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Spatial Profile (spatial + profile)
Selected AbstractsFast Reciprocating Probe Assembly for the KSTARCONTRIBUTIONS TO PLASMA PHYSICS, Issue 5-6 2006J. G. Bak Abstract A fast reciprocating probe assembly (FRPA) that can scan a distance of up to 32.5 cm with a maximum speed of 1.7 m/s was fabricated to obtain the spatial profile of basic plasma parameters in the edge region of the KSTAR plasma during a plasma discharge of 20 s. The probe driving mechanism consists of two parts; first a slow movement driven by a servo motor system and then a fast reciprocating movement actuated by a pneumatic system. A performance test of the drive system, which is remotely controlled by a PC, was carried out. The prototype of the probe head for the KSTAR FRPA was fabricated as a modular type for easy replacement. It was installed in the fast injection probe assembly (FIPA) in the Hanbit magnetic mirror device, and a radial plasma parameter profile measurement was carried out. The performance test results of the drive system and the profile measurements using the probe head are presented. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Noncontact measurement of deep tissue absorption coefficient using Spatially Resolved Near-Infrared SpectroscopyIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 4 2007Masatsugu Niwayama Member Abstract We examined the influence of probe-tissue distance on the relationship between the deep tissue absorption coefficient and the spatial profile of light intensity by Monte Carlo simulation and in vivo experiments, using noncontact spatially resolved near-infrared spectroscopy (SRS). These results suggest that noncontact SRS can be reliably used for noncontact measurement of the absorption coefficient and oxygen saturation of deep tissues. © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] The estimation of the Sunyaev,Zel'dovich effects with unbiased multifiltersMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2005D. Herranz ABSTRACT In this work we study the performance of linear multifilters for the estimation of the amplitudes of the thermal and kinematic Sunyaev,Zel'dovich (SZ) effects. We show that when both effects are present, estimation of these effects with standard matched multifilters is intrinsically biased. This bias is due to the fact that both signals have basically the same spatial profile. We find a new family of multifilters related to the matched multifilters that cancel this systematic bias, hence we call them unbiased matched multifilters. We test the unbiased matched multifilters and compare them with the standard matched multifilters using simulations that reproduce the future Planck mission observations. We find that in the case of the standard matched multifilters the systematic bias in the estimation of the kinematic Sunyaev,Zel'dovich effect can be very large, even greater than the statistical error bars. Unbiased matched multifilters cancel this kind of bias effectively. In concordance with other works in the literature, our results indicate that the sensitivity and resolution of Planck will not be enough to give reliable estimations of the kinematic Sunyaev,Zel'dovich effects of individual clusters. However, as the estimation with the unbiased matched multifilters is not intrinsically biased, it can be possible to use them to study statistically any peculiar cosmological bulk flows via the kinematic SZ effect. [source] Cellular patterns in the inner retina of adult zebrafish: Quantitative analyses and a computational model of their formationTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 1 2004David A. Cameron Abstract The mechanisms that control cellular pattern formation in the growing vertebrate central nervous system are poorly understood. In an effort to reveal mechanistic rules of cellular pattern formation in the central nervous system, quantitative spatial analysis and computational modeling techniques were applied to cellular patterns in the inner retina of the adult zebrafish. All the analyzed cell types were arrayed in nonrandom patterns tending toward regularity; specifically, they were locally anticlustered. Over relatively large spatial scales, only one cell type exhibited consistent evidence for pattern regularity, suggesting that cellular pattern formation in the inner retina is dominated by local anticlustering mechanisms. Cross-correlation analyses revealed independence between the patterns of different cell types, suggesting that cellular pattern formation may involve multiple, independent, homotypic anticlustering mechanisms. A computational model of cellular pattern formation in the growing zebrafish retina was developed, which featured an inhibitory, homotypic signaling mechanism, arising from differentiated cells, that controlled the spatial profile of cell fate decisions. By adjusting the spatial profile of this decaying-exponential signal, the model provided good estimates of all the cellular patterns that were observed in vivo, as objectively judged by quantitative spatial pattern analyses. The results support the hypothesis that cellular pattern formation in the inner retina of zebrafish is dominated by a set of anticlustering mechanisms that may control events at, or near, the spatiotemporal point of cell fate decision. J. Comp. Neurol. 