Adhesion, Stiffness and Instability in Atomically Thin MoS2 Bubbles

We measured the work of separation of single and few-layer MoS2 membranes from a SiOx substrate using a mechanical blister test, and found a value of 220 +- 35 mJ/m^2. Our measurements were also used to determine the 2D Young's modulus of a single MoS2 layer to be 160 +- 40 N/m. We then studied the delamination mechanics of pressurized MoS2 bubles, demonstrating both stable and unstable transitions between the bubbles' laminated and delaminated states as the bubbles were inflated. When they were deflated, we observed edge pinning and a snap-in transition which are not accounted for by the previously reported models. We attribute this result to adhesion hysteresis and use our results to estimate the work of adhesion of our membranes to be 42 +- 20 mJ/m^2

Voltage gated inter-cation selective ion channels from graphene nanopores

With the ability to selectively control ionic flux, biological protein ion channels perform a fundamental role in many physiological processes. For practical applications that require the functionality of a biological ion channel, graphene provides a promising solid-state alternative, due to its atomic thinness and mechanical strength. Here, we demonstrate that nanopores introduced into graphene membranes, as large as 50 nm in diameter, exhibit inter-cation selectivity with a ~20x preference for K+ over divalent cations and can be modulated by an applied gate voltage. Liquid atomic force microscopy of the graphene devices reveals surface nanobubbles near the pore to be responsible for the observed selective behavior. Molecular dynamics simulations indicate that translocation of ions across the pore likely occurs via a thin water layer at the edge of the pore and the nanobubble. Our results demonstrate a significant improvement in the inter-cation selectivity displayed by a solid-state nanopore device and by utilizing the pores in a de-wetted state, offers an approach to fabricating selective graphene membranes that does not rely on the fabrication of sub-nm pores

Associations of Near-Surface Soil Moisture and Annual Plant Community Dynamics

Invasive species have become an increasingly large concern, particularly in already degraded ecosystems, such as sagebrush (Artemisia tridentata)-steppe of the Intermountain West. Much of this ecosystem is already infested with large cheatgrass (Bromus tectorum) stands and is potentially at risk for future invasions depending on biotic and abiotic conditions. In these ecosystems, the existing vegetation, whether native or non-native, may not effectively utilize the soil moisture resources in the upper portion of the soil, termed the growth pool. If the existing vegetation does not effectively utilize moisture in the growth pool, an open resource is left for the establishment of other plants, including invasives. Through a combination of soil moisture modeling and observational studies, we identified three potential invasion pathways, particularly by annual plants, into a cheatgrass-dominated system, all consistent with the fluctuating resource hypothesis, and all resulting from an available water resource in the growth pool. Results suggest these arid and semi-arid systems are likely to be protected from novel invasive species by complete utilization of growth pool soil water resources by any existing vegetation, whether native or non-native. Our results also suggest the same features which make the site more prone to novel annual invaders may also be useful in guiding establishment of desired vegetation during restoration efforts

NESTING ACTIVITY BUDGETS AND ANTIPREDATOR BEHAVIORS OF MISSISSIPPI SANDHILL CRANES

We studied activity budgets and antipredator behaviors of Mississippi sandhill cranes (Grus canadensis pulla) to determine if parental behavior influenced nest outcomes. We used infrared motion-activated cameras to capture behavioral sequences from 21 nests over a 2-year period. Overall activity budgets were similar among crane pairs regardless of nest outcome. Specific activity patterns did predict nest outcomes; pairs at unsuccessful nests spent more time away from the nest and more time manipulating nest contents than successful pairs, while pairs at nests that were lost to predation cooperated poorly and started the nest a month later on average than successful nests. Wild-reared birds gave more agonistic displays toward potential threats than captive-reared birds, but both wild- and captive-reared birds successfully defended nests from potential predators. The results suggest that behavior patterns of nesting pairs can be used to predict likely nest outcome, and that birds differ in their ability to defend nests from predators. We suggest that training in antipredator behavior during captive rearing may increase behavioral competence and reduce losses to nest predators

