Mentally simulated movements in virtual reality: does Fitts's law hold in motor imagery?

PubMed

Decety, J; Jeannerod, M

1995-12-14

This study was designed to investigate mentally simulated actions in a virtual reality environment. Naive human subjects (n = 15) were instructed to imagine themselves walking in a three-dimensional virtual environment toward gates of different apparent widths placed at three different apparent distances. Each subject performed nine blocks of six trials in a randomised order. The response time (reaction time and mental walking time) was measured as the duration between an acoustic go signal and a motor signal produced by the subject. There was a combined effect on response time of both gate width and distance. Response time increased for decreasing apparent gate widths when the gate was placed at different distances. These results support the notion that mentally simulated actions are governed by central motor rules.

Stiff self-interacting strings at high temperature QCD

NASA Astrophysics Data System (ADS)

S Bakry, A.; Chen, X.; Deliyergiyev, M.; Galal, A.; Khalaf, A.; M Pengming, P.

2018-03-01

We investigate the implications of Nambu-Goto (NG), Lüscher Weisz (LW) and Polyakov-Kleinert (PK) effective string actions for the Casimir energy and the width of the quantum delocalization of the string in 4-dim pure SU(3) Yang-Mills lattice gauge theory. At a temperature closer to the critical point T/Tc=0.9, we found that the next to leading-order (NLO) contributions from the expansion of the NG string in addition to the boundary terms in LW action to decrease the deviations from the lattice data in the intermediate distance scales for both the quark-antiquark QQ̅ potential and broadening of the color tube compared to the free string approximation. We conjecture possible stiffness of the QCD string through studying the effects of extrinsic curvature term in PK action and find a good fitting behavior for the lattice Monte-Carlo data at both long and intermediate quark separations regions.

Functional dissociation between action and perception of object shape in developmental visual object agnosia.

PubMed

Freud, Erez; Ganel, Tzvi; Avidan, Galia; Gilaie-Dotan, Sharon

2016-03-01

According to the two visual systems model, the cortical visual system is segregated into a ventral pathway mediating object recognition, and a dorsal pathway mediating visuomotor control. In the present study we examined whether the visual control of action could develop normally even when visual perceptual abilities are compromised from early childhood onward. Using his fingers, LG, an individual with a rare developmental visual object agnosia, manually estimated (perceptual condition) the width of blocks that varied in width and length (but not in overall size), or simply picked them up across their width (grasping condition). LG's perceptual sensitivity to target width was profoundly impaired in the manual estimation task compared to matched controls. In contrast, the sensitivity to object shape during grasping, as measured by maximum grip aperture (MGA), the time to reach the MGA, the reaction time and the total movement time were all normal in LG. Further analysis, however, revealed that LG's sensitivity to object shape during grasping emerged at a later time stage during the movement compared to controls. Taken together, these results demonstrate a dissociation between action and perception of object shape, and also point to a distinction between different stages of the grasping movement, namely planning versus online control. Moreover, the present study implies that visuomotor abilities can develop normally even when perceptual abilities developed in a profoundly impaired fashion. Copyright © 2016 Elsevier Ltd. All rights reserved.

The dynamic range of response set activation during action sequencing.

PubMed

Behmer, Lawrence P; Crump, Matthew J C

2017-03-01

We show that theories of response scheduling for sequential action can be discriminated on the basis of their predictions for the dynamic range of response set activation during sequencing, which refers to the momentary span of activation states for completed and to-be-completed actions in a response set. In particular, theories allow that future actions in a plan are partially activated, but differ with respect to the width of the range, which refers to the number of future actions that are partially activated. Similarly, theories differ on the width of the range for recently completed actions that are assumed to be rapidly deactivated or gradually deactivated in a passive fashion. We validate a new typing task for measuring momentary activation states of actions across a response set during action sequencing. Typists recruited from Amazon Mechanical Turk copied a paragraph by responding to a "go" signal that usually cued the next letter but sometimes cued a near-past or future letter (n-3, -2, -1, 0, +2, +3). The activation states for producing letters across go-signal positions can be inferred from RTs and errors. In general, we found evidence of graded parallel activation for future actions and rapid deactivation of more distal past actions. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Internal and external radiative widths in the combined R -matrix and potential-model formalism

NASA Astrophysics Data System (ADS)

Mukhamedzhanov, A. M.; Shubhchintak, Bertulani, C. A.; Hao, T. V. Nhan

2017-02-01

By using the R -matrix approach we calculate the radiative width for a resonance decaying to a bound state through electric-dipole E 1 transitions. The total radiative width is determined by the interference of the nuclear internal and external radiative width amplitudes. For a given channel radius the external radiative width amplitude is model independent and is determined by the asymptotic normalization coefficient (ANC) of the bound state to which the resonance decays. It also depends on the partial resonance width. To calculate the internal radiative width amplitude we show that a single-particle-potential model is appropriate. We compare our results with a few experimental data.

Potential Safety Effects of Lane Width and Shoulder Width on Two-Lane Rural State Highways in Idaho

DOT National Transportation Integrated Search

2012-07-01

This study provides a comprehensive evaluation of the relationship between crash rates and shoulder width and lane width for two-lane rural state highways in Idaho. Crash Modification Factors (CMFs) for shoulder width and lane width were developed us...

Theory of Arachnid Prey Localization

NASA Astrophysics Data System (ADS)

Stürzl, W.; Kempter, R.; van Hemmen, J. L.

2000-06-01

Sand scorpions and many other arachnids locate their prey through highly sensitive slit sensilla at the tips (tarsi) of their eight legs. This sensor array responds to vibrations with stimulus-locked action potentials encoding the target direction. We present a neuronal model to account for stimulus angle determination using a population of second-order neurons, each receiving excitatory input from one tarsus and inhibition from a triad opposite to it. The input opens a time window whose width determines a neuron's firing probability. Stochastic optimization is realized through tuning the balance between excitation and inhibition. The agreement with experiments on the sand scorpion is excellent.

Variable Action Potential Backpropagation during Tonic Firing and Low-Threshold Spike Bursts in Thalamocortical But Not Thalamic Reticular Nucleus Neurons.

PubMed

Connelly, William M; Crunelli, Vincenzo; Errington, Adam C

2017-05-24

Backpropagating action potentials (bAPs) are indispensable in dendritic signaling. Conflicting Ca 2+ -imaging data and an absence of dendritic recording data means that the extent of backpropagation in thalamocortical (TC) and thalamic reticular nucleus (TRN) neurons remains unknown. Because TRN neurons signal electrically through dendrodendritic gap junctions and possibly via chemical dendritic GABAergic synapses, as well as classical axonal GABA release, this lack of knowledge is problematic. To address this issue, we made two-photon targeted patch-clamp recordings from rat TC and TRN neuron dendrites to measure bAPs directly. These recordings reveal that "tonic"' and low-threshold-spike (LTS) "burst" APs in both cell types are always recorded first at the soma before backpropagating into the dendrites while undergoing substantial distance-dependent dendritic amplitude attenuation. In TC neurons, bAP attenuation strength varies according to firing mode. During LTS bursts, somatic AP half-width increases progressively with increasing spike number, allowing late-burst spikes to propagate more efficiently into the dendritic tree compared with spikes occurring at burst onset. Tonic spikes have similar somatic half-widths to late burst spikes and undergo similar dendritic attenuation. In contrast, in TRN neurons, AP properties are unchanged between LTS bursts and tonic firing and, as a result, distance-dependent dendritic attenuation remains consistent across different firing modes. Therefore, unlike LTS-associated global electrical and calcium signals, the spatial influence of bAP signaling in TC and TRN neurons is more restricted, with potentially important behavioral-state-dependent consequences for synaptic integration and plasticity in thalamic neurons. SIGNIFICANCE STATEMENT In most neurons, action potentials (APs) initiate in the axosomatic region and propagate into the dendritic tree to provide a retrograde signal that conveys information about the level of cellular output to the locations that receive most input: the dendrites. In thalamocortical and thalamic reticular nucleus neurons, the site of AP generation and the true extent of backpropagation remain unknown. Using patch-clamp recordings, this study measures dendritic propagation of APs directly in these neurons. In either cell type, high-frequency low-threshold spike burst or lower-frequency tonic APs undergo substantial voltage attenuation as they spread into the dendritic tree. Therefore, backpropagating spikes in these cells can only influence signaling in the proximal part of the dendritic tree. Copyright © 2017 Connelly et al.

An infrared optical pacing system for screening cardiac electrophysiology in human cardiomyocytes.

PubMed

McPheeters, Matthew T; Wang, Yves T; Werdich, Andreas A; Jenkins, Michael W; Laurita, Kenneth R

2017-01-01

Human cardiac myocytes derived from pluripotent stem cells (hCM) have invigorated interest in genetic disease mechanisms and cardiac safety testing; however, the technology to fully assess electrophysiological function in an assay that is amenable to high throughput screening has lagged. We describe a fully contactless system using optical pacing with an infrared (IR) laser and multi-site high fidelity fluorescence imaging to assess multiple electrophysiological parameters from hCM monolayers in a standard 96-well plate. Simultaneous multi-site action potentials (FluoVolt) or Ca2+ transients (Fluo4-AM) were measured, from which high resolution maps of conduction velocity and action potential duration (APD) were obtained in a single well. Energy thresholds for optical pacing were determined for cell plating density, laser spot size, pulse width, and wavelength and found to be within ranges reported previously for reliable pacing. Action potentials measured using FluoVolt and a microelectrode exhibited the same morphology and rate of depolarization. Importantly, we show that this can be achieved accurately with minimal damage to hCM due to optical pacing or fluorescence excitation. Finally, using this assay we demonstrate that hCM exhibit reproducible changes in repolarization and impulse conduction velocity for Flecainide and Quinidine, two well described reference compounds. In conclusion, we demonstrate a high fidelity electrophysiological screening assay that incorporates optical pacing with IR light to control beating rate of hCM monolayers.

Sorting Out Effects of Active Stream Restoration: Channel Morphology, Channel Change Processes and Potential Controls

NASA Astrophysics Data System (ADS)

McDowell, P. F.

2017-12-01

In many active restoration projects, instream structures or modifications are designed to produce specific change in channel form, such as reduced W:D or increased pool depth, yet there is little monitoring to evaluate effectiveness. Active restoration often takes place within a context of other land management changes that can have an effect on channel form. Thus, the effects of active restoration are difficult to separate from the effects of other management actions. We measured morphologic response to restoration designs on sections of the Middle Fork John Day River, a gravel-cobble bed river under a cattle grazing regime in the Blue Mountain of Oregon. Since 2000, restoration actions have included elimination of cattle grazing in the riparian zone (passive restoration), riparian planting of woody vegetation, instream log structures for fish habitat and pool maintenance, and elimination of a major flow diversion. We listed the hypothetical effects of each of these management changes, showing overlap among effects of active and passive restoration. Repeat cross-section and longitudinal profile surveys over eight years, and repeat aerial imagery, documented changes in channel width, depth and bed morphology, and processes of change (bank erosion or aggradation, point bar erosion or aggradation, bed incision or aggradation), in two restored reaches and two adjacent control (unrestored) reaches. Morphologic changes were modest. Bankfull cross-section area, width, and W:D all decreased slightly in both restored reaches. Control reaches were unchanged or increased slightly. Processes of change were markedly different among the four reaches, with different reaches dominated by different processes. One restored reach was dominated by slight bed aggradation, increased pool depth and deep pools/km, while the other restored reach was dominated by bank erosion, bar aggradation and slight bed incision, along with increased deep pools/km. The longitudinal profile showed significant re-arrangement of bed morphology. The spatial context of processes and controls allows some separation of the effectiveness of different management actions. Active restoration directly increased pool depth, but passive restoration apparently had more impact on aggradation/degradation and width.

Serial Spike Time Correlations Affect Probability Distribution of Joint Spike Events.

PubMed

Shahi, Mina; van Vreeswijk, Carl; Pipa, Gordon

2016-01-01

Detecting the existence of temporally coordinated spiking activity, and its role in information processing in the cortex, has remained a major challenge for neuroscience research. Different methods and approaches have been suggested to test whether the observed synchronized events are significantly different from those expected by chance. To analyze the simultaneous spike trains for precise spike correlation, these methods typically model the spike trains as a Poisson process implying that the generation of each spike is independent of all the other spikes. However, studies have shown that neural spike trains exhibit dependence among spike sequences, such as the absolute and relative refractory periods which govern the spike probability of the oncoming action potential based on the time of the last spike, or the bursting behavior, which is characterized by short epochs of rapid action potentials, followed by longer episodes of silence. Here we investigate non-renewal processes with the inter-spike interval distribution model that incorporates spike-history dependence of individual neurons. For that, we use the Monte Carlo method to estimate the full shape of the coincidence count distribution and to generate false positives for coincidence detection. The results show that compared to the distributions based on homogeneous Poisson processes, and also non-Poisson processes, the width of the distribution of joint spike events changes. Non-renewal processes can lead to both heavy tailed or narrow coincidence distribution. We conclude that small differences in the exact autostructure of the point process can cause large differences in the width of a coincidence distribution. Therefore, manipulations of the autostructure for the estimation of significance of joint spike events seem to be inadequate.

Serial Spike Time Correlations Affect Probability Distribution of Joint Spike Events

PubMed Central

Shahi, Mina; van Vreeswijk, Carl; Pipa, Gordon

2016-01-01

Detecting the existence of temporally coordinated spiking activity, and its role in information processing in the cortex, has remained a major challenge for neuroscience research. Different methods and approaches have been suggested to test whether the observed synchronized events are significantly different from those expected by chance. To analyze the simultaneous spike trains for precise spike correlation, these methods typically model the spike trains as a Poisson process implying that the generation of each spike is independent of all the other spikes. However, studies have shown that neural spike trains exhibit dependence among spike sequences, such as the absolute and relative refractory periods which govern the spike probability of the oncoming action potential based on the time of the last spike, or the bursting behavior, which is characterized by short epochs of rapid action potentials, followed by longer episodes of silence. Here we investigate non-renewal processes with the inter-spike interval distribution model that incorporates spike-history dependence of individual neurons. For that, we use the Monte Carlo method to estimate the full shape of the coincidence count distribution and to generate false positives for coincidence detection. The results show that compared to the distributions based on homogeneous Poisson processes, and also non-Poisson processes, the width of the distribution of joint spike events changes. Non-renewal processes can lead to both heavy tailed or narrow coincidence distribution. We conclude that small differences in the exact autostructure of the point process can cause large differences in the width of a coincidence distribution. Therefore, manipulations of the autostructure for the estimation of significance of joint spike events seem to be inadequate. PMID:28066225

Variability of acute extracellular action potential measurements with multisite silicon probes

PubMed Central

Scott, Kimberly M.; Du, Jiangang; Lester, Henry A.; Masmanidis, Sotiris C.

2012-01-01

Device miniaturization technologies have led to significant advances in sensors for extracellular measurements of electrical activity in the brain. Multisite, silicon-based probes containing implantable electrode arrays afford greater coverage of neuronal activity than single electrodes and therefore potentially offer a more complete view of how neuronal ensembles encode information. However, scaling up the number of sites is not sufficient to ensure capture of multiple neurons, as action potential signals from extracellular electrodes may vary due to numerous factors. In order to understand the large-scale recording capabilities and potential limitations of multisite probes, it is important to quantify this variability, and to determine whether certain key device parameters influence the recordings. Here we investigate the effect of four parameters, namely, electrode surface, width of the structural support shafts, shaft number, and position of the recording site relative to the shaft tip. This study employs acutely implanted silicon probes containing up to 64 recording sites, whose performance is evaluated by the metrics of noise, spike amplitude, and spike detection probability. On average, we find no significant effect of device geometry on spike amplitude and detection probability but we find significant differences among individual experiments, with the likelihood of detecting spikes varying by a factor of approximately three across trials. PMID:22971352

Improving the theoretical prediction for the Bs - B̅s width difference: matrix elements of next-to-leading order ΔB = 2 operators

NASA Astrophysics Data System (ADS)

Davies, Christine; Harrison, Judd; Lepage, G. Peter; Monahan, Christopher; Shigemitsu, Junko; Wingate, Matthew

2018-03-01

We present lattice QCD results for the matrix elements of R2 and other dimension-7, ΔB = 2 operators relevant for calculations of Δs, the Bs - B̅s width difference. We have computed correlation functions using 5 ensembles of the MILC Collaboration's 2+1 + 1-flavour gauge field configurations, spanning 3 lattice spacings and light sea quarks masses down to the physical point. The HISQ action is used for the valence strange quarks, and the NRQCD action is used for the bottom quarks. Once our analysis is complete, the theoretical uncertainty in the Standard Model prediction for ΔΓs will be substantially reduced.

Zonal variations in K+ currents in vestibular crista calyx terminals

PubMed Central

Meredith, Frances L.

2014-01-01

We developed a rodent crista slice to investigate regional variations in electrophysiological properties of vestibular afferent terminals. Thin transverse slices of the gerbil crista ampullaris were made and electrical properties of calyx terminals in central zones (CZ) and peripheral zones (PZ) compared with whole cell patch clamp. Spontaneous action potential firing was observed in 25% of current-clamp recordings and was either regular or irregular in both zones. Firing was abolished when extracellular choline replaced Na+ but persisted when hair cell mechanotransduction channels or calyx AMPA receptors were blocked. This suggests that ion channels intrinsic to the calyx can generate spontaneous firing. In response to depolarizing voltage steps, outward K+ currents were observed at potentials above −60 mV. K+ currents in PZ calyces showed significantly more inactivation than currents in CZ calyces. Underlying K+ channel populations contributing to these differences were investigated. The KCNQ channel blocker XE991 dihydrochloride blocked a slowly activating, sustained outward current in both PZ and CZ calyces, indicating the presence of KCNQ channels. Mean reduction was greatest in PZ calyces. XE991 also reduced action potential firing frequency in CZ and PZ calyces and broadened mean action potential width. The K+ channel blocker 4-aminopyridine (10–50 μM) blocked rapidly activating, moderately inactivating currents that were more prevalent in PZ calyces. α-Dendrotoxin, a selective blocker of KV1 channels, reduced outward currents in CZ calyces but not in PZ calyces. Regional variations in K+ conductances may contribute to different firing responses in calyx afferents. PMID:25343781

Zonal variations in K+ currents in vestibular crista calyx terminals.

PubMed

Meredith, Frances L; Rennie, Katherine J

2015-01-01

We developed a rodent crista slice to investigate regional variations in electrophysiological properties of vestibular afferent terminals. Thin transverse slices of the gerbil crista ampullaris were made and electrical properties of calyx terminals in central zones (CZ) and peripheral zones (PZ) compared with whole cell patch clamp. Spontaneous action potential firing was observed in 25% of current-clamp recordings and was either regular or irregular in both zones. Firing was abolished when extracellular choline replaced Na(+) but persisted when hair cell mechanotransduction channels or calyx AMPA receptors were blocked. This suggests that ion channels intrinsic to the calyx can generate spontaneous firing. In response to depolarizing voltage steps, outward K(+) currents were observed at potentials above -60 mV. K(+) currents in PZ calyces showed significantly more inactivation than currents in CZ calyces. Underlying K(+) channel populations contributing to these differences were investigated. The KCNQ channel blocker XE991 dihydrochloride blocked a slowly activating, sustained outward current in both PZ and CZ calyces, indicating the presence of KCNQ channels. Mean reduction was greatest in PZ calyces. XE991 also reduced action potential firing frequency in CZ and PZ calyces and broadened mean action potential width. The K(+) channel blocker 4-aminopyridine (10-50 μM) blocked rapidly activating, moderately inactivating currents that were more prevalent in PZ calyces. α-Dendrotoxin, a selective blocker of KV1 channels, reduced outward currents in CZ calyces but not in PZ calyces. Regional variations in K(+) conductances may contribute to different firing responses in calyx afferents. Copyright © 2015 the American Physiological Society.

Functional role of A-type potassium currents in rat presympathetic PVN neurones

PubMed Central

Sonner, Patrick M; Stern, Javier E

2007-01-01

Despite the fact that paraventricular nucleus (PVN) neurones innervating the rostral ventrolateral medulla (RVLM) play important roles in the control of sympathetic function both in physiological and pathological conditions, the precise mechanisms controlling their activity are still incompletely understood. In the present study, we evaluated whether the transient outward potassium current IA is expressed in PVN-RVLM neurones, characterized its biophysical and pharmacological properties, and determined its role in shaping action potentials and firing discharge in these neurones. Patch-clamp recordings obtained from retrogradely labelled, PVN-RVLM neurones indicate that a 4-AP sensitive, TEA insensitive current, with biophysical properties consistent with IA, is present in these neurones. Pharmacological blockade of IA depolarized resting Vm and prolonged Na+ action potential duration, by increasing its width and by slowing down its decay time course. Interestingly, blockade of IA either increased or decreased the firing activity of PVN-RVLM neurones, supporting the presence of subsets of PVN-RVLM neurones differentially modulated by IA. In all cases, the effects of IA on firing activity were prevented by a broad spectrum Ca2+ channel blocker. Immunohistochemical studies suggest that IA in PVN-RVLM neurons is mediated by Kv1.4 and/or Kv4.3 channel subunits. Overall, our results demonstrate the presence of IA in PVN-RVLM neurones, which actively modulates their action potential waveform and firing activity. These studies support IA as an important intrinsic mechanism controlling neuronal excitability in this central presympathetic neuronal population. PMID:17525115

Role of wave packet width in quantum molecular dynamics in fusion reactions near barrier

NASA Astrophysics Data System (ADS)

Cao, X. G.; Ma, Y. G.; Zhang, G. Q.; Wang, H. W.; Anastasi, A.; Curciarello, F.; De Leo, V.

2014-05-01

The dynamical fusion process of 48Ca + 144Sm with different impact parameters near barrier is studied by an extended quantum molecular dynamics (EQMD) model, where width of wavepacket is dynamically treated based on variational principle. The time evolution of different energy components such as potential energy, kinetic energy, Coulomb energy and Pauli potential are analyzed when dynamical or fixed width is assumed in calculation. It is found that the dynamical wavepacket width can enhance the dissipation of incident energy and the fluctuations, which are important to form compound nuclei. Moreover, we compare the fusion barrier dependence on the incident energy when it is determined by both dynamical and fixed wavepacket width.

Action Potential Broadening in Capsaicin-Sensitive DRG Neurons from Frequency-Dependent Reduction of Kv3 Current

PubMed Central

Liu, Pin W.; Blair, Nathaniel T.

2017-01-01

Action potential (AP) shape is a key determinant of cellular electrophysiological behavior. We found that in small-diameter, capsaicin-sensitive dorsal root ganglia neurons corresponding to nociceptors (from rats of either sex), stimulation at frequencies as low as 1 Hz produced progressive broadening of the APs. Stimulation at 10 Hz for 3 s resulted in an increase in AP width by an average of 76 ± 7% at 22°C and by 38 ± 3% at 35°C. AP clamp experiments showed that spike broadening results from frequency-dependent reduction of potassium current during spike repolarization. The major current responsible for frequency-dependent reduction of overall spike-repolarizing potassium current was identified as Kv3 current by its sensitivity to low concentrations of 4-aminopyridine (IC50 <100 μm) and block by the peptide inhibitor blood depressing substance I (BDS-I). There was a small component of Kv1-mediated current during AP repolarization, but this current did not show frequency-dependent reduction. In a small fraction of cells, there was a component of calcium-dependent potassium current that showed frequency-dependent reduction, but the contribution to overall potassium current reduction was almost always much smaller than that of Kv3-mediated current. These results show that Kv3 channels make a major contribution to spike repolarization in small-diameter DRG neurons and undergo frequency-dependent reduction, leading to spike broadening at moderate firing frequencies. Spike broadening from frequency-dependent reduction in Kv3 current could mitigate the frequency-dependent decreases in conduction velocity typical of C-fiber axons. SIGNIFICANCE STATEMENT Small-diameter dorsal root ganglia (DRG) neurons mediating nociception and other sensory modalities express many types of potassium channels, but how they combine to control firing patterns and conduction is not well understood. We found that action potentials of small-diameter rat DRG neurons showed spike broadening at frequencies as low as 1 Hz and that spike broadening resulted predominantly from frequency-dependent inactivation of Kv3 channels. Spike width helps to control transmitter release, conduction velocity, and firing patterns and understanding the role of particular potassium channels can help to guide new pharmacological strategies for targeting pain-sensing neurons selectively. PMID:28877968

Action Potential Broadening in Capsaicin-Sensitive DRG Neurons from Frequency-Dependent Reduction of Kv3 Current.

PubMed

Liu, Pin W; Blair, Nathaniel T; Bean, Bruce P

2017-10-04

Action potential (AP) shape is a key determinant of cellular electrophysiological behavior. We found that in small-diameter, capsaicin-sensitive dorsal root ganglia neurons corresponding to nociceptors (from rats of either sex), stimulation at frequencies as low as 1 Hz produced progressive broadening of the APs. Stimulation at 10 Hz for 3 s resulted in an increase in AP width by an average of 76 ± 7% at 22°C and by 38 ± 3% at 35°C. AP clamp experiments showed that spike broadening results from frequency-dependent reduction of potassium current during spike repolarization. The major current responsible for frequency-dependent reduction of overall spike-repolarizing potassium current was identified as Kv3 current by its sensitivity to low concentrations of 4-aminopyridine (IC 50 <100 μm) and block by the peptide inhibitor blood depressing substance I (BDS-I). There was a small component of Kv1-mediated current during AP repolarization, but this current did not show frequency-dependent reduction. In a small fraction of cells, there was a component of calcium-dependent potassium current that showed frequency-dependent reduction, but the contribution to overall potassium current reduction was almost always much smaller than that of Kv3-mediated current. These results show that Kv3 channels make a major contribution to spike repolarization in small-diameter DRG neurons and undergo frequency-dependent reduction, leading to spike broadening at moderate firing frequencies. Spike broadening from frequency-dependent reduction in Kv3 current could mitigate the frequency-dependent decreases in conduction velocity typical of C-fiber axons. SIGNIFICANCE STATEMENT Small-diameter dorsal root ganglia (DRG) neurons mediating nociception and other sensory modalities express many types of potassium channels, but how they combine to control firing patterns and conduction is not well understood. We found that action potentials of small-diameter rat DRG neurons showed spike broadening at frequencies as low as 1 Hz and that spike broadening resulted predominantly from frequency-dependent inactivation of Kv3 channels. Spike width helps to control transmitter release, conduction velocity, and firing patterns and understanding the role of particular potassium channels can help to guide new pharmacological strategies for targeting pain-sensing neurons selectively. Copyright © 2017 the authors 0270-6474/17/379705-10$15.00/0.

Calculation of stochastic broadening due to low mn magnetic perturbation in the simple map in action-angle coordinates

NASA Astrophysics Data System (ADS)

Hinton, Courtney; Punjabi, Alkesh; Ali, Halima

2009-11-01

The simple map is the simplest map that has topology of divertor tokamaks [A. Punjabi, H. Ali, T. Evans, and A. Boozer, Phys. Let. A 364, 140--145 (2007)]. Recently, the action-angle coordinates for simple map are analytically calculated, and simple map is constructed in action-angle coordinates [O. Kerwin, A. Punjabi, and H. Ali, Phys. Plasmas 15, 072504 (2008)]. Action-angle coordinates for simple map cannot be inverted to real space coordinates (R,Z). Because there is logarithmic singularity on the ideal separatrix, trajectories cannot cross separatrix [op cit]. Simple map in action-angle coordinates is applied to calculate stochastic broadening due to the low mn magnetic perturbation with mode numbers m=1, and n=±1. The width of stochastic layer near the X-point scales as 0.63 power of the amplitude δ of low mn perturbation, toroidal flux loss scales as 1.16 power of δ, and poloidal flux loss scales as 1.26 power of δ. Scaling of width deviates from Boozer-Rechester scaling by 26% [A. Boozer, and A. Rechester, Phys. Fluids 21, 682 (1978)]. This work is supported by US Department of Energy grants DE-FG02-07ER54937, DE-FG02-01ER54624 and DE-FG02-04ER54793.

Effect of 1.8 GHz radiofrequency electromagnetic radiation on novel object associative recognition memory in mice

PubMed Central

Wang, Kai; Lu, Jun-Mei; Xing, Zhen-He; Zhao, Qian-Ru; Hu, Lin-Qi; Xue, Lei; Zhang, Jie; Mei, Yan-Ai

2017-01-01

Mounting evidence suggests that exposure to radiofrequency electromagnetic radiation (RF-EMR) can influence learning and memory in rodents. In this study, we examined the effects of single exposure to 1.8 GHz RF-EMR for 30 min on subsequent recognition memory in mice, using the novel object recognition task (NORT). RF-EMR exposure at an intensity of >2.2 W/kg specific absorption rate (SAR) power density induced a significant density-dependent increase in NORT index with no corresponding changes in spontaneous locomotor activity. RF-EMR exposure increased dendritic-spine density and length in hippocampal and prefrontal cortical neurons, as shown by Golgi staining. Whole-cell recordings in acute hippocampal and medial prefrontal cortical slices showed that RF-EMR exposure significantly altered the resting membrane potential and action potential frequency, and reduced the action potential half-width, threshold, and onset delay in pyramidal neurons. These results demonstrate that exposure to 1.8 GHz RF-EMR for 30 min can significantly increase recognition memory in mice, and can change dendritic-spine morphology and neuronal excitability in the hippocampus and prefrontal cortex. The SAR in this study (3.3 W/kg) was outside the range encountered in normal daily life, and its relevance as a potential therapeutic approach for disorders associated with recognition memory deficits remains to be clarified. PMID:28303965

Influence of gate width on gate-channel carrier mobility in AlGaN/GaN heterostructure field-effect transistors

NASA Astrophysics Data System (ADS)

Yang, Ming; Ji, Qizheng; Gao, Zhiliang; Zhang, Shufeng; Lin, Zhaojun; Yuan, Yafei; Song, Bo; Mei, Gaofeng; Lu, Ziwei; He, Jihao

2017-11-01

For the fabricated AlGaN/GaN heterostructure field-effect transistors (HFETs) with different gate widths, the gate-channel carrier mobility is experimentally obtained from the measured current-voltage and capacitance-voltage curves. Under each gate voltage, the mobility gets lower with gate width increasing. Analysis shows that the phenomenon results from the polarization Coulomb field (PCF) scattering, which originates from the irregularly distributed polarization charges at the AlGaN/GaN interface. The device with a larger gate width is with a larger PCF scattering potential and a stronger PCF scattering intensity. As a function of gate width, PCF scattering potential shows a same trend with the mobility variation. And the theoretically calculated mobility values fits well with the experimentally obtained values. Varying gate widths will be a new perspective for the improvement of device characteristics by modulating the gate-channel carrier mobility.

Anomalous broadening and shift of emission lines in a femtosecond laser plasma filament in air

NASA Astrophysics Data System (ADS)

Ilyin, A. A.; Golik, S. S.; Shmirko, K. A.; Mayor, A. Yu.; Proschenko, D. Yu.

2017-12-01

The temporal evolution of the width and shift of N I 746.8 and O I 777.4 nm lines is investigated in a filament plasma produced by a tightly focused femtosecond laser pulse (0.9 mJ, 48 fs). The nitrogen line shift and width are determined by the joint action of electron impact shift and the far-off resonance AC Stark effect. The intensive (I = 1.2·1010 W/cm2) electric field of ASE (amplified spontaneous emission) and post-pulses result in a possible LS coupling break for the O I 3p 5P level and the generation of Rabi sidebands. The blueshifted main femtosecond pulse and Rabi sideband cause the stimulated emission of the N2 1+ system. The maximal widths of emission lines are approximately 6.7 times larger than the calculated Stark widths.

Width of the confining string in Yang-Mills theory.

PubMed

Gliozzi, F; Pepe, M; Wiese, U-J

2010-06-11

We investigate the transverse fluctuations of the confining string connecting two static quarks in (2+1)D SU(2) Yang-Mills theory using Monte Carlo calculations. The exponentially suppressed signal is extracted from the large noise by a very efficient multilevel algorithm. The resulting width of the string increases logarithmically with the distance between the static quark charges. Corrections at intermediate distances due to universal higher-order terms in the effective string action are calculated analytically. They accurately fit the numerical data.

Effect of extending grating length and width on human visually evoked potentials.

PubMed

Mihaylova, Milena S; Hristov, Ivan; Racheva, Kalina; Totev, Tsvetalin; Mitov, Dimitar

2015-01-01

Visually evoked potentials (VEPs) were elicited by Gabor gratings with different lengths and widths at three spatial frequencies (SFs): low, 1.45 c/deg, medium, 2.9 c/deg and high, 5.8 c/deg and at a contrast 3 times above the detection threshold at each SF. An increase of grating length enhanced N1 amplitude at occipital and parietal positions stronger than the increase of grating width at aspect ratios (length : width) above 4:1. The stronger effect of stimulus length than width was reflected also in the amplitude of the later P1 component at central and parietal positions. The larger effect of stimulus length than width on the VEP amplitude was SF specific: it was stronger at 5.8 c/deg, smaller at 2.9 c/deg and vanished at 1.45 c/deg. The results obtained suggest anisotropy in the physiological mechanisms that underlie grating perception and involve bottom- up processes initiated in the occipital cortex.

The effects of shape crowding on grasping.

PubMed

Chen, Juan; Jayawardena, Sanasi; Goodale, Melvyn Alan

2015-03-10

Crowding refers to the deleterious effect of nearby objects on the identification of a target in the peripheral visual field. A recent study (Chen, Sperandio, & Goodale, 2015) showed that when a three-dimensional (3D) disk was crowded by disks of different sizes, participants could scale their grip aperture to the size of the target, even when they could not perceive its size. It is still unclear, however, whether or not grasping can also escape to some degree the crowding of other object features, such as shape. To test this, we presented 3D rectangular blocks in isolation or crowded by other blocks in the periphery. The target and flanking blocks had the same surface area but different dimensions. Participants were required either to grasp the target block across its width or to estimate its width. We found that, consistent with what we observed earlier with size, participants can also scale their grasp to the width of the target block even when they could not perceive its width. To further explore whether or not the effect of crowding on grasping depends on how proficient people are with their right hand, we had right-handed participants perform the same test but with their left hand. We found that left-hand grasping did not escape the crowding effect on shape perception at all. Taken together, our results suggest that people can also use invisible shape information to guide actions and that this ability depends on the proficiency of the action. © 2015 ARVO.

Secondhand tobacco smoke exposure differentially alters nucleus tractus solitarius neurons at two different ages in developing non-human primates

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

Sekizawa, Shin-ichi, E-mail: ssekizawa@ucdavis.ed; Joad, Jesse P.; Pinkerton, Kent E.

Exposing children to secondhand tobacco smoke (SHS) is associated with increased risk for asthma, bronchiolitis and SIDS. The role for changes in the developing CNS contributing to these problems has not been fully explored. We used rhesus macaques to test the hypothesis that SHS exposure during development triggers neuroplastic changes in the nucleus tractus solitarius (NTS), where lung sensory information related to changes in airway and lung function is first integrated. Pregnant monkeys were exposed to filtered air (FA) or SHS for 6 h/day, 5 days/week starting at 50-day gestational age. Mother/infant pairs continued the exposures postnatally to age 3more » or 13 months, which may be equivalent to approximately 1 or 4 years of human age, respectively. Whole-cell recordings were made of second-order NTS neurons in transverse brainstem slices. To target the consequences of SHS exposure based on neuronal subgroups, we classified NTS neurons into two phenotypes, rapid-onset spiking (RS) and delayed-onset spiking (DS), and then evaluated intrinsic and synaptic excitabilities in FA-exposed animals. RS neurons showed greater cell excitability especially at age of 3 months while DS neurons received greater amplitudes of excitatory postsynaptic currents (EPSCs). Developmental neuroplasticity such as increases in intrinsic and synaptic excitabilities were detected especially in DS neurons. In 3 month olds, SHS exposure effects were limited to excitatory changes in RS neurons, specifically increases in evoked EPSC amplitudes and increased spiking responses accompanied by shortened action potential width. By 13 months, the continued SHS exposure inhibited DS neuronal activity; decreases in evoked EPSC amplitudes and blunted spiking responses accompanied by prolonged action potential width. The influence of SHS exposure on age-related and phenotype specific changes may be associated with age-specific respiratory problems, for which SHS exposure can increase the risk, such as SIDS and bronchiolitis in infants and asthma in older children.« less

Can stream and riparian restoration offset climate change impacts to salmon populations?

PubMed

Justice, Casey; White, Seth M; McCullough, Dale A; Graves, David S; Blanchard, Monica R

2017-03-01

Understanding how stream temperature responds to restoration of riparian vegetation and channel morphology in context of future climate change is critical for prioritizing restoration actions and recovering imperiled salmon populations. We used a deterministic water temperature model to investigate potential thermal benefits of riparian reforestation and channel narrowing to Chinook Salmon populations in the Upper Grande Ronde River and Catherine Creek basins in Northeast Oregon, USA. A legacy of intensive land use practices in these basins has significantly reduced streamside vegetation and increased channel width across most of the stream network, resulting in water temperatures that far exceed the optimal range for salmon growth and survival. By combining restoration scenarios with climate change projections, we were able to evaluate whether future climate impacts could be offset by restoration actions. A combination of riparian restoration and channel narrowing was predicted to reduce peak summer water temperatures by 6.5 °C on average in the Upper Grande Ronde River and 3.0 °C in Catherine Creek in the absence of other perturbations. These results translated to increases in Chinook Salmon parr abundance of 590% and 67% respectively. Although projected climate change impacts on water temperature for the 2080s time period were substantial (i.e., median increase of 2.7 °C in the Upper Grande Ronde and 1.5 °C in Catherine Creek), we predicted that basin-wide restoration of riparian vegetation and channel width could offset these impacts, reducing peak summer water temperatures by about 3.5 °C in the Upper Grande Ronde and 1.8 °C in Catherine Creek. These results underscore the potential for riparian and stream channel restoration to mitigate climate change impacts to threatened salmon populations in the Pacific Northwest. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

Secondhand tobacco smoke exposure differentially alters nucleus tractus solitarius neurons at two different ages in developing non-human primates.

PubMed

Sekizawa, Shin-Ichi; Joad, Jesse P; Pinkerton, Kent E; Bonham, Ann C

2010-01-15

Exposing children to secondhand tobacco smoke (SHS) is associated with increased risk for asthma, bronchiolitis and SIDS. The role for changes in the developing CNS contributing to these problems has not been fully explored. We used rhesus macaques to test the hypothesis that SHS exposure during development triggers neuroplastic changes in the nucleus tractus solitarius (NTS), where lung sensory information related to changes in airway and lung function is first integrated. Pregnant monkeys were exposed to filtered air (FA) or SHS for 6 h/day, 5 days/week starting at 50-day gestational age. Mother/infant pairs continued the exposures postnatally to age 3 or 13 months, which may be equivalent to approximately 1 or 4 years of human age, respectively. Whole-cell recordings were made of second-order NTS neurons in transverse brainstem slices. To target the consequences of SHS exposure based on neuronal subgroups, we classified NTS neurons into two phenotypes, rapid-onset spiking (RS) and delayed-onset spiking (DS), and then evaluated intrinsic and synaptic excitabilities in FA-exposed animals. RS neurons showed greater cell excitability especially at age of 3 months while DS neurons received greater amplitudes of excitatory postsynaptic currents (EPSCs). Developmental neuroplasticity such as increases in intrinsic and synaptic excitabilities were detected especially in DS neurons. In 3 month olds, SHS exposure effects were limited to excitatory changes in RS neurons, specifically increases in evoked EPSC amplitudes and increased spiking responses accompanied by shortened action potential width. By 13 months, the continued SHS exposure inhibited DS neuronal activity; decreases in evoked EPSC amplitudes and blunted spiking responses accompanied by prolonged action potential width. The influence of SHS exposure on age-related and phenotype specific changes may be associated with age-specific respiratory problems, for which SHS exposure can increase the risk, such as SIDS and bronchiolitis in infants and asthma in older children.

Capillary transport of water through textile-reinforced concrete applied in repairing and/or strengthening cracked RC structures

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

Lieboldt, M.; Mechtcherine, V., E-mail: mechtcherine@tu-dresden.de

2013-10-15

The use of textile-reinforced concrete (TRC) has great potential for innovative solutions in repairing, protecting, and strengthening concrete and RC structures. The article at hand reports on an investigation on composite concrete specimens made of cracked ordinary concrete as substrate and textile-reinforced concrete (TRC) as a cover layer for its strengthening and repair. The TRC cover layer was assessed with regard to its effectiveness as a protective layer against the ingress of water through capillary action. Since in real applications such TRC layers may be cracked or presumed to be so, thereby activating the load-carrying function of the textile reinforcement,more » the TRC layer was cracked for purposes of this study. The water transport in the cracked ordinary concrete specimens without the TRC layer was used as a reference. Gravimetric measurements and neutron radiography served as the testing techniques. In ordinary concrete quick and deep ingress of water through relatively wide macro-cracks of approximately 100 μm width, followed by transport through the capillary pore system, caused saturation of large areas in a rather short time. TRC applied to the RC surface reduced the ingress of water to a large extent. Its small crack widths of 15 to 20 μm changed suction behaviour fundamentally. In the cracked substrate of ordinary concrete, capillary suction was prevented, and transport through the pore system of the matrix became the prevailing transport mechanism of capillary action. Not only was the mechanism altered, but the transport of water deep into inner regions was markedly retarded as well.« less

Stark parameter dependence of the rest core charge of the emitters for multiply charged ions spectral lines

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

Šćepanović, M., E-mail: mara.scepanovic@gmail.com; Purić, J.

2016-03-25

Stark width and shift simultaneous dependence on the upper level ionization potential and rest core charge of the emitter has been evaluated and discussed. It has been verified that the found relations, connecting Stark broadening parameters with upper level ionization potential and rest core charge of the emitters for particular electron temperature and density, can be used for prediction of Stark line width and shift data in case of ions for which observed data, or more detailed calculations, are not yet available. Stark widths and shifts published data are used to demonstrate the existence of other kinds of regularities withinmore » similar spectra of different elements and their ionization stages. The emphasis is on the Stark parameter dependence on the upper level ionization potential and on the rest core charge for the lines from similar spectra of multiply charged ions. The found relations connecting Stark widths and shift parameters with upper level ionization potential, rest core charge and electron temperature were used for a prediction of new Stark broadening data, thus avoiding much more complicated procedures.« less

Weaker control of the electrical properties of cerebellar granule cells by tonically active GABAA receptors in the Ts65Dn mouse model of Down’s syndrome

PubMed Central

2013-01-01

Background Down’s syndrome (DS) is caused by triplication of all or part of human chromosome 21 and is characterized by a decrease in the overall size of the brain. One of the brain regions most affected is the cerebellum, in which the number of granule cells (GCs) is markedly decreased. GCs process sensory information entering the cerebellum via mossy fibres and pass it on to Purkinje cells and inhibitory interneurons. How GCs transform incoming signals depends on their input–output relationship, which is adjusted by tonically active GABAA receptor channels. Results We report that in the Ts65Dn mouse model of DS, in which cerebellar volume and GC number are decreased as in DS, the tonic GABAA receptor current in GCs is smaller than in wild-type mice and is less effective in moderating input resistance and raising the minimum current required for action potential firing. We also find that tonically active GABAA receptors curb the height and broaden the width of action potentials in wild-type GCs but not in Ts65Dn GCs. Single-cell real-time quantitative PCR reveals that these electrical differences are accompanied by decreased expression of the gene encoding the GABAA receptor β3 subunit but not genes coding for some of the other GABAA receptor subunits expressed in GCs (α1, α6, β2 and δ). Conclusions Weaker moderation of excitability and action potential waveform in GCs of the Ts65Dn mouse by tonically active GABAA receptors is likely to contribute to atypical transfer of information through the cerebellum. Similar changes may occur in DS. PMID:23870245

Calculations of antiproton-nucleus quasi-bound states using the Paris N bar N potential

NASA Astrophysics Data System (ADS)

Hrtánková, Jaroslava; Mareš, Jiří

2018-01-01

An optical potential constructed using the p bar N scattering amplitudes derived from the 2009 version of the Paris N bar N potential is applied in calculations of p bar quasi-bound states in selected nuclei across the periodic table. A proper self-consistent procedure for treating energy dependence of the amplitudes in a nucleus appears crucial for evaluating p bar binding energies and widths. Particular attention is paid to the role of P-wave amplitudes. While the P-wave potential nearly does not affect calculated p bar binding energies, it reduces considerably the corresponding widths. The Paris S-wave potential supplemented by a phenomenological P-wave term yields in dynamical calculations p bar binding energies Bpbar ≈ 200 MeV and widths Γpbar ∼ 200- 230 MeV, which is very close to the values obtained within the RMF model consistent with p bar -atom data.

An infrared optical pacing system for high-throughput screening of cardiac electrophysiology in human cardiomyocytes (Conference Presentation)

NASA Astrophysics Data System (ADS)

McPheeters, Matt T.; Wang, Yves T.; Laurita, Kenneth R.; Jenkins, Michael W.

2017-02-01

Cardiomyocytes derived from human induced pluripotent stem cells (hiPS-HCM) have the potential to provide individualized therapies for patients and to test drug candidates for cardiac toxicity. In order for hiPS-CM to be useful for such applications, there is a need for high-throughput technology to rapidly assess cardiac electrophysiology parameters. Here, we designed and tested a fully contactless optical mapping (OM) and optical pacing (OP) system capable of imaging and point stimulation of hiPS-CM in small wells. OM allowed us to characterize cardiac electrophysiological parameters (conduction velocity, action potential duration, etc.) using voltage-sensitive dyes with high temporal and spatial resolution over the entire well. To improve OM signal-to-noise ratio, we tested a new voltage-sensitive dye (Fluovolt) for accuracy and phototoxicity. Stimulation is essential because most electrophysiological parameters are rate dependent; however, traditional methods utilizing electrical stimulation is difficult in small wells. To overcome this limitation, we utilized OP (λ = 1464 nm) to precisely control heart rate with spatial precision without the addition of exogenous agents. We optimized OP parameters (e.g., well size, pulse width, spot size) to achieve robust pacing and minimize the threshold radiant exposure. Finally, we tested system sensitivity using Flecainide, a drug with well described action on multiple electrophysiological properties.

Properties of charmonia in a hot equilibrated medium

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

Giannuzzi, Floriana; Mannarelli, Massimo

2009-09-01

We investigate the properties of charmonia in a thermal medium, showing that with increasing temperature the decay widths of these mesons behave in a nontrivial way. Our analysis is based on a potential model with interaction potential extracted from thermal lattice QCD calculations of the free-energy of a static quark-antiquark pair. We find that in the crossover region some decay widths are extremely enhanced. In particular, at temperatures T{approx}T{sub c} the decay widths of the J/{psi} that depend on the value of the wave function at the origin are enhanced with respect to the values in vacuum by about amore » factor 2. In the same temperature range the decay width of the process {chi}{sub cJ}{yields}J/{psi}+{gamma} is enhanced by approximately a factor 6 with respect to the value in vacuum. At higher temperatures the charmonia states dissociate and the widths of both decay processes become vanishing small.« less

Assessing the Electrode-Neuron Interface with the Electrically Evoked Compound Action Potential, Electrode Position, and Behavioral Thresholds.

PubMed

DeVries, Lindsay; Scheperle, Rachel; Bierer, Julie Arenberg

2016-06-01

Variability in speech perception scores among cochlear implant listeners may largely reflect the variable efficacy of implant electrodes to convey stimulus information to the auditory nerve. In the present study, three metrics were applied to assess the quality of the electrode-neuron interface of individual cochlear implant channels: the electrically evoked compound action potential (ECAP), the estimation of electrode position using computerized tomography (CT), and behavioral thresholds using focused stimulation. The primary motivation of this approach is to evaluate the ECAP as a site-specific measure of the electrode-neuron interface in the context of two peripheral factors that likely contribute to degraded perception: large electrode-to-modiolus distance and reduced neural density. Ten unilaterally implanted adults with Advanced Bionics HiRes90k devices participated. ECAPs were elicited with monopolar stimulation within a forward-masking paradigm to construct channel interaction functions (CIF), behavioral thresholds were obtained with quadrupolar (sQP) stimulation, and data from imaging provided estimates of electrode-to-modiolus distance and scalar location (scala tympani (ST), intermediate, or scala vestibuli (SV)) for each electrode. The width of the ECAP CIF was positively correlated with electrode-to-modiolus distance; both of these measures were also influenced by scalar position. The ECAP peak amplitude was negatively correlated with behavioral thresholds. Moreover, subjects with low behavioral thresholds and large ECAP amplitudes, averaged across electrodes, tended to have higher speech perception scores. These results suggest a potential clinical role for the ECAP in the objective assessment of individual cochlear implant channels, with the potential to improve speech perception outcomes.

Diatomic predissociation line widths

NASA Technical Reports Server (NTRS)

Child, M. S.

1973-01-01

Predissociation by rotation and curve crossing in diatomic molecules is discussed. The pattern of predissociation line widths is seen as providing a highly sensitive yardstick for the determination of unknown potential curves. In addition, the computation of such a pattern for given potential curves is considered a matter of routine, unless the predissociation happens to occur from an adiabatic potential curve. Analytic formulas are used to provide physical insight into the details of the predissociation pattern, to the extent that a direct inversion procedure is developed for determination of the repulsive potential curves for Type 1 predissociations.

A theory of vibrational prey localization in two dimensions: the sand scorpion

NASA Astrophysics Data System (ADS)

van Hemmen, J. Leo

2000-03-01

Sand scorpions, and many other arachnids, find their prey at night by localizing the source of mechanical waves produced by prey movements. Substrate vibrations propagating through sand evoke stimulus-locked action potentials from slit sensilla on the scorpion's eight `feet' (tarsi). We present a neuronal model to account for stimulus angle determination in a two-dimensional plane using a population of second-order neurons, each receiving excitatory input from one tarsus and inhibition from a triad opposite to it. This input opens a time window whose width determines the firing probability of each of the second-order neurons. The population then `votes' for the direction. Stochastic resonance is realized through tuning the balance between excitation and inhibition. The agreement with behavioral experiments on sand scorpions is excellent.

Changes in intrinsic excitability of ganglion cells in degenerated retinas of RCS rats.

PubMed

Ren, Yi-Ming; Weng, Chuan-Huang; Zhao, Cong-Jian; Yin, Zheng-Qin

2018-01-01

To evaluate the intrinsic excitability of retinal ganglion cells (RGCs) in degenerated retinas. The intrinsic excitability of various morphologically defined RGC types using a combination of patch-clamp recording and the Lucifer yellow tracer in retinal whole-mount preparations harvested from Royal College of Surgeons (RCS) rats, a common retinitis pigmentosa (RP) model, in a relatively late stage of retinal degeneration (P90) were investigated. Several parameters of RGC morphologies and action potentials (APs) were measured and compared to those of non-dystrophic control rats, including dendritic stratification, dendritic field diameter, peak amplitude, half width, resting membrane potential, AP threshold, depolarization to threshold, and firing rates. Compared with non-dystrophic control RGCs, more depolarizations were required to reach the AP threshold in RCS RGCs with low spontaneous spike rates and in RCS OFF cells (especially A2o cells), and RCS RGCs maintained their dendritic morphologies, resting membrane potentials and capabilities to generate APs. RGCs are relatively well preserved morphologically and functionally, and some cells are more susceptible to decreased excitability during retinal degeneration. These findings provide valuable considerations for optimizing RP therapeutic strategies.

Electric and magnetic superlattices in trilayer graphene

NASA Astrophysics Data System (ADS)

Uddin, Salah; Chan, K. S.

2016-01-01

The properties of one dimensional Kronig-Penney type of periodic electric and vector potential on ABC-trilayer graphene superlattices are investigated. The energy spectra obtained with periodic vector potentials shows the emergence of extra Dirac points in the energy spectrum with finite energies. For identical barrier and well widths, the original as well as the extra Dirac points are located in the ky = 0 plane. An asymmetry between the barrier and well widths causes a shift in the extra Dirac points away from the ky = 0 plane. Extra Dirac points having same electron hole crossing energy as that of the original Dirac point as well as finite energy Dirac points are generated in the energy spectrum when periodic electric potential is applied to the system. By applying electric and vector potential together, the symmetry of the energy spectrum about the Fermi level is broken. A tunable band gap is induced in the energy spectrum by applying both electric and vector potential simultaneously with different barrier and well widths.

Aircraft evacuations through type-III exits II : effects of individual subject differences.

DOT National Transportation Integrated Search

1995-08-01

Simulated emergency egress from Type III over-wing exits was studied to support regulatory action by the FAA. Passageway width from the aircraft center aisle to the Type-III exit was the major variable of interest; effects of individual subject attri...

Estimation of potential maximum biomass of trout in Wyoming streams to assist management decisions

USGS Publications Warehouse

Hubert, W.A.; Marwitz, T.D.; Gerow, K.G.; Binns, N.A.; Wiley, R.W.

1996-01-01

Fishery managers can benefit from knowledge of the potential maximum biomass (PMB) of trout in streams when making decisions on the allocation of resources to improve fisheries. Resources are most likely to he expended on streams with high PMB and with large differences between PMB and currently measured biomass. We developed and tested a model that uses four easily measured habitat variables to estimate PMB (upper 90th percentile of predicted mean bid mass) of trout (Oncorhynchus spp., Salmo trutta, and Salvelinus fontinalis) in Wyoming streams. The habitat variables were proportion of cover, elevation, wetted width, and channel gradient. The PMB model was constructed from data on 166 stream reaches throughout Wyoming and validated on an independent data set of 50 stream reaches. Prediction of PMB in combination with estimation of current biomass and information on habitat quality can provide managers with insight into the extent to which management actions may enhance trout biomass.

Interference in the g g → h → γ γ On-Shell Rate and the Higgs Boson Total Width

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

Campbell, John; Carena, Marcela; Harnik, Roni

We consider interference between the Higgs signal and QCD background inmore » $$gg\\rightarrow h \\rightarrow \\gamma\\gamma$$ and its effect on the on-shell Higgs rate. The existence of sizable strong phases leads to destructive interference of about 2% of the on-shell cross section in the Standard Model. This effect can be enhanced by beyond the standard model physics. In particular, since it scales differently from the usual rates, the presence of interference allows indirect limits to be placed on the Higgs width in a novel way, using on-shell rate measurements. Our study motivates further QCD calculations to reduce uncertainties. We discuss potential width-sensitive observables, both using total and differential rates and find that the HL-LHC can potentially indirectly probe widths of order tens of MeV.« less

Motor units in the human medial gastrocnemius muscle are not spatially localized or functionally grouped.

PubMed

Héroux, Martin E; Brown, Harrison J; Inglis, J Timothy; Siegmund, Gunter P; Blouin, Jean-Sébastien

2015-08-15

Human medial gastrocnemius (MG) motor units (MUs) are thought to occupy small muscle territories or regions, with low-threshold units preferentially located distally. We used intramuscular recordings to measure the territory of muscle fibres from MG MUs and determine whether these MUs are grouped by recruitment threshold or joint action (ankle plantar flexion and knee flexion). The territory of MUs from the MG muscle varied from somewhat localized to highly distributed, with approximately half the MUs spanning at least half the length and width of the muscle. There was also no evidence of regional muscle activity based on MU recruitment thresholds or joint action. The CNS does not have the means to selectively activate regions of the MG muscle based on task requirements. Human medial gastrocnemius (MG) motor units (MUs) are thought to occupy small muscle territories, with low-threshold units preferentially located distally. In this study, subjects (n = 8) performed ramped and sustained isometric contractions (ankle plantar flexion and knee flexion; range: ∼1-40% maximal voluntary contraction) and we measured MU territory size with spike-triggered averages from fine-wire electrodes inserted along the length (seven electrodes) or across the width (five electrodes) of the MG muscle. Of 69 MUs identified along the length of the muscle, 32 spanned at least half the muscle length (≥ 6.9 cm), 11 of which spanned all recording sites (13.6-17.9 cm). Distal fibres had smaller pennation angles (P < 0.05), which were accompanied by larger territories in MUs with fibres located distally (P < 0.05). There was no distal-to-proximal pattern of muscle activation in ramp contraction (P = 0.93). Of 36 MUs identified across the width of the muscle, 24 spanned at least half the muscle width (≥ 4.0 cm), 13 of which spanned all recording sites (8.0-10.8 cm). MUs were not localized (length or width) based on recruitment threshold or contraction type, nor was there a relationship between MU territory size and recruitment threshold (Spearman's rho = -0.20 and 0.13, P > 0.18). MUs in the human MG have larger territories than previously reported and are not localized based on recruitment threshold or joint action. This indicates that the CNS does not have the means to selectively activate regions of the MG muscle based on task requirements. © 2015 The Authors. The Journal of Physiology © 2015 The Physiological Society.

Spatial channel interactions in cochlear implants

NASA Astrophysics Data System (ADS)

Tang, Qing; Benítez, Raul; Zeng, Fan-Gang

2011-08-01

The modern multi-channel cochlear implant is widely considered to be the most successful neural prosthesis owing to its ability to restore partial hearing to post-lingually deafened adults and to allow essentially normal language development in pre-lingually deafened children. However, the implant performance varies greatly in individuals and is still limited in background noise, tonal language understanding, and music perception. One main cause for the individual variability and the limited performance in cochlear implants is spatial channel interaction from the stimulating electrodes to the auditory nerve and brain. Here we systematically examined spatial channel interactions at the physical, physiological, and perceptual levels in the same five modern cochlear implant subjects. The physical interaction was examined using an electric field imaging technique, which measured the voltage distribution as a function of the electrode position in the cochlea in response to the stimulation of a single electrode. The physiological interaction was examined by recording electrically evoked compound action potentials as a function of the electrode position in response to the stimulation of the same single electrode position. The perceptual interactions were characterized by changes in detection threshold as well as loudness summation in response to in-phase or out-of-phase dual-electrode stimulation. To minimize potentially confounding effects of temporal factors on spatial channel interactions, stimulus rates were limited to 100 Hz or less in all measurements. Several quantitative channel interaction indexes were developed to define and compare the width, slope and symmetry of the spatial excitation patterns derived from these physical, physiological and perceptual measures. The electric field imaging data revealed a broad but uniformly asymmetrical intracochlear electric field pattern, with the apical side producing a wider half-width and shallower slope than the basal side. In contrast, the evoked compound action potential and perceptual channel interaction data showed much greater individual variability. It is likely that actual reduction in neural and higher level interactions, instead of simple sharpening of the electric current field, would be the key to predicting and hopefully improving the variable cochlear implant performance. The present results are obtained with auditory prostheses but can be applied to other neural prostheses, in which independent spatial channels, rather than a high stimulation rate, are critical to their performance.

Aircraft evacuations through type-III exits I : effects of seat placement at the exit.

DOT National Transportation Integrated Search

1995-07-01

Simulated emergency egress from Type III over-wing exits was studied to support regulatory action by the FAA. Passageway width and seat encroachment distance adjacent to the Type-III exit were the major variables of interest. : Methods. Two subject g...

Numerical calculation of the decay widths, the decay constants, and the decay energy spectra of the resonances of the delta-shell potential

NASA Astrophysics Data System (ADS)

de la Madrid, Rafael

2017-06-01

We express the resonant energies of the delta-shell potential in terms of the Lambert W function, and we calculate their decay widths and decay constants. The ensuing numerical results strengthen the interpretation of such decay widths and constants as a way to quantify the coupling between a resonance and the continuum. We calculate explicitly the decay energy spectrum of the resonances of the delta-shell potential, and we show numerically that the lineshape of such spectrum is not the same as, and can be very different from, the Breit-Wigner (Lorentzian) distribution. We argue that the standard Golden Rule cannot describe the interference of two resonances, and we show how to describe such interference by way of the decay energy spectrum of two resonant states.

A feasibility study of multi-site,intracellular recordings from mammalian neurons by extracellular gold mushroom-shaped microelectrodes.

PubMed

Ojovan, Silviya M; Rabieh, Noha; Shmoel, Nava; Erez, Hadas; Maydan, Eilon; Cohen, Ariel; Spira, Micha E

2015-09-14

The development of multi-electrode array platforms for large scale recording of neurons is at the forefront of neuro-engineering research efforts. Recently we demonstrated, at the proof-of-concept level, a breakthrough neuron-microelectrode interface in which cultured Aplysia neurons tightly engulf gold mushroom-shaped microelectrodes (gMμEs). While maintaining their extracellular position, the gMμEs record synaptic- and action-potentials with characteristic features of intracellular recordings. Here we examined the feasibility of using gMμEs for intracellular recordings from mammalian neurons. To that end we experimentally examined the innate size limits of cultured rat hippocampal neurons to engulf gMμEs and measured the width of the "extracellular" cleft formed between the neurons and the gold surface. Using the experimental results we next analyzed the expected range of gMμEs-neuron electrical coupling coefficients. We estimated that sufficient electrical coupling levels to record attenuated synaptic- and action-potentials can be reached using the gMμE-neuron configuration. The definition of the engulfment limits of the gMμEs caps diameter at ≤2-2.5 μm and the estimated electrical coupling coefficients from the simulations pave the way for rational development and application of the gMμE based concept for in-cell recordings from mammalian neurons.

Does prism width from the shell prismatic layer have a random distribution?

NASA Astrophysics Data System (ADS)

Vancolen, Séverine; Verrecchia, Eric

2008-10-01

A study of the distribution of the prism width inside the prismatic layer of Unio tumidus (Philipsson 1788, Diss Hist-Nat, Berling, Lundæ) from Lake Neuchâtel, Switzerland, has been conducted in order to determine whether or not this distribution is random. Measurements of 954 to 1,343 prism widths (depending on shell sample) have been made using a scanning electron microscope in backscattered electron mode. A white noise test has been applied to the distribution of prism sizes (i.e. width). It shows that there is no temporal cycle that could potentially influence their formation and growth. These results suggest that prism widths are randomly distributed, and related neither to external rings nor to environmental constraints.

