996 research outputs found

    Primordial helium recombination III: Thomson scattering, isotope shifts, and cumulative results

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    Upcoming precision measurements of the temperature anisotropy of the cosmic microwave background (CMB) at high multipoles will need to be complemented by a more complete understanding of recombination, which determines the damping of anisotropies on these scales. This is the third in a series of papers describing an accurate theory of HeI and HeII recombination. Here we describe the effect of Thomson scattering, the 3^3He isotope shift, the contribution of rare decays, collisional processes, and peculiar motion. These effects are found to be negligible: Thomson and 3^3He scattering modify the free electron fraction xex_e at the level of several ×104\times 10^{-4}. The uncertainty in the 23Po11S2^3P^o-1^1S rate is significant, and for conservative estimates gives uncertainties in xex_e of order 10310^{-3}. We describe several convergence tests for the atomic level code and its inputs, derive an overall CC_\ell error budget, and relate shifts in xe(z)x_e(z) to the changes in CC_\ell, which are at the level of 0.5% at =3000\ell =3000. Finally, we summarize the main corrections developed thus far. The remaining uncertainty from known effects is 0.3\sim 0.3% in xex_e.Comment: 19 pages, 15 figures, to be submitted to PR

    Amateur versus professional: Does the recovery of forensic evidence differ depending on who assesses the crime scene?

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    Volume crime offences such as domestic burglary are commonly assessed for forensic opportunities by the first attending officer present at the scene. Conversely, less serious volume crime offences such as thefts from motor vehicles are very frequent and are routinely assessed for forensic opportunities by the victim talking to the police over the telephone. It is not clear whether this difference in attendance policy leads to differences in the types and quantity of forensic material recovered. The current study explored whether there was a benefit to evidence recovery for attended as opposed to non-attended assessments. Five hundred thefts from motor vehicles offences recorded by Northamptonshire Police (UK) between 14 January 2010 and 28 February 2011 were analysed; 250 were attended forensic assessments and 250 were non-attended assessments. Significant differences were found between the two scenarios, with attended assessments more likely to yield DNA, property and trace substance material. Conversely, fingerprints were more likely to be recovered at non-attended assessments. Despite the fruitful findings of the current study, future research would benefit from establishing the methods used by the first attending officer and forensic investigator when assessing and gathering evidence. Similarly, it is unclear whether these differences in forensic material are reflected in the identification of an offender and subsequently in the solving of the crime

    Prenatal development is linked to bronchial reactivity: epidemiological and animal model evidence

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    Chronic cardiorespiratory disease is associated with low birthweight suggesting the importance of the developmental environment. Prenatal factors affecting fetal growth are believed important, but the underlying mechanisms are unknown. The influence of developmental programming on bronchial hyperreactivity is investigated in an animal model and evidence for comparable associations is sought in humans. Pregnant Wistar rats were fed either control or protein-restricted diets throughout pregnancy. Bronchoconstrictor responses were recorded from offspring bronchial segments. Morphometric analysis of paraffin-embedded lung sections was conducted. In a human mother-child cohort ultrasound measurements of fetal growth were related to bronchial hyperreactivity, measured at age six years using methacholine. Protein-restricted rats' offspring demonstrated greater bronchoconstriction than controls. Airway structure was not altered. Children with lesser abdominal circumference growth during 11-19 weeks' gestation had greater bronchial hyperreactivity than those with more rapid abdominal growth. Imbalanced maternal nutrition during pregnancy results in offspring bronchial hyperreactivity. Prenatal environmental influences might play a comparable role in humans

    Confirmation of SBS 1150+599A As An Extremely Metal-Poor Planetary Nebula

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    SBS 1150+599A is a blue stellar object at high galactic latitude discovered in the Second Byurakan Survey. New high-resolution images of SBS 1150+599A are presented, demonstrating that it is very likely to be an old planetary nebula in the galactic halo, as suggested by Tovmassian et al (2001). An H-alpha image taken with the WIYN 3.5-m telescope and its "tip/tilt" module reveals the diameter of the nebula to be 9.2", comparable to that estimated from spectra by Tovmassian et al. Lower limits to the central star temperature were derived using the Zanstra hydrogen and helium methods to determine that the star's effective temperature must be > 68,000K and that the nebula is optically thin. New spectra from the MMT and FLWO telescopes are presented, revealing the presence of strong [Ne V] lambda 3425, indicating that the central star temperature must be > 100,000K. With the revised diameter, new central star temperature, and an improved central star luminosity, we can constrain photoionization models for the nebula significantly better than before. Because the emission-line data set is sparse, the models are still not conclusive. Nevertheless, we confirm that this nebula is an extremely metal-poor planetary nebula, having a value for O/H that is less than 1/100 solar, and possibly as low as 1/500 solar.Comment: 19 pages, 6 figures. Accepted for publication in the Astronomical Journa

    Evidence for dark energy from the cosmic microwave background alone using the Atacama Cosmology Telescope lensing measurements

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    For the first time, measurements of the cosmic microwave background radiation (CMB) alone favor cosmologies with w=1w=-1 dark energy over models without dark energy at a 3.2-sigma level. We demonstrate this by combining the CMB lensing deflection power spectrum from the Atacama Cosmology Telescope with temperature and polarization power spectra from the Wilkinson Microwave Anisotropy Probe. The lensing data break the geometric degeneracy of different cosmological models with similar CMB temperature power spectra. Our CMB-only measurement of the dark energy density ΩΛ\Omega_\Lambda confirms other measurements from supernovae, galaxy clusters and baryon acoustic oscillations, and demonstrates the power of CMB lensing as a new cosmological tool.Comment: 4 pages, 3 figures; replaced with version accepted by Physical Review Letters, added sentence on models with non-standard primordial power spectr

    Adipose‐Derived Stem Cells Induce Angiogenesis via Microvesicle Transport of miRNA‐31

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135340/1/sct3201654440.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/135340/2/Supplemental_Information.pd
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