3,989 research outputs found
Nonlinear evolution of the r-modes in neutron stars.
The evolution of a neutron-star -mode driven unstable by gravitational radiation is studied here using numerical solutions of the full nonlinear fluid equations. The dimensionless amplitude of the mode grows to order unity before strong shocks develop which quickly damp the mode. In this simulation the star loses about of its initial angular momentum and of its rotational kinetic energy before the mode is damped. The nonlinear evolution causes the fluid to develop strong differential rotation which is concentrated near the surface and poles of the star
Generalized Hamilton-Jacobi equations for nonholonomic dynamics
Employing a suitable nonlinear Lagrange functional, we derive generalized
Hamilton-Jacobi equations for dynamical systems subject to linear velocity
constraints. As long as a solution of the generalized Hamilton-Jacobi equation
exists, the action is actually minimized (not just extremized)
Microbiological alterations in the conjunctiva of hot tub-soaking ophthalmologists (MACHO): a randomized double-blind clinical trial
Background: To determine if there is a difference in the quantity of microbial flora of the conjunctiva in individuals practicing head submersion (“dunkâ€) versus no head submersion (“no-dunkâ€) during hot tub use.
Methods: In this double-blind randomized clinical trial, healthy volunteers aged ≥ 18 years were recruited. Participants were randomized to head submersion versus no head submersion during a 15-minute hot tub soak. Study personnel, masked to the dunk or no-dunk group assignment, obtained conjunctival cultures before and immediately after hot tub use. De-identified specimens were submitted to the clinical microbiology laboratory for culture and analysis. The main outcome measure was the difference in the quantity of organisms cultured from the conjunctiva before and after hot tub exposure, as determined using a defined ordinal scale. A two-tailed Student’s t-test was performed to compare the total microbial colony counts between the two arms. Simpson’s diversity was used to measure the changes in organism diversity between the arms.
Results: Of 36 enrolled subjects, 19 were randomly assigned to the dunk and 17 were assigned to the no-dunk groups. Water samples obtained from all hot tubs were culture negative. Eleven of 19 eyes (58%) from the dunk group and eight of 17 eyes (47%) from the no-dunk group had negative conjunctival bacterial cultures before and after hot tub exposure. However, six of 19 eyes (32%) and four of 17 eyes (24%) of the dunk and no-dunk groups, respectively, were culture-positive after, but not before hot tub exposure. The quantity of organisms before and after hot tub exposure was not significantly different between the two arms (P = 0.12). However, the dunk group only showed a small increase in the quantity of organisms after as compared to before hot tub use (P = 0.03). None of the samples from subjects or hot tubs were culture-positive for Acanthamoeba.
Conclusion: Head submersion in a public hot tubs during a 15-minute soak does not appear to change conjunctival flora, as determined by culture plate yield
Flux Stabilization in 6 Dimensions: D-terms and Loop Corrections
We analyse D-terms induced by gauge theory fluxes in the context of
6-dimensional supergravity models. On the one hand, this is arguably the
simplest concrete setting in which the controversial idea of `D-term uplifts'
can be investigated. On the other hand, it is a very plausible intermediate
step on the way from a 10d string theory model to 4d phenomenology. Our
specific results include the flux-induced one-loop correction to the scalar
potential coming from charged hypermultiplets. Furthermore, we comment on the
interplay of gauge theory fluxes and gaugino condensation in the present
context, demonstrate explicitly how the D-term arises from the gauging of one
of the compactification moduli, and briefly discuss further ingredients that
may be required for the construction of a phenomenologically viable model. In
particular, we show how the 6d dilaton and volume moduli can be simultaneously
stabilized, in the spirit of KKLT, by the combination of an R symmetry twist, a
gaugino condensate, and a flux-induced D-term.Comment: 24 pages, 1 figure v2:minor correction
Detection strategies for scalar gravitational waves with interferometers and resonant spheres
We compute the response and the angular pattern function of an interferometer
for a scalar component of gravitational radiation in Brans-Dicke theory. We
examine the problem of detecting a stochastic background of scalar GWs and
compute the scalar overlap reduction function in the correlation between an
interferometer and the monopole mode of a resonant sphere. While the
correlation between two interferometers is maximized taking them as close as
possible, the interferometer-sphere correlation is maximized at a finite value
of f*d, where `f' is the resonance frequency of the sphere and `d' the distance
between the detectors. This defines an optimal resonance frequency of the
sphere as a function of the distance. For the correlation between the Virgo
interferometer located near Pisa and a sphere located in Frascati, near Rome,
we find an optimal resonance frequency f=590 Hz. We also briefly discuss the
difficulties in applying this analysis to the dilaton and moduli fields
predicted by string theory.Comment: 26 pages, Latex, 4 Postscript figures. Various minor improvements,
misprint in eqs. 42, 127, 138 corrected, references adde
Angiogenic gene expression and vascular density are reflected in ultrasonographic features of synovitis in early Rheumatoid Arthritis: an observational study.
