence on BMI. There was no evidence of homophily on screen time in either school, while only one of the schools showed homophily on playing active sports. There was, however, evidence of social influence on screen time in one of the schools, and playing active sports in both schools. These results suggest that both homophily and social influence are important in understanding patterns of adolescent obesity. Intervention efforts should take into consideration peers’ influence on one another, rather than treating “high risk” adolescents in isolation
A measurement of from the Gross-Llewellyn Smith Sum Rule
We extract a set of values for the Gross-Llewellyn Smith sum rule at
different values of 4-momentum transfer squared (), by combining revised
CCFR neutrino data with data from other neutrino deep-inelastic scattering
experiments for . A comparison with the order
theoretical predictions yields a determination of
at the scale of the Z-boson mass of . This measurement
provides a new and useful test of perturbative QCD at low , because of the
low uncertainties in the higher order calculations.Comment: 4 pages, 4 figure
Neutrino Interactions In Oscillation Experiments
We calculate neutrino induced cross-sections relevant for oscillation
experiments, including the -lepton threshold for quasi-elastic, resonance
and deep inelastic scattering. In addition to threshold effects, we include
nuclear corrections for heavy targets which are moderate for quasi-elastic and
large for single pion production. Nuclear effects for deep inelastic reactions
are small. We present cross sections together with their nuclear corrections
for various channels which are useful for interpreting the experimental results
and for determining parameters of the neutrino sector..Comment: 24 pages, 18 figure
Nuclear Structure Functions in the Large x Large Q^2 Kinematic Region in Neutrino Deep Inelastic Scattering
Data from the CCFR E770 Neutrino Deep Inelastic Scattering (DIS) experiment
at Fermilab contain events with large Bjorken x (x>0.7) and high momentum
transfer (Q^2>50 (GeV/c)^2). A comparison of the data with a model based on no
nuclear effects at large x, shows a significant excess of events in the data.
Addition of Fermi gas motion of the nucleons in the nucleus to the model does
not explain the excess. Adding a higher momentum tail due to the formation of
``quasi-deuterons'' makes some improvement. An exponentially falling F_2
\propto e^-s(x-x_0) at large x, predicted by ``multi-quark clusters'' and
``few-nucleon correlations'', can describe the data. A value of s=8.3 \pm
0.7(stat.)\pm 0.7(sys.) yields the best agreement with the data.Comment: 4 pages, 4 figures, 1 table. Sibmitted to PR
A Precise Measurement of the Weak Mixing Angle in Neutrino-Nucleon Scattering
We report a precise measurement of the weak mixing angle from the ratio of
neutral current to charged current inclusive cross-sections in deep-inelastic
neutrino-nucleon scattering. The data were gathered at the CCFR neutrino
detector in the Fermilab quadrupole-triplet neutrino beam, with neutrino
energies up to 600 GeV. Using the on-shell definition, , we obtain .Comment: 10 pages, Nevis Preprint #1498 (Submitted to Phys. Rev. Lett.
Long-term exposure to ambient particulate matter and prevalence of subclinical atherosclerosis in the Multiethnic Study of Atherosclerosis (MESA)
http://deepblue.lib.umich.edu/bitstream/2027.42/57884/1/Long Term Exposure to Ambient Particulate Matter and Prevalance of Subclinical Athersclerosis in the Multiethnic Study of Atherosclerosis .pd
Search for charged Higgs decays of the top quark using hadronic tau decays
We present the result of a search for charged Higgs decays of the top quark,
produced in collisions at 1.8 TeV. When the charged
Higgs is heavy and decays to a tau lepton, which subsequently decays
hadronically, the resulting events have a unique signature: large missing
transverse energy and the low-charged-multiplicity tau. Data collected in the
period 1992-1993 at the Collider Detector at Fermilab, corresponding to
18.70.7~pb, exclude new regions of combined top quark and charged
Higgs mass, in extensions to the standard model with two Higgs doublets.Comment: uuencoded, gzipped tar file of LaTeX and 6 Postscript figures; 11 pp;
submitted to Phys. Rev.
Inclusive jet cross section in collisions at TeV
The inclusive jet differential cross section has been measured for jet
transverse energies, , from 15 to 440 GeV, in the pseudorapidity region
0.10.7. The results are based on 19.5 pb of data
collected by the CDF collaboration at the Fermilab Tevatron collider. The data
are compared with QCD predictions for various sets of parton distribution
functions. The cross section for jets with GeV is significantly
higher than current predictions based on O() perturbative QCD
calculations. Various possible explanations for the high- excess are
discussed.Comment: 8 pages with 2 eps uu-encoded figures Submitted to Physical Review
Letter
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