1,683 research outputs found
Changes in left atrial deformation in hypertrophic cardiomyopathy: Evaluation by vector velocity imaging.
OBJECTIVES: Hypertrophic cardiomyopathy (HCM) represents a generalized myopathic process affecting both ventricular and atrial myocardium. We assessed the global and regional left atrial (LA) function and its relation to left ventricular (LV) mechanics and clinical status in patients with HCM using Vector Velocity Imaging (VVI). METHODS: VVI of the LA and LV was acquired from apical four- and two-chamber views of 108 HCM patients (age 40 ± 19years, 56.5% men) and 33 healthy subjects, all had normal LV systolic function. The LA subendocardium was traced to obtain atrial volumes, ejection fraction, velocities, and strain (ϵ)/strain rate (SR) measurements. RESULTS: Left atrial reservoir (ϵsys,SRsys) and conduit (early diastolic SRe) function were significantly reduced in HCM compared to controls (P - 1.8s(- 1) was 81% sensitive and 30% specific, SRa> - 1.5s(- 1) was 73% sensitive and 40% specific. By multivariate analysis global LVϵsys and LV septal thickness are independent predictors for LAϵsys, while end systolic diameter is the only independent predictor for SRsys, P < .001. CONCLUSION: Left atrial reservoir and conduit function as measured by VVI were significantly impaired while contractile function was preserved among HCM patients. Left atrial deformation was greatly influenced by LV mechanics and correlated to severity of phenotype
Remote Sensing Satellites Planning System
A Remote Sensing Satellites Planning system (RSSP) for satellite constellations is responsible for managing these satellites by assigning the imaging tasks to each satellite in the constellation such that the loads are balanced and the resources are well used. The proposed system can be used with heterogeneous constellations that consist of satellites whose different specifications, different orbits' types and/or different payload types. This problem is a combinatorial optimization NP-hard problem modeled in this paper as a Constraint Satisfaction Problem using the Constraint Programming Technique. The output plan is obtained using one of three objective functions (gain maximization, area maximization, and image quality maximization) using four search algorithms (simulated annealing, hill climbing, tabu search and late acceptance) and different planning horizons (one track, one day and one month)
Numerical Experimental Investigation of Solidification Thickness around Cylindrical Surfaces for HVAC Cold Storage Systems
Thermal Ice Storage System (TISS) is an innovative way of storing night-time off-peak energy for daytime peak USAge. In many locations, demand for electrical power peaks during summer time. Air-conditioning equipment are the main reason accounting for as much as half of the power demand during the hot mid-day hours when electricity is most expensive. Since utilities have spare electrical generating capacity at night, electricity generated during this ldquo;off-peakrdquo; is much less expensive. In this research a numerical model for Latent Heat Storage (LHS) cylindrical tank has been obtained from a numerical package, ANSYS software ver. 15, and compared to an experimental data gathered from similar tank. The data showed good agreement with the experimental data with an error of 9%. The numerical model can be used to estimate ice thickness and tank geometries for any future work
Frequency-dependent magnetotransport and particle dynamics in magnetic modulation systems
We analyze the dynamics of a charged particle moving in the presence of
spatially-modulated magnetic fields. From Poincare surfaces of section and
Liapunov exponents for characteristic trajectories we find that the fraction of
pinned and runaway quasiperiodic orbits {\em vs}. chaotic orbits depends
strongly on the ratio of cyclotron radius to the structure parameters, as well
as on the amplitude of the modulated field. We present a complete
characterization of the dynamical behavior of such structures, and investigate
the contribution to the magnetoconductivity from all different orbits using a
classical Kubo formula. Although the DC conductivity of the system depends
strongly on the pinned and runaway trajectories, the frequency response
reflects the topology of all different orbits, and even their unusual temporal
behavior.Comment: Submitted to PRB - 14 figure files - REVTEX tex
Strategic Communication and Public Engagement: The UAE E-Brainstorming Session
In the context of the conference’s topic of ‘Strategic Communication and Public Engagement’ comes this case study, which illustrates the creative use of social media in crowdsourcing ideas from the public with the goal of formulating government policy in the United Arab Emirates (UAE). Unlike the usual model of top-down policy formulation in many developing countries, the UAE government adopted an experiment entitled ‘The UAE Brainstorming Session’, which is the country’s first technology-based citizen engagement event that leveraged the highly popular social media platforms to elicit ideas and suggestions about public services. Specifically, two under-performing national sectors were targeted; public health and education. Citizens and residents were invited to identify the main issues in these two sectors and offer their suggestions to address them. The UAE Prime Minister personally tweeted inviting everyone to participate. The public response to this initiative was substantial, with 82,000 new ideas delivered by several social media channels. A ministerial committee then shortlisted the best ideas, suggestions, and these were subsequently discussed in a strategic cabinet retreat. The next step was government approval of several initiatives, which were subsequently implemented. Lessons learned from this case study can be beneficial to many countries that are considering similar technology-based initiatives that utilize popular and accessible social media as public policy tools and instruments of citizen engagement. Keywords: Strategic Communication; Citizen Engagement; Social Media; United Arab Emirates Government
