286 research outputs found

    Relativistic Magnetohydrodynamics: Renormalized eigenvectors and full wave decomposition Riemann solver

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    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

    Minimally implicit Runge-Kutta methods for Resistive Relativistic MHD

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    The Relativistic Resistive Magnetohydrodynamic (RRMHD) equations are a hyperbolic system of partial differential equations used to describe the dynamics of relativistic magnetized fluids with a finite conductivity. Close to the ideal magnetohydrodynamic regime, the source term proportional to the conductivity becomes potentially stiff and cannot be handled with standard explicit time integration methods. We propose a new class of methods to deal with the stiffness fo the system, which we name Minimally Implicit Runge-Kutta methods. These methods avoid the development of numerical instabilities without increasing the computational costs in comparison with explicit methods, need no iterative extra loop in order to recover the primitive (physical) variables, the analytical inversion of the implicit operator is trivial and the several stages can actually be viewed as stages of explicit Runge-Kutta methods with an effective time-step. We test these methods with two different one-dimensional test beds in varied conductivity regimes, and show that our second-order schemes satisfy the theoretical expectations

    Effectiveness of Virtual Reality on Functional Performance after Spinal Cord Injury: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

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    A spinal cord injury (SCI) usually results in a significant limitation in the functional outcomes, implying a challenge to the performance of activities of daily living. The main aim of this study is to analyze the effectiveness of virtual reality to improve functional performance in patients with SCI. The search was performed between October and December 2019 in Cumulative Index to Nursing and Allied Health Literature (CINAHL), Medline, Cochrane Central Register of Controlled Trials, Physiotherapy Evidence Database (PEDro), PubMed, Scopus, Web of Science, and Embase. The methodological quality of the studies was evaluated through the PEDro scale, and the risk of bias was evaluated with the Cochrane collaboration's tool. Seven articles were included in this systematic review, and five of them in the meta-analysis. Statistical analysis showed favorable results for functional performance in control group performing conventional therapy, measured by the functional independence measure (standardized mean difference (SMD)= -0.70; 95% confidence interval: -1.25 to -0.15). Results were inconclusive for other outcomes. Most studies have not shown beneficial effects on functional performance compared with conventional physical therapy. The results obtained showed that virtual reality may not be more effective than conventional physical therapy in improving functional performance in patients with SCI

    Surface waters of the NW Iberian margin: upwelling on the shelf versus outwelling of upwelled waters from the Rías Baixas

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    A set of hydrographic surveys were carried out in the Ría of Vigo (NW Spain) at 2–4 d intervals during four 2–3 week periods in 1997, covering contrasting seasons. Residual exchange fluxes with the adjacent shelf were estimated with a 2-D, non-steady-state, salinity–temperature weighted box model. Exchange fluxes consist of a steady-state term (dependent on the variability of continental runoff) and a non-steady-state term (dependent on the time changes of density gradients in the embayment). More than 95% of the short-time-scale variability of the exchange fluxes in the middle and outer ría can be explained by the non-steady-state term that, in turns, is correlated (R2>75%) with the offshore Ekman transport. Conversely, 96% of the variability of exchange fluxes in the inner ría rely on the steady-state term. The outer and middle ría are under the direct influence of coastal upwelling, which enhances the positive residual circulation pattern by an order of magnitude: from 10 2 to 10 3 m3s−1. On the contrary, downwelling provokes a reversal of the circulation in the outer ría. The position of the downwelling front along the embayment depends on the relative importance of Ekman transport (Qx, m3s−1km−1) and continental runoff (R, m3s−1). When Qx/ R>7±2 the reversal of the circulation affects the middle ría. Our results are representative for the ‘Rías Baixas’, four large coastal indentations in NW Spain. During the upwelling season (spring and summer), 60% of shelf surface waters off the ‘Rías Baixas’ consist of fresh Eastern North Atlantic Central Water (ENACW) upwelled in situ. The remaining 40% consists of upwelled ENACW that previously enters the rías and it is subsequently outwelled after thermohaline modification. During the downwelling season (autumn and winter), 40% of the warm and salty oceanic subtropic surface water, which piled on the shelf by the predominant southerly winds, enters the rias

