4,208 research outputs found
A model for analysis of the temperature field downstream of a heated jet injected into an isothermal crossflow at an angle of 90 deg
The temperature distribution downstream of a heated jet entering an isothermal crossflow at an angle of 90 deg is predicted using two conduction models with energy sources above the point of injection, in one case a point source and in the second a line source. The models use effective turbulent diffusivities that are determined empirically from previous measurements. Temperatures predicted by the models are compared to experimental results
A study to determine the incidence and prevalence of newly discovered human immunodeficiency virus infection during the prenatal care period.
OBJECTIVES: This study asked the following questions: 1) Does HIV testing in pregnancy identify women who previously were not known to be HIV positive? 2) When in pregnancy are women identified as HIV infected? 3) Does HIV seroconversion occur during the prenatal care period? METHODS: Medical records of 97 women from two primarily indigent care hospitals in Houston, TX who were found to be HIV positive at delivery were reviewed to determine if they had tested positive during the prenatal care period. Demographics and time of gestation of the prenatal testing also were recorded. The outcome measures were: 1) number of women found positive during prenatal care; 2) week of gestation at discovery of HIV positivity; and 3) number of women seroconverting between the initiation of prenatal care and delivery. RESULTS: Thirty women were known to be HIV positive prior to pregnancy. Fifty-six women were found to be positive during prenatal care and the seropositivity of 44 was discovered before the 34th week of pregnancy. Ten women were found to be positive at their first prenatal visit, which occurred after the 34th week. Date of testing was unknown for two women. Eleven women who received no prenatal care were found to be HIV positive at delivery. There were no seroconversions while women were under prenatal care. CONCLUSIONS: HIV testing at delivery did not find any HIV-positive women who had tested negative during prenatal care. Testing is very important for women who do not receive prenatal care. Making certain that high-risk women get into prenatal care also is very important
Joint Bayesian component separation and CMB power spectrum estimation
We describe and implement an exact, flexible, and computationally efficient
algorithm for joint component separation and CMB power spectrum estimation,
building on a Gibbs sampling framework. Two essential new features are 1)
conditional sampling of foreground spectral parameters, and 2) joint sampling
of all amplitude-type degrees of freedom (e.g., CMB, foreground pixel
amplitudes, and global template amplitudes) given spectral parameters. Given a
parametric model of the foreground signals, we estimate efficiently and
accurately the exact joint foreground-CMB posterior distribution, and therefore
all marginal distributions such as the CMB power spectrum or foreground
spectral index posteriors. The main limitation of the current implementation is
the requirement of identical beam responses at all frequencies, which restricts
the analysis to the lowest resolution of a given experiment. We outline a
future generalization to multi-resolution observations. To verify the method,
we analyse simple models and compare the results to analytical predictions. We
then analyze a realistic simulation with properties similar to the 3-yr WMAP
data, downgraded to a common resolution of 3 degree FWHM. The results from the
actual 3-yr WMAP temperature analysis are presented in a companion Letter.Comment: 23 pages, 16 figures; version accepted for publication in ApJ -- only
minor changes, all clarifications. More information about the WMAP3 analysis
available at http://www.astro.uio.no/~hke under the Research ta
Instability of reconstruction of the low CMB multipoles
We discuss the problem of the bias of the Internal Linear Combination (ILC)
CMB map and show that it is closely related to the coefficient of
cross-correlation K(l) of the true CMB and the foreground for each multipole l.
We present analysis of the cross-correlation for the WMAP ILC quadrupole and
octupole from the first (ILC(I)) and the third (ILC(III)) year data releases
and show that these correlations are about -0.52-0.6. Analysing 10^4 Monte
Carlo simulations of the random Gaussian CMB signals, we show that the
distribution function for the corresponding coefficient of the
cross-correlation has a polynomial shape P(K,l)\propto(1-K^2)^(l-1). We show
that the most probable value of the cross-correlation coefficient of the ILC
and foreground quadrupole has two extrema at K ~= +/-0.58$. Thus, the ILC(III)
quadrupole represents the most probable value of the coefficient K. We analyze
the problem of debiasing of the ILC CMB and pointed out that reconstruction of
the bias seems to be very problematic due to statistical uncertainties. In
addition, instability of the debiasing illuminates itself for the quadrupole
and octupole components through the flip-effect, when the even (l+m) modes can
be reconstructed with significant error. This error manifests itself as
opposite, in respect to the true sign of even low multipole modes, and leads to
significant changes of the coefficient of cross-correlation with the
foreground. We show that the CMB realizations, whose the sign of quadrupole
(2,0) component is negative (and the same, as for all the foregrounds), the
corresponding probability to get the positive sign after implementation of the
ILC method is about 40%.Comment: 11 pages, 5 figure
Film cooling following injection through inclined circular tubes
Film cooling following air injection through inclined flat plate holes into turbulent boundary laye
Hot pixel contamination in the CMB correlation function?
Recently, it was suggested that the map-making procedure, which is applied to
the time-ordered CMB data by the WMAP team, might be flawed by hot pixels. This
could lead to a bias in the pixels having an angular distance of about 141
degrees from hot pixels due to the differential measuring process of the
satellite WMAP. Here, the bias is confirmed, and the temperature two-point
correlation function C(theta) is reevaluated by excluding the affected pixels.
