Single- and multi-channel underwater acoustic communication channel capacity: a computational study.

PubMed

Hayward, Thomas J; Yang, T C

2007-09-01

Acoustic communication channel capacity determines the maximum data rate that can be supported by an acoustic channel for a given source power and source/receiver configuration. In this paper, broadband acoustic propagation modeling is applied to estimate the channel capacity for a time-invariant shallow-water waveguide for a single source-receiver pair and for vertical source and receiver arrays. Without bandwidth constraints, estimated single-input, single-output (SISO) capacities approach 10 megabitss at 1 km range, but beyond 2 km range they decay at a rate consistent with previous estimates by Peloquin and Leinhos (unpublished, 1997), which were based on a sonar equation calculation. Channel capacities subject to source bandwidth constraints are approximately 30-90% lower than for the unconstrained case, and exhibit a significant wind speed dependence. Channel capacity is investigated for single-input, multi-output (SIMO) and multi-input, multi-output (MIMO) systems, both for finite arrays and in the limit of a dense array spanning the entire water column. The limiting values of the SIMO and MIMO channel capacities for the modeled environment are found to be about four times higher and up to 200-400 times higher, respectively, than for the SISO case. Implications for underwater acoustic communication systems are discussed.

Ramification of Channel Networks Incised by Groundwater Flow

NASA Astrophysics Data System (ADS)

Yi, R. S.; Seybold, H. F.; Petroff, A. P.; Devauchelle, O.; Rothman, D.

2011-12-01

The geometry of channel networks has been a source of fascination since at least Leonardo da Vinci's time. Yet a comprehensive understanding of ramification---the mechanism of branching by which a stream network acquires its geometric complexity---remains elusive. To investigate the mechanisms of ramification and network growth, we consider channel growth driven by groundwater flow as a model system, analogous to a medical scientist's laboratory rat. We test our theoretical predictions through analysis of a particularly compelling example found on the Florida Panhandle north of Bristol. As our ultimate goal is to understand ramification and growth dynamics of the entire network, we build a computational model based on the following growth hypothesis: Channels grow in the direction that captures the maximum water flux. When there are two such directions, tips bifurcate. The direction of growth can be determined from the expansion of the ground water field around each tip, where each coefficient in this expansion has a physical interpretation. The first coefficient in the expansion determines the ground water discharge, leading to a straight growth of the channel. The second term describes the asymmetry in the water field leading to a bending of the stream in the direction of maximal water flux. The ratio between the first and the third coefficient determines a critical distance rc over which the tip feels inhomogeneities in the ground water table. This initiates then the splitting of the tip. In order to test our growth hypothesis and to determine rc, we grow the Florida network backward. At each time step we calculate the solution of the ground water field and determine the appropriate expansion coefficients around each tip. Comparing this simulation result to the predicted values provides us with a stringent measure for rc and the significance of our growth hypothesis.

Controllable Ag nanostructure patterning in a microfluidic channel for real-time SERS systems.

PubMed

Leem, Juyoung; Kang, Hyun Wook; Ko, Seung Hwan; Sung, Hyung Jin

2014-03-07

We present a microfluidic patterning system for fabricating nanostructured Ag thin films via a polyol method. The fabricated Ag thin films can be used immediately in a real-time SERS sensing system. The Ag thin films are formed on the inner surfaces of a microfluidic channel so that a Ag-patterned Si wafer and a Ag-patterned PDMS channel are produced by the fabrication. The optimum sensing region and fabrication duration for effective SERS detection were determined. As SERS active substrates, the patterned Ag thin films exhibit an enhancement factor (EF) of 4.25 × 10(10). The Ag-patterned polymer channel was attached to a glass substrate and used as a microfluidic sensing system for the real-time monitoring of biomolecule concentrations. This microfluidic patterning system provides a low-cost process for the fabrication of materials that are useful in medical and pharmaceutical detection and can be employed in mass production.

Theoretical and experimental studies of turbo product code with time diversity in free space optical communication.

PubMed

Han, Yaoqiang; Dang, Anhong; Ren, Yongxiong; Tang, Junxiong; Guo, Hong

2010-12-20

In free space optical communication (FSOC) systems, channel fading caused by atmospheric turbulence degrades the system performance seriously. However, channel coding combined with diversity techniques can be exploited to mitigate channel fading. In this paper, based on the experimental study of the channel fading effects, we propose to use turbo product code (TPC) as the channel coding scheme, which features good resistance to burst errors and no error floor. However, only channel coding cannot cope with burst errors caused by channel fading, interleaving is also used. We investigate the efficiency of interleaving for different interleaving depths, and then the optimum interleaving depth for TPC is also determined. Finally, an experimental study of TPC with interleaving is demonstrated, and we show that TPC with interleaving can significantly mitigate channel fading in FSOC systems.

CAN LARGE TIME DELAYS OBSERVED IN LIGHT CURVES OF CORONAL LOOPS BE EXPLAINED IN IMPULSIVE HEATING?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lionello, Roberto; Linker, Jon A.; Mikić, Zoran

The light curves of solar coronal loops often peak first in channels associated with higher temperatures and then in those associated with lower temperatures. The delay times between the different narrowband EUV channels have been measured for many individual loops and recently for every pixel of an active region observation. The time delays between channels for an active region exhibit a wide range of values. The maximum time delay in each channel pair can be quite large, i.e., >5000 s. These large time delays make-up 3%–26% (depending on the channel pair) of the pixels where a trustworthy, positive time delaymore » is measured. It has been suggested that these time delays can be explained by simple impulsive heating, i.e., a short burst of energy that heats the plasma to a high temperature, after which the plasma is allowed to cool through radiation and conduction back to its original state. In this paper, we investigate whether the largest observed time delays can be explained by this hypothesis by simulating a series of coronal loops with different heating rates, loop lengths, abundances, and geometries to determine the range of expected time delays between a set of four EUV channels. We find that impulsive heating cannot address the largest time delays observed in two of the channel pairs and that the majority of the large time delays can only be explained by long, expanding loops with photospheric abundances. Additional observations may rule out these simulations as an explanation for the long time delays. We suggest that either the time delays found in this manner may not be representative of real loop evolution, or that the impulsive heating and cooling scenario may be too simple to explain the observations, and other potential heating scenarios must be explored.« less

Gating by Cyclic Gmp and Voltage in the α Subunit of the Cyclic Gmp–Gated Channel from Rod Photoreceptors

PubMed Central

Benndorf, Klaus; Koopmann, Rolf; Eismann, Elisabeth; Kaupp, U. Benjamin

1999-01-01

Gating by cGMP and voltage of the α subunit of the cGMP-gated channel from rod photoreceptor was examined with a patch-clamp technique. The channels were expressed in Xenopus oocytes. At low [cGMP] (<20 μM), the current displayed strong outward rectification. At low and high (700 μM) [cGMP], the channel activity was dominated by only one conductance level. Therefore, the outward rectification at low [cGMP] results solely from an increase in the open probability, P o. Kinetic analysis of single-channel openings revealed two exponential distributions. At low [cGMP], the larger P o at positive voltages with respect to negative voltages is caused by an increased frequency of openings in both components of the open-time distribution. In macroscopic currents, depolarizing voltage steps, starting from −100 mV, generated a time-dependent current that increased with the step size (activation). At low [cGMP] (20 μM), the degree of activation was large and the time course was slow, whereas at saturating [cGMP] (7 mM) the respective changes were small and fast. The dose–response relation at −100 mV was shifted to the right and saturated at significantly lower P o values with respect to that at +100 mV (0.77 vs. 0.96). P o was determined as function of the [cGMP] (at +100 and −100 mV) and voltage (at 20, 70, and 700 μM, and 7 mM cGMP). Both relations could be fitted with an allosteric state model consisting of four independent cGMP-binding reactions and one voltage-dependent allosteric opening reaction. At saturating [cGMP] (7 mM), the activation time course was monoexponential, which allowed us to determine the individual rate constants for the allosteric reaction. For the rapid rate constants of cGMP binding and unbinding, lower limits are determined. It is concluded that an allosteric model consisting of four independent cGMP-binding reactions and one voltage-dependent allosteric reaction, describes the cGMP- and voltage-dependent gating of cGMP-gated channels adequately. PMID:10498668

Quantum Yield of Single Surface Plasmons Generated by a Quantum Dot Coupled with a Silver Nanowire.

PubMed

Li, Qiang; Wei, Hong; Xu, Hongxing

2015-12-09

The interactions between surface plasmons (SPs) in metal nanostructures and excitons in quantum emitters (QEs) lead to many interesting phenomena and potential applications that are strongly dependent on the quantum yield of SPs. The difficulty in distinguishing all the possible exciton recombination channels hinders the experimental determination of SP quantum yield. Here, we experimentally measured for the first time the quantum yield of single SPs generated by the exciton-plasmon coupling in a system composed of a single quantum dot and a silver nanowire (NW). By utilizing the SP guiding property of the NW, the decay rates of all the exciton recombination channels, i.e., direct free space radiation channel, SP generation channel, and nonradiative damping channel, are quantitatively obtained. It is determined that the optimum emitter-NW coupling distance for the largest SP quantum yield is about 10 nm, resulting from the different distance-dependent decay rates of the three channels. These results are important for manipulating the coupling between plasmonic nanostructures and QEs and developing on-chip quantum plasmonic devices for potential nanophotonic and quantum information applications.

Clearance of yellow pigments lutein and zeathanxin in channel catfish reared at different water temperatures

USDA-ARS?s Scientific Manuscript database

A study was conducted to determine clearance time of yellow pigments lutein and zeaxanthin in channel catfish at various temperatures. Fish of initial weight of 13.4 g were stocked into flow-through aquaria and fed once daily with a yellow pigment enhanced diet for 11 weeks when the yellow color be...

Method and apparatus for characterizing propagation delays of integrated circuit devices

NASA Technical Reports Server (NTRS)

Blaes, Brent R. (Inventor); Buehler, Martin G. (Inventor)

1987-01-01

Propagation delay of a signal through a channel is measured by cyclically generating a first step-wave signal for transmission through the channel to a two-input logic element and a second step-wave signal with a controlled delay to the second input terminal of the logic element. The logic element determines which signal is present first at its input terminals and stores a binary signal indicative of that determination for control of the delay of the second signal which is advanced or retarded for the next cycle until both the propagation delayed first step-wave signal and the control delayed step-wave signal are coincident. The propagation delay of the channel is then determined by measuring the time between the first and second step-wave signals out of the controlled step-wave signal generator.

Rapid water transportation through narrow one-dimensional channels by restricted hydrogen bonds.

PubMed

Ohba, Tomonori; Kaneko, Katsumi; Endo, Morinobu; Hata, Kenji; Kanoh, Hirofumi

2013-01-29

Water plays an important role in controlling chemical reactions and bioactivities. For example, water transportation through water channels in a biomembrane is a key factor in bioactivities. However, molecular-level mechanisms of water transportation are as yet unknown. Here, we investigate water transportation through narrow and wide one-dimensional (1D) channels on the basis of water-vapor adsorption rates and those determined by molecular dynamics simulations. We observed that water in narrow 1D channels was transported 3-5 times faster than that in wide 1D channels, although the narrow 1D channels provide fewer free nanospaces for water transportation. This rapid transportation is attributed to the formation of fewer hydrogen bonds between water molecules adsorbed in narrow 1D channels. The water-transportation mechanism provides the possibility of rapid communication through 1D channels and will be useful in controlling reactions and activities in water systems.

Quantum channels from reflections on moving mirrors.

PubMed

Gianfelici, Giulio; Mancini, Stefano

2017-11-16

Light reflection on a mirror can be thought as a simple physical effect. However if this happens when the mirror moves a rich scenario opens up. Here we aim at analyzing it from a quantum communication perspective. In particular, we study the kind of quantum channel that arises from (Gaussian) light reflection upon an accelerating mirror. Two competing mechanisms emerge in such a context, namely photons production by the mirror's motion and interference between modes. As consequence we find out a quantum amplifier channel and quantum lossy channel respectively below and above a threshold frequency (that depends on parameters determining mirror's acceleration). Exactly at the threshold frequency the channel behaves like a purely classical additive channel, while it becomes purely erasure for large frequencies. In addition the time behavior of the channel is analyzed by employing wave packets expansion of the light field.

Like/dislike analysis using EEG: determination of most discriminative channels and frequencies.

PubMed

Yılmaz, Bülent; Korkmaz, Sümeyye; Arslan, Dilek Betül; Güngör, Evrim; Asyalı, Musa H

2014-02-01

In this study, we have analyzed electroencephalography (EEG) signals to investigate the following issues, (i) which frequencies and EEG channels could be relatively better indicators of preference (like or dislike decisions) of consumer products, (ii) timing characteristic of "like" decisions during such mental processes. For this purpose, we have obtained multichannel EEG recordings from 15 subjects, during total of 16 epochs of 10 s long, while they were presented with some shoe photographs. When they liked a specific shoe, they pressed on a button and marked the time of this activity and the particular epoch was labeled as a LIKE case. No button press meant that the subject did not like the particular shoe that was displayed and corresponding epoch designated as a DISLIKE case. After preprocessing, power spectral density (PSD) of EEG data was estimated at different frequencies (4, 5, …, 40 Hz) using the Burg method, for each epoch corresponding to one shoe presentation. Each subject's data consisted of normalized PSD values (NPVs) from all LIKE and DISLIKE cases/epochs coming from all 19 EEG channels. In order to determine the most discriminative frequencies and channels, we have utilized logistic regression, where LIKE/DISLIKE status was used as a categorical (binary) response variable and corresponding NPVs were the continuously valued input variables or predictors. We observed that when all the NPVs (total of 37) are used as predictors, the regression problem was becoming ill-posed due to large number of predictors (compared to the number of samples) and high correlation among predictors. To circumvent this issue, we have divided the frequency band into low frequency (LF) 4-19 Hz and high frequency (HF) 20-40 Hz bands and analyzed the influence of the NPV in these bands separately. Then, using the p-values that indicate how significantly estimated predictor weights are different than zero, we have determined the NPVs and channels that are more influential in determining the outcome, i.e., like/dislike decision. In the LF band, 4 and 5 Hz were found to be the most discriminative frequencies (MDFs). In the HF band, none of the frequencies seemed offer significant information. When both male and female data was used, in the LF band, a frontal channel on the left (F7-A1) and a temporal channel on the right (T6-A2) were found to be the most discriminative channels (MDCs). In the HF band, MDCs were central (Cz-A1) and occipital on the left (O1-A1) channels. The results of like timings suggest that male and female behavior for this set of stimulant images were similar. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Results of gamma activity traverses made in process tube channels and VSR channels at 105-KW

DOE Office of Scientific and Technical Information (OSTI.GOV)

Greene, M.C. Jr.

1955-02-03

Activity traverses were made at Hanford reactor 105-KW in VSR channels 23, 29, 37, 46, 55, 63 and 69 and in process channels 4669, 4569, 4668, 4670 and 4769. These traverses were made during cleaning operations to assist in the location of any contaminated material in these channels and again after completion of the cleaning operations to determine if all of the contaminated material was removed. Upon completion of the cleaning of the VSR channels and process channels activity traverses were made in all of the channels. The results of these traverses show that no detectable amounts of contaminated materialmore » were present in any of these channels. The traverses made in the VSR channels all show a large peak in the lower part of the pile indicating that the metal in the lower part of the pile received as much as five times the integrated exposure received by the metal in the upper half of the pile. 15 figs.« less

Extracting Cell Stiffness from Real-Time Deformability Cytometry: Theory and Experiment.

PubMed

Mietke, Alexander; Otto, Oliver; Girardo, Salvatore; Rosendahl, Philipp; Taubenberger, Anna; Golfier, Stefan; Ulbricht, Elke; Aland, Sebastian; Guck, Jochen; Fischer-Friedrich, Elisabeth

2015-11-17

Cell stiffness is a sensitive indicator of physiological and pathological changes in cells, with many potential applications in biology and medicine. A new method, real-time deformability cytometry, probes cell stiffness at high throughput by exposing cells to a shear flow in a microfluidic channel, allowing for mechanical phenotyping based on single-cell deformability. However, observed deformations of cells in the channel not only are determined by cell stiffness, but also depend on cell size relative to channel size. Here, we disentangle mutual contributions of cell size and cell stiffness to cell deformation by a theoretical analysis in terms of hydrodynamics and linear elasticity theory. Performing real-time deformability cytometry experiments on both model spheres of known elasticity and biological cells, we demonstrate that our analytical model not only predicts deformed shapes inside the channel but also allows for quantification of cell mechanical parameters. Thereby, fast and quantitative mechanical sampling of large cell populations becomes feasible. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

Extracting Cell Stiffness from Real-Time Deformability Cytometry: Theory and Experiment

PubMed Central

Mietke, Alexander; Otto, Oliver; Girardo, Salvatore; Rosendahl, Philipp; Taubenberger, Anna; Golfier, Stefan; Ulbricht, Elke; Aland, Sebastian; Guck, Jochen; Fischer-Friedrich, Elisabeth

2015-01-01

Cell stiffness is a sensitive indicator of physiological and pathological changes in cells, with many potential applications in biology and medicine. A new method, real-time deformability cytometry, probes cell stiffness at high throughput by exposing cells to a shear flow in a microfluidic channel, allowing for mechanical phenotyping based on single-cell deformability. However, observed deformations of cells in the channel not only are determined by cell stiffness, but also depend on cell size relative to channel size. Here, we disentangle mutual contributions of cell size and cell stiffness to cell deformation by a theoretical analysis in terms of hydrodynamics and linear elasticity theory. Performing real-time deformability cytometry experiments on both model spheres of known elasticity and biological cells, we demonstrate that our analytical model not only predicts deformed shapes inside the channel but also allows for quantification of cell mechanical parameters. Thereby, fast and quantitative mechanical sampling of large cell populations becomes feasible. PMID:26588562

Infinite capacity multi-server queue with second optional service channel

NASA Astrophysics Data System (ADS)

Ke, Jau-Chuan; Wu, Chia-Huang; Pearn, Wen Lea

2013-02-01

This paper deals with an infinite-capacity multi-server queueing system with a second optional service (SOS) channel. The inter-arrival times of arriving customers, the service times of the first essential service (FES) and the SOS channel are all exponentially distributed. A customer may leave the system after the FES channel with probability (1-θ), or at the completion of the FES may immediately require a SOS with probability θ (0 <= θ <= 1). The formulae for computing the rate matrix and stationary probabilities are derived by means of a matrix analytical approach. A cost model is developed to determine the optimal values of the number of servers and the two service rates, simultaneously, at the minimal total expected cost per unit time. Quasi-Newton method are employed to deal with the optimization problem. Under optimal operating conditions, numerical results are provided in which several system performance measures are calculated based on assumed numerical values of the system parameters.

Single-channel mixed signal blind source separation algorithm based on multiple ICA processing

NASA Astrophysics Data System (ADS)

Cheng, Xiefeng; Li, Ji

2017-01-01

Take separating the fetal heart sound signal from the mixed signal that get from the electronic stethoscope as the research background, the paper puts forward a single-channel mixed signal blind source separation algorithm based on multiple ICA processing. Firstly, according to the empirical mode decomposition (EMD), the single-channel mixed signal get multiple orthogonal signal components which are processed by ICA. The multiple independent signal components are called independent sub component of the mixed signal. Then by combining with the multiple independent sub component into single-channel mixed signal, the single-channel signal is expanded to multipath signals, which turns the under-determined blind source separation problem into a well-posed blind source separation problem. Further, the estimate signal of source signal is get by doing the ICA processing. Finally, if the separation effect is not very ideal, combined with the last time's separation effect to the single-channel mixed signal, and keep doing the ICA processing for more times until the desired estimated signal of source signal is get. The simulation results show that the algorithm has good separation effect for the single-channel mixed physiological signals.

Combining molecular dynamics and an electrodiffusion model to calculate ion channel conductance

NASA Astrophysics Data System (ADS)

Wilson, Michael A.; Nguyen, Thuy Hien; Pohorille, Andrew

2014-12-01

Establishing the relation between the structures and functions of protein ion channels, which are protein assemblies that facilitate transmembrane ion transport through water-filled pores, is at the forefront of biological and medical sciences. A reliable way to determine whether our understanding of this relation is satisfactory is to reproduce the measured ionic conductance over a broad range of applied voltages. This can be done in molecular dynamics simulations by way of applying an external electric field to the system and counting the number of ions that traverse the channel per unit time. Since this approach is computationally very expensive we develop a markedly more efficient alternative in which molecular dynamics is combined with an electrodiffusion equation. This alternative approach applies if steady-state ion transport through channels can be described with sufficient accuracy by the one-dimensional diffusion equation in the potential given by the free energy profile and applied voltage. The theory refers only to line densities of ions in the channel and, therefore, avoids ambiguities related to determining the surface area of the channel near its endpoints or other procedures connecting the line and bulk ion densities. We apply the theory to a simple, model system based on the trichotoxin channel. We test the assumptions of the electrodiffusion equation, and determine the precision and consistency of the calculated conductance. We demonstrate that it is possible to calculate current/voltage dependence and accurately reconstruct the underlying (equilibrium) free energy profile, all from molecular dynamics simulations at a single voltage. The approach developed here applies to other channels that satisfy the conditions of the electrodiffusion equation.

Spatial and Temporal Varying Thresholds for Cloud Detection in Satellite Imagery

NASA Technical Reports Server (NTRS)

Jedlovec, Gary; Haines, Stephanie

2007-01-01

A new cloud detection technique has been developed and applied to both geostationary and polar orbiting satellite imagery having channels in the thermal infrared and short wave infrared spectral regions. The bispectral composite threshold (BCT) technique uses only the 11 micron and 3.9 micron channels, and composite imagery generated from these channels, in a four-step cloud detection procedure to produce a binary cloud mask at single pixel resolution. A unique aspect of this algorithm is the use of 20-day composites of the 11 micron and the 11 - 3.9 micron channel difference imagery to represent spatially and temporally varying clear-sky thresholds for the bispectral cloud tests. The BCT cloud detection algorithm has been applied to GOES and MODIS data over the continental United States over the last three years with good success. The resulting products have been validated against "truth" datasets (generated by the manual determination of the sky conditions from available satellite imagery) for various seasons from the 2003-2005 periods. The day and night algorithm has been shown to determine the correct sky conditions 80-90% of the time (on average) over land and ocean areas. Only a small variation in algorithm performance occurs between day-night, land-ocean, and between seasons. The algorithm performs least well. during he winter season with only 80% of the sky conditions determined correctly. The algorithm was found to under-determine clouds at night and during times of low sun angle (in geostationary satellite data) and tends to over-determine the presence of clouds during the day, particularly in the summertime. Since the spectral tests use only the short- and long-wave channels common to most multispectral scanners; the application of the BCT technique to a variety of satellite sensors including SEVERI should be straightforward and produce similar performance results.

Modified superposition: A simple time series approach to closed-loop manual controller identification

NASA Technical Reports Server (NTRS)

Biezad, D. J.; Schmidt, D. K.; Leban, F.; Mashiko, S.

1986-01-01

Single-channel pilot manual control output in closed-tracking tasks is modeled in terms of linear discrete transfer functions which are parsimonious and guaranteed stable. The transfer functions are found by applying a modified super-position time series generation technique. A Levinson-Durbin algorithm is used to determine the filter which prewhitens the input and a projective (least squares) fit of pulse response estimates is used to guarantee identified model stability. Results from two case studies are compared to previous findings, where the source of data are relatively short data records, approximately 25 seconds long. Time delay effects and pilot seasonalities are discussed and analyzed. It is concluded that single-channel time series controller modeling is feasible on short records, and that it is important for the analyst to determine a criterion for best time domain fit which allows association of model parameter values, such as pure time delay, with actual physical and physiological constraints. The purpose of the modeling is thus paramount.

Adaptation of a cubic smoothing spline algortihm for multi-channel data stitching at the National Ignition Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, C; Adcock, A; Azevedo, S

2010-12-28

Some diagnostics at the National Ignition Facility (NIF), including the Gamma Reaction History (GRH) diagnostic, require multiple channels of data to achieve the required dynamic range. These channels need to be stitched together into a single time series, and they may have non-uniform and redundant time samples. We chose to apply the popular cubic smoothing spline technique to our stitching problem because we needed a general non-parametric method. We adapted one of the algorithms in the literature, by Hutchinson and deHoog, to our needs. The modified algorithm and the resulting code perform a cubic smoothing spline fit to multiple datamore » channels with redundant time samples and missing data points. The data channels can have different, time-varying, zero-mean white noise characteristics. The method we employ automatically determines an optimal smoothing level by minimizing the Generalized Cross Validation (GCV) score. In order to automatically validate the smoothing level selection, the Weighted Sum-Squared Residual (WSSR) and zero-mean tests are performed on the residuals. Further, confidence intervals, both analytical and Monte Carlo, are also calculated. In this paper, we describe the derivation of our cubic smoothing spline algorithm. We outline the algorithm and test it with simulated and experimental data.« less

Long-Term Stage, Stage-Residual, and Width Data for Streams in the Piedmont Physiographic Region, Georgia

USGS Publications Warehouse

Riley, Jeffrey W.; Jacobson, Robert B.

2009-01-01

This report presents the data used to assess geomorphic adjustment of streams over time and to changing land-use conditions. Thirty-seven U.S. Geological Survey streamgages were selected within the Piedmont physiographic region of Georgia. Width, depth, stage, and discharge data from these streams were analyzed to assess channel stability and determine if systematic adjustments of channel morphology could be related to time or land use and land cover. Residual analyses of stage-discharge data were used to infer channel stability, which could then be used as an indicator of habitat stability. Streamgages, representing a gradient of urbanization, were selected to test hypotheses regarding stream stability and adjustment to urban conditions. Results indicate that 14 sites exhibited long-term channel stability, 11 were degrading, 6 were aggrading, and 6 showed variability in response over the study period.

GPS Integrity Channel RTCA Working Group recommendations

NASA Astrophysics Data System (ADS)

Kalafus, Rudolph M.

Recommendations made by a working group established by the Radio Technical Commission for Aeronautics are presented for the design of a wide-area broadcast service to provide indications on the status of GPS satellites. The integrity channel requirements and operational goals are outlined. Six integrity channel system concepts are considered and system design and time-to-alarm considerations are examined. The recommended system includes the broadcast of a coarse range measurement for each satellite which will enable the on-board GPS receiver to determine whether or not the navigation accuracy is within prescribed limits.

The delayed rectifier potassium conductance in the sarcolemma and the transverse tubular system membranes of mammalian skeletal muscle fibers

PubMed Central

DiFranco, Marino; Quinonez, Marbella

2012-01-01

A two-microelectrode voltage clamp and optical measurements of membrane potential changes at the transverse tubular system (TTS) were used to characterize delayed rectifier K currents (IKV) in murine muscle fibers stained with the potentiometric dye di-8-ANEPPS. In intact fibers, IKV displays the canonical hallmarks of KV channels: voltage-dependent delayed activation and decay in time. The voltage dependence of the peak conductance (gKV) was only accounted for by double Boltzmann fits, suggesting at least two channel contributions to IKV. Osmotically treated fibers showed significant disconnection of the TTS and displayed smaller IKV, but with similar voltage dependence and time decays to intact fibers. This suggests that inactivation may be responsible for most of the decay in IKV records. A two-channel model that faithfully simulates IKV records in osmotically treated fibers comprises a low threshold and steeply voltage-dependent channel (channel A), which contributes ∼31% of gKV, and a more abundant high threshold channel (channel B), with shallower voltage dependence. Significant expression of the IKV1.4 and IKV3.4 channels was demonstrated by immunoblotting. Rectangular depolarizing pulses elicited step-like di-8-ANEPPS transients in intact fibers rendered electrically passive. In contrast, activation of IKV resulted in time- and voltage-dependent attenuations in optical transients that coincided in time with the peaks of IKV records. Normalized peak attenuations showed the same voltage dependence as peak IKV plots. A radial cable model including channels A and B and K diffusion in the TTS was used to simulate IKV and average TTS voltage changes. Model predictions and experimental data were compared to determine what fraction of gKV in the TTS accounted simultaneously for the electrical and optical data. Best predictions suggest that KV channels are approximately equally distributed in the sarcolemma and TTS membranes; under these conditions, >70% of IKV arises from the TTS. PMID:22851675

Physiological Maturation of Regenerating Hair Cells

NASA Technical Reports Server (NTRS)

Baird, Richard A.

2003-01-01

The bullfrog saccule, a sensor of gravity and substrate-borne vibration, is a model system for hair cell transduction. Saccular hair cells also increase in number throughout adult life and rapidly recover after hair cell damage, making this organ an ideal system for studying hair cell development, repair, and regeneration. We have used of hair cell and supporting cell immunocytochemical markers to identify damaged hair cells and hair cell precursors in organotypic cultures of the bullfrog saccule. We then used an innovative combination of confocal, electron, and time-lapse microscopy to study the fate of damaged hair cells and the origin of new hair cells after gentamicin ototoxicity in normal and mitotically blocked saccular cultures. These studies have shown that gentamicin ototoxicity produces both lethal and sublethal hair cell damage. They have also shown that hair cell recovery in this organ takes place by both the repair of sublethally damaged hair cells and by the replacement of lost hair cells by mitotic regeneration. In parallel studies, we have used biophysical and molecular biological techniques to study the differentiation and innervation of developing, repairing, and regenerating hair cells. More specifically, we have used RT-PCR to obtain the bullfrog homologues of L-type voltage- gated calcium (L-VGCC) and large-conductance Ca(2+)-activated potassium (BK) channel genes. We have then obtained probes for these genes and, using in situ hybridization, begun to examine their expression in the bullfrog saccule and amphibian papilla. We have also used fluorescent-labeled channel toxins and channel toxin derivatives to determine the time of appearance of L-type voltage-gated calcium (L-VGCC) and Ca(2+)-activated potassium (BK) channels and to study dynamic changes in the number, distribution, and co-localization of these proteins in developing, repairing, and regenerating hair cells. Using time-lapse microscopy, we are also studying the dynamic relationship between ion channel clustering and synaptic formation in hair cells and afferent neurons. In future studies, we will determine when hair cell precursors acquire electrical tuning, and, using whole-cell patch-clamp techniques, identify and characterize their L-VGCC and BK currents. We will also use biophysical techniques to determine the number of L-VGCC and BK channels and the size and gating kinetics of their underlying L-VGCC and BK conductances, correlating these variables with the amplitude and frequency of membrane oscillations produced by intracellular current steps. We expect these studies to determine how hair cells regulate ion channel expression to achieve specific physiological responses.

Incremental Holocene slip rates from the Hope fault at Hossack Station, Marlborough fault zone, South Island, New Zealand

NASA Astrophysics Data System (ADS)

Hatem, A. E.; Dolan, J. F.; Langridge, R.; Zinke, R. W.; McGuire, C. P.; Rhodes, E. J.; Van Dissen, R. J.

2015-12-01

The Marlborough fault system, which links the Alpine fault with the Hikurangi subduction zone within the complex Australian-Pacific plate boundary zone, partitions strain between the Wairau, Awatere, Clarence and Hope faults. Previous best estimates of dextral strike-slip along the Hope fault are ≤ ~23 mm/yr± 4 mm/year. Those rates, however, are poorly constrained and could be improved using better age determinations in conjunction with measurements of fault offsets using high-resolution imagery. In this study, we use airborne lidar- and field-based mapping together with the subsurface geometry of offset channels at the Hossack site 12 km ESE of Hanmer Springs to more precisely determine stream offsets that were previously identified by McMorran (1991). Specifically, we measured fault offsets of ~10m, ~75 m, and ~195m. Together with 65 radiocarbon ages on charcoal, peat, and wood and 25 pending post-IR50-IRSL225 luminescence ages from the channel deposits, these offsets yield three different fault slip rates for the early Holocene, the late Holocene, and the past ca. 500-1,000 years. Using the large number of age determinations, we document in detail the timing of initiation and abandonment of each channel, enhancing the geomorphic interpretation at the Hossack site as channels deform over many earthquake cycles. Our preliminary incremental slip rate results from the Hossack site may indicate temporally variable strain release along the Hope fault. This study is part of a broader effort aimed at determining incremental slip rates and paleo-earthquake ages and displacements from all four main Marlborough faults. Collectively, these data will allow us to determine how the four main Marlborough faults have work together during Holocene-late Pleistocene to accommodate plate-boundary deformation in time and space.

Electrostatics at the membrane define MscL channel mechanosensitivity and kinetics.

PubMed

Zhong, Dalian; Blount, Paul

2014-12-01

The bacterial mechanosensitive channel of large conductance (MscL) serves as a biological emergency release valve, preventing the occurrence of cell lysis caused by acute osmotic stress. Its tractable nature allows it to serve as a paradigm for how a protein can directly sense membrane tension. Although much is known of the importance of the hydrophobicity of specific residues in channel gating, it has remained unclear whether electrostatics at the membrane plays any role. We studied MscL chimeras derived from functionally distinct orthologues: Escherichia coli and Staphylococcus aureus. Dissection of one set led to an observation that changing the charge of a single residue, K101, of E. coli (Ec)-MscL, effects a channel phenotype: when mutated to a negative residue, the channel is less mechanosensitive and has longer open dwell times. Assuming electrostatic interactions, we determined whether they are due to protein-protein or protein-lipid interactions by performing site-directed mutagenesis elsewhere in the protein and reconstituting channels into defined lipids, with and without negative head groups. We found that although both interactions appear to play some role, the primary determinant of the channel phenotype seems to be protein-lipid electrostatics. The data suggest a model for the role of electrostatic interactions in the dynamics of MscL gating. © FASEB.

Changes in Inward Rectifier K+ Channels in Hepatic Stellate Cells During Primary Culture

PubMed Central

Lee, Dong Hyeon; Kong, In Deok; Lee, Joong-Woo

2008-01-01

Purpose This study examined the expression and function of inward rectifier K+ channels in cultured rat hepatic stellate cells (HSC). Materials and Methods The expression of inward rectifier K+ channels was measured using real-time RT-PCR, and electrophysiological properties were determined using the gramicidin-perforated patch-clamp technique. Results The dominant inward rectifier K+ channel subtypes were Kir2.1 and Kir6.1. These dominant K+ channel subtypes decreased significantly during the primary culture throughout activation process. HSC can be classified into two subgroups: one with an inward-rectifying K+ current (type 1) and the other without (type 2). The inward current was blocked by Ba2+ (100 µM) and enhanced by high K+ (140 mM), more prominently in type 1 HSC. There was a correlation between the amplitude of the Ba2+-sensitive current and the membrane potential. In addition, Ba2+ (300 µM) depolarized the membrane potential. After the culture period, the amplitude of the inward current decreased and the membrane potential became depolarized. Conclusion HSC express inward rectifier K+ channels, which physiologically regulate membrane potential and decrease during the activation process. These results will potentially help determine properties of the inward rectifier K+ channels in HSC as well as their roles in the activation process. PMID:18581597

Markov Chain-Like Quantum Biological Modeling of Mutations, Aging, and Evolution.

PubMed

Djordjevic, Ivan B

2015-08-24

Recent evidence suggests that quantum mechanics is relevant in photosynthesis, magnetoreception, enzymatic catalytic reactions, olfactory reception, photoreception, genetics, electron-transfer in proteins, and evolution; to mention few. In our recent paper published in Life, we have derived the operator-sum representation of a biological channel based on codon basekets, and determined the quantum channel model suitable for study of the quantum biological channel capacity. However, this model is essentially memoryless and it is not able to properly model the propagation of mutation errors in time, the process of aging, and evolution of genetic information through generations. To solve for these problems, we propose novel quantum mechanical models to accurately describe the process of creation spontaneous, induced, and adaptive mutations and their propagation in time. Different biological channel models with memory, proposed in this paper, include: (i) Markovian classical model, (ii) Markovian-like quantum model, and (iii) hybrid quantum-classical model. We then apply these models in a study of aging and evolution of quantum biological channel capacity through generations. We also discuss key differences of these models with respect to a multilevel symmetric channel-based Markovian model and a Kimura model-based Markovian process. These models are quite general and applicable to many open problems in biology, not only biological channel capacity, which is the main focus of the paper. We will show that the famous quantum Master equation approach, commonly used to describe different biological processes, is just the first-order approximation of the proposed quantum Markov chain-like model, when the observation interval tends to zero. One of the important implications of this model is that the aging phenotype becomes determined by different underlying transition probabilities in both programmed and random (damage) Markov chain-like models of aging, which are mutually coupled.

Markov Chain-Like Quantum Biological Modeling of Mutations, Aging, and Evolution

PubMed Central

Djordjevic, Ivan B.

2015-01-01

Recent evidence suggests that quantum mechanics is relevant in photosynthesis, magnetoreception, enzymatic catalytic reactions, olfactory reception, photoreception, genetics, electron-transfer in proteins, and evolution; to mention few. In our recent paper published in Life, we have derived the operator-sum representation of a biological channel based on codon basekets, and determined the quantum channel model suitable for study of the quantum biological channel capacity. However, this model is essentially memoryless and it is not able to properly model the propagation of mutation errors in time, the process of aging, and evolution of genetic information through generations. To solve for these problems, we propose novel quantum mechanical models to accurately describe the process of creation spontaneous, induced, and adaptive mutations and their propagation in time. Different biological channel models with memory, proposed in this paper, include: (i) Markovian classical model, (ii) Markovian-like quantum model, and (iii) hybrid quantum-classical model. We then apply these models in a study of aging and evolution of quantum biological channel capacity through generations. We also discuss key differences of these models with respect to a multilevel symmetric channel-based Markovian model and a Kimura model-based Markovian process. These models are quite general and applicable to many open problems in biology, not only biological channel capacity, which is the main focus of the paper. We will show that the famous quantum Master equation approach, commonly used to describe different biological processes, is just the first-order approximation of the proposed quantum Markov chain-like model, when the observation interval tends to zero. One of the important implications of this model is that the aging phenotype becomes determined by different underlying transition probabilities in both programmed and random (damage) Markov chain-like models of aging, which are mutually coupled. PMID:26305258

Spatially Controlled Relay Beamforming

NASA Astrophysics Data System (ADS)

Kalogerias, Dionysios

This thesis is about fusion of optimal stochastic motion control and physical layer communications. Distributed, networked communication systems, such as relay beamforming networks (e.g., Amplify & Forward (AF)), are typically designed without explicitly considering how the positions of the respective nodes might affect the quality of the communication. Optimum placement of network nodes, which could potentially improve the quality of the communication, is not typically considered. However, in most practical settings in physical layer communications, such as relay beamforming, the Channel State Information (CSI) observed by each node, per channel use, although it might be (modeled as) random, it is both spatially and temporally correlated. It is, therefore, reasonable to ask if and how the performance of the system could be improved by (predictively) controlling the positions of the network nodes (e.g., the relays), based on causal side (CSI) information, and exploitting the spatiotemporal dependencies of the wireless medium. In this work, we address this problem in the context of AF relay beamforming networks. This novel, cyber-physical system approach to relay beamforming is termed as "Spatially Controlled Relay Beamforming". First, we discuss wireless channel modeling, however, in a rigorous, Bayesian framework. Experimentally accurate and, at the same time, technically precise channel modeling is absolutely essential for designing and analyzing spatially controlled communication systems. In this work, we are interested in two distinct spatiotemporal statistical models, for describing the behavior of the log-scale magnitude of the wireless channel: 1. Stationary Gaussian Fields: In this case, the channel is assumed to evolve as a stationary, Gaussian stochastic field in continuous space and discrete time (say, for instance, time slots). Under such assumptions, spatial and temporal statistical interactions are determined by a set of time and space invariant parameters, which completely determine the mean and covariance of the underlying Gaussian measure. This model is relatively simple to describe, and can be sufficiently characterized, at least for our purposes, both statistically and topologically. Additionally, the model is rather versatile and there is existing experimental evidence, supporting its practical applicability. Our contributions are summarized in properly formulating the whole spatiotemporal model in a completely rigorous mathematical setting, under a convenient measure theoretic framework. Such framework greatly facilitates formulation of meaningful stochastic control problems, where the wireless channel field (or a function of it) can be regarded as a stochastic optimization surface.. 2. Conditionally Gaussian Fields, when conditioned on a Markovian channel state: This is a completely novel approach to wireless channel modeling. In this approach, the communication medium is assumed to behave as a partially observable (or hidden) system, where a hidden, global, temporally varying underlying stochastic process, called the channel state, affects the spatial interactions of the actual channel magnitude, evaluated at any set of locations in the plane. More specifically, we assume that, conditioned on the channel state, the wireless channel constitutes an observable, conditionally Gaussian stochastic process. The channel state evolves in time according to a known, possibly non stationary, non Gaussian, low dimensional Markov kernel. Recognizing the intractability of general nonlinear state estimation, we advocate the use of grid based approximate nonlinear filters as an effective and robust means for recursive tracking of the channel state. We also propose a sequential spatiotemporal predictor for tracking the channel gains at any point in time and space, providing real time sequential estimates for the respective channel gain map. In this context, our contributions are multifold. Except for the introduction of the layered channel model previously described, this line of research has resulted in a number of general, asymptotic convergence results, advancing the theory of grid-based approximate nonlinear stochastic filtering. In particular, sufficient conditions, ensuring asymptotic optimality are relaxed, and, at the same time, the mode of convergence is strengthened. Although the need for such results initiated as an attempt to theoretically characterize the performance of the proposed approximate methods for statistical inference, in regard to the proposed channel modeling approach, they turn out to be of fundamental importance in the areas of nonlinear estimation and stochastic control. The experimental validation of the proposed channel model, as well as the related parameter estimation problem, termed as "Markovian Channel Profiling (MCP)", fundamentally important for any practical deployment, are subject of current, ongoing research. Second, adopting the first of the two aforementioned channel modeling approaches, we consider the spatially controlled relay beamforming problem for an AF network with a single source, a single destination, and multiple, controlled at will, relay nodes. (Abstract shortened by ProQuest.).

Characterization of mixing in an electroosmotically stirred continuous micro mixer

NASA Astrophysics Data System (ADS)

Beskok, Ali

2005-11-01

We present theoretical and numerical studies of mixing in a straight micro channel with zeta potential patterned surfaces. A steady pressure driven flow is maintained in the channel in addition to a time dependent electroosmotic flow, generated by a stream-wise AC electric field. The zeta potential patterns are placed critically in the channel to achieve spatially asymmetric time-dependent flow patterns that lead to chaotic stirring. Fixing the geometry, we performed parametric studies of passive particle motion that led to generation of Poincare sections and characterization of chaotic strength by finite time Lyapunov exponents. The parametric studies were performed as a function of the Womersley number (normalized AC frequency) and the ratio of Poiseuille flow and electroosmotic velocities. After determining the non-dimensional parameters that led to high chaotic strength, we performed spectral element simulations of species transport and mixing at high Peclet numbers, and characterized mixing efficiency using the Mixing Index inverse. Mixing lengths proportional to the natural logarithm of the Peclet number are reported. Using the optimum non-dimensional parameters and the typical magnitudes involved in electroosmotic flows, we were able to determine the physical dimensions and operation conditions for a prototype micro-mixer.

Growth and Filling Regularities of Filamentary Channels in Non-Metallic Inorganic Coatings Under Anodic Oxidation of Valve Metals. Mathematical Modeling

NASA Astrophysics Data System (ADS)

Mamaev, A. I.; Mamaeva, V. A.; Kolenchin, N. F.; Chubenko, A. K.; Kovalskaya, Ya. B.; Dolgova, Yu. N.; Beletskaya, E. Yu.

2015-12-01

Theoretical models are developed for growth and filling processes in filamentary channels of nanostructured non-metallic coatings produced by anodizing and microplasma oxidation. Graphical concentration distributions are obtained for channel-reacting anions, cations, and sparingly soluble reaction products depending on the time of electric current transmission and the length of the filamentary channel. Graphical distributions of the front moving velocity for the sparingly soluble compound are presented. The resulting model representation increases the understanding of the anodic process nature and can be used for a description and prediction of porous anodic film growth and filling. It is shown that the character of the filamentary channel growth and filling causes a variety of processes determining the textured metal - nonmetallic inorganic coating phase boundary formation.

Structural implications of weak Ca2+ block in Drosophila cyclic nucleotide–gated channels

PubMed Central

Lam, Yee Ling; Zeng, Weizhong; Derebe, Mehabaw Getahun

2015-01-01

Calcium permeability and the concomitant calcium block of monovalent ion current (“Ca2+ block”) are properties of cyclic nucleotide–gated (CNG) channel fundamental to visual and olfactory signal transduction. Although most CNG channels bear a conserved glutamate residue crucial for Ca2+ block, the degree of block displayed by different CNG channels varies greatly. For instance, the Drosophila melanogaster CNG channel shows only weak Ca2+ block despite the presence of this glutamate. We previously constructed a series of chimeric channels in which we replaced the selectivity filter of the bacterial nonselective cation channel NaK with a set of CNG channel filter sequences and determined that the resulting NaK2CNG chimeras displayed the ion selectivity and Ca2+ block properties of the parent CNG channels. Here, we used the same strategy to determine the structural basis of the weak Ca2+ block observed in the Drosophila CNG channel. The selectivity filter of the Drosophila CNG channel is similar to that of most other CNG channels except that it has a threonine at residue 318 instead of a proline. We constructed a NaK chimera, which we called NaK2CNG-Dm, which contained the Drosophila selectivity filter sequence. The high resolution structure of NaK2CNG-Dm revealed a filter structure different from those of NaK and all other previously investigated NaK2CNG chimeric channels. Consistent with this structural difference, functional studies of the NaK2CNG-Dm chimeric channel demonstrated a loss of Ca2+ block compared with other NaK2CNG chimeras. Moreover, mutating the corresponding threonine (T318) to proline in Drosophila CNG channels increased Ca2+ block by 16 times. These results imply that a simple replacement of a threonine for a proline in Drosophila CNG channels has likely given rise to a distinct selectivity filter conformation that results in weak Ca2+ block. PMID:26283200

Structural implications of weak Ca2+ block in Drosophila cyclic nucleotide-gated channels.

PubMed

Lam, Yee Ling; Zeng, Weizhong; Derebe, Mehabaw Getahun; Jiang, Youxing

2015-09-01

Calcium permeability and the concomitant calcium block of monovalent ion current ("Ca(2+) block") are properties of cyclic nucleotide-gated (CNG) channel fundamental to visual and olfactory signal transduction. Although most CNG channels bear a conserved glutamate residue crucial for Ca(2+) block, the degree of block displayed by different CNG channels varies greatly. For instance, the Drosophila melanogaster CNG channel shows only weak Ca(2+) block despite the presence of this glutamate. We previously constructed a series of chimeric channels in which we replaced the selectivity filter of the bacterial nonselective cation channel NaK with a set of CNG channel filter sequences and determined that the resulting NaK2CNG chimeras displayed the ion selectivity and Ca(2+) block properties of the parent CNG channels. Here, we used the same strategy to determine the structural basis of the weak Ca(2+) block observed in the Drosophila CNG channel. The selectivity filter of the Drosophila CNG channel is similar to that of most other CNG channels except that it has a threonine at residue 318 instead of a proline. We constructed a NaK chimera, which we called NaK2CNG-Dm, which contained the Drosophila selectivity filter sequence. The high resolution structure of NaK2CNG-Dm revealed a filter structure different from those of NaK and all other previously investigated NaK2CNG chimeric channels. Consistent with this structural difference, functional studies of the NaK2CNG-Dm chimeric channel demonstrated a loss of Ca(2+) block compared with other NaK2CNG chimeras. Moreover, mutating the corresponding threonine (T318) to proline in Drosophila CNG channels increased Ca(2+) block by 16 times. These results imply that a simple replacement of a threonine for a proline in Drosophila CNG channels has likely given rise to a distinct selectivity filter conformation that results in weak Ca(2+) block. © 2015 Lam et al.

A content analysis of advertisements related to oral health in children's Tamil television channels--a preliminary report.

PubMed

Sukumaran, Aparna; Diwakar, Madankumar P; Shastry, Shivakumar M

2012-05-01

This study was conducted to examine the nature, content, and duration of advertisements broadcasted during children's Tamil television channels and to determine the extent to which television advertising changes during school holiday and non-holiday periods and between prime time and non-prime time broadcast. Television broadcasts on two main children's Tamil television channels were video-recorded over 16 days between 17.00-19.00 hours (non-prime time) and 19.00-21.00 hours (prime time). For each commercial, the type of product advertised, as well as the duration (in seconds), was recorded. Advertisements were categorized as 'food' and 'non-food'. The former category was further subdivided into 'sugar-rich foods' and 'other foods'. The sugar-rich foods were further categorized as liquid, solid and sticky, and slowly dissolving sugars. Commercials related to the promotion of oral health products and non-food products were also recorded. Among the total of 128 h of television programmes recorded, advertising accounted for 10.15% (13.01 hours). The advertisement of sugar-rich food products, non-food and oral hygiene products occupied 50.36%, 38.41% and 1.90%, respectively, of the total advertising time. Solid and sticky products made up 100% of advertisements in this category on Chithiram television channel, compared with 62.5% of advertisements on Chutti television channel. It was concluded that the advertising of sugar-rich foods, particularly solid and sticky food products, was broadcasted more in Chithiram television channel, during school holidays and during prime time. © 2011 The Authors. International Journal of Paediatric Dentistry © 2011 BSPD, IAPD and Blackwell Publishing Ltd.

Life-threatening false alarm rejection in ICU: using the rule-based and multi-channel information fusion method.

PubMed

Liu, Chengyu; Zhao, Lina; Tang, Hong; Li, Qiao; Wei, Shoushui; Li, Jianqing

2016-08-01

False alarm (FA) rates as high as 86% have been reported in intensive care unit monitors. High FA rates decrease quality of care by slowing staff response times while increasing patient burdens and stresses. In this study, we proposed a rule-based and multi-channel information fusion method for accurately classifying the true or false alarms for five life-threatening arrhythmias: asystole (ASY), extreme bradycardia (EBR), extreme tachycardia (ETC), ventricular tachycardia (VTA) and ventricular flutter/fibrillation (VFB). The proposed method consisted of five steps: (1) signal pre-processing, (2) feature detection and validation, (3) true/false alarm determination for each channel, (4) 'real-time' true/false alarm determination and (5) 'retrospective' true/false alarm determination (if needed). Up to four signal channels, that is, two electrocardiogram signals, one arterial blood pressure and/or one photoplethysmogram signal were included in the analysis. Two events were set for the method validation: event 1 for 'real-time' and event 2 for 'retrospective' alarm classification. The results showed that 100% true positive ratio (i.e. sensitivity) on the training set were obtained for ASY, EBR, ETC and VFB types, and 94% for VTA type, accompanied by the corresponding true negative ratio (i.e. specificity) results of 93%, 81%, 78%, 85% and 50% respectively, resulting in the score values of 96.50, 90.70, 88.89, 92.31 and 64.90, as well as with a final score of 80.57 for event 1 and 79.12 for event 2. For the test set, the proposed method obtained the score of 88.73 for ASY, 77.78 for EBR, 89.92 for ETC, 67.74 for VFB and 61.04 for VTA types, with the final score of 71.68 for event 1 and 75.91 for event 2.

Upgrades and Real Time Ntm Control Application of the Ece Radiometer on Asdex Upgrade

NASA Astrophysics Data System (ADS)

Hicks, N. K.; Suttrop, W.; Behler, K.; Giannone, L.; Manini, A.; Maraschek, M.; Raupp, G.; Reich, M.; Sips, A. C. C.; Stober, J.; Treutterer, W.; ASDEX Upgrade Team; Cirant, S.

2009-04-01

The 60-channel electron cyclotron emission (ECE) radiometer diagnostic on the ASDEX Upgrade tokamak is presently being upgraded to include a 1 MHz sampling rate data acquisition system. This expanded capability allows electron temperature measurements up to 500 kHz (anti-aliasing filter cut-off) with spatial resolution ~1 cm, and will thus provide measurement of plasma phenomena on the MHD timescale, such as neoclassical tearing modes (NTMs). The upgraded and existing systems may be run in parallel for comparison, and some of the first plasma measurements using the two systems together are presented. A particular planned application of the upgraded radiometer is integration into a real-time NTM stabilization loop using targeted deposition of electron cyclotron resonance heating (ECRH). For this loop, it is necessary to determine the locations of the NTM and ECRH deposition using ECE measurements. As the magnetic island of the NTM repeatedly rotates through the ECE line of sight, electron temperature fluctuations at the NTM frequency are observed. The magnetic perturbation caused by the NTM is independently measured using Mirnov coils, and a correlation profile between these magnetic measurements and the ECE data is constructed. The phase difference between ECE oscillations on opposite sides of the island manifests as a zero-crossing of the correlation profile, which determines the NTM location in ECE channel space. To determine the location of ECRH power deposition, the power from a given gyrotron may be modulated at a particular frequency. Correlation analysis of this modulated signal and the ECE data identifies a particular ECE channel associated with the deposition of that gyrotron. Real time equilibrium reconstruction allows the ECE channels to be translated into flux surface and spatial coordinates for use in the feedback loop.

Brownian Dynamics simulations of model colloids in channel geometries and external fields

NASA Astrophysics Data System (ADS)

Siems, Ullrich; Nielaba, Peter

2018-04-01

We review the results of Brownian Dynamics simulations of colloidal particles in external fields confined in channels. Super-paramagnetic Brownian particles are well suited two- dimensional model systems for a variety of problems on different length scales, ranging from pedestrian walking through a bottleneck to ions passing ion-channels in living cells. In such systems confinement into channels can have a great influence on the diffusion and transport properties. Especially we will discuss the crossover from single file diffusion in a narrow channel to the diffusion in the extended two-dimensional system. Therefore a new algorithm for computing the mean square displacement (MSD) on logarithmic time scales is presented. In a different study interacting colloidal particles were dragged over a washboard potential and are additionally confined in a two-dimensional micro-channel. In this system kink and anti-kink solitons determine the depinning process of the particles from the periodic potential.

Transient electroosmotic flow induced by AC electric field in micro-channel with patchwise surface heterogeneities.

PubMed

Luo, Win-Jet

2006-03-15

This paper investigates two-dimensional, time-dependent electroosmotic flow driven by an AC electric field via patchwise surface heterogeneities distributed along the micro-channel walls. The time-dependent flow fields through the micro-channel are simulated for various patchwise heterogeneous surface patterns using the backwards-Euler time stepping numerical method. Different heterogeneous surface patterns are found to create significantly different electrokinetic transport phenomena. The transient behavior characteristics of the generated electroosmotic flow are then discussed in terms of the influence of the patchwise surface heterogeneities, the direction of the applied AC electric field, and the velocity of the bulk flow. It is shown that the presence of oppositely charged surface heterogeneities on the micro-channel walls results in the formation of localized flow circulations within the bulk flow. These circulation regions grow and decay periodically in phase with the applied periodic AC electric field intensity. The location and rotational direction of the induced circulations are determined by the directions of the bulk flow velocity and the applied electric field.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bradler, Kamil; Hayden, Patrick; Touchette, Dave

Coding theorems in quantum Shannon theory express the ultimate rates at which a sender can transmit information over a noisy quantum channel. More often than not, the known formulas expressing these transmission rates are intractable, requiring an optimization over an infinite number of uses of the channel. Researchers have rarely found quantum channels with a tractable classical or quantum capacity, but when such a finding occurs, it demonstrates a complete understanding of that channel's capabilities for transmitting classical or quantum information. Here we show that the three-dimensional capacity region for entanglement-assisted transmission of classical and quantum information is tractable formore » the Hadamard class of channels. Examples of Hadamard channels include generalized dephasing channels, cloning channels, and the Unruh channel. The generalized dephasing channels and the cloning channels are natural processes that occur in quantum systems through the loss of quantum coherence or stimulated emission, respectively. The Unruh channel is a noisy process that occurs in relativistic quantum information theory as a result of the Unruh effect and bears a strong relationship to the cloning channels. We give exact formulas for the entanglement-assisted classical and quantum communication capacity regions of these channels. The coding strategy for each of these examples is superior to a naieve time-sharing strategy, and we introduce a measure to determine this improvement.« less

Identification of the pH sensor and activation by chemical modification of the ClC-2G Cl- channel.

PubMed

Stroffekova, K; Kupert, E Y; Malinowska, D H; Cuppoletti, J

1998-10-01

Rabbit and human ClC-2G Cl- channels are voltage sensitive and activated by protein kinase A and low extracellular pH. The objective of the present study was to investigate the mechanism involved in acid activation of the ClC-2G Cl- channel and to determine which amino acid residues play a role in this acid activation. Channel open probability (Po) at +/-80 mV holding potentials increased fourfold in a concentration-dependent manner with extracellular H+ concentration (that is, extracellular pH, pHtrans), with an apparent acidic dissociation constant of pH 4.95 +/- 0.27. 1-Ethyl-3(3-dimethylaminopropyl)carbodiimide-catalyzed amidation of the channel with glycine methyl ester increased Po threefold at pHtrans 7.4, at which the channel normally exhibits low Po. With extracellular pH reduction (protonation) or amidation, increased Po was due to a significant increase in open time constants and a significant decrease in closed time constants of the channel gating, and this effect was insensitive to applied voltage. With the use of site-directed mutagenesis, the extracellular region EELE (amino acids 416-419) was identified as the pH sensor and amino acid Glu-419 was found to play the key or predominant role in activation of the ClC-2G Cl- channel by extracellular acid.

FIBER AND INTEGRATED OPTICS: Detection of the optical anisotropy in KTP:Rb waveguides

NASA Astrophysics Data System (ADS)

Buritskiĭ, K. S.; Dianov, Evgenii M.; Maslov, Vladislav A.; Chernykh, V. A.; Shcherbakov, E. A.

1990-10-01

The optical characteristics of channel waveguides made of rubidium-activated potassium titanyl phosphate (KTP:Rb) were determined. The refractive index increment of such waveguides was found to exhibit a considerable anisotropy: Δnx / Δnz approx 2. A deviation of the distribution of the refractive index in a channel waveguide from the model distribution was observed for ion-exchange times in excess of 1 h.

Maximizing Ion Transmission from Atmospheric Pressure into the Vacuum of Mass Spectrometers with a Novel Electrospray Interface

PubMed Central

Krutchinsky, Andrew N.; Padovan, Júlio C.; Cohen, Herbert; Chait, Brian T.

2015-01-01

We have discovered that an electrode containing a conical channel with a small angular divergence can transmit into the vacuum almost 100% of an electrospray ion current produced at atmospheric pressure. Our first implementation of such a conical duct, which we term “ConDuct”, uses a conductive plastic pipette tip containing a ≈1.6° divergent channel at its entrance. We observed that the beam formed by the ConDuct electrode has a very low divergence (< 1°) and persisted for long distances in vacuum. Intrigued by these properties, we incorporated this electrode into a novel atmosphere-to-vacuum ion transmission interface, and devised a technique for evaluating its performance relative to commercial reference interfaces that contain heated metal capillaries. We determined that our new interface transmits at least 400 times more ions than the commercial Thermo LCQ DECA XP atmosphere-to-vacuum interface and 2–3 times more than the commercial interface in the Thermo Velos Orbitrap and the Q Exactive mass spectrometers. We conclude that it might be possible to optimize the properties of the transmitted ions further by manufacturing ConDuct inlet electrodes from metal rather than conductive plastic and by determining the optimum angle of channel divergence and channel length. PMID:25588722

Calcium dynamics regulating the timing of decision-making in C. elegans.

PubMed

Tanimoto, Yuki; Yamazoe-Umemoto, Akiko; Fujita, Kosuke; Kawazoe, Yuya; Miyanishi, Yosuke; Yamazaki, Shuhei J; Fei, Xianfeng; Busch, Karl Emanuel; Gengyo-Ando, Keiko; Nakai, Junichi; Iino, Yuichi; Iwasaki, Yuishi; Hashimoto, Koichi; Kimura, Koutarou D

2017-05-23

Brains regulate behavioral responses with distinct timings. Here we investigate the cellular and molecular mechanisms underlying the timing of decision-making during olfactory navigation in Caenorhabditis elegans . We find that, based on subtle changes in odor concentrations, the animals appear to choose the appropriate migratory direction from multiple trials as a form of behavioral decision-making. Through optophysiological, mathematical and genetic analyses of neural activity under virtual odor gradients, we further find that odor concentration information is temporally integrated for a decision by a gradual increase in intracellular calcium concentration ([Ca 2+ ] i ), which occurs via L-type voltage-gated calcium channels in a pair of olfactory neurons. In contrast, for a reflex-like behavioral response, [Ca 2+ ] i rapidly increases via multiple types of calcium channels in a pair of nociceptive neurons. Thus, the timing of neuronal responses is determined by cell type-dependent involvement of calcium channels, which may serve as a cellular basis for decision-making.

Single-File Escape of Colloidal Particles from Microfluidic Channels

NASA Astrophysics Data System (ADS)

Locatelli, Emanuele; Pierno, Matteo; Baldovin, Fulvio; Orlandini, Enzo; Tan, Yizhou; Pagliara, Stefano

2016-07-01

Single-file diffusion is a ubiquitous physical process exploited by living and synthetic systems to exchange molecules with their environment. It is paramount to quantify the escape time needed for single files of particles to exit from constraining synthetic channels and biological pores. This quantity depends on complex cooperative effects, whose predominance can only be established through a strict comparison between theory and experiments. By using colloidal particles, optical manipulation, microfluidics, digital microscopy, and theoretical analysis we uncover the self-similar character of the escape process and provide closed-formula evaluations of the escape time. We find that the escape time scales inversely with the diffusion coefficient of the last particle to leave the channel. Importantly, we find that at the investigated microscale, bias forces as tiny as 10-15 N determine the magnitude of the escape time by drastically reducing interparticle collisions. Our findings provide crucial guidelines to optimize the design of micro- and nanodevices for a variety of applications including drug delivery, particle filtering, and transport in geometrical constrictions.

Calcium dynamics regulating the timing of decision-making in C. elegans

PubMed Central

Tanimoto, Yuki; Yamazoe-Umemoto, Akiko; Fujita, Kosuke; Kawazoe, Yuya; Miyanishi, Yosuke; Yamazaki, Shuhei J; Fei, Xianfeng; Busch, Karl Emanuel; Gengyo-Ando, Keiko; Nakai, Junichi; Iino, Yuichi; Iwasaki, Yuishi; Hashimoto, Koichi; Kimura, Koutarou D

2017-01-01

Brains regulate behavioral responses with distinct timings. Here we investigate the cellular and molecular mechanisms underlying the timing of decision-making during olfactory navigation in Caenorhabditis elegans. We find that, based on subtle changes in odor concentrations, the animals appear to choose the appropriate migratory direction from multiple trials as a form of behavioral decision-making. Through optophysiological, mathematical and genetic analyses of neural activity under virtual odor gradients, we further find that odor concentration information is temporally integrated for a decision by a gradual increase in intracellular calcium concentration ([Ca2+]i), which occurs via L-type voltage-gated calcium channels in a pair of olfactory neurons. In contrast, for a reflex-like behavioral response, [Ca2+]i rapidly increases via multiple types of calcium channels in a pair of nociceptive neurons. Thus, the timing of neuronal responses is determined by cell type-dependent involvement of calcium channels, which may serve as a cellular basis for decision-making. DOI: http://dx.doi.org/10.7554/eLife.21629.001 PMID:28532547

Measuring kinetics of complex single ion channel data using mean-variance histograms.

PubMed

Patlak, J B

1993-07-01

The measurement of single ion channel kinetics is difficult when those channels exhibit subconductance events. When the kinetics are fast, and when the current magnitudes are small, as is the case for Na+, Ca2+, and some K+ channels, these difficulties can lead to serious errors in the estimation of channel kinetics. I present here a method, based on the construction and analysis of mean-variance histograms, that can overcome these problems. A mean-variance histogram is constructed by calculating the mean current and the current variance within a brief "window" (a set of N consecutive data samples) superimposed on the digitized raw channel data. Systematic movement of this window over the data produces large numbers of mean-variance pairs which can be assembled into a two-dimensional histogram. Defined current levels (open, closed, or sublevel) appear in such plots as low variance regions. The total number of events in such low variance regions is estimated by curve fitting and plotted as a function of window width. This function decreases with the same time constants as the original dwell time probability distribution for each of the regions. The method can therefore be used: 1) to present a qualitative summary of the single channel data from which the signal-to-noise ratio, open channel noise, steadiness of the baseline, and number of conductance levels can be quickly determined; 2) to quantify the dwell time distribution in each of the levels exhibited. In this paper I present the analysis of a Na+ channel recording that had a number of complexities. The signal-to-noise ratio was only about 8 for the main open state, open channel noise, and fast flickers to other states were present, as were a substantial number of subconductance states. "Standard" half-amplitude threshold analysis of these data produce open and closed time histograms that were well fitted by the sum of two exponentials, but with apparently erroneous time constants, whereas the mean-variance histogram technique provided a more credible analysis of the open, closed, and subconductance times for the patch. I also show that the method produces accurate results on simulated data in a wide variety of conditions, whereas the half-amplitude method, when applied to complex simulated data shows the same errors as were apparent in the real data. The utility and the limitations of this new method are discussed.

Trace analysis of glyphosate in water by capillary electrophoresis on a chip with high sample volume loadability.

PubMed

Horčičiak, Michal; Masár, Marián; Bodor, Róbert; Danč, Ladislav; Bel, Peter

2012-03-01

A new method for the determination of trace glyphosate (GLYP), non-selective pesticide, by CZE with online ITP pre-treatment of drinking waters on a column-coupling (CC) chip has been developed. CC chip was equipped with two injection channels of 0.9 and 9.9 μL volumes, two separation channels of 9.3 μL total volume and a pair of conductivity detectors. A very effective ITP sample clean-up performed in the first channel at low pH (3.2) was introduced for quick CZE resolution and detection of GLYP carried out at higher pH (6.1) in the second channel on the CC chip. The LOD for GLYP was estimated at 2.5 μg/L (15 nmol/L) using a 9.9 |mL volume of the injection channel. ITP-CZE analyses of model and real samples have provided very favorable intra-day (0.1-1.2% RSD) and inter-day (2.9% RSD) repeatabilities of the migration time for GLYP while 0.2-6.9% RSD values were typical for the peak area data. Recoveries of GLYP in spiked drinking water varied in the range of 99-109%. A minimum pre-treatment of drinking water (degassing and dilution) and a short analysis time (ca. 10 min) were distinctive features of ITP-CZE determinations of GLYP on the CC chip with high sample volume loaded, as well. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Turbidite pathways in Cascadia Basin and Tufts abyssal plain, Part A, Astoria Channel, Blanco Valley, and Gorda Basin

USGS Publications Warehouse

Wolf, Stephen C.; Hamer, Michael R.

1999-01-01

This open-file report was prepared in support of the USGS Earthquake Hazards of Cascadia Project. The primary objective of this phase of the project is to determine recurrence intervals of turbidites in Cascadia basin-floor channel systems and evaluate implications of this event record for the paleoseismic history of the Cascadia subduction zone. The purpose of this study is to determine whether the canyon/channel systems themselves are blocked or deformed in such a way that the downstream turbidite stratigraphy might be biased. To accomplish this investigation approximately 7500 kilometers of pre-existing 3.5 KHz seismic data were evaluated to determine the direction and extent of the Astoria Channel/pathway system, which originates at the base of the Astoria Fan. Additionally, distribution and thickness of turbidite sediment sequences were determined along each identified pathway. Bathymetery and distance were used to determine gradients along the main pathway axis and for each of the secondary pathways that feed into it. Channel pathways were identified on the basis of channel phyisiography, where visible at the seafloor, subbottom channel configuration, and acoustic packets of sediments that might represent turbidite deposits. A principal result of this study is that the Astoria Channel/pathway extends continuously from the base of the Astoria Fan southward along the base of the continental slope through the Blanco Valley, then heads southwestward through the Gorda Basin and into the region of the Escanaba Trough. Additionally it was determined that the Astoria Channel is filled and basically buried for it's full length south of 44 degrees latitude. The 44 North Slump, as defined by Goldfinger (1999, see Map 3 ref.), may have been instrumental in blocking the pathway and thus contributed to the filling of the channel/pathway. Sheets 1 and 2 show the Astoria and secondary turbidite pathways highlighted in blue. Ship survey tracklines are shown for the area studied; they are time and date coded, and color keyed to each ship ID data base listed at the bottom of each sheet. The first letter in the cruise ID is an abbreviation letter for the ship name, the following numbers represent the consecutive cruise number of that year, followed by the year number. The letters at the end of the ID represent the survey area, ie. NC- northern California, NP- north Pacific. Locations of selected sample seismic sections illustrated on sheets 3-5 also are shown. Scales for each of the sheets are the same as for sheets 3-5, which allows for overlaying of track data onto the interpretations shown on Maps A-C. Sheets 3 (MAP A), 4 (MAP B), and 5 (MAP C) show channel pathway location, bathymetric depth based on the USGS COW data base (Ca/Or/Wa), pathway morphology, and thickness of turbidite sediment fill at various locations. The interpreted turbidite sediments are color highlighted on the selected seismic sections to differentiate them from the typical deep sea sediments below and to the side of the turbidite pathways. Thickness of sediment fill, in meters, is shown along major pathways in white circular highlights. The data and interpretations rest on a background of USGS GLORIA side scan sonar imagery (1984) to illustrate the relationship of pathway position to sub sea features. Channel distance points are plotted along channel centerlines at 20,000 m intervals. These points begin at the start of each interpreted channel pathway. A bathymetric depth was assigned to each distance point. These data points were then used to construct channel gradient curves for the Astoria, Eel, Bear Valley, and Mendocino channel pathways. These gradients are plotted on sheet 6 of this report and illustrate the similarities and differences between each of the pathways. Sheet 7 shows various views of the Mendocino/Mattole Canyon heads as an example of useful derivative information of the Seabeam bathymetric data. These views illustrate that the Mendocino pathway probably was directed from it's canyon mouth, to the northwest at an earlier time, but was diverted to the west along the base of the Mendocino Ridge by a major fault event in the recent past. Offset of the southwest channel wall is readily evident in views B and D. This apparent disruption complicates the turbidite history of the Mendocino pathway.

Stability of parallel electroosmotic flow subject to an axial modulated electric field

NASA Astrophysics Data System (ADS)

Suresh, Vinod; Homsy, George

2001-11-01

The stability of parallel electroosmotic flow in a micro-channel subjected to an AC electric field is studied. A spatially uniform time harmonic electric field is applied along the length of a two-dimensional micro-channel containing a dilute electrolytic solution, resulting in a time periodic parallel flow. The top and bottom walls of the channel are maintained at constant potential. The base state ion concentrations and double layer potential are determined using the Poisson-Boltzmann equation in the Debye-Hückel approximation. Experiments by other workers (Santiago et. al., unpublished) have shown that such a system can exhibit instabilities that take the form of mixing motion occurring in the bulk flow outside the double layer. It is shown that such instabilities can potentially result from the coupling of disturbances in the ion concentrations or electric potential to the base state velocity or ion concentrations, respectively. The stability boundary of the system is determined using Floquet theory and its dependence on the modulation frequency and amplitude of the axial electric field is studied.

Nanoscale distribution of presynaptic Ca(2+) channels and its impact on vesicular release during development.

PubMed

Nakamura, Yukihiro; Harada, Harumi; Kamasawa, Naomi; Matsui, Ko; Rothman, Jason S; Shigemoto, Ryuichi; Silver, R Angus; DiGregorio, David A; Takahashi, Tomoyuki

2015-01-07

Synaptic efficacy and precision are influenced by the coupling of voltage-gated Ca(2+) channels (VGCCs) to vesicles. But because the topography of VGCCs and their proximity to vesicles is unknown, a quantitative understanding of the determinants of vesicular release at nanometer scale is lacking. To investigate this, we combined freeze-fracture replica immunogold labeling of Cav2.1 channels, local [Ca(2+)] imaging, and patch pipette perfusion of EGTA at the calyx of Held. Between postnatal day 7 and 21, VGCCs formed variable sized clusters and vesicular release became less sensitive to EGTA, whereas fixed Ca(2+) buffer properties remained constant. Experimentally constrained reaction-diffusion simulations suggest that Ca(2+) sensors for vesicular release are located at the perimeter of VGCC clusters (<30 nm) and predict that VGCC number per cluster determines vesicular release probability without altering release time course. This "perimeter release model" provides a unifying framework accounting for developmental changes in both synaptic efficacy and time course. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

Numerical studies of the polymer melt flow in the extruder screw channel and the forming tool

NASA Astrophysics Data System (ADS)

Ershov, S. V.; Trufanova, N. M.

2017-06-01

To date, polymer compositions based on polyethylene or PVC is widely used as insulating materials. These materials processing conjugate with a number of problems during selection of the rational extrusion regimes. To minimize the time and cost when determining the technological regime uses mathematical modeling techniques. The paper discusses heat and mass transfer processes in the extruder screw channel, output adapter and the cable head. During the study were determined coefficients for three rheological models based on obtained viscosity vs. shear rate experimental data. Also a comparative analysis of this viscosimetric laws application possibility for studying polymer melt flow during its processing on the extrusion equipment was held. As a result of numerical study the temperature, viscosity and shear rate fields in the extruder screw channel and forming tool were obtained.

Landscape assessment of side channel plugs and associated cumulative side channel attrition across a large river floodplain.

PubMed

Reinhold, Ann Marie; Poole, Geoffrey C; Bramblett, Robert G; Zale, Alexander V; Roberts, David W

2018-04-24

Determining the influences of anthropogenic perturbations on side channel dynamics in large rivers is important from both assessment and monitoring perspectives because side channels provide critical habitat to numerous aquatic species. Side channel extents are decreasing in large rivers worldwide. Although riprap and other linear structures have been shown to reduce side channel extents in large rivers, we hypothesized that small "anthropogenic plugs" (flow obstructions such as dikes or berms) across side channels modify whole-river geomorphology via accelerating side channel senescence. To test this hypothesis, we conducted a geospatial assessment, comparing digitized side channel areas from aerial photographs taken during the 1950s and 2001 along 512 km of the Yellowstone River floodplain. We identified longitudinal patterns of side channel recruitment (created/enlarged side channels) and side channel attrition (destroyed/senesced side channels) across n = 17 river sections within which channels were actively migrating. We related areal measures of recruitment and attrition to the density of anthropogenic side channel plugs across river sections. Consistent with our hypothesis, a positive spatial relationship existed between the density of anthropogenic plugs and side channel attrition, but no relationship existed between plug density and side channel recruitment. Our work highlights important linkages among side channel plugs and the persistence and restoration of side channels across floodplain landscapes. Specifically, management of small plugs represents a low-cost, high-benefit restoration opportunity to facilitate scouring flows in side channels to enable the persistence of these habitats over time.

Concurrent Transmission Based on Channel Quality in Ad Hoc Networks: A Game Theoretic Approach

NASA Astrophysics Data System (ADS)

Chen, Chen; Gao, Xinbo; Li, Xiaoji; Pei, Qingqi

In this paper, a decentralized concurrent transmission strategy in shared channel in Ad Hoc networks is proposed based on game theory. Firstly, a static concurrent transmissions game is used to determine the candidates for transmitting by channel quality threshold and to maximize the overall throughput with consideration of channel quality variation. To achieve NES (Nash Equilibrium Solution), the selfish behaviors of node to attempt to improve the channel gain unilaterally are evaluated. Therefore, this game allows each node to be distributed and to decide whether to transmit concurrently with others or not depending on NES. Secondly, as there are always some nodes with lower channel gain than NES, which are defined as hunger nodes in this paper, a hunger suppression scheme is proposed by adjusting the price function with interferences reservation and forward relay, to fairly give hunger nodes transmission opportunities. Finally, inspired by stock trading, a dynamic concurrent transmission threshold determination scheme is implemented to make the static game practical. Numerical results show that the proposed scheme is feasible to increase concurrent transmission opportunities for active nodes, and at the same time, the number of hunger nodes is greatly reduced with the least increase of threshold by interferences reservation. Also, the good performance on network goodput of the proposed model can be seen from the results.

Voltage-Gated Lipid Ion Channels

PubMed Central

Blicher, Andreas; Heimburg, Thomas

2013-01-01

Synthetic lipid membranes can display channel-like ion conduction events even in the absence of proteins. We show here that these events are voltage-gated with a quadratic voltage dependence as expected from electrostatic theory of capacitors. To this end, we recorded channel traces and current histograms in patch-experiments on lipid membranes. We derived a theoretical current-voltage relationship for pores in lipid membranes that describes the experimental data very well when assuming an asymmetric membrane. We determined the equilibrium constant between closed and open state and the open probability as a function of voltage. The voltage-dependence of the lipid pores is found comparable to that of protein channels. Lifetime distributions of open and closed events indicate that the channel open distribution does not follow exponential statistics but rather power law behavior for long open times. PMID:23823188

High-current discharge channel contraction in high density gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rutberg, Ph. G.; Bogomaz, A. A.; Pinchuk, M. E.

Research results for discharges at current amplitudes of 0.5-1.6 MA and current rise rate of {approx}10{sup 10} A/s are presented. The discharge is performed in the hydrogen environment at the initial pressure of 5-35 MPa. Initiation is implemented by a wire explosion. The time length of the first half-period of the discharge current is 70-150 {mu}s. Under such conditions, discharge channel contraction is observed; the contraction is followed by soft x-ray radiation. The phenomena are discussed, which are determined by high density of the gas surrounding the discharge channel. These phenomena are increase of the current critical value, where themore » channel contraction begins and growth of temperature in the axis region of the channel, where the initial density of the gas increases.« less

Changes in Channel Geometry through the Holocene in the Le Sueur River, South-Central Minnesota, USA

NASA Astrophysics Data System (ADS)

Targos, Courtney Ann

Paleochannels preserved on terraces via meander cutoffs during an incisional period record the channel geometry and thus discharge at distinct points in time throughout a river's history. We measured paleochannel geometry on terraces throughout the Le Sueur River in south-central Minnesota, to track how channel geometry has changed over the last 13,400 years. A rapid drop in base level 13,400 yr B.P. triggered knickpoint migration and valley incision that is ongoing today. Since the 1800's, the area has developed rapidly with an increase in agriculture and associated drainage, directly impacting river discharge by increasing water input to the river. Five paleochannels were identified on terraces along the Le Sueur River from 1m-resolution lidar data. Ground Penetrating Radar (GPR) was used to obtain a subsurface image across paleomeanders to estimate the geometry of paleochannels. Paleochannel geometry and estimated discharge were then compared to modern conditions to assess how much change has occurred. Three lines were run across each paleochannel perpendicular to the historic water flow. Each of the 15 lines were processed using the EKKO Project 2 software supplied by Sensors and Software to sharpen the images, making it easier to identify the paleochannel geometry. Paleodischarge was determined using the Law of the Wall and Manning's Equation, using modern slope and roughness conditions. OSL samples were collected from overbank deposits on terraces to determine the time of channel abandonment, and supplemented with terrace ages obtained from a numerical model of valley incision. Paleodischarge coupled with depositional ages provide a history of flow conditions on the Le Sueur River. Results show an increase in channel widths from the time paleochannels were occupied to modern channel dimensions from an average of 20 meters to 35 meters. The change was not constant through time, as all paleochannels analyzed on terraces had similar-sized channels. The best way to determine paleogeometry was using the 'best interpretation' of GPR data couple with coring data; and paleodischarge was best estimated using Manning's equation with an n value of 0.035. Results show an increase in discharge compared to paleochannels of a factor of two. Uncertainty estimates in GPR-based paleogeometry can change paleodischarge calculations by 50 %. Incremental flood frequency analyses, based on data obtained from the Red Jacket stream gage at the outlet of the Le Sueur, suggest a 1.5- and 2-year flood of 102 m3/s and 154 m3/s, respectively, which is comparable to estimations of bankfull based on current channel geometry at the Red Jacket gage, validating the methodology. Problems associated with paleogeometry estimations are primarily due to meander bend preservation in the subsurface, challenging GPR interpretation. The increase in channel geometry and discharge implies that the increase in flow associated with drainage and climate change since the area's development has greatly impacted the Le Sueur River. This resulted in a change in channel morphometry through increased erosion along the bluffs and banks, widening channels. This increase in erosion has directly impacted the amount of sediment delivered to the rivers from banks and bluffs, increasing the fine sediment load in this turbidity-impaired river system.