INTRODUCTION: Neovascularization contributes to the development of sustained synovial inflammation in the early stages of Rheumatoid Arthritis. Ultrasound (US) provides an indirect method of assessing synovial blood flow and has been shown to correlate with clinical disease activity in patients with Rheumatoid Arthritis. This study examines the relationship of US determined synovitis with synovial vascularity, angiogenic/lymphangiogenic factors and cellular mediators of inflammation in a cohort of patients with early Rheumatoid Arthritis (RA) patients prior to therapeutic intervention with disease modifying therapy or corticosteroids. METHODS: An ultrasound guided synovial biopsy of the supra-patella pouch was performed in 12 patients with early RA prior to treatment. Clinical, US and biochemical assessments were undertaken prior to the procedure. Ultrasound images and histological samples were obtained from the supra-patella pouch. Histological samples were stained for Factor VIII and a-SMA (a-smooth muscle actin). Using digital imaging analysis a vascular area score was recorded. QT-PCR (quantitative-PCR) of samples provided quantification of angiogenic and lymphangiogenic gene expression and immunohistochemistry stained tissue was scored for macrophage, T cell and B cell infiltration using an existing semi-quantitative score. RESULTS: Power Doppler showed a good correlation with histological vascular area (Spearman r--0.73) and angiogenic factors such as vascular endothelial growth factor-A (VEGF-A), Angiopoietin 2 and Tie-2. In addition, lymphangiogenic factors such as VEGF-C and VEGF-R3 correlated well with US assessment of synovitis. A significant correlation was also found between power Doppler and synovial thickness, pro-inflammatory cytokines and sub-lining macrophage infiltrate. Within the supra-patella pouch there was no significant difference in US findings, gene expression or inflammatory cell infiltrate between any regions of synovium biopsied. CONCLUSION: Ultrasound assessment of synovial tissue faithfully reflects synovial vascularity. Both grey scale and power Doppler synovitis in early RA patients correlate with a pro-angiogenic and lymphangiogenic gene expression profile. In early RA both grey scale and power Doppler synovitis are associated with a pro-inflammatory cellular and cytokine profile providing considerable validity in its use as an objective assessment of synovial inflammation in clinical practice
Spectral Energy Distributions of Local Luminous And Ultraluminous Infrared Galaxies
Luminous and ultraluminous infrared galaxies ((U)LIRGs) are the most extreme
star forming galaxies in the universe. The local (U)LIRGs provide a unique
opportunity to study their multi-wavelength properties in detail for comparison
to their more numerous counterparts at high redshifts. We present common large
aperture photometry at radio through X-ray wavelengths, and spectral energy
distributions (SEDs) for a sample of 53 nearby LIRGs and 11 ULIRGs spanning log
(LIR/Lsun) = 11.14-12.57 from the flux-limited Great Observatories All-sky LIRG
Survey (GOALS). The SEDs for all objects are similar in that they show a broad,
thermal stellar peak and a dominant FIR thermal dust peak, where nuLnu(60um) /
nuLnu(V) increases from ~2-30 with increasing LIR. When normalized at
IRAS-60um, the largest range in the luminosity ratio,
R(lambda)=log[nuLnu(lambda)/nuLnu(60um)] observed over the full sample is seen
in the Hard X-rays (HX=2-10 keV). A small range is found in the Radio (1.4GHz),
where the mean ratio is largest. Total infrared luminosities, LIR(8-1000um),
dust temperatures, and dust masses were computed from fitting thermal dust
emission modified blackbodies to the mid-infrared (MIR) through submillimeter
SEDs. The new results reflect an overall ~0.02 dex lower luminosity than the
original IRAS values. Total stellar masses were computed by fitting stellar
population synthesis models to the observed near-infrared (NIR) through
ultraviolet (UV) SEDs. Mean stellar masses are found to be log(M/Msun) =
10.79+/-0.40. Star formation rates have been determined from the infrared
(SFR_IR~45Msun/yr) and from the monochromatic UV luminosities
(SFR_UV~1.3Msun/yr), respectively. Multiwavelength AGN indicators have be used
to select putative AGN: about 60% of the ULIRGs would have been classified as
an AGN by at least one of the selection criteria.Comment: 39 pages, including 12 figures and 11 tables; accepted for
publication in ApJ
Overdensities of Y-dropout Galaxies from the Brightest-of-Reionizing Galaxies Survey: A Candidate Protocluster at Redshift z~8
Theoretical and numerical modeling of dark-matter halo assembly predicts that
the most luminous galaxies at high redshift are surrounded by overdensities of
fainter companions. We test this prediction with HST observations acquired by
our Brightest of Reionizing Galaxies (BoRG) survey, which identified four very
bright z~8 candidates as Y-dropout sources in four of the 23 non-contiguous
