A Fixed-Complexity MIMO Detector Based on the Complex Sphere Decoder

A new detection algorithm for uncoded multiple input-multiple output (MIMO) systems based on the complex version of the sphere decoder (SD) is presented in this paper. The algorithm performs a fixed number of operations to detect the symbols, independent of the noise level. The algorithm achieves this by combining a novel channel matrix preprocessing with a search through a small subset of the complete receive constellation. Simulation results show it has only a very small bit error ratio (BER) degradation compared to the original SD while being suited for a fully-pipelined hardware implementation due to its fixed complexity. 1

Intense Electromagnetic Outbursts from Collapsing Hypermassive Neutron Stars

We study the gravitational collapse of a magnetized neutron star using a novel numerical approach able to capture both the dynamics of the star and the behavior of the surrounding plasma. In this approach, a fully general relativistic magnetohydrodynamics implementation models the collapse of the star and provides appropriate boundary conditions to a force-free model which describes the stellar exterior. We validate this strategy by comparing with known results for the rotating monopole and aligned rotator solutions and then apply it to study both rotating and non-rotating stellar collapse scenarios, and contrast the behavior with what is obtained when employing the electrovacuum approximation outside the star. The non-rotating electrovacuum collapse is shown to agree qualitatively with a Newtonian model of the electromagnetic field outside a collapsing star. We illustrate and discuss a fundamental difference between the force-free and electrovacuum solutions, involving the appearance of large zones of electric-dominated field in the vacuum case. This provides a clear demonstration of how dissipative singularities appear generically in the non-linear time-evolution of force-free fluids. In both the rotating and non-rotating cases, our simulations indicate that the collapse induces a strong electromagnetic transient. In the case of sub-millisecond rotation, the magnetic field experiences strong winding and the transient carries much more energy. This result has important implications for models of gamma-ray bursts.Comment: 28 pages, 20 figures (quality lowered to reduce sizes). Improved initial data and matching condition results in a lower, but still important, energy emission. Added appendix with a discussion on effects of transition laye

Factors that contribute to balance and mobility impairments in individuals with Huntington's disease

AbstractMobility and balance problems are common and often debilitating features of Huntington's disease (HD). In this exploratory study we aimed to investigate the influence of disease severity, severity of motor deficits, lower limb muscle strength, cognition, executive function, lean muscle mass and reactivity on mobility and balance.Twenty-two individuals with HD were recruited from the North Metropolitan Area Mental Health Service, Perth, Australia. Pertinent demographic, genetic and disease progression information was recorded prior to testing. Balance was assessed using dynamic and static balance tasks. Mobility was assessed using self-paced and fast-paced mobility measures. Cognitive and executive measures were used to assess verbal learning and memory, information processing speed, attention, response inhibition and cognitive flexibility. Lower limb muscle strength was evaluated by maximal isokinetic and isometric voluntary contractions. Lean tissue mass was quantified using Dual-energy X-ray absorptiometry. Reactivity was measured using Moyart equipment.Univariate and multivariate linear regression statistical models were used to examine the influence of these measures on mobility and balance. Univariate analyses showed that disease severity as well as measures of information processing speed, attention, cognitive flexibility, response inhibition and lower limb strength, were strongly related with mobility and balance. Additionally multivariate analyses showed that disease severity, cognitive flexibility and knee flexion strength together were better able to explain mobility and balance performance than any single measure (50–85%).In conclusion, our preliminary results suggest that as well as disease severity, cognitive and executive impairment and reduced lower limb strength contribute significantly to mobility and balance problems

Factors that contribute to balance and mobility impairments in individuals with Huntington\u27s disease

Mobility and balance problems are common and often debilitating features of Huntington\u27s disease (HD). In this exploratory study we aimed to investigate the influence of disease severity, severity of motor deficits, lower limb muscle strength, cognition, executive function, lean muscle mass and reactivity on mobility and balance.Twenty-two individuals with HD were recruited from the North Metropolitan Area Mental Health Service, Perth, Australia. Pertinent demographic, genetic and disease progression information was recorded prior to testing. Balance was assessed using dynamic and static balance tasks. Mobility was assessed using self-paced and fast-paced mobility measures. Cognitive and executive measures were used to assess verbal learning and memory, information processing speed, attention, response inhibition and cognitive flexibility. Lower limb muscle strength was evaluated by maximal isokinetic and isometric voluntary contractions. Lean tissue mass was quantified using Dual-energy X-ray absorptiometry. Reactivity was measured using Moyart equipment.Univariate and multivariate linear regression statistical models were used to examine the influence of these measures on mobility and balance. Univariate analyses showed that disease severity as well as measures of information processing speed, attention, cognitive flexibility, response inhibition and lower limb strength, were strongly related with mobility and balance. Additionally multivariate analyses showed that disease severity, cognitive flexibility and knee flexion strength together were better able to explain mobility and balance performance than any single measure (50-85%).In conclusion, our preliminary results suggest that as well as disease severity, cognitive and executive impairment and reduced lower limb strength contribute significantly to mobility and balance problems