Small Ion Channel Linking Molecular Simulations and Electrophysiology

NASA Technical Reports Server (NTRS)

Pohorille, Andrzej

2017-01-01

Ion channels are pore-forming protein assemblies that mediate the transport of small ions across cell membranes. Otherwise, membrane bilayers would be almost impermeable to ions incapable to traverse the low dielectric constant, hydrophobic membrane core. Ion channels are ubiquitous to all life forms. In humans and other higher organisms they play the central role in conducting nerve impulses, cardiac functions, muscle contraction and apoptosis. On the other extreme of biological complexity, viral ion channels (viroporins) influence many stages of the virus infection cycle either through regulating virus replication, such as entry, assembly and release or modulating the electrochemical balance in the subcellular compartments of host cells. Ion channels were crucial components of protocells. Their emergence facilitated adaptation of nascent life to different environmental conditions. The earliest ion channels must have been much simpler than most of their modern ancestors. Viral channels are among only a few naturally occurring models to study the structure, function and evolution of primordial channels. Experimental studies of these properties are difficult and often unreliable. In principle, computational methods, and molecular dynamics (MD) simulations in particular, can aid in providing information about both the structure and the function of ion channels. However, MD suffers from its own problems, such as inability to access sufficiently long time scales or limited accuracy of force fields. It is, therefore, essential to determine the reliability of MD simulations. We propose to do so on the basis of two criteria. One is channel stability on time scales that extend for several microseconds or longer. The other is the ability to reproduce the measured ionic conductance as a function of applied voltage. If both the stability and the calculated ionic conductance are satisfactory it will greatly increase our confidence that the structure and the function of a channel are described sufficiently accurately. To our knowledge, long time scale stability (approx.10 micro-sec) and the correct electrophysiology have been shown so far for only one channel - the synthetic LS3 hexamer). In this presentation, this approach will be discussed in application to two viral channels - Vpu, encoded by the HIV-1 genome and p7 of hepatitis C.

Finite-Horizon $H_\\infty $ Consensus for Multiagent Systems With Redundant Channels via An Observer-Type Event-Triggered Scheme.

PubMed

Xu, Wenying; Wang, Zidong; Ho, Daniel W C

2018-05-01

This paper is concerned with the finite-horizon consensus problem for a class of discrete time-varying multiagent systems with external disturbances and missing measurements. To improve the communication reliability, redundant channels are introduced and the corresponding protocol is constructed for the information transmission over redundant channels. An event-triggered scheme is adopted to determine whether the information of agents should be transmitted to their neighbors. Subsequently, an observer-type event-triggered control protocol is proposed based on the latest received neighbors' information. The purpose of the addressed problem is to design a time-varying controller based on the observed information to achieve the consensus performance in a finite horizon. By utilizing a constrained recursive Riccati difference equation approach, some sufficient conditions are obtained to guarantee the consensus performance, and the controller parameters are also designed. Finally, a numerical example is provided to demonstrate the desired reliability of redundant channels and the effectiveness of the event-triggered control protocol.

Dynamic hybrid materials for constitutional self-instructed membranes.

PubMed

Cazacu, Adinela; Legrand, Yves-Marie; Pasc, Andreea; Nasr, Gihane; Van der Lee, Arie; Mahon, Eugene; Barboiu, Mihail

2009-05-19

Constitutional self-instructed membranes were developed and used for mimicking the adaptive structural functionality of natural ion-channel systems. These membranes are based on dynamic hybrid materials in which the functional self-organized macrocycles are reversibly connected with the inorganic silica through hydrophobic noncovalent interactions. Supramolecular columnar ion-channel architectures can be generated by reversible confinement within scaffolding hydrophobic silica mesopores. They can be structurally determined by using X-ray diffraction and morphologically tuned by alkali-salts templating. From the conceptual point of view, these membranes express a synergistic adaptive behavior: the simultaneous binding of the fittest cation and its anion would be a case of "homotropic allosteric interactions," because in time it increases the transport efficiency of the pore-contained superstructures by a selective evolving process toward the fittest ion channel. The hybrid membranes presented here represent dynamic constitutional systems evolving over time to form the fittest ion channels from a library of molecular and supramolecular components, or selecting the fittest ion pairs from a mixture of salts demonstrating flexible adaptation.

Is channel segmentation necessary to reach a multiethnic population with weight-related health promotion? An analysis of use and perception of communication channels

PubMed Central

Nierkens, Vera; Cremer, Stephan W.; Verhoeff, Arnoud; Stronks, Karien

2014-01-01

Objective To explore similarities and differences in the use and perception of communication channels to access weight-related health promotion among women in three ethnic minority groups. The ultimate aim was to determine whether similar channels might reach ethnic minority women in general or whether segmentation to ethnic groups would be required. Design Eight ethnically homogeneous focus groups were conducted among 48 women of Ghanaian, Antillean/Aruban, or Afro-Surinamese background living in Amsterdam. Our questions concerned which communication channels they usually used to access weight-related health advice or information about programs and whose information they most valued. The content analysis of data was performed. Results The participants mentioned four channels – regular and traditional healthcare, general or ethnically specific media, multiethnic and ethnic gatherings, and interpersonal communication with peers in the Netherlands and with people in the home country. Ghanaian women emphasized ethnically specific channels (e.g., traditional healthcare, Ghanaian churches). They were comfortable with these channels and trusted them. They mentioned fewer general channels – mainly limited to healthcare – and if discussed, negative perceptions were expressed. Antillean women mentioned the use of ethnically specific channels (e.g., communication with Antilleans in the home country) on balance with general audience–oriented channels (e.g., regular healthcare). Perceptions were mixed. Surinamese participants discussed, in a positive manner, the use of general audience–oriented channels, while they said they did not use traditional healthcare or advice from Surinam. Local language proficiency, time resided in the Netherlands, and approaches and messages received seemed to explain channel use and perception. Conclusion The predominant differences in channel use and perception among the ethnic groups indicate a need for channel segmentation to reach a multiethnic target group with weight-related health promotion. The study results reveal possible segmentation criteria besides ethnicity, such as local language proficiency and time since migration, worthy of further investigation. PMID:24750018

Is channel segmentation necessary to reach a multiethnic population with weight-related health promotion? An analysis of use and perception of communication channels.

PubMed

Hartman, Marieke A; Nierkens, Vera; Cremer, Stephan W; Verhoeff, Arnoud; Stronks, Karien

2015-01-01

To explore similarities and differences in the use and perception of communication channels to access weight-related health promotion among women in three ethnic minority groups. The ultimate aim was to determine whether similar channels might reach ethnic minority women in general or whether segmentation to ethnic groups would be required. Eight ethnically homogeneous focus groups were conducted among 48 women of Ghanaian, Antillean/Aruban, or Afro-Surinamese background living in Amsterdam. Our questions concerned which communication channels they usually used to access weight-related health advice or information about programs and whose information they most valued. The content analysis of data was performed. The participants mentioned four channels - regular and traditional health care, general or ethnically specific media, multiethnic and ethnic gatherings, and interpersonal communication with peers in the Netherlands and with people in the home country. Ghanaian women emphasized ethnically specific channels (e.g., traditional health care, Ghanaian churches). They were comfortable with these channels and trusted them. They mentioned fewer general channels - mainly limited to health care - and if discussed, negative perceptions were expressed. Antillean women mentioned the use of ethnically specific channels (e.g., communication with Antilleans in the home country) on balance with general audience-oriented channels (e.g., regular health care). Perceptions were mixed. Surinamese participants discussed, in a positive manner, the use of general audience-oriented channels, while they said they did not use traditional health care or advice from Surinam. Local language proficiency, time resided in the Netherlands, and approaches and messages received seemed to explain channel use and perception. The predominant differences in channel use and perception among the ethnic groups indicate a need for channel segmentation to reach a multiethnic target group with weight-related health promotion. The study results reveal possible segmentation criteria besides ethnicity, such as local language proficiency and time since migration, worthy of further investigation.

Meteor burst communications for LPI applications

NASA Astrophysics Data System (ADS)

Schilling, D. L.; Apelewicz, T.; Lomp, G. R.; Lundberg, L. A.

A technique that enhances the performance of meteor-burst communications is described. The technique, the feedback adaptive variable rate (FAVR) system, maintains a feedback channel that allows the transmitted bit rate to mimic the time behavior of the received power so that a constant bit energy is maintained. This results in a constant probability of bit error in each transmitted bit. Experimentally determined meteor-burst channel characteristics and FAVR system simulation results are presented.

Oscillation-Mark Formation and Liquid-Slag Consumption in Continuous Casting Mold

NASA Astrophysics Data System (ADS)

Yang, Jie; Meng, Xiangning; Wang, Ning; Zhu, Miaoyong

2017-04-01

Traditional understanding on the complex multiphysics phenomenon of the meniscus in the oscillating mold for continuously cast steel, including oscillation-mark formation and liquid-slag consumption, has never considered the shape influence of the flux channel between the mold wall and the solidifying shell surface. Based on the reciprocating oscillation of mold, this study was carried out to calculate theoretically the periodic pressure and the liquid-slag layer thickness in the flux channel for the upper and the lower meniscus that possess different shapes in combination with a transient equilibrium profile of the flux channel as well as the sinusoidal and the nonsinusoidal oscillation modes of mold. The effect of flux channel shape on the multiphysics phenomenon in the meniscus was determined by the physical oscillation simulation by using an experimental cold model mold. The results show that the shape difference between the upper and the lower meniscus leads to the opposite direction of pressure in the flux channel. The pressure in the opposite direction plays a respective role in oscillation-mark formation and liquid-slag consumption in an oscillation cycle of mold, and thus, it makes a new mechanism for explaining the multiphysics phenomenon in the meniscus. The oscillation mark is initially formed by the rapid increase of positive channel pressure in the upper meniscus, and most of the liquid slag is infiltrated into the flux channel by the negative channel pressure in the lower meniscus from the end of a positive strip time to the beginning of the next positive strip time, including the negative strip time in between. Furthermore, the physical characteristics of the lubrication behavior in the meniscus are summarized, including liquid-slag infiltration, solidifying shell deformation, and the thickness change of the liquid-slag layer.

Ammonium sorption to channel and riparian sediments: A transient storage pool for dissolved inorganic nitrogen

USGS Publications Warehouse

Triska, Frank J.; Jackman, Alan P.; Duff, John H.; Avanzino, Ronald J.

1994-01-01

Sediment (0.5 mm–2.0 mm grain size) was incubated in nylon bags (200 μm mesh) below the water table in the channel and in two transects of shallow wells perpendicular to the banks (to 18 m) of a third-order stream during August, 1987. One transect of wells drained steep old-growth forest, and the other a steep 23 year-old clear-cut partially regenerated in alder. At approximately 6-week intervals between October, 1987, and June, 1988, bags were retrieved. Total exchangeable ammonium was determined on sediment, and dissolved oxygen, nitrate and ammonium were determined in stream and well water. Exchangeable ammonium ranged from 10 μeq/100 g of sediment in the stream where nitrification potential and subsurface exchange with stream water were high, to 115 μeq/100 g sediment 18 m inland where channel water-groundwater mixing and nitrification potential were both low. Sorbed ammonium was highest during summer/autumn base flow and lowest during winter storm flow. Both channel and well water contained measurable dissolved oxygen at all times. Ammonium concentration was typically < 10 μg-N/L in channel water, increased with distance inland, but did not exceed 365 μg-N/L at any site. Nitrate concentration was typically higher in well water than channel water. Nitrate levels increased dramatically in wells at the base of the clear-cut following the onset of autumn rains. The results indicate a potential for temporary storage of ammonium on riparian sediments which may influence biotic nitrogen cycling, and alter the timing and form of dissolved inorganic nitrogen transport from the watershed.

Error Rates and Channel Capacities in Multipulse PPM

NASA Technical Reports Server (NTRS)

Hamkins, Jon; Moision, Bruce

2007-01-01

A method of computing channel capacities and error rates in multipulse pulse-position modulation (multipulse PPM) has been developed. The method makes it possible, when designing an optical PPM communication system, to determine whether and under what conditions a given multipulse PPM scheme would be more or less advantageous, relative to other candidate modulation schemes. In conventional M-ary PPM, each symbol is transmitted in a time frame that is divided into M time slots (where M is an integer >1), defining an M-symbol alphabet. A symbol is represented by transmitting a pulse (representing 1) during one of the time slots and no pulse (representing 0 ) during the other M 1 time slots. Multipulse PPM is a generalization of PPM in which pulses are transmitted during two or more of the M time slots.

SK2 channels regulate mitochondrial respiration and mitochondrial Ca2+ uptake.

PubMed

Honrath, Birgit; Matschke, Lina; Meyer, Tammo; Magerhans, Lena; Perocchi, Fabiana; Ganjam, Goutham K; Zischka, Hans; Krasel, Cornelius; Gerding, Albert; Bakker, Barbara M; Bünemann, Moritz; Strack, Stefan; Decher, Niels; Culmsee, Carsten; Dolga, Amalia M

2017-05-01

Mitochondrial calcium ([Ca 2+ ] m ) overload and changes in mitochondrial metabolism are key players in neuronal death. Small conductance calcium-activated potassium (SK) channels provide protection in different paradigms of neuronal cell death. Recently, SK channels were identified at the inner mitochondrial membrane, however, their particular role in the observed neuroprotection remains unclear. Here, we show a potential neuroprotective mechanism that involves attenuation of [Ca 2+ ] m uptake upon SK channel activation as detected by time lapse mitochondrial Ca 2+ measurements with the Ca 2+ -binding mitochondria-targeted aequorin and FRET-based [Ca 2+ ] m probes. High-resolution respirometry revealed a reduction in mitochondrial respiration and complex I activity upon pharmacological activation and overexpression of mitochondrial SK2 channels resulting in reduced mitochondrial ROS formation. Overexpression of mitochondria-targeted SK2 channels enhanced mitochondrial resilience against neuronal death, and this effect was inhibited by overexpression of a mitochondria-targeted dominant-negative SK2 channel. These findings suggest that SK channels provide neuroprotection by reducing [Ca 2+ ] m uptake and mitochondrial respiration in conditions, where sustained mitochondrial damage determines progressive neuronal death.

SK2 channels regulate mitochondrial respiration and mitochondrial Ca2+ uptake

PubMed Central

Honrath, Birgit; Matschke, Lina; Meyer, Tammo; Magerhans, Lena; Perocchi, Fabiana; Ganjam, Goutham K; Zischka, Hans; Krasel, Cornelius; Gerding, Albert; Bakker, Barbara M; Bünemann, Moritz; Strack, Stefan; Decher, Niels; Culmsee, Carsten; Dolga, Amalia M

2017-01-01

Mitochondrial calcium ([Ca2+]m) overload and changes in mitochondrial metabolism are key players in neuronal death. Small conductance calcium-activated potassium (SK) channels provide protection in different paradigms of neuronal cell death. Recently, SK channels were identified at the inner mitochondrial membrane, however, their particular role in the observed neuroprotection remains unclear. Here, we show a potential neuroprotective mechanism that involves attenuation of [Ca2+]m uptake upon SK channel activation as detected by time lapse mitochondrial Ca2+ measurements with the Ca2+-binding mitochondria-targeted aequorin and FRET-based [Ca2+]m probes. High-resolution respirometry revealed a reduction in mitochondrial respiration and complex I activity upon pharmacological activation and overexpression of mitochondrial SK2 channels resulting in reduced mitochondrial ROS formation. Overexpression of mitochondria-targeted SK2 channels enhanced mitochondrial resilience against neuronal death, and this effect was inhibited by overexpression of a mitochondria-targeted dominant-negative SK2 channel. These findings suggest that SK channels provide neuroprotection by reducing [Ca2+]m uptake and mitochondrial respiration in conditions, where sustained mitochondrial damage determines progressive neuronal death. PMID:28282037

Molecular Frame Reconstruction Using Time-Domain Photoionization Interferometry.

PubMed

Marceau, Claude; Makhija, Varun; Platzer, Dominique; Naumov, A Yu; Corkum, P B; Stolow, Albert; Villeneuve, D M; Hockett, Paul

2017-08-25

Photoionization of molecular species is, essentially, a multipath interferometer with both experimentally controllable and intrinsic molecular characteristics. In this work, XUV photoionization of impulsively aligned molecular targets (N_{2}) is used to provide a time-domain route to "complete" photoionization experiments, in which the rotational wave packet controls the geometric part of the photoionization interferometer. The data obtained is sufficient to determine the magnitudes and phases of the ionization matrix elements for all observed channels, and to reconstruct molecular frame interferograms from lab frame measurements. In principle, this methodology provides a time-domain route to complete photoionization experiments and the molecular frame, which is generally applicable to any molecule (no prerequisites), for all energies and ionization channels.

Study of the character of the time dependence of the ratio of signals in the IR and visible channels of a radiometric apparatus when fragments of space junk are observed

NASA Astrophysics Data System (ADS)

Pavlov, N. I.; Él'Ts, E. É.

2006-01-01

A more accurate expression is derived for determining the specific load of fragments of space junk via the time dependence of the ratio of signals in the IR and visible channels of on-board radiometric observation apparatus. Results are presented of a calculation of the time behavior of this ratio when aluminum and plastic debris is observed on near-earth orbits. The cases considered here involve constant heating of the debris by solar radiation and the variation of this heating according to a harmonic law because the debris rotates around its center of mass.

Lightning propagation and flash density in squall lines as determined with radar

NASA Technical Reports Server (NTRS)

Mazur, V.; Rust, W. D.

1983-01-01

Lightning echo rise times and range-time variations due to discharge propagation are determined using S and L band radars, and the evolution of precipitation reflectivity and the associated lightning activity in squall lines is investigated using VHF and L band radars. The rise time of radar echoes can be explained by ionized channel propagation through the radar beams. Speeds of at least 250,000 m/s are found from measurements of the radial velocity of streamer propagation along the antenna beam. The range-time variations in lightning echoes indicate that either new ionization occurs as streamers develop into different parts of the cloud, channel delay occurs during which adequate ionization exists for radar detection, or continuing current occurs. Determinations of the lightning flash density for a squall line in the U.S. show that the maximum lightning density tends to be near the leading edge of the precipitation cores in developing cells. Long discharges are produced as a cell in the squall line develops and the total lightning density increases, although short discharges predominate. As the cell dissipates, short flashes diminish or cease and the long flashes dominate the lightning activity.

Bank accretion and the development of vegetated depositional surfaces along modified alluvial channels

USGS Publications Warehouse

Hupp, C.R.; Simon, A.

1991-01-01

This paper describes the recovery of stable bank form and development of vegetated depositional surfaces along the banks of channelized West Tennessee streams. Most perennial streams in West Tennessee were straightened and dredged since the turn of the century. Patterns of fluvial ecological responses to channelization have previously been described by a six-stage model. Dendrogeomorphic (tree-ring) techniques allowed the determination of location, timing, amount, and rate of bank-sediment deposition. Channel cross sections and ecological analyses made at 101 locations along 12 streams, encompassing bends and straight reaches, show that channel and bank processes initially react vertically to channelization through downcutting. A depositional surface forms on banks once bed-degradation and heightened bank mass wasting processes have eased or slowed. The formation of this depositional surface marks the beginning of bank recovery from channelization. Dominating lateral processes, characteristic of stable or natural channels, return during the formation and expansion of the depositional surface, suggesting a relation with thalweg deflection, point-bar development, and meanderloop extension. Characteristic woody riparian vegetation begins to grow as this depositional surface develops and becomes part of the process and form of restabilizing banks. The depositional surface initially forms low on the bank and tends to maintain a slope of about 24??. Mean accretion rates ranges from 5.9 cm/yr on inside bends to 0 cm/yr on most outside bends; straight reaches have a mean-accretion rate of 4.2 cm/yr. The relatively stable, convex upward, depositional surface expands and ultimately attaches to the flood plain. The time required for the recovery process to reach equilibrium averaged about 50 years. Indicative pioneer speccies of woody riparian vegetation include black willow, river birch, silver maple, and boxelder. Stem densities generally decrease with time after and initial flush of about 160 stems per 100 m2. Together bank accretion and vegetative regrowth appear to be the most important environmental processes involved in channel bank recovery from channelization or rejuvenation. ?? 1991.

Diazoxide triggers cardioprotection against apoptosis induced by oxidative stress.

PubMed

Ichinose, Masashi; Yonemochi, Hidetoshi; Sato, Toshiaki; Saikawa, Tetsunori

2003-06-01

Although mitochondrial ATP-sensitive potassium (mitoK(ATP)) channels have been reported to reduce the extent of apoptosis, the critical timing of mitoK(ATP) channel opening required to protect myocytes against apoptosis remains unclear. In the present study, we examined whether the mitoK(ATP) channel serves as a trigger of cardioprotection against apoptosis induced by oxidative stress. Apoptosis of cultured neonatal rat cardiomyocytes was determined by flow cytometry (light scatter and propidium iodide/annexin V-FITC fluorescence) and by nuclear staining with Hoechst 33342. Mitochondrial membrane potential (DeltaPsi) was measured by flow cytometry of cells stained with rhodamine-123 (Rh-123). Exposure to H(2)O(2) (500 microM) induced apoptosis, and the percentage of apoptotic cells increased progressively and peaked at 2 h. This H(2)O(2)-induced apoptosis was associated with the loss of DeltaPsi, and the time course of decrease in Rh-123 fluorescence paralleled that of apoptosis. Pretreatment of cardiomyocytes with diazoxide (100 microM), a putative mitoK(ATP) channel opener, for 30 min before exposure to H(2)O(2) elicited transient and mild depolarization of DeltaPsi and consequently suppressed both apoptosis and DeltaPsi loss after 2-h exposure to H(2)O(2). These protective effects of diazoxide were abrogated by the mitoK(ATP) channel blocker 5-hydroxydecanoate (500 microM) but not by the sarcolemmal K(ATP) channel blocker HMR-1098 (30 microM). Our results suggest for the first time that diazoxide-induced opening of mitoK(ATP) channels triggers cardioprotection against apoptosis induced by oxidative stress in rat cardiomyocytes.

Cross-talk between ATP-regulated K+ channels and Na+ transport via cellular metabolism in frog skin principal cells.

PubMed Central

Urbach, V; Van Kerkhove, E; Maguire, D; Harvey, B J

1996-01-01

Isolated frog skin epithelium, mounted in an Ussing chamber and bathed in standard NaCl Ringer solution, recycles K+ across the basolateral membrane of principal cells through an inward-rectifier K+ channel (Kir) operating in parallel with a Na+-K+-ATPase pump. Here we report on the metabolic control of the Kir channel using patch clamping, short-circuit current measurement and enzymatic determination of cellular (ATP (ATPi). 2. The constitutively active Kir channel in the basolateral membrane has the characteristics of an ATP-regulated K+ channel and is now classed as a KATP channel. In excised inside-out patches the open probability (Po) of KATP channels was reduced by ATPi with half-maximum inhibition at an ATPi concentration of 50 microM. 3. ATPi measured (under normal Na+ transport conditions) with luciferin-luciferase was 1.50 +/- 0.23 mM (mean +/- S.E.M.; range, 0.4-3.3 mM n = 11). Thus the KATP channel would be expected to be inactive in intact cells if ATPi was the sole regulator of channel activity. KATP channels which were inactivated by 1 mM ATPi in excised patches could be reactivated by addition of 100 microM ADP on the cytosolic side. When added alone, ADP blocks this channel with half-maximal inhibition at [ADPi] > 5 mM. 4. Sulphonylureas inhibit single KATP channels in cell-attached patches as well as the total basolateral K+ current measured in frog skin epithelia perforated with nystatin on the apical side. 5. Na+-K+-ATPase activity is a major determinant of cytosolic ATP. Blocking the pump activity with ouabain produced a time-dependent increase in ATPi and reduced the open probability of KATP channels in cell-attached membranes. 6. We conclude that the ratio of ATP/ADP is an important metabolic coupling factor between the rate of Na+-K+ pumping and K+ recycling. Images Figure 9 PMID:9011625

Bypass valve and coolant flow controls for optimum temperatures in waste heat recovery systems

DOEpatents

Meisner, Gregory P

2013-10-08

Implementing an optimized waste heat recovery system includes calculating a temperature and a rate of change in temperature of a heat exchanger of a waste heat recovery system, and predicting a temperature and a rate of change in temperature of a material flowing through a channel of the waste heat recovery system. Upon determining the rate of change in the temperature of the material is predicted to be higher than the rate of change in the temperature of the heat exchanger, the optimized waste heat recovery system calculates a valve position and timing for the channel that is configurable for achieving a rate of material flow that is determined to produce and maintain a defined threshold temperature of the heat exchanger, and actuates the valve according to the calculated valve position and calculated timing.

Lessons Learned from AIRS: Improved Determination of Surface and Atmospheric Temperatures Using Only Shortwave AIRS Channels

NASA Technical Reports Server (NTRS)

Susskind, Joel

2011-01-01

This slide presentation reviews the use of shortwave channels available to the Atmospheric Infrared Sounder (AIRS) to improve the determination of surface and atmospheric temperatures. The AIRS instrument is compared with the Infrared Atmospheric Sounding Interferometer (IASI) on-board the MetOp-A satellite. The objectives of the AIRS/AMSU were to (1) provide real time observations to improve numerical weather prediction via data assimilation, (2) Provide observations to measure and explain interannual variability and trends and (3) Use of AIRS product error estimates allows for QC optimized for each application. Successive versions in the AIRS retrieval methodology have shown significant improvement.

Review of correlation techniques

NASA Technical Reports Server (NTRS)

Bowhill, S. A.

1983-01-01

Correlation analysis in MST radar to determine the scattered power, Doppler frequency and correlation time for a noisy signal is examined. It is assumed that coherent detection was employed, with two accurately balanced quadrature receiving channels and that coherent integration is performed with a window length significantly less than the correlation time of the signal.

Functional Characterization of Cnidarian HCN Channels Points to an Early Evolution of Ih.

PubMed

Baker, Emma C; Layden, Michael J; van Rossum, Damian B; Kamel, Bishoy; Medina, Monica; Simpson, Eboni; Jegla, Timothy

2015-01-01

HCN channels play a unique role in bilaterian physiology as the only hyperpolarization-gated cation channels. Their voltage-gating is regulated by cyclic nucleotides and phosphatidylinositol 4,5-bisphosphate (PIP2). Activation of HCN channels provides the depolarizing current in response to hyperpolarization that is critical for intrinsic rhythmicity in neurons and the sinoatrial node. Additionally, HCN channels regulate dendritic excitability in a wide variety of neurons. Little is known about the early functional evolution of HCN channels, but the presence of HCN sequences in basal metazoan phyla and choanoflagellates, a protozoan sister group to the metazoans, indicate that the gene family predates metazoan emergence. We functionally characterized two HCN channel orthologs from Nematostella vectensis (Cnidaria, Anthozoa) to determine which properties of HCN channels were established prior to the emergence of bilaterians. We find Nematostella HCN channels share all the major functional features of bilaterian HCNs, including reversed voltage-dependence, activation by cAMP and PIP2, and block by extracellular Cs+. Thus bilaterian-like HCN channels were already present in the common parahoxozoan ancestor of bilaterians and cnidarians, at a time when the functional diversity of voltage-gated K+ channels was rapidly expanding. NvHCN1 and NvHCN2 are expressed broadly in planulae and in both the endoderm and ectoderm of juvenile polyps.

An Experimental Device for Real Time Determination of Slant Path Atmospheric Contrast Transmittance.

DTIC Science & Technology

1982-03-01

copies ftom th Defense Technical Information Caster. AN others ioM apply to the National Technical Information Service. UNCLASSIFIED SECURITV...EXPERIMENTAL DEVICE FOR REAL TIME DETERMINATION OF SLANT PATH ATMOSPHERIC CONTRAST TRANSMITTANCE Richard W. Johnson 1. INTRODUCTION 2. BASIC CONCEPTS As...and z is an altitude parameter. primary optical channel uses a cosine corrected and PE- ASSIG SYSTM DEPIS1ttt STAGE I DSIN STAGEM Pgormiy TES

Landscape assessment of side channel plugs and associated cumulative side channel attrition across a large river floodplain

USGS Publications Warehouse

Reinhold, Ann Marie; Poole, Geoffrey C.; Bramblett, Robert G.; Zale, Alexander V.; Roberts, David W.

2018-01-01

Determining the influences of anthropogenic perturbations on side channel dynamics in large rivers is important from both assessment and monitoring perspectives because side channels provide critical habitat to numerous aquatic species. Side channel extents are decreasing in large rivers worldwide. Although riprap and other linear structures have been shown to reduce side channel extents in large rivers, we hypothesized that small “anthropogenic plugs” (flow obstructions such as dikes or berms) across side channels modify whole-river geomorphology via accelerating side channel senescence. To test this hypothesis, we conducted a geospatial assessment, comparing digitized side channel areas from aerial photographs taken during the 1950s and 2001 along 512 km of the Yellowstone River floodplain. We identified longitudinal patterns of side channel recruitment (created/enlarged side channels) and side channel attrition (destroyed/senesced side channels) across n = 17 river sections within which channels were actively migrating. We related areal measures of recruitment and attrition to the density of anthropogenic side channel plugs across river sections. Consistent with our hypothesis, a positive spatial relationship existed between the density of anthropogenic plugs and side channel attrition, but no relationship existed between plug density and side channel recruitment. Our work highlights important linkages among side channel plugs and the persistence and restoration of side channels across floodplain landscapes. Specifically, management of small plugs represents a low-cost, high-benefit restoration opportunity to facilitate scouring flows in side channels to enable the persistence of these habitats over time.

Cardiac sodium channel Markov model with temperature dependence and recovery from inactivation.

PubMed Central

Irvine, L A; Jafri, M S; Winslow, R L

1999-01-01

A Markov model of the cardiac sodium channel is presented. The model is similar to the CA1 hippocampal neuron sodium channel model developed by Kuo and Bean (1994. Neuron. 12:819-829) with the following modifications: 1) an additional open state is added; 2) open-inactivated transitions are made voltage-dependent; and 3) channel rate constants are exponential functions of enthalpy, entropy, and voltage and have explicit temperature dependence. Model parameters are determined using a simulated annealing algorithm to minimize the error between model responses and various experimental data sets. The model reproduces a wide range of experimental data including ionic currents, gating currents, tail currents, steady-state inactivation, recovery from inactivation, and open time distributions over a temperature range of 10 degrees C to 25 degrees C. The model also predicts measures of single channel activity such as first latency, probability of a null sweep, and probability of reopening. PMID:10096885

A morphology independent methodology for quantifying planview river change and characteristics from remotely sensed imagery

DOE PAGES

Rowland, Joel C.; Shelef, Eitan; Pope, Paul A.; ...

2016-07-15

Remotely sensed imagery of rivers has long served as a means for characterizing channel properties and detection of planview change. In the last decade the dramatic increase in the availability of satellite imagery and processing tools has created the potential to greatly expand the spatial and temporal scale of our understanding of river morphology and dynamics. To date, the majority of GIS and automated analyses of planview changes in rivers from remotely sensed data has been developed for single-threaded meandering river systems. These methods have limited applicability to many of the earth's rivers with complex multi-channel planforms. Here we presentmore » the methodologies of a set of analysis algorithms collectively called Spatially Continuous Riverbank Erosion and Accretion Measurements (SCREAM). SCREAM analyzes planview river metrics regardless of river morphology. These algorithms quantify both the erosion and accretion rates of riverbanks from binary masks of channels generated from imagery acquired at two time periods. Additionally, the program quantifies the area of change between river channels and the surrounding floodplain and area of islands lost or formed between these two time periods. To examine variations in erosion rates in relation to local channel attributes and make rate comparisons between river systems of varying sizes, the program determines channel widths and bank curvature at every bank pixel. SCREAM was developed and tested on rivers with diverse and complex planform morphologies in imagery acquired from a range of observational platforms with varying spatial resolutions. Here, validation and verification of SCREAM-generated metrics against manual measurements show no significant measurement errors in determination of channel width, erosion, and bank aspects. SCREAM has the potential to provide data for both the quantitative examination of the controls on erosion rates and for the comparison of these rates across river systems ranging broadly in size and planform morphology.« less

Bandwidth and Detection of Packet Length Covert Channels

DTIC Science & Technology

2011-03-01

Shared Resource Matrix ( SRM ): Develop a matrix of all resources on one side and on the other all the processes. Then, determine which process uses which...system calls. This method is similar to that of the SRM . Covert channels have also been created by modulating packet timing, data and headers of net- work...analysis, noninterference analysis, SRM method, and the covert flow tree method [4]. These methods can be used during the design phase of a system. Less

Tracking sediment through the Holocene: Determining anthropogenic contributions to a sediment-rich agricultural system, north-central USA

NASA Astrophysics Data System (ADS)

Gran, Karen; Belmont, Patrick; Finnegan, Noah

2013-04-01

Management and restoration of sediment-impaired streams requires quantification of sediment sources and pathways of transport. Addressing the role of humans in altering the magnitude and sources of sediment supplied to a catchment is notoriously challenging. Here, we explore how humans have amplified erosion in geomorphically-sensitive portions of the predominantly-agricultural Minnesota River basin in north-central USA. In the Minnesota River basin, the primary sources of sediment are classified generally as upland agricultural field vs. near-channel sources, with near-channel sources including stream banks, bluffs, and ravines. Using aerial lidar data, repeat terrestrial lidar scans of bluffs, ravine monitoring, historic air photo analyses, and sediment fingerprinting, we have developed a sediment budget to determine the relative importance of each source in a tributary to the Minnesota River, the Le Sueur River. We then investigate how these sources have changed through time, from changes evident over the past few decades to changes associated with valley evolution over the past 13,400 years. The Minnesota River valley was carved ~13,400 years ago through catastrophic drainage of glacial Lake Agassiz. As the Minnesota River valley incised, knickpoints have migrated upstream into tributaries, carving out deep valleys where the most actively eroding near-channel sediment sources occur. The modern sediment budget, closed for the time period 2000 to 2010, shows that the majority of the fine sediment load in the Le Sueur River comes from bluffs and other near-channel sources in the deeply-incised knick zone. Numerical modeling of valley evolution constrained by mapped and dated strath terraces cut into the glacial till presents an opportunity to compare the modern sediment budget to that of the river prior to anthropogenic modification. This comparison reveals a natural background or "pre-agriculture" rate of erosion from near-channel sources to be 3-5 times lower than modern near-channel erosion rates. Notably, depositional records from a naturally-dammed lake downstream on the upper Mississippi River show a more dramatic 10-fold increase in deposition rates from pre-agricultural times to the present. Sediment fingerprinting shows that pre-agriculture sediment loads were dominated by near-channel sediment sources. As deposition rates rose in the late 1800s and early 1900s, the sources shifted increasingly to agricultural soil erosion. In the past few decades, deposition rates have remained high, but sediment fingerprinting indicates yet another significant shift back to near-channel sources. On-going changes in basin hydrology, from both installation of agricultural drainage systems and on-going climate change have put more water in the rivers, increasing rates of near-channel bank and bluff erosion. This most recent shift in sediment sources has significant implications for turbidity management in the Minnesota River basin.

Flow model for open-channel reach or network

USGS Publications Warehouse

Schaffranek, R.W.

1987-01-01

Formulation of a one-dimensional model for simulating unsteady flow in a single open-channel reach or in a network of interconnected channels is presented. The model is both general and flexible in that it can be used to simulate a wide range of flow conditions for various channel configurations. It is based on a four-point (box), implicit, finite-difference approximation of the governing nonlinear flow equations with user-definable weighting coefficients to permit varying the solution scheme from box-centered to fully forward. Unique transformation equations are formulated that permit correlation of the unknowns at the extremities of the channels, thereby reducing coefficient matrix and execution time requirements. Discharges and water-surface elevations computed at intermediate locations within a channel are determined following solution of the transformation equations. The matrix of transformation and boundary-condition equations is solved by Gauss elimination using maximum pivot strategy. Two diverse applications of the model are presented to illustrate its broad utility. (USGS)

Varifocal liquid lens based on microelectrofluidic technology.

PubMed

Chang, Jong-hyeon; Jung, Kyu-Dong; Lee, Eunsung; Choi, Minseog; Lee, Seungwan; Kim, Woonbae

2012-11-01

This Letter presents a tunable liquid lens based on microelectrofluidic technology. In the microelectrofluidic lens (MEFL), electrowetting in the hydrophobic surface channel induces the Laplace pressure difference between two fluidic interfaces on the lens aperture and the surface channel. Then, the pressure difference makes the lens curvature tunable. In spite of the contact angle saturation, the narrow surface channel increases the Laplace pressure to have a wide range of optical power variation in the MEFL. The magnitude of the applied voltage determines the lens curvature in the analog mode MEFL. Digital operation is also possible when the control electrodes of the MEFL are patterned to have an array. The lens aperture and maximum surface channel diameter were designed to 3.2 mm and 6.4 mm, respectively, with a channel height of 0.2 mm for an optical power range between +210 and -30 D. By switching the control electrodes, the averaged transit time in steps and turnaround time were as low as 2.4 ms and 16.5 ms, respectively, in good agreement with the simulation results. It is expected that the proposed MEFL may be widely used with advantages of wide variation of the optical power with fast and precise controllability in a digital manner.

TRPV2 enhances axon outgrowth through its activation by membrane stretch in developing sensory and motor neurons.

PubMed

Shibasaki, Koji; Murayama, Namie; Ono, Katsuhiko; Ishizaki, Yasuki; Tominaga, Makoto

2010-03-31

Thermosensitive TRP (thermo TRP) channels are well recognized for their contributions to sensory transduction, responding to a wide variety of stimuli including temperature, nociceptive stimuli, touch, and osmolarity. However, the precise roles for the thermo TRP channels during development have not been determined. To explore the functional importance of thermo TRP channels during neural development, the temporal expression was determined in embryonic mice. Interestingly, TRPV2 expression was detected in spinal motor neurons in addition to the dorsal root ganglia from embryonic day 10.5 and was localized in axon shafts and growth cones, suggesting that the channel is important for axon outgrowth regulation. We revealed that endogenous TRPV2 was activated in a membrane stretch-dependent manner in developing neurons by knocking down the TRPV2 function with dominant-negative TRPV2 and TRPV2-specific shRNA and significantly promoted axon outgrowth. Thus, for the first time we revealed that TRPV2 is an important regulator for axon outgrowth through its activation by membrane stretch during development.

Measuring kinetics of complex single ion channel data using mean-variance histograms.

PubMed Central

Patlak, J B

1993-01-01

The measurement of single ion channel kinetics is difficult when those channels exhibit subconductance events. When the kinetics are fast, and when the current magnitudes are small, as is the case for Na+, Ca2+, and some K+ channels, these difficulties can lead to serious errors in the estimation of channel kinetics. I present here a method, based on the construction and analysis of mean-variance histograms, that can overcome these problems. A mean-variance histogram is constructed by calculating the mean current and the current variance within a brief "window" (a set of N consecutive data samples) superimposed on the digitized raw channel data. Systematic movement of this window over the data produces large numbers of mean-variance pairs which can be assembled into a two-dimensional histogram. Defined current levels (open, closed, or sublevel) appear in such plots as low variance regions. The total number of events in such low variance regions is estimated by curve fitting and plotted as a function of window width. This function decreases with the same time constants as the original dwell time probability distribution for each of the regions. The method can therefore be used: 1) to present a qualitative summary of the single channel data from which the signal-to-noise ratio, open channel noise, steadiness of the baseline, and number of conductance levels can be quickly determined; 2) to quantify the dwell time distribution in each of the levels exhibited. In this paper I present the analysis of a Na+ channel recording that had a number of complexities. The signal-to-noise ratio was only about 8 for the main open state, open channel noise, and fast flickers to other states were present, as were a substantial number of subconductance states. "Standard" half-amplitude threshold analysis of these data produce open and closed time histograms that were well fitted by the sum of two exponentials, but with apparently erroneous time constants, whereas the mean-variance histogram technique provided a more credible analysis of the open, closed, and subconductance times for the patch. I also show that the method produces accurate results on simulated data in a wide variety of conditions, whereas the half-amplitude method, when applied to complex simulated data shows the same errors as were apparent in the real data. The utility and the limitations of this new method are discussed. Images FIGURE 2 FIGURE 4 FIGURE 8 FIGURE 9 PMID:7690261

Real-time reliable determination of binding kinetics of DNA hybridization using a multi-channel graphene biosensor

NASA Astrophysics Data System (ADS)

Xu, Shicai; Zhan, Jian; Man, Baoyuan; Jiang, Shouzhen; Yue, Weiwei; Gao, Shoubao; Guo, Chengang; Liu, Hanping; Li, Zhenhua; Wang, Jihua; Zhou, Yaoqi

2017-03-01

Reliable determination of binding kinetics and affinity of DNA hybridization and single-base mismatches plays an essential role in systems biology, personalized and precision medicine. The standard tools are optical-based sensors that are difficult to operate in low cost and to miniaturize for high-throughput measurement. Biosensors based on nanowire field-effect transistors have been developed, but reliable and cost-effective fabrication remains a challenge. Here, we demonstrate that a graphene single-crystal domain patterned into multiple channels can measure time- and concentration-dependent DNA hybridization kinetics and affinity reliably and sensitively, with a detection limit of 10 pM for DNA. It can distinguish single-base mutations quantitatively in real time. An analytical model is developed to estimate probe density, efficiency of hybridization and the maximum sensor response. The results suggest a promising future for cost-effective, high-throughput screening of drug candidates, genetic variations and disease biomarkers by using an integrated, miniaturized, all-electrical multiplexed, graphene-based DNA array.

Overlapping Binding Sites of Structurally Different Antiarrhythmics Flecainide and Propafenone in the Subunit Interface of Potassium Channel Kv2.1*

PubMed Central

Madeja, Michael; Steffen, Wibke; Mesic, Ivana; Garic, Bojan; Zhorov, Boris S.

2010-01-01

Kv2.1 channels, which are expressed in brain, heart, pancreas, and other organs and tissues, are important targets for drug design. Flecainide and propafenone are known to block Kv2.1 channels more potently than other Kv channels. Here, we sought to explore structural determinants of this selectivity. We demonstrated that flecainide reduced the K+ currents through Kv2.1 channels expressed in Xenopus laevis oocytes in a voltage- and time-dependent manner. By systematically exchanging various segments of Kv2.1 with those from Kv1.2, we determined flecainide-sensing residues in the P-helix and inner helix S6. These residues are not exposed to the inner pore, a conventional binding region of open channel blockers. The flecainide-sensing residues also contribute to propafenone binding, suggesting overlapping receptors for the drugs. Indeed, propafenone and flecainide compete for binding in Kv2.1. We further used Monte Carlo-energy minimizations to map the receptors of the drugs. Flecainide docking in the Kv1.2-based homology model of Kv2.1 predicts the ligand ammonium group in the central cavity and the benzamide moiety in a niche between S6 and the P-helix. Propafenone also binds in the niche. Its carbonyl group accepts an H-bond from the P-helix, the amino group donates an H-bond to the P-loop turn, whereas the propyl group protrudes in the pore and blocks the access to the selectivity filter. Thus, besides the binding region in the central cavity, certain K+ channel ligands can expand in the subunit interface whose residues are less conserved between K+ channels and hence may be targets for design of highly desirable subtype-specific K+ channel drugs. PMID:20709754

Flows and hypoxic blackwater events in managed ephemeral river channels

NASA Astrophysics Data System (ADS)

Hladyz, Sally; Watkins, Susanne C.; Whitworth, Kerry L.; Baldwin, Darren S.

2011-04-01

SummaryAs pressure increases on the availability of water resources worldwide, especially in the face of climatic change, it is probable that the likelihood of streams undergoing at least some periods of drying will increase in arid and semi-arid regions. This has implications for the ongoing management of waterways in these areas. One area of concern is the potential occurrence of hypoxic blackwater events upon re-instatement of flows in creek and river channels following periods of drying. Hypoxic blackwater events are characterised by high levels of dissolved organic carbon (DOC), the metabolism of which results in low dissolved oxygen (DO) in the water column, which can cause fish and crustacean mortality. Therefore, understanding hypoxic blackwater events is important in order to reduce the potential for fish mortalities and other water quality impacts from both managed and natural flows. In this study, we set out to determine the factors that influenced the occurrence of a hypoxic blackwater event in the Edward-Wakool river system, in southern NSW, Australia during the previous austral summer (2008-2009). Standing stocks of plant litter, emergent macrophytes and river red gum saplings ( Eucalyptus camaldulensis Dehn.), as well as rates of litterfall, were determined in dry and inundated channels. A series of mesocosm experiments were undertaken to determine which carbon source was the greatest contributor to DOC and to DO depletion, and what loadings could result in hypoxia. These experiments were then used to create a simple algorithm relating carbon loading in a dry channel to DOC in the overlying water column following inundation. Results revealed that plant litter was the main contributor to water column DOC and to DO depletion. Litter loadings equal to or greater than 370 g m -2 were found to cause DO in a shallow (20 cm) water column at 20 °C to fall to zero within two days. This loading was approximately half of that found in dry channels in the Edward-Wakool system - thus, initial inundation of these channels at a low flow rate during summer (or when water temperature is equal to or greater than 20 °C) is highly likely to trigger a hypoxic blackwater event. In addition, one month of litterfall in summer was calculated to be sufficient to deliver enough carbon to dry channels to create a hypoxic blackwater event. These findings suggest that to reduce the likelihood of a hypoxic blackwater event occurring as a result of managed flows in ephemeral systems; (1) the principal source(s) of DOC as well as the pathway and timing of accumulation in dry channels should be identified, and (2) the timing of the re-instatement of flows in a dry channel should be considered in light of the timing of maximum rates of accumulation of the principal source(s) of DOC.

Timing and efficacy of Ca2+ channel activation in hippocampal mossy fiber boutons.

PubMed

Bischofberger, Josef; Geiger, Jörg R P; Jonas, Peter

2002-12-15

The presynaptic Ca2+ signal is a key determinant of transmitter release at chemical synapses. In cortical synaptic terminals, however, little is known about the kinetic properties of the presynaptic Ca2+ channels. To investigate the timing and magnitude of the presynaptic Ca2+ inflow, we performed whole-cell patch-clamp recordings from mossy fiber boutons (MFBs) in rat hippocampus. MFBs showed large high-voltage-activated Ca(2+) currents, with a maximal amplitude of approximately 100 pA at a membrane potential of 0 mV. Both activation and deactivation were fast, with time constants in the submillisecond range at a temperature of approximately 23 degrees C. An MFB action potential (AP) applied as a voltage-clamp command evoked a transient Ca2+ current with an average amplitude of approximately 170 pA and a half-duration of 580 microsec. A prepulse to +40 mV had only minimal effects on the AP-evoked Ca2+ current, indicating that presynaptic APs open the voltage-gated Ca2+ channels very effectively. On the basis of the experimental data, we developed a kinetic model with four closed states and one open state, linked by voltage-dependent rate constants. Simulations of the Ca2+ current could reproduce the experimental data, including the large amplitude and rapid time course of the current evoked by MFB APs. Furthermore, the simulations indicate that the shape of the presynaptic AP and the gating kinetics of the Ca2+ channels are tuned to produce a maximal Ca2+ influx during a minimal period of time. The precise timing and high efficacy of Ca2+ channel activation at this cortical glutamatergic synapse may be important for synchronous transmitter release and temporal information processing.

Toward more accurate basal boundary conditions: a new 2-D model of distributed and channelised subglacial drainage

NASA Astrophysics Data System (ADS)

Werder, M. A.; Hewitt, I. J.; Schoof, C.; Flowers, G. E.

2012-04-01

Basal boundary conditions are one of the least constrained components of today's ice sheet models. To get at these one needs to know the distributed basal water pressure. We present a new glacier drainage system model to contribute to this missing piece of the puzzle. This two dimensional mathematical/numerical model combines distributed and channelised drainage at the ice-bed interface coupled to a water storage component. Notably the model determines the location of the channels as part of the solution. This is achieved by allowing channels (modelled as R-channels) to form on any of the edges of the unstructured triangular grid used to discretise the model. The distributed system is represented by a water sheet which is a continuum description of a linked-cavity system and exchanges water with the channels along their length. Water storage is parameterised as a function of the subglacial water pressure, which can be interpreted as storage in an englacial aquifer or due to elastic processes. The parabolic equation that determines the water pressure is solved using finite elements, the time evolution of the water sheet thickness and channel diameter are governed by local differential equations that are integrated using explicit methods. To explore the model's properties, we apply it to synthetic ice sheet catchments with areas up to 3000km2. We present steady state drainage system configurations and evaluate their channel-network properties (fractal dimensions, channel spacing). We find that an arborescent channel network forms whose density depends on the water sheet conductivity relative to water input. As a further experiment, we force the model with a seasonally and diurnally varying melt water input to investigate how the modelled drainage system evolves on these time scales: a channelised system grows up glacier as meltwater is delivered to the bed in spring and collapses in autumn. Water pressure is highest just before the formation of channels and then drops. Conversely, the diurnal variations in discharge affect the drainage system morphology only slightly. Instead they lead to large water pressure variations which lag meltwater input and coincide with changes in the volume of stored water. By incorporating an evolving R-channel network within a continuum model of distributed water drainage and storage, this 2-D model succeeds in qualitatively reproducing many of the observed and postulated features of the glacier drainage system.

Test of the principle of operation of a wideband magnetic direction finder for lightning return strokes

NASA Technical Reports Server (NTRS)

Herrman, B. D.; Uman, M. A.; Brantley, R. D.; Krider, E. P.

1976-01-01

The principle of operation of a wideband crossed-loop magnetic-field direction finder is studied by comparing the bearing determined from the NS and EW magnetic fields at various times up to 155 microsec after return stroke initiation with the TV-determined lightning channel base direction. For 40 lightning strokes in the 3 to 12 km range, the difference between the bearings found from magnetic fields sampled at times between 1 and 10 microsec and the TV channel-base data has a standard deviation of 3-4 deg. Included in this standard deviation is a 2-3 deg measurement error. For fields sampled at progressively later times, both the mean and the standard deviation of the difference between the direction-finder bearing and the TV bearing increase. Near 150 microsec, means are about 35 deg and standard deviations about 60 deg. The physical reasons for the late-time inaccuracies in the wideband direction finder and the occurrence of these effects in narrow-band VLF direction finders are considered.

The Effect of a Transcranial Channel as a Skull/Brain Interface in High-Definition Transcranial Direct Current Stimulation—A Computational Study

NASA Astrophysics Data System (ADS)

Seo, Hyeon; Kim, Hyoung-Ihl; Jun, Sung Chan

2017-01-01

A transcranial channel is an interface between the skull and brain; it consists of a biocompatible and highly conductive material that helps convey the current induced by transcranial direct current stimulation (tDCS) to the target area. However, it has been proposed only conceptually, and there has been no concrete study of its efficacy. In this work, we conducted a computational investigation of this conceptual transcranial model with high-definition tDCS, inducing focalized neuromodulation to determine whether inclusion of a transcranial channel performs effectively. To do so, we constructed an anatomically realistic head model and compartmental pyramidal neuronal models. We analyzed membrane polarization by extracellular stimulation and found that the inclusion of a transcranial channel induced polarization at the target area 11 times greater than conventional HD-tDCS without the transcranial channel. Furthermore, the stimulation effect of the transcranial channel persisted up to approximately 80%, even when the stimulus electrodes were displaced approximately 5 mm from the target area. We investigated the efficacy of the transcranial channel and found that greatly improved stimulation intensity and focality may be achieved. Thus, the use of these channels may be promising for clinical treatment.

The Effect of a Transcranial Channel as a Skull/Brain Interface in High-Definition Transcranial Direct Current Stimulation-A Computational Study.

PubMed

Seo, Hyeon; Kim, Hyoung-Ihl; Jun, Sung Chan

2017-01-13

A transcranial channel is an interface between the skull and brain; it consists of a biocompatible and highly conductive material that helps convey the current induced by transcranial direct current stimulation (tDCS) to the target area. However, it has been proposed only conceptually, and there has been no concrete study of its efficacy. In this work, we conducted a computational investigation of this conceptual transcranial model with high-definition tDCS, inducing focalized neuromodulation to determine whether inclusion of a transcranial channel performs effectively. To do so, we constructed an anatomically realistic head model and compartmental pyramidal neuronal models. We analyzed membrane polarization by extracellular stimulation and found that the inclusion of a transcranial channel induced polarization at the target area 11 times greater than conventional HD-tDCS without the transcranial channel. Furthermore, the stimulation effect of the transcranial channel persisted up to approximately 80%, even when the stimulus electrodes were displaced approximately 5 mm from the target area. We investigated the efficacy of the transcranial channel and found that greatly improved stimulation intensity and focality may be achieved. Thus, the use of these channels may be promising for clinical treatment.

Mitochondrial benzodiazepine receptor linked to inner membrane ion channels by nanomolar actions of ligands.

PubMed Central

Kinnally, K W; Zorov, D B; Antonenko, Y N; Snyder, S H; McEnery, M W; Tedeschi, H

1993-01-01

The mitochrondrial benzodiazepine receptor (mBzR) binds a subset of benzodiazepines and isoquinoline carboxamides with nanomolar affinity and consists of the voltage-dependent anion channel, the adenine nucleotide translocator, and an 18-kDa protein. The effect of ligands of the mBzR on two inner mitochondrial membrane channel activities was determined with patch-clamp techniques. The relative inhibitory potencies of the drugs resemble their binding affinities for the mBzR. Ro5-4864 and protoporphyrin IX inhibit activity of the multiple conductance channel (MCC) and the mitochondrial centum-picosiemen (mCtS) channel activities at nanomolar concentrations. PK11195 inhibits mCtS activity at similar levels. Higher concentrations of protoporphyrin IX induce MCC but possibly not mCtS activity. Clonazepam, which has low affinity for mBzR, is at least 500 times less potent at both channel activities. Ro15-1788, which also has a low mBzR affinity, inhibits MCC at very high concentrations (16 microM). The findings indicate an association of these two channel activities with the proteins forming the mBzR complex and are consistent with an interaction of inner and outer membrane channels. PMID:7679505

The use of GIS tools in determining the intensity of meandering of rivers based on the example of Noteć River (Poland)

NASA Astrophysics Data System (ADS)

Szatten, Dawid; Rabant, Hubert; Nadolny, Grzegorz

2017-11-01

The study used the tools of Geographic Information System (GIS) in the analysis of the intensity of meandering of Noteć River, calculated using indicators proposed by Brice [16], Leopold et al. [17], Rust [15] and Rosgen [18]. In this work the emphasis is placed on showing the suitability of using modelling software and spatial data. The study was based on archival cartographic materials and orthophotomap presenting the current course of the river channel. The software of geographic information system used for analysis was ArcMap v.10.0. The rate of meandering of the river in a multiyear period 1876-2013 and four typical scenarios of the development of river channel were determined. Comparing them with the types of human intervention in the fluvial system, the dynamics of transformation channel in the analysed period of time was specified. These types are characteristic for all the meandering rivers. These scenarios can determine the amount of anthropopressure and to evaluate the usefulness of GIS in the analysis of transformations of the fluvial system.

Hydrology, geomorphology, and flood profiles of Lemon Creek, Juneau, Alaska

USGS Publications Warehouse

Host, Randy H.; Neal, Edward G.

2005-01-01

Lemon Creek near Juneau, Alaska has a history of extensive gravel mining, which straightened and deepened the stream channel in the lower reaches of the study area. Gravel mining and channel excavation began in the 1940s and continued through the mid-1980s. Time sequential aerial photos and field investigations indicate that the channel morphology is reverting to pre-disturbance conditions through aggradation of sediment and re-establishment of braided channels, which may result in decreased channel conveyance and increased flooding potential. Time sequential surveys of selected channel cross sections were conducted in an attempt to determine rates of channel aggradation/degradation throughout three reaches of the study area. In order to assess flooding potential in the lower reaches of the study area the U.S. Army Corps of Engineers Hydrologic Engineering Center River Analysis System model was used to estimate the water-surface elevations for the 2-, 10-, 25-, 50-, and 100-year floods. A regionally based regression equation was used to estimate the magnitude of floods for the selected recurrence intervals. Forty-two cross sections were surveyed to define the hydraulic characteristics along a 1.7-mile reach of the stream. High-water marks from a peak flow of 1,820 cubic feet per second, or about a 5-year flood, were surveyed and used to calibrate the model throughout the study area. The stream channel at a bridge in the lower reach could not be simulated without violating assumptions of the model. A model without the lower bridge indicates flood potential is limited to a small area.

Dynamic hybrid materials for constitutional self-instructed membranes

PubMed Central

Cazacu, Adinela; Legrand, Yves-Marie; Pasc, Andreea; Nasr, Gihane; Van der Lee, Arie; Mahon, Eugene; Barboiu, Mihail

2009-01-01

Constitutional self-instructed membranes were developed and used for mimicking the adaptive structural functionality of natural ion-channel systems. These membranes are based on dynamic hybrid materials in which the functional self-organized macrocycles are reversibly connected with the inorganic silica through hydrophobic noncovalent interactions. Supramolecular columnar ion-channel architectures can be generated by reversible confinement within scaffolding hydrophobic silica mesopores. They can be structurally determined by using X-ray diffraction and morphologically tuned by alkali-salts templating. From the conceptual point of view, these membranes express a synergistic adaptive behavior: the simultaneous binding of the fittest cation and its anion would be a case of “homotropic allosteric interactions,” because in time it increases the transport efficiency of the pore-contained superstructures by a selective evolving process toward the fittest ion channel. The hybrid membranes presented here represent dynamic constitutional systems evolving over time to form the fittest ion channels from a library of molecular and supramolecular components, or selecting the fittest ion pairs from a mixture of salts demonstrating flexible adaptation. PMID:19416909

Man-induced channel adjustment in Tennessee streams

USGS Publications Warehouse

Robbins, C.H.; Simon, Andrew

1983-01-01

Channel modifications in Tennessee, particularly in the western part, have led to large-scale instabilities in the channelized rivers and may have contributed to several bridge failures. These modifications, together with land-use practices, led to downcutting, headward erosion, downstream aggradation, accelerated scour, and bank instabilities. Changes in gradient by channel straightening caused more severe channel response than did dredging or clearing. Large-scale changes continue to occur in all the channelized rivers: the Obion River, its forks, and the South Fork Forked Deer River. However, the non-channelized Hatchie River in west Tennessee not only withstood the natural stresses imposed by the wet years of 1973 to 1975 but continues to exhibit characteristics of stability. Water-surface slope, the primary dependent variable, proved to be a sensitive and descriptive parameter useful in determining channel adjustment. Adjustments to man-induced increases in channel-slope are described by inverse exponential functions of the basic form S=ae(-b(t)); where ' S ' is some function describing channel-slope, ' t ' is the number of years since completion of channel work, and ' a ' and ' b ' are coefficients. Response times for the attainment of ' equilibrium ' channel slopes are a function of the magnitude and extent of the imposed modifications. The adjusted profile gradients attained by the streams following channelization are similar to the predisturbed profile gradients, where no alteration to channel length was made. Where the channels were straightened by constructing cut-offs, thus shortening channel length, then slope adjustments (reduction) proceed past the predisturbed profile gradients, to new profiles with lower gradients. (USGS)

Inner/Outer nuclear membrane fusion in nuclear pore assembly: biochemical demonstration and molecular analysis.

PubMed

Fichtman, Boris; Ramos, Corinne; Rasala, Beth; Harel, Amnon; Forbes, Douglass J

2010-12-01

Nuclear pore complexes (NPCs) are large proteinaceous channels embedded in double nuclear membranes, which carry out nucleocytoplasmic exchange. The mechanism of nuclear pore assembly involves a unique challenge, as it requires creation of a long-lived membrane-lined channel connecting the inner and outer nuclear membranes. This stabilized membrane channel has little evolutionary precedent. Here we mapped inner/outer nuclear membrane fusion in NPC assembly biochemically by using novel assembly intermediates and membrane fusion inhibitors. Incubation of a Xenopus in vitro nuclear assembly system at 14°C revealed an early pore intermediate where nucleoporin subunits POM121 and the Nup107-160 complex were organized in a punctate pattern on the inner nuclear membrane. With time, this intermediate progressed to diffusion channel formation and finally to complete nuclear pore assembly. Correct channel formation was blocked by the hemifusion inhibitor lysophosphatidylcholine (LPC), but not if a complementary-shaped lipid, oleic acid (OA), was simultaneously added, as determined with a novel fluorescent dextran-quenching assay. Importantly, recruitment of the bulk of FG nucleoporins, characteristic of mature nuclear pores, was not observed before diffusion channel formation and was prevented by LPC or OA, but not by LPC+OA. These results map the crucial inner/outer nuclear membrane fusion event of NPC assembly downstream of POM121/Nup107-160 complex interaction and upstream or at the time of FG nucleoporin recruitment.

An alternative method for calibration of flow field flow fractionation channels for hydrodynamic radius determination: The nanoemulsion method (featuring multi angle light scattering).

PubMed

Bolinsson, Hans; Lu, Yi; Hall, Stephen; Nilsson, Lars; Håkansson, Andreas

2018-01-19

This study suggests a novel method for determination of the channel height in asymmetrical flow field-flow fractionation (AF4), which can be used for calibration of the channel for hydrodynamic radius determinations. The novel method uses an oil-in-water nanoemulsion together with multi angle light scattering (MALS) and elution theory to determine channel height from an AF4 experiment. The method is validated using two orthogonal methods; first, by using standard particle elution experiments and, secondly, by imaging an assembled and carrier liquid filled channel by x-ray computed tomography (XCT). It is concluded that the channel height can be determined with approximately the same accuracy as with the traditional channel height determination technique. However, the nanoemulsion method can be used under more challenging conditions than standard particles, as the nanoemulsion remains stable in a wider pH range than the previously used standard particles. Moreover, the novel method is also more cost effective. Copyright © 2017 Elsevier B.V. All rights reserved.

Coupling the Near and Far Field Models for Performance Assessment of Repositories for Spent Nuclear Fuel

NASA Astrophysics Data System (ADS)

Liu, L.; Neretnieks, I.

2006-12-01

ABSTRACT In our conceptualisation, water flows in channels in fractures in fractured rocks such as granites. In the Swedish concept for a repository for spent nuclear fuel the canisters containing the spent fuel are embedded in a buffer in holes below the floor of tunnels. The deposition holes can be intersected by fractures with channels with flowing water. The flow in individual channels is determined by the transmissivity properties of the network of the channels. The flowrate around a deposition hole and in the excavation damaged zone around the tunnels will control the rate of mass transfer of corrosive agents and of escaping nuclides. We call the carrying capacity of the solutes an equivalent flowrate. An escaping nuclide will reach the flowing water in the channel and be transported further into the channel network, mixing with water from other channels at some channel intersections and dividing into several channels at other intersection. In order to follow a nuclide from any leaking canister to the effluent points at the ground surface we have integrated our channel network model CHAN3D with our near field mass transfer model NUCTRAN. The NUCTRAN code, based on a compartment model can calculate the release of nuclides from a defective canister through different pathways into the near field of a repository from the local flowrates in the channels near the deposition hole obtained from CHAN3D. The network model CHAN3D uses observed transmissivity distributions and flowing fracture frequencies in boreholes to set up the 3-dimensional network of stochastic fractures. Deterministic fracture zones are described as such with their hydraulic, properties, sizes, locations and extensions. When available, information on fracture length distributions e.g. power law distributions and correlations between sizes and transmissivities are included in the network model. Once flowrates in all channels in the network have been calculated all equivalent flowrates for all canister positions can be calculated. The rate of transport of corrosive agents to and the releases of nuclides from any damaged canister are then calculated. For any given canister location the channel network model is then used to calculate the paths of the nuclides from the canister through the network by particle tracking. A large number of particles are released one by one from the canister and followed from one channel intersection to the next. A mixing rule is used at an intersection to decide which exit the particle takes. We mostly assume full mixing at intersections. The residence time and the ratio of flow wetted surface to flowrate along every path the particles traverse is summed. This information is sufficient to determine the residence time distribution (RTD) of the nuclides along that path also when they are subject to retardation by surface sorption and matrix diffusion. Actually this information is also sufficient to determine the RTD of arbitrary length decay chains subject to some minor (unimportant) simplifying assumptions. In this paper, we discuss in detail the coupling concept of how to integrate the near and far field models, together with the method of how to include transmissive fractures following a power law length distribution and fracture zones into CHAN3D in order to significantly decrease the computer time without loss of important features of the far field. The simulation results regarding a hypothetical repository located at the Forsmark area, Sweden, are also presented and discussed. Our study suggests that the integrated model can be used as an efficient tool to simulate the release of nuclides, including decay chains, from a repository and the transport to recipients.

Ultrasonic flow measurements for irrigation process monitoring

NASA Astrophysics Data System (ADS)

Ziani, Elmostafa; Bennouna, Mustapha; Boissier, Raymond

2004-02-01

This paper presents the state of the art of the general principle of liquid flow measurements by ultrasonic method, and problems of flow measurements. We present an ultrasonic flowmeter designed according to smart sensors concept, for the measurement of irrigation water flowing through pipelines or open channels, using the ultrasonic transit time approach. The new flowmeter works on the principle of measuring time delay differences between sound pulses transmitted upstream and downstream in the flowing liquid. The speed of sound in the flowing medium is eliminated as a variable because the flowrate calculations are based on the reciprocals of the transmission times. The transit time difference is digitally measured by means of a suitable, microprocessor controlled logic. This type of ultrasonic flowmeter will be widely used in industry and water management, it is well studied in this work, followed by some experimental results. For pressurized channels, we use one pair of ultrasonic transducer arranged in proper positions and directions of the pipe, in this case, to determine the liquid velocity, a real time on-line analysis taking account the geometries of the hydraulic system, is applied to the obtained ultrasonic data. In the open channels, we use a single or two pairs of ultrasonic emitter-receiver according to the desired performances. Finally, the goals of this work consist in integrating the smart sensor into irrigation systems monitoring in order to evaluate potential advantages and demonstrate their performance, on the other hand, to understand and use ultrasonic approach for determining flow characteristics and improving flow measurements by reducing errors caused by disturbances of the flow profiles.

Turbulent flow through channels in a viscously deforming matrix

NASA Astrophysics Data System (ADS)

Meyer, Colin; Hewitt, Ian; Neufeld, Jerome

2017-11-01

Channels of liquid melt form within a surrounding solid matrix in a variety of natural settings, for example, lava tubes and water flow through glaciers. Channels of water on the underside of glaciers, known as Rothlisberger (R-) channels, are essential components of subglacial hydrologic systems and can control the rate of glacier sliding. Water flow through these channels is turbulent, and dissipation melts open the channel while viscous creep of the surrounding closes the channel leading to the possibility of a steady state. Here we present an analogous laboratory experiment for R-channels. We pump warm water from the bottom into a tank of corn syrup and a channel forms. The pressure is lower in the water than in the corn syrup, therefore the syrup creeps inward. At the same time, the water ablates the corn syrup through dissolution and shear erosion, which we measure by determining the change in height of the syrup column over the course of the experiment. We find that the creep closure is much stronger than turbulent ablation which leads to traveling solitary waves along the water-syrup interface. These waves or `magmons' have been previously observed in experiments and theory for laminar magma melt conduits. We compliment our experiments with numerical simulations. David Crighton Fellowship.

Determining slack tide with a GPS receiver on an anchored buoy

NASA Astrophysics Data System (ADS)

Valk, M.; Savenije, H. H. G.; Tiberius, C. C. J. M.; Luxemburg, W. M. J.

2014-07-01

In this paper we present a novel method to determine the time of occurrence of tidal slack with a GPS receiver mounted on an anchored buoy commonly used to delineate shipping lanes in estuaries and tidal channels. Slack tide occurs when the tide changes direction from ebb to flood flow or from flood to ebb. The determination of this point in time is not only useful for shipping and salvaging, it is also important information for calibrating tidal models, for determining the maximum salt intrusion and for the further refinement of the theory on tidal propagation. The accuracy of the timing is well within 10 min and the method - able to operate in real time - is relatively cheap and easy to implement on a permanent basis or in short field campaigns.

Determining slack tide with a GPS receiver on an anchored buoy

NASA Astrophysics Data System (ADS)

Valk, M.; Savenije, H. H. G.; Tiberius, C. C. J. M.; Luxemburg, W. M. J.

2013-11-01

In this paper we present a novel method to determine the time of occurrence of tidal slack with a GPS receiver mounted on an anchored buoy commonly used to delineate shipping lanes in estuaries and tidal channels. Slack tide occurs when the tide changes direction from ebb to flood flow, or from flood to ebb. The determination of this point in time is not only useful for shipping and salvaging, it is also important information for calibrating tidal models, for determining the maximum salt intrusion and for the further refinement of the theory on tidal propagation. The accuracy of the timing is well within 10 min and the method - able to operate in real-time - is relatively cheap and easy to implement on a permanent basis or in short field campaigns.

Matrix Analysis of Traditional Chinese Medicine Differential Diagnoses in Gulf War Illness.

PubMed

Taylor-Swanson, Lisa; Chang, Joe; Schnyer, Rosa; Hsu, Kai-Yin; Schmitt, Beth Ann; Conboy, Lisa A

2018-03-08

To qualitatively categorize Traditional Chinese Medicine (TCM) differential diagnoses in a sample of veterans with Gulf War Illness (GWI) pre- and postacupuncture treatment. The authors randomized 104 veterans diagnosed with GWI to a 6-month acupuncture intervention that consisted of either weekly or biweekly individualized acupuncture treatments. TCM differential diagnoses were recorded at baseline and at 6 months. These TCM diagnoses were evaluated using Matrix Analysis to determine co-occurring patterns of excess, deficiency, and channel imbalances. These diagnoses were examined within and between participants to determine patterns of change and to assess stability of TCM diagnoses over time. Frequencies of diagnoses of excess, deficiency, and channel patterns were tabulated. Diagnoses of excess combined with deficiency decreased from 43% at baseline to 39% of the sample at 6 months. Excess+deficiency+channel imbalances decreased from 26% to 17%, while deficiency+channel imbalances decreased from 11% to 4% over the study duration. The authors observed a trend over time of decreased numbers of individuals presenting with all three types of differential diagnosis combinations. This may suggest that fewer people were diagnosed with concurrent excess, deficiency, and channel imbalances and perhaps a lessening in the complexity of their presentation. This is the first published article that organizes and defines TCM differential diagnoses using Matrix Analysis; currently, there are no TCM frameworks for GWI. These findings are preliminary given the sample size and the amount of missing data at 6 months. Characterization of the TCM clinical presentation of veterans suffering from GWI may help us better understand the potential role that East Asian medicine may play in managing veterans with GWI and the design of effective acupuncture treatments based on TCM. The development of a TCM manual for treating GWI is merited.

How has alcohol advertising in traditional and online media in Australia changed? Trends in advertising expenditure 1997-2011.

PubMed

White, Victoria; Faulkner, Agatha; Coomber, Kerri; Azar, Denise; Room, Robin; Livingston, Michael; Chikritzhs, Tanya; Wakefield, Melanie

2015-09-01

The aim of this study was to determine changes in advertising expenditures across eight media channels for the four main alcohol beverage types and alcohol retailers in Australia. Yearly advertising expenditures between January 1997 and December 2011 obtained from a leading media-monitoring company. Media channels assessed were: free-to-air television, newspapers, magazines, radio, outdoors (billboards), cinema, direct mail (from 2005) and online (from 2008). Data were categorised into alcohol retailers (e.g. supermarkets, off-licences) or four alcoholic beverage types (beer, wine, spirits, premixed spirits/cider). Regression analyses examined associations between year and expenditure. Total alcohol advertising expenditure peaked in 2007, then declined to 2011 (P = 0.02). Television advertising expenditure declined between 2000 and 2011 (P < 0.001), while outdoor advertising expenditure increased between 1997 and 2007. Alcohol retailers' advertising expenditure increased over time (P < 0.001), and from the mid-2000s exceeded expenditure for any single beverage category. For both beer and spirits, television advertising expenditure declined over time (beer: P < 0.001; spirits: P < 0.001) while outdoor advertising expenditure increased (beer: P < 0.001; spirits: P = 0.02). However, the number of advertised beer (P < 0.001), spirits (P < 0.001) and wine (P = 0.01) products increased over time. Retailers are playing an increasing role in advertising alcohol. As our study excluded non-traditional advertising media (e.g. sponsorships, in-store) we cannot determine whether declines in television advertising have been offset by increases in advertising in newer media channels. However, our findings that media channels used for alcohol advertising have changed over time highlights the need for adequate controls on alcohol advertising in all media channels. [White V, Faulkner A, Coomber K, Azar D, Room R, Livingston M, Chikritzhs T, Wakefield M. How has alcohol advertising in traditional and online media in Australia changed? Trends in advertising expenditure 1997-2011. Drug Alcohol Rev 2015]2015;34:521-530. © 2015 Australasian Professional Society on Alcohol and other Drugs.

Electrical characterization of single cells using polysilicon wire ion sensor in an isolation window.

PubMed

Wu, You-Lin; Hsu, Po-Yen; Hsu, Chung-Ping; Wang, Chih-Cheng; Lee, Li-Wen; Lin, Jing-Jenn

2011-10-01

A polysilicon wire (PSW) sensor can detect the H(+) ion density (pH value) of the medium coated on its surface, and different cells produce different extracellular acidification and hence different H(+) ion densities. Based on this, we used a PSW sensor in combination with a mold-cast polydimethylsiloxane (PDMS) isolation window to detect the adhesion, apoptosis and extracellular acidification of single normal cells and single cancer cells. Single living human normal cells WI38, MRC5, and BEAS-2B as well as non-small-cell lung cancer (NSCLC) cells A549, H1299, and CH27 were cultivated separately inside the isolation window. The current flowing through the PSW channel was measured. From the PSW channel current change as a function of time, we determined the cell adhesion time by observing the time required for the current change to saturate, since a stable extracellular ion density was established after the cells were completely adhered to the PSW surface. The apoptosis of cells can also be determined when the channel current change drops to zero. We found that all the NSCLC cells had a higher channel current change and hence a lower pH value than the normal cells anytime after they were seeded. The corresponding average pH values were 5.86 for A549, 6.00 for H1299, 6.20 for CH27, 6.90 for BEAS-2B, 6.96for MRC5, and 7.02 for WI38, respectively, after the cells were completely adhered to the PSW surface. Our results show that NSCLC cells have a stronger cell-substrate adhesion and a higher extracellular acidification rate than normal cells.

Drivers and effects of Karenia mikimotoi blooms in the western English Channel

NASA Astrophysics Data System (ADS)

Barnes, Morvan K.; Tilstone, Gavin H.; Smyth, Timothy J.; Widdicombe, Claire E.; Gloël, Johanna; Robinson, Carol; Kaiser, Jan; Suggett, David J.

2015-09-01

Naturally occurring red tides and harmful algal blooms (HABs) are of increasing importance in the coastal environment and can have dramatic effects on coastal benthic and epipelagic communities worldwide. Such blooms are often unpredictable, irregular or of short duration, and thus determining the underlying driving factors is problematic. The dinoflagellate Karenia mikimotoi is an HAB, commonly found in the western English Channel and thought to be responsible for occasional mass finfish and benthic mortalities. We analysed a 19-year coastal time series of phytoplankton biomass to examine the seasonality and interannual variability of K. mikimotoi in the western English Channel and determine both the primary environmental drivers of these blooms as well as the effects on phytoplankton productivity and oxygen conditions. We observed high variability in timing and magnitude of K. mikimotoi blooms, with abundances reaching >1000 cells mL-1 at 10 m depth, inducing up to a 12-fold increase in the phytoplankton carbon content of the water column. No long-term trends in the timing or magnitude of K. mikimotoi abundance were evident from the data. Key driving factors were identified as persistent summertime rainfall and the resultant input of low-salinity high-nutrient river water. The largest bloom in 2009 was associated with highest annual primary production and led to considerable oxygen depletion at depth, most likely as a result of enhanced biological breakdown of bloom material; however, this oxygen depletion may not affect zooplankton. Our data suggests that K. mikimotoi blooms are not only a key and consistent feature of western English Channel productivity, but importantly can potentially be predicted from knowledge of rainfall or river discharge.

Measurement of bridge scour at the SR-32 crossing of the Sacramento River at Hamilton City, California, 1987-92

USGS Publications Warehouse

Blodgett, J.C.; Harris, Carroll D.; ,

1993-01-01

A study of the State Route 32 crossing of the Sacramento River near Hamilton City, California, is being made to determine those channel and bridge factors that contribute to scour at the site. Three types of scour data have been measured-channel bed (natural) scour, constriction (general) scour, and local (bridge-pier induced) scour. During the years 1979-93, a maximum of 3.4 ft of channel bed scour, with a mean of 1.4 ft, has been measured. Constriction scour, which may include channel bed scour, has been measured at the site nine times during the years 1987-92. The calculated amount of constriction scour ranged from 0.2 to 3.0 ft, assuming the reference is the mean bed elevation. Local scour was measured four times at the site in 1991 and 1992 and ranged from -2.1 (fill) to 11.6 ft , with the calculated amounts dependent on the bed reference elevation and method of computation used. Surveys of the channel bed near the bridge piers indicate the horizontal location of lowest bed elevation (maximum depth of scour) may vary at least 17 ft between different surveys at the same pier and most frequently is located downstream from the upstream face of the pier.

Historical channel-planform change of the Little Colorado River near Winslow, Arizona

USGS Publications Warehouse

Block, Debra L.

2014-01-01

This study evaluates channel-planform adjustment on an alluvial reach of the Little Colorado River and documents the geomorphic evolution of the channel through an analysis of aerial photographs and orthophotographs for the period 1936–2010. The Little Colorado River has adjusted to the effects of an extreme flood in 1923 and a subsequent decline in peak discharge and mean annual flow by channel narrowing: the channel width and area of the river have decreased by approximately 90 percent over the study period. Although deposition historically exceeds erosion, lateral migration exacerbates localized erosion, particularly near hydraulic controls. Despite repeated cutoff and avulsion, the Little Colorado River has steadily increased in length and sinuosity over a period of 74 years. Changes in temperature and precipitation are likely affecting the discharge of the Little Colorado River near and downstream of Winslow, Ariz. Nonparametric methods of trend detection determine whether the probability distribution of temperature, precipitation, and peak streamflow has changed over time. Time-series plots of temperature and precipitation show statistically significant trends at the 99-percent-confidence level when evaluated with a Mann-Kendall test. An increasing trend was indicated in mean daily minimum air temperature (Tmin), whereas decreasing trends were indicated in both annual precipitation (Pann) and monsoon-seasonal precipitation (Pjas), as well as in peak discharge.

Dynamic reservoir-condition microtomography of reactive transport in complex carbonates: Effect of initial pore structure and initial brine pH

NASA Astrophysics Data System (ADS)

Menke, H. P.; Bijeljic, B.; Blunt, M. J.

