Very weak solutions and large uniqueness classes of stationary Navier–Stokes equations in bounded domains of R2

AbstractExtending the notion of very weak solutions, developed recently in the three-dimensional case, to bounded domains Ω⊂R2 we obtain a new class of unique solutions u in Lq(Ω), q>2, to the stationary Navier–Stokes system −Δu+u⋅∇u+∇p=f, divu=k, u|∂Ω=g with data f,k,g of low regularity. As a main consequence we obtain a new uniqueness class also for classical weak or strong solutions. Indeed, such a solution is unique if its Lq-norm is sufficiently small or the data satisfy the uniqueness condition of a very weak solution

Self-propelled micro-swimmers in a Brinkman fluid

We prove an existence, uniqueness, and regularity result for the motion of a self-propelled micro-swimmer in a particulate viscous medium, modelled as a Brinkman fluid. A suitable functional setting is introduced to solve the Brinkman system for the velocity field and the pressure of the fluid by variational techniques. The equations of motion are written by imposing a self-propulsion constraint, thus allowing the viscous forces and torques to be the only ones acting on the swimmer. From an infinite-dimensional control on the shape of the swimmer, a system of six ordinary differential equations for the spatial position and the orientation of the swimmer is obtained. This is dealt with standard techniques for ordinary differential equations, once the coefficients are proved to be measurable and bounded. The main result turns out to extend an analogous result previously obtained for the Stokes system

Global regularity criterion for the 3D Navier-Stokes equations involving one entry of the velocity gradient tensor

In this paper we provide a sufficient condition, in terms of only one of the nine entries of the gradient tensor, i.e., the Jacobian matrix of the velocity vector field, for the global regularity of strong solutions to the three-dimensional Navier-Stokes equations in the whole space, as well as for the case of periodic boundary conditions

A geometric condition implying energy equality for solutions of 3D Navier-Stokes equation

We prove that every weak solution $u$ to the 3D Navier-Stokes equation that belongs to the class $L^3L^{9/2}$ and \n u belongs to $L^3L^{9/5}$ localy away from a 1/2-H\"{o}lder continuous curve in time satisfies the generalized energy equality. In particular every such solution is suitable.Comment: 10 page

On the existence of traveling waves in the 3D Boussinesq system

We extend earlier work on traveling waves in premixed flames in a gravitationally stratified medium, subject to the Boussinesq approximation. For three-dimensional channels not aligned with the gravity direction and under the Dirichlet boundary conditions in the fluid velocity, it is shown that a non-planar traveling wave, corresponding to a non-zero reaction, exists, under an explicit condition relating the geometry of the crossection of the channel to the magnitude of the Prandtl and Rayleigh numbers, or when the advection term in the flow equations is neglected.Comment: 15 pages, to appear in Communications in Mathematical Physic

Impact of actin filament stabilization on adult hippocampal and olfactory bulb neurogenesis

Rearrangement of the actin cytoskeleton is essential for dynamic cellular processes. Decreased actin turnover and rigidity of cytoskeletal structures have been associated with aging and cell death. Gelsolin is a Ca(2+)-activated actin-severing protein that is widely expressed throughout the adult mammalian brain. Here, we used gelsolin-deficient (Gsn(-/-)) mice as a model system for actin filament stabilization. In Gsn(-/-) mice, emigration of newly generated cells from the subventricular zone into the olfactory bulb was slowed. In vitro, gelsolin deficiency did not affect proliferation or neuronal differentiation of adult neural progenitors cells (NPCs) but resulted in retarded migration. Surprisingly, hippocampal neurogenesis was robustly induced by gelsolin deficiency. The ability of NPCs to intrinsically sense excitatory activity and thereby implement coupling between network activity and neurogenesis has recently been established. Depolarization-induced [Ca(2+)](i) increases and exocytotic neurotransmitter release were enhanced in Gsn(-/-) synaptosomes. Importantly, treatment of Gsn(-/-) synaptosomes with mycotoxin cytochalasin D, which, like gelsolin, produces actin disassembly, decreased enhanced Ca(2+) influx and subsequent exocytotic norepinephrine release to wild-type levels. Similarly, depolarization-induced glutamate release from Gsn(-/-) brain slices was increased. Furthermore, increased hippocampal neurogenesis in Gsn(-/-) mice was associated with a special microenvironment characterized by enhanced density of perfused vessels, increased regional cerebral blood flow, and increased endothelial nitric oxide synthase (NOS-III) expression in hippocampus. Together, reduced filamentous actin turnover in presynaptic terminals causes increased Ca(2+) influx and, subsequently, elevated exocytotic neurotransmitter release acting on neural progenitors. Increased neurogenesis in Gsn(-/-) hippocampus is associated with a special vascular niche for neurogenesis

Folate deficiency induces neurodegeneration and brain dysfunction in mice lacking uracil DNA glycosylase