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Negative selection and stringency modulation in phage-assisted constinuous evolution
Phage-assisted continuous evolution (PACE) uses a modified filamentous bacteriophage life cycle to dramatically accelerate laboratory evolution experiments. In this work we expand the scope and capabilities of the PACE method with two key advances that enable the evolution of biomolecules with radically altered or highly specific new activities. First, we implemented small molecule-controlled modulation of selection stringency that enables otherwise inaccessible activities to be evolved directly from inactive starting libraries through a period of evolutionary drift. Second, we developed a general negative selection that enables continuous counter-selection against undesired activities. We integrated these developments to continuously evolve mutant T7 RNA polymerase enzymes with ∼10,000-fold altered, rather than merely broadened, substrate specificities during a single three-day PACE experiment. The evolved enzymes exhibit specificity for their target substrate that exceeds that of wild-type RNA polymerases for their cognate substrates, while maintaining wild-type-like levels of activity
Bipolar- Radon Transform
This paper presents the bipolar- Radon transform (BRT)that map a function into its integrals over two types of circles. By using the bipolar coordinates, this transform reduces to the normal Radon transform Radon transform(RT). (BRT)can be applied for tomography .A direct example and the inversion are presented
Z-Scan Measurement For The Thermo-Optic Coefficient and Transmitted Beam Profile Of 1.8-Dihydroxy-Naphthalin-3, 6 Disulfonic Acid-[2-(4-azo)]-N-(5-Methyl-3-Isoxazolyl)-Benzene Sulfonamide
The nonlinear optical properties of an azo dye (1.8-Dihydroxy-naphthalin-3, 6 disulfonic acid- [2- (4-azo)]-N-(5-methyl-3-isoxazolyl)-benzene sulfonamide) are studied by using z-scan and diffraction ring technique with continuous wave (cw) laser at a wavelength of 532 nm. The obtained results for the nonlinear refractive index , , and the thermo-optic coefficients , , are found to be of the order of Wcm-2 and K-1 respectively. The transmitted beam profiles, the distribution of intensity corresponding to the sample positions and D- distribution of rings number of each pattern variation for the azo dye samples have been studied. These results indicate that the azo dye is a promising candidate for applications in nonlinear optical devices. Keywords: Nonlinear refractive index, Thermo-optic coefficients, Diffraction ring.
Investigating the association between obesity and asthma in 6- to 8-year-old Saudi children:a matched case-control study
Background: Previous studies have demonstrated an association between obesity and asthma, but there remains considerable uncertainty about whether this reflects an underlying causal relationship. Aims: To investigate the association between obesity and asthma in pre-pubertal children and to investigate the roles of airway obstruction and atopy as possible causal mechanisms. Methods: We conducted an age- and sex-matched case–control study of 1,264 6- to 8-year-old schoolchildren with and without asthma recruited from 37 randomly selected schools in Madinah, Saudi Arabia. The body mass index (BMI), waist circumference and skin fold thickness of the 632 children with asthma were compared with those of the 632 control children without asthma. Associations between obesity and asthma, adjusted for other potential risk factors, were assessed separately in boys and girls using conditional logistic regression analysis. The possible mediating roles of atopy and airway obstruction were studied by investigating the impact of incorporating data on sensitisation to common aeroallergens and measurements of lung function. Results: BMI was associated with asthma in boys (odds ratio (OR)=1.14, 95% confidence interval (CI), 1.08–1.20; adjusted OR=1.11, 95% CI, 1.03–1.19) and girls (OR=1.37, 95% CI, 1.26–1.50; adjusted OR=1.38, 95% CI, 1.23–1.56). Adjusting for forced expiratory volume in 1 s had a negligible impact on these associations, but these were attenuated following adjustment for allergic sensitisation, particularly in girls (girls: OR=1.25; 95% CI, 0.96–1.60; boys: OR=1.09, 95% CI, 0.99–1.19). Conclusions: BMI is associated with asthma in pre-pubertal Saudi boys and girls; this effect does not appear to be mediated through respiratory obstruction, but in girls this may at least partially be mediated through increased risk of allergic sensitisation
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