2017-05-01

We study the impact of brine acidity and initial pore structure on the dynamics of fluid/solid reaction at high Péclet numbers and low Damköhler numbers. A laboratory μ-CT scanner was used to image the dissolution of Ketton, Estaillades, and Portland limestones in the presence of CO2-acidified brine at reservoir conditions (10 MPa and 50 °C) at two injected acid strengths for a period of 4 h. Each sample was scanned between 6 and 10 times at ∼4 μm resolution and multiple effluent samples were extracted. The images were used as inputs into flow simulations, and analysed for dynamic changes in porosity, permeability, and reaction rate. Additionally, the effluent samples were used to verify the image-measured porosity changes. We find that initial brine acidity and pore structure determine the type of dissolution. Dissolution is either uniform where the porosity increases evenly both spatially and temporally, or occurs as channelling where the porosity increase is concentrated in preferential flow paths. Ketton, which has a relatively homogeneous pore structure, dissolved uniformly at pH = 3.6 but showed more channelized flow at pH = 3.1. In Estaillades and Portland, increasingly complex carbonates, channelized flow was observed at both acidities with the channel forming faster at lower pH. It was found that the effluent pH, which is higher than that injected, is a reasonably good indicator of effective reaction rate during uniform dissolution, but a poor indicator during channelling. The overall effective reaction rate was up to 18 times lower than the batch reaction rate measured on a flat surface at the effluent pH, with the lowest reaction rates in the samples with the most channelized flow, confirming that transport limitations are the dominant mechanism in determining reaction dynamics at the fluid/solid boundary.

Recent progress in computational approaches to studying the M2 proton channel and its implication to drug design against influenza viruses.

PubMed

Du, Qi-Shi; Huang, Ri-Bo

2012-05-01

For quite a long period of time in history, many intense efforts have been made to determine the 3D (three-dimensional) structure of the M2 proton channel. The reason why the M2 proton channel has attracted so many attentions is because (1) it is the key for really understanding the life cycle of influenza viruses, and (2) it is indispensable for conducting rational drug design against the flu viruses. Recently, the long-sough 3D structures of the M2 proton channels for both influenza A and B viruses were consecutively successfully determined by the high-resolution NMR spectroscopy (Schnell J.R. and Chou, J.J., Nature, 2008, 451: 591-595; Wang, J., Pielak, R.M., McClintock, M.A., and Chou, J.J., Nature Structural & Molecular Biology, 2009,16: 1267-1271). Such a milestone work has provided a solid structural basis for in-depth understanding the action mechanism of the M2 channel and rationally designing effective drugs against influenza viruses. This review is devoted to, with the focus on the M2 proton channel of influenza A, addressing a series of relevant problems, such as how to correctly understand the novel allosteric inhibition mechanism inferred from the NMR structure that is completely different from the traditional view, what the possible impacts are to the previous functional studies in this area, and what kind of new strategy can be stimulated for drug development against influenza.

Measurement and Modeling of Narrowband Channels for Ultrasonic Underwater Communications

PubMed Central

Cañete, Francisco J.; López-Fernández, Jesús; García-Corrales, Celia; Sánchez, Antonio; Robles, Encarnación; Rodrigo, Francisco J.; Paris, José F.

2016-01-01

Underwater acoustic sensor networks are a promising technology that allow real-time data collection in seas and oceans for a wide variety of applications. Smaller size and weight sensors can be achieved with working frequencies shifted from audio to the ultrasonic band. At these frequencies, the fading phenomena has a significant presence in the channel behavior, and the design of a reliable communication link between the network sensors will require a precise characterization of it. Fading in underwater channels has been previously measured and modeled in the audio band. However, there have been few attempts to study it at ultrasonic frequencies. In this paper, a campaign of measurements of ultrasonic underwater acoustic channels in Mediterranean shallow waters conducted by the authors is presented. These measurements are used to determine the parameters of the so-called κ-μ shadowed distribution, a fading model with a direct connection to the underlying physical mechanisms. The model is then used to evaluate the capacity of the measured channels with a closed-form expression. PMID:26907281

Correlated Lightning Mapping Array (LMA) and Radar Observations of the Initial Stages of Florida Triggered Lightning Discharges

NASA Technical Reports Server (NTRS)

Hill, J. D.; Pilkey, J.; Uman, M, A.; Jordan, D. M.; Biggerstaff, M. I.; Rison, W.; Blakeslee, R.

2012-01-01

We characterize the geometrical and electrical characteristics of the initial stages of nine Florida triggered lightning discharges using a Lightning Mapping Array (LMA), a C-band SMART radar, and measured channel-base currents. We determine initial channel and subsequent branch lengths, average initial channel and branch propagation speeds, and channel-base current at the time of each branch initiation. The channel-base current is found to not change significantly when branching occurs, an unexpected result. The initial stage of Florida triggered lightning typically transitions from vertical to horizontal propagation at altitudes of 3-6 km, near the typical 0 C level of 4-5 km and several kilometers below the expected center of the negative cloud-charge region at 7-8 km. The data presented potentially provide information on thunderstorm electrical and hydrometeor structure and discharge propagation physics. LMA source locations were obtained from VHF sources of positive impulsive currents as small as 10 A, in contrast to expectations found in the literature.

Ambipolar Graphene-Quantum Dot Hybrid Vertical Photodetector with a Graphene Electrode.

PubMed

Che, Yongli; Zhang, Yating; Cao, Xiaolong; Zhang, Haiting; Song, Xiaoxian; Cao, Mingxuan; Yu, Yu; Dai, Haitao; Yang, Junbo; Zhang, Guizhong; Yao, Jianquan

2017-09-20

A strategy to fabricate an ambipolar near-infrared vertical photodetector (VPD) by sandwiching a photoactive material as a channel film between the bottom graphene and top metal electrodes was developed. The channel length in the vertical architecture was determined by the channel layer thickness, which can provide an ultrashort channel length without the need for a high-precision manufacturing process. The performance of VPDs with two types of semiconductor layers, a graphene-PbS quantum dot hybrid (GQDH) and PbS quantum dots (QDs), was measured. The GQDH VPD showed better photoelectric properties than the QD VPD because of the high mobility of graphene doped in the channel. The GQDH VPD exhibited excellent photoresponse properties with a responsivity of 1.6 × 10 4 A/W in the p-type regime and a fast response speed with a rise time of 8 ms. The simple manufacture and the promising photoresponse of the GQDH VPDs reveal that an easy and effective way to fabricate high-performance ambipolar photodetectors was developed.

Wavelet Packet Feature Assessment for High-Density Myoelectric Pattern Recognition and Channel Selection toward Stroke Rehabilitation.

PubMed

Wang, Dongqing; Zhang, Xu; Gao, Xiaoping; Chen, Xiang; Zhou, Ping

2016-01-01

This study presents wavelet packet feature assessment of neural control information in paretic upper limb muscles of stroke survivors for myoelectric pattern recognition, taking advantage of high-resolution time-frequency representations of surface electromyogram (EMG) signals. On this basis, a novel channel selection method was developed by combining the Fisher's class separability index and the sequential feedforward selection analyses, in order to determine a small number of appropriate EMG channels from original high-density EMG electrode array. The advantages of the wavelet packet features and the channel selection analyses were further illustrated by comparing with previous conventional approaches, in terms of classification performance when identifying 20 functional arm/hand movements implemented by 12 stroke survivors. This study offers a practical approach including paretic EMG feature extraction and channel selection that enables active myoelectric control of multiple degrees of freedom with paretic muscles. All these efforts will facilitate upper limb dexterity restoration and improved stroke rehabilitation.

Analysis of temperature profiles for investigating stream losses beneath ephemeral channels

USGS Publications Warehouse

Constantz, Jim; Stewart, Amy E.; Niswonger, Richard G.; Sarma, Lisa

2002-01-01

Continuous estimates of streamflow are challenging in ephemeral channels. The extremely transient nature of ephemeral streamflows results in shifting channel geometry and degradation in the calibration of streamflow stations. Earlier work suggests that analysis of streambed temperature profiles is a promising technique for estimating streamflow patterns in ephemeral channels. The present work provides a detailed examination of the basis for using heat as a tracer of stream/groundwater exchanges, followed by a description of an appropriate heat and water transport simulation code for ephemeral channels, as well as discussion of several types of temperature analysis techniques to determine streambed percolation rates. Temperature‐based percolation rates for three ephemeral stream sites are compared with available surface water estimates of channel loss for these sites. These results are combined with published results to develop conclusions regarding the accuracy of using vertical temperature profiles in estimating channel losses. Comparisons of temperature‐based streambed percolation rates with surface water‐based channel losses indicate that percolation rates represented 30% to 50% of the total channel loss. The difference is reasonable since channel losses include both vertical and nonvertical component of channel loss as well as potential evapotranspiration losses. The most significant advantage of the use of sediment‐temperature profiles is their robust and continuous nature, leading to a long‐term record of the timing and duration of channel losses and continuous estimates of streambed percolation. The primary disadvantage is that temperature profiles represent the continuous percolation rate at a single point in an ephemeral channel rather than an average seepage loss from the entire channel.

Crystallization of the Large Membrane Protein Complex Photosystem I in a Microfluidic Channel

PubMed Central

Abdallah, Bahige G.; Kupitz, Christopher; Fromme, Petra; Ros, Alexandra

2014-01-01

Traditional macroscale protein crystallization is accomplished non-trivially by exploring a range of protein concentrations and buffers in solution until a suitable combination is attained. This methodology is time consuming and resource intensive, hindering protein structure determination. Even more difficulties arise when crystallizing large membrane protein complexes such as photosystem I (PSI) due to their large unit cells dominated by solvent and complex characteristics that call for even stricter buffer requirements. Structure determination techniques tailored for these ‘difficult to crystallize’ proteins such as femtosecond nanocrystallography are being developed, yet still need specific crystal characteristics. Here, we demonstrate a simple and robust method to screen protein crystallization conditions at low ionic strength in a microfluidic device. This is realized in one microfluidic experiment using low sample amounts, unlike traditional methods where each solution condition is set up separately. Second harmonic generation microscopy via Second Order Nonlinear Imaging of Chiral Crystals (SONICC) was applied for the detection of nanometer and micrometer sized PSI crystals within microchannels. To develop a crystallization phase diagram, crystals imaged with SONICC at specific channel locations were correlated to protein and salt concentrations determined by numerical simulations of the time-dependent diffusion process along the channel. Our method demonstrated that a portion of the PSI crystallization phase diagram could be reconstructed in excellent agreement with crystallization conditions determined by traditional methods. We postulate that this approach could be utilized to efficiently study and optimize crystallization conditions for a wide range of proteins that are poorly understood to date. PMID:24191698

Multiple channel coincidence detector and controller for microseismic data analysis

DOEpatents

Fasching, George E.

1976-11-16

A multiple channel coincidence detector circuit is provided for analyzing data either in real time or recorded data on a magnetic tape during an experiment for determining location and progression of fractures in an oil field or the like while water is being injected at high pressure in wells located in the field. The circuit is based upon the utilization of a set of parity generator trees combined with monostable multivibrators to detect the occurrence of two events at any pair of channel input terminals that are within a preselected time frame and have an amplitude above a preselected magnitude. The parity generators perform an exclusive OR function in a timing circuit composed of monostable multivibrators that serve to yield an output when two events are present in the preselected time frame. Any coincidences falling outside this time frame are considered either noise or not otherwise useful in the analysis of the recorded data. Input pulses of absolute magnitude below the low-level threshold setting of a bipolar low-level threshold detector are unwanted and therefore rejected. A control output is provided for a utilization device from a coincidence hold circuit that may be used to halt a tape search unit at the time of coincidence or perform other useful control functions.

Potassium channels: the importance of transport signals.

PubMed

Griffith, L C

2001-03-20

The number, type and distribution of ion channels on a neuron's surface determine its electrical response to stimulation. One way that a cell determines how many molecules of each channel type are sent to the surface has been eludicated in a recent study of intrinsic protein transport signals within potassium channels.

On the number of channels needed to classify vowels: Implications for cochlear implants

NASA Astrophysics Data System (ADS)

Fourakis, Marios; Hawks, John W.; Davis, Erin

2005-09-01

In cochlear implants the incoming signal is analyzed by a bank of filters. Each filter is associated with an electrode to constitute a channel. The present research seeks to determine the number of channels needed for optimal vowel classification. Formant measurements of vowels produced by men and women [Hillenbrand et al., J. Acoust. Soc. Am. 97, 3099-3111 (1995)] were converted to channel assignments. The number of channels varied from 4 to 20 over two frequency ranges (180-4000 and 180-6000 Hz) in equal bark steps. Channel assignments were submitted to linear discriminant analysis (LDA). Classification accuracy increased with the number of channels, ranging from 30% with 4 channels to 98% with 20 channels, both for the female voice. To determine asymptotic performance, LDA classification scores were plotted against the number of channels and fitted with quadratic equations. The number of channels at which no further improvement occurred was determined, averaging 19 across all conditions with little variation. This number of channels seems to resolve the frequency range spanned by the first three formants finely enough to maximize vowel classification. This resolution may not be achieved using six or eight channels as previously proposed. [Work supported by NIH.

Vertical displacements inherited from pre-Neogene time in the Gulfes of Sigacik and Kusadasi (Western Anatolia) by multi channel seismic and chirp data

NASA Astrophysics Data System (ADS)

Gurcay, S.; Cifci, G.; Dondurur, D.; Sozbilir, H.

2012-12-01

Gulfes of Sigacik and Kusadasi (Western Anatolia) are located south of the Middle Eastern Aegean depression which formed by vertical displacements along the NB- to N-trending structural planes. This study consists of the results of the multi-channel seismic reflection and chirp data acquisition by K. Piri Reis, research vessel of Dokuz Eylül University (Izmir-TURKEY), in Sigacik Gulf and Kusadasi Gulf (West Anatolia) in August-2005 and in March-2008. Data were acquired approximately along the 1300km seismic lines. Two main seismic units, lower unit (Pre-Neogene) and upper unit (Neogene), can easily be determined on multi channel seismic sections. It is also observed on seismic sections that there are many active faults deform these units. Two main submarine basins can be determined from multi-channel seismic sections, Sigacik Basin and Kusadasi Basin. The upper unit in Sigacik Basin is deformed generally by strike slip faults. But there are some faults that have sharp vertical movements on lower unit. Some of these vertical movements are followed by strike-slip active faults along the upper unit indicating that these normal movements have changed to lateral movements, recently.

Using an experimental manipulation to determine the effectiveness of a stock enhancement program

USGS Publications Warehouse

Stewart, David R.; Long, James M.

2015-01-01

We used an experimental manipulation to determine the impact of stocking 178 mm channel catfish Ictalurus punctatus in six impoundments. The study design consisted of equal numbers (two) of control, ceased-stock, and stocked treatments that were sampled one year before and two years after stocking. Relative abundance, growth, size structure, and average weight significantly changed over time based on samples collected with hoop nets. Catch rates decreased at both ceased-stock lakes and increased for one stocked lake, while growth rates changed for at least one ceased-stock and stocked lake. The average weight of channel catfish in the ceased-stock treatment increased by 6% and 25%, whereas weight decreased by 28% and 78% in both stocked lakes. The variability in observed responses between lakes in both ceased-stock and stocked treatments indicates that a one-size-fits-all stocking agenda is impractical, suggesting lake specific and density-dependent mechanisms affect channel catfish population dynamics.

Alluvial cover controlling the width, slope and sinuosity of bedrock channels

NASA Astrophysics Data System (ADS)

Turowski, Jens Martin

2018-02-01

Bedrock channel slope and width are important parameters for setting bedload transport capacity and for stream-profile inversion to obtain tectonics information. Channel width and slope development are closely related to the problem of bedrock channel sinuosity. It is therefore likely that observations on bedrock channel meandering yields insights into the development of channel width and slope. Active meandering occurs when the bedrock channel walls are eroded, which also drives channel widening. Further, for a given drop in elevation, the more sinuous a channel is, the lower is its channel bed slope in comparison to a straight channel. It can thus be expected that studies of bedrock channel meandering give insights into width and slope adjustment and vice versa. The mechanisms by which bedrock channels actively meander have been debated since the beginning of modern geomorphic research in the 19th century, but a final consensus has not been reached. It has long been argued that whether a bedrock channel meanders actively or not is determined by the availability of sediment relative to transport capacity, a notion that has also been demonstrated in laboratory experiments. Here, this idea is taken up by postulating that the rate of change of both width and sinuosity over time is dependent on bed cover only. Based on the physics of erosion by bedload impacts, a scaling argument is developed to link bedrock channel width, slope and sinuosity to sediment supply, discharge and erodibility. This simple model built on sediment-flux-driven bedrock erosion concepts yields the observed scaling relationships of channel width and slope with discharge and erosion rate. Further, it explains why sinuosity evolves to a steady-state value and predicts the observed relations between sinuosity, erodibility and storm frequency, as has been observed for meandering bedrock rivers on Pacific Arc islands.

Standardizing the atomic description, axis and centre of biological ion channels.

PubMed

Kaats, Adrian J; Galiana, Henrietta L; Nadeau, Jay L

2007-09-15

A general representation of the atomic co-ordinates of a biological ion channel is obtained from a definition of channel axis and centre. Through rotation and translation of the channel, its centre becomes the origin of the standard co-ordinate system, and the channel axis becomes the system's z-axis. A method for determining the channel axis and centre based on the concepts of mass centre and mass moment of inertia is presented. The method for determining the channel axis can be directly applied to channels that adhere to two specific conditions regarding their geometry and mass distribution. Specific examples are given for Gramicidin A (GA), and the mammalian potassium channel Kv 1.2. For channels that do not adhere to these conditions, minor modifications of these procedures can be applied in determining the channel axis. Specific examples are given for the outer membrane bacterial porin OmpF, and for the staphylococcal pore-forming toxin alpha-hemolysin (alpha HL). The definitions and procedures presented are made in an effort to establish a standard basis for performing, sharing, and comparing computations in a consistent manner.

Timing and Duration of Flow in Ephemeral Streams of the Sierra Vista Subwatershed of the Upper San Pedro Basin, Cochise County, Southeastern Arizona

USGS Publications Warehouse

Gungle, Bruce

2006-01-01

Frequency, timing, and duration of streamflow were monitored in 20 ephemeral-stream channels across the Sierra Vista Subwatershed of the Upper San Pedro Basin, southeastern Arizona, during an 18-month period. One channel (Walnut Gulch) had Agricultural Research Service streamflow-gaging stations in place. The sediments of the remaining 19 ephemeral-stream channels were instrumented with multiple temperature loggers along the channel lengths. A thermograph-interpretation technique was developed in order to determine frequency, timing, and duration of streamflow in these channels. Streamflow onset was characterized by exceedance of a critical minimum drop in temperature within the channel sediments during any 15-minute interval, whereas streamflow cessation was identified by the local temperature minimum that immediately followed the critical temperature drop. All data for the 18-month period from December 1, 2000, to May 31, 2002, were analyzed in terms of monsoon (June 1 to September 19) and nonmonsoon (September 20 to May 31) periods. Nonmonsoon precipitation during the 2000-2002 study period (excludes October and November 2000) was 82 percent and 39 percent of the 30-year average, respectively, whereas monsoon precipitation during 2001 was 99 percent of the 30-year average. Ephemeral streamflow was detected at least once during the monitoring period at 87 percent of the monitoring sites (45 of the 52 sites that returned useful data; includes 4 streamflow-gaging stations). The summer monsoon period accounted for 82 percent of all streamflow events by number and 71 percent of all events by total streamflow duration. Nonmonsoon streamflow events peaked in number, total streamflow duration, and mean streamflow duration midway between the Huachuca Mountains and the San Pedro River on the west side of the subwatershed. These three streamflow parameters dropped off sharply about 10 kilometers from the mountain front. The number and total duration of nonmonsoon streamflows on the east side of the subwatershed trended downward with increased distance from the mountain fronts. Monsoon streamflow events were more evenly distributed across the subwatershed than nonmonsoon events, and the number and duration of streamflows generally trended upward with distance from the mountain fronts. Additional years of data are needed to determine whether these patterns are consistent year to year, or were due to randomness in the spatial distribution of precipitation. Streamflows in three ephemeral-stream channels were analyzed in detail. More than two-thirds of the streamflow events detected in each of these channels occurred at no more than one monitoring site along the channel length. In only one of the three channels-Garden Canyon-was a streamflow event detected at all logger sites along its length. Five temperature loggers provided data from urbanized areas, and these loggers detected streamflow more than 50 percent more often and of a duration nearly three times greater than did temperature loggers across the rural parts of the subwatershed. Because historical records do not indicate that more precipitation occurs in the urbanized area than in the rural areas, the increased frequency of flow detection in the urban area is attributed to an increase in runoff from the impervious surfaces throughout the urbanized area.

The extent and nature of television food advertising to children in Xi'an, China.

PubMed

Li, Danyang; Wang, Ting; Cheng, Yue; Zhang, Min; Yang, Xue; Zhu, Zhonghai; Liu, Danli; Yang, Wenfang; Zeng, Lingxia

2016-08-11

To explore the extent and nature of television food advertising especially unhealthy food advertising to primary school children in Xi'an, China. Television data were recorded for 2 weekdays and 2 weekend days between 6:00 and 22:00 during May and June in 2012 from a total of five television channels most popular with children in Xi'an. Pearson χ (2) tests and logistic regression were applied to determine differences in the proportion of healthy food, unhealthy food and miscellaneous food advertisements for different channels, programs, dates, viewing periods and the use of persuasive marketing tactics. Of the 5527 advertisements transcribed, 25.5 % were for food, among which 48.1 % were considered to be unhealthy. The frequency of food advertisements was 6 per hour per channel, including 3 unhealthy food advertisements. Compared with healthy and miscellaneous food advertisements, more unhealthy food advertisements were shown during afternoon, weekends and children's non-peak viewing times as well as on children's television channels, central television channels and non-children's programmes. Unhealthy foods contributed the highest proportion of all food advertisements containing promotional characters (51.7 %) and premium offers (59.1 %). Both promotional characters and premium offers appeared more on non-children's television channels. The majority of food advertisements were for unhealthy food. More unhealthy food ads were shown in children's non-peak time and afternoon as well as non-children's channels. More children-oriented persuasive marketing tactics were used in unhealthy food ads especially in non-children's channels. Therefore, intervening in the entrance of unhealthy foods into the market and establishing regulations related to food advertising especially unhealthy food advertisements are important strategies to prevent children's exposure to unhealthy food and childhood obesity.

The role of cystic fibrosis transmembrane conductance regulator phenylalanine 508 side chain in ion channel gating

PubMed Central

Cui, Liying; Aleksandrov, Luba; Hou, Yue-Xian; Gentzsch, Martina; Chen, Jey-Hsin; Riordan, John R; Aleksandrov, Andrei A

2006-01-01

Cystic fibrosis transmembrane conductance regulator (CFTR) is an ion channel employing the ABC transporter structural motif. Deletion of a single residue (Phe508) in the first nucleotide-binding domain (NBD1), which occurs in most patients with cystic fibrosis, impairs both maturation and function of the protein. However, substitution of the Phe508 with small uncharged amino acids, including cysteine, is permissive for maturation. To explore the possible role of the phenylalanine aromatic side chain in channel gating we introduced a cysteine at this position in cysless CFTR, enabling its selective chemical modification by sulfhydryl reagents. Both cysless and wild-type CFTR ion channels have identical mean open times when activated by different nucleotide ligands. Moreover, both channels could be locked in an open state by introducing an ATPase inhibiting mutation (E1371S). However, the introduction of a single cysteine (F508C) prevented the cysless E1371S channel from maintaining the permanently open state, allowing closing to occur. Chemical modification of cysless E1371S/F508C by sulfhydryl reagents was used to probe the role of the side chain in ion channel function. Specifically, benzyl-methanethiosulphonate modification of this variant restored the gating behaviour to that of cysless E1371S containing the wild-type phenylalanine at position 508. This provides the first direct evidence that a specific interaction of the Phe508 aromatic side chain plays a role in determining the residency time in the closed state. Thus, despite the fact that this aromatic side chain is not essential for CFTR folding, it is important in the ion channel function. PMID:16484308

Calcium channel currents in bovine adrenal chromaffin cells and their modulation by anaesthetic agents.

PubMed Central

Charlesworth, P; Pocock, G; Richards, C D

1994-01-01

1. The calcium channel currents of bovine adrenal chromaffin cells were characterized using a variety of voltage pulse protocols and selective channel blockers before examination of their modulation by anaesthetic agents. 2. All the anaesthetics studied (halothane, methoxyflurane, etomidate and methohexitone) inhibited the calcium channel currents in a concentration-dependent manner and increased the rate of current decay. 3. The anaesthetics did not shift the current-voltage relation nor did they change the voltage for half-maximal channel activation derived from analysis of the voltage dependence of the tail currents. None of the anaesthetics appeared to alter the time constant of tail current decay. 4. To complement earlier studies of the inhibitory actions of anaesthetics on K(+)-evoked catecholamine secretion and the associated Ca2+ uptake, the IC50 values for etomidate and methohexitone were determined using a biochemical assay. The IC50 values for anaesthetic inhibition of calcium channel currents corresponded closely with those for inhibition of K(+)-evoked calcium uptake and catecholamine secretion. 5. The inhibitory effect of the volatile anaesthetics and etomidate is best explained by dual action: a reduction in the probability of channel opening coupled with an increase in the rate of channel inactivation. Methohexitone appeared to inhibit the currents by a use-dependent slow block. PMID:7707224

The Effect of a Transcranial Channel as a Skull/Brain Interface in High-Definition Transcranial Direct Current Stimulation—A Computational Study

PubMed Central

Seo, Hyeon; Kim, Hyoung-Ihl; Jun, Sung Chan

2017-01-01

A transcranial channel is an interface between the skull and brain; it consists of a biocompatible and highly conductive material that helps convey the current induced by transcranial direct current stimulation (tDCS) to the target area. However, it has been proposed only conceptually, and there has been no concrete study of its efficacy. In this work, we conducted a computational investigation of this conceptual transcranial model with high-definition tDCS, inducing focalized neuromodulation to determine whether inclusion of a transcranial channel performs effectively. To do so, we constructed an anatomically realistic head model and compartmental pyramidal neuronal models. We analyzed membrane polarization by extracellular stimulation and found that the inclusion of a transcranial channel induced polarization at the target area 11 times greater than conventional HD-tDCS without the transcranial channel. Furthermore, the stimulation effect of the transcranial channel persisted up to approximately 80%, even when the stimulus electrodes were displaced approximately 5 mm from the target area. We investigated the efficacy of the transcranial channel and found that greatly improved stimulation intensity and focality may be achieved. Thus, the use of these channels may be promising for clinical treatment. PMID:28084429

On-chip polarimetry for high-throughput screening of nanoliter and smaller sample volumes

NASA Technical Reports Server (NTRS)

Bachmann, Brian O. (Inventor); Bornhop, Darryl J. (Inventor); Dotson, Stephen (Inventor)

2012-01-01

A polarimetry technique for measuring optical activity that is particularly suited for high throughput screening employs a chip or substrate (22) having one or more microfluidic channels (26) formed therein. A polarized laser beam (14) is directed onto optically active samples that are disposed in the channels. The incident laser beam interacts with the optically active molecules in the sample, which slightly alter the polarization of the laser beam as it passes multiple times through the sample. Interference fringe patterns (28) are generated by the interaction of the laser beam with the sample and the channel walls. A photodetector (34) is positioned to receive the interference fringe patterns and generate an output signal that is input to a computer or other analyzer (38) for analyzing the signal and determining the rotation of plane polarized light by optically active material in the channel from polarization rotation calculations.

DCP-collected absolute target reflectance signatures assist accurate interpretation of ERTS-1 imagery

NASA Technical Reports Server (NTRS)

Weber, F. P.

1973-01-01

Data collection platforms (DCP's) are being used at a Black Hills, South Dakota, test site (MMC 226A) to record radiometric measurements needed to determine solar and atmospheric parameters that affect ERTS-1 multispectral scanner radiance measurements. A total of 72 channels of analog data transmitted from an unattended ground truth site via three DCP's at least six times a day. The system has operated with only minor problems since September, sending forth daily measurements of biophysical responses and atmospheric conditions. Comparisons of scene radiance data calculated from ERTS images with that measured on the ground show the image-measured values to be 35 percent higher for the green channel and 20 percent higher for the red channel for the same scene targets. Radiance values for channels 6 and 7 are nearly the same from the ground data and from the imagery.

Alcohol modulation of BK channel gating depends on β subunit composition

PubMed Central

Kuntamallappanavar, Guruprasad

2016-01-01

In most mammalian tissues, Ca2+i/voltage-gated, large conductance K+ (BK) channels consist of channel-forming slo1 and auxiliary (β1–β4) subunits. When Ca2+i (3–20 µM) reaches the vicinity of BK channels and increases their activity at physiological voltages, β1- and β4-containing BK channels are, respectively, inhibited and potentiated by intoxicating levels of ethanol (50 mM). Previous studies using different slo1s, lipid environments, and Ca2+i concentrations—all determinants of the BK response to ethanol—made it impossible to determine the specific contribution of β subunits to ethanol action on BK activity. Furthermore, these studies measured ethanol action on ionic current under a limited range of stimuli, rendering no information on the gating processes targeted by alcohol and their regulation by βs. Here, we used identical experimental conditions to obtain single-channel and macroscopic currents of the same slo1 channel (“cbv1” from rat cerebral artery myocytes) in the presence and absence of 50 mM ethanol. First, we assessed the role five different β subunits (1,2,2-IR, 3-variant d, and 4) in ethanol action on channel function. Thus, two phenotypes were identified: (1) ethanol potentiated cbv1-, cbv1+β3-, and cbv1+β4-mediated currents at low Ca2+i while inhibiting current at high Ca2+i, the potentiation–inhibition crossover occurring at 20 µM Ca2+i; (2) for cbv1+β1, cbv1+wt β2, and cbv1+β2-IR, this crossover was shifted to ∼3 µM Ca2+i. Second, applying Horrigan–Aldrich gating analysis on both phenotypes, we show that ethanol fails to modify intrinsic gating and the voltage-dependent parameters under examination. For cbv1, however, ethanol (a) drastically increases the channel’s apparent Ca2+ affinity (nine-times decrease in Kd) and (b) very mildly decreases allosteric coupling between Ca2+ binding and channel opening (C). The decreased Kd leads to increased channel activity. For cbv1+β1, ethanol (a) also decreases Kd, yet this decrease (two times) is much smaller than that of cbv1; (b) reduces C; and (c) decreases coupling between Ca2+ binding and voltage sensing (parameter E). Decreased allosteric coupling leads to diminished BK activity. Thus, we have identified critical gating modifications that lead to the differential actions of ethanol on slo1 with and without different β subunits. PMID:27799321

Location of acoustic radiators and inversion for energy density using radio-frequency sources and thunder recordings

NASA Astrophysics Data System (ADS)

Anderson, J.; Johnson, J. B.; Arechiga, R. O.; Edens, H. E.; Thomas, R. J.

2011-12-01

We use radio frequency (VHF) pulse locations mapped with the New Mexico Tech Lightning Mapping Array (LMA) to study the distribution of thunder sources in lightning channels. A least squares inversion is used to fit channel acoustic energy radiation with broadband (0.01 to 500 Hz) acoustic recordings using microphones deployed local (< 10 km) to the lightning. We model the thunder (acoustic) source as a superposition of line segments connecting the LMA VHF pulses. An optimum branching algorithm is used to reconstruct conductive channels delineated by VHF sources, which we discretize as a superposition of finely-spaced (0.25 m) acoustic point sources. We consider total radiated thunder as a weighted superposition of acoustic waves from individual channels, each with a constant current along its length that is presumed to be proportional to acoustic energy density radiated per unit length. Merged channels are considered as a linear sum of current-carrying branches and radiate proportionally greater acoustic energy. Synthetic energy time series for a given microphone location are calculated for each independent channel. We then use a non-negative least squares inversion to solve for channel energy densities to match the energy time series determined from broadband acoustic recordings across a 4-station microphone network. Events analyzed by this method have so far included 300-1000 VHF sources, and correlations as high as 0.5 between synthetic and recorded thunder energy were obtained, despite the presence of wind noise and 10-30 m uncertainty in VHF source locations.

Mechanism of hERG channel block by the psychoactive indole alkaloid ibogaine.

PubMed

Thurner, Patrick; Stary-Weinzinger, Anna; Gafar, Hend; Gawali, Vaibhavkumar S; Kudlacek, Oliver; Zezula, Juergen; Hilber, Karlheinz; Boehm, Stefan; Sandtner, Walter; Koenig, Xaver

2014-02-01

Ibogaine is a psychoactive indole alkaloid. Its use as an antiaddictive agent has been accompanied by QT prolongation and cardiac arrhythmias, which are most likely caused by human ether a go-go-related gene (hERG) potassium channel inhibition. Therefore, we studied in detail the interaction of ibogaine with hERG channels heterologously expressed in mammalian kidney tsA-201 cells. Currents through hERG channels were blocked regardless of whether ibogaine was applied via the extracellular or intracellular solution. The extent of inhibition was determined by the relative pH values. Block occurred during activation of the channels and was not observed for resting channels. With increasing depolarizations, ibogaine block grew and developed faster. Steady-state activation and inactivation of the channel were shifted to more negative potentials. Deactivation was slowed, whereas inactivation was accelerated. Mutations in the binding site reported for other hERG channel blockers (Y652A and F656A) reduced the potency of ibogaine, whereas an inactivation-deficient double mutant (G628C/S631C) was as sensitive as wild-type channels. Molecular drug docking indicated binding within the inner cavity of the channel independently of the protonation of ibogaine. Experimental current traces were fit to a kinetic model of hERG channel gating, revealing preferential binding of ibogaine to the open and inactivated state. Taken together, these findings show that ibogaine blocks hERG channels from the cytosolic side either in its charged form alone or in company with its uncharged form and alters the currents by changing the relative contribution of channel states over time.

Unconstrained Capacities of Quantum Key Distribution and Entanglement Distillation for Pure-Loss Bosonic Broadcast Channels.

PubMed

Takeoka, Masahiro; Seshadreesan, Kaushik P; Wilde, Mark M

2017-10-13

We consider quantum key distribution (QKD) and entanglement distribution using a single-sender multiple-receiver pure-loss bosonic broadcast channel. We determine the unconstrained capacity region for the distillation of bipartite entanglement and secret key between the sender and each receiver, whenever they are allowed arbitrary public classical communication. A practical implication of our result is that the capacity region demonstrated drastically improves upon rates achievable using a naive time-sharing strategy, which has been employed in previously demonstrated network QKD systems. We show a simple example of a broadcast QKD protocol overcoming the limit of the point-to-point strategy. Our result is thus an important step toward opening a new framework of network channel-based quantum communication technology.

FIBER AND INTEGRATED OPTICS: New method for determination of the parameters of a channel waveguide

NASA Astrophysics Data System (ADS)

Galechyan, M. G.; Dianov, Evgenii M.; Lyndin, N. M.; Sychugov, V. A.; Tishchenko, A. V.; Usievich, B. A.

1992-02-01

A new method for the determination of the parameters of channel integrated optical waveguides is proposed. This method is based on measuring the spectral transmission of a system comprising the investigated waveguide and single-mode fiber waveguides, which are brought into contact with the channel waveguide. The results are reported of an investigation of two channel waveguides formed in glass by a variety of methods and characterized by different refractive index profiles. The proposed method is found to be suitable for determination of the parameters of the refractive index profile of the investigated channel waveguides.

A User Guide to PARET/ANL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Olson, A. P.; Dionne, B.; Marin-Lafleche, A.

2015-01-01

PARET was originally created in 1969 at what is now Idaho National Laboratory (INL), to analyze reactivity insertion events in research and test reactor cores cooled by light or heavy water, with fuel composed of either plates or pins. The use of PARET is also appropriate for fuel assemblies with curved fuel plates when their radii of curvatures are large with respect to the fuel plate thickness. The PARET/ANL version of the code has been developed at Argonne National Laboratory (ANL) under the sponsorship of the U.S. Department of Energy/NNSA, and has been used by the Reactor Conversion Program tomore » determine the expected transient behavior of a large number of reactors. PARET/ANL models the various fueled regions of a reactor core as channels. Each of these channels consists of a single flat fuel plate/pin (including cladding and, optionally, a gap) with water coolant on each side. In slab geometry the coolant channels for a given fuel plate are of identical dimensions (mirror symmetry), but they can be of different thickness in each channel. There can be many channels, but each channel is independent and coupled only through reactivity feedback effects to the whole core. The time-dependent differential equations that represent the system are replaced by an equivalent set of finite-difference equations in space and time, which are integrated numerically. PARET/ANL uses fundamentally the same numerical scheme as RELAP5 for the time-integration of the point-kinetics equations. The one-dimensional thermal-hydraulic model includes temperature-dependent thermal properties of the solid materials, such as heat capacity and thermal conductivity, as well as the transient heat production and heat transfer from the fuel meat to the coolant. Temperature- and pressure-dependent thermal properties of the coolant such as enthalpy, density, thermal conductivity, and viscosity are also used in determining parameters such as friction factors and heat transfer coefficients. The code first determines the steady-state solution for the initial state. Then the solution of the transient is obtained by integration in time and space. Multiple heat transfer, DNB and flow instability correlations are available. The code was originally developed to model reactors cooled by an open loop, which was adequate for rapid transients in pool-type cores. An external loop model appropriate for Miniature Neutron Source Reactors (MNSR’s) was also added to PARET/ANL to model natural circulation within the vessel, heat transfer from the vessel to pool and heat loss by evaporation from the pool. PARET/ANL also contains models for decay heat after shutdown, control rod reactivity versus time or position, time-dependent pump flow, and loss-of-flow event with flow reversal as well as logic for trips on period, power, and flow. Feedback reactivity effects from coolant density changes and temperature changes are represented by tables. Feedback reactivity from fuel heat-up (Doppler Effect) is represented by a four-term polynomial in powers of fuel temperature. Photo-neutrons produced in beryllium or in heavy water may be included in the point-kinetics equations by using additional delayed neutron groups.« less

Automatic pickup of arrival time of channel wave based on multi-channel constraints

NASA Astrophysics Data System (ADS)

Wang, Bao-Li

2018-03-01

Accurately detecting the arrival time of a channel wave in a coal seam is very important for in-seam seismic data processing. The arrival time greatly affects the accuracy of the channel wave inversion and the computed tomography (CT) result. However, because the signal-to-noise ratio of in-seam seismic data is reduced by the long wavelength and strong frequency dispersion, accurately timing the arrival of channel waves is extremely difficult. For this purpose, we propose a method that automatically picks up the arrival time of channel waves based on multi-channel constraints. We first estimate the Jaccard similarity coefficient of two ray paths, then apply it as a weight coefficient for stacking the multichannel dispersion spectra. The reasonableness and effectiveness of the proposed method is verified in an actual data application. Most importantly, the method increases the degree of automation and the pickup precision of the channel-wave arrival time.

Single cell analysis of voltage-gated potassium channels that determines neuronal types of rat hypothalamic paraventricular nucleus neurons.

PubMed

Lee, S K; Lee, S; Shin, S Y; Ryu, P D; Lee, S Y

2012-03-15

The hypothalamic paraventricular nucleus (PVN), a site for the integration of both the neuroendocrine and autonomic systems, has heterogeneous cell composition. These neurons are classified into type I and type II neurons based on their electrophysiological properties. In the present study, we investigated the molecular identification of voltage-gated K+ (Kv) channels, which determines a distinctive characteristic of type I PVN neurons, by means of single-cell reverse transcription-polymerase chain reaction (RT-PCR) along with slice patch clamp recordings. In order to determine the mRNA expression profiles, firstly, the PVN neurons of male rats were classified into type I and type II neurons, and then, single-cell RT-PCR and single-cell real-time RT-PCR analysis were performed using the identical cell. The single-cell RT-PCR analysis revealed that Kv1.2, Kv1.3, Kv1.4, Kv4.1, Kv4.2, and Kv4.3 were expressed both in type I and in type II neurons, and several Kv channels were co-expressed in a single PVN neuron. However, we found that the expression densities of Kv4.2 and Kv4.3 were significantly higher in type I neurons than in type II neurons. Taken together, several Kv channels encoding A-type K+ currents are present both in type I and in type II neurons, and among those, Kv4.2 and Kv4.3 are the major Kv subunits responsible for determining the distinct electrophysiological properties. Thus these 2 Kv subunits may play important roles in determining PVN cell types and regulating PVN neuronal excitability. This study further provides key molecular mechanisms for differentiating type I and type II PVN neurons. Copyright © 2012 IBRO. Published by Elsevier Ltd. All rights reserved.

Turbulence- and particle-resolved modeling of self-formed channels

NASA Astrophysics Data System (ADS)

Schmeeckle, M. W.

2016-12-01

A numerical model is presented that combines a large eddy simulation (LES) of turbulent water motion and a discrete element method (DEM) simulation of all sediment particles forming a small alluvial river. All simulations are begun with a relatively narrow and deep channel and a constant body force is applied to the fluid. At very small applied force at the critical shear stress for sediment motion the channel becomes wider and shallower. Transport on the banks becomes very small with larger transport at the center of the channel. However, even the very small bank transport resulted in continued net downslope motion and channel widening; bedload diffusion from higher transport areas of the channel is not sufficient to counteract downslope transport. This simulation will be extended over much longer times to determine whether an equilibrium straight channel with transport is possible without varying the water discharge. Simulations at slightly higher fluid forcing results in the development of alternate bars. Particle size segregation occurs in all simulations at multiple scales. At the smallest scale, turbulent structures induce small scale depressions; larger particles preferentially move to lower elevations of the depressions. Sloping beds at banks and bars also increase size segregation. However, bar translation mixes segregated sediments. Granular modeling of river channels appears to be a fruitful method for testing and developing continuum ideas of channel pattern formation and size segregation.

Turbulence-and particle-resolved modeling of self-formed channels

NASA Astrophysics Data System (ADS)

Schmeeckle, M. W.

2017-12-01

A numerical model is presented that combines a large eddy simulation (LES) of turbulent water motion and a discrete element method (DEM) simulation of all sediment particles forming a small alluvial river. All simulations are begun with a relatively narrow and deep channel and a constant body force is applied to the fluid. At very small applied force at the critical shear stress for sediment motion the channel becomes wider and shallower. Transport on the banks becomes very small with larger transport at the center of the channel. However, even the very small bank transport resulted in continued net downslope motion and channel widening; bedload diffusion from higher transport areas of the channel is not sufficient to counteract downslope transport. This simulation will be extended over much longer times to determine whether an equilibrium straight channel with transport is possible without varying the water discharge. Simulations at slightly higher fluid forcing results in the development of alternate bars. Particle size segregation occurs in all simulations at multiple scales. At the smallest scale, turbulent structures induce small scale depressions; larger particles preferentially move to lower elevations of the depressions. Sloping beds at banks and bars also increase size segregation. However, bar translation mixes segregated sediments. Granular modeling of river channels appears to be a fruitful method for testing and developing continuum ideas of channel pattern formation and size segregation.

Kv4 channels underlie A-currents with highly variable inactivation time courses but homogeneous other gating properties in the nucleus tractus solitarii.

PubMed

Strube, Caroline; Saliba, Layal; Moubarak, Estelle; Penalba, Virginie; Martin-Eauclaire, Marie-France; Tell, Fabien; Clerc, Nadine

2015-04-01

In the nucleus of the tractus solitarii (NTS), a large proportion of neurones express transient A-type potassium currents (I KA) having deep influence on the fidelity of the synaptic transmission of the visceral primary afferent inputs to second-order neurones. Up to now, the strong impact of I KA within the NTS was considered to result exclusively from its variation in amplitude, and its molecular correlate(s) remained unknown. In order to identify which Kv channels underlie I KA in NTS neurones, the gating properties and the pharmacology of this current were determined using whole cell patch clamp recordings in slices. Complementary information was brought by immunohistochemistry. Strikingly, two neurone subpopulations characterized by fast or slow inactivation time courses (respectively about 50 and 200 ms) were discriminated. Both characteristics matched those of the Kv4 channel subfamily. The other gating properties, also matching the Kv4 channel ones, were homogeneous through the NTS. The activation and inactivation occurred at membrane potentials around the threshold for generating action potentials, and the time course of recovery from inactivation was rapid. Pharmacologically, I KA in NTS neurones was found to be resistant to tetraethylammonium (TEA), sea anemone toxin blood-depressing substance (BDS) and dendrotoxin (DTX), whereas Androctonus mauretanicus mauretanicus toxin 3 (AmmTX3), a scorpion toxin of the α-KTX 15 family that has been shown to block all the members of the Kv4 family, inhibited 80 % of I KA irrespectively of its inactivation time course. Finally, immunohistochemistry data suggested that, among the Kv4 channel subfamily, Kv4.3 is the prevalent subunit expressed in the NTS.

Modulation of BK channel voltage gating by different auxiliary β subunits

PubMed Central

Contreras, Gustavo F.; Neely, Alan; Alvarez, Osvaldo; Gonzalez, Carlos; Latorre, Ramon

2012-01-01

Calcium- and voltage-activated potassium channels (BK) are regulated by a multiplicity of signals. The prevailing view is that different BK gating mechanisms converge to determine channel opening and that these gating mechanisms are allosterically coupled. In most instances the pore forming α subunit of BK is associated with one of four alternative β subunits that appear to target specific gating mechanisms to regulate the channel activity. In particular, β1 stabilizes the active configuration of the BK voltage sensor having a large effect on BK Ca2+ sensitivity. To determine the extent to which β subunits regulate the BK voltage sensor, we measured gating currents induced by the pore-forming BK α subunit alone and with the different β subunits expressed in Xenopus oocytes (β1, β2IR, β3b, and β4). We found that β1, β2, and β4 stabilize the BK voltage sensor in the active conformation. β3 has no effect on voltage sensor equilibrium. In addition, β4 decreases the apparent number of charges per voltage sensor. The decrease in the charge associated with the voltage sensor in α β4 channels explains most of their biophysical properties. For channels composed of the α subunit alone, gating charge increases slowly with pulse duration as expected if a significant fraction of this charge develops with a time course comparable to that of K+ current activation. In the presence of β1, β2, and β4 this slow component develops in advance of and much more rapidly than ion current activation, suggesting that BK channel opening proceeds in two steps. PMID:23112204

KATP Channel Expression and Genetic Polymorphisms Associated with Progression and Survival in Amyotrophic Lateral Sclerosis.

PubMed

Vidal-Taboada, José M; Pugliese, Marco; Salvadó, Maria; Gámez, Josep; Mahy, Nicole; Rodríguez, Manuel J

2018-02-28

The ATP-sensitive potassium (K ATP ) channel directly regulates the microglia-mediated inflammatory response following CNS injury. To determine the putative role of the K ATP channel in amyotrophic lateral sclerosis (ALS) pathology, we investigated whether ALS induces changes in K ATP channel expression in the spinal cord and motor cortex. We also characterized new functional variants of human ABCC8, ABCC9, KCNJ8, and KCNJ11 genes encoding for the K ATP channel and analyzed their association with ALS risk, rate of progression, and survival in a Spanish ALS cohort. The expression of ABCC8 and KCNJ8 genes was enhanced in the spinal cord of ALS samples, and KCNJ11 increased in motor cortex of ALS samples, as determined by real-time polymerase chain reaction. We then sequenced the exons and regulatory regions of K ATP channel genes from a subset of 28 ALS patients and identified 50 new genetic variants. For the case-control association analysis, we genotyped five selected polymorphisms with predicted functional relevance in 185 Spanish ALS (134 spinal ALS and 51 bulbar ALS) patients and 493 controls. We found that bulbar ALS patients presenting the G/G genotype of the rs4148646 variant of ABCC8 and the T/T genotype of the rs5219 variant of KCNJ11 survived longer than other ALS patients presenting other genotypes. Also, the C/C genotype of the rs4148642 variant of ABCC8 and the T/C genotype of the rs148416760 variant of ABCC9 modified the progression rate in spinal ALS patients. Our results suggest that the K ATP channel plays a role in the pathophysiological mechanisms of ALS.

Soil plutonium and cesium in stream channels and banks of Los Alamos liquid effluent-receiving areas.

PubMed

Nyhan, J W; White, G C; Trujillo, G

1982-10-01

Stream channel sediments and adjacent bank soils found in three intermittent streams used for treated liquid effluent disposal at Los Alamos, New Mexico were sampled to determine the distribution of 238Pu, 239,240Pu and 137Cs. Radionuclide concentrations and inventories were determined as functions of distance downstream from the waste outfall and from the center of the stream channel, soil sampling depth, stream channel-bank physiography, and the waste use history of each disposal area. Radionuclide concentrations in channel sediments were inversely related to distances up to 10 km downstream from the outfalls. For sites receiving appreciable waste effluent additions, contaminant concentrations in bank soils decreased with perpendicular distances greater than 0.38 m from the stream channel, and with stream bank sampling depths greater than 20-40 cm. Concentrations and total inventories of radionuclides in stream bank soils generally decreased as stream bank height increased. Inventory estimates of radionuclides in channel sediments exhibited coefficients of variation that ranged 0.41-2.6, reflecting the large variation in radionuclide concentrations at each site. Several interesting temporal relationships of these radionuclides in intermittent streams were gleaned from the varying waste use histories of the three effluent-receiving areas. Eleven yr after liquid wastes were added to one canyon, the major radionuclide inventories were found in the stream bank soils, unlike most of the other currently-used receiving areas. A period of time greater than 6 yr seems to be required before the plutonium in liquid wastes currently added to the canyon is approximately equilibrated with the plutonium in the bank soils. These observations are discussed relative to waste management practices in these southwestern intermittent streams.

A Novel Feature Optimization for Wearable Human-Computer Interfaces Using Surface Electromyography Sensors

PubMed Central

Zhang, Xiong; Zhao, Yacong; Zhang, Yu; Zhong, Xuefei; Fan, Zhaowen

2018-01-01

The novel human-computer interface (HCI) using bioelectrical signals as input is a valuable tool to improve the lives of people with disabilities. In this paper, surface electromyography (sEMG) signals induced by four classes of wrist movements were acquired from four sites on the lower arm with our designed system. Forty-two features were extracted from the time, frequency and time-frequency domains. Optimal channels were determined from single-channel classification performance rank. The optimal-feature selection was according to a modified entropy criteria (EC) and Fisher discrimination (FD) criteria. The feature selection results were evaluated by four different classifiers, and compared with other conventional feature subsets. In online tests, the wearable system acquired real-time sEMG signals. The selected features and trained classifier model were used to control a telecar through four different paradigms in a designed environment with simple obstacles. Performance was evaluated based on travel time (TT) and recognition rate (RR). The results of hardware evaluation verified the feasibility of our acquisition systems, and ensured signal quality. Single-channel analysis results indicated that the channel located on the extensor carpi ulnaris (ECU) performed best with mean classification accuracy of 97.45% for all movement’s pairs. Channels placed on ECU and the extensor carpi radialis (ECR) were selected according to the accuracy rank. Experimental results showed that the proposed FD method was better than other feature selection methods and single-type features. The combination of FD and random forest (RF) performed best in offline analysis, with 96.77% multi-class RR. Online results illustrated that the state-machine paradigm with a 125 ms window had the highest maneuverability and was closest to real-life control. Subjects could accomplish online sessions by three sEMG-based paradigms, with average times of 46.02, 49.06 and 48.08 s, respectively. These experiments validate the feasibility of proposed real-time wearable HCI system and algorithms, providing a potential assistive device interface for persons with disabilities. PMID:29543737

The hydraulic geometry of narrow and deep channels; evidence for flow optimisation and controlled peatland growth

NASA Astrophysics Data System (ADS)

Nanson, Rachel A.; Nanson, Gerald C.; Huang, He Qing

2010-04-01

At-a-station and bankfull hydraulic geometry analyses of peatland channels at Barrington Tops, New South Wales, Australia, reveal adjustments in self-forming channels in the absence of sediment load. Using Rhodes ternary diagram, comparisons are made with hydraulic geometry data from self-forming channels carrying bedload in alluvial settings elsewhere. Despite constraints on channel depths caused at some locations by the restricted thickness of peat, most stations have cohesive, near-vertical, well-vegetated banks, and width/depth (w/d) ratios of ∼ 2 that are optimal for sediment-free flow. Because banks are strong, resist erosion and can stand nearly vertical, and depth is sometimes constrained, adjustments to discharge are accommodated largely by changes in velocity. These findings are consistent with the model of maximum flow efficiency and the overarching least action principle in open channels. The bankfull depth of freely adjusting laterally active channels in clastic alluvium is well known to be related to the thickness of floodplain alluvium and a similar condition appears to apply to these swamps that grow in situ and are formed almost entirely of organic matter. The thickness of peat in these swamps rarely exceeds that required to form a bankfull channel of optimum w/d ratio for the transport of sediment-free water. Swamp vegetation is highly dependent on proximity to the water table. To maintain a swamp-channel and associated floodplain system, the channels must flow with sufficient water much of the time; they not only offer an efficient morphology for flow but do so in a way that enables bankfull conditions to occur many times a year. They also prevent the swamp from growing above a level linked to the depth of the channel. Once the channel attains the most efficient cross section, further growth of the swamp vertically is restricted by enhanced flow velocities and limited flow depths. This means that the volume of peat in such swamps is determined by the hydraulic efficiency of their channels. The development and maintenance of the hydraulic geometry of these swamp channels is biogeomorphic and biohydraulic in nature and yet accords to the same optimising principles that govern the formation of self-adjusting channels and floodplains in clastic alluvium.

Gait-Cycle-Driven Transmission Power Control Scheme for a Wireless Body Area Network.

PubMed

Zang, Weilin; Li, Ye

2018-05-01

In a wireless body area network (WBAN), walking movements can result in rapid channel fluctuations, which severely degrade the performance of transmission power control (TPC) schemes. On the other hand, these channel fluctuations are often periodic and are time-synchronized with the user's gait cycle, since they are all driven from the walking movements. In this paper, we propose a novel gait-cycle-driven transmission power control (G-TPC) for a WBAN. The proposed G-TPC scheme reinforces the existing TPC scheme by exploiting the periodic channel fluctuation in the walking scenario. In the proposed scheme, the user's gait cycle information acquired by an accelerometer is used as beacons for arranging the transmissions at the time points with the ideal channel state. The specific transmission power is then determined by using received signal strength indication (RSSI). An experiment was conducted to evaluate the energy efficiency and reliability of the proposed G-TPC based on a CC2420 platform. The results reveal that compared to the original RSSI/link-quality-indication-based TPC, G-TPC reduces energy consumption by 25% on the sensor node and reduce the packet loss rate by 65%.

Effect of Intensive Plastic Deformation on Microstructure and Mechanical Properties of Aluminum Alloys

NASA Astrophysics Data System (ADS)

Rakhadilov, Bauyrzhan; Uazyrkhanova, Gulzhaz; Myakinin, Alexandr; Uazyrkhanova, Zhuldyz

2016-08-01

In work it was studied the influence of intensive plastic deformation on structure and mechanical properties of aluminum alloys. Intensive plastic deformation was carried out by using equal-channel angular extrusion. It is shown that the most efficient angle of intersection of the channels is the angle of Φ=120°, which ensures defect-free parts at the highest possible level of accumulated strain (e=8). It is established that the intensive milling grain structures in aluminum alloys AMG6 and AMC occurs at ECAE-12 passes, while the intersection angle of the channels of 120°. After ECAE-12 in aluminum alloys the grain refinement reaches to the size of ∼⃒1.0-1.5 gm. It is determined that as a result of equal channel angular pressing, the microhardness of alloy AMG6 increases almost 4 times in comparison with the initial state, the microhardness of alloy AMC increases by almost 4.5 times in comparison with the initial state. It is shown that ECAE-12 mass loss is reduced to 5.4 and 5.6 mg, which shows an increase in wear-resistance of aluminum alloys AMG6 and AMC 13-14 %.

Adiabatic perturbation theory of electronic stopping in insulators

DOE PAGES

Horsfield, Andrew P.; Lim, Anthony; Foulkes, W. M. C.; ...

2016-06-02

A model able to explain the complicated structure of electronic stopping at low velocities in insulating materials is presented. It is shown to be in good agreement with results obtained from time-dependent density-functional theory for the stopping of a channeling Si atom in a Si crystal. If we define the repeat frequency f=v/λ, where λ is the periodic repeat length of the crystal along the direction the channeling atom is traveling, and v is the velocity of the channeling atom, we find that electrons experience a perturbing force that varies in time at integer multiples l of f. This enablesmore » electronic excitations at low atom velocity, but their contributions diminish rapidly with increasing values of l. The expressions for stopping power are derived using adiabatic perturbation theory for many-electron systems, and they are then specialized to the case of independent electrons. Lastly, a simple model for the nonadiabatic matrix elements is described, along with the procedure for determining its parameters.« less

Residence times in a hypersaline lagoon: Using salinity as a tracer

NASA Astrophysics Data System (ADS)

Mudge, Stephen M.; Icely, John D.; Newton, Alice

2008-04-01

Generally the waters of the Ria Formosa Lagoon, Portugal have a short residence time, in the order of 0.5 days (Tett, P., Gilpin, L., Svendsen, H., Erlandsson, C.P., Larsson, U., Kratzer, S., Fouilland, E., Janzen, C., Lee, J., Grenz, C., Newton, A., Ferreira, J.G., Fernandes, T., Scory, S., 2003. Eutrophication and some European waters of restricted exchange. Continental Shelf Research 23, 1635-1671). This estimation is based on the measurements of currents and the modelling of water exchange at the outlets to the ocean. However, observations of the temperature and salinity in the inner channels imply that residence time is greater in these regions of the lagoon. To resolve this apparent contradiction, spatial measurements of the temperature and salinity were made with a meter for conductivity, temperature and depth along the principal channels of the western portion of the lagoon, with a sampling frequency of two per second. Evaporation rates of 5.4 mm day -1 were measured in a salt extraction pond adjacent to the lagoon and used to determine the residence time through salinity differences with the incoming seawater. In June 2004, the water flooding in from the ocean had an average salinity of 36.07 which contrasted with a maximum of 37.82 at mid ebb on a spring tide, corresponding to a residence time of >7 days; the mean residence time was 2.4 days. As the tide flooded into the channels, the existing water was advected back into the lagoon. Although there was a small amount of mixing with water from another inlet, the water body from the inner lagoon essentially remained distinct with respect to temperature and salinity characteristics. The residence time of the water was further prolonged at the junction between the main channels, where distinct boundaries were observed between the different water masses. As the water ebbed out, the shallow Western Channel was essentially isolated from the rest of the outer lagoon, and the water from this channel was forced down the Ramalhete Channel, from where it was unable to exit the lagoon in one tidal cycle due to the extensive path length of ˜14 km to the sea. Although the overall exchange rate of water is short in the outer lagoon, this study emphasizes that management models should take into account additional complexities that might arise from the much longer exchange rates of the inner lagoon. For example, the principal sewage discharge for the urban area of Faro is into the section of the Ramalhete Channel where efficient flushing is impeded by the relatively high residence times of the water body in this channel. The implementation of the techniques used for this study are a quick and relatively cost effective approach to testing assumptions about water quality and exchange in shallow coastal systems.

Spatial distribution of calcium-gated chloride channels in olfactory cilia.

PubMed

French, Donald A; Badamdorj, Dorjsuren; Kleene, Steven J

2010-12-30

In vertebrate olfactory receptor neurons, sensory cilia transduce odor stimuli into changes in neuronal membrane potential. The voltage changes are primarily caused by the sequential openings of two types of channel: a cyclic-nucleotide-gated (CNG) cationic channel and a calcium-gated chloride channel. In frog, the cilia are 25 to 200 µm in length, so the spatial distributions of the channels may be an important determinant of odor sensitivity. To determine the spatial distribution of the chloride channels, we recorded from single cilia as calcium was allowed to diffuse down the length of the cilium and activate the channels. A computational model of this experiment allowed an estimate of the spatial distribution of the chloride channels. On average, the channels were concentrated in a narrow band centered at a distance of 29% of the ciliary length, measured from the base of the cilium. This matches the location of the CNG channels determined previously. This non-uniform distribution of transduction proteins is consistent with similar findings in other cilia. On average, the two types of olfactory transduction channel are concentrated in the same region of the cilium. This may contribute to the efficient detection of weak stimuli.

High repetition rate laser induced fluorescence applied to Surfatron Induced Plasmas

NASA Astrophysics Data System (ADS)

van der Mullen, J. J. A. M.; Palomares, J. M.; Carbone, E. A. D.; Graef, W.; Hübner, S.

2012-05-01

The reaction kinetics in the excitation space of Ar and the conversion space of Ar-molecule mixtures are explored using a combination of high rep-rate YAG-Dye laser systems with a well defined and easily controllable Surfatron Induced Plasma set-up. Applying the method of Saturation Time Resolved Laser Induced Fluorescence (SaTiRe-LIF), we could trace excitation and conversion channels and determine rates of electron and heavy particle excitation kinetics. The time resolved density disturbances observed in the Ar excitation space, which are initiated by the laser, reveal the excitation channels and corresponding rates; responses of the molecular radiation in Ar-molecule mixtures corresponds to the presence of conversion processes induced by heavy particle excitation kinetics.

Quantum and Private Capacities of Low-Noise Channels

NASA Astrophysics Data System (ADS)

Leditzky, Felix; Leung, Debbie; Smith, Graeme

2018-04-01

We determine both the quantum and the private capacities of low-noise quantum channels to leading orders in the channel's distance to the perfect channel. It has been an open problem for more than 20 yr to determine the capacities of some of these low-noise channels such as the depolarizing channel. We also show that both capacities are equal to the single-letter coherent information of the channel, again to leading orders. We thus find that, in the low-noise regime, superadditivity and degenerate codes have a negligible benefit for the quantum capacity, and shielding does not improve the private capacity beyond the quantum capacity, in stark contrast to the situation when noisier channels are considered.

20 CFR 200.2 - The general course and method by which the Board's functions are channeled and determined.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 20 Employees' Benefits 1 2010-04-01 2010-04-01 false The general course and method by which the Board's functions are channeled and determined. 200.2 Section 200.2 Employees' Benefits RAILROAD... the Board's functions are channeled and determined. (a) Retirement and death benefits. (1) Retirement...

Analysis of apolipoprotein genes and their involvement in disease response of channel catfish after bacterial infection.

PubMed

Yang, Yujia; Fu, Qiang; Zhou, Tao; Li, Yun; Liu, Shikai; Zeng, Qifan; Wang, Xiaozhu; Jin, Yulin; Tian, Changxu; Qin, Zhenkui; Dunham, Rex; Liu, Zhanjiang

2017-02-01

Apolipoproteins are protein component of plasma lipoproteins. They exert crucial roles in lipoprotein metabolism and serve as enzyme cofactors, receptor ligands, and lipid transfer carriers in mammals. In teleosts, apolipoproteins are also involved in diverse processes including embryonic and ontogenic development, liver and digestive system organogenesis, and innate immunity. In this study, we identified a set of 19 apolipoprotein genes in channel catfish (Ictalurus punctatus). Phylogenetic analysis and syntenic analysis were conducted to determine their identities and evolutionary relationships. The expression signatures of apolipoproteins in channel catfish were determined in healthy tissues and after infections with two major bacterial pathogens, Edwardsiella ictaluri and Flavobacterium columnare. In healthy channel catfish, most apolipoprotein genes exhibited tissue-specific expression patterns in channel catfish. After ESC and columnaris infections, 5 and 7 apolipoprotein genes were differentially expressed respectively, which presented a pathogen-specific and time-dependent pattern of regulation. After ESC infection, three exchangeable apolipoproteins (apoA-IB, apoC-I, and apoE-B) were suppressed in catfish intestine, while two nonexchangeable apolipoproteins (apoB-A and apoB-B) were slightly up-regulated. After columnaris infection, apoB-B, apoD-B, and apoE-A were significantly down-regulated in catfish gill, while apoF, apoL-IV, apoO-like, and apo-14 kDa showed significantly up-regulation. Taken together, these results suggested that apolipoprotein genes may play significant roles in innate immune responses to bacterial pathogens in channel catfish. Copyright © 2016 Elsevier Ltd. All rights reserved.

FFM water mockup studies of the near-wake region of permeable flow blockages. [LMFBR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sheppard, J. D.

1976-10-01

An experimental study of transport in the near-wake region of permeable, planar flow blockages was conducted in a vertical-flow channel with a hexagonal cross section. Experiments included measurements of axial pressure distributions along channel walls exposed to the free stream and wake region and pressure differences between the free stream and wake regions at fixed axial positions. Further, time constants for scalar decay in the near-wake region were determined by salt conductivity tests. A single blockage geometry was used in all tests; the blockage, which was attached to the channel wall, obstructed 58 percent of the cross section when themore » blockage was solid. For one series of tests, discrete jets were machined into the blockage and water was metered into the recirculation zone at velocities of the order of the mean channel velocity. Increased jet velocity reduced the resistence time of salt in the recirculation zone, and when the jet velocity was as high as the accelerated free stream flow at the vena contracta, counterrotating cells were introduced in the recirculating zone. In a second series of tests, uniformly spaced holes were drilled in the blockages to give blockage porosities of 11 and 24 percent. The residence time of salt in the near wake decreased significantly as the blockage porosity was increased to 24 percent.« less

Analysis of uncertainties and convergence of the statistical quantities in turbulent wall-bounded flows by means of a physically based criterion

NASA Astrophysics Data System (ADS)

Andrade, João Rodrigo; Martins, Ramon Silva; Thompson, Roney Leon; Mompean, Gilmar; da Silveira Neto, Aristeu

2018-04-01

The present paper provides an analysis of the statistical uncertainties associated with direct numerical simulation (DNS) results and experimental data for turbulent channel and pipe flows, showing a new physically based quantification of these errors, to improve the determination of the statistical deviations between DNSs and experiments. The analysis is carried out using a recently proposed criterion by Thompson et al. ["A methodology to evaluate statistical errors in DNS data of plane channel flows," Comput. Fluids 130, 1-7 (2016)] for fully turbulent plane channel flows, where the mean velocity error is estimated by considering the Reynolds stress tensor, and using the balance of the mean force equation. It also presents how the residual error evolves in time for a DNS of a plane channel flow, and the influence of the Reynolds number on its convergence rate. The root mean square of the residual error is shown in order to capture a single quantitative value of the error associated with the dimensionless averaging time. The evolution in time of the error norm is compared with the final error provided by DNS data of similar Reynolds numbers available in the literature. A direct consequence of this approach is that it was possible to compare different numerical results and experimental data, providing an improved understanding of the convergence of the statistical quantities in turbulent wall-bounded flows.

Hydromorphological parameters of natural channel behavior in conditions of the Hercynian System and the flysch belt of the Western Carpathians on the territory of the Czech Republic

NASA Astrophysics Data System (ADS)

Kujanová, Kateřina; Matoušková, Milada; Kliment, Zdeněk

2016-04-01

A fundamental prerequisite for assessing the current ecological status of streams is the establishment of reference conditions for each stream type that serve as a benchmark. The hydromorphological reference conditions reflect the natural channel behavior, which is extremely variable. Significant parameters of natural channel behavior were determined using a combination of four selected statistical methods: Principal Component Analysis, Agglomerative Hierarchical Clustering, correlation, and regression. Macroscale analyses of data about altitude, stream order, channel slope, valley floor slope, sinuosity, and characteristics of the hydrological regime were conducted for 3197 reaches of major rivers in the Czech Republic with total length of 15,636 km. On the basis of selected significant parameters and their threshold values, channels were classified into groups of river characteristics based on shared behaviors. The channel behavior within these groups was validated using hydromorphological characteristics of natural channels determined during field research at reference sites. Classification of channels into groups confirmed the fundamental differences between channel behavior under conditions of the Hercynian System and the flysch belt of the Western Carpathians in the Czech Republic and determined a specific group in the flattened high areas of mountains in the Bohemian Massif. Validating confirmed the distinctions between groups of river characteristics and the uniqueness of each one; it also emphasized the benefits of using qualitative data and riparian zone characteristics for describing channel behavior. Channel slope, entrenchment ratio, bed structure, and d50 were determined as quantitative characteristics of natural channel behavior.

Determination of optimum "multi-channel surface wave method" field parameters.

DOT National Transportation Integrated Search

2012-12-01

Multi-channel surface wave methods (especially the multi-channel analyses of surface wave method; MASW) are routinely used to : determine the shear-wave velocity of the subsurface to depths of 100 feet for site classification purposes. Users are awar...

Ground beetle communities in a mountain river subjected to restoration: The Raba River, Polish Carpathians.

PubMed

Bednarska, Agnieszka J; Wyżga, Bartłomiej; Mikuś, Paweł; Kędzior, Renata

2018-01-01

Effects of passive restoration of mountain rivers on the organisms inhabiting exposed riverine sediments are considerably less understood than those concerning aquatic biota. Thus, the effects of a recovery of the Raba River after abandonment of maintenance of its channelization scheme on ground beetle (Coleoptera: Carabidae) communities were investigated by comparing 6 unmanaged cross-sections and 6 cross-sections from adjacent channelized reaches. In each cross-section, ground beetles were collected from 12 sampling sites in spring, summer, and autumn, and 8 habitat parameters characterizing the cross-sections and sampling sites were determined. Within a few years after abandonment of the Raba River channelization scheme, the width of this gravel-bed river increased up to three times and its multi-thread pattern became re-established. Consequently, unmanaged river cross-sections had significantly larger channel width and more low-flow channels and eroding cutbanks than channelized cross-sections. Moreover, sampling sites in the unmanaged cross-sections were typified by significantly steeper average surface slope and larger average distance from low-flow channels than the sites in channelized cross-sections. In total, 3992 individuals from 78 taxa were collected during the study. The ground beetle assemblages were significantly more abundant and richer in species in the unmanaged than in the channelized cross-sections but no significant differences in carabid diversity indices between the two cross-section types were recorded. Redundancy Analysis indicated active river zone width as the only variable explaining differences in abundance and species richness among the cross-sections. Multiple regression analysis indicated species diversity to predominantly depend on the degree of plant cover and substrate grain size. The study showed that increased availability of exposed sediments in the widened river reaches allowed ground beetles to increase their abundance and species richness within a few years after the onset of river restoration, but more time may be needed for development of more diverse carabid communities. Copyright © 2017 Elsevier B.V. All rights reserved.

Modeling-independent elucidation of inactivation pathways in recombinant and native A-type Kv channels.

PubMed

Fineberg, Jeffrey D; Ritter, David M; Covarrubias, Manuel

2012-11-01

A-type voltage-gated K(+) (Kv) channels self-regulate their activity by inactivating directly from the open state (open-state inactivation [OSI]) or by inactivating before they open (closed-state inactivation [CSI]). To determine the inactivation pathways, it is often necessary to apply several pulse protocols, pore blockers, single-channel recording, and kinetic modeling. However, intrinsic hurdles may preclude the standardized application of these methods. Here, we implemented a simple method inspired by earlier studies of Na(+) channels to analyze macroscopic inactivation and conclusively deduce the pathways of inactivation of recombinant and native A-type Kv channels. We investigated two distinct A-type Kv channels expressed heterologously (Kv3.4 and Kv4.2 with accessory subunits) and their native counterparts in dorsal root ganglion and cerebellar granule neurons. This approach applies two conventional pulse protocols to examine inactivation induced by (a) a simple step (single-pulse inactivation) and (b) a conditioning step (double-pulse inactivation). Consistent with OSI, the rate of Kv3.4 inactivation (i.e., the negative first derivative of double-pulse inactivation) precisely superimposes on the profile of the Kv3.4 current evoked by a single pulse because the channels must open to inactivate. In contrast, the rate of Kv4.2 inactivation is asynchronous, already changing at earlier times relative to the profile of the Kv4.2 current evoked by a single pulse. Thus, Kv4.2 inactivation occurs uncoupled from channel opening, indicating CSI. Furthermore, the inactivation time constant versus voltage relation of Kv3.4 decreases monotonically with depolarization and levels off, whereas that of Kv4.2 exhibits a J-shape profile. We also manipulated the inactivation phenotype by changing the subunit composition and show how CSI and CSI combined with OSI might affect spiking properties in a full computational model of the hippocampal CA1 neuron. This work unambiguously elucidates contrasting inactivation pathways in neuronal A-type Kv channels and demonstrates how distinct pathways might impact neurophysiological activity.

Dual-color quantum dot detection of a heterotetrameric potassium channel (hKCa3.1).

PubMed

Waschk, Daniel E J; Fabian, Anke; Budde, Thomas; Schwab, Albrecht

2011-04-01

Potassium channels play a key role in establishing the cell membrane potential and are expressed ubiquitously. Today, more than 70 mammalian K(+) channel genes are known. The diversity of K(+) channels is further increased by the fact that different K(+) channel family members may assemble to form heterotetramers. We present a method based on fluorescence microscopy to determine the subunit composition of a tetrameric K(+) channel. We generated artificial "heteromers" of the K(+) channel hK(Ca)3.1 by coexpressing two differently tagged hK(Ca)3.1 constructs containing either an extracellular hemagglutinin (HA) or an intracellular V5 epitope. hK(Ca)3.1 channel subunits were detected in the plasma membrane of MDCK-F cells or HEK293 cells by labeling the extra- and intracellular epitopes with differently colored quantum dots (QDs). As previously shown for the extracellular part of hK(Ca)3.1 channels, its intracellular domain can also bind only one QD label at a time. When both channel subunits were coexpressed, 27.5 ± 1.8% and 24.9 ± 2.1% were homotetramers consisting of HA- and V5-tagged subunits, respectively. 47.6 ± 3.2% of the channels were heteromeric and composed of both subunits. The frequency distribution of HA- and V5-tagged homo- and heteromeric hK(Ca)3.1 channels is reminiscent of the binomial distribution (a + b)(2) = a(2) + 2ab + b(2). Along these lines, our findings are consistent with the notion that hK(Ca)3.1 channels are assembled from two homomeric dimers and not randomly from four independent subunits. We anticipate that our technique will be applicable to other heteromeric membrane proteins, too.

Weighing the evidence for a ternary protein complex mediating A-type K+ currents in neurons.

PubMed

Maffie, Jonathon; Rudy, Bernardo

2008-12-01

The subthreshold-operating A-type K(+) current in neurons (I(SA)) has important roles in the regulation of neuronal excitability, the timing of action potential firing and synaptic integration and plasticity. The channels mediating this current (Kv4 channels) have been implicated in epilepsy, the control of dopamine release, and the regulation of pain plasticity. It has been proposed that Kv4 channels in neurons are ternary complexes of three types of protein: pore forming subunits of the Kv4 subfamily and two types of auxiliary subunits, the Ca(2+) binding proteins KChIPs and the dipeptidyl peptidase-like proteins (DPPLs) DPP6 (also known as DPPX) and DPP10 (4 molecules of each per channel for a total of 12 proteins in the complex). Here we consider the evidence supporting this hypothesis. Kv4 channels in many neurons are likely to be ternary complexes of these three types of protein. KChIPs and DPPLs are required to efficiently traffic Kv4 channels to the plasma membrane and regulate the functional properties of the channels. These proteins may also be important in determining the localization of the channels to specific neuronal compartments, their dynamics, and their response to neuromodulators. A surprisingly large number of additional proteins have been shown to modify Kv4 channels in heterologous expression systems, but their association with native Kv4 channels in neurons has not been properly validated. A critical consideration of the evidence suggests that it is unlikely that association of Kv4 channels with these additional proteins is widespread in the CNS. However, we cannot exclude that some of these proteins may associate with the channels transiently or in specific neurons or neuronal compartments, or that they may associate with the channels in other tissues.

Response Time Analysis and Test of Protection System Instrument Channels for APR1400 and OPR1000

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Chang Jae; Han, Seung; Yun, Jae Hee

2015-07-01

Safety limits are required to maintain the integrity of physical barriers designed to prevent the uncontrolled release of radioactive materials in nuclear power plants. The safety analysis establishes two critical constraints that include an analytical limit in terms of a measured or calculated variable, and a specific time after the analytical limit is reached to begin protective action. Keeping with the nuclear regulations and industry standards, satisfying these two requirements will ensure that the safety limit will not be exceeded during the design basis event, either an anticipated operational occurrence or a postulated accident. Various studies on the setpoint determinationmore » methodology for the safety-related instrumentation have been actively performed to ensure that the requirement of the analytical limit is satisfied. In particular, the protection setpoint methodology for the advanced power reactor 1400 (APP1400) and the optimized power reactor 1000 (OPR1000) has been recently developed to cover both the design basis event and the beyond design basis event. The developed setpoint methodology has also been quantitatively validated using specific computer programs and setpoint calculations. However, the safety of nuclear power plants cannot be fully guaranteed by satisfying the requirement of the analytical limit. In spite of the response time verification requirements of nuclear regulations and industry standards, it is hard to find the studies on the systematically integrated methodology regarding the response time evaluation. In cases of APR1400 and OPR1000, the response time analysis for the plant protection system is partially included in the setpoint calculation and the response time test is separately performed via the specific plant procedure. The test technique has a drawback which is the difficulty to demonstrate completeness of timing test. The analysis technique has also a demerit of resulting in extreme times that not actually possible. Thus, the establishment of the systematic response time evaluation methodology is needed to justify the conformance to the response time requirement used in the safety analysis. This paper proposes the response time evaluation methodology for APR1400 and OPR1000 using the combined analysis and test technique to confirm that the plant protection system can meet the analytical response time assumed in the safety analysis. In addition, the results of the quantitative evaluation performed for APR1400 and OPR1000 are presented in this paper. The proposed response time analysis technique consists of defining the response time requirement, determining the critical signal path for the trip parameter, allocating individual response time to each component on the signal path, and analyzing the total response time for the trip parameter, and demonstrates that the total analyzed response time does not exceed the response time requirement. The proposed response time test technique is composed of defining the response time requirement, determining the critical signal path for the trip parameter, determining the test method for each component on the signal path, performing the response time test, and demonstrates that the total test result does not exceed the response time requirement. The total response time should be tested in a single test that covers from the sensor to the final actuation device on the instrument channel. When the total channel is not tested in a single test, separate tests on groups of components or single components including the total instrument channel shall be combined to verify the total channel response. For APR1400 and OPR1000, the ramp test technique is used for the pressure and differential pressure transmitters and the step function testing technique is applied to the signal processing equipment and final actuation device. As a result, it can be demonstrated that the response time requirement is satisfied by the combined analysis and test technique. Therefore, the proposed methodology in this paper plays a crucial role in guaranteeing the safety of the nuclear power plants systematically satisfying one of two critical requirements from the safety analysis. (authors)« less

Analysis of Factors Limiting Bacterial Growth in PDMS Mother Machine Devices.

PubMed

Yang, Da; Jennings, Anna D; Borrego, Evalynn; Retterer, Scott T; Männik, Jaan

2018-01-01

The microfluidic mother machine platform has attracted much interest for its potential in studies of bacterial physiology, cellular organization, and cell mechanics. Despite numerous experiments and development of dedicated analysis software, differences in bacterial growth and morphology in narrow mother machine channels compared to typical liquid media conditions have not been systematically characterized. Here we determine changes in E. coli growth rates and cell dimensions in different sized dead-end microfluidic channels using high resolution optical microscopy. We find that E. coli adapt to the confined channel environment by becoming narrower and longer compared to the same strain grown in liquid culture. Cell dimensions decrease as the channel length increases and width decreases. These changes are accompanied by increases in doubling times in agreement with the universal growth law. In channels 100 μm and longer, cell doublings can completely stop as a result of frictional forces that oppose cell elongation. Before complete cessation of elongation, mechanical stresses lead to substantial deformation of cells and changes in their morphology. Our work shows that mechanical forces rather than nutrient limitation are the main growth limiting factor for bacterial growth in long and narrow channels.

