R2D2 - a symmetric measurement of reactor neutrinos free of systematical errors

We discuss a symmetric setup for a reactor neutrino oscillation experiment consisting of two reactors separated by about 1 km, and two symmetrically placed detectors, one close to each reactor. We show that such a configuration allows a determination of $\sin^22\theta_{13}$ which is essentially free of systematical errors, if it is possible to separate the contributions of the two reactors in each detector sufficiently. This can be achieved either by considering data when in an alternating way only one reactor is running or by directional sensitivity obtained from the neutron displacement in the detector.Comment: 11 pages, 3 figures, clarifications added, some numbers in relation with the neutron displacement corrected, version to appear in JHE

Boundary-Layer Instability Measurements in a Mach-6 Quiet Tunnel

Several experiments have been performed in the Boeing/AFOSR Mach-6 Quiet Tunnel at Purdue University. A 7 degree half angle cone at 6 degree angle of attack with temperature-sensitive paint (TSP) and PCB pressure transducers was tested under quiet flow. The stationary crossflow vortices appear to break down to turbulence near the lee ray for sufficiently high Reynolds numbers. Attempts to use roughness elements to control the spacing of hot streaks on a flared cone in quiet flow did not succeed. Roughness was observed to damp the second-mode waves in areas influenced by the roughness, and wide roughness spacing allowed hot streaks to form between the roughness elements. A forward-facing cavity was used for proof-of-concept studies for a laser perturber. The lowest density at which the freestream laser perturbations could be detected was 1.07 x 10(exp -2) kilograms per cubic meter. Experiments were conducted to determine the transition characteristics of a streamwise corner flow at hypersonic velocities. Quiet flow resulted in a delayed onset of hot streak spreading. Under low Reynolds number flow hot streak spreading did not occur along the model. A new shock tube has been built at Purdue. The shock tube is designed to create weak shocks suitable for calibrating sensors, particularly PCB-132 sensors. PCB-132 measurements in another shock tube show the shock response and a linear calibration over a moderate pressure range

Automatic Hotspots Detection for Intracellular Calcium Analysis in Fluorescence Microscopic Videos

In recent years, life-cell imaging techniques and their software applications have become powerful tools to investigate complex biological mechanisms such as calcium signalling. In this paper, we propose an automated framework to detect areas inside cells that show changes in their calcium concentration i.e. the regions of interests or hotspots, based on videos taken after loading living mouse cardiomyocytes with fluorescent calcium reporter dyes. The proposed system allows an objective and efficient analysis through the following four key stages: (1) Pre-processing to enhance video quality, (2) First level segmentation to detect candidate hotspots based on adaptive thresholding on the frame level, (3) Second-level segmentation to fuse and identify the best hotspots from the entire video by proposing the concept of calcium fluorescence hit-ratio, and (4) Extraction of the changes of calcium fluorescence over time per hotspot. From the extracted signals, different measurements are calculated such as maximum peak amplitude, area under the curve, peak frequency, and inter-spike interval of calcium changes. The system was tested using calcium imaging data collected from Heart muscle cells. The paper argues that the automated proposal offers biologists a tool to speed up the processing time and mitigate the consequences of inter-intra observer variability

Autonomous Bursting in a Homoclinic System

A continuous train of irregularly spaced spikes, peculiar of homoclinic chaos, transforms into clusters of regularly spaced spikes, with quiescent periods in between (bursting regime), by feeding back a low frequency portion of the dynamical output. Such autonomous bursting results to be extremely robust against noise; we provide experimental evidence of it in a CO2 laser with feedback. The phenomen here presented display qualitative analogies with bursting phenomena in neurons.Comment: Submitted to Phys. Rev. Lett., 14 pages, 5 figure

P2Y1 and P2Y12 receptor cross-talk in calcium signalling: Evidence from nonstarved and long-term serum-deprived glioma C6 cells

The current work presents results of experiments on the calcium response evoked by the stimulation by extracellular nucleotides occurring in control, nonstarved glioma C6 cells and in cells after long-term (96 h) serum starvation. Three nucleotide receptors were studied: P2Y1, P2Y2 and P2Y12. Two of them, P2Y1 and P2Y2, directly stimulate calcium response. The protein level of the P2Y2 receptor did not change during the serum starvation, while P2Y1 protein level fell dramatically. Observed changes in the calcium response generated by P2Y1 are directly correlated with the receptor protein level as well as with the amount of calcium present in the intracellular calcium stores, partially depleted during starvation process. The third receptor, P2Y12, did not directly evoke calcium response, however it is activated by the same ligand as P2Y1. The experiments with AR-C69941MX, the P2Y12-specific antagonist, indicated that in control and serum-starved cells, calcium response evoked by P2Y1 receptor is potentiated by the activity of P2Y12-dependent signaling pathways. This potentiation may be mediated by P2Y12 inhibitory effect on the plasma membrane calcium pump. The calcium influx enhanced by the cooperation of P2Y1 and P2Y12 receptor activity directly depends on the capacitative calcium entrance mechanism

A multiscale hybrid model for pro-angiogenic calcium signals in a vascular endothelial cell