Simple map in action-angle coordinates

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

Kerwin, Olivia; Punjabi, Alkesh; Ali, Halima

A simple map [A. Punjabi, A. Verma, and A. Boozer, Phys. Rev. Lett. 69, 3322 (1992)] is the simplest map that has the topology of divertor tokamaks [A. Punjabi, H. Ali, T. Evans, and A. Boozer, Phys. Lett. A 364, 140 (2007)]. Here, action-angle coordinates, the safety factor, and the equilibrium generating function for the simple map are calculated analytically. The simple map in action-angle coordinates is derived from canonical transformations. This map cannot be integrated across the separatrix surface because of the singularity in the safety factor there. The stochastic broadening of the ideal separatrix surface in action-angle representationmore » is calculated by adding a perturbation to the simple map equilibrium generating function. This perturbation represents the spatial noise and field errors typical of the DIII-D [J. L. Luxon and L. E. Davis, Fusion Technol. 8, 441 (1985)] tokamak. The stationary Fourier modes of the perturbation have poloidal and toroidal mode numbers (m,n,)=((3,1),(4,1),(6,2),(7,2),(8,2),(9,3),(10,3),(11,3)) with amplitude {delta}=0.8x10{sup -5}. Near the X-point, about 0.12% of toroidal magnetic flux inside the separatrix, and about 0.06% of the poloidal flux inside the separatrix is lost. When the distance from the O-point to the X-point is 1 m, the width of stochastic layer near the X-point is about 1.4 cm. The average value of the action on the last good surface is 0.19072 compared to the action value of 3/5{pi} on the separatrix. The average width of stochastic layer in action coordinate is 2.7x10{sup -4}, while the average area of the stochastic layer in action-angle phase space is 1.69017x10{sup -3}. On average, about 0.14% of action or toroidal flux inside the ideal separatrix is lost due to broadening. Roughly five times more toroidal flux is lost in the simple map than in DIII-D for the same perturbation [A. Punjabi, H. Ali, A. Boozer, and T. Evans, Bull. Amer. Phys. Soc. 52, 124 (2007)].« less

Simple map in action-angle coordinates

NASA Astrophysics Data System (ADS)

Kerwin, Olivia; Punjabi, Alkesh; Ali, Halima

2008-07-01

A simple map [A. Punjabi, A. Verma, and A. Boozer, Phys. Rev. Lett. 69, 3322 (1992)] is the simplest map that has the topology of divertor tokamaks [A. Punjabi, H. Ali, T. Evans, and A. Boozer, Phys. Lett. A 364, 140 (2007)]. Here, action-angle coordinates, the safety factor, and the equilibrium generating function for the simple map are calculated analytically. The simple map in action-angle coordinates is derived from canonical transformations. This map cannot be integrated across the separatrix surface because of the singularity in the safety factor there. The stochastic broadening of the ideal separatrix surface in action-angle representation is calculated by adding a perturbation to the simple map equilibrium generating function. This perturbation represents the spatial noise and field errors typical of the DIII-D [J. L. Luxon and L. E. Davis, Fusion Technol. 8, 441 (1985)] tokamak. The stationary Fourier modes of the perturbation have poloidal and toroidal mode numbers (m,n,)={(3,1),(4,1),(6,2),(7,2),(8,2),(9,3),(10,3),(11,3)} with amplitude δ =0.8×10-5. Near the X-point, about 0.12% of toroidal magnetic flux inside the separatrix, and about 0.06% of the poloidal flux inside the separatrix is lost. When the distance from the O-point to the X-point is 1m, the width of stochastic layer near the X-point is about 1.4cm. The average value of the action on the last good surface is 0.19072 compared to the action value of 3/5π on the separatrix. The average width of stochastic layer in action coordinate is 2.7×10-4, while the average area of the stochastic layer in action-angle phase space is 1.69017×10-3. On average, about 0.14% of action or toroidal flux inside the ideal separatrix is lost due to broadening. Roughly five times more toroidal flux is lost in the simple map than in DIII-D for the same perturbation [A. Punjabi, H. Ali, A. Boozer, and T. Evans, Bull. Amer. Phys. Soc. 52, 124 (2007)].

Stream Width Dynamics in a Small Headwater Catchment

NASA Astrophysics Data System (ADS)

Barefoot, E. A.; Pavelsky, T.; Allen, G. H.; Zimmer, M. A.; McGlynn, B. L.

2016-12-01

Changing streamflow conditions cause small, ephemeral and intermittent stream networks to expand and contract, while simultaneously driving widening and narrowing of streams. The resulting dynamic surface area of ephemeral streams impacts critical hydrological and biogeochemical processes, including air-water gas exchange, solute transport, and sediment transport. Despite the importance of these dynamics, to our knowledge there exists no complete study of how stream widths vary throughout an entire catchment in response to changing streamflow conditions. Here we present the first characterization of how variable hydrologic conditions impact the distribution of stream widths in a 48 ha headwater catchment in the Stony Creek Research Watershed, NC, USA. We surveyed stream widths longitudinally every 5 m on 12 occasions over a range of stream discharge from 7 L/s to 128 L/s at the catchment outlet. We hypothesize that the shape and location of the stream width distribution are driven by the action of two interrelated mechanisms, network extension and at-a-station widening, both of which increase with discharge. We observe that during very low flow conditions, network extension more significantly influences distribution location, and during high flow conditions stream widening is the dominant driver. During moderate flows, we observe an approximately 1 cm rightward shift in the distribution peak with every additional 10 L/s of increased discharge, which we attribute to a greater impact of at-a-station widening on distribution location. Aside from this small shift, the qualitative location and shape of the stream width distribution are largely invariant with changing streamflow. We suggest that the basic characteristics of stream width distributions constitute an equilibrium between the two described mechanisms across variable hydrologic conditions.

No Bridge Too High: Infants Decide Whether to Cross Based on the Probability of Falling not the Severity of the Potential Fall

ERIC Educational Resources Information Center

Kretch, Kari S.; Adolph, Karen E.

2013-01-01

Do infants, like adults, consider both the probability of falling and the severity of a potential fall when deciding whether to cross a bridge? Crawling and walking infants were encouraged to cross bridges varying in width over a small drop-off, a large drop-off, or no drop-off. Bridge width affects the probability of falling, whereas drop-off…

Dynamic localization in optical and Zeeman lattices in the presence of spin-orbit coupling

NASA Astrophysics Data System (ADS)

Kartashov, Yaroslav V.; Konotop, Vladimir V.; Zezyulin, Dmitry A.; Torner, Lluis

2016-12-01

The dynamic localization of a two-level atom in a periodic potential under the action of spin-orbit coupling and a weak harmonically varying linear force is studied. We consider optical and Zeeman potentials that are either in phase or out of phase in two spinor components, respectively. The expectation value for the position of the atom after one oscillation period of the linear force is recovered in authentic resonances or in pseudoresonances. The frequencies of the linear force corresponding to authentic resonances are determined by the band structure of the periodic potential and are affected by the spin-orbit coupling. The width or dispersion of the wave packet in authentic resonances is usually minimal. The frequencies corresponding to pseudoresonances do not depend on the type of potential and on the strength of the spin-orbit coupling, while the evolution of excitations at the corresponding frequencies is usually accompanied by significant dispersion. Pseudoresonances are determined by the initial phase of the linear force and by the quasimomentum of the wave packet. Due to the spinor nature of the system, the motion of the atom is accompanied by periodic, but not harmonic, spin oscillations. Under the action of spin-orbit coupling the oscillations of the wave packet can be nearly completely suppressed in optical lattices. Dynamic localization in Zeeman lattices is characterized by doubling of the resonant oscillation periods due to band crossing at the boundary of the Brillouin zone. We also show that higher harmonics in the Fourier expansion of the energy band lead to effective dispersion, which can be strong enough to prevent dynamic localization of the Bloch wave packet.

Physiological properties of anatomically identified axo-axonic cells in the rat hippocampus.

PubMed

Buhl, E H; Han, Z S; Lörinczi, Z; Stezhka, V V; Karnup, S V; Somogyi, P

1994-04-01

1. The properties of a well-defined type of GABAergic local circuit neuron, the axo-axonic cell (n = 17), were investigated in rat hippocampal slice preparations. During intracellular recording we injected axo-axonic cells with biocytin and subsequently identified them with correlated light and electron microscopy. Employing an immunogold-silver intensification technique we showed that one of the physiologically characterized cells was immunoreactive for gamma-aminobutyric acid (GABA). 2. Axo-axonic cells were encountered in the dentate gyrus (n = 5) as well as subfields CA3 (n = 2) and CA1 (n = 10). They generally had smooth, beaded dendrites that extended throughout all hippocampal layers. Their axons ramified densely in the cell body layers and in the subjacent stratum oriens or hilus, respectively. Tested with electron microscopy, labeled terminals (n = 53) established synapses exclusively with the axon initial segment of principal cells in strata oriens and pyramidale and rarely in lower radiatum. Within a 400-microns slice a single CA1 axo-axonic cell was estimated to be in synaptic contact with 686 pyramidal cells. 3. Axo-axonic cells (n = 14) had a mean resting membrane potential of -65.1 mV, an average input resistance of 73.9 M omega, and a mean time constant of 7.7 ms. Action potentials were of short duration (389-microseconds width at half-amplitude) and had a mean amplitude of 64.1 mV. 4. Nine of 10 tested cells showed a varying degree of spike frequency adaptation in response to depolarizing current injection. Current-evoked action potentials were usually curtailed by a deep (10.2 mV) short-latency afterhyperpolarization (AHP) with a mean duration of 28.1 ms. 5. Cells with strong spike frequency accommodation (n = 5) had a characteristic firing pattern with numerous spike doublets. These appeared to be triggered by an underlying depolarizing afterpotential. In the same cells, prolonged bursts of action potentials were followed by a prominent long-duration AHP with a mean time constant of 1.15 s. 6. Axo-axonic cells responded to the stimulation of afferent pathways with short-latency excitatory postsynaptic potentials (EPSPs) or at higher stimulation intensity with up to three action potentials. Axo-axonic cells in the dentate gyrus could be activated by stimulating the CA3 area as well as the perforant path, whereas in the CA1 area responses were elicited after shocks to the perforant path, Schaffer collaterals, and the stratum oriens-alveus border. 7. In the CA1 area the EPSP amplitude increased in response to membrane hyperpolarization.(ABSTRACT TRUNCATED AT 400 WORDS)

OMEGA System Performance Assessment and Coverage Evaluation (PACE) Workstation Design and Implementation. Volume 2

DTIC Science & Technology

1991-02-15

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76 FR 23485 - Safety Zone; Red River

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-27

...-AA00 Safety Zone; Red River AGENCY: Coast Guard, DHS. ACTION: Temporary final rule. SUMMARY: The Coast Guard is establishing a temporary safety zone for all waters of the Red River in the State of North..., extending the entire width of the river. This safety zone is needed to protect persons and vessels from...

Methamphetamine Regulation of Firing Activity of Dopamine Neurons

PubMed Central

Lin, Min; Sambo, Danielle

2016-01-01

Methamphetamine (METH) is a substrate for the dopamine transporter that increases extracellular dopamine levels by competing with dopamine uptake and increasing reverse transport of dopamine via the transporter. METH has also been shown to alter the excitability of dopamine neurons. The mechanism of METH regulation of the intrinsic firing behaviors of dopamine neurons is less understood. Here we identified an unexpected and unique property of METH on the regulation of firing activity of mouse dopamine neurons. METH produced a transient augmentation of spontaneous spike activity of midbrain dopamine neurons that was followed by a progressive reduction of spontaneous spike activity. Inspection of action potential morphology revealed that METH increased the half-width and produced larger coefficients of variation of the interspike interval, suggesting that METH exposure affected the activity of voltage-dependent potassium channels in these neurons. Since METH has been shown to affect Ca2+ homeostasis, the unexpected findings that METH broadened the action potential and decreased the amplitude of afterhyperpolarization led us to ask whether METH alters the activity of Ca2+-activated potassium (BK) channels. First, we identified BK channels in dopamine neurons by their voltage dependence and their response to a BK channel blocker or opener. While METH suppressed the amplitude of BK channel-mediated unitary currents, the BK channel opener NS1619 attenuated the effects of METH on action potential broadening, afterhyperpolarization repression, and spontaneous spike activity reduction. Live-cell total internal reflection fluorescence microscopy, electrophysiology, and biochemical analysis suggest METH exposure decreased the activity of BK channels by decreasing BK-α subunit levels at the plasma membrane. SIGNIFICANCE STATEMENT Methamphetamine (METH) competes with dopamine uptake, increases dopamine efflux via the dopamine transporter, and affects the excitability of dopamine neurons. Here, we identified an unexpected property of METH on dopamine neuron firing activity. METH transiently increased the spontaneous spike activity of dopamine neurons followed by a progressive reduction of the spontaneous spike activity. METH broadened the action potentials, increased coefficients of variation of the interspike interval, and decreased the amplitude of afterhyperpolarization, which are consistent with changes in the activity of Ca2+-activated potassium (BK) channels. We found that METH decreased the activity of BK channels by stimulating BK-α subunit trafficking. Thus, METH modulation of dopamine neurotransmission and resulting behavioral responses is, in part, due to METH regulation of BK channel activity. PMID:27707972

What sets the minimum tokamak scrape-off layer width?

NASA Astrophysics Data System (ADS)

Joseph, Ilon

2016-10-01

The heat flux width of the tokamak scrape-off layer is on the order of the poloidal ion gyroradius, but the ``heuristic drift'' physics model is still not completely understood. In the absence of anomalous transport, neoclassical transport sets the minimum width. For plateau collisionality, the ion temperature width is set by qρi , while the electron temperature width scales as the geometric mean q(ρeρi) 1 / 2 and is close to qρi in magnitude. The width is enhanced because electrons are confined by the sheath potential and have a much longer time to radially diffuse before escaping to the wall. In the Pfirsch-Schluter regime, collisional diffusion increases the width by the factor (qR / λ) 1 / 2 where qR is the connection length and λ is the mean free path. This qualitatively agrees with the observed transition in the scaling law for detached plasmas. The radial width of the SOL electric field is determined by Spitzer parallel and ``neoclassical'' radial electric conductivity and has a similar scaling to that for thermal transport. Prepared under US DOE contract DE-AC52-07NA27344.

Changes in intrinsic excitability of ganglion cells in degenerated retinas of RCS rats

PubMed Central

Ren, Yi-Ming; Weng, Chuan-Huang; Zhao, Cong-Jian; Yin, Zheng-Qin

2018-01-01

AIM To evaluate the intrinsic excitability of retinal ganglion cells (RGCs) in degenerated retinas. METHODS The intrinsic excitability of various morphologically defined RGC types using a combination of patch-clamp recording and the Lucifer yellow tracer in retinal whole-mount preparations harvested from Royal College of Surgeons (RCS) rats, a common retinitis pigmentosa (RP) model, in a relatively late stage of retinal degeneration (P90) were investigated. Several parameters of RGC morphologies and action potentials (APs) were measured and compared to those of non-dystrophic control rats, including dendritic stratification, dendritic field diameter, peak amplitude, half width, resting membrane potential, AP threshold, depolarization to threshold, and firing rates. RESULTS Compared with non-dystrophic control RGCs, more depolarizations were required to reach the AP threshold in RCS RGCs with low spontaneous spike rates and in RCS OFF cells (especially A2o cells), and RCS RGCs maintained their dendritic morphologies, resting membrane potentials and capabilities to generate APs. CONCLUSION RGCs are relatively well preserved morphologically and functionally, and some cells are more susceptible to decreased excitability during retinal degeneration. These findings provide valuable considerations for optimizing RP therapeutic strategies. PMID:29862172

Nanosecond pulsed electric field thresholds for nanopore formation in neural cells

NASA Astrophysics Data System (ADS)

Roth, Caleb C.; Tolstykh, Gleb P.; Payne, Jason A.; Kuipers, Marjorie A.; Thompson, Gary L.; DeSilva, Mauris N.; Ibey, Bennett L.

2013-03-01

The persistent influx of ions through nanopores created upon cellular exposure to nanosecond pulse electric fields (nsPEF) could be used to modulate neuronal function. One ion, calcium (Ca), is important to action potential firing and regulates many ion channels. However, uncontrolled hyper-excitability of neurons leads to Ca overload and neurodegeneration. Thus, to prevent unintended consequences of nsPEF-induced neural stimulation, knowledge of optimum exposure parameters is required. We determined the relationship between nsPEF exposure parameters (pulse width and amplitude) and nanopore formation in two cell types: rodent neuroblastoma (NG108) and mouse primary hippocampal neurons (PHN). We identified thresholds for nanoporation using Annexin V and FM1-43, to detect changes in membrane asymmetry, and through Ca influx using Calcium Green. The ED50 for a single 600 ns pulse, necessary to cause uptake of extracellular Ca, was 1.76 kV/cm for NG108 and 0.84 kV/cm for PHN. At 16.2 kV/cm, the ED50 for pulse width was 95 ns for both cell lines. Cadmium, a nonspecific Ca channel blocker, failed to prevent Ca uptake suggesting that observed influx is likely due to nanoporation. These data demonstrate that moderate amplitude single nsPEF exposures result in rapid Ca influx that may be capable of controllably modulating neurological function.

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

Campbell, John; Carena, Marcela; Harnik, Roni

We consider interference between the Higgs signal and QCD background inmore » $$gg\\rightarrow h \\rightarrow \\gamma\\gamma$$ and its effect on the on-shell Higgs rate. The existence of sizable strong phases leads to destructive interference of about 2% of the on-shell cross section in the Standard Model. This effect can be enhanced by beyond the standard model physics. In particular, since it scales differently from the usual rates, the presence of interference allows indirect limits to be placed on the Higgs width in a novel way, using on-shell rate measurements. Our study motivates further QCD calculations to reduce uncertainties. We discuss potential width-sensitive observables, both using total and differential rates and find that the HL-LHC can potentially indirectly probe widths of order tens of MeV.« less

The effects of narrow and elevated path walking on aperture crossing.

PubMed

Hackney, Amy L; Cinelli, Michael E; Denomme, Luke T; Frank, James S

2015-06-01

The study investigated the impact that action capabilities have on identifying possibilities for action, particularly how postural threat influences the passability of apertures. To do this, the ability to maintain balance was challenged by manipulating the level of postural threat while walking. First, participants walked along a 7m path and passed through two vertical obstacles spaced 1.1-1.5×the shoulder width apart during normal walking. Next, postural threat was manipulated by having participants complete the task either walking on a narrow, ground level path or on an elevated/narrow path. Despite a decrease in walking speed as well as an increase in trunk sway in both the narrow and elevated/narrow walking conditions, the passability of apertures was only affected when the consequence of instability was greatest. In the elevated/narrow walking condition, individuals maintained a larger critical point (rotated their shoulders for larger aperture widths) compared to normal walking. However, this effect was not observed for the narrow path walking suggesting that the level of postural threat was not enough to impose similar changes to the critical point. Therefore, it appears that manipulating action capabilities by increasing postural threat does indeed influence aperture crossing behavior, however the consequence associated with instability must be high before both gait characteristics and the critical point are affected. Copyright © 2015 Elsevier B.V. All rights reserved.

Heavy quarkonia in a potential model: binding energy, decay width, and survival probability

NASA Astrophysics Data System (ADS)

Srivastava, P. K.; Chaturvedi, O. S. K.; Thakur, Lata

2018-06-01

Recently a lot of progress has been made in deriving the heavy quark potential within a QCD medium. In this article we have considered heavy quarkonium in a hot quark gluon plasma phase. The heavy-quark potential has been modeled properly for short as well as long distances. The potential at long distances is modeled as a QCD string which is screened at the same scale as the Coulomb field. We have numerically solved the 1+1-dimensional Schrodinger equation for this potential and obtained the eigen wavefunction and binding energy for the 1 S and 2 S states of charmonium and bottomonium. Further, we have calculated the decay width and dissociation temperature of quarkonium states in the QCD plasma. Finally, we have used our recently proposed unified model with these new values of decay widths to calculate the survival probability of the various quarkonium states with respect to centrality at relativistic heavy ion collider and large hadron collider energies. This study provides a unified, consistent and comprehensive description of spectroscopic properties of various quarkonium states at finite temperatures along with their nuclear modification factor at different collision energies.

Comparison of Trajectory Models in Calculations of N2-broadened Half-widths and N2-induced Line Shifts for the Rotational Band of H2O-16 and Comparison with Measurements

NASA Technical Reports Server (NTRS)

Lamouroux, J.; Gamache, R. R.; Laraia, A. L.; Ma, Q.; Tipping, R. H.

2012-01-01

In this work, Complex Robert-Bonamy calculations of half-widths and line shifts were done for N2-broadening of water for 1639 transitions in the rotational band using two models for the trajectories. The first is a model correct to second order in time, the Robert-Bonamy parabolic approximation. The second is the solution of Hamilton's equations. Both models use the isotropic part of the atom-atom potential to determine the trajectories. The present calculations used an intermolecular potential expanded to 20th order to assure the convergence of the half-widths and line shifts. The aim of the study is to assess if the difference in the half-widths and line shifts determined from the two trajectory models is greater than the accuracy requirements of the spectroscopic and remote sensing communities. The results of the calculations are compared with measurements of the half-widths and line shifts. It is shown that the effects of the trajectory model greatly exceed the needs of current remote sensing measurements and that line shape parameters calculated using trajectories determined by solving Hamilton's equations agree better with measurement.

The orientation distribution of tunneling-related quantities

NASA Astrophysics Data System (ADS)

Seif, W. M.; Refaie, A. I.; Botros, M. M.

2018-03-01

In the nuclear tunneling processes involving deformed nuclei, most of the tunneling-related quantities depend on the relative orientations of the participating nuclei. In the presence of different multipole deformations, we study the variation of a few relevant quantities for the α-decay and the sub-barrier fusion processes, in an orientation degree of freedom. The knocking frequency and the penetration probability are evaluated within the Wentzel-Kramers-Brillouin approximation. The interaction potential is calculated with Skyrme-type nucleon-nucleon interaction. We found that the width of the potential pocket, the Coulomb barrier radius, the penetration probability, the α-decay width, and the fusion cross-section follow consistently the orientation-angle variation of the radius of the deformed nucleus. The orientation distribution patterns of the pocket width, the barrier radius, the logarithms of the penetrability, the decay width, and the fusion cross-section are found to be highly analogous to pattern of the deformed-nucleus radius. The curve patterns of the orientation angle distributions of the internal pocket depth, the Coulomb barrier height and width, as well as the knocking frequency simulate inversely the variation of the deformed nucleus radius. The predicted orientation behaviors will be of a special interest in predicting the optimum orientations for the tunneling processes.

3D nano-structures for laser nano-manipulation

PubMed Central

Seniutinas, Gediminas; Gervinskas, Gediminas; Brasselet, Etienne; Juodkazis, Saulius

2013-01-01

Summary The resputtering of gold films from nano-holes defined in a sacrificial PMMA mask, which was made by electron beam lithography, was carried out with a dry plasma etching tool in order to form well-like structures with a high aspect ratio (height/width ≈ 3–4) at the rims of the nano-holes. The extraordinary transmission through the patterns of such nano-wells was investigated experimentally and numerically. By doing numerical simulations of 50-nm and 100-nm diameter polystyrene beads in water and air, we show the potential of such patterns for self-induced back-action (SIBA) trapping. The best trapping conditions were found to be a trapping force of 2 pN/W/μm2 (numerical result) exerted on a 50-nm diameter bead in water. The simulations were based on the analytical Lorentz force model. PMID:24062979

Constraints on the synchronization of entorhinal cortex stellate cells

NASA Astrophysics Data System (ADS)

Crotty, Patrick; Lasker, Eric; Cheng, Sen

2012-07-01

Synchronized oscillations of large numbers of central neurons are believed to be important for a wide variety of cognitive functions, including long-term memory recall and spatial navigation. It is therefore plausible that evolution has optimized the biophysical properties of central neurons in some way for synchronized oscillations to occur. Here, we use computational models to investigate the relationships between the presumably genetically determined parameters of stellate cells in layer II of the entorhinal cortex and the ability of coupled populations of these cells to synchronize their intrinsic oscillations: in particular, we calculate the time it takes circuits of two or three cells with initially randomly distributed phases to synchronize their oscillations to within one action potential width, and the metabolic energy they consume in doing so. For recurrent circuit topologies, we find that parameters giving low intrinsic firing frequencies close to those actually observed are strongly advantageous for both synchronization time and metabolic energy consumption.

Action Potential Energy Efficiency Varies Among Neuron Types in Vertebrates and Invertebrates

PubMed Central

Sengupta, Biswa; Stemmler, Martin; Laughlin, Simon B.; Niven, Jeremy E.

2010-01-01

The initiation and propagation of action potentials (APs) places high demands on the energetic resources of neural tissue. Each AP forces ATP-driven ion pumps to work harder to restore the ionic concentration gradients, thus consuming more energy. Here, we ask whether the ionic currents underlying the AP can be predicted theoretically from the principle of minimum energy consumption. A long-held supposition that APs are energetically wasteful, based on theoretical analysis of the squid giant axon AP, has recently been overturned by studies that measured the currents contributing to the AP in several mammalian neurons. In the single compartment models studied here, AP energy consumption varies greatly among vertebrate and invertebrate neurons, with several mammalian neuron models using close to the capacitive minimum of energy needed. Strikingly, energy consumption can increase by more than ten-fold simply by changing the overlap of the Na+ and K+ currents during the AP without changing the APs shape. As a consequence, the height and width of the AP are poor predictors of energy consumption. In the Hodgkin–Huxley model of the squid axon, optimizing the kinetics or number of Na+ and K+ channels can whittle down the number of ATP molecules needed for each AP by a factor of four. In contrast to the squid AP, the temporal profile of the currents underlying APs of some mammalian neurons are nearly perfectly matched to the optimized properties of ionic conductances so as to minimize the ATP cost. PMID:20617202

Action potential energy efficiency varies among neuron types in vertebrates and invertebrates.

PubMed

Sengupta, Biswa; Stemmler, Martin; Laughlin, Simon B; Niven, Jeremy E

2010-07-01

The initiation and propagation of action potentials (APs) places high demands on the energetic resources of neural tissue. Each AP forces ATP-driven ion pumps to work harder to restore the ionic concentration gradients, thus consuming more energy. Here, we ask whether the ionic currents underlying the AP can be predicted theoretically from the principle of minimum energy consumption. A long-held supposition that APs are energetically wasteful, based on theoretical analysis of the squid giant axon AP, has recently been overturned by studies that measured the currents contributing to the AP in several mammalian neurons. In the single compartment models studied here, AP energy consumption varies greatly among vertebrate and invertebrate neurons, with several mammalian neuron models using close to the capacitive minimum of energy needed. Strikingly, energy consumption can increase by more than ten-fold simply by changing the overlap of the Na(+) and K(+) currents during the AP without changing the APs shape. As a consequence, the height and width of the AP are poor predictors of energy consumption. In the Hodgkin-Huxley model of the squid axon, optimizing the kinetics or number of Na(+) and K(+) channels can whittle down the number of ATP molecules needed for each AP by a factor of four. In contrast to the squid AP, the temporal profile of the currents underlying APs of some mammalian neurons are nearly perfectly matched to the optimized properties of ionic conductances so as to minimize the ATP cost.

The Complex Action Recognition via the Correlated Topic Model

PubMed Central

Tu, Hong-bin; Xia, Li-min; Wang, Zheng-wu

2014-01-01

Human complex action recognition is an important research area of the action recognition. Among various obstacles to human complex action recognition, one of the most challenging is to deal with self-occlusion, where one body part occludes another one. This paper presents a new method of human complex action recognition, which is based on optical flow and correlated topic model (CTM). Firstly, the Markov random field was used to represent the occlusion relationship between human body parts in terms of an occlusion state variable. Secondly, the structure from motion (SFM) is used for reconstructing the missing data of point trajectories. Then, we can extract the key frame based on motion feature from optical flow and the ratios of the width and height are extracted by the human silhouette. Finally, we use the topic model of correlated topic model (CTM) to classify action. Experiments were performed on the KTH, Weizmann, and UIUC action dataset to test and evaluate the proposed method. The compared experiment results showed that the proposed method was more effective than compared methods. PMID:24574920

Development of a relationship between external measurements and reinforcement stress

NASA Astrophysics Data System (ADS)

Brault, Andre; Hoult, Neil A.; Lees, Janet M.

2015-03-01

As many countries around the world face an aging infrastructure crisis, there is an increasing need to develop more accurate monitoring and assessment techniques for reinforced concrete structures. One of the challenges associated with assessing existing infrastructure is correlating externally measured parameters such as crack widths and surface strains with reinforcement stresses as this is dependent on a number of variables. The current research investigates how the use of distributed fiber optic sensors to measure reinforcement strain can be correlated with digital image correlation measurements of crack widths to relate external crack width measurements to reinforcement stresses. An initial set of experiments was undertaken involving a series of small-scale beam specimens tested in three-point bending with variable reinforcement properties. Relationships between crack widths and internal reinforcement strains were observed including that both the diameter and number of bars affected the measured maximum strain and crack width. A model that uses measured crack width to estimate reinforcement strain was presented and compared to the experimental results. The model was found to provide accurate estimates of load carrying capacity for a given crack width, however, the model was potentially less accurate when crack widths were used to estimate the experimental reinforcement strains. The need for more experimental data to validate the conclusions of this research was also highlighted.

Tuning the Energy Gap of SiCH3 Nanomaterials Under Elastic Strain

NASA Astrophysics Data System (ADS)

Ma, Shengqian; Li, Feng; Geng, Jiguo; Zhu, Mei; Li, Suyan; Han, Juguang

2018-05-01

SiCH3 nanomaterials have been studied using the density functional theory. When the nanosheets and nanoribbons (armchair and zigzag) are introduced, their energy gap is modulated under elastic strain and width. The results show that the band gap of SiCH3 nanomaterials can be easily tuned using elastic strains and widths. Surprisingly, the band gap can be modulated along two directions, namely, compressing and stretching. The band gap decreases when increasing stretching strain or decreasing compressing strain. In addition, the band gap decreases when increasing the nanoribbon width. For energy gap engineering, the band gap can be tuned by strains and widths. Therefore, the SiCH3 nanomaterials play important roles in potential applications for strain sensors, electronics, and optical electronics.

A balancing act: physical balance, through arousal, influences size perception.

PubMed

Geuss, Michael N; Stefanucci, Jeanine K; de Benedictis-Kessner, Justin; Stevens, Nicholas R

2010-10-01

Previous research has demonstrated that manipulating vision influences balance. Here, we question whether manipulating balance can influence vision and how it may influence vision--specifically, the perception of width. In Experiment 1, participants estimated the width of beams while balanced and unbalanced. When unbalanced, participants judged the widths to be smaller. One possible explanation is that unbalanced participants did not view the stimulus as long as when balanced because they were focused on remaining balanced. In Experiment 2, we tested this notion by limiting viewing time. Experiment 2 replicated the findings of Experiment 1, but viewing time had no effect on width judgments. In Experiment 3, participants' level of arousal was manipulated, because the balancing task likely produced arousal. While jogging, participants judged the beams to be smaller. In Experiment 4, participants completed another arousing task (counting backward by sevens) that did not involve movement. Again, participants judged the beams to be smaller when aroused. Experiment 5A raised participants' level of arousal before estimating the board widths (to control for potential dual-task effects) and showed that heightened arousal still influenced perceived width of the boards. Collectively, heightened levels of arousal, caused by multiple manipulations (including balance), influenced perceived width.

Glycogen synthase kinase 3 beta alters anxiety-, depression-, and addiction-related behaviors and neuronal activity in the nucleus accumbens shell

PubMed Central

Crofton, Elizabeth J.; Nenov, Miroslav N.; Zhang, Yafang; Scala, Federico; Page, Sean A.; McCue, David L.; Li, Dingge; Hommel, Jonathan D.; Laezza, Fernanda; Green, Thomas A.

2017-01-01

Psychiatric disorders such as anxiety, depression and addiction are often comorbid brain pathologies thought to share common mechanistic biology. As part of the cortico-limbic circuit, the nucleus accumbens shell (NAcSh) plays a fundamental role in integrating information in the circuit, such that modulation of NAcSh circuitry alters anxiety, depression, and addiction-related behaviors. Intracellular kinase cascades in the NAcSh have proven important mediators of behavior. To investigate glycogen-synthase kinase 3 (GSK3) beta signaling in the NAcSh in vivo we knocked down GSK3beta expression with a novel adeno-associated viral vector (AAV2) and assessed changes in anxiety- and depression-like behavior and cocaine self-administration in GSK3beta knockdown rats. GSK3beta knockdown reduced anxiety-like behavior while increasing depression-like behavior and cocaine self-administration. Correlative electrophysiological recordings in acute brain slices were used to assess the effect of AAV-shGSK3beta on spontaneous firing and intrinsic excitability of tonically active interneurons (TANs), cells required for input and output signal integration in the NAcSh and for processing reward-related behaviors. Loose-patch recordings showed that TANs transduced by AAV-shGSK3beta exhibited reduction in tonic firing and increased spike half width. When assessed by whole-cell patch clamp recordings these changes were mirrored by reduction in action potential firing and accompanied by decreased hyperpolarization-induced depolarizing sag potentials, increased action potential current threshold, and decreased maximum rise time. These results suggest that silencing of GSK3beta in the NAcSh increases depression- and addiction-related behavior, possibly by decreasing intrinsic excitability of TANs. However, this study does not rule out contributions from other neuronal sub-types. PMID:28126496

Clarithromycin increases neuronal excitability in CA3 pyramidal neurons through a reduction in GABAergic signaling

PubMed Central

Elder, Courtney C.; García, Paul S.

2016-01-01

Antibiotics are used in the treatment and prevention of bacterial infections, but effects on neuron excitability have been documented. A recent study demonstrated that clarithromycin alleviates daytime sleepiness in hypersomnia patients (Trotti LM, Saini P, Freeman AA, Bliwise DL, García PS, Jenkins A, Rye DB. J Psychopharmacol 28: 697–702, 2014). To explore the potential application of clarithromycin as a stimulant, we performed whole cell patch-clamp recordings in rat pyramidal cells from the CA3 region of hippocampus. In the presence of the antibiotic, rheobase current was reduced by 50%, F-I relationship (number of action potentials as a function of injected current) was shifted to the left, and the resting membrane potential was more depolarized. Clarithromycin-induced hyperexcitability was dose dependent; doses of 30 and 300 μM clarithromycin significantly increased the firing frequency and membrane potential compared with controls (P = 0.003, P < 0.0001). We hypothesized that clarithromycin enhanced excitability by reducing GABAA receptor activation. Clarithromycin at 30 μM significantly reduced (P = 0.001) the amplitude of spontaneous miniature inhibitory GABAergic currents and at 300 μM had a minor effect on action potential width. Additionally, we tested the effect of clarithromycin in an ex vivo seizure model by evaluating its effect on spontaneous local field potentials. Bath application of 300 μM clarithromycin enhanced burst frequency twofold compared with controls (P = 0.0006). Taken together, these results suggest that blocking GABAergic signaling with clarithromycin increases cellular excitability and potentially serves as a stimulant, facilitating emergence from anesthesia or normalizing vigilance in hypersomnia and narcolepsy. However, the administration of clarithromycin should be carefully considered in patients with seizure disorders. NEW & NOTEWORTHY Clinical administration of the macrolide antibiotic clarithromycin has been associated with side effects such as mania, agitation, and delirium. Here, we investigated the adverse effects of this antibiotic on CA3 pyramidal cell excitability. Clarithromycin induces hyperexcitability in single neurons and is related to a reduction in GABAergic signaling. Our results support a potentially new application of clarithromycin as a stimulant to facilitate emergence from anesthesia or to normalize vigilance. PMID:27733592

Potential of lattice Boltzmann to model droplets on chemically stripe-patterned substrates

NASA Astrophysics Data System (ADS)

Patrick Jansen, H.; Sotthewes, K.; Zandvliet, Harold J. W.; Kooij, E. Stefan

2016-01-01

Lattice Boltzmann modelling (LBM) has recently been applied to a range of different wetting situations. Here we demonstrate its potential in representing complex kinetic effects encountered in droplets on chemically stripe-patterned surfaces. An ultimate example of the power of LBM is provided by comparing simulations and experiments of impacting droplets with varying Weber numbers. Also, the shape evolution of droplets is discussed in relation to their final shape. The latter can then be compared to Surface Evolver (SE) results, since under the proper boundary conditions both approaches should yield the same configuration in a static state. During droplet growth in LBM simulations, achieved by increasing the density within the droplet, the contact line initially advances in the direction parallel to the stripes, therewith increasing its aspect ratio. Once the volume becomes too large the droplet starts wetting additional stripes, leading to a lower aspect ratio. The maximum aspect ratio is shown to be a function of the width ratio of the hydrophobic and hydrophilic stripes and also their absolute widths. In the limit of sufficiently large stripe widths the aspect ratio is solely dependent on the relative stripe widths. The maximum droplet aspect ratio in the LBM simulations is compared to SE simulations and results are shown to be in good agreement. Additionally, we also show the ability of LBM to investigate single stripe wetting, enabling determination of the maximum aspect ratio that can be achieved in the limit of negligible hydrophobic stripe width, under the constraint that the stripe widths are large enough such that they are not easily crossed.

Influences of spatial and temporal variation on fish-habitat relationships defined by regression quantiles

Treesearch

Jason B. Dunham; Brian S. Cade; James W. Terrell

2002-01-01

We used regression quantiles to model potentially limiting relationships between the standing crop of cutthroat trout Oncorhynchus clarki and measures of stream channel morphology. Regression quantile models indicated that variation in fish density was inversely related to the width:depth ratio of streams but not to stream width or depth alone. The...

Overlap and partitioning of the ecological and isotopic niches

Treesearch

Elizabeth A. Flaherty; Merav Ben-David

2010-01-01

Recently, it was proposed that stable isotope patterns can be used to quantify the width of the ecological niche of animals. However, the potential effects of habitat use on isotopic patterns of consumers have not been fully explored and consequently isotopic patterns may yield deceptive estimates of niche width. Here, we simulated four different scenarios of a...

75 FR 41764 - Safety Zone; Mississippi River, Mile 840.0 to 839.8

Federal Register 2010, 2011, 2012, 2013, 2014

2010-07-19

...-AA00 Safety Zone; Mississippi River, Mile 840.0 to 839.8 AGENCY: Coast Guard, DHS. ACTION: Temporary... Mississippi River, Mile 840.0 to 839.8, extending the entire width of the river. This safety zone is needed to... Purpose On July 24, 2010 the Red Bull North America will be conducting a flying aircraft regatta at mile...

75 FR 53193 - Safety Zone; Mississippi River, Mile 427.3 to 427.5

Federal Register 2010, 2011, 2012, 2013, 2014

2010-08-31

... Zone; Mississippi River, Mile 427.3 to 427.5 AGENCY: Coast Guard, DHS. ACTION: Temporary final rule... River, Mile 427.3 to 427.5, extending the entire width of the river. This safety zone is needed to... 5, 2010 the City of Keithsburg will be conducting a fireworks display at mile 427.4 on the Upper...

78 FR 46258 - Safety Zone; Upper Mississippi River, Mile 662.8 to 663.9

Federal Register 2010, 2011, 2012, 2013, 2014

2013-07-31

...-AA00 Safety Zone; Upper Mississippi River, Mile 662.8 to 663.9 AGENCY: Coast Guard, DHS. ACTION... Upper Mississippi River, from mile 662.8 to 663.9, extending the entire width of the river. This safety... mile 662.8 to 663.9 on the Upper Mississippi River. Anticipated traffic on the river presents safety...

76 FR 36316 - Safety Zone; Upper Mississippi River, Mile 180.0 to 179.0

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-22

...-AA00 Safety Zone; Upper Mississippi River, Mile 180.0 to 179.0 AGENCY: Coast Guard, DHS. ACTION... Upper Mississippi River, from Mile 180.0 to 179.0, extending the entire width of the river. This safety... combat capabilities between Mile 180.0 and 179.0 on the Upper Mississippi River. This event presents...

Features of the rupture of free hanging liquid film under the action of a thermal load

NASA Astrophysics Data System (ADS)

Ovcharova, Alla S.

2011-10-01

We consider a deformation and a rupture of a thin liquid film which is hanging between two solid flat walls under the action of concentrated thermal load action. A two-dimensional model is applied to describe the motion of thin layers of viscous non-isothermal liquid under micro-gravity conditions. For flow simulation, two-dimensional Navier-Stokes equations are used. A computational analysis of the influence of thermal loads on the deformation and the rupture behavior of the thin freely hanging film is carried out. It is shown that the rupture of the thin film with generation of a droplet can occur under the thermal beam of specific width acting on the free surface of the film. The results of the model problem solutions are presented.

Frequency non-degenerate phase-sensitive optical parametric amplification based on four-wave-mixing in width-modulated silicon waveguides.

PubMed

Wang, Zhaolu; Liu, Hongjun; Sun, Qibing; Huang, Nan; Li, Xuefeng

2014-12-15

A width-modulated silicon waveguide is proposed to realize non-degenerate phase sensitive optical parametric amplification. It is found that the relative phase at the input of the phase sensitive amplifier (PSA) θIn-PSA can be tuned by tailoring the width and length of the second segment of the width-modulated silicon waveguide, which will influence the gain in the parametric amplification process. The maximum gain of PSA is larger by 9 dB compared with the phase insensitive amplifier (PIA) gain, and the gain bandwidth of PSA is larger by 35 nm compared with the gain bandwidth of PIA. Our on-chip PSA can find important potential applications in highly integrated optical circuits for optical chip-to-chip communication and computers.

Elevation and stream-size thresholds affect distributions of native and exotic warmwater fishes in Wyoming

USGS Publications Warehouse

Quist, M.C.; Hubert, W.A.; Rahel, F.J.

2004-01-01

This study was conducted to assess the influence of elevation and stream width on the occurrence of 28 native and six exotic fish species using data collected (1954-2003) from 1,114 stream reaches in Wyoming. Medians and ranges of elevation and stream width were used to assess how elevation and stream width influenced the occurrence of individual species and to indicate which species had large and small ranges of distribution. Twenty-four species were common at elevations below 1,550 m and 31 species occurred in streams less than 20 m wide. The six exotic species had the potential to overlap all of the native species with regard to both elevation and stream width. In general, species that were collected over a wide range of elevations were also collected over a wide range of stream widths. Red shiner (Cyprinella lutrensis) and river carpsucker (Carpiodes carpio) occurred over the smallest elevation ranges ( 2,500 m). Longnose sucker and white sucker (Catostomus commersoni) occurred over the greatest ranges in stream widths (> 90 m), and brook stickleback (Culaea inconstans), black bullhead (Ameiurus melas), and quillback (Carpiodes cyprinus) were found over the lowest ranges in stream widths (< 12 m). The distributions of native and exotic species in streams that transition from the Rocky Mountains to the Great Plains were largely explained by elevation and stream width.

Qualitative analysis of gain spectra of InGaAlAs/InP lasing nano-heterostructure

NASA Astrophysics Data System (ADS)

Lal, Pyare; Yadav, Rashmi; Sharma, Meha; Rahman, F.; Dalela, S.; Alvi, P. A.

2014-08-01

This paper deals with the studies of lasing characteristics along with the gain spectra of compressively strained and step SCH based In0.71Ga0.21Al0.08As/InP lasing nano-heterostructure within TE polarization mode, taking into account the variation in well width of the single quantum well of the nano-heterostructure. In addition, the compressive conduction and valence bands dispersion profiles for quantum well of the material composition In0.71Ga0.21Al0.08As at temperature 300 K and strain 1.12% have been studied using 4 × 4 Luttinger Hamiltonian. For the proposed nano-heterostructure, the quantum well width dependence of differential gain, refractive index change and relaxation oscillation frequency with current density have been studied. Moreover, the G-J characteristics of the nano-heterostructure at different well widths have also been investigated, that provided significant information about threshold current density, threshold gain and transparency current density. The results obtained in the study of nano-heterostructure suggest that the gain and relaxation oscillation frequency both are decreased with increasing quantum well width but the required lasing wavelength is found to shift towards higher values. On behalf of qualitative analysis of the structure, the well width of 6 nm is found more suitable for lasing action at the wavelength of 1.55 μm due to minimum optical attenuation and minimum dispersion within the waveguide. The results achieved are, therefore, very important in the emerging area of nano-optoelectronics.

Patient DF's visual brain in action: Visual feedforward control in visual form agnosia.

PubMed

Whitwell, Robert L; Milner, A David; Cavina-Pratesi, Cristiana; Barat, Masihullah; Goodale, Melvyn A

2015-05-01

Patient DF, who developed visual form agnosia following ventral-stream damage, is unable to discriminate the width of objects, performing at chance, for example, when asked to open her thumb and forefinger a matching amount. Remarkably, however, DF adjusts her hand aperture to accommodate the width of objects when reaching out to pick them up (grip scaling). While this spared ability to grasp objects is presumed to be mediated by visuomotor modules in her relatively intact dorsal stream, it is possible that it may rely abnormally on online visual or haptic feedback. We report here that DF's grip scaling remained intact when her vision was completely suppressed during grasp movements, and it still dissociated sharply from her poor perceptual estimates of target size. We then tested whether providing trial-by-trial haptic feedback after making such perceptual estimates might improve DF's performance, but found that they remained significantly impaired. In a final experiment, we re-examined whether DF's grip scaling depends on receiving veridical haptic feedback during grasping. In one condition, the haptic feedback was identical to the visual targets. In a second condition, the haptic feedback was of a constant intermediate width while the visual target varied trial by trial. Despite this incongruent feedback, DF still scaled her grip aperture to the visual widths of the target blocks, showing only normal adaptation to the false haptically-experienced width. Taken together, these results strengthen the view that DF's spared grasping relies on a normal mode of dorsal-stream functioning, based chiefly on visual feedforward processing. Copyright © 2014 Elsevier B.V. All rights reserved.

Dependence of paranodal junctional gap width on transverse bands.

PubMed

Rosenbluth, Jack; Petzold, Chris; Peles, Elior

2012-08-15

Mouse mutants with paranodal junctional (PNJ) defects display variable degrees of neurological impairment. In this study we compare control paranodes with those from three mouse mutants that differ with respect to a conspicuous PNJ component, the transverse bands (TBs). We hypothesize that TBs link the apposed junctional membranes together at a fixed distance and thereby determine the width of the junctional gap, which may in turn determine the extent to which nodal action currents can be short-circuited underneath the myelin sheath. Electron micrographs of aldehyde-fixed control PNJs, in which TBs are abundant, show a consistent junctional gap of ∼3.5 nm. In Caspr-null PNJs, which lack TBs entirely, the gap is wider (∼6-7 nm) and more variable. In CST-null PNJs, which have only occasional TBs, the mean PNJ gap width is comparable to that in Caspr-null mice. In the shaking mutant, in contrast, which has approximately 60% of the normal complement of TBs, mean PNJ gap width is not significantly different from that in controls. Correspondingly, shaking mice are much less impaired neurologically than either Caspr-null or CST-null mice. We conclude that in the absence or gross diminution of TBs, mean PNJ gap width increases significantly and suggest that this difference could underlie some of the neurological impairment seen in those mutants. Surprisingly, even in the absence of TBs, paranodes are to some extent maintained in their usual form, implying that in addition to TBs, other factors govern the formation and maintenance of overall paranodal structure. Copyright © 2012 Wiley Periodicals, Inc.

Silicon ribbon growth by a capillary action shaping technique

NASA Technical Reports Server (NTRS)

Schwuttke, G. H.; Ciszek, T. F.; Kran, A.

1976-01-01

The technique of silicon ribbon growth by the capillary action shaping is assessed for applicability to photovoltaic power device material. Ribbons 25 mm in width and up to 0.5 m in length have been grown from SiC dies, and some new characteristics of growth from such dies have been identified. Thermal modifiers have been studied, and systems were developed which reduce the frozen-in stress un silicon ribbons and improve the thickness uniformity of the ribbons. Preliminary spreading resistance measurements indicate that neither surface striations nor twin boundaries give rise to appreciable resistivity variations, but that large-angle grain boundaries cause local resistivity increases of up to 200%.

Differences in delta13C and diameter growth among remnant Scots pine populations in Scotland.

PubMed

Brendel, Oliver; Handley, Linda; Griffiths, Howard

2002-10-01

Published data suggest that differences in wood cellulose carbon isotope composition (delta13C) and xylem ring width among natural populations of Scots pine in Scotland (Pinus sylvestris L.) are attributable to the persistence of palaeotypes of various post-glacial migratory origins. We assessed differences in wood cellulose delta13C and ring width among Scottish Scots pine populations grown in a clone bank and in natural stands at various locations in northern and central Scotland. Ring width and wood cellulose delta13C varied significantly among natural stands. Potential water deficit was positively correlated with wood cellulose delta13C and xylem ring width in the natural stands. Neither wood cellulose delta13C nor xylem ring width of clone bank trees correlated with any climate variables at the sites from which the trees originated, indicating little adaptation to climate for these traits. Xylem ring width showed a site x population interaction for the growth sites (i.e., natural stands versus clone bank), but wood cellulose delta13C did not. These results suggest that climate variation in Scotland has not resulted in significant genetic variation in wood cellulose delta13C or xylem ring width in post-glacial populations.

Sites of action of elevated CO2 on leaf development in rice: discrimination between the effects of elevated CO2 and nitrogen deficiency.

PubMed

Tsutsumi, Koichi; Konno, Masae; Miyazawa, Shin-Ichi; Miyao, Mitsue

2014-02-01

Elevated CO2 concentrations (eCO2) trigger various plant responses. Despite intensive studies of these responses, the underlying mechanisms remain obscure. In this work, we investigated when and how leaf physiology and anatomy are affected by eCO2 in rice plants. We analyzed the most recently fully expanded leaves that developed successively after transfer of the plant to eCO2. To discriminate between the effects of eCO2 and those of nitrogen deficiency, we used three different levels of N application. We found that a decline in the leaf soluble protein content (on a leaf area basis) at eCO2 was only observed under N deficiency. The length and width of the leaf blade were reduced by both eCO2 and N deficiency, whereas the blade thickness was increased by eCO2 but was not affected by N deficiency. The change in length by eCO2 became detectable in the secondly fully expanded leaf, and those in width and thickness in the thirdly fully expanded leaf, which were at the leaf developmental stages P4 and P3, respectively, at the onset of the eCO2 treatment. The decreased blade length at eCO2 was associated with a decrease in the epidermal cell number on the adaxial side and a reduction in cell length on the abaxial side. The decreased width resulted from decreased numbers of small vascular bundles and epidermal cell files. The increased thickness was ascribed mainly to enhanced development of bundle sheath extensions at the ridges of vascular bundles. These observations enable us to identify the sites of action of eCO2 on rice leaf development.

75 FR 28769 - Safety Zone; Osage River, Mile 016.8 to 017.2

Federal Register 2010, 2011, 2012, 2013, 2014

2010-05-24

...-AA00 Safety Zone; Osage River, Mile 016.8 to 017.2 AGENCY: Coast Guard, DHS. ACTION: Notice of proposed... Osage River, Mile 016.8 to 017.2, extending the entire width of the river. This safety zone is needed to... between mile 016.8 and 017.2 on the Osage River. This event presents safety hazards to the navigation of...

75 FR 55973 - Safety Zone; Illinois River, Mile 000.5 to 001.5

Federal Register 2010, 2011, 2012, 2013, 2014

2010-09-15

...-AA00 Safety Zone; Illinois River, Mile 000.5 to 001.5 AGENCY: Coast Guard, DHS. ACTION: Temporary final... River, Mile 000.5 to 001.5, extending the entire width of the river. This safety zone is needed to... 18, 2010 the City of Grafton will be conducting a land based fireworks display at mile 001.0 on the...

76 FR 77901 - Safety Zone; Upper Mississippi River, Mile 389.4 to 403.1

Federal Register 2010, 2011, 2012, 2013, 2014

2011-12-15

...-AA00 Safety Zone; Upper Mississippi River, Mile 389.4 to 403.1 AGENCY: Coast Guard, DHS. ACTION... Upper Mississippi River, from Mile 389.4 to 403.1, extending the entire width of the river located on... 389.4 to 403.1 on the Upper Mississippi River. Under 5 U.S.C. 553(d)(3), the Coast Guard finds that...

Recording evoked potentials during deep brain stimulation: development and validation of instrumentation to suppress the stimulus artefact.

PubMed

Kent, A R; Grill, W M

2012-06-01

The clinical efficacy of deep brain stimulation (DBS) for the treatment of movement disorders depends on the identification of appropriate stimulation parameters. Since the mechanisms of action of DBS remain unclear, programming sessions can be time consuming, costly and result in sub-optimal outcomes. Measurement of electrically evoked compound action potentials (ECAPs) during DBS, generated by activated neurons in the vicinity of the stimulating electrode, could offer insight into the type and spatial extent of neural element activation and provide a potential feedback signal for the rational selection of stimulation parameters and closed-loop DBS. However, recording ECAPs presents a significant technical challenge due to the large stimulus artefact, which can saturate recording amplifiers and distort short latency ECAP signals. We developed DBS-ECAP recording instrumentation combining commercial amplifiers and circuit elements in a serial configuration to reduce the stimulus artefact and enable high fidelity recording. We used an electrical circuit equivalent model of the instrumentation to understand better the sources of the stimulus artefact and the mechanisms of artefact reduction by the circuit elements. In vitro testing validated the capability of the instrumentation to suppress the stimulus artefact and increase gain by a factor of 1000 to 5000 compared to a conventional biopotential amplifier. The distortion of mock ECAP (mECAP) signals was measured across stimulation parameters, and the instrumentation enabled high fidelity recording of mECAPs with latencies of only 0.5 ms for DBS pulse widths of 50 to 100 µs/phase. Subsequently, the instrumentation was used to record in vivo ECAPs, without contamination by the stimulus artefact, during thalamic DBS in an anesthetized cat. The characteristics of the physiological ECAP were dependent on stimulation parameters. The novel instrumentation enables high fidelity ECAP recording and advances the potential use of the ECAP as a feedback signal for the tuning of DBS parameters.

Dynamics of action potential backpropagation in basal dendrites of prefrontal cortical pyramidal neurons.

PubMed

Zhou, Wen-Liang; Yan, Ping; Wuskell, Joseph P; Loew, Leslie M; Antic, Srdjan D

2008-02-01

Basal dendrites of neocortical pyramidal neurons are relatively short and directly attached to the cell body. This allows electrical signals arising in basal dendrites to strongly influence the neuronal output. Likewise, somatic action potentials (APs) should readily propagate back into the basilar dendritic tree to influence synaptic plasticity. Two recent studies, however, determined that sodium APs are severely attenuated in basal dendrites of cortical pyramidal cells, so that they completely fail in distal dendritic segments. Here we used the latest improvements in the voltage-sensitive dye imaging technique (Zhou et al., 2007) to study AP backpropagation in basal dendrites of layer 5 pyramidal neurons of the rat prefrontal cortex. With a signal-to-noise ratio of > 15 and minimal temporal averaging (only four sweeps) we were able to sample AP waveforms from the very last segments of individual dendritic branches (dendritic tips). We found that in short- (< 150 microm) and medium (150-200 microm in length)-range basal dendrites APs backpropagated with modest changes in AP half-width or AP rise-time. The lack of substantial changes in AP shape and dynamics of rise is inconsistent with the AP-failure model. The lack of substantial amplitude boosting of the third AP in the high-frequency burst also suggests that in short- and medium-range basal dendrites backpropagating APs were not severely attenuated. Our results show that the AP-failure concept does not apply in all basal dendrites of the rat prefrontal cortex. The majority of synaptic contacts in the basilar dendritic tree actually received significant AP-associated electrical and calcium transients.

Aging-Related Hyperexcitability in CA3 Pyramidal Neurons Is Mediated by Enhanced A-Type K+ Channel Function and Expression.

PubMed

Simkin, Dina; Hattori, Shoai; Ybarra, Natividad; Musial, Timothy F; Buss, Eric W; Richter, Hannah; Oh, M Matthew; Nicholson, Daniel A; Disterhoft, John F

2015-09-23

Aging-related impairments in hippocampus-dependent cognition have been attributed to maladaptive changes in the functional properties of pyramidal neurons within the hippocampal subregions. Much evidence has come from work on CA1 pyramidal neurons, with CA3 pyramidal neurons receiving comparatively less attention despite its age-related hyperactivation being postulated to interfere with spatial processing in the hippocampal circuit. Here, we use whole-cell current-clamp to demonstrate that aged rat (29-32 months) CA3 pyramidal neurons fire significantly more action potentials (APs) during theta-burst frequency stimulation and that this is associated with faster AP repolarization (i.e., narrower AP half-widths and enlarged fast afterhyperpolarization). Using a combination of patch-clamp physiology, pharmacology, Western blot analyses, immunohistochemistry, and array tomography, we demonstrate that these faster AP kinetics are mediated by enhanced function and expression of Kv4.2/Kv4.3 A-type K(+) channels, particularly within the perisomatic compartment, of CA3 pyramidal neurons. Thus, our study indicates that inhibition of these A-type K(+) channels can restore the intrinsic excitability properties of aged CA3 pyramidal neurons to a young-like state. Significance statement: Age-related learning deficits have been attributed, in part, to altered hippocampal pyramidal neuronal function with normal aging. Much evidence has come from work on CA1 neurons, with CA3 neurons receiving comparatively less attention despite its age-related hyperactivation being postulated to interfere with spatial processing. Hence, we conducted a series of experiments to identify the cellular mechanisms that underlie the hyperexcitability reported in the CA3 region. Contrary to CA1 neurons, we demonstrate that postburst afterhyperpolarization is not altered with aging and that aged CA3 pyramidal neurons are able to fire significantly more action potentials and that this is associated with faster action potential repolarization through enhanced expression of Kv4.2/Kv4.3 A-type K(+) channels, particularly within the cell bodies of CA3 pyramidal neurons. Copyright © 2015 the authors 0270-6474/15/3513206-13$15.00/0.

Aging-Related Hyperexcitability in CA3 Pyramidal Neurons Is Mediated by Enhanced A-Type K+ Channel Function and Expression

PubMed Central

Simkin, Dina; Hattori, Shoai; Ybarra, Natividad; Musial, Timothy F.; Buss, Eric W.; Richter, Hannah; Oh, M. Matthew

2015-01-01

Aging-related impairments in hippocampus-dependent cognition have been attributed to maladaptive changes in the functional properties of pyramidal neurons within the hippocampal subregions. Much evidence has come from work on CA1 pyramidal neurons, with CA3 pyramidal neurons receiving comparatively less attention despite its age-related hyperactivation being postulated to interfere with spatial processing in the hippocampal circuit. Here, we use whole-cell current-clamp to demonstrate that aged rat (29–32 months) CA3 pyramidal neurons fire significantly more action potentials (APs) during theta-burst frequency stimulation and that this is associated with faster AP repolarization (i.e., narrower AP half-widths and enlarged fast afterhyperpolarization). Using a combination of patch-clamp physiology, pharmacology, Western blot analyses, immunohistochemistry, and array tomography, we demonstrate that these faster AP kinetics are mediated by enhanced function and expression of Kv4.2/Kv4.3 A-type K+ channels, particularly within the perisomatic compartment, of CA3 pyramidal neurons. Thus, our study indicates that inhibition of these A-type K+ channels can restore the intrinsic excitability properties of aged CA3 pyramidal neurons to a young-like state. SIGNIFICANCE STATEMENT Age-related learning deficits have been attributed, in part, to altered hippocampal pyramidal neuronal function with normal aging. Much evidence has come from work on CA1 neurons, with CA3 neurons receiving comparatively less attention despite its age-related hyperactivation being postulated to interfere with spatial processing. Hence, we conducted a series of experiments to identify the cellular mechanisms that underlie the hyperexcitability reported in the CA3 region. Contrary to CA1 neurons, we demonstrate that postburst afterhyperpolarization is not altered with aging and that aged CA3 pyramidal neurons are able to fire significantly more action potentials and that this is associated with faster action potential repolarization through enhanced expression of Kv4.2/Kv4.3 A-type K+ channels, particularly within the cell bodies of CA3 pyramidal neurons. PMID:26400949

Interference in the gg→h→γγ On-Shell Rate and the Higgs Boson Total Width.

PubMed

Campbell, John; Carena, Marcela; Harnik, Roni; Liu, Zhen

2017-11-03

We consider interference between the Higgs signal and QCD background in gg→h→γγ and its effect on the on-shell Higgs rate. The existence of sizable strong phases leads to destructive interference of about 2% of the on-shell cross section in the standard model. This effect can be enhanced by beyond the standard model physics. In particular, since it scales differently from the usual rates, the presence of interference allows indirect limits to be placed on the Higgs width in a novel way, using on-shell rate measurements. Our study motivates further QCD calculations to reduce uncertainties. We discuss possible width-sensitive observables, both using total and differential rates and find that the HL-LHC can potentially indirectly constrain widths of order tens of MeV.

Precision calculation of the lowest 1S resonance in e-H scattering. [electron-hydrogen scattering

NASA Technical Reports Server (NTRS)

Ho, Y. K.; Bhatia, A. K.; Temkin, A.

1977-01-01

The position and width of the lowest resonance in electron-hydrogen scattering have been calculated using a Hylleraas correlation function with up to 95 terms in the optical potential formalism. The results should be useful as calibration points for experimental electron scattering purposes. A formula relating the conventional (Breit-Wigner) width with the Feschbach formalism is derived.

VizieR Online Data Catalog: Chemical abundances of 8 metal-poor stars (Ishigaki+, 2014)

NASA Astrophysics Data System (ADS)

Ishigaki, M. N.; Aoki, W.; Arimoto, N.; Okamoto, S.

2014-01-01

Equivalent widths and chemical abundances of the six giant stars in Bootes I dwarf spheroidal galaxy (Boo-009, Boo-094, Boo-117, Boo-121, Boo-127, Boo-911) and the two Milky Way halo stars (HD216143, HD85773) are presented. For each spectral line, excitation potential, loggf values, measured equivalent widths and abundances are given. (2 data files).

Continuous modulations of femtosecond laser-induced periodic surface structures and scanned line-widths on silicon by polarization changes.

PubMed

Han, Weina; Jiang, Lan; Li, Xiaowei; Liu, Pengjun; Xu, Le; Lu, YongFeng

2013-07-01

Large-area, uniform laser-induced periodic surface structures (LIPSS) are of wide potential industry applications. The continuity and processing precision of LIPSS are mainly determined by the scanning intervals of adjacent scanning lines. Therefore, continuous modulations of LIPSS and scanned line-widths within one laser scanning pass are of great significance. This study proposes that by varying the laser (800 nm, 50 fs, 1 kHz) polarization direction, LIPSS and the scanned line-widths on a silicon (111) surface can be continuously modulated with high precision. It shows that the scanned line-width reaches the maximum when the polarization direction is perpendicular to the scanning direction. As an application example, the experiments show large-area, uniform LIPSS can be fabricated by controlling the scanning intervals based on the one-pass scanned line-widths. The simulation shows that the initially formed LIPSS structures induce directional surface plasmon polaritons (SPP) scattering along the laser polarization direction, which strengthens the subsequently anisotropic LIPSS fabrication. The simulation results are in good agreement with the experiments, which both support the conclusions of continuous modulations of the LIPSS and scanned line-widths.

Measurement and dynamics of the spatial distribution of an electron localized at a metal-dielectric interface

NASA Astrophysics Data System (ADS)

Bezel, Ilya; Gaffney, Kelly J.; Garrett-Roe, Sean; Liu, Simon H.; Miller, André D.; Szymanski, Paul; Harris, Charles B.

2004-01-01

The ability of time- and angle-resolved two-photon photoemission to estimate the size distribution of electron localization in the plane of a metal-adsorbate interface is discussed. It is shown that the width of angular distribution of the photoelectric current is inversely proportional to the electron localization size within the most common approximations in the description of image potential states. The localization of the n=1 image potential state for two monolayers of butyronitrile on Ag(111) is used as an example. For the delocalized n=1 state, the shape of the signal amplitude as a function of momentum parallel to the surface changes rapidly with time, indicating efficient intraband relaxation on a 100 fs time scale. For the localized state, little change was observed. The latter is related to the constant size distribution of electron localization, which is estimated to be a Gaussian with a 15±4 Å full width at half maximum in the plane of the interface. A simple model was used to study the effect of a weak localization potential on the overall width of the angular distribution of the photoemitted electrons, which exhibited little sensitivity to the details of the potential. This substantiates the validity of the localization size estimate.

Electro-osmotic flow in a rotating rectangular microchannel

PubMed Central

Ng, Chiu-On; Qi, Cheng

2015-01-01

An analytical model is presented for low-Rossby-number electro-osmotic flow in a rectangular channel rotating about an axis perpendicular to its own. The flow is driven under the combined action of Coriolis, pressure, viscous and electric forces. Analytical solutions in the form of eigenfunction expansions are developed for the problem, which is controlled by the rotation parameter (or the inverse Ekman number), the Debye parameter, the aspect ratio of the channel and the distribution of zeta potentials on the channel walls. Under the conditions of fast rotation and a thin electric double layer (EDL), an Ekman–EDL develops on the horizontal walls. This is essentially an Ekman layer subjected to electrokinetic effects. The flow structure of this boundary layer as a function of the Ekman layer thickness normalized by the Debye length is investigated in detail in this study. It is also shown that the channel rotation may have qualitatively different effects on the flow rate, depending on the channel width and the zeta potential distributions. Axial and secondary flows are examined in detail to reveal how the development of a geostrophic core may lead to a rise or fall of the mean flow. PMID:26345088

Prevalence and Size of Periapical Radiolucencies Using Cone-beam Computed Tomography in Teeth without Apparent Intraoral Radiographic Lesions: A New Periapical Index with a Clinical Recommendation.

