2,414 research outputs found
Testing for Photometric Variability at the L/T Boundary
We construct K_s-band light curves for nine field L and T
brown dwarfs using the Palomar 60 inch Telescope. Results of a robust
statistical analysis indicate that about half the targets show significant
evidence for variability. Two of these variable targets have marginally
significant peaks in the Lomb-Scargle periodogram. The phased light
curves show evidence for periodic behavior on timescales of about 1.5
and 3.0 hours
Positivity of Quasilocal Mass
Motivated by the important work of Brown adn York on quasilocal energy, we
propose definitions of quasilocal energy and momentum surface energy of a
spacelike 2-surface with positive intrinsic curvature in a spacetime. We show
that the quasilocal energy of the boundary of a compact spacelike hypersurface
which satisfies the local energy condition is strictly positive unless the
spacetime is flat along the spacelike hypersurface.Comment: 4 pages; final published versio
Estimating charitable giving by will bequest for Giving USA
In a typical year since 2000, Giving USA has estimated that living individuals contributed 75 percent of total charitable gifts and that estates contributed about 7 or 8 percent, with institutional donors donating the balance. The estimating procedure used for estate contributions relies extensively on amounts claimed by estate tax returns as deductions for charitable contributions. Giving USA supplements the tax return data with an estimate of giving by estates that fall below the tax filing threshold. As the estate tax filing threshold began increasing and tax rates began decreasing in 2001, a number of authors (Joulfaian 2000; Gale & Bakija; Greene and McClelland) predict declining charitable contributions from bequest gifts. With fewer estates tax returns filed, and the possibility that none will be filed after 2010, the impact of the reduced tax rates must be measured using new methods that do not rely so extensively on tax return data. Giving USA has been investigating and continues to investigate alternative methods to estimate charitable bequests that do not rely so heavily on estate tax return data. This paper reports the results of this effort and describes the bequest estimating procedure adopted for use in Giving USA beginning with the 2005 edition. This procedure incorporates survey results showing bequest amounts received at higher educational institutions and estimates charitable bequests made by estates below the federal filing threshold. The paper concludes that to track changes resulting from lowered tax rates and higher filing thresholds adequately, alternative data sources will need to be developed
Homozygous in-frame deletion in CATSPERE in a man producing spermatozoa with loss of CatSper function and compromised fertilizing capacity
STUDY QUESTIONDoes a man (patient 1) with a previously described deficiency in principle cation channel of sperm (CatSper) function have a mutation in the CatSper-epsilon (CATSPERE) and/or CatSper-zeta (CATSPERZ) gene?SUMMARY ANSWERPatient 1 has a homozygous in-frame 6-bp deletion in exon 18 (c.2393_2398delCTATGG, rs761237686) of CATSPERE.WHAT IS KNOWN ALREADYCatSper is the principal calcium channel of mammalian spermatozoa. Spermatozoa from patient 1 had a specific loss of CatSper function and were unable to fertilize at IVF. Loss of CatSper function could not be attributed to genetic abnormalities in coding regions of seven CatSper subunits. Two additional subunits (CatSper-epsilon (CATPSERE) and CatSper-zeta (CATSPERZ)) were recently identified, and are now proposed to contribute to the formation of the mature channel complex.STUDY DESIGN, SIZE, DURATIONThis was a basic medical research study analysing genomic data from a single patient (patient 1) for defects in CATSPERE and CATSPERZ.PARTICIPANTS/MATERIALS, SETTING, METHODSThe original exome sequencing data for patient 1 were analysed for mutations in CATSPERE and CATSPERZ. Sanger sequencing was conducted to confirm the presence of a rare variant.MAIN RESULTS AND THE ROLE OF CHANCEPatient 1 is homozygous for an in-frame 6-bp deletion in exon 18 (c.2393_2398delCTATGG, rs761237686) of CATSPERE that is predicted to be highly deleterious.LIMITATIONS, REASONS FOR CAUTIONThe nature of the molecular deficit caused by the rs761237686 variant and whether it is exclusively responsible for the loss of CatSper function remain to be elucidated.WIDER IMPLICATIONS OF THE FINDINGSPopulation genetics are available for a significant number of predicted deleterious variants of CatSper subunits. The consequence of homozygous and compound heterozygous forms on sperm fertilization potential could be significant. Selective targeting of CatSper subunit expression maybe a feasible strategy for the development of novel contraceptives.STUDY FUNDING/COMPETING INTEREST(S)This study was funded by project grants from the MRC (MR/K013343/1 and MR/012492/1), Chief Scientist Office/NHS research Scotland. This work was also supported by NIH R01GM111802, Pew Biomedical Scholars Award 00028642 and Packer Wentz Endowment Will to P.V.L. C.L.R.B is the editor-in-chief of Molecular Human Reproduction, has received lecturing fees from Merck and Ferring, and is on the Scientific Advisory Panel for Ohana BioSciences. C.L.R.B was chair of the World Health Organization Expert Synthesis Group on Diagnosis of Male infertility (2012–2016)