Tracking down the origins of Advanced LIGO noise: 2 examples

NASA Astrophysics Data System (ADS)

Berger, Beverly K.; LIGO Scientific Collaboration Collaboration

2016-03-01

For Advanced LIGO to reach design sensitivity various sources of instrumental and environmental noise must be identified and ameliorated. We discuss 2 efforts to search for the origin of noise bursts (glitches) at LIGO Hanford. Advanced LIGO monitors thousands of channels in addition to the gravitational wave channel. These can be studied to find correlations between the gravitational wave channel and other sensor signals. The first type of glitch had a frequency of 50 Hz and a rate of 1 per minute. It was found that the glitches were correlated with ground motion in the end station of the X-arm where the offending air compressor was tracked down and turned off. The second example manifests itself as a sudden, but brief, drop in the range occurring, typically, several times per day at LIGO Hanford and less frequently at LIGO Livingston. These range-drop glitches appear in the gravitational-wave channel. Although correlations with these glitches can be seen in many channels, it cannot be easily determined whether these channels are responding as an effect of this type of very strong glitch or whether they might be related to their cause or causes. To date, the cause of the range-drop glitches is not known.

Analysis of Factors Limiting Bacterial Growth in PDMS Mother Machine Devices

DOE PAGES

Yang, Da; Jennings, Anna D.; Borrego, Evalynn; ...

2018-05-01

The microfluidic mother machine platform has attracted much interest for its potential in studies of bacterial physiology, cellular organization, and cell mechanics. Despite numerous experiments and development of dedicated analysis software, differences in bacterial growth and morphology in narrow mother machine channels compared to typical liquid media conditions have not been systematically characterized. Here we determine changes in E. coli growth rates and cell dimensions in different sized dead-end microfluidic channels using high resolution optical microscopy. We find that E. coli adapt to the confined channel environment by becoming narrower and longer compared to the same strain grown in liquidmore » culture. Cell dimensions decrease as the channel length increases and width decreases. These changes are accompanied by increases in doubling times in agreement with the universal growth law. In channels 100 μm and longer, cell doublings can completely stop as a result of frictional forces that oppose cell elongation. Before complete cessation of elongation, mechanical stresses lead to substantial deformation of cells and changes in their morphology. Lastly, our work shows that mechanical forces rather than nutrient limitation are the main growth limiting factor for bacterial growth in long and narrow channels.« less

Analysis of Factors Limiting Bacterial Growth in PDMS Mother Machine Devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Da; Jennings, Anna D.; Borrego, Evalynn

The microfluidic mother machine platform has attracted much interest for its potential in studies of bacterial physiology, cellular organization, and cell mechanics. Despite numerous experiments and development of dedicated analysis software, differences in bacterial growth and morphology in narrow mother machine channels compared to typical liquid media conditions have not been systematically characterized. Here we determine changes in E. coli growth rates and cell dimensions in different sized dead-end microfluidic channels using high resolution optical microscopy. We find that E. coli adapt to the confined channel environment by becoming narrower and longer compared to the same strain grown in liquidmore » culture. Cell dimensions decrease as the channel length increases and width decreases. These changes are accompanied by increases in doubling times in agreement with the universal growth law. In channels 100 μm and longer, cell doublings can completely stop as a result of frictional forces that oppose cell elongation. Before complete cessation of elongation, mechanical stresses lead to substantial deformation of cells and changes in their morphology. Lastly, our work shows that mechanical forces rather than nutrient limitation are the main growth limiting factor for bacterial growth in long and narrow channels.« less

Monolithic Microfluidic Mixing-Spraying Devices for Time-Resolved Cryo-Electron Microscopy

PubMed Central

Lu, Zonghuan; Shaikh, Tanvir R.; Barnard, David; Meng, Xing; Mohamed, Hisham; Yassin, Aymen; Mannella, Carmen A.; Agrawal, Rajendra K.; Lu, Toh-Ming

2009-01-01

The goal of time-resolved cryo-electron microscopy is to determine structural models for transient functional states of large macromolecular complexes such as ribosomes and viruses. The challenge of time-resolved cryo-electron microscopy is to rapidly mix reactants, and then, following a defined time interval, to rapidly deposit them as a thin film and freeze the sample to the vitreous state. Here we describe a methodology in which reaction components are mixed and allowed to react, and are then sprayed onto an EM grid as it is being plunged into cryogen. All steps are accomplished by a monolithic, microfabricated silicon device that incorporates a mixer, reaction channel, and pneumatic sprayer in a single chip. We have found that microdroplets produced by air atomization spread to sufficiently thin films on a millisecond time scale provided that the carbon supporting film is made suitably hydrophilic. The device incorporates two T-mixers flowing into a single channel of four butterfly-shaped mixing elements that ensure effective mixing, followed by a microfluidic reaction channel whose length can be varied to achieve the desired reaction time. The reaction channel is flanked by two ports connected to compressed humidified nitrogen gas (at 50 psi) to generate the spray. The monolithic mixer-sprayer is incorporated into a computer-controlled plunging apparatus. To test the mixing performance and the suitability of the device for preparation of biological macromolecules for cryo-EM, ribosomes and ferritin were mixed in the device and sprayed onto grids. Three-dimensional reconstructions of the ribosomes demonstrated retention of native structure, and 30S and 50S subunits were shown to be capable of reassociation into ribosomes after passage through the device. PMID:19683579

A fully automated and scalable timing probe-based method for time alignment of the LabPET II scanners

NASA Astrophysics Data System (ADS)

Samson, Arnaud; Thibaudeau, Christian; Bouchard, Jonathan; Gaudin, Émilie; Paulin, Caroline; Lecomte, Roger; Fontaine, Réjean

2018-05-01

A fully automated time alignment method based on a positron timing probe was developed to correct the channel-to-channel coincidence time dispersion of the LabPET II avalanche photodiode-based positron emission tomography (PET) scanners. The timing probe was designed to directly detect positrons and generate an absolute time reference. The probe-to-channel coincidences are recorded and processed using firmware embedded in the scanner hardware to compute the time differences between detector channels. The time corrections are then applied in real-time to each event in every channel during PET data acquisition to align all coincidence time spectra, thus enhancing the scanner time resolution. When applied to the mouse version of the LabPET II scanner, the calibration of 6 144 channels was performed in less than 15 min and showed a 47% improvement on the overall time resolution of the scanner, decreasing from 7 ns to 3.7 ns full width at half maximum (FWHM).

Reoccupation of floodplains by rivers and its relation to the age structure of floodplain vegetation

USGS Publications Warehouse

Konrad, Christopher P.

2012-01-01

River channel dynamics over many decades provide a physical control on the age structure of floodplain vegetation as a river occupies and abandons locations. Floodplain reoccupation by a river, in particular, determines the interval of time during which vegetation can establish and mature. A general framework for analyzing floodplain reoccupation and a time series model are developed and applied to five alluvial rivers in the United States. Channel dynamics in these rivers demonstrate time-scale dependence with short-term oscillation in active channel area in response to floods and subsequent vegetation growth and progressive lateral movement that accounts for much of the cumulative area occupied by the rivers over decades. Rivers preferentially reoccupy locations recently abandoned causing a decreasing probability of reoccupation with time since abandonment. For a typical case, a river is 10 times more likely to reoccupy an area it abandoned in the past decade than it is to reoccupy an area it abandoned 30 yrs ago. The decreasing probability of reoccupation over time is consistent with observations of persistent stands of late seral stage floodplain forest. A power function provides a robust approach for estimating the cumulative area occupied by a river and the age structure of riparian forests resulting from a specific historical sequence of streamflow in comparison to either linear or exponential alternatives.

Equalization filters for multiple-channel electromyogram arrays

PubMed Central

Clancy, Edward A.; Xia, Hongfang; Christie, Anita; Kamen, Gary

2007-01-01

Multiple channels of electromyogram activity are frequently transduced via electrodes, then combined electronically to form one electrophysiologic recording, e.g. bipolar, linear double difference and Laplacian montages. For high quality recordings, precise gain and frequency response matching of the individual electrode potentials is achieved in hardware (e.g., an instrumentation amplifier for bipolar recordings). This technique works well when the number of derived signals is small and the montages are pre-determined. However, for array electrodes employing a variety of montages, hardware channel matching can be expensive and tedious, and limits the number of derived signals monitored. This report describes a method for channel matching based on the concept of equalization filters. Monopolar potentials are recorded from each site without precise hardware matching. During a calibration phase, a time-varying linear chirp voltage is applied simultaneously to each site and recorded. Based on the calibration recording, each monopolar channel is digitally filtered to “correct” for (equalize) differences in the individual channels, and then any derived montages subsequently created. In a hardware demonstration system, the common mode rejection ratio (at 60 Hz) of bipolar montages improved from 35.2 ± 5.0 dB (prior to channel equalization) to 69.0 ± 5.0 dB (after equalization). PMID:17614134

Distribution of dehydration rates generated by maximal Gardos-channel activation in normal and sickle red blood cells.

PubMed

Lew, Virgilio L; Tiffert, Teresa; Etzion, Zipora; Perdomo, Deisy; Daw, Nuala; Macdonald, Lynn; Bookchin, Robert M

2005-01-01

The Ca(2+)-activated K+ channels of human red blood cells (RBCs) (Gardos channels, hIK1, hSK4) can mediate rapid cell dehydration, of particular relevance to the pathophysiology of sickle cell disease. Previous investigations gave widely discrepant estimates of the number of Gardos channels per RBC, from as few as 1 to 3 to as many as 300, with large cell-to-cell differences, suggesting that RBCs could differ extensively in their susceptibility to dehydration by elevated Ca2+. Here we investigated the distribution of dehydration rates induced by maximal and uniform Ca2+ loads in normal (AA) and sickle (SS) RBCs by measuring the time-dependent changes in osmotic fragility and RBC volume distributions. We found a remarkable conservation of osmotic lysis and volume distribution profiles during Ca(2+)-induced dehydration, indicating overall uniformity of dehydration rates among AA and SS RBCs. In light of these results, alternative interpretations were suggested for the previously proposed low estimates and heterogeneity of channel numbers per cell. The results support the view that stochastic Ca2+ permeabilization rather than Gardos-channel variation is the main determinant selecting which SS cells dehydrate through Gardos channels in each sickling episode.

Determination of the functioning parameters in asymmetrical flow field-flow fractionation with an exponential channel.

PubMed

Déjardin, P

2013-08-30

The flow conditions in normal mode asymmetric flow field-flow fractionation are determined to approach the high retention limit with the requirement d≪l≪w, where d is the particle diameter, l the characteristic length of the sample exponential distribution and w the channel height. The optimal entrance velocity is determined from the solute characteristics, the channel geometry (exponential to rectangular) and the membrane properties, according to a model providing the velocity fields all over the cell length. In addition, a method is proposed for in situ determination of the channel height. Copyright © 2013 Elsevier B.V. All rights reserved.

Systems and methods for short range RF communication

NASA Technical Reports Server (NTRS)

Hershey, John Erik (Inventor); Tomlinson, Harold Woodruff (Inventor); DeCristofaro, Richard Anthony (Inventor); Ross, John Anderson Fergus (Inventor); Sexton, Daniel White (Inventor)

2012-01-01

A method transmitting a message over at least one of a plurality of channels of a communications network is provided. The method comprises the steps of detecting a presence of jamming pulses in the at least one of the plurality of channels. The characteristics of the jamming pulses in the at least one of the plurality of channels is determined wherein the determined characteristics define at least interstices between the jamming pulses. The message is transmitted over the at least one of the plurality of channels wherein the message is transmitted within the interstices of the jamming pulse determined from the step of determining characteristics of the jamming pulses.

Decreased expression of Kv7 channels in Hirchsprung's disease.

PubMed

O'Donnell, Anne-Marie; Coyle, David; Puri, Prem

2017-07-01

Voltage-dependent K + channels (Kv channels) participate in electrical rhythmicity and smooth muscle responses and are regulated by excitatory and inhibitory neurotransmitters. Kv channels also participate in the interstitial cell of Cajal (ICC) and smooth muscle cell (SMC) responses to neural inputs. The Kv family consists of 12 subfamilies, Kv1-Kv12, with five members of the Kv7 family identified to date: Kv7.1-Kv7.5. A recent study identified the potassium channel Kv7.5 as having a role in the excitability of ICC-IM in the mouse colon. We therefore designed this study to test the hypothesis that Kv7 channels are present in the normal human colon and are reduced in Hirschprung's disease (HSCR). HSCR tissue specimens were collected at the time of pull-through surgery (n=10), while normal control tissue specimens were obtained at the time of colostomy closure in patients with imperforate anus (n=10). Kv7.3-Kv7.5 immunohistochemistry was performed and visualized using confocal microscopy to assess their distribution. Western blot analysis was undertaken to determine Kv7.3-Kv7.5 protein quantification. Kv7.3 and Kv7.4-immunoreactivity was co-localized with neuron and ICC markers, while Kv7.5 was found to be expressed on both ICCs and SMCs. Western blot analysis revealed similar levels of Kv7.3 and Kv7.5 expression in the normal colon and HSCR colon, while Kv7.4 proteins were found to be markedly decreased in ganglionic specimens and decreased further in aganglionic specimens. A deficiency of Kv7.4 channels in the ganglionic and aganglionic bowel may place a role in colonic dysmotility in HSCR. Copyright © 2017 Elsevier Inc. All rights reserved.

Channel Noise-Enhanced Synchronization Transitions Induced by Time Delay in Adaptive Neuronal Networks with Spike-Timing-Dependent Plasticity

NASA Astrophysics Data System (ADS)

Xie, Huijuan; Gong, Yubing; Wang, Baoying

In this paper, we numerically study the effect of channel noise on synchronization transitions induced by time delay in adaptive scale-free Hodgkin-Huxley neuronal networks with spike-timing-dependent plasticity (STDP). It is found that synchronization transitions by time delay vary as channel noise intensity is changed and become most pronounced when channel noise intensity is optimal. This phenomenon depends on STDP and network average degree, and it can be either enhanced or suppressed as network average degree increases depending on channel noise intensity. These results show that there are optimal channel noise and network average degree that can enhance the synchronization transitions by time delay in the adaptive neuronal networks. These findings could be helpful for better understanding of the regulation effect of channel noise on synchronization of neuronal networks. They could find potential implications for information transmission in neural systems.

Hydrologic conditions in the Chicod Creek basin, North Carolina, before and during channel modifications, 1975-81

USGS Publications Warehouse

Watkins, S.A.; Simmons, C.E.

1984-01-01

Beginning in late 1978, stream channels throughout the 60-square mile Chicod Creek basin underwent extensive modification to increase drainage efficiency and reduce flooding potential. Drainage modifications in this Coastal Plain basin, consisting primarily of channel excavation and clearing of channel blockages, were completed in December 1981. The hydrologic condition of the basin before and during modification was determined from observed data. Observed data indicate hydrologic changes occurred in selected basin characteristics. For example, water levels in the surficial aquifer within 250 feet of Juniper Branch declined as much as 0.4 feet during modifications; at distances greater than 250 feet from the stream, ground-water levels did not change. Base flows increased, and suspended-sediment concentrations for high flows were several times greater than before channel modifications. Increases in selected chemical constituent concentrations in stream water during modifications were as follows: calcium, 12 percent; sodium, 18 percent; bicarbonate, 84 percent; and phosphorous, 80 percent. Significant changes were not found in either pesticide concentrations or coliform bacteria counts.

Heat transfer and pressure drop in rectangular channels with crossing fins (a Review)

NASA Astrophysics Data System (ADS)

Sokolov, N. P.; Polishchuk, V. G.; Andreev, K. D.; Rassokhin, V. A.; Zabelin, N. A.

2015-06-01

Channels with crossing finning find wide use in the cooling paths of high-temperature gas turbine blade systems. At different times, different institutions carried out experimental investigations of heat transfer and pressure drop in channels with coplanar finning of opposite walls for obtaining semiempirical dependences of Nusselt criteria (dimensionless heat-transfer coefficients) and pressure drop coefficients on the operating Reynolds number and relative geometrical parameters (or their complexes). The shape of experimental channels, the conditions of experiments, and the used variables were selected so that they would be most suited for solving particular practical tasks. Therefore, the results obtained in processing the experimental data have large scatter and limited use. This article considers the results from experimental investigations of different authors. In comparing the results, additional calculations were carried out for bringing the mathematical correlations to the form of dependences from the same variables. Generalization of the results is carried out. In the final analysis, universal correlations are obtained for determining the pressure drop coefficients and Nusselt number values for the flow of working medium in channels with coplanar finning.

Spectrum Access In Cognitive Radio Using a Two-Stage Reinforcement Learning Approach

NASA Astrophysics Data System (ADS)

Raj, Vishnu; Dias, Irene; Tholeti, Thulasi; Kalyani, Sheetal

2018-02-01

With the advent of the 5th generation of wireless standards and an increasing demand for higher throughput, methods to improve the spectral efficiency of wireless systems have become very important. In the context of cognitive radio, a substantial increase in throughput is possible if the secondary user can make smart decisions regarding which channel to sense and when or how often to sense. Here, we propose an algorithm to not only select a channel for data transmission but also to predict how long the channel will remain unoccupied so that the time spent on channel sensing can be minimized. Our algorithm learns in two stages - a reinforcement learning approach for channel selection and a Bayesian approach to determine the optimal duration for which sensing can be skipped. Comparisons with other learning methods are provided through extensive simulations. We show that the number of sensing is minimized with negligible increase in primary interference; this implies that lesser energy is spent by the secondary user in sensing and also higher throughput is achieved by saving on sensing.

Periodic perturbations in Shaker K+ channel gating kinetics by deletions in the S3–S4 linker

PubMed Central

Gonzalez, Carlos; Rosenman, Eduardo; Bezanilla, Francisco; Alvarez, Osvaldo; Latorre, Ramon

2001-01-01

Upon depolarization positive charges contained in the transmembrane segment S4 of voltage-dependent channels are displaced from the cytoplasmic to the external milieu. This charge movement leads to channel opening. In Shaker K+ channels four positively charged arginines in the S4 domain are transferred from the internal to the external side of the channel during activation. The distance traveled by the S4 segment during activation is unknown, but large movements should be constrained by the S3–S4 linker. Constructing deletion mutants, we show that the activation time constant and the midpoint of the voltage activation curve of the Shaker K+ channel macroscopic currents becomes a periodic function of the S3–S4 linker length for linkers shorter than 7 aa residues. The periodicity is that typical of α-helices. Moreover, a linker containing only 3 aa is enough to recover the wild-type phenotype. The deletion method revealed the importance of the S3–S4 linker in determining the channel gating kinetics and indicated that the α-helical nature of S4 extends toward its N terminus. These results support the notion that a small displacement of the S4 segment suffices to displace the four gating charges involved in channel opening. PMID:11493701

CTF Preprocessor User's Manual

DOE Office of Scientific and Technical Information (OSTI.GOV)

Avramova, Maria; Salko, Robert K.

2016-05-26

This document describes how a user should go about using the CTF pre- processor tool to create an input deck for modeling rod-bundle geometry in CTF. The tool was designed to generate input decks in a quick and less error-prone manner for CTF. The pre-processor is a completely independent utility, written in Fortran, that takes a reduced amount of input from the user. The information that the user must supply is basic information on bundle geometry, such as rod pitch, clad thickness, and axial location of spacer grids--the pre-processor takes this basic information and determines channel placement and connection informationmore » to be written to the input deck, which is the most time-consuming and error-prone segment of creating a deck. Creation of the model is also more intuitive, as the user can specify assembly and water-tube placement using visual maps instead of having to place them by determining channel/channel and rod/channel connections. As an example of the benefit of the pre-processor, a quarter-core model that contains 500,000 scalar-mesh cells was read into CTF from an input deck containing 200,000 lines of data. This 200,000 line input deck was produced automatically from a set of pre-processor decks that contained only 300 lines of data.« less

Pressure-Dependent Yields and Product Branching Ratios in the Broadband Photolysis of Chlorine Nitrate

NASA Technical Reports Server (NTRS)

Nickolaisen, Scott L.; Sander, Stanley P.; Friedl, Randall R.

1996-01-01

The photolysis of chlorine nitrate was studied using broadband flash photolysis coupled with long-path ultraviolet-visible absorption spectroscopy. Branching ratios for the Cl + NO3 and ClO + NO2 product channels were determined from time-dependent measurements of ClO and NO3 concentrations. Yields of the ClO and NO3 products displayed a dependence on the bath gas density and the spectral distribution of the photolysis pulse. Product yields decreased with increasing bath gas density regardless of the spectral distribution of the photolysis pulse; however, the decrease in product yield was much more pronounced when photolysis was limited to longer wavelengths. For photolysis in a quartz cell (lambda > 200 nm) the yield decreased by a factor of 2 over the pressure 10-100 Torr. In a Pyrex cell (lambda > 300 nm), the yield decreased by a factor of 50 over the same pressure range. When photolysis was limited to lambda > 350 nm, the yield decreased by a factor of 250. Branching ratios for the photolysis channels [ClONO2 + h.nu yields ClO + NO2 (1a) and ClONO2 + h.nu yields Cl + NO3 (lb)] were determined from the relative ClO and NO3 product yields at various pressures. Although the absolute product yield displayed a pressure dependence, the branching between the two channels was independent of pressure. The relative branching ratios (assuming negligible contributions from other channels) are 0.61 +/- 0.20 for channel 1a and 0.39 +/- 0.20 for channel lb for photolysis with lambda > 200 nm and 0.44 +/- 0.08 for channel 1a and 0.56 +/- 0.08 for channel 1b for photolysis with lambda > 300 nm. The implications of these results for the chemistry of the lower stratosphere are discussed.

The problem of predicting the size distribution of sediment supplied by hillslopes to rivers

NASA Astrophysics Data System (ADS)

Sklar, Leonard S.; Riebe, Clifford S.; Marshall, Jill A.; Genetti, Jennifer; Leclere, Shirin; Lukens, Claire L.; Merces, Viviane

2017-01-01

Sediments link hillslopes to river channels. The size of sediments entering channels is a key control on river morphodynamics across a range of scales, from channel response to human land use to landscape response to changes in tectonic and climatic forcing. However, very little is known about what controls the size distribution of particles eroded from bedrock on hillslopes, and how particle sizes evolve before sediments are delivered to channels. Here we take the first steps toward building a geomorphic transport law to predict the size distribution of particles produced on hillslopes and supplied to channels. We begin by identifying independent variables that can be used to quantify the influence of five key boundary conditions: lithology, climate, life, erosion rate, and topography, which together determine the suite of geomorphic processes that produce and transport sediments on hillslopes. We then consider the physical and chemical mechanisms that determine the initial size distribution of rock fragments supplied to the hillslope weathering system, and the duration and intensity of weathering experienced by particles on their journey from bedrock to the channel. We propose a simple modeling framework with two components. First, the initial rock fragment sizes are set by the distribution of spacing between fractures in unweathered rock, which is influenced by stresses encountered by rock during exhumation and by rock resistance to fracture propagation. That initial size distribution is then transformed by a weathering function that captures the influence of climate and mineralogy on chemical weathering potential, and the influence of erosion rate and soil depth on residence time and the extent of particle size reduction. Model applications illustrate how spatial variation in weathering regime can lead to bimodal size distributions and downstream fining of channel sediment by down-valley fining of hillslope sediment supply, two examples of hillslope control on river sediment size. Overall, this work highlights the rich opportunities for future research into the controls on the size of sediments produced on hillslopes and delivered to channels.

Removal of inactivation causes time-invariant sodium current decays

PubMed Central

1988-01-01

The kinetic properties of the closing of Na channels were studied in frog skeletal muscle to obtain information about the dependence of channel closing on the past history of the channel. Channel closing was studied in normal and modified channels. Chloramine-T was used to modify the channels so that inactivation was virtually removed. A series of depolarizing prepulse potentials was used to activate Na channels, and a -140-mV postpulse was used to monitor the closing of the channels. Unmodified channels decay via a biexponential process with time constants of 72 and 534 microseconds at 12 degrees C. The observed time constants do not depend upon the potential used to activate the channels. The contribution of the slow component to the total decay increases as the activating prepulse is lengthened. After inactivation is removed, the biexponential character of the decay is retained, with no change in the magnitude of the time constants. However, increases in the duration of the activating prepulse over the range where the current is maximal 1-75 ms) produce identical biexponential decays. The presence of biexponential decays suggests that either two subtypes of Na channels are found in muscle, or Na channels can exist in one of two equally conductive states. The time- invariant decays observed suggest that channel closure does not depend upon their past history. PMID:2852208

Construction dynamics of a lava channel

NASA Astrophysics Data System (ADS)

Harris, Andrew J. L.; Favalli, Massimiliano; Mazzarini, Francesco; Hamilton, Christopher W.

2009-05-01

We use a kinematic GPS and laser range finder survey of a 200 m-long section of the Muliwai a Pele lava channel (Mauna Ulu, Kilauea) to examine the construction processes and flow dynamics responsible for the channel-levee structure. The levees comprise three packages. The basal package comprises an 80-150 m wide 'a'a flow in which a ˜2 m deep and ˜11 m wide channel became centred. This is capped by a second package of thin (<45 cm thick) sheets of pahoehoe extending no more than 50 m from the channel. The upper-most package comprises localised 'a'a overflows. The channel itself contains two blockages located 130 m apart and composed of levee chunks veneered with overflow lava. The channel was emplaced over 50 h, spanning 30 May-2 June, 1974, with the flow front arriving at our section (4.4 km from the vent) 8 h after the eruption began. The basal 'a'a flow thickness yields effusion rates of 35 m3 s-1 for the opening phase, with the initial flow advancing across the mapped section at ˜10 m/min. Short-lived overflows of fluid pahoehoe then built the levee cap, increasing the apparent channel depth to 4.8 m. There were at least six pulses at 90-420 m3 s-1, causing overflow of limited extent lasting no more than 5 min. Brim-full flow conditions were thus extremely short-lived. During a dominant period of below-bank flow, flow depth was ˜2 m with an effusion rate of ˜35 m3 s-1, consistent with the mean output rate (obtained from the total flow bulk volume) of 23-54 m3 s-1. During pulses, levee chunks were plucked and floated down channel to form blockages. In a final low effusion rate phase, lava ponded behind the lower blockage to form a syn-channel pond that fed 'a'a overflow. After the end of the eruption the roofed-over pond continued to drain through the lower blockage, causing the roof to founder. Drainage emplaced inflated flows on the channel floor below the lower blockage for a further ˜10 h. The complex processes involved in levee-channel construction of this short-lived case show that care must be taken when using channel dimensions to infer flow dynamics. In our case, the full channel depth is not exposed. Instead the channel floor morphology reflects late stage pond filling and drainage rather than true channel-contained flow. Components of the compound levee relate to different flow regimes operating at different times during the eruption and associated with different effusion rates, flow dynamics and time scales. For example, although high effusion rate, brim-full flow was maintained for a small fraction of the channel lifetime, it emplaced a pile of pahoehoe overflow units that account for 60% of the total levee height. We show how time-varying volume flux is an important parameter in controlling channel construction dynamics. Because the complex history of lava delivery to a channel system is recorded by the final channel morphology, time-varying flow dynamics can be determined from the channel morphology. Developing methods for quantifying detailed flux histories for effusive events from the evidence in outcrop is therefore highly valuable. We here achieve this by using high-resolution spatial data for a channel system at Kilauea. This study not only indicates those physical and dynamic characteristics that are typical for basaltic lava flows on Hawaiian volcanoes, but also a methodology that can be widely applied to effusive basaltic eruptions.

Analysis of radiometric signal in sedimentating suspension flow in open channel

NASA Astrophysics Data System (ADS)

Zych, Marcin; Hanus, Robert; Petryka, Leszek; Świsulski, Dariusz; Doktor, Marek; Mastej, Wojciech

2015-05-01

The article discusses issues related to the estimation of the sedimentating solid particles average flow velocity in an open channel using radiometric methods. Due to the composition of the compound, which formed water and diatomite, received data have a very weak signal to noise ratio. In the process analysis the known determining of the solid phase transportation time delay the classical cross-correlation function is the most reliable method. The use of advanced frequency analysis based on mutual spectral density function and wavelet transform of recorded signals allows a reduction of the noise contribution.

Optical reading of field-effect transistors by phase-space absorption quenching in a single InGaAs quantum well conducting channel

NASA Astrophysics Data System (ADS)

Chemla, D. S.; Bar-Joseph, I.; Klingshirn, C.; Miller, D. A. B.; Kuo, J. M.

1987-03-01

Absorption switching in a semiconductor quantum well by electrically varying the charge density in the quantum well conducting channel of a selectively doped heterostructure transistor is reported for the first time. The phase-space absorption quenching (PAQ) is observed at room temperature in an InGaAs/InAlAs grown on InP FET, and it shows large absorption coefficient changes with relatively broad spectral bandwidth. This PAQ is large enough to be used for direct optical determination of the logic state of the FET.

A photoelectric technique for measuring lightning-channel propagation velocities from a mobile laboratory

NASA Technical Reports Server (NTRS)

Mach, Douglas M.; Rust, W. David

1989-01-01

The present device for lightning channel propagation-velocity determination employs eight photodetectors mounted behind precision horizontal slits in the focal plane of a photographic camera lens. The eight photodetector pulses, IRIG-B time, and slow and fast electric field-change waveforms are recorded on a 14-track analog tape recorder. A comparison of the present results with those obtained by a streaking camera shows no significant differences between the velocities obtained from the same strokes with the two systems; neither is there any difference in pulse characteristics or in the velocities calculated from them.

Design test request No. 1263 K Reactor graphite key and VSR channel sleeve test

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kempf, F.J.

1964-12-10

The objectives of this test were: (1) Determine the coefficient of friction between two adjacent layers of K Reactor graphite at room temperature. (2) Determine the average load required to cause failure of an unirradiated K Reactor side reflector bar, when subjected to tensile loading applied through the reflector keys. (3) Determine the average load at failure and the average deflection at failure of a single VSR channel key when loaded in keyways with clearances equal to those used in original stack construction. (4) Determine the average load and deflection required to break the four K Reactor VSR keys whenmore » loaded simultaneously in both `3-layer` and `7-layer` mockups. Also determine the mode of key failure; i.e., shear, flexure or combined compression and bending. Following these key rupture tests, determine the strength and deflection characteristics of the proposed K Reactor VSR channel sleeve when loaded in a manner identical to that used to fracture the keys. (5) Determine the average load and deflection at failure of both the proposed K Reactor VSR channel sleeves and the proposed C Reactor sleeves when subjected to crushing loads. (6) Determine the extent of damage to the proposed K Reactor VSR channel sleeve when subjected to the following vertical rod loading conditions. (a) Full rod drop in a channel mockup which has been misaligned 2 1/2 inches. (b) Full rod drop in a channel which has been misaligned an amount equal to the maximum flexibility of a `universal` VSR.« less

Channel and Timeslot Co-Scheduling with Minimal Channel Switching for Data Aggregation in MWSNs

PubMed Central

Yeoum, Sanggil; Kang, Byungseok; Lee, Jinkyu; Choo, Hyunseung

2017-01-01

Collision-free transmission and efficient data transfer between nodes can be achieved through a set of channels in multichannel wireless sensor networks (MWSNs). While using multiple channels, we have to carefully consider channel interference, channel and time slot (resources) optimization, channel switching delay, and energy consumption. Since sensor nodes operate on low battery power, the energy consumed in channel switching becomes an important challenge. In this paper, we propose channel and time slot scheduling for minimal channel switching in MWSNs, while achieving efficient and collision-free transmission between nodes. The proposed scheme constructs a duty-cycled tree while reducing the amount of channel switching. As a next step, collision-free time slots are assigned to every node based on the minimal data collection delay. The experimental results demonstrate that the validity of our scheme reduces the amount of channel switching by 17.5%, reduces energy consumption for channel switching by 28%, and reduces the schedule length by 46%, as compared to the existing schemes. PMID:28471416

Channel and Timeslot Co-Scheduling with Minimal Channel Switching for Data Aggregation in MWSNs.

PubMed

Yeoum, Sanggil; Kang, Byungseok; Lee, Jinkyu; Choo, Hyunseung

2017-05-04

Collision-free transmission and efficient data transfer between nodes can be achieved through a set of channels in multichannel wireless sensor networks (MWSNs). While using multiple channels, we have to carefully consider channel interference, channel and time slot (resources) optimization, channel switching delay, and energy consumption. Since sensor nodes operate on low battery power, the energy consumed in channel switching becomes an important challenge. In this paper, we propose channel and time slot scheduling for minimal channel switching in MWSNs, while achieving efficient and collision-free transmission between nodes. The proposed scheme constructs a duty-cycled tree while reducing the amount of channel switching. As a next step, collision-free time slots are assigned to every node based on the minimal data collection delay. The experimental results demonstrate that the validity of our scheme reduces the amount of channel switching by 17.5%, reduces energy consumption for channel switching by 28%, and reduces the schedule length by 46%, as compared to the existing schemes.

Hard X-ray time profiles and acceleration processes in large solar flares

NASA Technical Reports Server (NTRS)

Bai, T.; Ramaty, R.

1979-01-01

The hard X-ray time profiles of the (1972) August 4 and 7 flares are investigated, taking into account a comparison of the time profiles of different energy channels. It is shown that for these flares the temporal features of the intensity profiles of higher energy channels are delayed with respect to those of channel 1. The delay time gradually increases to approximately 5 sec as the channel number increases from 1 to 5, and it jumps to approximately 15 sec for channels 6 and 7. A description is presented of a model in which the delay and other characteristics of the observed time profiles in channels 1-5 are self-consistently explained by the increase of the electron energy loss time with electron energy.

Valley dynamics of intravalley and intervalley multiexcitonic states in monolayer WS2

NASA Astrophysics Data System (ADS)

Fu, Jiyong; Bezerra, Andre; Qu, Fanyao

2018-03-01

We present a comprehensive model comprising of a complete set of rate equations, which account for charge transfer among multiexcitonic channels including excitons, trions, and biexcitons, to investigate valley (locked with spin) dynamics in monolayer WS2. The steady-state photoluminescence (PL) spectra, underlying the laser power dependence of excitonic populations, are also determined. Our computed PL for all excitonic states agrees with the experimental data of Paradisanos et al. [Appl. Phys. Lett. 110, 193102 (2017), 10.1063/1.4983285]. We find that the relative weight of PL, stemmed from different excitonic channels, strongly depends on the laser power even under dynamical conditions. Remarkably, the biexciton channel, having the weakest PL intensity at low laser powers, tends to prevail in PL over other excitonic states as the power strengthens. In addition, by accounting for intervalley scatterings, which enable transfer of excitonic states from one valley to the other, we determine the valley polarization, which strongly depends on intervalley scatterings and the exciton generation rates in the two valleys. On the other hand, the valley polarization for all excitonic channels is found almost independent of the laser power, consistent with experimental measurements as well. Finally, the valley dynamics involving both intra- and intervalley trions is discussed. Our model and numerical outcome should be beneficial to experiments especially featuring the interplay of multiexcitonic channels in, e.g., elucidating experimental data, estimating central excitonic quantities including recombination times and transition rates, and in widening possible new experimental scopes.

Electroosmotic flow in microchannels with arbitrary geometry and arbitrary distribution of wall charge.

PubMed

Xuan, Xiangchun; Li, Dongqing

2005-09-01

General solutions are developed for direct current (DC) and alternating current (AC) electroosmotic flows in microfluidic channels with arbitrary cross-sectional geometry and arbitrary distribution of wall charge (zeta potential). The applied AC electric field can also be of arbitrary waveform. By proposing a nondimensional time scale varpi defined as the ratio of the diffusion time of momentum across the electric double-layer thickness to the period of the applied electric field, we demonstrate analytically that the Helmholtz-Smoluchowski electroosmotic velocity is an appropriate slip condition for AC electroosmotic flows in typical microfluidic applications. With this slip condition approach, electroosmotic flows in rectangular and asymmetric trapezoidal microchannels with nonuniform wall charge, as examples, are investigated. The unknown constants in the proposed general solutions are numerically determined with a least-squares method through matching the boundary conditions. We find that the wall charge affects significantly the electroosmotic flow while the channel geometry does not. Moreover, the flow feature is characterized by another nondimensional time scale Omega defined as the ratio of the diffusion time of momentum across the channel hydraulic radius to the period of the applied electric field. The onset of phase shift between AC electroosmotic velocity and applied electric field is also examined analytically.

Purity of Gaussian states: Measurement schemes and time evolution in noisy channels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paris, Matteo G.A.; Illuminati, Fabrizio; Serafini, Alessio

2003-07-01

We present a systematic study of the purity for Gaussian states of single-mode continuous variable systems. We prove the connection of purity to observable quantities for these states, and show that the joint measurement of two conjugate quadratures is necessary and sufficient to determine the purity at any time. The statistical reliability and the range of applicability of the proposed measurement scheme are tested by means of Monte Carlo simulated experiments. We then consider the dynamics of purity in noisy channels. We derive an evolution equation for the purity of general Gaussian states both in thermal and in squeezed thermalmore » baths. We show that purity is maximized at any given time for an initial coherent state evolving in a thermal bath, or for an initial squeezed state evolving in a squeezed thermal bath whose asymptotic squeezing is orthogonal to that of the input state.« less

Role of Piezo Channels in Ultrasound-stimulated Dental Stem Cells.

PubMed

Gao, Qianhua; Cooper, Paul R; Walmsley, A Damien; Scheven, Ben A

2017-07-01

Piezo1 and Piezo2 are mechanosensitive membrane ion channels. We hypothesized that Piezo proteins may play a role in transducing ultrasound-associated mechanical signals and activate downstream mitogen-activated protein kinase (MAPK) signaling processes in dental cells. In this study, the expression and role of Piezo channels were investigated in dental pulp stem cells (DPSCs) and periodontal ligament stem cells (PDLSCs) after treatment with low-intensity pulsed ultrasound (LIPUS). Cell proliferation was evaluated by bromodeoxyuridine incorporation. Western blots were used to analyze the proliferating cell nuclear antigen as well as the transcription factors c-fos and c-jun. Enzyme-linked immunosorbent assay and Western blotting were used to determine the activation of MAPK after LIPUS treatment. Ruthenium red (RR), a Piezo ion channel blocker, was applied to determine the functional role of Piezo proteins in LIPUS-stimulated cell proliferation and MAPK signaling. Western blotting showed the presence of Piezo1 and Piezo2 in both dental cell types. LIPUS treatment significantly increased the level of the Piezo proteins in DPSCs after 24 hours; however, no significant effects were observed in PDLSCs. Treatment with RR significantly inhibited LIPUS-stimulated DPSC proliferation but not PDLSC proliferation. Extracellular signal-related kinase (ERK) 1/2 MAPK was consistently activated in DPSCs over a 24-hour time period after LIPUS exposure, whereas phosphorylated c-Jun N-terminal kinase and p38 mitogen-activated protein kinase MAPK were mainly increased in PDLSCs. RR affected MAPK signaling in both dental cell types with its most prominent effects on ERK1/2/MAPK phosphorylation levels; the significant inhibition of LIPUS-induced stimulation of ERK1/2 activation in DPSCs by RR suggests that stimulation of DPSC proliferation by LIPUS involves Piezo-mediated regulation of ERK1/2 MAPK signaling. This study for the first time supports the role of Piezo ion channels in transducing the LIPUS response in dental stem cells. Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Regional Relations in Bankfull Channel Characteristics determined from flow measurements at selected stream-gaging stations in West Virginia, 1911-2002

USGS Publications Warehouse

Messinger, Terence; Wiley, Jeffrey B.

2004-01-01

Three bankfull channel characteristics?cross-sectional area, width, and depth?were significantly correlated with drainage area in regression equations developed for two regions in West Virginia. Channel characteristics were determined from analysis of flow measurements made at 74 U.S. Geological Survey stream-gaging stations at flows between 0.5 and 5.0 times bankfull flow between 1911 and 2002. Graphical and regression analysis were used to delineate an 'Eastern Region' and a 'Western Region,' which were separated by the boundary between the Appalachian Plateaus and Valley and Ridge Physiographic Provinces. Streams that drained parts of both provinces had channel characteristics typical of the Eastern Region, and were grouped with it. Standard error for the six regression equations, three for each region, ranged between 8.7 and 16 percent. Cross-sectional area and depth were greater relative to drainage area for the Western Region than they were for the Eastern Region. Regression equations were defined for streams draining between 46.5 and 1,619 square miles for the Eastern Region, and between 2.78 and 1,354 square miles for the Western Region. Stream-gaging stations with two or more cross sections where flow had been measured at flows between 0.5 and 5.0 times the 1.5-year flow showed poor replication of channel characteristics compared to the 95-percent confidence intervals of the regression, suggesting that within-reach variability for the stream-gaging stations may be substantial. A disproportionate number of the selected stream-gaging stations were on large (drainage area greater than 100 square miles) streams in the central highlands of West Virginia, and only one stream-gaging station that met data-quality criteria was available to represent the region within about 50 miles of the Ohio River north of Parkersburg, West Virginia. Many of the cross sections were at bridges, which can change channel shape. Although the data discussed in this report may not be representative of channelcharacteristics on many or most streams, the regional equations in this report provide useful information for field identification of bankfull indicators.

UHF RiverSonde observations of water surface velocity at Threemile Slough, California

USGS Publications Warehouse

Teague, C.C.; Barrick, D.E.; Lilleboe, P.M.; Cheng, R.T.; Ruhl, C.A.

2005-01-01

A UHF RiverSonde system, operating near 350 MHz, has been in operation at Threemile Slough in central California, USA since September 2004. The water in the slough is dominated by tidal effects, with flow reversals four times a day and a peak velocity of about 0.8 m/s in each direction. Water level and water velocity are continually measured by the U. S. Geological Survey at the experiment site. The velocity is measured every 15 minutes by an ultrasonic velocity meter (UVM) which determines the water velocity from two-way acoustic propagation time-difference measurements made across the channel. The RiverSonde also measures surface velocity every 15 minutes using radar resonant backscatter techniques. Velocity and water level data are retrieved through a radio data link and a wideband internet connection. Over a period of several months, the radar-derived mean surface velocity has been very highly correlated with the UVM index velocity several meters below the surface, with a coefficient of determination R2 of 0.976 and an RMS difference of less than 10 cm/s. The wind has a small but measurable effect on the velocities measured by both instruments. In addition to the mean surface velocity across the channel, the RiverSonde system provides an estimate of the cross-channel variation of the surface velocity. ?? 2005 IEEE.

Automated Detection of Clouds in Satellite Imagery

NASA Technical Reports Server (NTRS)

Jedlovec, Gary

2010-01-01

Many different approaches have been used to automatically detect clouds in satellite imagery. Most approaches are deterministic and provide a binary cloud - no cloud product used in a variety of applications. Some of these applications require the identification of cloudy pixels for cloud parameter retrieval, while others require only an ability to mask out clouds for the retrieval of surface or atmospheric parameters in the absence of clouds. A few approaches estimate a probability of the presence of a cloud at each point in an image. These probabilities allow a user to select cloud information based on the tolerance of the application to uncertainty in the estimate. Many automated cloud detection techniques develop sophisticated tests using a combination of visible and infrared channels to determine the presence of clouds in both day and night imagery. Visible channels are quite effective in detecting clouds during the day, as long as test thresholds properly account for variations in surface features and atmospheric scattering. Cloud detection at night is more challenging, since only courser resolution infrared measurements are available. A few schemes use just two infrared channels for day and night cloud detection. The most influential factor in the success of a particular technique is the determination of the thresholds for each cloud test. The techniques which perform the best usually have thresholds that are varied based on the geographic region, time of year, time of day and solar angle.

S-acylation dependent post-translational cross-talk regulates large conductance calcium- and voltage- activated potassium (BK) channels

PubMed Central

Shipston, Michael J.

2014-01-01

Mechanisms that control surface expression and/or activity of large conductance calcium-activated potassium (BK) channels are important determinants of their (patho)physiological function. Indeed, BK channel dysfunction is associated with major human disorders ranging from epilepsy to hypertension and obesity. S-acylation (S-palmitoylation) represents a major reversible, post-translational modification controlling the properties and function of many proteins including ion channels. Recent evidence reveals that both pore-forming and regulatory subunits of BK channels are S-acylated and control channel trafficking and regulation by AGC-family protein kinases. The pore-forming α-subunit is S-acylated at two distinct sites within the N- and C-terminus, each site being regulated by different palmitoyl acyl transferases (zDHHCs) and acyl thioesterases (APTs). S-acylation of the N-terminus controls channel trafficking and surface expression whereas S-acylation of the C-terminal domain determines regulation of channel activity by AGC-family protein kinases. S-acylation of the regulatory β4-subunit controls ER exit and surface expression of BK channels but does not affect ion channel kinetics at the plasma membrane. Furthermore, a significant number of previously identified BK-channel interacting proteins have been shown, or are predicted to be, S-acylated. Thus, the BK channel multi-molecular signaling complex may be dynamically regulated by this fundamental post-translational modification and thus S-acylation likely represents an important determinant of BK channel physiology in health and disease. PMID:25140154

Short range RF communication for jet engine control

NASA Technical Reports Server (NTRS)

Sexton, Daniel White (Inventor); Hershey, John Erik (Inventor)

2007-01-01

A method transmitting a message over at least one of a plurality of radio frequency (RF) channels of an RF communications network is provided. The method comprises the steps of detecting a presence of jamming pulses in the at least one of the plurality of RF channels. The characteristics of the jamming pulses in the at least one of the plurality of RF channels is determined wherein the determined characteristics define at least interstices between the jamming pulses. The message is transmitted over the at least one of the plurality of RF channels wherein the message is transmitted within the interstices of the jamming pulse determined from the step of determining characteristics of the jamming pulses.

Introduction of the ASGARD Code

NASA Technical Reports Server (NTRS)

Bethge, Christian; Winebarger, Amy; Tiwari, Sanjiv; Fayock, Brian

2017-01-01

ASGARD stands for 'Automated Selection and Grouping of events in AIA Regional Data'. The code is a refinement of the event detection method in Ugarte-Urra & Warren (2014). It is intended to automatically detect and group brightenings ('events') in the AIA EUV channels, to record event parameters, and to find related events over multiple channels. Ultimately, the goal is to automatically determine heating and cooling timescales in the corona and to significantly increase statistics in this respect. The code is written in IDL and requires the SolarSoft library. It is parallelized and can run with multiple CPUs. Input files are regions of interest (ROIs) in time series of AIA images from the JSOC cutout service (http://jsoc.stanford.edu/ajax/exportdata.html). The ROIs need to be tracked, co-registered, and limited in time (typically 12 hours).

Fluid-structure-interaction of a flag in a channel flow

NASA Astrophysics Data System (ADS)

Liu, Yingzheng; Yu, Yuelong; Zhou, Wenwu; Wang, Weizhe

2017-11-01

The unsteady flow field and flapping dynamics of an inverted flag in water channel are investigated using time resolved particle image velocimetry (TR-PIV) measurements. The dynamically deformed profiles of the inverted flag are determined by a novel algorithm that combines morphological image processing and principle component analysis. Instantaneous flow field, phase averaged vorticity, time-mean flow field and turbulent kinematic energy are addressed for the flow. Four modes are discovered as the dimensionless bending stiffness decreases, i.e., the straight mode, the biased mode, the flapping mode and the deflected mode. Among all modes, the flapping mode is characterized by large flapping amplitude and the reverse von Kármán vortex street wake, which is potential to enhance heat transfer remarkably. National Natural Science Foundation of China.

A data acquisition system for coincidence imaging using a conventional dual head gamma camera

NASA Astrophysics Data System (ADS)

Lewellen, T. K.; Miyaoka, R. S.; Jansen, F.; Kaplan, M. S.

1997-06-01

A low cost data acquisition system (DAS) was developed to acquire coincidence data from an unmodified General Electric Maxxus dual head scintillation camera. A high impedance pick-off circuit provides position and energy signals to the DAS without interfering with normal camera operation. The signals are pulse-clipped to reduce pileup effects. Coincidence is determined with fast timing signals derived from constant fraction discriminators. A charge-integrating FERA 16 channel ADC feeds position and energy data to two CAMAC FERA memories operated as ping-pong buffers. A Macintosh PowerPC running Labview controls the system and reads the CAMAC memories. A CAMAC 12-channel scaler records singles and coincidence rate data. The system dead-time is approximately 10% at a coincidence rate of 4.0 kHz.

Studies of radio frequency interference at Parkes Observatory

NASA Astrophysics Data System (ADS)

Backus, Peter R.; Laroque, Sam; Tarter, Jill C.; Dreher, John; Gullers, Kent; Patrick, Alan; Heiligman, Gary

1997-01-01

From February through early June 1995, Project Phoenix conducted SETI observations of 209 stars over the frequency range from 1195 to 3005 MHz. A byproduct of this search is a unique data set suitable for studying the Radio Frequency Interference (RFI) environment at the Parkes 64-m telescope in New South Wales, Australia. RFI is an increasing problem for SETI and other radio astronomy observations conducted outside of the 'protected' frequency bands. The data analyzed for this paper were 'mean baseline' spectra in Left and Right Circular Polarization (LCP, RCP), integrated for either 138 or 276 s, covering a 10-MHz bandwidth with 15,552 channels at a resolution of 643 Hz. Channels were identified as contaminated by RFI when the power in the channel exceeded the mean noise by 3 percent. The 'spectral occupancy', the fraction of time RFI was seen, was determined for each channel. The RFI occupancy for LCP and RCP are distinctly different. Approximately 100 MHz of the spectrum was too heavily contaminated for SETI observations.

Research on Intelligent Control System of DC SQUID Magnetometer Parameters for Multi-channel System

NASA Astrophysics Data System (ADS)

Chen, Hua; Yang, Kang; Lu, Li; Kong, Xiangyan; Wang, Hai; Wu, Jun; Wang, Yongliang

2018-07-01

In a multi-channel SQUID measurement system, adjusting device parameters to optimal condition for all channels is time-consuming. In this paper, an intelligent control system is presented to determine the optimal working point of devices which is automatic and more efficient comparing to the manual one. An optimal working point searching algorithm is introduced as the core component of the control system. In this algorithm, the bias voltage V_bias is step scanned to obtain the maximal value of the peak-to-peak current value I_pp of the SQUID magnetometer modulation curve. We choose this point as the optimal one. Using the above control system, more than 30 weakly damped SQUID magnetometers with area of 5 × 5 mm^2 or 10 × 10 mm^2 are adjusted and a 36-channel magnetocardiography system perfectly worked in a magnetically shielded room. The average white flux noise is 15 {μ Φ }_0/Hz^{1/2}.

Antisense oligonucleotides suppress cell-volume-induced activation of chloride channels.

PubMed

Gschwentner, M; Nagl, U O; Wöll, E; Schmarda, A; Ritter, M; Paulmichl, M

1995-08-01

Cell volume regulation is an essential feature of most cells. After swelling in hypotonic media, the simultaneous activation of potassium and chloride channels is believed to be the initial, time-determining step in cell volume regulation. The activation of both pathways is functionally linked and enables the cells to lose ions and water, subsequently leading to cell shrinkage and readjustment of the initial volume. NIH 3T3 fibroblasts efficiently regulate their volume after swelling and bear chloride channels that are activated by decreasing extracellular osmolarity. The chloride current elicited in these cells after swelling is reminiscent of the current found in oocytes expressing an outwardly rectifying chloride current termed ICln. Introduction of antisense oligodeoxynucleotides complementary to the first 30 nucleotides of the coding region of the ICln channel into NIH 3T3 fibroblasts suppresses the activation of the swelling-induced chloride current. The experiments directly demonstrate an unambiguous link between a volume-activated chloride current and a cloned protein involved in chloride transport.

Research on Intelligent Control System of DC SQUID Magnetometer Parameters for Multi-channel System

NASA Astrophysics Data System (ADS)

Chen, Hua; Yang, Kang; Lu, Li; Kong, Xiangyan; Wang, Hai; Wu, Jun; Wang, Yongliang

2018-03-01

In a multi-channel SQUID measurement system, adjusting device parameters to optimal condition for all channels is time-consuming. In this paper, an intelligent control system is presented to determine the optimal working point of devices which is automatic and more efficient comparing to the manual one. An optimal working point searching algorithm is introduced as the core component of the control system. In this algorithm, the bias voltage V_bias is step scanned to obtain the maximal value of the peak-to-peak current value I_pp of the SQUID magnetometer modulation curve. We choose this point as the optimal one. Using the above control system, more than 30 weakly damped SQUID magnetometers with area of 5 × 5 mm^2 or 10 × 10 mm^2 are adjusted and a 36-channel magnetocardiography system perfectly worked in a magnetically shielded room. The average white flux noise is 15 μΦ_0/Hz^{1/2}.

High Mobility SiGe/Si Transistor Structures on Sapphire Substrates Using Ion Implantation

NASA Technical Reports Server (NTRS)

Alterovitz, S. A.; Mueller, C. H.; Croke, E. T.

2003-01-01

High mobility n-type SiGe/Si transistor structures have been fabricated on sapphire substrates by ion implanting phosphorus ions into strained 100 Angstrom thick silicon channels for the first time. The strained Si channels were sandwiched between Si(sub 0.7)Ge(sub 0.3) layers, which, in turn, were deposited on Si(sub 0.7)Ge(sub 0.3) virtual substrates and graded SiGe buffer layers. After the molecular beam epitaxy (MBE) film growth process was completed, ion thick silicon channels implantation and post-annealing were used to introduce donors. The phosphorous ions were preferentially located in the Si channel at a peak concentration of approximately 1x10(exp 18)/cu cm. Room temperature electron mobilities exceeding 750 sq cm/V-sec at carrier densities of 1x10(exp 12)/sq cm were measured. Electron concentration appears to be the key factor that determines mobility, with the highest mobility observed for electron densities in the 1 - 2x10(exp 12)/sq cm range.

Substance P modulation of TRPC3/7 channels improves respiratory rhythm regularity and ICAN-dependent pacemaker activity

PubMed Central

Ben-Mabrouk, Faiza; Tryba, Andrew Kieran

2011-01-01

Neuromodulators, such as Substance P (SubP) play an important role in modulating many rhythmic activities driven by central pattern generators (e.g., locomotion, respiration). However, the mechanism by which SubP enhances breathing regularity has not been determined. Here, we used mouse brainstem slices containing the pre-Bötzinger Complex (Pre-BötC) to demonstrate, for the first time, that SubP activates transient receptor protein canonical (TRPC) channels to enhance respiratory rhythm regularity. Moreover, SubP enhancement of network regularity is accomplished via selective enhancement of ICAN-dependent intrinsic bursting properties. In contrast to INaP-dependant pacemakers, ICAN-dependant pacemaker bursting activity is TRPC dependent. Western Blots reveal TRPC3 and TRPC7 channels are expressed in rhythmically active ventral respiratory group (VRG) island preparations. Taken together, these data suggest that SubP-mediated activation of TRPC3/7 channels underlies rhythmic ICAN-dependent pacemaker activity and enhances the regularity of respiratory rhythm activity. PMID:20345918

Substance P modulation of TRPC3/7 channels improves respiratory rhythm regularity and ICAN-dependent pacemaker activity.

PubMed

Ben-Mabrouk, Faiza; Tryba, Andrew K

2010-04-01

Neuromodulators, such as substance P (SubP), play an important role in modulating many rhythmic activities driven by central pattern generators (e.g. locomotion, respiration). However, the mechanism by which SubP enhances breathing regularity has not been determined. Here, we used mouse brainstem slices containing the pre-Bötzinger complex to demonstrate, for the first time, that SubP activates transient receptor protein canonical (TRPC) channels to enhance respiratory rhythm regularity. Moreover, SubP enhancement of network regularity is accomplished via selective enhancement of ICAN (inward non-specific cation current)-dependent intrinsic bursting properties. In contrast to INaP (persistent sodium current)-dependent pacemakers, ICAN-dependent pacemaker bursting activity is TRPC-dependent. Western Blots reveal TRPC3 and TRPC7 channels are expressed in rhythmically active ventral respiratory group island preparations. Taken together, these data suggest that SubP-mediated activation of TRPC3/7 channels underlies rhythmic ICAN-dependent pacemaker activity and enhances the regularity of respiratory rhythm activity.

Validation of a highly integrated SiPM readout system with a TOF-PET demonstrator

NASA Astrophysics Data System (ADS)

Niknejad, T.; Setayeshi, S.; Tavernier, S.; Bugalho, R.; Ferramacho, L.; Di Francesco, A.; Leong, C.; Rolo, M. D.; Shamshirsaz, M.; Silva, J. C.; Silva, R.; Silveira, M.; Zorraquino, C.; Varela, J.

2016-12-01

We have developed a highly integrated, fast and compact readout electronics for Silicon Photomultiplier (SiPM) based Time of Flight Positron Emission Tomography (TOF-PET) scanners. The readout is based on the use of TOP-PET Application Specific Integrated Circuit (PETsys TOFPET1 ASIC) with 64 channels, each with its amplifier, discriminator, Time to Digital Converter (TDC) and amplitude determination using Time Over Threshold (TOT). The ASIC has 25 ps r.m.s. intrinsic time resolution and fully digital output. The system is optimised for high rates, good timing, low power consumption and low cost. For validating the readout electronics, we have built a technical PET scanner, hereafter called ``demonstrator'', with 2'048 SiPM channels. The PET demonstrator has 16 compact Detector Modules (DM). Each DM has two ASICs reading 128 SiPM pixels in one-to-one coupling to 128 Lutetium Yttrium Orthosilicate (LYSO) crystals measuring 3.1 × 3.1 × 15 mm3 each. The data acquisition system for the demonstrator has two Front End Boards type D (FEB/D), each collecting the data of 1'024 channels (8 DMs), and transmitting assembled data frames through a serial link (4.8 Gbps), to a single Data Acquisition (DAQ) board plugged into the Peripheral Component Interconnect Express (PCIe) bus of the data acquisition PC. Results obtained with this PET demonstrator are presented.

A Pre-Emptive Horizontal Channel Borrowing and Vertical Traffic Overflowing Channel Allocation Scheme for Overlay Networks

NASA Astrophysics Data System (ADS)

Zhao, Fang-Ming; Jiang, Ling-Ge; He, Chen

In this paper, a channel allocation scheme is studied for overlay wireless networks to optimize connection-level QoS. The contributions of our work are threefold. First, a channel allocation strategy using both horizontal channel borrowing and vertical traffic overflowing (HCBVTO) is presented and analyzed. When all the channels in a given macrocell are used, high-mobility real-time handoff requests can borrow channels from adjacent homogeneous cells. In case that the borrowing requests fail, handoff requests may also be overflowed to heterogeneous cells, if possible. Second, high-mobility real-time service is prioritized by allowing it to preempt channels currently used by other services. And third, to meet the high QoS requirements of some services and increase the utilization of radio resources, certain services can be transformed between real-time services and non-real-time services as necessary. Simulation results demonstrate that the proposed schemes can improve system performance.

Positron emission tomography wrist detector

DOEpatents

Schlyer, David J.; O'Connor, Paul; Woody, Craig; Junnarkar, Sachin Shrirang; Radeka, Veljko; Vaska, Paul; Pratte, Jean-Francois

2006-08-15

A method of serially transferring annihilation information in a compact positron emission tomography (PET) scanner includes generating a time signal representing a time-of-occurrence of an annihilation event, generating an address signal representing a channel detecting the annihilation event, and generating a channel signal including the time and address signals. The method also includes generating a composite signal including the channel signal and another similarly generated channel signal concerning another annihilation event. An apparatus that serially transfers annihilation information includes a time signal generator, address signal generator, channel signal generator, and composite signal generator. The time signal is asynchronous and the address signal is synchronous to a clock signal. A PET scanner includes a scintillation array, detection array, front-end array, and a serial encoder. The serial encoders include the time signal generator, address signal generator, channel signal generator, and composite signal generator.

Tracking channel bed resiliency in forested mountain catchments using high temporal resolution channel bed movement

NASA Astrophysics Data System (ADS)

Conklin, M. H.; Martin, S.

2017-12-01

This study uses continuous-recording load cell pressure sensors in four, high-elevation (1500-1800 m), Sierra Nevada, headwater streams, to collect high temporal resolution, bedload-movement data for investigating the channel bed movement patterns within these streams for water years 2012-2014. Data show an annual pattern where channel bed material in the thalweg starts to build up in early fall, peaks around peak snow melt, and scours back to baseline levels during hydrograph drawdown and baseflow. This pattern is punctuated by disturbance and recovery of channel bed material associated with short-term, storm events. We propose conceptual model, linking sediment sources at the channel margins to patterns of channel bed fill and scour in the thalweg, based on this and earlier work showing in-stream sources for bedload material. The material in the thalweg represents a balance between sediment supply from the channel margins and sporadic, conveyor-belt-like, downstream transport in the thalweg. The conceptual model highlights not only the importance of production and transport rates but also that seasonal connectedness between the margins and thalweg is a key sediment control, determining both the accumulation rate of sediment stores at the margins, and the redistribution of sediment from margins to thalweg that "feeds" the conveyor-belt. Disturbance and recovery cycles are observed at multiple temporal scales, but long term, the channel beds are stable, suggesting the beds act as short-term storage for sediment, but are in equilibrium interannually. The feasibility of use for these sensors in forested mountain stream environments is tested. Despite a high failure rate (50%), load cell pressure sensors show potential for high-temporal-resolution bedload measurements, allowing for the collection of channel bed movement data to move beyond time-integrated change measurements - where many of the subtleties of bedload movement patterns may be missed - to continuous and/or real-time measurements. This type of high-temporal-resolution data provides insight into short term cycles of bedload movement in high gradient, forested, mountain streams.

Tracking channel bed resiliency in forested mountain catchments using high temporal resolution channel bed movement

NASA Astrophysics Data System (ADS)

Martin, Sarah E.; Conklin, Martha H.

2018-01-01

This study uses continuous-recording load cell pressure sensors in four, high-elevation (1500-1800 m), Sierra Nevada headwater streams to collect high-temporal-resolution, bedload-movement data for investigating the channel bed movement patterns within these streams for water years 2012-2014. Data show an annual pattern where channel bed material in the thalweg starts to build up in early fall, peaks around peak snow melt, and scours back to baseline levels during hydrograph drawdown and base flow. This pattern is punctuated by disturbance and recovery of channel bed material associated with short-term storm events. A conceptual model, linking sediment sources at the channel margins to patterns of channel bed fill and scour in the thalweg, is proposed building on the results of Martin et al. (2014). The material in the thalweg represents a balance between sediment supply from the channel margins and sporadic, conveyor-belt-like downstream transport in the thalweg. The conceptual model highlights not only the importance of production and transport rates but also that seasonal connectedness between the margins and thalweg is a key sediment control, determining the accumulation rate of sediment stores at the margins and the redistribution of sediment from margins to thalweg that feeds the conveyor belt. Disturbance and recovery cycles are observed at multiple temporal scales; but long term, the channel beds are stable, suggesting that the beds act as short-term storage for sediment but are in equilibrium interannually. The feasibility of use for these sensors in forested mountain stream environments is tested. Despite a high failure rate (50%), load cell pressure sensors show potential for high-temporal-resolution bedload measurements, allowing for the collection of channel bed movement data to move beyond time-integrated change measurements - where many of the subtleties of bedload movement patterns may be missed - to continuous and/or real-time measurements. This type of high-temporal-resolution data provides insight into short-term cycles of bedload movement in high gradient, forested mountain streams.

Dead-time optimized time-correlated photon counting instrument with synchronized, independent timing channels

NASA Astrophysics Data System (ADS)

Wahl, Michael; Rahn, Hans-Jürgen; Gregor, Ingo; Erdmann, Rainer; Enderlein, Jörg

2007-03-01

Time-correlated single photon counting is a powerful method for sensitive time-resolved fluorescence measurements down to the single molecule level. The method is based on the precisely timed registration of single photons of a fluorescence signal. Historically, its primary goal was the determination of fluorescence lifetimes upon optical excitation by a short light pulse. This goal is still important today and therefore has a strong influence on instrument design. However, modifications and extensions of the early designs allow for the recovery of much more information from the detected photons and enable entirely new applications. Here, we present a new instrument that captures single photon events on multiple synchronized channels with picosecond resolution and over virtually unlimited time spans. This is achieved by means of crystal-locked time digitizers with high resolution and very short dead time. Subsequent event processing in programmable logic permits classical histogramming as well as time tagging of individual photons and their streaming to the host computer. Through the latter, any algorithms and methods for the analysis of fluorescence dynamics can be implemented either in real time or offline. Instrument test results from single molecule applications will be presented.

Voltage-Gated Na+ Channels are Modulated by Glucose and Involved in Regulating Cellular Insulin Content of INS-1 Cells.

PubMed

Chen, Chong; Wang, Songhua; Hu, Qingjuan; Zeng, Lvming; Peng, Hailong; Liu, Chao; Huang, Li-Ping; Song, Hao; Li, Yuping; Yao, Li-Hua; Meng, Wei

2018-01-01

Islet beta cells (β-cells) are unique cells that play a critical role in glucose homeostasis by secreting insulin in response to increased glucose levels. Voltage-gated ion channels in β-cells, such as K+ and Ca2+ channels, contribute to insulin secretion. The response of voltage-gated Na+ channels (VGSCs) in β-cells to the changes in glucose levels remains unknown. This work aims to determine the role of extracellular glucose on the regulation of VGSC. The effect of glucose on VGSC currents (INa) was investigated in insulin-secreting β-cell line (INS-1) cells of rats using whole-cell patch clamp techniques, and the effects of glucose on insulin content and cell viability were determined using Enzyme-Linked Immunosorbent Assay (ELISA) and Methylthiazolyldiphenyl-tetrazolium Bromide (MTT) assay methods respectively. Our results show that extracellular glucose application can inhibit the peak of INa in a concentration-dependent manner. Glucose concentration of 18 mM reduced the amplitude of INa, suppressed the INa of steady-state activation, shifted the steady-state inactivation curves of INa to negative potentials, and prolonged the time course of INa recovery from inactivation. Glucose also enhanced the activity-dependent attenuation of INa and reduced the fraction of activated channels. Furthermore, 18 mM glucose or low concentration of tetrodotoxin (TTX, a VGSC-specific blocker) partially inhibited the activity of VGSC and also improved insulin synthesis. These results revealed that extracellular glucose application enhances the insulin synthesis in INS-1 cells and the mechanism through the partial inhibition on INa channel is involved. Our results innovatively suggest that VGSC plays a vital role in modulating glucose homeostasis. © 2018 The Author(s). Published by S. Karger AG, Basel.

River Sensitivity and Catchment Connectivity: Key Controls on Geomorphic Response and Effectiveness

NASA Astrophysics Data System (ADS)

Lisenby, P.; Fryirs, K.; Croke, J.

2016-12-01

The sensitivity of river channels to adjustment and the dynamics of sediment connectivity along a channel network are key controls on the capacity (ability) for a river system to adjust, i.e. the severity, distribution, and type of geomorphic response to disturbance events. In turn, the cumulative impact of geomorphic responses compared with event magnitude will determine the geomorphic effectiveness of a single disturbance event. River sensitivity and sediment connectivity can change significantly over space and time, and vary with changes in internal factors such as channel type and geomorphic landform and external factors such as event sequencing and lithological controls. Correspondingly, the capacity for a geomorphic system to respond to disturbance events will also vary, so that geomorphic effectiveness is not definitively characterized by a static relationship between event magnitude and geomorphic response, but rather is a dynamic comparison between geomorphic response and an actively changing capacity for geomorphic adjustment. Herein, we use the Lockyer Valley, Queensland as a case study to illustrate the variability of river sensitivity and sediment connectivity. We relate this variability to the potential and capacity for geomorphic channel response. We find that the sensitivity to and capacity for geomorphic adjustment varies significantly with channel morphometry and valley position. Additionally, the nature of bedload sediment connectivity changes with the distribution of geomorphic landforms and channel weirs that can impede sediment transference through the system. This variability of river sensitivity and sediment connectivity will control the nature of geomorphic response to disturbance events within the Lockyer Valley. Ultimately, determinations of geomorphic effectiveness for disturbance events will depend on comparisons of their geomorphic impacts with the capacity of the Lockyer geomorphic system to respond.

Code-division-multiplexed readout of large arrays of TES microcalorimeters

NASA Astrophysics Data System (ADS)

Morgan, K. M.; Alpert, B. K.; Bennett, D. A.; Denison, E. V.; Doriese, W. B.; Fowler, J. W.; Gard, J. D.; Hilton, G. C.; Irwin, K. D.; Joe, Y. I.; O'Neil, G. C.; Reintsema, C. D.; Schmidt, D. R.; Ullom, J. N.; Swetz, D. S.

2016-09-01

Code-division multiplexing (CDM) offers a path to reading out large arrays of transition edge sensor (TES) X-ray microcalorimeters with excellent energy and timing resolution. We demonstrate the readout of X-ray TESs with a 32-channel flux-summed code-division multiplexing circuit based on superconducting quantum interference device (SQUID) amplifiers. The best detector has energy resolution of 2.28 ± 0.12 eV FWHM at 5.9 keV and the array has mean energy resolution of 2.77 ± 0.02 eV over 30 working sensors. The readout channels are sampled sequentially at 160 ns/row, for an effective sampling rate of 5.12 μs/channel. The SQUID amplifiers have a measured flux noise of 0.17 μΦ0/√Hz (non-multiplexed, referred to the first stage SQUID). The multiplexed noise level and signal slew rate are sufficient to allow readout of more than 40 pixels per column, making CDM compatible with requirements outlined for future space missions. Additionally, because the modulated data from the 32 SQUID readout channels provide information on each X-ray event at the row rate, our CDM architecture allows determination of the arrival time of an X-ray event to within 275 ns FWHM with potential benefits in experiments that require detection of near-coincident events.

Enhancing Electromagnetic Side-Channel Analysis in an Operational Environment

NASA Astrophysics Data System (ADS)

Montminy, David P.

Side-channel attacks exploit the unintentional emissions from cryptographic devices to determine the secret encryption key. This research identifies methods to make attacks demonstrated in an academic environment more operationally relevant. Algebraic cryptanalysis is used to reconcile redundant information extracted from side-channel attacks on the AES key schedule. A novel thresholding technique is used to select key byte guesses for a satisfiability solver resulting in a 97.5% success rate despite failing for 100% of attacks using standard methods. Two techniques are developed to compensate for differences in emissions from training and test devices dramatically improving the effectiveness of cross device template attacks. Mean and variance normalization improves same part number attack success rates from 65.1% to 100%, and increases the number of locations an attack can be performed by 226%. When normalization is combined with a novel technique to identify and filter signals in collected traces not related to the encryption operation, the number of traces required to perform a successful attack is reduced by 85.8% on average. Finally, software-defined radios are shown to be an effective low-cost method for collecting side-channel emissions in real-time, eliminating the need to modify or profile the target encryption device to gain precise timing information.

The use of dwell time cross-correlation functions to study single-ion channel gating kinetics.

PubMed Central

Ball, F G; Kerry, C J; Ramsey, R L; Sansom, M S; Usherwood, P N

1988-01-01

The derivation of cross-correlation functions from single-channel dwell (open and closed) times is described. Simulation of single-channel data for simple gating models, alongside theoretical treatment, is used to demonstrate the relationship of cross-correlation functions to underlying gating mechanisms. It is shown that time irreversibility of gating kinetics may be revealed in cross-correlation functions. Application of cross-correlation function analysis to data derived from the locust muscle glutamate receptor-channel provides evidence for multiple gateway states and time reversibility of gating. A model for the gating of this channel is used to show the effect of omission of brief channel events on cross-correlation functions. PMID:2462924

Correspondence between the distribution of hydrodynamic time parameters and the distribution of biological and chemical variables in a semi-enclosed coral reef lagoon

NASA Astrophysics Data System (ADS)

Torréton, Jean-Pascal; Rochelle-Newall, Emma; Jouon, Aymeric; Faure, Vincent; Jacquet, Séverine; Douillet, Pascal

2007-09-01

Hydrodynamic modeling can be used to spatially characterize water renewal rates in coastal ecosystems. Using a hydrodynamic model implemented over the semi-enclosed Southwest coral lagoon of New Caledonia, a recent study computed the flushing lag as the minimum time required for a particle coming from outside the lagoon (open ocean) to reach a specific station [Jouon, A., Douillet, P., Ouillon, S., Fraunié, P., 2006. Calculations of hydrodynamic time parameters in a semi-opened coastal zone using a 3D hydrodynamic model. Continental Shelf Research 26, 1395-1415]. Local e -flushing time was calculated as the time requested to reach a local grid mesh concentration of 1/e from the precedent step. Here we present an attempt to connect physical forcing to biogeochemical functioning of this coastal ecosystem. An array of stations, located in the lagoonal channel as well as in several bays under anthropogenic influence, was sampled during three cruises. We then tested the statistical relationships between the distribution of flushing indices and those of biological and chemical variables. Among the variables tested, silicate, chlorophyll a and bacterial biomass production present the highest correlations with flushing indices. Correlations are higher with local e-flushing times than with flushing lags or the sum of these two indices. In the bays, these variables often deviate from the relationships determined in the main lagoon channel. In the three bays receiving significant riverine inputs, silicate is well above the regression line, whereas data from the bay receiving almost insignificant freshwater inputs generally fit the lagoon channel regressions. Moreover, in the three bays receiving important urban and industrial effluents, chlorophyll a and bacterial production of biomass generally display values exceeding the lagoon channel regression trends whereas in the bay under moderate anthropogenic influence values follow the regressions obtained in the lagoon channel. The South West lagoon of New Caledonia can hence be viewed as a coastal mesotrophic ecosystem that is flushed by oligotrophic oceanic waters which subsequently replace the lagoonal waters with water considerably impoverished in resources for microbial growth. This flushing was high enough during the periods of study to influence the distribution of phytoplankton biomass, bacterial production of biomass and silicate concentrations in the lagoon channel as well as in some of the bay areas.

Suprachiasmatic nucleus function and circadian entrainment are modulated by G protein-coupled inwardly rectifying (GIRK) channels

PubMed Central

Hablitz, L M; Molzof, H E; Paul, J R; Johnson, R L; Gamble, K L

2014-01-01

Abstract G protein signalling within the central circadian oscillator, the suprachiasmatic nucleus (SCN), is essential for conveying time-of-day information. We sought to determine whether G protein-coupled inwardly rectifying potassium channels (GIRKs) modulate SCN physiology and circadian behaviour. We show that GIRK current and GIRK2 protein expression are greater during the day. Pharmacological inhibition of GIRKs and genetic loss of GIRK2 depolarized the day-time resting membrane potential of SCN neurons compared to controls. Behaviourally, GIRK2 knockout (KO) mice failed to shorten free running period in response to wheel access in constant darkness and entrained more rapidly to a 6 h advance of a 12 h:12 h light–dark (LD) cycle than wild-type (WT) littermate controls. We next examined whether these effects were due to disrupted signalling of neuropeptide Y (NPY), which is known to mediate non-photic phase shifts, attenuate photic phase shifts and activate GIRKs. Indeed, GIRK2 KO SCN slices had significantly fewer silent cells in response to NPY, likely contributing to the absence of NPY-induced phase advances of PER2::LUC rhythms in organotypic SCN cultures from GIRK2 KO mice. Finally, GIRK channel activation is sufficient to cause a non-photic-like phase advance of PER2::LUC rhythms on a Per2Luc+/− background. These results suggest that rhythmic regulation of GIRK2 protein and channel function in the SCN contributes to day-time resting membrane potential, providing a mechanism for the fine tuning responses to non-photic and photic stimuli. Further investigation could provide insight into disorders with circadian disruption comorbidities such as epilepsy and addiction, in which GIRK channels have been implicated. PMID:25217379

Eight-channel time-resolved tissue oximeter for functional muscle studies

NASA Astrophysics Data System (ADS)

Cubeddu, Rinaldo; Biscotti, Giovanni; Pifferi, Antonio; Taroni, Paola; Torricelli, Alessandro; Ferrari, Marco; Quaresima, Valentina

2003-07-01

A portable instrument for tissue oximetry based on time-resolved reflectance spectroscopy was developed. The output pulses of 2 laser diodes (683 and 785 nm, 80 MHz pulse repetition rate, 1 mW average power, 100 ps FWHM) are delayed and coupled into a multimode graded-index fiber (50/125 μm and injected into the tissue. The reflectance photons are collected by 8 independent 1 mm fibers and detected by a 16-anode photomultiplier. A time-correlated single photon counting PC board is used for the parallel acquisition of the curves. Simultaneous estimate of the transport scattering and absorption coefficients is achieved by best fitting of time-resolved reflectance curves with a standard model of Diffusion Theory. The performances of the system were tested on phantoms in terms of stability, reproducibility among channels, and accuracy in the determination of the optical properties. Preliminary in vivo measurements were performed on healthy volunteers to monitor spatial changes in calf (medical and lateral gastrocnemius) oxygen hemoglobin saturation and blood volume during dynamic plantar flexion exercise.

An integrative time-varying frequency detection and channel sounding method for dynamic plasma sheath

NASA Astrophysics Data System (ADS)

Shi, Lei; Yao, Bo; Zhao, Lei; Liu, Xiaotong; Yang, Min; Liu, Yanming

2018-01-01

The plasma sheath-surrounded hypersonic vehicle is a dynamic and time-varying medium and it is almost impossible to calculate time-varying physical parameters directly. The in-fight detection of the time-varying degree is important to understand the dynamic nature of the physical parameters and their effect on re-entry communication. In this paper, a constant envelope zero autocorrelation (CAZAC) sequence based on time-varying frequency detection and channel sounding method is proposed to detect the plasma sheath electronic density time-varying property and wireless channel characteristic. The proposed method utilizes the CAZAC sequence, which has excellent autocorrelation and spread gain characteristics, to realize dynamic time-varying detection/channel sounding under low signal-to-noise ratio in the plasma sheath environment. Theoretical simulation under a typical time-varying radio channel shows that the proposed method is capable of detecting time-variation frequency up to 200 kHz and can trace the channel amplitude and phase in the time domain well under -10 dB. Experimental results conducted in the RF modulation discharge plasma device verified the time variation detection ability in practical dynamic plasma sheath. Meanwhile, nonlinear phenomenon of dynamic plasma sheath on communication signal is observed thorough channel sounding result.

An optical channel modeling of a single mode fiber

NASA Astrophysics Data System (ADS)

Nabavi, Neda; Liu, Peng; Hall, Trevor James

2018-05-01

The evaluation of the optical channel model that accurately describes the single mode fibre as a coherent transmission medium is reviewed through analytical, numerical and experimental analysis. We used the numerical modelling of the optical transmission medium and experimental measurements to determine the polarization drift as a function of time for a fixed length of fibre. The probability distribution of the birefringence vector was derived, which is associated to the 'Poole' equation. The theory and experimental evidence that has been disclosed in the literature in the context of polarization mode dispersion - Stokes & Jones formulations and solutions for key statistics by integration of stochastic differential equations has been investigated. Besides in-depth definition of the single-mode fibre-optic channel, the modelling which concerns an ensemble of fibres each with a different instance of environmental perturbation has been analysed.

Anatomy and growth pattern of Amazon deep-sea fan as revealed by long-range side-scan sonar (GLORIA) and high-resolution seismic studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Damuth, J.E.; Flood, R.D.; Kowsmann, R.O.