    Functional anatomy of the calcaneum and talus in Cercopithecinae (Mammalia, Primates, Cercopithecidae)

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    Among the species of the order Primates exist a huge variety of forms and habitats. This heterogeneity has encouraged the evolution and development of a great number of locomotor adaptations to different environments. Thus, nowadays there are both arboreal and terrestrial groups within the order. The subfamily Cercopithecinae present taxa with both kinds of locomotor behaviours, although the most of them are adapted to a ground life-style. This group probably has an arboreal ancestor and its radiation is relatively recent. Consequently, species belonged to this group present mixed features or sometimes not too much derived ones. Likewise, it is important the fact that the evolutionary history and phylogeny of the group could influence in some characteristics. Both the calcaneum and the talus are two of the largest bones of the foot and are good for inferring the kind of locomotion. For this reason, it has been used these two tarsal bones to study the morphology of eight species of cercopithecines and then deduce functional implications of the kind of locomotion.Dentro del orden Primates existe una gran variedad de especies distribuidas a lo largo de hábitats muy diversos. Dicha Heterogeneidad ha fomentado la evolución y desarrollo de un gran número de adaptaciones locomotoras a los diferentes ambientes en los que habitan. Así, existen en la actualidad tanto grupos arborícolas como terrestres. La subfamilia Cercopithecinae agrupa una serie de taxones que representan ambos comportamientos locomotores, aunque la mayoría de las especies están adaptadas a una vida en el suelo. Se supone que este grupo desciende de un ancestro arborícola y que su radiación es relativamente reciente. En consecuencia, las especies de este grupo presentan características mixtas o poco derivadas en algunas ocasiones. asimismo, es importante tener en cuenta la influencia que la herencia filogenética puede tener sobre alguno de estos rasgos. El calcáneo y el astrágalo son dos de los huesos más grandes del pie y ambos son buenos indicadores del tipo de locomoción. Por este motivo, se han utilizado estos dos tarsales para llevar a cabo el estudio de la morfología de ocho especies de cercopitecoideos, de tal manera que luego se ha podido hacer una serie de inferencias funcionales en cuanto al tipo de locomocón de las mismas

    Dynamic procedure for daily PM56 ETo mapping conducive to site-specific irrigation recommendations in areas covered by agricultural weather networks.

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    [EN] Modern agriculture is underpinned by actual meteorological data registered using automated meteorological stations forming networks specifically created for advising purposes. In many cases, those data used to be accessible online by means of APIs (Application Programming Interface). One of the most common cases is the irrigation-advice weather network implemented with the aim of obtaining ETo values to be used in irrigation recommendations. However, those punctual values of ETo scattered throughout the territory do not allow to produce specific irrigation recommendations for each farm. The only way of disposing site-specific values of ETo is by compiling maps that describe its spatial variation. With this objective, a new dynamic procedure based on an existing regression-based technique of interpolation was proposed. Using the meteorological data registered at the end of each day, maximum and minimum temperature, maximum and minimum relative humidity, wind velocity, and radiation maps were interpolated and then, an ETo map was derived. The proposed procedure demonstrated a special adaptation capacity to the synoptic pattern of each day using some geographical features or others, as appropriate to explain the spatial variability of the interpolated meteorological variable. In those months where radiation plays a key role in the ETo value (growing season), ETo maps obtained were especially fine-grained in areas with significant relief. This procedure improved other contrasted methodologies they were compared with. The impact of using the nearest-weather-station ETo vs interpolated value on a daily water needs was investigated and near 10% average value of error was encountered in the case study.This study has received funding from the eGROUNDWATER project (GA n. 1921) , part of the PRIMA program supported by the European Union 's Horizon 2020 research and innovation program, and the WATER4CAST project (PROMETEO/2021/074) , which is funded by the Conselleria de Innovacion, Universidades, Ciencia y Sociedad Digital de la Comunitat Valenciana.Meteorological data were provided by SIAR: " Sistema de Informacion Agroclimatica para el Regadio. Ministerio de Agricultura, Pesca y Alimentacion" . Special thanks to Carlos Garrido Garrido and Ivan Cilleros Fuentetaja for providing us an API-SIAR access. Thanks to Luis Bonet for giving us permission to use the picture of the IVIA-SIAR automated station.Garcia-Prats, A.; Carricondo-Antón, JM.; Jiménez Bello, MA.; Manzano Juarez, J.; López Pérez, E.; Pulido-Velazquez, M. (2023). Dynamic procedure for daily PM56 ETo mapping conducive to site-specific irrigation recommendations in areas covered by agricultural weather networks. Agricultural Water Management. 287:1-18. https://doi.org/10.1016/j.agwat.2023.10841511828

