Development, implementation and application of a Stochastic Rotation Dynamics algorithm for granular matter

In this work we present an extension of the well-known particle based stochastic rotation dynamics method for the simulation of hydrodynamics of granular gases. We use an effective local coefficient of restitution to render energy dissipation dependent on local macroscopic observables, while locally conserving density and momentum. We derive the granular Boltzmann equation and demonstrate that our model obeys linear granular hydrodynamic equations. Furthermore, we derive a formula for the kinematic viscosity of the model fluid in two dimensions. We present results from simulations with a software implementation for general purpose graphics cards, that we successfully test and benchmarked with analytical predictions for standard stochastic rotation dynamics. For the granular system we observe that our prediction of the kinematic viscosity compares well with the results obtained from simulations. In this context we find that for low shear driving the fluid becomes unstable and develops shear bands. In the simulations of a freely cooling granular gas the temperature evolution follows the prediction of Haff’s law over several orders of magnitude in both time and temperature. Furthermore, we observe clustering for lower coefficients of restitution. The emergence and dynamics of the cluster compare well with expectations based on theory, experiments and simulations. The clustering sets in as the global Mach number exceeds one. Subsequently, density fluctuations grow while we observe a change in the power law of the temperature evolution. The clusters exhibit a higher cooling rate than dilute regions, hence, density and temperature become anti-correlated. This locally leads to supersonic flow. After their emergence, clusters move, collide and thus grow further. The velocity distribution function compares well with theoretical predictions. The shape of the reduced velocity distribution function changes with time as predicted, and the evolution of the second Sonine coefficient qualitative matches with analytical predictions. In our discussion we provide criteria for the selection of model parameters, and identify the effects of the finite system size

Antidepressant Medications in Pregnancy

Selective serotonin reuptake inhibitors (SSRIs) are considered first-line agents for the treatment of depression in pregnant women. SSRIs and tricyclic antidepressants (TCAs) are considered safe and effective in pregnant women, although some studies have indicated increased short-term neonatal adverse effects after exposure to antidepressants in the third trimester.[Strength of recommendation: B, based on cohort studies.

Estudio comparativo entre técnicas analíticas y mineralométricas para la prospección de Sn en la provincia de Orense

[Resumen] El presente estudio forma parte de uno de los capítulos de la tesis doctoral de uno de los autores sobre «Los sedimentos fluviales en la prospección de Sn y W en el oeste de la provincia de Orense». Su objetivo es el estudiar en unas áreas concretas con presencia cierta de mineralización, las anomalías de un determinado elemento, el Sn en este caso, y conocer su dispersión así como algunos de los caracteres de los sedimentos fluviales y de sus concentrados, la determinación de las granulometrías dominantes en cada caso y aquellas en las que se localizan los mayores contenidos estanníferos para, en definitiva, llegar a establecer una normativa válida en todas las áreas similares para la prospección de minerales de Sn de interés económic

Squirmer rods as elongated microswimmers: flow fields and confinement

Microswimmers or active elements, such as bacteria and active filaments, have an elongated shape, which determines their individual and collective dynamics. There is still a need to identify what role long-range hydrodynamic interactions play in their fascinating dynamic structure formation. We construct rods of different aspect ratios using several spherical squirmer model swimmers. With the help of the mesoscale simulation method of multi-particle collision dynamics we analyze the flow fields of these squirmer rods both in a bulk fluid and in Hele-Shaw geometries of different slab widths. Based on the hydrodynamic multipole expansion either for bulk or confinement between two parallel plates, we categorize the different multipole contributions of neutral as well as pusher-type squirmer rods. We demonstrate how confinement alters the radial decay of the flow fields for a given force or source multipole moment compared to the bulk fluid.DFG, 163436311, SFB 910: Kontrolle selbstorganisierender nichtlinearer Systeme: Theoretische Methoden und AnwendungskonzepteTU Berlin, Open-Access-Mittel - 202

Computer simulations of discotic liquid crystals in nanoconfinement

Discotics, that is liquid crystals formed by disk-like molecules, draw interest due to their applications as conductive nanowires confined in nanoporous templates. In this work we study the influence of different sizes of cylindrical nanoconfinement and surface anchoring on the phase behaviour of a discotic Gay-Berne fluid. The phase behaviour strongly differs from the bulk. We observe radially aligned nematic and radial poly-domain columnar configurations. Mono-domain hexagonal columnar phases were found with both face- and edge-on anchoring. Furthermore, geometrical frustration of hexagonal columnar and crystal phases is observed. Smaller pores with edge-on anchoring exhibit a configuration with a columnar outer layer and an isotropic core. The phase behaviour is investigated by means of several order parameters, some specific for the special orientational configuration in cylindrical confinement. We investigate the structure by means of radial distribution functions, and the dynamics using van Hove correlation functions

Case report: intra-tendinous ganglion of the anterior cruciate ligament in a young footballer

A 20-year-old male medical student and keen rugby player presented with a 12-month history of progressively worsening right knee pain and stiffness with no history of trauma. Clinical examination revealed effusion and posterior knee pain exacerbated by end range movement and an extension lag of 15 degrees. Physiotherapy to improve the range of motion proved unsuccessful. Magnetic resonance imaging showed that the ACL was grossly thickened and displaced by material reported as mucoid in nature. There were also areas of focally high signal in relation to its tibial attachment and intra osseous small cysts. Arthroscopic examination revealed a ganglion related to the tibial attachment of the ACL and gross thickening and discoloration of the ACL. Biopsies were taken showing foci of mucoid degeneration in the ACL. A large intra-ACL mass of brownish coloured tissue was excised arthroscopically. Already at 2 weeks follow up the patient had greatly improved range of movement and was pain free. However, upon returning to rugby, joint instability was noticed and a tear of the ACL was confirmed. This rare clinical condition can be diagnosed with MRI and arthroscopic debridement effectively relieves symptoms. This case report illustrates that augmentation or reconstruction may end up being the definitive treatment for athletes. It may also offer some support to the argument that mucoid degeneration and ganglion cyst formation share a similar pathogenesis to intra-osseous cyst formation