Cytosolic calcium machinery is one of the principal signaling mechanisms by which endothelial cells (ECs) respond to external stimuli during several biological processes, including vascular progression in both physiological and pathological conditions. Low concentrations of angiogenic factors (such as VEGF) activate in fact complex pathways involving, among others, second messengers arachidonic acid (AA) and nitric oxide (NO), which in turn control the activity of plasma membrane calcium channels. The subsequent increase in the intracellular level of the ion regulates fundamental biophysical properties of ECs (such as elasticity, intrinsic motility, and chemical strength), enhancing their migratory capacity. Previously, a number of continuous models have represented cytosolic calcium dynamics, while EC migration in angiogenesis has been separately approached with discrete, lattice-based techniques. These two components are here integrated and interfaced to provide a multiscale and hybrid Cellular Potts Model (CPM), where the phenomenology of a motile EC is realistically mediated by its calcium-dependent subcellular events. The model, based on a realistic 3-D cell morphology with a nuclear and a cytosolic region, is set with known biochemical and electrophysiological data. In particular, the resulting simulations are able to reproduce and describe the polarization process, typical of stimulated vascular cells, in various experimental conditions.Moreover, by analyzing the mutual interactions between multilevel biochemical and biomechanical aspects, our study investigates ways to inhibit cell migration: such strategies have in fact the potential to result in pharmacological interventions useful to disrupt malignant vascular progressio

An air-stable DPP-thieno-TTF copolymer for single-material solar cell devices and field effect transistors

Following an approach developed in our group to incorporate tetrathiafulvalene (TTF) units into conjugated polymeric systems, we have studied a low band gap polymer incorporating TTF as a donor component. This polymer is based on a fused thieno-TTF unit that enables the direct incorporation of the TTF unit into the polymer, and a second comonomer based on the diketopyrrolopyrrole (DPP) molecule. These units represent a donor–acceptor copolymer system, p(DPP-TTF), showing strong absorption in the UV–visible region of the spectrum. An optimized p(DPP-TTF) polymer organic field effect transistor and a single material organic solar cell device showed excellent performance with a hole mobility of up to 5.3 × 10–2 cm2/(V s) and a power conversion efficiency (PCE) of 0.3%, respectively. Bulk heterojunction organic photovoltaic devices of p(DPP-TTF) blended with phenyl-C71-butyric acid methyl ester (PC71BM) exhibited a PCE of 1.8%

Disentangling astroglial physiology with a realistic cell model in silico

Electrically non-excitable astroglia take up neurotransmitters, buffer extracellular K+ and generate Ca2+ signals that release molecular regulators of neural circuitry. The underlying machinery remains enigmatic, mainly because the sponge-like astrocyte morphology has been difficult to access experimentally or explore theoretically. Here, we systematically incorporate multi-scale, tri-dimensional astroglial architecture into a realistic multi-compartmental cell model, which we constrain by empirical tests and integrate into the NEURON computational biophysical environment. This approach is implemented as a flexible astrocyte-model builder ASTRO. As a proof-of-concept, we explore an in silico astrocyte to evaluate basic cell physiology features inaccessible experimentally. Our simulations suggest that currents generated by glutamate transporters or K+ channels have negligible distant effects on membrane voltage and that individual astrocytes can successfully handle extracellular K+ hotspots. We show how intracellular Ca2+ buffers affect Ca2+ waves and why the classical Ca2+ sparks-and-puffs mechanism is theoretically compatible with common readouts of astroglial Ca2+ imaging

Measurement of Receptor-Activated Phosphoinositide Turnover in Rat Brain: Nonequivalence of Inositol Phosphate and CDP-Diacylglycerol Formation

Two methods for the measurement of receptor-activated phosphoinositide turnover were evaluated for their degree of correspondence in slices of rat brain; they involved the Li + -dependent accumulations of either [ 3 H]-inositol-labeled inositol phosphates or [ 3 H]cytidine-labeled CDP-diacylglycerol. In contrast to the expectation that the ratio of these two responses would remain approximately constant, varying degrees of correspondence were obtained. The two extremes are exemplified by carbachol, which elicited large increases in both inositol phosphate and CDP-diacylglycerol labeling, and endothelin, which gave a robust inositol phosphate response with little or no accumulation of 3 H-CDP-diacylglycerol. No instance of the presence of the latter response in the absence of 3 H-inositol phosphate accumulation was observed. Measurement of 3 H-CDP-diacylglycerol accumulation thus may add additional insight into the regulation of phosphoinositide turnover and the complex actions of Li + .Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66135/1/j.1471-4159.1993.tb03258.x.pd

Sweet taste pleasantness is modulated by morphine and naltrexone

Rodent models highlight the key role of µ-opioid receptor (MOR) signaling in palatable food consumption. In humans however, the effects of MOR stimulation on eating and food liking remain unclear. In a bidirectional psychopharmacological cross-over study, 49 healthy men underwent a sweet taste paradigm following double-blind administration of the MOR agonist morphine, placebo, and the opioid antagonist nalt rexone. We hypothesized that behaviors regulated by the endogenous MOR system would be enhanced by MOR agonism, and decreased by antagonism. The strongest drug effects were expected for the sweetest (high-calorie) sucrose solution, as reported in rodents. However, very sweet sucrose-water solutions are considered sickly and aversive by many people (called sweet dislikers). Since both sweet likers and dislikers were tested, we were able to assess whether MOR manipulations affect pleasantness ratings differently depending on both subjective and objective value. As hypothesized, MOR stimulation with morphine increased pleasantness of the sweetest of five sucrose solutions, without enhancing pleasantness of the lower-sucrose solutions. For opioid antagonism, an opposite pattern was observed for the sweetest drink only. This bidirectional effect of agonist and antagonist treatment is consistent with rodent findings that MOR manipulations most strongly affect the highest-calorie foods. Importantly, the observed drug effects on pleasantness of the sweetest drink did not differ between sweet likers and dislikers. We speculate that the MOR system promotes survival in part by increasing concordance between the objective (caloric) and subjective (hedonic) value of food stimuli, so that feeding behaviour becomes more focused on the richest food available