Observations of interstellar helium pickup ions in the inner heliosphere

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98161/1/jgra50227.pd

Regulation of the Immune Balance During Allogeneic Hematopoietic Stem Cell Transplantation by Vitamin D

One of the most promising therapeutic approaches for numerous hematological malignancies represents the allogeneic hematopoietic stem cell transplantation (allo-HSCT). One major complication is the development of the life-threatening graft-vs.-host disease (GvHD) which limits beneficial effects of graft-vs.-leukemia (GvL) responses during allo-HSCT. Strengthening GvL effects without induction of severe GvHD is essential to decrease the relapse rate after allo-HSCT. An interesting player in this context is vitamin D3 since it has modulatory capacity in both preventing GvHD and boosting GvL responses. Current studies claim that vitamin D3 induces an immunosuppressive environment by dendritic cell (DC)-dependent generation of regulatory T cells (Tregs). Since vitamin D3 is known to support the antimicrobial defense by re-establishing the physical barrier as well as releasing defensins and antimicrobial peptides, it might also improve graft-vs.-infection (GvI) effects in patients. Beyond that, alloreactive T cells might be attenuated by vitamin D3-mediated inhibition of proliferation and activation. Despite the inhibitory effects of vitamin D3 on T cells, anti-tumor responses of GvL might be reinforced by vitamin D3-triggered phagocytic activity and antibody-based immunotherapy. Therefore, vitamin D3 treatment does not only lead to a shift from a pro-inflammatory toward a tolerogenic state but also promotes tumoricidal activity of immune cells. In this review we focus on vitamin D3 and its immunomodulatory effects by enhancing anti-tumor activity while alleviating harmful allogeneic responses in order to restore the immune balance

Refinement and Pattern Formation in Neural Circuits by the Interaction of Traveling Waves with Spike-Timing Dependent Plasticity

Traveling waves in the developing brain are a prominent source of highly correlated spiking activity that may instruct the refinement of neural circuits. A candidate mechanism for mediating such refinement is spike-timing dependent plasticity (STDP), which translates correlated activity patterns into changes in synaptic strength. To assess the potential of these phenomena to build useful structure in developing neural circuits, we examined the interaction of wave activity with STDP rules in simple, biologically plausible models of spiking neurons. We derive an expression for the synaptic strength dynamics showing that, by mapping the time dependence of STDP into spatial interactions, traveling waves can build periodic synaptic connectivity patterns into feedforward circuits with a broad class of experimentally observed STDP rules. The spatial scale of the connectivity patterns increases with wave speed and STDP time constants. We verify these results with simulations and demonstrate their robustness to likely sources of noise. We show how this pattern formation ability, which is analogous to solutions of reaction-diffusion systems that have been widely applied to biological pattern formation, can be harnessed to instruct the refinement of postsynaptic receptive fields. Our results hold for rich, complex wave patterns in two dimensions and over several orders of magnitude in wave speeds and STDP time constants, and they provide predictions that can be tested under existing experimental paradigms. Our model generalizes across brain areas and STDP rules, allowing broad application to the ubiquitous occurrence of traveling waves and to wave-like activity patterns induced by moving stimuli

On the hydrodynamic stability of two viscous incompressible fluids in parallel uniform shearing motion

A new problem in hydrodynamic stability is investigated. Given two contiguous plane sheets of viscous incompressible fluids, bounded on one side by a solid wall and unbounded on the other, the problem is to study the hydrodynamic stability when the fluids are in longitudinal, laminar, uniform shearing motion. The mathematical analysis, based on small disturbance theory, leads to a characteristic vague problem in a system of two linear ordinary differential equations. The case for which forces due to gravity and surface tension are negligible compared with inertia and viscous forces is studied in detail, and the results are presented graphically for all fluid combinations of possible interest