2,851 research outputs found
Search for Gamma-ray Emission from Dark Matter Annihilation in the Small Magellanic Cloud with the Fermi Large Area Telescope
The Small Magellanic Cloud (SMC) is the second-largest satellite galaxy of
the Milky Way and is only 60 kpc away. As a nearby, massive, and dense object
with relatively low astrophysical backgrounds, it is a natural target for dark
matter indirect detection searches. In this work, we use six years of Pass 8
data from the Fermi Large Area Telescope to search for gamma-ray signals of
dark matter annihilation in the SMC. Using data-driven fits to the gamma-ray
backgrounds, and a combination of N-body simulations and direct measurements of
rotation curves to estimate the SMC DM density profile, we found that the SMC
was well described by standard astrophysical sources, and no signal from dark
matter annihilation was detected. We set conservative upper limits on the dark
matter annihilation cross section. These constraints are in agreement with
stronger constraints set by searches in the Large Magellanic Cloud and approach
the canonical thermal relic cross section at dark matter masses lower than 10
GeV in the and channels.Comment: 17 pages, 11 figures. Accepted by PR
Identification and characterization of an irreversible inhibitor of CDK2
Irreversible inhibitors that modify cysteine or lysine
residues within a protein kinase ATP binding site offer, through their distinctive mode of action, an alternative to ATP-competitive agents. 4-((6-(Cyclohexylmethoxy)-
9H-purin-2-yl)amino)benzenesulfonamide (NU6102) is a potent and selective ATP-competitive inhibitor of CDK2 in which the sulfonamide moiety is positioned close to a pair of lysine residues. Guided by the CDK2/NU6102 structure, we designed 6-(cyclohexylmethoxy)-N-(4-(vinylsulfonyl)phenyl)-9H-purin-2-amine (NU6300), which binds covalently to CDK2 as shown by a co-complex crystal
structure. Acute incubation with NU6300 produced a durable inhibition of Rb phosphorylation in SKUT-1B cells, consistent with it acting as an irreversible CDK2 inhibitor. NU6300 is the first covalent CDK2 inhibitor to be described, and illustrates the potential of vinyl sulfones for the design of more potent and selective compounds
Singing fin whale swimming behavior in the Central North Pacific
This research was supported by Commander, U.S. Pacific Fleet (Code N465JR, Award Number N0007020WR0EP8F), the Office of Naval Research (Code 322, Award Number N0001421WX00156), and tool development necessary for this analysis was supported by the U.S. Navy's Living Marine Resources Program (Award Number N0002520WR0141R).Male fin whales sing using 20 Hz pulses produced in regular patterns of inter-note intervals, but little is known about fin whale swimming behavior while they are singing. Even less is known about fin whales in Hawaiian waters because they have rarely been sighted during surveys and passive acoustic monitoring has been limited to sparse hydrophone systems that do not have localization capabilities. We hypothesized that fin whale kinematics may be related to their singing behavior, or external variables such as time and sea state. To investigate this hypothesis, we analyzed 115 tracks containing 50,034 unique notes generated from passive acoustic recordings on an array of 14 hydrophones from 2011 to 2017 at the U.S. Navy Pacific Missile Range Facility off Kauai, Hawaii. Fin whales swam at an average speed of 1.1 m/s over relatively direct paths. We incorporated the whales' speed and turning angle into hidden Markov models to identify different behavioral states based on the whales' movements. We found that fin whale kinematic behavioral state was related to the vocalization rate (also known as cue rate) and time of day. When cue rate was higher, fin whales were more likely to swim slower and turn more than when cue rate was lower. During the night, fin whales were also more likely to swim slower and turn more than during the day. In addition, we examined whether the presence of singing fin whales was related to time and sea state using generalized additive models. Fin whale track presence was affected by day of the year and song season, and possibly also wind speed and wave height. Although the track kinematics from the fin whale tracks presented here are limited to a subset of whales that are acoustically active, they provide some of the only detailed movements of fin whales in the region and can be compared against fin whale swim speeds in other regions. Understanding how fin whale swimming behavior varies based on their vocalization patterns, time, and environmental factors will help us to contextualize potential changes in whale behavior during Navy training and testing on the range.Publisher PDFPeer reviewe