1988-08-01

Imaging of the Amazon deep-sea fan with long-range side-scan sonar (GLORIA) has, for the first time, revealed the anatomy, trends, and growth pattern of distributary channels on this fan. Only one channel-levee system was active at any given time and extended from the Amazon Submarine Canyon downslope onto the lower fan (> 4,200 m). Formation of new channel-levee systems occurred when a currently active channel-levee system was cut off and abandoned through avulsion, and a new channel-levee system was established nearby. Through time, successive channel-levee formation and abandonment built two broad levee complexes consisting of groups of overlapping, coalescing segmentsmore » of channel-levee systems across the present fan surface. These, plus older, now buried levee complexes, indicate that fan growth is radially outward and downslope through development of successive levee complexes. The most striking characteristic of the distributary channels is their intricate, often recurving, meanders with sinuosities of up to 2.5. Cutoffs and abandoned meander loops indicate that the channels migrate laterally through time. Channel bifurcation results predominantly from avulsion when flows breach a channel levee, thereby abandoning the present channel and establishing a new channel-levee segment nearby. No clear evidence of channel branching (i.e., division of a single channel into two active segments) or braiding was observed. 22 figs.« less

Real-time software-based end-to-end wireless visual communications simulation platform

NASA Astrophysics Data System (ADS)

Chen, Ting-Chung; Chang, Li-Fung; Wong, Andria H.; Sun, Ming-Ting; Hsing, T. Russell

1995-04-01

Wireless channel impairments pose many challenges to real-time visual communications. In this paper, we describe a real-time software based wireless visual communications simulation platform which can be used for performance evaluation in real-time. This simulation platform consists of two personal computers serving as hosts. Major components of each PC host include a real-time programmable video code, a wireless channel simulator, and a network interface for data transport between the two hosts. The three major components are interfaced in real-time to show the interaction of various wireless channels and video coding algorithms. The programmable features in the above components allow users to do performance evaluation of user-controlled wireless channel effects without physically carrying out these experiments which are limited in scope, time-consuming, and costly. Using this simulation platform as a testbed, we have experimented with several wireless channel effects including Rayleigh fading, antenna diversity, channel filtering, symbol timing, modulation, and packet loss.

Diazo Printing of ERTS Color Composites

NASA Technical Reports Server (NTRS)

Mcmurtry, G. J.; Petersen, G. W. (Principal Investigator); Kowalik, W. S.

1975-01-01

The author has identified the following significant results. ERTS-1 color composites were made with the help of a Diazo developer and printer. Five single channel, density standards were established, using typical ERTS images, in order to determine exposure time. These standards were used to develop a graph from which the exposure time for any transparency can be estimated. Exposure times varied from 3 to 30 minutes, and clear colored polyester sheets from two manufactures were used with slightly different, but equally successful, results.

On the Performance of Adaptive Data Rate over Deep Space Ka-Bank Link: Case Study Using Kepler Data

NASA Technical Reports Server (NTRS)

Gao, Jay L.

2016-01-01

Future missions envisioned for both human and robotic exploration demand increasing communication capacity through the use of Ka-band communications. The Ka-band channel, being more sensitive to weather impairments, presents a unique trade-offs between data storage, latency, data volume and reliability. While there are many possible techniques for optimizing Ka-band operations such as adaptive modulation and coding and site-diversity, this study focus exclusively on the use of adaptive data rate (ADR) to achieve significant improvement in the data volume-availability tradeoff over a wide range of link distances for near Earth and Mars exploration. Four years of Kepler Ka-band downlink symbol signal-to-noise (SNR) data reported by the Deep Space Network were utilized to characterize the Ka-band channel statistics at each site and conduct various what-if performance analysis for different link distances. We model a notional closed-loop adaptive data rate system in which an algorithm predicts the channel condition two-way light time (TWLT) into the future using symbol SNR reported in near-real time by the ground receiver and determines the best data rate to use. Fixed and adaptive margins were used to mitigate errors in channel prediction. The performance of this closed-loop adaptive data rate approach is quantified in terms of data volume and availability and compared to the actual mission configuration and a hypothetical, optimized single rate configuration assuming full a priori channel knowledge.

Laboratory modeling and analysis of aircraft-lightning interactions

NASA Technical Reports Server (NTRS)

Turner, C. D.; Trost, T. F.

1982-01-01

Modeling studies of the interaction of a delta wing aircraft with direct lightning strikes were carried out using an approximate scale model of an F-106B. The model, which is three feet in length, is subjected to direct injection of fast current pulses supplied by wires, which simulate the lightning channel and are attached at various locations on the model. Measurements are made of the resulting transient electromagnetic fields using time derivative sensors. The sensor outputs are sampled and digitized by computer. The noise level is reduced by averaging the sensor output from ten input pulses at each sample time. Computer analysis of the measured fields includes Fourier transformation and the computation of transfer functions for the model. Prony analysis is also used to determine the natural frequencies of the model. Comparisons of model natural frequencies extracted by Prony analysis with those for in flight direct strike data usually show lower damping in the in flight case. This is indicative of either a lightning channel with a higher impedance than the wires on the model, only one attachment point, or short streamers instead of a long channel.

A RSSI-based parameter tracking strategy for constrained position localization

NASA Astrophysics Data System (ADS)

Du, Jinze; Diouris, Jean-François; Wang, Yide

2017-12-01

In this paper, a received signal strength indicator (RSSI)-based parameter tracking strategy for constrained position localization is proposed. To estimate channel model parameters, least mean squares method (LMS) is associated with the trilateration method. In the context of applications where the positions are constrained on a grid, a novel tracking strategy is proposed to determine the real position and obtain the actual parameters in the monitored region. Based on practical data acquired from a real localization system, an experimental channel model is constructed to provide RSSI values and verify the proposed tracking strategy. Quantitative criteria are given to guarantee the efficiency of the proposed tracking strategy by providing a trade-off between the grid resolution and parameter variation. The simulation results show a good behavior of the proposed tracking strategy in the presence of space-time variation of the propagation channel. Compared with the existing RSSI-based algorithms, the proposed tracking strategy exhibits better localization accuracy but consumes more calculation time. In addition, a tracking test is performed to validate the effectiveness of the proposed tracking strategy.

Development of a drift-correction procedure for a direct-reading spectrometer

NASA Technical Reports Server (NTRS)

Chapman, G. B., II; Gordon, W. A.

1977-01-01

A procedure which provides automatic correction for drifts in the radiometric sensitivity of each detector channel in a direct-reading emission spectrometer is described. Such drifts are customarily controlled by the regular analyses of standards, which provide corrections for changes in the excitational, optical, and electronic components of the instrument. This standardization procedure, however, corrects for the optical and electronic drifts. It is a step that must be taken if the time, effort, and cost of processing standards is to be minimized. This method of radiometric drift correction uses a 1,000-W tungsten-halogen reference lamp to illuminate each detector through the same optical path as that traversed during sample analysis. The responses of the detector channels to this reference light are regularly compared with channel response to the same light intensity at the time of analytical calibration in order to determine and correct for drift. Except for placing the lamp in position, the procedure is fully automated and compensates for changes in spectral intensity due to variations in lamp current. A discussion of the implementation of this drift-correction system is included.

Energy, time, and channel evolution in catastrophically disturbed fluvial systems

USGS Publications Warehouse

Simon, A.

1992-01-01

Specific energy is shown to decrease nonlinearly with time during channel evolution and provides a measure of reductions in available energy at the channel bed. Data from two sites show convergence towards a minimum specific energy with time. Time-dependent reductions in specific energy at a point act in concert with minimization of the rate of energy dissipation over a reach during channel evolution as the fluvial systems adjust to a new equilibrium.

Sedimentation rate and lateral migration of tidal channels in the Lagoon of Venice (Northern Italy)

NASA Astrophysics Data System (ADS)

Donnici, Sandra; Madricardo, Fantina; Serandrei-Barbero, Rossana

2017-11-01

Tidal channels are crucial for the functioning of highly valuable coastal environments, such as estuaries and lagoons. Their properties, however, are currently less understood than those of river systems. To elucidate their past behaviour, an extensive geophysical investigation was performed to reconstruct the evolution of channels and tidal surfaces in the central part of the Lagoon of Venice (Italy) over the past 5000 years. Comparing high-spatial-resolution acoustic data and sedimentary facies analyses of 41 cores, 29 of which were radiocarbon dated, revealed the sedimentation rates in different lagoonal environments and allowed the migration of two large meanders to be reconstructed. The average sedimentation rate of the study succession in the different sedimentary environments was 1.27 mm yr-1. The lateral migration rates were 13-23 m/century. This estimate is consistent with the lateral migration rates determined by comparing aerial photographs of recent channels. Comparing the buried channels with historical and current maps showed that, in general, the number of active channels is now reduced. Their morphology was sometimes simplified by artificial interventions. An understanding of the impact of the artificial interventions over time is useful for the management and conservation of tidal environments, particularly for the Lagoon of Venice, where management authorities are currently debating the possible deepening and rectification of large navigation channels.

Identifying Levee Breach Hotspots via Fine Resolution 2D Hydrodynamic Modeling - a Case Study in the Obion River

NASA Astrophysics Data System (ADS)

Bhuyian, M. N. M.; Kalyanapu, A. J.; Dullo, T. T.; VandenBerge, D.

2017-12-01

The Obion River, located in North-West Tennessee was channelized in last century to increase flow capacity and reduce flooding. Upstream of the river mainly consists of multiple tributaries that merge near Rives. The lowest water level (LWL) downstream of Rives has increased about four feet since 1980. It is estimated that this phenomenon could reduce 20% of channel conveyance if water surface slope is assumed same as channel slope. Reduction in conveyance would result in a frequent exposure to flood stage and higher stage for a given flood. Bed level change and exposure to flood stage are critical to levee safety. In the Obion River, levee breach was responsible for flooding in instances even when flood stage was lower than the levee crest. In such a circumstance, accurate simulation of inundation extent via conventional flood model is challenging because, the flood models consider ground data as static and cannot accommodate breaching unless the location of breaching is specified. Therefore, the objective of this study is to propose an approach for determining hotspots of levee breach via fine resolution hydrodynamic modeling to reduce uncertainty in flood inundation modeling. A two-dimensional LiDAR based hydrodynamic model for the Obion River would be used to determine levee breach hotspots using simulated flow parameters (i.e. current velocity, change in stage, time of exposure to high stage etc.) for a design flood event. Identifying breaching hotspots would allow determining probabilistic flood extent under probable breaching conditions. This should reduce uncertainty in inundation mapping in a channelized riverine system.

Expression of Inwardly Rectifying Potassium Channel Subunits in Native Human Retinal Pigment Epithelium

PubMed Central

Yang, Dongli; Zhang, Xiaoming; Hughes, Bret A.

2008-01-01

Previously, we demonstrated that the inwardly rectifying K+ (Kir) channel subunit Kir7.1 is highly expressed in bovine and human retinal pigment epithelium (RPE). The purpose of this study was to determine whether any of the 14 other members of the Kir gene family are expressed in native human RPE. Conventional reverse transcription-polymerase chain reaction (RT-PCR) analysis indicated that in addition to Kir7.1, 7 other Kir channel subunits (Kir1.1, Kir2.1, Kir2.2, Kir3.1, Kir3.4, Kir4.2 and Kir6.1) are expressed in the RPE, whereas in neural retina, all 14 of the Kir channel subunits examined are expressed. The identities of RT-PCR products in the RPE were confirmed by DNA sequencing. Real-time RT-PCR analysis showed, however, that transcripts of these channels are significantly less abundant than Kir7.1 in the RPE. Western blot analysis of the Kir channel subunits detected in the RPE by RT-PCR revealed the expression of Kir2.1, Kir3.1, Kir3.4, Kir4.2, Kir6.1, and possibly Kir2.2, but not Kir1.1, in both human RPE and neural retina. Our results indicate that human RPE expresses at least 5 other Kir channel subtypes in addition to Kir7.1, suggesting that multiple members of the Kir channel family may function in this epithelium. PMID:18653180

Visualization of hydraulic conditions inside the feed channel of Reverse Osmosis: A practical comparison of velocity between empty and spacer-filled channel.

PubMed

Haidari, A H; Heijman, S G J; van der Meer, W G J

2016-12-01

It is widely accepted that our understanding about the membrane process increases by investigation of the hydraulic conditions of membranes. While numerical studies have been broadly used for this purpose, the experimental studies of a comparable resolution are scarce. In this study, we compared the pressure drop, the temporal and the spatial velocity maps of a spacer-filled channel and an empty channel of the same size to determine the effect of presence of the feeds spacer on hydraulic conditions. The velocity maps are obtained experimentally by using of the Particle Image Velocimetry (PIV) technique. Application of the feed spacer caused 2-8.5 higher pressure drop increase in the experimental conditions in this research. The flow had a spatial distribution in the form of a unimodal symmetric curve of normal distribution in the empty channel and a bimodal asymmetric curve in the spacer-filled channel. The bimodal curve indicates the presence of high- and low-velocity zones. Additionally, the low-velocity zones showed also a lower variation of velocity in time, which indicates the high fouling potential of these locations. The results from this study may be uses for validation of numerical studies. Copyright © 2016 Elsevier Ltd. All rights reserved.

Defining the factors that affect solute permeation of gap junction channels.

PubMed

Valiunas, Virginijus; Cohen, Ira S; Brink, Peter R

2018-01-01

This review focuses on the biophysical properties and structure of the pore and vestibule of homotypic gap junction channels as they relate to channel permeability and selectivity. Gap junction channels are unique in their sole role to connect the cytoplasm of two adjacent cells. In general, these channels are considered to be poorly selective, possess open probabilities approximating unity, and exhibit mean open times ranging from milliseconds to seconds. These properties suggest that such channels can function as delivery pathways from cell to cell for solutes that are significantly larger than monovalent ions. We have taken quantitative data from published works concerning unitary conductance, ion flux, and permeability for homotypic connexin 43 (Cx43), Cx40, Cx26, Cx50, and Cx37, and performed a comparative analysis of conductance and/or ion/solute flux versus diffusion coefficient. The analysis of monovalent cation flux portrays the pore as equivalent to an aqueous space where hydrogen bonding and weak interactions with binding sites dominate. For larger solutes, size, shape and charge are also significant components in determining the permeation rate. This article is part of a Special Issue entitled: Gap Junction Proteins edited by Jean Claude Herve. Copyright © 2017 Elsevier B.V. All rights reserved.

Space shuttle orbit maneuvering engine reusable thrust chamber. Task 13: Subscale helium ingestion and two dimensional heating test report

NASA Technical Reports Server (NTRS)

Tobin, R. D.

1974-01-01

Descriptions are given of the test hardware, facility, procedures, and results of electrically heated tube, channel and panel tests conducted to determine effects of helium ingestion, two dimensional conduction, and plugged coolant channels on operating limits of convectively cooled chambers typical of space shuttle orbit maneuvering engine designs. Helium ingestion in froth form, was studied in tubular and rectangular single channel test sections. Plugged channel simulation was investigated in a three channel panel. Burn-out limits (transition of film boiling) were studied in both single channel and panel test sections to determine 2-D conduction effects as compared to tubular test results.

Star sensor/mapper with a self deployable, high-attenuation light shade for SAS-B

NASA Technical Reports Server (NTRS)

Schenkel, F. W.; Finkel, A.

1972-01-01

A star sensor/mapper to determine positional data for the small astronomy satellites was tested to detect stars of plus 4 visual magnitude. It utilizes two information channels with memory so that it can be used with a low-data-rate telemetry system. One channel yields star amplitude information; the other yields the time of star occurrence as the star passes across an N-slit reticle/photomultiplier detector system. Some of the features of the star sensor/mapper are its low weight of 6.5 pounds, low power consumption of 0.4 watt, bandwidth switching to match the satellite spin rate, optical equalization of sensitivity over the 5-by-10 deg field of view, and self-deployable sunshade. The attitude determination accuracy is 3 arc minutes. This is determined by such parameters as the reticle configuration, optical train, and telemetry readout. The optical and electronic design of the star sensor/mapper, its expansion capabilities, and its features are discussed.

Bayesian sparse channel estimation

NASA Astrophysics Data System (ADS)

Chen, Chulong; Zoltowski, Michael D.

2012-05-01

In Orthogonal Frequency Division Multiplexing (OFDM) systems, the technique used to estimate and track the time-varying multipath channel is critical to ensure reliable, high data rate communications. It is recognized that wireless channels often exhibit a sparse structure, especially for wideband and ultra-wideband systems. In order to exploit this sparse structure to reduce the number of pilot tones and increase the channel estimation quality, the application of compressed sensing to channel estimation is proposed. In this article, to make the compressed channel estimation more feasible for practical applications, it is investigated from a perspective of Bayesian learning. Under the Bayesian learning framework, the large-scale compressed sensing problem, as well as large time delay for the estimation of the doubly selective channel over multiple consecutive OFDM symbols, can be avoided. Simulation studies show a significant improvement in channel estimation MSE and less computing time compared to the conventional compressed channel estimation techniques.

Identification of new deep sea sinuous channels in the eastern Arabian Sea.

PubMed

Mishra, Ravi; Pandey, D K; Ramesh, Prerna; Clift, Peter D

2016-01-01

Deep sea channel systems are recognized in most submarine fans worldwide as well as in the geological record. The Indus Fan is the second largest modern submarine fan, having a well-developed active canyon and deep sea channel system. Previous studies from the upper Indus Fan have reported several active channel systems. In the present study, deep sea channel systems were identified within the middle Indus Fan using high resolution multibeam bathymetric data. Prominent morphological features within the survey block include the Raman Seamount and Laxmi Ridge. The origin of the newly discovered channels in the middle fan has been inferred using medium resolution satellite bathymetry data. Interpretation of new data shows that the highly sinuous deep sea channel systems also extend to the east of Laxmi Ridge, as well as to the west of Laxmi Ridge, as previously reported. A decrease in sinuosity southward can be attributed to the morphological constraints imposed by the elevated features. These findings have significance in determining the pathways for active sediment transport systems, as well as their source characterization. The geometry suggests a series of punctuated avulsion events leading to the present array of disconnected channels. Such channels have affected the Laxmi Basin since the Pliocene and are responsible for reworking older fan sediments, resulting in loss of the original erosional signature supplied from the river mouth. This implies that distal fan sediments have experienced significant signal shredding and may not represent the erosion and weathering conditions within the onshore basin at the time of sedimentation.

Evaluation of CAESAR-Lisflood as a tool for modelling river channel change and floodplain sediment residence times.

NASA Astrophysics Data System (ADS)

Feeney, Christopher; Smith, Hugh; Chiverrell, Richard; Hooke, Janet; Cooper, James

2017-04-01

Sediment residence time represents the duration of particle storage, from initial deposition to remobilisation, within reservoirs such as floodplains. Residence time influences rates of downstream redistribution of sediment and associated contaminants and is a useful indicator of landform stability and hence, preservation potential of alluvial archives of environmental change. River channel change controls residence times, reworking sediments via lateral migration, avulsion and incision through floodplain deposits. As reworking progresses, the floodplain age distribution is 'updated', reflecting the time since 'older' sediments were removed and replaced with 'younger' ones. The relationship between ages and the spatial extents they occupy can be used to estimate the average floodplain sediment residence times. While dating techniques, historic maps and remote sensing can reconstruct age distributions from historic reworking, modelling provides advantages, including: i) capturing detailed river channel changes and resulting floodplain ages over longer timescales and higher resolutions than from historic mapping, and ii) control over inputs to simulate hypothetical scenarios to investigate the effects of different environmental drivers on residence times. CAESAR-Lisflood is a landform evolution model capable of simulating variable channel width, divergent flow, and both braided and meandering planforms. However, the model's ability to accurately simulate channel changes requires evaluation if it is to be useful for quantitative evaluation of floodplain sediment residence times. This study aims to simulate recent historic river channel changes along ten 1 km reaches in northern England. Simulation periods were defined by available overlapping historic map and mean daily flow datasets, ranging 27-39 years. LiDAR-derived 2 m DEMs were modified to smooth out present-day channels and burn in historic channel locations. To reduce run times, DEMs were resampled to coarser resolutions based on the size of the channel and historic rate of lateral channel migration. Separate pre-defined coarse and finer channel bed and floodplain grain size distributions were used, respectively, in combination with constructed reach DEMs for model simulations. Calibration was performed by modifying selected parameters to obtain best fits between observed and modelled channel planforms. Initial simulations suggest the model can broadly reproduce observed planform change and is comparable in terms of channel sinuosities and the mean radius of curvature. As such, CAESAR-Lisflood may provide a useful tool for evaluating floodplain sediment residence times under environmental change scenarios.

Energy loss in spark gap switches

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oreshkin, V. I., E-mail: oreshkin@ovpe.hcei.tsc.ru; Lavrinovich, I. V.; National Research Tomsk Polytechnic University, Lenin Avenue 30, 634050 Tomsk

2014-04-15

The paper reports on numerical study of the energy loss in spark gap switches. The operation of the switches is analyzed using the Braginsky model which allows calculation of the time dependence of the spark channel resistance. The Braginsky equation is solved simultaneously with generator circuit equations for different load types. Based on the numerical solutions, expressions which determine both the energy released in a spark gap switch and the switching time are derived.

Precise determination of neutron binding energy of 64Cu

NASA Astrophysics Data System (ADS)

Telezhnikov, S. A.; Granja, C.; Honzatko, J.; Pospisil, S.; Tomandl, I.

2016-05-01

The neutron binding energy in 64Cu has been accurately measured in thermal neutron capture. A composite target of natural Cu and NaCl was used on a high flux neutron beam using a large measuring time. The γ-ray spectrum emitted in the ( n, γ) reaction was measured with a HPGe detector in large statistics (up to 106 events per channel). Intrinsic limitations of HPGe detectors, which restrict the accuracy of energy calibration, were determined. The value B n of 64Cu was determined as 7915.867(24) keV.

Widely tunable chaotic fiber laser for WDM-PON detection

NASA Astrophysics Data System (ADS)

Zhang, Juan; Yang, Ling-zhen; Xu, Nai-jun; Wang, Juan-fen; Zhang, Zhao-xia; Liu, Xiang-lian

2014-05-01

A widely tunable high precision chaotic fiber laser is proposed and experimentally demonstrated. A tunable fiber Bragg grating (TFBG) filter is used as a tuning element to determine the turning range from 1533 nm to 1558 nm with a linewidth of 0.5 nm at any wavelength. The wide tuning range is capable of supporting 32 wavelength-division multiplexing (WDM) channels with 100 GHz channel spacing. All single wavelengths are found to be chaotic with 10 GHz bandwidth. The full width at half maximum (FWHM) of the chaotic correlation curve of the different wavelengths is on a picosecond time scale, thereby offering millimeter spatial resolution in WDM detection.

Photonic Doppler Velocimetry Multiplexing Techniques: Evaluation of Photonic Techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Edward Daykin

This poster reports progress related to photonic technologies. Specifically, the authors developed diagnostic system architecture for a Multiplexed Photonic Doppler Velocimetry (MPDV) that incorporates frequency and time-division multiplexing into existing PDV methodology to provide increased channel count. Current MPDV design increases number of data records per digitizer channel 8x, and also operates as a laser-safe (Class 3a) system. Further, they applied heterodyne interferometry to allow for direction-of-travel determination and enable high-velocity measurements (>10 km/s) via optical downshifting. They also leveraged commercially available, inexpensive and robust components originally developed for telecom applications. Proposed MPDV architectures employ only commercially available, fiber-coupled hardware.

Time Domain and Frequency Domain Deterministic Channel Modeling for Tunnel/Mining Environments.

PubMed

Zhou, Chenming; Jacksha, Ronald; Yan, Lincan; Reyes, Miguel; Kovalchik, Peter

2017-01-01

Understanding wireless channels in complex mining environments is critical for designing optimized wireless systems operated in these environments. In this paper, we propose two physics-based, deterministic ultra-wideband (UWB) channel models for characterizing wireless channels in mining/tunnel environments - one in the time domain and the other in the frequency domain. For the time domain model, a general Channel Impulse Response (CIR) is derived and the result is expressed in the classic UWB tapped delay line model. The derived time domain channel model takes into account major propagation controlling factors including tunnel or entry dimensions, frequency, polarization, electrical properties of the four tunnel walls, and transmitter and receiver locations. For the frequency domain model, a complex channel transfer function is derived analytically. Based on the proposed physics-based deterministic channel models, channel parameters such as delay spread, multipath component number, and angular spread are analyzed. It is found that, despite the presence of heavy multipath, both channel delay spread and angular spread for tunnel environments are relatively smaller compared to that of typical indoor environments. The results and findings in this paper have application in the design and deployment of wireless systems in underground mining environments.

Time Domain and Frequency Domain Deterministic Channel Modeling for Tunnel/Mining Environments

PubMed Central

Zhou, Chenming; Jacksha, Ronald; Yan, Lincan; Reyes, Miguel; Kovalchik, Peter

2018-01-01

Understanding wireless channels in complex mining environments is critical for designing optimized wireless systems operated in these environments. In this paper, we propose two physics-based, deterministic ultra-wideband (UWB) channel models for characterizing wireless channels in mining/tunnel environments — one in the time domain and the other in the frequency domain. For the time domain model, a general Channel Impulse Response (CIR) is derived and the result is expressed in the classic UWB tapped delay line model. The derived time domain channel model takes into account major propagation controlling factors including tunnel or entry dimensions, frequency, polarization, electrical properties of the four tunnel walls, and transmitter and receiver locations. For the frequency domain model, a complex channel transfer function is derived analytically. Based on the proposed physics-based deterministic channel models, channel parameters such as delay spread, multipath component number, and angular spread are analyzed. It is found that, despite the presence of heavy multipath, both channel delay spread and angular spread for tunnel environments are relatively smaller compared to that of typical indoor environments. The results and findings in this paper have application in the design and deployment of wireless systems in underground mining environments.† PMID:29457801

Trafficking Mechanisms Underlying Neuronal Voltage-gated Ion Channel Localization at the Axon Initial Segment

PubMed Central

Vacher, Helene; Trimmer, James S.

2012-01-01

Summary Voltage-gated ion channels are diverse and fundamental determinants of neuronal intrinsic excitability. Voltage-gated K+ (Kv) and Na+ (Nav) channels play complex yet fundamentally important roles in determining intrinsic excitability. The Kv and Nav channels located at the axon initial segment (AIS) play a unique and especially important role in generating neuronal output in the form of anterograde axonal and backpropagating action potentials, Aberrant intrinsic excitability in individual neurons within networks contributes to synchronous neuronal activity leading to seizures. Mutations in ion channel genes gives rise to a variety of seizure-related “Channelopathies”, and many of the ion channel subunits associated with epilepsy mutations are localized at the AIS, making this a hotspot for epileptogenesis. Here we review the cellular mechanisms that underlie the trafficking of Kv and Nav channels found at the AIS, and how Kv and Nav channel mutations associated with epilepsy can alter these processes. PMID:23216576

Local heat/mass transfer and pressure drop in a two-pass rib-roughened channel for turbine airfoil cooling

NASA Technical Reports Server (NTRS)

Han, J. C.; Chandra, P. R.

1987-01-01

The heat transfer characteristics of turbulent air flow in a multipass channel were studied via the naphthalene sublimation technique. The naphthalene-coated test section, consisting of two straight, square channels joined by a 180 deg turn, resembled the internal cooling passages of gas turbine airfoils. The top and bottom surfaces of the test channel were roughened by rib turbulators. The rib height-to-hydraulic diameter ratio (e/D) were 0.063 and 0.094, and the rib pitch-to-height ratio (P/e) were 10 and 20. The local heat/mass transfer coefficients on the roughened top wall and on the smooth divider and side walls of the test channel were determined for three Reynolds numbers of 15, 30, and 60, thousand, and for three angles of attack (alpha) of 90, 60, and 45 deg. Results showed that the local Sherwood numbers on the ribbed walls were 1.5 to 6.5 times those for a fully developed flow in a smooth square duct. The average ribbed-wall Sherwood numbers were 2.5 to 3.5 times higher than the fully developed values, depending on the rib angle of attack and the Reynolds number. The results also indicated that, before the turn, the heat/mass transfer coefficients in the cases of alpha = 60 and 45 deg were higher than those in the case of alpha=90 deg. However, after the turn, the heat/mass transfer coefficients in the oblique-rib cases were lower than those in the transverse rib case. Correlations for the average Sherwood number ratios for individual channel surfaces and for the overall Sherwood number ratios are reported. Correlations for the fully developed friction factors and for the loss coefficients are also provided.

A framework for spatial and temporal analysis of hillslope-channel coupling in a dryland basin 2401

USDA-ARS?s Scientific Manuscript database

The long-term evolution of channel longitudinal profiles within drainage basins is partly determined by the relative balance of hillslope sediment supply to channels and the evacuation of channel sediment. However, the lack of theoretical understanding of the physical processes of hillslope-channel...

Smooth Muscle Ion Channels and Regulation of Vascular Tone in Resistance Arteries and Arterioles

PubMed Central

Tykocki, Nathan R.; Boerman, Erika M.; Jackson, William F.

2017-01-01

Vascular tone of resistance arteries and arterioles determines peripheral vascular resistance, contributing to the regulation of blood pressure and blood flow to, and within the body’s tissues and organs. Ion channels in the plasma membrane and endoplasmic reticulum of vascular smooth muscle cells (SMCs) in these blood vessels importantly contribute to the regulation of intracellular Ca2+ concentration, the primary determinant of SMC contractile activity and vascular tone. Ion channels provide the main source of activator Ca2+ that determines vascular tone, and strongly contribute to setting and regulating membrane potential, which, in turn, regulates the open-state-probability of voltage gated Ca2+ channels (VGCCs), the primary source of Ca2+ in resistance artery and arteriolar SMCs. Ion channel function is also modulated by vasoconstrictors and vasodilators, contributing to all aspects of the regulation of vascular tone. This review will focus on the physiology of VGCCs, voltage-gated K+ (KV) channels, large-conductance Ca2+-activated K+ (BKCa) channels, strong-inward-rectifier K+ (KIR) channels, ATP-sensitive K+ (KATP) channels, ryanodine receptors (RyRs), inositol 1,4,5-trisphosphate receptors (IP3Rs), and a variety of transient receptor potential (TRP) channels that contribute to pressure-induced myogenic tone in resistance arteries and arterioles, the modulation of the function of these ion channels by vasoconstrictors and vasodilators, their role in the functional regulation of tissue blood flow and their dysfunction in diseases such as hypertension, obesity, and diabetes. PMID:28333380

The initial-value problem for viscous channel flows

NASA Technical Reports Server (NTRS)

Criminale, W. O.; Jackson, T. L.; Lasseigne, D. G.

1995-01-01

Plane viscous channel flows are perturbed and the ensuing initial-value problems are investigated in detail. Unlike traditional methods where traveling wave normal modes are assumed for solution, this works offers a means whereby completely arbitrary initial input can be specified without having to resort to eigenfunction expansions. The full temporal behavior, including both early time transients and the long time asymptotics, can be determined for any initial disturbance. Effects of three-dimensionality can be assessed. The bases for the analysis are: (a) linearization of the governing equations; (b) Fourier decomposition in the spanwise and streamwise directions of the flow; and (c) direct numerical integration of the resulting partial differential equations. All of the stability data that are known for such flows can be reproduced. Also, the optimal initial condition can be determined in a straight forward manner and such optimal conditions clearly reflect transient growth data that is easily determined by a rational choice of a basis for the initial conditions. Although there can be significant transient growth for subcritical values of the Reynolds number using this approach it does not appear possible that arbitrary initial conditions will lead to the exceptionally large transient amplitudes that have been determined by optimization of normal modes. The approach is general and can be applied to other classes of problems where only a finite discrete spectrum exists, such as the boundary layer for example.

Inter-Satellite Calibration Linkages for the Visible and Near-Infrared Channels of the Advanced Very High Resolution Radiometer on the NOAA-7, -9, and -11 Spacecraft. Revised

NASA Technical Reports Server (NTRS)

NagarajaRao, C. R.; Chen, J.

1996-01-01

The post-launch degradation of the visible (channel 1: 0.58- 068 microns) and near-infrared (channel 2: approx. 0.72 - l.l microns) channels of the Advanced Very High Resolution Radiometer (AVHRR) on the NOAA-7, -9, and -11 Polar-orbiting Operational Environmental Satellites (POES) was estimated using the south-eastern part of the Libyan Desert as a radiometrically stable calibration target. The relative annual degradation rates, in per cent, for the two channels are, respectively: 3.6 and 4.3 (NOAA-7); 5.9 and 3.5 (NOAA-9); and 1.2 and 2.0 (NOAA-11). Using the relative degradation rates thus determined, in conjunction with absolute calibrations based on congruent path aircraft/satellite radiance measurements over White Sands, New Mexico (USA), the variation in time of the absolute gain or slope of the AVHRR on NOAA-9 was evaluated. Inter-satellite calibration linkages were established, using the AVHRR on NOAA-9 as a normalization standard. Formulae for the calculation of calibrated radiances and albedos (AVHRR usage), based on these interlinkages, are given for the three AVHRRs.

Decoding the attended speech stream with multi-channel EEG: implications for online, daily-life applications

NASA Astrophysics Data System (ADS)

Mirkovic, Bojana; Debener, Stefan; Jaeger, Manuela; De Vos, Maarten

2015-08-01

Objective. Recent studies have provided evidence that temporal envelope driven speech decoding from high-density electroencephalography (EEG) and magnetoencephalography recordings can identify the attended speech stream in a multi-speaker scenario. The present work replicated the previous high density EEG study and investigated the necessary technical requirements for practical attended speech decoding with EEG. Approach. Twelve normal hearing participants attended to one out of two simultaneously presented audiobook stories, while high density EEG was recorded. An offline iterative procedure eliminating those channels contributing the least to decoding provided insight into the necessary channel number and optimal cross-subject channel configuration. Aiming towards the future goal of near real-time classification with an individually trained decoder, the minimum duration of training data necessary for successful classification was determined by using a chronological cross-validation approach. Main results. Close replication of the previously reported results confirmed the method robustness. Decoder performance remained stable from 96 channels down to 25. Furthermore, for less than 15 min of training data, the subject-independent (pre-trained) decoder performed better than an individually trained decoder did. Significance. Our study complements previous research and provides information suggesting that efficient low-density EEG online decoding is within reach.

Definition and evaluation of the data-link layer of PACnet

NASA Astrophysics Data System (ADS)

Alsafadi, Yasser H.; Martinez, Ralph; Sanders, William H.

1991-07-01

PACnet is a 200-500 Mbps dual-ring fiber optic network designed to implement a picture archiving and communication system (PACS) in a hospital environment. The network consists of three channels: an image transfer channel, a command and control channel, and a real-time data channel. An initial network interface unit (NIU) design for PACnet consisted of a functional description of the protocols and NIU major components. In order to develop a demonstration prototype, additional definition of protocol algorithms of each channel is necessary. Using the International Standards Organization/Open Systems Interconnection (ISO/OSI) reference model as a guide, the definition of the data link layer is extended. This definition covers interface service specifications for the two constituent sublayers: logical link control (LLC) and medium access control (MAC). Furthermore, it describes procedures for data transfer, mechanisms of error detection and fault recovery. A performance evaluation study was then made to determine how the network performs under various application scenarios. The performance evaluation study was performed using stochastic activity networks, which can formally describe the network behavior. The results of the study demonstrate the feasibility of PACnet as an integrated image, data, and voice network for PACS.

Wireless acquisition of multi-channel seismic data using the Seismobile system

NASA Astrophysics Data System (ADS)

Isakow, Zbigniew

2017-11-01

This paper describes the wireless acquisition of multi-channel seismic data using a specialized mobile system, Seismobile, designed for subsoil diagnostics for transportation routes. The paper presents examples of multi-channel seismic records obtained during system tests in a configuration with 96 channels (4 landstreamers of 24-channel) and various seismic sources. Seismic waves were generated at the same point using different sources: a 5-kg hammer, a Gisco's source with a 90-kg pile-driver, and two other the pile-drivers of 45 and 70 kg. Particular attention is paid to the synchronization of source timing, the measurement of geometry by autonomous GPS systems, and the repeatability of triggering measurements constrained by an accelerometer identifying the seismic waveform. The tests were designed to the registration, reliability, and range of the wireless transmission of survey signals. The effectiveness of the automatic numbering of measuring modules was tested as the system components were arranged and fixed to the streamers. After measurements were completed, the accuracy and speed of data downloading from the internal memory (SDHC 32GB WiFi) was determined. Additionally, the functionality of automatic battery recharging, the maximum survey duration, and the reliability of battery discharge signalling were assessed.

Giga-seal formation alters properties of sodium channels of human myoballs.

PubMed

Fahlke, C; Rüdel, R

1992-03-01

The influence of giga-seal formation on the properties of the Na+ channels within the covered membrane patch was investigated with a whole-cell pipette and a patch pipette applied to the same cell. Current kinetics, current/voltage relation and channel densities were determined in three combinations: (i) voltage-clamping and current recording with the whole-cell pipette, (ii) voltage-clamping with the whole-cell pipette and current recording with the patch pipette and, (iii) voltage-clamping and current recording with the patch pipette. The Hodgkin-Huxley (1952) parameters tau m and tau h were smaller for the patch currents than for the whole cell, and the h infinity curve was shifted in the negative direction. The channel density was of the order of 10 times smaller. All effects were independent of the extracellular Ca2+ concentration. The capacitive current generated in the patch by the whole-cell Na+ current and its effect on the transmembrane voltage of the patch were evaluated. The kinetic parameters of the Na+ channels in the patch did not depend on whether the voltage was clamped with the whole-cell pipette or the patch pipette. Thus, the results are not due to spurious voltage.

Solution structure and function of the "tandem inactivation domain" of the neuronal A-type potassium channel Kv1.4.

PubMed

Wissmann, Ralph; Bildl, Wolfgang; Oliver, Dominik; Beyermann, Michael; Kalbitzer, Hans-Robert; Bentrop, Detlef; Fakler, Bernd

2003-05-02

Cumulative inactivation of voltage-gated (Kv) K(+) channels shapes the presynaptic action potential and determines timing and strength of synaptic transmission. Kv1.4 channels exhibit rapid "ball-and-chain"-type inactivation gating. Different from all other Kvalpha subunits, Kv1.4 harbors two inactivation domains at its N terminus. Here we report the solution structure and function of this "tandem inactivation domain" using NMR spectroscopy and patch clamp recordings. Inactivation domain 1 (ID1, residues 1-38) consists of a flexible N terminus anchored at a 5-turn helix, whereas ID2 (residues 40-50) is a 2.5-turn helix made up of small hydrophobic amino acids. Functional analysis suggests that only ID1 may work as a pore-occluding ball domain, whereas ID2 most likely acts as a "docking domain" that attaches ID1 to the cytoplasmic face of the channel. Deletion of ID2 slows inactivation considerably and largely impairs cumulative inactivation. Together, the concerted action of ID1 and ID2 may promote rapid inactivation of Kv1.4 that is crucial for the channel function in short term plasticity.

The calcium-activated potassium channel KCa3.1 plays a central role in the chemotactic response of mammalian neutrophils

PubMed Central

Henríquez, C.; Riquelme, T. T.; Vera, D.; Julio-Kalajzić, F.; Ehrenfeld, P.; Melvin, J. E.; Figueroa, C. D.; Sarmiento, J.; Flores, C. A.

2017-01-01

Aim Neutrophils are the first cells to arrive at sites of injury. Nevertheless, many inflammatory diseases are characterized by an uncontrolled infiltration and action of these cells. Cell migration depends on volume changes that are governed by ion channel activity, but potassium channels in neutrophil have not been clearly identified. We aim to test whether KCa3.1 participates in neutrophil migration and other relevant functions of the cell. Methods Cytometer and confocal measurements to determine changes in cell volume were used. Cells isolated from human, mouse and horse were tested for KCa3.1-dependent chemotaxis. Chemokinetics, calcium handling and release of reactive oxygen species were measured to determine the role of KCa3.1 in those processes. A mouse model was used to test for neutrophil recruitment after acute lung injury in vivo. Results We show for the first time that KCa3.1 is expressed in mammalian neutrophils. When the channel is inhibited by a pharmacological blocker or by genetic silencing, it profoundly affects cell volume regulation, and chemotactic and chemokinetic properties of the cells. We also demonstrated that pharmacological inhibition of KCa3.1 did not affect calcium entry or reactive oxygen species production in neutrophils. Using a mouse model of acute lung injury, we observed that Kca3.1−/− mice are significantly less effective at recruiting neutrophils into the site of inflammation. Conclusions These results demonstrate that KCa3.1 channels are key actors in the migration capacity of neutrophils, and its inhibition did not affect other relevant cellular functions. PMID:26138196

Association between findings on palmarodorsal radiographic images and detection of a fracture in the proximal sesamoid bones of forelimbs obtained from cadavers of racing Thoroughbreds.

PubMed

Anthenill, Lucy A; Stover, Susan M; Gardner, Ian A; Hill, Ashley E; Lee, Christina M; Anderson, Mark L; Barr, Bradd C; Read, Deryck H; Johnson, Bill J; Woods, Leslie W; Daft, Barbara M; Kinde, Hailu; Moore, Janet D; Farman, Cynthia A; Odani, Jenee S; Pesavento, Patricia A; Uzal, Francisco A; Case, James T; Ardans, Alex A

2006-05-01

To determine the distribution for limbs and bones in horses with fractures of the proximal sesamoid bones and relationships with findings on palmarodorsal radiographic images. Proximal sesamoid bones obtained from both forelimbs of cadavers of 328 racing Thoroughbreds. Osteophytes; large vascular channels; and fracture location, orientation, configuration, and margin distinctness were categorized by use of high-detail contact palmarodorsal radiographs. Distributions of findings were determined. Relationships between radiographic findings and fracture characteristics were examined by use of chi2 and logistic regression techniques. Fractures were detected in 136 (41.5%) horses. Biaxial fractures were evident in 109 (80%) horses with a fracture. Osteophytes and large vascular channels were evident in 266 (81%) and 325 (99%) horses, respectively. Medial bones typically had complete transverse or split transverse simple fractures, indistinct fracture margins, > 1 vascular channel that was > 1 mm in width, and osteophytes in abaxial wing and basilar middle or basilar abaxial locations. Lateral bones typically had an oblique fracture and distinct fracture margins. Odds of proximal sesamoid bone fracture were approximately 2 to 5 times higher in bones without radiographic evidence of osteophytes or large vascular channels, respectively. Biaxial fractures of proximal sesamoid bones were common in cadavers of racing Thoroughbreds. Differences between medial and lateral bones for characteristics associated with fracture may relate to differences in fracture pathogeneses for these bones. Osteophytes and vascular channels were common findings; however, fractures were less likely to occur in bones with these features.

Regulation of Cardiac ATP-sensitive Potassium Channel Surface Expression by Calcium/Calmodulin-dependent Protein Kinase II*

PubMed Central

Sierra, Ana; Zhu, Zhiyong; Sapay, Nicolas; Sharotri, Vikas; Kline, Crystal F.; Luczak, Elizabeth D.; Subbotina, Ekaterina; Sivaprasadarao, Asipu; Snyder, Peter M.; Mohler, Peter J.; Anderson, Mark E.; Vivaudou, Michel; Zingman, Leonid V.; Hodgson-Zingman, Denice M.

2013-01-01

Cardiac ATP-sensitive potassium (KATP) channels are key sensors and effectors of the metabolic status of cardiomyocytes. Alteration in their expression impacts their effectiveness in maintaining cellular energy homeostasis and resistance to injury. We sought to determine how activation of calcium/calmodulin-dependent protein kinase II (CaMKII), a central regulator of calcium signaling, translates into reduced membrane expression and current capacity of cardiac KATP channels. We used real-time monitoring of KATP channel current density, immunohistochemistry, and biotinylation studies in isolated hearts and cardiomyocytes from wild-type and transgenic mice as well as HEK cells expressing wild-type and mutant KATP channel subunits to track the dynamics of KATP channel surface expression. Results showed that activation of CaMKII triggered dynamin-dependent internalization of KATP channels. This process required phosphorylation of threonine at 180 and 224 and an intact 330YSKF333 endocytosis motif of the KATP channel Kir6.2 pore-forming subunit. A molecular model of the μ2 subunit of the endocytosis adaptor protein, AP2, complexed with Kir6.2 predicted that μ2 docks by interaction with 330YSKF333 and Thr-180 on one and Thr-224 on the adjacent Kir6.2 subunit. Phosphorylation of Thr-180 and Thr-224 would favor interactions with the corresponding arginine- and lysine-rich loops on μ2. We concluded that calcium-dependent activation of CaMKII results in phosphorylation of Kir6.2, which promotes endocytosis of cardiac KATP channel subunits. This mechanism couples the surface expression of cardiac KATP channels with calcium signaling and reveals new targets to improve cardiac energy efficiency and stress resistance. PMID:23223335

Modeling-independent elucidation of inactivation pathways in recombinant and native A-type Kv channels

PubMed Central

Fineberg, Jeffrey D.; Ritter, David M.

2012-01-01

A-type voltage-gated K+ (Kv) channels self-regulate their activity by inactivating directly from the open state (open-state inactivation [OSI]) or by inactivating before they open (closed-state inactivation [CSI]). To determine the inactivation pathways, it is often necessary to apply several pulse protocols, pore blockers, single-channel recording, and kinetic modeling. However, intrinsic hurdles may preclude the standardized application of these methods. Here, we implemented a simple method inspired by earlier studies of Na+ channels to analyze macroscopic inactivation and conclusively deduce the pathways of inactivation of recombinant and native A-type Kv channels. We investigated two distinct A-type Kv channels expressed heterologously (Kv3.4 and Kv4.2 with accessory subunits) and their native counterparts in dorsal root ganglion and cerebellar granule neurons. This approach applies two conventional pulse protocols to examine inactivation induced by (a) a simple step (single-pulse inactivation) and (b) a conditioning step (double-pulse inactivation). Consistent with OSI, the rate of Kv3.4 inactivation (i.e., the negative first derivative of double-pulse inactivation) precisely superimposes on the profile of the Kv3.4 current evoked by a single pulse because the channels must open to inactivate. In contrast, the rate of Kv4.2 inactivation is asynchronous, already changing at earlier times relative to the profile of the Kv4.2 current evoked by a single pulse. Thus, Kv4.2 inactivation occurs uncoupled from channel opening, indicating CSI. Furthermore, the inactivation time constant versus voltage relation of Kv3.4 decreases monotonically with depolarization and levels off, whereas that of Kv4.2 exhibits a J-shape profile. We also manipulated the inactivation phenotype by changing the subunit composition and show how CSI and CSI combined with OSI might affect spiking properties in a full computational model of the hippocampal CA1 neuron. This work unambiguously elucidates contrasting inactivation pathways in neuronal A-type Kv channels and demonstrates how distinct pathways might impact neurophysiological activity. PMID:23109714

Diel movement and habitat use by paddlefish in Navigation Pool 8 of the upper Mississippi River

USGS Publications Warehouse

Zigler, Steven J.; Dewey, Michael R.; Knights, Brent C.

1999-01-01

We studied diel movement and habitat use by paddlefish Polyodon spathula implanted with radio transmitters in Navigation Pool 8 of the upper Mississippi River. We radio-tracked five paddlefish during three randomly chosen 24-h periods each month in May, Aug, and Oct 1995. Paddlefish were located by boat one to three times every 3 h during each 24-h period. At each location, geographic coordinates were determined with a global positioning system receiver using the Precise Positioning Service, and depth was measured with a depth sounder. Location coordinates were plotted with ARC/INFO software on a Geographic Information System land–water coverage. Movement distances were calculated as the linear distance between sequential locations. Radio-tagged paddlefish usually remained in a secondary channel that had low current velocity during all seasons, whereas main channel, main channel border, tailwater, and backwater habitats were seldom used. Paddlefish strongly selected areas that were deep; about 62% of paddlefish locations were in areas with more than 6 m of depth, although this habitat constituted only 14.5% of the total study area. However, paddlefish used significantly shallower areas during the night than during the day. Paddlefish moved significantly larger distances at night than during the day in spring and fall, but differences in movement among diel periods during summer were not significant. Our research suggests that radiotelemetry studies that need to determine depth use or movement of paddlefish during small time scales may need to incorporate a diel component. However, study objectives to determine use of general habitat types by radio-marked paddlefish can be adequately met by tracking during the day.

Predicting seasonal variations in coastal seabird habitats in the English Channel and the Bay of Biscay

NASA Astrophysics Data System (ADS)

Virgili, A.; Lambert, C.; Pettex, E.; Dorémus, G.; Van Canneyt, O.; Ridoux, V.

2017-07-01

Seabirds, like all animals, have to live in suitable habitats to fulfil their energetic needs for both somatic and reproductive growth and maintenance. Apart from migration trips, all coastal seabirds are linked to the coast, because they need to return daily to land for resting or breeding. Their use of marine habitats strongly depends on their biology, but also on environmental conditions, and can be described using habitat models. This study aimed to: (1) identify the processes that mostly influence seabird distributions along the coasts of the English Channel and the Bay of Biscay; (2) determine seasonal variations of these processes, (3) provide prediction maps that describe the species distributions. We collected data of coastal seabird sightings from aerial surveys carried out in the English Channel and the eastern North Atlantic in the winter 2011-2012 and summer 2012. We classified seabirds into morphological groups and described their habitats using physiographic and oceanographic variables in Generalised Additive Models (GAMs). Finally, we produced maps of predicted distributions by season for each group. The distributions of coastal seabirds were essentially determined by the distance to the nearest coast, with a weaker influence of oceanographic variables. The nature of the substrate, sand or rock, combined with the timing of reproduction, also contributed to determine seasonal at-sea distributions for some species. The highest densities were predicted near the coast, particularly in bays and estuaries for strictly coastal species with possible variations depending on the season. From this study, we were able to predict the seasonal distribution of the studied species according to varying environmental parameters that changed over time, allowing us to understand better their behaviour and ecology.

Photon Quenching of the Paranormal (Time) Channel: A Brief Note,

DTIC Science & Technology

1977-04-20

The photon interaction constitutes a time-differentiating operation imposed upon nonobjective, ’ paranormal ’, 4-dimensional spacetime reality...physically materialize a mental phenomenon if the paranormal channel (time channel) is intact and not squelched by photon interaction. Tulpas may then be

DETECT: a MATLAB toolbox for event detection and identification in time series, with applications to artifact detection in EEG signals.

PubMed

Lawhern, Vernon; Hairston, W David; Robbins, Kay

2013-01-01

Recent advances in sensor and recording technology have allowed scientists to acquire very large time-series datasets. Researchers often analyze these datasets in the context of events, which are intervals of time where the properties of the signal change relative to a baseline signal. We have developed DETECT, a MATLAB toolbox for detecting event time intervals in long, multi-channel time series. Our primary goal is to produce a toolbox that is simple for researchers to use, allowing them to quickly train a model on multiple classes of events, assess the accuracy of the model, and determine how closely the results agree with their own manual identification of events without requiring extensive programming knowledge or machine learning experience. As an illustration, we discuss application of the DETECT toolbox for detecting signal artifacts found in continuous multi-channel EEG recordings and show the functionality of the tools found in the toolbox. We also discuss the application of DETECT for identifying irregular heartbeat waveforms found in electrocardiogram (ECG) data as an additional illustration.

DETECT: A MATLAB Toolbox for Event Detection and Identification in Time Series, with Applications to Artifact Detection in EEG Signals

PubMed Central

Lawhern, Vernon; Hairston, W. David; Robbins, Kay

2013-01-01

Recent advances in sensor and recording technology have allowed scientists to acquire very large time-series datasets. Researchers often analyze these datasets in the context of events, which are intervals of time where the properties of the signal change relative to a baseline signal. We have developed DETECT, a MATLAB toolbox for detecting event time intervals in long, multi-channel time series. Our primary goal is to produce a toolbox that is simple for researchers to use, allowing them to quickly train a model on multiple classes of events, assess the accuracy of the model, and determine how closely the results agree with their own manual identification of events without requiring extensive programming knowledge or machine learning experience. As an illustration, we discuss application of the DETECT toolbox for detecting signal artifacts found in continuous multi-channel EEG recordings and show the functionality of the tools found in the toolbox. We also discuss the application of DETECT for identifying irregular heartbeat waveforms found in electrocardiogram (ECG) data as an additional illustration. PMID:23638169

Real-time analysis system for gas turbine ground test acoustic measurements.

PubMed

Johnston, Robert T

2003-10-01

This paper provides an overview of a data system upgrade to the Pratt and Whitney facility designed for making acoustic measurements on aircraft gas turbine engines. A data system upgrade was undertaken because the return-on-investment was determined to be extremely high. That is, the savings on the first test series recovered the cost of the hardware. The commercial system selected for this application utilizes 48 input channels, which allows either 1/3 octave and/or narrow-band analyses to be preformed real-time. A high-speed disk drive allows raw data from all 48 channels to be stored simultaneously while the analyses are being preformed. Results of tests to ensure compliance of the new system with regulations and with existing systems are presented. Test times were reduced from 5 h to 1 h of engine run time per engine configuration by the introduction of this new system. Conservative cost reduction estimates for future acoustic testing are 75% on items related to engine run time and 50% on items related to the overall length of the test.

A flexible 32-channel time-to-digital converter implemented in a Xilinx Zynq-7000 field programmable gate array

NASA Astrophysics Data System (ADS)

Wang, Yonggang; Kuang, Jie; Liu, Chong; Cao, Qiang; Li, Deng

2017-03-01

A high performance multi-channel time-to-digital converter (TDC) is implemented in a Xilinx Zynq-7000 field programmable gate array (FPGA). It can be flexibly configured as either 32 TDC channels with 9.9 ps time-interval RMS precision, 16 TDC channels with 6.9 ps RMS precision, or 8 TDC channels with 5.8 ps RMS precision. All TDCs have a 380 M Samples/second measurement throughput and a 2.63 ns measurement dead time. The performance consistency and temperature dependence of TDC channels are also evaluated. Because Zynq-7000 FPGA family integrates a feature-rich dual-core ARM based processing system and 28 nm Xilinx programmable logic in a single device, the realization of high performance TDCs on it will make the platform more widely used in time-measuring related applications.

Somatotopical feedback versus non-somatotopical feedback for phantom digit sensation on amputees using electrotactile stimulation.

PubMed

Zhang, Dingguo; Xu, Heng; Shull, Peter B; Liu, Jianrong; Zhu, Xiangyang

2015-05-02

Transcutaneous electrical stimulation can provide amputees with tactile feedback for better manipulating an advanced prosthesis. In general, there are two ways to transfer the stimulus to the skin: somatotopical feedback (SF) that stimulates the phantom digit somatotopy on the stump and non-somatotopical feedback (NF) that stimulates other positions on the human body. To investigate the difference between SF and NF, electrotactile experiments were conducted on seven amputees. Electrical stimulation was applied via a complete phantom map to the residual limb (SF) and to the upper arm (NF) separately. The behavior results of discrimination accuracy and response time were used to examine: 1) performance differences between SF and NF for discriminating position, type and strength of tactile feedback; 2) performance differences between SF and NF for one channel (1C), three channels (3C), and five channels (5C). NASA-TLX standardized testing was used to determine differences in mental workload between SF and NF. The grand-averaged discrimination accuracy for SF was 6% higher than NF, and the average response time for SF was 600 ms faster than NF. SF is better than NF for position, type, strength, and the overall modality regarding both accuracy and response time except for 1C modality (p<0.001). Among the six modalities of stimulation channels, performance of 1C/SF was the best, which was similar to that of 1C/NF and 3C/SF; performance of 3C/NF was similar to that of 5C/SF; performance of 5C/NF was the worst. NASA-TLX scores indicated that mental workload increased as the number of stimulation channels increased. We quantified the difference between SF and NF, and the influence of different number of stimulation channels. SF was better than NF in general, but the practical issues such as the limited area of stumps could constrain the use of SF. We found that more channels increased the amount and richness of information to the amputee while fewer channels resulted in higher performance, and thus the 3C/SF modality was a good compromise. Based on this study, we provide possible solutions to the practical problems involving the implementation of tactile feedback for amputees. These results are expected to promote the application of SF and NF tactile feedback for amputees in the future.

Localization and Molecular Determinants of the Hanatoxin Receptors on the Voltage-Sensing Domains of a K+ Channel

PubMed Central

Li-Smerin, Yingying; Swartz, Kenton J.

2000-01-01

Hanatoxin inhibits voltage-gated K+ channels by modifying the energetics of activation. We studied the molecular determinants and physical location of the Hanatoxin receptors on the drk1 voltage-gated K+ channel. First, we made multiple substitutions at three previously identified positions in the COOH terminus of S3 to examine whether these residues interact intimately with the toxin. We also examined a region encompassing S1–S3 using alanine-scanning mutagenesis to identify additional determinants of the toxin receptors. Finally, guided by the structure of the KcsA K+ channel, we explored whether the toxin interacts with the peripheral extracellular surface of the pore domain in the drk1 K+ channel. Our results argue for an intimate interaction between the toxin and the COOH terminus of S3 and suggest that the Hanatoxin receptors are confined within the voltage-sensing domains of the channel, at least 20–25 Å away from the central pore axis. PMID:10828242

Time-reversal imaging for classification of submerged elastic targets via Gibbs sampling and the Relevance Vector Machine.

PubMed

Dasgupta, Nilanjan; Carin, Lawrence

2005-04-01

Time-reversal imaging (TRI) is analogous to matched-field processing, although TRI is typically very wideband and is appropriate for subsequent target classification (in addition to localization). Time-reversal techniques, as applied to acoustic target classification, are highly sensitive to channel mismatch. Hence, it is crucial to estimate the channel parameters before time-reversal imaging is performed. The channel-parameter statistics are estimated here by applying a geoacoustic inversion technique based on Gibbs sampling. The maximum a posteriori (MAP) estimate of the channel parameters are then used to perform time-reversal imaging. Time-reversal implementation requires a fast forward model, implemented here by a normal-mode framework. In addition to imaging, extraction of features from the time-reversed images is explored, with these applied to subsequent target classification. The classification of time-reversed signatures is performed by the relevance vector machine (RVM). The efficacy of the technique is analyzed on simulated in-channel data generated by a free-field finite element method (FEM) code, in conjunction with a channel propagation model, wherein the final classification performance is demonstrated to be relatively insensitive to the associated channel parameters. The underlying theory of Gibbs sampling and TRI are presented along with the feature extraction and target classification via the RVM.

Monitoring and Acquisition Real-time System (MARS)

NASA Technical Reports Server (NTRS)

Holland, Corbin

2013-01-01

MARS is a graphical user interface (GUI) written in MATLAB and Java, allowing the user to configure and control the Scalable Parallel Architecture for Real-Time Acquisition and Analysis (SPARTAA) data acquisition system. SPARTAA not only acquires data, but also allows for complex algorithms to be applied to the acquired data in real time. The MARS client allows the user to set up and configure all settings regarding the data channels attached to the system, as well as have complete control over starting and stopping data acquisition. It provides a unique "Test" programming environment, allowing the user to create tests consisting of a series of alarms, each of which contains any number of data channels. Each alarm is configured with a particular algorithm, determining the type of processing that will be applied on each data channel and tested against a defined threshold. Tests can be uploaded to SPARTAA, thereby teaching it how to process the data. The uniqueness of MARS is in its capability to be adaptable easily to many test configurations. MARS sends and receives protocols via TCP/IP, which allows for quick integration into almost any test environment. The use of MATLAB and Java as the programming languages allows for developers to integrate the software across multiple operating platforms.

Implementation and extension of the impulse transfer function method for future application to the space shuttle project. Volume 1: Analysis and correlation studies

NASA Technical Reports Server (NTRS)

Mantus, M.; Pardo, H.

1973-01-01

Computer programming, data processing, and a correlation study that employed data collected in the first phase test were used to demonstrate that standard test procedures and equipment could be used to collect a significant number of transfer functions from tests of the Lunar Module test article LTA-11. The testing consisted of suspending the vehicle from the apex fittings of the outrigger trusses through a set of air springs to simulate the free-free state. Impulsive loadings were delivered, one at a time, at each of the landing gear's attachment points, in three mutually perpendicular directions; thus a total of 36 impulses were applied to the vehicle. Time histories of each pulse were recorded on magnetic tape along with 40 channels of strain gage response and 28 channels of accelerometer response. Since an automated data processing system was not available, oscillograph playbacks were made of all 2400 time histories as a check on the validity of the data taken. In addition, one channel of instrumentation was processed to determine its response to a set of forcing functions from a prior LTA-11 drop test. This prediction was compared with drop test results as a first measure of accuracy.

Evaluation of a stream channel-type system for southeast Alaska.

Treesearch

M.D. Bryant; P.E. Porter; S.J. Paustian

1991-01-01

Nine channel types within a hierarchical channel-type classification system (CTCS) were surveyed to determine relations between salmonid densities and species distribution, and channel type. Two other habitat classification systems and the amount of large woody debris also were compared to species distribution and salmonid densities, and to stream channel types....

Tuning the ion selectivity of tetrameric cation channels by changing the number of ion binding sites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Derebe, Mehabaw G.; Sauer, David B.; Zeng, Weizhong

2015-11-30

Selective ion conduction across ion channel pores is central to cellular physiology. To understand the underlying principles of ion selectivity in tetrameric cation channels, we engineered a set of cation channel pores based on the nonselective NaK channel and determined their structures to high resolution. These structures showcase an ensemble of selectivity filters with a various number of contiguous ion binding sites ranging from 2 to 4, with each individual site maintaining a geometry and ligand environment virtually identical to that of equivalent sites in K{sup +} channel selectivity filters. Combined with single channel electrophysiology, we show that only themore » channel with four ion binding sites is K{sup +} selective, whereas those with two or three are nonselective and permeate Na{sup +} and K{sup +} equally well. These observations strongly suggest that the number of contiguous ion binding sites in a single file is the key determinant of the channel's selectivity properties and the presence of four sites in K{sup +} channels is essential for highly selective and efficient permeation of K{sup +} ions.« less

Characterization of interactions between Nedd4 and beta and gammaENaC using surface plasmon resonance.

PubMed

Asher, C; Chigaev, A; Garty, H

2001-09-07

Cell surface expression of the epithelial Na(+) channel ENaC is regulated by the ubiquitin ligase Nedd4. Binding of the WW domains of Nedd4 to the PY region in the carboxy tails of beta and gammaENaC, results in channel ubiquitination and degradation. Kinetic analysis of these interactions has been done using surface plasmon resonance. Synthetic peptides corresponding to the PY regions of beta and gammaENaC were immobilized on a sensor chip and "real-time" kinetics of their binding to recombinant WW proteins was determined. Specificity of the interactions was established by competition experiment, as well as by monitoring effects of a point mutation known to impair Nedd4/ENaC binding. These data provides the first determination of association, dissociation and equilibrium constants for the interactions between WW2 and beta or gammaENaC. Copyright 2001 Academic Press.

Multichannel imager for littoral zone characterization

NASA Astrophysics Data System (ADS)

Podobna, Yuliya; Schoonmaker, Jon; Dirbas, Joe; Sofianos, James; Boucher, Cynthia; Gilbert, Gary

2010-04-01

This paper describes an approach to utilize a multi-channel, multi-spectral electro-optic (EO) system for littoral zone characterization. Advanced Coherent Technologies, LLC (ACT) presents their EO sensor systems for the surf zone environmental assessment and potential surf zone target detection. Specifically, an approach is presented to determine a Surf Zone Index (SZI) from the multi-spectral EO sensor system. SZI provides a single quantitative value of the surf zone conditions delivering an immediate understanding of the area and an assessment as to how well an airborne optical system might perform in a mine countermeasures (MCM) operation. Utilizing consecutive frames of SZI images, ACT is able to measure variability over time. A surf zone nomograph, which incorporates targets, sensor, and environmental data, including the SZI to determine the environmental impact on system performance, is reviewed in this work. ACT's electro-optical multi-channel, multi-spectral imaging system and test results are presented and discussed.

Hidden Markov analysis of mechanosensitive ion channel gating.

PubMed

Khan, R Nazim; Martinac, Boris; Madsen, Barry W; Milne, Robin K; Yeo, Geoffrey F; Edeson, Robert O

2005-02-01

Patch clamp data from the large conductance mechanosensitive channel (MscL) in E. coli was studied with the aim of developing a strategy for statistical analysis based on hidden Markov models (HMMs) and determining the number of conductance levels of the channel, together with mean current, mean dwell time and equilibrium probability of occupancy for each level. The models incorporated state-dependent white noise and moving average adjustment for filtering, with maximum likelihood parameter estimates obtained using an EM (expectation-maximisation) based iteration. Adjustment for filtering was included as it could be expected that the electronic filter used in recording would have a major effect on obviously brief intermediate conductance level sojourns. Preliminary data analysis revealed that the brevity of intermediate level sojourns caused difficulties in assignment of data points to levels as a result of over-estimation of noise variances. When reasonable constraints were placed on these variances using the better determined noise variances for the closed and fully open levels, idealisation anomalies were eliminated. Nevertheless, simulations suggested that mean sojourn times for the intermediate levels were still considerably over-estimated, and that recording bandwidth was a major limitation; improved results were obtained with higher bandwidth data (10 kHz sampled at 25 kHz). The simplest model consistent with these data had four open conductance levels, intermediate levels being approximately 20%, 51% and 74% of fully open. The mean lifetime at the fully open level was about 1 ms; estimates for the three intermediate levels were 54-92 micros, probably still over-estimates.

Experimental test of 200 W Hall thruster with titanium wall

NASA Astrophysics Data System (ADS)

Ding, Yongjie; Sun, Hezhi; Peng, Wuji; Xu, Yu; Wei, Liqiu; Li, Hong; Li, Peng; Su, Hongbo; Yu, Daren

2017-05-01

We designed a 200 W Hall thruster based on the technology of pushing down a magnetic field with two permanent magnetic rings. Boron nitride (BN) is an important insulating wall material for Hall thrusters. The discharge characteristics of the designed Hall thruster were studied by replacing BN with titanium (Ti). Experimental results show that the designed Hall thruster can discharge stably for a long time under a Ti channel. Experiments were performed to determine whether the channel and cathode are electrically connected. When the channel wall and cathode are insulated, the divergence angle of the plume increases, but the performance of the Hall thruster is improved in terms of thrust, specific impulse, anode efficiency, and thrust-to-power ratio. Ti exhibits a powerful antisputtering capability, a low emanation rate of gas, and a large structural strength, making it a potential candidate wall material in the design of low-power Hall thrusters.

Coupled π π , K K ¯ scattering in P -wave and the ρ resonance from lattice QCD

DOE PAGES

Wilson, David J.; Briceño, Raúl A.; Dudek, Jozef J.; ...

2015-11-02

In this study, we determine elastic and coupled-channel amplitudes for isospin-1 meson-meson scattering inmore » $P$-wave, by calculating correlation functions using lattice QCD with light quark masses such that $$m_\\pi = 236$$ MeV in a cubic volume of $$\\sim (4 \\,\\mathrm{fm})^3$$. Variational analyses of large matrices of correlation functions computed using operator constructions resembling $$\\pi\\pi$$, $$K\\overline{K}$$ and $$q\\bar{q}$$, in several moving frames and several lattice irreducible representations, leads to discrete energy spectra from which scattering amplitudes are extracted. In the elastic $$\\pi\\pi$$ scattering region we obtain a detailed energy-dependence for the phase-shift, corresponding to a $$\\rho$$ resonance, and we extend the analysis into the coupled-channel $$K\\overline{K}$$ region for the first time, finding a small coupling between the channels.« less

Water quality prediction of marine recreational beaches receiving watershed baseflow and stormwater runoff in southern California, USA.

PubMed

He, Li-Ming Lee; He, Zhen-Li

2008-05-01

Beach advisories are issued to the public in California when the concentration of fecal indicator bacteria (FIB), including total coliform, fecal coliform (or Escherichia coli), and Enterococcus, exceed their recreational water health standards, or when the amount of a rainfall event is above the pre-determined threshold. However, it is not fully understood about how and to what degree stormwater runoff or baseflow exerts impacts on beach water quality. Furthermore, current laboratory methods used to determine the FIB levels take 18-96 h, which is too slow to keep pace with changes in FIB levels in water. Thus, a beach may not be posted when it is contaminated, and may be posted under advisory when bacterial levels have already decreased to within water quality standards. The study was designed to address the above critical issues. There were large temporal and spatial variations in FIB concentrations along two popular State Beaches in San Diego, CA, USA. The rainstorm-induced runoff from the watersheds exerts significant impacts on the marine recreational water quality of the beaches adjacent to lagoons during the first 24-48 h after a rain event. The large volume of stormwater runoff discharging to beaches caused high FIB concentrations in beach water not only at the lagoon outlet channel and the mixing zone, but also at the locations 90 m away from the channel northward or southward along the shoreline. The geomorphology of beach shoreline, distance from the outlet channel, wind strength, wind direction, tide height, wave height, rainfall, time lapse after a rainstorm, or channel flow rate played a role in affecting the distribution of FIB concentrations in beach water. Despite the great temporal and spatial variability of FIB concentrations along a shoreline, the artificial neural network-based models developed in this study are capable of successfully predicting FIB concentrations at different beaches, different locations, and different times under baseflow or rainstorm conditions. The models are based on readily measurable variables including temperature, conductivity, pH, turbidity, channel water flow, rainfall, and/or time lapse after a rainstorm. The established models will help fill the current gap between beach posting and actual water quality and make more meaningful and effective decisions on beach closures and advisories.

Channel and hillslope processes revisited in the Arroyo de los Frijoles watershed near Santa Fe, New Mexico

USGS Publications Warehouse

Gellis, Allen C.; Emmett, William W.; Leopold, Luna Bergere

2005-01-01

Detailed documentation of geomorphic changes in the landscape of more than a few years is rarely possible. Channel cross sections, channel profiles, sediment deposition behind dams, and hillslope-erosion plots, originally benchmarked within several watersheds outside Santa Fe, New Mexico, in the 1950’s and 1960’s, for a 1966 report that documented processes and rates of arid-region sediment production and deposition, were resurveyed in the mid-1990’s. Many of the original study sites were relocated and surveyed in the mid-1990’s to determine subsequent channel and hillslope changes and to determine whether trends of channel and hillslope aggradation and degradation that were evident in the 1950’s and 1960’s have continued. In general, the net change in channel geometry has been small over the last 30–40 years. The average change in cross-sectional area of 32 resurveyed cross sections was erosion of 0.27 square meter, which equates to a 4-percent increase in cross-sectional area. The average net change in thalweg elevation for 51 resurveyed cross sections was degradation of 0.04 meter. Unpublished data (1964–68) from the scour chains showed that 371 chains had an average scour of 0.14 ± 0.14 meter and that 372 chains showed an average fill of 0.13 + 0.11 meter. Scour, found in the original study (1958–64) to be proportional to the square root of discharge, was confirmed with the addition of unpublished data (1964–68). The observed channel changes have no consistent trend, compared either to results observed in the original 1966 study or to distance from the watershed divide. The conclusion drawn in the original study was that most channels were aggrading; the resurvey showed that aggradation did not continue.An increase in housing and population in the Arroyo de los Frijoles watershed since the 1950’s has led to more roads. Channel degradation is most noticeable at road crossings. The greatest degradation of the main channel Arroyo de los Frijoles, 1.53 meters, and the greatest aggradation, 0.38 meter, occur downstream and upstream, respectively, from a culvert in a dirt road. Periods of high average annual rainfall intensity reported for Santa Fe for 1853–80 immediately preceded late 19th century arroyo incision, and another period of high-intensity rainfall began in 1967. This may indicate that climatic factors are again favorable for arroyo incision in this part of New Mexico; data from this resurvey, however, do not provide evidence of a renewed cycle of erosion.At a 1930’s Civilian Conservation Corps-constructed dam on Coyote C. Arroyo, the measured sediment yield from 1966 to 1993 was 139 metric tonnes per square kilometer per year. Sediment yields have decreased through time because of either a decrease in the trap efficiency of the reservoir over time or a decrease in sediment delivery to the reservoir because of upstream channel storage. The effects of base-level rise on the channel profile were documented in 1993 through resurveys of sediment deposits behind two small dams, Big Sweat Dam and Little Sweat Dam. Both dams, built in 1960, showed sediment deposition that extends 20 and 9.3 meters upstream, respectively, and the 1993 sediment gradient was nearly the same as the unaffected channel upstream. Big Sweat Dam showed fluctuations in channel gradient within 5.3 meters of the dam, which may be a result of local scour following complete filling of the dam, scour from increased sinuosity, or differences in the location of surveying stations over time. The sinuosity of the channel has increased over time, presumably from a reduction in slope. Channel gradients 0 to 11.0 meters upstream from Little Sweat Dam have remained constant at about 0.028 from 1964 to 1993.Measurement of erosion or hillslope-erosion plots show that average values of surface erosion range from 0.019 to 0.096 centimeters per year and are within values reported for regional erosion and denudation studies. Sediment yield from the Slopewash Tributary erosion plot was 307 metric tonnes per square kilometer per year. The reproducibility and accuracy of the resurveys from the 1950’s to the 1990’s attest to the concepts used to quantify geomorphic features established in the Vigil Network. With relatively simple techniques, more than 30 years of geomorphic change were observed in this study.

Quantum Yield of Cyclobutane Pyrimidine Dimer Formation Via the Triplet Channel Determined by Photosensitization.

PubMed

Liu, Lizhe; Pilles, Bert M; Gontcharov, Julia; Bucher, Dominik B; Zinth, Wolfgang

2016-01-21

UV-induced formation of the cyclobutane pyrimidine dimer (CPD) lesion is investigated by stationary and time-resolved photosensitization experiments. The photosensitizer 2'-methoxyacetophenone with high intersystem crossing efficiency and large absorption cross-section in the UV-A range was used. A diffusion controlled reaction model is presented. Time-resolved experiments confirmed the validity of the reaction model and provided information on the dynamics of the triplet sensitization process. With a series of concentration dependent stationary illumination experiments, we determined the quantum efficiency for CPD formation from the triplet state of the thymine dinucleotide TpT to be 4 ± 0.2%.

Lightning Return-Stroke Current Waveforms Aloft, from Measured Field Change, Current, and Channel Geometry

NASA Technical Reports Server (NTRS)

Willett, J. C.; LeVine, D. M.; Idone, V. P.

2006-01-01

Three-dimensional reconstructions of six rocket-triggered lightning channels are derived from stereo photographs. These reconstructed channels are used to infer the behavior of the current in return strokes above the ground from current waveforms measured at the channel base and electric-field-change waveforms measured at a range of 5.2 kilometers for 24 return strokes in these channels. Streak photographs of 14 of the same strokes are analyzed to determine the rise times, propagation speeds, and amplitudes of relative light intensity for comparison with the electrical inferences. Results include the following: 1) The fine structure of the field-change waveforms that were radiated by these subsequent return strokes can be explained, in large part, by channel geometry. 2) The average 10 - 90% rise time of the stroke current increased by about a factor of seven in our sample, from an observed 0.31 plus or minus 0.17 microseconds at the surface to an inferred 2.2 plus or minus 0.5 microcseconds at 1 kilometer path length above the surface. 3) The three-dimensional propagation speed of the current front averaged 1.80 plus or minus 0.24 X 10(exp 8) meters per second over channel lengths typically greater than 1 kilometer. 4) Assuming that the measured current was entirely due to the return stroke forced an unreasonably large and abrupt reduction in inferred current amplitude over the first few tens of meters above the surface, especially in cases when the leader was bright relative to its stroke. Therefore, a significant fraction of the current at the surface was probably due to the leader, at least in such cases. 5) Peak return-stroke currents decreased by approximately 37 plus or minus 12% from 100 meters to 1 kilometer of path length above the surface. Because of uncertainty about how to partition the measured current between leader and return stroke, we are unable to infer the variation of current amplitude near the ground.

Spin-resolved electron waiting times in a quantum-dot spin valve

NASA Astrophysics Data System (ADS)

Tang, Gaomin; Xu, Fuming; Mi, Shuo; Wang, Jian

2018-04-01

We study the electronic waiting-time distributions (WTDs) in a noninteracting quantum-dot spin valve by varying spin polarization and the noncollinear angle between the magnetizations of the leads using the scattering matrix approach. Since the quantum-dot spin valve involves two channels (spin up and down) in both the incoming and outgoing channels, we study three different kinds of WTDs, which are two-channel WTD, spin-resolved single-channel WTD, and cross-channel WTD. We analyze the behaviors of WTDs in short times, correlated with the current behaviors for different spin polarizations and noncollinear angles. Cross-channel WTD reflects the correlation between two spin channels and can be used to characterize the spin-transfer torque process. We study the influence of the earlier detection on the subsequent detection from the perspective of cross-channel WTD, and define the influence degree quantity as the cumulative absolute difference between cross-channel WTDs and first-passage time distributions to quantitatively characterize the spin-flip process. We observe that influence degree versus spin-transfer torque for different noncollinear angles as well as different polarizations collapse into a single curve showing universal behaviors. This demonstrates that cross-channel WTDs can be a pathway to characterize spin correlation in spintronics system.

Prioritized packet video transmission over time-varying wireless channel using proactive FEC

NASA Astrophysics Data System (ADS)

Kumwilaisak, Wuttipong; Kim, JongWon; Kuo, C.-C. Jay

2000-12-01

Quality of video transmitted over time-varying wireless channels relies heavily on the coordinated effort to cope with both channel and source variations dynamically. Given the priority of each source packet and the estimated channel condition, an adaptive protection scheme based on joint source-channel criteria is investigated via proactive forward error correction (FEC). With proactive FEC in Reed Solomon (RS)/Rate-compatible punctured convolutional (RCPC) codes, we study a practical algorithm to match the relative priority of source packets and instantaneous channel conditions. The channel condition is estimated to capture the long-term fading effect in terms of the averaged SNR over a preset window. Proactive protection is performed for each packet based on the joint source-channel criteria with special attention to the accuracy, time-scale match, and feedback delay of channel status estimation. The overall gain of the proposed protection mechanism is demonstrated in terms of the end-to-end wireless video performance.

Fluorescence multiplexing with time-resolved and spectral discrimination using a near-IR detector.

PubMed

Zhu, Li; Stryjewski, Wieslaw; Lassiter, Suzanne; Soper, Steven A

2003-05-15

We report on the design and performance of a two-color, time-resolved detector for the acquisition of both steady-state and time-resolved fluorescence data acquired in real time during the capillary gel electrophoresis separation of DNA sequencing fragments. The detector consisted of a pair of pulsed laser diodes operating at 680 and 780 nm. The diode heads were coupled directly to single-mode fibers, which were terminated into a single fiber mounted via a FC/PC connector to the detector body. The detector contained a dichroic filter, which directed the dual-laser beams to an objective. The objective focused the laser light into a capillary gel column and also collected the resulting fluorescence emission. The dual-color emission was transmitted through the dichroic and focused onto a multimode fiber (core diameter 50 microm), which carried the luminescence to a pair of single-photon avalanche diodes (SPADs). The emission was sorted spectrally using a second dichroic onto one of two SPADs and isolated using appropriate interference filters (710- or 810-nm channel). The dual-color detector demonstrated a time response of 450 and 510 ps (fwhm) for the 710- and 810-nm channels, respectively. The mass detection limits for two near-IR dye-labeled sequencing primers electrophoresed in a capillary gel column were found to be 7.1 x 10(-21) and 3.2 x 10(-20) mol (SNR = 3) for the 710- and 810-nm detector channels, respectively. In addition, no leakage of luminescence excited at 680 nm was observed in the 810-nm channel or 780-nm excited luminescence into the 710-nm channel. An M13mp18 template was sequenced in a single capillary gel column using a two-color, two-lifetime format. The read length was found to be 650 base pairs for the test template at a calling accuracy of 95.1% using a linear poly(dimethylacrylamide) (POP6) gel column, with the read length determined primarily by the electrophoretic resolution produced by the sieving gel.