Method for obtaining the wheel-rail contact location and its application to the normal problem calculation through CONTACT

[EN] This work presents a robust methodology for calculating inter-penetration areas between railway wheel and rail surfaces, the profiles of which are defined by a series of points. The method allows general three-dimensional displacements of the wheelset to be considered, and its characteristics make it especially suitable for dynamic simulations where the wheel-rail contact is assumed to be flexible. The technique is based on the discretization of the geometries of the surfaces in contact, considering the wheel as a set of truncated cones and the rail as points. By means of this approach, it is possible to reduce the problem to the calculation of the intersections between cones and lines, the solution for which has a closed-form expression. The method has been used in conjunction with the CONTACT algorithm in order to solve the static normal contact problem when the lateral displacement of the wheelset, its yaw angle and the vertical force applied in the wheelset centroid are prescribed. The results consist of smooth functions when the dependent coordinates are represented as a function of the independent ones, lacking the jump discontinuities that are present when a rigid contact model is adopted. Example results are shown and assessed for the normal contact problem for different lateral and yaw positions of the wheelset on the track.This work was supported by the financial contribution of the European Union’s Shift2Rail programme (RUN2Rail project, grant number 777564), the Spanish Ministry of Economy, Industry and Competitiveness and the European Regional Development Fund (projects TRA2013-45596-C2-1-R and TRA2017-84701-R).Baeza González, LM.; Thompson, DJ.; Squicciarini, G.; Denia, FD. (2018). Method for obtaining the wheel-rail contact location and its application to the normal problem calculation through CONTACT. Vehicle System Dynamics. 56(11):1734-1746. https://doi.org/10.1080/00423114.2018.1439178S173417465611Garg, V. K., & Dukkipati, R. V. (1984). Wheel–Rail Rolling Contact Theories. Dynamics of Railway Vehicle Systems, 103-134. doi:10.1016/b978-0-12-275950-5.50009-2Wickens, A. H. (1965). The dynamic stability of railway vehicle wheelsets and bogies having profiled wheels. International Journal of Solids and Structures, 1(3), 319-341. doi:10.1016/0020-7683(65)90037-5DE PATER, A. D. (1988). The Geometrical Contact between Track and Wheelset. Vehicle System Dynamics, 17(3), 127-140. doi:10.1080/00423118808968898Yang G. Dynamic analysis of railway wheelsets and complete vehicle systems (PhD thesis). Delft: Delft University of Technology; 1993.Negretti, D. (2012). A third-order approximation method for three-dimensional wheel–rail contact. Vehicle System Dynamics, 50(3), 431-448. doi:10.1080/00423114.2011.595804Shabana AA, Zaazaa KE, Escalona JL, et al. Modeling two-point wheel/rail contacts using constraint and elastic-force approaches. In: Paidoussis MP, editor. ASME 2002 International Mechanical Engineering Congress and Exposition; 2002 Nov 17–22; New Orleans, Louisiana: American Society of Mechanical Engineers, Rail Transportation Division (Publication) RTD, p. 35–50.Netter, H., Schupp, G., Rulka, W., & Schroeder, K. (1998). NEW ASPECTS OF CONTACT MODELLING AND VALIDATION WITHIN MULTIBODY SYSTEM SIMULATION OF RAILWAY VEHICLES. Vehicle System Dynamics, 29(sup1), 246-269. doi:10.1080/00423119808969563Pombo, J., Ambrósio, J., & Silva, M. (2007). A new wheel–rail contact model for railway dynamics. Vehicle System Dynamics, 45(2), 165-189. doi:10.1080/00423110600996017Polach, O. (2010). Characteristic parameters of nonlinear wheel/rail contact geometry. Vehicle System Dynamics, 48(sup1), 19-36. doi:10.1080/00423111003668203Santamaría, J., Vadillo, E. G., & Gómez, J. (2006). A comprehensive method for the elastic calculation of the two-point wheel–rail contact. Vehicle System Dynamics, 44(sup1), 240-250. doi:10.1080/00423110600870337Cuperus, J. L., & Venter, G. (2016). Numerical simulation and parameterisation of rail–wheel normal contact. Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit, 231(4), 419-430. doi:10.1177/0954409716631009Chollet, H., Sébès, M., Maupu, J. L., & Ayasse, J. B. (2013). The VOCO multi-body software in the context of real-time simulation. Vehicle System Dynamics, 51(4), 570-580. doi:10.1080/00423114.2013.768771Pascal, J.-P., & Soua, B. (2016). Solving conformal contacts using multi-Hertzian techniques. Vehicle System Dynamics, 54(6), 784-813. doi:10.1080/00423114.2016.1161201Piotrowski, J., & Chollet, H. (2005). Wheel–rail contact models for vehicle system dynamics including multi-point contact. Vehicle System Dynamics, 43(6-7), 455-483. doi:10.1080/00423110500141144Vollebregt EAH, Weidemann C, Kienberger A. Use of “CONTACT” in multi-body vehicle dynamics and profile wear simulation: initial results. in: S. Iwinicki (Ed.) 22nd International Symposium on Dynamics of Vehicles on Roads and Tracks (IAVSD2011), Manchester: Manchester Metropolitan University; 2011.Liu, B., Bruni, S., & Vollebregt, E. (2016). A non-Hertzian method for solving wheel–rail normal contact problem taking into account the effect of yaw. Vehicle System Dynamics, 54(9), 1226-1246. doi:10.1080/00423114.2016.1196823Kalker, J. J. (1990). Three-Dimensional Elastic Bodies in Rolling Contact. Solid Mechanics and Its Applications. doi:10.1007/978-94-015-7889-9Pombo, J., & Ambrosio, J. (2005). A computational efficient general wheel-rail contact detection method. Journal of Mechanical Science and Technology, 19(S1), 411-421. doi:10.1007/bf02916162Kaiser, I., & Popp, K. (2006). Interaction of elastic wheelsets and elastic rails: modelling and simulation. Vehicle System Dynamics, 44(sup1), 932-939. doi:10.1080/00423110600907675Falomi, S., Malvezzi, M., & Meli, E. (2011). Multibody modeling of railway vehicles: Innovative algorithms for the detection of wheel–rail contact points. Wear, 271(1-2), 453-461. doi:10.1016/j.wear.2010.10.039Meli, E., Magheri, S., & Malvezzi, M. (2011). Development and implementation of a differential elastic wheel–rail contact model for multibody applications. Vehicle System Dynamics, 49(6), 969-1001. doi:10.1080/00423114.2010.504854Burgelman N. The wheel–rail contact problem in vehicle dynamic simulation, in: Railahead Group [PhD thesis]. Technische Universiteit Delft; 2016.Ren, Z., Iwnicki, S. D., & Xie, G. (2011). A new method for determining wheel–rail multi-point contact. Vehicle System Dynamics, 49(10), 1533-1551. doi:10.1080/00423114.2010.539237Yang, X., Gu, S., Zhou, S., Zhou, Y., & Lian, S. (2015). A method for improved accuracy in three dimensions for determining wheel/rail contact points. Vehicle System Dynamics, 53(11), 1620-1640. doi:10.1080/00423114.2015.1066508Johnson, K. L. (1985). Contact Mechanics. doi:10.1017/cbo9781139171731European Standards, Railway applications – testing for the acceptance of running characteristics of railway vehicles – testing of running behaviour and stationary tests, in: EN 14363:2005

