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 $\sim10^{10}$ M$_{\odot}$, 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 $1-2\sigma$ 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 $b\bar{b}$ and $\tau^+\tau^-$ 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 CaCu3_{3}Ti4_{4}O12_{12}

We investigated the dielectric response of CaCu$_3$Ti$_4$O$_{12}$ (CCTO) thin films grown epitaxially on LaAlO$_3$ (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 $\epsilon'\sim10^2$. The film conductance and dielectric response decrease upon decrease of the temperature with dielectric response being dominated by the power law frequency dependence. Below $\sim$80 K, the dielectric response of the films is frequency independent with $\epsilon'$ close to $10^2$. 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 ABO3_3 quantum materials

Hexagonal $AB$O$_3$ oxides ($A$, $B$ = 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 $AB$O$_3$ perovskites. As bulk materials, most of the focus in this materials class has been on the rare earth manganites, $R$MnO$_3$ ($R$ = rare earth); these materials display coupled ferroelectricity and antiferromagnetic order. In this review, we focus on the thin film manifestations of the hexagonal $AB$O$_3$ 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 $R$FeO$_3$ 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