Commensurability oscillations due to pinned and drifting orbits in a two-dimensional lateral surface superlattice

We have simulated conduction in a two-dimensional electron gas subject to a weak two-dimensional periodic potential, $V_x \cos(2\pi x/a) + V_y \cos(2\pi y/a)$. The usual commensurability oscillations in $\rho_{xx}(B)$ are seen with $V_x$ alone. An increase of $V_y$ suppresses these oscillations, rather than introducing the additional oscillations in $\rho_{yy}(B)$ expected from previous perturbation theories. We show that this behavior arises from drift of the guiding center of cyclotron motion along contours of an effective potential. Periodic modulation in the magnetic field can be treated in the same way.Comment: 3 pages text, 4 eps figures, revte

MINIMIZING THE F-35C AIRCRAFT MAINTENANCE DOWNTIME

The Navy currently operates three F-35C squadrons, who have recently faced readiness challenges due to maintenance downtime. The current readiness levels attained to date will not suffice when the platform embarks on its first deployment in 2021. These readiness shortfalls prompted the authors to complete a Pareto analysis to determine the top maintenance-related degraders by the type of maintenance involved. Subsequently, the authors utilized process improvement tools to assess the efficiency of the current maintenance processes and investigated areas that could benefit from the authors’ analysis. The authors make recommendations to implement parallel maintenance processes and standardize the administrative documentation procedures, which have the potential to reduce maintenance downtime, increase aircraft readiness, and facilitate a means to perform more robust future aviation maintenance process analyses.http://archive.org/details/minimizingthefca1094564160Lieutenant, United States NavyLieutenant Commander, United States NavyApproved for public release; distribution is unlimited

Transient but not genetic loss of miR-451 attenuates the development of pulmonary arterial hypertension

<b>Rationale:</b> MicroRNAs are small non-coding RNAs involved in the regulation of gene expression and have recently been implicated in the development of pulmonary arterial hypertension (PAH). Previous work established that miR-451 is up-regulated in rodent models of PAH.<p></p> <b>Objectives:</b> The role of miR-451 in the pulmonary circulation is unknown. We therefore sought to assess the involvement of miR-451 in the development of pulmonary arterial hypertension.<p></p> <b>Methods:</b> Silencing of miR-451 was performed in vivo using miR-451 knockout mice and an antimiR targeting mature miR-451 in rats. Coupled with exposure to hypoxia, indices of pulmonary arterial hypertension were assessed. The effect of modulating miR-451 on human pulmonary artery smooth muscle cell proliferation and migration was analysed.<p></p> <b>Measurements and Main Results:</b> We observed a reduction in systolic right ventricular pressure in hypoxic rats pre-treated with antimiR-451 compared to hypoxia alone (47.7 ± 1.36mmHg and 56.0 ± 2.03mmHg respectively, p<0.01). In miR-451 knockout mice following exposure to chronic hypoxia, no significant differences were observed compared to wild type hypoxic mice. In vitro analysis demonstrated that over-expression of miR-451 in human pulmonary artery smooth muscle cells promoted migration under serum-free conditions. No effect on cellular proliferation was observed.<p></p> <b>Conclusions:</b> Transient inhibition of miR-451 attenuated the development of pulmonary arterial hypertension in hypoxia exposed rats. Genetic deletion of miR-451 had no beneficial effect on indices of pulmonary arterial hypertension, potentially due to pathway redundancy compensating for the loss of miR-451.<p></p&gt

Development of a low-maintenance measurement approach to continuously estimate methane emissions: a case study