PubMed

Torabinejad, Mahmoud; Rice, Dwight D; Maktabi, Omar; Oyoyo, Udochukwu; Abramovitch, Kenneth

2018-03-01

The purpose of this study was to determine the prevalence and size of periapical radiolucencies using cone-beam computed tomographic (CBCT) imaging in teeth without apparent signs of intraoral radiographic lesions. One hundred twenty roots from 53 patients who had been determined to have no signs of intraoral radiographic lesions were included in this study. Limited-volume CBCT scans were taken at 0.125-mm 3 voxel size. The widest area of apical radiolucency of each root canal-treated tooth was measured and assigned a numeric score based on the CBCT-Endodontic Radiolucency Index (ERI). CBCT data were evaluated by 2 radiologists with an interclass correlation coefficient of 0.96. The majority of roots (53.3%) had periodontal ligament widths ≤0.5 mm; 26.7% had radiolucency widths of 0.5 < x ≤ 1 mm, 15.0% had radiolucency widths of 1.0 < x ≤ 1.5 mm, 0.8% had radiolucency widths of 1.5 < x ≤ 2.0 mm, 1.7% had radiolucency widths of 2.0 < x ≤ 2.5 mm, and 2.5% had radiolucency widths of >2.5 mm. Patient age, recall interval, tooth type, and arch type had no statistically significant effect on the ERI distribution. Twenty percent of teeth with successful root canal treatment based on conventional periapical imaging had CBCT radiolucencies measuring greater than 1 mm. Because these radiolucencies may not be pathological changes, clinicians are cautioned against overtreatment of them before determining the true nature of these findings. Clinical studies with long follow-up times are needed to determine the proper course of actions for these cases. Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

CONTROL ROD

DOEpatents

Zinn, W.H.; Ross, H.V.

1958-11-18

A control rod is described for a nuclear reactor. In certaln reactor designs it becomes desirable to use a control rod having great width but relatively llttle thickness. This patent is addressed to such a need. The neutron absorbing material is inserted in a triangular tube, leaving volds between the circular insert and the corners of the triangular tube. The material is positioned within the tube by the use of dummy spacers to achleve the desired absorption pattern, then the ends of the tubes are sealed with suitable plugs. The tubes may be welded or soldered together to form two flat surfaces of any desired width, and covered with sheetmetal to protect the tubes from damage. This design provides a control member that will not distort under the action of outside forces or be ruptured by gases generated within the jacketed control member.

Skyrmion dynamics in width-varying nanotracks and implications for skyrmionic applications

NASA Astrophysics Data System (ADS)

Chen, Xing; Kang, Wang; Zhu, Daoqian; Zhang, Xichao; Lei, Na; Zhang, Youguang; Zhou, Yan; Zhao, Weisheng

2017-11-01

A comprehensive study of the magnetic skyrmion dynamics in terms of size, velocity, energy, and stability in width-varying nanotracks is reported by micromagnetic simulations. We find that the diameter of a skyrmion reduces with the decrease in the nanotrack width in the spin Hall effect (SHE)-induced skyrmion motion. Accordingly, the skyrmion energy increases giving rise to the growing instability of the skyrmion. It is also numerically demonstrated that the velocity of the skyrmion varies during the motion, since the repulsive force of the nanotrack edges acting on the skyrmion as well as the driving force created by the SHE associated with the size of the skyrmion have a joint impact on the skyrmion motion dynamics in the width-varying nanotrack. In addition, one interesting finding reveals that skyrmions with small sizes, which may be inaccessible to typical approaches by means of directly injecting a spin-polarized current, could be obtained by utilizing this structure. This finding is potential for generating nanoscale skyrmions in skyrmionic applications with ultra-dense density. Finally, inspired by the skyrmion dynamics in the width-varying nanotrack, a general summary on the tradeoff between the nanotrack width (storage density) and the skyrmion velocity (data access speed) is given by further analyzing the skyrmion dynamics in parallel nanotracks with different widths, which may provide guidelines in designing racetrack-type skyrmionic applications.

Cluster-model calculations of exotic decays from heavy nuclei

NASA Astrophysics Data System (ADS)

Buck, B.; Merchant, A. C.

1989-05-01

A cluster model employing a local, effective cluster-core potential is used to investigate exotic decay from heavy nuclei as a quantum tunneling phenomenon within a semiclassical approximation. Excellent agreement with all reported experimental measurements of the decay widths for 14C and 24Ne emission is obtained. As an added bonus, the width for alpha particle emission from 212Po is also calculated in good agreement with experiment.

Superluminal tunneling of a relativistic half-integer spin particle through a potential barrier

NASA Astrophysics Data System (ADS)

Nanni, Luca

2017-11-01

This paper investigates the problem of a relativistic Dirac half-integer spin free particle tunneling through a rectangular quantum-mechanical barrier. If the energy difference between the barrier and the particle is positive, and the barrier width is large enough, there is proof that the tunneling may be superluminal. For first spinor components of particle and antiparticle states, the tunneling is always superluminal regardless the barrier width. Conversely, the second spinor components of particle and antiparticle states may be either subluminal or superluminal depending on the barrier width. These results derive from studying the tunneling time in terms of phase time. For the first spinor components of particle and antiparticle states, it is always negative while for the second spinor components of particle and antiparticle states, it is always positive, whatever the height and width of the barrier. In total, the tunneling time always remains positive for particle states while it becomes negative for antiparticle ones. Furthermore, the phase time tends to zero, increasing the potential barrier both for particle and antiparticle states. This agrees with the interpretation of quantum tunneling that the Heisenberg uncertainty principle provides. This study's results are innovative with respect to those available in the literature. Moreover, they show that the superluminal behaviour of particles occurs in those processes with high-energy confinement.

Two-Photon Holographic Stimulation of ReaChR

PubMed Central

Chaigneau, Emmanuelle; Ronzitti, Emiliano; Gajowa, Marta A.; Soler-Llavina, Gilberto J.; Tanese, Dimitrii; Brureau, Anthony Y. B.; Papagiakoumou, Eirini; Zeng, Hongkui; Emiliani, Valentina

2016-01-01

Optogenetics provides a unique approach to remotely manipulate brain activity with light. Reaching the degree of spatiotemporal control necessary to dissect the role of individual cells in neuronal networks, some of which reside deep in the brain, requires joint progress in opsin engineering and light sculpting methods. Here we investigate for the first time two-photon stimulation of the red-shifted opsin ReaChR. We use two-photon (2P) holographic illumination to control the activation of individually chosen neurons expressing ReaChR in acute brain slices. We demonstrated reliable action potential generation in ReaChR-expressing neurons and studied holographic 2P-evoked spiking performances depending on illumination power and pulse width using an amplified laser and a standard femtosecond Ti:Sapphire oscillator laser. These findings provide detailed knowledge of ReaChR's behavior under 2P illumination paving the way for achieving in depth remote control of multiple cells with high spatiotemporal resolution deep within scattering tissue. PMID:27803649

Reversibility of electrophysiological changes induced by chronic high-altitude hypoxia in adult rat heart.

PubMed

Chouabe, C; Amsellem, J; Espinosa, L; Ribaux, P; Blaineau, S; Mégas, P; Bonvallet, R

2002-04-01

Recent studies indicate that regression of left ventricular hypertrophy normalizes membrane ionic current abnormalities. This work was designed to determine whether regression of right ventricular hypertrophy induced by permanent high-altitude exposure (4,500 m, 20 days) in adult rats also normalizes changes of ventricular myocyte electrophysiology. According to the current data, prolonged action potential, decreased transient outward current density, and increased inward sodium/calcium exchange current density normalized 20 days after the end of altitude exposure, whereas right ventricular hypertrophy evidenced by both the right ventricular weight-to-heart weight ratio and the right ventricular free wall thickness measurement normalized 40 days after the end of altitude exposure. This morphological normalization occurred at both the level of muscular tissue, as shown by the decrease toward control values of some myocyte parameters (perimeter, capacitance, and width), and the level of the interstitial collagenous connective tissue. In the chronic high-altitude hypoxia model, the regression of right ventricular hypertrophy would not be a prerequisite for normalization of ventricular electrophysiological abnormalities.

Effects of varying duty cycle and pulse width on high-intensity focused ultrasound (HIFU)-induced transcranial thrombolysis.

PubMed

Hölscher, Thilo; Raman, Rema; Fisher, David J; Ahadi, Golnaz; Zadicario, Eyal; Voie, Arne

2013-01-01

The goal was to test the effects of various combinations of pulse widths (PW) and duty cycles (DC) on high-intensity focused ultrasound (HIFU)-induced sonothrombolysis efficacy using an in vitro flow model. An ExAblate™ 4000 HIFU headsystem (InSightec, Inc., Israel) was used. Artificial blood clots were placed into test tubes inside a human calvarium and exposed to pulsatile flow. Four different duty cycles were tested against four different pulse widths. For all study groups, an increase in thrombolysis efficacy could be seen in association with increasing DC and/or PW (p < 0.0001). Using transcranial HIFU, significant thrombolysis can be achieved within seconds and without the use of lytic drugs in vitro. Longer duty cycles in combination with longer pulse widths seem to have the highest potential to optimize clot lysis efficacy.

Effects of varying duty cycle and pulse width on high-intensity focused ultrasound (HIFU)-induced transcranial thrombolysis

PubMed Central

2013-01-01

The goal was to test the effects of various combinations of pulse widths (PW) and duty cycles (DC) on high-intensity focused ultrasound (HIFU)-induced sonothrombolysis efficacy using an in vitro flow model. An ExAblate™ 4000 HIFU headsystem (InSightec, Inc., Israel) was used. Artificial blood clots were placed into test tubes inside a human calvarium and exposed to pulsatile flow. Four different duty cycles were tested against four different pulse widths. For all study groups, an increase in thrombolysis efficacy could be seen in association with increasing DC and/or PW (p < 0.0001). Using transcranial HIFU, significant thrombolysis can be achieved within seconds and without the use of lytic drugs in vitro. Longer duty cycles in combination with longer pulse widths seem to have the highest potential to optimize clot lysis efficacy. PMID:25512862

[Protective role of autotypic contacts under cerebellar neural net injury by toxic doses of NO-generative compounds].

PubMed

Samosudova, N V; Reutov, V P; Larionova, N P; Chaĭlakhian, L M

2005-01-01

In the present work, cerebellar neural net injury was induced by toxic doses of NO-generative compound (NaNO2). A protective role of glial cells was revealed in such conditions. The present results were compared with those of the previous work concerning the action of high concentration glutamate on the frog cerebellum (Samosudova et al., 1996). In both cases we observed the appearance of spiral-like structures--"wrappers)"--involving several rows of transformed glial processes with smaller width and bridges connecting the inner sides of row (autotypic contact). A statistic analysis was made according to both previous and present data. We calculated the number and width of rows, and intervals between bridges depending on experimental conditions. As the injury increased (stimulation in the NO-presence), the row number in "wrappers" also increased, while the row width and intervals between bridges decreased. The presence of autotypic contacts in glial "wrappers" enables us to suppose the involvement of adhesive proteins--cadherins in its formation. The obtained data suggested that the formation of spiral structures--"wrappers" may be regarded as a compensative-adaptive reaction on the injury of cerebellar neural net glutamate and NO-generative compounds.

The impact of individual and combined abiotic factors on daily otolith growth in a coral reef fish

NASA Astrophysics Data System (ADS)

Wenger, Amelia S.; Whinney, James; Taylor, Brett; Kroon, Frederieke

2016-06-01

Coral reefs are increasingly subjected to both local and global stressors, however, there is limited information on how reef organisms respond to their combined effects under natural conditions. This field study examined the growth response of the damselfish Neopomacentrus bankieri to the individual and combined effects of multiple abiotic factors. Turbidity, temperature, tidal movement, and wave action were recorded every 10 minutes for four months, after which the daily otolith growth of N. bankieri was aligned with corresponding abiotic conditions. Temperature was the only significant driver of daily otolith increment width, with increasing temperatures resulting in decreasing width. Although tidal movement was not a significant driver of increment width by itself, the combined effect of tidal movement and temperature had a greater negative effect on growth than temperature alone. Our results indicate that temperature can drive changes in growth even at very fine scales, and demonstrate that the cumulative impact of abiotic factors can be substantially greater than individual effects. As abiotic factors continue to change in intensity and duration, the combined impacts of them will become increasingly important drivers of physiological and ecological change.

The impact of individual and combined abiotic factors on daily otolith growth in a coral reef fish.

PubMed

Wenger, Amelia S; Whinney, James; Taylor, Brett; Kroon, Frederieke

2016-06-28

Coral reefs are increasingly subjected to both local and global stressors, however, there is limited information on how reef organisms respond to their combined effects under natural conditions. This field study examined the growth response of the damselfish Neopomacentrus bankieri to the individual and combined effects of multiple abiotic factors. Turbidity, temperature, tidal movement, and wave action were recorded every 10 minutes for four months, after which the daily otolith growth of N. bankieri was aligned with corresponding abiotic conditions. Temperature was the only significant driver of daily otolith increment width, with increasing temperatures resulting in decreasing width. Although tidal movement was not a significant driver of increment width by itself, the combined effect of tidal movement and temperature had a greater negative effect on growth than temperature alone. Our results indicate that temperature can drive changes in growth even at very fine scales, and demonstrate that the cumulative impact of abiotic factors can be substantially greater than individual effects. As abiotic factors continue to change in intensity and duration, the combined impacts of them will become increasingly important drivers of physiological and ecological change.

The impact of individual and combined abiotic factors on daily otolith growth in a coral reef fish

PubMed Central

Wenger, Amelia S.; Whinney, James; Taylor, Brett; Kroon, Frederieke

2016-01-01

Coral reefs are increasingly subjected to both local and global stressors, however, there is limited information on how reef organisms respond to their combined effects under natural conditions. This field study examined the growth response of the damselfish Neopomacentrus bankieri to the individual and combined effects of multiple abiotic factors. Turbidity, temperature, tidal movement, and wave action were recorded every 10 minutes for four months, after which the daily otolith growth of N. bankieri was aligned with corresponding abiotic conditions. Temperature was the only significant driver of daily otolith increment width, with increasing temperatures resulting in decreasing width. Although tidal movement was not a significant driver of increment width by itself, the combined effect of tidal movement and temperature had a greater negative effect on growth than temperature alone. Our results indicate that temperature can drive changes in growth even at very fine scales, and demonstrate that the cumulative impact of abiotic factors can be substantially greater than individual effects. As abiotic factors continue to change in intensity and duration, the combined impacts of them will become increasingly important drivers of physiological and ecological change. PMID:27350589

Point Cloud Based Approach to Stem Width Extraction of Sorghum

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

Jin, Jihui; Zakhor, Avideh

A revolution in the field of genomics has produced vast amounts of data and furthered our understanding of the genotypephenotype map, but is currently constrained by manually intensive or limited phenotype data collection. We propose an algorithm to estimate stem width, a key characteristic used for biomass potential evaluation, from 3D point cloud data collected by a robot equipped with a depth sensor in a single pass in a standard field. The algorithm applies a two step alignment to register point clouds in different frames, a Frangi filter to identify stemlike objects in the point cloud and an orientation basedmore » filter to segment out and refine individual stems for width estimation. Individually, detected stems which are split due to occlusions are merged and then registered with previously found stems in previous camera frames in order to track temporally. We then refine the estimates to produce an accurate histogram of width estimates per plot. Since the plants in each plot are genetically identical, distributions of the stem width per plot can be useful in identifying genetically superior sorghum for biofuels.« less

Magnetization dynamics of Ni80Fe20 nanowires with continuous width modulation

NASA Astrophysics Data System (ADS)

Xiong, L. L.; Kostylev, M.; Adeyeye, A. O.

2017-06-01

A systematic investigation of the magnetization reversal and the dynamic behaviors of uncoupled Ni80Fe20 nanowires (NWs) with artificial continuous width modulation is presented. In contrast with the single resonance mode observed in the homogeneous NWs from the broadband ferromagnetic resonance spectroscopy, the NWs with continuous width modulation display three to five distinct resonance modes with increasing wire thickness in the range from 5 to 70 nm due to the nonuniform demagnetizing field. The highest frequency mode and the frequency difference between the two distinct highest modes are shown to be markedly sensitive to the NW thickness. Interestingly, we found that these modes can be described in terms of the quantization of the standing spin waves due to confined varied width. In addition, the easy axis coercive field for the width modulated NWs is much higher than homogeneous NWs of the same thickness when less than 70 nm. Our experimental results are in good qualitative agreement with the micromagnetic simulations. The results may find potential applications in the design and optimization of tunable magnonic filters.

Point Cloud Based Approach to Stem Width Extraction of Sorghum

DOE PAGES

Jin, Jihui; Zakhor, Avideh

2017-01-29

A revolution in the field of genomics has produced vast amounts of data and furthered our understanding of the genotypephenotype map, but is currently constrained by manually intensive or limited phenotype data collection. We propose an algorithm to estimate stem width, a key characteristic used for biomass potential evaluation, from 3D point cloud data collected by a robot equipped with a depth sensor in a single pass in a standard field. The algorithm applies a two step alignment to register point clouds in different frames, a Frangi filter to identify stemlike objects in the point cloud and an orientation basedmore » filter to segment out and refine individual stems for width estimation. Individually, detected stems which are split due to occlusions are merged and then registered with previously found stems in previous camera frames in order to track temporally. We then refine the estimates to produce an accurate histogram of width estimates per plot. Since the plants in each plot are genetically identical, distributions of the stem width per plot can be useful in identifying genetically superior sorghum for biofuels.« less

Quantum confinement of exciton-polaritons in a structured (Al,Ga)As microcavity

NASA Astrophysics Data System (ADS)

Kuznetsov, Alexander S.; Helgers, Paul L. J.; Biermann, Klaus; Santos, Paulo V.

2018-05-01

The realization of quantum functionalities with polaritons in an all-semiconductor platform requires the control of the energy and spatial overlap of the wave functions of single polaritons trapped in potentials with precisely controlled shape and size. In this study we reach the confinement of microcavity polaritons in traps with an effective potential width down to 1 µm, produced by patterning the active region of the (Al,Ga)As microcavity between two molecular beam epitaxy growth runs. We correlate spectroscopic and structural data to show that the smooth surface relief of the patterned traps translates into a graded confinement potential characterized by lateral interfaces with a finite lateral width. We show that the structuring method is suitable for the fabrication of arrays of proximal traps, supporting hybridization between adjacent lattice sites.

Navigability Potential of Washington Rivers and Streams Determined with Hydraulic Geometry and a Geographic Information System

USGS Publications Warehouse

Magirl, Christopher S.; Olsen, Theresa D.

2009-01-01

Using discharge and channel geometry measurements from U.S. Geological Survey streamflow-gaging stations and data from a geographic information system, regression relations were derived to predict river depth, top width, and bottom width as a function of mean annual discharge for rivers in the State of Washington. A new technique also was proposed to determine bottom width in channels, a parameter that has received relatively little attention in the geomorphology literature. These regression equations, when combined with estimates of mean annual discharge available in the National Hydrography Dataset, enabled the prediction of hydraulic geometry for any stream or river in the State of Washington. Predictions of hydraulic geometry can then be compared to thresholds established by the Washington State Department of Natural Resources to determine navigability potential of rivers. Rivers with a mean annual discharge of 1,660 cubic feet per second or greater are 'probably navigable' and rivers with a mean annual discharge of 360 cubic feet per second or less are 'probably not navigable'. Variance in the dataset, however, leads to a relatively wide range of prediction intervals. For example, although the predicted hydraulic depth at a mean annual discharge of 1,660 cubic feet per second is 3.5 feet, 90-percent prediction intervals indicate that the actual hydraulic depth may range from 1.8 to 7.0 feet. This methodology does not determine navigability - a legal concept determined by federal common law - instead, this methodology is a tool for predicting channel depth, top width, and bottom width for rivers and streams in Washington.

A Novel Single-Stage Procedure for Increasing the Width of Attached Gingiva and Eliminating the Aberrant Frenal Attachment

PubMed Central

Kumar, Santhosh; Suresh P, Gautham; Anand, K. Meena

2015-01-01

Common treatment for buccal gingival recession caused by an aberrant frenal attachment includes elimination of the frenum and treatment of the gingival recession by soft tissue graft to increase the width of the attached gingiva that in turn results in root coverage. Keratinised gingival, if present in adequate amount, maintains the gingival health by protecting the marginal gingiva. This not only considers the desires of the patient but also explores the potential regenerative capacity of the tissues. This report describes a novel single-stage procedure for increasing the width of the attached gingiva and eliminating the aberrant frenal attachment.  PMID:25759860

Genome-wide association study of rice grain width variation.

PubMed

Zheng, Xiao-Ming; Gong, Tingting; Ou, Hong-Ling; Xue, Dayuan; Qiao, Weihua; Wang, Junrui; Liu, Sha; Yang, Qingwen; Olsen, Kenneth M

2018-04-01

Seed size is variable within many plant species, and understanding the underlying genetic factors can provide insights into mechanisms of local environmental adaptation. Here we make use of the abundant genomic and germplasm resources available for rice (Oryza sativa) to perform a large-scale genome-wide association study (GWAS) of grain width. Grain width varies widely within the crop and is also known to show climate-associated variation across populations of its wild progenitor. Using a filtered dataset of >1.9 million genome-wide SNPs in a sample of 570 cultivated and wild rice accessions, we performed GWAS with two complementary models, GLM and MLM. The models yielded 10 and 33 significant associations, respectively, and jointly yielded seven candidate locus regions, two of which have been previously identified. Analyses of nucleotide diversity and haplotype distributions at these loci revealed signatures of selection and patterns consistent with adaptive introgression of grain width alleles across rice variety groups. The results provide a 50% increase in the total number of rice grain width loci mapped to date and support a polygenic model whereby grain width is shaped by gene-by-environment interactions. These loci can potentially serve as candidates for studies of adaptive seed size variation in wild grass species.

Amplification of anharmonicities in multiphoton vibrational action spectra.

PubMed

Calvo, F; Parneix, P

2012-01-16

The influence of one or several infrared laser pulses on the stability of bare and argon-tagged sodium chloride clusters is investigated theoretically by a combination of computational methods involving explicit molecular dynamics and properly calibrated unimolecular rate theories. The fragmentation spectra obtained by varying the laser frequency in the far-IR range is compared to the linear absorption spectrum resulting from the dipole moment autocorrelation function. Under appropriate laser field parameters, the action spectra are found to resemble the absorption spectra quite accurately in terms of positions, line widths, and even relative intensities. However, the action spectra exhibit residual and systematic redshifts of a few percent, which are partly due to the finite spectral bandwidth but are amplified by the progressive heating by the laser. A quantitative analysis suggests that these anharmonicity effects should generally arise upon multiple photon absorption. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ultra Barrier Topsheet Film for Flexible Photovoltaics with 3M Company

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

Funkenbusch, Arnie; Ruth, Charles

2014-12-30

In this DOE sponsored program, 3M achieved the critical UBT features to enable durable flexible high efficiency modules to be produced by a range of customers who have now certified the 3M UBT and are actively developing said flexible modules. The specific objectives and accomplishments of the work under this program were; Scale-up the current Generation-1 UBT from 12” width, as made on 3M’s pilot line, to 1+meter width full-scale manufacturing, while maintaining baseline performance metrics (see table below); This objective was fully met; Validate service life of Generation-1 UBT for the 25+ year lifetime demanded by the photovoltaic market;more » Aggressive testing revealed potential failure modes in the Gen 1 UBT. Deficiencies were identified and corrective action taken in the Gen 2 UBT; Develop a Generation-2 UBT on the pilot line, targeting improved performance relative to baseline, including higher %T (percent transmission), lower water vapor transmission rate (WVTR) with targets based on what the technology needs for 25 year lifetime, proven lifetime of 25 years in solar module construction in the field, and lower cost; Testing of UBT Gen 2 under a wide range of conditions presented in this report failed to reveal any failure mode. Therefore UBT Gen 2 is known to be highly durable. 3M will continue to test towards statistically validating a 25 year lifetime under 3M funding; Transfer Generation-2 UBT from the pilot line to the full-scale manufacturing line within three years; and This objective was fully met.« less

Action potentials reliably invade axonal arbors of rat neocortical neurons

PubMed Central

Cox, Charles L.; Denk, Winfried; Tank, David W.; Svoboda, Karel

2000-01-01

Neocortical pyramidal neurons have extensive axonal arborizations that make thousands of synapses. Action potentials can invade these arbors and cause calcium influx that is required for neurotransmitter release and excitation of postsynaptic targets. Thus, the regulation of action potential invasion in axonal branches might shape the spread of excitation in cortical neural networks. To measure the reliability and extent of action potential invasion into axonal arbors, we have used two-photon excitation laser scanning microscopy to directly image action-potential-mediated calcium influx in single varicosities of layer 2/3 pyramidal neurons in acute brain slices. Our data show that single action potentials or bursts of action potentials reliably invade axonal arbors over a range of developmental ages (postnatal 10–24 days) and temperatures (24°C-30°C). Hyperpolarizing current steps preceding action potential initiation, protocols that had previously been observed to produce failures of action potential propagation in cultured preparations, were ineffective in modulating the spread of action potentials in acute slices. Our data show that action potentials reliably invade the axonal arbors of neocortical pyramidal neurons. Failures in synaptic transmission must therefore originate downstream of action potential invasion. We also explored the function of modulators that inhibit presynaptic calcium influx. Consistent with previous studies, we find that adenosine reduces action-potential-mediated calcium influx in presynaptic terminals. This reduction was observed in all terminals tested, suggesting that some modulatory systems are expressed homogeneously in most terminals of the same neuron. PMID:10931955

An Investigation of the Mechanics and Sticking Region of a One-Repetition Maximum Close-Grip Bench Press versus the Traditional Bench Press

PubMed Central

Lockie, Robert G.; Callaghan, Samuel J.; Moreno, Matthew R.; Risso, Fabrice G.; Liu, Tricia M.; Stage, Alyssa A.; Birmingham-Babauta, Samantha A.; Stokes, John J.; Giuliano, Dominic V.; Lazar, Adrina; Davis, DeShaun L.; Orjalo, Ashley J.

2017-01-01

The close-grip bench press (CGBP) is a variation of the traditional bench press (TBP) that uses a narrower grip (~95% of biacromial distance (BAD)) and has potential application for athletes performing explosive arm actions from positions where the hands are held close to the torso. Limited research has investigated CGBP mechanics compared to the TBP. Twenty-seven resistance-trained individuals completed a one-repetition maximum TBP and CGBP. The TBP was performed with the preferred grip; the CGBP with a grip width of 95% BAD. A linear position transducer measured lift distance and duration; peak and mean power, velocity, and force; distance and time when peak power occurred; and work. Pre-sticking region (PrSR), sticking region, and post-sticking region distance and duration for each lift was measured. A repeated measures ANOVA was used to derive differences between TBP and CGBP mechanics (p < 0.01); effect sizes (d) were also calculated. A greater load was lifted in the TBP, thus mean force was greater (d = 0.16–0.17). Peak power and velocity were higher in the CGBP, which had a longer PrSR distance (d = 0.49–1.32). The CGBP could emphasize power for athletes that initiate explosive upper-body actions with the hands positioned close to the torso.

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

Hermeston, Mark W.

Franklin County noxious weed management along BPA rights-of-ways, transmission structures, roads, and switches listed in Attachment 1. Attachment 1 identifies the ROW, ROW width, and ROW length of the proposed action. Includes all BPA 115kV, 230kV, and 500 kV ROWs in Franklin County, Washington. BPA proposes to clear noxious and/or unwanted low-growing vegetation in all BPA ROWs in Franklin County, Washington. In a cooperative effort, BPA, through landowners and the Franklin County Weed Control Board, plan to eradicate noxious plants and other unwanted, low-growing vegetation within the ROW width including all structures and access roads. BPA’s overall goal is tomore » eradicate all noxious and unwanted vegetation through chemical treatment and reseeding. Selective and nonselective chemical treatment using spot, local and broadcast methods. All work will be executed in accordance with the National Electrical Safety Code and BPA standards. Work is to begin in March 2002.« less

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

Hermeston, Mark W.

Benton County noxious weed management along BPA rights-of-ways, transmission structures, roads, and switches listed in Attachment 1. Attachment 1 identifies the ROW, ROW width, and ROW length of the proposed action. Includes all BPA 115kV, 230kV, 345kV and 500 kV ROWs in Benton County, Washington. BPA proposes to clear noxious and/or unwanted low-growing vegetation in all BPA ROWs in Benton County, Washington. In a cooperative effort, BPA, through landowners and the Benton County Weed Control Board, plan to eradicate noxious plants and other unwanted, low-growing vegetation within the ROW width including all structures and access roads. BPA’s overall goal ismore » to eradicate all noxious and unwanted vegetation through chemical treatment and reseeding. Selective and nonselective chemical treatment using spot, local and broadcast methods. All work will be executed in accordance with the National Electrical Safety Code and BPA standards. Work is to begin in March 2002.« less

Food deprivation and prior anoxic coma have opposite effects on the activity of a visual interneuron in the locust.

PubMed

Cross, Kevin P; Britton, Samantha; Mangulins, Rebecca; Money, Tomas G A; Robertson, R Meldrum

2017-04-01

We compared how different metabolic stressors, anoxic coma and food deprivation, affected signaling in neural tissue. We used the locust's Descending Contralateral Movement Detector (DCMD) interneuron because its large axon, high firing frequencies, and rapid conduction velocity make it energetically expensive. We exposed locusts to a 30min anoxic coma or 1day of food deprivation and found contrasting effects on signaling within the axon. After a prior anoxic coma, the DCMD fired fewer high-frequency (>200Hz) action potentials (APs) (Control: 12.4±1.6; Coma: 6.3±0.9) with a reduction in axonal conduction velocity (CV) at all frequencies (∼4-8%) when presented with a standard looming visual stimulus. Prior anoxic coma was also associated with a loss of supernormal conduction by reducing both the number of supernormal APs and the firing frequency with the highest CV. Initially, food deprivation caused a significant increase in the number of low- and high-frequency APs with no differences observed in CV. After controlling for isolation, food deprivation resulted in an increase in high-frequency APs (>200Hz: Control: 17.1±1.7; Food-deprived: 19.9±1.3) and an increase in relative conduction velocity for frequencies >150Hz (∼2%). Action potentials of food-deprived animals had a smaller half-width (Control: 0.45±0.02ms; Food-deprived: 0.40±0.01ms) and decay time (Control: 0.62±0.03ms; Food-deprived: 0.54±0.02ms). Our data indicate that the effects of metabolic stress on neural signaling can be stressor-dependent. Copyright © 2017 Elsevier Ltd. All rights reserved.

Seasonal climate signals from multiple tree ring metrics: A case study of Pinus ponderosa in the upper Columbia River Basin

NASA Astrophysics Data System (ADS)

Dannenberg, Matthew P.; Wise, Erika K.

2016-04-01

Projected changes in the seasonality of hydroclimatic regimes are likely to have important implications for water resources and terrestrial ecosystems in the U.S. Pacific Northwest. The tree ring record, which has frequently been used to position recent changes in a longer-term context, typically relies on signals embedded in the total ring width of tree rings. Additional climatic inferences at a subannual temporal scale can be made using alternative tree ring metrics such as earlywood and latewood widths and the density of tree ring latewood. Here we examine seasonal precipitation and temperature signals embedded in total ring width, earlywood width, adjusted latewood width, and blue intensity chronologies from a network of six Pinus ponderosa sites in and surrounding the upper Columbia River Basin of the U.S. Pacific Northwest. We also evaluate the potential for combining multiple tree ring metrics together in reconstructions of past cool- and warm-season precipitation. The common signal among all metrics and sites is related to warm-season precipitation. Earlywood and latewood widths differ primarily in their sensitivity to conditions in the year prior to growth. Total and earlywood widths from the lowest elevation sites also reflect cool-season moisture. Effective correlation analyses and composite-plus-scale tests suggest that combining multiple tree ring metrics together may improve reconstructions of warm-season precipitation. For cool-season precipitation, total ring width alone explains more variance than any other individual metric or combination of metrics. The composite-plus-scale tests show that variance-scaled precipitation reconstructions in the upper Columbia River Basin may be asymmetric in their ability to capture extreme events.

Relationship between red cell distribution width and early renal injury in patients with gestational diabetes mellitus.

PubMed

Cheng, Dong; Zhao, Jiangtao; Jian, Liguo; Ding, Tongbin; Liu, Shichao

2016-09-01

Previous studies found that red cell distribution width was related to adverse cardiovascular events. However, few studies reported the relationship between red cell distribution width and early-stage renal injury in pregnant women with gestational diabetes mellitus. Using a cross-sectional design, 334 pregnant women with gestational diabetes mellitus were enrolled according to the criterion of inclusion and exclusion. Demographic and clinical examination data were collected. Depended on the urine albumin, study population were divided into case group (n = 118) and control group (n = 216). Compared with control group, the case group tend to be higher red cell distribution width level (13.6 ± 0.9 vs.12.5 ± 0.6, p < 0.001). The red cell distribution width was positively associated with albuminuria creatinine ratio (r = 0.567, p < 0.001). Multiple logistic regressions showed that red cell distribution width was still associated with early-stage renal injury after adjusting for many other potential cofounders. Compared with the first quartile, the risk ratio of the second, the third and the fourth quartile were 1.38 (95%CI: 1.06-1.80), 1.57 (95%CI: 1.21-2.97), 2.71 (95%CI: 2.08-3.54), respectively. Besides, systolic blood pressure, estimated glomerular filtration rate, uric acid and blood urea nitrogen were also significantly associated with renal injury in gestational diabetes mellitus patients. The elevated red cell distribution width level might be a predictor of early-stage renal injury in pregnant women with gestational diabetes mellitus. As an easy and routine examination index, red cell distribution width may provide better clinical guidance when combined with other important indices.

[Patterns of action potential firing in cortical neurons of neonatal mice and their electrophysiological property].

PubMed

Furong, Liu; Shengtian, L I

2016-05-25

To investigate patterns of action potential firing in cortical heurons of neonatal mice and their electrophysiological properties. The passive and active membrane properties of cortical neurons from 3-d neonatal mice were observed by whole-cell patch clamp with different voltage and current mode. Three patterns of action potential firing were identified in response to depolarized current injection. The effects of action potential firing patterns on voltage-dependent inward and outward current were found. Neurons with three different firing patterns had different thresholds of depolarized current. In the morphology analysis of action potential, the three type neurons were different in rise time, duration, amplitude and threshold of the first action potential evoked by 80 pA current injection. The passive properties were similar in three patterns of action potential firing. These results indicate that newborn cortical neurons exhibit different patterns of action potential firing with different action potential parameters such as shape and threshold.

Sub-Fourier characteristics of a δ-kicked-rotor resonance.

PubMed

Talukdar, I; Shrestha, R; Summy, G S

2010-07-30

We experimentally investigate the sub-Fourier behavior of a δ-kicked-rotor resonance by performing a measurement of the fidelity or overlap of a Bose-Einstein condensate exposed to a periodically pulsed standing wave. The temporal width of the fidelity resonance peak centered at the Talbot time and zero initial momentum exhibits an inverse cube pulse number (1/N3)-dependent scaling compared to a 1/N2 dependence for the mean energy width at the same resonance. A theoretical analysis shows that for an accelerating potential the width of the resonance in acceleration space depends on 1/N3, a property which we also verify experimentally. Such a sub-Fourier effect could be useful for high precision gravity measurements.

Automated Defect and Correlation Length Analysis of Block Copolymer Thin Film Nanopatterns

PubMed Central

Murphy, Jeffrey N.; Harris, Kenneth D.; Buriak, Jillian M.

2015-01-01

Line patterns produced by lamellae- and cylinder-forming block copolymer (BCP) thin films are of widespread interest for their potential to enable nanoscale patterning over large areas. In order for such patterning methods to effectively integrate with current technologies, the resulting patterns need to have low defect densities, and be produced in a short timescale. To understand whether a given polymer or annealing method might potentially meet such challenges, it is necessary to examine the evolution of defects. Unfortunately, few tools are readily available to researchers, particularly those engaged in the synthesis and design of new polymeric systems with the potential for patterning, to measure defects in such line patterns. To this end, we present an image analysis tool, which we have developed and made available, to measure the characteristics of such patterns in an automated fashion. Additionally we apply the tool to six cylinder-forming polystyrene-block-poly(2-vinylpyridine) polymers thermally annealed to explore the relationship between the size of each polymer and measured characteristics including line period, line-width, defect density, line-edge roughness (LER), line-width roughness (LWR), and correlation length. Finally, we explore the line-edge roughness, line-width roughness, defect density, and correlation length as a function of the image area sampled to determine each in a more rigorous fashion. PMID:26207990

Electronic Structure of Helium Atom in a Quantum Dot

NASA Astrophysics Data System (ADS)

Saha, Jayanta K.; Bhattacharyya, S.; Mukherjee, T. K.

2016-03-01

Bound and resonance states of helium atom have been investigated inside a quantum dot by using explicitly correlated Hylleraas type basis set within the framework of stabilization method. To be specific, precise energy eigenvalues of bound 1sns (1Se) (n = 1-6) states and the resonance parameters i.e. positions and widths of 1Se states due to 2sns (n = 2-5) and 2pnp (n = 2-5) configurations of confined helium below N = 2 ionization threshold of He+ have been estimated. The two-parameter (Depth and Width) finite oscillator potential is used to represent the confining potential due to the quantum dot. It has been explicitly demonstrated that the electronic structural properties become sensitive functions of the dot size. It is observed from the calculations of ionization potential that the stability of an impurity ion within a quantum dot may be manipulated by varying the confinement parameters. A possibility of controlling the autoionization lifetime of doubly excited states of two-electron ions by tuning the width of the quantum cavity is also discussed here. TKM Gratefully Acknowledges Financial Support under Grant No. 37(3)/14/27/2014-BRNS from the Department of Atomic Energy, BRNS, Government of India. SB Acknowledges Financial Support under Grant No. PSW-160/14-15(ERO) from University Grants Commission, Government of India

Bounding the Higgs boson width through interferometry.

PubMed

Dixon, Lance J; Li, Ye

2013-09-13

We study the change in the diphoton-invariant-mass distribution for Higgs boson decays to two photons, due to interference between the Higgs resonance in gluon fusion and the continuum background amplitude for gg→γγ. Previously, the apparent Higgs mass was found to shift by around 100 MeV in the standard model in the leading-order approximation, which may potentially be experimentally observable. We compute the next-to-leading-order QCD corrections to the apparent mass shift, which reduce it by about 40%. The apparent mass shift may provide a way to measure, or at least bound, the Higgs boson width at the Large Hadron Collider through "interferometry." We investigate how the shift depends on the Higgs width, in a model that maintains constant Higgs boson signal yields. At Higgs widths above 30 MeV, the mass shift is over 200 MeV and increases with the square root of the width. The apparent mass shift could be measured by comparing with the ZZ* channel, where the shift is much smaller. It might be possible to measure the shift more accurately by exploiting its strong dependence on the Higgs transverse momentum.

Widths of atomic 4s and 4p vacancy states, 46 less than or equal to Z less than or equal to 50

NASA Technical Reports Server (NTRS)

Hsiungchen, M.; Crasemann, B.; Yin, L. I.; Tsang, T.; Adler, I.

1975-01-01

Auger and X-ray photoelectron spectra involving N1, N2, and N3 vacancy states of Pd, Ag, Cd, In, and Sn were measured and compared with results of free atom calculations. As previously observed in Cu and Zn Auger spectra that involve 3d-band electrons, free-atom characteristics with regard to widths and structure were found in the Ag and Cd M4-N4,5N4,5 and M5-N4,5N4,5 Auger spectra that arise from transitions of 4d-band electrons. Theoretical N1 widths computed with calculated free-atom Auger energies agree well with measurements. Theory however predicts wider N2 than N3 vacancy states (as observed for Xe), while the measured N2 and N3 widths are nearly equal to each other and to the average of the calculated N2 and N3 widths. The calculations are made difficult by the exceedingly short lifetime of some 4p vacancies and by the extreme sensitivity of super-Coster-Kronig rates, which dominate the deexcitation, to the transition energy and to the fine details of the atomic potential.

Central excitability contributes to supramaximal volitional contractions in human incomplete spinal cord injury

PubMed Central

Thompson, Christopher K; Lewek, Michael D; Jayaraman, Arun; Hornby, T George

2011-01-01

Abstract Despite greater muscle fatigue in individuals with spinal cord injury (SCI) when compared to neurologically intact subjects using neuromuscular electrical stimulation (NMES) protocols, few studies have investigated the extent of volitional fatigue in motor incomplete SCI. Using an established protocol of 20 repeated, intermittent, maximal volitional effort (MVE) contractions, we previously demonstrated that subjects with incomplete SCI unexpectedly demonstrated a 15% increase in peak knee extensor torques within the first five MVEs with minimal evidence of fatigue after 20 contraction. In the present study, we investigated potential segmental mechanisms underlying this supramaximal torque generation. Changes in twitch properties and maximum compound muscle action potentials (M-waves) were assessed prior to and following one, three and five MVEs, revealing a significant 17% increase only in maximum twitch torques after a single MVE. Despite this post-activation potentiation of the muscle, use of conventional NMES protocols to elicit repeated muscular contractions resulted in a significant decrease in evoked torque generation, suggesting limited the muscular contributions to the observed phenomenon. To evaluate potential central mechanisms underlying the augmented torques, non-linear responses to wide-pulse width (1 ms), low-intensity, variable-frequency (25–100 Hz) NMES were also tested prior to and following repeated MVEs. When variable-frequency NMES was applied following the repeated MVEs, augmented and prolonged torques were observed and accompanied by sustained quadriceps electromyographic activity often lasting >2s after stimulus termination. Such data suggest a potential contribution of elevated spinal excitability to the reserve in volitional force generation in incomplete SCI. PMID:21610138

Flower-like Na2O nanotip synthesis via femtosecond laser ablation of glass

PubMed Central

2012-01-01

The current state-of-the-art in nanotip synthesis relies on techniques that utilize elaborate precursor chemicals, catalysts, or vacuum conditions, and any combination thereof. To realize their ultimate potential, synthesized nanotips require simpler fabrication techniques that allow for control over their final nano-morphology. We present a unique, dry, catalyst-free, and ambient condition method for creating densely clustered, flower-like, sodium oxide (Na2O) nanotips with controllable tip widths. Femtosecond laser ablation of a soda-lime glass substrate at a megahertz repetition rate, with nitrogen flow, was employed to generate nanotips with base and head widths as small as 100 and 20 nm respectively, and lengths as long as 10 μm. Control of the nanotip widths was demonstrated via laser dwell time with longer dwell times producing denser clusters of thinner nanotips. Energy dispersive X-ray analysis reveals that nanotip composition is Na2O. A new formation mechanism is proposed, involving an electrostatic effect between ionized nitrogen and polar Na2O. The synthesized nanotips may potentially be used in antibacterial and hydrogen storage applications. PMID:22809176

Electroosmotic flow in a rectangular channel with variable wall zeta-potential: comparison of numerical simulation with asymptotic theory.

PubMed

Datta, Subhra; Ghosal, Sandip; Patankar, Neelesh A

2006-02-01

Electroosmotic flow in a straight micro-channel of rectangular cross-section is computed numerically for several situations where the wall zeta-potential is not constant but has a specified spatial variation. The results of the computation are compared with an earlier published asymptotic theory based on the lubrication approximation: the assumption that any axial variations take place on a long length scale compared to a characteristic channel width. The computational results are found to be in excellent agreement with the theory even when the scale of axial variations is comparable to the channel width. In the opposite limit when the wavelength of fluctuations is much shorter than the channel width, the lubrication theory fails to describe the solution either qualitatively or quantitatively. In this short wave limit the solution is well described by Ajdari's theory for electroosmotic flow between infinite parallel plates (Ajdari, A., Phys. Rev. E 1996, 53, 4996-5005.) The infinitely thin electric double layer limit is assumed in the theory as well as in the simulation.

Adsorption behaviors of supercritical Lennard-Jones fluid in slit-like pores.

PubMed

Li, Yingfeng; Cui, Mengqi; Peng, Bo; Qin, Mingde

2018-05-18

Understanding the adsorption behaviors of supercritical fluid in confined space is pivotal for coupling the supercritical technology and the membrane separation technology. Based on grand canonical Monte Carlo simulations, the adsorption behaviors of a Lennard-Jones (LJ) fluid in slit-like pores at reduced temperatures over the critical temperature, T c *  = 1.312, are investigated; and impacts of the wall-fluid interactions, the pore width, and the temperature are taken into account. It is found that even if under supercritical conditions, the LJ fluid can undergo a "vapor-liquid phase transition" in confined space, i.e., the adsorption density undergoes a sudden increase with the bulk density. A greater wall-fluid attractive potential, a smaller pore width, and a lower temperature will bring about a stronger confinement effect. Besides, the adsorption pressure reaches a local minimum when the bulk density equals to a certain value, independent of the wall-fluid potential or pore width. The insights in this work have both practical and theoretical significances. Copyright © 2018 Elsevier Inc. All rights reserved.

All Features Great and Small-the Potential Roles of the Baculum and Penile Spines in Mammals.

PubMed

Orr, Teri J; Brennan, Patricia L R

2016-10-01

Mammalian penises are morphologically diverse, including a highly variable and taxonomically informative baculum (os penis), and variable penile spines, both of which are possessed by many-but not all-species. To understand the evolution of genital morphologies, as well as the potential role of both the baculum, and penile spines that directly interact with female reproductive tract, we undertook a comparative study of male penile spines and their relationship with the baculum across all mammalian orders. Specifically, we investigated several factors that may explain the presence or absence of penile spines in mammals, including mating system, risk of sperm competition, female reproductive physiology, presence and width of the baculum, and phylogenetic history. We observed that the presence of both the baculum and penile spines is correlated with residual testes size, suggesting a potential role in sexual selection for these traits. We found no association between the presence of spines and mating system, or with the presence/width of the baculum, although relative testes mass was marginally associated with baculum width. We found no relationship between baculum presence or width and mating system. We also noted that spines presence or absence have an order-level distribution, and clear phylogenetic patterns of distribution across mammals. It is likely that spine morphology and distribution, not just presence, play an important role in genital evolution in mammals, but these features are poorly described in most groups. Quantitative data collection in most mammalian taxa would be useful to further elucidate the evolution of the complex genital morphology of this group. © The Author 2016. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology. All rights reserved. For permissions please email: journals.permissions@oup.com.

Dipole-dipole interaction in cavity QED: The weak-coupling, nondegenerate regime

NASA Astrophysics Data System (ADS)

Donaire, M.; Muñoz-Castañeda, J. M.; Nieto, L. M.

2017-10-01

We compute the energies of the interaction between two atoms placed in the middle of a perfectly reflecting planar cavity, in the weak-coupling nondegenerate regime. Both inhibition and enhancement of the interactions can be obtained by varying the size of the cavity. We derive exact expressions for the dyadic Green's function of the cavity field which mediates the interactions and apply time-dependent quantum perturbation theory in the adiabatic approximation. We provide explicit expressions for the van der Waals potentials of two polarizable atomic dipoles and the electrostatic potential of two induced dipoles. We compute the van der Waals potentials in three different scenarios: two atoms in their ground states, two atoms excited, and two dissimilar atoms with one of them excited. In addition, we calculate the phase-shift rate of the two-atom wave function in each case. The effect of the two-dimensional confinement of the electromagnetic field on the dipole-dipole interactions is analyzed. This effect depends on the atomic polarization. For dipole moments oriented parallel to the cavity plates, both the electrostatic and the van der Waals interactions are exponentially suppressed for values of the cavity width much less than the interatomic distance, whereas for values of the width close to the interatomic distance, the strength of both interactions is higher than their values in the absence of cavity. For dipole moments perpendicular to the plates, the strength of the van der Waals interaction decreases for values of the cavity width close to the interatomic distance, while it increases for values of the width much less than the interatomic distance with respect to its strength in the absence of cavity. We illustrate these effects by computing the dipole-dipole interactions between two alkali atoms in circular Rydberg states.

Role of action potential configuration and the contribution of Ca2+ and K+ currents to isoprenaline-induced changes in canine ventricular cells

PubMed Central

Szentandrássy, N; Farkas, V; Bárándi, L; Hegyi, B; Ruzsnavszky, F; Horváth, B; Bányász, T; Magyar, J; Márton, I; Nánási, PP

2012-01-01

BACKGROUND AND PURPOSE Although isoprenaline (ISO) is known to activate several ion currents in mammalian myocardium, little is known about the role of action potential morphology in the ISO-induced changes in ion currents. Therefore, the effects of ISO on action potential configuration, L-type Ca2+ current (ICa), slow delayed rectifier K+ current (IKs) and fast delayed rectifier K+ current (IKr) were studied and compared in a frequency-dependent manner using canine isolated ventricular myocytes from various transmural locations. EXPERIMENTAL APPROACH Action potentials were recorded with conventional sharp microelectrodes; ion currents were measured using conventional and action potential voltage clamp techniques. KEY RESULTS In myocytes displaying a spike-and-dome action potential configuration (epicardial and midmyocardial cells), ISO caused reversible shortening of action potentials accompanied by elevation of the plateau. ISO-induced action potential shortening was absent in endocardial cells and in myocytes pretreated with 4-aminopyridine. Application of the IKr blocker E-4031 failed to modify the ISO effect, while action potentials were lengthened by ISO in the presence of the IKs blocker HMR-1556. Both action potential shortening and elevation of the plateau were prevented by pretreatment with the ICa blocker nisoldipine. Action potential voltage clamp experiments revealed a prominent slowly inactivating ICa followed by a rise in IKs, both currents increased with increasing the cycle length. CONCLUSIONS AND IMPLICATIONS The effect of ISO in canine ventricular cells depends critically on action potential configuration, and the ISO-induced activation of IKs– but not IKr– may be responsible for the observed shortening of action potentials. PMID:22563726

Role of action potential configuration and the contribution of C²⁺a and K⁺ currents to isoprenaline-induced changes in canine ventricular cells.

PubMed

Szentandrássy, N; Farkas, V; Bárándi, L; Hegyi, B; Ruzsnavszky, F; Horváth, B; Bányász, T; Magyar, J; Márton, I; Nánási, P P

2012-10-01

Although isoprenaline (ISO) is known to activate several ion currents in mammalian myocardium, little is known about the role of action potential morphology in the ISO-induced changes in ion currents. Therefore, the effects of ISO on action potential configuration, L-type Ca²⁺ current (I(Ca)), slow delayed rectifier K⁺ current (I(Ks)) and fast delayed rectifier K⁺ current (I(Kr)) were studied and compared in a frequency-dependent manner using canine isolated ventricular myocytes from various transmural locations. Action potentials were recorded with conventional sharp microelectrodes; ion currents were measured using conventional and action potential voltage clamp techniques. In myocytes displaying a spike-and-dome action potential configuration (epicardial and midmyocardial cells), ISO caused reversible shortening of action potentials accompanied by elevation of the plateau. ISO-induced action potential shortening was absent in endocardial cells and in myocytes pretreated with 4-aminopyridine. Application of the I(Kr) blocker E-4031 failed to modify the ISO effect, while action potentials were lengthened by ISO in the presence of the I(Ks) blocker HMR-1556. Both action potential shortening and elevation of the plateau were prevented by pretreatment with the I(Ca) blocker nisoldipine. Action potential voltage clamp experiments revealed a prominent slowly inactivating I(Ca) followed by a rise in I(Ks) , both currents increased with increasing the cycle length. The effect of ISO in canine ventricular cells depends critically on action potential configuration, and the ISO-induced activation of I(Ks) - but not I(Kr) - may be responsible for the observed shortening of action potentials. © 2012 The Authors. British Journal of Pharmacology © 2012 The British Pharmacological Society.

Nanocrystals with linear and branched topology

DOEpatents

Alivisatos, A. Paul; Milliron, Delia; Manna, Liberato; Hughes, Steven M.

2007-12-04

Disclosed herein are nanostructures comprising distinct dots and rods coupled through potential barriers of tuneable height and width, and arranged in three dimensional space at well defined angles and distances. Such control allows investigation of potential applications ranging from quantum information processing to artificial photosynthesis.

Width-Dependent Band Gap in Armchair Graphene Nanoribbons Reveals Fermi Level Pinning on Au(111)

PubMed Central

2017-01-01

We report the energy level alignment evolution of valence and conduction bands of armchair-oriented graphene nanoribbons (aGNR) as their band gap shrinks with increasing width. We use 4,4″-dibromo-para-terphenyl as the molecular precursor on Au(111) to form extended poly-para-phenylene nanowires, which can subsequently be fused sideways to form atomically precise aGNRs of varying widths. We measure the frontier bands by means of scanning tunneling spectroscopy, corroborating that the nanoribbon’s band gap is inversely proportional to their width. Interestingly, valence bands are found to show Fermi level pinning as the band gap decreases below a threshold value around 1.7 eV. Such behavior is of critical importance to understand the properties of potential contacts in GNR-based devices. Our measurements further reveal a particularly interesting system for studying Fermi level pinning by modifying an adsorbate’s band gap while maintaining an almost unchanged interface chemistry defined by substrate and adsorbate. PMID:29049879

Manufacturing the Horns of Dilemma: A Theory of Operational Initiative

DTIC Science & Technology

2015-05-21

Tsung offers insight, and offers the second compelling component to a theory of initiative. According to Mao, “Freedom of action is the very life of...unphased advances that might lead to entrapment by a numerically superior foe.”81 By conducting coordinated operations across the width of its front...doubtful whether firepower-based operations alone can in all cases unsettle an enemy and cause it to experience distress and defeat to the extent that it

Characteristics of action potentials and their underlying outward currents in rat taste receptor cells.

PubMed

Chen, Y; Sun, X D; Herness, S

1996-02-01

1. Taste receptor cells produce action potentials as a result of transduction mechanisms that occur when these cells are stimulated with tastants. These action potentials are thought to be key signaling events in relaying information to the central nervous system. We explored the ionic basis of action potentials from dissociated posterior rat taste cells using the patch-clamp recording technique in both voltage-clamp and current-clamp modes. 2. Action potentials were evoked by intracellular injection of depolarizing current pulses from a holding potential of -80 mV. The threshold potential for firing of action potentials was approximately -35 mV; the input resistance of these cells averaged 6.9 G omega. With long depolarizing pulses, two or three action potentials could be elicited with successive attenuation of the spike height. Afterhyperpolarizations were observed often. 3. Both sodium and calcium currents contribute to depolarizing phases of the action potential. Action potentials were blocked completely in the presence of the sodium channel blocker tetrodotoxin. Calcium contributions could be visualized as prolonged calcium plateaus when repolarizing potassium currents were blocked and barium was used as a charge carrier. 4. Outward currents were composed of sustained delayed rectifier current, transient potassium current, and calcium-activated potassium current. Transient and sustained potassium currents activated close to -30 mV and increased monotonically with further depolarization. Up to half the outward current inactivated with decay constants on the order of seconds. Sustained and transient currents displayed steep voltage dependence in conductance and inactivation curves. Half inactivation occurred at -20 +/- 3.1 mV (mean +/- SE) with a decrease of 11.2 +/- 0.5 mV per e-fold. Half maximal conductance occurred at 3.6 +/- 1.8 mV and increased 12.2 +/- 0.6 mV per e-fold. Calcium-activated potassium current was evidenced by application of apamin and the use of calcium-free bathing solution. It was most obvious at more depolarized holding potentials that inactivated much of the transient and sustained outward currents. 5. Potassium currents contribute to both the repolarization and afterhyperpolarization phases of the action potential. These currents were blocked by bath application of tetraethylammonium, which also substantially broadened the action potential. Application of 4-aminopyridine was able to selectively block transient potassium currents without affecting sustained currents. This also broadened the action potential as well as eliminated the afterhyperpolarization. 6. A second type of action potential was observed that differed in duration. These slow action potentials had t1/2 durations of 9.6 ms compared with 1.4 ms for fast action potentials. Input resistances of the two groups were indistinguishable. Approximately one-fourth of the cells eliciting action potentials were of the slow type. 7. Cells eliciting fast action potentials had large outward currents capable of producing a quick repolarization, whereas cells with slow action potentials had small outward currents by comparison. The average values of fast cells were 2,563 pA and 1.4 ms compared with 373 pA and 9.6 ms for slow cells. Current and duration values were related exponentially. No significant difference was noted for inward currents. 8. These results suggest that many taste receptor cells conduct action potentials, which may be classified broadly into two groups on the basis of action potential duration and potassium current magnitude. These groups may be related to cell turnover. The physiological role of action potentials remains to be elucidated but may be important for communication within the taste bud as well as to the afferent nerve.

The study of laser pulse width on efficiency of Ho:YAG laser lithotripsy

NASA Astrophysics Data System (ADS)

Zhang, Jian J.; Rutherford, Jonathan; Solomon, Metasebya; Cheng, Brian; Xuan, Jason R.; Gong, Jason; Yu, Honggang; Xia, Michael; Yang, Xirong; Hasenberg, Thomas; Curran, Sean

2017-02-01

When treating ureteral calculi, retropulsion can be reduced by using a longer pulse width without compromising fragmentation efficiency (from the studies by David S. Finley et al. and Hyun Wook Kang et al.). In this study, a lab build Ho:YAG laser was used as the laser pulse source, with pulse energy from 0.2J up to 3.0 J, and electrical pump pulse width from 150 us up to 1000 us. The fiber used in the investigation is a 365 μm core diameter fiber, SureFlexTM, Model S-LLF365. Plaster of Paris calculus phantoms were ablated at different energy levels (0.2, 0.5, 1, 2, 3J) and with different number of pulses (1, 3, 10) using different electrical pump pulse width (333, 667, 1000 μs). The dynamics of the recoil action of a calculus phantom was monitored using a high-speed camera with frame rate up to 1 million frame per second (Photron Fastcam SA5); and the laser-induced craters were evaluated with a 3-D digital microscope (Keyence VHX-900F). A design of experiment software (DesignExpert-10, Minneapolis, MN, USA) is used in this study for the best fit of surface response on volume of dusting and retropulsion amplitude. The numerical formulas for the response surfaces of dusting speed and retropulsion amplitude are generated. More detailed investigation on the optimal conditions for dusting of other kinds of stone samples and the fiber size effect will be conducted as a future study.

Anthropometric growth study of the ear in a Chinese population.

PubMed

Zhao, Shichun; Li, Dianguo; Liu, Zhenzhong; Wang, Yibiao; Liu, Lei; Jiang, Duyin; Pan, Bo

2018-04-01

A large number of anthropometric studies of the auricle have been reported in different nations, but little data were available in the Chinese population. The aim of this study was to analyze growth changes in the ear by measuring the width and length of ears in a Chinese population. A total of 480 participants were enrolled and classified into 1-, 3-, 5-, 7-, 9-, 12-, 14-, and 18-year groups (half were boys and half were girls in each group). Ear length, ear width, body weight, and body length were measured and recorded; ear index was calculated according to ear length and ear width. The growth of auricle and differences between genders were analyzed. Growth of ear in relation to body height and weight and the degree of emphasis on the length and width of the auricle were also analyzed. Ear length and width increased with age. Ear length achieved its mature size in both 14-year-old males and females. Ear width reached its mature size in males at 7 years and in females at 5 years. Different trends of ear index were shown between males and females. People in this population paid more attention to the length than the width of the auricle. The data indicated that ear development followed increase in age. There were gender and ethnic difference in the development of ear. These results may have potential implications for the diagnosis of congenital malformations, syndromes, and planning of ear reconstruction surgery. Copyright © 2017 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.

Study of modulation property to incident laser by surface micro-defects on KH2PO4 crystal

NASA Astrophysics Data System (ADS)

Chen, Ming-Jun; Cheng, Jian; Li, Ming-Quan; Xiao, Yong

2012-06-01

KH2PO4 crystal is a crucial optical component of inertial confinement fusion. Modulation of an incident laser by surface micro-defects will induce the growth of surface damage, which largely restricts the enhancement of the laser induced damage threshold. The modulation of an incident laser by using different kinds of surface defects are simulated by employing the three-dimensional finite-difference time-domain method. The results indicate that after the modulation of surface defects, the light intensity distribution inside the crystal is badly distorted, with the light intensity enhanced symmetrically. The relations between modulation properties and defect geometries (e.g., width, morphology, and depth of defects) are quite different for different defects. The modulation action is most obvious when the width of surface defects reaches 1.064 μm. For defects with smooth morphology, such as spherical pits, the degree of modulation is the smallest and the light intensity distribution seems relatively uniform. The degree of modulation increases rapidly with the increase of the depth of surface defects and becomes stable when the depth reaches a critical value. The critical depth is 1.064 μm for cuboid pits and radial cracks, while for ellipsoidal pits the value depends on both the width and the length of the defects.

[Dependence of anti-inflammatory effects of high peak-power pulsed electromagnetic radiation of extremely high frequency on exposure parameters].

PubMed

Gapeev, A B; Mikhaĭlik, E N; Rubanik, A V; Cheremis, N K

2007-01-01

A pronounced anti-inflammatory effect of high peak-power pulsed electromagnetic radiation of extremely high frequency was shown for the first time in a model of zymosan-induced footpad edema in mice. Exposure to radiation of specific parameters (35, 27 GHz, peak power 20 kW, pulse widths 400-600 ns, pulse repetition frequency 5-500 Hz) decreased the exudative edema and local hyperthermia by 20% compared to the control. The kinetics and the magnitude of the anti-inflammatory effect were comparable with those induced by sodium diclofenac at a dose of 3 mg/kg. It was found that the anti-inflammatory effect linearly increased with increasing pulse width at a fixed pulse repetition frequency and had threshold dependence on the average incident power density of the radiation at a fixed pulse width. When animals were whole-body exposed in the far-field zone of radiator, the optimal exposure duration was 20 min. Increasing the average incident power density upon local exposure of the inflamed paw accelerated both the development of the anti-inflammatory effect and the reactivation time. The results obtained will undoubtedly be of great importance in the hygienic standardization of pulsed electromagnetic radiation and in further studies of the mechanisms of its biological action.

Velocity-induced heavy quarkonium dissociation using the gauge-gravity correspondence

NASA Astrophysics Data System (ADS)

Patra, Binoy Krishna; Khanchandani, Himanshu; Thakur, Lata

2015-10-01

Using the gauge-gravity duality, we have obtained the potential between a heavy quark and an antiquark pair, which is moving perpendicular to the direction of orientation, in a strongly coupled supersymmetric hot plasma. For this purpose we work on a metric in the gravity side, viz. Ouyang-Klebanov-Strassler black hole geometry, of which the dual in the gauge theory side runs with the energy and hence proves to be a better background for thermal QCD. The potential obtained has a confining term both in the vacuum and in a medium, in addition to the Coulomb term alone, usually reported in the literature. As the velocity of the pair is increased, the screening of the potential gets weakened, which may be understood by the decrease of the effective temperature with the increase of the velocity. The crucial observation of our work is that, beyond a critical separation of the heavy quark pair, the potential develops an imaginary part which is nowadays understood to be the main source of dissociation. The imaginary part is found to vanish at small r , thus agreeing with the perturbative result. Finally we have estimated the thermal width for the ground and first excited states and found that nonzero rapidities lead to an increase of thermal width. This implies that the moving quarkonia dissociate more easily than the static ones, which agrees with other calculations. However, the width in our case is larger than other calculations due to the presence of confining terms.

