An analytic approximation to the Diffusion Coefficient for the periodic Lorentz Gas

An approximate stochastic model for the topological dynamics of the periodic triangular Lorentz gas is constructed. The model, together with an extremum principle, is used to find a closed form approximation to the diffusion coefficient as a function of the lattice spacing. This approximation is superior to the popular Machta and Zwanzig result and agrees well with a range of numerical estimates.Comment: 13 pages, 4 figure

Mobile On-board Vehicle Event Recorder: MOVER

The rapid development of smart-phone technology in recent years has lead to many smart-phone owners owning out-of-date devices, equipped with useful technologies, which are no longer in use. These devices are valuable resources that can be harnessed to improve users’ lives. This project aims at leveraging these older, unused devices to help improve road safety, specifically through the improved response time of emergency services to accident locations. An Android application — Mobile On-board Vehicle Event Recorder (MOVER) — was designed and built for the purpose of detecting car accidents through the use of acceleration thresholds. Driving data was gathered and crash simulations were run. With this data, testing and analysis were conducted in order to determine an acceleration threshold that separates normal driving from accident situations as accurately as possible. With this application, users can leverage their previous or current mobile devices to improve road safety - for themselves, and their area as a whole. A promising level of accuracy was achieved, but significant improvements can be made to the application. Large opportunity for future work exists in the field, and hopefully through the development of this application, other researchers may be more inclined to investigate and test such future work

Tumor necrosis Factor (TNF) Bioactivity at the site of an acute cell-Mediated immune response is Preserved in rheumatoid arthritis Patients responding to anti-TNF Therapy

The impact of anti-tumor necrosis factor (TNF) therapies on inducible TNF-dependent activity in humans has never been evaluated in vivo. We aimed to test the hypothesis that patients responding to anti-TNF treatments exhibit attenuated TNF-dependent immune responses at the site of an immune challenge. We developed and validated four context-specific TNF-inducible transcriptional signatures to quantify TNF bioactivity in transcriptomic data. In anti-TNF treated rheumatoid arthritis (RA) patients, we measured the expression of these biosignatures in blood, and in skin biopsies from the site of tuberculin skin tests (TSTs) as a human experimental model of multivariate cell-mediated immune responses. In blood, anti-TNF therapies attenuated TNF bioactivity following ex vivo stimulation. However, at the site of the TST, TNF-inducible gene expression and genome-wide transcriptional changes associated with cell-mediated immune responses were comparable to that of RA patients receiving methotrexate only. These data demonstrate that anti-TNF agents in RA patients do not inhibit inducible TNF activity at the site of an acute inflammatory challenge in vivo, as modeled by the TST. We hypothesize instead that their therapeutic effects are limited to regulating TNF activity in chronic inflammation or by alternative non-canonical pathways

Modeling Molecular-Line Emission from Circumstellar Disks

Molecular lines hold valuable information on the physical and chemical composition of disks around young stars, the likely progenitors of planetary systems. This invited contribution discusses techniques to calculate the molecular emission (and absorption) line spectrum based on models for the physical and chemical structure of protoplanetary disks. Four examples of recent research illutrate these techniques in practice: matching resolved molecular-line emission from the disk around LkCa15 with theoertical models for the chemistry; evaluating the two-dimensional transfer of ultraviolet radiation into the disk, and the effect on the HCN/CN ratio; far-infrared CO line emission from a superheated disk surface layer; and inward motions in the disk around L1489 IRS.Comment: 6 pages, no figures. To appear in "The Dense Interstellar Medium in Galaxies", Procs. Fourth Cologne-Bonn-Zermatt-Symposiu

Gravitational Collapse and Fragmentation in Molecular Clouds with Adaptive Mesh Refinement

We describe a powerful methodology for numerical solution of 3-D self-gravitational hydrodynamics problems with extremely high resolution. Our method utilizes the technique of local adaptive mesh refinement (AMR), employing multiple grids at multiple levels of resolution. These grids are automatically and dynamically added and removed as necessary to maintain adequate resolution. This technology allows for the solution of problems in a manner that is both more efficient and more versatile than other fixed and variable resolution methods. The application of AMR to simulate the collapse and fragmentation of a molecular cloud, a key step in star formation, is discussed. Such simulations involve many orders of magnitude of variation in length scale as fragments form. In this paper we briefly describe the methodology and present an illustrative application for nonisothermal cloud collapse. We describe the numerical Jeans condition, a criterion for stability of self-gravitational hydrodynamics problems. We show the first well-resolved nonisothermal evolutionary sequence beginning with a perturbed dense molecular cloud core that leads to the formation of a binary system consisting of protostellar cores surrounded by distinct protostellar disks. The scale of the disks, of order 100 AU, is consistent with observations of gaseous disks surrounding single T-Tauri stars and debris disks surrounding systems such as $\beta$ Pictoris.Comment: 10 pages, 6 figures (color postscript). To appear in the proceedings of Numerical Astrophysics 1998, Tokyo, March 10-13, 199