The chemical breakdown of organic matter in landfills represents a significant source of methane gas (CH4). Current estimates suggest that landfills are responsible for between 3% and 19% of global anthropogenic emissions. The net CH4 emissions resulting from biogeochemical processes and their modulation by microbes in landfills are poorly constrained by imprecise knowledge of environmental constraints. The uncertainty in absolute CH4 emissions from landfills is therefore considerable. This study investigates a new method to estimate the temporal variability of CH4 emissions using meteorological and CH4 concentration measurements downwind of a landfill site in Suffolk, UK from July to September 2014, taking advantage of the statistics that such a measurement approach offers versus shorter-term, but more complex and instantaneously accurate, flux snapshots. Methane emissions were calculated from CH4 concentrations measured 700 m from the perimeter of the landfill with observed concentrations ranging from background to 46.4 ppm. Using an atmospheric dispersion model, we estimate a mean emission flux of 709 μg m−2 s−1 over this period, with a maximum value of 6.21 mg m−2 s−1, reflecting the wide natural variability in biogeochemical and other environmental controls on net site emission. The emissions calculated suggest that meteorological conditions have an influence on the magnitude of CH4 emissions. We also investigate the factors responsible for the large variability observed in the estimated CH4 emissions, and suggest that the largest component arises from uncertainty in the spatial distribution of CH4 emissions within the landfill area. The results determined using the low-maintenance approach discussed in this paper suggest that a network of cheaper, less precise CH4 sensors could be used to measure a continuous CH4 emission time series from a landfill site, something that is not practical using far-field approaches such as tracer release methods. Even though there are limitations to the approach described here, this easy, low-maintenance, low-cost method could be used by landfill operators to estimate time-averaged CH4 emissions and their impact downwind by simultaneously monitoring plume advection and CH4 concentrations

Assessment of the learning curve in health technologies: a systematic review

Objective: We reviewed and appraised the methods by which the issue of the learning curve has been addressed during health technology assessment in the past. Method: We performed a systematic review of papers in clinical databases (BIOSIS, CINAHL, Cochrane Library, EMBASE, HealthSTAR, MEDLINE, Science Citation Index, and Social Science Citation Index) using the search term "learning curve:" Results: The clinical search retrieved 4,571 abstracts for assessment, of which 559 (12%) published articles were eligible for review. Of these, 272 were judged to have formally assessed a learning curve. The procedures assessed were minimal access (51%), other surgical (41%), and diagnostic (8%). The majority of the studies were case series (95%). Some 47% of studies addressed only individual operator performance and 52% addressed institutional performance. The data were collected prospectively in 40%, retrospectively in 26%, and the method was unclear for 31%. The statistical methods used were simple graphs (44%), splitting the data chronologically and performing a t test or chi-squared test (60%), curve fitting (12%), and other model fitting (5%). Conclusions: Learning curves are rarely considered formally in health technology assessment. Where they are, the reporting of the studies and the statistical methods used are weak. As a minimum, reporting of learning should include the number and experience of the operators and a detailed description of data collection. Improved statistical methods would enhance the assessment of health technologies that require learning

Assessing the learning curve effect in health technologies: Lessons from the non-clinical literature

Introduction: Many health technologies exhibit some form of learning effect, and this represents a barrier to rigorous assessment. It has been shown that the statistical methods used are relatively crude. Methods to describe learning curves in fields outside medicine, for example, psychology and engineering, may be better. Methods: To systematically search non–health technology assessment literature (for example, PsycLit and Econlit databases) to identify novel statistical techniques applied to learning curves. Results: The search retrieved 9,431 abstracts for assessment, of which 18 used a statistical technique for analyzing learning effects that had not previously been identified in the clinical literature. The newly identified methods were combined with those previously used in health technology assessment, and categorized into four groups of increasing complexity: a) exploratory data analysis; b) simple data analysis; c) complex data analysis; and d) generic methods. All the complex structured data techniques for analyzing learning effects were identified in the nonclinical literature, and these emphasized the importance of estimating intra- and interindividual learning effects. Conclusion: A good dividend of more sophisticated methods was obtained by searching in nonclinical fields. These methods now require formal testing on health technology data sets

Body mass estimates of phytosaurs (Archosauria: Parasuchidae) from the Petrified Forest Formation (Chinle Group: Revueltian : early-mid Norian) based on skull and limb bone measurements