Folate deficiency and resultant increased homocysteine levels have been linked experimentally and epidemiologically with neurodegenerative conditions like stroke and dementia. Moreover, folate deficiency has been implicated in the pathogenesis of psychiatric disorders, most notably depression. We hypothesized that the pathogenic mechanisms include uracil misincorporation and, therefore, analyzed the effects of folate deficiency in mice lacking uracil DNA glycosylase (Ung-/-) versus wild-type controls. Folate depletion increased nuclear mutation rates in Ung-/- embryonic fibroblasts, and conferred death of cultured Ung-/- hippocampal neurons. Feeding animals a folate-deficient diet (FD) for 3 months induced degeneration of CA3 pyramidal neurons in Ung-/- but not Ung+/+ mice along with decreased hippocampal expression of brain-derived neurotrophic factor protein and decreased brain levels of antioxidant glutathione. Furthermore, FD induced cognitive deficits and mood alterations such as anxious and despair-like behaviors that were aggravated in Ung-/- mice. Independent of Ung genotype, FD increased plasma homocysteine levels, altered brain monoamine metabolism, and inhibited adult hippocampal neurogenesis. These results indicate that impaired uracil repair is involved in neurodegeneration and neuropsychiatric dysfunction induced by experimental folate deficiency

Evaluation of Cage Designs and Feeding Regimes for Honey Bee (Hymenoptera: Apidae) Laboratory Experiments

The aim of this study was to improve cage systems for maintaining adult honey bee (Apis mellifera L.) workers under in vitro laboratory conditions. To achieve this goal, we experimentally evaluated the impact of different cages, developed by scientists of the international research network COLOSS (Prevention of honey bee COlony LOSSes), on the physiology and survival of honey bees. We identified three cages that promoted good survival of honey bees. The bees from cages that exhibited greater survival had relatively lower titers of deformed wing virus, suggesting that deformed wing virus is a significant marker reflecting stress level and health status of the host. We also determined that a leak- and drip-proof feeder was an integral part of a cage system and a feeder modified from a 20-ml plastic syringe displayed the best result in providing steady food supply to bees. Finally, we also demonstrated that the addition of protein to the bees' diet could significantly increase the level of vitellogenin gene expression and improve bees' survival. This international collaborative study represents a critical step toward improvement of cage designs and feeding regimes for honey bee laboratory experiment

Five-years surveillance of invasive aspergillosis in a university hospital

<p>Abstract</p> <p>Background</p> <p>As the most common invasive fungal infection, invasive aspergillosis (IA) remains a serious complication in immunocompromised patients, leading to increased mortality. Antifungal therapy is expensive and may result in severe adverse effects.</p> <p>The aim of this study was to determine the incidence of invasive aspergillosis (IA) cases in a tertiary care university hospital using a standardized surveillance method.</p> <p>Methods</p> <p>All inpatients at our facility were screened for presence of the following parameters: positive microbiological culture, pathologist's diagnosis and antifungal treatment as reported by the hospital pharmacy. Patients fulfilling one or more of these indicators were further reviewed and, if appropriate, classified according to international consensus criteria (EORTC).</p> <p>Results</p> <p>704 patients were positive for at least one of the indicators mentioned above. Applying the EORTC criteria, 214 IA cases were detected, of which 56 were proven, 25 probable and 133 possible. 44 of the 81 (54%) proven and probable cases were considered health-care associated. 37 of the proven/probable IA cases had received solid organ transplantation, an additional 8 had undergone stem cell transplantation, and 10 patients were suffering from some type of malignancy. All the other patients in this group were also suffering from severe organic diseases, required long treatment and experienced several clinical complications. 7 of the 56 proven cases would have been missed without autopsy. After the antimycotic prophylaxis regimen was altered, we noticed a significant decrease (p = 0.0004) of IA during the investigation period (2003-2007).</p> <p>Conclusion</p> <p>Solid organ and stem cell transplantation remain important risk factors for IA, but several other types of immunosuppression should also be kept in mind. Clinical diagnosis of IA may be difficult (in this study 13% of all proven cases were diagnosed by autopsy only). Thus, we confirm the importance of IA surveillance in all high-risk patients.</p

The association between maternal and partner experienced racial discrimination and prenatal perceived stress, prenatal and postnatal depression: findings from the growing up in New Zealand cohort study

Background A growing number of studies document the association between maternal experiences of racial discrimination and adverse children’s outcomes, but our understanding of how experiences of racial discrimination are associated with pre- and post-natal maternal mental health, is limited. In addition, existent literature rarely takes into consideration racial discrimination experienced by the partner. Methods We analysed data from the Growing Up in New Zealand study to examine the burden of lifetime and past year experiences of racial discrimination on prenatal and postnatal mental health among Māori, Pacific, and Asian women in New Zealand (NZ), and to study the individual and joint contribution of mother’s and partner’s experiences of lifetime and past year racial discrimination to women’s prenatal and postnatal mental health. Results Our findings show strong associations between lifetime and past year experiences of ethnically-motivated interpersonal attacks and unfair treatment on mother’s mental health. Māori, Pacific, and Asian women who had experienced unfair treatment by a health professional in their lifetime were 66 % more likely to suffer from postnatal depression, compared to women who did not report these experiences. We found a cumulative effect of lifetime experiences of ethnically-motivated personal attacks on poor maternal mental health if both the mother and the partner had experienced a racist attack. Conclusions Experiences of racial discrimination have severe direct consequences for the mother’s mental health. Given the importance of mother’s mental health for the basic human needs of a healthy child, racism and racial discrimination should be addressed