Relativistic Magnetohydrodynamics: Renormalized eigenvectors and full wave decomposition Riemann solver

We obtain renormalized sets of right and left eigenvectors of the flux vector Jacobians of the relativistic MHD equations, which are regular and span a complete basis in any physical state including degenerate ones. The renormalization procedure relies on the characterization of the degeneracy types in terms of the normal and tangential components of the magnetic field to the wavefront in the fluid rest frame. Proper expressions of the renormalized eigenvectors in conserved variables are obtained through the corresponding matrix transformations. Our work completes previous analysis that present different sets of right eigenvectors for non-degenerate and degenerate states, and can be seen as a relativistic generalization of earlier work performed in classical MHD. Based on the full wave decomposition (FWD) provided by the the renormalized set of eigenvectors in conserved variables, we have also developed a linearized (Roe-type) Riemann solver. Extensive testing against one- and two-dimensional standard numerical problems allows us to conclude that our solver is very robust. When compared with a family of simpler solvers that avoid the knowledge of the full characteristic structure of the equations in the computation of the numerical fluxes, our solver turns out to be less diffusive than HLL and HLLC, and comparable in accuracy to the HLLD solver. The amount of operations needed by the FWD solver makes it less efficient computationally than those of the HLL family in one-dimensional problems. However its relative efficiency increases in multidimensional simulations.Comment: 50 pages, 17 figures (2 in color). Submitted to ApJ Suppl. Se

Family history of breast and ovarian cancer and triple negative subtype in hispanic/latina women.