Band Gap Engineering with Ultralarge Biaxial Strains in Suspended Monolayer MoS2

We demonstrate the continuous and reversible tuning of the optical band gap of suspended monolayer MoS2 membranes by as much as 500 meV by applying very large biaxial strains. By using chemical vapor deposition (CVD) to grow crystals that are highly impermeable to gas, we are able to apply a pressure difference across suspended membranes to induce biaxial strains. We observe the effect of strain on the energy and intensity of the peaks in the photoluminescence (PL) spectrum, and find a linear tuning rate of the optical band gap of 99 meV/%. This method is then used to study the PL spectra of bilayer and trilayer devices under strain, and to find the shift rates and Gr\"uneisen parameters of two Raman modes in monolayer MoS2. Finally, we use this result to show that we can apply biaxial strains as large as 5.6% across micron sized areas, and report evidence for the strain tuning of higher level optical transitions.Comment: Nano Lett., Article ASA

Impact of alpha-tocopherol deficiency and supplementation on sacrocaudalis and gluteal muscle fiber histopathology and morphology in horses.

BackgroundA subset of horses deficient in alpha-tocopherol (α-TP) develop muscle atrophy and vitamin E-responsive myopathy (VEM) characterized by mitochondrial alterations in the sacrocaudalis dorsalis medialis muscle (SC).ObjectivesTo quantify muscle histopathologic abnormalities in subclinical α-TP deficient horses before and after α-TP supplementation and compare with retrospective (r)VEM cases.AnimalsProspective study; 16 healthy α-TP-deficient Quarter Horses. Retrospective study; 10 retrospective vitamin E-responsive myopathy (rVEM) cases .MethodsBlood, SC, and gluteus medius (GM) biopsy specimens were obtained before (day 0) and 56 days after 5000 IU/450 kg horse/day PO water dispersible liquid α-TP (n = 8) or control (n = 8). Muscle fiber morphology and mitochondrial alterations were compared in samples from days 0 and 56 and in rVEM cases.ResultsMitochondrial alterations more common than our reference range (<2.5% affected fibers) were present in 3/8 control and 4/8 treatment horses on day 0 in SC but not in GM (mean, 2.2; range, 0%-10% of fibers). Supplementation with α-TP for 56 days did not change the percentage of fibers with mitochondrial alterations or anguloid atrophy, or fiber size in GM or SC. Clinical rVEM horses had significantly more mitochondrial alterations (rVEM SC, 13% ± 7%; GM, 3% ± 2%) and anguloid atrophy compared to subclinical day 0 horses.Conclusions and clinical importanceClinically normal α-TP-deficient horses can have mitochondrial alterations in the SC that are less severe than in atrophied VEM cases and do not resolve after 56 days of α-TP supplementation. Preventing α-TP deficiency may be of long-term importance for mitochondrial viability

Regression discontinuity analysis for pharmacovigilance:statin example reflected trial findings showing little evidence of harm

OBJECTIVES: The study aims to explore the use of regression discontinuity analysis (RDA) to examine effects of prescription of statins on total cholesterol and adverse outcomes (type 2 diabetes, rhabdomyolysis and myopathy, myalgia and myositis, liver disease, CVD, and mortality). STUDY DESIGN AND SETTING: We conducted a prospective cohort study using the Clinical Practice Research Datalink including patients with QRISK scores of 10 to 30 in 2010 to 2013 who were last followed-up in October 2016. Comparing patients with QRISK≥20 and QRISK<20, we explored RDA assumptions, provided proof of concept analyses (total cholesterol as outcome), and investigated the effect of statins prescription on adverse outcomes. RESULT: RDA confirmed statin prescription reduced total cholesterol (Mean difference (MD) -1.33 mmol/L, 95%Confidence Interval (CI) -1.93 to -0.73). RDA provided little evidence for adverse effects on diabetes, myalgia and myositis, liver disease, CVD, or mortality. The RDA analysis findings are similar to RCT results. Findings from non-RDA analysis agree with published observational studies. CONCLUSION: RDA can be used with large routine clinical datasets to provide evidence on effects of medications which are prescribed according to a threshold. Testable RDA assumptions were satisfied, but confidence intervals were wide, partly due to the low compliance with the prescribing threshold