State and location dependence of action potential metabolic cost in cortical pyramidal neurons.

PubMed

Hallermann, Stefan; de Kock, Christiaan P J; Stuart, Greg J; Kole, Maarten H P

2012-06-03

Action potential generation and conduction requires large quantities of energy to restore Na(+) and K(+) ion gradients. We investigated the subcellular location and voltage dependence of this metabolic cost in rat neocortical pyramidal neurons. Using Na(+)/K(+) charge overlap as a measure of action potential energy efficiency, we found that action potential initiation in the axon initial segment (AIS) and forward propagation into the axon were energetically inefficient, depending on the resting membrane potential. In contrast, action potential backpropagation into dendrites was efficient. Computer simulations predicted that, although the AIS and nodes of Ranvier had the highest metabolic cost per membrane area, action potential backpropagation into the dendrites and forward propagation into axon collaterals dominated energy consumption in cortical pyramidal neurons. Finally, we found that the high metabolic cost of action potential initiation and propagation down the axon is a trade-off between energy minimization and maximization of the conduction reliability of high-frequency action potentials.

Are there any narrow K--nuclear states?

NASA Astrophysics Data System (ADS)

Hrtánková, Jaroslava; Mareš, Jiří

2017-07-01

We performed self-consistent calculations of K--nuclear quasi-bound states using a single-nucleon K- optical potential derived from chiral meson-baryon coupled-channel interaction models, supplemented by a phenomenological K- multinucleon potential introduced recently to achieve good fits to kaonic atom data [1]. Our calculations show that the effect of K- multinucleon interactions on K- widths in nuclei is decisive. The resulting widths are considerably larger than corresponding binding energies. Moreover, when the density dependence of the K--multinucleon interactions derived in the fits of kaonic atoms is extended to the nuclear interior, the only two models acceptable after imposing as additional constraint the single-nucleon fraction of K- absorption at rest do not yield any kaonic nuclear bound state in majority of considered nuclei.

Simple Map in Action-Angle Coordinates.

NASA Astrophysics Data System (ADS)

Kerwin, Olivia; Punjabi, Alkesh; Ali, Halima

2008-04-01

The simple map is the simplest map that has the topology of a divertor tokamak. The simple map has three canonical representations: (i) the natural coordinates - toroidal magnetic flux and poloidal angle (ψ,θ), (ii) the physical coordinates - the physical variables (R,Z) or (X,Y), and (iii) the action-angle coordinates - (J,θ) or magnetic coordinates (ψ, θ). All three are canonical coordinates for field lines. The simple map in the (X,Y) representation has been studied extensively ^1, 2. Here we analytically calculate the action-angle coordinates and safety factor q for the simple map. We construct the equilibrium generating function for the simple map in action-angle coordinates. We derive the simple map in action-angle representation, and calculate the stochastic broadening of the ideal separatrix due to topological noise in action-angle representation. We also show how the geometric effects such as elongation, the height, and width of the ideal separatrix surface can be investigated using a slight modification of the simple map in action-angle representation. This work is supported by the following grants US Department of Energy - OFES DE-FG02-01ER54624 and DE-FG02-04ER54793 and National Science Foundation - HRD-0630372 and 0411394. [1] A. Punjabi, H. Ali, T. Evans, and A. Boozer, Phys Lett A, 364 140-145 (2007). [2] A. Punjabi, A. Verma, and A. Boozer, Phys.Rev. Lett. 69, 3322 (1992).

Voltage-gated sodium channel expression and action potential generation in differentiated NG108-15 cells.

PubMed

Liu, Jinxu; Tu, Huiyin; Zhang, Dongze; Zheng, Hong; Li, Yu-Long

2012-10-25

The generation of action potential is required for stimulus-evoked neurotransmitter release in most neurons. Although various voltage-gated ion channels are involved in action potential production, the initiation of the action potential is mainly mediated by voltage-gated Na+ channels. In the present study, differentiation-induced changes of mRNA and protein expression of Na+ channels, Na+ currents, and cell membrane excitability were investigated in NG108-15 cells. Whole-cell patch-clamp results showed that differentiation (9 days) didn't change cell membrane excitability, compared to undifferentiated state. But differentiation (21 days) induced the action potential generation in 45.5% of NG108-15 cells (25/55 cells). In 9-day-differentiated cells, Na+ currents were mildly increased, which was also found in 21-day differentiated cells without action potential. In 21-day differentiated cells with action potential, Na+ currents were significantly enhanced. Western blot data showed that the expression of Na+ channels was increased with differentiated-time dependent manner. Single-cell real-time PCR data demonstrated that the expression of Na+ channel mRNA was increased by 21 days of differentiation in NG108-15 cells. More importantly, the mRNA level of Na+ channels in cells with action potential was higher than that in cells without action potential. Differentiation induces expression of voltage-gated Na+ channels and action potential generation in NG108-15 cells. A high level of the Na+ channel density is required for differentiation-triggered action potential generation.

Physical and chemical changes in the foreshore of an estuarine beach: Implications for viability and development of horseshoe crab Limulus polyphemus eggs

USGS Publications Warehouse

Jackson, N.L.; Smith, D.R.; Nordstrom, K.F.

2008-01-01

Knowledge of conditions that favor development of eggs is important for management of species whose population growth is sensitive to early life history survival. Viability and development of the eggs of horseshoe crabs Limulus polyphemus on a sand and gravel beach were evaluated using data gathered on Delaware Bay, USA, from 18 May to 19 June 2004. Eggs were transplanted to pouches and buried in the foreshore for up to 6 wk. Viability and developmental stage were estimated as a function of oxygen and temperature gradients across the foreshore. These gradients were related to the characteristics of the intertidal foreshore sediments, beach water table changes, and frequency of inundation due to tide and swash/backwash processes. Results demonstrate the importance of interstitial temperature for development to larvae and the passive role of sediment characteristics on moisture retention and temperature. Percentage of eggs remaining in egg stage was similar across the foreshore, but more eggs developed to embryos at 0.45 of foreshore width, where moisture and gravel content were greater and interstitial temperature was lower. More eggs developed to larvae at 0.60 and 0.75 of foreshore width, where moisture and gravel content were less but interstitial temperature was higher. The beach above 0.75 of foreshore width came under the influence of wave action or full tidal inundation only during high wave heights or spring tides, and pouches at 0.75 of foreshore width were inundated only 19% of the time. Periodic wetting at this elevation did not reduce overall viability of the eggs. High wave energy events resulted in sediment activation depths to pouches at 0.30 of foreshore width, where loss of eggs due to wave activation was the most important control on the development of eggs. ?? Inter-Research 2008.

The Waist Width of Skis Influences the Kinematics of the Knee Joint in Alpine Skiing

PubMed Central

Zorko, Martin; Nemec, Bojan; Babič, Jan; Lešnik, Blaz; Supej, Matej

2015-01-01

Recently alpine skis with a wider waist width, which medially shifts the contact between the ski edge and the snow while turning, have appeared on the market. The aim of this study was to determine the knee joint kinematics during turning while using skis of different waist widths (65mm, 88mm, 110mm). Six highly skilled skiers performed ten turns on a predefined course (similar to a giant slalom course). The relation of femur and tibia in the sagital, frontal and coronal planes was captured by using an inertial motion capture suit, and Global Navigation Satellite System was used to determine the skiers’ trajectories. With respect of the outer ski the knee joint flexion, internal rotation and abduction significantly decreased with the increase of the ski waist width for the greatest part of the ski turn. The greatest abduction with the narrow ski and the greatest external rotation (lowest internal rotation) with the wide ski are probably the reflection of two different strategies of coping the biomechanical requirements in the ski turn. These changes in knee kinematics were most probably due to an active adaptation of the skier to the changed biomechanical conditions using wider skis. The results indicated that using skis with large waist widths on hard, frozen surfaces could bring the knee joint unfavorably closer to the end of the range of motion in transversal and frontal planes as well as potentially increasing the risk of degenerative knee injuries. Key points The change in the skis’ waist width caused a change in the knee joint movement strategies, which had a tendency to adapt the skier to different biomechanical conditions. The use of wider skis or, in particular, skis with a large waist width, on a hard or frozen surface, could unfavourably bring the knee joint closer to the end of range of motion in transversal and frontal planes as well as may potentially increase the risk of degenerative knee injuries. The overall results of the abduction and internal rotation in respect to turn radii and ground reaction forces indicated that the knee joint movements are likely one of the key points in alpine skiing techniques. However, the skiing equipment used can still significantly influence the movement strategy. PMID:26336348

Kinematic measurement from panned cinematography.

PubMed

Gervais, P; Bedingfield, E W; Wronko, C; Kollias, I; Marchiori, G; Kuntz, J; Way, N; Kuiper, D

1989-06-01

Traditional 2-D cinematography has used a stationary camera with its optical axis perpendicular to the plane of motion. This method has constrained the size of the object plane or has introduced potential errors from a small subject image size with large object field widths. The purpose of this study was to assess a panning technique that could overcome the inherent limitations of small object field widths, small object image sizes and limited movement samples. The proposed technique used a series of reference targets in the object field that provided the necessary scales and origin translations. A 102 m object field was panned. Comparisons between criterion distances and film measured distances for field widths of 46 m and 22 m resulted in absolute mean differences that were comparable to that of the traditional method.

Spin-resolved conductance of Dirac electrons through multibarrier arrays

NASA Astrophysics Data System (ADS)

Dahal, Dipendra; Gumbs, Godfrey; Iurov, Andrii

We use a transfer matrix method to calculate the transmission coefficient of Dirac electrons through an arbitrary number of square potential barrier in gapped monolayer graphene(MLG) and bilayer graphene (BLG). The widths of barriers may not be chosen equal. The shift in the angle of incidence and the width of the barrier required for resonance are investigated numerically for both MLG and BLG. We compare the effects due to energy gap on these two transmission coefficient for each of these two structures (MLG and BLG). We present our results as functions of barrier width, height as well as incoming electron energy as well as band gap and examine the conditions for which perfect reflection or transmission occurs. Our transmission data are further used to calculate conductivity.

Effects of premature stimulation on HERG K+ channels

PubMed Central

Lu, Yu; Mahaut-Smith, Martyn P; Varghese, Anthony; Huang, Christopher L-H; Kemp, Paul R; Vandenberg, Jamie I

2001-01-01

The unusual kinetics of human ether-à-go-go-related gene (HERG) K+ channels are consistent with a role in the suppression of arrhythmias initiated by premature beats. Action potential clamp protocols were used to investigate the effect of premature stimulation on HERG K+ channels, transfected in Chinese hamster ovary cells, at 37 °C. HERG K+ channel currents peaked during the terminal repolarization phase of normally paced action potential waveforms. However, the magnitude of the current and the time point at which conductance was maximal depended on the type of action potential waveform used (epicardial, endocardial, Purkinje fibre or atrial). HERG K+ channel currents recorded during premature action potentials consisted of an early transient outward current followed by a sustained outward current. The magnitude of the transient current component showed a biphasic dependence on the coupling interval between the normally paced and premature action potentials and was maximal at a coupling interval equivalent to 90% repolarization (APD90) for ventricular action potentials. The largest transient current response occurred at shorter coupling intervals for Purkinje fibre (APD90– 20 ms) and atrial (APD90– 30 ms) action potentials. The magnitude of the sustained current response following premature stimulation was similar to that recorded during the first action potential for ventricular action potential waveforms. However, for Purkinje and atrial action potentials the sustained current response was significantly larger during the premature action potential than during the normally paced action potential. A Markov model that included three closed states, one open and one inactivated state with transitions permitted between the pre-open closed state and the inactivated state, successfully reproduced our results for the effects of premature stimuli, both during square pulse and action potential clamp waveforms. These properties of HERG K+ channels may help to suppress arrhythmias initiated by early afterdepolarizations and premature beats in the ventricles, Purkinje fibres or atria. PMID:11744759

The delayed rectifier, IKI, is the major conductance in type I vestibular hair cells across vestibular end organs

NASA Technical Reports Server (NTRS)

Ricci, A. J.; Rennie, K. J.; Correia, M. J.

1996-01-01

Hair cells were dissociated from the semicircular canal, utricle, lagena and saccule of white king pigeons. Type I hair cells were identified morphologically based on the ratios of neck width to cuticular plate width (NPR < 0.72) as well as neck width to cell body width (NBR < 0.64). The perforated patch variant of the whole-cell recording technique was used to measure electrical properties from type I hair cells. In voltage-clamp, the membrane properties of all identified type I cells were dominated by a predominantly outward potassium current, previously characterized in semicircular canal as IKI. Zero-current potential, activation, deactivation, slope conductance, pharmacologic and steady-state properties of the complex currents were not statistically different between type I hair cells of different vestibular end organs. The voltage dependence causes a significant proportion of this conductance to be active about the cell's zero-current potential. The first report of the whole-cell activation kinetics of the conductance is presented, showing a voltage dependence that could be best fit by an equation for a single exponential. Results presented here are the first data from pigeon dissociated type I hair cells from utricle, saccule and lagena suggesting that the basolateral conductances of a morphologically identified population of type I hair cells are conserved between functionally different vestibular end organs; the major conductance being a delayed rectifier characterized previously in semicircular canal hair cells as IKI.

Scenario Studies on Effects of Soil Infiltration Rates, Land Slope, and Furrow Irrigation Characteristics on Furrow Irrigation-Induced Erosion.

PubMed

Dibal, Jibrin M; Ramalan, A A; Mudiare, O J; Igbadun, H E

2014-01-01

Furrow irrigation proceeds under several soil-water-furrow hydraulics interaction dynamics. The soil erosion consequences from such interactions in furrow irrigation in Samaru had remained uncertain. A furrow irrigation-induced erosion (FIIE) model was used to simulate the potential severity of soil erosion in irrigated furrows due to interactive effects of infiltration rates, land slope, and some furrow irrigation characteristics under different scenarios. The furrow irrigation characteristics considered were furrow lengths, widths, and stream sizes. The model itself was developed using the dimensional analysis approach. The scenarios studied were the interactive effects of furrow lengths, furrow widths, and slopes steepness; infiltration rates and furrow lengths; and stream sizes, furrow lengths, and slopes steepness on potential furrow irrigation-induced erosion, respectively. The severity of FIIE was found to relate somewhat linearly with slope and stream size, and inversely with furrow lengths and furrow width. The worst soil erosion (378.05 t/ha/yr) was found as a result of the interactive effects of 0.65 m furrow width, 50 m furrow length, and 0.25% slope steepness; and the least soil erosion (0.013 t/ha/yr) was induced by the combined effects of 0.5 l/s, 200 m furrow length, and 0.05% slope steepness. Evidently considering longer furrows in furrow irrigation designs would be a better alternative of averting excessive FIIE.

Final Environmental Assessment for Wildlife Control Actions at Williams Lake, Buckley Air Force Base, Colorado

DTIC Science & Technology

2012-06-01

Reservoir Quincy Reservoir A U R O R AD E N V E R 6th Avenue P eñ a B lv d. Denver International Airport Aurora Airport Centennial Airport N 0...of the Continental Divide. The Denver Basin is a structural depression that is 300 miles long and 200 miles wide and was formed about 67 million...hydrologic analysis: Basin contributing drainage area Width of the subwatershed Subwatershed slope Percent Imperviousness Depression storage

Electrophysiology of neurones of the inferior mesenteric ganglion of the cat.

PubMed Central

Julé, Y; Szurszewski, J H

1983-01-01

Intracellular recordings were obtained from cells in vitro in the inferior mesenteric ganglia of the cat. Neurones could be classified into three types: non-spontaneous, irregular discharging and regular discharging neurones. Non-spontaneous neurones had a stable resting membrane potential and responded with action potentials to indirect preganglionic nerve stimulation and to intracellular injection of depolarizing current. Irregular discharging neurones were characterized by a discharge of excitatory post-synaptic potentials (e.p.s.p.s.) which sometimes gave rise to action potentials. This activity was abolished by hexamethonium bromide, chlorisondamine and d-tubocurarine chloride. Tetrodotoxin and a low Ca2+ -high Mg2+ solution also blocked on-going activity in irregular discharging neurones. Regular discharging neurones were characterized by a rhythmic discharge of action potentials. Each action potential was preceded by a gradual depolarization of the intracellularly recorded membrane potential. Intracellular injection of hyperpolarizing current abolished the regular discharge of action potential. No synaptic potentials were observed during hyperpolarization of the membrane potential. Nicotinic, muscarinic and adrenergic receptor blocking drugs did not modify the discharge of action potentials in regular discharging neurones. A low Ca2+ -high Mg2+ solution also had no effect on the regular discharge of action potentials. Interpolation of an action potential between spontaneous action potentials in regular discharging neurones reset the rhythm of discharge. It is suggested that regular discharging neurones were endogenously active and that these neurones provided synaptic input to irregular discharging neurones. PMID:6140310

Electrophysiology of neurones of the inferior mesenteric ganglion of the cat.

PubMed

Julé, Y; Szurszewski, J H

1983-11-01

Intracellular recordings were obtained from cells in vitro in the inferior mesenteric ganglia of the cat. Neurones could be classified into three types: non-spontaneous, irregular discharging and regular discharging neurones. Non-spontaneous neurones had a stable resting membrane potential and responded with action potentials to indirect preganglionic nerve stimulation and to intracellular injection of depolarizing current. Irregular discharging neurones were characterized by a discharge of excitatory post-synaptic potentials (e.p.s.p.s.) which sometimes gave rise to action potentials. This activity was abolished by hexamethonium bromide, chlorisondamine and d-tubocurarine chloride. Tetrodotoxin and a low Ca2+ -high Mg2+ solution also blocked on-going activity in irregular discharging neurones. Regular discharging neurones were characterized by a rhythmic discharge of action potentials. Each action potential was preceded by a gradual depolarization of the intracellularly recorded membrane potential. Intracellular injection of hyperpolarizing current abolished the regular discharge of action potential. No synaptic potentials were observed during hyperpolarization of the membrane potential. Nicotinic, muscarinic and adrenergic receptor blocking drugs did not modify the discharge of action potentials in regular discharging neurones. A low Ca2+ -high Mg2+ solution also had no effect on the regular discharge of action potentials. Interpolation of an action potential between spontaneous action potentials in regular discharging neurones reset the rhythm of discharge. It is suggested that regular discharging neurones were endogenously active and that these neurones provided synaptic input to irregular discharging neurones.

Delayed onset of changes in soma action potential genesis in nociceptive A-beta DRG neurons in vivo in a rat model of osteoarthritis

PubMed Central

Wu, Qi; Henry, James L

2009-01-01

Background Clinical data on osteoarthritis (OA) suggest widespread changes in sensory function that vary during the progression of OA. In previous studies on a surgically-induced animal model of OA we have observed that changes in structure and gene expression follow a variable trajectory over the initial days and weeks. To investigate mechanisms underlying changes in sensory function in this model, the present electrophysiological study compared properties of primary sensory nociceptive neurons at one and two months after model induction with properties in naïve control animals. Pilot data indicated no difference in C- or Aδ-fiber associated neurons and therefore the focus is on Aβ-fiber nociceptive neurons. Results At one month after unilateral derangement of the knee by cutting the anterior cruciate ligament and removing the medial meniscus, the only changes observed in Aβ-fiber dorsal root ganglion (DRG) neurons were in nociceptor-like unresponsive neurons bearing a hump on the repolarization phase; these changes consisted of longer half width, reflecting slowed dynamics of AP genesis, a depolarized Vm and an increased AP amplitude. At two months, changes observed were in Aβ-fiber high threshold mechanoreceptors, which exhibited shorter AP duration at base and half width, shorter rise time and fall time, and faster maximum rising rate/maximum falling rate, reflecting accelerated dynamics of AP genesis. Conclusion These data indicate that Aβ nociceptive neurons undergo significant changes that vary in time and occur later than changes in structure and in nociceptive scores in this surgically induced OA model. Thus, if changes in Aβ-fiber nociceptive neurons in this model reflect a role in OA pain, they may relate to mechanisms underlying pain associated with advanced OA. PMID:19785765

Dynamics of action potential initiation in the GABAergic thalamic reticular nucleus in vivo.

PubMed

Muñoz, Fabián; Fuentealba, Pablo

2012-01-01

Understanding the neural mechanisms of action potential generation is critical to establish the way neural circuits generate and coordinate activity. Accordingly, we investigated the dynamics of action potential initiation in the GABAergic thalamic reticular nucleus (TRN) using in vivo intracellular recordings in cats in order to preserve anatomically-intact axo-dendritic distributions and naturally-occurring spatiotemporal patterns of synaptic activity in this structure that regulates the thalamic relay to neocortex. We found a wide operational range of voltage thresholds for action potentials, mostly due to intrinsic voltage-gated conductances and not synaptic activity driven by network oscillations. Varying levels of synchronous synaptic inputs produced fast rates of membrane potential depolarization preceding the action potential onset that were associated with lower thresholds and increased excitability, consistent with TRN neurons performing as coincidence detectors. On the other hand the presence of action potentials preceding any given spike was associated with more depolarized thresholds. The phase-plane trajectory of the action potential showed somato-dendritic propagation, but no obvious axon initial segment component, prominent in other neuronal classes and allegedly responsible for the high onset speed. Overall, our results suggest that TRN neurons could flexibly integrate synaptic inputs to discharge action potentials over wide voltage ranges, and perform as coincidence detectors and temporal integrators, supported by a dynamic action potential threshold.

Investigation of deformation effects on the decay properties of 12 C + α Cluster states in 16O

NASA Astrophysics Data System (ADS)

Soylu, A.; Koyuncu, F.; Coban, A.; Bayrak, O.; Freer, M.

2018-04-01

We have analyzed the elastic scattering angular distributions data of the α +12C reaction over a wide energy range (Elab = 28 . 2 to 35.5 MeV) within the framework of the Optical Model formalism. A double folding (DF) type real potential was used with a phenomenological Woods-Saxon-squared (WS2) type imaginary potential. Good agreement between the calculations and experimental data was obtained. By using the real DF potential we have calculated the properties of the α-cluster states in 16O by using the Gamow code as well as the α-decay widths by using the WKB method. We implemented a 12C + α cluster framework for the calculation of the excitation energies and decay widths of 16O as a function of the orientation of the planar 12C nucleus with respect to the α-particle. These calculations showed strong sensitivity of the widths and excitation energies to the orientation. Branching ratios were also calculated and though less sensitive to the 12C orientation, it was found that 12Cgs + α structure, with the α-particle orbiting the 12C in its ground state, is dominant. This work demonstrates that deformation, and the orientation, of 12C plays a crucial role in the understanding of the nature of the α-cluster states in 16O.

Channel Width Change as a Potential Sediment Source, Minnesota River Basin

NASA Astrophysics Data System (ADS)

Lauer, J. W.; Echterling, C.; Lenhart, C. F.; Rausch, R.; Belmont, P.

2017-12-01

Turbidity and suspended sediment are important management considerations along the Minnesota River. The system has experience large and relatively consistent increases in both discharge and channel width over the past century. Here we consider the potential role of channel cross section enlargement as a sediment source. Reach-average channel width was digitized from aerial images dated between 1937 and 2015 along multiple sub-reaches of the Minnesota River and its major tributaries. Many of the sub-reaches include several actively migrating bends. The analysis shows relatively consistent increases in width over time, with average increase rates of 0.4 percent per year. Extrapolation to the river network using a regional relationship for cross-sectional area vs. drainage area indicates that large tributaries and main-stem reaches account for most of the bankfull cross-sectional volume in the basin. Larger tributaries and the main stem thus appear more important for widening related sediment production than small tributaries. On a basin-wide basis, widening could be responsible for a gross supply of more sediment than has been gaged at several main-stem sites, indicating that there may be important sinks for both sand and silt/clay size material distributed throughout the system. Sediment storage is probably largest along the lowest-slope reaches of the main stem. While channel width appears to have adjusted relatively quickly in response to discharge and other hydraulic modifications, net storage of sediment in floodplains probably occurs sufficiently slowly that depth adjustment will lag width adjustment significantly. Detailed analysis of the lower Minnesota River using a river segmenting approach allows for a more detailed assessment of reach-scale processes. Away from channel cutoffs, elongation of the channel at eroding bends is consistent with rates observed on other actively migrating rivers. However, the sinuosity increase has been more than compensated by several natural and engineered cutoffs. The sinuosity change away from cutoffs probably plays a relatively modest role in the reach's sediment budget. However, point bars and abandoned oxbow lakes are important zones of sediment storage that may be large enough to account for much of the widening-related production of sand in the reach.

Investigating Effects of Fused-Deposition Modeling (FDM) Processing Parameters on Flexural Properties of ULTEM 9085 using Designed Experiment.

PubMed

Gebisa, Aboma Wagari; Lemu, Hirpa G

2018-03-27

Fused-deposition modeling (FDM), one of the additive manufacturing (AM) technologies, is an advanced digital manufacturing technique that produces parts by heating, extruding and depositing filaments of thermoplastic polymers. The properties of FDM-produced parts apparently depend on the processing parameters. These processing parameters have conflicting advantages that need to be investigated. This article focuses on an investigation into the effect of these parameters on the flexural properties of FDM-produced parts. The investigation is carried out on high-performance ULTEM 9085 material, as this material is relatively new and has potential application in the aerospace, military and automotive industries. Five parameters: air gap, raster width, raster angle, contour number, and contour width, with a full factorial design of the experiment, are considered for the investigation. From the investigation, it is revealed that raster angle and raster width have the greatest effect on the flexural properties of the material. The optimal levels of the process parameters achieved are: air gap of 0.000 mm, raster width of 0.7814 mm, raster angle of 0°, contour number of 5, and contour width of 0.7814 mm, leading to a flexural strength of 127 MPa, a flexural modulus of 2400 MPa, and 0.081 flexural strain.

Investigating Effects of Fused-Deposition Modeling (FDM) Processing Parameters on Flexural Properties of ULTEM 9085 using Designed Experiment

PubMed Central

Gebisa, Aboma Wagari

2018-01-01

Fused-deposition modeling (FDM), one of the additive manufacturing (AM) technologies, is an advanced digital manufacturing technique that produces parts by heating, extruding and depositing filaments of thermoplastic polymers. The properties of FDM-produced parts apparently depend on the processing parameters. These processing parameters have conflicting advantages that need to be investigated. This article focuses on an investigation into the effect of these parameters on the flexural properties of FDM-produced parts. The investigation is carried out on high-performance ULTEM 9085 material, as this material is relatively new and has potential application in the aerospace, military and automotive industries. Five parameters: air gap, raster width, raster angle, contour number, and contour width, with a full factorial design of the experiment, are considered for the investigation. From the investigation, it is revealed that raster angle and raster width have the greatest effect on the flexural properties of the material. The optimal levels of the process parameters achieved are: air gap of 0.000 mm, raster width of 0.7814 mm, raster angle of 0°, contour number of 5, and contour width of 0.7814 mm, leading to a flexural strength of 127 MPa, a flexural modulus of 2400 MPa, and 0.081 flexural strain. PMID:29584674

[Brain Mechanisms for Measuring Time: Population Coding of Durations].

PubMed

Hayashi, Masamichi J

2016-11-01

Temporal processing is crucial in many aspects of our perception and action. While there is mounting evidence for the encoding mechanisms of spatial ("where") and identity ("what") information, those of temporal information ("when") remain largely unknown. Recent studies suggested that, similarly to the basic visual stimulus features such as orientation, motion direction, and numerical quantity, event durations are also represented by a population of neurons that are tuned for specific, preferred durations. This paper first reviews recent psychophysical studies on duration aftereffect. Changes in the three parameters (response gain, shift, and width of tuning curves) are then discussed that may need to be taken into account in the putative duration-channel model. Next, the potential neural basis of the duration channels is examined by overviewing recent neuroimaging and electrophysiological studies on time perception. Finally, this paper proposes a general neural basis of timing that commonly represents time-differences independent of stimulus types (e.g., a single duration v.s. multiple brief events). This extends the idea of the "when pathway" from the perception of temporal order to the general timing mechanisms for the perception of duration, temporal frequency, and synchrony.

Pulse Responses of the Conducting Polymer Poly(3,4-ethylenedioxythiophene): Poly(styrenesulfonate)-Based Junctions

NASA Astrophysics Data System (ADS)

Zeng, Fei; Li, Xiaojun; Li, Sizhao; Chang, Chiating; Hu, Yuandong

2017-03-01

Pulse responses were studied for the heterojunctions within the structure of Ti/poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS)/Ti. The pulse response was found to resemble that of the action potential after the pulse width was modulated to a time scale of nanoseconds. Using the pulse as a stimulation protocol to simulate synaptic plasticity produced spike rate-dependent plasticity-like phenomena. Thus, the application scope of this conducting polymer-based memristor can be extended from a time scale of milliseconds to one of nanoseconds, depending on the requirement of neuromorphic circuits. Current oscillations were observed with a period within 100 ns. The mechanisms of the behavior response were analyzed according to memristor protocol. An interface barrier is thought to primarily account for the origin of the capacitive feature and the charge q, i.e., one of the basic characteristic of the memristor. The chain structure of this conducting polymer should primarily account for the origin of its inductive feature and the flux φ, i.e., another basic characteristic of the memristor.

Diversification of intrinsic motoneuron electrical properties during normal development and botulinum toxin-induced muscle paralysis in early postnatal mice.

PubMed

Nakanishi, S T; Whelan, P J

2010-05-01

During early postnatal development, between birth and postnatal days 8-11, mice start to achieve weight-bearing locomotion. In association with the progression of weight-bearing locomotion there are presumed developmental changes in the intrinsic electrical properties of spinal -motoneurons. However, these developmental changes in the properties of -motoneuron properties have not been systematically explored in mice. Here, data are presented documenting the developmental changes of selected intrinsic motoneuron electrical properties, including statistically significant changes in action potential half-width, intrinsic excitability and diversity (quantified as coefficient of variation) of rheobase current, afterhyperpolarization half-decay time, and input resistance. In various adult mammalian preparations, the maintenance of intrinsic motoneuron electrical properties is dependent on activity and/or transmission-sensitive motoneuron-muscle interactions. In this study, we show that botulinum toxin-induced muscle paralysis led to statistically significant changes in the normal development of intrinsic motoneuron electrical properties in the postnatal mouse. This suggests that muscle activity during early neonatal life contributes to the development of normal motoneuron electrical properties.

Mechanisms and consequences of action potential burst firing in rat neocortical pyramidal neurons

PubMed Central

Williams, Stephen R; Stuart, Greg J

1999-01-01

Electrophysiological recordings and pharmacological manipulations were used to investigate the mechanisms underlying the generation of action potential burst firing and its postsynaptic consequences in visually identified rat layer 5 pyramidal neurons in vitro.Based upon repetitive firing properties and subthreshold membrane characteristics, layer 5 pyramidal neurons were separated into three classes: regular firing and weak and strong intrinsically burst firing.High frequency (330 ± 10 Hz) action potential burst firing was abolished or greatly weakened by the removal of Ca2+ (n = 5) from, or by the addition of the Ca2+ channel antagonist Ni2+ (250–500 μm; n = 8) to, the perfusion medium.The blockade of apical dendritic sodium channels by the local dendritic application of TTX (100 nm; n = 5) abolished or greatly weakened action potential burst firing, as did the local apical dendritic application of Ni2+ (1 mm; n = 5).Apical dendritic depolarisation resulted in low frequency (157 ± 26 Hz; n = 6) action potential burst firing in regular firing neurons, as classified by somatic current injection. The intensity of action potential burst discharges in intrinsically burst firing neurons was facilitated by dendritic depolarisation (n = 11).Action potential amplitude decreased throughout a burst when recorded somatically, suggesting that later action potentials may fail to propagate axonally. Axonal recordings demonstrated that each action potential in a burst is axonally initiated and that no decrement in action potential amplitude is apparent in the axon > 30 μm from the soma.Paired recordings (n = 16) from synaptically coupled neurons indicated that each action potential in a burst could cause transmitter release. EPSPs or EPSCs evoked by a presynaptic burst of action potentials showed use-dependent synaptic depression.A postsynaptic, TTX-sensitive voltage-dependent amplification process ensured that later EPSPs in a burst were amplified when generated from membrane potentials positive to -60 mV, providing a postsynaptic mechanism that counteracts use-dependent depression at synapses between layer 5 pyramidal neurons. PMID:10581316

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

St James, S; Bloch, C; Saini, J

Purpose: Proton pencil beam scanning is used clinically across the United States. There are no current guidelines on tolerances for daily QA specific to pencil beam scanning, specifically related to the individual spot properties (spot width). Using a stochastic method to determine tolerances has the potential to optimize tolerances on individual spots and decrease the number of false positive failures in daily QA. Individual and global spot tolerances were evaluated. Methods: As part of daily QA for proton pencil beam scanning, a field of 16 spots (corresponding to 8 energies) is measured using an array of ion chambers (Matrixx, IBA).more » Each individual spot is fit to two Gaussian functions (x,y). The spot width (σ) in × and y are recorded (32 parameters). Results from the daily QA were retrospectively analyzed for 100 days of data. The deviations of the spot widths were histogrammed and fit to a Gaussian function. The stochastic spot tolerance was taken to be the mean ± 3σ. Using these results, tolerances were developed and tested against known deviations in spot width. Results: The individual spot tolerances derived with the stochastic method decreased in 30/32 instances. Using the previous tolerances (± 20% width), the daily QA would have detected 0/20 days of the deviation. Using a tolerance of any 6 spots failing the stochastic tolerance, 18/20 days of the deviation would have been detected. Conclusion: Using a stochastic method we have been able to decrease daily tolerances on the spot widths for 30/32 spot widths measured. The stochastic tolerances can lead to detection of deviations that previously would have been picked up on monthly QA and missed by daily QA. This method could be easily extended for evaluation of other QA parameters in proton spot scanning.« less

Using LandSat and SRTM datasets to develop relationships for estimating bankfull channel widths in the Amazon Basin

NASA Astrophysics Data System (ADS)

Gummadi, V.; He, Y.; Beighley, E. R.

2007-12-01

Modeling fine scale spatial and temporal processes of the hydrologic cycle over continental to global extents is vital for assessing the potential impacts of climate and land use change on global water resources and related systems. Significant advancement in understanding and predicting the magnitude, trend, timing and partitioning of terrestrial water stores and fluxes requires the development of methodologies and knowledge for extracting representative hydraulic geometries from remote sensing data products and field data, suitable for estimating inundation characteristics and water storage changes which are limited for much of the globe. In this research, relationships between channel and floodplain widths and spatial drainage characteristics are developed for the Amazon Basin. Channel and floodplain widths were measured using SRTM data and LandSat TM/ETM imagery at 510 sites. The study sites were selected based on the Pfafstetter decomposition methodology which provides an irregular model grid based on repeatedly subdividing landscape units into nine subunits consisting of basins and interbasins. The selected sites encompass all possible combinations of Pfafstetter modeling units (ex., basins of interbasins, interbasins of basins, etc.). The 510 study sites are within the Amazon Basin with drainage areas ranging 10 to 5.4 million sq km and mean watershed ground slopes ranging from 0.4 and 30 percent. Preliminary results indicate that channel widths can be predicted using drainage area and mean watershed slope (R2 = 0.85). Floodplain widths can be predicted using channel width and the local slope (R2 = 0.70). Using the Purus watershed, a sub-basin to the Amazon (350,000 sq km), effects of channel and floodplain widths on simulated hydrographs are presented.

High-Frequency Stimulation of Dorsal Column Axons: Potential Underlying Mechanism of Paresthesia-Free Neuropathic Pain Relief.

PubMed

Arle, Jeffrey E; Mei, Longzhi; Carlson, Kristen W; Shils, Jay L

2016-06-01

Spinal cord stimulation (SCS) treats neuropathic pain through retrograde stimulation of dorsal column axons and their inhibitory effects on wide dynamic range (WDR) neurons. Typical SCS uses frequencies from 50-100 Hz. Newer stimulation paradigms use high-frequency stimulation (HFS) up to 10 kHz and produce pain relief but without paresthesia. Our hypothesis is that HFS preferentially blocks larger diameter axons (12-15 µm) based on dynamics of ion channel gates and the electric potential gradient seen along the axon, resulting in inhibition of WDR cells without paresthesia. We input field potential values from a finite element model of SCS into an active axon model with ion channel subcomponents for fiber diameters 1-20 µm and simulated dynamics on a 0.001 msec time scale. Assuming some degree of wave rectification seen at the axon, action potential (AP) blockade occurs as hypothesized, preferentially in larger over smaller diameters with blockade in most medium and large diameters occurring between 4.5 and 10 kHz. Simulations show both ion channel gate and virtual anode dynamics are necessary. At clinical HFS frequencies and pulse widths, HFS preferentially blocks larger-diameter fibers and concomitantly recruits medium and smaller fibers. These effects are a result of interaction between ion gate dynamics and the "activating function" (AF) deriving from current distribution over the axon. The larger fibers that cause paresthesia in low-frequency simulation are blocked, while medium and smaller fibers are recruited, leading to paresthesia-free neuropathic pain relief by inhibiting WDR cells. © 2016 International Neuromodulation Society.

Strong localization induced anomalous temperature dependence exciton emission above 300 K from SnO{sub 2} quantum dots

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

Pan, S. S., E-mail: sspan@issp.ac.cn, E-mail: ghli@issp.ac.cn; Li, F. D.; Liu, Q. W.

2015-05-07

SnO{sub 2} quantum dots (QDs) are potential materials for deep ultraviolet (DUV) light emitting devices. In this study, we report the temperature and excitation power-dependent exciton luminescence from SnO{sub 2} QDs. The exciton emission exhibits anomalous blue shift, accompanied with band width reduction with increasing temperature and excitation power above 300 K. The anomalous temperature dependences of the peak energy and band width are well interpreted by the strongly localized carrier thermal hopping process and Gaussian shape of band tails states, respectively. The localized wells and band tails at conduction minimum are considered to be induced by the surface oxygen defectsmore » and local potential fluctuation in SnO{sub 2} QDs.« less

Comparison of time-frequency distribution techniques for analysis of spinal somatosensory evoked potential.

PubMed

Hu, Y; Luk, K D; Lu, W W; Holmes, A; Leong, J C

2001-05-01

Spinal somatosensory evoked potential (SSEP) has been employed to monitor the integrity of the spinal cord during surgery. To detect both temporal and spectral changes in SSEP waveforms, an investigation of the application of time-frequency analysis (TFA) techniques was conducted. SSEP signals from 30 scoliosis patients were analysed using different techniques; short time Fourier transform (STFT), Wigner-Ville distribution (WVD), Choi-Williams distribution (CWD), cone-shaped distribution (CSD) and adaptive spectrogram (ADS). The time-frequency distributions (TFD) computed using these methods were assessed and compared with each other. WVD, ADS, CSD and CWD showed better resolution than STFT. Comparing normalised peak widths, CSD showed the sharpest peak width (0.13+/-0.1) in the frequency dimension, and a mean peak width of 0.70+/-0.12 in the time dimension. Both WVD and CWD produced cross-term interference, distorting the TFA distribution, but this was not seen with CSD and ADS. CSD appeared to give a lower mean peak power bias (10.3%+/-6.2%) than ADS (41.8%+/-19.6%). Application of the CSD algorithm showed both good resolution and accurate spectrograms, and is therefore recommended as the most appropriate TFA technique for the analysis of SSEP signals.

Magnetic dipole transitions of Bc and Bc* mesons in the relativistic independent quark model

NASA Astrophysics Data System (ADS)

Patnaik, Sonali; Dash, P. C.; Kar, Susmita; Patra, Sweta P.; Barik, N.

2017-12-01

We study M1-transitions involving mesons: Bc(1 s ), Bc*(1 s ), Bc(2 s ), Bc*(2 s ), Bc(3 s ), and Bc*(3 s ) in the relativistic independent quark (RIQ) model based on a flavor independent average potential in the scalar-vector harmonic form. The transition form factor for Bc*→Bcγ is found to have analytical continuation from spacelike to physical timelike region. Our predicted coupling constant gBc*Bc=0.34 GeV-1 and decay width Γ (Bc*→Bcγ )=23 eV agree with other model predictions. In view of possible observation of Bc and Bc* s-wave states at LHC and Z-factory and potential use of theoretical estimate on M1-transitions, we investigate the allowed as well as hindered transitions of orbitally excited Bc-meson states and predict their decay widths in overall agreement with other model predictions. We consider the typical case of Bc*(1 s )→Bc(1 s )γ , where our predicted decay width which is found quite sensitive to the mass difference between Bc* and Bc mesons may help in determining the mass of Bc* experimentally.

Kinetic effects on the currents determining the stability of a magnetic island in tokamaks

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

Poli, E., E-mail: emanuele.poli@ipp.mpg.de; Bergmann, A.; Casson, F. J.

The role of the bootstrap and polarization currents for the stability of neoclassical tearing modes is investigated employing both a drift kinetic and a gyrokinetic approach. The adiabatic response of the ions around the island separatrix implies, for island widths below or around the ion thermal banana width, density flattening for islands rotating at the ion diamagnetic frequency, while for islands rotating at the electron diamagnetic frequency the density is unperturbed and the only contribution to the neoclassical drive arises from electron temperature flattening. As for the polarization current, the full inclusion of finite orbit width effects in the calculationmore » of the potential developing in a rotating island leads to a smoothing of the discontinuous derivatives exhibited by the analytic potential on which the polarization term used in the modeling is based. This leads to a reduction of the polarization-current contribution with respect to the analytic estimate, in line with other studies. Other contributions to the perpendicular ion current, related to the response of the particles around the island separatrix, are found to compete or even dominate the polarization-current term for realistic island rotation frequencies.« less

Convection-Diffusion Layer in an "Open Space" for Local Surface Treatment and Microfabrication using a Four-Aperture Microchemical Pen.

PubMed

Mao, Sifeng; Zhang, Yong; Zhang, Weifei; Zeng, Hulie; Nakajima, Hizuru; Lin, Jin-Ming; Uchiyama, Katsumi

2017-09-06

A four-aperture microchemical pen was used to produce a stable convection-diffusion layer in an "open space" for microreactions and microfabrication. The process represents a new method for microreactions and microfabrication in a convection-diffusion layer. To prove the concept of a convection-diffusion layer in an "open space", bovine serum albumin was labeled with 4-fluoro-7-nitro-2,1,3-benzoxadiazole to confirm that the small convection-diffusion layer was effective for local surface treatment. To demonstrate the potential for microfabrication, silver patterns were fabricated on a glass surface with a convection-diffusion layer by using the silver-mirror reaction. The widths of each silver pattern could be easily controlled from 10 to 60 μm. Patterned silver lines with uniform widths or gradient widths were prepared. This is the first proof of concept study of a convection-diffusion layer in an "open space" used in local surface treatment and microfabrication on a surface. The microchemical pen represents a potential method for the region-selective microtreatment of tissues, cells, and other biological interfaces. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The potential of materials analysis by electron rutherford backscattering as illustrated by a case study of mouse bones and related compounds.

PubMed

Vos, Maarten; Tökési, Károly; Benkö, Ilona

2013-06-01

Electron Rutherford backscattering (ERBS) is a new technique that could be developed into a tool for materials analysis. Here we try to establish a methodology for the use of ERBS for materials analysis of more complex samples using bone minerals as a test case. For this purpose, we also studied several reference samples containing Ca: calcium carbonate (CaCO(3)) and hydroxyapatite and mouse bone powder. A very good understanding of the spectra of CaCO(3) and hydroxyapatite was obtained. Quantitative interpretation of the bone spectrum is more challenging. A good fit of these spectra is only obtained with the same peak widths as used for the hydroxyapatite sample, if one allows for the presence of impurity atoms with a mass close to that of Na and Mg. Our conclusion is that a meaningful interpretation of spectra of more complex samples in terms of composition is indeed possible, but only if widths of the peaks contributing to the spectra are known. Knowledge of the peak widths can either be developed by the study of reference samples (as was done here) or potentially be derived from theory.

Status of quarkonia-like negative and positive parity states in a relativistic confinement scheme

NASA Astrophysics Data System (ADS)

Bhavsar, Tanvi; Shah, Manan; Vinodkumar, P. C.

2018-03-01

Properties of quarkonia-like states in the charm and bottom sector have been studied in the frame work of relativistic Dirac formalism with a linear confinement potential. We have computed the mass spectroscopy and decay properties (vector decay constant and leptonic decay width) of several quarkonia-like states. The present study is also intended to identify some of the unexplained states as mixed P-wave and mixed S-D-wave states of charmonia and bottomonia. The results indicate that the X(4140) state can be an admixture of two P states of charmonium. And the charmonium-like states X(4630) and X(4660) are the admixed state of S-D-waves. Similarly, the X(10610) state recently reported by Belle II can be mixed P-states of bottomonium. In the relativistic framework we have computed the vector decay constant and the leptonic decay width for S wave charmonium and bottomonium. The leptonic decay widths for the J^{PC} = 1^{-} mixed states are also predicted. Further, both the masses and the leptonic decay width are considered for the identification of the quarkonia-like states.

Potential Interference of Oil Vehicles on Genital Tubercle Development during the Fetal Period in ICR Mice.

PubMed

Nishioka, Yasushi; Tamai, Kazuki; Onda, Masanari; Hiromori, Youhei; Kimura, Tomoki; Hu, Jianying; Nagase, Hisamitsu; Nakanishi, Tsuyoshi

2018-01-01

Corn oil, sesame oil, and 10% ethanol in corn oil are commonly used as dosing vehicles in toxicology studies. Since these vegetable oils contain bioactive compounds, it is important for toxicology studies to characterize the toxicities of the dosing vehicles themselves. It has been recently proposed that the width of the genital tubercle (GT), the dorsal-ventral length (D-V length) of the GT, and urethral tube closure in mouse fetuses can be used as novel markers for monitoring sexual development in mice. However, how these parameters are influenced by the dosing vehicles themselves remains unclear. Therefore, we evaluated the effects of corn oil, sesame oil, and 10% ethanol in corn oil on GT width, D-V length, and GT morphology in ICR mice. Our results showed that all three vehicles influenced GT width and D-V length, but not GT morphology, suggesting that the effects of dosing vehicles themselves might need to be considered when GT width or D-V length is used as a parameter to evaluate the effects of chemicals on GT development.

Mass spectra and decay properties of the c\\bar{c} meson

NASA Astrophysics Data System (ADS)

Chaturvedi, Raghav; Kumar Rai, Ajay

2018-06-01

In this article we present the result of c\\bar{c} meson mass calculation by solving the Schrödinger equation numerically considering the Coulomb plus linear potential. The spin-hyperfine, spin-orbit and tensor components of one-gluon-exchange interactions are employed to obtain the mass spectra of c\\bar{c} meson. The calculated mass spectra are compared with the latest results of PDG and are found to be in good accordance. The Regge trajectories of the calculated mass spectra have also been constructed. The values of the wave function are extracted and employed to calculate the leptonic decay constant, γγ, gg, e+e-, light hadron (LH) and γγγ decay widths of S-wave 0^{-+} and 1^{- -} states of c\\bar{c} meson, the widths have been calculated by Van Royen-Weisskopf formula and by NRQCD mechanism incorporating relativistic corrections of order ν2. The γγ and gg decay widths of χ0 and χ2 states of c\\bar{c} meson have also been calculated. The calculated decay constants and widths have been compared with the experimental results.

The human ether-a-go-go-related gene (hERG) current inhibition selectively prolongs action potential of midmyocardial cells to augment transmural dispersion.

PubMed

Yasuda, C; Yasuda, S; Yamashita, H; Okada, J; Hisada, T; Sugiura, S

2015-08-01

The majority of drug induced arrhythmias are related to the prolongation of action potential duration following inhibition of rapidly activating delayed rectifier potassium current (I(Kr)) mediated by the hERG channel. However, for arrhythmias to develop and be sustained, not only the prolongation of action potential duration but also its transmural dispersion are required. Herein, we evaluated the effect of hERG inhibition on transmural dispersion of action potential duration using the action potential clamp technique that combined an in silico myocyte model with the actual I(Kr) measurement. Whole cell I(Kr) current was measured in Chinese hamster ovary cells stably expressing the hERG channel. The measured current was coupled with models of ventricular endocardial, M-, and epicardial cells to calculate the action potentials. Action potentials were evaluated under control condition and in the presence of 1, 10, or 100 μM disopyramide, an hERG inhibitor. Disopyramide dose-dependently increased the action potential durations of the three cell types. However, action potential duration of M-cells increased disproportionately at higher doses, and was significantly different from that of epicardial and endocardial cells (dispersion of repolarization). By contrast, the effects of disopyramide on peak I(Kr) and instantaneous current-voltage relation were similar in all cell types. Simulation study suggested that the reduced repolarization reserve of M-cell with smaller amount of slowly activating delayed rectifier potassium current levels off at longer action potential duration to make such differences. The action potential clamp technique is useful for studying the mechanism of arrhythmogenesis by hERG inhibition through the transmural dispersion of repolarization.

Effects of copper vapor laser (CVL) on mice skin: histologic evaluation of damage and tissue stimulation

NASA Astrophysics Data System (ADS)

Nunes, Syllene; Moreno, E.; Oliveira, H.; Osaka, J.; Salvador, G.; Michalany, N.; Tolosa, E.

2002-10-01

This study was to evaluate the effects of the CVL with low energy and short pulse widths. 18 female mice, C57BL/6 (9-11 weeks old) were distributed into four groups. The control group (CG) wasn't exposed to laser beam . Group L1 had 2 laser expositions with 24 hours gap between them (0.5W). Group L2 had 3 expositions (0.5W and 0.25W) and group L3 had 4 expositions (0.25 W). It was used a CVL prototype (5lOnm, 13 Khz, pulse width of 20 ms and spot size of 0.8cm). 7 days after last laser pulse no groups presented actinic keratosis, tumors or collagen changes. CVL had effective action on pilosebaceous units. High energy with few short pulses induced hair follicles proliferation while low energy with many repetitive short pulses showed increased and specific tissue damage besides hair plugging.

Design and test of a simple fast electromagnetic inductive gas valve for planar pulsed inductive plasma thruster

NASA Astrophysics Data System (ADS)

Guo, Dawei; Cheng, Mousen; Li, Xiaokang

2017-10-01

In support of our planar pulsed inductive plasma thruster research, a fast electromagnetic inductive valve for a gas propellant injection system has been built and tested. A new and important design feature is the use of a conical diaphragm as the action part, which greatly contributes to the virtue of simplicity for adopting the resultant force of the diaphragm deformation as the closing force. An optical transmission technique is adopted to measure the opening and closing characters of the valve while the gas throughput is determined by measuring the pressure change per pulse in a test chamber with a capacitance manometer. The experimental results revealed that the delay time before the valve reaction is less than 40 μs, and the valve pulse width is no longer than 160 μs full width at half maximum. The valve delivers 0-2.5 mg of argon gas per pulse varied by adjusting the drive voltage and gas pressure.

Design and test of a simple fast electromagnetic inductive gas valve for planar pulsed inductive plasma thruster.

PubMed

Guo, Dawei; Cheng, Mousen; Li, Xiaokang

2017-10-01

In support of our planar pulsed inductive plasma thruster research, a fast electromagnetic inductive valve for a gas propellant injection system has been built and tested. A new and important design feature is the use of a conical diaphragm as the action part, which greatly contributes to the virtue of simplicity for adopting the resultant force of the diaphragm deformation as the closing force. An optical transmission technique is adopted to measure the opening and closing characters of the valve while the gas throughput is determined by measuring the pressure change per pulse in a test chamber with a capacitance manometer. The experimental results revealed that the delay time before the valve reaction is less than 40 μs, and the valve pulse width is no longer than 160 μs full width at half maximum. The valve delivers 0-2.5 mg of argon gas per pulse varied by adjusting the drive voltage and gas pressure.

Method and Apparatus for Separating Particles by Dielectrophoresis

NASA Technical Reports Server (NTRS)

Pant, Kapil (Inventor); Wang, Yi (Inventor); Bhatt, Ketan (Inventor); Prabhakarpandian, Balabhasker (Inventor)

2014-01-01

Particle separation apparatus separate particles and particle populations using dielectrophoretic (DEP) forces generated by one or more pairs of electrically coupled electrodes separated by a gap. Particles suspended in a fluid are separated by DEP forces generated by the at least one electrode pair at the gap as they travel over a separation zone comprising the electrode pair. Selected particles are deflected relative to the flow of incoming particles by DEP forces that are affected by controlling applied potential, gap width, and the angle linear gaps with respect to fluid flow. The gap between an electrode pair may be a single, linear gap of constant gap, a single linear gap having variable width, or a be in the form of two or more linear gaps having constant or variable gap width having different angles with respect to one another and to the flow.

Formation of a vortex at the edge of a plate

NASA Technical Reports Server (NTRS)

Anton, Leo

1956-01-01

The flow about the plate of infinite width may be represented as a potential flow with discontinuity surfaces which extend from the plate edges. For prescribed form and vortex distribution of the discontinuity surfaces, the velocity field may be calculated by means of a conformal representation. One condition is that the velocity at the plate edges must be finite. However, it is not sufficient for determination of the form and vortex distribution of the surface. However, on the basis of a similitude requirement one succeeds in finding a solution of this problem for the plate of infinite width which is correct for the very beginning of the motion of the fluid. Starting from this solution, the further development of the vortex distribution and shape of the surface are observed in the case of a plate of finite width.

Line width measurement below 60 nm using an optical interferometer and artificial neural network

NASA Astrophysics Data System (ADS)

See, Chung W.; Smith, Richard J.; Somekh, Michael G.; Yacoot, Andrew

2007-03-01

We have recently described a technique for optical line-width measurements. The system currently is capable of measuring line-width down to 60 nm with a precision of 2 nm, and potentially should be able to measure down to 10nm. The system consists of an ultra-stable interferometer and artificial neural networks (ANNs). The former is used to generate optical profiles which are input to the ANNs. The outputs of the ANNs are the desired sample parameters. Different types of samples have been tested with equally impressive results. In this paper we will discuss the factors that are essential to extend the application of the technique. Two of the factors are signal conditioning and sample classification. Methods, including principal component analysis, that are capable of performing these tasks will be considered.

Dynamics of Action Potential Initiation in the GABAergic Thalamic Reticular Nucleus In Vivo

PubMed Central

Muñoz, Fabián; Fuentealba, Pablo

2012-01-01

Understanding the neural mechanisms of action potential generation is critical to establish the way neural circuits generate and coordinate activity. Accordingly, we investigated the dynamics of action potential initiation in the GABAergic thalamic reticular nucleus (TRN) using in vivo intracellular recordings in cats in order to preserve anatomically-intact axo-dendritic distributions and naturally-occurring spatiotemporal patterns of synaptic activity in this structure that regulates the thalamic relay to neocortex. We found a wide operational range of voltage thresholds for action potentials, mostly due to intrinsic voltage-gated conductances and not synaptic activity driven by network oscillations. Varying levels of synchronous synaptic inputs produced fast rates of membrane potential depolarization preceding the action potential onset that were associated with lower thresholds and increased excitability, consistent with TRN neurons performing as coincidence detectors. On the other hand the presence of action potentials preceding any given spike was associated with more depolarized thresholds. The phase-plane trajectory of the action potential showed somato-dendritic propagation, but no obvious axon initial segment component, prominent in other neuronal classes and allegedly responsible for the high onset speed. Overall, our results suggest that TRN neurons could flexibly integrate synaptic inputs to discharge action potentials over wide voltage ranges, and perform as coincidence detectors and temporal integrators, supported by a dynamic action potential threshold. PMID:22279567

Evaluation of cumulative dose for cone‐beam computed tomography (CBCT) scans within phantoms made from different compositions using Monte Carlo simulations

PubMed Central

Martin, Colin J.; Sankaralingam, Marimuthu; Oomen, Kurian; Gentle, David J.

2015-01-01

Measurement of cumulative dose f(0,150) with a small ionization chamber within standard polymethyl methacrylate (PMMA) CT head and body phantoms, 150 mm in length, is a possible practical method for cone‐beam computed tomography (CBCT) dosimetry. This differs from evaluating cumulative dose under scatter equilibrium conditions within an infinitely long phantom f(0,∞), which is proposed by AAPM TG‐111 for CBCT dosimetry. The aim of this study was to investigate the feasibility of using f(0,150) to estimate values for f(0,∞) in long head and body phantoms made of PMMA, polyethylene (PE), and water, using beam qualities for tube potentials of 80−140 kV. The study also investigated the possibility of using 150 mm PE phantoms for assessment of f(0,∞) within long PE phantoms, the ICRU/AAPM phantom. The influence of scan parameters, composition, and length of the phantoms was investigated. The capability of f(0,150) to assess f(0,∞) has been defined as the efficiency and assessed in terms of the ratios ϵ(f(0,150)/f(0,∞)). The efficiencies were calculated using Monte Carlo simulations for an On‐Board Imager (OBI) system mounted on a TrueBeam linear accelerator. Head and body scanning protocols with beams of width 40−500 mm were used. Efficiencies ϵ(PMMA/PMMA) and ϵ(PE/PE) as a function of beam width exhibited three separate regions. For beam widths <150 mm, ϵ(PMMA/PMMA) and ϵ(PE/PE) values were greater than 90% for the head and body phantoms. The efficiency values then fell rapidly with increasing beam width before levelling off at 74% for ϵ(PMMA/PMMA) and 69% for ϵ(PE/PE) for a 500 mm beam width. The quantities ϵ(PMMA/PE) and ϵ(PMMA/Water) varied with beam width in a different manner. Values at the centers of the phantoms for narrow beams were lower and increased to a steady state for ∼100−150 mm wide beams, before declining with increasing the beam width, whereas values at the peripheries decreased steadily with beam width. Results for ϵ(PMMA/PMMA) were virtually independent of tube potential, but there was more variation for ϵ(PMMA/PE) and ϵ(PMMA/Water). f(0,150) underestimated f(0,∞) for beam widths used for CBCT scans, thus it is necessary to use long phantoms, or apply conversion factors (Cfs) to measurements with standard PMMA CT phantoms. The efficiency values have been used to derive (Cfs) to allow evaluation of f(0,∞) from measurements of f(0,150). The (Cfs) only showed a weak dependence on scan parameters and scanner type, and so may be suitable for general application. PACS number: 87.55.K‐, 87.57.Q‐, 87.57.uq. PMID:26699590

Decision making and action implementation: evidence for an early visually triggered motor activation specific to potential actions.

PubMed

Tandonnet, Christophe; Garry, Michael I; Summers, Jeffery J

2013-07-01

To make a decision may rely on accumulating evidence in favor of one alternative until a threshold is reached. Sequential-sampling models differ by the way of accumulating evidence and the link with action implementation. Here, we tested a model's prediction of an early action implementation specific to potential actions. We assessed the dynamics of action implementation in go/no-go and between-hand choice tasks by transcranial magnetic stimulation of the motor cortex (single- or paired-pulse TMS; 3-ms interstimulus interval). Prior to implementation of the selected action, the amplitude of the motor evoked potential first increased whatever the visual stimulus but only for the hand potentially involved in the to-be-produced action. These findings suggest that visual stimuli can trigger an early motor activation specific to potential actions, consistent with race-like models with continuous transmission between decision making and action implementation. Copyright © 2013 Society for Psychophysiological Research.

The effects of saxitoxin and tetrodotoxin on nerve conduction in the presence of lithium ions and of magnesium ions

PubMed Central

Evans, M. H.

1969-01-01

1. It has been shown that nerve fibres from rat cauda equina will conduct action potentials after immersion in saline in which lithium chloride is substituted for sodium chloride. 2. Both saxitoxin and tetrodotoxin inhibit lithium-generated action potentials. The concentration of toxin needed to inhibit the lithium-generated action potentials is similar to that needed to inhibit sodium-generated action potentials. 3. If magnesium chloride is added to the saline to give a concentration of 10-15 mM there is usually a slight fall in amplitude of the compound action potential. Saxitoxin and tetrodotoxin now inhibit the action potential to a greater degree than in the absence of magnesium ions. PMID:5789802

Actions and mechanisms of action of novel analogues of sotalol on guinea-pig and rabbit ventricular cells.

PubMed Central

Connors, S. P.; Gill, E. W.; Terrar, D. A.

1992-01-01

1. The actions and mechanisms of action of novel analogues of sotalol which prolong cardiac action potentials were investigated in guinea-pig and rabbit isolated ventricular cells. 2. In guinea-pig and rabbit cells the compounds significantly prolonged action potential duration at 20% and 90% repolarization levels without affecting resting membrane potential. In guinea-pig but not rabbit cells there was an increase in action potential amplitude and in rabbit cells there was no change in the shape or position of the 'notch' in the action potential. 3. Possible mechanisms of action were studied in more detail in the case of compound II (1-(4-methanesulphonamidophenoxy)-3-(N-methyl 3,4 dichlorophenylethylamino)-2-propanol). Prolongation of action potential duration continued to occur in the presence of nisoldipine, and calcium currents recorded under voltage-clamp conditions were not reduced by compound II (1 microM). Action potential prolongation by compound II was also unaffected in the presence of 10 microM tetrodotoxin. 4. Compound II (1 microM) did not influence IK1 assessed from the current during ramp changes in membrane potential (20 mV s-1) over the range -90 to -10 mV. 5. Compound II (1 microM) blocked time-dependent delayed rectifier potassium current (IK) activated by step depolarizations and recorded as an outward tail following repolarization. When a submaximal concentration (50 nM) was applied there was no change in the apparent reversal potential of IK.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1393293

Force versus fury: Sex differences in the relationships among physical and psychological threat potential, the facial width-to-height ratio, and judgements of aggressiveness.

PubMed

MacDonell, Elliott T; Geniole, Shawn N; McCormick, Cheryl M

2018-06-07

Individuals with larger facial width-to-height ratios (FWHRs) are judged as more threatening, and engage in more threat-related behavior, than do individuals with smaller FWHRs. Here we identified components of threat potential that are related to the FWHR. In Study 1, the FWHR was correlated positively with physical threat potential (bicep size) in women and with both physical and psychological (anger proneness) threat potential in men. Behavioral aggression was measured in a subset of these participants using the Point Subtraction Aggression Paradigm (costly aggression) and a Money Allocation Task (non-costly aggression). Psychological (but not physical) threat potential predicted non-costly aggression and physical (but not psychological) threat potential predicted costly aggression. In Study 2, a separate set of participants judged the anger proneness, strength, or aggressiveness of male participants photographed in Study 1. Participants' judgements of all three characteristics were associated with the FWHR, and there were sex differences in how aggressiveness was conceptualized (for women, aggressiveness was associated with anger proneness, for men, aggressiveness was associated with strength). These results are consistent with the hypothesis that the FWHR may be an adaptation to cue the threat potential of men. © 2018 Wiley Periodicals, Inc.

Alteration of neural action potential patterns by axonal stimulation: the importance of stimulus location.

