Anisotropic unstable ion distribution functions downstream of the solar wind termination shock

International audienceIn this paper we demonstrate that solar wind ions, passing over the quasiperpendicular portion of the solar wind MHD termination shock, unavoidably develop strongly pronounced pitchangle anisotropies. In order to prove that, we solve the Boltzmann-Vlasov equation for the ions, kinetically describing the ion passage over the MHD structure of the shock. With the solution of the anisotropic downstream ion distribution function we may also calculate higher order velocity moments of this distribution enabling us to calculate anisotropic downstream ion pressures. From these latter results we derive the conclusion that in most likely cases the downstream ion distribution will be mirror-mode unstable and with its free thermal energy will effectively drive magnetosonic turbulences. We estimate the energy that is pumped into this turbulence until marginal stability is achieved. In this newly established intermediate quasi-equilibrium state, as we can show, one can find 35 to 50 percent of the original energy sitting in the thermal mode perpendicular to the magnetic field in the form of magnetosonic turbulences, perhaps already identified by Voyager-1 as downstream trains of magnetic holes and humps. We discuss several consequences of this new quasi-equilibrium MHD plasma state downsstream of the shock

Two-Particle Dark State in the Transport through a Triple Quantum Dot

We study transport through a triple quantum dot in a triangular geometry with applied bias such that both singly- and doubly- charged states participate. We describe the formation of electronic dark states -- coherent superpositions that block current flow -- in the system, and focus on the formation of a two-electron dark state. We discuss the conditions under which such a state forms and describe the signatures that it leaves in transport properties such as the differential conductance and shotnoise.Comment: (9 pages, 7 figures), we now consider two different sets of charging energie

Curvature effects on lipid packing and dynamics in liposomes revealed by coarse grained molecular dynamics simulations

The molecular packing details of lipids in planar bilayers are well characterized. For curved bilayers, however, little data is available. In this paper we study the effect of temperature and membrane composition on the structural and dynamical properties of a liposomal membrane in the limit of high curvature (liposomal diameter of 15-20 nm), using coarse grained molecular dynamics simulations. Both pure dipalmitoyl phosphatidylcholine (DPPC) liposomes and binary mixtures of DPPC and either dipalmitoyl phosphatidylethanolamine (DPPE) or polyunsaturated dilinoleylphosphatidylcholine (DLiPC) lipids are modeled. We take special care in the equilibration of the liposomes requiring lipid flip-flopping, which can be facilitated by the temporary insertion of artificial pores. The equilibrated liposomes show some remarkable properties. Curvature induces membrane thinning and reduces the thermal expansivity of the membrane. In the inner monolayer the lipid head groups are very closely packed and dehydrated, and the lipids tails relatively disordered. The opposite packing effects are seen in the outer monolayer. In addition, we noticed an increased tendency of the lipid tails to backfold toward the interface in the outer monolayer. The distribution of lipids over the monolayers was found to be strongly temperature dependent. Higher temperatures favor more equally populated monolayers. Relaxation times of the lipid tails were found to increase with increasing curvature, with the lipid tails in the outer monolayer showing a significant slower dynamics compared to the lipid tails in the inner monolayer. In the binary systems there is a clear tendency toward partial transversal demixing of the two components, with especially DPPE enriched in the inner monolayer. This observation is in line with a static shape concept which dictates that inverted-cone shaped lipids such as DPPE and DLiPC would prefer the concave volume of the inner monolayer. However, our results for DLiPC show that another effect comes into play that is almost equally strong and provides a counter-acting driving force toward the outer, rather than the inner monolayer. This effect is the ability of the polyunsaturated tails of DLiPC to backfold, which is advantageous in the outer monolayer. We speculate that polyunsaturated lipids in biological membranes may play an important role in stabilizing both positive and negative regions of curvature.</p

Perforatationstrauma im Gesichtsschädel. Eine ungewöhnliche Verletzung beim Skifahren

Facial perforation injuries are very rare. We describe a case of a 48-year-old man who sustained a perforation trauma from an 11 cm long wooden tree branch in the middle of the face in a skiing accident. He suffered from additional injuries, such as fractures of the ribs and hand, but was neurologically without pathologic findings and was cardiopulmonary stable.The branch penetrated the head from the sinus maxillaris through the maxilla just missing the internal and external carotid arteries and ending just short of the cervical vertebra. The patient was transported to a center for oral and maxillofacial surgery and underwent several operations.He could return to his normal social and professional life 8 months after the accident

On the formation of the welding seams with high speed

Целью настоящей работы является определение направлений исследований по установлению возможности повышения качества формирования сварочных швов с повышенной скоростью формирования тела шва. В статье вопрос решается путём отклонения сварочной дуги углом вперед, поперечным магнитным полем. Дополнительное магнитное поле в зоне сварки генерируют, пропуская часть сварочного тока по присадочной проволоке. Проволока подается в сварочную ванну позади дуги параллельно электроду в плоскости свариваемого стыка, в направлении, противоположном току дуги. Проведенный анализ отечественных и зарубежных литературных источников по рассматриваемой теме показал, что современный подход к определению влияния на повышение качества формирования сварочных швов с повышенной скоростью формирования тела шва, за счет дополнительного поперечного магнитного поля является актуальным в настоящее время и недостаточно изучен. Приведены сведения о формировании тела шва при скоростной сварке вольфрамовым электродом с присадочной проволокой, которые могут быть использованы для повышения производительности сварочных работ.The aim of this work is to determine the areas of research to establish the possibility of improving the quality of the formation of welds with an increased rate of formation of the joint body. In the article the problem is solved by the deviation of the arc angle forward transverse magnetic field. Additional magnetic field generated in the welding zone by passing part of the welding current for the filler wire. The wire is fed into the weld puddle behind the arc electrode in the plane parallel to the welded joint, in a direction opposite to the arc current. The analysis of domestic and foreign literature on the topic has shown that the modern approach to determine the effect on the improvement of quality of formation of welds with an increased rate of formation of the joint body, due to the additional transverse magnetic field is relevant in the present and not fully understood. Information is given about the formation of a seam in the tungsten electrode welding with filler wire, which can be used to improve the performance of welding