Calmodulin as a major calcium buffer shaping vesicular release and short-term synaptic plasticity : facilitation through buffer dislocation

Action potential-dependent release of synaptic vesicles and short-term synaptic plasticity are dynamically regulated by the endogenous Ca2+ buffers that shape [Ca2+] profiles within a presynaptic bouton. Calmodulin is one of the most abundant presynaptic proteins and it binds Ca2+ faster than any other characterized endogenous neuronal Ca2+ buffer. Direct effects of calmodulin on fast presynaptic Ca2+ dynamics and vesicular release however have not been studied in detail. Using experimentally constrained three-dimensional diffusion modeling of Ca2+ influx–exocytosis coupling at small excitatory synapses we show that, at physiologically relevant concentrations, Ca2+ buffering by calmodulin plays a dominant role in inhibiting vesicular release and in modulating short-term synaptic plasticity. We also propose a novel and potentially powerful mechanism for short-term facilitation based on Ca2+-dependent dynamic dislocation of calmodulin molecules from the plasma membrane within the active zone

Chemically modified mechanical pulp of wood chips of different breeds

The results of studies that allow to establish the feasibility of using a modified aspen wood as a raw material for thermomechanical pulp (TMP) in the production of newsprint. Modification of wood chips can increase the proportion of aspen wood in combination with spruce up to 30% without reducing the strength of quality newsprint. When this process is accelerated and the grinding timber increases reactivity of hemicelluloses and lignin, but also leads to lower energy consumption

Synaptotagmin 1 oligomers clamp and regulate different modes of neurotransmitter release

Release of neurotransmitters relies on submillisecond coupling of synaptic vesicle fusion to the triggering signal: AP-evoked presynaptic Ca2+ influx. The key player that controls exocytosis of the synaptic vesicle is the Ca2+ sensor synaptotagmin 1 (Syt1). While the Ca2+ activation of Syt1 has been extensively characterized, how Syt1 reversibly clamps vesicular fusion remains enigmatic. Here, using a targeted mutation combined with fluorescence imaging and electrophysiology, we show that the structural feature of Syt1 to self-oligomerize provides the molecular basis for clamping of spontaneous and asynchronous release but is not required for triggering of synchronous release. Our findings propose a mechanistic model that explains how Syt1 oligomers regulate different modes of transmitter release in neuronal synapses

An investigation of silicon carbide-water nanofluid for heat transfer applications

Thermal conductivity and mechanical effects of silicon carbide nanoparticles uniformly dispersed in water were investigated. Mean size of SiC particles was 170 nm with a polydispersity of 30% as determined from small-angle x-ray scattering and dynamic light scattering techniques. Room temperature viscosity of the nanofluids ranged from 2 to 3 cP for nominal nanoparticle loadings 4 – 7 vol %. On a normalized basis with water, viscosity of the nanofluids did not significantly change with the test temperature up to 85 °C. Optical microscopy of diluted nanofluid showed no agglomeration of the nanoparticles. Thermal conductivity of the fluid was measured as a function of the nominal nanoparticle loading ranging from 1 to 7 vol %. Enhancement in thermal conductivity was approximately 28% over that of water at 7 vol % particle loadings under ambient conditions. Enhancements in thermal conductivities for the nanofluids with varying nanoparticle loadings were maintained at test temperatures up to 70 °C. Results of thermal conductivity have been rationalized based on the existing theories of heat transfer in fluids. Implications of using this nanofluid for engineering cooling applications are discussed.Universidad de Chicago Argonne LLC (EE. UU.)-DE-AC02-06CH1135

Democratization in a passive dendritic tree : an analytical investigation

One way to achieve amplification of distal synaptic inputs on a dendritic tree is to scale the amplitude and/or duration of the synaptic conductance with its distance from the soma. This is an example of what is often referred to as “dendritic democracy”. Although well studied experimentally, to date this phenomenon has not been thoroughly explored from a mathematical perspective. In this paper we adopt a passive model of a dendritic tree with distributed excitatory synaptic conductances and analyze a number of key measures of democracy. In particular, via moment methods we derive laws for the transport, from synapse to soma, of strength, characteristic time, and dispersion. These laws lead immediately to synaptic scalings that overcome attenuation with distance. We follow this with a Neumann approximation of Green’s representation that readily produces the synaptic scaling that democratizes the peak somatic voltage response. Results are obtained for both idealized geometries and for the more realistic geometry of a rat CA1 pyramidal cell. For each measure of democratization we produce and contrast the synaptic scaling associated with treating the synapse as either a conductance change or a current injection. We find that our respective scalings agree up to a critical distance from the soma and we reveal how this critical distance decreases with decreasing branch radius

Взаимодействие электромагнитного поля с неоднородностями электромагнитных кристаллов

Розглянуто особливості взаємодії електромагнітного поля з різними типами неоднорідностей електромагнітних кристалів. Приведено розподіли напруженості електричного поляThe interaction of electromagnetic field with different types of electromagnetic crystals’ inhomogeneities is considered. Distributions of electric field are presented.Рассмотрены особенности взаимодействия электромагнитного поля с разными типами неоднородностей электромагнитных кристаллов. Приведены распределения напряженности электрического поля

Эффективность неоднородностей электромагнитных кристаллов

Проаналізована ефективність поодиноких та подвійних неоднорідностей електромагнітних кристалів. Наведені характеристики, що ілюструють результати моделюванняEfficiency of electromagnetic crystals single and double discontinuities is analyzed. Characteristics illustrating results of modeling are presentedПроанализирована эффективность одиночных и двойных неоднородностей электромагнитных кристаллов. Приведены характеристики, иллюстрирующие результаты моделировани

Angular Forces Around Transition Metals in Biomolecules

Quantum-mechanical analysis based on an exact sum rule is used to extract an semiclassical angle-dependent energy function for transition metal ions in biomolecules. The angular dependence is simple but different from existing classical potentials. Comparison of predicted energies with a computer-generated database shows that the semiclassical energy function is remarkably accurate, and that its angular dependence is optimal.Comment: Tex file plus 4 postscript figure