PubMed

Crago, Patrick E; Makowski, Nathaniel S

2014-10-01

Stimulation of peripheral nerves is often superimposed on ongoing motor and sensory activity in the same axons, without a quantitative model of the net action potential train at the axon endpoint. We develop a model of action potential patterns elicited by superimposing constant frequency axonal stimulation on the action potentials arriving from a physiologically activated neural source. The model includes interactions due to collision block, resetting of the neural impulse generator, and the refractory period of the axon at the point of stimulation. Both the mean endpoint firing rate and the probability distribution of the action potential firing periods depend strongly on the relative firing rates of the two sources and the intersite conduction time between them. When the stimulus rate exceeds the neural rate, neural action potentials do not reach the endpoint and the rate of endpoint action potentials is the same as the stimulus rate, regardless of the intersite conduction time. However, when the stimulus rate is less than the neural rate, and the intersite conduction time is short, the two rates partially sum. Increases in stimulus rate produce non-monotonic increases in endpoint rate and continuously increasing block of neurally generated action potentials. Rate summation is reduced and more neural action potentials are blocked as the intersite conduction time increases. At long intersite conduction times, the endpoint rate simplifies to being the maximum of either the neural or the stimulus rate. This study highlights the potential of increasing the endpoint action potential rate and preserving neural information transmission by low rate stimulation with short intersite conduction times. Intersite conduction times can be decreased with proximal stimulation sites for muscles and distal stimulation sites for sensory endings. The model provides a basis for optimizing experiments and designing neuroprosthetic interventions involving motor or sensory stimulation.

The role of Na-Ca exchange current in the cardiac action potential.

PubMed

Janvier, N C; Boyett, M R

1996-07-01

Since 1981, when Mullins published his provocative book proposing that the Na-Ca exchanger is electrogenic, it has been shown, first by computer simulation by Noble and later by experiment by various investigators, that inward iNaCa triggered by the Ca2+ transient is responsible for the low plateau of the atrial action potential and contributes to the high plateau of the ventricular action potential. Reduction or complete block of inward iNaCa by buffering intracellular Ca2+ with EGTA or BAPTA, by blocking SR Ca2+ release or by substituting extracellular Na+ with Li+ can result in a shortening of the action potential. The effect of block of outward iNaCa or complete block of both inward and outward iNaCa on the action potential has not been investigated experimentally, because of the lack of a suitable blocker, and remains a goal for the future. An increase in the intracellular Na+ concentration (after the application of cardiac glycoside or an increase in heart rate) or an increase in extracellular Ca2+ are believed to lead to an outward shift in iNaCa at plateau potentials and a shortening of the action potential. Changes in the Ca2+ transient are expected to result in changes in inward iNaCa and thus the action potential. This may explain the shortening of the premature action potential as well as the prolongation of the action potential when a muscle is allowed to shorten during the action potential. Inward iNaCa may play an important role in both normal and abnormal pacemaker activity in the heart.

In Situ Height and Width Estimation of Sorghum Plants from 2.5d Infrared Images

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

Baharav, Tavor; Bariya, Mohini; Zakhor, Avideh

Plant phenotyping, or the measurement of plant traits such as stem width and plant height, is a critical step in the development and evaluation of higher yield biofuel crops. Phenotyping allows biologists to quantitatively estimate the biomass of plant varieties and therefore their potential for biofuel production. Manual phenotyping is costly, time-consuming, and errorprone, requiring a person to walk through the fields measuring individual plants with a tape measure and notebook. In this work we describe an alternative system consisting of an autonomous robot equipped with two infrared cameras that travels through fields, collecting 2.5D image data of sorghum plants.more » We develop novel image processing based algorithms to estimate plant height and stem width from the image data. Our proposed method has the advantage of working in situ using images of plants from only one side. This allows phenotypic data to be collected nondestructively throughout the growing cycle, providing biologists with valuable information on crop growth patterns. Our approach first estimates plant heights and stem widths from individual frames. It then uses tracking algorithms to refine these estimates across frames and avoid double counting the same plant in multiple frames. The result is a histogram of stem widths and plant heights for each plot of a particular genetically engineered sorghum variety. In-field testing and comparison with human collected ground truth data demonstrates that our system achieves 13% average absolute error for stem width estimation and 15% average absolute error for plant height estimation.« less

In Situ Height and Width Estimation of Sorghum Plants from 2.5d Infrared Images

DOE PAGES

Baharav, Tavor; Bariya, Mohini; Zakhor, Avideh

2017-01-29

Plant phenotyping, or the measurement of plant traits such as stem width and plant height, is a critical step in the development and evaluation of higher yield biofuel crops. Phenotyping allows biologists to quantitatively estimate the biomass of plant varieties and therefore their potential for biofuel production. Manual phenotyping is costly, time-consuming, and errorprone, requiring a person to walk through the fields measuring individual plants with a tape measure and notebook. In this work we describe an alternative system consisting of an autonomous robot equipped with two infrared cameras that travels through fields, collecting 2.5D image data of sorghum plants.more » We develop novel image processing based algorithms to estimate plant height and stem width from the image data. Our proposed method has the advantage of working in situ using images of plants from only one side. This allows phenotypic data to be collected nondestructively throughout the growing cycle, providing biologists with valuable information on crop growth patterns. Our approach first estimates plant heights and stem widths from individual frames. It then uses tracking algorithms to refine these estimates across frames and avoid double counting the same plant in multiple frames. The result is a histogram of stem widths and plant heights for each plot of a particular genetically engineered sorghum variety. In-field testing and comparison with human collected ground truth data demonstrates that our system achieves 13% average absolute error for stem width estimation and 15% average absolute error for plant height estimation.« less

Simulation of action potential propagation in plants.

PubMed

Sukhov, Vladimir; Nerush, Vladimir; Orlova, Lyubov; Vodeneev, Vladimir

2011-12-21

Action potential is considered to be one of the primary responses of a plant to action of various environmental factors. Understanding plant action potential propagation mechanisms requires experimental investigation and simulation; however, a detailed mathematical model of plant electrical signal transmission is absent. Here, the mathematical model of action potential propagation in plants has been worked out. The model is a two-dimensional system of excitable cells; each of them is electrically coupled with four neighboring ones. Ion diffusion between excitable cell apoplast areas is also taken into account. The action potential generation in a single cell has been described on the basis of our previous model. The model simulates active and passive signal transmission well enough. It has been used to analyze theoretically the influence of cell to cell electrical conductivity and H(+)-ATPase activity on the signal transmission in plants. An increase in cell to cell electrical conductivity has been shown to stimulate an increase in the length constant, the action potential propagation velocity and the temperature threshold, while the membrane potential threshold being weakly changed. The growth of H(+)-ATPase activity has been found to induce the increase of temperature and membrane potential thresholds and the reduction of the length constant and the action potential propagation velocity. Copyright © 2011 Elsevier Ltd. All rights reserved.

An EQT-based cDFT approach for thermodynamic properties of confined fluid mixtures

NASA Astrophysics Data System (ADS)

Motevaselian, M. H.; Aluru, N. R.

2017-04-01

We present an empirical potential-based quasi-continuum theory (EQT) to predict the structure and thermodynamic properties of confined fluid mixtures. The central idea in the EQT is to construct potential energies that integrate important atomistic details into a continuum-based model such as the Nernst-Planck equation. The EQT potentials can be also used to construct the excess free energy functional, which is required for the grand potential in the classical density functional theory (cDFT). In this work, we use the EQT-based grand potential to predict various thermodynamic properties of a confined binary mixture of hydrogen and methane molecules inside graphene slit channels of different widths. We show that the EQT-cDFT predictions for the structure, surface tension, solvation force, and local pressure tensor profiles are in good agreement with the molecular dynamics simulations. Moreover, we study the effect of different bulk compositions and channel widths on the thermodynamic properties. Our results reveal that the composition of methane in the mixture can significantly affect the ordering of molecules and thermodynamic properties under confinement. In addition, we find that graphene is selective to methane molecules.

The confining baryonic Y-strings on the lattice

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

Bakry, Ahmed S.; Chen, Xurong; Zhang, Peng-Ming

2016-01-22

In a string picture, the nucleon is conjectured as consisting of a Y-shaped gluonic string ended by constituent quarks. In this proceeding, we summarize our results on revealing the signature of the confining Y-bosonic string in the gluonic profile due to a system of three static quarks on the lattice at finite temperature. The analysis of the action density unveils a background of a filled-Δ distribution. However, we found that these Δ-shaped profiles are comprised of three Y-shaped Gaussian-like flux tubes. The length of the revealed Y-string-like distribution is maximum near the deconfinement point and approaches the geometrical minimal nearmore » the end of the QCD plateau. The action density width profile returns good fits to a baryonic string model for the junction fluctuations at large quark source separation.« less

Hybrid mode-locked erbium-doped all-fiber soliton laser with a distributed polarizer.

PubMed

Chernykh, D S; Krylov, A A; Levchenko, A E; Grebenyukov, V V; Arutunyan, N R; Pozharov, A S; Obraztsova, E D; Dianov, E M

2014-10-10

A soliton-type erbium-doped all-fiber ring laser hybrid mode-locked with a co-action of arc-discharge single-walled carbon nanotubes (SWCNTs) and nonlinear polarization evolution (NPE) is demonstrated. For the first time, to the best of our knowledge, boron nitride-doped SWCNTs were used as a saturable absorber for passive mode-locking initiation. Moreover, the NPE was introduced through the implementation of the short-segment polarizing fiber. Owing to the NPE action in the laser cavity, significant pulse length shortening as well as pulse stability improvement were observed as compared with a SWCNTs-only mode-locked laser. The shortest achieved pulse width of near transform-limited solitons was 222 fs at the output average power of 9.1 mW and 45.5 MHz repetition frequency, corresponding to the 0.17 nJ pulse energy.

An Analytical Model of Joule Heating in Piezoresistive Microcantilevers

PubMed Central

Ansari, Mohd Zahid; Cho, Chongdu

2010-01-01

The present study investigates Joule heating in piezoresistive microcantilever sensors. Joule heating and thermal deflections are a major source of noise in such sensors. This work uses analytical and numerical techniques to characterise the Joule heating in 4-layer piezoresistive microcantilevers made of silicon and silicon dioxide substrates but with the same U-shaped silicon piezoresistor. A theoretical model for predicting the temperature generated due to Joule heating is developed. The commercial finite element software ANSYS Multiphysics was used to study the effect of electrical potential on temperature and deflection produced in the cantilevers. The effect of piezoresistor width on Joule heating is also studied. Results show that Joule heating strongly depends on the applied potential and width of piezoresistor and that a silicon substrate cantilever has better thermal characteristics than a silicon dioxide cantilever. PMID:22163433

An analytical model of joule heating in piezoresistive microcantilevers.

PubMed

Ansari, Mohd Zahid; Cho, Chongdu

2010-01-01

The present study investigates Joule heating in piezoresistive microcantilever sensors. Joule heating and thermal deflections are a major source of noise in such sensors. This work uses analytical and numerical techniques to characterise the Joule heating in 4-layer piezoresistive microcantilevers made of silicon and silicon dioxide substrates but with the same U-shaped silicon piezoresistor. A theoretical model for predicting the temperature generated due to Joule heating is developed. The commercial finite element software ANSYS Multiphysics was used to study the effect of electrical potential on temperature and deflection produced in the cantilevers. The effect of piezoresistor width on Joule heating is also studied. Results show that Joule heating strongly depends on the applied potential and width of piezoresistor and that a silicon substrate cantilever has better thermal characteristics than a silicon dioxide cantilever.

Inducing repetitive action potential firing in neurons via synthesized photoresponsive nanoscale cellular prostheses.

PubMed

Lu, Siyuan; Madhukar, Anupam

2013-02-01

Recently we reported an analysis that examined the potential of synthesized photovoltaic functional abiotic nanosystems (PVFANs) to modulate membrane potential and activate action potential firing in neurons. Here we extend the analysis to delineate the requirements on the electronic energy levels and the attendant photophysical properties of the PVFANs to induce repetitive action potential under continuous light, a capability essential for the proposed potential application of PVFANs as retinal cellular prostheses to compensate for loss of photoreceptors. We find that repetitive action potential firing demands two basic characteristics in the electronic response of the PVFANs: an exponential dependence of the PVFAN excited state decay rate on the membrane potential and a three-state system such that, following photon absorption, the electron decay from the excited state to the ground state is via intermediate state(s) whose lifetime is comparable to the refractory time following an action potential. In this study, the potential of synthetic photovoltaic functional abiotic nanosystems (PVFANs) is examined under continuous light to modulate membrane potential and activate action potential firing in neurons with the proposed potential application of PVFANs as retinal cellular prostheses. Copyright © 2013 Elsevier Inc. All rights reserved.

Fracture and crack growth in orthotropic laminates. Part 1: Analysis of a hybrid, unidirectional laminate with damage

NASA Technical Reports Server (NTRS)

Goree, J. G.

1982-01-01

The fracture behavior of unifirectional hybrid (buffer strip) composite laminates is studied. Three particular solutions are discussed: (1) broken fibers in a unidirectional half plane; (2) adjoined half planes of different fiber and matrix properties and (3) the solution of two half planes bounding a third distinct region of finite width. This finite width region represents a buffer strip and the potential of this strip to arrest a crack that originates in one of the half planes is investigated. The analysis is based on a materials modeling approach using the classical shear lag assumption to described the stress transfer between fibers. Explicit fiber and matrix properties of the three regions are retained and changes in the laminate behavior as a function of the relative material properties, buffer strip width and initial crack length are discussed.

Computing resonance energies, widths, and wave functions using a Lanczos method in real arithmetic.

PubMed

Tremblay, Jean Christophe; Carrington, Tucker

2005-06-22

We introduce new ideas for calculating resonance energies and widths. It is shown that a non-Hermitian-Lanczos approach can be used to compute eigenvalues of H+W, where H is the Hamiltonian and W is a complex absorbing potential (CAP), without evaluating complex matrix-vector products. This is done by exploiting the link between a CAP-modified Hamiltonian matrix and a real but nonsymmetric matrix U suggested by Mandelshtam and Neumaier [J. Theor. Comput. Chem. 1, 1 (2002)] and using a coupled-two-term Lanczos procedure. We use approximate resonance eigenvectors obtained from the non-Hermitian-Lanczos algorithm and a very good CAP to obtain very accurate energies and widths without solving eigenvalue problems for many values of the CAP strength parameter and searching for cusps. The method is applied to the resonances of HCO. We compare properties of the method with those of established approaches.

Minimum Weight Design of a Leaf Spring Tapered in Thickness and Width for the Hubble Space Telescope-Space Support Equipment

NASA Technical Reports Server (NTRS)

Rodriguez, P. I.

1990-01-01

A linear elastic solution to the problem of minimum weight design of cantilever beams with variable width and depth is presented. The solution shown is for the specific application of the Hubble Space Telescope maintenance mission hardware. During these maintenance missions, delicate instruments must be isolated from the potentially damaging vibration environment of the space shuttle cargo bay during the ascent and descent phases. The leaf springs are designed to maintain the isolation system natural frequency at a level where load transmission to the instruments in a minimum. Nonlinear programming is used for the optimization process. The weight of the beams is the objective function with the deflection and allowable bending stress as the constraint equations. The design variables are the width and depth of the beams at both the free and the fixed ends.

Effects of K(+) channel openers on spontaneous action potentials in detrusor smooth muscle of the guinea-pig urinary bladder.

PubMed

Takagi, Hiroaki; Hashitani, Hikaru

2016-10-15

The modulation of spontaneous excitability in detrusor smooth muscle (DSM) upon the pharmacological activation of different populations of K(+) channels was investigated. Effects of distinct K(+) channel openers on spontaneous action potentials in DSM of the guinea-pig bladder were examined using intracellular microelectrode techniques. NS1619 (10μM), a large conductance Ca(2+)-activated K(+) (BK) channel opener, transiently increased action potential frequency and then prevented their generation without hyperpolarizing the membrane in a manner sensitive to iberiotoxin (IbTX, 100nM). A higher concentration of NS1619 (30μM) hyperpolarized the membrane and abolished action potential firing. NS309 (10μM) and SKA31 (100μM), small conductance Ca(2+)-activated K(+) (SK) channel openers, dramatically increased the duration of the after-hyperpolarization and then abolished action potential firing in an apamin (100nM)-sensitive manner. Flupirtine (10μM), a Kv7 channel opener, inhibited action potential firing without hyperpolarizing the membrane in a manner sensitive to XE991 (10μM), a Kv7 channel blocker. BRL37344 (10μM), a β3-adrenceptor agonist, or rolipram (10nM), a phosphodiesterase 4 inhibitor, also inhibited action potential firing. A higher concentration of rolipram (100nM) hyperpolarized the DSM and abolished the action potentials. IbTX (100nM) prevented the rolipram-induced blockade of action potentials but not the hyperpolarization. BK and Kv7 channels appear to predominantly contribute to the stabilization of DSM excitability. Spare SK channels could be pharmacologically activated to suppress DSM excitability. BK channels appear to be involved in the cyclic AMP-induced inhibition of action potentials but not the membrane hyperpolarization. Copyright © 2016 Elsevier B.V. All rights reserved.

Pathological prolongation of action potential duration as a cause of the reduced alpha-adrenoceptor-mediated negative inotropy in streptozotocin-induced diabetic mice myocardium.

PubMed

Kanae, Haruna; Hamaguchi, Shogo; Wakasugi, Yumi; Kusakabe, Taichi; Kato, Keisuke; Namekata, Iyuki; Tanaka, Hikaru

2017-11-01

Effect of pathological prolongation of action potential duration on the α-adrenoceptor-mediated negative inotropy was studied in streptozotocin-induced diabetic mice myocardium. In streptozotocin-treated mouse ventricular myocardium, which had longer duration of action potential than that in control mice, the negative inotropic response induced by phenylephrine was smaller than that in control mice. 4-Aminopyridine prolonged the action potential duration and decreased the negative inotropy in control mice. Cromakalim shortened the action potential duration and increased the negative inotropy in streptozotocin-treated mice. These results suggest that the reduced α-adrenoceptor-mediated inotropy in the diabetic mouse myocardium is partly due to its prolonged action potential. Copyright © 2017 The Authors. Production and hosting by Elsevier B.V. All rights reserved.

Determination of cable parameters in skeletal muscle fibres during repetitive firing of action potentials.

PubMed

Riisager, Anders; Duehmke, Rudy; Nielsen, Ole Bækgaard; Huang, Christopher L; Pedersen, Thomas Holm

2014-10-15

Recent studies in rat muscle fibres show that repetitive firing of action potentials causes changes in fibre resting membrane conductance (Gm) that reflect regulation of ClC-1 Cl(-) and KATP K(+) ion channels. Methodologically, these findings were obtained by inserting two microelectrodes at close proximity in the same fibres enabling measurements of fibre input resistance (Rin) in between action potential trains. Since the fibre length constant (λ) could not be determined, however, the calculation of Gm relied on the assumptions that the specific cytosolic resistivity (Ri) and muscle fibre volume remained constant during the repeated action potential firing. Here we present a three-microelectrode technique that enables determinations of multiple cable parameters in action potential-firing fibres including Rin and λ as well as waveform and conduction velocities of fully propagating action potentials. It is shown that in both rat and mouse extensor digitorum longus (EDL) fibres, action potential firing leads to substantial changes in both muscle fibre volume and Ri. The analysis also showed, however, that regardless of these changes, rat and mouse EDL fibres both exhibited initial decreases in Gm that were eventually followed by a ∼3-fold, fully reversible increase in Gm after the firing of 1450-1800 action potentials. Using this three-electrode method we further show that the latter rise in Gm was closely associated with excitation failures and loss of action potential signal above -20 mV. © 2014 The Authors. The Journal of Physiology © 2014 The Physiological Society.

Determination of cable parameters in skeletal muscle fibres during repetitive firing of action potentials

PubMed Central

Riisager, Anders; Duehmke, Rudy; Nielsen, Ole Bækgaard; Huang, Christopher L; Pedersen, Thomas Holm

2014-01-01

Recent studies in rat muscle fibres show that repetitive firing of action potentials causes changes in fibre resting membrane conductance (Gm) that reflect regulation of ClC-1 Cl− and KATP K+ ion channels. Methodologically, these findings were obtained by inserting two microelectrodes at close proximity in the same fibres enabling measurements of fibre input resistance (Rin) in between action potential trains. Since the fibre length constant (λ) could not be determined, however, the calculation of Gm relied on the assumptions that the specific cytosolic resistivity (Ri) and muscle fibre volume remained constant during the repeated action potential firing. Here we present a three-microelectrode technique that enables determinations of multiple cable parameters in action potential-firing fibres including Rin and λ as well as waveform and conduction velocities of fully propagating action potentials. It is shown that in both rat and mouse extensor digitorum longus (EDL) fibres, action potential firing leads to substantial changes in both muscle fibre volume and Ri. The analysis also showed, however, that regardless of these changes, rat and mouse EDL fibres both exhibited initial decreases in Gm that were eventually followed by a ∼3-fold, fully reversible increase in Gm after the firing of 1450–1800 action potentials. Using this three-electrode method we further show that the latter rise in Gm was closely associated with excitation failures and loss of action potential signal above −20 mV. PMID:25128573

Martin County, FL, Case Study: Physical and Economic Performance of Martin County Federal Shore Protection Project During 2004 Tropical Season. Flood and Coastal Storm Damage Reduction Program

DTIC Science & Technology

2009-08-01

the landward toe of the dune along with the loss of upland width associated with erosion and volume of sand placed in each reach for emergency dune ...landward toe of the dune for the with-project design cross- section is approximately 49 cu yd/ft. All but one of the representative without-project profiles...2004, 9.2 million dollars in emergency protective actions including seawalls, revetments and construction of emergency dune features are estimated to

Synaptic depolarization is more effective than back-propagating action potentials during induction of associative long-term potentiation in hippocampal pyramidal neurons.

PubMed

Hardie, Jason; Spruston, Nelson

2009-03-11

Long-term potentiation (LTP) requires postsynaptic depolarization that can result from EPSPs paired with action potentials or larger EPSPs that trigger dendritic spikes. We explored the relative contribution of these sources of depolarization to LTP induction during synaptically driven action potential firing in hippocampal CA1 pyramidal neurons. Pairing of a weak test input with a strong input resulted in large LTP (approximately 75% increase) when the weak and strong inputs were both located in the apical dendrites. This form of LTP did not require somatic action potentials. When the strong input was located in the basal dendrites, the resulting LTP was smaller (< or =25% increase). Pairing the test input with somatically evoked action potentials mimicked this form of LTP. Thus, back-propagating action potentials may contribute to modest LTP, but local synaptic depolarization and/or dendritic spikes mediate a stronger form of LTP that requires spatial proximity of the associated synaptic inputs.

Age- and Sex-Dependent Impact of Repeated Social Stress on Intrinsic and Synaptic Excitability of the Rat Prefrontal Cortex

PubMed Central

Urban, Kimberly R.; Valentino, Rita J.

2017-01-01

Abstract Stress is implicated in psychiatric illnesses that are characterized by impairments in cognitive functions that are mediated by the medial prefrontal cortex (mPFC). Because sex and age determine stress vulnerability, the effects of repeated social stress occurring during early adolescence, mid-adolescence, or adulthood on the cellular properties of male and female rat mPFC Layer V neurons in vitro were examined. Repeated resident–intruder stress produced age- and sex-specific effects on mPFC intrinsic and synaptic excitability. Mid-adolescents were particularly vulnerable to effects on intrinsic excitability. The maximum number of action potentials (APs) evoked by increasing current intensity was robustly decreased in stressed male and female mid-adolescent rats compared with age-matched controls. These effects were associated with stress-induced changes in AP half-width, amplitude, threshold, and input resistance. Social stress at all ages generally decreased synaptic excitability by decreasing the amplitude of spontaneous excitatory postsynaptic potentials. The results suggest that whereas social stress throughout life can diminish the influence of afferents driving the mPFC, social stress during mid-adolescence additionally affects intrinsic characteristics of mPFC neurons that determine excitability. The depressant effects of social stress on intrinsic and synaptic mPFC neurons may underlie its ability to affect executive functions and emotional responses, particularly during adolescence. PMID:28013234

Age- and Sex-Dependent Impact of Repeated Social Stress on Intrinsic and Synaptic Excitability of the Rat Prefrontal Cortex.

PubMed

Urban, Kimberly R; Valentino, Rita J

2017-01-01

Stress is implicated in psychiatric illnesses that are characterized by impairments in cognitive functions that are mediated by the medial prefrontal cortex (mPFC). Because sex and age determine stress vulnerability, the effects of repeated social stress occurring during early adolescence, mid-adolescence, or adulthood on the cellular properties of male and female rat mPFC Layer V neurons in vitro were examined. Repeated resident-intruder stress produced age- and sex-specific effects on mPFC intrinsic and synaptic excitability. Mid-adolescents were particularly vulnerable to effects on intrinsic excitability. The maximum number of action potentials (APs) evoked by increasing current intensity was robustly decreased in stressed male and female mid-adolescent rats compared with age-matched controls. These effects were associated with stress-induced changes in AP half-width, amplitude, threshold, and input resistance. Social stress at all ages generally decreased synaptic excitability by decreasing the amplitude of spontaneous excitatory postsynaptic potentials. The results suggest that whereas social stress throughout life can diminish the influence of afferents driving the mPFC, social stress during mid-adolescence additionally affects intrinsic characteristics of mPFC neurons that determine excitability. The depressant effects of social stress on intrinsic and synaptic mPFC neurons may underlie its ability to affect executive functions and emotional responses, particularly during adolescence. © The Author 2016. Published by Oxford University Press.

Cardiac action potential imaging

NASA Astrophysics Data System (ADS)

Tian, Qinghai; Lipp, Peter; Kaestner, Lars

2013-06-01

Action potentials in cardiac myocytes have durations in the order of magnitude of 100 milliseconds. In biomedical investigations the documentation of the occurrence of action potentials is often not sufficient, but a recording of the shape of an action potential allows a functional estimation of several molecular players. Therefore a temporal resolution of around 500 images per second is compulsory. In the past such measurements have been performed with photometric approaches limiting the measurement to one cell at a time. In contrast, imaging allows reading out several cells at a time with additional spatial information. Recent developments in camera technologies allow the acquisition with the required speed and sensitivity. We performed action potential imaging on isolated adult cardiomyocytes of guinea pigs utilizing the fluorescent membrane potential sensor di-8-ANEPPS and latest electron-multiplication CCD as well as scientific CMOS cameras of several manufacturers. Furthermore, we characterized the signal to noise ratio of action potential signals of varying sets of cameras, dye concentrations and objective lenses. We ensured that di-8-ANEPPS itself did not alter action potentials by avoiding concentrations above 5 μM. Based on these results we can conclude that imaging is a reliable method to read out action potentials. Compared to conventional current-clamp experiments, this optical approach allows a much higher throughput and due to its contact free concept leaving the cell to a much higher degree undisturbed. Action potential imaging based on isolated adult cardiomyocytes can be utilized in pharmacological cardiac safety screens bearing numerous advantages over approaches based on heterologous expression of hERG channels in cell lines.

A simple model for the generation of the vestibular evoked myogenic potential (VEMP).

PubMed

Wit, Hero P; Kingma, Charlotte M

2006-06-01

To describe the mechanism by which the vestibular evoked myogenic potential is generated. Vestibular evoked myogenic potential generation is modeled by adding a large number of muscle motor unit action potentials. These action potentials occur randomly in time along a 100 ms long time axis. But because between approximately 15 and 20 ms after a loud short sound stimulus (almost) no action potentials are generated during VEMP measurements in human subjects, no action potentials are present in the model during this time. The evoked potential is the result of the lack of amplitude cancellation in the averaged surface electromyogram at the edges of this 5 ms long time interval. The relatively simple model describes generation and some properties of the vestibular evoked myogenic potential very well. It is shown that, in contrast with other evoked potentials (BAEPs, VERs), the vestibular evoked myogenic potential is the result of an interruption of activity and not that of summed synchronized neural action potentials.

Interaction—Induced Spectroscopy of H2 in the Fullerenes

NASA Astrophysics Data System (ADS)

Lewis, John Courtenay; Herman, Roger M.

2006-11-01

Carbon nanostructures of various sorts have been the subject of intensive research since their discoveries in the latter part of the 20th century. Much of this research has been motivated by the intrinsic interest of these structures, though their potential as hydrogen storage media has also attracted attention. It was realized that the carbon-hydrogen interactions in these media would induce dipole moments which might lead to observable absorption of infrared spectra, and this work will be reviewed and extended in this paper. The fundamental vibration-rotation spectrum, of H2 in a fcc C60 lattice (fullerite) at room temperature was first observed by S. A. FitzGerald and coworkers, who have subsequently extended their observations to near liquid nitrogen temperatures. Herman and Lewis have discussed the theoretical aspects of H2 in carbon nanotube bundles and in fullerite. We have developed a detailed theory for the spectrum of H2 in fullerite. This theory assumes that the H2 - C potential can be accurately approximated by an exp-6 potential, the parameters of which are then obtained by fitting the line frequencies in FitzGerald's spectra. We have also obtained a model for the H2 induced dipole moment based on the calculations of Frommhold and coworkers on the induced dipole in H2 - He. With one adjustable parameter this model gives a good account of the observed intensities. In work to date the line width has been taken as an empirical parameter. However, the line width is in principal determinable from the H2 - C potential and induced dipole moment, together with the known properties of the phonon modes in fullerite. We conclude this paper with a discussion of the line width problem for H2 in fullerite.

Evaluation of the retail market potential for locally produced paper birch lumber in Alaska.

Treesearch

David L. Nicholls

2002-01-01

An evaluation of the retail market potential for random-width paper birch ( Betula papyrifera Marsh.) lumber in Alaska was conducted. Information from lumber manufacturers and retail managers was used to identify current barriers to customer acceptance of locally produced paper birch lumber. Major retail markets and paper birch producing regions throughout Alaska were...

A rabbit ventricular action potential model replicating cardiac dynamics at rapid heart rates.

PubMed

Mahajan, Aman; Shiferaw, Yohannes; Sato, Daisuke; Baher, Ali; Olcese, Riccardo; Xie, Lai-Hua; Yang, Ming-Jim; Chen, Peng-Sheng; Restrepo, Juan G; Karma, Alain; Garfinkel, Alan; Qu, Zhilin; Weiss, James N

2008-01-15

Mathematical modeling of the cardiac action potential has proven to be a powerful tool for illuminating various aspects of cardiac function, including cardiac arrhythmias. However, no currently available detailed action potential model accurately reproduces the dynamics of the cardiac action potential and intracellular calcium (Ca(i)) cycling at rapid heart rates relevant to ventricular tachycardia and fibrillation. The aim of this study was to develop such a model. Using an existing rabbit ventricular action potential model, we modified the L-type calcium (Ca) current (I(Ca,L)) and Ca(i) cycling formulations based on new experimental patch-clamp data obtained in isolated rabbit ventricular myocytes, using the perforated patch configuration at 35-37 degrees C. Incorporating a minimal seven-state Markovian model of I(Ca,L) that reproduced Ca- and voltage-dependent kinetics in combination with our previously published dynamic Ca(i) cycling model, the new model replicates experimentally observed action potential duration and Ca(i) transient alternans at rapid heart rates, and accurately reproduces experimental action potential duration restitution curves obtained by either dynamic or S1S2 pacing.

Typical gray matter axons in mammalian brain fail to conduct action potentials faithfully at fever-like temperatures.

PubMed

Pekala, Dobromila; Szkudlarek, Hanna; Raastad, Morten

2016-10-01

We studied the ability of typical unmyelinated cortical axons to conduct action potentials at fever-like temperatures because fever often gives CNS symptoms. We investigated such axons in cerebellar and hippocampal slices from 10 to 25 days old rats at temperatures between 30 and 43°C. By recording with two electrodes along axonal pathways, we confirmed that the axons were able to initiate action potentials, but at temperatures >39°C, the propagation of the action potentials to a more distal recording site was reduced. This temperature-sensitive conduction may be specific for the very thin unmyelinated axons because similar recordings from myelinated CNS axons did not show conduction failures. We found that the conduction fidelity improved with 1 mmol/L TEA in the bath, probably due to block of voltage-sensitive potassium channels responsible for the fast repolarization of action potentials. Furthermore, by recording electrically activated antidromic action potentials from the soma of cerebellar granule cells, we showed that the axons failed less if they were triggered 10-30 msec after another action potential. This was because individual action potentials were followed by a depolarizing after-potential, of constant amplitude and shape, which facilitated conduction of the following action potentials. The temperature-sensitive conduction failures above, but not below, normal body temperature, and the failure-reducing effect of the spike's depolarizing after-potential, are two intrinsic mechanisms in normal gray matter axons that may help us understand how the hyperthermic brain functions. © 2016 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society.

3D printing of biomimetic microstructures for cancer cell migration.

PubMed

Huang, Tina Qing; Qu, Xin; Liu, Justin; Chen, Shaochen

2014-02-01

To understand the physical behavior and migration of cancer cells, a 3D in vitro micro-chip in hydrogel was created using 3D projection printing. The micro-chip has a honeycomb branched structure, aiming to mimic 3D vascular morphology to test, monitor, and analyze differences in the behavior of cancer cells (i.e. HeLa) vs. non-cancerous cell lines (i.e. 10 T1/2). The 3D Projection Printing system can fabricate complex structures in seconds from user-created designs. The fabricated microstructures have three different channel widths of 25, 45, and 120 microns wide to reflect a range of blood vessel diameters. HeLa and 10 T1/2 cells seeded within the micro-chip were then analyzed for morphology and cell migration speed. 10 T1/2 cells exhibited greater changes in morphology due to channel size width than HeLa cells; however, channel width had a limited effect on 10 T1/2 cell migration while HeLa cancer cell migration increased as channel width decreased. This physiologically relevant 3D cancer tissue model has the potential to be a powerful tool for future drug discoveries and cancer migration studies.

Width and string tension of the flux tube in SU(2) lattice gauge theory at high temperature

NASA Astrophysics Data System (ADS)

Chagdaa, S.; Galsandorj, E.; Laermann, E.; Purev, B.

2018-02-01

We study the profiles of the flux tube between a static quark and an antiquark in quenched SU(2) lattice gauge theory at temperatures around the deconfinement phase transition. The physical width of the flux tube and the string tension have been determined from the transverse profiles and the q\\bar{q} potential, respectively. Exploiting the computational power of a GPU accelerator in our flux tube investigation, we achieve much higher statistics through which we can increase the signal to noise ratio of our observables in the simulation. This has allowed the investigation of larger lattices as well as larger separations between the quarks than in our previous work. The improved accuracy gives us better results for the width and the string tension. The physical width of the flux tube increases with the temperature up to around T c while keeping its increasing dependence on the q\\bar{q} separation. The string tension results are compared for two different sizes of the lattice. As the lattice becomes larger and finer together with the improved precision, the temperature dependent string tension tends to have a smaller value than the previous one.

Effect of channel size on sweet potato storage root enlargement in the Tuskegee University hydroponic nutrient film system

NASA Technical Reports Server (NTRS)

Morris, Carlton E.; Martinez, Edwin; Bonsi, C. K.; Mortley, Desmond G.; Hill, Walter A.; Ogbuehi, Cyriacus R.; Loretan, Phil A.

1989-01-01

The potential of the sweet potato as a food source for future long term manned space missions is being evaluated for NASA's Controlled Ecological Life Support Systems (CELSS) program. Sweet potatoes have been successfully grown in a specially designed Tuskegee University nutrient film technique (TU NFT) system. This hydroponic system yielded storage roots as high as 1790 g/plant fresh weight. In order to determine the effect of channel size on the yield of sweet potatoes, the width and depth of the growing channels were varied in two separate experiments. Widths were studied using the rectangular TU NFT channels with widths of 15 cm (6 in), 30 cm (12 in) and 45 cm (18 in). Channel depths of 5 cm (2 in), 10 cm (4 in), and 15 cm (6 in) were studied using a standard NASA fan shaped Biomass Production Chamber (BPC) channel. A comparison of preliminary results indicated that, except for storage root number, the growth and yield of sweet potatoes were not affected by channel width. Storage root yield was affected by channel depth although storage root number and foliage growth were not. Both experiments are being repeated.

CD-measurement technique for hole patterns on stencil mask

NASA Astrophysics Data System (ADS)

Ishikawa, Mikio; Yusa, Satoshi; Takikawa, Tadahiko; Fujita, Hiroshi; Sano, Hisatake; Hoga, Morihisa; Hayashi, Naoya

2004-12-01

EB lithography has a potential to successfully form hole patterns as small as 80 nm with a stencil mask. In a previous paper we proposed a technique using a HOLON dual-mode critical dimension (CD) SEM ESPA-75S in the transmission mode for CD measurement of line-and-space patterns on a stencil mask. In this paper we extend our effort of developing a CD measurement technique to contact hole features and determine it in comparison of measured values between features on mask and those printed on wafer. We have evaluated the width method and the area methods using designed 80-500 nm wide contact hole patterns on a large area membrane mask and their resist images on wafer printed by a LEEPL3000. We find that 1) the width method and the area methods show an excellent mask-wafer correlation for holes over 110 nm, and 2) the area methods show a better mask-wafer correlation than the width method does for holes below 110 nm. We conclude that the area calculated from the transmission SEM image is more suitable in defining the hole dimensions than the width for contact holes on a stencil mask.

Imaging Voltage in Genetically Defined Neuronal Subpopulations with a Cre Recombinase-Targeted Hybrid Voltage Sensor.

PubMed

Bayguinov, Peter O; Ma, Yihe; Gao, Yu; Zhao, Xinyu; Jackson, Meyer B

2017-09-20

Genetically encoded voltage indicators create an opportunity to monitor electrical activity in defined sets of neurons as they participate in the complex patterns of coordinated electrical activity that underlie nervous system function. Taking full advantage of genetically encoded voltage indicators requires a generalized strategy for targeting the probe to genetically defined populations of cells. To this end, we have generated a mouse line with an optimized hybrid voltage sensor (hVOS) probe within a locus designed for efficient Cre recombinase-dependent expression. Crossing this mouse with Cre drivers generated double transgenics expressing hVOS probe in GABAergic, parvalbumin, and calretinin interneurons, as well as hilar mossy cells, new adult-born neurons, and recently active neurons. In each case, imaging in brain slices from male or female animals revealed electrically evoked optical signals from multiple individual neurons in single trials. These imaging experiments revealed action potentials, dynamic aspects of dendritic integration, and trial-to-trial fluctuations in response latency. The rapid time response of hVOS imaging revealed action potentials with high temporal fidelity, and enabled accurate measurements of spike half-widths characteristic of each cell type. Simultaneous recording of rapid voltage changes in multiple neurons with a common genetic signature offers a powerful approach to the study of neural circuit function and the investigation of how neural networks encode, process, and store information. SIGNIFICANCE STATEMENT Genetically encoded voltage indicators hold great promise in the study of neural circuitry, but realizing their full potential depends on targeting the sensor to distinct cell types. Here we present a new mouse line that expresses a hybrid optical voltage sensor under the control of Cre recombinase. Crossing this line with Cre drivers generated double-transgenic mice, which express this sensor in targeted cell types. In brain slices from these animals, single-trial hybrid optical voltage sensor recordings revealed voltage changes with submillisecond resolution in multiple neurons simultaneously. This imaging tool will allow for the study of the emergent properties of neural circuits and permit experimental tests of the roles of specific types of neurons in complex circuit activity. Copyright © 2017 the authors 0270-6474/17/379305-15$15.00/0.

Alteration of neural action potential patterns by axonal stimulation: the importance of stimulus location

PubMed Central

Crago, Patrick E; Makowski, Nathan S

2014-01-01

Objective Stimulation of peripheral nerves is often superimposed on ongoing motor and sensory activity in the same axons, without a quantitative model of the net action potential train at the axon endpoint. Approach We develop a model of action potential patterns elicited by superimposing constant frequency axonal stimulation on the action potentials arriving from a physiologically activated neural source. The model includes interactions due to collision block, resetting of the neural impulse generator, and the refractory period of the axon at the point of stimulation. Main Results Both the mean endpoint firing rate and the probability distribution of the action potential firing periods depend strongly on the relative firing rates of the two sources and the intersite conduction time between them. When the stimulus rate exceeds the neural rate, neural action potentials do not reach the endpoint and the rate of endpoint action potentials is the same as the stimulus rate, regardless of the intersite conduction time. However, when the stimulus rate is less than the neural rate, and the intersite conduction time is short, the two rates partially sum. Increases in stimulus rate produce non-monotonic increases in endpoint rate and continuously increasing block of neurally generated action potentials. Rate summation is reduced and more neural action potentials are blocked as the intersite conduction time increases.. At long intersite conduction times, the endpoint rate simplifies to being the maximum of either the neural or the stimulus rate. Significance This study highlights the potential of increasing the endpoint action potential rate and preserving neural information transmission by low rate stimulation with short intersite conduction times. Intersite conduction times can be decreased with proximal stimulation sites for muscles and distal stimulation sites for sensory endings. The model provides a basis for optimizing experiments and designing neuroprosthetic interventions involving motor or sensory stimulation. PMID:25161163

Alteration of neural action potential patterns by axonal stimulation: the importance of stimulus location

NASA Astrophysics Data System (ADS)

Crago, Patrick E.; Makowski, Nathaniel S.

2014-10-01

Objective. Stimulation of peripheral nerves is often superimposed on ongoing motor and sensory activity in the same axons, without a quantitative model of the net action potential train at the axon endpoint. Approach. We develop a model of action potential patterns elicited by superimposing constant frequency axonal stimulation on the action potentials arriving from a physiologically activated neural source. The model includes interactions due to collision block, resetting of the neural impulse generator, and the refractory period of the axon at the point of stimulation. Main results. Both the mean endpoint firing rate and the probability distribution of the action potential firing periods depend strongly on the relative firing rates of the two sources and the intersite conduction time between them. When the stimulus rate exceeds the neural rate, neural action potentials do not reach the endpoint and the rate of endpoint action potentials is the same as the stimulus rate, regardless of the intersite conduction time. However, when the stimulus rate is less than the neural rate, and the intersite conduction time is short, the two rates partially sum. Increases in stimulus rate produce non-monotonic increases in endpoint rate and continuously increasing block of neurally generated action potentials. Rate summation is reduced and more neural action potentials are blocked as the intersite conduction time increases. At long intersite conduction times, the endpoint rate simplifies to being the maximum of either the neural or the stimulus rate. Significance. This study highlights the potential of increasing the endpoint action potential rate and preserving neural information transmission by low rate stimulation with short intersite conduction times. Intersite conduction times can be decreased with proximal stimulation sites for muscles and distal stimulation sites for sensory endings. The model provides a basis for optimizing experiments and designing neuroprosthetic interventions involving motor or sensory stimulation.

Effect of an educational game on university students' learning about action potentials.

PubMed

Luchi, Kelly Cristina Gaviao; Montrezor, Luís Henrique; Marcondes, Fernanda K

2017-06-01

The aim of this study was to evaluate the effect of an educational game that is used for teaching the mechanisms of the action potentials in cell membranes. The game was composed of pieces representing the intracellular and extracellular environments, ions, ion channels, and the Na + -K + -ATPase pump. During the game activity, the students arranged the pieces to demonstrate how the ions move through the membrane in a resting state and during an action potential, linking the ion movement with a graph of the action potential. To test the effect of the game activity on student understanding, first-year dental students were given the game to play at different times in a series of classes teaching resting membrane potential and action potentials. In all experiments, students who played the game performed better in assessments. According to 98% of the students, the game supported the learning process. The data confirm the students' perception, indicating that the educational game improved their understanding about action potentials. Copyright © 2017 the American Physiological Society.

Understanding the electrical behavior of the action potential in terms of elementary electrical sources.

PubMed

Rodriguez-Falces, Javier

2015-03-01

A concept of major importance in human electrophysiology studies is the process by which activation of an excitable cell results in a rapid rise and fall of the electrical membrane potential, the so-called action potential. Hodgkin and Huxley proposed a model to explain the ionic mechanisms underlying the formation of action potentials. However, this model is unsuitably complex for teaching purposes. In addition, the Hodgkin and Huxley approach describes the shape of the action potential only in terms of ionic currents, i.e., it is unable to explain the electrical significance of the action potential or describe the electrical field arising from this source using basic concepts of electromagnetic theory. The goal of the present report was to propose a new model to describe the electrical behaviour of the action potential in terms of elementary electrical sources (in particular, dipoles). The efficacy of this model was tested through a closed-book written exam. The proposed model increased the ability of students to appreciate the distributed character of the action potential and also to recognize that this source spreads out along the fiber as function of space. In addition, the new approach allowed students to realize that the amplitude and sign of the extracellular electrical potential arising from the action potential are determined by the spatial derivative of this intracellular source. The proposed model, which incorporates intuitive graphical representations, has improved students' understanding of the electrical potentials generated by bioelectrical sources and has heightened their interest in bioelectricity. Copyright © 2015 The American Physiological Society.

Impact of Increased Football Field Width on Player High-Speed Collision Rate.

PubMed

Joseph, Jacob R; Khalsa, Siri S; Smith, Brandon W; Park, Paul

2017-07-01

High-acceleration head impact is a known risk for mild traumatic brain injury (mTBI) based on studies using helmet accelerometry. In football, offensive and defensive players are at higher risk of mTBI due to increased speed of play. Other collision sport studies suggest that increased playing surface size may contribute to reductions in high-speed collisions. We hypothesized that wider football fields lead to a decreased rate of high-speed collisions. Computer football game simulation was developed using MATLAB. Four wide receivers were matched against 7 defensive players. Each offensive player was randomized to one of 5 typical routes on each play. The ball was thrown 3 seconds into play; ball flight time was 2 seconds. Defensive players were delayed 0.5 second before reacting to ball release. A high-speed collision was defined as the receiver converging with a defensive player within 0.5 second of catching the ball. The simulation counted high-speed collisions for 1 team/season (65 plays/game for 16 games/season = 1040 plays/season) averaged during 10 seasons, and was validated against existing data using standard field width (53.3 yards). Field width was increased in 1-yard intervals up to 58.3 yards. Using standard field width, 188 ± 4 high-speed collisions were seen per team per season (18% of plays). When field width increased by 3 yards, high-speed collision rate decreased to 135 ± 3 per team per season (28% decrease; P < 0.0001). Even small increases in football field width can lead to substantial decline in high-speed collisions, with potential for reducing instances of mTBI in football players. Copyright © 2017 Elsevier Inc. All rights reserved.

Influences of spatial and temporal variation on fish-habitat relationships defined by regression quantiles

USGS Publications Warehouse

Dunham, J.B.; Cade, B.S.; Terrell, J.W.

2002-01-01

We used regression quantiles to model potentially limiting relationships between the standing crop of cutthroat trout Oncorhynchus clarki and measures of stream channel morphology. Regression quantile models indicated that variation in fish density was inversely related to the width:depth ratio of streams but not to stream width or depth alone. The spatial and temporal stability of model predictions were examined across years and streams, respectively. Variation in fish density with width:depth ratio (10th-90th regression quantiles) modeled for streams sampled in 1993-1997 predicted the variation observed in 1998-1999, indicating similar habitat relationships across years. Both linear and nonlinear models described the limiting relationships well, the latter performing slightly better. Although estimated relationships were transferable in time, results were strongly dependent on the influence of spatial variation in fish density among streams. Density changes with width:depth ratio in a single stream were responsible for the significant (P < 0.10) negative slopes estimated for the higher quantiles (>80th). This suggests that stream-scale factors other than width:depth ratio play a more direct role in determining population density. Much of the variation in densities of cutthroat trout among streams was attributed to the occurrence of nonnative brook trout Salvelinus fontinalis (a possible competitor) or connectivity to migratory habitats. Regression quantiles can be useful for estimating the effects of limiting factors when ecological responses are highly variable, but our results indicate that spatiotemporal variability in the data should be explicitly considered. In this study, data from individual streams and stream-specific characteristics (e.g., the occurrence of nonnative species and habitat connectivity) strongly affected our interpretation of the relationship between width:depth ratio and fish density.

Lithologic controls on valley width and strath terrace formation

NASA Astrophysics Data System (ADS)

Schanz, Sarah A.; Montgomery, David R.

2016-04-01

Valley width and the degree of bedrock river terrace development vary with lithology in the Willapa and Nehalem river basins, Pacific Northwest, USA. Here, we present field-based evidence for the mechanisms by which lithology controls floodplain width and bedrock terrace formation in erosion-resistant and easily friable lithologies. We mapped valley surfaces in both basins, dated straths using radiocarbon, compared valley width versus drainage area for basalt and sedimentary bedrock valleys, and constructed slope-area plots. In the friable sedimentary bedrock, valleys are 2 to 3 times wider, host flights of strath terraces, and have concavity values near 1; whereas the erosion-resistant basalt bedrock forms narrow valleys with poorly developed, localized, or no bedrock terraces and a channel steepness index half that of the friable bedrock and an average channel concavity of about 0.5. The oldest dated strath terrace on the Willapa River, T2, was active for nearly 10,000 years, from 11,265 to 2862 calibrated years before present (cal YBP), whereas the youngest terrace, T1, is Anthropocene in age and recently abandoned. Incision rates derived from terrace ages average 0.32 mm y- 1 for T2 and 11.47 mm y- 1 for T1. Our results indicate bedrock weathering properties influence valley width through the creation of a dense fracture network in the friable bedrock that results in high rates of lateral erosion of exposed bedrock banks. Conversely, the erosion-resistant bedrock has concavity values more typical of detachment-limited streams, exhibits a sparse fracture network, and displays evidence for infrequent episodic block erosion and plucking. Lithology thereby plays a direct role on the rates of lateral erosion, influencing valley width and the potential for strath terrace planation and preservation.

Selective activation of heteromeric SK channels contributes to action potential repolarization in mouse atrial myocytes.

PubMed

Hancock, Jane M; Weatherall, Kate L; Choisy, Stéphanie C; James, Andrew F; Hancox, Jules C; Marrion, Neil V

2015-05-01

Activation of small conductance calcium-activated potassium (SK) channels is proposed to contribute to repolarization of the action potential in atrial myocytes. This role is controversial, as these cardiac SK channels appear to exhibit an uncharacteristic pharmacology. The objectives of this study were to resolve whether activation of SK channels contributes to atrial action potential repolarization and to determine the likely subunit composition of the channel. The effect of 2 SK channel inhibitors was assessed on outward current evoked in voltage clamp and on action potential duration in perforated patch and whole-cell current clamp recording from acutely isolated mouse atrial myocytes. The presence of SK channel subunits was assessed using immunocytochemistry. A significant component of outward current was reduced by the SK channel blockers apamin and UCL1684. Block by apamin displayed a sensitivity indicating that this current was carried by homomeric SK2 channels. Action potential duration was significantly prolonged by UCL1684, but not by apamin. This effect was accompanied by an increase in beat-to-beat variability and action potential triangulation. This pharmacology was matched by that of expressed heteromeric SK2-SK3 channels in HEK293 cells. Immunocytochemistry showed that atrial myocytes express both SK2 and SK3 channels with an overlapping expression pattern. Only proposed heteromeric SK2-SK3 channels are physiologically activated to contribute to action potential repolarization, which is indicated by the difference in pharmacology of evoked outward current and prolongation of atrial action potential duration. The effect of blocking this channel on the action potential suggests that SK channel inhibition during cardiac function has the potential to be proarrhythmic. Copyright © 2015 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

Urocortin2 prolongs action potential duration and modulates potassium currents in guinea pig myocytes and HEK293 cells.

PubMed

Yang, Li-Zhen; Zhu, Yi-Chun

2015-07-05

We previously reported that activation of corticotropin releasing factor receptor type 2 by urocortin2 up-regulates both L-type Ca(2+) channels and intracellular Ca(2+) concentration in ventricular myocytes and plays an important role in cardiac contractility and arrhythmogenesis. This study goal was to further test the hypothesis that urocortin2 may modulate action potentials as well as rapidly and slowly activating delayed rectifier potassium currents. With whole cell patch-clamp techniques, action potentials and slowly activating delayed rectifier potassium currents were recorded in isolated guinea pig ventricular myocytes, respectively. And rapidly activating delayed rectifier potassium currents were tested in hERG-HEK293 cells. Urocortin2 produced a time- and concentration-dependent prolongation of action potential duration. The EC50 values of action potential duration and action potential duration at 90% of repolarization were 14.73 and 24.3nM respectively. The prolongation of action potential duration of urocortin2 was almost completely or partly abolished by H-89 (protein kinase A inhibitor) or KB-R7943 (Na(+)/Ca(2+) exchange inhibitor) pretreatment respectively. And urocortin2 caused reduction of rapidly activating delayed rectifier potassium currents in hERG-HEK293 cells. In addition, urocortin2 slowed the rate of slowly activating delayed rectifier potassium channel activation, and rightward shifted the threshold of slowly activating delayed rectifier potassium currents to more positive potentials. Urocortin2 prolonged action potential duration via activation of protein kinase A and Na(+)/ Ca(2+) exchange in isolated guinea pig ventricular myocytes in a time- and concentration- dependent manner. In hERG-HEK293 cells, urocortin2 reduced rapidly activating delayed rectifier potassium current density which may contribute to action potential duration prolongation. Copyright © 2015 Elsevier B.V. All rights reserved.

Population of computational rabbit-specific ventricular action potential models for investigating sources of variability in cellular repolarisation.

PubMed

Gemmell, Philip; Burrage, Kevin; Rodriguez, Blanca; Quinn, T Alexander

2014-01-01

Variability is observed at all levels of cardiac electrophysiology. Yet, the underlying causes and importance of this variability are generally unknown, and difficult to investigate with current experimental techniques. The aim of the present study was to generate populations of computational ventricular action potential models that reproduce experimentally observed intercellular variability of repolarisation (represented by action potential duration) and to identify its potential causes. A systematic exploration of the effects of simultaneously varying the magnitude of six transmembrane current conductances (transient outward, rapid and slow delayed rectifier K(+), inward rectifying K(+), L-type Ca(2+), and Na(+)/K(+) pump currents) in two rabbit-specific ventricular action potential models (Shannon et al. and Mahajan et al.) at multiple cycle lengths (400, 600, 1,000 ms) was performed. This was accomplished with distributed computing software specialised for multi-dimensional parameter sweeps and grid execution. An initial population of 15,625 parameter sets was generated for both models at each cycle length. Action potential durations of these populations were compared to experimentally derived ranges for rabbit ventricular myocytes. 1,352 parameter sets for the Shannon model and 779 parameter sets for the Mahajan model yielded action potential duration within the experimental range, demonstrating that a wide array of ionic conductance values can be used to simulate a physiological rabbit ventricular action potential. Furthermore, by using clutter-based dimension reordering, a technique that allows visualisation of multi-dimensional spaces in two dimensions, the interaction of current conductances and their relative importance to the ventricular action potential at different cycle lengths were revealed. Overall, this work represents an important step towards a better understanding of the role that variability in current conductances may play in experimentally observed intercellular variability of rabbit ventricular action potential repolarisation.

Population of Computational Rabbit-Specific Ventricular Action Potential Models for Investigating Sources of Variability in Cellular Repolarisation

PubMed Central

Gemmell, Philip; Burrage, Kevin; Rodriguez, Blanca; Quinn, T. Alexander

2014-01-01

Variability is observed at all levels of cardiac electrophysiology. Yet, the underlying causes and importance of this variability are generally unknown, and difficult to investigate with current experimental techniques. The aim of the present study was to generate populations of computational ventricular action potential models that reproduce experimentally observed intercellular variability of repolarisation (represented by action potential duration) and to identify its potential causes. A systematic exploration of the effects of simultaneously varying the magnitude of six transmembrane current conductances (transient outward, rapid and slow delayed rectifier K+, inward rectifying K+, L-type Ca2+, and Na+/K+ pump currents) in two rabbit-specific ventricular action potential models (Shannon et al. and Mahajan et al.) at multiple cycle lengths (400, 600, 1,000 ms) was performed. This was accomplished with distributed computing software specialised for multi-dimensional parameter sweeps and grid execution. An initial population of 15,625 parameter sets was generated for both models at each cycle length. Action potential durations of these populations were compared to experimentally derived ranges for rabbit ventricular myocytes. 1,352 parameter sets for the Shannon model and 779 parameter sets for the Mahajan model yielded action potential duration within the experimental range, demonstrating that a wide array of ionic conductance values can be used to simulate a physiological rabbit ventricular action potential. Furthermore, by using clutter-based dimension reordering, a technique that allows visualisation of multi-dimensional spaces in two dimensions, the interaction of current conductances and their relative importance to the ventricular action potential at different cycle lengths were revealed. Overall, this work represents an important step towards a better understanding of the role that variability in current conductances may play in experimentally observed intercellular variability of rabbit ventricular action potential repolarisation. PMID:24587229

Action potential propagation: ion current or intramembrane electric field?

PubMed

Martí, Albert; Pérez, Juan J; Madrenas, Jordi

2018-01-01

The established action potential propagation mechanisms do not satisfactorily explain propagation on myelinated axons given the current knowledge of biological channels and membranes. The flow across ion channels presents two possible effects: the electric potential variations across the lipid bilayers (action potential) and the propagation of an electric field through the membrane inner part. The proposed mechanism is based on intra-membrane electric field propagation, this propagation can explain the action potential saltatory propagation and its constant delay independent of distance between Ranvier nodes in myelinated axons.

Recording evoked potentials during deep brain stimulation: development and validation of instrumentation to suppress the stimulus artefact

PubMed Central

Kent, A R; Grill, W M

2012-01-01

Deep brain stimulation (DBS) is an effective treatment for movement disorders, but the selection of stimulus parameters is a clinical burden and often yields sub-optimal outcomes for patients. Measurement of electrically evoked compound action potentials (ECAPs) during DBS could offer insight into the type and spatial extent of neural element activation and provide a potential feedback signal for the rational selection of stimulus parameters and closed-loop DBS. However, recording ECAPs presents a significant technical challenge due to the large stimulus artefact, which can saturate recording amplifiers and distort short latency ECAP signals. We developed DBS-ECAP recording instrumentation combining commercial amplifiers and circuit elements in a serial configuration to reduce the stimulus artefact and enable high fidelity recording. We used an electrical circuit equivalent model of the instrumentation to understand better the sources of the stimulus artefact and the mechanisms of artefact reduction by the circuit elements. In vitro testing validated the capability of the instrumentation to suppress the stimulus artefact and increase gain by a factor of 1,000 to 5,000 compared to a conventional biopotential amplifier. The distortion of mock ECAP (mECAP) signals was measured across stimulation parameters, and the instrumentation enabled high fidelity recording of mECAPs with latencies of only 0.5 ms for DBS pulse widths of 50 to 100 μs/phase. Subsequently, the instrumentation was used to record in vivo ECAPs, without contamination by the stimulus artefact, during thalamic DBS in an anesthetized cat. The characteristics of the physiological ECAP were dependent on stimulation parameters. The novel instrumentation enables high fidelity ECAP recording and advances the potential use of the ECAP as a feedback signal for the tuning of DBS parameters. PMID:22510375

Antidromic propagation of action potentials in branched axons: implications for the mechanisms of action of deep brain stimulation.

PubMed

Grill, Warren M; Cantrell, Meredith B; Robertson, Matthew S

2008-02-01

Electrical stimulation of the central nervous system creates both orthodromically propagating action potentials, by stimulation of local cells and passing axons, and antidromically propagating action potentials, by stimulation of presynaptic axons and terminals. Our aim was to understand how antidromic action potentials navigate through complex arborizations, such as those of thalamic and basal ganglia afferents-sites of electrical activation during deep brain stimulation. We developed computational models to study the propagation of antidromic action potentials past the bifurcation in branched axons. In both unmyelinated and myelinated branched axons, when the diameters of each axon branch remained under a specific threshold (set by the antidromic geometric ratio), antidromic propagation occurred robustly; action potentials traveled both antidromically into the primary segment as well as "re-orthodromically" into the terminal secondary segment. Propagation occurred across a broad range of stimulation frequencies, axon segment geometries, and concentrations of extracellular potassium, but was strongly dependent on the geometry of the node of Ranvier at the axonal bifurcation. Thus, antidromic activation of axon terminals can, through axon collaterals, lead to widespread activation or inhibition of targets remote from the site of stimulation. These effects should be included when interpreting the results of functional imaging or evoked potential studies on the mechanisms of action of DBS.

Surgical anatomy of round window and its implications for cochlear implantation.

PubMed

Singla, A; Sahni, D; Gupta, A K; Loukas, M; Aggarwal, A

2014-04-01

The objective of this work was to study the morphometry and morphology of the round window (RW) and its relationships with the internal carotid artery, jugular bulb (JB), facial nerve and oval window (OW). Fifty cadaveric temporal bones were microdissected to expose the medial wall of the middle ear. The areas around the RW were cleared and its shape, height and width were noted. Its distances from the carotid canal (CC), jugular fossa (JF), facial canal (FC), and OW were measured. Oval, round, triangular, comma, quadrangular, and pear shapes of RW were observed. The average height and width of the RW were 1.62 ± 0.77 mm and 1.15 ± 0.39 mm, respectively. There was a statistically significant correlation (r = 0.4, P < 0.01) between the height and width. The distances between the RW and the CC, JF, FC, and OW were in the ranges 4.39-11.05 mm, 0.38-8.65 mm, 2.99-6.3 mm, and 1.39-3.57 mm, respectively. In 8% of cases, the distance between the RW and the JF was <1 mm. There were no statistically significant differences with regard to age group, gender, or side. Electrode insertion can be challenging in cases where the height and width of the RW are <1 mm. The thin bone separating the roof of the JF from the RW (<1 mm in 8%) highlights a potential risk of injury to the JB during cochleostomy placement. This information could be useful for selecting cochlear implant electrodes in order to avoid potential risks to vital neurovascular structures during implant surgery. Copyright © 2013 Wiley Periodicals, Inc.

Minocycline inhibits D-amphetamine-elicited action potential bursts in a central snail neuron.

PubMed

Chen, Y-H; Lin, P-L; Wong, R-W; Wu, Y-T; Hsu, H-Y; Tsai, M-C; Lin, M-J; Hsu, Y-C; Lin, C-H

2012-10-25

Minocycline is a second-generation tetracycline that has been reported to have powerful neuroprotective properties. In our previous studies, we found that d-amphetamine (AMPH) elicited action potential bursts in an identifiable RP4 neuron of the African snail, Achatina fulica Ferussac. This study sought to determine the effects of minocycline on the AMPH-elicited action potential pattern changes in the central snail neuron, using the two-electrode voltage clamping method. Extracellular application of AMPH at 300 μM elicited action potential bursts in the RP4 neuron. Minocycline dose-dependently (300-900 μM) inhibited the action potential bursts elicited by AMPH. The inhibitory effects of minocycline on AMPH-elicited action potential bursts were restored by forskolin (50 μM), an adenylate cyclase activator, and by dibutyryl cAMP (N(6),2'-O-Dibutyryladenosine 3',5'-cyclic monophosphate; 1mM), a membrane-permeable cAMP analog. Co-administration of forskolin (50 μM) plus tetraethylammonium chloride (TEA; 5mM) or co-administration of TEA (5mM) plus dibutyryl cAMP (1mM) also elicited action potential bursts, which were prevented and inhibited by minocycline. In addition, minocycline prevented and inhibited forskolin (100 μM)-elicited action potential bursts. Notably, TEA (50mM)-elicited action potential bursts in the RP4 neuron were not affected by minocycline. Minocycline did not affect steady-state outward currents of the RP4 neuron. However, minocycline did decrease the AMPH-elicited steady-state current changes. Similarly, minocycline decreased the effects of forskolin-elicited steady-state current changes. Pretreatment with H89 (N-[2-(p-Bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide dihydrochloride; 10 μM), a protein kinase A inhibitor, inhibited AMPH-elicited action potential bursts and decreased AMPH-elicited steady-state current changes. These results suggest that the cAMP-protein kinase A signaling pathway and the steady-state current are involved in the inhibitory effects of minocycline upon AMPH-elicited action potential bursts. Copyright © 2012 IBRO. Published by Elsevier Ltd. All rights reserved.

