381 research outputs found
Self-Describing Fiducials for GPS-Denied Navigation of Unmanned Aerial Vehicles
Accurate estimation of an Unmanned Aerial Vehicleâs (UAVâs) location is critical for the operation of the UAV when it is controlled completely by its onboard processor. This can be particularly challenging in environments in which GPS is not available (GPS-denied). Many of the options previously explored for estimation of a UAVâs location without the use of GPS require more sophisticated processors than can feasibly be mounted on a UAV because of weight, size, and power restrictions. Many options are also aimed at indoor operation without the range capabilities to scale to outdoor operations. This research explores an alternative method of GPS-denied navigation which utilizes line-of-sight measurements to self-describing fiducials to aid in position determination. Each self-describing fiducial is an easily identifiable object fixed at a specific location. Each fiducial relays data containing its specific location to the observing UAV. The UAV can measure its relative position to the fiducial using camera images. This measurement can be combined with measurements from an Inertial Measurement Unit (IMU) to obtain a more accurate estimate of the UAVâs location. In this research, a simulation is used to validate and assess the performance of algorithms used to estimate the UAVâs position using these measurements. This research analyzes the effectiveness of the estimation algorithm when used with various IMUs and fiducial spacings. The effect of how quickly camera images of fiducials can be captured and processed is also analyzed. Preparations for demonstrating this system with hardware are then presented and discussed, including options for fiducial type and a way to measure the true position of the UAV. The results from the simulated scenarios and the hardware demonstration preparation are analyzed, and future work is discussed
Casino Drink Policies: Limiting Third-Party Liability
In their efforts to provide an atmosphere or hospitality to their casino customers, many operators will provide complimentary alcoholic beverage service. This practice is fraught with liability, particularly in venues outside of Nevada. Conscientious operators must take every precaution to mitigate the possibility of lawsuit
The Selah Study Skills Program A Total Approach to Aid Students with Learning Disabilities
This paper attempts to communicate the following five aspects of the Selah Study Skills program: (1) why and how the program was started, (2) identification, testing, and diagnosis of the disabled learner, (3) educational therapy used, (4) supportive educational therapy used, and (5) evaluation and prognosis of the Study Skills program
At close quarters: combatting Facebook design, features and temporalities in social research
As researchers we often find ourselves grappling with social media platforms and data âat close quartersâ. Although social media platforms were created for purposes other than academic research â which are apparent in their architecture and temporalities â they offer opportunities for researchers to repurpose them for the collection, generation and analysis of rich datasets. At the same time, this repurposing raises an evolving range of practical and methodological challenges at the small and large scale. We draw on our experiences and empirical data from two research projects, one using Facebook Community Pages and the other repurposing Facebook Activity Logs. This article reflects critically on the specific challenges we faced using these platform features, on their common roots, and the tactics we adopted in response. De Certeauâs distinction between strategy and tactics provides a useful framework for exploring these struggles as located in the practice of doing social research â which often ends up being tactical. This article argues that we have to collectively discuss, demystify and devise tactics to mitigate the strategies and temporalities deeply embedded in platforms, corresponding as far as possible to the temporalities and the aims of our research. Although combat at close quarters is inevitable in social media research, dialogue between researchers is more than ever needed to tip the scales in our favour
N-d scattering above the deuteron breakup threshold
The complex Kohn variational principle and the (correlated) Hyperspherical
Harmonics technique are applied to study the N--d scattering above the deuteron
breakup threshold. The configuration with three outgoing nucleons is explicitly
taken into account by solving a set of differential equations with outgoing
boundary conditions. A convenient procedure is used to obtain the correct
boundary conditions at values of the hyperradius fm. The
inclusion of the Coulomb potential is straightforward and does not give
additional difficulties. Numerical results have been obtained for a simple
s-wave central potential. They are in nice agreement with the benchmarks
produced by different groups using the Faddeev technique. Comparisons are also
done with experimental elastic N--d cross section at several energies.Comment: LaTeX, 13 pages, 3 figure
Lower gastrointestinal bleedingâComputed Tomographic Angiography, Colonoscopy or both?
