306 research outputs found
New Active Magnetic Bearing Requirements for Compressors in API 617 Eighth Edition
TutorialActive magnetic bearings (AMBs) are being used for an increasing number of compressors in the oil and gas industry. The applications include cryogenic compressor-expanders, subsea processing, pipeline and other process compressors. The use of AMBs allows totally sealed machines, reduced maintenance, elimination of the lube oil system, enhanced monitoring and diagnostic capability, and provides extremely high levels of reliability. Over the past several decades, these bearings have gone from unique, one-of-a-kind demonstrations to being the bearing of choice in an increasing number of applications. To address the more widespread use of AMB supported rotors, the eighth edition of API 617 includes a new annex which, for the first time, presents an extensive set of specifications that AMB supported compressors and compressor/expanders must meet for API service. The requirements of this annex cover basic design issues, rotordynamics, testing, and auxiliary bearings. This tutorial presents an overview of the new requirements and their rationale, resulting from a joint effort and balance of AMB manufacturers, turbo machinery OEMs and end user experience. Special considerations related to the unique requirements and issues related to rotordynamics are presented. Several examples will be discussed
International Courts as Agents of Legal Change: Evidence from LGBT Rights in Europe
Do international court judgments influence the behavior of actors other than the parties to a dispute? Are international courts agents of policy change or do their judgments merely reflect evolving social and political trends? The authors develop a theory that specifies the conditions under which international courts can use their interpretive discretion to have system-wide effects. The authors examine the theory in the context of European Court of Human Rights (ECtHR) rulings on lesbian, gay, bisexual and transgender (LGBT) issues by creating a new dataset that matches these rulings with laws in all Council of Europe (CoE) member states. The authors also collect data on LGBT policies unaffected by ECtHR judgments to control for the confounding effect of evolving trends in national policies. The authors find that ECtHR judgments against one country substantially increase the probability of national-level policy change across Europe. The marginal effects of the judgments are especially high where public acceptance of sexual minorities is low, but where national courts can rely on ECtHR precedents to invalidate domestic laws or where the government in power is not ideologically opposed to LGBT equality. The authors conclude by exploring the implications of our findings for other international courts
Radio Sources from a 31 GHz Sky Survey with the Sunyaev-Zel'dovich Array
We present the first sample of 31-GHz selected sources to flux levels of 1
mJy. From late 2005 to mid 2007, the Sunyaev-Zel'dovich Array (SZA) observed
7.7 square degrees of the sky at 31 GHz to a median rms of 0.18 mJy/beam. We
identify 209 sources at greater than 5 sigma significance in the 31 GHz maps,
ranging in flux from 0.7 mJy to ~200 mJy. Archival NVSS data at 1.4 GHz and
observations at 5 GHz with the Very Large Array are used to characterize the
sources. We determine the maximum-likelihood integrated source count to be
N(>S) = (27.2 +- 2.5) deg^-2 x (S_mJy)^(-1.18 +- 0.12) over the flux range 0.7
- 15 mJy. This result is significantly higher than predictions based on 1.4-GHz
selected samples, a discrepancy which can be explained by a small shift in the
spectral index distribution for faint 1.4-GHz sources. From comparison with
previous measurements of sources within the central arcminute of massive
clusters, we derive an overdensity of 6.8 +- 4.4, relative to field sources.Comment: 13 pages, 5 figure
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COSMOS: Python library for massively parallel workflows
