483 research outputs found
Homotopy Theoretic Models of Type Theory
We introduce the notion of a logical model category which is a Quillen model
category satisfying some additional conditions. Those conditions provide enough
expressive power that one can soundly interpret dependent products and sums in
it. On the other hand, those conditions are easy to check and provide a wide
class of models some of which are listed in the paper.Comment: Corrected version of the published articl
Pregnancy complications as markers for subsequent maternal cardiovascular disease: Validation of a maternal recall questionnaire
Background: We designed and tested the validity of a questionnaire to characterize maternal recall of pregnancy complications associated with increased future cardiovascular disease risk, based on the 2011 American Heart Association (AHA) guidelines. Methods: A maternal recall questionnaire of pregnancy history was administered to 971 patients who had participated in a previous cohort study of 1,608 pregnant women. Medical records from the study pregnancy served as the gold standard. Prevalence, sensitivity (sens), specificity (spec), positive predictive value (PPV), negative predictive value (NPV), and/or Spearman's correlation coefficients (r) were calculated for each question. Results: A total of 526 (54%) individuals recontacted responded. Respondents were more likely to be older, white, educated, and nulliparous and were less likely to deliver low-birthweight infants in the study pregnancy than were individuals who did not respond. Mean length of recall was 4.35 years (standard deviation [SD] 0.46) postpartum. Maternal recall was most accurate for gestational diabetes (sens: 92%, spec: 98%, PPV: 79%, NPV: 99%), infant birthweight (r=0.95), and gestation length (r=0.85). Maternal recall was modest for preeclampsia (sens: 79%, spec: 97%, PPV: 68%, NPV: 98%) and pregnancy-associated hypertension, including preeclampsia or gestational hypertension (sens: 60%, spec: 95%, PPV: 64%, NPV: 94%). Conclusions: This validation study demonstrated that the majority of women could accurately recall a history of gestational diabetes, infant birthweight, and gestational age at delivery, 4 years postpartum on average. Recall of preeclampsia and pregnancy-associated hypertension overall was modest. Maternal report of these pregnancy conditions may help clinicians identify women at increased risk for cardiovascular disease
Cross Section Measurement of Charged Pion Photoproduction from Hydrogen and Deuterium
We have measured the differential cross section for the gamma n --> pi- p and
gamma p --> pi+ n reactions at center of mass angle of 90 degree in the photon
energy range from 1.1 to 5.5 GeV at Jefferson Lab (JLab). The data at photon
energies greater than 3.3 GeV exhibit a global scaling behavior for both pi-
and pi+ photoproduction, consistent with the constituent counting rule and the
existing pi+ photoproduction data. Possible oscillations around the scaling
value are suggested by these new data The data show enhancement in the scaled
cross section at a center-of-mass energy near 2.2 GeV. The cross section ratio
of exclusive pi- to pi+ photoproduction at high energy is consistent with the
prediction based on one-hard-gluon-exchange diagrams
Measurement of the proton electric to magnetic form factor ratio from \vec ^1H(\vec e, e'p)
We report the first precision measurement of the proton electric to magnetic
form factor ratio from spin-dependent elastic scattering of longitudinally
polarized electrons from a polarized hydrogen internal gas target. The
measurement was performed at the MIT-Bates South Hall Ring over a range of
four-momentum transfer squared from 0.15 to 0.65 (GeV/c).
Significantly improved results on the proton electric and magnetic form factors
are obtained in combination with previous cross-section data on elastic
electron-proton scattering in the same region.Comment: 4 pages, 2 figures, submitted to PR
Scaling of the F_2 structure function in nuclei and quark distributions at x>1
We present new data on electron scattering from a range of nuclei taken in
Hall C at Jefferson Lab. For heavy nuclei, we observe a rapid falloff in the
cross section for , which is sensitive to short range contributions to the
nuclear wave-function, and in deep inelastic scattering corresponds to probing
extremely high momentum quarks. This result agrees with higher energy muon
scattering measurements, but is in sharp contrast to neutrino scattering
measurements which suggested a dramatic enhancement in the distribution of the
`super-fast' quarks probed at x>1. The falloff at x>1 is noticeably stronger in
^2H and ^3He, but nearly identical for all heavier nuclei.Comment: 5 pages, 4 figures, to be submitted to physical revie
Cross Section Measurements of Charged Pion Photoproduction in Hydrogen and Deuterium from 1.1 to 5.5 GeV
The differential cross section for the gamma +n --> pi- + p and the gamma + p
--> pi+ n processes were measured at Jefferson Lab. The photon energies ranged
from 1.1 to 5.5 GeV, corresponding to center-of-mass energies from 1.7 to 3.4
GeV. The pion center-of-mass angles varied from 50 degree to 110 degree. The
pi- and pi+ photoproduction data both exhibit a global scaling behavior at high
energies and high transverse momenta, consistent with the constituent counting
rule prediction and the existing pi+ data. The data suggest possible
substructure of the scaling behavior, which might be oscillations around the
scaling value. The data show an enhancement in the scaled cross section at
center-of-mass energy near 2.2 GeV. The differential cross section ratios at
high energies and high transverse momenta can be described by calculations
based on one-hard-gluon-exchange diagrams.Comment: 18 pages, 19 figure
New measurements of high-momentum nucleons and short-range structures in nuclei
We present new measurements of electron scattering from high-momentum
nucleons in nuclei. These data allow an improved determination of the strength
of two-nucleon correlations for several nuclei, including light nuclei where
clustering effects can, for the first time, be examined. The data also include
the kinematic region where three-nucleon correlations are expected to dominate.Comment: 5 pages, 3 figures. Results from JLab E02-01
Probing Quark-Gluon Interactions with Transverse Polarized Scattering
We have extracted QCD matrix elements from our data on double polarized
inelastic scattering of electrons on nuclei. We find the higher twist matrix
element \tilde{d_2}, which arises strictly from quark- gluon interactions, to
be unambiguously non zero. The data also reveal an isospin dependence of higher
twist effects if we assume that the Burkhardt-Cottingham Sum rule is valid. The
fundamental Bjorken sum rule obtained from the a0 matrix element is satisfied
at our low momentum transfer.Comment: formerly "Nachtmann Moments of the Proton and Deuteron Spin Structure
Functions
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