522 research outputs found
The Spatial Structure of An Accretion Disk
Based on the microlensing variability of the two-image gravitational lens
HE1104-1805 observed between 0.4 and 8 microns, we have measured the size and
wavelength-dependent structure of the quasar accretion disk. Modeled as a power
law in temperature, T proportional to R^-beta, we measure a B-band (0.13
microns in the rest frame) half-light radius of R_{1/2,B} = 6.7 (+6.2 -3.2) x
10^15 cm (68% CL) and a logarithmic slope of beta=0.61 (+0.21 -0.17) for our
standard model with a logarithmic prior on the disk size. Both the scale and
the slope are consistent with simple thin disk models where beta=3/4 and
R_{1/2,B} = 5.9 x 10^15 cm for a Shakura-Sunyaev disk radiating at the
Eddington limit with 10% efficiency. The observed fluxes favor a slightly
shallower slope, beta=0.55 (+0.03 -0.02), and a significantly smaller size for
beta=3/4.Comment: 5 pages, 4 figures, submitted to Ap
A small source in Q2237+0305 ?
Microlensing in Q2237+0305 between 1985 and 1995 (eg. Irwin et al. 1989;
Corrigan et al. 1991; Ostensen et al. 1996) has been interpreted in two
different ways; as microlensing by stellar mass objects of a continuum source
having dimensions significantly smaller than the microlens Einstein radius (ER)
(eg. Wambsganss, Paczynski & Schneider 1990; Rauch & Blandford 1991), and as
microlensing by very low mass objects of a source as large as 5 ER (Refsdal &
Stabell 1993; Haugan 1996). In this paper we present evidence in favour of a
small source. Limits on the source size (in units of ER) are obtained from the
combination of limits on the number of microlens Einstein radii crossed by the
source during the monitoring period with two separate light-curve features.
Firstly, recently published monitoring data (Wozniak et al. 2000; OGLE web
page) show large variations (~0.8-1.5 magnitudes) between image brightnesses
over a period of 700 days or ~15% of the monitoring period. Secondly, the 1988
peak in the image A light-curve had a duration that is a small fraction (<0.02)
of the monitoring period. Such rapid microlensing rises and short microlensing
peaks only occur for small sources. We find that the observed large-rapid
variation limits the source size to be <0.2 ER (95% confidence). The width of
the light-curve peak provides a stronger constraint of <0.02 ER (99%
confidence). The Einstein radius (projected into the source plane) of the
average microlens mass (m) in Q2237+0305 is ER ~ 10^{17}\sqrt{m} cm. The
interpretation that stars are responsible for microlensing in Q2237+0305
therefore results in limits on the continuum source size that are consistent
with current accretion disc theory.Comment: 8 pages, 3 figures, accepted for publication in M.N.R.A.
Comparison of particle trajectories and collision operators for collisional transport in nonaxisymmetric plasmas
In this work, we examine the validity of several common simplifying
assumptions used in numerical neoclassical calculations for nonaxisymmetric
plasmas, both by using a new continuum drift-kinetic code and by considering
analytic properties of the kinetic equation. First, neoclassical phenomena are
computed for the LHD and W7-X stellarators using several versions of the
drift-kinetic equation, including the commonly used incompressible-ExB-drift
approximation and two other variants, corresponding to different effective
particle trajectories. It is found that for electric fields below roughly one
third of the resonant value, the different formulations give nearly identical
results, demonstrating the incompressible ExB-drift approximation is quite
accurate in this regime. However, near the electric field resonance, the models
yield substantially different results. We also compare results for various
collision operators, including the full linearized Fokker-Planck operator. At
low collisionality, the radial transport driven by radial gradients is nearly
identical for the different operators, while in other cases it is found to be
important that collisions conserve momentum
Investigation of the effects of a high fish diet on inflammatory cytokines, blood pressure, and lipids in healthy older Australians