Phytosaurs were the largest and most common semi-aquatic predators of the Late Triassic. Although their skulls are relatively common in the fossil record, articulated, or even associated skeletons are extremely rare, so it has always been difficult to gauge just how large (mass or length) an individual phytosaur may have been. Body mass in particular is an important physiological variable, often used for the scaling of organs, biomass determination, biomechanics, and locomotion. We take advantage of phytosaurs’ general similarity to extant crocodilians to attempt to reconstruct body mass and length based on measurements of the skulls and limbs of phytosaurs from the Upper Triassic Snyder and Canjilon quarries in north-central New Mexico. These quarries, in the Painted Desert Member of the Petrified Forest Formation (Revueltian: early-mid Norian) preserve catastrophic death assemblages that appear to well-represent discrete populations of phytosaurs. We also utilize a snout-vent measurement based on an articulated skeleton from the Canjilon quarry to compare the accuracy of different equations based on discrete limb elements. Body mass estimates for Snyder quarry phytosaurs range between 25 and 500 kg, with most specimens yielding estimates of approximately 200-350 kg. The Canjilon quarry sample encompasses fewer juveniles and more robust adults, including one individual that may have weighed as much as 535 kg. From equations based on nine extant crocodilian genera, these Revueltian phytosaurs appear to have approached 4.5 m total body length for a ~ 400 kg phytosaur. The prevalence of subadult to adult phytosaurs in both quarries based on body mass estimates corroborates qualitative estimates of the population structure based on skull sizes alone, thereby reinforcing the hypothesis that both quarries are catastrophic assemblages

Values driven policy in designing environments for children and young people's education, health and wellbeing

The new millennium coincided with a reappraisal of value in UK construction and calls from a wide range of influential individuals, professional institutions and government bodies for the industry to exceed stakeholders’ expectations and develop integrated teams that can deliver world class products and services. As such value is certainly topical, but the importance of values as a separate but related concept is less well understood. This paper addresses the construction industry’s need to deliver public buildings that can regenerate communities, transform schools, modernise healthcare facilities and inspire children in a way that will make a real difference to their lives. Doing this requires a strong service and estates vision driven not only by the technical building solutions, but also by practitioners aspirations. Stakeholder engagement is seen by the Government as a way to bring about this reform, however the stakeholder consultation tools that are being deployed by providers and clients alike may be limited in how they translate values, attitudes and good teaching, learning and healthcare practices into building design. The purpose of this paper is to present the need to understand with greater meaning the values and cultures of schools and healthcare facilities during construction briefing and delivery and how the spirits of users can be harnessed to ensure the success and transformation of a new facility. It presents a longitudinal case study in which various tools and approaches have been developed and applied to address this need within education capital projects. It also draws on value, values and stakeholder literature in education and healthcare. The importance of this paper is to extend the range of methodological tools used in construction to structure the effects of meaning, culture and values on the construction industry’s processes, products and building operation and to translate learning between the education, health and social care sectors. It also hopes to encourage construction providers to extend their service and explore the opportunity to employ a similar methodology, particularly in the public sector environment where there is a growing need for multi-agency service integration

Strategic asset management and master planning within the healthcare sector: exploring the theoretical need for evidence based change management in strategic planning

The delivery of health and social care in the UK is undergoing profound change and being redesigned to provide high quality, person-centred services and improved capacity and performance. This is taking place in a context of: change in asset ownership; moves towards increased local autonomy in the provision of services; and the introduction of national, evidence-based standards and inspection. There has been considerable activity surrounding the planning, design and operation of healthcare services and facilities, however, Strategic Asset Management as a field of literature has not sufficiently developed in line with this change in emphasis. The recent move towards PFI, LIFT and World Class Commissioning within the NHS (National Health Service), has meant that roles and responsibilities for estates are shifting alongside commissioning competencies; however, the impact of this shift on the built healing environment is not well understood. Strategic Asset Management on a regional scale requires: reliable predictive data; effective tools and processes for developing and modelling future scenarios; and people with the appropriate skills and expertise, although these are not always available. As such, these factors need to be better understood and the stakeholders responsible for them defined