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© 2018 American Chemical Society. Transition metal dichalcogenides (TMDs) are particularly sensitive to mechanical strain because they are capable of experiencing high atomic displacements without nucleating defects to release excess energy. Being promising for photonic applications, it has been shown that as certain phases of layered TMDs MX2 (M = Mo or W; X = S, Se, or Te) are scaled to a thickness of one monolayer, the photoluminescence response is dramatically enhanced due to the emergence of a direct electronic band gap compared with their multilayer or bulk counterparts, which typically exhibit indirect band gaps. Recently, mechanical strain has also been predicted to enable direct excitonic recombination in these materials, in which large changes in the photoluminescence response will occur during an indirect-to-direct band gap transition brought on by elastic tensile strain. Here, we demonstrate an enhancement of 2 orders of magnitude in the photoluminescence emission intensity in uniaxially strained single crystalline WSe2 bilayers. Through a theoretical model that includes experimentally relevant system conditions, we determine this amplification to arise from a significant increase in direct excitonic recombination. Adding confidence to the high levels of elastic strain achieved in this report, we observe strain-independent, mode-dependent Grüneisen parameters over the entire range of tensile strain (1-3.59%), which were obtained as 1.149 ± 0.027, 0.307 ± 0.061, and 0.357 ± 0.103 for the E2g, A1g, and A21g optical phonon modes, respectively. These results can inform the predictive strain-engineered design of other atomically thin indirect semiconductors, in which a decrease in out-of-plane bonding strength may lead to an increase in the strength of strain-coupled optoelectronic effects.

Visual sensitivity can be tuned by differential expression of opsin genes. Among African cichlid fishes, seven cone opsin genes are expressed in different combinations to produce diverse visual sensitivities. To determine the genetic architecture controlling these adaptive differences, we analysed genetic crosses between species expressing different complements of opsin genes. Quantitative genetic analyses suggest that expression is controlled by only a few loci with correlations among some genes. Genetic mapping identifies clear evidence of trans-acting factors in two chromosomal regions that contribute to differences in opsin expression as well as one cis-regulatory region. Therefore, both cis and trans regulation are important. The simple genetic architecture suggested by these results may explain why opsin gene expression is evolutionarily labile, and why similar patterns of expression have evolved repeatedly in different lineages.

Influenza A viruses pose a major public health threat by causing seasonal epidemics and sporadic pandemics. Their epidemiological success relies on airborne transmission from person to person; however, the viral properties governing airborne transmission of influenza A viruses are complex. Influenza A virus infection is mediated via binding of the viral haemagglutinin (HA) to terminally attached α2,3 or α2,6 sialic acids on cell surface glycoproteins. Human influenza A viruses preferentially bind α2,6-linked sialic acids whereas avian influenza A viruses bind α2,3-linked sialic acids on complex glycans on airway epithelial cells. Historically, influenza A viruses with preferential association with α2,3-linked sialic acids have not been transmitted efficiently by the airborne route in ferrets. Here we observe efficient airborne transmission of a 2009 pandemic H1N1 (H1N1pdm) virus (A/California/07/2009) engineered to preferentially bind α2,3-linked sialic acids. Airborne transmission was associated with rapid selection of virus with a change at a single HA site that conferred binding to long-chain α2,6-linked sialic acids, without loss of α2,3-linked sialic acid binding. The transmissible virus emerged in experimentally infected ferrets within 24 hours after infection and was remarkably enriched in the soft palate, where long-chain α2,6-linked sialic acids predominate on the nasopharyngeal surface. Notably, presence of long-chain α2,6-linked sialic acids is conserved in ferret, pig and human soft palate. Using a loss-of-function approach with this one virus, we demonstrate that the ferret soft palate, a tissue not normally sampled in animal models of influenza, rapidly selects for transmissible influenza A viruses with human receptor (α2,6-linked sialic acids) preference., National Institutes of Health (U.S.), United States. Dept. of Health and Human Services (Contract HHSN272200900007C), National Institute of Allergy and Infectious Diseases (U.S.) Genomic Centers for Infectious Diseases (Program U19-AI-110819)

This paper employs a new national data set to estimate constant quality dwelling prices for four regions of the country. The data set, collected by the National Association of Realtors, provides sale prices, locations, and characteristics of 5581 dwellings sold during the years 1986–1992 inclusive. The paper provides the first national hedonic analysis based upon transaction prices of sample dwellings. The estimated equation implies that more than half of dwelling price increases during the period resulted from quality improvements in dwellings.

As part of the effort to develop a "weather translation model", we propose a new method of airspace capacity estimation when the NAS is impacted by convective weather. We base it on the premise, accepted by other researches, that the capacity of an airspace sector or center is a function of the geometric structure of traffic flows that traverse this airspace (in addition, of course, to the location of the weather). By computing an augmented weather impacted traffic index (WITI) metric that takes into account the spread of convection blocking a traffic flow, and relating it to a "maximum WITI" metric for each flow, we are able to generate reasonably good estimates of airspace capacity degradation. We discuss verification metrics and methods, as well as potential caveats. This approach is first tested using actual convective weather data; after that, initial results are presented that use convective forecast data.

In this paper, we present a new method for quantifying the impact of forecast convective weather on the National Airspace System (NAS). Data generated by a convective forecast product (broad areas, percentage coverage and confidence level) is converted to a format similar to the actual convective weather data (detailed reports on a NAS-wide fine grid). From this, we build a NAS weather impact index showing how the forecast and actual weather might have impacted the air traffic. The aim of the project is to better understand how the accuracy of the weather impact forecast (not just the weather forecast in itself) affects NAS operational response strategies. The results are compared for several convective seasons and typical cases are discussed.

Five commercially available infant radiant warmer systems were characterized through radiant-energy measurements at the mattress surface under identical environmental conditions. Average irradiance levels for each warmer were then calculated. In addition, all systems were thermally evaluated for warm-up time using the International IEC standard black anodized aluminum disk simulator. Warm-up time and radiant-energy bed mapping tests were conducted in manual mode. To assess thermal performance under dynamic conditions, skin and core temperatures were measured using a patient simulator test-load device. Dynamic patient simulator response-time data and side-wall temperature data are provided. The radiative heat contribution from the warmer side walls on patient simulator core and skin temperatures was demonstrated. Extreme differences in warmer performances and energy to the mattress surface are documented. Differences in infant radiant warmer performances are principally due to heater-element composition, reflector design, and heater-to-mattress distance.

A comparative study was made of damage to simulated kidney stones from spherical sector and focused hydrodynamic shock waves. Plaster cylinders of 40 bar static compressive strength were subjected to spherical shock waves with a time constant of 7 μsec generated by a conical shock tube. Near total destruction of the 2.5 cm by 2.5 cm cylinders to fine particles occurred with a single shock at a peak pressure of 0.85 kbar; onset of visible erosion at 0.5 kbar. Similar experiments performed in the diffraction region at a distance of 10 cm beyond the end of th shock tube with three repeated shocks of 0.34 kbar resulted in significant erosion. Similar targets located at the second focus of a semi‐ellipsoid reflector were subjected to multiple shock waves generated by an underwater electric arc located at the first focus. Progressive target erosion to fine particles occurred at the second focus as several hundred shocks were provided at the high pressure singularity. These experiments offer empirical insight important to modelling the response of calculi imbedded in biological tissue; e.g., kidneystones and gallstones, to shock waves of varied characteristics. Sector shock waves appear to offer potential for much more efficient and less traumatic medical application than focused shocks.