23 research outputs found
A Model of Habitability Within the Milky Way Galaxy
We present a model of the Galactic Habitable Zone (GHZ), described in terms
of the spatial and temporal dimensions of the Galaxy that may favour the
development of complex life. The Milky Way galaxy is modelled using a
computational approach by populating stars and their planetary systems on an
individual basis using Monte-Carlo methods. We begin with well-established
properties of the disk of the Milky Way, such as the stellar number density
distribution, the initial mass function, the star formation history, and the
metallicity gradient as a function of radial position and time. We vary some of
these properties, creating four models to test the sensitivity of our
assumptions. To assess habitability on the Galactic scale, we model supernova
rates, planet formation, and the time required for complex life to evolve. Our
study improves on other literature on the GHZ by populating stars on an
individual basis and by modelling SNII and SNIa sterilizations by selecting
their progenitors from within this preexisting stellar population. Furthermore,
we consider habitability on tidally locked and non-tidally locked planets
separately, and study habitability as a function of height above and below the
Galactic midplane. In the model that most accurately reproduces the properties
of the Galaxy, the results indicate that an individual SNIa is ~5.6 \times more
lethal than an individual SNII on average. In addition, we predict that ~1.2%
of all stars host a planet that may have been capable of supporting complex
life at some point in the history of the Galaxy. Of those stars with a
habitable planet, ~75% of planets are predicted to be in a tidally locked
configuration with their host star. The majority of these planets that may
support complex life are found towards the inner Galaxy, distributed within,
and significantly above and below, the Galactic midplane.Comment: Accepted for publication in Astrobiology. 40 pages, 12 figures, 3
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A low density of the Extragalactic Background Light revealed by the H.E.S.S. spectra of the BLLac objects 1ES 1101-232 and H 2356-309
The unexpectedly hard spectra measured by HESS for the BLLacs 1ES 1101-232 and H 2356-309 has allowed an upper limit on the Extragalactic Background Light (EBL) to be derived in the optical/near-infrared range, which is very close to the lower limit given by the resolved galaxy counts. This result seems to exclude a large contribution to the EBL from other sources (e.g. Population III stars) and indicates that the intergalactic space is more transparent to gamma-rays than previously thought. A brief discussion of EBL absorption effects on blazar spectra and further observational tests to check this conclusion are presented, including the selection of new candidates for observations with Cherenkov telescopes
Race, the Vaginal Microbiome, and Spontaneous Preterm Birth
Previous studies have investigated the associations between the vaginal microbiome and preterm birth, with the aim of determining whether differences in community patterns meaningfully alter risk and could therefore be the target of intervention. We report on vaginal microbial analysis of a nested case-control subset of the Pregnancy, Infection, and Nutrition (PIN) Study, including 464 White women (375 term birth and 89 spontaneous preterm birth, sPTB) and 360 Black women (276 term birth and 84 sPTB). We found that the microbiome of Black women has higher alpha-diversity, higher abundance of Lactobacillus iners, and lower abundance of Lactobacillus crispatus. However, among women who douche, there were no significant differences in microbiome by race. The sPTB-associated microbiome exhibited a lower abundance of L. crispatus, while alpha diversity and L. iners were not significantly associated with sPTB. For each order of magnitude increase in the normalized relative abundance of L. crispatus, multivariable adjusted odds of sPTB decreased by approximately 20% (odds ratio, 0.81; 95% confidence interval, 0.70, 0.94). When we considered the impact of douching, associations between the microbiome and sPTB were limited to women who do not douche. We also observed strong intercorrelations between a range of maternal factors, including poverty, education, marital status, age, douching, and race, with microbiome effect sizes in the range of 1.8 to 5.2% in univariate models. Therefore, race may simply be a proxy for other socially driven factors that differentiate microbiome community structures. Future work will continue to refine reliable microbial biomarkers for preterm birth across diverse cohorts
Dietary phytochemicals induce p53‐ and caspase‐independent cell death in human neuroblastoma cells
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