WikiDo
Not formally publishedThe Internet has allowed collaboration on an unprecedented scale. Wikipedia, Luis Von Ahn’s ESP game, and reCAPTCHA have proven that tasks typically performed by expensive in-house or outsourced teams can instead be delegated to the mass of Internet computer users. These success stories show the opportunity for crowdsourcing other tasks, such as allowing computer users to help each other answer questions like “How do I make my computer do X?”. Such a system would reduce IT cost, user frustration, and machine downtime. The current approach to crowd-sourcing IT tasks, however, only allows users to collaborate on generating text. Anyone who goes through the process of searching help wikis and user forums hoping to find a solution for some computer problem knows the inefficacy and the frustration accompanying such a process. Text is ambiguous and often incomplete, particularly when written by non-experts. This paper presents WikiDo, a system that enables the mass of non-expert users to help each other answer how-to computer questions by actually performing the task rather than documenting its solution.National Science Foundation (U.S.) (grant IIS-0835652
North Pacific minke whales call rapidly when calling conspecifics are nearby
This research was supported by Commander, U.S. Pacific Fleet (Code N465JR, Award Number N0007020WR0EP8F) and tool development utilized for this analysis was supported by the U.S. Navy’s Living Marine Resources Program (Award Number N0002520WR0141R).North Pacific minke whale (Balaenoptera acutorostrata) boing calls are commonly detected in Hawaiian waters. When producing boing vocalizations, minke whales seem to be in one of two calling behavioral states. Most often minke whales produce boings with inter-call intervals of several minutes, but sometimes minke whales call rapidly with inter-call intervals of less than a minute. Since minke whales are difficult to detect visually, cue-rate-based density estimation using passive acoustic monitoring has been proposed. However, the variables that influence cue rate or calling rate are poorly understood in most whales, including minke whales. We collected passive acoustic recordings from 47 bottom-mounted hydrophones at the Pacific Missile Range Facility’s instrumented range off the coast of Kauaʻi, Hawaiʻi to test the hypothesis that minke whales call more rapidly when closer in proximity to other calling conspecifics. A total of 599 days of data were recorded between August 2012 and July 2017 and were automatically post-processed to detect, classify, and localize calls. Localized calls were grouped into tracks and manually validated, resulting in 509 individual tracks composed of 36,033 calls within a 16 x 39 km focal study area. Tracked minke whales exhibited a strong bimodal call rate with means of one call every 6.85 min (σ= 2.54 min) and 0.63 min (σ= 0.36 min). We ran hidden Markov models to quantify the relationship between call rate and the distance to the nearest calling conspecific. Overall, the probability of the higher call rate occurring increased as the distance to the nearest conspecific decreased, and the probability of the lower call rate occurring increased as the distance to the nearest conspecific increased. We also examined individual track data and found that minke whales may also exhibit other responses (i.e. increased speed, changes in heading, and cessation of calling) when calling conspecifics are nearby. These findings provide new information about minke whale calling behavior in what is likely a breeding area.Publisher PDFPeer reviewe
Genetic and morphometric divergence of an invasive bird : the introduced house sparrow (Passer domesticus) in Brazil
Introduced species are interesting systems for the study of contemporary evolution in new environments because of their spatial and temporal scales. For this study we had three aims: (i) to determine how genetic diversity and genetic differentiation of introduced populations of the house sparrow (Passer domesticus) in Brazil varies with range expansion, (ii) to determine how genetic diversity and differentiation in Brazil compares to ancestral European populations; and (iii) to determine whether selection or genetic drift has been more influential on phenotypic divergence. We used six microsatellite markers to genotype six populations from Brazil and four populations from Europe. We found slightly reduced levels of genetic diversity in