A vortex-based subgrid stress model for large-eddy simulation

A class of subgrid stress (SGS) models for large-eddy simulation (LES) is presented based on the idea of structure-based Reynolds-stress closure. The subgrid structure of the turbulence is assumed to consist of stretched vortices whose orientations are determined by the resolved velocity field. An equation which relates the subgrid stress to the structure orientation and the subgrid kinetic energy, together with an assumed Kolmogorov energy spectrum for the subgrid vortices, gives a closed coupling of the SGS model dynamics to the filtered Navier-Stokes equations for the resolved flow quantities. The subgrid energy is calculated directly by use of a local balance between the total dissipation and the sum of the resolved-scale dissipation and production by the resolved scales. Simple one- and two-vortex models are proposed and tested in which the subgrid vortex orientations are either fixed by the local resolved velocity gradients, or rotate in response to the evolution of the gradient field. These models are not of the eddy viscosity type. LES calculations with the present models are described for 32^(3) decaying turbulence and also for forced 32^(3) box turbulence at Taylor Reynolds numbers R-lambda in the range R(lambda)similar or equal to 30 (fully resolved) to R-lambda=infinity. The models give good agreement with experiment for decaying turbulence and produce negligible SGS dissipation for forced turbulence in the limit of fully resolved flow

Sturdier DNA nanotubes via ligation

DNA nanotubes are crystalline self-assemblies of DNA tiles ~10 nm in diameter that readily grow tens of micrometers in length. Easy assembly, programmability, and stiffness make them interesting for many applications, but DNA nanotubes begin to melt at temperatures below 40 °C, break open when deposited on mica or scanned by AFM, and disintegrate in deionized water. These weaknesses can be traced to the presence of discontinuities in the phosphate backbone, called nicks. The nanotubes studied here have five nicks, one in the core of a tile and one at each corner. We report the successful ligation of all four corner nicks by T4 DNA ligase. Although ligation does not change the nanotubes’ stiffness, ligated nanotubes withstand temperatures over 70 °C, resist breaking during AFM, and are stable in pure water for over a month. Ligated DNA nanotubes are thus physically and chemically sturdy enough to withstand the manipulations necessary for many technological applications

Modeling the risk factors associated with the neck disorders during manual material handling tasks

Work-related musculoskeletal disorders (MSD) of the neck or cervical spine result in longer sick leaves, substantial levels of human suffering, and high costs for society. Epidemiological studies clearly indicate strong associations between MSD of the neck and the work activities requiring forceful arm exertions and heavy lifting. However, studies evaluating the loading of the cervical spine during forceful arm exertions and heavy lifting tasks are limited. Major neck muscles, the sternocleidomastoid and the upper trapezius, run parallel to the cervical spine and couple the shoulder to the skull. It was hypothesized that such anatomical orientation may require these muscles to play an active role in supporting the shoulder during lifting activities and thus affecting the compressive forces acting on the cervical spine. The loading of the cervical spine during a variety of manual material handling tasks was studied using electromyography (EMG) and biomechanical modeling techniques. In the EMG study, thirty healthy participants simulated isometric lifting, pushing, and pulling tasks at different heights (e.g., knuckle, elbow, shoulder, and overhead) exerting 25%, 50%, and 75% of their respective maximum static strengths in different neck postures (e.g., neutral, fully flexed, and fully extended neck postures). An increase in the weight significantly affected the activation of neck muscles (P\u3c0.001). Independent of the weight lifted, the sternocleidomastoid showed the highest activation at the extended neck posture, while the upper trapezius showed the highest activation at the flexed neck posture (P\u3c0.001). The activities of the neck muscles increased significantly with an increase in lifting height from elbow to shoulder to overhead (P\u3c0.001). A biomechanical model of the neck consisting of four bilateral pairs of muscles was formulated and a double optimization procedure was used to determine the forces generated by the neck muscles. The total compressive forces exerted by the four neck muscles at the C4-C5 level during isometric lifting task at elbow height were 72.6(19.4), 128.5(37.7), and 184.4(56.1) N, corresponding to the 25%, 50%, and 75% weight conditions. The results of this study demonstrate that the neck muscles play an active role during lifting activities and may influence MSD development due to resulting physiological changes

BRIGE: Translating Robotic Technology for Inclusive Fitness: An Innovative Robotic Rowing Exoskeleton (RRE) Development Project