Quality of terrestrial data derived from UAV photogrammetry: a case study of the Hetao irrigation district in northern China

NASA Astrophysics Data System (ADS)

Zhang, Hongming; Baartman, Jantiene E. M.; Yang, Xiaomei; Gai, Lingtong; Geissen, Violette

2017-04-01

Most crops in northern China are irrigated, but the topography affects water use, soil erosion, runoff and yields,. Technologies for collecting high-resolution topographic data are essential for adequately assessing these effects. Ground surveys and techniques of light detection and ranging have good accuracy, but data acquisition can be time-consuming and expensive for large catchments. Recent rapid technological development has provided new, flexible, high-resolution methods for collecting topographic data, such as photogrammetry using unmanned aerial vehicles (UAVs). The accuracy of UAV photogrammetry for generating high-resolution digital elevation models (DEMs) and for determining the width of irrigation channels, however, has not been assessed. We used a fixed-wing UAV for collecting high-resolution (0.15 m) topographic data for the Hetao irrigation district, the third largest irrigation district in China. We surveyed 112 ground checkpoints (GCPs) using a real-time kinematic global positioning system to evaluate the accuracy of the DEMs and channel widths. A comparison of manually measured channel widths with the widths derived from the DEMs indicated that the DEM-derived widths had vertical and horizontal root mean square errors of 13.0 and 7.9 cm, respectively. UAV photogrammetric data can thus be used for land surveying, digital mapping, calculating channel capacity, monitoring crops, and predicting yields, with the advantages of economy, speed, and ease.

Hydrology of the Chicod Creek basin, North Carolina, prior to channel improvements

USGS Publications Warehouse

Simmons, Clyde E.; Aldridge, Mary C.

1980-01-01

Extensive modification and excavation of stream channels in the 6-square mile Chicod Creek basin began in mid-1979 to reduce flooding and improve stream runoff conditions. The effects of channel improvements on this Coastal Pain basin 's hydrology will be determined from data collected prior to, during, and for several years following channel alternations. This report summarizes the findings of data collected prior to these improvements. During the 3-year study period, flow data collected from four stream gaging stations in the basin show that streams are dry approximately 10 percent of the time. Chemical analyses of water samples from the streams and from eight shallow groundwater observation wells indicate that water discharge from the surficial aquifer is the primary source of streamflow during rainless periods. Concentrations of Kjeldahl nitrogen, total nitrogen, and total phosphorus were often 5 to 10 times greater at Chicod Creek sites than those at nearby baseline sites. It is probable that runoff from farming and livestock operations contributes significantly to these elevated concentrations in Chicod Creek. The only pesticides detected in stream water were low levels of DDT and dieldrin, which occurred during storm runoff. A much wider range of pesticides, however, are found associated with streambed materials. The ratio of fecal coliform counts to those of fecal streptococcus indicate that the streams receive fecal wastes from livestock and poultry operations.

Chronic deficit in the expression of voltage-gated potassium channel Kv3.4 subunit in the hippocampus of pilocarpine-treated epileptic rats

PubMed Central

Pacheco Otalora, Luis F.; Skinner, Frank; Oliveira, Mauro S.; Dotson, Bianca Farrel; Arshadmansab, Massoud F.; Pandari, Tarun; Garcia, Ileana; Robles, Leslie; Rosas, Gerardo; Mello, Carlos F.; Ermolinsky, Boris S.; Garrido-Sanabria, Emilio R.

2010-01-01

Voltage gated K+ channels (Kv) are a highly diverse group of channels critical in determining neuronal excitability. Deficits of Kv channel subunit expression and function have been implicated in the pathogenesis of epilepsy. In this study, we investigate whether the expression of the specific subunit Kv3.4 is affected during epileptogenesis following pilocarpine-induced status epilepticus. For this purpose, we used immunohistochemistry, Western blotting assays and comparative analysis of gene expression using TaqMan-based probes and delta-delta cycle threshold (Δ ΔCT) method of quantitative real-time polymerase chain reaction (qPCR) technique in samples obtained from age-matched control and epileptic rats. A marked down-regulation of Kv3.4 immunoreactivity was detected in the stratum lucidum and hilus of dentate gyrus in areas corresponding to the mossy fiber system of chronically epileptic rats. Correspondingly, a 20% reduction of Kv3.4 protein levels was detected in the hippocampus of chronic epileptic rats. Real-time quantitative PCR analysis of gene expression revealed that a significant 33% reduction of transcripts for Kv3.4 (gene Kcnc4) occurred after 1 month of pilocarpine-induced status epilepticus and persisted during the chronic phase of the model. These data indicate a reduced expression of Kv3.4 channels at protein and transcript levels in the epileptic hippocampus. Down-regulation of Kv3.4 in mossy fibers may contribute to enhanced presynaptic excitability leading to recurrent seizures in the pilocarpine model of temporal lobe epilepsy. PMID:20971086

Microwave Heating of a Liquid Stably Flowing in a Circular Channel Under the Conditions of Nonstationary Radiative-Convective Heat Transfer

NASA Astrophysics Data System (ADS)

Salomatov, V. V.; Puzyrev, E. M.; Salomatov, A. V.

2018-05-01

A class of nonlinear problems of nonstationary radiative-convective heat transfer under the microwave action with a small penetration depth is considered in a stabilized coolant flow in a circular channel. The solutions to these problems are obtained, using asymptotic procedures at the stages of nonstationary and stationary convective heat transfer on the heat-radiating channel surface. The nonstationary and stationary stages of the solution are matched, using the "longitudinal coordinate-time" characteristic. The approximate solutions constructed on such principles correlate reliably with the exact ones at the limiting values of the operation parameters, as well as with numerical and experimental data of other researchers. An important advantage of these solutions is that they allow the determination of the main regularities of the microwave and thermal radiation influence on convective heat transfer in a channel even before performing cumbersome calculations. It is shown that, irrespective of the heat exchange regime (nonstationary or stationary), the Nusselt number decreases and the rate of the surface temperature change increases with increase in the intensity of thermal action.

Transport and fluctuation-dissipation relations in asymptotic and preasymptotic diffusion across channels with variable section.

PubMed

Forte, Giuseppe; Cecconi, Fabio; Vulpiani, Angelo

2014-12-01

We study the asymptotic and preasymptotic diffusive properties of Brownian particles in channels whose section varies periodically in space. The effective diffusion coefficient D(eff) is numerically determined by the asymptotic behavior of the root mean square displacement in different geometries, considering even cases of steep variations of the channel boundaries. Moreover, we compared the numerical results to the predictions from the various corrections proposed in the literature to the well known Fick-Jacobs approximation. Building an effective one-dimensional equation for the longitudinal diffusion, we obtain an approximation for the effective diffusion coefficient. Such a result goes beyond a perturbation approach, and it is in good agreement with the actual values obtained by the numerical simulations. We discuss also the preasymptotic diffusion which is observed up to a crossover time whose value, in the presence of strong spatial variation of the channel cross section, can be very large. In addition, we show how the Einstein's relation between the mean drift induced by a small external field and the mean square displacement of the unperturbed system is valid in both asymptotic and preasymptotic regimes.

Electron energy balance and ionization in the channel of a stationary plasma thruster

DOE Office of Scientific and Technical Information (OSTI.GOV)

Veselovzorov, A. N., E-mail: Veselovzorov-AN@nrcki.ru; Pogorelov, A. A.; Svirskiy, E. B.

2016-03-15

The paper presents results of numerical simulations of the electron dynamics in the field of the azimuthal and longitudinal waves excited in the channel of a stationary plasma thruster (SPT). The simulations are based on the experimentally determined wave characteristics. The simulation results show that the azimuthal wave displayed as ionization instability enhances electron transport along the thruster channel. It is established that the electron transport rate in the azimuthal wave increases as compared to the rate of diffusion caused by electron scattering from neutral atoms in proportion to the ratio between the times of electron− neutral collisions responsible formore » ionization and elastic electron scattering, respectively. An expression governing the plasma conductivity is derived with allowance for electron interaction with the azimuthal wave. The Hall parameter, the electron component of the discharge current, and the electron heating power in the thruster channel are calculated for two model SPTs operating with krypton and xenon. The simulation results agree well with the results of experimental studies of these two SPTs.« less

Initial results from a cryogenic proton irradiation of a p-channel CCD

NASA Astrophysics Data System (ADS)

Gow, J. P. D.; Wood, D.; Burt, D.; Hall, D. J.; Dryer, B.; Holland, A. D.; Murray, N. J.

2015-08-01

The displacement damage hardness that can be achieved using p-channel charge coupled devices (CCD) was originally demonstrated in 1997 and since then a number of other studies have demonstrated an improved tolerance to radiationinduced CTI when compared to n-channel CCDs. A number of recent studies have also shown that the temperature history of the device after the irradiation impacts the performance of the detector, linked to the mobility of defects at different temperatures. This study describes the initial results from an e2v technologies p-channel CCD204 irradiated at 153 K with a 10 MeV equivalent proton fluences of 1.24×109 and 1.24×1011 protons.cm-2. The number of defects identified using trap pumping, dark current and cosmetic quality immediately after irradiation and over a period of 150 hours after the irradiation with the device held at 153 K and then after different periods of time at room temperature are described. The device also exhibited a flatband voltage shift of around 30 mV per krad, determined by the reduction in full well capacity.

Postirradiation behavior of p-channel charge-coupled devices irradiated at 153 K

NASA Astrophysics Data System (ADS)

Gow, Jason P. D.; Wood, Daniel; Murray, Neil J.; Burt, David; Hall, David J.; Dryer, Ben; Holland, Andrew D.

2016-04-01

The displacement damage hardness that can be achieved using p-channel charge-coupled devices (CCD) was originally demonstrated in 1997, and since then a number of other studies have demonstrated an improved tolerance to radiation-induced charge transfer inefficiency when compared to n-channel CCDs. A number of recent studies have also shown that the temperature history of the device after the irradiation impacts the performance of the detector, linked to the mobility of defects at different temperatures. The initial results from an e2v technologies p-channel CCD204 irradiated at 153 K with 10-MeV equivalent proton fluences of 1.24×109 and 1.24×1011 protons cm-2 is described. The dark current, cosmetic quality, and the number of defects identified using trap pumping immediately were monitored after the irradiation for a period of 150 h with the device held at 153 K and then after different periods of time at room temperature. The device also exhibited a flatband voltage shift of around 30 mV/krad, determined by the reduction in full well capacity.

Regimes of Two-Phase Flow in Short Rectangular Channel

NASA Astrophysics Data System (ADS)

Chinnov, Evgeny A.; Guzanov, Vladimir V.; Cheverda, Vyacheslav; Markovich, Dmitry M.; Kabov, Oleg A.

2009-08-01

Experimental study of two-phase flow in the short rectangular horizontal channel with height 440 μm has been performed. Characteristics of liquid motion inside the channel have been registered and measured by the Laser Induced Fluorescence technique. New information has allowed determining more precisely the characteristics of churn regime and boundaries between different regimes of two-phase flow. It was shown that formation of some two-phase flow regimes and transitions between them are determined by instability of the flow in the lateral parts of the channel.

A Lossless Multichannel Bio-Signal Compression Based on Low-Complexity Joint Coding Scheme for Portable Medical Devices

PubMed Central

Kim, Dong-Sun; Kwon, Jin-San

2014-01-01

Research on real-time health systems have received great attention during recent years and the needs of high-quality personal multichannel medical signal compression for personal medical product applications are increasing. The international MPEG-4 audio lossless coding (ALS) standard supports a joint channel-coding scheme for improving compression performance of multichannel signals and it is very efficient compression method for multi-channel biosignals. However, the computational complexity of such a multichannel coding scheme is significantly greater than that of other lossless audio encoders. In this paper, we present a multichannel hardware encoder based on a low-complexity joint-coding technique and shared multiplier scheme for portable devices. A joint-coding decision method and a reference channel selection scheme are modified for a low-complexity joint coder. The proposed joint coding decision method determines the optimized joint-coding operation based on the relationship between the cross correlation of residual signals and the compression ratio. The reference channel selection is designed to select a channel for the entropy coding of the joint coding. The hardware encoder operates at a 40 MHz clock frequency and supports two-channel parallel encoding for the multichannel monitoring system. Experimental results show that the compression ratio increases by 0.06%, whereas the computational complexity decreases by 20.72% compared to the MPEG-4 ALS reference software encoder. In addition, the compression ratio increases by about 11.92%, compared to the single channel based bio-signal lossless data compressor. PMID:25237900

Effects of stochastic sodium channels on extracellular excitation of myelinated nerve fibers.

PubMed

Mino, Hiroyuki; Grill, Warren M

2002-06-01

The effects of the stochastic gating properties of sodium channels on the extracellular excitation properties of mammalian nerve fibers was determined by computer simulation. To reduce computation time, a hybrid multicompartment cable model including five central nodes of Ranvier containing stochastic sodium channels and 16 flanking nodes containing detenninistic membrane dynamics was developed. The excitation properties of the hybrid cable model were comparable with those of a full stochastic cable model including 21 nodes of Ranvier containing stochastic sodium channels, indicating the validity of the hybrid cable model. The hybrid cable model was used to investigate whether or not the excitation properties of extracellularly activated fibers were influenced by the stochastic gating of sodium channels, including spike latencies, strength-duration (SD), current-distance (IX), and recruitment properties. The stochastic properties of the sodium channels in the hybrid cable model had the greatest impact when considering the temporal dynamics of nerve fibers, i.e., a large variability in latencies, while they did not influence the SD, IX, or recruitment properties as compared with those of the conventional deterministic cable model. These findings suggest that inclusion of stochastic nodes is not important for model-based design of stimulus waveforms for activation of motor nerve fibers. However, in cases where temporal fine structure is important, for example in sensory neural prostheses in the auditory and visual systems, the stochastic properties of the sodium channels may play a key role in the design of stimulus waveforms.

Developing and exploring a theory for the lateral erosion of bedrock channels for use in landscape evolution models

NASA Astrophysics Data System (ADS)

Langston, Abigail L.; Tucker, Gregory E.

2018-01-01

Understanding how a bedrock river erodes its banks laterally is a frontier in geomorphology. Theories for the vertical incision of bedrock channels are widely implemented in the current generation of landscape evolution models. However, in general existing models do not seek to implement the lateral migration of bedrock channel walls. This is problematic, as modeling geomorphic processes such as terrace formation and hillslope-channel coupling depends on the accurate simulation of valley widening. We have developed and implemented a theory for the lateral migration of bedrock channel walls in a catchment-scale landscape evolution model. Two model formulations are presented, one representing the slow process of widening a bedrock canyon and the other representing undercutting, slumping, and rapid downstream sediment transport that occurs in softer bedrock. Model experiments were run with a range of values for bedrock erodibility and tendency towards transport- or detachment-limited behavior and varying magnitudes of sediment flux and water discharge in order to determine the role that each plays in the development of wide bedrock valleys. The results show that this simple, physics-based theory for the lateral erosion of bedrock channels produces bedrock valleys that are many times wider than the grid discretization scale. This theory for the lateral erosion of bedrock channel walls and the numerical implementation of the theory in a catchment-scale landscape evolution model is a significant first step towards understanding the factors that control the rates and spatial extent of wide bedrock valleys.

Volatile Organic Analyzer (VOA) in 2006: Repair, Revalidation, and Restart of Elektron Event

NASA Technical Reports Server (NTRS)

Limero, Thomas

2007-01-01

The Volatile Organic Analyzer (VOA) was launched to the International Space Station (ISS) in August 2001 and was the first instrument to provide near real-time measurement of volatile organic compounds in a spacecraft atmosphere. The VOA performed an analysis of the ISS air approximately twice a month for most of its operation through May 2003. This intermittent operation, caused by a software interface issue with the ISS communication bus, slowed the validation of the VOA. However, operational validation was completed in 2003 when analysis of air samples collected in grab sample containers (GSCs) compared favorably with simultaneous VOA runs (1). The VOA has two channels that provide redundant function, albeit at slightly reduced performance, when only one channel is operating (2). Most target compounds can be detected on both channels. In January 2003, the VOA identified a malfunction in the channel 2 preconcentrator and it shut down that channel. The anomaly profile suggested that a fuse might have failed, but the root cause could not be determined. In May 2003, channel 1 was shut down when the detector s elevated temperature could not longer be maintained. Since both VOA channels were now deactivated, VOA operations ended until an in-flight repair could be planned and executed. This paper describes the process to repair the VOA and to revalidate it for operations, and then an account is given of the VOA s contribution following a contingency event on ISS.

Channel effect of the modified powdery mixture of ammonium nitrate and fuel oil

NASA Astrophysics Data System (ADS)

Wu, Chun-Ping; Liu, Lian-Sheng; Wang, Xu-Guang; Liu, Yong; Wang, Yin-Jun

2010-10-01

The modified powdery mixture of ammonium nitrate and fuel oil (MPANFO) is a new breed of industrial explosives developed years ago in China. As one of the important properties of an industrial explosive, the channel effect of MPANFO was reported in this paper. A series of experiments were conducted to determine the channel effect of MPANFO. The blasthole diameter range was estimated to avoid the channel effect of MPANFO. Three empirical formulae for predicting the detonation length of MPANFO were provided in terms of the channel effect. Experiments and theoretical analysis indicate that the channel effect of MPANFO is very serious. The reason why the channel effect of MPANFO is worse than that of other industrial explosives is explained at a theoretical level. In addition, some properties of MPANFO, such as sympathetic distance, detonation velocity and brisance, are determined.

The CaV2.3 R-type voltage-gated Ca2+ channel in mouse sleep architecture.

PubMed

Siwek, Magdalena Elisabeth; Müller, Ralf; Henseler, Christina; Broich, Karl; Papazoglou, Anna; Weiergräber, Marco

2014-05-01

Voltage-gated Ca(2+) channels (VGCCs) are key elements in mediating thalamocortical rhythmicity. Low-voltage activated (LVA) CaV 3 T-type Ca(2+) channels have been related to thalamic rebound burst firing and to generation of non-rapid eye movement (NREM) sleep. High-voltage activated (HVA) CaV 1 L-type Ca(2+) channels, on the opposite, favor the tonic mode of action associated with higher levels of vigilance. However, the role of the HVA Non-L-type CaV2.3 Ca(2+) channels, which are predominantly expressed in the reticular thalamic nucleus (RTN), still remains unclear. Recently, CaV2.3(-/-) mice were reported to exhibit altered spike-wave discharge (SWD)/absence seizure susceptibility supported by the observation that CaV2.3 mediated Ca(2+) influx into RTN neurons can trigger small-conductance Ca(2+)-activated K(+)-channel type 2 (SK2) currents capable of maintaining thalamic burst activity. Based on these studies we investigated the role of CaV2.3 R-type Ca(2+) channels in rodent sleep. The role of CaV2.3 Ca(2+) channels was analyzed in CaV2.3(-/-) mice and controls in both spontaneous and artificial urethane-induced sleep, using implantable video-EEG radiotelemetry. Data were analyzed for alterations in sleep architecture using sleep staging software and time-frequency analysis. CaV2.3 deficient mice exhibited reduced wake duration and increased slow-wave sleep (SWS). Whereas mean sleep stage durations remained unchanged, the total number of SWS epochs was increased in CaV2.3(-/-) mice. Additional changes were observed for sleep stage transitions and EEG amplitudes. Furthermore, urethane-induced SWS mimicked spontaneous sleep results obtained from CaV2.3 deficient mice. Quantitative Real-time PCR did not reveal changes in thalamic CaV3 T-type Ca(2+) channel expression. The detailed mechanisms of SWS increase in CaV2.3(-/-) mice remain to be determined. Low-voltage activated CaV2.3 R-type Ca(2+) channels in the thalamocortical loop and extra-thalamocortical circuitries substantially regulate rodent sleep architecture thus representing a novel potential target for pharmacological treatment of sleep disorders in the future.

Suppression of the Eag1 potassium channel sensitizes glioblastoma cells to injury caused by temozolomide.

PubMed

Sales, Thais Torquato; Resende, Fernando Francisco Borges; Chaves, Natália Lemos; Titze-De-Almeida, Simoneide Souza; Báo, Sônia Nair; Brettas, Marcella Lemos; Titze-De-Almeida, Ricardo

2016-10-01

Glioblastoma multiforme (GBM) is the most aggressive type of human primary brain tumor. The standard treatment protocol includes radiotherapy in combination with temozolomide (TMZ). Despite advances in GBM treatment, the survival time of patients diagnosed with glioma is 14.5 months. Regarding tumor biology, various types of cancer cell overexpress the ether à go-go 1 (Eag1) potassium channel. Therefore, the present study examined the role of Eag1 in the cell damage caused by TMZ on the U87MG glioblastoma cell line. Eag1 was inhibited using a channel blocker (astemizole) or silenced by a short-hairpin RNA expression vector (pKv10.1-3). pKv10.1-3 (0.2 µg) improved the Eag1 silencing caused by 250 µM TMZ, as determined by reverse transcription-quantitative polymerase chain reaction and immunocytochemistry. Additionally, inhibiting Eag1 with the vector or astemizole (5 µM) reduced glioblastoma cell viability and sensitized cells to TMZ. Cell viability decreased by 63% for pKv10.1-3 + TMZ compared with 34% for TMZ alone, and by 77% for astemizole + TMZ compared with 46% for TMZ alone, as determined by MTT assay. In addition, both the vector and astemizole increased the apoptosis rate of glioblastoma cells triggered by TMZ, as determined by an Annexin V apoptosis assay. Collectively, the current data reveal that Eag1 has a role in the damage caused to glioblastoma by TMZ. Furthermore, suppression of this channel can improve the action of TMZ on U87MG glioblastoma cells. Thus, silencing Eag1 is a promising strategy to improve GBM treatment and merits additional studies in animal models of glioma.

Morphological changes of Gumara River channel over 50 years, upper Blue Nile basin, Ethiopia

NASA Astrophysics Data System (ADS)

Abate, Mengiste; Nyssen, Jan; Steenhuis, Tammo S.; Moges, Michael M.; Tilahun, Seifu A.; Enku, Temesgen; Adgo, Enyew

2015-06-01

In response to anthropogenic disturbances, alluvial rivers adjust their geometry. The alluvial river channels in the upper Blue Nile basin have been disturbed by human-induced factors since a longtime. This paper examines channel adjustment along a 38-km stretch of the Gumara River which drains towards Lake Tana and then to the Blue Nile. Over a 50 years period, agriculture developed rapidly in the catchment and flooding of the alluvial plain has become more frequent in recent times. The objectives of this study were to document the changes in channel planform and cross-section of the Gumara River and to investigate whether the changes could have contributed to the frequent flooding or vice versa. Two sets of aerial photographs (1957 and 1980) were scanned, and then orthorectified. Recent channel planform information was extracted from SPOT images of 2006 and Google Earth. Channel planform and bed morphology (vertical changes) were determined for these nearly 50 years period. The vertical changes were determined based on aggradation along a permanent structure, historic information on river cross-sections at a hydrological gauging station, and field observations. The results indicate that the lower reach of Gumara near its mouth has undergone major planform changes. A delta with approx. 1.12 km2 of emerged land was created between 1957 and 1980 and an additional 1 km2 of land has been added between 1980 and 2006. The sinuosity of the river changed only slightly: negatively (-1.1% i.e. meandering decreased) for the period from 1957 to 1980 and positively (+3.0%) for the period 1980-2006. Comparison of cross-sections at the hydrological gauging station showed that the deepest point in the river bed aggraded by 2.91 m for the period 1963-2009. The importance of sediment deposition in the stream and on its banks is related to land degradation in the upper catchment, and to artificial rising of Lake Tana level that creates a backwater effect and sediment deposition in Gumara River. Direct anthropogenic impacts (irrigation activities and building of dykes along the river banks) have contributed to the huge deposition in the river bed. Where the abstraction of water for irrigation is intensive, seepage water through the banks has contributed to river bank failure. In general, this study showed that changes to the planform at the mouth of the river and to the riverbed level are substantial. Moreover, the study indicated that the flood carrying capacity of the Gumara River channel has diminished in recent times.

Electrodiffusion kinetics of ionic transport in a simple membrane channel.

PubMed

Valent, Ivan; Petrovič, Pavol; Neogrády, Pavel; Schreiber, Igor; Marek, Miloš

2013-11-21

We employ numerical techniques for solving time-dependent full Poisson-Nernst-Planck (PNP) equations in 2D to analyze transient behavior of a simple ion channel subject to a sudden electric potential jump across the membrane (voltage clamp). Calculated spatiotemporal profiles of the ionic concentrations and electric potential show that two principal exponential processes can be distinguished in the electrodiffusion kinetics, in agreement with original Planck's predictions. The initial fast process corresponds to the dielectric relaxation, while the steady state is approached in a second slower exponential process attributed to the nonlinear ionic redistribution. Effects of the model parameters such as the channel length, height of the potential step, boundary concentrations, permittivity of the channel interior, and ionic mobilities on electrodiffusion kinetics are studied. Numerical solutions are used to determine spatiotemporal profiles of the electric field, ionic fluxes, and both the conductive and displacement currents. We demonstrate that the displacement current is a significant transient component of the total electric current through the channel. The presented results provide additional information about the classical voltage-clamp problem and offer further physical insights into the mechanism of electrodiffusion. The used numerical approach can be readily extended to multi-ionic models with a more structured domain geometry in 2D or 3D, and it is directly applicable to other systems, such as synthetic nanopores, nanofluidic channels, and nanopipettes.

Measurement of surface tension and viscosity by open capillary techniques

DOEpatents

Rye,Robert R. , Yost,Frederick G.

1998-01-01

An open-channel capillary is provided, having preferably a v-shaped groove in a flat wettable surface. The groove has timing marks and a source marker in which the specimen to be tested is deposited. The time of passage between the timing marks is recorded, and the ratio of surface tension .gamma. to viscosity .mu. is determined from the equation given below: ##EQU1## where h.sub.0 is the groove depth, .alpha. is the groove angle, .theta. is the liquid/solid contact angle, and t is the flow time. It has been shown by the

Time reversal communication system

DOEpatents

Candy, James V.; Meyer, Alan W.

2008-12-02

A system of transmitting a signal through a channel medium comprises digitizing the signal, time-reversing the digitized signal, and transmitting the signal through the channel medium. The channel medium may be air, earth, water, tissue, metal, and/or non-metal.

Channel heads in mountain catchments subject to human impact - The Skrzyczne range in Southern Poland

NASA Astrophysics Data System (ADS)

Wrońska-Wałach, Dominika; Żelazny, Mirosław; Małek, Stanisław; Krakowian, Katarzyna; Dąbek, Natalia

2018-05-01

Channel heads in mountain catchments are increasingly influenced by human activity. The disturbance of mountain headwater areas in moderate latitudes by the clearing of trees and the associated logging, road building and hydrotechnical constructions contribute to changes in the water cycle and consequently may induce a change in channel head development. Here we examine channel heads in the Beskid Śląski Mts., one of the areas most affected by ecological disaster in the Polish Flysch Carpathians. An ecological disaster associated with the decline of spruce trees in the 1980s and 1990s caused a substantial decrease (of about 50%) in the land area occupied by spruce forest in the Beskid Śląski Mts. As a result, headwater areas were subject to multidirectional changes in the environment. The purpose of this paper is to determine the detailed characteristics of channel heads currently developing in the analyzed headwater areas, as well as to identify independent factors that affect the evolution of channel heads. Geomorphological mapping was conducted in 2012 in the vicinity of springs in the study area. One-way ANOVA was used to determine the significance of differences between mean values calculated for groups identified based on: i) geomorphologic processes (hollows with rock veneer - h, spring niches - sn, gullies - g), ii) location vs. transformation of channel heads (forested areas vs., deforested areas with road constructions). Principal component analysis (PCA) was used to determine the structure and general patterns associated with relationships between the parameters of a channel head and its contribution area, as well as to identify and interpret new (orthogonal) spaces defined using distinct factors. As far as we know, this kind of approach has been never applied before. A total of 80 channel heads surrounding 104 springs were surveyed close to the main ridge in the study area. A total of 14 morphometric parameters were taken into account in this study. The analyzed landforms substantially differ from one another in relation to groups identified based on morphogenetic processes and with respect to time. Multidimensional PCA analysis made it possible to identify three independent, main factors that together explain 81.9% of total variance. It was concluded that the major factor today is human impact, which alters natural geomorphic processes. The second factor is connected with the type of water circulation. The third factor, which explains only 12.7% of variance, is a geologic factor defined in terms of structural integrity. Although our results are region-specific, at least some general conclusions may be drawn. The main general conclusion is that multidimensional human impact may lead to an increase in the fragmentation of mountain headwater areas over the long term.

Looking for a light Higgs boson in the Zγ→ll̄γ channel

DOE PAGES

Gainer, James S.; Keung, Wai-Yee; Low, Ian; ...

2012-08-24

The final state obtained when a Higgs boson decays to a photon and a Z boson has been mostly overlooked in current searches for a light Higgs boson. However, when the Z boson decays leptonically, all final state particles in this channel can be measured, allowing for accurate reconstructions of the Higgs mass and angular correlations. We determine the sensitivity of the Large Hadron Collider (LHC) running at center of mass energies of 8 and 14 TeV to Standard Model (SM) Higgs bosons with masses in the 120–130 GeV range. For the 8 TeV LHC, sensitivity to several times themore » SM cross section times branching ratio may be obtained with 20 inverse femtobarns of integrated luminosity, while for the 14 TeV LHC, the SM rate is probed with about 100 inverse femtobarns of integrated luminosity.« less

Time-dependent mean-field determination of the excitation energy in transfer reactions: Application to the reaction 238U on 12C at 6.14 MeV/nucleon

NASA Astrophysics Data System (ADS)

Scamps, G.; Rodríguez-Tajes, C.; Lacroix, D.; Farget, F.

2017-02-01

The internal excitation of nuclei after multinucleon transfer is estimated by using the time-dependent mean-field theory. Transfer probabilities for each channel as well as the energy loss after reseparation are calculated. By combining these two pieces of information, we show that the excitation energy distribution of the transfer fragments can be obtained separately for the different transfer channels. The method is applied to the reaction involving a 238U beam on a 12C target, which has recently been measured at GANIL. It is shown that the excitation energy calculated with the microscopic theory compares well with the experimental observation, provided that the competition with fusion is properly taken into account. The reliability of the excitation energy is further confirmed by the comparison with the phenomenological heavy-ion phase-space model at higher center-of-mass energies.

The STAR Detector Upgrades and Electromagnetic Probes in Beam Energy Scan Phase II

NASA Astrophysics Data System (ADS)

Yang, Chi

The Beam Energy Scan Phase II at RHIC, BES-II, is scheduled from year 2019 to 2020 and will explore the high baryon density region of the QCD phase diagram with high precision. The program will focus on the interesting energy region determined from the results of BES-I. Some of the key measurements anticipated are the chiral symmetry restoration and QGP thermal radiation in the dilepton and direct photon channels. The measurements will be possible with an order of magnitude better statistics provided by the electron cooling upgrade of RHIC and with the detector upgrades planned to extend STAR experimental reach. The upgrades are: the inner Time Projection Chamber sectors (iTPC), the Event Plane Detector (EPD), and the end-cap Time of Flight (eTOF). We present the BES-II program details and the physics opportunities in the dilepton and direct photon channels enabled by the upgrades.

Energy conservation in ad hoc multimedia networks using traffic-shaping mechanisms

NASA Astrophysics Data System (ADS)

Chandra, Surendar

2003-12-01

In this work, we explore network traffic shaping mechanisms that deliver packets at pre-determined intervals; allowing the network interface to transition to a lower power consuming sleep state. We focus our efforts on commodity devices, IEEE 802.11b ad hoc mode and popular streaming formats. We argue that factors such as the lack of scheduling clock phase synchronization among the participants and scheduling delays introduced by back ground tasks affect the potential energy savings. Increasing the periodic transmission delays to transmit data infrequently can offset some of these effects at the expense of flooding the wireless channel for longer periods of time; potentially increasing the time to acquire the channel for non-multimedia traffic. Buffering mechanisms built into media browsers can mitigate the effects of these added delays from being mis-interpreted as network congestion. We show that practical implementations of such traffic shaping mechanisms can offer significant energy savings.

Image analysis for maintenance of coating quality in nickel electroplating baths--real time control.

PubMed

Vidal, M; Amigo, J M; Bro, R; van den Berg, F; Ostra, M; Ubide, C

2011-11-07

The aim of this paper is to show how it is possible to extract analytical information from images acquired with a flatbed scanner and make use of this information for real time control of a nickel plating process. Digital images of plated steel sheets in a nickel bath are used to follow the process under degradation of specific additives. Dedicated software has been developed for making the obtained results accessible to process operators. This includes obtaining the RGB image, to select the red channel data exclusively, to calculate the histogram of the red channel data and to calculate the mean colour value (MCV) and the standard deviation of the red channel data. MCV is then used by the software to determine the concentration of the additives Supreme Plus Brightner (SPB) and SA-1 (for confidentiality reasons, the chemical contents cannot be further detailed) present in the bath (these two additives degrade and their concentration changes during the process). Finally, the software informs the operator when the bath is generating unsuitable quality plating and suggests the amount of SPB and SA-1 to be added in order to recover the original plating quality. Copyright © 2011 Elsevier B.V. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Quashie, Edwin E.; Saha, Bidhan C.; Correa, Alfredo A.

Here, we present an ab initio study of the electronic stopping power of protons in copper over a wide range of proton velocities v = 0.02–10a.u. where we take into account nonlinear effects. Time-dependent density functional theory coupled with molecular dynamics is used to study electronic excitations produced by energetic protons. A plane-wave pseudopotential scheme is employed to solve the time-dependent Kohn-Sham equations for a moving ion in a periodic crystal. The electronic excitations and the band structure determine the stopping power of the material and alter the interatomic forces for both channeling and off-channeling trajectories. Our off-channeling results aremore » in quantitative agreement with experiments, and at low velocity they unveil a crossover region of superlinear velocity dependence (with a power of ~1.5) in the velocity range v = 0.07–0.3a.u., which we associate to the copper crystalline electronic band structure. The results are rationalized by simple band models connecting two separate regimes. We find that the limit of electronic stopping v → 0 is not as simple as phenomenological models suggest and it is plagued by band-structure effects.« less

Ethanol-mediated relaxation of guinea pig urinary bladder smooth muscle: involvement of BK and L-type Ca2+ channels

PubMed Central

Malysz, John; Afeli, Serge A. Y.; Provence, Aaron

2013-01-01

Mechanisms underlying ethanol (EtOH)-induced detrusor smooth muscle (DSM) relaxation and increased urinary bladder capacity remain unknown. We investigated whether the large conductance Ca2+-activated K+ (BK) channels or L-type voltage-dependent Ca2+ channels (VDCCs), major regulators of DSM excitability and contractility, are targets for EtOH by patch-clamp electrophysiology (conventional and perforated whole cell and excised patch single channel) and isometric tension recordings using guinea pig DSM cells and isolated tissue strips, respectively. EtOH at 0.3% vol/vol (∼50 mM) enhanced whole cell BK currents at +30 mV and above, determined by the selective BK channel blocker paxilline. In excised patches recorded at +40 mV and ∼300 nM intracellular Ca2+ concentration ([Ca2+]), EtOH (0.1–0.3%) affected single BK channels (mean conductance ∼210 pS and blocked by paxilline) by increasing the open channel probability, number of open channel events, and open dwell-time constants. The amplitude of single BK channel currents and unitary conductance were not altered by EtOH. Conversely, at ∼10 μM but not ∼2 μM intracellular [Ca2+], EtOH (0.3%) decreased the single BK channel activity. EtOH (0.3%) affected transient BK currents (TBKCs) by either increasing frequency or decreasing amplitude, depending on the basal level of TBKC frequency. In isolated DSM strips, EtOH (0.1–1%) reduced the amplitude and muscle force of spontaneous phasic contractions. The EtOH-induced DSM relaxation, except at 1%, was attenuated by paxilline. EtOH (1%) inhibited L-type VDCC currents in DSM cells. In summary, we reveal the involvement of BK channels and L-type VDCCs in mediating EtOH-induced urinary bladder relaxation accommodating alcohol-induced diuresis. PMID:24153429

Distributed Channel Allocation and Time Slot Optimization for Green Internet of Things.

PubMed

Ding, Kaiqi; Zhao, Haitao; Hu, Xiping; Wei, Jibo

2017-10-28

In sustainable smart cities, power saving is a severe challenge in the energy-constrained Internet of Things (IoT). Efficient utilization of limited multiple non-overlap channels and time resources is a promising solution to reduce the network interference and save energy consumption. In this paper, we propose a joint channel allocation and time slot optimization solution for IoT. First, we propose a channel ranking algorithm which enables each node to rank its available channels based on the channel properties. Then, we propose a distributed channel allocation algorithm so that each node can choose a proper channel based on the channel ranking and its own residual energy. Finally, the sleeping duration and spectrum sensing duration are jointly optimized to maximize the normalized throughput and satisfy energy consumption constraints simultaneously. Different from the former approaches, our proposed solution requires no central coordination or any global information that each node can operate based on its own local information in a total distributed manner. Also, theoretical analysis and extensive simulations have validated that when applying our solution in the network of IoT: (i) each node can be allocated to a proper channel based on the residual energy to balance the lifetime; (ii) the network can rapidly converge to a collision-free transmission through each node's learning ability in the process of the distributed channel allocation; and (iii) the network throughput is further improved via the dynamic time slot optimization.

Precision of channel catfish catch estimates using hoop nets in larger Oklahoma reservoirs

USGS Publications Warehouse

Stewart, David R.; Long, James M.

2012-01-01

Hoop nets are rapidly becoming the preferred gear type used to sample channel catfish Ictalurus punctatus, and many managers have reported that hoop nets effectively sample channel catfish in small impoundments (<200 ha). However, the utility and precision of this approach in larger impoundments have not been tested. We sought to determine how the number of tandem hoop net series affected the catch of channel catfish and the time involved in using 16 tandem hoop net series in larger impoundments (>200 ha). Hoop net series were fished once, set for 3 d; then we used Monte Carlo bootstrapping techniques that allowed us to estimate the number of net series required to achieve two levels of precision (relative standard errors [RSEs] of 15 and 25) at two levels of confidence (80% and 95%). Sixteen hoop net series were effective at obtaining an RSE of 25 with 80% and 95% confidence in all but one reservoir. Achieving an RSE of 15 was often less effective and required 18-96 hoop net series given the desired level of confidence. We estimated that an hour was needed, on average, to deploy and retrieve three hoop net series, which meant that 16 hoop net series per reservoir could be "set" and "retrieved" within a day, respectively. The estimated number of net series to achieve an RSE of 25 or 15 was positively associated with the coefficient of variation (CV) of the sample but not with reservoir surface area or relative abundance. Our results suggest that hoop nets are capable of providing reasonably precise estimates of channel catfish relative abundance and that the relationship with the CV of the sample reported herein can be used to determine the sampling effort for a desired level of precision.

Comparison of multichannel wide dynamic range compression and ChannelFree processing in open canal hearing instruments.

PubMed

Plyler, Patrick N; Reber, Monika Bertges; Kovach, Amanda; Galloway, Elisabeth; Humphrey, Elizabeth

2013-02-01

Multichannel wide dynamic range compression (WDRC) and ChannelFree processing have similar goals yet differ significantly in terms of signal processing. Multichannel WDRC devices divide the input signal into separate frequency bands; a separate level is determined within each frequency band; and compression in each band is based on the level within each band. ChannelFree processing detects the wideband level, and gain adjustments are based on the wideband signal level and adjusted up to 20,000 times per second. Although both signal processing strategies are currently available in hearing aids, it is unclear if differences in these signal processing strategies affect the performance and/or preference of the end user. The purpose of the research was to determine the effects of multichannel wide dynamic range compression and ChannelFree processing on performance and/or preference of listeners using open-canal hearing instruments. An experimental study in which subjects were exposed to a repeated measures design was utilized. Fourteen adult listeners with mild sloping to moderately severe sensorineural hearing loss participated (mean age 67 yr). Participants completed two 5 wk trial periods for each signal processing strategy. Probe microphone, behavioral and subjective measures were conducted unaided and aided at the end of each trial period. Behavioral and subjective results for both signal processing strategies were significantly better than unaided results; however, behavioral and subjective results were not significantly different between the signal processing strategies. Multichannel WDRC and ChannelFree processing are both effective signal processing strategies that provide significant benefit for hearing instrument users. Overall preference between the strategies may be related to the degree of hearing loss of the user, high-frequency in-situ levels, and/or acceptance of background noise. American Academy of Audiology.

The calcium-activated potassium channel KCa3.1 plays a central role in the chemotactic response of mammalian neutrophils.

PubMed

Henríquez, C; Riquelme, T T; Vera, D; Julio-Kalajzić, F; Ehrenfeld, P; Melvin, J E; Figueroa, C D; Sarmiento, J; Flores, C A

2016-01-01

Neutrophils are the first cells to arrive at sites of injury. Nevertheless, many inflammatory diseases are characterized by an uncontrolled infiltration and action of these cells. Cell migration depends on volume changes that are governed by ion channel activity, but potassium channels in neutrophil have not been clearly identified. We aim to test whether KCa3.1 participates in neutrophil migration and other relevant functions of the cell. Cytometer and confocal measurements to determine changes in cell volume were used. Cells isolated from human, mouse and horse were tested for KCa3.1-dependent chemotaxis. Chemokinetics, calcium handling and release of reactive oxygen species were measured to determine the role of KCa3.1 in those processes. A mouse model was used to test for neutrophil recruitment after acute lung injury in vivo. We show for the first time that KCa3.1 is expressed in mammalian neutrophils. When the channel is inhibited by a pharmacological blocker or by genetic silencing, it profoundly affects cell volume regulation, and chemotactic and chemokinetic properties of the cells. We also demonstrated that pharmacological inhibition of KCa3.1 did not affect calcium entry or reactive oxygen species production in neutrophils. Using a mouse model of acute lung injury, we observed that Kca3.1(-/-) mice are significantly less effective at recruiting neutrophils into the site of inflammation. These results demonstrate that KCa3.1 channels are key actors in the migration capacity of neutrophils, and its inhibition did not affect other relevant cellular functions. © 2015 Scandinavian Physiological Society. Published by John Wiley & Sons Ltd.

Channeling, channel density and mass recovery in aquifer transport, with application to the MADE experiment

NASA Astrophysics Data System (ADS)

Fiori, A.

2014-12-01

Channeling effects in heterogeneous formations are studied through a new quantity denoted as channel density a(x,t). Focusing on advection only, a(x,t) is defined as the relative number of streamtubes (or channels) containing solute between x and x + dx at a given time t, regardless of the mass that they carry. The channel density generally differs from the widely employed longitudinal mass distribution m(x,t), and their difference increases with time and the degree of heterogeneity. The difference between a and m reflects the nonuniformity of mass distribution relative to the plume geometry. In particular, the "fast" channels typically carry a larger fraction of mass than their share in their relative volume, which in turn can be rather small. Detecting such channels by a network of monitoring wells may be a challenging task, which might explain the poor solute recovery of some field experiments at increasing times. After application of the proposed concepts to the simple case of stratified formations, we model the channel density and mass distribution pertaining to the MADE experiment, which exhibited poor mass recovery at large times. The results presented in this study emphasize the possible channeling effects at MADE and the general difficulty in sampling the leading edge of the plume, which in turn may contain a significant fraction of the plume mass.

Channel noise-induced temporal coherence transitions and synchronization transitions in adaptive neuronal networks with time delay

NASA Astrophysics Data System (ADS)

Gong, Yubing; Xie, Huijuan

2017-09-01

Using spike-timing-dependent plasticity (STDP), we study the effect of channel noise on temporal coherence and synchronization of adaptive scale-free Hodgkin-Huxley neuronal networks with time delay. It is found that the spiking regularity and spatial synchronization of the neurons intermittently increase and decrease as channel noise intensity is varied, exhibiting transitions of temporal coherence and synchronization. Moreover, this phenomenon depends on time delay, STDP, and network average degree. As time delay increases, the phenomenon is weakened, however, there are optimal STDP and network average degree by which the phenomenon becomes strongest. These results show that channel noise can intermittently enhance the temporal coherence and synchronization of the delayed adaptive neuronal networks. These findings provide a new insight into channel noise for the information processing and transmission in neural systems.

Inactivation gating determines nicotine blockade of human HERG channels.

PubMed

Wang, H Z; Shi, H; Liao, S J; Wang, Z

1999-09-01

We have previously found that nicotine blocked multiple K+ currents, including the rapid component of delayed rectifier K+ currents (IKr), by interacting directly with the channels. To shed some light on the mechanisms of interaction between nicotine and channels, we performed detailed analysis on the human ether-à-go-go-related gene (HERG) channels, which are believed to be equivalent to the native I(Kr) when expressed in Xenopus oocytes. Nicotine suppressed the HERG channels in a concentration-dependent manner with greater potency with voltage protocols, which favor channel inactivation. Nicotine caused dramatic shifts of the voltage-dependent inactivation curve to more negative potentials and accelerated the inactivation process. Conversely, maneuvers that weakened the channel inactivation gating considerably relieved the blockade. Elevating the extracellular K+ concentration from 5 to 20 mM increased the nicotine concentration (by approximately 100-fold) needed to achieve the same degree of inhibition. Moreover, nicotine lost its ability to block the HERG channels when a single mutation was introduced to a residue located after transmembrane domain 6 (S631A) to remove the rapid channel inactivation. Our data suggest that the inactivation gating determines nicotine blockade of the HERG channels.

Structure-based assessment of disease-related mutations in human voltage-gated sodium channels.

PubMed

Huang, Weiyun; Liu, Minhao; Yan, S Frank; Yan, Nieng

2017-06-01

Voltage-gated sodium (Na v ) channels are essential for the rapid upstroke of action potentials and the propagation of electrical signals in nerves and muscles. Defects of Na v channels are associated with a variety of channelopathies. More than 1000 disease-related mutations have been identified in Na v channels, with Na v 1.1 and Na v 1.5 each harboring more than 400 mutations. Na v channels represent major targets for a wide array of neurotoxins and drugs. Atomic structures of Na v channels are required to understand their function and disease mechanisms. The recently determined atomic structure of the rabbit voltage-gated calcium (Ca v ) channel Ca v 1.1 provides a template for homology-based structural modeling of the evolutionarily related Na v channels. In this Resource article, we summarized all the reported disease-related mutations in human Na v channels, generated a homologous model of human Na v 1.7, and structurally mapped disease-associated mutations. Before the determination of structures of human Na v channels, the analysis presented here serves as the base framework for mechanistic investigation of Na v channelopathies and for potential structure-based drug discovery.

Domain model for Ca2(+)-inactivation of Ca2+ channels at low channel density.

PubMed Central

Sherman, A; Keizer, J; Rinzel, J

1990-01-01

The "shell" model for Ca2(+)-inactivation of Ca2+ channels is based on the accumulation of Ca2+ in a macroscopic shell beneath the plasma membrane. The shell is filled by Ca2+ entering through open channels, with the elevated Ca2+ concentration inactivating both open and closed channels at a rate determined by how fast the shell is filled. In cells with low channel density, the high concentration Ca2+ "shell" degenerates into a collection of nonoverlapping "domains" localized near open channels. These domains form rapidly when channels open and disappear rapidly when channels close. We use this idea to develop a "domain" model for Ca2(+)-inactivation of Ca2+ channels. In this model the kinetics of formation of an inactivated state resulting from Ca2+ binding to open channels determines the inactivation rate, a mechanism identical with that which explains single-channel recordings on rabbit-mesenteric artery Ca2+ channels (Huang Y., J. M. Quayle, J. F. Worley, N. B. Standen, and M. T. Nelson. 1989. Biophys. J. 56:1023-1028). We show that the model correctly predicts five important features of the whole-cell Ca2(+)-inactivation for mouse pancreatic beta-cells (Plants, T. D. 1988. J. Physiol. 404:731-747) and that Ca2(+)-inactivation has only minor effects on the bursting electrical activity of these cells. PMID:2174274

Using King Vision video laryngoscope with a channeled blade prolongs time for tracheal intubation in different training levels, compared to non-channeled blade.

PubMed

Kriege, Marc; Alflen, Christian; Noppens, Ruediger R

2017-01-01

It is generally accepted that using a video laryngoscope is associated with an improved visualization of the glottis. However, correctly placing the endotracheal tube might be challenging. Channeled video laryngoscopic blades have an endotracheal tube already pre-loaded, allowing to advance the tube once the glottis is visualized. We hypothesized that use of a channel blade with pre-loaded endotracheal tube results in a faster intubation, compared to a curved Macintosh blade video laryngoscope. After ethical approval and informed consent, patients were randomized to receive endotracheal Intubation with either the King Vision® video laryngoscope with curved blade (control) or channeled blade (channeled). Success rate, evaluation of the glottis view (percentage of glottic opening (POGO), Cormack&Lehane (C&L)) and intubating time were evaluated. Over a two-month period, a total of 46 patients (control n = 23; channeled n = 23) were examined. The first attempt success rates were comparable between groups (control 100% (23/23) vs. channeled 96% (22/23); p = 0.31). Overall intubation time was significantly shorter with control (median 40 sec; IQR [24-58]), compared to channeled (59 sec [40-74]; p = 0.03). There were no differences in glottis visualization between groups. Compared with the King Vision channeled blade, time for tracheal intubation was shorter with the control group using a non-channeled blade. First attempt success and visualization of the glottis were comparable. These data do not support the hypothesis that a channeled blade is superior to a curved video laryngoscopic blade without tube guidance. ClinicalTrials.gov NCT02344030.

Communication: Determining the structure of the N{sub 2}Ar van der Waals complex with laser-based channel-selected Coulomb explosion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Chengyin, E-mail: cywu@pku.edu.cn; Liu, Yunquan; Gong, Qihuang

2014-04-14

We experimentally reconstructed the structure of the N{sub 2}Ar van der Waals complex with the technique of laser-based channel-selected Coulomb explosion imaging. The internuclear distance between the N{sub 2} center of mass and the Ar atom, i.e., the length of the van der Waals bond, was determined to be 3.88 Å from the two-body explosion channels. The angle between the van der Waals bond and the N{sub 2} principal axis was determined to be 90° from the three-body explosion channels. The reconstructed structure was contrasted with our high level ab initio calculations. The agreement demonstrated the potential application of laser-basedmore » Coulomb explosion in imaging transient molecular structure, particularly for floppy van der Waals complexes, whose structures remain difficult to be determined by conventional spectroscopic methods.« less

Estimation of sea surface temperature from remote sensing in the 11-13 micron window region

NASA Technical Reports Server (NTRS)

Prabhakara, C.; Dalu, G.; Kunde, V. G.

1974-01-01

The Nimbus 3 and 4 IRIS spectral data in the 11-13 micron water vapor window region are analyzed to determine the sea surface temperature (SST). The high spectral resolution data of IRIS are averaged over approximately 1 micron wide intervals to simulate channels of a radiometer to measure the SST. Three channels are utilized to measure SST over cloud-free oceans. However, two of these channels are sufficient in routine SST determination. The differential absorption properties of water vapor in the two channels enable one to determine the water vapor absorption correction without detailed knowledge of the vertical profiles of temperature and water vapor. The feasibility of determining the SST is demonstrated globally with Nimbus 3 data where cloud-free areas can be selected with the help of albedo data from the MRIR experiment on board the same satellite.

Cardiac transient outward potassium current: a pulse chemistry model of frequency-dependent properties.

PubMed

Liu, L; Krinsky, V I; Grant, A O; Starmer, C F

1996-01-01

Recent voltage-clamp studies of isolated myocytes have demonstrated widespread occurrence of a transient outward current (I(to)) carried by potassium ions. In the canine ventricle, this current is well developed in epicardial cells but not in endocardial cells. The resultant spatial dispersion of refractoriness is potentially proarrhythmic and may be amplified by channel blockade. The inactivation and recovery time constants of this channel are in excess of several hundred milliseconds, and consequently channel availability is frequency dependent at physiological stimulation rates. When the time constants associated with transitions between different channel conformations are rapid relative to drug binding kinetics, the interactions between drugs and an ion channel can be approximated by a sequence of first-order reactions, in which binding occurs in pulses in response to pulse train stimulation (pulse chemistry). When channel conformation transition time constants do not meet this constraint, analytical characterizations of the drug-channel interaction must then be modified to reflect the channel time-dependent properties. Here we report that the rate and steady-state amount of frequency-dependent inactivation of I(to) are consistent with a generalization of the channel blockade model: channel availability is reduced in a pulsatile exponential pattern as the stimulation frequency is increased, and the rate of reduction is a linear function of the pulse train depolarizing and recovery intervals. I(to) was reduced in the presence of quinidine. After accounting for the use-dependent availability of I(to) channels, we found little evidence of an additional use-dependent component of block after exposure to quinidine, suggesting that quinidine reacts with both open and closed I(to) channels as though the binding site is continuously accessible. The model provides a useful tool for assessing drug-channel interactions when the reaction cannot be continuously monitored.

Quantum biological channel modeling and capacity calculation.

PubMed

Djordjevic, Ivan B

2012-12-10

Quantum mechanics has an important role in photosynthesis, magnetoreception, and evolution. There were many attempts in an effort to explain the structure of genetic code and transfer of information from DNA to protein by using the concepts of quantum mechanics. The existing biological quantum channel models are not sufficiently general to incorporate all relevant contributions responsible for imperfect protein synthesis. Moreover, the problem of determination of quantum biological channel capacity is still an open problem. To solve these problems, we construct the operator-sum representation of biological channel based on codon basekets (basis vectors), and determine the quantum channel model suitable for study of the quantum biological channel capacity and beyond. The transcription process, DNA point mutations, insertions, deletions, and translation are interpreted as the quantum noise processes. The various types of quantum errors are classified into several broad categories: (i) storage errors that occur in DNA itself as it represents an imperfect storage of genetic information, (ii) replication errors introduced during DNA replication process, (iii) transcription errors introduced during DNA to mRNA transcription, and (iv) translation errors introduced during the translation process. By using this model, we determine the biological quantum channel capacity and compare it against corresponding classical biological channel capacity. We demonstrate that the quantum biological channel capacity is higher than the classical one, for a coherent quantum channel model, suggesting that quantum effects have an important role in biological systems. The proposed model is of crucial importance towards future study of quantum DNA error correction, developing quantum mechanical model of aging, developing the quantum mechanical models for tumors/cancer, and study of intracellular dynamics in general.

Channel Measurements for Automatic Vehicle Monitoring Systems

DOT National Transportation Integrated Search

1974-03-01

Co-channel and adjacent channel electromagnetic interference measurements were conducted on the Sierra Research Corp. and the Chicago Transit Authority automatic vehicle monitoring systems. These measurements were made to determine if the automatic v...

RD Optimized, Adaptive, Error-Resilient Transmission of MJPEG2000-Coded Video over Multiple Time-Varying Channels

NASA Astrophysics Data System (ADS)

Bezan, Scott; Shirani, Shahram

2006-12-01

To reliably transmit video over error-prone channels, the data should be both source and channel coded. When multiple channels are available for transmission, the problem extends to that of partitioning the data across these channels. The condition of transmission channels, however, varies with time. Therefore, the error protection added to the data at one instant of time may not be optimal at the next. In this paper, we propose a method for adaptively adding error correction code in a rate-distortion (RD) optimized manner using rate-compatible punctured convolutional codes to an MJPEG2000 constant rate-coded frame of video. We perform an analysis on the rate-distortion tradeoff of each of the coding units (tiles and packets) in each frame and adapt the error correction code assigned to the unit taking into account the bandwidth and error characteristics of the channels. This method is applied to both single and multiple time-varying channel environments. We compare our method with a basic protection method in which data is either not transmitted, transmitted with no protection, or transmitted with a fixed amount of protection. Simulation results show promising performance for our proposed method.

Ca2+ release by inositol-trisphosphorothioate in isolated triads of rabbit skeletal muscle.

PubMed Central

Valdivia, C; Valdivia, H H; Potter, B V; Coronado, R

1990-01-01

The effectiveness of the nonmetabolizable second messenger analogue DL-myo-inositol 1,4,5-trisphosphorothioate (IPS3) described by Cooke, A. M., R. Gigg, and B. V. L. Potter, (1987b. Jour. Chem. Soc. Chem. Commun. 1525-1526.) was examined in triads purified from rabbit skeletal muscle. A Ca2+ electrode uptake-release assay was used to determine the size and sensitivity of the IPS3-releasable pool of Ca2+ in isolated triads. Uptake was initiated by 1 mM MgATP, pCa 5.8, pH 7.5 Release was initiated when the free Ca2+ had lowered to pCa approximately 7. We found that 5-25 microM myo-inositol 1,4,5-trisphosphate (IP3), and separately IPS3, consistently released 5-20% of the Ca2+ pool actively loaded into triads. Single channel recording was used to determine if ryanodine receptor Ca2+ release channels were affected by IPS3 at the same myoplasmic Ca2+ and IPS3 concentrations. Open probability of ryanodine receptor Ca2+ release channels was monitored in triads fused to bilayers over long periods (200 s) in the absence and following addition of 30 microM IPS3 to the same channel. At myoplasmic pCa approximately 7, IPS3 had no effect in the absence of MgATP (Po = 0.0094 +/- 0.001 in control and Po = 0.01 +/- 0.006 after IPS3) and slightly increased activity in the presence of 1 mM MgATP (Po = 0.024 +/- 0.03 in control and Po = 0.05 +/- 0.03 after IPS3). Equally small effects were observed at higher myoplasmic Ca2+. The onset of channel activation by IPS3 or IP3 was slow, on the time scale 20-60 s. We suggest that in isolated triads of rabbit skeletal muscle, IP3-induced release of stored Ca2+ is probably not mediated by the opening of Ca2+ release channels. PMID:2168221

Changes in habitat availability for outmigrating juvenile salmon (Oncorhychus spp.) following estuary restoration

USGS Publications Warehouse

Ellings, Christopher S.; Davis, Melanie; Grossman, Eric E.; Hodgson, Sayre; Turner, Kelley L.; Woo PR, Isa; Nakai, Glynnis; Takekawa, Jean E.; Takekawa, John Y.

2016-01-01

The restoration of the Nisqually River Delta (Washington, U.S.A.) represents one of the largest efforts toward reestablishing the ecosystem function and resilience of modified habitat in the Puget Sound, particularly for anadromous salmonid species. The opportunity for outmigrating salmon to access and benefit from the expansion of available tidal habitat can be quantified by several physical attributes, which are related to the ecological and physiological responses of juvenile salmon. We monitored a variety of physical parameters to measure changes in opportunity potential from historic, pre-restoration, and post-restoration habitat conditions at several sites across the delta. These parameters included channel morphology, water quality, tidal elevation, and landscape connectivity. We conducted fish catch surveys across the delta to determine if salmon was utilizing restored estuary habitat. Overall major channel area increased 42% and major channel length increased 131% from pre- to post-restoration conditions. Furthermore, the results of our tidal inundation model indicated that major channels were accessible up to 75% of the time, as opposed to 30% pre-restoration. Outmigrating salmon utilized this newly accessible habitat as quickly as 1 year post-restoration. The presence of salmon in restored tidal channels confirmed rapid post-restoration increases in opportunity potential on the delta despite habitat quality differences between restored and reference sites.

Physiological and content considerations for a second low frequency channel for bass management, subwoofers, and low frequency enhancement (LFE)

NASA Astrophysics Data System (ADS)

Miller, Robert E. (Robin)

2005-04-01

Perception of very low frequencies (VLF) below 125 Hz reproduced by large woofers and subwoofers (SW), encompassing 3 octaves of the 10 regarded as audible, has physiological and content aspects. Large room acoustics and vibrato add VLF fluctuations, modulating audible carrier frequencies to >1 Hz. By convention, sounds below 90 Hz produce no interaural cues useful for spatial perception or localization, therefore bass management redirects the VLF range from main channels to a single (monaural) subwoofer channel, even if to more than one subwoofer. Yet subjects claim they hear a difference between a single subwoofer channel and two (stereo bass). If recordings contain spatial VLF content, is it possible physiologically to perceive interaural time/phase difference (ITD/IPD) between 16 and 125 Hz? To what extent does this perception have a lifelike quality; to what extent is it localization? If a first approximation of localization, would binaural SWs allow a higher crossover frequency (smaller satellite speakers)? Reported research supports the Jeffress model of ITD determination in brain structures, and extending the accepted lower frequency limit of IPD. Meanwhile, uncorrelated very low frequencies exist in all tested multi-channel music and movie content. The audibility, recording, and reproduction of uncorrelated VLF are explored in theory and experiments.

CLAG3 Self-Associates in Malaria Parasites and Quantitatively Determines Nutrient Uptake Channels at the Host Membrane.

PubMed

Gupta, Ankit; Balabaskaran-Nina, Praveen; Nguitragool, Wang; Saggu, Gagandeep S; Schureck, Marc A; Desai, Sanjay A

2018-05-08

Malaria parasites increase host erythrocyte permeability to ions and nutrients via a broad-selectivity channel known as the plasmodial surface anion channel (PSAC), linked to parasite-encoded CLAG3 and two associated proteins. These proteins lack the multiple transmembrane domains typically present in channel-forming proteins, raising doubts about their precise roles. Using the virulent human Plasmodium falciparum parasite, we report that CLAG3 undergoes self-association and that this protein's expression determines channel phenotype quantitatively. We overcame epigenetic silencing of clag3 paralogs and engineered parasites that express two CLAG3 isoforms simultaneously. Stoichiometric expression of these isoforms yielded intermediate channel phenotypes, in agreement with observed trafficking of both proteins to the host membrane. Coimmunoprecipitation and surface labeling revealed formation of CLAG3 oligomers. In vitro selections applied to these transfectant lines yielded distinct mutants with correlated changes in channel activity. These findings support involvement of the identified oligomers in PSAC formation and parasite nutrient acquisition. IMPORTANCE Malaria parasites are globally important pathogens that evade host immunity by replicating within circulating erythrocytes. To facilitate intracellular growth, these parasites increase erythrocyte nutrient uptake through an unusual ion channel. The parasite CLAG3 protein is a key determinant of this channel, but its lack of homology to known ion channels has raised questions about possible mechanisms. Using a new method that allows simultaneous expression of two different CLAG3 proteins, we identify self-association of CLAG3. The two expressed isoforms faithfully traffic to and insert in the host membrane, while remaining associated with two unrelated parasite proteins. Both the channel phenotypes and molecular changes produced upon selections with a highly specific channel inhibitor are consistent with a multiprotein complex that forms the nutrient pore. These studies support direct involvement of the CLAG3 protein in channel formation and are relevant to antimalarial drug discovery projects targeting parasite nutrient acquisition.

A Hybrid OFDM-TDM Architecture with Decentralized Dynamic Bandwidth Allocation for PONs

PubMed Central

Cevik, Taner

2013-01-01

One of the major challenges of passive optical networks is to achieve a fair arbitration mechanism that will prevent possible collisions from occurring at the upstream channel when multiple users attempt to access the common fiber at the same time. Therefore, in this study we mainly focus on fair bandwidth allocation among users, and present a hybrid Orthogonal Frequency Division Multiplexed/Time Division Multiplexed architecture with a dynamic bandwidth allocation scheme that provides satisfying service qualities to the users depending on their varying bandwidth requirements. Unnecessary delays in centralized schemes occurring during bandwidth assignment stage are eliminated by utilizing a decentralized approach. Instead of sending bandwidth demands to the optical line terminal (OLT) which is the only competent authority, each optical network unit (ONU) runs the same bandwidth demand determination algorithm. ONUs inform each other via signaling channel about the status of their queues. This information is fed to the bandwidth determination algorithm which is run by each ONU in a distributed manner. Furthermore, Light Load Penalty, which is a phenomenon in optical communications, is mitigated by limiting the amount of bandwidth that an ONU can demand. PMID:24194684

Time domain passivity controller for 4-channel time-delay bilateral teleoperation.

PubMed

Rebelo, Joao; Schiele, Andre

2015-01-01

This paper presents an extension of the time-domain passivity control approach to a four-channel bilateral controller under the effects of time delays. Time-domain passivity control has been used successfully to stabilize teleoperation systems with position-force and position-position controllers; however, the performance with such control architectures is sub-optimal both with and without time delays. This work extends the network representation of the time-domain passivity controller to the four-channel architecture, which provides perfect transparency to the user without time delay. The proposed architecture is based on modelling the controllers as dependent voltage sources and using only series passivity controllers. The obtained results are shown on a one degree-of-freedom setup and illustrate the stabilization behaviour of the proposed controller when time delay is present in the communication channel.

Multi-channel lock-in amplifier assisted femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectroscopy with efficient rejection of superfluorescence background.

PubMed

Mao, Pengcheng; Wang, Zhuan; Dang, Wei; Weng, Yuxiang

2015-12-01

Superfluorescence appears as an intense background in femtosecond time-resolved fluorescence noncollinear optical parametric amplification spectroscopy, which severely interferes the reliable acquisition of the time-resolved fluorescence spectra especially for an optically dilute sample. Superfluorescence originates from the optical amplification of the vacuum quantum noise, which would be inevitably concomitant with the amplified fluorescence photons during the optical parametric amplification process. Here, we report the development of a femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectrometer assisted with a 32-channel lock-in amplifier for efficient rejection of the superfluorescence background. With this spectrometer, the superfluorescence background signal can be significantly reduced to 1/300-1/100 when the seeding fluorescence is modulated. An integrated 32-bundle optical fiber is used as a linear array light receiver connected to 32 photodiodes in one-to-one mode, and the photodiodes are further coupled to a home-built 32-channel synchronous digital lock-in amplifier. As an implementation, time-resolved fluorescence spectra for rhodamine 6G dye in ethanol solution at an optically dilute concentration of 10(-5)M excited at 510 nm with an excitation intensity of 70 nJ/pulse have been successfully recorded, and the detection limit at a pump intensity of 60 μJ/pulse was determined as about 13 photons/pulse. Concentration dependent redshift starting at 30 ps after the excitation in time-resolved fluorescence spectra of this dye has also been observed, which can be attributed to the formation of the excimer at a higher concentration, while the blueshift in the earlier time within 10 ps is attributed to the solvation process.

Multi-channel lock-in amplifier assisted femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectroscopy with efficient rejection of superfluorescence background

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mao, Pengcheng; Wang, Zhuan; Dang, Wei

Superfluorescence appears as an intense background in femtosecond time-resolved fluorescence noncollinear optical parametric amplification spectroscopy, which severely interferes the reliable acquisition of the time-resolved fluorescence spectra especially for an optically dilute sample. Superfluorescence originates from the optical amplification of the vacuum quantum noise, which would be inevitably concomitant with the amplified fluorescence photons during the optical parametric amplification process. Here, we report the development of a femtosecond time-resolved fluorescence non-collinear optical parametric amplification spectrometer assisted with a 32-channel lock-in amplifier for efficient rejection of the superfluorescence background. With this spectrometer, the superfluorescence background signal can be significantly reduced to 1/300–1/100more » when the seeding fluorescence is modulated. An integrated 32-bundle optical fiber is used as a linear array light receiver connected to 32 photodiodes in one-to-one mode, and the photodiodes are further coupled to a home-built 32-channel synchronous digital lock-in amplifier. As an implementation, time-resolved fluorescence spectra for rhodamine 6G dye in ethanol solution at an optically dilute concentration of 10{sup −5}M excited at 510 nm with an excitation intensity of 70 nJ/pulse have been successfully recorded, and the detection limit at a pump intensity of 60 μJ/pulse was determined as about 13 photons/pulse. Concentration dependent redshift starting at 30 ps after the excitation in time-resolved fluorescence spectra of this dye has also been observed, which can be attributed to the formation of the excimer at a higher concentration, while the blueshift in the earlier time within 10 ps is attributed to the solvation process.« less

Hydrographic charting from Landsat satellite - A comparison with aircraft imagery

NASA Technical Reports Server (NTRS)

Middleton, E. M.; Barker, J. L.

1976-01-01

The relative capabilities of two remote-sensing systems in measuring depth and, consequently, bottom contours in sandy-bottomed and sediment-laden coastal waters were determined quantitatively. The Multispectral Scanner (MSS), orbited on the Landsat-2 satellite, and the Ocean Color Scanner (OCS), flown on U-2 aircraft, were used for this evaluation. Analysis of imagery taken simultaneously indicates a potential for hydrographic charting of marine coastal and shallow shelf areas, even when water turbidity is a factor. Several of the eight optical channels examined on the OCS were found to be sensitive to depth or depth-related information. The greatest sensitivity was in OCS-4 (0.544 plus or minus 0.012 micron) from which contours corresponding to depths up to 12 m were determined. The sharpness of these contours and their spatial stability through time suggests that upwelling radiance is a measure of bottom reflectance and not of water turbidity. The two visible channels on Landsat's MSS were less sensitive in the discrimination of contours, with depths up to 8 m in the high-gain mode (3 X) determined in MSS-4 (0.5 to 0.6 micron).

Hydrographic charting from LANDSAT Satellite: A comparison with aircraft imagery

NASA Technical Reports Server (NTRS)

Middleton, E. M.; Barker, J. L.

1976-01-01

The relative capabilities of two remote-sensing systems in measuring depth and, consequently, bottom contours in sandy-bottomed and sediment-laden coastal waters were determined quantitatively. The multispectral scanner (MSS), orbited on the LANDSAT-2 Satellite, and the ocean color scanner (OCS), flown on U-2 aircraft, were used. Analysis of imagery taken simultaneously indicates a potential for hydrographic charting of marine coastal and shallow shelf areas, even when water turbidity is a factor. Several of the eight optical channels examined on the OCS were found to be sensitive to depth or depth-related information. The greatest sensitivity was in OCS-4(0.544 + or - 0.012 microns) from which contours corresponding to depths up to 12m were determined. The sharpness of these contours and their spatial stability through time suggests that upwelling radiance is a measure of bottom reflectance and not of water turbidity. The two visible channels on LANDSAT's MSS were less sensitive in the discrimination of contours, with depths up to 8m in the high-gain mode (3x) determined in MSS-4(0.5 to 0.6 microns).

The CaV2.3 R-Type Voltage-Gated Ca2+ Channel in Mouse Sleep Architecture

PubMed Central

Siwek, Magdalena Elisabeth; Müller, Ralf; Henseler, Christina; Broich, Karl; Papazoglou, Anna; Weiergräber, Marco

2014-01-01

Study Objectives: Voltage-gated Ca2+ channels (VGCCs) are key elements in mediating thalamocortical rhythmicity. Low-voltage activated (LVA) CaV 3 T-type Ca2+ channels have been related to thalamic rebound burst firing and to generation of non-rapid eye movement (NREM) sleep. High-voltage activated (HVA) CaV 1 L-type Ca2+ channels, on the opposite, favor the tonic mode of action associated with higher levels of vigilance. However, the role of the HVA Non-L-type CaV2.3 Ca2+ channels, which are predominantly expressed in the reticular thalamic nucleus (RTN), still remains unclear. Recently, CaV2.3−/− mice were reported to exhibit altered spike-wave discharge (SWD)/absence seizure susceptibility supported by the observation that CaV2.3 mediated Ca2+ influx into RTN neurons can trigger small-conductance Ca2+-activated K+-channel type 2 (SK2) currents capable of maintaining thalamic burst activity. Based on these studies we investigated the role of CaV2.3 R-type Ca2+ channels in rodent sleep. Methods: The role of CaV2.3 Ca2+ channels was analyzed in CaV2.3−/− mice and controls in both spontaneous and artificial urethane-induced sleep, using implantable video-EEG radiotelemetry. Data were analyzed for alterations in sleep architecture using sleep staging software and time-frequency analysis. Results: CaV2.3 deficient mice exhibited reduced wake duration and increased slow-wave sleep (SWS). Whereas mean sleep stage durations remained unchanged, the total number of SWS epochs was increased in CaV2.3−/− mice. Additional changes were observed for sleep stage transitions and EEG amplitudes. Furthermore, urethane-induced SWS mimicked spontaneous sleep results obtained from CaV2.3 deficient mice. Quantitative Real-time PCR did not reveal changes in thalamic CaV3 T-type Ca2+ channel expression. The detailed mechanisms of SWS increase in CaV2.3−/− mice remain to be determined. Conclusions: Low-voltage activated CaV2.3 R-type Ca2+ channels in the thalamocortical loop and extra-thalamocortical circuitries substantially regulate rodent sleep architecture thus representing a novel potential target for pharmacological treatment of sleep disorders in the future. Citation: Siwek ME, Müller R, Henseler C, Broich K, Papazoglou A, Weiergräber M. The CaV2.3 R-type voltage-gated Ca2+ channel in mouse sleep architecture. SLEEP 2014;37(5):881-892. PMID:24790266

Studies to determine the effectiveness of longitudinal channelizing devices in work zones.

DOT National Transportation Integrated Search

2011-01-01

This report describes the methodology and results of analyses performed to determine whether the following longitudinal : channelizing device (LCD) applications improve the traffic safety and operations of work zones relative to the use of standard :...

Multi-Channel Optical Coherence Elastography Using Relative and Absolute Shear-Wave Time of Flight

PubMed Central

Elyas, Eli; Grimwood, Alex; Erler, Janine T.; Robinson, Simon P.; Cox, Thomas R.; Woods, Daniel; Clowes, Peter; De Luca, Ramona; Marinozzi, Franco; Fromageau, Jérémie; Bamber, Jeffrey C.

2017-01-01

Elastography, the imaging of elastic properties of soft tissues, is well developed for macroscopic clinical imaging of soft tissues and can provide useful information about various pathological processes which is complementary to that provided by the original modality. Scaling down of this technique should ply the field of cellular biology with valuable information with regard to elastic properties of cells and their environment. This paper evaluates the potential to develop such a tool by modifying a commercial optical coherence tomography (OCT) device to measure the speed of shear waves propagating in a three-dimensional (3D) medium. A needle, embedded in the gel, was excited to vibrate along its long axis and the displacement as a function of time and distance from the needle associated with the resulting shear waves was detected using four M-mode images acquired simultaneously using a commercial four-channel swept-source OCT system. Shear-wave time of arrival (TOA) was detected by tracking the axial OCT-speckle motion using cross-correlation methods. Shear-wave speed was then calculated from inter-channel differences of TOA for a single burst (the relative TOA method) and compared with the shear-wave speed determined from positional differences of TOA for a single channel over multiple bursts (the absolute TOA method). For homogeneous gels the relative method provided shear-wave speed with acceptable precision and accuracy when judged against the expected linear dependence of shear modulus on gelatine concentration (R2 = 0.95) and ultimate resolution capabilities limited by 184μm inter-channel distance. This overall approach shows promise for its eventual provision as a research tool in cancer cell biology. Further work is required to optimize parameters such as vibration frequency, burst length and amplitude, and to assess the lateral and axial resolutions of this type of device as well as to create 3D elastograms. PMID:28107368

HAI, a new airborne, absolute, twin dual-channel, multi-phase TDLAS-hygrometer: background, design, setup, and first flight data

NASA Astrophysics Data System (ADS)

Buchholz, Bernhard; Afchine, Armin; Klein, Alexander; Schiller, Cornelius; Krämer, Martina; Ebert, Volker

2017-01-01

The novel Hygrometer for Atmospheric Investigation (HAI) realizes a unique concept for simultaneous gas-phase and total (gas-phase + evaporated cloud particles) water measurements. It has been developed and successfully deployed for the first time on the German HALO research aircraft. This new instrument combines direct tunable diode laser absorption spectroscopy (dTDLAS) with a first-principle evaluation method to allow absolute water vapor measurements without any initial or repetitive sensor calibration using a reference gas or a reference humidity generator. HAI contains two completely independent dual-channel (closed-path, open-path) spectrometers, one at 1.4 and one at 2.6 µm, which together allow us to cover the entire atmospheric H2O range from 1 to 40 000 ppmv with a single instrument. Both spectrometers each comprise a separate, wavelength-individual extractive, closed-path cell for total water (ice and gas-phase) measurements. Additionally, both spectrometers couple light into a common open-path cell outside of the aircraft fuselage for a direct, sampling-free, and contactless determination of the gas-phase water content. This novel twin dual-channel setup allows for the first time multiple self-validation functions, in particular a reliable, direct, in-flight validation of the open-path channels. During the first field campaigns, the in-flight deviations between the independent and calibration-free channels (i.e., closed-path to closed-path and open-path to closed-path) were on average in the 2 % range. Further, the fully autonomous HAI hygrometer allows measurements up to 240 Hz with a minimal integration time of 1.4 ms. The best precision is achieved by the 1.4 µm closed-path cell at 3.8 Hz (0.18 ppmv) and by the 2.6 µm closed-path cell at 13 Hz (0.055 ppmv). The requirements, design, operation principle, and first in-flight performance of the hygrometer are described and discussed in this work.

Inactivation of A currents and A channels on rat nodose neurons in culture

PubMed Central

1989-01-01

Cultured sensory neurons from nodose ganglia were investigated with whole-cell patch-clamp techniques and single-channel recordings to characterize the A current. Membrane depolarization from -40 mV holding potential activated the delayed rectifier current (IK) at potentials positive to -30 mV; this current had a sigmoidal time course and showed little or no inactivation. In most neurons, the A current was completely inactivated at the -40 mV holding potential and required hyperpolarization to remove the inactivation; the A current was isolated by subtracting the IK evoked by depolarizations from -40 mV from the total outward current evoked by depolarizations from -90 mV. The decay of the A current on several neurons had complex kinetics and was fit by the sum of three exponentials whose time constants were 10- 40 ms, 100-350 ms, and 1-3 s. At the single-channel level we found that one class of channel underlies the A current. The conductance of A channels varied with the square root of the external K concentration: it was 22 pS when exposed to 5.4 mM K externally, the increased to 40 pS when exposed to 140 mM K externally. A channels activated rapidly upon depolarization and the latency to first opening decreased with depolarization. The open time distributions followed a single exponential and the mean open time increased with depolarization. A channels inactivate in three different modes: some A channels inactivated with little reopening and gave rise to ensemble averages that decayed in 10-40 ms; other A channels opened and closed three to four times before inactivating and gave rise to ensemble averages that decayed in 100-350 ms; still other A channels opened and closed several hundred times and required seconds to inactivate. Channels gating in all three modes contributed to the macroscopic A current from the whole cell, but their relative contribution differed among neurons. In addition, A channels could go directly from the closed, or resting, state to the inactivated state without opening, and the probability for channels inactivating in this way was greater at less depolarized voltages. In addition, a few A channels appeared to go reversibly from a mode where inactivation occurred rapidly to a slow mode of inactivation. PMID:2592953

Empirical Constraints on the Origin of Fast Radio Bursts: Volumetric Rates and Host Galaxy Demographics as a Test of Millisecond Magnetar Connection

NASA Astrophysics Data System (ADS)

Nicholl, M.; Williams, P. K. G.; Berger, E.; Villar, V. A.; Alexander, K. D.; Eftekhari, T.; Metzger, B. D.