Exact solution of finite parabolic potential disc-like quantum dot with and without electric field R. Djelti, S. Bentata and Z. Aziz: Trimer barrier hight effect oh the nature of the electronic state of the superlatice GaAs/AlxGa1-xAs Bibhas K. Dutta and Prasanta K. Mahapatra: Study of velocity-dependent collision effects on Lamb dip and crossover resonances in three-level system

NASA Astrophysics Data System (ADS)

Hassanien, H. H.; Abdelmoly, S. S.; Elmeshad, N.

The exact series solutions of finite parabolic potential disc-like quantum dot are given in the absence and presence of uniform applied electric field. We define some normalized parameters. From the complex eigenenergy E=E0 - i G/2, due to the electric field, we calculate the resonance width G of a bounded state. The ground and the first excited state of the electron and the hole are obtained with and without the electric field. The corresponding envelope functions are presented as a function of the disc dimensionality, radius R and half-width L.

Holographic insulator/superconductor transition with exponential nonlinear electrodynamics probed by entanglement entropy

NASA Astrophysics Data System (ADS)

Yao, Weiping; Yang, Chaohui; Jing, Jiliang

2018-05-01

From the viewpoint of holography, we study the behaviors of the entanglement entropy in insulator/superconductor transition with exponential nonlinear electrodynamics (ENE). We find that the entanglement entropy is a good probe to the properties of the holographic phase transition. Both in the half space and the belt space, the non-monotonic behavior of the entanglement entropy in superconducting phase versus the chemical potential is general in this model. Furthermore, the behavior of the entanglement entropy for the strip geometry shows that the confinement/deconfinement phase transition appears in both insulator and superconductor phases. And the critical width of the confinement/deconfinement phase transition depends on the chemical potential and the exponential coupling term. More interestingly, the behaviors of the entanglement entropy in their corresponding insulator phases are independent of the exponential coupling factor but depends on the width of the subsystem A.

Selective effects of an octopus toxin on action potentials

PubMed Central

Dulhunty, Angela; Gage, Peter W.

1971-01-01

1. A lethal, water soluble toxin (Maculotoxin, MTX) with a molecular weight less than 540, can be extracted from the salivary glands of an octopus (Hapalochlaena maculosa). 2. MTX blocks action potentials in sartorius muscle fibres of toads without affecting the membrane potential. Delayed rectification is not inhibited by the toxin. 3. At low concentrations (10-6-10-5 g/ml.) MTX blocks action potentials only after a certain number have been elicited. The number of action potentials, which can be defined accurately, depends on the concentration of MTX and the concentration of sodium ions in the extracellular solution. 4. The toxin has no post-synaptic effect at the neuromuscular junction and it is concluded that it blocks neuromuscular transmission by inhibiting action potentials in motor nerve terminals. PMID:4330930

Reliability and determinants of anogenital distance and penis dimensions in male newborns from Chiapas, México

PubMed Central

Romano-Riquer, S. Patricia; Hernández-Ávila, Mauricio; Gladen, Beth C.; Cupul-Uicab, Lea A.; Longnecker, Matthew P.

2013-01-01

Summary Development of the perineum as well as the external genitalia is determined by dihydrotestosterone, resulting in a greater anogenital distance (AGD) in males than females. In animal experiments with hormonally active agents, anogenital distance is used as a bioassay of fetal androgen action. Use of anogenital distance in human studies has been rare. Because anogenital distance has been an easy-to-measure, sensitive outcome in animal studies, we developed an anthropometric protocol for measurement of anogenital distance in human males. In this paper we describe the method for measurement of three anogenital distances, their reliability, and an assessment of predictors for each in the context of an epidemiological study. We compare the reliabilities and predictors to those for stretched penis length and penis width. A cross-sectional study of 781 newly-delivered male infants was conducted in 2002–2003 in Chiapas, México. Replicate measures were obtained on nearly all subjects. The reliability of the measures of anogenital distance (0.82–0.91) were higher than for stretched penis length (0.78) and width (0.75). Birthweight and gestational length were more strongly related to anogenital distance than to penis length. Anogenital distance was not related to penis length (r = 0.03). Our large study clearly shows that AGD can be measured well in newborn males, and that the measurements were more reliable than those of penis length. Whether AGD measures in humans relate to clinically important outcomes, however, remains to be determined, as does its utility as a measure of androgen action in epidemiological studies. PMID:17439530

Relationship between size and latency of action potentials in human muscle sympathetic nerve activity.

PubMed

Salmanpour, Aryan; Brown, Lyndon J; Steinback, Craig D; Usselman, Charlotte W; Goswami, Ruma; Shoemaker, J Kevin

2011-06-01

We employed a novel action potential detection and classification technique to study the relationship between the recruitment of sympathetic action potentials (i.e., neurons) and the size of integrated sympathetic bursts in human muscle sympathetic nerve activity (MSNA). Multifiber postganglionic sympathetic nerve activity from the common fibular nerve was collected using microneurography in 10 healthy subjects at rest and during activation of sympathetic outflow using lower body negative pressure (LBNP). Burst occurrence increased with LBNP. Integrated burst strength (size) varied from 0.22 ± 0.07 V at rest to 0.28 ± 0.09 V during LBNP. Sympathetic burst size (i.e., peak height) was directly related to the number of action potentials within a sympathetic burst both at baseline (r = 0.75 ± 0.13; P < 0.001) and LBNP (r = 0.75 ± 0.12; P < 0.001). Also, the amplitude of detected action potentials within sympathetic bursts was directly related to the increased burst size at both baseline (r = 0.59 ± 0.16; P < 0.001) and LBNP (r = 0.61 ± 0.12; P < 0.001). In addition, the number of detected action potentials and the number of distinct action potential clusters within a given sympathetic burst were correlated at baseline (r = 0.7 ± 0.1; P < 0.001) and during LBNP (r = 0.74 ± 0.03; P < 0.001). Furthermore, action potential latency (i.e., an inverse index of neural conduction velocity) was decreased as a function of action potential size at baseline and LBNP. LBNP did not change the number of action potentials and unique clusters per sympathetic burst. It was concluded that there exists a hierarchical pattern of recruitment of additional faster conducting neurons of larger amplitude as the sympathetic bursts become stronger (i.e., larger amplitude bursts). This fundamental pattern was evident at rest and was not altered by the level of baroreceptor unloading applied in this study.

All optical experimental design for neuron excitation, inhibition, and action potential detection

NASA Astrophysics Data System (ADS)

Walsh, Alex J.; Tolstykh, Gleb; Martens, Stacey; Sedelnikova, Anna; Ibey, Bennett L.; Beier, Hope T.

2016-03-01

Recently, infrared light has been shown to both stimulate and inhibit excitatory cells. However, studies of infrared light for excitatory cell inhibition have been constrained by the use of invasive and cumbersome electrodes for cell excitation and action potential recording. Here, we present an all optical experimental design for neuronal excitation, inhibition, and action potential detection. Primary rat neurons were transfected with plasmids containing the light sensitive ion channel CheRiff. CheRiff has a peak excitation around 450 nm, allowing excitation of transfected neurons with pulsed blue light. Additionally, primary neurons were transfected with QuasAr2, a fast and sensitive fluorescent voltage indicator. QuasAr2 is excited with yellow or red light and therefore does not spectrally overlap CheRiff, enabling imaging and action potential activation, simultaneously. Using an optic fiber, neurons were exposed to blue light sequentially to generate controlled action potentials. A second optic fiber delivered a single pulse of 1869nm light to the neuron causing inhibition of the evoked action potentials (by the blue light). When used in concert, these optical techniques enable electrode free neuron excitation, inhibition, and action potential recording, allowing research into neuronal behaviors with high spatial fidelity.

Visual cues for the retrieval of landmark memories by navigating wood ants.

PubMed

Harris, Robert A; Graham, Paul; Collett, Thomas S

2007-01-23

Even on short routes, ants can be guided by multiple visual memories. We investigate here the cues controlling memory retrieval as wood ants approach a one- or two-edged landmark to collect sucrose at a point along its base. In such tasks, ants store the desired retinal position of landmark edges at several points along their route. They guide subsequent trips by retrieving the appropriate memory and moving to bring the edges in the scene toward the stored positions. The apparent width of the landmark turns out to be a powerful cue for retrieving the desired retinal position of a landmark edge. Two other potential cues, the landmark's apparent height and the distance that the ant walks, have little effect on memory retrieval. A simple model encapsulates these conclusions and reproduces the ants' routes in several conditions. According to this model, the ant stores a look-up table. Each entry contains the apparent width of the landmark and the desired retinal position of vertical edges. The currently perceived width provides an index for retrieving the associated stored edge positions. The model accounts for the population behavior of ants and the idiosyncratic training routes of individual ants. Our results imply binding between the edge of a shape and its width and, further, imply that assessing the width of a shape does not depend on the presence of any particular local feature, such as a landmark edge. This property makes the ant's retrieval and guidance system relatively robust to edge occlusions.

Progress towards modeling tokamak boundary plasma turbulence and understanding its role in setting divertor heat flux widths

NASA Astrophysics Data System (ADS)

Chen, B.; Xu, X. Q.; Xia, T. Y.; Li, N. M.; Porkolab, M.; Edlund, E.; LaBombard, B.; Terry, J.; Hughes, J. W.; Ye, M. Y.; Wan, Y. X.

2018-05-01

The heat flux distributions on divertor targets in H-mode plasmas are serious concerns for future devices. We seek to simulate the tokamak boundary plasma turbulence and heat transport in the edge localized mode-suppressed regimes. The improved BOUT++ model shows that not only Ip but also the radial electric field Er plays an important role on the turbulence behavior and sets the heat flux width. Instead of calculating Er from the pressure gradient term (diamagnetic Er), it is calculated from the plasma transport equations with the sheath potential in the scrape-off layer and the plasma density and temperature profiles inside the separatrix from the experiment. The simulation results with the new Er model have better agreement with the experiment than using the diamagnetic Er model: (1) The electromagnetic turbulence in enhanced Dα H-mode shows the characteristics of quasi-coherent modes (QCMs) and broadband turbulence. The mode spectra are in agreement with the phase contrast imaging data and almost has no change in comparison to the cases which use the diamagnetic Er model; (2) the self-consistent boundary Er is needed for the turbulence simulations to get the consistent heat flux width with the experiment; (3) the frequencies of the QCMs are proportional to Er, while the divertor heat flux widths are inversely proportional to Er; and (4) the BOUT++ turbulence simulations yield a similar heat flux width to the experimental Eich scaling law and the prediction from the Goldston heuristic drift model.

Calculation of the Energy-Band Structure of the Kronig-Penney Model Using the Nearly-Free and Tightly-Bound-Electron Approximations

ERIC Educational Resources Information Center

Wetsel, Grover C., Jr.

1978-01-01

Calculates the energy-band structure of noninteracting electrons in a one-dimensional crystal using exact and approximate methods for a rectangular-well atomic potential. A comparison of the two solutions as a function of potential-well depth and ratio of lattice spacing to well width is presented. (Author/GA)

Effect of Organic Blocking Layer on the Energy Storage Characteristics of High-Permittivity Sol-Gel Thin Film Based on Neat 2-Cyanoethyltrimethoxysilane

NASA Astrophysics Data System (ADS)

Kim, Yunsang; Kathaperumal, Mohanalingam; Pan, Ming-Jen; Perry, Joseph

2014-03-01

Organic-inorganic hybrid sol-gel materials with polar groups that can undergo reorientational polarization provide a potential route to dielectric materials for energy storage. We have investigated the influence of nanoscale polymeric layer on dielectric and energy storage properties of 2-cyanoethyltrimethoxysilane (CNETMS) films. Two polymeric materials, fluoropolymer (CYTOP) and poly(p-phenylene oxide, PPO), are examined as potential materials to control charge injection from electrical contacts into CNETMS films by means of a potential barrier, whose width and height are defined by thickness and permittivity. Blocking layers ranging from 20 nm to 200 nm were deposited on CNETMS films by spin casting and subjected to thermal treatment. Polarization-electric field measurements show 30% increase in extractable energy density with PPO/CNETMS bilayers, relative to CNETMS alone, due to improved breakdown strength. Conduction current of the bilayers indicate that onset of charge conduction at high field is much delayed, which can be translated into effective suppression of charge injection and probability of breakdown events. The results will be discussed in regards to film morphology, field partitioning, width and height of potential barrier, charge trapping and loss of bilayers.

Determination of the Stresses Produced by the Landing Impact in the Bulkheads of a Seaplane Bottom

NASA Technical Reports Server (NTRS)

Darevsky, V. M.

1944-01-01

The present report deals with the determination of the impact stresses in the bulkhead floors of a seaplane bottom. The dynamic problem is solved on the assumption of a certain elastic system, the floor being assumed as a weightless elastic beam with concentrated masses at the ends (due to the mass of the float) and with a spring which replaces the elastic action of the keel in the center. The distributed load on the floor is that due to the hydrodynamic force acting over a certain portion of the bottom. The pressure distribution over the width of the float is assumed to follow the Wagner law. The formulas given for the maximum bending moment are derived on the assumption that the keel is relatively elastic, in which case it can be shown that at each instant of time the maximum bending moment is at the point of juncture of the floor with the keel. The bending moment at this point is a function of the half width of the wetted surface c and reaches its maximum value when c is approximately equal to b/2 where b is the half width of the float. In general, however, for computing the bending moment the values of the bending moment at the keel for certain values of c are determined and a curve is drawn. The illustrative sample computation gave for the stresses a result approximately equal to that obtained by the conventional factory computation.

Cortical Action Potential Backpropagation Explains Spike Threshold Variability and Rapid-Onset Kinetics

PubMed Central

Yu, Yuguo; Shu, Yousheng; McCormick, David A.

2008-01-01

Neocortical action potential responses in vivo are characterized by considerable threshold variability, and thus timing and rate variability, even under seemingly identical conditions. This finding suggests that cortical ensembles are required for accurate sensorimotor integration and processing. Intracellularly, trial-to-trial variability results not only from variation in synaptic activities, but also in the transformation of these into patterns of action potentials. Through simultaneous axonal and somatic recordings and computational simulations, we demonstrate that the initiation of action potentials in the axon initial segment followed by backpropagation of these spikes throughout the neuron results in a distortion of the relationship between the timing of synaptic and action potential events. In addition, this backpropagation also results in an unusually high rate of rise of membrane potential at the foot of the action potential. The distortion of the relationship between the amplitude time course of synaptic inputs and action potential output caused by spike back-propagation results in the appearance of high spike threshold variability at the level of the soma. At the point of spike initiation, the axon initial segment, threshold variability is considerably less. Our results indicate that spike generation in cortical neurons is largely as expected by Hodgkin—Huxley theory and is more precise than previously thought. PMID:18632930

Median and ulnar muscle and sensory evoked potentials.

PubMed

Felsenthal, G

1978-08-01

The medical literature was reviewed to find suggested clinical applications of the study of the amplitude of evoked muscle action potentials (MAP) and sensory action potentials (SAP). In addition, the literature was reviewed to ascertain the normal amplitude and duration of the evoked MAP and SAP as well as the factors affecting the amplitude: age, sex, temperature, ischemia. The present study determined the normal amplitude and duration of the median and ulnar MAP and SAP in fifty normal subjects. The amplitude of evoked muscle or sensory action potentials depends on multiple factors. Increased skin resistance, capacitance, and impedance at the surface of the recording electrode diminishes the amplitude. Similarly, increased distance from the source of the action potential diminishes its amplitude. Increased interelectrode distance increases the amplitude of the bipolarly recorded sensory action potential until a certain interelectrode distance is exceeded and the diphasic response becomes tri- or tetraphasic. Artifact or poor technique may reduce the potential difference between the recording electrodes or obscure the late positive phase of the action potential and thus diminish the peak to peak amplitude measurement. Intraindividual comparison indicated a marked difference of amplitude in opposite hands. The range of the MAP of the abductor pollicis brevis in one hand was 40.0--100% of the response in the opposite hand. For the abductor digiti minimi, the MAP was 58.5--100% of the response of the opposite hand. The median and ulnar SAP was between 50--100% of the opposite SAP. Consequent to these findings the effect of hand dominance on the amplitude of median and ulnar evoked muscle and sensory action potentials was studied in 41 right handed volunteers. The amplitudes of the median muscle action potential (p less than 0.02) and the median and ulnar sensory action potentials (p less than 0.001) were significantly less in the dominant hand. There was no significant difference between the ulnar muscle action potentials or for the median and ulnar distal motor and sensory latencies in the right and left hands of this group of volunteers.

Line shape parameters for the H2O-H2 collision system for application to exoplanet and planetary atmospheres

NASA Astrophysics Data System (ADS)

Renaud, Candice L.; Cleghorn, Kara; Hartmann, Léna; Vispoel, Bastien; Gamache, Robert R.

2018-05-01

Water can be detected throughout the universe: in comets, asteroids, dwarf planets, the inner and outer planets in our solar system, cool stars, brown dwarfs, and on many exoplanets. Here the focus is on locations rich in hydrogen gas. To properly study these environments, there is a need for the line shape parameters for H2O transitions in collision with hydrogen. This work presents calculations of the half-width and line shift, made using the Modified Complex Robert-Bonamy (MCRB) formalism, at a number of temperatures. It is shown that this collision system is strongly off-resonance. For such conditions, the atom-atom part of the intermolecular potential dominates the interaction of the radiating and perturbing molecules. The atom-atom parameters were adjusted by fitting the H2O-H2 measurements of Brown and Plymate (1996). Several techniques were used to extract lines for which there is more confidence in the quality of the data. The final potential yields results that agree with the measurements with ∼0.3% difference and a 5.9% standard deviation. Using this potential, MCRB calculations were made for all transitions in the pure rotation, ν2, ν1, and ν3 bands. The structure of the line shape parameters and the temperature dependence of the half-width, as a function of the rotational and vibrational quantum numbers, are discussed. It is shown that the power law model of the T-dependence of the half-width is inadequate over large temperature ranges.

Ionotropic glutamate receptor GluA4 and T-type calcium channel Cav 3.1 subunits control key aspects of synaptic transmission at the mouse L5B-POm giant synapse.

PubMed

Seol, Min; Kuner, Thomas

2015-12-01

The properties and molecular determinants of synaptic transmission at giant synapses connecting layer 5B (L5B) neurons of the somatosensory cortex (S1) with relay neurons of the posteriomedial nucleus (POm) of the thalamus have not been investigated in mice. We addressed this by using direct electrical stimulation of fluorescently labelled single corticothalamic terminals combined with molecular perturbations and whole-cell recordings from POm relay neurons. Consistent with their function as drivers, we found large-amplitude excitatory postsynaptic currents (EPSCs) and multiple postsynaptic action potentials triggered by a single presynaptic action potential. To study the molecular basis of these two features, ionotropic glutamate receptors and low voltage-gated T-type calcium channels were probed by virus-mediated genetic perturbation. Loss of GluA4 almost abolished the EPSC amplitude, strongly delaying the onset of action potential generation, but maintaining the number of action potentials generated per presynaptic action potential. In contrast, knockdown of the Cav 3.1 subunit abrogated the driver function of the synapse at a typical resting membrane potential of -70 mV. However, when depolarizing the membrane potential to -60 mV, the synapse relayed single action potentials. Hence, GluA4 subunits are required to produce an EPSC sufficiently large to trigger postsynaptic action potentials within a defined time window after the presynaptic action potential, while Cav 3.1 expression is essential to establish the driver function of L5B-POm synapses at hyperpolarized membrane potentials. © 2015 The Authors. European Journal of Neuroscience published by Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

Novel ultrasonic real-time scanner featuring servo controlled transducers displaying a sector image.

PubMed

Matzuk, T; Skolnick, M L

1978-07-01

This paper describes a new real-time servo controlled sector scanner that produces high resolution images and has functionally programmable features similar to phased array systems, but possesses the simplicity of design and low cost best achievable in a mechanical sector scanner. The unique feature is the transducer head which contains a single moving part--the transducer--enclosed within a light-weight, hand held, and vibration free case. The frame rate, sector width, stop action angle, are all operator programmable. The frame rate can be varied from 12 to 30 frames s-1 and the sector width from 0 degrees to 60 degrees. Conversion from sector to time motion (T/M) modes are instant and two options are available, a freeze position high density T/M and a low density T/M obtainable simultaneously during sector visualization. Unusual electronic features are: automatic gain control, electronic recording of images on video tape in rf format, and ability to post-process images during video playback to extract T/M display and to change time gain control (tgc) and image size.

Engineering double-well potentials with variable-width annular Josephson tunnel junctions

NASA Astrophysics Data System (ADS)

Monaco, Roberto

2016-11-01

Long Josephson tunnel junctions are non-linear transmission lines that allow propagation of current vortices (fluxons) and electromagnetic waves and are used in various applications within superconductive electronics. Recently, the Josephson vortex has been proposed as a new superconducting qubit. We describe a simple method to create a double-well potential for an individual fluxon trapped in a long elliptic annular Josephson tunnel junction characterized by an intrinsic non-uniform width. The distance between the potential wells and the height of the inter-well potential barrier are controlled by the strength of an in-plane magnetic field. The manipulation of the vortex states can be achieved by applying a proper current ramp across the junction. The read-out of the state is accomplished by measuring the vortex depinning current in a small magnetic field. An accurate one-dimensional sine-Gordon model for this strongly non-linear system is presented, from which we calculate the position-dependent fluxon rest-mass, its Hamiltonian density and the corresponding trajectories in the phase space. We examine the dependence of the potential properties on the annulus eccentricity and its electrical parameters and address the requirements for observing quantum-mechanical effects, as discrete energy levels and tunneling, in this two-state system.

Low concentrations of procaine and diethylaminoethanol reduce the excitability but not the action potential amplitude of hippocampal pyramidal cells.

PubMed

Butterworth, J F; Cole, L R

1990-10-01

To determine whether concentrations of diethylaminoethanol (DEAE) and procaine below those that reduce the amplitude of action potentials might alter the excitability of brain cells, a single microelectrode intracellular recording technique was used to measure firing threshold and action potential amplitude of pyramidal cells in rat hippocampal slices. At low concentrations of both DEAE (less than or equal to 5 mM) and procaine (less than or equal to 0.5 mM), firing threshold was significantly increased (P less than 0.01), whereas action potential spike amplitude was minimally altered. At higher concentrations, both drugs significantly decreased action potential spike amplitude (P less than 0.025) as well as increased firing threshold (P less than 0.001). Diethylaminoethanol tended to increase threshold relatively more than procaine, when drug concentrations that similarly reduced action potential amplitude were compared. All actions of DEAE and procaine were reversible. Inhibition of action potentials by DEAE and procaine was clearly concentration-dependent (P less than or equal to 0.015). Diethylaminoethanol effects on threshold were marginally concentration-dependent (P = 0.08); procaine did not demonstrate clear concentration-dependent effects (P = 0.33) over the concentrations tested in this study. These similar actions of procaine and DEAE on brain cells suggest a mechanism by which intravenous local anesthetics may contribute to the general anesthetic state. Moreover, it appears possible that procaine metabolism and DEAE accumulation may underlie the prolonged effects sometimes seen after intravenous procaine administration.

78 FR 34031 - Burned Area Emergency Response, Forest Service

Federal Register 2010, 2011, 2012, 2013, 2014

2013-06-06

...) Evaluate potential threats to critical values; (2) determine the risk level for each threat; (3) identify... actions that meet the objectives; (6) evaluate potential response actions on likelihood for timely... stabilization actions. Improved the descriptive guidelines for employing response actions involving...

Impact of nanosecond pulsed electric fields on primary hippocampal neurons

NASA Astrophysics Data System (ADS)

Roth, Caleb C.; Payne, Jason A.; Kuipers, Marjorie A.; Thompson, Gary L.; Wilmink, Gerald J.; Ibey, Bennett L.

2012-02-01

Cellular exposure to nanosecond pulsed electric fields (nsPEF) are believed to cause immediate creation of nanopores in the plasma membrane. These nanopores enable passage of small ions, but remain impermeable to larger molecules like propidium iodide. Previous work has shown that nanopores are stable for minutes after exposure, suggesting that formation of nanopores in excitable cells could lead to prolonged action potential inhibition. Previously, we measured the formation of nanopores in neuroblastoma cells by measuring the influx of extracellular calcium by preloading cells with Calcium Green-AM. In this work, we explored the impact of changing the width of a single nsPEF, at constant amplitude, on uptake of extracellular calcium ions by primary hippocampal neurons (PHN). Calcium Green was again used to measure the influx of extracellular calcium and FM1-43 was used to monitor changes in membrane conformation. The observed thresholds for nanopore formation in PHN by nsPEF were comparable to those measured in neuroblastoma. This work is the first study of nsPEF effects on PHN and strongly suggests that neurological inhibition by nanosecond electrical pulses is highly likely at doses well below irreversible damage.

Giant quadrupole and monopole resonances in /sup 28/Si

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

Lui, Y.; Bronson, J.D.; Youngblood, D.H.

1985-05-01

Inelastic alpha scattering measurements have been performed for /sup 28/Si at small angles including zero degrees. A total of 66% of the E0 energy-weighted sum rule was identified (using a Satchler version 2 form factor) centered at E/sub x/ = 17.9 MeV having a width of 4.8 MeV and 34% of the E2 energy-weighted sum rule was identified above E/sub x/ = 15.3 MeV centered at 19.0 MeV with a width of 4.4 MeV. The dependence of the extracted E0 strength on form factor and optical potential was explored.

Active action potential propagation but not initiation in thalamic interneuron dendrites

PubMed Central

Casale, Amanda E.; McCormick, David A.

2012-01-01

Inhibitory interneurons of the dorsal lateral geniculate nucleus of the thalamus modulate the activity of thalamocortical cells in response to excitatory input through the release of inhibitory neurotransmitter from both axons and dendrites. The exact mechanisms by which release can occur from dendrites are, however, not well understood. Recent experiments using calcium imaging have suggested that Na/K based action potentials can evoke calcium transients in dendrites via local active conductances, making the back-propagating action potential a candidate for dendritic neurotransmitter release. In this study, we employed high temporal and spatial resolution voltage-sensitive dye imaging to assess the characteristics of dendritic voltage deflections in response to Na/K action potentials in interneurons of the mouse dorsal lateral geniculate nucleus. We found that trains or single action potentials elicited by somatic current injection or local synaptic stimulation led to action potentials that rapidly and actively back-propagated throughout the entire dendritic arbor and into the fine filiform dendritic appendages known to release GABAergic vesicles. Action potentials always appeared first in the soma or proximal dendrite in response to somatic current injection or local synaptic stimulation, and the rapid back-propagation into the dendritic arbor depended upon voltage-gated sodium and TEA-sensitive potassium channels. Our results indicate that thalamic interneuron dendrites integrate synaptic inputs that initiate action potentials, most likely in the axon initial segment, that then back-propagate with high-fidelity into the dendrites, resulting in a nearly synchronous release of GABA from both axonal and dendritic compartments. PMID:22171033

Irreducible correlation functions of the S matrix in the coordinate representation: application in calculating Lorentzian half-widths and shifts.

PubMed

Ma, Q; Tipping, R H; Boulet, C

2006-01-07

By introducing the coordinate representation, the derivation of the perturbation expansion of the Liouville S matrix is formulated in terms of classically behaved autocorrelation functions. Because these functions are characterized by a pair of irreducible tensors, their number is limited to a few. They represent how the overlaps of the potential components change with a time displacement, and under normal conditions, their magnitudes decrease by several orders of magnitude when the displacement reaches several picoseconds. The correlation functions contain all dynamical information of the collision processes necessary in calculating half-widths and shifts and can be easily derived with high accuracy. Their well-behaved profiles, especially the rapid decrease of the magnitude, enables one to transform easily the dynamical information contained in them from the time domain to the frequency domain. More specifically, because these correlation functions are well time limited, their continuous Fourier transforms should be band limited. Then, the latter can be accurately replaced by discrete Fourier transforms and calculated with a standard fast Fourier transform method. Besides, one can easily calculate their Cauchy principal integrations and derive all functions necessary in calculating half-widths and shifts. A great advantage resulting from introducing the coordinate representation and choosing the correlation functions as the starting point is that one is able to calculate the half-widths and shifts with high accuracy, no matter how complicated the potential models are and no matter what kind of trajectories are chosen. In any case, the convergence of the calculated results is always guaranteed. As a result, with this new method, one can remove some uncertainties incorporated in the current width and shift studies. As a test, we present calculated Raman Q linewidths for the N2-N2 pair based on several trajectories, including the more accurate "exact" ones. Finally, by using this new method as a benchmark, we have carried out convergence checks for calculated values based on usual methods and have found that some results in the literature are not converged.

Event-Related Potentials Discriminate Familiar and Unusual Goal Outcomes in 5-Month-Olds and Adults

ERIC Educational Resources Information Center

Michel, Christine; Kaduk, Katharina; Ní Choisdealbha, Áine; Reid, Vincent M.

2017-01-01

Previous event-related potential (ERP) work has indicated that the neural processing of action sequences develops with age. Although adults and 9-month-olds use a semantic processing system, perceiving actions activates attentional processes in 7-month-olds. However, presenting a sequence of action context, action execution and action conclusion…

Understanding the Electrical Behavior of the Action Potential in Terms of Elementary Electrical Sources

ERIC Educational Resources Information Center

Rodriguez-Falces, Javier

2015-01-01

A concept of major importance in human electrophysiology studies is the process by which activation of an excitable cell results in a rapid rise and fall of the electrical membrane potential, the so-called action potential. Hodgkin and Huxley proposed a model to explain the ionic mechanisms underlying the formation of action potentials. However,…

Detachable glass microelectrodes for recording action potentials in active moving organs.

PubMed

Barbic, Mladen; Moreno, Angel; Harris, Tim D; Kay, Matthew W

2017-06-01

Here, we describe new detachable floating glass micropipette electrode devices that provide targeted action potential recordings in active moving organs without requiring constant mechanical constraint or pharmacological inhibition of tissue motion. The technology is based on the concept of a glass micropipette electrode that is held firmly during cell targeting and intracellular insertion, after which a 100-µg glass microelectrode, a "microdevice," is gently released to remain within the moving organ. The microdevices provide long-term recordings of action potentials, even during millimeter-scale movement of tissue in which the device is embedded. We demonstrate two different glass micropipette electrode holding and detachment designs appropriate for the heart (sharp glass microdevices for cardiac myocytes in rats, guinea pigs, and humans) and the brain (patch glass microdevices for neurons in rats). We explain how microdevices enable measurements of multiple cells within a moving organ that are typically difficult with other technologies. Using sharp microdevices, action potential duration was monitored continuously for 15 min in unconstrained perfused hearts during global ischemia-reperfusion, providing beat-to-beat measurements of changes in action potential duration. Action potentials from neurons in the hippocampus of anesthetized rats were measured with patch microdevices, which provided stable base potentials during long-term recordings. Our results demonstrate that detachable microdevices are an elegant and robust tool to record electrical activity with high temporal resolution and cellular level localization without disturbing the physiological working conditions of the organ. NEW & NOTEWORTHY Cellular action potential measurements within tissue using glass micropipette electrodes usually require tissue immobilization, potentially influencing the physiological relevance of the measurement. Here, we addressed this limitation with novel 100-µg detachable glass microelectrodes that can be precisely positioned to provide long-term measurements of action potential duration during unconstrained tissue movement. Copyright © 2017 the American Physiological Society.

Suppression of the Nonlinear Zeeman Effect and Heading Error in Earth-Field-Range Alkali-Vapor Magnetometers.

PubMed

Bao, Guzhi; Wickenbrock, Arne; Rochester, Simon; Zhang, Weiping; Budker, Dmitry

2018-01-19

The nonlinear Zeeman effect can induce splitting and asymmetries of magnetic-resonance lines in the geophysical magnetic-field range. This is a major source of "heading error" for scalar atomic magnetometers. We demonstrate a method to suppress the nonlinear Zeeman effect and heading error based on spin locking. In an all-optical synchronously pumped magnetometer with separate pump and probe beams, we apply a radio-frequency field which is in phase with the precessing magnetization. This results in the collapse of the multicomponent asymmetric magnetic-resonance line with ∼100  Hz width in the Earth-field range into a single peak with a width of 22 Hz, whose position is largely independent of the orientation of the sensor within a range of orientation angles. The technique is expected to be broadly applicable in practical magnetometry, potentially boosting the sensitivity and accuracy of Earth-surveying magnetometers by increasing the magnetic-resonance amplitude, decreasing its width, and removing the important and limiting heading-error systematic.

Self-healing of early age cracks in cement-based materials by mineralization of carbonic anhydrase microorganism

PubMed Central

Qian, Chunxiang; Chen, Huaicheng; Ren, Lifu; Luo, Mian

2015-01-01

This research investigated the self-healing potential of early age cracks in cement-based materials incorporating the bacteria which can produce carbonic anhydrase. Cement-based materials specimens were pre-cracked at the age of 7, 14, 28, 60 days to study the repair ability influenced by cracking time, the width of cracks were between 0.1 and 1.0 mm to study the healing rate influenced by width of cracks. The experimental results indicated that the bacteria showed excellent repairing ability to small cracks formed at early age of 7 days, cracks below 0.4 mm was almost completely closed. The repair effect reduced with the increasing of cracking age. Cracks width influenced self-healing effectiveness significantly. The transportation of CO2and Ca2+ controlled the self-healing process. The computer simulation analyses revealed the self-healing process and mechanism of microbiologically precipitation induced by bacteria and the depth of precipitated CaCO3 could be predicted base on valid Ca2+. PMID:26583014

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

Phillips, Benjamin R.; Baldridge, W. Scott; Gable, Carl W.

Finite volume calculations of the flow of rhyolite are presented to investigate the fate of viscous magmas flowing in planar fractures with realistic length to width ratios of up to 2500:1. Heat and mass transfer for a melt with a temperature dependent viscosity and the potential to undergo phase change are considered. Magma driving pressures and dike widths are chosen to satisfy simple elastic considerations. These models are applied within a parameter space relevant to the Banco Bonito rhyolite flow, Valles caldera, New Mexico. We estimate a maximum eruption duration for the event of ~200 days, realized at a minimummore » possible dike width of 5-6 m and driving pressure of 7-8 MPa. Simplifications in the current model may warrant scaling of these results. However, we demonstrate the applicability of our model to magma dynamics issues and suggest that such models may be used to infer information about both the timing of an eruption and the evolution of the associated magma source.« less

Origin of multiple band gap values in single width nanoribbons

PubMed Central

Goyal, Deepika; Kumar, Shailesh; Shukla, Alok; Kumar, Rakesh

2016-01-01

Deterministic band gap in quasi-one-dimensional nanoribbons is prerequisite for their integrated functionalities in high performance molecular-electronics based devices. However, multiple band gaps commonly observed in graphene nanoribbons of the same width, fabricated in same slot of experiments, remain unresolved, and raise a critical concern over scalable production of pristine and/or hetero-structure nanoribbons with deterministic properties and functionalities for plethora of applications. Here, we show that a modification in the depth of potential wells in the periodic direction of a supercell on relative shifting of passivating atoms at the edges is the origin of multiple band gap values in nanoribbons of the same width in a crystallographic orientation, although they carry practically the same ground state energy. The results are similar when calculations are extended from planar graphene to buckled silicene nanoribbons. Thus, the findings facilitate tuning of the electronic properties of quasi-one-dimensional materials such as bio-molecular chains, organic and inorganic nanoribbons by performing edge engineering. PMID:27808172

Quadratic adaptive algorithm for solving cardiac action potential models.

PubMed

Chen, Min-Hung; Chen, Po-Yuan; Luo, Ching-Hsing

2016-10-01

An adaptive integration method is proposed for computing cardiac action potential models accurately and efficiently. Time steps are adaptively chosen by solving a quadratic formula involving the first and second derivatives of the membrane action potential. To improve the numerical accuracy, we devise an extremum-locator (el) function to predict the local extremum when approaching the peak amplitude of the action potential. In addition, the time step restriction (tsr) technique is designed to limit the increase in time steps, and thus prevent the membrane potential from changing abruptly. The performance of the proposed method is tested using the Luo-Rudy phase 1 (LR1), dynamic (LR2), and human O'Hara-Rudy dynamic (ORd) ventricular action potential models, and the Courtemanche atrial model incorporating a Markov sodium channel model. Numerical experiments demonstrate that the action potential generated using the proposed method is more accurate than that using the traditional Hybrid method, especially near the peak region. The traditional Hybrid method may choose large time steps near to the peak region, and sometimes causes the action potential to become distorted. In contrast, the proposed new method chooses very fine time steps in the peak region, but large time steps in the smooth region, and the profiles are smoother and closer to the reference solution. In the test on the stiff Markov ionic channel model, the Hybrid blows up if the allowable time step is set to be greater than 0.1ms. In contrast, our method can adjust the time step size automatically, and is stable. Overall, the proposed method is more accurate than and as efficient as the traditional Hybrid method, especially for the human ORd model. The proposed method shows improvement for action potentials with a non-smooth morphology, and it needs further investigation to determine whether the method is helpful during propagation of the action potential. Copyright © 2016 Elsevier Ltd. All rights reserved.

77 FR 34302 - Approval and Promulgation of Implementation Plans; Tennessee: Prevention of Significant...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-11

... the average width of a human hair) are considered to be ``fine particles'' and are also known as PM 2... various chemical reactions. The health effects associated with exposure to PM 2.5 include potential...

Breaking Through the Multi-Mesa-Channel Width Limited of Normally Off GaN HEMTs Through Modulation of the Via-Hole-Length.

PubMed

Chien, Cheng-Yen; Wu, Wen-Hsin; You, Yao-Hong; Lin, Jun-Huei; Lee, Chia-Yu; Hsu, Wen-Ching; Kuan, Chieh-Hsiung; Lin, Ray-Ming

2017-12-01

We present new normally off GaN high-electron-mobility transistors (HEMTs) that overcome the typical limitations in multi-mesa-channel (MMC) width through modulation of the via-hole-length to regulate the charge neutrality screen effect. We have prepared enhancement-mode (E-mode) GaN HEMTs having widths of up to 300 nm, based on an enhanced surface pinning effect. E-mode GaN HEMTs having MMC structures and widths as well as via-hole-lengths of 100 nm/2 μm and 300 nm/6 μm, respectively, exhibited positive threshold voltages (V th ) of 0.79 and 0.46 V, respectively. The on-resistances of the MMC and via-hole-length structures were lower than those of typical tri-gate nanoribbon GaN HEMTs. In addition, the devices not only achieved the E-mode but also improved the power performance of the GaN HEMTs and effectively mitigated the device thermal effect. We controlled the via-hole-length sidewall surface pinning effect to obtain the E-mode GaN HEMTs. Our findings suggest that via-hole-length normally off GaN HEMTs have great potential for use in next-generation power electronics.

Sub-0.1 μm optical track width measurement

NASA Astrophysics Data System (ADS)

Smith, Richard J.; See, Chung W.; Somekh, Mike G.; Yacoot, Andrew

2005-08-01

In this paper, we will describe a technique that combines a common path scanning optical interferometer with artificial neural networks (ANN), to perform track width measurements that are significantly beyond the capability of conventional optical systems. Artificial neural networks have been used for many different applications. In the present case, ANNs are trained using profiles of known samples obtained from the scanning interferometer. They are then applied to tracks that have not previously been exposed to the networks. This paper will discuss the impacts of various ANN configurations, and the processing of the input signal on the training of the network. The profiles of the samples, which are used as the inputs to the ANNs, are obtained with a common path scanning optical interferometer. It provides extremely repeatable measurements, with very high signal to noise ratio, both are essential for the working of the ANNs. The characteristics of the system will be described. A number of samples with line widths ranging from 60nm-3μm have been measured to test the system. The system can measure line widths down to 60nm with a standard deviation of 3nm using optical wavelength of 633nm and a system numerical aperture of 0.3. These results will be presented in detail along with a discussion of the potential of this technique.

Human ossicular-joint flexibility transforms the peak amplitude and width of impulsive acoustic stimulia)

PubMed Central

Gottlieb, Peter K.; Vaisbuch, Yona

2018-01-01

The role of the ossicular joints in the mammalian middle ear is still debated. This work tests the hypothesis that the two synovial joints filter potentially damaging impulsive stimuli by transforming both the peak amplitude and width of these impulses before they reach the cochlea. The three-dimensional (3D) velocity along the ossicular chain in unaltered cadaveric human temporal bones (N = 9), stimulated with acoustic impulses, is measured in the time domain using a Polytec (Waldbronn, Germany) CLV-3D laser Doppler vibrometer. The measurements are repeated after fusing one or both of the ossicular joints with dental cement. Sound transmission is characterized by measuring the amplitude, width, and delay of the impulsive velocity profile as it travels from the eardrum to the cochlea. On average, fusing both ossicular joints causes the stapes velocity amplitude and width to change by a factor of 1.77 (p = 0.0057) and 0.78 (p = 0.011), respectively. Fusing just the incudomalleolar joint has a larger effect on amplitude (a factor of 2.37), while fusing just the incudostapedial joint decreases the stapes velocity on average. The 3D motion of the ossicles is altered by fusing the joints. Finally, the ability of current computational models to predict this behavior is also evaluated.

Fano resonances of a ring-shaped "hexamer" cluster at near-infrared wavelength

NASA Astrophysics Data System (ADS)

Liu, Tong-Tong; Xia, Feng; Sun, Peng; Liu, Li-Li; Du, Wei; Li, Meng-Xue; Kong, Wei-Jin; Wan, Yong; Dong, Li-Feng; Yun, Mao-Jin

2018-03-01

Fano resonances have been studied intensely in the last decade, since it is an important way to decrease the resonance line width and enhance local electric field. However, achieving a Fano line-shape with both narrow line width and high spectral contrast ratio is still a challenge. In this paper, we theoretically predict the Fano resonance induced by the extinction of normal plane wave in a ring-shaped hexamer cluster at near-infrared wavelength. In order to obtain the narrow Fano line width and high spectral contrast ratio, the relationships between the Fano line-shape and the parameters of the nanostructure are analyzed in detail. The nanostructure is simulated by using commercial software based on finite element method. The simulation results show that when the structural parameters are optimized, the Fano line width can be narrowed down 0.028 eV with a contrast ratio of 86%, and the local electric field enhancement factor at the Fano resonance wavelength can reach to 36. Furthermore, the effective mode volume of the structure is 3.9 ×10-23m3 which is lower than the available literature. These results indicate many potential applications of the Fano resonance in multiwavelength surface-enhanced Raman scattering and biosensing.

An Experimental Determination of Losses in a 3-Port Wave Rotor

NASA Technical Reports Server (NTRS)

Wilson, Jack

1996-01-01

Wave rotors, used in a gas turbine topping cycle, offer a potential route to higher specific power and lower specific fuel consumption. In order to exploit this potential properly, it is necessary to have some realistic means of calculating wave rotor performance, taking losses into account, so that wave rotors can be designed for good performance. This in turn requires a knowledge of the loss mechanisms. The experiment reported here was designed as a statistical experiment to identify the losses due to finite passage opening time, friction, and leakage. For simplicity, the experiment used a 3-port, flow divider, wave cycle, but the results should be applicable to other cycles. A 12 inch diameter rotor was used, with two different lengths, 9 inches and 18 inches, and two different passage widths, 0.25 inch and 0.54 inch, in order to vary friction and opening time. To vary leakage, moveable end-walls were provided so that the rotor to end-wall gap could be adjusted. The experiment is described, and the results are presented, together with a parametric fit to the data. The fit shows that there will be an optimum passage width for a given wave rotor, since, as the passage width increases, friction losses decrease, but opening-time losses increase, and vice-versa. Leakage losses can be made small at reasonable gap sizes.

Effects of tacrolimus on action potential configuration and transmembrane ion currents in canine ventricular cells.

PubMed

Szabó, László; Szentandrássy, Norbert; Kistamás, Kornél; Hegyi, Bence; Ruzsnavszky, Ferenc; Váczi, Krisztina; Horváth, Balázs; Magyar, János; Bányász, Tamás; Pál, Balázs; Nánási, Péter P

2013-03-01

Tacrolimus is a commonly used immunosuppressive agent which causes cardiovascular complications, e.g., hypertension and hypertrophic cardiomyopathy. In spite of it, there is little information on the cellular cardiac effects of the immunosuppressive agent tacrolimus in larger mammals. In the present study, therefore, the concentration-dependent effects of tacrolimus on action potential morphology and the underlying ion currents were studied in canine ventricular cardiomyocytes. Standard microelectrode, conventional whole cell patch clamp, and action potential voltage clamp techniques were applied in myocytes enzymatically dispersed from canine ventricular myocardium. Tacrolimus (3-30 μM) caused a concentration-dependent reduction of maximum velocity of depolarization and repolarization, action potential amplitude, phase-1 repolarization, action potential duration, and plateau potential, while no significant change in the resting membrane potential was observed. Conventional voltage clamp experiments revealed that tacrolimus concentrations ≥3 μM blocked a variety of ion currents, including I(Ca), I(to), I(K1), I(Kr), and I(Ks). Similar results were obtained under action potential voltage clamp conditions. These effects of tacrolimus developed rapidly and were fully reversible upon washout. The blockade of inward currents with the concomitant shortening of action potential duration in canine myocytes is the opposite of those observed previously with tacrolimus in small rodents. It is concluded that although tacrolimus blocks several ion channels at higher concentrations, there is no risk of direct interaction with cardiac ion channels when applying tacrolimus in therapeutic concentrations.

TRPM4 non-selective cation channels influence action potentials in rabbit Purkinje fibres.

PubMed

Hof, Thomas; Sallé, Laurent; Coulbault, Laurent; Richer, Romain; Alexandre, Joachim; Rouet, René; Manrique, Alain; Guinamard, Romain

2016-01-15

The transient receptor potential melastatin 4 (TRPM4) inhibitor 9-phenanthrol reduces action potential duration in rabbit Purkinje fibres but not in ventricle. TRPM4-like single channel activity is observed in isolated rabbit Purkinje cells but not in ventricular cells. The TRPM4-like current develops during the notch and early repolarization phases of the action potential in Purkinje cells. Transient receptor potential melastatin 4 (TRPM4) Ca(2+)-activated non-selective cation channel activity has been recorded in cardiomyocytes and sinus node cells from mammals. In addition, TRPM4 gene mutations are associated with human diseases of cardiac conduction, suggesting that TRPM4 plays a role in this aspect of cardiac function. Here we evaluate the TRPM4 contribution to cardiac electrophysiology of Purkinje fibres. Ventricular strips with Purkinje fibres were isolated from rabbit hearts. Intracellular microelectrodes recorded Purkinje fibre activity and the TRPM4 inhibitor 9-phenanthrol was applied to unmask potential TRPM4 contributions to the action potential. 9-Phenanthrol reduced action potential duration measured at the point of 50 and 90% repolarization with an EC50 of 32.8 and 36.1×10(-6) mol l(-1), respectively, but did not modulate ventricular action potentials. Inside-out patch-clamp recordings were used to monitor TRPM4 activity in isolated Purkinje cells. TRPM4-like single channel activity (conductance = 23.8 pS; equal permeability for Na(+) and K(+); sensitivity to voltage, Ca(2+) and 9-phenanthrol) was observed in 43% of patches from Purkinje cells but not from ventricular cells (0/16). Action potential clamp experiments performed in the whole-cell configuration revealed a transient inward 9-phenanthrol-sensitive current (peak density = -0.65 ± 0.15 pA pF(-1); n = 5) during the plateau phases of the Purkinje fibre action potential. These results show that TRPM4 influences action potential characteristics in rabbit Purkinje fibres and thus could modulate cardiac conduction and be involved in triggering arrhythmias. © 2015 The Authors. The Journal of Physiology © 2015 The Physiological Society.

14 CFR 1216.306 - Actions normally requiring an EIS.

Code of Federal Regulations, 2013 CFR

2013-01-01

... normally requiring an EIS. (a) NASA will prepare an EIS for actions with the potential to significantly... action or mitigation of its potentially significant impacts. (b) Typical NASA actions normally requiring... material greater than the quantity for which the NASA Nuclear Flight Safety Assurance Manager may grant...

The optimal distance between two electrode tips during recording of compound nerve action potentials in the rat median nerve

PubMed Central

Li, Yongping; Lao, Jie; Zhao, Xin; Tian, Dong; Zhu, Yi; Wei, Xiaochun

2014-01-01

The distance between the two electrode tips can greatly influence the parameters used for recording compound nerve action potentials. To investigate the optimal parameters for these recordings in the rat median nerve, we dissociated the nerve using different methods and compound nerve action potentials were orthodromically or antidromically recorded with different electrode spacings. Compound nerve action potentials could be consistently recorded using a method in which the middle part of the median nerve was intact, with both ends dissociated from the surrounding fascia and a ground wire inserted into the muscle close to the intact part. When the distance between two stimulating electrode tips was increased, the threshold and supramaximal stimulating intensity of compound nerve action potentials were gradually decreased, but the amplitude was not changed significantly. When the distance between two recording electrode tips was increased, the amplitude was gradually increased, but the threshold and supramaximal stimulating intensity exhibited no significant change. Different distances between recording and stimulating sites did not produce significant effects on the aforementioned parameters. A distance of 5 mm between recording and stimulating electrodes and a distance of 10 mm between recording and stimulating sites were found to be optimal for compound nerve action potential recording in the rat median nerve. In addition, the orthodromic compound action potential, with a biphasic waveform that was more stable and displayed less interference (however also required a higher threshold and higher supramaximal stimulus), was found to be superior to the antidromic compound action potential. PMID:25206798

Modulation of hERG potassium channel gating normalizes action potential duration prolonged by dysfunctional KCNQ1 potassium channel

PubMed Central

Zhang, Hongkang; Zou, Beiyan; Yu, Haibo; Moretti, Alessandra; Wang, Xiaoying; Yan, Wei; Babcock, Joseph J.; Bellin, Milena; McManus, Owen B.; Tomaselli, Gordon; Nan, Fajun; Laugwitz, Karl-Ludwig; Li, Min

2012-01-01

Long QT syndrome (LQTS) is a genetic disease characterized by a prolonged QT interval in an electrocardiogram (ECG), leading to higher risk of sudden cardiac death. Among the 12 identified genes causal to heritable LQTS, ∼90% of affected individuals harbor mutations in either KCNQ1 or human ether-a-go-go related genes (hERG), which encode two repolarizing potassium currents known as IKs and IKr. The ability to quantitatively assess contributions of different current components is therefore important for investigating disease phenotypes and testing effectiveness of pharmacological modulation. Here we report a quantitative analysis by simulating cardiac action potentials of cultured human cardiomyocytes to match the experimental waveforms of both healthy control and LQT syndrome type 1 (LQT1) action potentials. The quantitative evaluation suggests that elevation of IKr by reducing voltage sensitivity of inactivation, not via slowing of deactivation, could more effectively restore normal QT duration if IKs is reduced. Using a unique specific chemical activator for IKr that has a primary effect of causing a right shift of V1/2 for inactivation, we then examined the duration changes of autonomous action potentials from differentiated human cardiomyocytes. Indeed, this activator causes dose-dependent shortening of the action potential durations and is able to normalize action potentials of cells of patients with LQT1. In contrast, an IKr chemical activator of primary effects in slowing channel deactivation was not effective in modulating action potential durations. Our studies provide both the theoretical basis and experimental support for compensatory normalization of action potential duration by a pharmacological agent. PMID:22745159

Short infrared laser pulses block action potentials in neurons

NASA Astrophysics Data System (ADS)

Walsh, Alex J.; Tolstykh, Gleb P.; Martens, Stacey L.; Ibey, Bennett L.; Beier, Hope T.

2017-02-01

Short infrared laser pulses have many physiological effects on cells including the ability to stimulate action potentials in neurons. Here we show that short infrared laser pulses can also reversibly block action potentials. Primary rat hippocampal neurons were transfected with the Optopatch2 plasmid, which contains both a blue-light activated channel rhodopsin (CheRiff) and a red-light fluorescent membrane voltage reporter (QuasAr2). This optogenetic platform allows robust stimulation and recording of action potential activity in neurons in a non-contact, low noise manner. For all experiments, QuasAr2 was imaged continuously on a wide-field fluorescent microscope using a Krypton laser (647 nm) as the excitation source and an EMCCD camera operating at 1000 Hz to collect emitted fluorescence. A co-aligned Argon laser (488 nm, 5 ms at 10Hz) provided activation light for CheRiff. A 200 mm fiber delivered infrared light locally to the target neuron. Reversible action potential block in neurons was observed following a short infrared laser pulse (0.26-0.96 J/cm2; 1.37-5.01 ms; 1869 nm), with the block persisting for more than 1 s with exposures greater than 0.69 J/cm2. Action potential block was sustained for 30 s with the short infrared laser pulsed at 1-7 Hz. Full recovery of neuronal activity was observed 5-30s post-infrared exposure. These results indicate that optogenetics provides a robust platform for the study of action potential block and that short infrared laser pulses can be used for non-contact, reversible action potential block.

Yield Strength Testing in Human Cadaver Nasal Septal Cartilage and L-Strut Constructs.

PubMed

Liu, Yuan F; Messinger, Kelton; Inman, Jared C

2017-01-01

To our knowledge, yield strength testing in human nasal septal cartilage has not been reported to date. An understanding of the basic mechanics of the nasal septum may help surgeons decide how much of an L-strut to preserve and how much grafting is needed. To determine the factors correlated with yield strength of the cartilaginous nasal septum and to explore the association between L-strut width and thickness in determining yield strength. In an anatomy laboratory, yield strength of rectangular pieces of fresh cadaver nasal septal cartilage was measured, and regression was performed to identify the factors correlated with yield strength. To measure yield strength in L-shaped models, 4 bonded paper L-struts models were constructed for every possible combination of the width and thickness, for a total of 240 models. Mathematical modeling using the resultant data with trend lines and surface fitting was performed to quantify the associations among L-strut width, thickness, and yield strength. The study dates were November 1, 2015, to April 1, 2016. The factors correlated with nasal cartilage yield strength and the associations among L-strut width, thickness, and yield strength in L-shaped models. Among 95 cartilage pieces from 12 human cadavers (mean [SD] age, 67.7 [12.6] years) and 240 constructed L-strut models, L-strut thickness was the only factor correlated with nasal septal cartilage yield strength (coefficient for thickness, 5.54; 95% CI, 4.08-7.00; P < .001), with an adjusted R2 correlation coefficient of 0.37. The mean (SD) yield strength R2 varied with L-strut thickness exponentially (0.93 [0.06]) for set widths, and it varied with L-strut width linearly (0.82 [0.11]) or logarithmically (0.85 [0.17]) for set thicknesses. A 3-dimensional surface model of yield strength with L-strut width and thickness as variables was created using a 2-dimensional gaussian function (adjusted R2 = 0.94). Estimated yield strengths were generated from the model to allow determination of the desired yield strength with different permutations of L-strut width and thickness. In this study of human cadaver nasal septal cartilage, L-strut thickness was significantly associated with yield strength. In a bonded paper L-strut model, L-strut thickness had a more important role in determining yield strength than L-strut width. Surgeons should consider the thickness of potential L-struts when determining the amount of cartilaginous septum to harvest and graft. NA.

Somatic spikes regulate dendritic signaling in small neurons in the absence of backpropagating action potentials.

PubMed

Myoga, Michael H; Beierlein, Michael; Regehr, Wade G

2009-06-17

Somatic spiking is known to regulate dendritic signaling and associative synaptic plasticity in many types of large neurons, but it is unclear whether somatic action potentials play similar roles in small neurons. Here we ask whether somatic action potentials can also influence dendritic signaling in an electrically compact neuron, the cerebellar stellate cell (SC). Experiments were conducted in rat brain slices using a combination of imaging and electrophysiology. We find that somatic action potentials elevate dendritic calcium levels in SCs. There was little attenuation of calcium signals with distance from the soma in SCs from postnatal day 17 (P17)-P19 rats, which had dendrites that averaged 60 microm in length, and in short SC dendrites from P30-P33 rats. Somatic action potentials evoke dendritic calcium increases that are not affected by blocking dendritic sodium channels. This indicates that dendritic signals in SCs do not rely on dendritic sodium channels, which differs from many types of large neurons, in which dendritic sodium channels and backpropagating action potentials allow somatic spikes to control dendritic calcium signaling. Despite the lack of active backpropagating action potentials, we find that trains of somatic action potentials elevate dendritic calcium sufficiently to release endocannabinoids and retrogradely suppress parallel fiber to SC synapses in P17-P19 rats. Prolonged SC firing at physiologically realistic frequencies produces retrograde suppression when combined with low-level group I metabotropic glutamate receptor activation. Somatic spiking also interacts with synaptic stimulation to promote associative plasticity. These findings indicate that in small neurons the passive spread of potential within dendrites can allow somatic spiking to regulate dendritic calcium signaling and synaptic plasticity.

Dental arch changes associated with rapid maxillary expansion: A retrospective model analysis study

PubMed Central

D’Souza, Ivor M; Kumar, H. C. Kiran; Shetty, K. Sadashiva

2015-01-01

Introduction: Transverse deficiency of the maxilla is a common clinical problem in orthodontics and dentofacial orthopedics. Transverse maxillary deficiency, isolated or associated with other dentofacial deformities, results in esthetic and functional impairment giving rise to several clinical manifestations such as asymmetrical facial growth, positional and functional mandibular deviations, altered dentofacial esthetics, adverse periodontal responses, unstable dental tipping, and other functional problems. Orthopedic maxillary expansion is the preferred treatment approach to increase the maxillary transverse dimension in young patients by splitting of the mid palatal suture. This orthopedic procedure has lately been subject of renewed interest in orthodontic treatment mechanics because of its potential for increasing arch perimeter to alleviate crowding in the maxillary arch without adversely affecting facial profile. Hence, the present investigation was conducted to establish a correlation between transverse expansion and changes in the arch perimeter, arch width and arch length. Methods: For this purpose, 10 subjects (five males, five females) were selected who had been treated by rapid maxillary expansion (RME) using hyrax rapid palatal expander followed by fixed mechanotherapy (PEA). Pretreatment (T1), postexpansion (T2), and posttreatment (T3) dental models were compared for dental changes brought about by RME treatment and its stability at the end of fixed mechanotherapy. After model measurements were made, the changes between T1–T2, T2–T3 and T1–T3 were determined for each patient. The mean difference between T1–T2, T2–T3 and T1–T3 were compared to assess the effects of RME on dental arch measurements. Results are expressed as mean ± standard deviation and are compared by repeated measures analysis of variance followed by a post-hoc test. Arch perimeter changes are correlated with changes in arch widths at the canine, premolar and molar regions. Results: The intercanine arch width increased by 2.9 mm, inter first premolar width increased by 3.2 mm, inter second premolar width increased by 4.6 mm, intermolar width increased by 4.4 mm, arch perimeter increased by 3.2 mm, arch length decreased by 1.8 mm from pretreatment to posttreatment. There is a strong positive correlation of arch perimeter with intercanine width (r2 = 0.99), interpremolar width (r2 = 0.99) and intermolar width (r2 = 0.98), indicating that there is a significant increase in arch perimeter with increase in arch width at the canine, premolars and molar regions. Conclusion: Findings of this study demonstrate that there was a significant increase in the intercanine, inter first premolar, inter second premolar intermolar arch width and arch perimeter from pretreatment to postexpansion, which was stable at the end of fixed mechanotherapy (PEA). There was a nonsignificant decrease in arch length from pretreatment to postexpansion that further decreased nonsignificantly from postexpansion to posttreatment. PMID:25684912

[Geographic variation of seed morphological traits of Picea schrenkiana var. tianschanica in Tianshan Mountains, Xinjiang of Northwest China].

PubMed

Liu, Gui-Feng; Zang, Run-Guo; Liu, Hua; Bai, Zhi-Qiang; Guo, Zhong-Jun; Ding, Yi

2012-06-01

Taking the Picea schrenkiana var. tianschanica forests at three sites with different longitudes (Zhaosu, Tianchi, and Qitai) in Tianshan Mountains as the objects, the cones were collected along an altitudinal gradient to analyze the variation of their seed morphological traits (seed scale length and width, seed scale length/width ratio, seed wing length and width, seed wing length/ width ratio, seed length and width, and seed length/width ratio). All the seed traits except seed width tended to decrease with increasing altitude. The seed traits except seed wing width, seed width, and seed length/width ratio all had significant negative correlations with altitude. Seed scale length and width and seed scale length/width ratio had significant positive correlations with longitude. Seed scale length, seed scale length/width ratio, and seed wing length/width ratio had significant negative correlations with slope degree. No significant correlations were observed between the seed traits except seed wing width and the slope aspect. Altitude was the main factor affecting the seed scale length, seed scale length/width ratio, and seed wing length/width ratio.

Strip-Bark Morphology and Radial Growth Trends in Ancient Pinus sibirica Trees From Central Mongolia

NASA Astrophysics Data System (ADS)

Leland, Caroline; Cook, Edward R.; Andreu-Hayles, Laia; Pederson, Neil; Hessl, Amy; Anchukaitis, Kevin J.; Byambasuren, Oyunsanaa; Nachin, Baatarbileg; Davi, Nicole; D'Arrigo, Rosanne; Griffin, Kevin; Bishop, Daniel A.; Rao, Mukund Palat

2018-03-01

Some of the oldest and most important trees used for dendroclimatic reconstructions develop strip-bark morphology, in which only a portion of the stem contains living tissue. Yet the ecophysiological factors initiating strip bark and the potential effect of cambial dieback on annual ring widths and tree-ring estimates of past climate remain poorly understood. Using a combination of field observations and tree-ring data, we investigate the causes and timing of cambial dieback events in Pinus sibirica strip-bark trees from central Mongolia and compare the radial growth rates and trends of strip-bark and whole-bark trees over the past 515 years. Results indicate that strip bark is more common on the southern aspect of trees, and dieback events were most prevalent in the 19th century, a cold and dry period. Further, strip-bark and whole-bark trees have differing centennial trends, with strip-bark trees exhibiting notably large increases in ring widths at the beginning of the 20th century. We find a steeper positive trend in the strip-bark chronology relative to the whole-bark chronology when standardizing with age-dependent splines. We hypothesize that localized warming on the southern side of stems due to solar irradiance results in physiological damage and dieback and leads to increasing tree-ring increment along the living portion of strip-bark trees. Because the impact of cambial dieback on ring widths likely varies depending on species and site, we suggest conducting a comparison of strip-bark and whole-bark ring widths before statistically treating ring-width data for climate reconstructions.