WFC3 fields observed. We extend here the search for Y-dropouts to fainter
luminosities (M_* galaxies with M_AB\sim-20), with detections at >5sigma
confidence (compared to >8sigma confidence adopted earlier) identifying 17 new
candidates. We demonstrate that there is a correlation between number counts of
faint and bright Y-dropouts at >99.84% confidence. Field BoRG58, which contains
the best bright z\sim8 candidate (M_AB=-21.3), has the most significant
overdensity of faint Y-dropouts. Four new sources are located within 70arcsec
(corresponding to 3.1 comoving Mpc at z=8) from the previously known brighter
z\sim8 candidate. The overdensity of Y-dropouts in this field has a physical
origin to high confidence (p>99.975%), independent of completeness and
contamination rate of the Y-dropout selection. We modeled the overdensity by
means of cosmological simulations and estimate that the principal dark matter
halo has mass M_h\sim(4-7)x10^11Msun (\sim5sigma density peak) and is
surrounded by several M_h\sim10^11Msun halos which could host the fainter
dropouts. In this scenario, we predict that all halos will eventually merge
into a M_h>2x10^14Msun galaxy cluster by z=0. Follow-up observations with
ground and space based telescopes are required to secure the z\sim8 nature of
the overdensity, discover new members, and measure their precise redshift.Comment: Minor revision: ApJ accepted [17 pages (emulateapj style), 7 figures,
2 tables
IAT-TiMeS: Intra-Arterial Thrombectomy Transfer Metric Study in Texas
Objective: We aim to report intra-arterial thrombectomy transfer metrics for ischemic stroke patients that were transferred to hub hospitals for possible intra-arterial thrombectomy in multiple geographic regions throughout the state of Texas and to identify potential barriers and delays in the intra-arterial thrombectomy transfer process.
Method: We prospectively collected data from 8 participating Texas comprehensive stroke/thrombectomy capable centers from 7 major regions in the State of Texas. We collected baseline clinical and imaging data related to the pre-transfer evaluation, transfer metrics, and post-transfer clinical and imaging data.
Results: A total of 103 acute ischemic stroke patients suspected/confirmed to have large vessel occlusions between December 2016 to May 2019 that were transferred to hubs as possible intra-arterial thrombectomy candidates were enrolled. A total of 56 (54%) patients were sent from the spoke to the hub via ground ambulance with 47 (46%) patients traveling via air ambulance. The median spoke arrival to hub arrival time was 174 min, median spoke arrival to departure from spoke was 131 min, and median travel time was 39 min. The spoke arrival time to transfer initiation was 68 min. CT-perfusion obtained at the spoke and earlier initiation of transfer were statistically associated with shorter transfer times.
Conclusion: Transfer of intra-arterial thrombectomy patients in Texas may take over 4 h from spoke arrival to hub arrival. This time may be shortened by earlier transfer initiation and acceptance
Glaucomatous Optic Neuropathy Associated with Nocturnal Dip in Blood Pressure: Findings from the Maracaibo Aging Study
Purpose—To determine which nocturnal blood pressure (BP) parameters (low levels or extreme dipper status) are associated with an increased risk of glaucomatous damage in Hispanics.
Design—Observational cross-sectional study.
Participants—A subset (n=93) of the participants from the Maracaibo Aging Study (MAS) who met the study eligibility criteria were included. These participants — who were at least 40 years of age — had measurements for optical tomography coherence, visual field tests, 24-hour BP, office BP, and intraocular pressureHg.
Methods—Univariate and multivariate logistic regression analyses under the generalized estimating equations (GEE) framework were used to examine the relationships between glaucomatous damage and BP parameters, with particular attention to drops in nocturnal BP. Main Outcome Measures—Glaucomatous optic neuropathy (GON) based on the presence of optic nerve damage and visual field defects.
Results—The mean age was 61.9 years, and 87.1% were women. Of 185 eyes evaluated, 50 (27.0%) had signs of GON. Individuals with GON had significantly lower 24-hour and nighttime diastolic BP levels than those without. However, results of the multivariate GEE models indicated that the glaucomatous damage was not related to the average systolic or diastolic BP levels measured over 24 hours, daytime, or nighttime. In contrast, extreme drops in nighttime systolic and diastolic BP (\u3e20% compared with daytime BP) were significant risk factors for glaucomatous damage (odds ratio=19.78 and 5.55, respectively). Conclusions—In this population, the link between nocturnal BP and GON is determined by extreme dipping effects rather than low nocturnal BP levels alone. Further studies considering extreme drops in nocturnal BP in individuals at high risk of glaucoma are warranted
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