Brazilian compared to native European populations. However, among introduced populations of Brazil, we found no association between genetic diversity and time since introduction. Moreover, overall genetic differentiation among introduced populations was low indicating that the expansion took place from large populations in which genetic drift effects would likely have been weak. We found significant phenotypic divergence among sites in Brazil. Given the absence of a spatial genetic pattern, divergent selection and not genetic drift seems to be the main force behind most of the phenotypic divergence encountered. Unravelling whether microevolution (e.g., allele frequency change), phenotypic plasticity, or both mediated phenotypic divergence is challenging and will require experimental work (e.g., common garden experiments or breeding programs)
Teleseisms monitoring using chirped-pulse φOTDR
Monitoring of seismic activity around the word is a topic of high interest for the analysis and understanding of deep Earth dynamics. However, the deployment of a homogeneous network of seismic stations both onshore and offshore poses a strong economic challenge that makes this solution practically inviable. Using the pre-existing fiber optical network for seismic monitoring arises as an excellent solution with important advantages in terms of ubiquity and cost. In this communication, we present the detection of an M8.2 earthquake occurred in Fiji Island using distributed acoustic sensing based on chirped-pulse φOTDR. Two sensors were placed simultaneously at two different locations at >9,000 km from the earthquake epicenter: a metropolitan area and a submarine environment. The recorded data is postprocessed using a 2D linear filter to cancel out environmental noise. The resulting signals are compared with the signals acquired by nearby seismometers. The attained good matching between the recorded data and the seismometer data shows the strong potential of the use of the already-deployed communication fiber network for teleseism monitoring
Metric Features of a Dipolar Model
The lattice spin model, with nearest neighbor ferromagnetic exchange and long
range dipolar interaction, is studied by the method of time series for
observables based on cluster configurations and associated partitions, such as
Shannon entropy, Hamming and Rohlin distances. Previous results based on the
two peaks shape of the specific heat, suggested the existence of two possible
transitions. By the analysis of the Shannon entropy we are able to prove that
the first one is a true phase transition corresponding to a particular melting
process of oriented domains, where colored noise is present almost
independently of true fractality. The second one is not a real transition and
it may be ascribed to a smooth balancing between two geometrical effects: a
progressive fragmentation of the big clusters (possibly creating fractals), and
the slow onset of a small clusters chaotic phase. Comparison with the nearest
neighbor Ising ferromagnetic system points out a substantial difference in the
cluster geometrical properties of the two models and in their critical
behavior.Comment: 20 pages, 15 figures, submitted to JPhys
Chandra X-Ray Observatory Observations of the Globular Cluster M71
We observed the nearby, low-density globular cluster M71 (NGC 6838) with the
Chandra X-ray Observatory to study its faint X-ray populations. Five X-ray
sources were found inside the cluster core radius, including the known
eclipsing binary millisecond pulsar (MSP) PSR J1953+1846A. The X-ray light
curve of the source coincident with this MSP shows marginal evidence for
periodicity at the binary period of 4.2 h. Its hard X-ray spectrum and
luminosity resemble those of other eclipsing binary MSPs in 47 Tuc, suggesting
a similar shock origin of the X-ray emission. A further 24 X-ray sources were
found within the half-mass radius, reaching to a limiting luminosity of 1.5
10^30 erg/s (0.3-8 keV). From a radial distribution analysis, we find that
18+/-6 of these 29 sources are associated with M71, somewhat more than
predicted, and that 11+/-6 are background sources, both galactic and
extragalactic. M71 appears to have more X-ray sources between L_X=10^30--10^31
erg/s than expected by extrapolating from other studied clusters using either
mass or collision frequency. We explore the spectra and variability of these
sources, and describe the results of ground-based optical counterpart searches.Comment: 36 pages including 7 figures and 8 tables, accepted by The
Astrophysical Journa
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