880 research outputs found
Educational Media Company at Virginia Tech, Inc. v. Swecker: First Amendment Lite Waters Down Commercial Speech Protection
Visualization of defect-induced excitonic properties of the edges and grain boundaries in synthesized monolayer molybdenum disulfide
Atomically thin two-dimensional (2D) transition metal dichalcogenides (TMDCs)
are attractive materials for next generation nanoscale optoelectronic
applications. Understanding nanoscale optical behavior of the edges and grain
boundaries of synthetically grown TMDCs is vital for optimizing their
optoelectronic properties. Elucidating the nanoscale optical properties of 2D
materials through far-field optical microscopy requires a diffraction-limited
optical beam diameter sub-micron in size. Here we present our experimental work
on spatial photoluminescence (PL) scanning of large size ( microns)
monolayer MoS grown by chemical vapor deposition (CVD) using a diffraction
limited blue laser beam spot (wavelength 405 nm) with a beam diameter as small
as 200 nm allowing us to probe nanoscale excitonic phenomena which was not
observed before. We have found several important features: (i) there exists a
sub-micron width strip ( nm) along the edges that fluoresces brighter than the region far inside; (ii) there is another brighter
wide region consisting of parallel fluorescing lines ending at the corners of
the zig-zag peripheral edges; (iii) there is a giant blue shifted A-excitonic
peak, as large as meV, in the PL spectra from the edges. Using
density functional theory calculations, we attribute this giant blue shift to
the adsorption of oxygen dimers at the edges, which reduces the excitonic
binding energy. Our results not only shed light on defect-induced excitonic
properties, but also offer an attractive route to tailor optical properties at
the TMDC edges through defect engineering.Comment: 10 pages, 4 figures in Journal of Physical Chemistry C, 201
An Accounting International Experience Course
Accounting students need practical opportunities to personally experience other cultures and international business practices if they are to effectively compete in today’s global marketplace. In order to address this need, the Department of Accounting at Murray State University offers an international experience course which includes a short-term study tour of London. This paper examines the rationale for an accounting international experience course, provides an overview of the class and presents a suggested itinerary for the London trip
Meta-Learning Related Tasks With Recurrent Networks: Optimization And Generalization
There have been recent interest in meta-learning systems: I.e., networks that are trained to learn across multiple tasks. This paper focuses on optimization and generalization of a meta-learning system based on recurrent networks. The optimization investigates the influence of diverse structures and parameters on its performance. We demonstrate the generalization (robustness) of our meta-learning system to learn across multiple tasks including tasks unseen during the meta training phase. We introduce a meta-cost function (Mean Squared Fair Error) that enhances the performance of the system by not penalizing it during transitions to learning a new task. Evaluation results are presented for Boolean and quadratic functions datasets. The best performance is obtained using a Long Short-Term Memory (LSTM) topology without a forget gate and with a clipped memory cell. The results demonstrate i) the impact of different LSTM architectures, parameters, and error functions on the meta-learning process; ii) that the mean squared fair error function does improve performance for best learning; and iii) the robustness of our meta-learning framework as it generalizes well when tested on tasks unseen during meta-training. Comparison between No-Forget-Gate LSTM and Gated Recurrent Unit also suggest that absence of a memory cell tends to degrade performance
New insights into the evolutionary rate of HIV-1 at the within-host and epidemiological levels
