21,951 research outputs found
Big Bang Nucleosynthesis with Independent Neutrino Distribution Functions
We have performed new Big Bang Nucleosynthesis calculations which employ
arbitrarily-specified, time-dependent neutrino and antineutrino distribution
functions for each of up to four neutrino flavors. We self-consistently couple
these distributions to the thermodynamics, the expansion rate and scale
factor-time/temperature relationship, as well as to all relevant weak,
electromagnetic, and strong nuclear reaction processes in the early universe.
With this approach, we can treat any scenario in which neutrino or antineutrino
spectral distortion might arise. These scenarios might include, for example,
decaying particles, active-sterile neutrino oscillations, and active-active
neutrino oscillations in the presence of significant lepton numbers. Our
calculations allow lepton numbers and sterile neutrinos to be constrained with
observationally-determined primordial helium and deuterium abundances. We have
modified a standard BBN code to perform these calculations and have made it
available to the community.Comment: 9 pages, 5 figure
Weak Interaction Rate Coulomb Corrections in Big Bang Nucleosynthesis
We have applied a fully relativistic Coulomb wave correction to the weak
reactions in the full Kawano/Wagoner Big Bang Nucleosynthesis (BBN) code. We
have also added the zero temperature radiative correction. We find that using
this higher accuracy Coulomb correction results in good agreement with previous
work, giving only a modest 0.04 percent increase in helium mass fraction over
correction prescriptions applied previously in BBN calculations. We have
calculated the effect of these corrections on other light element abundance
yields in BBN and we have studied these yields as functions of electron
neutrino lepton number. This has allowed insights into the role of the Coulomb
correction in the setting of the neutron-to-proton ratio during the BBN epoch.
We find that the lepton capture processes' contributions to this ratio are only
second order in the Coulomb correction.Comment: 8 pages, 3 figure
Hierarchical Character-Word Models for Language Identification
Social media messages' brevity and unconventional spelling pose a challenge
to language identification. We introduce a hierarchical model that learns
character and contextualized word-level representations for language
identification. Our method performs well against strong base- lines, and can
also reveal code-switching
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Sceloporus cautus
Number of Pages: 5Integrative BiologyGeological Science
Long-term outcomes of a randomized clinical trial of supervised exercise, percutaneous transluminal angioplasty or combined treatment for patients with intermittent claudication due to femoropopliteal disease
Background: To compare the long-term outcomes of angioplasty (PTA), supervised exercise (SEP) and combined treatment (PTA+SEP) in patients with intermittent claudication (IC) due to femoropopliteal disease. Methods: Patients recruited to PTA, SEP and PTA+SEP arms of RCT were invited for long-term follow-up from 2010 to 2011.Indicators of limb ischaemia were recorded (ankle-brachial pressure indices, treadmill walking distances (ICD, MWD, PRWD). Duplex ultrasound was also performed. Patients completed SF36 and Vascuqol quality of life(QOL) questionnaires. Results: Of the 178 patients recruited in the trial, 139 were alive at the time of follow-up (PTA=46, SEP=47, PTA+SEP=46). Assessments were completed for 111 patients. Median time to follow-up was 5.2years (IQR 3.8-7.4years). Median age of patients at follow up was 75years. 62.2%(N=69) of patients were symptomatic.16.2%(N= 18) had experienced major cardiovascular event since their last follow-up visit. Intra-group analysis: Improvement was observed in ankle brachial pressure index (ABPI) in all groups. QOL outcomes were inconsistent across individual groups. Inter-group analysis: PTA and PTA+SEP groups demonstrated a significantly higher ABPI as compared to SEP group. No significant difference was observed in walking distances, QOL outcomes, restenosis rates, and new ipsilateral and contralateral lesions on duplex scan. Patients required re-interventions in all group (PTA=14, SEP=10, PTA+SEP=6). Number of re-interventions was higher in PTA group(N=29) as compared to SEP(N=17) and PTA+SEP(N=9) but failed to reach statistical significance. Conclusion: PTA, SEP and combined treatment are equally effective long-term treatment options for patients with femoropopliteal claudication. Addition of SEP to PTA can reduce the symptomatic restenosis and re-intervention rates
Obstetrician-assessed maternal health at pregnancy predicts offspring future health
Background:
We aimed to examine the association between obstetrician assessment of maternal physical health at the time of pregnancy and offspring cardiovascular disease risk.<p></p>
Methods and Principal Findings:
We examined this association in a birth cohort of 11,106 individuals, with 245,000 person years of follow-up. We were concerned that any associations might be explained by residual confounding, particularly by family socioeconomic position. In order to explore this we used multivariable regression models in which we adjusted for a range of indicators of socioeconomic position and we explored the specificity of the association. Specificity of association was explored by examining associations with other health related outcomes. Maternal physical health was associated with cardiovascular disease: adjusted (socioeconomic position, complications of pregnancy, birthweight and childhood growth at mean age 5) hazard ratio comparing those described as having poor or very poor health at the time of pregnancy to those with good or very good health was 1.55 (95%CI: 1.05, 2.28) for coronary heart disease, 1.91 (95%CI: 0.99, 3.67) for stroke and 1.57 (95%CI: 1.13, 2.18) for either coronary heart disease or stroke. However, this association was not specific. There were strong associations for other outcomes that are known to be related to socioeconomic position (3.61 (95%CI: 1.04, 12.55) for lung cancer and 1.28 (95%CI:1.03, 1.58) for unintentional injury), but not for breast cancer (1.10 (95%CI:0.48, 2.53)).<p></p>
Conclusions and Significance:
These findings demonstrate that a simple assessment of physical health (based on the appearance of eyes, skin, hair and teeth) of mothers at the time of pregnancy is a strong indicator of the future health risk of their offspring for common conditions that are associated with poor socioeconomic position and unhealthy behaviours. They do not support a specific biological link between maternal health across her life course and future risk of cardiovascular disease in her offspring.<p></p>
TDRSS momentum unload planning
A knowledge-based system is described which monitors TDRSS telemetry for problems in the momentum unload procedure. The system displays TDRSS telemetry and commands in real time via X-windows. The system constructs a momentum unload plan which agrees with the preferences of the attitude control specialists and the momentum growth characteristics of the individual spacecraft. During the execution of the plan, the system monitors the progress of the procedure and watches for unexpected problems
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