1,304 research outputs found
The Initial Mass Function of Low-Mass Stars and Brown Dwarfs in Young Clusters
We have obtained images of the Trapezium Cluster (140" x 140"; 0.3 pc x 0.3
pc) with the Hubble Space Telescope Near-Infrared Camera and Multi-Object
Spectrometer (NICMOS). Combining these data with new ground-based K-band
spectra (R=800) and existing spectral types and photometry and the models of
D'Antona & Mazzitelli, we find that the distributions of ages of comparable
samples of stars in the Trapezium, rho Oph, and IC 348 indicate median ages of
\~0.4 Myr for the first two regions and ~1-2 Myr for the latter. The low-mass
IMFs in these sites of clustered star formation are similar over a wide range
of stellar densities and other environmental conditions. With current data, we
cannot rule out modest variations in the substellar mass functions among these
clusters. We then make the best estimate of the true form of the IMF in the
Trapezium by using the evolutionary models of Baraffe et al. and an empirically
adjusted temperature scale and compare this mass function to recent results for
the Pleiades and the field. All of these data are consistent with an IMF that
is flat or rises slowly from the substellar regime to about 0.6 Msun, and then
rolls over into a power law that continues from about 1 Msun to higher masses
with a slope similar to or somewhat larger than the Salpeter value of 1.35. For
the Trapezium, this behavior holds from our completeness limit of ~0.02 Msun
and probably, after a modest completeness correction, even from 0.01-0.02 Msun.
These data include ~50 likely brown dwarfs. We test the predictions of theories
of the IMF against various properties of the observed IMF.Comment: 34 pages, 13 figures, for color image see
http://cfa-www.harvard.edu/~kluhman/trap/colorimage.jp
A reminder of the association between Clostridium septicum and colonic adenocarcinoma
We present the case of a patient, with previously unknown liver metastases, presenting with a liver abscess and Clostridium septicum septicaemia. C. septicum is known to be associated with both malignancy and immunosuppression and therefore in patients where this organism is isolated, efforts must be made to exclude an occult underlying malignancy or haematological disorder
Impact Monitoring of the National Scale Up of Zinc Treatment for Childhood Diarrhea in Bangladesh: Repeat Ecologic Surveys
Charles Larson and colleagues find that 23 months into a national campaign to scale up zinc treatment for diarrhea in children under age 5 years, only 10% of children with diarrhea in rural areas and 20%â25% in urban/municipal areas were getting the treatment
Goldstone Fermion Dark Matter
We propose that the fermionic superpartner of a weak-scale Goldstone boson
can be a natural WIMP candidate. The p-wave annihilation of this `Goldstone
fermion' into pairs of Goldstone bosons automatically generates the correct
relic abundance, whereas the XENON100 direct detection bounds are evaded due to
suppressed couplings to the Standard Model. Further, it is able to avoid
indirect detection constraints because the relevant s-wave annihilations are
small. The interactions of the Goldstone supermultiplet can induce non-standard
Higgs decays and novel collider phenomenology.Comment: 25 pages, 6 figures. References added, minor typos corrected.
Submitted to JHE
Modeling the Residential Infiltration of Outdoor PM2.5 in the Multi-Ethnic Study of Atherosclerosis and Air Pollution (MESA Air)
Background: Epidemiologic studies of fine particulate matter [aerodynamic diameter †2.5 Όm (PM2.5)] typically use outdoor concentrations as exposure surrogates. Failure to account for variation in residential infiltration efficiencies (Finf) will affect epidemiologic study results
The dipeptide Phe-Phe amide attenuates signs of hyperalgesia, allodynia and nociception in diabetic mice using a mechanism involving the sigma receptor system
<p>Abstract</p> <p>Background</p> <p>Previous studies have demonstrated that intrathecal administration of the substance P amino-terminal metabolite substance P<sub>1-7 </sub>(SP<sub>1-7</sub>) and its C-terminal amidated congener induced antihyperalgesic effects in diabetic mice. In this study, we studied a small synthetic dipeptide related to SP<sub>1-7 </sub>and endomorphin-2, i.e. Phe-Phe amide, using the tail-flick test and von Frey filament test in diabetic and non-diabetic mice.</p> <p>Results</p> <p>Intrathecal treatment with the dipeptide increased the tail-flick latency in both diabetic and non-diabetic mice. This effect of Phe-Phe amide was significantly greater in diabetic mice than non-diabetic mice. The Phe-Phe amide-induced antinociceptive effect in both diabetic and non-diabetic mice was reversed by the Ï<sub>1 </sub>receptor agonist (+)-pentazocine. Moreover, Phe-Phe amide attenuated mechanical allodynia in diabetic mice, which was reversible by (+)-pentazocine. The expression of spinal Ï1 receptor mRNA and protein did not differ between diabetic mice and non-diabetic mice. On the other hand, the expression of phosphorylated extracellular signal-regulated protein kinase 1 (ERK1) and ERK2 proteins was enhanced in diabetic mice. (+)-Pentazocine caused phosphorylation of ERK1 and ERK2 proteins in non-diabetic mice, but not in diabetic mice.</p> <p>Conclusions</p> <p>These results suggest that the spinal Ï<sub>1 </sub>receptor system might contribute to diabetic mechanical allodynia and thermal hyperalgesia, which could be potently attenuated by Phe-Phe amide.</p