Replicating the Networking, Mentoring and Venture Creation Benefits of Entrepreneurship Centres on a Shoestring: A Student-centred Approach to Entrepreneurship Education and Venture Creation

As support for both university-level entrepreneurial education and the use of experiential learning methods to foster student entrepreneurs increases, so too have the number of university-established or affiliated entrepreneurship centers. The activity at the center of this study aimed to combine experiential learning methods with assets associated with entrepreneurship centers, including venture creation, networking, and mentoring. Students were invited to participate in a competition wherein they were guided through the business creation process and pitched their ideas to investor judges who chose the winner and provided capital start-up funding and consulting. This research puts forth that university faculty at institutions without entrepreneurship centers can organize experiences to provide the benefits of entrepreneurship centers. The study used interviews to find that many of the benefits of entrepreneurship centers were able to be replicated using this method. The project is outlined, outcomes are analyzed, and the results and lessons learned are discussed

Terrestrial exposure of a fresh Martian meteorite causes rapid changes in hydrogen isotopes and water concentrations

Determining the hydrogen isotopic compositions and H2O contents of meteorites and their components is important for addressing key cosmochemical questions about the abundance and source(s) of water in planetary bodies. However, deconvolving the effects of terrestrial contamination from the indigenous hydrogen isotopic compositions of these extraterrestrial materials is not trivial, because chondrites and some achondrites show only small deviations from terrestrial values such that even minor contamination can mask the indigenous values. Here we assess the effects of terrestrial weathering and contamination on the hydrogen isotope ratios and H2O contents of meteoritic minerals through monitored terrestrial weathering of Tissint, a recent Martian fall. Our findings reveal the rapidity with which this weathering affects nominally anhydrous phases in extraterrestrial materials, which illustrates the necessity of sampling the interiors of even relatively fresh meteorite falls and underlines the importance of sample return missions

Effect of implementing a heart failure admission care bundle on hospital readmission and mortality rates: interrupted time series study

This study aimed to evaluate the impact of developing and implementing a care bundle intervention to improve care for patients with acute heart failure admitted to a large London hospital. The intervention comprised three elements, targeted within 24 hours of admission: N-terminal pro-B-type natriuretic peptide (NT-proBNP) test, transthoracic Doppler two-dimensional echocardiography and specialist review by cardiology team. The SHIFT-Evidence approach to quality improvement was used. During implementation, July 2015–July 2017, 1169 patients received the intervention. An interrupted time series design was used to evaluate impact on patient outcomes, including 15 618 admissions for 8951 patients. Mixed-effects multiple Poisson and log-linear regression models were fitted for count and continuous outcomes, respectively. Effect sizes are slope change ratios pre-intervention and post-intervention. The intervention was associated with reductions in emergency readmissions between 7 and 90 days (0.98, 95% CI 0.97 to 1.00), although not readmissions between 0 and 7 days post-discharge. Improvements were seen in in-hospital mortality (0.96, 95% CI 0.95 to 0.98), and there was no change in trend for hospital length of stay. Care process changes were also evaluated. Compliance with NT-proBNP testing was already high in 2014/2015 (162 of 163, 99.4%) and decreased slightly, with increased numbers audited, to 2016/2017 (1082 of 1101, 98.2%). Over this period, rates of echocardiography (84.7–98.9%) and specialist input (51.6–90.4%) improved. Care quality and outcomes can be improved for patients with acute heart failure using a care bundle approach. A systematic approach to quality improvement, and robust evaluation design, can be beneficial in supporting successful improvement and learning

A comparison of the seasonal movements of tiger sharks and green turtles provides insight into their predator-prey relationship

During the reproductive season, sea turtles use a restricted area in the vicinity of their nesting beaches, making them vulnerable to predation. At Raine Island (Australia), the highest density green turtle Chelonia mydas rookery in the world, tiger sharks Galeocerdo cuvier have been observed to feed on green turtles, and it has been suggested that they may specialise on such air-breathing prey. However there is little information with which to examine this hypothesis. We compared the spatial and temporal components of movement behaviour of these two potentially interacting species in order to provide insight into the predator-prey relationship. Specifically, we tested the hypothesis that tiger shark movements are more concentrated at Raine Island during the green turtle nesting season than outside the turtle nesting season when turtles are not concentrated at Raine Island. Turtles showed area-restricted search behaviour around Raine Island for ~3–4 months during the nesting period (November–February). This was followed by direct movement (transit) to putative foraging grounds mostly in the Torres Straight where they switched to area-restricted search mode again, and remained resident for the remainder of the deployment (53–304 days). In contrast, tiger sharks displayed high spatial and temporal variation in movement behaviour which was not closely linked to the movement behaviour of green turtles or recognised turtle foraging grounds. On average, tiger sharks were concentrated around Raine Island throughout the year. While information on diet is required to determine whether tiger sharks are turtle specialists our results support the hypothesis that they target this predictable and plentiful prey during turtle nesting season, but they might not focus on this less predictable food source outside the nesting season