Mechanisms of femtosecond laser-induced refractive index modification of poly(methyl methacrylate)

The mechanisms of refractive index change in poly(methyl methacrylate) by frequency doubled femtosecond laser pulses are investigated. It is demonstrated that positive refractive index modificaton can be caused by a combination of depolymerization and crosslinking

Cerebellum and apraxia

Classical tenits posit that the role of the cerebellum is limited to pure sensorimotor control. However, evidence from clinical and imaging studies shows that the cerebellum is crucially involved in nonmotor cognitive and affective functions. Schmahmann and Sherman (1998) [1] introduced the cerebellar cognitive affective syndrome (CCAS), characterised by executive, visuo-spatial, affective and linguistic impairments caused by cerebellar pathology. Apraxia, as a planning, organisation and execution disorder of a skilled motor action (not caused by motor, sensory or intellectual impairment) [2], may be regarded to form part of the executive cluster of CCAS. Indeed, several anatomoclinical studies have confirmed involvement of the cerebellum in at least some types of apraxia, which adds to the nonmotor role of the cerebellum. According to Hugo Liepmann [3], apraxia is thought to evolve from a disruption of the creation, activation or retrieval of movement formulae. These formulae represent the idea of a movement as a visual or acoustic image and are stored in the left parietal lobe. The left prefrontal area subsequently associates these formulae with an inherently stored innervatory pattern to transfer the information to the left primary motor areas. The corpus callosum transfers this information to the right motor cortex if the movement is to be executed by the left limb [3]. Based on some recent clinical evidence we hypothesize that the cerebellum forms an intrinsic part of this connectionist model of Liepmann

Secretory vesicles are preferentially targeted to areas of low molecular SNARE density

Intercellular communication is commonly mediated by the regulated fusion, or exocytosis, of vesicles with the cell surface. SNARE (soluble N-ethymaleimide sensitive factor attachment protein receptor) proteins are the catalytic core of the secretory machinery, driving vesicle and plasma membrane merger. Plasma membrane SNAREs (tSNAREs) are proposed to reside in dense clusters containing many molecules, thus providing a concentrated reservoir to promote membrane fusion. However, biophysical experiments suggest that a small number of SNAREs are sufficient to drive a single fusion event. Here we show, using molecular imaging, that the majority of tSNARE molecules are spatially separated from secretory vesicles. Furthermore, the motilities of the individual tSNAREs are constrained in membrane micro-domains, maintaining a non-random molecular distribution and limiting the maximum number of molecules encountered by secretory vesicles. Together our results provide a new model for the molecular mechanism of regulated exocytosis and demonstrate the exquisite organization of the plasma membrane at the level of individual molecular machines

High-Performance, Wearable Thermoelectric Generator Based on a Highly Aligned Carbon Nanotube Sheet

A high-performance, wearable thermoelectric generator (TEG) was fabricated with a highly aligned carbon nanotube (CNT) sheet. The aligned CNT sheet exhibits extraordinary electrical conductivity compared to disordered CNT sheets and also can be directly fabricated as a continuous TEG without metal electrode interconnects. This provides a significant reduction in contact resistance between TE legs and electrodes compared to traditional TEGs, resulting in higher power output. In addition, the continuity of the module without any disconnected parts provides high degrees of mechanical stability and durability. This robust and scalable approach to flexible TEG fabrication paves the way for CNT applications in lightweight, flexible, and wearable electronics

Nicotinic Acid Adenine Dinucleotide Phosphate Potentiates Neurite Outgrowth

Ca2+ regulates a spectrum of cellular processes including many aspects of neuronal function. Ca2+-sensitive events such as neurite extension and axonal guidance are driven by Ca2+ signals that are precisely organized in both time and space. These complex cues result from both Ca2+ influx across the plasma membrane and the mobilization of intracellular Ca2+ stores. In the present study, using rat cortical neurons, we have examined the effects of the novel intracellular Ca 2+-mobilizing messenger nicotinic acid adenine dinucleotide phosphate (NAADP) on neurite length and cytosolic Ca2+ levels. We show that NAADP potentiates neurite extension in response to serum and nerve growth factor and stimulates increases in cytosolic Ca2+ from bafilomycin- sensitive Ca2+ stores. Simultaneous blockade of inositol trisphosphate and ryanodine receptors abolished the effects of NAADP on neurite length and reduced the magnitude of NAADP-mediated Ca2+ signals. This is the first report demonstrating functional NAADP receptors in a mammalian neuron. Interplay between NAADP receptors and more established intracellular Ca2+ channels may therefore play important signaling roles in the nervous system