It is shown that the most significant effect occurs in C(theta) at the largest
angles near theta = 180 degrees. Furthermore, the corrected correlation
function C(theta) is applied to the cubic topology of the Universe, and it is
found that such a multi-connected universe matches the temperature correlation
better than the LCDM concordance model, provided the cubic length scale is
close to L=4 measured in units of the Hubble length
Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Data Processing, Sky Maps, and Basic Results
We present new full-sky temperature and polarization maps in five frequency
bands from 23 to 94 GHz, based on data from the first five years of the WMAP
sky survey. The five-year maps incorporate several improvements in data
processing made possible by the additional years of data and by a more complete
analysis of the instrument calibration and in-flight beam response. We present
several new tests for systematic errors in the polarization data and conclude
that Ka band data (33 GHz) is suitable for use in cosmological analysis, after
foreground cleaning. This significantly reduces the overall polarization
uncertainty. With the 5 year WMAP data, we detect no convincing deviations from
the minimal 6-parameter LCDM model: a flat universe dominated by a cosmological
constant, with adiabatic and nearly scale-invariant Gaussian fluctuations.
Using WMAP data combined with measurements of Type Ia supernovae and Baryon
Acoustic Oscillations, we find (68% CL uncertainties): Omega_bh^2 = 0.02267 \pm
0.00059, Omega_ch^2 = 0.1131 \pm 0.0034, Omega_Lambda = 0.726 \pm 0.015, n_s =
0.960 \pm 0.013, tau = 0.084 \pm 0.016, and Delta_R^2 = (2.445 \pm 0.096) x
10^-9. From these we derive: sigma_8 = 0.812 \pm 0.026, H_0 = 70.5 \pm 1.3
km/s/Mpc, z_{reion} = 10.9 \pm 1.4, and t_0 = 13.72 \pm 0.12 Gyr. The new limit
on the tensor-to-scalar ratio is r < 0.22 (95% CL). We obtain tight,
simultaneous limits on the (constant) dark energy equation of state and spatial
curvature: -0.14 < 1+w < 0.12 and -0.0179 < Omega_k < 0.0081 (both 95% CL). The
number of relativistic degrees of freedom (e.g. neutrinos) is found to be
N_{eff} = 4.4 \pm 1.5, consistent with the standard value of 3.04. Models with
N_{eff} = 0 are disfavored at >99.5% confidence.Comment: 46 pages, 13 figures, and 7 tables. Version accepted for publication,
ApJS, Feb-2009. Includes 5-year dipole results and additional references.
Also available at
http://lambda.gsfc.nasa.gov/product/map/dr3/map_bibliography.cf
Non-detection of a statistically anisotropic power spectrum in large-scale structure
We search a sample of photometric luminous red galaxies (LRGs) measured by
the Sloan Digital Sky Survey (SDSS) for a quadrupolar anisotropy in the
primordial power spectrum, in which P(\vec{k}) is an isotropic power spectrum
P(k) multiplied by a quadrupolar modulation pattern. We first place limits on
the 5 coefficients of a general quadrupole anisotropy. We also consider
axisymmetric quadrupoles of the form P(\vec{k}) = P(k){1 +
g_*[(\hat{k}\cdot\hat{n})^2-1/3]} where \hat{n} is the axis of the anisotropy.
When we force the symmetry axis \hat{n} to be in the direction (l,b)=(94
degrees,26 degrees) identified in the recent Groeneboom et al. analysis of the
cosmic microwave background, we find g_*=0.006+/-0.036 (1 sigma). With uniform
priors on \hat{n} and g_* we find that -0.41<g_*<+0.38 with 95% probability,
with the wide range due mainly to the large uncertainty of asymmetries aligned
with the Galactic Plane. In none of these three analyses do we detect evidence
for quadrupolar power anisotropy in large scale structure.Comment: 23 pages; 10 figures; 3 tables; replaced with version published in
JCAP (added discussion of scale-varying quadrupolar anisotropy
Energy spectra of the ocean's internal wave field: theory and observations
The high-frequency limit of the Garrett and Munk spectrum of internal waves
in the ocean and the observed deviations from it are shown to form a pattern
consistent with the predictions of wave turbulence theory. In particular, the
high frequency limit of the Garrett and Munk spectrum constitutes an {\it
exact} steady state solution of the corresponding kinetic equation.Comment: 4 pages, one color figur
Dietary assessment of British police force employees: A description of diet record coding procedures and cross-sectional evaluation of dietary energy intake reporting (The Airwave Health Monitoring Study)
Objectives: Dietary intake is a key aspect of occupational health. To capture the characteristics of dietary behaviour that is affected by occupational environment that may affect disease risk, a collection of prospective multiday dietary records is required. The aims of this paper are to: (1) collect multiday dietary data in the Airwave Health Monitoring Study, (2) describe the di etary coding procedures applied and (3) investigate the plausibility of dietary reporting in this occupational cohort. Design: A dietary coding protocol for this large-scale study was developed to minimise coding error rate. Participants (n 4412) who completed 7-day food records were included for cross-sectional analyses. Energy intake (EI) misreporting was estimated using the Goldberg method. Multivariate logistic regression models were applied to determine participant characteristics associated with EI misreporting. Setting: British police force employees enrolled (2007-2012) into the Airwave Health Monitoring Study. Results: The mean code error rate per food diary was 3.7% (SD 3.2%). The strongest predictors of EI under-reporting were body mass index (BMI) and physical activity. Compared with participants with BMI 30 kg/m2 had increased odds of being classified as under-reporting EI (men OR 5.20 95% CI 3.92 to 6.89; women OR 2.66 95% CI 1.85 to 3.83). Men and women in the highest physical activity category compared with the lowest were also more likely to be classified as underreporting (men OR 3.33 95% CI 2.46 to 4.50; women OR 4.34 95% CI 2.91 to 6.55). Conclusions: A reproducible dietary record coding procedure has been developed to minimise coding error in complex 7-day diet diaries. The prevalence of EI under-reporting is comparable with existing national UK cohorts and, in agreement with previous studies, classification of under-reporting was biased towards specific subgroups of participants
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