Summary: Efficient workflows to shepherd clinically generated genomic data through the multiple stages of a next-generation sequencing pipeline are of critical importance in translational biomedical science. Here we present COSMOS, a Python library for workflow management that allows formal description of pipelines and partitioning of jobs. In addition, it includes a user interface for tracking the progress of jobs, abstraction of the queuing system and fine-grained control over the workflow. Workflows can be created on traditional computing clusters as well as cloud-based services. Availability and implementation: Source code is available for academic non-commercial research purposes. Links to code and documentation are provided at http://lpm.hms.harvard.edu and http://wall-lab.stanford.edu. Contact: [email protected] or [email protected]. Supplementary information: Supplementary data are available at Bioinformatics online
LoCuSS: A Comparison of Sunyaev-Zel'dovich Effect and Gravitational Lensing Measurements of Galaxy Clusters
We present the first measurement of the relationship between the
Sunyaev-Zel'dovich effect signal and the mass of galaxy clusters that uses
gravitational lensing to measure cluster mass, based on 14 X-ray luminous
clusters at z~0.2 from the Local Cluster Substructure Survey. We measure the
integrated Compton y-parameter, Y, and total projected mass of the clusters
(M_GL) within a projected clustercentric radius of 350 kpc, corresponding to
mean overdensities of 4000-8000 relative to the critical density. We find
self-similar scaling between M_GL and Y, with a scatter in mass at fixed Y of
32%. This scatter exceeds that predicted from numerical cluster simulations,
however, it is smaller than comparable measurements of the scatter in mass at
fixed T_X. We also find no evidence of segregation in Y between disturbed and
undisturbed clusters, as had been seen with T_X on the same physical scales. We
compare our scaling relation to the Bonamente et al. relation based on mass
measurements that assume hydrostatic equilibrium, finding no evidence for a
hydrostatic mass bias in cluster cores (M_GL = 0.98+/-0.13 M_HSE), consistent
with both predictions from numerical simulations and lensing/X-ray-based
measurements of mass-observable scaling relations at larger radii. Overall our
results suggest that the Sunyaev-Zel'dovich effect may be less sensitive than
X-ray observations to the details of cluster physics in cluster cores.Comment: Minor changes to match published version: 2009 ApJL 701:114-11
Joint analysis of X-ray and Sunyaev Zel'dovich observations of galaxy clusters using an analytic model of the intra-cluster medium
We perform a joint analysis of X-ray and Sunyaev Zel'dovich (SZ) effect data
using an analytic model that describes the gas properties of galaxy clusters.
The joint analysis allows the measurement of the cluster gas mass fraction
profile and Hubble constant independent of cosmological parameters. Weak
cosmological priors are used to calculate the overdensity radius within which
the gas mass fractions are reported. Such an analysis can provide direct
constraints on the evolution of the cluster gas mass fraction with redshift. We
validate the model and the joint analysis on high signal-to-noise data from the
Chandra X-ray Observatory and the Sunyaev-Zel'dovich Array for two clusters,
Abell 2631 and Abell 2204.Comment: ApJ in pres
Sunyaev Zel'dovich Effect Observations of Strong Lensing Galaxy Clusters: Probing the Over-Concentration Problem
We have measured the Sunyaev Zel'dovich (SZ) effect for a sample of ten
strong lensing selected galaxy clusters using the Sunyaev Zel'dovich Array
(SZA). The SZA is sensitive to structures on spatial scales of a few
arcminutes, while the strong lensing mass modeling constrains the mass at small
scales (typically < 30"). Combining the two provides information about the
projected concentrations of the strong lensing clusters. The Einstein radii we
measure are twice as large as expected given the masses inferred from SZ
scaling relations. A Monte Carlo simulation indicates that a sample randomly
drawn from the expected distribution would have a larger median Einstein radius
than the observed clusters about 3% of the time. The implied overconcentration
has been noted in previous studies with smaller samples of lensing clusters. It
persists for this sample, with the caveat that this could result from a
systematic effect such as if the gas fractions of the strong lensing clusters
are substantially below what is expected.Comment: submitte
a report from the Children's Oncology Group and the Utah Population Database
Relatively little is known about the epidemiology and factors underlying