Over calendar time, HIV-1 evolves considerably faster within individuals than it does at the epidemic level. This is a surprising observation since, from basic population genetic theory, we would expect the genetic substitution rate to be similar across different levels of biological organization. Three different mechanisms could potentially cause the observed mismatch in phylogenetic rates of divergence: temporal changes in selection pressure during the course of infection; frequent reversion of adaptive mutations after transmission; and the storage of the virus in the body followed by the preferential transmission of stored ancestral virus. We evaluate each of these mechanisms to determine whether they are likely to make a major contribution to the mismatch in phylogenetic rates. We conclude that the cycling of the virus through very long-lived memory CD4+ T cells, a process that we call ‘store and retrieve’, is probably the major contributing factor to the rate mismatch. The preferential transmission of ancestral virus needs to be integrated into evolutionary models if we are to accurately predict the evolution of immune escape, drug resistance and virulence in HIV-1 at the population level. Moreover, early infection viruses should be the major target for vaccine design, because these are the viral strains primarily involved in transmission
cAMP Control of HCN2 Channel Mg2+ Block Reveals Loose Coupling between the Cyclic Nucleotide-Gating Ring and the Pore
Hyperpolarization-activated cyclic nucleotide-regulated HCN channels underlie the Na+-K+ permeable IH pacemaker current. As with other voltage-gated members of the 6-transmembrane KV channel superfamily, opening of HCN channels involves dilation of a helical bundle formed by the intracellular ends of S6 albeit this is promoted by inward, not outward, displacement of S4. Direct agonist binding to a ring of cyclic nucleotide-binding sites, one of which lies immediately distal to each S6 helix, imparts cAMP sensitivity to HCN channel opening. At depolarized potentials, HCN channels are further modulated by intracellular Mg2+ which blocks the open channel pore and blunts the inhibitory effect of outward K+ flux. Here, we show that cAMP binding to the gating ring enhances not only channel opening but also the kinetics of Mg2+ block. A combination of experimental and simulation studies demonstrates that agonist acceleration of block is mediated via acceleration of the blocking reaction itself rather than as a secondary consequence of the cAMP enhancement of channel opening. These results suggest that the activation status of the gating ring and the open state of the pore are not coupled in an obligate manner (as required by the often invoked Monod-Wyman-Changeux allosteric model) but couple more loosely (as envisioned in a modular model of protein activation). Importantly, the emergence of second messenger sensitivity of open channel rectification suggests that loose coupling may have an unexpected consequence: it may endow these erstwhile “slow” channels with an ability to exert voltage and ligand-modulated control over cellular excitability on the fastest of physiologically relevant time scales
There, I\u27ve Said It Again
Man standing with arms open; I Love You written in white text surrounding man on pinkish red backgroundhttps://scholarsjunction.msstate.edu/cht-sheet-music/11152/thumbnail.jp
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Envelopes Found Early After Acquisition Compared to Those in the Chronically Infected Partner Do Not Have Enhanced Alpha4 Beta7 Binding or Utilization
Genetic Evidence for Modifying Oceanic Boundaries Relative to Fiji
We present the most comprehensive genetic characterization to date of five Fijian island populations: Viti Levu, Vanua Levu, Kadavu, the Lau Islands, and Rotuma, including non-recombinant Y (NRY) chromosome and mitochondrial DNA (mtDNA) haplotypes and haplogroups. As a whole, Fijians are genetically intermediate between Melanesians and Polynesians, but the individual Fijian island populations exhibit significant genetic structure reflecting different settlement experiences in which the Rotumans and the Lau Islanders were more influenced by Polynesians, and the other Fijian island populations were more influenced by Melanesians. In particular, Rotuman and Lau Islander NRY chromosomal and mtDNA haplogroup frequencies and Rotuman mtDNA hypervariable segment 1 (HVS1) region haplotypes more closely resemble those of Polynesians, while genetic markers of the other populations more closely resemble those of the Near Oceanic Melanesians. Our findings provide genetic evidence supportive of modifying regional boundaries relative to Fiji, as has been suggested by others based on a variety of non-genetic evidence. Specifically, for the traditional Melanesia/Polynesia/Micronesia scheme, our findings support moving the Melanesia-Polynesia boundary so as to include Rotuma and the Lau Islands in Polynesia. For the newer Near/Remote Oceania scheme, our findings support keeping Rotuma and the Lau Islands in Remote Oceania and locating the other Fijian island populations in an intermediate or “Central Oceania” region to better reflect the great diversity of Oceania
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