2017-07-01

The localization of the repeating fast radio burst (FRB) 121102 to a low-metallicity dwarf galaxy at z = 0.193, and its association with a luminous quiescent radio source, suggests the possibility that FRBs originate from magnetars, formed by the unusual supernovae that occur in such galaxies. We investigate this possibility via a comparison of magnetar birth rates, the FRB volumetric rate, and host galaxy demographics. We calculate average volumetric rates of possible millisecond magnetar production channels, such as superluminous supernovae (SLSNe), long and short gamma-ray bursts (GRBs), and general magnetar production via core-collapse supernovae (CCSNe). For each channel, we also explore the expected host galaxy demographics using their known properties. We determine for the first time the number density of FRB emitters (the product of their volumetric birth rate and lifetime), {R}{FRB}τ ≈ {10}4 Gpc-3, assuming that FRBs are predominantly emitted from repetitive sources similar to FRB 121102 and adopting a beaming factor of 0.1. By comparing rates, we find that production via rare channels (SLSNe, GRBs) implies a typical FRB lifetime of ˜30-300 years, in good agreement with other lines of argument. The total energy emitted over this time is consistent with the available energy stored in the magnetic field. On the other hand, any relation to magnetars produced via normal CCSNe leads to a very short lifetime of ˜0.5 years, in conflict with both theory and observation. We demonstrate that due to the diverse host galaxy distributions of the different progenitor channels, many possible sources of FRB birth can be ruled out with ≲ 10 host galaxy identifications. Conversely, targeted searches of galaxies that have previously hosted decades-old SLSNe and GRBs may be a fruitful strategy for discovering new FRBs and related quiescent radio sources, and determining the nature of their progenitors.

Mathematical modelling of non-stationary fluctuation analysis for studying channel properties of synaptic AMPA receptors

PubMed Central

Benke, Timothy A; Lüthi, Andreas; Palmer, Mary J; Wikström, Martin A; Anderson, William W; Isaac, John T R; Collingridge, Graham L

2001-01-01

The molecular properties of synaptic α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors are an important factor determining excitatory synaptic transmission in the brain. Changes in the number (N) or single-channel conductance (γ) of functional AMPA receptors may underlie synaptic plasticity, such as long-term potentiation (LTP) and long-term depression (LTD). These parameters have been estimated using non-stationary fluctuation analysis (NSFA). The validity of NSFA for studying the channel properties of synaptic AMPA receptors was assessed using a cable model with dendritic spines and a microscopic kinetic description of AMPA receptors. Electrotonic, geometric and kinetic parameters were altered in order to determine their effects on estimates of the underlying γ. Estimates of γ were very sensitive to the access resistance of the recording (RA) and the mean open time of AMPA channels. Estimates of γ were less sensitive to the distance between the electrode and the synaptic site, the electrotonic properties of dendritic structures, recording electrode capacitance and background noise. Estimates of γ were insensitive to changes in spine morphology, synaptic glutamate concentration and the peak open probability (Po) of AMPA receptors. The results obtained using the model agree with biological data, obtained from 91 dendritic recordings from rat CA1 pyramidal cells. A correlation analysis showed that RA resulted in a slowing of the decay time constant of excitatory postsynaptic currents (EPSCs) by approximately 150 %, from an estimated value of 3.1 ms. RA also greatly attenuated the absolute estimate of γ by approximately 50-70 %. When other parameters remain constant, the model demonstrates that NSFA of dendritic recordings can readily discriminate between changes in γvs. changes in N or Po. Neither background noise nor asynchronous activation of multiple synapses prevented reliable discrimination between changes in γ and changes in either N or Po. The model (available online) can be used to predict how changes in the different properties of AMPA receptors may influence synaptic transmission and plasticity. PMID:11731574

Geologic map of MTM -40252 and -40257 quadrangles, Reull Vallis region of Mars

USGS Publications Warehouse

Mest, Scott C.; Crown, David A.

2002-01-01

Mars Transverse Mercator (MTM) quadrangles -40252 and -40257 cover a portion of the highlands of Promethei Terra northeast of the Hellas basin. The map area consists of heavily cratered ancient highland materials of moderate to high relief, isolated knobs and massifs of rugged mountainous materials, extensive tracts of smooth and channeled plains, and other surficial deposits. Reull Vallis, an approximately 1,500 km-long outflow channel system, cuts through the southeast corner of the map area. Regional slopes are to the southwest, toward the Hellas basin, as indicated by Martian topographic maps and the orientations of channels along the northeast rim of the Hellas basin. The Martian highlands cover more than 60 percent of the planet's surface and are primarily in the southern hemisphere. Most of the highlands consist of rugged, densely cratered terrains believed to represent the final phase of heavy bombardment in the inner solar system about 4.0 billion years ago. Parts of the Martian highlands show evidence of extensive degradation and modification. The map area shows landforms created by numerous geologic processes, including tectonism, fluvial activity, and mass wasting. The occurrence of fluvial features, such as outflow channels and valley networks, has significant implications for past Martian conditions. Determining the geology of the highlands northeast of the Hellas basin provides a better understanding of the role and timing of volatile-driven activity in the evolution of the highlands. Photogeologic mapping at 1:500,000 scale from analysis of Viking Orbiter images complements geomorphic studies of Reull Vallis and other highland outflow systems, of drainage networks, and of highland debris aprons and regional geologic mapping studies of the highlands at the 1:2,000,000 scale and 1:1,000,000 scale. Crater size-frequency distributions have been compiled to constrain the relative ages of geologic units and determine the timing and extents of the observed geologic processes.

Digital Data Acquisition System for experiments with segmented detectors at National Superconducting Cyclotron Laboratory

NASA Astrophysics Data System (ADS)

Starosta, K.; Vaman, C.; Miller, D.; Voss, P.; Bazin, D.; Glasmacher, T.; Crawford, H.; Mantica, P.; Tan, H.; Hennig, W.; Walby, M.; Fallu-Labruyere, A.; Harris, J.; Breus, D.; Grudberg, P.; Warburton, W. K.

2009-11-01

A 624-channel Digital Data Acquisition System capable of instrumenting the Segmented Germanium Array at National Superconducting Cyclotron Laboratory has been implemented using Pixie-16 Digital Gamma Finder modules by XIA LLC. The system opens an opportunity for determination of the first interaction position of a γ ray in a SeGA detector from implementation of γ-ray tracking. This will translate into a significantly improved determination of angle of emission, and in consequence much better Doppler corrections for experiments with fast beams. For stopped-beam experiments the system provides means for zero dead time measurements of rare decays, which occur on time scales of microseconds.

The Use of Continuous Wavelet Transform Based on the Fast Fourier Transform in the Analysis of Multi-channel Electrogastrography Recordings.

PubMed

Komorowski, Dariusz; Pietraszek, Stanislaw

2016-01-01

This paper presents the analysis of multi-channel electrogastrographic (EGG) signals using the continuous wavelet transform based on the fast Fourier transform (CWTFT). The EGG analysis was based on the determination of the several signal parameters such as dominant frequency (DF), dominant power (DP) and index of normogastria (NI). The use of continuous wavelet transform (CWT) allows for better visible localization of the frequency components in the analyzed signals, than commonly used short-time Fourier transform (STFT). Such an analysis is possible by means of a variable width window, which corresponds to the scale time of observation (analysis). Wavelet analysis allows using long time windows when we need more precise low-frequency information, and shorter when we need high frequency information. Since the classic CWT transform requires considerable computing power and time, especially while applying it to the analysis of long signals, the authors used the CWT analysis based on the fast Fourier transform (FFT). The CWT was obtained using properties of the circular convolution to improve the speed of calculation. This method allows to obtain results for relatively long records of EGG in a fairly short time, much faster than using the classical methods based on running spectrum analysis (RSA). In this study authors indicate the possibility of a parametric analysis of EGG signals using continuous wavelet transform which is the completely new solution. The results obtained with the described method are shown in the example of an analysis of four-channel EGG recordings, performed for a non-caloric meal.

Introducing an R-package for calculating channel width and other basic metrics for irregular river polygons

NASA Astrophysics Data System (ADS)

Golly, Antonius; Turowski, Jens

2017-04-01

The width of fluvial streams and channel beds is an important metric for a large number of hydraulic, geomorphic and ecologic applications. For example, for a given discharge the local channel width determines the water flow velocity and thus the sediment transport capacity of a reach. Since streams often have irregular shapes with uneven channel banks, the channel width strongly varies along the channel. Although, the geometry of streams or their beds can be measured easily in the field (e.g. with a Total Station or GPS) or from maps or aerial images in a GIS, the width of the stream cannot be identified objectively without further data processing, since the results are more or less irregular polygons with sometimes bended shapes. An objective quantification of the channel width and other metrics requires automated algorithms that are applicable over a range of channel shapes and spatial scales. Here, we present a lightweight software suite with a small number of functions that process 2D or 3D geometrical data of channels or channel beds. The software, written as an R-package, accepts various text data formats and can be configured through five parameters. It creates interactive overview plots (if desired) and produces three basic channel metrics: the centerline, the channel width along the centerline and the slope along the centerline. The centerline is an optimized line that minimizes the distances to both channel banks. This centerline gives also a measure for the real length and slope of the channel. From this centerline perpendicular transects are generated which allow for the calculation of the channel width where they intersect with the channel banks. Briefly, we present an example and demonstrate the importance of these metrics in a use case of a steep stream, the Erlenbach stream in Switzerland. We were motivated to develop and publish the algorithm in an open-source framework, since only proprietary solutions were available at that time. The software is developed in R and is published under GNU GPL meaning it is free to use, edit and copy. This makes the software available also to users who do not own a MATLAB or ARCMAP license for which similar products exist.

Tracking channel-floodplain sediment exchange with conservative and non-conservative geochemical tracers

NASA Astrophysics Data System (ADS)

Belmont, Patrick; Stout, Justin

2013-04-01

Fine sediment is routed through landscapes and channel networks in a highly unsteady and non-uniform manner, potentially experiencing deposition and re-suspension many times during transport from source to sink. Developing a better understanding of sediment routing at the landscape scale is an intriguing challenge from a modeling perspective because it requires consideration of a multitude of processes that interact and vary in space and time. From an applied perspective, an improved understanding of sediment routing is essential for predicting how conservation and restoration practices within a watershed will influence water quality, to support land and water management decisions. Two key uncertainties in predicting sediment routing at the landscape scale are 1) determining the proportion of suspended sediment that is derived from terrestrial (soil) erosion versus channel (bank) erosion, and 2) constraining the proportion of sediment that is temporarily stored and re-suspended within the channel-floodplain complex. Sediment fingerprinting that utilizes a suite of conservative and non-conservative geochemical tracers associated with suspended sediment can provide insight regarding both of these key uncertainties. Here we present a model that tracks suspended sediment with associated conservative and non-conservative geochemical tracers. The model assumes that particle residence times are described by a bimodal distribution wherein some fraction of sediment is transported through the system in a relatively short time (< 1 year) and the remainder experiences temporary storage (of variable duration) within the channel-floodplain complex. We use the model to explore the downstream evolution of non-conservative tracers under equilibrium conditions (i.e., exchange between the channel and floodplain is allowed, but no net change in channel-floodplain storage can occur) to illustrate how the process of channel-floodplain storage and re-suspension can potentially bias interpretation of sediment fingerprinting results. We then apply the model to explain measurements of meteoric Beryllium-10, Lead-210, and Cesium-137 associated with suspended sediment in two very different rivers, one incising (Le Sueur River, south-central Minnesota, USA) and the other aggrading (Root River, southeastern Minnesota, USA) in response to base level fall and rise, respectively. The Le Sueur River exhibits a remarkably narrow range of tracer concentrations in source areas, which include agricultural fields, alluvial banks, and bluffs. Suspended sediment samples collected immediately above and below the 30 km long incising reach show a systematic shift in terrestrial sources in the downstream direction, indicated by changes in Beryllium-10 concentrations. The Root River indicates a more variable erosion history, with significant variability of Beryllium-10 concentrations in source areas (agricultural fields, forested hillslopes, and alluvial floodplains and terraces) and inverted Beryllium-10 depth profiles (higher concentrations at depth, suggesting unsteady erosion and significant storage of legacy sediment). Both rivers show a systematic disparity in normalized concentrations of conservative versus non-conservative tracers, indicating that significant storage and re-suspension occurs in both systems as the sediment is routed through the channel-floodplain complex.

Communication Channel Estimation and Waveform Design: Time Delay Estimation on Parallel, Flat Fading Channels

DTIC Science & Technology

2010-02-01

channels, so the channel gain is known on each realization and used in a coherent matched filter; and (c) Rayleigh channels with noncoherent matched...gain is known on each realization and used in a coherent matched filter (channel model 1A); and (c) Rayleigh channels with noncoherent matched filters...filters, averaged over Rayleigh channel realizations (channel model 1A). (b) Noncoherent matched filters with Rayleigh fading (channel model 3). MSEs are

Fading channel simulator

DOEpatents

Argo, Paul E.; Fitzgerald, T. Joseph

1993-01-01

Fading channel effects on a transmitted communication signal are simulated with both frequency and time variations using a channel scattering function to affect the transmitted signal. A conventional channel scattering function is converted to a series of channel realizations by multiplying the square root of the channel scattering function by a complex number of which the real and imaginary parts are each independent variables. The two-dimensional inverse-FFT of this complex-valued channel realization yields a matrix of channel coefficients that provide a complete frequency-time description of the channel. The transmitted radio signal is segmented to provide a series of transmitted signal and each segment is subject to FFT to generate a series of signal coefficient matrices. The channel coefficient matrices and signal coefficient matrices are then multiplied and subjected to inverse-FFT to output a signal representing the received affected radio signal. A variety of channel scattering functions can be used to characterize the response of a transmitter-receiver system to such atmospheric effects.

CLAG3 Self-Associates in Malaria Parasites and Quantitatively Determines Nutrient Uptake Channels at the Host Membrane

PubMed Central

Gupta, Ankit; Balabaskaran-Nina, Praveen; Nguitragool, Wang; Saggu, Gagandeep S.; Schureck, Marc A.

2018-01-01

ABSTRACT Malaria parasites increase host erythrocyte permeability to ions and nutrients via a broad-selectivity channel known as the plasmodial surface anion channel (PSAC), linked to parasite-encoded CLAG3 and two associated proteins. These proteins lack the multiple transmembrane domains typically present in channel-forming proteins, raising doubts about their precise roles. Using the virulent human Plasmodium falciparum parasite, we report that CLAG3 undergoes self-association and that this protein’s expression determines channel phenotype quantitatively. We overcame epigenetic silencing of clag3 paralogs and engineered parasites that express two CLAG3 isoforms simultaneously. Stoichiometric expression of these isoforms yielded intermediate channel phenotypes, in agreement with observed trafficking of both proteins to the host membrane. Coimmunoprecipitation and surface labeling revealed formation of CLAG3 oligomers. In vitro selections applied to these transfectant lines yielded distinct mutants with correlated changes in channel activity. These findings support involvement of the identified oligomers in PSAC formation and parasite nutrient acquisition. PMID:29739907

Ion-binding properties of a K+ channel selectivity filter in different conformations.

PubMed

Liu, Shian; Focke, Paul J; Matulef, Kimberly; Bian, Xuelin; Moënne-Loccoz, Pierre; Valiyaveetil, Francis I; Lockless, Steve W

2015-12-08

K(+) channels are membrane proteins that selectively conduct K(+) ions across lipid bilayers. Many voltage-gated K(+) (KV) channels contain two gates, one at the bundle crossing on the intracellular side of the membrane and another in the selectivity filter. The gate at the bundle crossing is responsible for channel opening in response to a voltage stimulus, whereas the gate at the selectivity filter is responsible for C-type inactivation. Together, these regions determine when the channel conducts ions. The K(+) channel from Streptomyces lividians (KcsA) undergoes an inactivation process that is functionally similar to KV channels, which has led to its use as a practical system to study inactivation. Crystal structures of KcsA channels with an open intracellular gate revealed a selectivity filter in a constricted conformation similar to the structure observed in closed KcsA containing only Na(+) or low [K(+)]. However, recent work using a semisynthetic channel that is unable to adopt a constricted filter but inactivates like WT channels challenges this idea. In this study, we measured the equilibrium ion-binding properties of channels with conductive, inactivated, and constricted filters using isothermal titration calorimetry (ITC). EPR spectroscopy was used to determine the state of the intracellular gate of the channel, which we found can depend on the presence or absence of a lipid bilayer. Overall, we discovered that K(+) ion binding to channels with an inactivated or conductive selectivity filter is different from K(+) ion binding to channels with a constricted filter, suggesting that the structures of these channels are different.

Limits on the Secular Drift of the TMI Calibration

NASA Astrophysics Data System (ADS)

Wilheit, T. T.; Farrar, S.; Jones, L.; Santos-Garcia, A.

2012-12-01

Data from the TRMM Microwave Imager (TMI) can be applied to the problem of determining the trend in oceanic precipitation over more than a decade. It is thus critical to know if the calibration of the instrument has any drift over this time scale. Recently a set of Windsat data with a self-consistent calibration covering July 2005 through June of 2006 and all of 2011 has become available. The mission of Windsat, determining the feasibility of measuring oceanic wind speed and direction, requires extraordinary attention to instrument calibration. With TRMM being in a low inclination orbit and Windsat in a near polar sun synchronous orbit, there are many observations coincident in space and nearly coincident in time. A data set has been assembled where the observations are averaged over 1 degree boxes of latitude and longitude and restricted to a maximum of 1 hour time difference. University of Central Florida (UCF) compares the two radiometers by computing radiances based on Global Data Assimilation System (GDAS) analyses for all channels of each radiometer for each box and computing double differences for corresponding channels. The algorithm is described in detail by Biswas et al., (2012). Texas A&M (TAMU) uses an independent implementation of GDAS-based algorithm and another where the radiances of Windsat are used to compute Sea Surface Temperature, Sea Surface Wind Speed, Precipitable Water and Cloud Liquid Water for each box. These are, in turn, used to compute the TMI radiances. These two algorithms have been described in detail by Wilheit (2012). Both teams apply stringent filters to the boxes to assure that the conditions are consistent with the model assumptions. Examination of both teams' results indicates that the drift is less than 0.04K over the 5 ½ year span for the 10 and 37 GHz channels of TMI. The 19 and 21 GHz channels have somewhat larger differences, but they are more influenced by atmospheric changes. Given the design of the instruments, it is hard to conceive of a calibration drift that would differ significantly across the channels. It also seems unlikely that TMI and Windsat are drifting synchronously. Thus we can place an upper limit of 0.01K/year on the calibration drift of the TMI. This value may be reduced with future refinement and the contributions of the other X-CAL teams. References Biswas, S.K., S. Farrar, K. Gopalan, A Santos-Garcia, L. Jones and S. Bilanow (2012), "Inter-Calibration of Microwave Radiometer Brightness Temperatures for the Global Precipitation Measurement Mission" to be published in TGRS. Wilheit, T., 2012 "Comparing Calibrations of Similar Conically-Scanning Window-Channel Microwave Radiometers" to be published in TGRS.

Mutations that stabilize the open state of the Erwinia chrisanthemi ligand-gated ion channel fail to change the conformation of the pore domain in crystals

PubMed Central

Gonzalez-Gutierrez, Giovanni; Lukk, Tiit; Agarwal, Vinayak; Papke, David; Nair, Satish K.; Grosman, Claudio

2012-01-01

The determination of structural models of the various stable states of an ion channel is a key step toward the characterization of its conformational dynamics. In the case of nicotinic-type receptors, different structures have been solved but, thus far, these different models have been obtained from different members of the superfamily. In the case of the bacterial member ELIC, a cysteamine-gated channel from Erwinia chrisanthemi, a structural model of the protein in the absence of activating ligand (and thus, conceivably corresponding to the closed state of this channel) has been previously generated. In this article, electrophysiological characterization of ELIC mutants allowed us to identify pore mutations that slow down the time course of desensitization to the extent that the channel seems not to desensitize at all for the duration of the agonist applications (>20 min). Thus, it seems reasonable to conclude that the probability of ELIC occupying the closed state is much lower for the ligand-bound mutants than for the unliganded wild-type channel. To gain insight into the conformation adopted by ELIC under these conditions, we solved the crystal structures of two of these mutants in the presence of a concentration of cysteamine that elicits an intracluster open probability of >0.9. Curiously, the obtained structural models turned out to be nearly indistinguishable from the model of the wild-type channel in the absence of bound agonist. Overall, our findings bring to light the limited power of functional studies in intact membranes when it comes to inferring the functional state of a channel in a crystal, at least in the case of the nicotinic-receptor superfamily. PMID:22474383

Root proliferation in decaying roots and old root channels: A nutrient conservation mechanism in oligotrophic mangrove forests?

USGS Publications Warehouse

McKee, K.L.

2001-01-01

1. In oligotrophic habitats, proliferation of roots in nutrient-rich microsites may contribute to overall nutrient conservation by plants. Peat-based soils on mangrove islands in Belize are characterized by the presence of decaying roots and numerous old root channels (0.1-3.5 cm diameter) that become filled with living and highly branched roots of Rhizophora mangle and Avicennia germinans. The objectives of this study were to quantify the proliferation of roots in these microsites and to determine what causes this response. 2. Channels formed by the refractory remains of mangrove roots accounted for only 1-2% of total soil volume, but the proportion of roots found within channels varied from 9 to 24% of total live mass. Successive generations of roots growing inside increasingly smaller root channels were also found. 3. When artificial channels constructed of PVC pipe were buried in the peat for 2 years, those filled with nutrient-rich organic matter had six times more roots than empty or sand-filled channels, indicating a response to greater nutrient availability rather than to greater space or less impedance to root growth. 4. Root proliferation inside decaying roots may improve recovery of nutrients released from decomposing tissues before they can be leached or immobilized in this intertidal environment. Greatest root proliferation in channels occurred in interior forest zones characterized by greater soil waterlogging, which suggests that this may be a strategy for nutrient capture that minimizes oxygen losses from the whole root system. 5. Improved efficiency of nutrient acquisition at the individual plant level has implications for nutrient economy at the ecosystem level and may explain, in part, how mangroves persist and grow in nutrient-poor environments.

The Possible Role of TASK Channels in Rank-Ordered Recruitment of Motoneurons in the Dorsolateral Part of the Trigeminal Motor Nucleus.

PubMed

Okamoto, Keiko; Emura, Norihito; Sato, Hajime; Fukatsu, Yuki; Saito, Mitsuru; Tanaka, Chie; Morita, Yukako; Nishimura, Kayo; Kuramoto, Eriko; Xu Yin, Dong; Furutani, Kazuharu; Okazawa, Makoto; Kurachi, Yoshihisa; Kaneko, Takeshi; Maeda, Yoshinobu; Yamashiro, Takashi; Takada, Kenji; Toyoda, Hiroki; Kang, Youngnam

2016-01-01

Because a rank-ordered recruitment of motor units occurs during isometric contraction of jaw-closing muscles, jaw-closing motoneurons (MNs) may be recruited in a manner dependent on their soma sizes or input resistances (IRs). In the dorsolateral part of the trigeminal motor nucleus (dl-TMN) in rats, MNs abundantly express TWIK (two-pore domain weak inwardly rectifying K channel)-related acid-sensitive-K(+) channel (TASK)-1 and TASK3 channels, which determine the IR and resting membrane potential. Here we examined how TASK channels are involved in IR-dependent activation/recruitment of MNs in the rat dl-TMN by using multiple methods. The real-time PCR study revealed that single large MNs (>35 μm) expressed TASK1 and TASK3 mRNAs more abundantly compared with single small MNs (15-20 μm). The immunohistochemistry revealed that TASK1 and TASK3 channels were complementarily distributed in somata and dendrites of MNs, respectively. The density of TASK1 channels seemed to increase with a decrease in soma diameter while there were inverse relationships between the soma size of MNs and IR, resting membrane potential, or spike threshold. Dual whole-cell recordings obtained from smaller and larger MNs revealed that the recruitment of MNs depends on their IRs in response to repetitive stimulation of the presumed Ia afferents. 8-Bromoguanosine-cGMP decreased IRs in small MNs, while it hardly changed those in large MNs, and subsequently decreased the difference in spike-onset latency between the smaller and larger MNs, causing a synchronous activation of MNs. These results suggest that TASK channels play critical roles in rank-ordered recruitment of MNs in the dl-TMN.

Kv11.1 (hERG)-induced cardiotoxicity: a molecular insight from a binding kinetics study of prototypical Kv11.1 (hERG) inhibitors

PubMed Central

Yu, Z; IJzerman, A P; Heitman, L H

2015-01-01

Background and Purpose Drug-induced arrhythmia due to blockade of the Kv11.1 channel (also known as the hERG K+ channel) is a frequent side effect. Previous studies have primarily focused on equilibrium parameters, i.e. affinity or potency, of drug candidates at the channel. The aim of this study was to determine the kinetics of the interaction with the channel for a number of known Kv11.1 blockers and to explore a possible correlation with the affinity or physicochemical properties of these compounds. Experimental Approach The affinity and kinetic parameters of 15 prototypical Kv11.1 inhibitors were evaluated in a number of [3H]-dofetilide binding assays. The lipophilicity (logKW-C8) and membrane partitioning (logKW-IAM) of these compounds were determined by means of HPLC analysis. Key Results A novel [3H]-dofetilide competition association assay was set up and validated, which allowed us to determine the binding kinetics of the Kv11.1 blockers used in this study. Interestingly, the compounds' affinities (Ki values) were correlated to their association rates rather than dissociation rates. Overall lipophilicity or membrane partitioning of the compounds were not correlated to their affinity or rate constants for the channel. Conclusions and Implications A compound's affinity for the Kv11.1 channel is determined by its rate of association with the channel, while overall lipophilicity and membrane affinity are not. In more general terms, our findings provide novel insights into the mechanism of action for a compound's activity at the Kv11.1 channel. This may help to elucidate how Kv11.1-induced cardiotoxicity is governed and how it can be circumvented in the future. PMID:25296617

Trigger probe for determining the orientation of the power distribution of an electron beam

DOEpatents

Elmer, John W [Danville, CA; Palmer, Todd A [Livermore, CA; Teruya, Alan T [Livermore, CA

2007-07-17

The present invention relates to a probe for determining the orientation of electron beams being profiled. To accurately time the location of an electron beam, the probe is designed to accept electrons from only a narrowly defined area. The signal produced from the probe is then used as a timing or triggering fiducial for an operably coupled data acquisition system. Such an arrangement eliminates changes in slit geometry, an additional signal feedthrough in the wall of a welding chamber and a second timing or triggering channel on a data acquisition system. As a result, the present invention improves the accuracy of the resulting data by minimizing the adverse effects of current slit triggering methods so as to accurately reconstruct electron or ion beams.

Controllability of a multichannel system

NASA Astrophysics Data System (ADS)

Ivanov, Sergei A.; Wang, Jun Min

2018-02-01

We consider the system consisting of K coupled acoustic channels with the different sound velocities cj. Channels are interacting at any point via the pressure and its time derivatives. Using the moment approach and the theory of exponential families with vector coefficients we establish two controllability results: the system is exactly controllable if (i) the control uj in the jth channel acts longer than the double travel time of a wave from the start to the end of the j-th channel; (ii) all controls uj act more than or equal to the maximal double travel time.

Emitter signal separation method based on multi-level digital channelization

NASA Astrophysics Data System (ADS)

Han, Xun; Ping, Yifan; Wang, Sujun; Feng, Ying; Kuang, Yin; Yang, Xinquan

2018-02-01

To solve the problem of emitter separation under complex electromagnetic environment, a signal separation method based on multi-level digital channelization is proposed in this paper. A two-level structure which can divide signal into different channel is designed first, after that, the peaks of different channels are tracked using the track filter and the coincident signals in time domain are separated in time-frequency domain. Finally, the time domain waveforms of different signals are acquired by reverse transformation. The validness of the proposed method is proved by experiment.

Impact of Dendrimer Terminal Group Chemistry on Blockage of the Anthrax Toxin Channel: A Single Molecule Study.

PubMed

Yamini, Goli; Kalu, Nnanya; Nestorovich, Ekaterina M

2016-11-15

Nearly all the cationic molecules tested so far have been shown to reversibly block K⁺ current through the cation-selective PA 63 channels of anthrax toxin in a wide nM-mM range of effective concentrations. A significant increase in channel-blocking activity of the cationic compounds was achieved when multiple copies of positively charged ligands were covalently linked to multivalent scaffolds, such as cyclodextrins and dendrimers. Even though multivalent binding can be strong when the individual bonds are relatively weak, for drug discovery purposes we often strive to design multivalent compounds with high individual functional group affinity toward the respective binding site on a multivalent target. Keeping this requirement in mind, here we perform a single-channel/single-molecule study to investigate kinetic parameters of anthrax toxin PA 63 channel blockage by second-generation (G2) poly(amido amine) (PAMAM) dendrimers functionalized with different surface ligands, including G2-NH₂, G2-OH, G2-succinamate, and G2-COONa. We found that the previously reported difference in IC 50 values of the G2-OH/PA 63 and G2-NH₂/PA 63 binding was determined by both on- and off-rates of the reversible dendrimer/channel binding reaction. In 1 M KCl, we observed a decrease of about three folds in k o n and a decrease of only about ten times in t r e s with G2-OH compared to G2-NH₂. At the same time for both blockers, k o n and t r e s increased dramatically with transmembrane voltage increase. PAMAM dendrimers functionalized with negatively charged succinamate, but not carboxyl surface groups, still had some residual activity in inhibiting the anthrax toxin channels. At 100 mV, the on-rate of the G2-succinamate binding was comparable with that of G2-OH but showed weaker voltage dependence when compared to G2-OH and G2-NH₂. The residence time of G2-succinamate in the channel exhibited opposite voltage dependence compared to G2-OH and G2-NH₂, increasing with the cis -negative voltage increase. We also describe kinetics of the PA 63 ion current modulation by two different types of the "imperfect" PAMAM dendrimers, the mixed-surface G2 75% OH 25% NH₂ dendrimer and G3-NH₂ dendron. At low voltages, both "imperfect" dendrimers show similar rate constants but significantly weaker voltage sensitivity when compared with the intact G2-NH₂ PAMAM dendrimer.

A permeation theory for single-file ion channels: one- and two-step models.

PubMed

Nelson, Peter Hugo

2011-04-28

How many steps are required to model permeation through ion channels? This question is investigated by comparing one- and two-step models of permeation with experiment and MD simulation for the first time. In recent MD simulations, the observed permeation mechanism was identified as resembling a Hodgkin and Keynes knock-on mechanism with one voltage-dependent rate-determining step [Jensen et al., PNAS 107, 5833 (2010)]. These previously published simulation data are fitted to a one-step knock-on model that successfully explains the highly non-Ohmic current-voltage curve observed in the simulation. However, these predictions (and the simulations upon which they are based) are not representative of real channel behavior, which is typically Ohmic at low voltages. A two-step association/dissociation (A/D) model is then compared with experiment for the first time. This two-parameter model is shown to be remarkably consistent with previously published permeation experiments through the MaxiK potassium channel over a wide range of concentrations and positive voltages. The A/D model also provides a first-order explanation of permeation through the Shaker potassium channel, but it does not explain the asymmetry observed experimentally. To address this, a new asymmetric variant of the A/D model is developed using the present theoretical framework. It includes a third parameter that represents the value of the "permeation coordinate" (fractional electric potential energy) corresponding to the triply occupied state n of the channel. This asymmetric A/D model is fitted to published permeation data through the Shaker potassium channel at physiological concentrations, and it successfully predicts qualitative changes in the negative current-voltage data (including a transition to super-Ohmic behavior) based solely on a fit to positive-voltage data (that appear linear). The A/D model appears to be qualitatively consistent with a large group of published MD simulations, but no quantitative comparison has yet been made. The A/D model makes a network of predictions for how the elementary steps and the channel occupancy vary with both concentration and voltage. In addition, the proposed theoretical framework suggests a new way of plotting the energetics of the simulated system using a one-dimensional permeation coordinate that uses electric potential energy as a metric for the net fractional progress through the permeation mechanism. This approach has the potential to provide a quantitative connection between atomistic simulations and permeation experiments for the first time.

Impact of Dendrimer Terminal Group Chemistry on Blockage of the Anthrax Toxin Channel: A Single Molecule Study

PubMed Central

Yamini, Goli; Kalu, Nnanya; Nestorovich, Ekaterina M.

2016-01-01

Nearly all the cationic molecules tested so far have been shown to reversibly block K+ current through the cation-selective PA63 channels of anthrax toxin in a wide nM–mM range of effective concentrations. A significant increase in channel-blocking activity of the cationic compounds was achieved when multiple copies of positively charged ligands were covalently linked to multivalent scaffolds, such as cyclodextrins and dendrimers. Even though multivalent binding can be strong when the individual bonds are relatively weak, for drug discovery purposes we often strive to design multivalent compounds with high individual functional group affinity toward the respective binding site on a multivalent target. Keeping this requirement in mind, here we perform a single-channel/single-molecule study to investigate kinetic parameters of anthrax toxin PA63 channel blockage by second-generation (G2) poly(amido amine) (PAMAM) dendrimers functionalized with different surface ligands, including G2-NH2, G2-OH, G2-succinamate, and G2-COONa. We found that the previously reported difference in IC50 values of the G2-OH/PA63 and G2-NH2/PA63 binding was determined by both on- and off-rates of the reversible dendrimer/channel binding reaction. In 1 M KCl, we observed a decrease of about three folds in kon and a decrease of only about ten times in tres with G2-OH compared to G2-NH2. At the same time for both blockers, kon and tres increased dramatically with transmembrane voltage increase. PAMAM dendrimers functionalized with negatively charged succinamate, but not carboxyl surface groups, still had some residual activity in inhibiting the anthrax toxin channels. At 100 mV, the on-rate of the G2-succinamate binding was comparable with that of G2-OH but showed weaker voltage dependence when compared to G2-OH and G2-NH2. The residence time of G2-succinamate in the channel exhibited opposite voltage dependence compared to G2-OH and G2-NH2, increasing with the cis-negative voltage increase. We also describe kinetics of the PA63 ion current modulation by two different types of the “imperfect” PAMAM dendrimers, the mixed-surface G2 75% OH 25% NH2 dendrimer and G3-NH2 dendron. At low voltages, both “imperfect” dendrimers show similar rate constants but significantly weaker voltage sensitivity when compared with the intact G2-NH2 PAMAM dendrimer. PMID:27854272

Moisture vapor transport channels for the improved attachment of a medical device to the human body.

PubMed

Cunningham, David D; Lowery, Michael G

2004-06-01

Attachment of a small, medical device to the human body for an extended period of time in an ambulatory setting requires the careful consideration of the physical form of the device and the physiological constraints limiting the time a device will stay on the skin. Factors such as the size of the device, the area of the device available for attachment to the skin, and the occlusive nature of the materials in the device are likely to affect adhesion. Here, plastic acrylic disks, 25 mm in diameter, containing a crisscross pattern of air-filled channels were tested on the forearm and abdomen using a moderately aggressive, unsupported, pressure-sensitive transfer adhesive in a pilot human clinical study. After vigorous exercise, droplets of moisture were observed in the channels followed by evaporation of the droplets over time. Disks without channels remained attached to the skin for about a day and a half, while disks containing 450 microm deep channels remained on the skin about three times longer. Little difference was found when the channel-to-channel spacing was increased from 1.3 to 1.6 mm, however 230 microm deep channels were less effective than 450 microm deep channels. Overall, the moisture vapor transport channels appear capable of reducing the moisture content of the outermost stratum corneum layer of the skin, increasing the strength of the stratum corneum, and increasing the time a device remains attached to the skin. The median trial-to-trial relative standard deviation of 45% observed in the pilot study can be used to design appropriately powered studies for the comparison of different device designs.

Simple Ion Channels: From Structure to Electrophysiology and Back

NASA Technical Reports Server (NTRS)

Pohorille, Andrzej

2018-01-01

A reliable way to establish whether our understanding of a channel is satisfactory is to reproduce its measured ionic conductance over a broad range of applied voltages in computer simulations. In molecular dynamics (MD), this can be done by way of applying an external electric field to the system and counting the number of ions that traverse the channel per unit time. Since this approach is computationally very expensive, we have developed a markedly more efficient alternative in which MD is combined with the electrodiffusion (ED) equation. In this approach, the assumptions of the ED equation can be rigorously tested, and the precision and consistency of the calculated conductance can be determined. We have demonstrated that the full current/voltage dependence and the underlying free energy profile for a simple channel can be reliably calculated from equilibrium or non-equilibrium MD simulations at a single voltage. To carry out MD simulations, a structural model of a channel has to be assumed, which is an important constraint, considering that high-resolution structures are available for only very few simple channels. If the comparison of calculated ionic conductance with electrophysiological data is satisfactory, it greatly increases our confidence that the structure and the function are described sufficiently accurately. We examined the validity of the ED for several channels embedded in phospholipid membranes - four naturally occurring channels: trichotoxin, alamethicin, p7 from hepatitis C virus (HCV) and Vpu from the HIV-1 virus, and a synthetic, hexameric channel, formed by a 21-residue peptide that contains only leucine and serine. All these channels mediate transport of potassium and chloride ions. It was found that the ED equation is satisfactory for these systems. In some of them experimental and calculated electrophysiological properties are in good agreement, whereas in others there are strong indications that the structural models are incorrect.

Global Pattern of The Evolutions of the Sub-Auroral Polarization Streams

NASA Astrophysics Data System (ADS)

He, F.; Zhang, X.; Wang, W.; Wan, W.

2017-12-01

Due to the spatial and temporal limitations of the in-situ measurements from the low altitude polar orbiting satellites or the ionospheric scan by incoherent scatter radars, the global configuration and evolution of SAPS are still not very clear. Here, we present multi-satellite observations of the evolution of subauroral polarization streams (SAPS) during the main phase of a server geomagnetic storm occurred on 31 March 2001. DMSP F12 to F15 observations indicate that the SAPS were first generated in the dusk sector at the beginning of the main phase. Then the SAPS channel expanded towards the midnight and moved to lower latitudes as the main phase went on. The peak velocity, latitudinal width, latitudinal alignment, and longitudinal span of the SAPS channels were highly dynamic during the storm main phase. The global evolution of the SAPS corresponds well with that of the region-2 field-aligned currents, which are mainly determined by the azimuthal pressure gradient of the ring current. Further studies on 37 storms and 30 isolated substorms indicate that the lifetime of the SAPS channel was proportional to the period of time for southward interplanetary magnetic field (IMF). The SAPS channel disappeared after northward turning of the IMF. During the recovery phase, if the IMF kept northward, no SAPS channel was generated, if the IMF turned to southward again, however, SAPS channel will be generated again with lifetime proportional to the duration of the southward IMF. During isolated substorms, the SAPS channel was also controlled by IMF. The SAPS channel was generated after substorm onset and the peak drift velocity of the SAPS channel achieved its maximum during the recovery phase of the substorm. It is suggested that, SAPS channel were mainly controlled by IMF, more works should be done with observations or simulations of investigate the global patterns of the SAPS and the magnetosphere-ionosphere couplings.

Connexin Channel Permeability to Cytoplasmic Molecules

PubMed Central

Harris, Andrew L.

2007-01-01

Connexin channels are known to be permeable to a variety of cytoplasmic molecules. The first observation of second messenger junctional permeability, made ∼30 years ago, sparked broad interest in gap junction channels as mediators of intercellular molecular signaling. Since then, much has been learned about the diversity of connexin channels with regard to isoform diversity, tissue and developmental distribution, modes of channel regulation, assembly and expression, biochemical modification and permeability, all of which appear to be dynamically regulated. This information has expanded the potential roles of connexin channels in development, physiology and disease, and made their elucidation much more complex - 30 years ago such an orchestra of junctional dynamics was unanticipated. Only recently, however, have investigators been able to directly address, in this more complex framework, the key issue: What specific biological molecules, second messengers and others, are able to permeate the various types of connexin channels, and how well? An important related issue, given the ever-growing list of connexin-related pathologies, is how these permeabilities are altered by disease-causing connexin mutations. Together, many studies show that a variety of cytoplasmic molecules can permeate the different types of connexin channels. A few studies reveal differences in permeation by different molecules through a particular type of connexin channel, and differences in permeation by a particular molecule through different types of connexin channels. This article describes and evaluates the various methods used to obtain these data, presents an annotated compilation of the results, and discusses the findings in the context of what can be inferred about mechanism of selectivity and potential relevance to signaling. The data strongly suggest that highly specific interactions take place between connexin pores and specific biological molecular permeants, and that those interactions determine which cytoplasmic molecules can permeate and how well. At this time, the nature of those interactions is unclear. One hopes that with more detailed permeability and structural information, the specific molecular mechanisms of the selectivity can be elucidated. PMID:17470375

Dynamics of laser-induced channel formation in water and influence of pulse duration on the ablation of biotissue under water with pulsed erbium-laser radiation

NASA Astrophysics Data System (ADS)

Ith, M.; Pratisto, H.; Altermatt, H. J.; Frenz, M.; Weber, H. P.

1994-12-01

The ability to use fiber-delivered erbium-laser radiation for non-contact arthroscopic meniscectomy in a liquid environment was studied. The laser radiation is transmitted through a water-vapor channel created by the leading part of the laser pulse. The dynamics of the channel formation around a submerged fiber tip was investigated with time-resolved flash photography. Strong pressure transients with amplitudes up to a few hundreds of bars measured with a needle hydrophone were found to accompany the channel formation process. Additional pressure transients in the range of kbars were observed after the laser pulse associated with the collapse of the vapor channel. Transmission measurements revealed that the duration the laser-induced channel stays open, and therefore the energy transmittable through it, is substantially determined by the laser pulse duration. The optimum pulse duration was found to be in the range between 250 and 350 µS. This was confirmed by histological evaluations of the laser incisions in meniscus: Increasing the pulse duration from 300 to 800 µs leads to a decrease in the crater depth from 1600 to 300 µm. A comparison of the histological examination after laser treatment through air and through water gave information on the influence of the vapor channel on the ablation efficiency, the cutting quality and the induced thermal damage in the adjacent tissue. The study shows that the erbium laser combined with an adequate fiber delivery system represents an effective surgical instrument liable to become increasingly accepted in orthopedic surgery.

Sediment supply versus local hydraulic controls on sediment transport and storage in a river with large sediment loads

USGS Publications Warehouse

Dean, David; Topping, David; Schmidt, John C.; Griffiths, Ronald; Sabol, Thomas

2016-01-01

The Rio Grande in the Big Bend region of Texas, USA, and Chihuahua and Coahuila, Mexico, undergoes rapid geomorphic changes as a result of its large sediment supply and variable hydrology; thus, it is a useful natural laboratory to investigate the relative importance of flow strength and sediment supply in controlling alluvial channel change. We analyzed a suite of sediment transport and geomorphic data to determine the cumulative influence of different flood types on changing channel form. In this study, physically based analyses suggest that channel change in the Rio Grande is controlled by both changes in flow strength and sediment supply over different spatial and temporal scales. Channel narrowing is primarily caused by substantial deposition of sediment supplied to the Rio Grande during tributary-sourced flash floods. Tributary floods have large suspended-sediment concentrations, occur for short durations, and attenuate rapidly downstream in the Rio Grande, depositing much of their sediment in downstream reaches. Long-duration floods on the mainstem have the capacity to enlarge the Rio Grande, and these floods, released from upstream dams, can either erode or deposit sediment in the Rio Grande depending upon the antecedent in-channel sediment supply and the magnitude and duration of the flood. Geomorphic and sediment transport analyses show that the locations and rates of sand erosion and deposition during long-duration floods are most strongly controlled by spatial changes in flow strength, largely through changes in channel slope. However, spatial differences in the in-channel sediment supply regulate sediment evacuation or accumulation over time in long reaches (greater than a kilometer).

Time evolving bed shear stress due the passage of gravity currents estimated with ADVP velocity measurements

NASA Astrophysics Data System (ADS)

Zordan, Jessica; Schleiss, Anton J.; Franca, Mário J.

2016-04-01

Density or gravity currents are geophysical flows driven by density gradients between two contacting fluids. The physical trigger mechanism of these phenomena lays in the density differences which may be caused by differences in the temperature, dissolved substances or concentration of suspended sediments. Saline density currents are capable to entrain bed sediments inducing signatures in the bottom of sedimentary basins. Herein, saline density currents are reproduced in laboratory over a movable bed. The experimental channel is of the lock-exchange type, it is 7.5 m long and 0.3 m wide, divided into two sections of comparable volumes by a sliding gate. An upstream reach serves as a head tank for the dense mixture; the current propagates through a downstream reach where the main measurements are made. Downstream of the channel a tank exist to absorb the reflection of the current and thus artifacts due to the limited length of the channel. High performance thermoplastic polyurethane simulating fine sediments forms the movable bed. Measures of 3D instantaneous velocities will be made with the use of the non-intrusive technique of the ADV (Acoustic Doppler Current Profiler). With the velocity measurements, the evolution in time of the channel-bed shear stress due the passage of gravity currents is estimated. This is in turn related to the observed erosion and to such parameters determinant for the dynamics of the current as initial density difference, lock length and channel slope. This work was funded by the ITN-Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme FP7-PEOPLE-2013-ITN under REA grant agreement n_607394-SEDITRANS.

Relative Time-scale for Channeling Events Within Chaotic Terrains, Margaritifer Sinus, Mars

NASA Technical Reports Server (NTRS)

Janke, D.

1985-01-01

A relative time scale for ordering channel and chaos forming events was constructed for areas within the Margaritifer Sinus region of Mars. Transection and superposition relationships of channels, chaotic terrain, and the surfaces surrounding them were used to create the relative time scale; crater density studies were not used. Channels and chaos in contact with one another were treated as systems. These systems were in turn treated both separately (in order to understand internal relationships) and as members of the suite of Martian erosional forms (in order to produce a combined, master time scale). Channeling events associated with chaotic terrain development occurred over an extended geomorphic period. The channels can be divided into three convenient groups: those that pre-date intercrater plains development post-plains, pre-chasma systems; and those associated with the development of the Vallis Marineris chasmata. No correlations with cyclic climatic changes, major geologic events in other regions on Mars, or triggering phenomena (for example, specific impact events) were found.

Surprising features of particle dynamics in channel-facilitated transport

NASA Astrophysics Data System (ADS)

Berezhkovskii, Alexander M.; Bezrukov, Sergey M.

2007-06-01

We analyze the consequences of interactions between the pore and the translocating molecule within the framework of a continuous diffusion model using the Smoluchowski equation with the radiation boundary conditions. We describe the solute-pore interaction in terms of the potential of mean force. Several of our analytical findings are quite counterintuitive. Three of the examples to be discussed here are: (i) "Sticking" to the channel slows down translocation (a particle spends more time in the channel) but increases the flux; (ii) If the potential well modeling the particle-channel interaction occupies only a part of the channel length, the average translocation time is non-monotonic in the width of the potential well, first increasing and then decreasing; (iii) At a finite potential bias applied to the channel, the mean "up-hill" and "downhill" particle translocation times (and their distributions) are identical.

Directed translocation of a flexible polymer through a cone-shaped nano-channel

NASA Astrophysics Data System (ADS)

Nikoofard, Narges; Khalilian, Hamidreza; Fazli, Hossein

2013-08-01

Translocation of a flexible polymer through a cone-shaped channel is studied, theoretically and using computer simulations. Our simulations show that the shape of the channel causes the polymer translocation to be a driven process. The effective driving force of entropic origin acting on the polymer is calculated as a function of the length and the apex-angle of the channel, theoretically. It is found that the translocation time is a non-monotonic function of the apex-angle of the channel. By increasing the apex-angle from zero, the translocation time shows a minimum and then a maximum. Also, it is found that regardless of the value of the apex-angle, the translocation time is a uniformly decreasing function of the channel length. The results of the theory and the simulation are in good qualitative agreement.

Lightning Return-Stroke Current Waveforms Aloft, From Measured Field Change, Current, and Channel Geometry

NASA Technical Reports Server (NTRS)

Willett, J. C.; LeVine, D. M.

2002-01-01

Direct current measurements are available near the attachment point from both natural cloud-to-ground lightning and rocket-triggered lightning, but little is known about the rise time and peak amplitude of return-stroke currents aloft. We present, as functions of height, current amplitudes, rise times, and effective propagation velocities that have been estimated with a novel remote-sensing technique from data on 24 subsequent return strokes in six different lightning flashes that were triggering at the NASA Kennedy Space Center, FL, during 1987. The unique feature of this data set is the stereo pairs of still photographs, from which three-dimensional channel geometries were determined previously. This has permitted us to calculate the fine structure of the electric-field-change (E) waveforms produced by these strokes, using the current waveforms measured at the channel base together with physically reasonable assumptions about the current distributions aloft. The computed waveforms have been compared with observed E waveforms from the same strokes, and our assumptions have been adjusted to maximize agreement. In spite of the non-uniqueness of solutions derived by this technique, several conclusions seem inescapable: 1) The effective propagation speed of the current up the channel is usually significantly (but not unreasonably) faster than the two-dimensional velocity measured by a streak camera for 14 of these strokes. 2) Given the deduced propagation speed, the peak amplitude of the current waveform often must decrease dramatically with height to prevent the electric field from being over-predicted. 3) The rise time of the current wave front must always increase rapidly with height in order to keep the fine structure of the calculated field consistent with the observations.

Numerical experiment to estimate the validity of negative ion diagnostic using photo-detachment combined with Langmuir probing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oudini, N.; Sirse, N.; Ellingboe, A. R.

2015-07-15

This paper presents a critical assessment of the theory of photo-detachment diagnostic method used to probe the negative ion density and electronegativity α = n{sub -}/n{sub e}. In this method, a laser pulse is used to photo-detach all negative ions located within the electropositive channel (laser spot region). The negative ion density is estimated based on the assumption that the increase of the current collected by an electrostatic probe biased positively to the plasma is a result of only the creation of photo-detached electrons. In parallel, the background electron density and temperature are considered as constants during this diagnostics. While the numericalmore » experiments performed here show that the background electron density and temperature increase due to the formation of an electrostatic potential barrier around the electropositive channel. The time scale of potential barrier rise is about 2 ns, which is comparable to the time required to completely photo-detach the negative ions in the electropositive channel (∼3 ns). We find that neglecting the effect of the potential barrier on the background plasma leads to an erroneous determination of the negative ion density. Moreover, the background electron velocity distribution function within the electropositive channel is not Maxwellian. This is due to the acceleration of these electrons through the electrostatic potential barrier. In this work, the validity of the photo-detachment diagnostic assumptions is questioned and our results illustrate the weakness of these assumptions.« less

Two-Channel Transparency-Optimized Control Architectures in Bilateral Teleoperation With Time Delay.

PubMed

Kim, Jonghyun; Chang, Pyung Hun; Park, Hyung-Soon

2013-01-01

This paper introduces transparency-optimized control architectures (TOCAs) using two communication channels. Two classes of two-channel TOCAs are found, thereby showing that two channels are sufficient to achieve transparency. These TOCAs achieve a greater level of transparency but poorer stability than three-channel TOCAs and four-channel TOCAs. Stability of the two-channel TOCAs has been enhanced while minimizing transparency degradation by adding a filter; and a combined use of the two classes of two-channel TOCAs is proposed for both free space and constrained motion, which involve switching between two TOCAs for transition between free space and constrained motions. The stability condition of the switched teleoperation system is derived for practical applications. Through the one degree-of-freedom (DOF) experiment, the proposed two-channel TOCAs were shown to operate stably, while achieving better transparency under time delay than the other TOCAs.

Two-Channel Transparency-Optimized Control Architectures in Bilateral Teleoperation With Time Delay

PubMed Central

Kim, Jonghyun; Chang, Pyung Hun; Park, Hyung-Soon

2013-01-01

This paper introduces transparency-optimized control architectures (TOCAs) using two communication channels. Two classes of two-channel TOCAs are found, thereby showing that two channels are sufficient to achieve transparency. These TOCAs achieve a greater level of transparency but poorer stability than three-channel TOCAs and four-channel TOCAs. Stability of the two-channel TOCAs has been enhanced while minimizing transparency degradation by adding a filter; and a combined use of the two classes of two-channel TOCAs is proposed for both free space and constrained motion, which involve switching between two TOCAs for transition between free space and constrained motions. The stability condition of the switched teleoperation system is derived for practical applications. Through the one degree-of-freedom (DOF) experiment, the proposed two-channel TOCAs were shown to operate stably, while achieving better transparency under time delay than the other TOCAs. PMID:23833548

Time interval measurement device based on surface acoustic wave filter excitation, providing 1 ps precision and stability.

PubMed

Panek, Petr; Prochazka, Ivan

2007-09-01

This article deals with the time interval measurement device, which is based on a surface acoustic wave (SAW) filter as a time interpolator. The operating principle is based on the fact that a transversal SAW filter excited by a short pulse can generate a finite signal with highly suppressed spectra outside a narrow frequency band. If the responses to two excitations are sampled at clock ticks, they can be precisely reconstructed from a finite number of samples and then compared so as to determine the time interval between the two excitations. We have designed and constructed a two-channel time interval measurement device which allows independent timing of two events and evaluation of the time interval between them. The device has been constructed using commercially available components. The experimental results proved the concept. We have assessed the single-shot time interval measurement precision of 1.3 ps rms that corresponds to the time of arrival precision of 0.9 ps rms in each channel. The temperature drift of the measured time interval on temperature is lower than 0.5 ps/K, and the long term stability is better than +/-0.2 ps/h. These are to our knowledge the best values reported for the time interval measurement device. The results are in good agreement with the error budget based on the theoretical analysis.

Delay grid multiplexing: simple time-based multiplexing and readout method for silicon photomultipliers

NASA Astrophysics Data System (ADS)

Won, Jun Yeon; Ko, Guen Bae; Lee, Jae Sung

2016-10-01

In this paper, we propose a fully time-based multiplexing and readout method that uses the principle of the global positioning system. Time-based multiplexing allows simplifying the multiplexing circuits where the only innate traces that connect the signal pins of the silicon photomultiplier (SiPM) channels to the readout channels are used as the multiplexing circuit. Every SiPM channel is connected to the delay grid that consists of the traces on a printed circuit board, and the inherent transit times from each SiPM channel to the readout channels encode the position information uniquely. Thus, the position of each SiPM can be identified using the time difference of arrival (TDOA) measurements. The proposed multiplexing can also allow simplification of the readout circuit using the time-to-digital converter (TDC) implemented in a field-programmable gate array (FPGA), where the time-over-threshold (ToT) is used to extract the energy information after multiplexing. In order to verify the proposed multiplexing method, we built a positron emission tomography (PET) detector that consisted of an array of 4  ×  4 LGSO crystals, each with a dimension of 3  ×  3  ×  20 mm3, and one- to-one coupled SiPM channels. We first employed the waveform sampler as an initial study, and then replaced the waveform sampler with an FPGA-TDC to further simplify the readout circuits. The 16 crystals were clearly resolved using only the time information obtained from the four readout channels. The coincidence resolving times (CRTs) were 382 and 406 ps FWHM when using the waveform sampler and the FPGA-TDC, respectively. The proposed simple multiplexing and readout methods can be useful for time-of-flight (TOF) PET scanners.

Performance of DPSK with convolutional encoding on time-varying fading channels

NASA Technical Reports Server (NTRS)

Mui, S. Y.; Modestino, J. W.

1977-01-01

The bit error probability performance of a differentially-coherent phase-shift keyed (DPSK) modem with convolutional encoding and Viterbi decoding on time-varying fading channels is examined. Both the Rician and the lognormal channels are considered. Bit error probability upper bounds on fully-interleaved (zero-memory) fading channels are derived and substantiated by computer simulation. It is shown that the resulting coded system performance is a relatively insensitive function of the choice of channel model provided that the channel parameters are related according to the correspondence developed as part of this paper. Finally, a comparison of DPSK with a number of other modulation strategies is provided.

Noise analysis of antibiotic permeation through bacterial channels

NASA Astrophysics Data System (ADS)

Nestorovich, Ekaterina M.; Danelon, Christophe; Winterhalter, Mathias; Bezrukov, Sergey M.

2003-05-01

Statistical analysis of high-resolution current recordings from a single ion channel reconstituted into a planar lipid membrane allows us to study transport of antibiotics at the molecular detail. Working with the general bacterial porin, OmpF, we demonstrate that addition of zwitterionic β-lactam antibiotics to the membrane-bathing solution introduces transient interruptions in the small-ion current through the channel. Time-resolved measurements reveal that one antibiotic molecule blocks one of the monomers in the OmpF trimer for characteristic times from microseconds to hundreds of microseconds. Spectral noise analysis enables us to perform measurements over a wide range of changing parameters. In all cases studied, the residence time of an antibiotic molecule in the channel exceeds the estimated time for free diffusion by orders of magnitude. This demonstrates that, in analogy to substrate-specific channels that evolved to bind specific metabolite molecules, antibiotics have 'evolved' to be channel-specific. The charge distribution of an efficient antibiotic complements the charge distribution at the narrowest part of the bacterial porin. Interaction of these charges creates a zone of attraction inside the channel and compensates the penetrating molecule's entropy loss and desolvation energy. This facilitates antibiotic translocation through the narrowest part of the channel and accounts for higher antibiotic permeability rates.

Acoustic MIMO communications in a very shallow water channel

NASA Astrophysics Data System (ADS)

Zhou, Yuehai; Cao, Xiuling; Tong, Feng

2015-12-01

Underwater acoustic channels pose significant difficulty for the development of high speed communication due to highly limited band-width as well as hostile multipath interference. Enlightened by rapid progress of multiple input multiple output (MIMO) technologies in wireless communication scenarios, MIMO systems offer a potential solution by enabling multiple spatially parallel communication channels to improve communication performance as well as capacity. For MIMO acoustic communications, deep sea channels offer substantial spatial diversity among multiple channels that can be exploited to address simultaneous multipath and co-channel interference. At the same time, there are increasing requirements for high speed underwater communication in very shallow water area (for example, a depth less than 10 m). In this paper, a space-time multichannel adaptive receiver consisting of multiple decision feedback equalizers (DFE) is adopted as the receiver for a very shallow water MIMO acoustic communication system. The performance of multichannel DFE receivers with relatively small number of receiving elements are analyzed and compared with that of the multichannel time reversal receiver to evaluate the impact of limited spatial diversity on multi-channel equalization and time reversal processing. The results of sea trials in a very shallow water channel are presented to demonstrate the feasibility of very shallow water MIMO acoustic communication.

Dynamics of 30 large channel bars in the Lower Mississippi River in response to river engineering from 1985 to 2015

NASA Astrophysics Data System (ADS)

Wang, Bo; Xu, Y. Jun

2018-01-01

Channel bars are a major depositional feature in alluvial rivers and their morphodynamics has been investigated intensively in the past several decades. However, relatively less is known about how channel bars in alluvial rivers respond to river engineering and regulations. In this study, we assessed 30-yr morphologic changes of 30 large emerged bars located in a 223 km reach of the highly regulated Lower Mississippi River from Vicksburg, Mississippi, to the Mississippi-Atchafalaya River diversion. Landsat imagery and river stage data between 1985 and 2015 were utilized to characterize bar morphologic features and quantify decadal changes. Based on bar surface areas estimated with the satellite images at different river stages, a rating curve was developed for each of the 30 bars to determine their volumes. Results from this study show that the highly regulated river reach favored the growth of mid-channel and attached bars, while more than half of the point bars showed degradation. Currently, the mid-channel and attached bars accounted for 38% and 34% of the total volume of the 30 bars. The average volume of a single mid-channel bar is over two times that of an attached bar and over four times that of a point bar. Overall, in the past three decades, the total volume of the studied 30 bars increased by 110,118,000 m3 (41%). Total dike length in a dike field was found mostly contributing to the bar volume increase. Currently, the emerged volume of the 30 bars was estimated approximately 378,183,000 m3. The total bar volume is equivalent to 530 million metric tons of coarse sand, based on an average measured bulk density of 1.4 t/m3 for the bar sediment. The findings show that these bars are large sediment reservoirs.

DSP-Based dual-polarity mass spectrum pattern recognition for bio-detection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Riot, V; Coffee, K; Gard, E

2006-04-21

The Bio-Aerosol Mass Spectrometry (BAMS) instrument analyzes single aerosol particles using a dual-polarity time-of-flight mass spectrometer recording simultaneously spectra of thirty to a hundred thousand points on each polarity. We describe here a real-time pattern recognition algorithm developed at Lawrence Livermore National Laboratory that has been implemented on a nine Digital Signal Processor (DSP) system from Signatec Incorporated. The algorithm first preprocesses independently the raw time-of-flight data through an adaptive baseline removal routine. The next step consists of a polarity dependent calibration to a mass-to-charge representation, reducing the data to about five hundred to a thousand channels per polarity. Themore » last step is the identification step using a pattern recognition algorithm based on a library of known particle signatures including threat agents and background particles. The identification step includes integrating the two polarities for a final identification determination using a score-based rule tree. This algorithm, operating on multiple channels per-polarity and multiple polarities, is well suited for parallel real-time processing. It has been implemented on the PMP8A from Signatec Incorporated, which is a computer based board that can interface directly to the two one-Giga-Sample digitizers (PDA1000 from Signatec Incorporated) used to record the two polarities of time-of-flight data. By using optimized data separation, pipelining, and parallel processing across the nine DSPs it is possible to achieve a processing speed of up to a thousand particles per seconds, while maintaining the recognition rate observed on a non-real time implementation. This embedded system has allowed the BAMS technology to improve its throughput and therefore its sensitivity while maintaining a large dynamic range (number of channels and two polarities) thus maintaining the systems specificity for bio-detection.« less

47 CFR 15.707 - Permissible channels of operation.

Code of Federal Regulations, 2010 CFR

2010-10-01

... of each such area as set forth in § 15.712(d). These channels will be listed in the TV bands database... on available channels as determined by the TV bands database and in accordance with the interference...

The Split Personality of Glutamate Transporters: A Chloride Channel and a Transporter.

PubMed

Cater, Rosemary J; Ryan, Renae M; Vandenberg, Robert J

2016-03-01

Transporters and ion channels are conventionally categorised into distinct classes of membrane proteins. However, some membrane proteins have a split personality and can function as both transporters and ion channels. The excitatory amino acid transporters (EAATs) in particular, function as both glutamate transporters and chloride (Cl(-)) channels. The EAATs couple the transport of glutamate to the co-transport of three Na(+) ions and one H(+) ion into the cell, and the counter-transport of one K(+) ion out of the cell. The EAAT Cl(-) channel is activated by the binding of glutamate and Na(+), but is thermodynamically uncoupled from glutamate transport and involves molecular determinants distinct from those responsible for glutamate transport. Several crystal structures of an EAAT archaeal homologue, GltPh, at different stages of the transport cycle, alongside numerous functional studies and molecular dynamics simulations, have provided extensive insights into the mechanism of substrate transport via these transporters. However, the molecular determinants involved in Cl(-) permeation, and the mechanism by which this channel is activated are not entirely understood. Here we will discuss what is currently known about the molecular determinants involved in EAAT-mediated Cl(-) permeation and the mechanisms that underlie their split personality.

Sulfhydryl oxidation modifies the calcium dependence of ryanodine-sensitive calcium channels of excitable cells.

PubMed Central

Marengo, J J; Hidalgo, C; Bull, R

1998-01-01

The calcium dependence of ryanodine-sensitive single calcium channels was studied after fusing with planar lipid bilayers sarcoendoplasmic reticulum vesicles isolated from excitable tissues. Native channels from mammalian or amphibian skeletal muscle displayed three different calcium dependencies, cardiac (C), mammalian skeletal (MS), and low fractional open times (low Po), as reported for channels from brain cortex. Native channels from cardiac muscle presented only the MS and C dependencies. Channels with the MS or low Po behaviors showed bell-shaped calcium dependencies, but the latter had fractional open times of <0.1 at all [Ca2+]. Channels with C calcium dependence were activated by [Ca2+] < 10 microM and were not inhibited by increasing cis [Ca2+] up to 0.5 mM. After oxidation with 2,2'-dithiodipyridine or thimerosal, channels with low Po or MS dependencies increased their activity. These channels modified their calcium dependencies sequentially, from low Po to MS and C, or from MS to C. Reduction with glutathione of channels with C dependence (native or oxidized) decreased their fractional open times in 0.5 mM cis [Ca2+], from near unity to 0.1-0.3. These results show that all native channels displayed at least two calcium dependencies regardless of their origin, and that these changed after treatment with redox reagents. PMID:9512024

Single-channel analysis of functional epithelial sodium channel (ENaC) stability at the apical membrane of A6 distal kidney cells

PubMed Central

Yu, Ling; Helms, My N.; Yue, Qiang; Eaton, Douglas C.

2008-01-01

Epithelial sodium channels (ENaC) play an essential role in maintaining total body fluid and electrolyte homeostasis. As such, abnormal expression of ENaC at the cell surface is linked to several important human diseases. Although the stability of ENaC subunits has been extensively studied by protein biochemical analysis, the half-life of the functional channel in the apical membrane remains controversial. Because the functional stability of the multisubunit channel may be more physiologically relevant than the stability of individual subunit proteins, we performed studies of functional ENaC channels using A6 epithelial cells, a Xenopus laevis distal nephron cell line. We recorded single-channel activity in over 400 cells with the translation blockers cycloheximide (CHX) or puromycin, as well as the intracellular protein trafficking inhibitors brefeldin A (BFA) or nocodazole. Our cell-attached, single-channel recordings allow us to quantify the channel density in the apical membrane, as well as to determine channel open probability (Po) from control (untreated) cells and from cells at different times of drug treatment. The data suggest that the half-life of ENaC channels is ∼3.5 h following puromycin, BFA, and nocodazole treatment. Furthermore, these three drugs had no significant effect on the Po of ENaC for at least 6 h after exposure. A decrease in apical channel number and Po was observed following 2 h of CHX inhibition of protein synthesis, and the apparent channel half-life was closer to 1.5 h following CHX treatment. Treatment of cells with the translation inhibitors does not alter the expression of the protease furin, and therefore changes in protease activity cannot explain changes in ENaC Po. Confocal images show that BFA and nocodazole both disrupt most of the Golgi apparatus after 1-h exposure. In cells with the Golgi totally disrupted by overnight exposure to BFA, 20% of apical ENaC channels remained functional. This result suggests that ENaC is delivered to the apical membrane via a pathway that might bypass the Golgi vesicular trafficking pathway, or that there might be two pools of channels with markedly different half-lives in the apical membrane. PMID:18784262

Single-channel analysis of functional epithelial sodium channel (ENaC) stability at the apical membrane of A6 distal kidney cells.

PubMed

Yu, Ling; Helms, My N; Yue, Qiang; Eaton, Douglas C

2008-11-01

Epithelial sodium channels (ENaC) play an essential role in maintaining total body fluid and electrolyte homeostasis. As such, abnormal expression of ENaC at the cell surface is linked to several important human diseases. Although the stability of ENaC subunits has been extensively studied by protein biochemical analysis, the half-life of the functional channel in the apical membrane remains controversial. Because the functional stability of the multisubunit channel may be more physiologically relevant than the stability of individual subunit proteins, we performed studies of functional ENaC channels using A6 epithelial cells, a Xenopus laevis distal nephron cell line. We recorded single-channel activity in over 400 cells with the translation blockers cycloheximide (CHX) or puromycin, as well as the intracellular protein trafficking inhibitors brefeldin A (BFA) or nocodazole. Our cell-attached, single-channel recordings allow us to quantify the channel density in the apical membrane, as well as to determine channel open probability (Po) from control (untreated) cells and from cells at different times of drug treatment. The data suggest that the half-life of ENaC channels is approximately 3.5 h following puromycin, BFA, and nocodazole treatment. Furthermore, these three drugs had no significant effect on the Po of ENaC for at least 6 h after exposure. A decrease in apical channel number and Po was observed following 2 h of CHX inhibition of protein synthesis, and the apparent channel half-life was closer to 1.5 h following CHX treatment. Treatment of cells with the translation inhibitors does not alter the expression of the protease furin, and therefore changes in protease activity cannot explain changes in ENaC Po. Confocal images show that BFA and nocodazole both disrupt most of the Golgi apparatus after 1-h exposure. In cells with the Golgi totally disrupted by overnight exposure to BFA, 20% of apical ENaC channels remained functional. This result suggests that ENaC is delivered to the apical membrane via a pathway that might bypass the Golgi vesicular trafficking pathway, or that there might be two pools of channels with markedly different half-lives in the apical membrane.

Pharmacological Conversion of a Cardiac Inward Rectifier into an Outward Rectifier Potassium Channel.

PubMed

Moreno-Galindo, Eloy G; Sanchez-Chapula, Jose A; Tristani-Firouzi, Martin; Navarro-Polanco, Ricardo A

2016-09-01

Potassium (K(+)) channels are crucial for determining the shape, duration, and frequency of action-potential firing in excitable cells. Broadly speaking, K(+) channels can be classified based on whether their macroscopic current outwardly or inwardly rectifies, whereby rectification refers to a change in conductance with voltage. Outwardly rectifying K(+) channels conduct greater current at depolarized membrane potentials, whereas inward rectifier channels conduct greater current at hyperpolarized membrane potentials. Under most circumstances, outward currents through inwardly rectifying K(+) channels are reduced at more depolarized potentials. However, the acetylcholine-gated K(+) channel (KACh) conducts current that inwardly rectifies when activated by some ligands (such as acetylcholine), and yet conducts current that outwardly rectifies when activated by other ligands (for example, pilocarpine and choline). The perplexing and paradoxical behavior of KACh channels is due to the intrinsic voltage sensitivity of the receptor that activates KACh channels, the M2 muscarinic receptor (M2R). Emerging evidence reveals that the affinity of M2R for distinct ligands varies in a voltage-dependent and ligand-specific manner. These intrinsic receptor properties determine whether current conducted by KACh channels inwardly or outwardly rectifies. This review summarizes the most recent concepts regarding the intrinsic voltage sensitivity of muscarinic receptors and the consequences of this intriguing behavior on cardiac physiology and pharmacology of KACh channels. Copyright © 2016 by The American Society for Pharmacology and Experimental Therapeutics.

Spin-analyzed SANS for soft matter applications

NASA Astrophysics Data System (ADS)

Chen, W. C.; Barker, J. G.; Jones, R.; Krycka, K. L.; Watson, S. M.; Gagnon, C.; Perevozchivoka, T.; Butler, P.; Gentile, T. R.

2017-06-01

The small angle neutron scattering (SANS) of nearly Q-independent nuclear spin-incoherent scattering from hydrogen present in most soft matter and biology samples may raise an issue in structure determination in certain soft matter applications. This is true at high wave vector transfer Q where coherent scattering is much weaker than the nearly Q-independent spin-incoherent scattering background. Polarization analysis is capable of separating coherent scattering from spin-incoherent scattering, hence potentially removing the nearly Q-independent background. Here we demonstrate SANS polarization analysis in conjunction with the time-of-flight technique for separation of coherent and nuclear spin-incoherent scattering for a sample of silver behenate back-filled with light water. We describe a complete procedure for SANS polarization analysis for separating coherent from incoherent scattering for soft matter samples that show inelastic scattering. Polarization efficiency correction and subsequent separation of the coherent and incoherent scattering have been done with and without a time-of-flight technique for direct comparisons. In addition, we have accounted for the effect of multiple scattering from light water to determine the contribution of nuclear spin-incoherent scattering in both the spin flip channel and non-spin flip channel when performing SANS polarization analysis. We discuss the possible gain in the signal-to-noise ratio for the measured coherent scattering signal using polarization analysis with the time-of-flight technique compared with routine unpolarized SANS measurements.

PHAZR: A phenomenological code for holeboring in air

NASA Astrophysics Data System (ADS)

Picone, J. M.; Boris, J. P.; Lampe, M.; Kailasanath, K.

1985-09-01

This report describes a new code for studying holeboring by a charged particle beam, laser, or electric discharge in a gas. The coordinates which parameterize the channel are radial displacement (r) from the channel axis and distance (z) along the channel axis from the energy source. The code is primarily phenomenological that is, we use closed solutions of simple models in order to represent many of the effects which are important in holeboring. The numerical simplicity which we gain from the use of these solutions enables us to estimate the structure of channel over long propagation distances while using a minimum of computer time. This feature makes PHAZR a useful code for those studying and designing future systems. Of particular interest is the design and implementation of the subgrid turbulence model required to compute the enhanced channel cooling caused by asymmetry-driven turbulence. The approximate equations of Boris and Picone form the basis of the model which includes the effects of turbulent diffusion and fluid transport on the turbulent field itself as well as on the channel parameters. The primary emphasis here is on charged particle beams, and as an example, we present typical results for an ETA-like beam propagating in air. These calculations demonstrate how PHAZAR may be used to investigate accelerator parameter space and to isolate the important physical parameters which determine the holeboring properties of a given system. The comparison with two-dimensional calculations provide a calibration of the subgrid turbulence model.

Stream channel responses to streamflow diversion on small streams of the Snake River drainage, Idaho

Treesearch

Carolyn C. Bohn; John G. King

2000-01-01

The effects on channels of small, low-head seasonal water diversions in the Snake River drainage were investigated. Channels below small diversions were compared to the channels immediately above the same diversions to determine if differences in flow conveyance, substrate sediment size distribution, or streamside vegetation density were present. Estimates of flow...

FPGA-based Trigger System for the Fermilab SeaQuest Experimentz

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shiu, Shiuan-Hal; Wu, Jinyuan; McClellan, Randall Evan

The SeaQuest experiment (Fermilab E906) detects pairs of energetic μ + and μ -produced in 120 GeV/c proton–nucleon interactions in a high rate environment. The trigger system we used consists of several arrays of scintillator hodoscopes and a set of field-programmable gate array (FPGA) based VMEbus modules. Signals from up to 96 channels of hodoscope are digitized by each FPGA with a 1-ns resolution using the time-to-digital convertor (TDC) firmware. The delay of the TDC output can be adjusted channel-by-channel in 1-ns step and then re-aligned with the beam RF clock. The hit pattern on the hodoscope planes is thenmore » examined against pre-determined trigger matrices to identify candidate muon tracks. Finally, information on the candidate tracks is sent to the 2nd-level FPGA-based track correlator to find candidate di-muon events. The design and implementation of the FPGA-based trigger system for SeaQuest experiment are presented.« less

FPGA-based trigger system for the Fermilab SeaQuest experimentz

NASA Astrophysics Data System (ADS)

Shiu, Shiuan-Hal; Wu, Jinyuan; McClellan, Randall Evan; Chang, Ting-Hua; Chang, Wen-Chen; Chen, Yen-Chu; Gilman, Ron; Nakano, Kenichi; Peng, Jen-Chieh; Wang, Su-Yin

2015-12-01

The SeaQuest experiment (Fermilab E906) detects pairs of energetic μ+ and μ- produced in 120 GeV/c proton-nucleon interactions in a high rate environment. The trigger system consists of several arrays of scintillator hodoscopes and a set of field-programmable gate array (FPGA) based VMEbus modules. Signals from up to 96 channels of hodoscope are digitized by each FPGA with a 1-ns resolution using the time-to-digital convertor (TDC) firmware. The delay of the TDC output can be adjusted channel-by-channel in 1-ns step and then re-aligned with the beam RF clock. The hit pattern on the hodoscope planes is then examined against pre-determined trigger matrices to identify candidate muon tracks. Information on the candidate tracks is sent to the 2nd-level FPGA-based track correlator to find candidate di-muon events. The design and implementation of the FPGA-based trigger system for SeaQuest experiment are presented.

FPGA-based Trigger System for the Fermilab SeaQuest Experimentz

DOE PAGES

Shiu, Shiuan-Hal; Wu, Jinyuan; McClellan, Randall Evan; ...

2015-09-10

The SeaQuest experiment (Fermilab E906) detects pairs of energetic μ + and μ -produced in 120 GeV/c proton–nucleon interactions in a high rate environment. The trigger system we used consists of several arrays of scintillator hodoscopes and a set of field-programmable gate array (FPGA) based VMEbus modules. Signals from up to 96 channels of hodoscope are digitized by each FPGA with a 1-ns resolution using the time-to-digital convertor (TDC) firmware. The delay of the TDC output can be adjusted channel-by-channel in 1-ns step and then re-aligned with the beam RF clock. The hit pattern on the hodoscope planes is thenmore » examined against pre-determined trigger matrices to identify candidate muon tracks. Finally, information on the candidate tracks is sent to the 2nd-level FPGA-based track correlator to find candidate di-muon events. The design and implementation of the FPGA-based trigger system for SeaQuest experiment are presented.« less

Cryptographic robustness of practical quantum cryptography: BB84 key distribution protocol

NASA Astrophysics Data System (ADS)

Molotkov, S. N.

2008-07-01

In real fiber-optic quantum cryptography systems, the avalanche photodiodes are not perfect, the source of quantum states is not a single-photon one, and the communication channel is lossy. For these reasons, key distribution is impossible under certain conditions for the system parameters. A simple analysis is performed to find relations between the parameters of real cryptography systems and the length of the quantum channel that guarantee secure quantum key distribution when the eavesdropper’s capabilities are limited only by fundamental laws of quantum mechanics while the devices employed by the legitimate users are based on current technologies. Critical values are determined for the rate of secure real-time key generation that can be reached under the current technology level. Calculations show that the upper bound on channel length can be as high as 300 km for imperfect photodetectors (avalanche photodiodes) with present-day quantum efficiency (η ≈ 20%) and dark count probability ( p dark ˜ 10-7).

Structural studies of enzyme-based microfluidic biofuel cells

NASA Astrophysics Data System (ADS)

Togo, Makoto; Takamura, Akimasa; Asai, Tatsuya; Kaji, Hirokazu; Nishizawa, Matsuhiko

An enzyme-based glucose/O 2 biofuel cell was constructed within a microfluidic channel to study the influence of electrode configuration and fluidic channel height on cell performance. The cell was composed of a bilirubin oxidase (BOD)-adsorbed O 2 cathode and a glucose anode prepared by co-immobilization of glucose dehydrogenase (GDH), diaphorase (Dp) and VK 3-pendant poly- L-lysine. The consumption of O 2 at the upstream cathode protected the downstream anode from interfering O 2 molecules, and consequently improved the cell performance (maximum cell current) ca. 10% for the present cell. The cell performance was also affected by the channel height. The output current and power of a 0.1 mm-height cell was significantly less than those of a 1 mm-height cell because of the depletion of O 2, as determined by the shape of the E- I curve at the cathode. On the other hand, the volume density of current and power was several times higher for the narrower cell.

Profiling optimization for big data transfer over dedicated channels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yun, D.; Wu, Qishi; Rao, Nageswara S

The transfer of big data is increasingly supported by dedicated channels in high-performance networks, where transport protocols play an important role in maximizing applicationlevel throughput and link utilization. The performance of transport protocols largely depend on their control parameter settings, but it is prohibitively time consuming to conduct an exhaustive search in a large parameter space to find the best set of parameter values. We propose FastProf, a stochastic approximation-based transport profiler, to quickly determine the optimal operational zone of a given data transfer protocol/method over dedicated channels. We implement and test the proposed method using both emulations based onmore » real-life performance measurements and experiments over physical connections with short (2 ms) and long (380 ms) delays. Both the emulation and experimental results show that FastProf significantly reduces the profiling overhead while achieving a comparable level of end-to-end throughput performance with the exhaustive search-based approach.« less

The unidirectional motion of two heat-conducting liquids in a flat channel

NASA Astrophysics Data System (ADS)

Andreev, V. K.; Cheremnykh, E. N.

2017-10-01

The unidirectional motion of two viscous incompressible liquids in a flat channel is studied. Liquids contact on a flat interface. External boundaries are fixed solid walls, on which the non-stationary temperature gradients are given. The motion is induced by a joint action of thermogravitational and thermocapillary forces and given total non - stationary fluid flow rate in layers. The corresponding initial boundary value problem is conjugate and inverse because the pressure gradients along axes channel have to be determined together with the velocity and temperature field. For this problem the exact stationary solution is found and a priori estimates of non - stationary solutions are obtained. In Laplace images the solution of the non - stationary problem is found in quadratures. It is proved, that the solution converges to a steady regime with time, if the temperature on the walls and the fluid flow rate are stabilized. The numerical calculations for specific liquid media good agree with the theoretical results.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Olivero, J.; Navas, V.; Perez, A.