Effects of the magnetic moment interaction between nucleons on observables in the 3N continuum
The influence of the magnetic moment interaction of nucleons on
nucleon-deuteron elastic scattering and breakup cross sections and on elastic
scattering polarization observables has been studied. Among the numerous
elastic scattering observables only the vector analyzing powers were found to
show a significant effect, and of opposite sign for the proton-deuteron and
neutron-deuteron systems. This finding results in an even larger discrepancy
than the one previously established between neutron-deuteron data and
theoretical calculations. For the breakup reaction the largest effect was found
for the final-state-interaction cross sections. The consequences of this
observation on previous determinations of the ^1S_0 scattering lengths from
breakup data are discussed.Comment: 24 pages, 6 ps figures, 1 png figur
Reduced inflammatory response in cigarette smoke exposed Mrp1/Mdr1a/1b deficient mice
<p>Abstract</p> <p>Background</p> <p>Tobacco smoke is the principal risk factor for chronic obstructive pulmonary disease (COPD), though the mechanisms of its toxicity are still unclear. The ABC transporters multidrug resistance-associated protein 1 (MRP1) and P-glycoprotein (P-gp/MDR1) extrude a wide variety of toxic substances across cellular membranes and are highly expressed in bronchial epithelium. Their impaired function may contribute to COPD development by diminished detoxification of noxious compounds in cigarette smoke.</p> <p>Methods</p> <p>We examined whether triple knock-out (TKO) mice lacking the genes for <it>Mrp1 </it>and <it>Mdr1a/1b </it>are more susceptible to develop COPD features than their wild-type (WT) littermates. TKO and WT mice (six per group) were exposed to 2 cigarettes twice daily by nose-only exposure or room air for 6 months. Inflammatory infiltrates were analyzed in lung sections, cytokines and chemokines in whole lung homogenates, emphysema by mean linear intercept. Multiple linear regression analysis with an interaction term was used to establish the statistical significances of differences.</p> <p>Results</p> <p>TKO mice had lower levels of interleukin (IL)-7, KC (mouse IL-8), IL-12p70, IL-17, TNF-alpha, G-CSF, GM-CSF and MIP-1-alpha than WT mice independent of smoke exposure (<it>P </it>< 0.05). IL-1-alpha, IL-6, IL-8, IL-13, IL-17, TNF-alpha, G-CSF, GM-CSF and MCP-1 increased after smoke exposure in both groups, but the increase in IL-8 was lower in TKO than WT mice (<it>P </it>< 0.05) with a same trend for G-CSF (<it>P </it>< 0.10). Smoke-induced increase in pulmonary inflammatory cells in WT mice was almost absent in TKO mice. The mean linear intercept was not different between groups.</p> <p>Conclusion</p> <p><it>Mrp1/Mdr1a/1b </it>knock-out mice have a reduced inflammatory response to cigarette smoke. In addition, the expression levels of several cytokines and chemokines were also lower in lungs of <it>Mrp1/Mdr1a/1b </it>knock-out mice independent of smoke exposure. Further studies are required to determine whether dysfunction of MRP1 and/or P-gp contribute to the pathogenesis of COPD.</p
A Prospective Study of Aspirin Use and the Risk of Gastrointestinal Bleeding in Men
Data regarding the influence of dose and duration of aspirin use on risk of gastrointestinal bleeding are conflicting.We conducted a prospective cohort study of 32,989 men enrolled in the Health Professionals Follow-up Study (HPFS) in 1994 who provided biennial aspirin data. We estimated relative risk of major gastrointestinal bleeding requiring hospitalization or a blood transfusion.During 14 years of follow-up, 707 men reported an episode of major gastrointestinal bleeding over 377,231 person-years. After adjusting for risk factors, regular aspirin use (â„2 times/week) had a multivariate relative risk (RR) of gastrointestinal bleeding of 1.32 (95% confidence interval [CI], 1.12-1.55) compared to non-regular use. The association was particularly evident for upper gastrointestinal bleeding (multivariate RR, 1.49; 95% CI, 1.16-1.92). Compared to men who denied any aspirin use, multivariate RRs of upper gastrointestinal bleeding were 1.05 (95% CI 0.71-1.52) for men who used 0.5-1.5 standard tablets/week, 1.31 (95% CI 0.88-1.95) for 2-5 aspirin/week, 1.63 (95% CI, 1.15-2.32) for 6-14 aspirin/week and 2.40 (95% CI, 1.10-5.22) for >14 aspirin/week (P(trend)<0.001). The relative risk also appeared to be dose-dependent among short-term users <5 years; P(trend)<.001) and long-term users (â„5 years; P(trend)â=â0.015). In contrast, after controlling for dose, increasing duration of use did not appear to be associated with risk (P(trend)â=â0.749).Regular aspirin use increases the risk of gastrointestinal bleeding, especially from the upper tract. However, risk of bleeding appears to be more strongly related to dose than to duration of use. Risk of bleeding should be minimized by using the lowest effective dose among short-term and long-term aspirin users
The three- and four-nucleon systems from chiral effective field theory
Recently developed chiral nucleon-nucleon (NN) forces at next-to-leading
order (NLO) that describe NN phase shifts up to about 100 MeV fairly well have
been applied to 3N and 4N systems. Faddeev-Yakubovsky equations have been
solved rigorously. The chiral NLO forces depend on a momentum cut-off \Lambda
lying between 540-600 MeV/c. The resulting 3N and 4N binding energies are in
the same range as found using standard NN potentials. In additon, low-energy 3N
scattering observables are very well reproduced like for standard NN forces.
Surprisingly, the long standing A_y-puzzle is resolved at NLO. The cut-off
dependence of the scattering observables is rather mild.Comment: 4 pp, revtex, 3 figure
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