BACKGROUND: Aging is a condition of chronic inflammation. In healthy Australians ≥64 years, the primary aim was to determine whether four servings/week of mixed fish (FISH) improves serum cytokines (i.e. C-reactive protein (CRP), IL-1, IL-6, TNF-α) compared to a diet low in fish (<1 serving/week, CONTROL); the secondary aims were to assess the effect of the diet on blood pressure and serum lipids (TC, HDL-C, TG, calculated LDL-C). METHODS: An 8-week randomized, parallel study, stratified by CRP (<3 mg/L vs. ≥3 mg/L) on entry to the study. Compliance was measured using 3-day weighed food records in weeks 1 and 7 of the study. A 12-h fasting blood sample was taken at baseline and 8-weeks for erythrocyte fatty acids as confirmation of compliance, and measurement of serum cytokines and lipids. Blood pressure was measured at both time points. RESULTS: EIGHTY PARTICIPANTS COMPLETED THE STUDY (MEAN (SD) AGE: 69.6 (5.8) years). During week 1 of the study, mean ± SEM daily dietary intake of very long chain omega-3 polyunsaturated fatty acids (VLCN n-3 PUFA) in FISH vs. CONTROL was 1,676±129 mg vs. 27±5 mg (p<0.001). Mean (SD) gram intake of study fish and meat was 121 (45) g and 123 (78) g, for those allocated to FISH and CONTROL, respectively. Mean ± SEM percentage VLCN n-3 PUFA in erythrocytes at 8-weeks was higher in those allocated to FISH vs. CONTROL (10.2±0.2% vs. 8.2±0.3%, p<0.001). There was no between-group difference in CRP (n=80), IL-1β (n=33) or IL-6 (n=21) concentrations, blood pressure, or lipids, at 8-weeks. CONCLUSIONS: Eight weeks consumption of four servings/week fish did not affect serum cytokine concentrations, blood pressure or lipids compared to a diet low in fish. In healthy older adults with low inflammatory burden, our results do not support that short-term consumption of mixed fish has a beneficial effect on selected cardiovascular biomarkers.Jessica A. Grieger, Michelle D. Miller, and Lynne Cobi
Strategies towards improving pharmacological management of asthma during pregnancy
Abstract not availableLuke E.Grzeskowiak, Jessica A.Grieger, Vicki L.Clifto
Using Estrus-Detection Patches to Vary Time of Insemination Improves Pregnancy Rates Compared with One Single Timed Insemination
Timed artificial insemination (TAI) of beef cows at a predetermined time is a management tool that reduces labor costs associated with conventional heat detection before insemination. Multiple research trials have examined timing of the individual components of the developed protocols associated with TAI. The 7-day CO-Synch + progesterone insert (controlled internal drug release; CIDR) protocol has been shown to initiate ovulation effectively in cycling and noncycling suckled beef cows, often producing pregnancy rates greater than 50% in beef cows. In the current research, we examined using two targeted insemination intervals depending on the occurrence of estrus. We hypothesized that by more closely synchronizing estrus and insemination that pregnancy rates would be increased. We further hypothesized that cows that do not demonstrate estrus and are subjected to a TAI protocol might benefit from an increased interval to insemination
Using Estrus-Detection Patches to Vary Time of Insemination Improves Pregnancy Rates Compared with One Single Timed Insemination
Timed artificial insemination (TAI) of beef cows at a predetermined time is a management tool that reduces labor costs associated with conventional heat detection before insemination. Multiple research trials have examined timing of the individual components of the developed protocols associated with TAI. The 7-day CO-Synch + progesterone insert (controlled internal drug release; CIDR) protocol has been shown to initiate ovulation effectively in cycling and noncycling suckled beef cows, often producing pregnancy rates greater than 50% in beef cows. In the current research, we examined using two targeted insemination intervals depending on the occurrence of estrus. We hypothesized that by more closely synchronizing estrus and insemination that pregnancy rates would be increased. We further hypothesized that cows that do not demonstrate estrus and are subjected to a TAI protocol might benefit from an increased interval to insemination
Parameters, practices, and preferences for regulatory review of emerging biotechnology products in food and agriculture
This paper evaluates the U.S. regulatory review of three emerging biotechnology products according to parameters, practices, and endpoints of assessments that are important to stakeholders and publics. First, we present a summary of the literature on variables that are important to non-expert publics in governing biotech products, including ethical, social, policy process, and risk and benefit parameters. Second, we draw from our USDA-funded project results that surveyed stakeholders with subject matter expertise about their attitudes towards important risk, benefit, sustainability, and societal impact parameters for assessing novel agrifood technologies, including biotech. Third, we evaluate the regulatory assessments of three food and agricultural biotechnology case studies that have been reviewed