Familial breast and ovarian cancer prevalence was assessed among 1150 women of Mexican descent enrolled in a case-only, binational breast cancer study. Logistic regression was conducted to compare odds of triple negative breast cancer (TNBC) to non-TNBC according to family history of breast and breast or ovarian cancer among 914 of these women. Prevalence of breast cancer family history in a first- and first- or second-degree relative was 13.1% and 24.1%, respectively; that for breast or ovarian cancer in a first-degree relative was 14.9%. After adjustment for age and country of residence, women with a first-degree relative with breast cancer were more likely to be diagnosed with TNBC than non-TNBC (OR=1.98; 95% CI, 1.26-3.11). The odds of TNBC compared to non-TNBC were 1.93 (95% CI, 1.26-2.97) for women with a first-degree relative with breast or ovarian cancer. There were non-significant stronger associations between family history and TNBC among women diagnosed at age <50 compared to ≥50 years for breast cancer in a first-degree relative (P-interaction = 0.14) and a first- or second-degree relative (P-interaction = 0.07). Findings suggest that familial breast cancers are associated with triple negative subtype, possibly related to BRCA mutations in Hispanic/Latina women, which are strongly associated with TNBC. Family history is an important tool to identify Hispanic/Latina women who may be at increased risk of TNBC, and could benefit from prevention and early detection strategies

Survey of rice storage facilities identifies research and education needs

More than 40 million hundredweights of rice are produced in California's Sacramento Valley every year. After harvest, the rice is stored in facilities on-farm or off-farm until it is transported to mills or to ports for export. We conducted a survey of storage operations to characterize grain storage and pest management practices to guide future UC Cooperative Extension research efforts. The results indicate that grain moisture content, temperature and insect pest management are the most important challenges for both on- and off-farm storage operations. Survey responses show high adoption of integrated pest management programs, with most storage operations relying on monitoring, thresholds, sanitation and aeration to manage pest problems. Fumigant use was reported more frequently in off-farm storage operations than on-farm operations. Cooperative Extension educational efforts should focus on grain and temperature monitoring, insect identification and safe use of fumigants. Research is needed to improve management of grain temperature and moisture content, and insect infestations

Evolución de las encuestas del fitness en España y a nivel mundial: un análisis de los últimos 5 años

Since 2006 the American College of Sport Medicine (ACSM) has annually published the Worldwide Survey of Fitness Trends and through them fitness professionals around the world are asked about their prediction of the most prominent trends in the fitness market for the following year. The results of fitness trends surveys are intended to help this industry make important business decisions for its growth and future development. Spain was the first country in the world to replicate the methodology of ACSM's Worldwide Survey, and now more and more regions are doing the same. There have been five editions of the Spanish survey allowing for the first evolutionary portrayal of fitness trends in this regional market that could be also compared and contrasted to the corresponding results of worldwide surveys. Results of these comparisons highlight differences of relevance and evolution over time of the main fitness trends between Spanish and Worldwide settings. A progressive divergence in both surveys is observed over time. Some of the main similarities and differences of regional and worldwide trends are identified, and their potential causes are discussed. As a conclusion, a comparison of both surveys underlines the interest to replicate at regional levels the ACSM Worldwide Fitness Trends Surveys to get a better understanding that links the knowledge about worldwide trends with specificities found in more specific geographic regions.Desde 2006, el Colegio Americano de Medicina del Deporte (ACSM) publica anualmente la Encuesta mundial de tendencias de fitness y, a través de ella, se pregunta a los profesionales del fitness de todo el mundo sobre su predicción acerca de las tendencias más destacadas en el mercado del fitness para el año siguiente. Los resultados de estas encuestas están destinados a ayudar a la industria del fitness a tomar decisiones comerciales importantes para su crecimiento y desarrollo futuro. España fue el primer país del mundo en replicar la metodología de la Encuesta Mundial de ACSM, y ahora cada vez más países y regiones están haciendo lo mismo. Se han realizado cinco ediciones de la encuesta española, que permiten la primera descripción evolutiva de las tendencias de fitness en este mercado regional, pudiendo también compararse y contrastarse con los resultados correspondientes de las encuestas mundiales. Los resultados de estas comparaciones destacan las diferencias en cuanto a relevancia y evolución en el tiempo de las principales tendencias de fitness entre los entornos español y mundial, observándose una divergencia progresiva en ambas encuestas a lo largo del tiempo. Durante el manuscrito se identifican las principales similitudes y diferencias de las tendencias regionales y mundiales, y se discuten sus posibles causas. Como conclusión, la comparación de ambas encuestas subraya el interés de replicar a nivel regional la Encuesta Mundial de Tendencias de Fitness del ACSM para obtener una mejor comprensión que vincule el conocimiento sobre las tendencias mundiales con las especificidades encontradas en regiones geográficas más específica