6,427 research outputs found
Classification of Quantum Hall Universality Classes by $\ W_{1+\infty}\ $ symmetry
We show how two-dimensional incompressible quantum fluids and their
excitations can be viewed as edge conformal field theories,
thereby providing an algebraic characterization of incompressibility. The
Kac-Radul representation theory of the algebra leads then to
a purely algebraic complete classification of hierarchical quantum Hall states,
which encompasses all measured fractions. Spin-polarized electrons in
single-layer devices can only have Abelian anyon excitations.Comment: 11 pages, RevTeX 3.0, MPI-Ph/93-75 DFTT 65/9
Energy Dissipation in Interstellar Cloud Collisions
We present a study of the kinetic energy dissipation in interstellar cloud
collisions. The main aim is to understand the dependence of the elasticity
(defined as the ratio of the final to the initial kinetic energy of the clouds)
on the velocity and mass ratio of the colliding clouds, magnetic field
strength, and gas metallicity for head-on collisions. The problem has been
studied both analytically and via numerical simulations. We have derived handy
analytical relationships that well approximate the analogous numerical results.
The main findings of this work are: (i) the kinetic energy dissipation in cloud
collisions is minimum (i.e. the collision elasticity is maximum) for a cloud
relative velocity ; (ii) the above minimum value is
proportional , where is the metallicity and is the cloud
size: the larger is the more dissipative (i.e. inelastic) the
collision will be; (iii) in general, we find that the energy dissipation
decreases when the magnetic field strength, and mass ratio of the clouds are
increased and the metallicity is decreased, respectively. We briefly discuss
the relevance of this study to the global structure of the interstellar medium
and to galaxy formation and evolution.Comment: 16 pages, aasms LaTeX, 7 figures. ApJ, accepte
Physical activity counseling in overweight and obese primary care patients: Outcomes of the VA-STRIDE randomized controlled trial.
The purpose of this 2-arm randomized clinical trial was to evaluate the effectiveness of a 12-month, expert system-based, print-delivered physical activity intervention in a primary care Veteran population in Pittsburgh, Pennsylvania. Participants were not excluded for many health conditions that typically are exclusionary criteria in physical activity trials. The primary outcome measures were physical activity reported using the Community Healthy Activities Model Program for Seniors (CHAMPS) questionnaire and an accelerometer-based activity assessment at baseline, 6, and 12 months. Of the 232 Veterans enrolled in the study, 208 (89.7%) were retained at the 6-month follow-up and 203 (87.5%) were retained at 12 months. Compared to the attention control, intervention participants had significantly increased odds of meeting the U.S. recommended guideline of âĽÂ 150 min/week of at least moderate-intensity physical activity at 12 months for the modified CHAMPS (odds ratio [OR] = 2.86; 95% CI: 1.03-7.96; p = 0.04) but not at 6 months (OR = 1.54; 95% CI: 0.56-4.23; p = 0.40). Based on accelerometer data, intervention participants had significantly increased odds of meeting âĽÂ 150 min/week of moderate-equivalent physical activity at 6 months (OR = 6.26; 95% CI: 1.26-31.22; p = 0.03) and borderline significantly increased odds at 12 months (OR = 4.73; 95% CI: 0.98-22.76; p = 0.053). An expert system physical activity counseling intervention can increase or sustain the proportion of Veterans in primary care meeting current recommendations for moderate-intensity physical activity. Trial Registration Clinical trials.gov identifier: NCT00731094 URL: http://www.clinicaltrials.gov/ct2/show/NCT00731094
Magnetohydrodynamics of Cloud Collisions in a Multi-phase Interstellar Medium
We extend previous studies of the physics of interstellar cloud collisions by
beginning investigation of the role of magnetic fields through 2D
magnetohydrodynamic (MHD) numerical simulations. We study head-on collisions
between equal mass, mildly supersonic diffuse clouds. We include a moderate
magnetic field and two limiting field geometries, with the field lines parallel
(aligned) and perpendicular (transverse) to the colliding cloud motion. We
explore both adiabatic and radiative cases, as well as symmetric and asymmetric
ones. We also compute collisions between clouds evolved through prior motion in
the intercloud medium and compare with unevolved cases.