Gold mining is an activity that has been increasing during the last ten years in Colombia. Most mining activities are carried out using mercury for gold amalgamation. In a recent publication we stated that in the Sur de Bolivar, the main gold mining zone in Colombia, the highest mercury concentration in hair was observed in fishermen. The Magdalena River, the largest and most important river in Colombia, receives all this contamination and carries it to the Atlantic Ocean through two means: The main river course and the Dique Channel. The Dique Channel is surrounded by many marshes, which are amore » major source of fish for nearly two hundred thousands people in northwestern Colombia. The goal of the present study was to determine, for the first time, the content of mercury in muscle tissue of the four most popular fish species purchased in some towns along the Dique Channel, to establish whether these concentrations fall within the WHO guidelines, and to identify those species which can be consumed with less risk. 11 refs., 1 fig., 2 tabs.« less

Acoustic measurement of bubble size and position in a piezo driven inkjet printhead

NASA Astrophysics Data System (ADS)

van der Bos, Arjan; Jeurissen, Roger; de Jong, Jos; Stevens, Richard; Versluis, Michel; Reinten, Hans; van den Berg, Marc; Wijshoff, Herman; Lohse, Detlef

2008-11-01

A bubble can be entrained in the ink channel of a piezo-driven inkjet printhead, where it grows by rectified diffusion. If large enough, the bubble counteracts the pressure buildup at the nozzle, resulting in nozzle failure. Here an acoustic sizing method for the volume and position of the bubble is presented. The bubble response is detected by the piezo actuator itself, operating in a sensor mode. The method used to determine the volume and position of the bubble is based on a linear model in which the interaction between the bubble and the channel are included. This model predicts the acoustic signal for a given position and volume of the bubble. The inverse problem is to infer the position and volume of the bubble from the measured acoustic signal. By solving it, we can thus acoustically measure size and position of the bubble. The validity of the presented method is supported by time-resolved optical observations of the dynamics of the bubble within an optically accessible ink-jet channel.

Omnichannel Customer Behavior: Key Drivers of Technology Acceptance and Use and Their Effects on Purchase Intention

PubMed Central

Juaneda-Ayensa, Emma; Mosquera, Ana; Sierra Murillo, Yolanda

2016-01-01

The advance of the Internet and new technologies over the last decade has transformed the retailing panorama. More and more channels are emerging, causing consumers to change their habits and shopping behavior. An omnichannel strategy is a form of retailing that, by enabling real interaction, allows customers to shop across channels anywhere and at any time, thereby providing them with a unique, complete, and seamless shopping experience that breaks down the barriers between channels. This paper aims to identify the factors that influence omnichannel consumers' behavior through their acceptance of and intention to use new technologies during the shopping process. To this end, an original model was developed to explain omnichannel shopping behavior based on the variables used in the UTAUT2 model and two additional factors: personal innovativeness and perceived security. The model was tested with a sample of 628 Spanish customers of the store Zara who had used at least two channels during their most recent shopping journey. The results indicate that the key determinants of purchase intention in an omnichannel context are, in order of importance: personal innovativeness, effort expectancy, and performance expectancy. The theoretical and managerial implications are discussed. PMID:27516749

Strain detection in crystalline heterostructures using bidimensional blocking patterns of channelled particles

NASA Astrophysics Data System (ADS)

Redondo-Cubero, A.; David-Bosne, E.; Wahl, U.; Miranda, P.; da Silva, M. R.; Correia, J. G.; Lorenz, K.

2018-03-01

Strain is a critical parameter affecting the growth and the performance of many semiconductor systems but, at the same time, the accurate determination of strain profiles in heterostructures can be challenging, especially at the nanoscale. Ion channelling/blocking is a powerful technique for the detection of the strain state of thin films, normally carried out through angular scans with conventional particle detectors. Here we report the novel application of position sensitive detectors for the evaluation of the strain in a series of AlInN/GaN heterostructures with different compositions and thicknesses. The tetragonal strain is varied from compressive to tensile and analysed through bidimensional blocking patterns. The results demonstrate that strain can be correctly quantified when compared to Monte Carlo channelling simulations, which are essential because of the presence of ion steering effects at the interface between the layer and the substrate. Despite this physical limitation caused by ion steering, our results show that full bidimensional patterns can be applied to detect fingerprints and enhance the accuracy for most critical cases, in which the angular shift associated to the lattice distortion is below the critical angle for channelling.

Influence of vascular network design on gas transfer in lung assist device technology.

PubMed

Bassett, Erik K; Hoganson, David M; Lo, Justin H; Penson, Elliot J N; Vacanti, Joseph P

2011-01-01

Blood oxygenators are vital for the critically ill, but their use is limited to the hospital setting. A portable blood oxygenator or a lung assist device for ambulatory or long-term use would greatly benefit patients with chronic lung disease. In this work, a biomimetic blood oxygenator system was developed which consisted of a microfluidic vascular network covered by a gas permeable silicone membrane. This system was used to determine the influence of key microfluidic parameters-channel size, oxygen exposure length, and blood shear rate-on blood oxygenation and carbon dioxide removal. Total gas transfer increased linearly with flow rate, independent of channel size and oxygen exposure length. On average, CO(2) transfer was 4.3 times higher than oxygen transfer. Blood oxygen saturation was also found to depend on the flow rate per channel but in an inverse manner; oxygenation decreased and approached an asymptote as the flow rate per channel increased. These relationships can be used to optimize future biomimetic vascular networks for specific lung applications: gas transfer for carbon dioxide removal in patients with chronic obstructive pulmonary disease or oxygenation for premature infants requiring complete lung replacement therapy.

Omnichannel Customer Behavior: Key Drivers of Technology Acceptance and Use and Their Effects on Purchase Intention.

PubMed

Juaneda-Ayensa, Emma; Mosquera, Ana; Sierra Murillo, Yolanda

2016-01-01

The advance of the Internet and new technologies over the last decade has transformed the retailing panorama. More and more channels are emerging, causing consumers to change their habits and shopping behavior. An omnichannel strategy is a form of retailing that, by enabling real interaction, allows customers to shop across channels anywhere and at any time, thereby providing them with a unique, complete, and seamless shopping experience that breaks down the barriers between channels. This paper aims to identify the factors that influence omnichannel consumers' behavior through their acceptance of and intention to use new technologies during the shopping process. To this end, an original model was developed to explain omnichannel shopping behavior based on the variables used in the UTAUT2 model and two additional factors: personal innovativeness and perceived security. The model was tested with a sample of 628 Spanish customers of the store Zara who had used at least two channels during their most recent shopping journey. The results indicate that the key determinants of purchase intention in an omnichannel context are, in order of importance: personal innovativeness, effort expectancy, and performance expectancy. The theoretical and managerial implications are discussed.

A robotic multi-channel platform for interstitial photodynamic therapy

PubMed Central

Sharikova, Anna V.; Finlay, Jarod C.; Dimofte, Andreea; Zhu, Timothy C.

2015-01-01

A custom-made robotic multichannel platform for interstitial photodynamic therapy (PDT) and diffuse optical tomography (DOT) was developed and tested in a phantom experiment. The system, which was compatible with the operating room (OR) environment, had 16 channels for independent positioning of light sources and/or isotropic detectors in separate catheters. Each channel’s motor had an optical encoder for position feedback, with resolution of 1.5 mm, and a maximum speed of 5 cm/s. Automatic calibration of detector positions was implemented using an optical diode beam that defined the starting position of each motor, and by means of feedback algorithms controlling individual channels. As a result, the accuracy of zero position of 0.1 mm for all channels was achieved. We have also employed scanning procedures where detectors automatically covered the appropriate range around source positions. Thus, total scan time for a typical optical properties (OP) measurement throughout the phantom was about 1.5 minutes with point sources. The OP were determined based on the measured light fluence rates. These enhancements allow a tremendous improvement of treatment quality for a bulk tumor compared to the systems employed in previous clinical trials. PMID:25914794

Donation and back-donation analyzed through a charge transfer model based on density functional theory.

PubMed

Orozco-Valencia, Ulises; Gázquez, José L; Vela, Alberto

2017-07-01

The net charge transfer process that occurs between two species, A and B, interacting with each other, may be decomposed into two processes: one in which A receives charge from B, which can be identified as the electrophilic channel for A or the nucleophilic channel for B, and a second in which A donates charge to B, which can be identified as the nucleophilic channel for A or the electrophilic channel for B. By determining the amount of charge associated with both processes through the minimization of the interaction energy associated with each case, the expressions for the amount of charge involved in each case can be expressed in terms of the directional chemical potentials and the hardnesses of the interacting species. The correlation between the charges obtained for the interaction between phosphine ligands of the type PRR'R'' and Ni, and the A 1 carbonyl stretching frequency provides support for their interpretation as measures of the electrophilicity and nucleophilicity of a chemical species, and, at the same time, allows one to describe the donation and back-donation processes in terms of the density functional theory of chemical reactivity.

Enhancing the sensitivity of fluorescence correlation spectroscopy by using time-correlated single photon counting.

PubMed

Lamb, D C; Müller, B K; Bräuchle, C

2005-10-01

Fluorescence correlation spectroscopy (FCS) and fluorescence cross-correlation spectroscopy (FCCS) are methods that extract information about a sample from the influence of thermodynamic equilibrium fluctuations on the fluorescence intensity. This method allows dynamic information to be obtained from steady state equilibrium measurements and its popularity has dramatically increased in the last 10 years due to the development of high sensitivity detectors and its combination with confocal microscopy. Using time-correlated single-photon counting (TCSPC) detection and pulsed excitation, information over the duration of the excited state can be extracted and incorporated in the analysis. In this short review, we discuss new methodologies that have recently emerged which incorporated fluorescence lifetime information or TCSPC data in the FCS and FCCS analysis. Time-gated FCS discriminates between which photons are to be incorporated in the analysis dependent upon their arrival time after excitation. This allows for accurate FCS measurements in the presence of fluorescent background, determination of sample homogeneity, and the ability to distinguish between static and dynamic heterogeneities. A similar method, time-resolved FCS can be used to resolve the individual correlation functions from multiple fluorophores through the different fluorescence lifetimes. Pulsed interleaved excitation (PIE) encodes the excitation source into the TCSPC data. PIE can be used to perform dual-channel FCCS with a single detector and allows elimination of spectral cross-talk with dual-channel detection. For samples that undergo fluorescence resonance energy transfer (FRET), quantitative FCCS measurements can be performed in spite of the FRET and the static FRET efficiency can be determined.

Effects of wall curvature on turbulence statistics

NASA Technical Reports Server (NTRS)

Moser, R. D.; Moin, P.

1985-01-01

A three-dimensional, time-dependent, direct numerical simulation of low-Reynolds number turbulent flow in a mildly curved channel was performed, and the results examined to determine the mechanism by which curvature affects wall-bounded turbulent shear flows. A spectral numerical method with about one-million modes was employed, and no explicit subgrid scale model was used. The effects of curvature on this flow were determined by comparing the concave and convex sides of the channel. The observed effects are consistent with experimental observations for mild curvature. The most significant difference in the turbulence statistics between the concave and convex sides is in the Reynolds shear stress. This is accompanied by significant differences in the terms of the Reynolds shear stress balance equations. In addition, it was found that stationary Taylor-Goertler vortices were present and that they had a significant effect on the flow by contributing to the mean Reynolds shear stress, and by enhancing the difference between the wall shear stresses.

A complex valued radial basis function network for equalization of fast time varying channels.

PubMed

Gan, Q; Saratchandran, P; Sundararajan, N; Subramanian, K R

1999-01-01

This paper presents a complex valued radial basis function (RBF) network for equalization of fast time varying channels. A new method for calculating the centers of the RBF network is given. The method allows fixing the number of RBF centers even as the equalizer order is increased so that a good performance is obtained by a high-order RBF equalizer with small number of centers. Simulations are performed on time varying channels using a Rayleigh fading channel model to compare the performance of our RBF with an adaptive maximum-likelihood sequence estimator (MLSE) consisting of a channel estimator and a MLSE implemented by the Viterbi algorithm. The results show that the RBF equalizer produces superior performance with less computational complexity.

A design of a valid signal selecting and position decoding ASIC for PET using silicon photomultipliers

NASA Astrophysics Data System (ADS)

Cho, M.; Lim, K.-t.; Kim, H.; Yeom, J.-y.; Kim, J.; Lee, C.; Choi, H.; Cho, G.

2017-01-01

In most cases, a PET system has numerous electrical components and channel circuits and thus it would rather be a bulky product. Also, most existing systems receive analog signals from detectors which make them vulnerable to signal distortions. For these reasons, channel reduction techniques are important. In this work, an ASIC for PET module is being proposed. An ASIC chip for 16 PET detector channels, VSSPDC, has been designed and simulated. The main function of the chip is 16-to-1 channel reduction, i.e., finding the position of only the valid signals, signal timing, and magnitudes in all 16 channels at every recorded event. The ASIC comprises four of 4-channel modules and a 2nd 4-to-1 router. A single channel module comprises a transimpedance amplifier for the silicon photomultipliers, dual comparators with high and low level references, and a logic circuitry. While the high level reference was used to test the validity of the signal, the low level reference was used for the timing. The 1-channel module of the ASIC produced an energy pulse by time-over-threshold method and it also produced a time pulse with a fixed delayed time. Since the ASIC chip outputs only a few digital pulses and does not require an external clock, it has an advantage over noise properties. The cadence simulation showed the good performance of the chip as designed.

Preliminary analysis of the Baranof Fan system, Gulf of Alaska, based on 2D seismic reflection and multibeam bathymetry data

NASA Astrophysics Data System (ADS)

LeVoir, M. A.; Gulick, S. P.; Reece, R.; Barth, G. A.; Childs, J. R.; Everson, E. D.; Hart, P. E.; Johnson, K. M.; Lester, W. R.; Sliter, R. W.

2011-12-01

The Baranof Fan is a large marine sedimentary system in the eastern Gulf of Alaska, straddling the border between the U.S. and Canada. The volume of the Fan is estimated to be > 200,000 km3. Little is known about the depositional timing, the tectonic and morphologic processes influencing its development, or the role of channel aggradation and avulsion in its progression. Both tectonic and climatic transitions likely influenced the formation and evolution of the Fan, with events including the onset of northern hemisphere glaciation, the Mid-Pleistocene transition, the transport of the Yakutat Terrane along the southeast Alaskan margin, and the uplift of the Coast Mountains. 2D seismic reflection and multibeam bathymetry data were collected in the Gulf of Alaska in June 2011 aboard the R/V Marcus G. Langseth as a part of the U.S. Extended Continental Shelf (ECS) program assessing potential opportunities under the United Nations Law of the Sea Convention. The purpose of the 2011 survey was to determine sediment thickness, velocity structure, stratigraphic architecture, and crustal structure on of the Gulf of Alaska seafloor in support of U.S. continental shelf maritime zone definition. The surveyed geologic features include the Surveyor and Baranof sedimentary systems, which control active sediment distribution in the Gulf of Alaska. Preliminary analysis of these data show four distinct buried channels throughout the mid to distal Baranof Fan, ranging in width from 5 - 9 km, which may have evolved into modern surface channels (ranging in width from 2 - 7 km) visible in both the seismic data and multibeam bathymetry. The location and trajectory of these buried channels, however, appears distinct from the modern Horizon and Mukluk Channels; the buried channels may have avulsed into the modern channel systems, or could possibly be older and now abandoned branches instrumental in building the westward part of the Fan. All of the imaged channels appear to be depositional, and consistently have thicker levees on their western banks, possibly due to effects of the Alaska Gyre at depth and/or the Coriolis. Preliminary velocity analysis from sonobuoy refraction data indicates that the thalwegs of buried channels do not exceed an 800 m depth within the 2 km thick Fan; we will seek to map a prominent reflector located beneath these channels from the Baranof system into the Surveyor system. New age dates from ashes sampled at DSDP Site 178 within the Surveyor Fan may thus provide constraints on the timing of deposition of the western Baranof Fan.

Performance Results of Some Candidate French Modems for the Aeronautical Satellite Communication Channel

DOT National Transportation Integrated Search

1978-05-01

Five candidate data, voice, and ranging modems were evaluated by the AEROSAT channel simulation facility to determine applicability for use in the aeronautical satellite communication channel for air traffic control. The modems were supplied by Telec...

Multi-channel time-reversal receivers for multi and 1-bit implementations

DOEpatents

Candy, James V.; Chambers, David H.; Guidry, Brian L.; Poggio, Andrew J.; Robbins, Christopher L.

2008-12-09

A communication system for transmitting a signal through a channel medium comprising digitizing the signal, time-reversing the digitized signal, and transmitting the signal through the channel medium. In one embodiment a transmitter is adapted to transmit the signal, a multiplicity of receivers are adapted to receive the signal, a digitizer digitizes the signal, and a time-reversal signal processor is adapted to time-reverse the digitized signal. An embodiment of the present invention includes multi bit implementations. Another embodiment of the present invention includes 1-bit implementations. Another embodiment of the present invention includes a multiplicity of receivers used in the step of transmitting the signal through the channel medium.

Systematic detection of long-term slow slip events along Hyuga-nada to central Shikoku, Nankai subduction zone, using GNSS data

NASA Astrophysics Data System (ADS)

Takagi, R.; Obara, K.; Uchida, N.

2017-12-01

Understanding slow earthquake activity improves our knowledge of slip behavior in brittle-ductile transition zone and subduction process including megathrust earthquakes. In order to understand overall picture of slow slip activity, it is important to make a comprehensive catalog of slow slip events (SSEs). Although short-term SSEs have been detected by GNSS and tilt meter records systematically, analysis of long-term slow slip events relies on individual slip inversions. We develop an algorism to systematically detect long-term SSEs and estimate source parameters of the SSEs using GNSS data. The algorism is similar to GRiD-MT (Tsuruoka et al., 2009), which is grid-based automatic determination of moment tensor solution. Instead of moment tensor fitting to long period seismic records, we estimate parameters of a single rectangle fault to fit GNSS displacement time series. First, we make a two dimensional grid covering possible location of SSE. Second, we estimate best-fit parameters (length, width, slip, and rake) of the rectangle fault at each grid point by an iterative damped least square method. Depth, strike, and dip are fixed on the plate boundary. Ramp function with duration of 300 days is used for expressing time evolution of the fault slip. Third, a grid maximizing variance reduction is selected as a candidate of long-term SSE. We also search onset of ramp function based on the grid search. We applied the method to GNSS data in southwest Japan to detect long-term SSEs in Nankai subduction zone. With current selection criteria, we found 13 events with Mw6.2-6.9 in Hyuga-nada, Bungo channel, and central Shikoku from 1998 to 2015, which include unreported events. Key finding is along strike migrations of long-term SSEs from Hyuga-nada to Bungo channel and from Bungo channel to central Shikoku. In particular, three successive events migrating northward in Hyuga-nada preceded the 2003 Bungo channel SSE, and one event in central Shikoku followed the 2003 SSE in Bungo channel. The space-time dimensions of the possible along-strike migration are about 300km in length and 6 years in time. Systematic detection with assumptions of various durations in the time evolution of SSE may improve the picture of SSE activity and possible interaction with neighboring SSEs.

Nonlinear theory of nonstationary low Mach number channel flows of freely cooling nearly elastic granular gases.

PubMed

Meerson, Baruch; Fouxon, Itzhak; Vilenkin, Arkady

2008-02-01

We employ hydrodynamic equations to investigate nonstationary channel flows of freely cooling dilute gases of hard and smooth spheres with nearly elastic particle collisions. This work focuses on the regime where the sound travel time through the channel is much shorter than the characteristic cooling time of the gas. As a result, the gas pressure rapidly becomes almost homogeneous, while the typical Mach number of the flow drops well below unity. Eliminating the acoustic modes and employing Lagrangian coordinates, we reduce the hydrodynamic equations to a single nonlinear and nonlocal equation of a reaction-diffusion type. This equation describes a broad class of channel flows and, in particular, can follow the development of the clustering instability from a weakly perturbed homogeneous cooling state to strongly nonlinear states. If the heat diffusion is neglected, the reduced equation becomes exactly soluble, and the solution develops a finite-time density blowup. The blowup has the same local features at singularity as those exhibited by the recently found family of exact solutions of the full set of ideal hydrodynamic equations [I. Fouxon, Phys. Rev. E 75, 050301(R) (2007); I. Fouxon,Phys. Fluids 19, 093303 (2007)]. The heat diffusion, however, always becomes important near the attempted singularity. It arrests the density blowup and brings about previously unknown inhomogeneous cooling states (ICSs) of the gas, where the pressure continues to decay with time, while the density profile becomes time-independent. The ICSs represent exact solutions of the full set of granular hydrodynamic equations. Both the density profile of an ICS and the characteristic relaxation time toward it are determined by a single dimensionless parameter L that describes the relative role of the inelastic energy loss and heat diffusion. At L>1 the intermediate cooling dynamics proceeds as a competition between "holes": low-density regions of the gas. This competition resembles Ostwald ripening (only one hole survives at the end), and we report a particular regime where the "hole ripening" statistics exhibits a simple dynamic scaling behavior.

Compact conscious animal positron emission tomography scanner

DOEpatents

Schyler, David J.; O'Connor, Paul; Woody, Craig; Junnarkar, Sachin Shrirang; Radeka, Veljko; Vaska, Paul; Pratte, Jean-Francois; Volkow, Nora

2006-10-24

A method of serially transferring annihilation information in a compact positron emission tomography (PET) scanner includes generating a time signal for an event, generating an address signal representing a detecting channel, generating a detector channel signal including the time and address signals, and generating a composite signal including the channel signal and similarly generated signals. The composite signal includes events from detectors in a block and is serially output. An apparatus that serially transfers annihilation information from a block includes time signal generators for detectors in a block and an address and channel signal generator. The PET scanner includes a ring tomograph that mounts onto a portion of an animal, which includes opposing block pairs. Each of the blocks in a block pair includes a scintillator layer, detection array, front-end array, and a serial encoder. The serial encoder includes time signal generators and an address signal and channel signal generator.

Invited Article: miniTimeCube

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, V. A., E-mail: vli2@hawaii.edu; Dorrill, R.; Duvall, M. J.

2016-02-15

We present the development of the miniTimeCube (mTC), a novel compact neutrino  detector. The mTC is a multipurpose detector, aiming to detect not only neutrinos but also fast/thermal neutrons. Potential applications include the counterproliferation of nuclear materials and the investigation of antineutrino short-baseline effects. The mTC is a plastic 0.2% {sup 10}B–doped scintillator (13 cm){sup 3} cube surrounded by 24 Micro-Channel Plate (MCP) photon detectors, each with an 8 × 8 anode totaling 1536 individual channels/pixels viewing the scintillator. It uses custom-made electronics modules which mount on top of the MCPs, making our detector compact and able to both distinguishmore » different types of events and reject noise in real time. The detector is currently deployed and being tested at the National Institute of Standards and Technology Center for Neutron Research nuclear reactor (20 MW{sub th}) in Gaithersburg MD. A shield for further tests is being constructed, and calibration and upgrades are ongoing. The mTC’s improved spatiotemporal resolution will allow for determination of incident particle directions beyond previous capabilities.« less

A new Caputo time fractional model for heat transfer enhancement of water based graphene nanofluid: An application to solar energy

NASA Astrophysics Data System (ADS)

Aman, Sidra; Khan, Ilyas; Ismail, Zulkhibri; Salleh, Mohd Zuki; Tlili, I.

2018-06-01

In this article the idea of Caputo time fractional derivatives is applied to MHD mixed convection Poiseuille flow of nanofluids with graphene nanoparticles in a vertical channel. The applications of nanofluids in solar energy are argued for various solar thermal systems. It is argued in the article that using nanofluids is an alternate source to produce solar energy in thermal engineering and solar energy devices in industries. The problem is modelled in terms of PDE's with initial and boundary conditions and solved analytically via Laplace transform method. The obtained solutions for velocity, temperature and concentration are expressed in terms of Wright's function. These solutions are significantly controlled by the variations of parameters including thermal Grashof number, Solutal Grashof number and nanoparticles volume fraction. Expressions for skin-friction, Nusselt and Sherwood numbers are also determined on left and right walls of the vertical channel with important numerical results in tabular form. It is found that rate of heat transfer increases with increasing nanoparticles volume fraction and Caputo time fractional parameters.

Cerebral cortex activation mapping upon electrical muscle stimulation by 32-channel time-domain functional near-infrared spectroscopy.

PubMed

Re, Rebecca; Muthalib, Makii; Contini, Davide; Zucchelli, Lucia; Torricelli, Alessandro; Spinelli, Lorenzo; Caffini, Matteo; Ferrari, Marco; Quaresima, Valentina; Perrey, Stephane; Kerr, Graham

2013-01-01

The application of different EMS current thresholds on muscle activates not only the muscle but also peripheral sensory axons that send proprioceptive and pain signals to the cerebral cortex. A 32-channel time-domain fNIRS instrument was employed to map regional cortical activities under varied EMS current intensities applied on the right wrist extensor muscle. Eight healthy volunteers underwent four EMS at different current thresholds based on their individual maximal tolerated intensity (MTI), i.e., 10 % < 50 % < 100 % < over 100 % MTI. Time courses of the absolute oxygenated and deoxygenated hemoglobin concentrations primarily over the bilateral sensorimotor cortical (SMC) regions were extrapolated, and cortical activation maps were determined by general linear model using the NIRS-SPM software. The stimulation-induced wrist extension paradigm significantly increased activation of the contralateral SMC region according to the EMS intensities, while the ipsilateral SMC region showed no significant changes. This could be due in part to a nociceptive response to the higher EMS current intensities and result also from increased sensorimotor integration in these cortical regions.

Determination of Flow Resistance Coefficient for Vegetation in Open Channel: Laboratory study

NASA Astrophysics Data System (ADS)

Aliza Ahmad, Noor; Ali, ZarinaMd; Arish, Nur Aini Mohd; Munirah Mat Daud, Azra; Fatin Amirah Alias, Nur

2018-04-01

This study focused on determination of flow resistances coefficient for grass in an open channel. Laboratory works were conducted to examine the effects of varying of roughness elements on the flume to determine flow resistance coefficient and also to determine the optimum flow resistance with five different flow rate, Q. Laboratory study with two type of vegetation which are Cow Grass and Pearl Grass were implementing to the bed of a flume. The roughness coefficient, n value is determine using Manning’s equation while Soil Conservation Services (SCS) method was used to determine the surface resistance. From the experiment, the flow resistance coefficient for Cow Grass in range 0.0008 - 0.0039 while Pearl Grass value for the flow resistance coefficient are in between 0.0013 - 0.0054. As a conclusion the vegetation roughness value in open channel are depends on density, distribution type of vegetation used and physical characteristic of the vegetation itself

Practical solutions for reducing container ships' waiting times at ports using simulation model

NASA Astrophysics Data System (ADS)

Sheikholeslami, Abdorreza; Ilati, Gholamreza; Yeganeh, Yones Eftekhari

2013-12-01

The main challenge for container ports is the planning required for berthing container ships while docked in port. Growth of containerization is creating problems for ports and container terminals as they reach their capacity limits of various resources which increasingly leads to traffic and port congestion. Good planning and management of container terminal operations reduces waiting time for liner ships. Reducing the waiting time improves the terminal's productivity and decreases the port difficulties. Two important keys to reducing waiting time with berth allocation are determining suitable access channel depths and increasing the number of berths which in this paper are studied and analyzed as practical solutions. Simulation based analysis is the only way to understand how various resources interact with each other and how they are affected in the berthing time of ships. We used the Enterprise Dynamics software to produce simulation models due to the complexity and nature of the problems. We further present case study for berth allocation simulation of the biggest container terminal in Iran and the optimum access channel depth and the number of berths are obtained from simulation results. The results show a significant reduction in the waiting time for container ships and can be useful for major functions in operations and development of container ship terminals.

Single-photon continuous-variable quantum key distribution based on the energy-time uncertainty relation.

PubMed

Qi, Bing

2006-09-15

We propose a new quantum key distribution protocol in which information is encoded on continuous variables of a single photon. In this protocol, Alice randomly encodes her information on either the central frequency of a narrowband single-photon pulse or the time delay of a broadband single-photon pulse, while Bob randomly chooses to do either frequency measurement or time measurement. The security of this protocol rests on the energy-time uncertainty relation, which prevents Eve from simultaneously determining both frequency and time information with arbitrarily high resolution. Since no interferometer is employed in this scheme, it is more robust against various channel noises, such as polarization and phase fluctuations.

A Froude-scaled model of a bedrock-alluvial channel reach: 2. Sediment cover

NASA Astrophysics Data System (ADS)

Hodge, Rebecca A.; Hoey, Trevor B.

2016-09-01

Previous research into sediment cover in bedrock-alluvial channels has focussed on total sediment cover, rather than the spatial distribution of cover within the channel. The latter is important because it determines the bedrock areas that are protected from erosion and the start and end of sediment transport pathways. We use a 1:10 Froude-scaled model of an 18 by 9 m reach of a bedrock-alluvial channel to study the production and erosion of sediment patches and hence the spatial relationships between flow, bed topography, and sediment dynamics. The hydraulic data from this bed are presented in the companion paper. In these experiments specified volumes of sediment were supplied at the upstream edge of the model reach as single inputs, at each of a range of discharges. This sediment formed patches, and once these stabilized, flow was steadily increased to erode the patches. In summary: (1) patches tend to initiate in the lowest areas of the bed, but areas of topographically induced high flow velocity can inhibit patch development; (2) at low sediment inputs the extent of sediment patches is determined by the bed topography and can be insensitive to the exact volume of sediment supplied; and (3) at higher sediment inputs more extensive patches are produced, stabilized by grain-grain and grain-flow interactions and less influenced by the bed topography. Bedrock topography can therefore be an important constraint on sediment patch dynamics, and topographic metrics are required that incorporate its within-reach variability. The magnitude and timing of sediment input events controls reach-scale sediment cover.

Coding for Communication Channels with Dead-Time Constraints

NASA Technical Reports Server (NTRS)

Moision, Bruce; Hamkins, Jon

2004-01-01

Coding schemes have been designed and investigated specifically for optical and electronic data-communication channels in which information is conveyed via pulse-position modulation (PPM) subject to dead-time constraints. These schemes involve the use of error-correcting codes concatenated with codes denoted constrained codes. These codes are decoded using an interactive method. In pulse-position modulation, time is partitioned into frames of Mslots of equal duration. Each frame contains one pulsed slot (all others are non-pulsed). For a given channel, the dead-time constraints are defined as a maximum and a minimum on the allowable time between pulses. For example, if a Q-switched laser is used to transmit the pulses, then the minimum allowable dead time is the time needed to recharge the laser for the next pulse. In the case of bits recorded on a magnetic medium, the minimum allowable time between pulses depends on the recording/playback speed and the minimum distance between pulses needed to prevent interference between adjacent bits during readout. The maximum allowable dead time for a given channel is the maximum time for which it is possible to satisfy the requirement to synchronize slots. In mathematical shorthand, the dead-time constraints for a given channel are represented by the pair of integers (d,k), where d is the minimum allowable number of zeroes between ones and k is the maximum allowable number of zeroes between ones. A system of the type to which the present schemes apply is represented by a binary- input, real-valued-output channel model illustrated in the figure. At the transmitting end, information bits are first encoded by use of an error-correcting code, then further encoded by use of a constrained code. Several constrained codes for channels subject to constraints of (d,infinity) have been investigated theoretically and computationally. The baseline codes chosen for purposes of comparison were simple PPM codes characterized by M-slot PPM frames separated by d-slot dead times.

River channel patterns: Braided, meandering, and straight

USGS Publications Warehouse

Leopold, Luna Bergere; Wolman, M. Gordon

1957-01-01

Channel pattern is used to describe the plan view of a reach of river as seen from an airplane, and includes meandering, braiding, or relatively straight channels.Natural channels characteristically exhibit alternating pools or deep reaches and riffles or shallow reaches, regardless of the type of pattern. The length of the pool or distance between riffles in a straight channel equals the straight line distance between successive points of inflection in the wave pattern of a meandering river of the same width. The points of inflection are also shallow points and correspond to riffles in the straight channel. This distance, which is half the wavelength of the meander, varies approximately as a linear function of channel width. In the data we analysed the meander wavelength, or twice the distance between successive riffles, is from 7 to 12 times the channel width. It is concluded that the mechanics which may lead to meandering operate in straight channels.River braiding is characterized by channel division around alluvial islands. The growth of an island begins as the deposition of a central bar which results from sorting and deposition of the coarser fractions of the load which locally cannot be transported. The bar grows downstream and in height by continued deposition on its surface, forcing the water into the flanking channels, which, to carry the flow, deepen and cut laterally into the original banks. Such deepening locally lowers the water surface and the central bar emerges as an island which becomes stabilized by vegetation. Braiding was observed in a small river in a laboratory. Measurements of the adjustments of velocity, depth, width, and slope associated with island development lead to the conclusion that braiding is one of the many patterns which can maintain quasi-equilibrium among discharge, load, and transporting ability. Braiding does not necessarily indicate an excess of total load.Channel cross section and pattern are ultimately controlled by the discharge and load provided by the drainage basin. It is important, therefore, to develop a picture of how the several variables involved in channel shape interact to result in observed channel characteristics. Such a rationale is summarized as follows:Channel width appears to be primarily a function of near-bankfull discharge, in conjunction with the inherent resistance of bed and bank to scour. Excessive width increases the shear on the bed at the expense of that on the bank and the reverse is true for very narrow widths. Because at high stages width adjustment can take place rapidly and with the evacuation or deposition of relatively small volumes of debris, achievement of a ,relatively stable width at high flow is a primary adjustment to which the further interadjustments between depth, velocity, slope, and roughness tend to accommodate.Channel roughness, to the extent that it is determined by particle size, is an independent factor related to the drainage basin rather than to the channel. Roughness in streams carrying fine material, however, is also a function of the dunes or other characteristics of bed configuration. Where roughness is independently determined as well as discharge and load, these studies indicate that a particular slope is associated with the roughness. At the width determined by the discharge, velocity and depth must be adjusted to satisfy quasi-equilibrium in accord with the particular slope. But if roughness also is variable, depending on the transitory configuration of the bed, then a number of combinations of velocity, depth, and slope will satisfy equilibrium.An increase in load at constant discharge, width, and caliber of load tends to be associated with an increasing slope if the roughness (dune or bed configuration) changes with the load. In the laboratory river an increase of load at constant discharge, width, and caliber resulted in progressive aggradation of long reaches of channel at constant slope.The adjustments of several variables tending toward the establishment of quasi-equilibrium in river channels lead to the different channel patterns observed in nature. For example, the data indicate that at a given discharge, meanders occur at smaller values of slope than do’ braids. Further, at the same slope braided channels are associated with higher bankfull discharges than are meanders. An additional example is provided by the division of discharge around islands in braided rivers which produces numerous small channels. The changes in slope, roughness, and channel shape which accompany this division are in accord with quasi-equilibrium adjustments observed in the comparison of large and small rivers.

Glutamate receptor-channel gating. Maximum likelihood analysis of gigaohm seal recordings from locust muscle.

PubMed Central

Bates, S E; Sansom, M S; Ball, F G; Ramsey, R L; Usherwood, P N

1990-01-01

Gigaohm recordings have been made from glutamate receptor channels in excised, outside-out patches of collagenase-treated locust muscle membrane. The channels in the excised patches exhibit the kinetic state switching first seen in megaohm recordings from intact muscle fibers. Analysis of channel dwell time distributions reveals that the gating mechanism contains at least four open states and at least four closed states. Dwell time autocorrelation function analysis shows that there are at least three gateways linking the open states of the channel with the closed states. A maximum likelihood procedure has been used to fit six different gating models to the single channel data. Of these models, a cooperative model yields the best fit, and accurately predicts most features of the observed channel gating kinetics. PMID:1696510

Tetrapentylammonium block of chloramine-T and veratridine modified rat brain type IIA sodium channels

PubMed Central

Ghatpande, A S; Rao, S; Sikdar, S K

2001-01-01

Tetrapentylammonium (TPeA) block of rat brain type IIA sodium channel α subunit was studied using whole cell patch clamp. Results indicate that TPeA blocks the inactivating brain sodium channel in a potential and use-dependent manner similar to that of the cardiac sodium channel. Removal of inactivation using chloramine-T (CT) unmasks a time-dependent block by TPeA consistent with slow blocking kinetics. On the other hand, no time dependence is observed when inactivation is abolished by modification with veratridine. TPeA does not bind in a potential-dependent fashion to veratridine-modified channels and does not significantly affect gating of veratridine-modified channels suggesting that high affinity binding of TPeA to the brain sodium channel is lost after veratridine modification. PMID:11309247

Molecular Identification of XY Sex-Reversed Female and YY Male Channel Catfish

USDA-ARS?s Scientific Manuscript database

Production of channel catfish leads U.S. aquaculture, and monosex culture may provide higher production efficiencies. Determination of phenotypic sex is labor intensive and not practical for large scale culture. Catfish have an X-Y sex determination system with monomorphic sex chromosomes. Hormonal...

Impact of a large flood on mountain river habitats, channel morphology, and valley infrastructure

NASA Astrophysics Data System (ADS)

Hajdukiewicz, Hanna; Wyżga, Bartłomiej; Mikuś, Paweł; Zawiejska, Joanna; Radecki-Pawlik, Artur

2016-11-01

The Biała River, Polish Carpathians, was considerably modified by channelization and channel incision in the twentieth century. To restore the Biała, establishing an erodible corridor was proposed in two river sections located in its mountain and foothill course. In these sections, longer, unmanaged channel reaches alternate with short, channelized reaches; and channel narrowing and incision increases in the downstream direction. In June 2010 an 80-year flood occurred on the river; and this study aims at determining its effects on physical habitat conditions for river biota, channel morphology, and valley-floor infrastructure. Surveys of 10 pairs of closely located, unmanaged and channelized cross sections, performed in 2009 and in the late summer 2010, allowed us to assess the flood-induced changes to physical habitat conditions. A comparison of channel planforms determined before (2009) and after (2012) the flood provided information on the degree of channel widening as well as changes in the width of particular elements of the river's active zone in eight stretches of the Biała. The impact of the flood on valley-floor infrastructure was confronted with the degree of river widening in unmanaged and channelized river reaches. Before the flood, unmanaged cross sections were typified by finer bed material and greater lateral variability in depth-averaged and near-bed flow velocity than channelized cross sections. The flood tended to equalize habitat conditions in both types of river cross sections, obliterating differences (in particular physical habitat parameters) between channelized and unmanaged channel reaches. River widening mostly reflected an increase in the area of channel bars, whereas the widening of low-flow channels was less pronounced. A comparison of channel planform from 2009 and 2012 indicated that intense channel incision typical of downstream sections limited river widening by the flood. Active channel width increased by half in the unmanaged cross sections and by one-third in the channelized cross sections. However, damage to the valley-floor infrastructure was practically limited to the channelized river reaches with reinforced channel banks. This indicates incompetent management of riparian areas rather than the degree of river widening as a principal reason for the economic losses during the flood.

A pulse-mode two channel rocket photometer

NASA Astrophysics Data System (ADS)

Petkov, N. P.

Benefits of vertical profile measurements of nighttime emission in the upper atmosphere are discussed. The block diagram of a two-channel rocket photometer with a common pulse operating mode for both channels is described. The requirements and features of the basic units are determined.

Application of amphipols for structure-functional analysis of TRP channels.

PubMed

Huynh, Kevin W; Cohen, Matthew R; Moiseenkova-Bell, Vera Y

2014-10-01

Amphipathic polymers (amphipols), such as A8-35 and SApol, are a new tool for stabilizing integral membrane proteins in detergent-free conditions for structural and functional studies. Transient receptor potential (TRP) ion channels function as tetrameric protein complexes in a diverse range of cellular processes including sensory transduction. Mammalian TRP channels share ~20 % sequence similarity and are categorized into six subfamilies: TRPC (canonical), TRPV (vanilloid), TRPA (ankyrin), TRPM (melastatin), TRPP (polycystin), and TRPML (mucolipin). Due to the inherent difficulties in purifying eukaryotic membrane proteins, structural studies of TRP channels have been limited. Recently, A8-35 was essential in resolving the molecular architecture of the nociceptor TRPA1 and led to the determination of a high-resolution structure of the thermosensitive TRPV1 channel by cryo-EM. Newly developed maltose-neopentyl glycol (MNG) detergents have also proven to be useful in stabilizing TRP channels for structural analysis. In this review, we will discuss the impacts of amphipols and MNG detergents on structural studies of TRP channels by cryo-EM. We will compare how A8-35 and MNG detergents interact with the hydrophobic transmembrane domains of TRP channels. In addition, we will discuss what these cryo-EM studies reveal on the importance of screening different types of surfactants toward determining high-resolution structures of TRP channels.

Application of amphipols for structure-functional analysis of TRP channels

PubMed Central

Huynh, Kevin W.; Cohen, Matthew R.; Moiseenkova-Bell, Vera Y.

2014-01-01

Amphipathic polymers (amphipols), such as A8-35 and SApol, are a new tool for stabilizing integral membrane proteins in detergent-free conditions for structural and functional studies. Transient receptor potential (TRP) ion channels function as tetrameric protein complexes in a diverse range of cellular processes including sensory transduction. Mammalian TRP channels share ~20% sequence similarity and are categorized into six subfamilies: TRPC (canonical), TRPV (vanilloid), TRPA (ankyrin), TRPM (melastatin), TRPP (polycystin), and TRPML (mucolipin). Due to the inherent difficulties in purifying eukaryotic membrane proteins, structural studies of TRP channels have been limited. Recently, A8-35 was essential in resolving the molecular architecture of the nociceptor TRPA1 and led to the determination of a high resolution structure of the thermosensitive TRPV1 channel by cryo-EM. Newly developed maltose-neopentyl glycol (MNG) detergents have also proven useful in stabilizing TRP channels for structural analysis. In this review, we will discuss the impact of amphipols and MNG detergents on structural studies of TRP channels by cryo-EM. We will compare how A8-35 and MNG detergents interact with the hydrophobic transmembrane (TM) domains of TRP channels. In addition, we will discuss what these cryo-EM studies reveal on the importance of screening different types of surfactants towards determining high resolution structures of TRP channels. PMID:24894720

On the mechanism of TBA block of the TRPV1 channel.

PubMed

Oseguera, Andrés Jara; Islas, León D; García-Villegas, Refugio; Rosenbaum, Tamara

2007-06-01

The transient receptor potential vanilloid 1 (TRPV1) channel is a nonselective cation channel activated by capsaicin and responsible for thermosensation. To date, little is known about the gating characteristics of these channels. Here we used tetrabutylammonium (TBA) to determine whether this molecule behaves as an ion conduction blocker in TRPV1 channels and to gain insight into the nature of the activation gate of this protein. TBA belongs to a family of classic potassium channel blockers that have been widely used as tools for determining the localization of the activation gate and the properties of the pore of several ion channels. We found TBA to be a voltage-dependent pore blocker and that the properties of block are consistent with an open-state blocker, with the TBA molecule binding to multiple open states, each with different blocker affinities. Kinetics of channel closure and burst-length analysis in the presence of blocker are consistent with a state-dependent blocking mechanism, with TBA interfering with closing of an activation gate. This activation gate may be located cytoplasmically with respect to the binding site of TBA ions, similar to what has been observed in potassium channels. We propose an allosteric model for TRPV1 activation and block by TBA, which explains our experimental data.

Channel infiltration from floodflows along the Pawnee River and its tributaries, west-central Kansas

USGS Publications Warehouse

Gillespie, James B.; Perry, C.A.

1988-01-01

Most of the streams is west-central Kansas are ephemeral. Natural recharge to the alluvial aquifers underlying these streams occurs during periods of storm runoff in the ephemeral channels. Proposed flood-retarding structures within the basin will alter the downstream runoff characteristics in these channels by reducing the peak flow and increasing the flow duration. Information concerning channel-infiltration rate, unsaturated and saturated flow, and lithology of the unsaturated zone as related to stream stage and duration was collected along the Pawnee River and its tributaries to determine the effects of the flood-retarding structures. The infiltration rate on ephemeral streams was determined at five sites within the Pawnee River Basin. Tests were conducted in channel infiltrometers constructed by isolating a section of channel with two plastic-lined wooden cofferdams. At two of the sites, perched groundwater mounds intersected the bottom of the channel and reduced the infiltration rate. At two other sites where the perched groundwater mounds did not reach the bottom of the channel, the infiltration rate was directly proportional to the stage. Comparison of infiltration from simulated controlled and uncontrolled floodflows at the five sites indicated an average increase of about 2% with the controlled floodflow. Cumulative infiltration for these simulations ranged from 0.5 to 14.8 acre-ft/mi of channel. (USGS)

Modeling channel interference in an orbital angular momentum-multiplexed laser link

NASA Astrophysics Data System (ADS)

Anguita, Jaime A.; Neifeld, Mark A.; Vasic, Bane V.

2009-08-01

We study the effects of optical turbulence on the energy crosstalk among constituent orbital angular momentum (OAM) states in a vortex-based multi-channel laser communication link and determine channel interference in terms of turbulence strength and OAM state separation. We characterize the channel interference as a function of C2n and transmit OAM state, and propose probability models to predict the random fluctuations in the received signals for such architecture. Simulations indicate that turbulence-induced channel interference is mutually correlated across receive channels.

Electronic band structure effects in the stopping of protons in copper [Electronic band structure non-linear effects in the stopping of protons in copper

DOE PAGES

Quashie, Edwin E.; Saha, Bidhan C.; Correa, Alfredo A.

2016-10-05

Here, we present an ab initio study of the electronic stopping power of protons in copper over a wide range of proton velocities v = 0.02–10a.u. where we take into account nonlinear effects. Time-dependent density functional theory coupled with molecular dynamics is used to study electronic excitations produced by energetic protons. A plane-wave pseudopotential scheme is employed to solve the time-dependent Kohn-Sham equations for a moving ion in a periodic crystal. The electronic excitations and the band structure determine the stopping power of the material and alter the interatomic forces for both channeling and off-channeling trajectories. Our off-channeling results aremore » in quantitative agreement with experiments, and at low velocity they unveil a crossover region of superlinear velocity dependence (with a power of ~1.5) in the velocity range v = 0.07–0.3a.u., which we associate to the copper crystalline electronic band structure. The results are rationalized by simple band models connecting two separate regimes. We find that the limit of electronic stopping v → 0 is not as simple as phenomenological models suggest and it is plagued by band-structure effects.« less

Effects of free and combined chlorine and exposure duration on rainbow trout, channel catfish, and emerald shiners

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brooks, A.S.; Bartos, J.M.

1984-11-01

Laboratory bioassays to determine the acute toxicity of monochloramine, dichloramine, hypochlorous acid, and hypochlorite ion to emerald shiners Notropis atherinoides, channel catfish Ictalurus punctatus, and rainbow trout Salmo gairdneri were conducted. Four exposure regimes typical of chlorination schedules at operating steam electric power plants were used. Fish were exposed for single 15-minute, 30-minute, 120-minute, and 4 x 30-minute periods. Based on median lethal concentrations (LC50s), the nominal solution of hypochlorous acid was the most toxic, followed closely by the solution dominated by dichloramine; nominal monochloramine and hypochlorite ion solutions had a third to a quarter the toxicity of the othermore » two. On the average, emerald shiners were 1.8 times more sensitive than channel catfish and 3.3 times more sensitive than rainbow trout to the four forms of chlorine. The fish were most tolerant of chlorine during short-duration exposures and least tolerant during the continuous 120-minute exposures. The differences in toxicity noted among the chlorine forms suggest that, when chlorination regimes and regulations are established, careful attention should be paid not only to total residual chlorine but to both the chlorine forms and fish species present and the duration of exposure. 24 references, 1 figure, 1 table.« less

Surface potentials measure ion concentrations near lipid bilayers during rapid solution changes.

PubMed Central

Laver, D R; Curtis, B A

1996-01-01

We describe a puffing method for changing solutions near one surface of lipid bilayers that allows simultaneous measurement of channel activity and extent of solution change at the bilayer surface. Ion adsorption to the lipid headgroups and screening of the bilayer surface charge by mobile ions provided a convenient probe for the ionic composition of the solution at the bilayer surface. Rapid ionic changes induced a shift in bilayer surface potential that generated a capacitive transient current under voltage-clamp conditions. This depended on the ion species and bilayer composition and was accurately described by the Stern-Gouy-Chapman theory. The time course of solute concentrations during solution changes could also be modeled by an exponential exchange of bath and puffing solutions with time constants ranging from 20 to 110 ms depending on the flow pressure. During changes in [Cs+] and [Ca2+] (applied separately or together) both the mixing model and capacitive currents predicted [Cs+] and [Ca2+] transients consistent with those determined experimentally from: 1) the known Cs(+)-dependent conductance of open ryanodine receptor channels and 2) the Ca(2+)-dependent gating of ryanodine receptor Ca2+ channels from cardiac and skeletal muscle. Images FIGURE 1 FIGURE 4 FIGURE 5 FIGURE 8 PMID:8842210

Direct Evidence of Conformational Changes Associated with Voltage Gating in a Voltage Sensor Protein by Time-Resolved X-ray/Neutron Interferometry

PubMed Central

2015-01-01

The voltage sensor domain (VSD) of voltage-gated cation (e.g., Na+, K+) channels central to neurological signal transmission can function as a distinct module. When linked to an otherwise voltage-insensitive, ion-selective membrane pore, the VSD imparts voltage sensitivity to the channel. Proteins homologous with the VSD have recently been found to function themselves as voltage-gated proton channels or to impart voltage sensitivity to enzymes. Determining the conformational changes associated with voltage gating in the VSD itself in the absence of a pore domain thereby gains importance. We report the direct measurement of changes in the scattering-length density (SLD) profile of the VSD protein, vectorially oriented within a reconstituted phospholipid bilayer membrane, as a function of the transmembrane electric potential by time-resolved X-ray and neutron interferometry. The changes in the experimental SLD profiles for both polarizing and depolarizing potentials with respect to zero potential were found to extend over the entire length of the isolated VSD’s profile structure. The characteristics of the changes observed were in qualitative agreement with molecular dynamics simulations of a related membrane system, suggesting an initial interpretation of these changes in terms of the VSD’s atomic-level 3-D structure. PMID:24697545

Flow and form in rehabilitation of large-river ecosystems: an example from the Lower Missouri River

USGS Publications Warehouse

Jacobson, R.B.; Galat, D.L.

2006-01-01

On large, intensively engineered rivers like the Lower Missouri, the template of the physical habitat is determined by the nearly independent interaction of channel form and flow regime. We evaluated the interaction between flow and form by modeling four combinations of modern and historical channel form and modern and historical flow regimes. The analysis used shallow, slow water (shallow-water habitat, SWH, defined as depths between 0 and 1.5 m, and current velocities between 0 and 0.75 m/s) as an indicator of habitat that has been lost on many intensively engineered rivers and one that is thought to be especially important in rearing of young fishes. Two-dimensional hydrodynamic models for modern and historical channels of the Lower Missouri River at Hermann, Missouri, indicate substantial differences between the two channels in total availability and spatial characteristics of SWH. In the modern channel, SWH is maximized at extremely low flows and in overbank flows, whereas the historical channel had substantially more SWH at all discharges and SWH increased with increasing discharge. The historical channel form produced 3-7 times the SWH area of the modern channel regardless of flow regime. The effect of flow regime is evident in increased within-year SWH variability with the natural flow regime, including significant seasonal peaks of SWH associated with spring flooding. Comparison with other reaches along the Lower Missouri River indicates that a) channel form is the dominant control of the availability of habitat even in reaches where the hydrograph is more intensively altered, and b) rehabilitation projects that move toward the historical condition can be successful in increasing topographic diversity and thereby decreasing sensitivity of the availability of habitat to flow regime. The relative efficacy of managing flow and form in creating SWH is useful information toward achieving socially acceptable rehabilitation of the ecosystem in large river systems.

Brownian dynamics study of ion transport in the vestibule of membrane channels.

PubMed

Li, S C; Hoyles, M; Kuyucak, S; Chung, S H

1998-01-01

Brownian dynamics simulations have been carried out to study the transport of ions in a vestibular geometry, which offers a more realistic shape for membrane channels than cylindrical tubes. Specifically, we consider a torus-shaped channel, for which the analytical solution of Poisson's equation is possible. The system is composed of the toroidal channel, with length and radius of the constricted region of 80 A and 4 A, respectively, and two reservoirs containing 50 sodium ions and 50 chloride ions. The positions of each of these ions executing Brownian motion under the influence of a stochastic force and a systematic electric force are determined at discrete time steps of 50 fs for up to 2.5 ns. All of the systematic forces acting on an ion due to the other ions, an external electric field, fixed charges in the channel protein, and the image charges induced at the water-protein boundary are explicitly included in the calculations. We find that the repulsive dielectric force arising from the induced surface charges plays a dominant role in channel dynamics. It expels an ion from the vestibule when it is deliberately put in it. Even in the presence of an applied electric potential of 100 mV, an ion cannot overcome this repulsive force and permeate the channel. Only when dipoles of a favorable orientation are placed along the sides of the transmembrane segment can an ion traverse the channel under the influence of a membrane potential. When the strength of the dipoles is further increased, an ion becomes detained in a potential well, and the driving force provided by the applied field is not sufficient to drive the ion out of the well. The trajectory of an ion navigating across the channel mostly remains close to the central axis of the pore lumen. Finally, we discuss the implications of these findings for the transport of ions across the membrane.

A simple method for the evaluation of microfluidic architecture using flow quantitation via a multiplexed fluidic resistance measurement.

PubMed

Leslie, Daniel C; Melnikoff, Brett A; Marchiarullo, Daniel J; Cash, Devin R; Ferrance, Jerome P; Landers, James P

2010-08-07

Quality control of microdevices adds significant costs, in time and money, to any fabrication process. A simple, rapid quantitative method for the post-fabrication characterization of microchannel architecture using the measurement of flow with volumes relevant to microfluidics is presented. By measuring the mass of a dye solution passed through the device, it circumvents traditional gravimetric and interface-tracking methods that suffer from variable evaporation rates and the increased error associated with smaller volumes. The multiplexed fluidic resistance (MFR) measurement method measures flow via stable visible-wavelength dyes, a standard spectrophotometer and common laboratory glassware. Individual dyes are used as molecular markers of flow for individual channels, and in channel architectures where multiple channels terminate at a common reservoir, spectral deconvolution reveals the individual flow contributions. On-chip, this method was found to maintain accurate flow measurement at lower flow rates than the gravimetric approach. Multiple dyes are shown to allow for independent measurement of multiple flows on the same device simultaneously. We demonstrate that this technique is applicable for measuring the fluidic resistance, which is dependent on channel dimensions, in four fluidically connected channels simultaneously, ultimately determining that one chip was partially collapsed and, therefore, unusable for its intended purpose. This method is thus shown to be widely useful in troubleshooting microfluidic flow characteristics.

Channel Protein Engineering: A Novel Approach Towards the Molecular Dissection Determinants in Ligand-Regulated Channels

DTIC Science & Technology

1991-01-23

lidocaine , within the lumen of the pore. Specific predictions for possible experimental mutations are made which can serve to test both the proposed...to the protein from the bilayer interior. 2. Synthesis of tetrameric synthetic channel proteins and demonstration of channel blockade by a local...Congress, Vancouver, Canada. S9.4, p. 2 4 (1990). Grove, A., J. M. Tomich and M. Montal. Design, synthesis and single channel characterization of d

Beamspace Multiple Input Multiple Output. Part II: Steerable Antennas in Mobile Ad Hoc Networks

DTIC Science & Technology

2016-09-01

to the transmitter with half the channel transfer function power , since the actual receiver dwells on each channel only half the time. Fourth diagram...steering in a wireless network to maximize signal power and minimize interference [8–10]. The ability to switch beams adds another diversity dimension to...channel transfer function power , since the actual receiver dwells on each channel only half the time. Fourth diagram: The transmit array sends four

Unraveling the electronic relaxation dynamics in photoexcited 2,4-difluoroaniline via femtosecond time-resolved photoelectron imaging

NASA Astrophysics Data System (ADS)

Ling, Fengzi; Li, Shuai; Wei, Jie; Liu, Kai; Wang, Yanmei; Zhang, Bing

2018-04-01

Time-resolved photoelectron imaging is employed to investigate the relaxation dynamics of the lowest two excited electronic states S1(ππ*) and S2(π3s/πσ*) in 2,4-difluoroaniline (24DFA). As the S1(ππ*) state is populated directly following 289 nm excitation, the population undergoes ultrafast intramolecular vibrational redistribution on a 540 fs time scale, followed by efficient intersystem crossing from S1(ππ*) to the triplet state within 379 ps, and the subsequent slower deactivation process of the triplet state. For excitation to the S2(π3s/πσ*) state at 238 nm, the population probably bifurcates into two decay channels. The dominant channel with 84 fs involves ultrafast internal conversion to the S1(ππ*) state, from which it relaxes to the electronic ground state on a 116 ps time scale. The other appears to involve motion along the S2(π3s/πσ*) potential energy surface. Our data also determine experimentally the electronic energies of S2(π3s/πσ*), S3(ππ*), and several Rydberg states in 24DFA.

A Galilean and tensorial invariant k-epsilon model for near wall turbulence

NASA Technical Reports Server (NTRS)

Yang, Z.; Shih, T. H.

1993-01-01

A k-epsilon model is proposed for wall bounded turbulent flows. In this model, the eddy viscosity is characterized by a turbulent velocity scale and a turbulent time scale. The time scale is bounded from below by the Kolmogorov time scale. The dissipation rate equation is reformulated using this time scale and no singularity exists at the wall. A new parameter R = k/S(nu) is introduced to characterize the damping function in the eddy viscosity. This parameter is determined by local properties of both the mean and the turbulent flow fields and is free from any geometry parameter. The proposed model is then Galilean and tensorial invariant. The model constants used are the same as in the high Reynolds number Standard k-epsilon Model. Thus, the proposed model will also be suitable for flows far from the wall. Turbulent channel flows and turbulent boundary layer flows with and without pressure gradients are calculated. Comparisons with the data from direct numerical simulations and experiments show that the model predictions are excellent for turbulent channel flows and turbulent boundary layers with favorable pressure gradients, good for turbulent boundary layers with zero pressure gradients, and fair for turbulent boundary layer with adverse pressure gradients.

Evaluation of Multi-Channel ADCs for Gamma-Ray Spectroscopy

NASA Astrophysics Data System (ADS)

Tan, Hui; Hennig, Wolfgang; Walby, Mark D.; Breus, Dimitry; Harris, Jackson

2013-04-01

As nuclear physicists increasingly design large scale experiments with hundreds or thousands of detector channels, there are growing needs for high density readout electronics with good timing and energy resolution that at the same time offer lower cost per channel compared to existing commercial solutions. Recent improvements in the design of commercial analog to digital converters (ADCs) have resulted in a variety of multi-channel ADCs that are natural choice for designing such high density readout modules. However, multi-channel ADCs typically are designed for medical imaging/ultrasound applications and therefore are not rated for their spectroscopic characteristics. In this work, we evaluated the gamma-ray spectroscopic performance of several multi-channel ADCs, including their energy resolution, nonlinearity, and timing resolution. Some of these ADCs demonstrated excellent energy resolution, 2.66% FWHM at 662 keV with a LaBr3 or 1.78 keV FWHM at 1332.5 keV with a high purity germanium (HPGe) detector, and sub-nanosecond timing resolution with LaBr 3. We present results from these measurements to illustrate their suitability for gamma-ray spectroscopy.

Decision making by superimposing information from parallel cognitive channels

NASA Astrophysics Data System (ADS)

Aityan, Sergey K.

1993-08-01

A theory of decision making with perception through parallel information channels is presented. Decision making is considered a parallel competitive process. Every channel can provide confirmation or rejection of a decision concept. Different channels provide different impact on the specific concepts caused by the goals and individual cognitive features. All concepts are divided into semantic clusters due to the goals and the system defaults. The clusters can be alternative or complimentary. The 'winner-take-all' concept nodes firing takes place within the alternative cluster. Concepts can be independently activated in the complimentary cluster. A cognitive channel affects a decision concept by sending an activating or inhibitory signal. The complimentary clusters serve for building up complex concepts by superimposing activation received from various channels. The decision making is provided by the alternative clusters. Every active concept in the alternative cluster tends to suppress the competitive concepts in the cluster by sending inhibitory signals to the other nodes of the cluster. The model accounts for a time delay in signal transmission between the nodes and explains decreasing of the reaction time if information is confirmed by different channels and increasing of the reaction time if deceiving information received from the channels.

Synchronous acquisition of multi-channel signals by single-channel ADC based on square wave modulation

NASA Astrophysics Data System (ADS)

Yi, Xiaoqing; Hao, Liling; Jiang, Fangfang; Xu, Lisheng; Song, Shaoxiu; Li, Gang; Lin, Ling

2017-08-01

Synchronous acquisition of multi-channel biopotential signals, such as electrocardiograph (ECG) and electroencephalograph, has vital significance in health care and clinical diagnosis. In this paper, we proposed a new method which is using single channel ADC to acquire multi-channel biopotential signals modulated by square waves synchronously. In this method, a specific modulate and demodulate method has been investigated without complex signal processing schemes. For each channel, the sampling rate would not decline with the increase of the number of signal channels. More specifically, the signal-to-noise ratio of each channel is n times of the time-division method or an improvement of 3.01 ×log2n dB, where n represents the number of the signal channels. A numerical simulation shows the feasibility and validity of this method. Besides, a newly developed 8-lead ECG based on the new method has been introduced. These experiments illustrate that the method is practicable and thus is potential for low-cost medical monitors.

A channel estimation scheme for MIMO-OFDM systems

NASA Astrophysics Data System (ADS)

He, Chunlong; Tian, Chu; Li, Xingquan; Zhang, Ce; Zhang, Shiqi; Liu, Chaowen

2017-08-01

In view of the contradiction of the time-domain least squares (LS) channel estimation performance and the practical realization complexity, a reduced complexity channel estimation method for multiple input multiple output-orthogonal frequency division multiplexing (MIMO-OFDM) based on pilot is obtained. This approach can transform the complexity of MIMO-OFDM channel estimation problem into a simple single input single output-orthogonal frequency division multiplexing (SISO-OFDM) channel estimation problem and therefore there is no need for large matrix pseudo-inverse, which greatly reduces the complexity of algorithms. Simulation results show that the bit error rate (BER) performance of the obtained method with time orthogonal training sequences and linear minimum mean square error (LMMSE) criteria is better than that of time-domain LS estimator and nearly optimal performance.

Optimization of airport security process

NASA Astrophysics Data System (ADS)

Wei, Jianan

2017-05-01

In order to facilitate passenger travel, on the basis of ensuring public safety, the airport security process and scheduling to optimize. The stochastic Petri net is used to simulate the single channel security process, draw the reachable graph, construct the homogeneous Markov chain to realize the performance analysis of the security process network, and find the bottleneck to limit the passenger throughput. Curve changes in the flow of passengers to open a security channel for the initial state. When the passenger arrives at a rate that exceeds the processing capacity of the security channel, it is queued. The passenger reaches the acceptable threshold of the queuing time as the time to open or close the next channel, simulate the number of dynamic security channel scheduling to reduce the passenger queuing time.

PLC-mediated PI(4,5)P2 hydrolysis regulates activation and inactivation of TRPC6/7 channels

PubMed Central

Itsuki, Kyohei; Imai, Yuko; Hase, Hideharu; Okamura, Yasushi; Inoue, Ryuji

2014-01-01

Transient receptor potential classical (or canonical) (TRPC)3, TRPC6, and TRPC7 are a subfamily of TRPC channels activated by diacylglycerol (DAG) produced through the hydrolysis of phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) by phospholipase C (PLC). PI(4,5)P2 depletion by a heterologously expressed phosphatase inhibits TRPC3, TRPC6, and TRPC7 activity independently of DAG; however, the physiological role of PI(4,5)P2 reduction on channel activity remains unclear. We used Förster resonance energy transfer (FRET) to measure PI(4,5)P2 or DAG dynamics concurrently with TRPC6 or TRPC7 currents after agonist stimulation of receptors that couple to Gq and thereby activate PLC. Measurements made at different levels of receptor activation revealed a correlation between the kinetics of PI(4,5)P2 reduction and those of receptor-operated TRPC6 and TRPC7 current activation and inactivation. In contrast, DAG production correlated with channel activation but not inactivation; moreover, the time course of channel inactivation was unchanged in protein kinase C–insensitive mutants. These results suggest that inactivation of receptor-operated TRPC currents is primarily mediated by the dissociation of PI(4,5)P2. We determined the functional dissociation constant of PI(4,5)P2 to TRPC channels using FRET of the PLCδ Pleckstrin homology domain (PHd), which binds PI(4,5)P2, and used this constant to fit our experimental data to a model in which channel gating is controlled by PI(4,5)P2 and DAG. This model predicted similar FRET dynamics of the PHd to measured FRET in either human embryonic kidney cells or smooth muscle cells, whereas a model lacking PI(4,5)P2 regulation failed to reproduce the experimental data, confirming the inhibitory role of PI(4,5)P2 depletion on TRPC currents. Our model also explains various PLC-dependent characteristics of channel activity, including limitation of maximum open probability, shortening of the peak time, and the bell-shaped response of total current. In conclusion, our studies demonstrate a fundamental role for PI(4,5)P2 in regulating TRPC6 and TRPC7 activity triggered by PLC-coupled receptor stimulation. PMID:24470487

Analysis of Stream Channel Geometry Temporal and Spatial Evolution after Historic Dam Removal - two French case studies

NASA Astrophysics Data System (ADS)

Slawson, Deborah; Manière, Louis; Marchandeau, Florent

2014-05-01

IRSTEA, in partnership with the French Office national de l'eau et des milieux aquatiques (ONEMA), has begun a study of channel geomorphology in small streams where dams have been removed or breached between two and 200 years ago, without any subsequent restoration of the channel in the legacy sediments. A preliminary analysis of two sites in the Morvan, Burgundy, will be presented; a dam breached at the beginning of the 20th century and another in the last decade. Using ergodic reasoning, historical and recent upstream and downstream channel geometry is being used to predict the future temporal and spatial scales of channel physical habitat restoration. With the implementation of the European Water Framework Directive (WFD), dam removal has become a more frequently used method for restoring stream ecological continuity. In France, these obstacles are ubiquitous in medium and small streams and considerably reduce lateral and longitudinal connectivity. Improvement in the hydromorphologically controlled, physical habitat, particularly flow and sediment transport regimes, is often essential to improvement in stream biology. However, dam removal may cause long-term disturbances in flow and sediment transport regimes. In the absence of channel restoration measures in addition to dam removal, these disturbances may result in long-term negative impacts on fish, macroinvertebrate, and riparian plant physical habitat. These negative impacts may include channel incision and lowering of the water table, disconnection from floodplains, increased stream power and bed scouring, and increased sediment load from headcutting and bank erosion. Over time, these negative impacts may resolve themselves. However, the time frame necessary for reestablishing adequate physical habitat is not well-known. Some studies have indicated that many decades or longer may be required, depending on a variety of factors. Under the WFD, the REstoring rivers FOR effective catchment Management (REFORM) project is stressing the use of reference condition benchmarks when identifying objectives for and designing stream restoration projects. To identify appropriate reference condition benchmarks, it is important to understand over what temporal and spatial scales physical habitat improvement may take place after dam removal, including: 1. defining the spatial and temporal objectives for physical habitat restoration as a result of dam removal and 2. determining if dam removal alone will be sufficient to achieve those objectives or if additional channel restoration measures might be required.

Free-Energy Calculations. A Mathematical Perspective

NASA Technical Reports Server (NTRS)

Pohorille, Andrzej

2015-01-01

Ion channels are pore-forming assemblies of transmembrane proteins that mediate and regulate ion transport through cell walls. They are ubiquitous to all life forms. In humans and other higher organisms they play the central role in conducting nerve impulses. They are also essential to cardiac processes, muscle contraction and epithelial transport. Ion channels from lower organisms can act as toxins or antimicrobial agents, and in a number of cases are involved in infectious diseases. Because of their important and diverse biological functions they are frequent targets of drug action. Also, simple natural or synthetic channels find numerous applications in biotechnology. For these reasons, studies of ion channels are at the forefront of biophysics, structural biology and cellular biology. In the last decade, the increased availability of X-ray structures has greatly advanced our understanding of ion channels. However, their mechanism of action remains elusive. This is because, in order to assist controlled ion transport, ion channels are dynamic by nature, but X-ray crystallography captures the channel in a single, sometimes non-native state. To explain how ion channels work, X-ray structures have to be supplemented with dynamic information. In principle, molecular dynamics (MD) simulations can aid in providing this information, as this is precisely what MD has been designed to do. However, MD simulations suffer from their own problems, such as inability to access sufficiently long time scales or limited accuracy of force fields. To assess the reliability of MD simulations it is only natural to turn to the main function of channels - conducting ions - and compare calculated ionic conductance with electrophysiological data, mainly single channel recordings, obtained under similar conditions. If this comparison is satisfactory it would greatly increase our confidence that both the structures and our computational methodologies are sufficiently accurate. Channel conductance, defined as the ratio of ionic current through the channel to applied voltage, can be calculated in MD simulations by way of applying an external electric field to the system and counting the number of ions that traverse the channel per unit time. If the current is small, a voltage significantly higher than the experimental one needs to be applied to collect sufficient statistics of ion crossing events. Then, the calculated conductance has to be extrapolated to the experimental voltage using procedures of unknown accuracy. Instead, we propose an alternative approach that applies if ion transport through channels can be described with sufficient accuracy by the one-dimensional diffusion equation in the potential given by the free energy profile and applied voltage. Then, it is possible to test the assumptions of the equation, recover the full voltage/current dependence, determine the reliability of the calculated conductance and reconstruct the underlying (equilibrium) free energy profile, all from MD simulations at a single voltage. We will present the underlying theory, model calculations that test this theory and simulations on ion conductance through a channel that has been extensively studied experimentally. To our knowledge this is the first case in which the complete, experimentally measured dependence of the current on applied voltage has been reconstructed from MD simulations.

Long-term impacts of land cover changes on stream channel loss.

PubMed

Julian, Jason P; Wilgruber, Nicholas A; de Beurs, Kirsten M; Mayer, Paul M; Jawarneh, Rana N

2015-12-15

Land cover change and stream channel loss are two related global environmental changes that are expanding and intensifying. Here, we examine how different types and transitions of land cover change impact stream channel loss across a large urbanizing watershed. We present historical land cover in the 666-km(2) Lake Thunderbird watershed in central Oklahoma (USA) over a 137 year period and coinciding stream channel length changes for the most recent 70 years of this period. Combining these two datasets allowed us to assess the interaction of land cover changes with stream channel loss. Over this period, the upper third of the watershed shifted from predominantly native grassland to an agricultural landscape, followed by widespread urbanization. The lower two-thirds of the watershed changed from a forested landscape to a mosaic of agriculture, urban, forest, and open water. Most channel length lost in the watershed over time was replaced by agriculture. Urban development gradually increased channel loss and disconnection from 1942 to 2011, particularly in the headwaters. Intensities of channel loss for both agriculture and urban increased over time. The two longest connected segments of channel loss came from the creation of two large impoundments, resulting in 46 km and 25 km of lost stream channel, respectively. Overall, the results from this study demonstrate that multiple and various land-use changes over long time periods can lead to rapid losses of large channel lengths as well as gradual (but increasing) losses of small channel lengths across all stream sizes. When these stream channel losses are taken into account, the environmental impacts of anthropogenic land-use change are compounded. Copyright © 2015 Elsevier B.V. All rights reserved.

Effects of channel noise on firing coherence of small-world Hodgkin-Huxley neuronal networks

NASA Astrophysics Data System (ADS)

Sun, X. J.; Lei, J. Z.; Perc, M.; Lu, Q. S.; Lv, S. J.

2011-01-01

We investigate the effects of channel noise on firing coherence of Watts-Strogatz small-world networks consisting of biophysically realistic HH neurons having a fraction of blocked voltage-gated sodium and potassium ion channels embedded in their neuronal membranes. The intensity of channel noise is determined by the number of non-blocked ion channels, which depends on the fraction of working ion channels and the membrane patch size with the assumption of homogeneous ion channel density. We find that firing coherence of the neuronal network can be either enhanced or reduced depending on the source of channel noise. As shown in this paper, sodium channel noise reduces firing coherence of neuronal networks; in contrast, potassium channel noise enhances it. Furthermore, compared with potassium channel noise, sodium channel noise plays a dominant role in affecting firing coherence of the neuronal network. Moreover, we declare that the observed phenomena are independent of the rewiring probability.

Differentiating the relative importance of land cover change and geomorphic processes on fine sediment sequestration in a logged watershed

NASA Astrophysics Data System (ADS)

Kasprak, Alan; Magilligan, Francis J.; Nislow, Keith H.; Renshaw, Carl E.; Snyder, Noah P.; Dade, W. Brian

2013-03-01

Timber harvest often results in accelerated soil erosion and subsequent elevated fine (< 2 mm) sediment delivery to channels causing deleterious effects to numerous aquatic species, particularly salmonid fishes. Here we determine, through sediment physical analyses (pebble counts, embeddedness surveys, and interstitial shelter space counts) and geochemical analyses (7Be and 210Pbex activities), the amount and timing of delivery of fine sediment currently found on streambeds of the Narraguagus River watershed in coastal Maine. The role of recent timber harvest, documented via aerial photo spatial analysis, on fine sediment delivery is contrasted with the ability of the glacially influenced topography and surficial geology to deliver fine sediment to streams and to influence channel substrate. Results show that of the land use and geomorphic variables examined, only 210Pbex activities were significantly correlated with the amount of upstream harvest (r2 = 0.49). Concurrently, we find that unit stream power (particularly the slope component) explains much of the variability in channel substrate and that slope and stream power are largely influenced by the legacy of Pleistocene glaciation on channel form. Results suggest a conceptual model whereby fine sediment delivery as a result of late twentieth century timber harvest is likely dampened because of the low gradient landscape of coastal Maine. While geochemical tracers indicate recent fine sediment delivery in harvested areas, channels are likely capable of quickly winnowing these fines from the channel bed. These results further suggest that under contemporary land use conditions, the geomorphic and geologic setting represents a first-order control on channel substrate and habitat suitability for salmonid fishes, including federally endangered Atlantic salmon (Salmo salar), in coastal drainages of northeastern Maine.

The intracellular region of ClC-3 chloride channel is in a partially folded state and a monomer.

PubMed

Li, Shu Jie; Kawazaki, Masanobu; Ogasahara, Kyoko; Nakagawa, Atsushi

2006-05-01

In contrast to bacterial ClC chloride channels, all eukaryotic ClC chloride channels have a conserved long intracellular region that makes up of the carboxyl terminus of the protein and is necessary for channel functions as a channel gate. Little is known, however, about the molecular structure of the intracellular region of ClC chloride channels so far. Here, for the first time, we have expressed and purified the intracellular region of the rat ClC-3 chloride channel (C-ClC-3) as a water-soluble protein under physiological conditions, and investigated its structural characteristics and assembly behavior by means of circular dichroism (CD) spectroscopy, differential scanning calorimetry (DSC), size exclusion chromatography and analytical ultracentrifugation. The far-UV CD spectra of C-ClC-3 in the native state and in the presence of urea clearly show that the protein has a significantly folded secondary structure consisting of alpha-helices and beta-sheets, while the near-UV CD spectra and DSC experiments indicate the protein is deficient in well-defined tertiary packing. Its Stokes radius is larger than its expected size as a folded globular protein, as determined on size exclusion chromatography. Furthermore, the DisEMBL program, a useful computational tool for the prediction of disordered/unstructured regions within a protein sequence, predicts that the protein is in a partially folded state. Based on these results, we conclude that C-ClC-3 is partially folded. On the other hand, both size exclusion chromatography and sedimentation equilibrium analysis show that C-ClC-3 exists as a monomer in solution, not a dimer like the whole ClC-3 molecule.

Comparison and evaluation of the Chang'E microwave radiometer data based on theoretical computation of brightness temperatures at the Apollo 15 and 17 sites

NASA Astrophysics Data System (ADS)

Hu, Guo-Ping; Chan, Kwing L.; Zheng, Yong-Chun; Tsang, Kang T.; Xu, Ao-Ao

2017-09-01

There are significant differences (in the order of 3 to 20 K) between the lunar brightness temperatures (TBs) as measured by the microwave radiometers (MRM) onboard Chang'E (CE)-1 and -2. To determine which set is more accurate, we have carried out a dataset comparison using theoretical calculations of the TBs (four frequency channels) versus local time at the Apollo 15 and 17 landing sites, where the thermal parameters are well-constrained by the in-situ measurements. Based on these parameters, we sought to constrain fits between theory and observation, as uncertainties still exist in parameters involved in the microwave transfer computation. We found that: (i) CE-1/2 TBs have almost constant biases (negative, different for different channels) from the theoretical TBs. The averaged biases for each channel are smaller for CE-1; (ii) TBs of the high frequency channels (19.35/37 GHz) show a better fit with theory than the low frequency channels. The channel 4 (37 GHz) TBs from CE-1 are consistently shifted by about 1 K from the theoretical values. Adjustments in the order of 20 K are instead needed for the two CE-2 low frequency channels (3/7.8 GHz). Based on this comparison, we conclude that the CE-1 dataset to be more accurate than CE-2 one in terms of temperature accuracy (not spatial resolution). We also offer a possible explanation for the significant TB differences between CE-1 and CE-2, and propose a possible recalibration method as a starting point towards the realignment of the two datasets.

Modeled and Observed Transitions Between Rip Currents and Alongshore Flows

NASA Astrophysics Data System (ADS)

Moulton, M.; Elgar, S.; Warner, J. C.; Raubenheimer, B.

2014-12-01

Predictions of rip currents, alongshore currents, and the temporal transitions between these circulation patterns are important for swimmer safety and for estimating the transport of sediments, biota, and pollutants in the nearshore. Here, field observations are combined with hydrodynamic modeling to determine the dominant processes that lead rip currents to turn on and off with changing waves, bathymetry, and tidal elevation. Waves, currents, mean sea levels, and bathymetry were measured near and within five shore-perpendicular channels (on average 2-m deep, 30-m wide) that were dredged with the propellers of a landing craft at different times on a long straight Atlantic Ocean beach near Duck, NC in summer 2012. The circulation was measured for a range of incident wave conditions and channel sizes, and included rapid transitions between strong (0.5 to 1 m/s) rip current jets flowing offshore through the channels and alongshore currents flowing across the channels with no rip currents. Meandering alongshore currents (alongshore currents combined with an offshore jet at the downstream edge of the channel) also were observed. Circulation patterns near and within idealized rip channels simulated with COAWST (a three-dimensional phase-averaged model that couples ROMS and SWAN) are compared with the observations. In addition, the model is used to investigate the hydrodynamic response to a range of wave conditions (angle, height, period) and bathymetries (channel width, depth, and length; tidal elevations; shape of sandbar or terrace). Rip current speeds are largest for the deepest perturbations, and decrease as incident wave angles become more oblique. For obliquely incident waves, the rip currents are shifted in the direction of the alongshore flow, with an increasing shift for increasing alongshore current speed or increasing bathymetric perturbation depth.