susceptibility to childhood rhabdomyosarcoma (RMS). To better characterize
genetic susceptibility to childhood RMS, we evaluated the role of family
history of cancer using data from the largest case–control study of RMS and
the Utah Population Database (UPDB). RMS cases (n = 322) were obtained from
the Children's Oncology Group (COG). Population-based controls (n = 322) were
pair-matched to cases on race, sex, and age. Conditional logistic regression
was used to evaluate the association between family history of cancer and
childhood RMS. The results were validated using the UPDB, from which 130 RMS
cases were identified and matched to controls (n = 1300) on sex and year of
birth. The results were combined to generate summary odds ratios (ORs) and 95%
confidence intervals (CI). Having a first-degree relative with a cancer
history was more common in RMS cases than controls (ORs = 1.39, 95% CI:
0.97–1.98). Notably, this association was stronger among those with embryonal
RMS (ORs = 2.44, 95% CI: 1.54–3.86). Moreover, having a first-degree relative
who was younger at diagnosis of cancer (<30 years) was associated with a
greater risk of RMS (ORs = 2.37, 95% CI: 1.34–4.18). In the largest analysis
of its kind, we found that most children diagnosed with RMS did not have a
family history of cancer. However, our results indicate an increased risk of
RMS (particularly embryonal RMS) in children who have a first-degree relative
with cancer, and among those whose relatives were diagnosed with cancer at <30
years of age
Cosmological Constraints from a 31 GHz Sky Survey with the Sunyaev-Zel'dovich Array
We present the results of a 6.1 square degree survey for clusters of galaxies
via their Sunyaev- Zel'dovich (SZ) effect at 31 GHz. From late 2005 to mid 2007
the Sunyaev-Zel'dovich Array (SZA) observed four fields of roughly 1.5 square
degrees each. One of the fields shows evidence for significant diffuse Galactic
emission, and we therefore restrict our analysis to the remaining 4.4 square
degrees. We estimate the cluster detectability for the survey using mock
observations of simulations of clusters of galaxies; and determine that, at
intermediate redshifts (z ~ 0.8), the survey is 50% complete to a limiting mass
(M200 rho mean) of ~ 6.0 x 10^14M_{solar}, with the mass limit decreasing at
higher redshifts. We detect no clusters at a significance greater than 5 times
the RMS noise level in the maps, and place an upper limit on \sigma_8, the
amplitude of mass density fluctuations on a scale of 8h^-1 Mpc, of 0.84 + 0.07
at 95% confidence, where the uncertainty reflects calibration and systematic
effects. This result is consistent with estimates from other cluster surveys
and CMB anisotropy experiments.Comment: 10 pages, 7 figures, 3 table
First Results from COPSS: The CO Power Spectrum Survey
We present constraints on the abundance of carbon monoxide in the early universe from the CO Power Spectrum Survey. We utilize a data set collected between 2005 and 2008 using the Sunyaev–Zel'dovich Array (SZA), which was previously used to measure arcminute-scale fluctuations of the cosmic microwave background. This data set features observations of 44 fields, covering an effective area of 1.7 square degrees, over a frequency range of 27–35 GHz. Using the technique of intensity mapping, we are able to probe the CO(1–0) transition, with sensitivity to spatial modes between k = 0.5–2 h Mpc^(−1) over a range in redshift of z = 2.3–3.3, spanning a comoving volume of 3.6 × 10^6 h^(−3) Mpc^3. We demonstrate our ability to mitigate foregrounds, and present estimates of the impact of continuum sources on our measurement. We constrain the CO power spectrum to P_(CO) < 2.6 × 10^4 μK^2 (h^(−1) Mpc)^3, or Δ^2_(CO)(k = 1 h Mpc^(−1)) < 1.3 × 10^3 μK^2, at 95% confidence. This limit resides near optimistic predictions for the CO power spectrum. Under the assumption that CO emission is proportional to halo mass during bursts of active star formation, this corresponds to a limit on the ratio of CO(1–0) luminosity to host halo mass of A_(CO) < 1.2 × 10^(−5) L⊙_ M_⊙^(−1). Further assuming a Milky Way-like conversion factor between CO luminosity and molecular gas mass (α_(CO) = 4.3 M_⊙ (K km s^(−1) pc^(−2))^(−1)), we constrain the global density of molecular gas to ρ_(z~3) (M_H_2) ⩽ 2.8 x 10^8 M_☉ Mpc^(-3)
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