We find that: In the (i) aligned case, adiabatic collisions, like their HD
counterparts, are very disruptive, independent of the cloud symmetry. However,
when radiative processes are taken into account, partial coalescence takes
place even in the asymmetric case, unlike the HD calculations. In the (ii)
transverse case, collisions between initially adjacent unevolved clouds are
almost unaffected by magnetic fields. However, the interaction with the
magnetized intercloud gas during the pre-collision evolution produces a region
of very high magnetic energy in front of the cloud. In collisions between
evolved clouds with transverse field geometry, this region acts like a
``bumper'', preventing direct contact between the clouds, and eventually
reverses their motion. The ``elasticity'', defined as the ratio of the final to
the initial kinetic energy of each cloud, is about 0.5-0.6 in the cases we
considered. This behavior is found both in adiabatic and radiative cases.Comment: 40 pages in AAS LaTeX v4.0, 13 figures (in degraded jpeg format).
Full resolution images as well as mpeg animations are available at
http://www.msi.umn.edu:80/Projects/twj/mhd-cc/ . Accepted for publication in
The Astrophysical Journa
Evaluating the relationship between interannual variations in the Antarctic ozone hole and Southern Hemisphere surface climate in chemistry-climate models
Studies have recently reported statistically significant relationships between observed year-to-year spring Antarctic ozone variability and the Southern Hemisphere Annular Mode and surface temperatures in spring-summer. This study investigates whether current chemistry-climate models (CCMs) can capture these relationships, in particular, the connection between November total column ozone (TCO) and Australian summer surface temperatures, where years with anomalously high TCO over the Antarctic polar cap tend to be followed by warmer summers. The interannual ozone-temperature teleconnection is examined over the historical period in the observations and simulations from the Whole Atmosphere Community Climate Model (WACCM) and nine other models participating in the Chemistry-Climate Model Initiative (CCMI). There is a systematic difference between the WACCM experiments forced with prescribed observed sea surface temperatures (SSTs) and those with an interactive ocean. Strong correlations between TCO and Australian temperatures are only obtained for the uncoupled experiment, suggesting that the SSTs could be important for driving both variations in Australian temperatures and the ozone hole, with no causal link between the two. Other CCMI models also tend to capture this relationship with more fidelity when driven by observed SSTs, though additional research and targeted modelling experiments are required to determine causality and further explore the role of model biases and observational uncertainty. The results indicate that CCMs can reproduce the relationship between spring ozone and summer Australian climate reported in observational studies, suggesting that incorporating ozone variability could improve seasonal predictions, however more work is required to understand the difference between the coupled and uncoupled simulations
Evaluating the relationship between interannual variations in the Antarctic ozone hole and Southern Hemisphere surface climate in chemistry-climate models
Studies have recently reported statistically significant relationships between observed year-to-year spring Antarctic ozone variability and the Southern Hemisphere Annular Mode and surface temperatures in spring-summer. This study investigates whether current chemistry-climate models (CCMs) can capture these relationships, in particular, the connection between November total column ozone (TCO) and Australian summer surface temperatures, where years with anomalously high TCO over the Antarctic polar cap tend to be followed by warmer summers. The interannual ozone-temperature teleconnection is examined over the historical period in the observations and simulations from the Whole Atmosphere Community Climate Model (WACCM) and nine other models participating in the Chemistry-Climate Model Initiative (CCMI). There is a systematic difference between the WACCM experiments forced with prescribed observed sea surface temperatures (SSTs) and those with an interactive ocean. Strong correlations between TCO and Australian temperatures are only obtained for the uncoupled experiment, suggesting that the SSTs could be important for driving both variations in Australian temperatures and the ozone hole, with no causal link between the two. Other CCMI models also tend to capture this relationship with more fidelity when driven by observed SSTs, though additional research and targeted modelling experiments are required to determine causality and further explore the role of model biases and observational uncertainty. The results indicate that CCMs can reproduce the relationship between spring ozone and summer Australian climate reported in observational studies, suggesting that incorporating ozone variability could improve seasonal predictions, however more work is required to understand the difference between the coupled and uncoupled simulations
The effects of nitroxyl (HNO) on soluble guanylate cyclase activity: interactions at ferrous heme and cysteine thiols
