867 research outputs found
Gas Concentration Measurements in Underground Waste Storage Tanks
Currently over 100 underground tanks at the Hanford facility in eastern Washington state are being used to store high-level radioactive waste. With plans for a long-term nuclear-waste repository in Nevada in place (though not yet approved), one promising use for these underground storage tanks is as a temporary waystation for waste destined for the Nevada repository. However, without a reasonable understanding of the chemical reactions going on within the tanks, transporting waste in and out of the tanks has been deemed to be unsafe.
One hazard associated with such storage mechanisms is explosion of flammable gases produced within the tank. Within many of the storage tanks is a sludge layer. This layer, which is a mixture of liquid and solids, contains most of the radioactive material. Radioactive decay and its associated heat can produce several flammable materials within this layer. Two components of particular concern are hydrogen (H2) and nitrous oxide (N2O), since they are highly volatile in the gaseous phase. Though the tanks have either forced or natural convection systems to vent these gases, the possibility of an explosion still exists.
Measurements of these gases are taken in several ways. Continuous measurements are taken in the headspace, which is the layer between the tank ceiling and the liquid (supernatant) or sludge layer below. In tanks where a supernatant layer sits atop the sludge layer, there are often rollovers or gas release events (GREs), where a large chunk of sludge, after attaining a certain void fraction, becomes buoyant, rising through the supernatant and releasing its associated gas composition to the headspace. Such changes trigger a sensor, and thus measurements are also taken at that time.
Lastly, a retained gas sample (RGS) can be taken from either the supernatant or sludge layer. Such a core sample is quite expensive, but can yield crucial data about the way gases are being produced in the sludge and convected through the supernatant.
Unfortunately, the measurements from these three populations do not seem to match. In particular, the ratio r = [N2O]/[H2] varies from population to population. r also varies from tank to tank, but this can more readily be explained in terms of the waste composition of each tank. Since H2 is more volatile than N2O (and since there are more sources of oxygen in the headspace), lower values of r correspond to more hazardous situations.
This variance in r is troubling, since we need to be able to explain why certain values of r are lower (and hence more dangerous) in certain areas of the tank. In this report we examine the data from three tanks. We first verify that the differences in r among populations is significant. We then postulate several mechanisms which could explain such a difference
Telephone-Based versus In-Person Delivery of Cognitive Behavioral Treatment for Veterans with Chronic Multisymptom Illness: A Controlled, Randomized Trial
Background:The goal of this randomized clinical trial was to examine the efficacy of a cognitive behavioral stress reduction treatment for reducing disability among veterans with chronic multisymptom illness (CMI).Method: Veterans (N=128) who endorsed symptoms of CMI were randomized to: usual care (n=43), in-person (n=42) or telephone-delivered cognitive behavioral stress management (n=43). Assessments were conducted at baseline, three months, and twelve months. The primary outcome was limitation in roles at work and home (i.e., ârole physicalâ). Reductions in catastrophizing cognitions were evaluated as a mechanism of action. Results: Intent-to-treat analyses showed no statistically significant main effect (F(2, 164)=.58, p=.56) or interaction effect (F(4,164)=.94, p=.45) for role physical. Over time, veterans improved in their physical function (F(2,170)=5.34, p2partial=.06), PTSD symptoms (F(2,170)=9.39, p2partial=.10), depressive symptoms (F(2,170)=10.81, p2partial=.11), and physical symptoms (F(2, 172)=12.65, p2partial=.13), but these improvements did not differ across study arms over time. Completer analyses yielded similar results. There were no differences in catastrophizing between arms. Conclusion: Findings suggest stress reduction may not be the right target for improving disability among veterans with CMI. Veterans with CMI may need intervention that directly impacts medical self-management to improve disability
A Two-way Coupled Polydispersed Simulation of Bubbly Flow Beneath a Plunging Liquid Jet
ABSTRACT Plunging liquid jets are commonly encountered in nature and are widely used in industrial applications (e.g., in waterfalls, waste-water treatment, the oxygenation of chemical liquids, etc.). Despite numerous experimental studies that have been devoted to this interesting problem, there have been very few two-phase flow simulations. The main difficulty is the lack of a quantitative model to simulate the air entrainment process, which plays a critical role in this problem. In this paper, we present a computational multiphase fluid dynamics (CMFD) approach for solving this problem. The main ingredients of this approach are a comprehensive subgrid air entrainment model that predicts the rate and location of the air entrainment and a two-fluid transport model in which bubbles of different sizes are modeled as a continuum fluid. Using this approach, a Reynolds-averaged Navier Stokes (RaNS) two-way coupled two-phase flow simulation of a plunging liquid jet with a diameter of 24mm and a liquid jet velocity around 3.5m/s was performed. We analyzed the simulated void fraction and bubble count rate profiles at three different depths beneath the average free surface, and compared them with experimental data. We observed good agreement at all locations
High-resolution, H band Spectroscopy of Be Stars with SDSS-III/APOGEE: I. New Be Stars, Line Identifications, and Line Profiles
APOGEE has amassed the largest ever collection of multi-epoch,
high-resolution (R~22,500), H-band spectra for B-type emission line (Be) stars.