Estimating the rate of intersubtype recombination in early HIV-1 group M strains
West Central Africa has been implicated as the epicenter of the HIV-1 epidemic, and almost all group M subtypes can be found there. Previous analysis of early HIV-1 group M sequences from Kinshasa in the Democratic Republic of Congo, formerly Zaire, revealed that isolates from a number of individuals fall in different positions in phylogenetic trees constructed from sequences from opposite ends of the genome as a result of recombination between viruses of different subtypes. Here, we use discrete ancestral trait mapping to develop a procedure for quantifying HIV-1 group M intersubtype recombination across phylogenies, using individuals' gag (p17) and env (gp41) subtypes. The method was applied to previously described HIV-1 group M sequences from samples obtained in Kinshasa early in the global radiation of HIV. Nine different p17 and gp41 intersubtype recombinant combinations were present in the data set. The mean number of excess ancestral subtype transitions (NEST) required to map individuals' p17 subtypes onto the gp14 phylogeny samples, compared to the number required to map them onto the p17 phylogenies, and vice versa, indicated that excess subtype transitions occurred at a rate of approximately 7 × 10(−3) to 8 × 10(−3) per lineage per year as a result of intersubtype recombination. Our results imply that intersubtype recombination may have occurred in approximately 20% of lineages evolving over a period of 30 years and confirm intersubtype recombination as a substantial force in generating HIV-1 group M diversity
The Need for Speed in Rodent Locomotion Analyses.
Locomotion analysis is now widely used across many animal species to understand the motor defects in disease, functional recovery following neural injury, and the effectiveness of various treatments. More recently, rodent locomotion analysis has become an increasingly popular method in a diverse range of research. Speed is an inseparable aspect of locomotion that is still not fully understood, and its effects are often not properly incorporated while analyzing data. In this hybrid manuscript, we accomplish three things: (1) review the interaction between speed and locomotion variables in rodent studies, (2) comprehensively analyze the relationship between speed and 162 locomotion variables in a group of 16 wild-type mice using the CatWalk gait analysis system, and (3) develop and test a statistical method in which locomotion variables are analyzed and reported in the context of speed. Notable results include the following: (1) over 90% of variables, reported by CatWalk, were dependent on speed with an average R2 value of 0.624, (2) most variables were related to speed in a nonlinear manner, (3) current methods of controlling for speed are insufficient, and (4) the linear mixed model is an appropriate and effective statistical method for locomotion analyses that is inclusive of speed-dependent relationships. Given the pervasive dependency of locomotion variables on speed, we maintain that valid conclusions from locomotion analyses cannot be made unless they are analyzed and reported within the context of speed
Mice Deficient in SFRP1 Exhibit Increased Adiposity, Dysregulated Glucose Metabolism
The molecular mechanisms involved in the development of obesity and related complications remain unclear. Wnt signaling plays an important role in preadipocyte differentiation and adipogenesis. The expression of a Wnt antagonist, secreted frizzled related protein 1 (SFRP1), is increased in response to initial weight gain, then levels are reduced under conditions of extreme obesity in both humans and animals. Here we report that loss of Sfrp1 exacerbates weight gain and glucose homeostasis in mice in response to diet induced obesity (DIO). Sfrp1-/- mice fed a high fat diet (HFD) exhibited an increase in body mass accompanied by increases in body fat percentage, visceral WAT mass, and adipocyte size. Fasting glucose levels are elevated, glucose clearance is impaired, hepatic gluconeogenesis regulators are aberrantly upregulated, and glucose transporters are repressed in Sfrp1-/- mice fed a HFD. Additionally, we observed increased steatosis in the livers of Sfrp1-/- mice. Our findings demonstrate that the expression of Sfrp1 is a critical factor required for maintaining appropriate cellular signaling in response to the onset of obesity
SN Hunt 248: a super-Eddington outburst from a massive cool hypergiant
We present photometric and spectroscopic observations of SN Hunt 248, a new
supernova (SN) impostor in NGC 5806, which began a multi-stage outburst in 2014
May. The initial '2014a' discovery brightening exhibited an absolute magnitude
of M~-12 and the spectral characteristics of a cool dense outflow, including
P-Cygni lines of Fe II, H I, Na I, and strong line blanketing from metals. The
source rapidly climbed and peaked near M~-15 mag after two additional weeks.
