Toward the Simulation of Flashing Cryogenic Liquids by a Fully Compressible Volume of Fluid Solver

We present a fully compressible single-fluid volume of fluid (VOF) solver with phase change for high-speed flows, where the atomization of the liquid can occur either by the aerodynamics or by the effect of the local pressure. The VOF approximation among a non-miscible phase (non-condensable gas) and a mixture of two fluids (liquid and vapor) represents the liquid core of the jet and its atomization. A barotropic model is used in combination with the equation of state (EoS) to link the mixture density to pressure and temperature. The solver is written with the aim to simulate high-pressure injection in gas–liquid systems, where the pressure of the liquid is great enough to cause significant compression of the surrounding gas. Being designed in an C++ object-oriented fashion, the solver is able to support any kind of EoS; the aim is to apply it to the simulation of the injection of liquid propellant in rocket engines. The present work includes the base development; a verification assessment of the code is provided by the solution of a set of numerical experiments to prove the boundedness, convergence and accuracy of the method. Experimental measurements of a cavitating microscopic in-nozzle flow, available in the literature, are finally used for a first validation with phase change

Synchronization of the Frenet-Serret linear system with a chaotic nonlinear system by feedback of states

A synchronization procedure of the generalized type in the sense of Rulkov et al [Phys. Rev. E 51, 980 (1995)] is used to impose a nonlinear Malasoma chaotic motion on the Frenet-Serret system of vectors in the differential geometry of space curves. This could have applications to the mesoscopic motion of biological filamentsComment: 12 pages, 7 figures, accepted at Int. J. Theor. Phy

Aporte de las plantas de Eichhornia crassipes a la acumulacion de materiales organicos e inorganicos

#Eichhornia crassipes est l'une des plantes les plus abondantes de la plaine d'inondation du fleuve Parana. Les détritus formés dans les îles flottantes s'accumulent à l'interface eau-sédiment ou bien dans le système racinaire des plantes. La quantité de matière organique et minérale déposée par #E. crassipes a été mesurée dans un réservoir (10 m x 2 m x 1,5 m de profondeur). Le réservoir a été rempli avec de l'eau d'un bras mort de la plaine d'inondation et #E. crassipes y a été ajoutée. Dans ces conditions la production nette des plantes a été de 1743 g/m2/an. La moyenne annuelle de matière organique sédimentée sous #E. crassipes a été de 5,1 g/m2/jour, avec des variations saisonnières significatives. Le maximum de dépôt de matière minérale et organique a eu lieu en mars et le minimum en août. La teneur en matière organique fine représentait 40 à 69% de ce dépôt. (Résumé d'auteur

H3++H_3^{++} molecular ions can exist in strong magnetic fields

Using the variational method it is shown that for magnetic fields $B\geq 10^{11}$ G there can exist a molecular ion $H_3^{++}$.Comment: LaTeX, 7 pp, 1 table, 4 figures. Title modified. Consideration of the longitudinal size of the system was adde

Control System for Less than Wind Turbines 1500W

Using wind power generation is another alternative for remote homes, where there is no electricity grid. Especially in Ecuador there are several places where the wind resource is really stable for the year, though at times the wind regime it becomes turbulent wind speeds become quite high exceeding 12 m / s affecting the wind turbine components.Generally in the Ecuadorian highlands are available permanent winds of medium intensity capable of generating electricity, but by having a system of turbulence for short periods of time it jeopardizes the deployed equipment and therefore the investments made by what this study guarantees the stability of small wind turbines that are very useful in our environment to generate electricity in field type housing shelters

The assessment of viscoelastic models for nonlinear soft materials

The increasing use of soft materials in robotics applications requires the development of mathematical models to describe their viscoelastic and nonlinear properties. The traditional linear viscoelastic models are unable to describe nonlinear strain-dependent behaviors. This limitation has been addressed by implementing a piecewise linearization (PL) in the simplest viscoelastic model, the Standard Linear Solid (SLS). In this work, we aim to implement the PL in a more complex model, the Wiechert model and compare the stress response of both linearized models. Therefore, the experimental data from the stress relaxation and tensile strength tests of six rubber-based materials is used to approximate the spring and dashpot constants of the SLS and the Wiechert model. Prior to implement the PL into the stress-strain curve of each material, the stress response from the Maxwell branches must be subtracted from this curve. By using the parameters obtained from fitting the Wiechert model into the stress relaxation curve, the response of both linearized models was improved. Due to the selection of constitutive equations evaluated, the linearized SLS model described the stress-strain curve more accurately. Finally, this work describes in details every step of the fitting process and highlights the benefits of using linearization methods to improve known models as an alternative of using highly complex models to describe the mechanical properties of soft materials

