2,567 research outputs found
Search for Gamma-ray Emission from Dark Matter Annihilation in the Large Magellanic Cloud with the Fermi Large Area Telescope
At a distance of 50 kpc and with a dark matter mass of
M, the Large Magellanic Cloud (LMC) is a natural target for indirect
dark matter searches. We use five years of data from the Fermi Large Area
Telescope (LAT) and updated models of the gamma-ray emission from standard
astrophysical components to search for a dark matter annihilation signal from
the LMC. We perform a rotation curve analysis to determine the dark matter
distribution, setting a robust minimum on the amount of dark matter in the LMC,
which we use to set conservative bounds on the annihilation cross section. The
LMC emission is generally very well described by the standard astrophysical
sources, with at most a excess identified near the kinematic center
of the LMC once systematic uncertainties are taken into account. We place
competitive bounds on the dark matter annihilation cross section as a function
of dark matter particle mass and annihilation channel.Comment: 33 pages, 22 figures Version 2: minor corrections and clarifications
after journal peer review proces
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
Group Supervision Attitudes: Supervisory Practices Fostering Resistance to Adoption of Evidence-Based Practices
The focus of this study was to qualitatively evaluate worker’s attitudes about clinical supervision. It is believed that poor attitudes toward clinical supervision can create barriers during supervision sessions. Fifty-one participants within a social services organization completed an open-ended questionnaire regarding their clinical supervision experiences. Results suggest four key areas which appear to be strong factors in workers’ experiences and attitudes regarding group supervision: a. facilitator’s skill level; b. creativity; c. utilization of technology; and d. applicability. For organizations interested in overcoming potential barriers to adopting best practices, effectively addressing workers’ negative attitudes toward group supervision would be a worthy endeavor
Secondary structure encodes a cooperative tertiary folding funnel in the Azoarcus ribozyme
A requirement for specific RNA folding is that the free-energy landscape discriminate against non-native folds. While tertiary interactions are critical for stabilizing the native fold, they are relatively non-specific, suggesting additional mechanisms contribute to tertiary folding specificity. In this study, we use coarse-grained molecular dynamics simulations to explore how secondary structure shapes the tertiary free-energy landscape of the Azoarcus ribozyme. We show that steric and connectivity constraints posed by secondary structure strongly limit the accessible conformational space of the ribozyme, and that these so-called topological constraints in turn pose strong free-energy penalties on forming different tertiary contacts. Notably, native A-minor and base-triple interactions form with low conformational free energy, while non-native tetraloop/tetraloop–receptor interactions are penalized by high conformational free energies. Topological constraints also give rise to strong cooperativity between distal tertiary interactions, quantitatively matching prior experimental measurements. The specificity of the folding landscape is further enhanced as tertiary contacts place additional constraints on the conformational space, progressively funneling the molecule to the native state. These results indicate that secondary structure assists the ribozyme in navigating the otherwise rugged tertiary folding landscape, and further emphasize topological constraints as a key force in RNA folding
pH‐sensitive residues in the p19 RNA silencing suppressor protein from carnation Italian ringspot virus affect siRNA binding stability
Tombusviruses , such as Carnation Italian ringspot virus (CIRV), encode a protein homodimer called p19 that is capable of suppressing RNA silencing in their infected hosts by binding to and sequestering short‐interfering RNA (siRNA) away from the RNA silencing pathway. P19 binding stability has been shown to be sensitive to changes in pH but the specific amino acid residues involved have remained unclear. Using constant pH molecular dynamics simulations, we have identified key pH‐dependent residues that affect CIRV p19–siRNA binding stability at various pH ranges based on calculated changes in the free energy contribution from each titratable residue. At high pH, the deprotonation of Lys60, Lys67, Lys71, and Cys134 has the largest effect on the binding stability. Similarly, deprotonation of several acidic residues (Asp9, Glu12, Asp20, Glu35, and/or Glu41) at low pH results in a decrease in binding stability. At neutral pH, residues Glu17 and His132 provide a small increase in the binding stability and we find that the optimal pH range for siRNA binding is between 7.0 and 10.0. Overall, our findings further inform recent experiments and are in excellent agreement with data on the pH‐dependent binding profile.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97527/1/2243_ftp.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/97527/2/PRO_2243_sm_SuppInfo.pd