The 128/238 APOGEE Be stars for which emission had never previously been
reported serve to increase the total number of known Be stars by ~6%. We focus
on identification of the H-band lines and analysis of the emission peak
velocity separations (v_p) and emission peak intensity ratios (V/R) of the
usually double-peaked H I and non-hydrogen emission lines. H I Br11 emission is
found to preferentially form in the circumstellar disks at an average distance
of ~2.2 stellar radii. Increasing v_p toward the weaker Br12--Br20 lines
suggests these lines are formed interior to Br11. By contrast, the observed IR
Fe II emission lines present evidence of having significantly larger formation
radii; distinctive phase lags between IR Fe II and H I Brackett emission lines
further supports that these species arise from different radii in Be disks.
Several emission lines have been identified for the first time including
~16895, a prominent feature in the spectra for almost a fifth of the sample
and, as inferred from relatively large v_p compared to the Br11-Br20, a tracer
of the inner regions of Be disks. Unlike the typical metallic lines observed
for Be stars in the optical, the H-band metallic lines, such as Fe II 16878,
never exhibit any evidence of shell absorption, even when the H I lines are
clearly shell-dominated. The first known example of a quasi-triple-peaked Br11
line profile is reported for HD 253659, one of several stars exhibiting intra-
and/or extra-species V/R and radial velocity variation within individual
spectra. Br11 profiles are presented for all discussed stars, as are full
APOGEE spectra for a portion of the sample.Comment: accepted in A
Correlation of the Real-time Particulate Matter Emissions Measurements of a ESP Remote Sensing Device (RSD) and a Dekati Electronic Tailpipe Sensor (ETaPS) with Gravimetrically Measured PM from a Total Exhaust Dilution Tunnel System
The Open Cluster Chemical Analysis and Mapping Survey: Local Galactic Metallicity Gradient with APOGEE using SDSS DR10
The Open Cluster Chemical Analysis and Mapping (OCCAM) Survey aims to produce
a comprehensive, uniform, infrared-based dataset for hundreds of open clusters,
and constrain key Galactic dynamical and chemical parameters from this sample.
This first contribution from the OCCAM survey presents analysis of 141 members
stars in 28 open clusters with high-resolution metallicities derived from a
large uniform sample collected as part of the SDSS-III/Apache Point Observatory
Galactic Evolution Experiment (APOGEE). This sample includes the first
high-resolution metallicity measurements for 22 open clusters. With this
largest ever uniformly observed sample of open cluster stars we investigate the
Galactic disk gradients of both [M/H] and [alpha/M]. We find basically no
gradient across this range in [alpha/M], but [M/H] does show a gradient for
R_{GC} < 10 kpc and a significant flattening beyond R_{GC} = 10 kpc. In
particular, whereas fitting a single linear trend yields an [M/H] gradient of
-0.09 +/- 0.03$ dex/kpc --- similar to previously measure gradients inside 13
kpc --- by independently fitting inside and outside 10 kpc separately we find a
significantly steeper gradient near the Sun (7.9 <= R_{GC} <= 10) than
previously found (-0.20 +/- 0.08 dex/kpc) and a nearly flat trend beyond 10 kpc
(-0.02 +/- 0.09 dex/kpc).Comment: 6 pages, 4 figures, ApJ letters, in pres
Paraneoplastic thrombocytosis in ovarian cancer
<p>Background: The mechanisms of paraneoplastic thrombocytosis in ovarian cancer and the role that
platelets play in abetting cancer growth are unclear.</p>
<p>Methods: We analyzed clinical data on 619 patients with epithelial ovarian cancer to test associations between platelet counts and disease outcome. Human samples and mouse
models of epithelial ovarian cancer were used to explore the underlying mechanisms
of paraneoplastic thrombocytosis. The effects of platelets on tumor growth and angiogenesis were ascertained.</p>
<p>Results: Thrombocytosis was significantly associated with advanced disease and shortened
survival. Plasma levels of thrombopoietin and interleukin-6 were significantly elevated
in patients who had thrombocytosis as compared with those who did not. In mouse
models, increased hepatic thrombopoietin synthesis in response to tumor-derived
interleukin-6 was an underlying mechanism of paraneoplastic thrombocytosis. Tumorderived interleukin-6 and hepatic thrombopoietin were also linked to thrombocytosis