Intellectual Merit: The opportunities for inclusion in fitness activity for disabled individuals, particularly those with severe disabilities, are extremely limited due to intrinsic, environmental, and social factors. This BRIGE project focuses on advancing robotic technology as a strategy to promote fitness opportunities for a range of individuals with disabilities. This project will 1) design, test, and build a prototype robotic device called Robotic Rowing Exoskeleton (RRE) that will augment movement, coordination, and strength in the activity of rowing; 2) yield a complete dynamics model of rowing biomechanics and parameter determination via human subject data; 3) provide a model system through which biomechanics and parameter determination using human subject data can be translated into precise robotic-assisted movement; 4) integrate electromyography and robotics to create a prototype that will be responsive to individual user needs; and 5) advance the development of an ongoing research program in robotic devices for improved quality of life. Broader Impacts: This project will be used as the foundation for the CIDER (Creating Investigator Diversity in Engineering Research) model with five major components. First, diverse students for whom the research agenda is personally relevant and compelling will be recruited to participate in all phases of the program. Second, each of the student researchers will engage in outreach in schools and a summer camp program for middle and high school students to perpetuate ongoing recruitment of diverse students into engineering research careers. Third, a video of RRE, its development, and its use will be made for on-site and virtual dissemination nationwide. Fourth, we will continue an ongoing program which hosts robotics demos for middle school and high school students, especially, women, to encourage them to pursue a career in Engineering. Finally, the model will be formalized and evaluated so that it can be expanded to encourage the involvement of other underrepresented groups in engineering

Friction of a slider on a granular layer: Non-monotonic thickness dependence and effect of boundary conditions

We investigate the effective friction encountered by a mass sliding on a granular layer as a function of bed thickness and boundary roughness conditions. The observed friction has minima for a small number of layers before it increases and saturates to a value which depends on the roughness of the sliding surface. We use an index-matched interstitial liquid to probe the internal motion of the grains with fluorescence imaging in a regime where the liquid has no significant effect on the measured friction. The shear profiles obtained as a function of depth show decrease in slip near the sliding surface as the layer thickness is increased. We propose that the friction depends on the degree of grain confinement relative to the sliding surfaces.Comment: 4 pages, 6 figure

Gauge transformation through an accelerated frame of reference

The Schr\"{o}dinger equation of a charged particle in a uniform electric field can be specified in either a time-independent or a time-dependent gauge. The wave-function solutions in these two gauges are related by a phase-factor reflecting the gauge symmetry of the problem. In this article we show that the effect of such a gauge transformation connecting the two wave-functions can be mimicked by the effect of two successive extended Galilean transformations connecting the two wave-function. An extended Galilean transformation connects two reference frames out of which one is accelerating with respect to the other.Comment: 7 Pages, Latex fil

THE INFLUENCE OF PYELONEPHRITIS COMPLICATIONS ON COURSE OF PREGNANCY AND LABOR

Pyelonephritis - nonspecific, infectious-inflammatory process with primary and primary lesion interstitial tissue walls and renal tubules, with subsequent involvement of glomerular and vascular system. Different pathological conditions, which provoked acute stage of chronical pyelonephritis among pregnant women has been analized. Among: anomalies of kidney development, glomerulonephritis, hypertonic disease, preeclampsia and oth. According retrospective investigation of case history of women of postpartum period which have complicated pyelonephritis of Chernivtsi region has been received such characteristics: general amount of cases of nephrological complicated diseases during 2010-2013 consists 87; ratio of these diseases consists: pyelonephritis - 78,16%, glomerulonephritis - 9,1% and oth. - 12,74%. Most part of all background conditions, which contributes development of acute stage of chronical pyelonephritis compound anomalies of kidney development (51%), among them the most - single left kidney (34%). Different groups of exciters of chronical pyelonephritis during pregnancy has been analized: Ar. Piogenes, Streptococcus spp., E. coli, Candida albicans, St. aureus, Enterobacter aerogenus, S. Haemolyticus, S. epidermidis. Negative results of bacteriological examination of urine after finishing course of antibioticotherapy has been founded efficacy of antibioticotherapy in pregnant women with complicated pyelonephritis. The disappearance or significant reduction in the severity of the clinical manifestations of the disease: negative Pasternatsky symptom, disappearance of pain in the lumbar region, the normalization of body temperature and reduce the intensity of other general clinical symptoms.Кафедра акушерства та гінекологі