under U.S. regulatory agencies and laws of the Coordinated Framework for the Regulation of Biotechnology, including gene-edited soybeans, beef cattle, and mustard greens. Evaluation of the regulatory review process was based on parameters identified in steps 1 and 2 which were deemed important to both publics and stakeholders. Based on this review, we then propose several policy options for U.S. federal agencies to strengthen their oversight processes to better align with a broader range of parameters to support sustainable agrifood products that rely on novel technologies. These policy options include 1) those that would not require new institutions or legal foundations (such as conducting Environmental Impact Statements and/or requiring a minimal level of safety data), 2) those that would require a novel institutional or cross-institutional framework (such as developing a publicly-available website and/or performing holistic sustainability assessments), and 3) those that would require the agencies to have additional legal authorities (such as requiring agencies to review biotech products according to a minimal set of health, environmental, and socio-economic parameters). Overall, the results of this analysis will be important for guiding policy practice and formulation in the regulatory assessment of emerging biotechnology products that challenge existing legal and institutional frameworks
Progress of the Felsenkeller shallow-underground accelerator for nuclear astrophysics
Low-background experiments with stable ion beams are an important tool for
putting the model of stellar hydrogen, helium, and carbon burning on a solid
experimental foundation. The pioneering work in this regard has been done by
the LUNA collaboration at Gran Sasso, using a 0.4 MV accelerator. In the
present contribution, the status of the project for a higher-energy underground
accelerator is reviewed. Two tunnels of the Felsenkeller underground site in
Dresden, Germany, are currently being refurbished for the installation of a 5
MV high-current Pelletron accelerator. Construction work is on schedule and
expected to complete in August 2017. The accelerator will provide intense, 50
uA, beams of 1H+, 4He+, and 12C+ ions, enabling research on astrophysically
relevant nuclear reactions with unprecedented sensitivity.Comment: Submitted to the Proceedings of Nuclei in the Cosmos XIV, 19-24 June
2016, Niigata/Japa
Strategies towards improving pharmacological management of asthma during pregnancy
Maternal asthma represents a significant burden to individuals and the healthcare system, affecting 1 in 10 pregnancies worldwide. Approximately 50% of asthmatic women experience a deterioration of asthma control at some stage during pregnancy, with a number requiring use of oral corticosteroids for the management of acute exacerbations. The presence of maternal asthma and exacerbations during pregnancy is a noted risk factor for a range of adverse perinatal outcomes including preterm birth, small-for-gestational age, pre-eclampsia, and gestational diabetes. These negative impacts highlight the need for evidence-based approaches for improving asthma management during pregnancy and subsequent perinatal outcomes. Despite this, relatively small progress has been made in enhancing the management of maternal asthma in the clinical setting. A major challenge in improving outcomes of asthmatic pregnancies is that there is no single simplified approach for improving outcomes, but rather the requirement to consider the dynamic relationship between a myriad of interrelated factors that ultimately determine an individual's ability to maintain adequate asthma control. Understanding how these factors are impacted by pregnancy and how they can be addressed through various interventions is therefore important in optimising health outcomes. This review summarises key factors involved in influencing outcomes associated with maternal asthma. This includes an overview of the use of asthma medications in pregnancy, while also considering the impacts of interrelated aspects such as medication adherence, health-seeking behaviours, biological and lifestyle factors, co-morbidities, and asthma self-management strategies on asthma control. Addressing such factors through multidisciplinary approaches towards treatment have potential to improve the health of mothers and their offspring. Optimising asthma control should be a high priority within the antenatal setting, with women advised about the importance of good asthma control, managing asthma actively throughout pregnancy by utilising their asthma medications, and managing exacerbations in a timely and effective manner
- …