in patients. Silencing thrombopoietin and interleukin-6 abrogated thrombocytosis in
tumor-bearing mice. Antiâinterleukin-6 antibody treatment significantly reduced platelet counts in tumor-bearing mice and in patients with epithelial ovarian cancer. In
addition, neutralizing interleukin-6 significantly enhanced the therapeutic efficacy of
paclitaxel in mouse models of epithelial ovarian cancer. The use of an antiplatelet
antibody to halve platelet counts in tumor-bearing mice significantly reduced tumor
growth and angiogenesis.</p>
<p>Conclusions: These findings support the existence of a paracrine circuit wherein increased production of thrombopoietic cytokines in tumor and host tissue leads to paraneoplastic
thrombocytosis, which fuels tumor growth. We speculate that countering paraneoplastic thrombocytosis either directly or indirectly by targeting these cytokines may have
therapeutic potential. </p>
Physicians Charged with Opioid-Analgesic Prescribing Offenses
Word counts: abstract = 249 , text = 4,329 ABSTRACT Objective. To provide a "big-picture" overview of the characteristics and outcomes of recent criminal and administrative cases in which physicians have been criminally prosecuted or charged by medical boards with offenses related to inappropriate prescribing of opioid analgesics. Design: We identified as many criminal and administrative cases of these types as possible that occurred between 1998 and 2006. Cases were identified using a wide variety of sources, including organizational and government-agency databases, published news accounts, and Websites. Factual characteristics of these cases and their outcomes, and of the physicians involved, then were further researched using additional sources and methods. Setting: Study findings are intended to apply to practicing U.S. patient care physicians as a whole. Patients or other participants: There were no patients or participants in this study. Outcome measures: We analyzed the numbers and types of cases and physicians involved, criminal and administrative charges brought, case outcomes and sanctions, specialties and other characteristics of the physicians involved. Results: The study identified 725 doctors, representing an estimated 0.1% of practicing patient care physicians, who were charged between 1998 and 2006 with criminal and/or administrative offenses related to prescribing opioid analgesics. A plurality of these (39.3%) were General Practice/Family Medicine physicians, compared with 3.5% who were self-identified or board-certified pain specialists. Physicians in this sample were more likely to be male, older, and not board certified (P<0.001). DEA criminal and complaint investigations averaged 658 per year (2003)(2004)(2005)(2006) and "for cause" surrenders of DEA registrations averaged 369.7 (2000-2006). Conclusions: Criminal or administrative charges and sanctions for prescribing opioid analgesics are rare. In addition, there appears to be little objective basis for concern that pain specialists have been "singled out" for prosecution or administrative sanctioning for such offenses
Seeing the way: visual sociology and the distance runner's perspective
Employing visual and autoethnographic data from a twoâyear research project on distance runners, this article seeks to examine the activity of seeing in relation to the activity of distance running. One of its methodological aims is to develop the linkage between visual and autoethnographic data in combining an observationâbased narrative and sociological analysis with photographs. This combination aims to convey to the reader not only some of the specific subcultural knowledge and particular ways of seeing, but also something of the runner's embodied feelings and experience of momentum en route. Via the combination of narrative and photographs we seek a more effective way of communicating just how distance runners see and experience their training terrain. The importance of subjecting mundane everyday practices to detailed sociological analysis has been highlighted by many sociologists, including those of an ethnomethodological perspective. Indeed, without the competence of social actors in accomplishing these mundane, routine understandings and practices, it is argued, there would in fact be no social order
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