471:11,25, 2004. © 2004 Wiley-Liss, Inc. [source] Ca2+ microdomains near plasma membrane Ca2+ channels: impact on cell functionTHE JOURNAL OF PHYSIOLOGY, Issue 13 2008Anant B. Parekh In eukaryotic cells, a rise in cytoplasmic Ca2+ can activate a plethora of responses that operate on time scales ranging from milliseconds to days. Inherent to the use of a promiscuous signal like Ca2+ is the problem of specificity: how can Ca2+ activate some responses but not others? We now know that the spatial profile of the Ca2+ signal is important Ca2+ does not simply rise uniformly throughout the cytoplasm upon stimulation but can reach very high levels locally, creating spatial gradients. The most fundamental local Ca2+ signal is the Ca2+ microdomain that develops rapidly near open plasmalemmal Ca2+ channels like voltage-gated L-type (Cav1.2) and store-operated CRAC channels. Recent work has revealed that Ca2+ microdomains arising from these channels are remarkably versatile in triggering a range of responses that differ enormously in both temporal and spatial profile. Here, I delineate basic features of Ca2+ microdomains and then describe how these highly local signals are used by Ca2+ -permeable channels to drive cellular responses. [source] A mathematical model of the impact of infused targeted cytotoxic agents on brain tumours: implications for detection, design and deliveryCELL PROLIFERATION, Issue 6 2002Lawrence M. Wein Motivated by the recent development of highly specific agents for brain tumours, we develop a mathematical model of the spatio-temporal dynamics of a brain tumour that receives an infusion of a highly specific cytotoxic agent (e.g. IL-4-PE, a cytotoxin comprised of IL-4 and a mutated form of Pseudomonas exotoxin). We derive an approximate but accurate mathematical formula for the tumour cure probability in terms of the tumour characteristics (size at time of detection, proliferation rate, diffusion coefficient), drug design (killing rate, loss rate and convection constants for tumour and tissue), and drug delivery (infusion rate, infusion duration). Our results suggest that high specificity is necessary but not sufficient to cure malignant gliomas; a nondispersed spatial profile of pretreatment tumour cells and/or good drug penetration are also required. The most important levers to improve tumour cure appear to be earlier detection, higher infusion rate, lower drug clearance rate and better convection into tumour, but not tissue. In contrast, the tumour cure probability is less sensitive to a longer infusion duration and enhancements in drug potency and drug specificity. [source] Temporal and spatial profiles of cell loss after spinal cord injury: Reduction by a metalloporphyrinJOURNAL OF NEUROSCIENCE RESEARCH, Issue 10 2007Xiang Ling Abstract This study presents quantitative temporal and spatial profiles of neuronal loss and apoptosis following a contusion spinal cord injury (50 g · cm). The profiles were evaluated by counting the cresol violet,stained surviving cells and the total number of TUNEL-positive cells and of TUNEL-positive neurons in sections 0, 4 mm from the epicenter and 1, 6, 12, 24, 48, and 72 hr and 1 week postinjury. We demonstrated that neurons continue to disappear over 1 week postinjury and that neuronal loss shifts to areas longer distances from the epicenter over time. TUNEL-positive cells in both gray and white matter appeared after 6 hr, gradually increased to a peak level after 48 hr, and declined by 72 hr postinjury. TUNEL-positive neurons peaked earlier and were present for 1 week, although the total number of neurons was reduced significantly by the end of the week. The neuronal loss and apoptosis were partially prevented by a metalloporphyrin [Mn(III) tetrakis (4-benzoic acid) porphyrin (MnTBAP)]. We demonstrated that MnTBAP (10 and 50 mg/kg, given intraperitoneally) significantly reduced neuronal death in the sections 1,2.5 mm rostral and 1 mm caudal from the epicenter compared with that in the vehicle-treated group, suggesting MnTBAP is more effective in the sections rostral than in those caudal to the epicenter. MnTBAP (10 mg/kg) significantly reduced the number of TUNEL-positive neurons in the sections 1 mm caudal from the epicenter. Our profiles provide a database for pharmacological intervention, and our results on MnTBAP treatment support an