During this bright '2014b' phase the spectrum became dominated by Balmer
emission and a stronger blue continuum, similar to the SN impostor SN 1997bs.
Archival images from the Hubble Space Telescope between 1997 and 2005 reveal a
luminous (4e5 Lsun) variable precursor star. Its location on the
Hertzsprung-Russell diagram is consistent with a massive (M_init~30 Msun) cool
hypergiant having an extremely dense wind and an Eddington ratio just below
unity. At the onset of the recent 2014a brightening, however, the object became
super-Eddington. The subsequent boost in luminosity during the 2014b phase
probably resulted from circumstellar interaction. SN Hunt 248 provides the
first case of a cool hypergiant undergoing a giant eruption reminiscent of
outbursts from luminous blue variable (LBV) stars. This lends support to the
hypothesis that some cool hypergiants, such as Rho Cas, could be LBVs
masquerading under a pseudo-photosphere created by their extremely dense winds.
Moreover, SN Hunt 248 demonstrates that eruptions stemming from such stars can
rival in peak luminosity the giant outbursts of much more massive systems like
Eta Car.Comment: Accepted to MNRAS on 2014 Dec 1. Post-proof version. 14 pages, 9
figure
Technology-Based Innovations in Child Maltreatment Prevention Programs: Examples from SafeCare®
Each year, hundreds of thousands of children in the U.S. are victims of child maltreatment. Experts recommend behavioral, skill-based parent training programs as a strategy for the prevention of child abuse and neglect. These programs can be enhanced using innovative technology strategies. This paper presents a brief history of the use of technology in SafeCare®, a home visiting program shown to prevent child neglect and physical abuse, and highlights current work that takes a technology-based hybrid approach to SafeCare delivery. With this unique approach, the provider brings a tablet computer to each session, and the parent interacts with the software to receive psychoeducation and modeling of target skills. The provider and parent then work together to practice the targeted skills until mastery is achieved. Initial findings from ongoing research of both of these strategies indicate that they show potential for improving engagement and use of positive parenting skills for parents and ease of implementation for providers. Future directions for technology enhancements in SafeCare are also presented
Molecular-orbital-free algorithm for excited states in time-dependent perturbation theory
A non-linear conjugate gradient optimization scheme is used to obtain
excitation energies within the Random Phase Approximation (RPA). The solutions
to the RPA eigenvalue equation are located through a variational
characterization using a modified Thouless functional, which is based upon an
asymmetric Rayleigh quotient, in an orthogonalized atomic orbital
representation. In this way, the computational bottleneck of calculating
molecular orbitals is avoided. The variational space is reduced to the
physically-relevant transitions by projections. The feasibility of an RPA
implementation scaling linearly with system size, N, is investigated by
monitoring convergence behavior with respect to the quality of initial guess
and sensitivity to noise under thresholding, both for well- and ill-conditioned
problems. The molecular- orbital-free algorithm is found to be robust and
computationally efficient providing a first step toward a large-scale, reduced
complexity calculation of time-dependent optical properties and linear
response. The algorithm is extensible to other forms of time-dependent
perturbation theory including, but not limited to, time-dependent Density
Functional theory.Comment: 9 pages, 7 figure
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