1,077 research outputs found
Evaluation of Automated Anthropometrics Produced By Smartphone-Based Machine Learning: A Comparison With Traditional Anthropometric Assessments
Automated visual anthropometrics produced by mobile applications are accessible and cost-effective with the potential to assess clinically relevant anthropometrics without a trained technician present. Thus, the aim of this study was to evaluate the precision and agreement of smartphone-based automated anthropometrics against reference tape measurements. Waist and hip circumference (WC; HC), waist-to-hip ratio (WHR), and waist-to-height ratio (W:HT), were collected from 115 participants (69 F) using a tape measure and two smartphone applications (MeThreeSixty®, myBVI®) across multiple smartphone types. Precision metrics were used to assess test-retest precision of the automated measures. Agreement between the circumferences produced by each mobile application and the reference were assessed using equivalence testing and other validity metrics. All mobile applications across smartphone types produced reliable estimates for each variable with ICCs ≥0.93 (all
Dust-to-Gas Ratio and Metallicity in Dwarf Galaxies
We examine the dust-to-gas ratio as a function of metallicity for dwarf
galaxies [dwarf irregular galaxies (dIrrs) and blue compact dwarf galaxies
(BCDGs)]. Using a one-zone model and adopting the instantaneous recycling
approximation, we prepare a set of basic equations which describes processes of
dust formation and destruction in a galaxy. Four terms are included for the
processes: dust formation from heavy elements ejected by stellar mass loss,
dust destruction in supernova remnants, dust destruction in star-forming
regions, and accretion of heavy elements onto preexisting dust grains. Solving
the equations, we compare the result with observational data of nearby dIrrs
and BCDGs. The solution is consistent with the data within the reasonable
ranges of model parameters constrained by the previous examinations. This means
that the model is successful in understanding the dust amount of nearby
galaxies. We also show that the accretion rate of heavy element onto
preexisting dust grains is less effective than the condensation of heavy
elements in dwarf galaxies.Comment: 14 pages LaTeX, 4 figures, to appear in Ap
Testing the Relation Between the Local and Cosmic Star Formation Histories
Recently, there has been great progress toward observationally determining
the mean star formation history of the universe. When accurately known, the
cosmic star formation rate could provide much information about Galactic
evolution, if the Milky Way's star formation rate is representative of the
average cosmic star formation history. A simple hypothesis is that our local
star formation rate is proportional to the cosmic mean. In addition, to specify
a star formation history, one must also adopt an initial mass function (IMF);
typically it is assumed that the IMF is a smooth function which is constant in
time. We show how to test directly the compatibility of all these assumptions,
by making use of the local (solar neighborhood) star formation record encoded
in the present-day stellar mass function. Present data suggests that at least
one of the following is false: (1) the local IMF is constant in time; (2) the
local IMF is a smooth (unimodal) function; and/or (3) star formation in the
Galactic disk was representative of the cosmic mean. We briefly discuss how to
determine which of these assumptions fail, and improvements in observations
which will sharpen this test.Comment: 14 pages in LaTeX (uses aaspp4.sty). 5 postscript figures. To appear
in the Astrophysical Journa
Bridging Scales: a Hybrid Model to Simulate Vascular Tumor Growth and Treatment Response
Cancer is a disease driven by random DNA mutations and the interaction of
many complex phenomena. To improve the understanding and ultimately find more
effective treatments, researchers leverage computer simulations mimicking the
tumor growth in silico. The challenge here is to account for the many phenomena
influencing the disease progression and treatment protocols. This work
introduces a computational model to simulate vascular tumor growth and the
response to drug treatments in 3D. It consists of two agent-based models for
the tumor cells and the vasculature. Moreover, partial differential equations
govern the diffusive dynamics of the nutrients, the vascular endothelial growth
factor, and two cancer drugs. The model focuses explicitly on breast cancer
cells over-expressing HER2 receptors and a treatment combining standard
chemotherapy (Doxorubicin) and monoclonal antibodies with anti-angiogenic
properties (Trastuzumab). However, large parts of the model generalize to other
scenarios. We show that the model qualitatively captures the effects of the
combination therapy by comparing our simulation results with previously
published pre-clinical data. Furthermore, we demonstrate the scalability of the
model and the associated C++ code by simulating a vascular tumor occupying a
volume of 400mm3 using a total of 92.5 million agents
The Star Formation History of IZw18
The star formation history in IZw18 has been inferred from HST/WFPC2 archival
data. This is done by comparing the derived V, B-V and V, V-I color-magnitude
diagrams and luminosity functions with synthetic ones, based on various sets of
stellar evolutionary tracks. At a distance of 10 Mpc, the stars resolved in the
field of IZw18 allow for a lookback time up to 1 Gyr. We find that the main
body is not experiencing its first episode of star formation. Instead, it has
been forming stars over the last 0.5-1 Gyr, at a rate of ~ 1-2 * 10**(-2) Msol
per year per kpc**2. A more intense activity of 6-16 * 10**(-2) Msol per year
per kpc**2 has taken place between 15 and 20 Myr ago. For the secondary body,
the lookback time is 0.2 Gyr at most and the uncertainty is much higher, due to