Computation of backwater and discharge at width constrictions of heavily vegetated flood plains

USGS Publications Warehouse

Schneider, V.R.; Board, J.W.; Colson, B.E.; Lee, F.N.; Druffel, Leroy

1977-01-01

The U.S. Geological Survey, cooperated with the Federal Highway Administration and the State Highway Departments of Mississippi, Alabama, and Louisiana, to develop a proposed method for computing backwater and discharge at width constrictions of heavily vegetated flood plains. Data were collected at 20 single opening sites for 31 floods. Flood-plain width varied from 4 to 14 times the bridge opening width. The recurrence intervals of peak discharge ranged from a 2-year flood to greater than a 100-year flood, with a median interval of 6 years. Measured backwater ranged from 0.39 to 3.16 feet. Backwater computed by the present standard Geological Survey method averaged 29 percent less than the measured, and that computed by the currently used Federal Highway Administration method averaged 47 percent less than the measured. Discharge computed by the Survey method averaged 21 percent more then the measured. Analysis of data showed that the flood-plain widths and the Manning 's roughness coefficient are larger than those used to develop the standard methods. A method to more accurately compute backwater and discharge was developed. The difference between the contracted and natural water-surface profiles computed using standard step-backwater procedures is defined as backwater. The energy loss terms in the step-backwater procedure are computed as the product of the geometric mean of the energy slopes and the flow distance in the reach was derived from potential flow theory. The mean error was 1 percent when using the proposed method for computing backwater and 3 percent for computing discharge. (Woodard-USGS)

Combining wood anatomy and stable isotope variations in a 600-year multi-parameter climate reconstruction from Corsican black pine

NASA Astrophysics Data System (ADS)

Szymczak, Sonja; Hetzer, Timo; Bräuning, Achim; Joachimski, Michael M.; Leuschner, Hanns-Hubert; Kuhlemann, Joachim

2014-10-01

We present a new multi-parameter dataset from Corsican black pine growing on the island of Corsica in the Western Mediterranean basin covering the period AD 1410-2008. Wood parameters measured include tree-ring width, latewood width, earlywood width, cell lumen area, cell width, cell wall thickness, modelled wood density, as well as stable carbon and oxygen isotopes. We evaluated the relationships between different parameters and determined the value of the dataset for climate reconstructions. Correlation analyses revealed that carbon isotope ratios are influenced by cell parameters determining cell size, whereas oxygen isotope ratios are influenced by cell parameters determining the amount of transportable water in the xylem. A summer (June to August) precipitation reconstruction dating back to AD 1185 was established based on tree-ring width. No long-term trends or pronounced periods with extreme high/low precipitation are recorded in our reconstruction, indicating relatively stable moisture conditions over the entire time period. By comparing the precipitation reconstruction with a summer temperature reconstruction derived from the carbon isotope chronologies, we identified summers with extreme climate conditions, i.e. warm-dry, warm-wet, cold-dry and cold-wet. Extreme climate conditions during summer months were found to influence cell parameter characteristics. Cold-wet summers promote the production of broad latewood composed of wide and thin-walled tracheids, while warm-wet summers promote the production of latewood with small thick-walled cells. The presented dataset emphasizes the potential of multi-parameter wood analysis from one tree species over long time scales.

Shining a light on galactic outflows: photoionized outflows

NASA Astrophysics Data System (ADS)

Chisholm, John; Tremonti, Christy A.; Leitherer, Claus; Chen, Yanmei; Wofford, Aida

2016-04-01

We study the ionization structure of galactic outflows in 37 nearby, star-forming galaxies with the Cosmic Origins Spectrograph on the Hubble Space Telescope. We use the O I, Si II, Si III, and Si IV ultraviolet absorption lines to characterize the different ionization states of outflowing gas. We measure the equivalent widths, line widths, and outflow velocities of the four transitions, and find shallow scaling relations between them and galactic stellar mass and star formation rate. Regardless of the ionization potential, lines of similar strength have similar velocities and line widths, indicating that the four transitions can be modelled as a comoving phase. The Si equivalent width ratios (e.g. Si IV/Si II) have low dispersion, and little variation with stellar mass; while ratios with O I and Si vary by a factor of 2 for a given stellar mass. Photoionization models reproduce these equivalent width ratios, while shock models under predict the relative amount of high ionization gas. The photoionization models constrain the ionization parameter (U) between -2.25 < log (U) < -1.5, and require that the outflow metallicities are greater than 0.5 Z⊙. We derive ionization fractions for the transitions, and show that the range of ionization parameters and stellar metallicities leads to a factor of 1.15-10 variation in the ionization fractions. Historically, mass outflow rates are calculated by converting a column density measurement from a single metal ion into a total hydrogen column density using an ionization fraction, thus mass outflow rates are sensitive to the assumed ionization structure of the outflow.

Curvature-induced domain wall pinning

NASA Astrophysics Data System (ADS)

Yershov, Kostiantyn V.; Kravchuk, Volodymyr P.; Sheka, Denis D.; Gaididei, Yuri

2015-09-01

It is shown that a local bend of a nanowire is a source of pinning potential for a transversal head-to-head (tail-to-tail) domain wall. Eigenfrequency of the domain wall free oscillations at the pinning potential and the effective friction are determined as functions of the curvature and domain wall width. The pinning potential originates from the effective curvature-induced Dzyaloshinsky-like term in the exchange energy. The theoretical results are verified by means of micromagnetic simulations for the case of parabolic shape of the wire bend.

Calculation of stochastic broadening due to noise and field errors in the simple map in action-angle coordinates

NASA Astrophysics Data System (ADS)

Hinton, Courtney; Punjabi, Alkesh; Ali, Halima

2008-11-01

The simple map is the simplest map that has topology of divertor tokamaks [1]. Recently, the action-angle coordinates for simple map are analytically calculated, and simple map is constructed in action-angle coordinates [2]. Action-angle coordinates for simple map can not be inverted to real space coordinates (R,Z). Because there is logarithmic singularity on the ideal separatrix, trajectories can not cross separatrix [2]. Simple map in action-angle coordinates is applied to calculate stochastic broadening due to magnetic noise and field errors. Mode numbers for noise + field errors from the DIII-D tokamak are used. Mode numbers are (m,n)=(3,1), (4,1), (6,2), (7,2), (8,2), (9,3), (10,3), (11,3), (12,3) [3]. The common amplitude δ is varied from 0.8X10-5 to 2.0X10-5. For this noise and field errors, the width of stochastic layer in simple map is calculated. This work is supported by US Department of Energy grants DE-FG02-07ER54937, DE-FG02-01ER54624 and DE-FG02-04ER54793 1. A. Punjabi, H. Ali, T. Evans, and A. Boozer, Phys. Let. A 364, 140--145 (2007). 2. O. Kerwin, A. Punjabi, and H. Ali, to appear in Physics of Plasmas. 3. A. Punjabi and H. Ali, P1.012, 35^th EPS Conference on Plasma Physics, June 9-13, 2008, Hersonissos, Crete, Greece.

The activity of spontaneous action potentials in developing hair cells is regulated by Ca(2+)-dependence of a transient K+ current.

PubMed

Levic, Snezana; Lv, Ping; Yamoah, Ebenezer N

2011-01-01

Spontaneous action potentials have been described in developing sensory systems. These rhythmic activities may have instructional roles for the functional development of synaptic connections. The importance of spontaneous action potentials in the developing auditory system is underpinned by the stark correlation between the time of auditory system functional maturity, and the cessation of spontaneous action potentials. A prominent K(+) current that regulates patterning of action potentials is I(A). This current undergoes marked changes in expression during chicken hair cell development. Although the properties of I(A) are not normally classified as Ca(2+)-dependent, we demonstrate that throughout the development of chicken hair cells, I(A) is greatly reduced by acute alterations of intracellular Ca(2+). As determinants of spike timing and firing frequency, intracellular Ca(2+) buffers shift the activation and inactivation properties of the current to more positive potentials. Our findings provide evidence to demonstrate that the kinetics and functional expression of I(A) are tightly regulated by intracellular Ca(2+). Such feedback mechanism between the functional expression of I(A) and intracellular Ca(2+) may shape the activity of spontaneous action potentials, thus potentially sculpting synaptic connections in an activity-dependent manner in the developing cochlea. © 2011 Levic et al.

Internal kinematics of disk galaxies in the local universe

NASA Astrophysics Data System (ADS)

Catinella, Barbara

2005-11-01

This dissertation makes use of a homogeneous sample of several thousand normal, non-interacting, spiral galaxies, for which I-band photometry and optical and/ or radio spectroscopy are available, to investigate the average kinematic properties of disk systems at low redshifts ( z [Special characters omitted.] 0.1). New long-slit Ha rotation curves (RCs) for 402 galaxies, which were incorporated into the larger sample, are presented in this work. The main goals of this thesis are: (a) The definition of a set of average, or template , RCs in bins covering a wide range of galaxy luminosity. The template relations represent an accurate description of the average circular velocity field of local spiral galaxies, and are intended to be a standard reference for more distant samples and to constrain theoretical models of galactic disks. (b) The characterization of the systematics associated with different velocity width measurement techniques, and the derivation of a robust measure of rotational velocity to be used for applications of the Tully-Fisher (TF) distance method. A direct cross-calibration of the optical and radio widths has been obtained. (c) The assessment of the impact of the limitations on optical line widths extracted from fixed apertures, such as those being collected for ~10 6 galaxies by the on-going Sloan Digital Sky Survey (SDSS). Since the SDSS fiber technique generally does not sample the full extent of a galaxy RC, the observed line widths yield rotational width measurements that depend on the redshifts of the objects, on the physical sizes of their line-emitting regions, and on the intrinsic shapes of their RCs. Numerical simulations of these biases have been carried out for galaxies with realistic circular velocity fields (described by the template RCs) in the redshift range covered by the SDSS spectroscopic sample. Statistical corrections to be applied to the aperture line widths as a function of galaxy redshift and luminosity have been derived, and their impact on the TF relation examined. The use of the SDSS line widths, corrected for aperture effects, has the potential to solve the debated issue of luminosity evolution of galaxies at intermediate redshifts.

78 FR 23740 - Notice of Availability of a Swine Brucellosis and Pseudorabies Proposed Action Plan

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-22

...] Notice of Availability of a Swine Brucellosis and Pseudorabies Proposed Action Plan AGENCY: Animal and... proposed action plan describing a potential new approach to managing swine brucellosis and pseudorabies...-0086) a notice that made a proposed action plan describing a potential new approach to managing swine...

Modulating anosognosia for hemiplegia: The role of dangerous actions in emergent awareness.

PubMed

D'Imperio, Daniela; Bulgarelli, Cristina; Bertagnoli, Sara; Avesani, Renato; Moro, Valentina

2017-07-01

Anosognosia for hemiplegia is a lack of awareness of motor deficits following a right hemisphere lesion. Residual forms of awareness co-occur with an explicit denial of hemiplegia. The term emergent awareness refers to a condition in which awareness of motor deficits is reported verbally during the actual performance of an action involving the affected body part. In this study, two tasks were used to explore the potential effects of i) attempting actions which are impossible for sufferers of hemiplegia and ii) attempting actions which are potentially dangerous. Sixteen hemiplegic patients (8 anosognosic, and 8 non-anosognosic) were asked to perform both potentially dangerous and neutral actions. Our results confirm an increase in emergent awareness in anosognosic patients during the execution of both of these types of action. Moreover, actions that are potentially dangerous improved the degree of awareness. However, lesions in the fronto-temporal areas appear to be associated with a reduced effect of action execution (emergent awareness) while lesions in the basal ganglia and amygdale and the white matter underlying the insula and fronto-temporal areas are associated with a lesser degree of improvement resulting from attempting to perform dangerous actions. Copyright © 2017 Elsevier Ltd. All rights reserved.

Generation of dark solitons and their instability dynamics in two-dimensional condensates

NASA Astrophysics Data System (ADS)

Verma, Gunjan; Rapol, Umakant D.; Nath, Rejish

2017-04-01

We analyze numerically the formation and the subsequent dynamics of two-dimensional matter wave dark solitons in a Thomas-Fermi rubidium condensate using various techniques. An initially imprinted sharp phase gradient leads to the dynamical formation of a stationary soliton as well as very shallow gray solitons, whereas a smooth gradient only creates gray solitons. The depth and hence, the velocity of the soliton is provided by the spatial width of the phase gradient, and it also strongly influences the snake-instability dynamics of the two-dimensional solitons. The vortex dipoles stemming from the unstable soliton exhibit rich dynamics. Notably, the annihilation of a vortex dipole via a transient dark lump or a vortexonium state, the exchange of vortices between either a pair of vortex dipoles or a vortex dipole and a single vortex, and so on. For sufficiently large width of the initial phase gradient, the solitons may decay directly into vortexoniums instead of vortex pairs, and also the decay rate is augmented. Later, we discuss alternative techniques to generate dark solitons, which involve a Gaussian potential barrier and time-dependent interactions, both linear and periodic. The properties of the solitons can be controlled by tuning the amplitude or the width of the potential barrier. In the linear case, the number of solitons and their depths are determined by the quench time of the interactions. For the periodic modulation, a transient soliton lattice emerges with its periodicity depending on the modulation frequency, through a wave number selection governed by the local Bogoliubov spectrum. Interestingly, for sufficiently low barrier potential, both Faraday pattern and soliton lattice coexist. The snake instability dynamics of the soliton lattice is characteristically modified if the Faraday pattern is present.

Thermal width of the upsilon at large 't Hooft coupling.

PubMed

Noronha, Jorge; Dumitru, Adrian

2009-10-09

We use the anti-de Sitter/conformal field theory correspondence to show that the heavy quark (static) potential in a strongly coupled plasma develops an imaginary part at finite temperature. Thus, deeply bound heavy quarkonia states acquire a small nonzero thermal width when the 't Hooft coupling lambda = g2N(c) > 1 and the number of colors N(c) --> infinity. In the dual gravity description, this imaginary contribution comes from thermal fluctuations around the bottom of the classical sagging string in the bulk that connects the heavy quarks located at the boundary. We predict a strong suppression of Upsilon's in heavy-ion collisions and discuss how this may be used to estimate the initial temperature.

Grazing incidence metal optics for the Berkeley Extreme Ultraviolet Explorer satellite - A progress report

NASA Technical Reports Server (NTRS)

Finley, D.; Malina, R. F.; Bowyer, S.

1985-01-01

The four flight Wolter-Schwarzschild mirrors currently under fabrication for the Extreme Ultraviolet Explorer (EUVE) satellite are described. The principal figuring operation of these grazing incidence metal mirrors (gold over nickel on an aluminum substrate) is carried out by diamond turning at the Lawrence Livermore National Laboratories. Turning has been accomplished and optical testing results analyzed for three of the mirrors. As-turned values of 1.7 arc sec full width at half maximum (FWHM) and half energy width (HEW) of 5 arc seconds in the visible have been achieved. These results illustrate the great potential of precision fabrication technology for the production of large grazing incidence optics.

[Effect of pulse magnetic field on distribution of neuronal action potential].

PubMed

Zheng, Yu; Cai, Di; Wang, Jin-Hai; Li, Gang; Lin, Ling

2014-08-25

The biological effect on the organism generated by magnetic field is widely studied. The present study was aimed to observe the change of sodium channel under magnetic field in neurons. Cortical neurons of Kunming mice were isolated, subjected to 15 Hz, 1 mT pulse magnetic stimulation, and then the currents of neurons were recorded by whole-cell patch clamp. The results showed that, under magnetic stimulation, the activation process of Na(+) channel was delayed, and the inactivation process was accelerated. Given the classic three-layer model, the polarization diagram of cell membrane potential distribution under pulse magnetic field was simulated, and it was found that the membrane potential induced was associated with the frequency and intensity of magnetic field. Also the effect of magnetic field-induced current on action potential was simulated by Hodgkin-Huxley (H-H) model. The result showed that the generation of action potential was delayed, and frequency and the amplitudes were decreased when working current was between -1.32 μA and 0 μA. When the working current was higher than 0 μA, the generation frequency of action potential was increased, and the change of amplitudes was not obvious, and when the working current was lower than -1.32 μA, the time of rising edge and amplitudes of action potential were decreased drastically, and the action potential was unable to generate. These results suggest that the magnetic field simulation can affect the distribution frequency and amplitude of action potential of neuron via sodium channel mediation.

Exteroceptive and Interoceptive Body-Self Awareness in Fibromyalgia Patients

PubMed Central

Valenzuela-Moguillansky, Camila; Reyes-Reyes, Alejandro; Gaete, María I.

2017-01-01

Fibromyalgia is a widespread chronic pain disease characterized by generalized musculoskeletal pain and fatigue. It substantially affects patients' relationship with their bodies and quality of life, but few studies have investigated the relationship between pain and body awareness in fibromyalgia. We examined exteroceptive and interoceptive aspects of body awareness in 30 women with fibromyalgia and 29 control participants. Exteroceptive body awareness was assessed by a body-scaled action-anticipation task in which participants estimated whether they could pass through apertures of different widths. Interoceptive sensitivity (IS) was assessed by a heartbeat detection task where participants counted their heartbeats during different time intervals. Interoceptive awareness was assessed by the Multidimensional Assessment of Interoceptive Awareness (MAIA). The “passability ratio” (the aperture size for a 50% positive response rate, divided by shoulder width), assessed by the body-scaled action-anticipation task, was higher for fibromyalgia participants, indicating disrupted exteroceptive awareness. Overestimating body size correlated positively with pain and its impact on functionality, but not with pain intensity. There was no difference in IS between groups. Fibromyalgia patients exhibited a higher tendency to note bodily sensations and decreased body confidence. In addition, the passability ratio and IS score correlated negatively across the whole sample, suggesting an inverse relationship between exteroceptive and interoceptive body awareness. There was a lower tendency to actively listen to the body for insight, with higher passability ratios across the whole sample. Based on our results and building on the fear-avoidance model, we outline a proposal that highlights possible interactions between exteroceptive and interoceptive body awareness and pain. Movement based contemplative practices that target sensory-motor integration and foster non-judgmental reconnection with bodily sensations are suggested to improve body confidence, functionality, and quality of life. PMID:28348526

Exteroceptive and Interoceptive Body-Self Awareness in Fibromyalgia Patients.

PubMed

Valenzuela-Moguillansky, Camila; Reyes-Reyes, Alejandro; Gaete, María I

2017-01-01

Fibromyalgia is a widespread chronic pain disease characterized by generalized musculoskeletal pain and fatigue. It substantially affects patients' relationship with their bodies and quality of life, but few studies have investigated the relationship between pain and body awareness in fibromyalgia. We examined exteroceptive and interoceptive aspects of body awareness in 30 women with fibromyalgia and 29 control participants. Exteroceptive body awareness was assessed by a body-scaled action-anticipation task in which participants estimated whether they could pass through apertures of different widths. Interoceptive sensitivity (IS) was assessed by a heartbeat detection task where participants counted their heartbeats during different time intervals. Interoceptive awareness was assessed by the Multidimensional Assessment of Interoceptive Awareness (MAIA). The "passability ratio" (the aperture size for a 50% positive response rate, divided by shoulder width), assessed by the body-scaled action-anticipation task, was higher for fibromyalgia participants, indicating disrupted exteroceptive awareness. Overestimating body size correlated positively with pain and its impact on functionality, but not with pain intensity. There was no difference in IS between groups. Fibromyalgia patients exhibited a higher tendency to note bodily sensations and decreased body confidence. In addition, the passability ratio and IS score correlated negatively across the whole sample, suggesting an inverse relationship between exteroceptive and interoceptive body awareness. There was a lower tendency to actively listen to the body for insight, with higher passability ratios across the whole sample. Based on our results and building on the fear-avoidance model, we outline a proposal that highlights possible interactions between exteroceptive and interoceptive body awareness and pain. Movement based contemplative practices that target sensory-motor integration and foster non-judgmental reconnection with bodily sensations are suggested to improve body confidence, functionality, and quality of life.

Intracellular recording of action potentials by nanopillar electroporation.

PubMed

Xie, Chong; Lin, Ziliang; Hanson, Lindsey; Cui, Yi; Cui, Bianxiao

2012-02-12

Action potentials have a central role in the nervous system and in many cellular processes, notably those involving ion channels. The accurate measurement of action potentials requires efficient coupling between the cell membrane and the measuring electrodes. Intracellular recording methods such as patch clamping involve measuring the voltage or current across the cell membrane by accessing the cell interior with an electrode, allowing both the amplitude and shape of the action potentials to be recorded faithfully with high signal-to-noise ratios. However, the invasive nature of intracellular methods usually limits the recording time to a few hours, and their complexity makes it difficult to simultaneously record more than a few cells. Extracellular recording methods, such as multielectrode arrays and multitransistor arrays, are non-invasive and allow long-term and multiplexed measurements. However, extracellular recording sacrifices the one-to-one correspondence between the cells and electrodes, and also suffers from significantly reduced signal strength and quality. Extracellular techniques are not, therefore, able to record action potentials with the accuracy needed to explore the properties of ion channels. As a result, the pharmacological screening of ion-channel drugs is usually performed by low-throughput intracellular recording methods. The use of nanowire transistors, nanotube-coupled transistors and micro gold-spine and related electrodes can significantly improve the signal strength of recorded action potentials. Here, we show that vertical nanopillar electrodes can record both the extracellular and intracellular action potentials of cultured cardiomyocytes over a long period of time with excellent signal strength and quality. Moreover, it is possible to repeatedly switch between extracellular and intracellular recording by nanoscale electroporation and resealing processes. Furthermore, vertical nanopillar electrodes can detect subtle changes in action potentials induced by drugs that target ion channels.

Intracellular recording of action potentials by nanopillar electroporation

NASA Astrophysics Data System (ADS)

Xie, Chong; Lin, Ziliang; Hanson, Lindsey; Cui, Yi; Cui, Bianxiao

2012-03-01

Action potentials have a central role in the nervous system and in many cellular processes, notably those involving ion channels. The accurate measurement of action potentials requires efficient coupling between the cell membrane and the measuring electrodes. Intracellular recording methods such as patch clamping involve measuring the voltage or current across the cell membrane by accessing the cell interior with an electrode, allowing both the amplitude and shape of the action potentials to be recorded faithfully with high signal-to-noise ratios. However, the invasive nature of intracellular methods usually limits the recording time to a few hours, and their complexity makes it difficult to simultaneously record more than a few cells. Extracellular recording methods, such as multielectrode arrays and multitransistor arrays, are non-invasive and allow long-term and multiplexed measurements. However, extracellular recording sacrifices the one-to-one correspondence between the cells and electrodes, and also suffers from significantly reduced signal strength and quality. Extracellular techniques are not, therefore, able to record action potentials with the accuracy needed to explore the properties of ion channels. As a result, the pharmacological screening of ion-channel drugs is usually performed by low-throughput intracellular recording methods. The use of nanowire transistors, nanotube-coupled transistors and micro gold-spine and related electrodes can significantly improve the signal strength of recorded action potentials. Here, we show that vertical nanopillar electrodes can record both the extracellular and intracellular action potentials of cultured cardiomyocytes over a long period of time with excellent signal strength and quality. Moreover, it is possible to repeatedly switch between extracellular and intracellular recording by nanoscale electroporation and resealing processes. Furthermore, vertical nanopillar electrodes can detect subtle changes in action potentials induced by drugs that target ion channels.

Action potential bursts in central snail neurons elicited by paeonol: roles of ionic currents

PubMed Central

Chen, Yi-hung; Lin, Pei-lin; Hsu, Hui-yu; Wu, Ya-ting; Yang, Han-yin; Lu, Dah-yuu; Huang, Shiang-suo; Hsieh, Ching-liang; Lin, Jaung-geng

2010-01-01

Aim: To investigate the effects of 2′-hydroxy-4′-methoxyacetophenone (paeonol) on the electrophysiological behavior of a central neuron (right parietal 4; RP4) of the giant African snail (Achatina fulica Ferussac). Methods: Intracellular recordings and the two-electrode voltage clamp method were used to study the effects of paeonol on the RP4 neuron. Results: The RP4 neuron generated spontaneous action potentials. Bath application of paeonol at a concentration of ≥500 μmol/L reversibly elicited action potential bursts in a concentration-dependent manner. Immersing the neurons in Co2+-substituted Ca2+-free solution did not block paeonol-elicited bursting. Pretreatment with the protein kinase A (PKA) inhibitor KT-5720 or the protein kinase C (PKC) inhibitor Ro 31-8220 did not affect the action potential bursts. Voltage-clamp studies revealed that paeonol at a concentration of 500 μmol/L had no remarkable effects on the total inward currents, whereas paeonol decreased the delayed rectifying K+ current (IKD) and the fast-inactivating K+ current (IA). Application of 4-aminopyridine (4-AP 5 mmol/L), an inhibitor of IA, or charybdotoxin 250 nmol/L, an inhibitor of the Ca2+-activated K+ current (IK(Ca)), failed to elicit action potential bursts, whereas tetraethylammonium chloride (TEA 50 mmol/L), an IKD blocker, successfully elicited action potential bursts. At a lower concentration of 5 mmol/L, TEA facilitated the induction of action potential bursts elicited by paeonol. Conclusion: Paeonol elicited a bursting firing pattern of action potentials in the RP4 neuron and this activity relates closely to the inhibitory effects of paeonol on the IKD. PMID:21042287

Consequences of converting graded to action potentials upon neural information coding and energy efficiency.

PubMed

Sengupta, Biswa; Laughlin, Simon Barry; Niven, Jeremy Edward

2014-01-01

Information is encoded in neural circuits using both graded and action potentials, converting between them within single neurons and successive processing layers. This conversion is accompanied by information loss and a drop in energy efficiency. We investigate the biophysical causes of this loss of information and efficiency by comparing spiking neuron models, containing stochastic voltage-gated Na(+) and K(+) channels, with generator potential and graded potential models lacking voltage-gated Na(+) channels. We identify three causes of information loss in the generator potential that are the by-product of action potential generation: (1) the voltage-gated Na(+) channels necessary for action potential generation increase intrinsic noise and (2) introduce non-linearities, and (3) the finite duration of the action potential creates a 'footprint' in the generator potential that obscures incoming signals. These three processes reduce information rates by ∼50% in generator potentials, to ∼3 times that of spike trains. Both generator potentials and graded potentials consume almost an order of magnitude less energy per second than spike trains. Because of the lower information rates of generator potentials they are substantially less energy efficient than graded potentials. However, both are an order of magnitude more efficient than spike trains due to the higher energy costs and low information content of spikes, emphasizing that there is a two-fold cost of converting analogue to digital; information loss and cost inflation.

Consequences of Converting Graded to Action Potentials upon Neural Information Coding and Energy Efficiency

PubMed Central

Sengupta, Biswa; Laughlin, Simon Barry; Niven, Jeremy Edward

2014-01-01

Information is encoded in neural circuits using both graded and action potentials, converting between them within single neurons and successive processing layers. This conversion is accompanied by information loss and a drop in energy efficiency. We investigate the biophysical causes of this loss of information and efficiency by comparing spiking neuron models, containing stochastic voltage-gated Na+ and K+ channels, with generator potential and graded potential models lacking voltage-gated Na+ channels. We identify three causes of information loss in the generator potential that are the by-product of action potential generation: (1) the voltage-gated Na+ channels necessary for action potential generation increase intrinsic noise and (2) introduce non-linearities, and (3) the finite duration of the action potential creates a ‘footprint’ in the generator potential that obscures incoming signals. These three processes reduce information rates by ∼50% in generator potentials, to ∼3 times that of spike trains. Both generator potentials and graded potentials consume almost an order of magnitude less energy per second than spike trains. Because of the lower information rates of generator potentials they are substantially less energy efficient than graded potentials. However, both are an order of magnitude more efficient than spike trains due to the higher energy costs and low information content of spikes, emphasizing that there is a two-fold cost of converting analogue to digital; information loss and cost inflation. PMID:24465197

Numerical Computation of Electric Field and Potential Along Silicone Rubber Insulators Under Contaminated and Dry Band Conditions

NASA Astrophysics Data System (ADS)

Arshad; Nekahi, A.; McMeekin, S. G.; Farzaneh, M.

2016-09-01

Electrical field distribution along the insulator surface is considered one of the important parameters for the performance evaluation of outdoor insulators. In this paper numerical simulations were carried out to investigate the electric field and potential distribution along silicone rubber insulators under various polluted and dry band conditions. Simulations were performed using commercially available simulation package Comsol Multiphysics based on the finite element method. Various pollution severity levels were simulated by changing the conductivity of pollution layer. Dry bands of 2 cm width were inserted at the high voltage end, ground end, middle part, shed, sheath, and at the junction of shed and sheath to investigate the effect of dry band location and width on electric field and potential distribution. Partial pollution conditions were simulated by applying pollution layer on the top and bottom surface respectively. It was observed from the simulation results that electric field intensity was higher at the metal electrode ends and at the junction of dry bands. Simulation results showed that potential distribution is nonlinear in the case of clean and partially polluted insulator and linear for uniform pollution layer. Dry band formation effect both potential and electric field distribution. Power dissipated along the insulator surface and the resultant heat generation was also studied. The results of this study could be useful in the selection of polymeric insulators for contaminated environments.

Precise measurement of electric potential, field, and charge density profiles across a biased GaAs p-n tunnel junction by in situ phase-shifting electron holography

NASA Astrophysics Data System (ADS)

Anada, Satoshi; Yamamoto, Kazuo; Sasaki, Hirokazu; Shibata, Naoya; Hori, Yujin; Kinugawa, Kouhei; Imamura, Akihiro; Hirayama, Tsukasa

2017-12-01

We combined an in situ biasing technique with phase-shifting electron holography, which can simultaneously achieve a high precision and high spatial resolution, to measure the electric potential, field, and charge density profiles across a GaAs p-n tunnel junction. A thin-film specimen was prepared by thinning one part of a bulk specimen using a cryo focused ion beam (FIB) system. We obtained precise electric potential profiles and successfully converted them into smooth electric field and charge density profiles without any fitting simulations. From the relationship between the applied voltage and measured height of the potential step across the p-n junction, the built-in potential of the p-n junction was determined to be 1.55 ± 0.02 V. The electric field profiles showed that the unbiased p-n junction had a depletion layer with a width of 24 ± 1 nm; the width increased to 26 ± 1 nm under a reverse bias of -0.3 V and decreased to 22 ± 1 nm under a forward bias of 0.5 V. Moreover, the charge density profiles indicated the presence of passivated dopants and/or trapped carriers even in the internal active layer of the specimen, with little damage introduced by FIB milling.

Signal-independent timescale analysis (SITA) and its application for neural coding during reaching and walking.

PubMed

Zacksenhouse, Miriam; Lebedev, Mikhail A; Nicolelis, Miguel A L

2014-01-01

What are the relevant timescales of neural encoding in the brain? This question is commonly investigated with respect to well-defined stimuli or actions. However, neurons often encode multiple signals, including hidden or internal, which are not experimentally controlled, and thus excluded from such analysis. Here we consider all rate modulations as the signal, and define the rate-modulations signal-to-noise ratio (RM-SNR) as the ratio between the variance of the rate and the variance of the neuronal noise. As the bin-width increases, RM-SNR increases while the update rate decreases. This tradeoff is captured by the ratio of RM-SNR to bin-width, and its variations with the bin-width reveal the timescales of neural activity. Theoretical analysis and simulations elucidate how the interactions between the recovery properties of the unit and the spectral content of the encoded signals shape this ratio and determine the timescales of neural coding. The resulting signal-independent timescale analysis (SITA) is applied to investigate timescales of neural activity recorded from the motor cortex of monkeys during: (i) reaching experiments with Brain-Machine Interface (BMI), and (ii) locomotion experiments at different speeds. Interestingly, the timescales during BMI experiments did not change significantly with the control mode or training. During locomotion, the analysis identified units whose timescale varied consistently with the experimentally controlled speed of walking, though the specific timescale reflected also the recovery properties of the unit. Thus, the proposed method, SITA, characterizes the timescales of neural encoding and how they are affected by the motor task, while accounting for all rate modulations.

A switching cost for motor planning

PubMed Central

Lefèvre, Philippe

2016-01-01

Movement planning consists of choosing the intended endpoint of the movement and selecting the motor program that will bring the effector on the endpoint. It is widely accepted that movement endpoint is updated on a trial-by-trial basis with respect to the observed errors and that the motor program for a given movement follows the rules of optimal feedback control. In this article, we show clear limitations of these theories. First, participants in the current study could not tune their motor program appropriately for each individual trial. This was true even when the participants selected the width of the target that they reached toward or when they had learned the appropriate motor program previously. These data are compatible with the existence of a switching cost for motor planning, which relates to the drop in performance due to an imposed switch of motor programs. This cost of switching shares many features of costs reported in cognitive task switching experiments and, when tested in the same participants, was correlated with it. Second, we found that randomly changing the width of a target over the course of a reaching experiment prevents the motor system from updating the endpoint of movements on the basis of the performance on the previous trial if the width of the target has changed. These results provide new insights into the process of motor planning and how it relates to optimal control theory and to an action selection based on the reward consequences of the motor program rather than that based on the observed error. PMID:27655964

A switching cost for motor planning.

PubMed

Orban de Xivry, Jean-Jacques; Lefèvre, Philippe

2016-12-01

Movement planning consists of choosing the intended endpoint of the movement and selecting the motor program that will bring the effector on the endpoint. It is widely accepted that movement endpoint is updated on a trial-by-trial basis with respect to the observed errors and that the motor program for a given movement follows the rules of optimal feedback control. In this article, we show clear limitations of these theories. First, participants in the current study could not tune their motor program appropriately for each individual trial. This was true even when the participants selected the width of the target that they reached toward or when they had learned the appropriate motor program previously. These data are compatible with the existence of a switching cost for motor planning, which relates to the drop in performance due to an imposed switch of motor programs. This cost of switching shares many features of costs reported in cognitive task switching experiments and, when tested in the same participants, was correlated with it. Second, we found that randomly changing the width of a target over the course of a reaching experiment prevents the motor system from updating the endpoint of movements on the basis of the performance on the previous trial if the width of the target has changed. These results provide new insights into the process of motor planning and how it relates to optimal control theory and to an action selection based on the reward consequences of the motor program rather than that based on the observed error. Copyright © 2016 the American Physiological Society.

Synchronization of action potentials during low-magnesium-induced bursting

PubMed Central

Johnson, Sarah E.; Hudson, John L.

2015-01-01

The relationship between mono- and polysynaptic strength and action potential synchronization was explored using a reduced external Mg2+ model. Single and dual whole cell patch-clamp recordings were performed in hippocampal cultures in three concentrations of external Mg2+. In decreased Mg2+ medium, the individual cells transitioned to spontaneous bursting behavior. In lowered Mg2+ media the larger excitatory synaptic events were observed more frequently and fewer transmission failures occurred, suggesting strengthened synaptic transmission. The event synchronization was calculated for the neural action potentials of the cell pairs, and it increased in media where Mg2+ concentration was lowered. Analysis of surrogate data where bursting was present, but no direct or indirect connections existed between the neurons, showed minimal action potential synchronization. This suggests the synchronization of action potentials is a product of the strengthening synaptic connections within neuronal networks. PMID:25609103

Synchronization of action potentials during low-magnesium-induced bursting.

PubMed

Johnson, Sarah E; Hudson, John L; Kapur, Jaideep

2015-04-01

The relationship between mono- and polysynaptic strength and action potential synchronization was explored using a reduced external Mg(2+) model. Single and dual whole cell patch-clamp recordings were performed in hippocampal cultures in three concentrations of external Mg(2+). In decreased Mg(2+) medium, the individual cells transitioned to spontaneous bursting behavior. In lowered Mg(2+) media the larger excitatory synaptic events were observed more frequently and fewer transmission failures occurred, suggesting strengthened synaptic transmission. The event synchronization was calculated for the neural action potentials of the cell pairs, and it increased in media where Mg(2+) concentration was lowered. Analysis of surrogate data where bursting was present, but no direct or indirect connections existed between the neurons, showed minimal action potential synchronization. This suggests the synchronization of action potentials is a product of the strengthening synaptic connections within neuronal networks. Copyright © 2015 the American Physiological Society.

Millisecond infrared laser pulses depolarize and elicit action potentials on in-vitro dorsal root ganglion neurons

PubMed Central

Paris, Lambert; Marc, Isabelle; Charlot, Benoit; Dumas, Michel; Valmier, Jean; Bardin, Fabrice

2017-01-01

This work focuses on the optical stimulation of dorsal root ganglion (DRG) neurons through infrared laser light stimulation. We show that a few millisecond laser pulse at 1875 nm induces a membrane depolarization, which was observed by the patch-clamp technique. This stimulation led to action potentials firing on a minority of neurons beyond an energy threshold. A depolarization without action potential was observed for the majority of DRG neurons, even beyond the action potential energy threshold. The use of ruthenium red, a thermal channel blocker, stops the action potential generation, but has no effects on membrane depolarization. Local temperature measurements reveal that the depolarization amplitude is sensitive to the amplitude of the temperature rise as well as to the time rate of change of temperature, but in a way which may not fully follow a photothermal capacitive mechanism, suggesting that more complex mechanisms are involved. PMID:29082085

[Effects of dauricine on action potentials and slow inward currents of guinea pig ventricular papillary muscles].

PubMed

Li, S N; Zhang, K Y

1992-11-01

Effects of dauricine (Dau) on the action potentials (AP), the slow action potentials (SAP), and the slow inward currents (Isi) of guinea pig ventricular papillary muscles were observed by means of intracellular microelectrode and single sucrose gap voltage clamp technique. In the early stage, Dau shortened action potential duration 100 (APD100) and effective refractory period (ERP) (ERP/APD < 1; P < 0.01), but did not affect APD20 and other parameters. In the late stage, Dau prolonged APD100, ERP, and APD20, significantly decreased action potential amplitude (APA), maximum velocity (Vmax), and overshot (OS) (ERP/APD > 1; P < 0.01), greatly diminished APA and OS of SAP induced by isoprenaline (P < 0.01), and remarkably inhibited Isi (P < 0.01). The results suggested that Dau exerted an inhibitory effect on Na+, Ca2+, and K+ channels.

Simulation of axonal excitability using a Spreadsheet template created in Microsoft Excel.

PubMed

Brown, A M

2000-08-01

The objective of this present study was to implement an established simulation protocol (A.M. Brown, A methodology for simulating biological systems using Microsoft Excel, Comp. Methods Prog. Biomed. 58 (1999) 181-90) to model axonal excitability. The simulation protocol involves the use of in-cell formulas directly typed into a spreadsheet and does not require any programming skills or use of the macro language. Once the initial spreadsheet template has been set up the simulations described in this paper can be executed with a few simple keystrokes. The model axon contained voltage-gated ion channels that were modeled using Hodgkin Huxley style kinetics. The basic properties of axonal excitability modeled were: (1) threshold of action potential firing, demonstrating that not only are the stimulus amplitude and duration critical in the generation of an action potential, but also the resting membrane potential; (2) refractoriness, the phenomenon of reduced excitability immediately following an action potential. The difference between the absolute refractory period, when no amount of stimulus will elicit an action potential, and relative refractory period, when an action potential may be generated by applying increased stimulus, was demonstrated with regard to the underlying state of the Na(+) and K(+) channels; (3) temporal summation, a process by which two sub-threshold stimuli can unite to elicit an action potential was shown to be due to conductance changes outlasting the first stimulus and summing with the second stimulus-induced conductance changes to drive the membrane potential past threshold; (4) anode break excitation, where membrane hyperpolarization was shown to produce an action potential by removing Na(+) channel inactivation that is present at resting membrane potential. The simulations described in this paper provide insights into mechanisms of axonal excitation that can be carried out by following an easily understood protocol.

Optical mapping of optogenetically shaped cardiac action potentials.

PubMed

Park, Sarah A; Lee, Shin-Rong; Tung, Leslie; Yue, David T

2014-08-19

Light-mediated silencing and stimulation of cardiac excitability, an important complement to electrical stimulation, promises important discoveries and therapies. To date, cardiac optogenetics has been studied with patch-clamp, multielectrode arrays, video microscopy, and an all-optical system measuring calcium transients. The future lies in achieving simultaneous optical acquisition of excitability signals and optogenetic control, both with high spatio-temporal resolution. Here, we make progress by combining optical mapping of action potentials with concurrent activation of channelrhodopsin-2 (ChR2) or halorhodopsin (eNpHR3.0), via an all-optical system applied to monolayers of neonatal rat ventricular myocytes (NRVM). Additionally, we explore the capability of ChR2 and eNpHR3.0 to shape action-potential waveforms, potentially aiding the study of short/long QT syndromes that result from abnormal changes in action potential duration (APD). These results show the promise of an all-optical system to acquire action potentials with precise temporal optogenetics control, achieving a long-sought flexibility beyond the means of conventional electrical stimulation.

Optical mapping of optogenetically shaped cardiac action potentials

PubMed Central

Park, Sarah A.; Lee, Shin-Rong; Tung, Leslie; Yue, David T.

2014-01-01

Light-mediated silencing and stimulation of cardiac excitability, an important complement to electrical stimulation, promises important discoveries and therapies. To date, cardiac optogenetics has been studied with patch-clamp, multielectrode arrays, video microscopy, and an all-optical system measuring calcium transients. The future lies in achieving simultaneous optical acquisition of excitability signals and optogenetic control, both with high spatio-temporal resolution. Here, we make progress by combining optical mapping of action potentials with concurrent activation of channelrhodopsin-2 (ChR2) or halorhodopsin (eNpHR3.0), via an all-optical system applied to monolayers of neonatal rat ventricular myocytes (NRVM). Additionally, we explore the capability of ChR2 and eNpHR3.0 to shape action-potential waveforms, potentially aiding the study of short/long QT syndromes that result from abnormal changes in action potential duration (APD). These results show the promise of an all-optical system to acquire action potentials with precise temporal optogenetics control, achieving a long-sought flexibility beyond the means of conventional electrical stimulation. PMID:25135113

The effects of a geometrical size, external electric fields and impurity on the optical gain of a quantum dot laser with a semi-parabolic spherical well potential

NASA Astrophysics Data System (ADS)

Owji, Erfan; Keshavarz, Alireza; Mokhtari, Hosein

2017-03-01

In this paper, a GaAs / Alx Ga1-x As quantum dot laser with a semi-parabolic spherical well potential is assumed. By using Runge-Kutta method the eigenenergies and the eigenstates of valence and conduct bands are obtained. The effects of geometrical sizes, external electric fields and hydrogen impurity on the different electronic transitions of the optical gain are studied. The results show that the optical gain peak increases and red-shifts, by increasing the width of well or barrier, while more increasing of the width causes blue-shift and decreases it. The hydrogen impurity decreases the optical gain peak and blue-shifts it. Also, the increasing of the external electric fields cause to increase the peak of the optical gain, and (blue) red shift it. Finally, the optical gain for 1s-1s and 2s-1s transitions is prominent, while it is so weak for other transitions.

The varieties of symmetric stellar rings and radial caustics in galaxy disks

NASA Technical Reports Server (NTRS)

Struck-Marcell, Curtis; Lotan, Pnina

1990-01-01

Numerical, restricted three-body and analytic calculations are used to study the formation and propagation of cylindrically symmetric stellar ring waves in galaxy disks. It is shown that such waves can evolve in a variety of ways, depending on the amplitude of the perturbation and the potential of the target galaxy. Rings can thicken as they propagate outward, remain at a nearly constant width, or be pinched off at large radii. Multiple, closely spaced rings can result from a low-amplitude collision, while an outer ring can appear well-separated from overlapping inner rings or an apparent lens structure in halo-dominated potentials. All the single-encounter rings consist of paired fold caustics. The simple, impulsive, kinematic oscillation equations appear to provide a remarkably accurate model of the numerical simulations. Simple analytic approximations to these equations permit very good estimates of oscillation periods and amplitudes, the evolution of ring widths, and ring birth and propagation characteristics.

Shape resonances of Be- and Mg- investigated with the method of analytic continuation

NASA Astrophysics Data System (ADS)

Čurík, Roman; Paidarová, I.; Horáček, J.

2018-05-01

The regularized method of analytic continuation is used to study the low-energy negative-ion states of beryllium (configuration 2 s2ɛ p 2P ) and magnesium (configuration 3 s2ɛ p 2P ) atoms. The method applies an additional perturbation potential and requires only routine bound-state multi-electron quantum calculations. Such computations are accessible by most of the free or commercial quantum chemistry software available for atoms and molecules. The perturbation potential is implemented as a spherical Gaussian function with a fixed width. Stability of the analytic continuation technique with respect to the width and with respect to the input range of electron affinities is studied in detail. The computed resonance parameters Er=0.282 eV, Γ =0.316 eV for the 2 p state of Be- and Er=0.188 eV, Γ =0.167 for the 3 p state of Mg- agree well with the best results obtained by much more elaborate and computationally demanding present-day methods.

Autogenous healing of sea-water exposed mortar: Quantification through a simple and rapid permeability test

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

Palin, D., E-mail: d.palin@tudelft.nl; Jonkers, H. M.; Wiktor, V.

Concrete has an autogenous ability to heal cracks potentially contributing to its functional water tightness and durability. Here, we quantify the crack-healing capacity of sea-water submerged mortar specimens through a simple and rapid permeability test. Defined crack width geometries were created in blast furnace slag cement specimens allowing healed specimens to be quantified against unhealed specimens. Specimens with 0.2 mm wide cracks were not permeable after 28 days submersion. Specimens with 0.4 mm cracks had decreases in permeability of 66% after 28 days submersion, and 50–53% after 56 days submersion. Precipitation of aragonite and brucite in the cracks was themore » main cause of crack healing. Healing potential was dependent on the initial crack width, thermodynamic considerations and the amount of ions available in the crack. To our knowledge, this is the first study to quantify the functional autogenous healing capacity of cracked sea-water exposed cementitious specimens.« less

Injury risk associated with playing actions during competitive soccer

PubMed Central

Rahnama, N; Reilly, T; Lees, A

2002-01-01

Objective: To assess the exposure of players to injury risk during English Premier League soccer matches in relation to selected factors. Methods: Injury risk was assessed by rating the injury potential of playing actions during competition with respect to (a) type of playing action, (b) period of the game, (c) zone of the pitch, and (d) playing either at home or away. In all, 10 games from the English Premier League 1999–2000 were chosen for analysis. A notation system was used whereby 16 soccer specific playing actions were classified into three categories: those inducing actual injury, those with a potential for injury (graded as mild, moderate, or high), and those deemed to have no potential for injury. The pitch was divided into 18 zones, and the position of each event was recorded along with time elapsed in the game, enabling six 15 minute periods to be defined. Results: Close to 18 000 actions were notated. On average (mean (SD)), 1788 (73) events (one every three seconds), 767 (99) events with injury potential (one every six seconds), and 2 (1) injuries (one every 45 minutes) per game were recorded. An overall injury incidence of 53 per 1000 playing hours was calculated. Receiving a tackle, receiving a "charge", and making a tackle were categorised as having a substantial injury risk, and goal catch, goal punch, kicking the ball, shot on goal, set kick, and heading the ball were all categorised as having a significant injury risk. All other actions were deemed low in risk. The first 15 minutes of each half contained the highest number of actions with mild injury potential, the last 15 minutes having the highest number of actions with moderate injury potential (p<0.01). The first and last 15 minutes of the game had the highest number of actions with high injury potential, although not significant. More actions with mild injury potential occurred in the goal area, and more actions with moderate and high injury potential occurred in the zone adjacent to the goal area (p<0.001). There was no significant difference between home and away with regard to injury potential. Conclusions: Playing actions with high injury risk were linked to contesting possession. Injury risk was highest in the first and last 15 minutes of the game, reflecting the intense engagements in the opening period and the possible effect of fatigue in the closing period. Injury risk was concentrated in the areas of the pitch where possession of the ball is most vigorously contested, which were specific attacking and defending zones close to the goal. Injury potential was no greater in away matches than at home. PMID:12351333

Spontaneous action potentials and neural coding in unmyelinated axons.

PubMed

O'Donnell, Cian; van Rossum, Mark C W

2015-04-01

The voltage-gated Na and K channels in neurons are responsible for action potential generation. Because ion channels open and close in a stochastic fashion, spontaneous (ectopic) action potentials can result even in the absence of stimulation. While spontaneous action potentials have been studied in detail in single-compartment models, studies on spatially extended processes have been limited. The simulations and analysis presented here show that spontaneous rate in unmyelinated axon depends nonmonotonically on the length of the axon, that the spontaneous activity has sub-Poisson statistics, and that neural coding can be hampered by the spontaneous spikes by reducing the probability of transmitting the first spike in a train.

Improving Cardiac Action Potential Measurements: 2D and 3D Cell Culture.

PubMed

Daily, Neil J; Yin, Yue; Kemanli, Pinar; Ip, Brian; Wakatsuki, Tetsuro

2015-11-01

Progress in the development of assays for measuring cardiac action potential is crucial for the discovery of drugs for treating cardiac disease and assessing cardiotoxicity. Recently, high-throughput methods for assessing action potential using induced pluripotent stem cell (iPSC) derived cardiomyocytes in both two-dimensional monolayer cultures and three-dimensional tissues have been developed. We describe an improved method for assessing cardiac action potential using an ultra-fast cost-effective plate reader with commercially available dyes. Our methods improve dramatically the detection of the fluorescence signal from these dyes and make way for the development of more high-throughput methods for cardiac drug discovery and cardiotoxicity.

Isoflurane modulates excitability in the mouse thalamus via GABA-dependent and GABA-independent mechanisms

PubMed Central

Ying, Shui-Wang; Werner, David F.; Homanics, Gregg E.; Harrison, Neil L.; Goldstein, Peter A.

2009-01-01

Summary GABAergic neurons in the reticular thalamic nucleus (RTN) synapse onto thalamocortical neurons in the ventrobasal (VB) thalamus, and this reticulo-thalamocortical pathway is considered an anatomic target for general anesthetic-induced unconsciousness. A mutant mouse was engineered to harbor two amino acid substitutions (S270H, L277A) in the GABAA receptor (GABAA-R) α1 subunit; this mutation abolished sensitivity to the volatile anesthetic isoflurane in recombinant GABAA-Rs, and reduced in vivo sensitivity to isoflurane in the loss-of-righting-reflex assay. We examined the effects of the double mutation on GABAA-R-mediated synaptic currents and isoflurane sensitivity by recording from thalamic neurons in brain slices. The double mutation accelerated the decay, and decreased the ½ width of, evoked inhibitory postsynaptic currents (eIPSCs) in VB neurons and attenuated isoflurane-induced prolongation of the eIPSC. The hypnotic zolpidem, a selective modulator of GABAA-Rs containing the α1 subunit, prolonged eIPSC duration regardless of genotype, indicating that mutant mice incorporate α1-subunit containing GABAA-Rs into synapses. In RTN neurons, which lack the α1 subunit, eIPSC duration was longer than in VB, regardless of genotype. Isoflurane reduced the efficacy of GABAergic transmission from RTN to VB, independent of genotype, suggesting a presynaptic action in RTN neurons. Consistent with this observation, isoflurane inhibited both tonic action potential and rebound burst firing in the presence of GABAA-R blockade. The suppressed excitability in RTN neurons is likely mediated by isoflurane-enhanced Ba2+-sensitive, but 4-aminopyridine-insenstive, potassium conductances. We conclude that isoflurane enhances inhibition of thalamic neurons in VB via GABAA-R-dependent, but in RTN via GABAA-R-independent, mechanisms. PMID:18948126

Action potentials contribute to epileptic high-frequency oscillations recorded with electrodes remote from neurons.

PubMed

Kobayashi, Katsuhiro; Akiyama, Tomoyuki; Ohmori, Iori; Yoshinaga, Harumi; Gotman, Jean

2015-05-01

The importance of epileptic high-frequency oscillations (HFOs) in electroencephalogram (EEG) is growing. Action potentials generating some HFOs are observed in the vicinity of neurons in experimental animals. However electrodes that are remote from neurons, as in case of clinical situations, should not record action potentials. We propose to resolve this question by a realistic simulation of epileptic neuronal network. The rat dentate gyrus with sclerosis was simulated in silico. We computed the current dipole moment generated by each granule cell and the field potentials in a measurement area far from neurons. The dentate gyrus was stimulated through synaptic input to evoke discharges resembling interictal epileptiform discharges, which had superimposed HFOs⩽295Hz that were recordable with remote electrodes and represented bursts of action potentials of granule cells. The increase in power of HFOs was associated with the progression of sclerosis, the reduction of GABAergic inhibition, and the increase in cell connectivity. Spectral frequency of HFOs had similar tendencies. HFOs recorded with electrodes remote from neurons could actually be generated by clusters of action potentials. The phenomenon of action potentials recorded with remote electrodes can possibly extend the clinical meaning of EEG. Copyright © 2014 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

A physical action potential generator: design, implementation and evaluation.

PubMed

Latorre, Malcolm A; Chan, Adrian D C; Wårdell, Karin

2015-01-01

The objective was to develop a physical action potential generator (Paxon) with the ability to generate a stable, repeatable, programmable, and physiological-like action potential. The Paxon has an equivalent of 40 nodes of Ranvier that were mimicked using resin embedded gold wires (Ø = 20 μm). These nodes were software controlled and the action potentials were initiated by a start trigger. Clinically used Ag-AgCl electrodes were coupled to the Paxon for functional testing. The Paxon's action potential parameters were tunable using a second order mathematical equation to generate physiologically relevant output, which was accomplished by varying the number of nodes involved (1-40 in incremental steps of 1) and the node drive potential (0-2.8 V in 0.7 mV steps), while keeping a fixed inter-nodal timing and test electrode configuration. A system noise floor of 0.07 ± 0.01 μV was calculated over 50 runs. A differential test electrode recorded a peak positive amplitude of 1.5 ± 0.05 mV (gain of 40x) at time 196.4 ± 0.06 ms, including a post trigger delay. The Paxon's programmable action potential like signal has the possibility to be used as a validation test platform for medical surface electrodes and their attached systems.

Direct detection of a single evoked action potential with MRS in Lumbricus terrestris.

PubMed

Poplawsky, Alexander J; Dingledine, Raymond; Hu, Xiaoping P

2012-01-01

Functional MRI (fMRI) measures neural activity indirectly by detecting the signal change associated with the hemodynamic response following brain activation. In order to alleviate the temporal and spatial specificity problems associated with fMRI, a number of attempts have been made to detect neural magnetic fields (NMFs) with MRI directly, but have thus far provided conflicting results. In this study, we used MR to detect axonal NMFs in the median giant fiber of the earthworm, Lumbricus terrestris, by examining the free induction decay (FID) with a sampling interval of 0.32 ms. The earthworm nerve cords were isolated from the vasculature and stimulated at the threshold of action potential generation. FIDs were acquired shortly after the stimulation, and simultaneous field potential recordings identified the presence or absence of single evoked action potentials. FIDs acquired when the stimulus did not evoke an action potential were summed as background. The phase of the background-subtracted FID exhibited a systematic change, with a peak phase difference of (-1.2 ± 0.3) × 10(-5) radians occurring at a time corresponding to the timing of the action potential. In addition, we calculated the possible changes in the FID magnitude and phase caused by a simulated action potential using a volume conductor model. The measured phase difference matched the theoretical prediction well in both amplitude and temporal characteristics. This study provides the first evidence for the direct detection of a magnetic field from an evoked action potential using MR. Copyright © 2011 John Wiley & Sons, Ltd.

The Direct Detection of a Single Evoked Action Potential with Magnetic Resonance Spectroscopy in Lumbricus Terrestris

PubMed Central

Poplawsky, Alexander J.; Dingledine, Raymond

2011-01-01

Functional MRI (fMRI) indirectly measures neural activity by detecting the signal change associated with the hemodynamic response following brain activation. In order to alleviate the temporal and spatial specificity problems associated with fMRI, a number of attempts have been made to detect neural magnetic fields (NMFs) with MRI directly, but have thus far provided conflicting results. In the present study, we used magnetic resonance to detect axonal NMFs in the median giant fiber of the earthworm, Lumbricus terrestris, by examining the free-induction decay (FID) with a sampling interval of 0.32 ms. The earthworm nerve cords were isolated from the vasculature and stimulated at the threshold of action potential generation. FIDs were acquired shortly after the stimulation and simultaneous field potential recordings identified the presence or absence of single evoked action potentials. FIDs acquired when the stimulus did not evoke an action potential were summed as background. The phase of the background-subtracted FID exhibited a systematic change, with a peak phase difference of [-1.2 ± 0.3] ×10-5 radians occurring at a time corresponding to the timing of the action potential. In addition, we calculated the possible changes in the FID magnitude and phase due to a simulated action potential using a volume conductor model. The measured phase difference matched the theoretical prediction well in both amplitude and temporal characteristics. This study provides the first evidence for the direct detection of a magnetic field from an evoked action potential using magnetic resonance. PMID:21728204

Channel sialic acids limit hERG channel activity during the ventricular action potential.

PubMed

Norring, Sarah A; Ednie, Andrew R; Schwetz, Tara A; Du, Dongping; Yang, Hui; Bennett, Eric S

2013-02-01

Activity of human ether-a-go-go-related gene (hERG) 1 voltage-gated K(+) channels is responsible for portions of phase 2 and phase 3 repolarization of the human ventricular action potential. Here, we questioned whether and how physiologically and pathophysiologically relevant changes in surface N-glycosylation modified hERG channel function. Voltage-dependent hERG channel gating and activity were evaluated as expressed in a set of Chinese hamster ovary (CHO) cell lines under conditions of full glycosylation, no sialylation, no complex N-glycans, and following enzymatic deglycosylation of surface N-glycans. For each condition of reduced glycosylation, hERG channel steady-state activation and inactivation relationships were shifted linearly by significant depolarizing ∼9 and ∼18 mV, respectively. The hERG window current increased significantly by 50-150%, and the peak shifted by a depolarizing ∼10 mV. There was no significant change in maximum hERG current density. Deglycosylated channels were significantly more active (20-80%) than glycosylated controls during phases 2 and 3 of action potential clamp protocols. Simulations of hERG current and ventricular action potentials corroborated experimental data and predicted reduced sialylation leads to a 50-70-ms decrease in action potential duration. The data describe a novel mechanism by which hERG channel gating is modulated through physiologically and pathophysiologically relevant changes in N-glycosylation; reduced channel sialylation increases hERG channel activity during the action potential, thereby increasing the rate of action potential repolarization.

Strip-bark and Whole-bark Siberian Pine Radial Growth Trends and Implications for Climate Reconstruction

NASA Astrophysics Data System (ADS)

Leland, C.; Cook, E. R.; Andreu-Hayles, L.; Pederson, N.; Hessl, A. E.; Anchukaitis, K. J.; Byambasuren, O.; Nachin, B.; Davi, N. K.; D'Arrigo, R.; Griffin, K. L.; Bishop, D. A.; Rao, M. P.

2017-12-01

Ancient trees can exhibit strip-bark morphology in which a portion of the cambium, the active layer of growth in the stem, dies in response to environmental stress. Partial cambial dieback has been linked to several different ecological and physiological factors, but the causes of dieback vary depending on site conditions. Further, the implications of such morphology on radial growth trends and its importance for tree-ring-based climate reconstructions remain unclear. We investigate the timing and potential environmental drivers of cambial dieback in Pinus sibirica trees from a xeric site in central Mongolia, and compare growth patterns of strip and whole-bark (full cambium) trees over the past 500 years. Cambial dieback occurred primarily on the southern side of trees, and was most common during the cold and dry 19th century. These unfavorable climatic conditions, combined with high exposure to solar radiation, suggested by the orientation of strip bark, might be responsible for cambial dieback. Increasing ring-width trends are gradual in most strip-bark trees, and do not immediately follow dieback dates detected for individual stems. However, a mean ring-width chronology of all strip-bark trees abruptly increases and significantly exceeds ring widths of coeval whole-bark trees in the early 20th century. After standardizing strip and whole-bark series to remove allometric trends, the differences in recent growth trends persist. Before using strip-bark trees for climate reconstruction, we suggest comparing strip and whole-bark ring-width trends in order to determine appropriate methods for removing potential morphology-related growth trends. We extend this study by analyzing stable carbon isotopes in tree rings to evaluate whether there are physiological differences between strip-bark and whole-bark trees, and to determine if δ13C can be used as an additional parameter for climate reconstruction.

Post-Wildfire Potential for Carbon and Nitrogen Sequestration in the Southwestern United States in Restored Ephemeral and Intermittent Stream Channels

NASA Astrophysics Data System (ADS)

Callegary, J. B.; Norman, L.; Eastoe, C. J.; Sankey, J. B.; Youberg, A.

2016-12-01

The Kemp's ridley sea turtle (Lepidochelys kempii) is the most endangered sea turtle in the world, largely due to the limited geographic range of its nesting habitat. In the U.S., the majority of nesting occurs along Padre Island National Seashore (PAIS) in Texas. There has been limited research regarding the connection between beach geomorphology and Kemp's ridley nesting patterns, but studies concerning other sea turtle species suggest that certain beach geomorphology variables, such as beach slope and width, influence nest site selection. This research investigates terrestrial habitat variability of the Kemp's ridley sea turtle and quantifies the connection between beach geomorphology and Kemp's ridley nest site selection on PAIS and South Padre Island, Texas. Airborne topographic lidar data collected annually along the Texas coast from 2009 through 2012 was utilized to extract beach geomorphology characteristics, such as beach slope and width, dune height, and surface roughness, among others. The coordinates of observed Kemp's ridley nests from corresponding years were integrated with the aforementioned data in statistical models, which analyzed the influence of both general trends in geomorphology and individual morphologic variables on nest site selection. This research identified the terrestrial habitat variability of the Kemp's ridley and quantified the range of geomorphic characteristics of nesting beaches. Initial results indicate that dune width, beach width, and wind speed are significant variables in relation to nest presence, using an alpha of 0.1. Higher wind speeds and narrower beaches and foredunes favor nest presence. The average nest elevation is 1.13 m above mean sea level, which corresponds to the area directly below the potential vegetation line, and the majority of nesting occurs between the elevations of 0.68 m and 1.4 m above mean sea level. The results of this study include new information regarding Kemp's ridley beach habitat and its influence on nesting patterns that could be useful for the conservation and management of the species.

Sodium and calcium currents shape action potentials in immature mouse inner hair cells

PubMed Central

Marcotti, Walter; Johnson, Stuart L; Rüsch, Alfons; Kros, Corné J

2003-01-01

Before the onset of hearing at postnatal day 12, mouse inner hair cells (IHCs) produce spontaneous and evoked action potentials. These spikes are likely to induce neurotransmitter release onto auditory nerve fibres. Since immature IHCs express both α1D (Cav1.3) Ca2+ and Na+ currents that activate near the resting potential, we examined whether these two conductances are involved in shaping the action potentials. Both had extremely rapid activation kinetics, followed by fast and complete voltage-dependent inactivation for the Na+ current, and slower, partially Ca2+-dependent inactivation for the Ca2+ current. Only the Ca2+ current is necessary for spontaneous and induced action potentials, and 29 % of cells lacked a Na+ current. The Na+ current does, however, shorten the time to reach the action-potential threshold, whereas the Ca2+ current is mainly involved, together with the K+ currents, in determining the speed and size of the spikes. Both currents increased in size up to the end of the first postnatal week. After this, the Ca2+ current reduced to about 30 % of its maximum size and persisted in mature IHCs. The Na+ current was downregulated around the onset of hearing, when the spiking is also known to disappear. Although the Na+ current was observed as early as embryonic day 16.5, its role in action-potential generation was only evident from just after birth, when the resting membrane potential became sufficiently negative to remove a sizeable fraction of the inactivation (half inactivation was at −71 mV). The size of both currents was positively correlated with the developmental change in action-potential frequency. PMID:12937295

[Applied anatomy of facial recess and posterior tympanum related to cochlear implantation].

PubMed

Zou, Tuanming; Xie, Nanping; Guo, Menghe; Shu, Fan; Zhang, Hongzheng

2012-05-01

To investigate the related parameters of temporal bone structure in the surgery of cochlear implantation through facial recess approach so as to offer a theoretical reference for the avoidance of facial nerve injury and the accurate localization. In a surgical simulation experiment, twenty human temporal bones were studied. The correlation parameters were measured under surgical microscope. Distance between suprameatal spine and short process of incus was (12.44 +/- 0.51) mm. Width from crotch of chorda tympani nerve to stylomastoid foramen was (2.67 +/- 0.51) mm. Distance between short process of incus and crotch of chorda tympani nerve was (15.22 +/- 0.83) mm. The location of maximal width of the facial recess into short process of incus, crotch of chorda tympani nerve were (6.28 +/- 0.41) mm, (9.81 +/- 0.71) mm, respectively. The maximal width of the facial recess was (2.73 +/- 0.20) mm. The value at level of stapes and round window were (2.48 +/- 0.20 mm) and (2.24 +/- 0.18) mm, respectively. Distance between pyramidalis eminence and anterior round window was (2.22 +/- 0.21) mm. Width from stapes to underneath round window was (2.16 +/- 0.14) mm. These parameters provide a reference value to determine the position of cochlear inserting the electrode array into the scale tympani and opening facial recess firstly to avoid potential damage to facial nerve in surgery.