It has been previously proposed that nitric oxide (NO) is the only biologically relevant nitrogen oxide capable of activating the enzyme soluble guanylate cyclase (sGC). However, recent reports implicate HNO as another possible activator of sGC. Herein, we examine the affect of HNO donors on the activity of purified bovine lung sGC and find that, indeed, HNO is capable of activating this enzyme. Like NO, HNO activation appears to occur via interaction with the regulatory ferrous heme on sGC. Somewhat unexpectedly, HNO does not activate the ferric form of the enzyme. Finally, HNO-mediated cysteine thiol modification appears to also affect enzyme activity leading to inhibition. Thus, sGC activity can be regulated by HNO via interactions at both the regulatory heme and cysteine thiols
Air quality evaluation of London Paddington train station
Enclosed railway stations hosting diesel trains are at risk of reduced air quality as a result of exhaust emissions that may endanger passengers and workers. Air quality measurements were conducted inside London Paddington Station, a semi-enclosed railway station where 70% of trains are powered by diesel engines. Particulate matter (PM2.5) mass was measured at five station locations. PM size, PM number, oxides of nitrogen (NOx), and sulfur dioxide (SO2) were measured at two station locations. Paddington Stationâs hourly mean PM2.5 mass concentrations averaged 16 Îźg/m3 [min 2, max 68]. Paddington Stationâs hourly mean NO2 concentrations averaged 73 ppb [49, 120] and SO2 concentrations averaged 25 ppb [15, 37]. While UK train stations are not required to comply with air quality standards, there were five instances where the hourly mean NO2 concentrations exceeded the EU hourly mean limits (106 ppb) for outdoor air quality. PM2.5, SO2, and NO2 concentrations were compared against Marylebone, a busy London roadside 1.5 km from the station. The comparisons indicated that train station air quality was more polluted than the nearby roadside. PM2.5 for at least one measurement location within Paddington Station was shown to be statistically higher (P-value < 0.05) than Marylebone on 3 out of 4 days. Measured NO2 within Paddington Station was statistically higher than Marylebone on 4 out of 5 days. Measured SO2 within Paddington Station was statistically higher than Marylebone on all 3 days.We thank the Engineering and Physical Sciences Research Council (EP/F034350/1) for funding the Energy Efficient Cities Initiative and the Schiff Foundation for doctoral studentship funding.This is the final version of the article. It first appeared from IOP via http://dx.doi.org/10.1088/1748-9326/10/9/09401
Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV
A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay
channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7
TeV is presented. The data were collected at the LHC, with the CMS detector,
and correspond to an integrated luminosity of 4.6 inverse femtobarns. No
significant excess is observed above the background expectation, and upper
limits are set on the Higgs boson production cross section. The presence of the
standard model Higgs boson with a mass in the 270-440 GeV range is excluded at
95% confidence level.Comment: Submitted to JHE
Exercise recommendations for people with bone metastases: Expert consensus for healthcare providers and clinical exercise professionals
Purpose: Exercise has been underutilized in people with advanced or incurable cancer despite the potential to improve physical function and reduce psychosocial morbidity, especially for people with bone metastases because of concerns over skeletal complications. The International Bone Metastases Exercise Working Group (IBMEWG) was formed to develop best practice recommendations for exercise programming for people with bone metastases on the basis of published research, clinical experience, and expert opinion. Methods: The IBMEWG undertook sequential steps to inform the recommendations: (1) modified Delphi survey, (2) systematic review, (3) cross-sectional survey to physicians and nurse practitioners, (4) in-person meeting of IBMEWG to review evidence from steps 1-3 to develop draft recommendations, and (5) stakeholder engagement. Results: Recommendations emerged from the contributing evidence and IBMEWG discussion for pre-exercise screening, exercise testing, exercise prescription, and monitoring of exercise response. Identification of individuals who are potentially at higher risk of exercise-related skeletal complication is a complex interplay of these factors: (1) lesion-related, (2) cancer and cancer treatmentârelated, and (3) the person-related. Exercise assessment and prescription requires consideration of the location and presentation of bone lesion(s) and should be delivered by qualified exercise professionals with oncology education and exercise prescription experience. Emphasis on postural alignment, controlled movement, and proper technique is essential. Conclusion: Ultimately, the perceived risk of skeletal complications should be weighed against potential health benefits on the basis of consultation between the person, health care team, and exercise professionals. These recommendations provide an initial framework to improve the integration of exercise programming into clinical care for people with bone metastases
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