the shallower diagrams and the small number of resolved stars. The derived
range of star formation rate is 3-10 * 10**(-3) Msol per year per kpc**2. The
IMF providing the best fit to the observed stellar populations in the main body
has a slope 1.5, much flatter than in any similar galaxy analyzed with the same
method. In the secondary body, it is peaked at 2.2, closer to Salpeter's slope
(2.35).Comment: 70 pages including 18 figures, to be published in The Astronomical
Journa
Associations Between Visceral Adipose Tissue Estimates Produced By Near-Infrared Spectroscopy, Mobile Anthropometrics, and Traditional Body Composition Assessments and Estimates Derived From Dual-Energy X-Ray Absorptiometry
Assessments of visceral adipose tissue (VAT) are critical in preventing metabolic disorders; however, there are limited measurement methods that are accurate and accessible for VAT. The purpose of this cross-sectional study was to evaluate the association between VAT estimates from consumer-grade devices and traditional anthropometrics and VAT and subcutaneous adipose tissue (SAT) from dual-energy X-ray absorptiometry (DXA). Data were collected from 182 participants (female = 114; White = 127; Black/African-American (BAA) = 48) which included anthropometrics and indices of VAT produced by near-infrared reactance spectroscopy (NIRS), visual body composition (VBC) and multifrequency BIA (MFBIA). VAT and SAT were collected using DXA. Bivariate and partial correlations were calculated between DXAVAT and DXASAT and other VAT estimates. All VAT indices had positive moderate–strong correlations with VAT (all P \u3c 0·001) and SAT (all P \u3c 0·001). Only waist:hip (r = 0·69), VATVBC (r = 0·84), and VATMFBIA (r = 0·86) had stronger associations with VAT than SAT (P \u3c 0·001). Partial associations between VATVBC and VATMFBIA were only stronger for VAT than SAT in White participants (r = 0·67, P \u3c 0·001) but not female, male, or BAA participants individually. Partial correlations for waist:hip were stronger for VAT than SAT, but only for male (r = 0·40, P \u3c 0·010) or White participants (r = 0·48, P \u3c 0·001). NIRS was amongst the weakest predictors of VAT which was highest in male participants (r = 0·39, P \u3c 0·010) but non-existent in BAA participants (r = –0·02, P \u3e 0·050) after adjusting for SAT. Both anthropometric and consumer-grade VAT indices are consistently better predictors of SAT than VAT. These data highlight the need for a standardised, but convenient, VAT estimation protocol that can account for the relationship between SAT and VAT that differs by sex/race
Lambda-Cold Dark Matter, Stellar Feedback, and the Galactic Halo Abundance Pattern
(Abridged) The hierarchical formation scenario for the stellar halo requires
the accretion and disruption of dwarf galaxies, yet low-metallicity halo stars
are enriched in alpha-elements compared to similar, low-metallicity stars in
dwarf spheroidal (dSph) galaxies. We address this primary challenge for the
hierarchical formation scenario for the stellar halo by combining chemical
evolution modelling with cosmologically-motivated mass accretion histories for
the Milky Way dark halo and its satellites. We demonstrate that stellar halo
and dwarf galaxy abundance patterns can be explained naturally within the LCDM
framework. Our solution relies fundamentally on the LCDM model prediction that
the majority of the stars in the stellar halo were formed within a few
relatively massive, ~5 x 10^10 Msun, dwarf irregular (dIrr)-size dark matter
halos, which were accreted and destroyed ~10 Gyr in the past. These systems
necessarily have short-lived, rapid star formation histories, are enriched
primarily by Type II supernovae, and host stars with enhanced [a/Fe]
abundances. In contrast, dwarf spheroidal galaxies exist within low-mass dark
matter hosts of ~10^9 Msun, where supernovae winds are important in setting the
intermediate [a/Fe] ratios observed. Our model includes enrichment from Type Ia
and Type II supernovae as well as stellar winds, and includes a
physically-motivated supernovae feedback prescription calibrated to reproduce
the local dwarf galaxy stellar mass - metallicity relation. We use
representative examples of the type of dark matter halos we expect to host a
destroyed ``stellar halo progenitor'' dwarf, a surviving dIrr, and a surviving
dSph galaxy, and show that their derived abundance patterns, stellar masses,
and gas masses are consistent with those observed for each type of system.Comment: 10 pages, 3 figures, version accepted by Ap
Low Mass Stars and the He3 Problem
The prediction of standard chemical evolution models of higher abundances of
He3 at the solar and present-day epochs than are observed indicates a possible
problem with the yield of He3 for stars in the range of 1-3 solar masses.
Because He3 is one of the nuclei produced in Big Bang Nucleosynthesis (BBN), it
is noted that galactic and stellar evolution uncertainties necessarily relax
constraints based on He3. We incorporate into chemical evolution models which
include outflow, the new yields for He3 of Boothroyd & Malaney (1995) which
predict that low mass stars are net destroyers of He3. Since these yields do
not account for the high \he3/H ratio observed in some planetary nebulae, we
also consider the possibility that some fraction of stars in the 1 - 3 solar
mass range do not destroy their He3 in theirpost main-sequence phase. We also
consider the possibility that the gas expelled by stars in these mass ranges
does not mix with the ISM instantaneously thus delaying the He3 produced in
these stars, according to standard yields, from reaching the ISM. In general,
we find that the Galactic D and He3 abundances can be fit regardless of whether
the primordial D/H value is high (2 x 10^{-4}) or low (2.5 x 10^{-5}).Comment: 20 pages, latex, 9 ps figure
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