important role for antioxidant therapy in spinal cord injury. © 2007 Wiley-Liss, Inc. [source] A new desktop instrument for measuring macular pigment optical density based on a novel technique for setting flicker thresholdsOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 2 2009Rob L. P. Van Der Veen Abstract A rapid portable technique for estimating macular pigment optical density (MPOD) in large populations is described. The new instrument utilises a novel method for setting flicker thresholds which is undemanding for naïve and elderly observers and easily operated by a non-technical person. The method has good repeatability (r = 0.97) and the data are comparable with an optical method based on retinal reflectometry (r = 0.78). MPOD spatial profiles are presented for seven normal observers and these are well described (r = 0.99) by a decaying exponential function consistent with previous reports. MPOD values are presented from 5581 (2435 females and 3146 males) individuals measured in 48 optometric practices. The mean MPOD of this population was 0.33 (S.D. ± 0.187) which is similar to previous large scale studies of MP. [source] Light emission from different ZnO junctions and nanostructuresPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2009M. Willander Abstract We will discuss our experimental results for optical spectra produced by hole-injection from different p-type organic and inorganic materials into n-type ZnO nanowires. The influence of different growth techniques and conditions on the nanowires and their emission spectral characteristics will then be analyzed and discussed. The latest findings on the mixture of the green emission band responsible for visible light emission from ZnO and the blue light emission from the organic polymer will be presented. Different high brightness light emitting diodes (HB-LEDs) from our grown ZnO nanowires are demonstrated. The p-type multi layer organic structures contain PEDOT:PSS as hole injectors combined with a hole transporting layer, and in some structures, a final top electron blocking/hole barrier stepping layer is placed. The purpose of this layer is to adjust the hole and electron emission from the corresponding junction side to optimize the LED performance. Structural scanning electron microscopy (SEM), electrical (I ,V characteristics), photoluminescence (PL) and electroluminescence (EL) characteristics of these devices are displayed. Theoretically, we study the superfluidity of a two-dimensional system of excitonic polaritons in an optical microcavity with an embedded quantum well. Using the effective low-energy action for thermodynamic phase fluctuations, we obtain an expression for the analogue of the superfluid density in the system in terms of the "current,current" correlation function. The Kosterlits,Thouless transition temperature to the superfluid state as a function of the controlling parameters is calculated. Two methods are considered for producing traps for a polariton system in an optical microcavity. The behaviour of a two-component Bose condensate of photons and excitons is analyzed theoretically for both types of the trap. The Bose condensate is described by the coupled system of equations of the Gross,Pitaevskii type. The approximate wave functions and the spatial profiles of coupled photon and exciton condensates are obtained. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Coherence length and time of excitons in ZnSe quantum wellsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3 2004B. Dal Don Abstract We investigate the in-plane transport of excitons in quantum wells by nano-photoluminescence. The experimental method is based on a confocal microscope with an enhanced resolution given by the introduction of a solid immersion lens. In combination with pulsed laser excitation and streak-camera detection, we have access to transport phenomena on a timescale faster than the time of scattering with acoustic phonons and a length scale of the light wavelength. We use ZnSe-based quantum wells as a model system since hot excitons with well defined excess energy can be formed assisted by the emission of optical phonons. This results e.g. in a periodic quenching of the excitonic transport length as function of excitation excess energy which, in comparison, is not found in GaAs quantum wells. Monte Carlo simulations of the nonlinear expansion of the luminescence spot observed as a function of time reveal the difference between the spatial profiles of the luminescence and the exciton density. The latter shows an oscillatory behaviour in time due to the dominant backscattering, when the first acoustic phonon is emitted. From this oscillation we can determine simultaneously the coherence time and length of the excitonic transport in ZnSe quantum wells. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||