Artritis séptica de rodilla por Streptococcus agalactiae: presentación de un caso y revisión de la literatura

Se describe un caso de artritis séptica de rodilla en un paciente diabético de 69 años. En el momento de la presentación se hallaba sometido a curas locales de una úlcera crónica en el mismo miembro y a antibioterapia oral inespecífica por supuesta infección urinaria. En el cultivo del líquido sinovial se identificó un Streptococcus agalactiae (Estreptococo del grupo B). La infección no remitió con antibioterapia intravenosa electiva e irrigación-aspiración articular repetidas, requiriendo desbridamiento quirúrgico y sinovectomía. A pesar de instaurarse un programa de rehabilitación intensiva la rodilla evolucionó a la rigidez. Se revisa la literatura al respecto, destacando la asociación de artritis por estreptococos del grupo B con pacientes diabéticos portadores de úlceras cutáneas crónicas, así como la potencial gravedad de estas infecciones.This report describes a case of knee septic arthritis in a 69-year-old diabetic patient. At the time of admission he was receiving local treatment for a chronic skin ulcer in the same extremity and inespecific oral antibiotherapy because of an urinary tract infection. Synovial fluid cultures showed a Streptococcus agalactiae (group B streptococcus). The infection had no response to specific parenteral antibiotherapy and repeated joint irrigations-aspirations, and therefore surgical desbridement and synovectomy was required. Despite of an intensive rehabilitation program, the affected knee developed ankylosis. In a review of literature, it is remarkable the association between group B streptococcal arthritis and chronic skin ulcers in diabetic patients and the potential severity of these infections

Age-related decline of de novo T cell responsiveness as a cause of COVID-19 severity

To the Editor, So far, little attention has been paid to the link between immunosenescence and the dramatic mortality rate of coronavirus disease 2019 (COVID-19) in older age groups. Indeed, the number of cases of COVID-19, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is very low among children and teenagers, in contrast to the increased frequency in adults and the elderly, who are also more at risk of developing very serious symptoms and death (Guan et al. 2020; Wu and McGoogan 2020). As shown in Fig. 1, a similar epidemiological profile was observed during previous coronavirus (severe acute respiratory syndrome coronavirus 1, SARS-CoV-1, and Middle east respiratory syndrome coronavirus, MERS-CoV) outbreaks (Jia et al. 2009; Salamatbakhsh et al. 2019). Notably, the same trend was also noted during West Nile virus and, with some exceptions in very young children, Ebolavirus outbreaks (Bower et al. 2016; Hayes et al. 2005). Likely this phenomenon is multifactorial. For instance, in elderly individuals with severe COVID-19, associated comorbidities are much more prevalent (Guan et al. 2020). In addition, the progressive accumulation of senescent cells during life may play a role in the vulnerability of old people to COVID-19, resulting in reduced functionality of the organs, such as the lungs, and facilitating conditions for the development of fibrosis. Moreover, senescent cells can generate a pro-inflammatory environment, referred to as SASP (for senescence-associated secretory phenotype), which includes many inflammatory cytokines (e.g., interleukin-6) and contributes to the basal hyperinflammatory status characteristic of the old person. This hyperinflammatory status might influence the expression of ACE2, CD147, cyclophilins, CD26, and other CoV-associated molecules in human tissues, thus favoring viral entry (Radzikowska et al. 2020). It likely also constitutes an already unbalanced pro-inflammatory background, on which the development of an exacerbated inflammatory response and acute respiratory distress syndrome may be facilitated upon SARS-CoV-2 infection

Exploring the Impact of Galactic Interactions and Mergers on the Central Star Formation of APEX/EDGE-CALIFA Galaxies

Galactic interactions and subsequent mergers are a paramount channel for galaxy evolution. In this work, we use the data from 236 star forming CALIFA galaxies with integrated molecular gas observations in their central region (approximately within an effective radius) -- from the APEX millimeter telescope and the CARMA millimeter telescope array. This sample includes isolated (126 galaxies) and interacting galaxies in different merging stages (110 galaxies; from pairs, merging and post-merger galaxies). We show that the impact of interactions and mergers in the center of galaxies is revealed as an increase in the fraction of molecular gas (compared to isolated galaxies). Furthermore, our results suggest that the change in star formation efficiency is the main driver for both an enhancement and/or suppression of the central star formation -- except in merging galaxies where the enhanced star formation appears to be driven by an increase of molecular gas. We suggest that gravitational torques due to the interaction and subsequent merger transport cold molecular gas inwards, increasing the gas fraction without necessarily increasing star formation.Comment: 3 Figures, 13 Pages. Accepted for publication in Ap