Evidence for power-law frequency dependence of intrinsic dielectric response in the CaCuTiO
We investigated the dielectric response of CaCuTiO (CCTO) thin
films grown epitaxially on LaAlO (001) substrates by Pulsed Laser
Deposition (PLD). The dielectric response of the films was found to be strongly
dominated by a power-law in frequency, typical of materials with localized
hopping charge carriers, in contrast to the Debye-like response of the bulk
material. The film conductivity decreases with annealing in oxygen, and it
suggests that oxygen deficit is a cause of the relatively high film
conductivity. With increase of the oxygen content, the room temperature
frequency response of the CCTO thin films changes from the response indicating
the presence of some relatively low conducting capacitive layers to purely
power law, and then towards frequency independent response with a relative
dielectric constant . The film conductance and dielectric
response decrease upon decrease of the temperature with dielectric response
being dominated by the power law frequency dependence. Below 80 K, the
dielectric response of the films is frequency independent with
close to . The results provide another piece of evidence for an
extrinsic, Maxwell-Wagner type, origin of the colossal dielectric response of
the bulk CCTO material, connected with electrical inhomogeneity of the bulk
material.Comment: v4: RevTeX, two-column, 9 pages, 7 figures; title modified, minor
content change in p.7, reference adde
Electromagnetic Form Factors of the Nucleon and Compton Scattering
We review the experimental and theoretical status of elastic electron
scattering and elastic low-energy photon scattering (with both real and virtual
photons) from the nucleon. As a consequence of new experimental facilities and
new theoretical insights, these subjects are advancing with unprecedented
precision. These reactions provide many important insights into the spatial
distributions and correlations of quarks in the nucleon.Comment: 47 pages, 18 figures, includes corrections and updates to published
manuscrip
Song Analysis Reveals a Permanent Population of the Mediterranean Lacewing Chrysoperla agilis (Neuroptera: Chrysopidae) Living in Central Alaska
Chrysoperla agilis Henry et al. (Neuroptera: Chrysopidae) is a widespread, nomadic lacewing in the carnea group of cryptic species. C. agilis has previously been found only in the warm parts of Europe, western Asia, and a few oceanic islands. Like others of the carnea group, C. agilis is identifiable only by its unique courtship song. Recently, a population with by the C. agilis song was discovered in central Alaska; based on its persistence over several years and its distribution over a wide area near Fairbanks, it seems to be permanent rather than transitory. To assess the relationship of this Western Hemisphere population to C. agilis in the Eastern Hemisphere, we 1) analyzed its courtship song, comparing it to the Eurasian song; 2) compared larval and adult morphology of Alaskan and Eurasian specimens; 3) inferred phylogenetic relationships of Alaskan and Eurasian specimens, by using sequences from the cox2 gene; and 4) crossed Alaskan with European individuals, raising their progeny and analyzing their "hybrid” songs. Alaskan C. agilis generally fell within the range of variation of Eurasian individuals for all acoustic and morphological traits, and their hybrid progeny were also acoustically indistinguishable. Phylogenetically, and despite current geographical isolation, Alaskan individuals clustered with Eurasian C. agilis rather than with Western Hemisphere taxa of the carnea group. We conclude that the Alaskan population is a bona fide member of C. agilis. Examination of the geographical pattern of song variation suggests that dispersal to Alaska took place quite recently in a west to east direction, via eastern Asia and the Bering Strai
Epitaxy of hexagonal ABO quantum materials
Hexagonal O oxides (, = cation) are a rich materials class for
realizing novel quantum phenomena. Their hexagonal symmetry, oxygen trigonal
bipyramid coordination and quasi-two dimensional layering give rise to
properties distinct from those of the cubic O perovskites. As bulk
materials, most of the focus in this materials class has been on the rare earth
manganites, MnO ( = rare earth); these materials display coupled
ferroelectricity and antiferromagnetic order. In this review, we focus on the
thin film manifestations of the hexagonal O oxides. We cover the
stability of the hexagonal oxides and substrates which can be used to template
the hexagonal structure. We show how the thin film geometry not only allows for
further tuning of the bulk-stable manganites but also the realization of
metastable hexagonal oxides such as the FeO that combine
ferroelectricity with weak ferromagnetic order. The thin film geometry is a
promising platform to stabilize additional metastable hexagonal oxides to
search for predicted high-temperature superconductivity and topological phases
in this materials class.Comment: The following article has been accepted by Applied Physics Review
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