    Virtual Reality Systems for Upper Limb Motor Function Recovery in Patients With Spinal Cord Injury: Systematic Review and Meta-Analysis

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    Background: Patients with spinal cord injury (SCI) usually present with different motor impairments, including a deterioration of upper limb motor function (ULMF), that limit their performance of activities of daily living and reduce their quality of life. Virtual reality (VR) is being used in neurological rehabilitation for the assessment and treatment of the physical impairments of this condition. Objective: A systematic review and meta-analysis was conducted to evaluate the effectiveness of VR on ULMF in patients with SCI compared with conventional physical therapy. Methods: The search was performed from October to December 2019 in Embase, Web of Science, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Scopus, Medline, Physiotherapy Evidence Database (PEDro), PubMed, and Cochrane Central Register of Controlled Trials. The inclusion criteria of selected studies were as follows: (1) comprised adults with SCI, (2) included an intervention with VR, (3) compared VR intervention with conventional physical therapy, (4) reported outcomes related to ULMF, and (5) was a controlled clinical trial. The Cochrane Collaboration's tool was used to evaluate the risk of bias. The RevMan 5.3 statistical software was used to obtain the meta-analysis according to the standardized mean difference (SMD) and 95% CIs. Results: Six articles were included in this systematic review. Four of them contributed information to the meta-analysis. A total of 105 subjects were analyzed. All of the studies used semi-immersive or nonimmersive VR systems. The statistical analysis showed nonsignificant results for the Nine-Hole Peg Test (SMD -0.93, 95% CI -1.95 to 0.09), muscle balance test (SMD -0.27, 95% CI -0.82 to 0.27), Motricity Index (SMD 0.16, 95% CI -0.37 to 0.68), Jebsen-Taylor Hand Function Test (JTHFT) subtests (writing, SMD -0.10, 95% CI -4.01 to 3.82; simulated page turning, SMD -0.99, 95% CI -2.01 to 0.02; simulated feeding, SMD -0.64, 95% CI -1.61 to 0.32; stacking checkers, SMD 0.99, 95% CI -0.02 to 2.00; picking up large light objects, SMD -0.42, 95% CI -1.37 to 0.54; and picking up large heavy objects, SMD 0.52, 95% CI -0.44 to 1.49), range of motion of shoulder abduction/adduction (SMD -0.23, 95% CI -1.48 to 1.03), shoulder flexion/extension (SMD 0.56, 95% CI -1.24 to 2.36), elbow flexion (SMD -0.36, 95% CI -1.14 to 0.42), elbow extension (SMD -0.21, 95% CI -0.99 to 0.57), wrist extension (SMD 1.44, 95% CI -2.19 to 5.06), and elbow supination (SMD -0.18, 95% CI -1.80 to 1.44). Favorable results were found for the JTHFT subtest picking up small common objects (SMD -1.33, 95% CI -2.42 to -0.24). Conclusions: The current evidence for VR interventions to improve ULMF in patients with SCI is limited. Future studies employing immersive systems to identify the key aspects that increase the clinical impact of VR interventions are needed, as well as research to prove the benefits of the use of VR in the rehabilitation of patients with SCI in the clinical setting

    Cutting edge: Regulation of exosome secretion by the integral MAL protein in T cells

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    Exosomes secreted by T cells play an important role in coordinating the immune response. HIV-1 Nef hijacks the route of exosome secretion of T cells to modulate the functioning of uninfected cells. Despite the importance of the process, the protein machinery involved in exosome biogenesis is yet to be identified. In this study, we show that MAL, a tetraspanning membrane protein expressed in human T cells, is present in endosomes that travel toward the plasma membrane for exosome secretion. In the absence of MAL, the release of exosome particles and markers was greatly impaired. This effect was accompanied by protein sorting defects at multivesicular endosomes that divert the exosomal marker CD63 to autophagic vacuoles. Exosome release induced by HIV-1 Nef was also dependent on MAL expression. Therefore,MAL is a critical element of the machinery for exosome secretion andmay constitute a target for modulating exosome secretion by human T cells. The Journal of Immunology, 2015, 195: 810–814.Peer Reviewe