Characterizing Genetic Diversity of Contemporary Pacific Chickens Using Mitochondrial DNA Analyses
Background\ud
Mitochondrial DNA (mtDNA) hypervariable region (HVR) sequences of prehistoric Polynesian chicken samples reflect dispersal of two haplogroupsâD and Eâby the settlers of the Pacific. The distribution of these chicken haplogroups has been used as an indicator of human movement. Recent analyses suggested similarities between prehistoric Pacific and South American chicken samples, perhaps reflecting prehistoric Polynesian introduction of the chicken into South America. These analyses have been heavily debated. The current distribution of the D and E lineages among contemporary chicken populations in the Western Pacific is unclear, but might ultimately help to inform debates about the movements of humans that carried them.\ud
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Objectives\ud
We sought to characterize contemporary mtDNA diversity among chickens in two of the earliest settled archipelagoes of Remote Oceania, the Marianas and Vanuatu.\ud
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Methods\ud
We generated HVR sequences for 43 chickens from four islands in Vanuatu, and for 5 chickens from Guam in the Marianas.\ud
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Results\ud
Forty samples from Vanuatu and three from Guam were assigned to haplogroup D, supporting this as a Pacific chicken haplogroup that persists in the Western Pacific. Two haplogroup E lineages were observed in Guam and two in Vanuatu. Of the E lineages in Vanuatu, one was identical to prehistoric Vanuatu and Polynesian samples and the other differed by one polymorphism. Contrary to our expectations, we observed few globally distributed domesticate lineages not associated with Pacific chicken dispersal. This might suggest less European introgression of chickens into Vanuatu than expected. If so, the E lineages might represent lineages maintained from ancient Pacific chicken introductions. The Vanuatu sample might thus provide an opportunity to distinguish between maintained ancestral Pacific chicken lineages and replacement by global domesticates through genomic analyses, which could resolve questions of contemporary haplogroup E chicken relationships and inform interpretations of debated sequences from archaeological samples
Submillimeter Studies of Prestellar Cores and Protostars: Probing the Initial Conditions for Protostellar Collapse
Improving our understanding of the initial conditions and earliest stages of
protostellar collapse is crucial to gain insight into the origin of stellar
masses, multiple systems, and protoplanetary disks. Observationally, there are
two complementary approaches to this problem: (1) studying the structure and
kinematics of prestellar cores observed prior to protostar formation, and (2)
studying the structure of young (e.g. Class 0) accreting protostars observed
soon after point mass formation. We discuss recent advances made in this area
thanks to (sub)millimeter mapping observations with large single-dish
telescopes and interferometers. In particular, we argue that the beginning of
protostellar collapse is much more violent in cluster-forming clouds than in
regions of distributed star formation. Major breakthroughs are expected in this
field from future large submillimeter instruments such as Herschel and ALMA.Comment: 12 pages, 9 figures, to appear in the proceedings of the conference
"Chemistry as a Diagnostic of Star Formation" (C.L. Curry & M. Fich eds.
Towards a Taxonomy of Cognitive RPA Components
Robotic Process Automation (RPA) is a discipline that is
increasingly growing hand in hand with Artificial Intelligence (AI) and
Machine Learning enabling the so-called cognitive automation. In such
context, the existing RPA platforms that include AI-based solutions clas sify their components, i.e. constituting part of a robot that performs a
set of actions, in a way that seems to obey market or business deci sions instead of common-sense rules. To be more precise, components
that present similar functionality are identified with different names and
grouped in different ways depending on the platform that provides the
components. Therefore, the analysis of different cognitive RPA platforms
to check their suitability for facing a specific need is typically a time consuming and error-prone task. To overcome this problem and to pro vide users with support in the development of an RPA project, this
paper proposes a method for the systematic construction of a taxonomy
of cognitive RPA components. Moreover, such a method is applied over
components that solve selected real-world use cases from the industry
obtaining promising resultsMinisterio de EconomĂa y Competitividad TIN2016-76956-C3-2-RJunta de AndalucĂa CEI-12-TIC021Centro para el Desarrollo TecnolĂłgico Industrial P011-19/E0
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