    Is Virtual Reality Effective for Balance Recovery in Patients with Spinal Cord Injury? A Systematic Review and Meta-Analysis

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    Virtual reality (VR) is an emerging tool used in the neurological rehabilitation of patients with spinal cord injury (SCI), focused on recovering balance, mobility, and motor function, among other functional outcomes. The main objective of this study was to analyze the effectiveness of VR systems to recover balance in patients with SCI. The literature search was performed between October and December 2019 in the following databases: Embase, Web of Science, CINAHL, Scopus, Medline, Physiotherapy Evidence Database (PEDro), PubMed, and the Cochrane Central Register of Controlled Trials. The methodological quality of each study was assessed using the Spinal Cord Injury Rehabilitation Evidence (SCIRE) system and the PEDro scale, while the risk of bias was analyzed by the Cochrane Collaboration's tool. A total of 12 studies, involving 188 participants, were included in the systematic review, of which two were included in the meta-analysis. Statistical analysis showed favorable results for balance measured by the modified Functional Reach Test (standardized mean difference (SMD) = 3.42; 95% confidence interval: 2.54 to 4.29) and by the t-shirt test (SMD= -2.29; 95% confidence interval: -3.00 to -1.59). The results showed that VR interventions provided potential benefits, in addition to conventional physical therapy, to recover balance in patients with SCI

    The fast-growing Brucella suis Biovar 5 depends on phosphoenolpyruvate carboxykinase and pyruvate phosphate dikinase but not on Fbp and GlpX fructose-1, 6-bisphosphatases or isocitrate lyase for full virulence in laboratory models

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    Bacteria of the genus Brucella infect a range of vertebrates causing a worldwide extended zoonosis. The best-characterized brucellae infect domestic livestock, behaving as stealthy facultative intracellular parasites. This stealthiness depends on envelope molecules with reduced pathogen-associated molecular patterns, as revealed by the low lethality and ability to persist in mice of these bacteria. Infected cells are often engorged with brucellae without signs of distress, suggesting that stealthiness could also reflect an adaptation of the parasite metabolism to use local nutrients without harming the cell. To investigate this, we compared key metabolic abilities of Brucella abortus 2308 Wisconsin (2308W), a cattle biovar 1 virulent strain, and B. suis 513, the reference strain of the ancestral biovar 5 found in wild rodents. B. suis 513 used a larger number of C substrates and showed faster growth rates in vitro, two features similar to those of B. microti, a species phylogenomically close to B. suis biovar 5 that infects voles. However, whereas B. microti shows enhanced lethality and reduced persistence in mice, B. suis 513 was similar to B. abortus 2308W in this regard. Mutant analyses showed that B. suis 513 and B. abortus 2308W were similar in that both depend on phosphoenolpyruvate synthesis for virulence but not on the classical gluconeogenic fructose-1, 6-bisphosphatases Fbp-GlpX or on isocitrate lyase (AceA). However, B. suis 513 used pyruvate phosphate dikinase (PpdK) and phosphoenolpyruvate carboxykinase (PckA) for phosphoenolpyruvate synthesis in vitro while B. abortus 2308W used only PpdK. Moreover, whereas PpdK dysfunction causes attenuation of B. abortus 2308W in mice, in B. suis, 513 attenuation occurred only in the double PckA-PpdK mutant. Also contrary to what occurs in B. abortus 2308, a B. suis 513 malic enzyme (Mae) mutant was not attenuated, and this independence of Mae and the role of PpdK was confirmed by the lack of attenuation of a double Mae-PckA mutant. Altogether, these results decouple fast growth rates from enhanced mouse lethality in the brucellae and suggest that an Fbp-GlpX-independent gluconeogenic mechanism is ancestral in this group and show differences in central C metabolic steps that may reflect a progressive adaptation to intracellular growth
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