A Kernel-based Lagrangian method for imperfectly-mixed chemical reactions

NASA Astrophysics Data System (ADS)

Schmidt, Michael J.; Pankavich, Stephen; Benson, David A.

2017-05-01

Current Lagrangian (particle-tracking) algorithms used to simulate diffusion-reaction equations must employ a certain number of particles to properly emulate the system dynamics-particularly for imperfectly-mixed systems. The number of particles is tied to the statistics of the initial concentration fields of the system at hand. Systems with shorter-range correlation and/or smaller concentration variance require more particles, potentially limiting the computational feasibility of the method. For the well-known problem of bimolecular reaction, we show that using kernel-based, rather than Dirac delta, particles can significantly reduce the required number of particles. We derive the fixed width of a Gaussian kernel for a given reduced number of particles that analytically eliminates the error between kernel and Dirac solutions at any specified time. We also show how to solve for the fixed kernel size by minimizing the squared differences between solutions over any given time interval. Numerical results show that the width of the kernel should be kept below about 12% of the domain size, and that the analytic equations used to derive kernel width suffer significantly from the neglect of higher-order moments. The simulations with a kernel width given by least squares minimization perform better than those made to match at one specific time. A heuristic time-variable kernel size, based on the previous results, performs on par with the least squares fixed kernel size.

The dependence of the action potential of the frog's heart on the external and intracellular sodium concentration

PubMed Central

Niedergerke, R.; Orkand, R. K.

1966-01-01

1. The overshoot of the action potential of the frog's heart was reduced when external sodium chloride was replaced by sucrose. However, the potential decrement was only 17·3 mV for a 10-fold reduction of sodium as compared with 58 mV expected on the basis of the sodium hypothesis of excitation. 2. Replacement of up to 75% of the external sodium by choline did not reduce the overshoot, provided atropine was present in sufficient concentrations to suppress any parasympathomimetic action. 3. The maximum rate of rise of the action potential markedly declined in low sodium fluids whether sucrose or choline chloride was used to replace sodium chloride. 4. The maximum rate of rise was reduced to only a small extent when external sodium was replaced by lithium. 5. Increasing the intracellular sodium concentration in exchange for lost potassium caused overshoots to decline. The effects resembled those obtained in similar experiments with skeletal muscle fibres (Desmedt, 1953). 6. Action potentials occurring under certain conditions even in the presence of very low external sodium concentrations (≤ 5% normal) also declined in height when the intracellular sodium concentration was increased. 7. The behaviour of the action potential in low external sodium concentrations may be explained by an action of calcium on the excitable membrane. PMID:5921833

The upper bound of Pier Scour defined by selected laboratory and field data

USGS Publications Warehouse

Benedict, Stephen; Caldwell, Andral W.

2015-01-01

The U.S. Geological Survey, in cooperation with the South Carolina Department of Transportation, conducted several field investigations of pier scour in South Carolina (Benedict and Caldwell, 2006; Benedict and Caldwell, 2009) and used that data to develop envelope curves defining the upper bound of pier scour. To expand upon this previous work, an additional cooperative investigation was initiated to combine the South Carolina data with pier-scour data from other sources and evaluate the upper bound of pier scour with this larger data set. To facilitate this analysis, a literature review was made to identify potential sources of published pier-scour data, and selected data were compiled into a digital spreadsheet consisting of approximately 570 laboratory and 1,880 field measurements. These data encompass a wide range of laboratory and field conditions and represent field data from 24 states within the United States and six other countries. This extensive database was used to define the upper bound of pier-scour depth with respect to pier width encompassing the laboratory and field data. Pier width is a primary variable that influences pier-scour depth (Laursen and Toch, 1956; Melville and Coleman, 2000; Mueller and Wagner, 2005, Ettema et al. 2011, Arneson et al. 2012) and therefore, was used as the primary explanatory variable in developing the upper-bound envelope curve. The envelope curve provides a simple but useful tool for assessing the potential maximum pier-scour depth for pier widths of about 30 feet or less.

On searching for observational manifestations of Alfvén waves in solar faculae

NASA Astrophysics Data System (ADS)

Kobanov, N. I.; Chupin, S. A.; Chelpanov, A. A.

2017-12-01

In an effort to detect torsional oscillations, we have studied the periodic half-width variations for several spectral lines in solar faculae. The duration of the series being analyzed was from 40 to 150 min. We have determined the dominant frequencies and amplitudes of the half-width oscillations and considered their phase relations to the intensity and line-of-sight velocity oscillations. Five-minute profile halfwidth oscillations with a peak-to-peak amplitude of ˜10 m ˚A are recorded with confidence in the upperphotospheric Si I 10 827 ˚A line in faculae. The chromospheric He I 10 830 A˚ and Hα line profiles shows ˜40-60 m ˚A variations in two frequency bands, 2.5-4 and 1-1.9 mHz. No center-to-limb dependence that, according to the theory, must accompany the torsional oscillations has been revealed in the behavior of the oscillation amplitudes. According to present views, these variations cannot be caused by periodic temperature and magnetic field changes. Our observations do not allow us to explain these variations by the sausage mode action either, which should manifest itself at the double frequency.

Rapid Ca2+ flux through the transverse tubular membrane, activated by individual action potentials in mammalian skeletal muscle

PubMed Central

Launikonis, Bradley S; Stephenson, D George; Friedrich, Oliver

2009-01-01

Periods of low frequency stimulation are known to increase the net Ca2+ uptake in skeletal muscle but the mechanism responsible for this Ca2+ entry is not known. In this study a novel high-resolution fluorescence microscopy approach allowed the detection of an action potential-induced Ca2+ flux across the tubular (t-) system of rat extensor digitorum longus muscle fibres that appears to be responsible for the net uptake of Ca2+ in working muscle. Action potentials were triggered in the t-system of mechanically skinned fibres from rat by brief field stimulation and t-system [Ca2+] ([Ca2+]t-sys) and cytoplasmic [Ca2+] ([Ca2+]cyto) were simultaneously resolved on a confocal microscope. When initial [Ca2+]t-sys was ≥ 0.2 mm a Ca2+ flux from t-system to the cytoplasm was observed following a single action potential. The action potential-induced Ca2+ flux and associated t-system Ca2+ permeability decayed exponentially and displayed inactivation characteristics such that further Ca2+ entry across the t-system could not be observed after 2–3 action potentials at 10 Hz stimulation rate. When [Ca2+]t-sys was closer to 0.1 mm, a transient rise in [Ca2+]t-sys was observed almost concurrently with the increase in [Ca2+]cyto following the action potential. The change in direction of Ca2+ flux was consistent with changes in the direction of the driving force for Ca2+. This is the first demonstration of a rapid t-system Ca2+ flux associated with a single action potential in mammalian skeletal muscle. The properties of this channel are inconsistent with a flux through the L-type Ca2+ channel suggesting that an as yet unidentified t-system protein is conducting this current. This action potential-activated Ca2+ flux provides an explanation for the previously described Ca2+ entry and accumulation observed with prolonged, intermittent muscle activity. PMID:19332499

Standardization of a Volumetric Displacement Measurement for Two-Body Abrasion Scratch Test Data Analysis

NASA Technical Reports Server (NTRS)

Street, K. W. Jr.; Kobrick, R. L.; Klaus, D. M.

2011-01-01

A limitation has been identified in the existing test standards used for making controlled, two-body abrasion scratch measurements based solely on the width of the resultant score on the surface of the material. A new, more robust method is proposed for analyzing a surface scratch that takes into account the full three-dimensional profile of the displaced material. To accomplish this, a set of four volume- displacement metrics was systematically defined by normalizing the overall surface profile to denote statistically the area of relevance, termed the Zone of Interaction. From this baseline, depth of the trough and height of the plowed material are factored into the overall deformation assessment. Proof-of-concept data were collected and analyzed to demonstrate the performance of this proposed methodology. This technique takes advantage of advanced imaging capabilities that allow resolution of the scratched surface to be quantified in greater detail than was previously achievable. When reviewing existing data analysis techniques for conducting two-body abrasive scratch tests, it was found that the ASTM International Standard G 171 specified a generic metric based only on visually determined scratch width as a way to compare abraded materials. A limitation to this method was identified in that the scratch width is based on optical surface measurements, manually defined by approximating the boundaries, but does not consider the three-dimensional volume of material that was displaced. With large, potentially irregular deformations occurring on softer materials, it becomes unclear where to systematically determine the scratch width. Specifically, surface scratches on different samples may look the same from a top view, resulting in an identical scratch width measurement, but may vary in actual penetration depth and/or plowing deformation. Therefore, two different scratch profiles would be measured as having identical abrasion properties, although they differ significantly.

Evidence to suggest that women's sexual behavior is influenced by hip width rather than waist-to-hip ratio.

PubMed

Simpson, Victoria J; Brewer, Gayle; Hendrie, Colin A

2014-10-01

Waist-to-hip ratio (WHR) is an important ornament display that signals women's health and fertility. Its significance derives from human development as a bipedal species. This required fundamental changes to hip morphology/musculature to accommodate the demands of both reproduction and locomotion. The result has been an obstetric dilemma whereby women's hips are only just wide enough to allow the passage of an infant. Childbirth therefore poses a significant hip width related threat to maternal mortality/risk of gynecological injury. It was predicted that this would have a significant influence on women's sexual behavior. To investigate this, hip width and WHR were measured in 148 women (M age = 20.93 + 0.17 years) and sexual histories were recorded via questionnaire. Data revealed that hip width per se was correlated with total number of sexual partners, total number of one night stands, percentage of sexual partners that were one night stands, number of sexual partners within the context of a relationship per year sexually active, and number of one night stands per year sexually active. By contrast, WHR was not correlated with any of these measures. Further analysis indicated that women who predominantly engaged in one night stand behavior had wider hips than those who did not. WHR was again without effect in this context. Women's hip morphology has a direct impact on their risk of potentially fatal childbirth related injury. It is concluded that when they have control over this, women's sexual behavior reflects this risk and is therefore at least in part influenced by hip width.

Subject-Specific Finite Element Analysis of the Carpal Tunnel Cross-Sectional to Examine Tunnel Area Changes in Response to Carpal Arch Loading

PubMed Central

Walia, Piyush; Erdemir, Ahmet; Li, Zong-Ming

2017-01-01

Background Manipulating the carpal arch width (i.e. distance between hamate and trapezium bones) has been suggested as a means to increase carpal tunnel cross-sectional area and alleviate median nerve compression. The purpose of this study was to develop a finite element model of the carpal tunnel and to determine an optimal force direction to maximize area. Methods A planar geometric model of carpal bones at hamate level was reconstructed from MRI with inter-carpal joint spaces filled with a linear elastic surrogate tissue. Experimental data with discrete carpal tunnel pressures (50, 100, 150, and 200 mmHg) and corresponding carpal bone movements were used to obtain material property of surrogate tissue by inverse finite element analysis. The resulting model was used to simulate changes of carpal arch widths and areas with directional variations of a unit force applied at the hook of hamate. Findings Inverse finite element model predicted the experimental area data within 1.5% error. Simulation of force applications showed that carpal arch width and area were dependent on the direction of force application, and minimal arch width and maximal area occurred at 138° (i.e. volar-radial direction) with respect to the hamate-to-trapezium axis. At this force direction, the width changed to 24.4 mm from its initial 25.1 mm (3% decrease), and the area changed to 301.6 mm2 from 290.3 mm2 (4% increase). Interpretation The findings of the current study guide biomechanical manipulation to gain tunnel area increase, potentially helping reduce carpal tunnel pressure and relieve symptoms of compression median neuropathy. PMID:28073093

Study on seismic performance of BFRP geogrid reinforced Tibetan rubble wall

NASA Astrophysics Data System (ADS)

Yang, Dan; Jia, Bin; Huang, Hui; Deng, Chuangli

2018-03-01

For the study of BFRP geogrid influence on Tibetan rubble wall seismic performance, in this paper, on the premise of not change the way of traditional masonry, laying and not join geogrid respectively on the the rubble wall, and carries on the cyclic loading experiment on them. The damage characteristics, crack width and seismic performance of the rubble walls with BFRP geogrid are studied. The experimental results show that the deformation of the rubble wall is mainly the shear deformation under the action of horizontal force, and the bearing capacity and energy dissipation capacity of the wall can be improved significantly after joining the geogrid.

Anomalous broadening and shift of emission lines in filaments

NASA Astrophysics Data System (ADS)

Ilyin, A. A.; Golik, S. S.; Shmirko, K. A.; Mayor, A. Yu.; Proschenko, D. Yu.

2017-11-01

The temporal evolution of width and shift of N I 746.8 and O I 777.4 nm lines is investigated in filament plasma produced by tightly focused femtosecond laser pulse (0.9 mJ, 48 fs). Nitrogen line shift is determined by joint action of electron impact shift and far-off resonance AC Stark effect. Intensive (I 1010 W/cm2 ) electric field of ASE and postpulses result in possible LS coupling break for O I 3p 5P level and generation of Rabi sidebands. The blue-shifted main femtosecond pulse and Rabi sideband cause the stimulated emission of N21+ system.

Deformation of Fluid Column by Action of Axial Vibration and Some Aspects of High-Rate Thermocapillary Convection

NASA Technical Reports Server (NTRS)

Feonychev, Alexander I.; Kalachinskaya, Irina S.; Pokhilko, Victor I.

1996-01-01

The deformation of the fluid column by an action of a low-frequency vibration is considered. It is shown that behavior of the free fluid surface depends on the frequency of applied vibration and its amplitude. In the area of very low frequencies when fluid has time to comment on travel of bounding solid walls limiting column, the harmonical oscillations of free surface with given frequency are observed. With increase of vibration frequency the steady-state relief on free fluid surface is formed. If the amplitude of vibration is very small and the frequency corresponding to the first peak in the vibration spectrum on the Mir orbital station, the deformation of free surface tends to zero. Fluid flow induced thermocapillary effect on deformed free surface is more unstable as in the case of smooth cylindrical surface. It was shown that width of heating zone affects very essentially the flow pattern and transition to oscillatory regime of thermocapillary convection.

Empirical analysis of online human dynamics

NASA Astrophysics Data System (ADS)

Zhao, Zhi-Dan; Zhou, Tao

2012-06-01

Patterns of human activities have attracted increasing academic interests, since the quantitative understanding of human behavior is helpful to uncover the origins of many socioeconomic phenomena. This paper focuses on behaviors of Internet users. Six large-scale systems are studied in our experiments, including the movie-watching in Netflix and MovieLens, the transaction in Ebay, the bookmark-collecting in Delicious, and the posting in FreindFeed and Twitter. Empirical analysis reveals some common statistical features of online human behavior: (1) The total number of user's actions, the user's activity, and the interevent time all follow heavy-tailed distributions. (2) There exists a strongly positive correlation between user's activity and the total number of user's actions, and a significantly negative correlation between the user's activity and the width of the interevent time distribution. We further study the rescaling method and show that this method could to some extent eliminate the different statistics among users caused by the different activities, yet the effectiveness depends on the data sets.

The action uncertainty principle for continuous measurements

NASA Astrophysics Data System (ADS)

Mensky, Michael B.

1996-02-01

The action uncertainty principle (AUP) for the specification of the most probable readouts of continuous quantum measurements is proved, formulated in different forms and analyzed (for nonlinear as well as linear systems). Continuous monitoring of an observable A(p,q,t) with resolution Δa( t) is considered. The influence of the measurement process on the evolution of the measured system (quantum measurement noise) is presented by an additional term δ F(t)A(p,q,t) in the Hamiltonian where the function δ F (generalized fictitious force) is restricted by the AUP ∫|δ F(t)| Δa( t) d t ≲ and arbitrary otherwise. Quantum-nondemolition (QND) measurements are analyzed with the help of the AUP. A simple uncertainty relation for continuous quantum measurements is derived. It states that the area of a certain band in the phase space should be of the order of. The width of the band depends on the measurement resolution while its length is determined by the deviation of the system, due to the measurement, from classical behavior.

Heavy ion action on yeast cells: Inhibition of ribosomal-RNA synthesis, loss of colony forming ability and induction of mutants

NASA Astrophysics Data System (ADS)

Kiefer, J.; Rase, S.; Schöpfer, F.; Schneider, E.; Weber, K.; Kraft, G.

The action of heavy ions (Ar to U) accelerated to specific energies up to about 10 MeV/u (u=atomic mass unit) on different functions of yeast cells was studied. Ribosomal-RNA synthesis is inhibited according to a single-hit mechanism. Inactivation cross-sections were linearly related to the ratio of the squares of the effective charge Z* and the velocity of the ions. It is concluded from the analysis that the range of the most energetic δ-electrons is larger than previously assumed. There is no such dependence for survival and induction of mutants. In both cases cross-sections increase with the ion's specific-energy indicating an important contribution of long-range δ-electrons. The analysis shows that diploid yeast is not killed by a single-hit mechanism even by very heavy ions if the track width is too small. The relative importance of the penumbral region is even more pronounced with the more sensitive strains.

Optical fiber nanoprobe preparation for near-field optical microscopy by chemical etching under surface tension and capillary action.

PubMed

Mondal, Samir K; Mitra, Anupam; Singh, Nahar; Sarkar, S N; Kapur, Pawan

2009-10-26

We propose a technique of chemical etching for fabrication of near perfect optical fiber nanoprobe (NNP). It uses photosensitive single mode optical fiber to etch in hydro fluoric (HF) acid solution. The difference in etching rate for cladding and photosensitive core in HF acid solution creates capillary ring along core-cladding boundary under a given condition. The capillary ring is filled with acid solution due to surface tension and capillary action. Finally it creates near perfect symmetric tip at the apex of the fiber as the height of the acid level in capillary ring decreases while width of the ring increases with continuous etching. Typical tip features are short taper length (approximately 4 microm), large cone angle (approximately 38 degrees ), and small probe tip dimension (<100 nm). A finite difference time domain (FDTD) analysis is also presented to compare near field optics of the NNP with conventional nanoprobe (CNP). The probe may be ideal for near field optical imaging and sensor applications.

The fabrication of vertically aligned and periodically distributed carbon nanotube bundles and periodically porous carbon nanotube films through a combination of laser interference ablation and metal-catalyzed chemical vapor deposition.

PubMed

Yuan, Dajun; Lin, Wei; Guo, Rui; Wong, C P; Das, Suman

2012-06-01

Scalable fabrication of carbon nanotube (CNT) bundles is essential to future advances in several applications. Here, we report on the development of a simple, two-step method for fabricating vertically aligned and periodically distributed CNT bundles and periodically porous CNT films at the sub-micron scale. The method involves laser interference ablation (LIA) of an iron film followed by CNT growth via iron-catalyzed chemical vapor deposition. CNT bundles with square widths ranging from 0.5 to 1.5 µm in width, and 50-200 µm in length, are grown atop the patterned catalyst over areas spanning 8 cm(2). The CNT bundles exhibit a high degree of control over square width, orientation, uniformity, and periodicity. This simple scalable method of producing well-placed and oriented CNT bundles demonstrates a high application potential for wafer-scale integration of CNT structures into various device applications, including IC interconnects, field emitters, sensors, batteries, and optoelectronics, etc.

Length scales and pinning of interfaces

PubMed Central

Tan, Likun

2016-01-01

The pinning of interfaces and free discontinuities by defects and heterogeneities plays an important role in a variety of phenomena, including grain growth, martensitic phase transitions, ferroelectricity, dislocations and fracture. We explore the role of length scale on the pinning of interfaces and show that the width of the interface relative to the length scale of the heterogeneity can have a profound effect on the pinning behaviour, and ultimately on hysteresis. When the heterogeneity is large, the pinning is strong and can lead to stick–slip behaviour as predicted by various models in the literature. However, when the heterogeneity is small, we find that the interface may not be pinned in a significant manner. This shows that a potential route to making materials with low hysteresis is to introduce heterogeneities at a length scale that is small compared with the width of the phase boundary. Finally, the intermediate setting where the length scale of the heterogeneity is comparable to that of the interface width is characterized by complex interactions, thereby giving rise to a non-monotone relationship between the relative heterogeneity size and the critical depinning stress. PMID:27002068

29 CFR 1990.147 - Final action.

Code of Federal Regulations, 2014 CFR

2014-07-01

...) IDENTIFICATION, CLASSIFICATION, AND REGULATION OF POTENTIAL OCCUPATIONAL CARCINOGENS Regulation of Potential Occupational Carcinogens § 1990.147 Final action. (a) Within one hundred twenty (120) days from the last day of... is classified as a Category I Potential Carcinogen or as a Category II Potential Carcinogen. If the...

29 CFR 1990.147 - Final action.

Code of Federal Regulations, 2012 CFR

2012-07-01

...) IDENTIFICATION, CLASSIFICATION, AND REGULATION OF POTENTIAL OCCUPATIONAL CARCINOGENS Regulation of Potential Occupational Carcinogens § 1990.147 Final action. (a) Within one hundred twenty (120) days from the last day of... is classified as a Category I Potential Carcinogen or as a Category II Potential Carcinogen. If the...

29 CFR 1990.147 - Final action.

Code of Federal Regulations, 2013 CFR

2013-07-01

...) IDENTIFICATION, CLASSIFICATION, AND REGULATION OF POTENTIAL OCCUPATIONAL CARCINOGENS Regulation of Potential Occupational Carcinogens § 1990.147 Final action. (a) Within one hundred twenty (120) days from the last day of... is classified as a Category I Potential Carcinogen or as a Category II Potential Carcinogen. If the...

29 CFR 1990.147 - Final action.

Code of Federal Regulations, 2011 CFR

2011-07-01

...) IDENTIFICATION, CLASSIFICATION, AND REGULATION OF POTENTIAL OCCUPATIONAL CARCINOGENS Regulation of Potential Occupational Carcinogens § 1990.147 Final action. (a) Within one hundred twenty (120) days from the last day of... is classified as a Category I Potential Carcinogen or as a Category II Potential Carcinogen. If the...

Effect of Exogenous Extracellular Nicotinamide Adenine Dinucleotide (NAD⁺) on Bioelectric Activity of the Pacemaker and Conduction System of the Heart.

PubMed

Pustovit, K B; Kuz'min, V S; Sukhova, G S

2015-06-01

In rat sinoatrial node, NAD(+) (10 μM) reduced the rate of spontaneous action potentials, duration of action potentials, and the velocity of slow diastolic depolarization, but the rate of action potential front propagation increases. In passed rabbit Purkinje fibers, NAD(+) (10 μM) reduced the duration of action potentials. Under conditions of spontaneous activity of Purkinje fibers, NAD(+) reduced the fi ring rate and the rate of slow diastolic depolarization. The effects of extracellular NAD(+) on bioelectric activity of the pacemaker (sinoatrial node) and conduction system of the heart (Purkinje fibers) are probably related to activation of P1 and P2 purinoceptors.

Coherent wave packet dynamics in a double-well potential in cavity

NASA Astrophysics Data System (ADS)

Zheng, Li; Li, Gang; Ding, Ming-Song; Wang, Yong-Liang; Zhang, Yun-Cui

2018-02-01

We investigate the coherent wave packet dynamics of a two-level atom trapped in a symmetric double-well potential in a near-resonance cavity. Prepared on one side of the double-well potential, the atom wave packet oscillates between the left and right wells, while recoil induced by the emitted photon from the atom entangles the atomic internal and external degrees of freedom. The collapse and revival of the tunneling occurs. Adjusting the width of the wave packets, one can modify the tunneling frequency and suppress the tunneling.

Observation of electric potential in organic thin-film transistor by bias-applied hard X-ray photoemission spectroscopy

NASA Astrophysics Data System (ADS)

Watanabe, Takeshi; Tada, Keisuke; Yasuno, Satoshi; Oji, Hiroshi; Yoshimoto, Noriyuki; Hirosawa, Ichiro

2016-03-01

The effect of gate voltage on electric potential in a pentacene (PEN) layer was studied by hard X-ray photoelectron spectroscopy under a bias voltage. It was observed that applying a negative gate voltage substantially increases the width of a C 1s peak. This suggested that injected and accumulated carriers in an organic thin film transistor channel modified the potential depth profile in PEN. It was also observed that the C 1s kinetic energy tends to increase monotonically with threshold voltage.

Conductance and refraction across a Barrier in Phosphorene

NASA Astrophysics Data System (ADS)

Dahal, Dipendra; Gumbs, Godfrey

The transmission coefficient and ballistic conductance for monolayer black phosphorene is calculated when a potential step or square barrier is present. The Landauer-B¨uttiker formalism is employed in our calculations of the conductance. We obtain the refractive index for the step potential barrier when an incident beam of electron travel along different paths so as to observe what role the anisotropy of the energy bands plays. Numerical results are presented for various potential heights and barrier widths and these are compared with those for gapless and gapped graphene.

Interacting steps with finite-range interactions: Analytical approximation and numerical results

NASA Astrophysics Data System (ADS)

Jaramillo, Diego Felipe; Téllez, Gabriel; González, Diego Luis; Einstein, T. L.

2013-05-01

We calculate an analytical expression for the terrace-width distribution P(s) for an interacting step system with nearest- and next-nearest-neighbor interactions. Our model is derived by mapping the step system onto a statistically equivalent one-dimensional system of classical particles. The validity of the model is tested with several numerical simulations and experimental results. We explore the effect of the range of interactions q on the functional form of the terrace-width distribution and pair correlation functions. For physically plausible interactions, we find modest changes when next-nearest neighbor interactions are included and generally negligible changes when more distant interactions are allowed. We discuss methods for extracting from simulated experimental data the characteristic scale-setting terms in assumed potential forms.

Applying the dual-isotope conceptual model to interpret physiological trends under uncontrolled conditions

EPA Science Inventory

The inter-relationships among δ13C and δ18O in tree ring cellulose and ring width have the potential to illuminate long-term physiological and environmental information in forest stands that have not been monitored. We examine how within-stand competition and environmental gradie...

The economics of potential reduction of the rural road system in Kansas : technical summary.

DOT National Transportation Integrated Search

2011-11-01

The increasing size of farms in Kansas has led to increasing farm vehicle size as well. Tractor and combine weight and width has increased and the majority of farmers deliver their grain in semi-trucks. Tandem axle trucks are used to deliver farm sup...

Modeling transient gain dynamics in a cladding-pumped Yb-doped fiber ampliefier pulsed at low repetition rates

NASA Technical Reports Server (NTRS)

Valley, G. C.; Wright, M.

2001-01-01

Simulations of 1-50 kHz repetition rate, pulsed Yb-fiber amplifiers show peak powers to 10 kW with half-widths < 30 ns, consistent with commercial amplifier performance. This device is a potential source for deep space-communication.

Rapid time course of action potentials in spines and remote dendrites of mouse visual cortex neurons.

PubMed

Holthoff, Knut; Zecevic, Dejan; Konnerth, Arthur

2010-04-01

Axonally initiated action potentials back-propagate into spiny dendrites of central mammalian neurons and thereby regulate plasticity at excitatory synapses on individual spines as well as linear and supralinear integration of synaptic inputs along dendritic branches. Thus, the electrical behaviour of individual dendritic spines and terminal dendritic branches is critical for the integrative function of nerve cells. The actual dynamics of action potentials in spines and terminal branches, however, are not entirely clear, mostly because electrode recording from such small structures is not feasible. Additionally, the available membrane potential imaging techniques are limited in their sensitivity and require substantial signal averaging for the detection of electrical events at the spatial scale of individual spines. We made a critical improvement in the voltage-sensitive dye imaging technique to achieve multisite recordings of backpropagating action potentials from individual dendritic spines at a high frame rate. With this approach, we obtained direct evidence that in layer 5 pyramidal neurons from the visual cortex of juvenile mice, the rapid time course of somatic action potentials is preserved throughout all cellular compartments, including dendritic spines and terminal branches of basal and apical dendrites. The rapid time course of the action potential in spines may be a critical determinant for the precise regulation of spike timing-dependent synaptic plasticity within a narrow time window.

22 CFR 161.8 - General description of the Department's NEPA process.

Code of Federal Regulations, 2010 CFR

2010-04-01

... § 161.8 General description of the Department's NEPA process. In reviewing proposed actions for potential environmental effects in the United States responsible action officers will follow the procedural... review the action to determine if it may cause potential significant environmental effects on the...

Prolonged action potential duration in cardiac ablation of PDK1 mice.

PubMed

Han, Zhonglin; Jiang, Yu; Yang, Zhongzhou; Cao, Kejiang; Wang, Dao W

2015-01-01

The involvement of the AGC protein kinase family in regulating arrhythmia has drawn considerable attention, but the underlying mechanisms are still not clear. The aim of this study is to explore the role of 3-phosphoinositide-dependent protein kinase-1 (PDK1), one of upstream protein kinases of the AGC protein kinase family, in the pathogenesis of dysregulated electrophysiological basis. PDK1(F/F) αMHC-Cre mice and PDK1(F/F) mice were divided into experiment group and control group. Using patch clamping technology, we explored action potential duration in both groups, and investigated the functions of transient outward potassium channel and L-type Ca(2+) channel to explain the abnormal action potential duration. Significant prolongation action potential duration was found in mice with PDK1 deletion. Further, the peak current of transient outward potassium current and L-type Ca(2+) current were decreased by 84% and 49% respectively. In addition, dysregulation of channel kinetics lead to action potential duration prolongation further. In conclusion, we have demonstrated that PDK1 participates in action potential prolongation in cardiac ablation of PDK1 mice. This effect is likely to be mediated largely through downregulation of transient outward potassium current. These findings indicate the modulation of the PDK1 pathway could provide a new mechanism for abnormal electrophysiological basis.

Back-Propagation of Physiological Action Potential Output in Dendrites of Slender-Tufted L5A Pyramidal Neurons

PubMed Central

Grewe, Benjamin F.; Bonnan, Audrey; Frick, Andreas

2009-01-01

Pyramidal neurons of layer 5A are a major neocortical output type and clearly distinguished from layer 5B pyramidal neurons with respect to morphology, in vivo firing patterns, and connectivity; yet knowledge of their dendritic properties is scant. We used a combination of whole-cell recordings and Ca2+ imaging techniques in vitro to explore the specific dendritic signaling role of physiological action potential patterns recorded in vivo in layer 5A pyramidal neurons of the whisker-related ‘barrel cortex’. Our data provide evidence that the temporal structure of physiological action potential patterns is crucial for an effective invasion of the main apical dendrites up to the major branch point. Both the critical frequency enabling action potential trains to invade efficiently and the dendritic calcium profile changed during postnatal development. In contrast to the main apical dendrite, the more passive properties of the short basal and apical tuft dendrites prevented an efficient back-propagation. Various Ca2+ channel types contributed to the enhanced calcium signals during high-frequency firing activity, whereas A-type K+ and BKCa channels strongly suppressed it. Our data support models in which the interaction of synaptic input with action potential output is a function of the timing, rate and pattern of action potentials, and dendritic location. PMID:20508744

A phantom axon setup for validating models of action potential recordings.

PubMed

Rossel, Olivier; Soulier, Fabien; Bernard, Serge; Guiraud, David; Cathébras, Guy

2016-08-01

Electrode designs and strategies for electroneurogram recordings are often tested first by computer simulations and then by animal models, but they are rarely implanted for long-term evaluation in humans. The models show that the amplitude of the potential at the surface of an axon is higher in front of the nodes of Ranvier than at the internodes; however, this has not been investigated through in vivo measurements. An original experimental method is presented to emulate a single fiber action potential in an infinite conductive volume, allowing the potential of an axon to be recorded at both the nodes of Ranvier and the internodes, for a wide range of electrode-to-fiber radial distances. The paper particularly investigates the differences in the action potential amplitude along the longitudinal axis of an axon. At a short radial distance, the action potential amplitude measured in front of a node of Ranvier is two times larger than in the middle of two nodes. Moreover, farther from the phantom axon, the measured action potential amplitude is almost constant along the longitudinal axis. The results of this new method confirm the computer simulations, with a correlation of 97.6 %.

Action potentials in retinal ganglion cells are initiated at the site of maximal curvature of the extracellular potential.

PubMed

Eickenscheidt, Max; Zeck, Günther

2014-06-01

The initiation of an action potential by extracellular stimulation occurs after local depolarization of the neuronal membrane above threshold. Although the technique shows remarkable clinical success, the site of action and the relevant stimulation parameters are not completely understood. Here we identify the site of action potential initiation in rabbit retinal ganglion cells (RGCs) interfaced to an array of extracellular capacitive stimulation electrodes. We determine which feature of the extracellular potential governs action potential initiation by simultaneous stimulation and recording RGCs interfaced in epiretinal configuration. Stimulation electrodes were combined to areas of different size and were presented at different positions with respect to the RGC. Based on stimulation by electrodes beneath the RGC soma and simultaneous sub-millisecond latency measurement we infer axonal initiation at the site of maximal curvature of the extracellular potential. Stimulation by electrodes at different positions along the axon reveals a nearly constant threshold current density except for a narrow region close to the cell soma. These findings are explained by the concept of the activating function modified to consider a region of lower excitability close to the cell soma. We present a framework how to estimate the site of action potential initiation and the stimulus required to cross threshold in neurons tightly interfaced to capacitive stimulation electrodes. Our results underscore the necessity of rigorous electrical characterization of the stimulation electrodes and of the interfaced neural tissue.

The cutting edge - Micro-CT for quantitative toolmark analysis of sharp force trauma to bone.

PubMed

Norman, D G; Watson, D G; Burnett, B; Fenne, P M; Williams, M A

2018-02-01

Toolmark analysis involves examining marks created on an object to identify the likely tool responsible for creating those marks (e.g., a knife). Although a potentially powerful forensic tool, knife mark analysis is still in its infancy and the validation of imaging techniques as well as quantitative approaches is ongoing. This study builds on previous work by simulating real-world stabbings experimentally and statistically exploring quantitative toolmark properties, such as cut mark angle captured by micro-CT imaging, to predict the knife responsible. In Experiment 1 a mechanical stab rig and two knives were used to create 14 knife cut marks on dry pig ribs. The toolmarks were laser and micro-CT scanned to allow for quantitative measurements of numerous toolmark properties. The findings from Experiment 1 demonstrated that both knives produced statistically different cut mark widths, wall angle and shapes. Experiment 2 examined knife marks created on fleshed pig torsos with conditions designed to better simulate real-world stabbings. Eight knives were used to generate 64 incision cut marks that were also micro-CT scanned. Statistical exploration of these cut marks suggested that knife type, serrated or plain, can be predicted from cut mark width and wall angle. Preliminary results suggest that knives type can be predicted from cut mark width, and that knife edge thickness correlates with cut mark width. An additional 16 cut marks walls were imaged for striation marks using scanning electron microscopy with results suggesting that this approach might not be useful for knife mark analysis. Results also indicated that observer judgements of cut mark shape were more consistent when rated from micro-CT images than light microscopy images. The potential to combine micro-CT data, medical grade CT data and photographs to develop highly realistic virtual models for visualisation and 3D printing is also demonstrated. This is the first study to statistically explore simulated real-world knife marks imaged by micro-CT to demonstrate the potential of quantitative approaches in knife mark analysis. Findings and methods presented in this study are relevant to both forensic toolmark researchers as well as practitioners. Limitations of the experimental methodologies and imaging techniques are discussed, and further work is recommended. Copyright © 2017 Elsevier B.V. All rights reserved.

Autonomous initiation and propagation of action potentials in neurons of the subthalamic nucleus.

PubMed

Atherton, Jeremy F; Wokosin, David L; Ramanathan, Sankari; Bevan, Mark D

2008-12-01

The activity of the subthalamic nucleus (STN) is intimately related to movement and is generated, in part, by voltage-dependent Na(+) (Na(v)) channels that drive autonomous firing. In order to determine the principles underlying the initiation and propagation of action potentials in STN neurons, 2-photon laser scanning microscopy was used to guide tight-seal whole-cell somatic and loose-seal cell-attached axonal/dendritic patch-clamp recordings and compartment-selective ion channel manipulation in rat brain slices. Action potentials were first detected in a region that corresponded most closely to the unmyelinated axon initial segment, as defined by Golgi and ankyrin G labelling. Following initiation, action potentials propagated reliably into axonal and somatodendritic compartments with conduction velocities of approximately 5 m s(-1) and approximately 0.7 m s(-1), respectively. Action potentials generated by neurons with axons truncated within or beyond the axon initial segment were not significantly different. However, axon initial segment and somatic but not dendritic or more distal axonal application of low [Na(+)] ACSF or the selective Na(v) channel blocker tetrodotoxin consistently depolarized action potential threshold. Finally, somatodendritic but not axonal application of GABA evoked large, rapid inhibitory currents in concordance with electron microscopic analyses, which revealed that the somatodendritic compartment was the principal target of putative inhibitory inputs. Together the data are consistent with the conclusions that in STN neurons the axon initial segment and soma express an excess of Na(v) channels for the generation of autonomous activity, while synaptic activation of somatodendritic GABA(A) receptors regulates the axonal initiation of action potentials.

Autonomous initiation and propagation of action potentials in neurons of the subthalamic nucleus

PubMed Central

Atherton, Jeremy F; Wokosin, David L; Ramanathan, Sankari; Bevan, Mark D

2008-01-01

The activity of the subthalamic nucleus (STN) is intimately related to movement and is generated, in part, by voltage-dependent Na+ (Nav) channels that drive autonomous firing. In order to determine the principles underlying the initiation and propagation of action potentials in STN neurons, 2-photon laser scanning microscopy was used to guide tight-seal whole-cell somatic and loose-seal cell-attached axonal/dendritic patch-clamp recordings and compartment-selective ion channel manipulation in rat brain slices. Action potentials were first detected in a region that corresponded most closely to the unmyelinated axon initial segment, as defined by Golgi and ankyrin G labelling. Following initiation, action potentials propagated reliably into axonal and somatodendritic compartments with conduction velocities of ∼5 m s−1 and ∼0.7 m s−1, respectively. Action potentials generated by neurons with axons truncated within or beyond the axon initial segment were not significantly different. However, axon initial segment and somatic but not dendritic or more distal axonal application of low [Na+] ACSF or the selective Nav channel blocker tetrodotoxin consistently depolarized action potential threshold. Finally, somatodendritic but not axonal application of GABA evoked large, rapid inhibitory currents in concordance with electron microscopic analyses, which revealed that the somatodendritic compartment was the principal target of putative inhibitory inputs. Together the data are consistent with the conclusions that in STN neurons the axon initial segment and soma express an excess of Nav channels for the generation of autonomous activity, while synaptic activation of somatodendritic GABAA receptors regulates the axonal initiation of action potentials. PMID:18832425

Influence of asymmetric attenuation of single and paired dendritic inputs on summation of synaptic potentials and initiation of action potentials.

PubMed

Fortier, Pierre A; Bray, Chelsea

2013-04-16

Previous studies revealed mechanisms of dendritic inputs leading to action potential initiation at the axon initial segment and backpropagation into the dendritic tree. This interest has recently expanded toward the communication between different parts of the dendritic tree which could preprocess information before reaching the soma. This study tested for effects of asymmetric voltage attenuation between different sites in the dendritic tree on summation of synaptic inputs and action potential initiation using the NEURON simulation environment. Passive responses due to the electrical equivalent circuit of the three-dimensional neuron architecture with leak channels were examined first, followed by the responses after adding voltage-gated channels and finally synaptic noise. Asymmetric attenuation of voltage, which is a function of asymmetric input resistance, was seen between all pairs of dendritic sites but the transfer voltages (voltage recorded at the opposite site from stimulation among a pair of dendritic sites) were equal and also summed linearly with local voltage responses during simultaneous stimulation of both sites. In neurons with voltage-gated channels, we reproduced the observations where a brief stimulus to the proximal ascending dendritic branch of a pyramidal cell triggers a local action potential but a long stimulus triggers a somal action potential. Combined stimulation of a pair of sites in this proximal dendrite did not alter this pattern. The attraction of the action potential onset toward the soma with a long stimulus in the absence of noise was due to the higher density of voltage-gated sodium channels at the axon initial segment. This attraction was, however, negligible at the most remote distal dendritic sites and was replaced by an effect due to high input resistance. Action potential onset occurred at the dendritic site of higher input resistance among a pair of remote dendritic sites, irrespective of which of these two sites received the synaptic input. Exploration of the parameter space showed how the gradient of voltage-gated channel densities and input resistances along a dendrite could draw the action potential onset away from the stimulation site. The attraction of action potential onset toward the higher density of voltage-gated channels in the soma during stimulation of the proximal dendrite was, however, reduced after the addition of synaptic noise. Copyright © 2012 IBRO. Published by Elsevier Ltd. All rights reserved.

Results of Detailed Modeling of the Narrow-Line Region of Seyfert Galaxies

NASA Technical Reports Server (NTRS)

Moore, David; Cohen, Ross D.

1996-01-01

We present model line profiles of [O II] lambda3727, [Ne III] lambda3869, [O I] lambda5007, [Fe VII] lambda6087, [Fe X] lambda6374, [O I] lambda6300, H(alpha) lambda6563, and [S 2] lambda6731. The profiles presented here illustrate explicitly the pronounced effects that collisional de-excitation, and that spatial variations in both the ionization parameter and cloud column density, have on Narrow-Line Region (NLR) model profiles. The above effects were included only qualitatively in a previous analytical treatment by Moore and Cohen. By making a direct correspondence between these model profiles and the analytical model profiles of Moore and Cohen, and by comparing with the observed profiles presented in a companion paper and also with those presented elsewhere in the literature, we strengthen some of the conclusions of Moore and Cohen. Most notably, we argue for constant ionization parameter, uniformly accelerated outflow of clouds that are individually stratified in ionization, and the interpretation of emission-line width correlations with ionization potential as a column density effect. For comparison with previous observational studies, such as our own in a companion paper, we also calculate profile parameters for some of the models, and we present and discuss the resulting line width correlations with critical density (n(sub cr)) and Ionization Potential (IP). Because the models we favor are those that produce extended profile wings as observed in high spectral resolution studies, the line width correlations of our favoured models are of particular interest. Line width correlations with n(sub cr) and/or IP result only if the width parameter is more sensitive to extended profile wings than is the Full Width at Half-Maximum (FWHM). Correlations between FWHM and n(sub cr) and/or IP result only after convolving the model profiles with a broad instrumental profile that simulates the lower spectral resolution used in early observational studies. The model in agreement with the greatest number of observational considerations has electron density decreasing outward from n(sub e) approx. equals 10(exp 6)/cu cm to n(sub e) approx. equals 10(exp 2)/cu cm and, due to collisional de-excitation effects in the lowest velocity clouds, it generates broad flat-topped profile peaks in the lines of lowest critical density (e.g., [O II] lambda3727 and [S II] lambda(lambda)6716, 6731). Because the observed profile peaks of both low and high critical density lines are often very similar, our favored model requires a contribution to NLR emission-line spectra from low-velocity, low-density, and low-ionization gas not included in the model NLR.

Ling's Adsorption Theory as a Mechanism of Membrane Potential Generation Observed in Both Living and Nonliving Systems.

PubMed

Tamagawa, Hirohisa; Funatani, Makoto; Ikeda, Kota

2016-01-26

The potential between two electrolytic solutions separated by a membrane impermeable to ions was measured and the generation mechanism of potential measured was investigated. From the physiological point of view, a nonzero membrane potential or action potential cannot be observed across the impermeable membrane. However, a nonzero membrane potential including action potential-like potential was clearly observed. Those observations gave rise to a doubt concerning the validity of currently accepted generation mechanism of membrane potential and action potential of cell. As an alternative theory, we found that the long-forgotten Ling's adsorption theory was the most plausible theory. Ling's adsorption theory suggests that the membrane potential and action potential of a living cell is due to the adsorption of mobile ions onto the adsorption site of cell, and this theory is applicable even to nonliving (or non-biological) system as well as living system. Through this paper, the authors emphasize that it is necessary to reconsider the validity of current membrane theory and also would like to urge the readers to pay keen attention to the Ling's adsorption theory which has for long years been forgotten in the history of physiology.

Effects of acetylcholine and noradrenalin on action potentials of isolated rabbit sinoatrial and atrial myocytes.

PubMed

Verkerk, Arie O; Geuzebroek, Guillaume S C; Veldkamp, Marieke W; Wilders, Ronald

2012-01-01

The autonomic nervous system controls heart rate and contractility through sympathetic and parasympathetic inputs to the cardiac tissue, with acetylcholine (ACh) and noradrenalin (NA) as the chemical transmitters. In recent years, it has become clear that specific Regulators of G protein Signaling proteins (RGS proteins) suppress muscarinic sensitivity and parasympathetic tone, identifying RGS proteins as intriguing potential therapeutic targets. In the present study, we have identified the effects of 1 μM ACh and 1 μM NA on the intrinsic action potentials of sinoatrial (SA) nodal and atrial myocytes. Single cells were enzymatically isolated from the SA node or from the left atrium of rabbit hearts. Action potentials were recorded using the amphotericin-perforated patch-clamp technique in the absence and presence of ACh, NA, or a combination of both. In SA nodal myocytes, ACh increased cycle length and decreased diastolic depolarization rate, whereas NA decreased cycle length and increased diastolic depolarization rate. Both ACh and NA increased maximum upstroke velocity. Furthermore, ACh hyperpolarized the maximum diastolic potential. In atrial myocytes stimulated at 2 Hz, both ACh and NA hyperpolarized the maximum diastolic potential, increased the action potential amplitude, and increased the maximum upstroke velocity. Action potential duration at 50 and 90% repolarization was decreased by ACh, but increased by NA. The effects of both ACh and NA on action potential duration showed a dose dependence in the range of 1-1000 nM, while a clear-cut frequency dependence in the range of 1-4 Hz was absent. Intermediate results were obtained in the combined presence of ACh and NA in both SA nodal and atrial myocytes. Our data uncover the extent to which SA nodal and atrial action potentials are intrinsically dependent on ACh, NA, or a combination of both and may thus guide further experiments with RGS proteins.

Effects of Acetylcholine and Noradrenalin on Action Potentials of Isolated Rabbit Sinoatrial and Atrial Myocytes

PubMed Central

Verkerk, Arie O.; Geuzebroek, Guillaume S. C.; Veldkamp, Marieke W.; Wilders, Ronald

2012-01-01

The autonomic nervous system controls heart rate and contractility through sympathetic and parasympathetic inputs to the cardiac tissue, with acetylcholine (ACh) and noradrenalin (NA) as the chemical transmitters. In recent years, it has become clear that specific Regulators of G protein Signaling proteins (RGS proteins) suppress muscarinic sensitivity and parasympathetic tone, identifying RGS proteins as intriguing potential therapeutic targets. In the present study, we have identified the effects of 1 μM ACh and 1 μM NA on the intrinsic action potentials of sinoatrial (SA) nodal and atrial myocytes. Single cells were enzymatically isolated from the SA node or from the left atrium of rabbit hearts. Action potentials were recorded using the amphotericin-perforated patch-clamp technique in the absence and presence of ACh, NA, or a combination of both. In SA nodal myocytes, ACh increased cycle length and decreased diastolic depolarization rate, whereas NA decreased cycle length and increased diastolic depolarization rate. Both ACh and NA increased maximum upstroke velocity. Furthermore, ACh hyperpolarized the maximum diastolic potential. In atrial myocytes stimulated at 2 Hz, both ACh and NA hyperpolarized the maximum diastolic potential, increased the action potential amplitude, and increased the maximum upstroke velocity. Action potential duration at 50 and 90% repolarization was decreased by ACh, but increased by NA. The effects of both ACh and NA on action potential duration showed a dose dependence in the range of 1–1000 nM, while a clear-cut frequency dependence in the range of 1–4 Hz was absent. Intermediate results were obtained in the combined presence of ACh and NA in both SA nodal and atrial myocytes. Our data uncover the extent to which SA nodal and atrial action potentials are intrinsically dependent on ACh, NA, or a combination of both and may thus guide further experiments with RGS proteins. PMID:22754533

The effects of gentamicin and penicillin/streptomycin on the electrophysiology of human induced pluripotent stem cell-derived cardiomyocytes in manual patch clamp and multi-electrode array system.

PubMed

Hyun, Soo-Wang; Kim, Bo-Ram; Lin, Dan; Hyun, Sung-Ae; Yoon, Seong Shoon; Seo, Joung-Wook

Cell culture media usually contains antibiotics including gentamicin or penicillin/streptomycin (PS) to protect cells from bacterial contamination. However, little is known about the effects of antibiotics on action potential and field potential parameters in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). The present study examined the effects of gentamicin (10, 25, and 50μg/ml) and PS (50, 100, and 200U/μg/ml) on electrophysiological activity in spontaneously beating hiPSC-CMs using manual patch clamp and multi-electrode array. We also measured mRNA expression of cardiac ion channels in hiPSC-CMs grown in media with or without gentamicin (25μg/ml) using reverse transcription-polymerase chain reaction. We recorded action potential and field potential of hiPSC-CMs grown in the presence or absence of gentamicin or PS. We also observed action potential parameters in hiPSC-CMs after short-term treatment with these antibiotics. Changes in action potential and field potential parameters were observed in hiPSC-CMs grown in media containing gentamicin or PS. Treatment with PS also affected action potential parameters in hiPSC-CMs. In addition, the mRNA expression of cardiac sodium and potassium ion channels was significantly attenuated in hiPSC-CMs grown in the presence of gentamicin (25μg/ml). The present findings suggested that gentamicin should not be used in the culture media of hiPSC-CMs used for the measurement of electrophysiological parameters. Our findings also suggest that 100U/100μg/ml of PS are the maximum appropriate concentrations of these antibiotics for recording action potential waveform, because they did not influence action potential parameters in these cells. Copyright © 2017. Published by Elsevier Inc.

Beta Function Quintessence Cosmological Parameters and Fundamental Constants I: Power and Inverse Power Law Dark Energy Potentials

NASA Astrophysics Data System (ADS)

Thompson, Rodger I.

2018-04-01

This investigation explores using the beta function formalism to calculate analytic solutions for the observable parameters in rolling scalar field cosmologies. The beta function in this case is the derivative of the scalar ϕ with respect to the natural log of the scale factor a, β (φ )=d φ /d ln (a). Once the beta function is specified, modulo a boundary condition, the evolution of the scalar ϕ as a function of the scale factor is completely determined. A rolling scalar field cosmology is defined by its action which can contain a range of physically motivated dark energy potentials. The beta function is chosen so that the associated "beta potential" is an accurate, but not exact, representation of the appropriate dark energy model potential. The basic concept is that the action with the beta potential is so similar to the action with the model potential that solutions using the beta action are accurate representations of solutions using the model action. The beta function provides an extra equation to calculate analytic functions of the cosmologies parameters as a function of the scale factor that are that are not calculable using only the model action. As an example this investigation uses a quintessence cosmology to demonstrate the method for power and inverse power law dark energy potentials. An interesting result of the investigation is that the Hubble parameter H is almost completely insensitive to the power of the potentials and that ΛCDM is part of the family of quintessence cosmology power law potentials with a power of zero.

Beta function quintessence cosmological parameters and fundamental constants - I. Power and inverse power law dark energy potentials

NASA Astrophysics Data System (ADS)

Thompson, Rodger I.

2018-07-01

This investigation explores using the beta function formalism to calculate analytic solutions for the observable parameters in rolling scalar field cosmologies. The beta function in this case is the derivative of the scalar φ with respect to the natural log of the scale factor a, β (φ)=d φ/d ln (a). Once the beta function is specified, modulo a boundary condition, the evolution of the scalar φ as a function of the scale factor is completely determined. A rolling scalar field cosmology is defined by its action which can contain a range of physically motivated dark energy potentials. The beta function is chosen so that the associated `beta potential' is an accurate, but not exact, representation of the appropriate dark energy model potential. The basic concept is that the action with the beta potential is so similar to the action with the model potential that solutions using the beta action are accurate representations of solutions using the model action. The beta function provides an extra equation to calculate analytic functions of the cosmologies parameters as a function of the scale factor that are not calculable using only the model action. As an example, this investigation uses a quintessence cosmology to demonstrate the method for power and inverse power law dark energy potentials. An interesting result of the investigation is that the Hubble parameter H is almost completely insensitive to the power of the potentials and that Λ cold dark matter is part of the family of quintessence cosmology power-law potentials with a power of zero.

Pulmonary Endpoints (Lung Carcinomas and Asbestosis) Following Inhalation Exposure to Asbestos

PubMed Central

Mossman, Brooke T.; Lippmann, Morton; Hesterberg, Thomas W.; Kelsey, Karl T.; Barchowsky, Aaron; Bonner, James C.

2011-01-01

Lung carcinomas and pulmonary fibrosis (asbestosis) occur in asbestos workers. Understanding the pathogenesis of these diseases is complicated because of potential confounding factors, such as smoking, which is not a risk factor in mesothelioma. The modes of action (MOA) of various types of asbestos in the development of lung cancers, asbestosis, and mesotheliomas appear to be different. Moreover, asbestos fibers may act differentially at various stages of these diseases, and have different potencies as compared to other naturally occurring and synthetic fibers. This literature review describes patterns of deposition and retention of various types of asbestos and other fibers after inhalation, methods of translocation within the lung, and dissolution of various fiber types in lung compartments and cells in vitro. Comprehensive dose-response studies at fiber concentrations inhaled by humans as well as bivariate size distributions (lengths and widths), types, and sources of fibers are rarely defined in published studies and are needed. Species-specific responses may occur. Mechanistic studies have some of these limitations, but have suggested that changes in gene expression (either fiber-catalyzed directly or by cell elaboration of oxidants), epigenetic changes, and receptor-mediated or other intracellular signaling cascades may play roles in various stages of the development of lung cancers or asbestosis. PMID:21534086

Independent role for presynaptic FMRP revealed by an FMR1 missense mutation associated with intellectual disability and seizures

PubMed Central

Myrick, Leila K.; Deng, Pan-Yue; Hashimoto, Hideharu; Oh, Young Mi; Cho, Yongcheol; Poidevin, Mickael J.; Suhl, Joshua A.; Visootsak, Jeannie; Cavalli, Valeria; Jin, Peng; Cheng, Xiaodong; Warren, Stephen T.; Klyachko, Vitaly A.

2015-01-01

Fragile X syndrome (FXS) results in intellectual disability (ID) most often caused by silencing of the fragile X mental retardation 1 (FMR1) gene. The resulting absence of fragile X mental retardation protein 1 (FMRP) leads to both pre- and postsynaptic defects, yet whether the pre- and postsynaptic functions of FMRP are independent and have distinct roles in FXS neuropathology remain poorly understood. Here, we demonstrate an independent presynaptic function for FMRP through the study of an ID patient with an FMR1 missense mutation. This mutation, c.413G > A (R138Q), preserves FMRP’s canonical functions in RNA binding and translational regulation, which are traditionally associated with postsynaptic compartments. However, neuronally driven expression of the mutant FMRP is unable to rescue structural defects at the neuromuscular junction in fragile x mental retardation 1 (dfmr1)-deficient Drosophila, suggesting a presynaptic-specific impairment. Furthermore, mutant FMRP loses the ability to rescue presynaptic action potential (AP) broadening in Fmr1 KO mice. The R138Q mutation also disrupts FMRP’s interaction with the large-conductance calcium-activated potassium (BK) channels that modulate AP width. These results reveal a presynaptic- and translation-independent function of FMRP that is linked to a specific subset of FXS phenotypes. PMID:25561520

Pulse-coupled mixed-mode oscillators: Cluster states and extreme noise sensitivity

NASA Astrophysics Data System (ADS)

Karamchandani, Avinash J.; Graham, James N.; Riecke, Hermann

2018-04-01

Motivated by rhythms in the olfactory system of the brain, we investigate the synchronization of all-to-all pulse-coupled neuronal oscillators exhibiting various types of mixed-mode oscillations (MMOs) composed of sub-threshold oscillations (STOs) and action potentials ("spikes"). We focus particularly on the impact of the delay in the interaction. In the weak-coupling regime, we reduce the system to a Kuramoto-type equation with non-sinusoidal phase coupling and the associated Fokker-Planck equation. Its linear stability analysis identifies the appearance of various cluster states. Their type depends sensitively on the delay and the width of the pulses. Interestingly, long delays do not imply slow population rhythms, and the number of emerging clusters only loosely depends on the number of STOs. Direct simulations of the oscillator equations reveal that for quantitative agreement of the weak-coupling theory the coupling strength and the noise have to be extremely small. Even moderate noise leads to significant skipping of STO cycles, which can enhance the diffusion coefficient in the Fokker-Planck equation by two orders of magnitude. Introducing an effective diffusion coefficient extends the range of agreement significantly. Numerical simulations of the Fokker-Planck equation reveal bistability and solutions with oscillatory order parameters that result from nonlinear mode interactions. These are confirmed in simulations of the full spiking model.

Pulsed magnetic stimulation modifies amplitude of action potentials in vitro via ionic channels-dependent mechanism.

PubMed

Ahmed, Zaghloul; Wieraszko, Andrzej

2015-07-01

This paper investigates the influence of pulsed magnetic fields (PMFs) on amplitude of evoked, compound action potential (CAP) recorded from the segments of sciatic nerve in vitro. PMFs were applied for 30 min at frequency of 0.16 Hz and intensity of 15 mT. In confirmation of our previous reports, PMF exposure enhanced amplitude of CAPs. The effect persisted beyond PMF activation period. As expected, CAP amplitude was attenuated by antagonists of sodium channel, lidocaine, and tetrodotoxin. Depression of the potential by sodium channels antagonists was reversed by subsequent exposure to PMFs. The effect of elevated potassium concentration and veratridine on the action potential was modified by exposure to PMFs as well. Neither inhibitors of protein kinase C and protein kinase A, nor known free radicals scavengers had any effects on PMF action. Possible mechanisms of PMF action are discussed. © 2015 Wiley Periodicals, Inc.

Na and Ca components of action potentials in amphioxus muscle cells

PubMed Central

Hagiwara, S.; Kidokoro, Y.

1971-01-01

1. The ionic mechanism of the action potential produced in lamella-like muscle cells of amphioxus, Branchiostoma californiense, was investigated with intracellular recording and polarization techniques. 2. The resting potential and action potential overshoot in normal saline are -53±5 mV (S.D.) and +29±10 mV (S.D.) respectively. 3. The action potential is eliminated by tetrodotoxin (3 μM) and by replacing NaCl in the saline with Tris-chloride but maintained by replacing Na with Li. 4. After elimination of the normal action potential by tetrodotoxin or replacing Na with Tris, the addition of procaine (7·3 mM) to the external saline makes the membrane capable of producing a regenerative potential change. 5. The peak potential of the regenerative response depends on external Ca concentration in a manner predicted by the Nernst equation with Ca concentrations close to normal. 6. The Ca dependent response is reversibly suppressed by Co or La ions. 7. Similar regenerative responses are obtained when Ca is substituted with Sr or Ba. 8. It is concluded that two independent mechanisms of ionic permeability increase occur in the membrane of amphioxus muscle cell, one to Na and the other to Ca. PMID:5158595

7 CFR 1945.19 - Reporting potential natural disasters and initial actions.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 7 Agriculture 13 2012-01-01 2012-01-01 false Reporting potential natural disasters and initial... Assistance-General § 1945.19 Reporting potential natural disasters and initial actions. (a) Purpose. The purpose of reporting potential natural disasters is to provide a systematic procedure for rapid reporting...

7 CFR 1945.19 - Reporting potential natural disasters and initial actions.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 7 Agriculture 13 2011-01-01 2009-01-01 true Reporting potential natural disasters and initial... Assistance-General § 1945.19 Reporting potential natural disasters and initial actions. (a) Purpose. The purpose of reporting potential natural disasters is to provide a systematic procedure for rapid reporting...

7 CFR 1945.19 - Reporting potential natural disasters and initial actions.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 7 Agriculture 13 2010-01-01 2009-01-01 true Reporting potential natural disasters and initial... Assistance-General § 1945.19 Reporting potential natural disasters and initial actions. (a) Purpose. The purpose of reporting potential natural disasters is to provide a systematic procedure for rapid reporting...

Action potentials recorded from bundles of very thin, gray matter axons in rat cerebellar slices using a grease-gap method.

PubMed

Palani, Damodharan; Pekala, Dobromila; Baginskas, Armantas; Szkudlarek, Hanna; Raastad, Morten

2012-07-15

We investigated the ability of a grease-gap method to record fast and slow changes of the membrane potential from bundles of gray matter axons. Their membrane potentials are of particular interest because these axons are different from most axons that have been investigated using intra-axonal or gap techniques. One of the main differences is that gray matter axons typically have closely spaced presynaptic specializations, called boutons or varicosities, distributed along their entire paths. In response to electrical activation of bundles of parallel fiber axons we were able to record small (128-416μV) but stable signals that we show most likely represented a fraction of the trans-membrane action potentials. A less-than 100% fraction prevents measurements of absolute values for membrane potentials, but the good signal-to-noise ratio (typically 10-16) allows detection of changes in resting membrane potential, action potentials and their after-potentials. Because very little is known about the shape of action potentials and after-potentials in these axons we used several independent methods to make it likely that the grease-gap signal was of intra-axonal origin. We demonstrate the utility of the method by showing that the action potentials in cerebellar parallel fibers and hippocampal Schaffer collaterals had a slowly decaying, depolarized after-potential. The method is ideal for pharmacological tests, which we demonstrate by showing that the slow after-potential was sensitive to 4-AP, and that the membrane potential was reduced by 200μM Ba(2+). Copyright © 2012 Elsevier B.V. All rights reserved.

Electrically evoked compound action potential amplitude growth functions and HiResolution programming levels in pediatric CII implant subjects.

PubMed

Eisen, Marc D; Franck, Kevin H

2004-12-01

To characterize the amplitude growth functions of the electrically evoked compound action potential (ECAP) in pediatric subjects implanted with the Clarion HiFocus electrode array with respect to electrode position and the presence or absence of a Silastic positioner. Electrophysiologic growth function data are compared with HiResolution (HiRes) psychophysical programming levels. ECAP growth functions were measured for all electrodes along the implant's array in 16 pediatric subjects. Nine of the patients were implanted with a Silastic positioner, whereas seven had no positioner. ECAP thresholds and growth function slopes were calculated. Fifteen of the 16 patients had psychophysical threshold and maximum comfort levels available. Programming levels and ECAP thresholds were compared within and among the subjects. ECAP thresholds showed variability among patients, ranging from 178 to 920 nA at 32 musec pulse width. ECAP thresholds did not depend on electrode position along the cochlea but were lower in the presence of the Silastic positioner (p < 0.001). Thresholds determined with the masker-probe versus the alternating polarity paradigms revealed moderate (r = 0.76) correlation. Growth function slopes also showed considerable variation among patients. Unlike thresholds, slopes decreased from apical to basal cochlear locations (p < 0.001) but showed no difference between the absence and presence of the positioner. Programming levels in HiRes were correlated with ECAP threshold levels. When ECAP thresholds were adjusted for each patient by the difference between M level and ECAP threshold at electrode 9, however, overall correlation between the two measurements was excellent (r = 0.98, N = 224). In pediatric subjects with the Clarion HiFocus electrode, ECAP growth function thresholds appear to decrease with the presence of the Silastic positioner but are unaffected by electrode position along the array. Growth function slope, however, depends on electrode position along the array but not on the presence of the positioner. ECAP programming levels can reliably predict stimulus intensities within the patients' dynamic ranges, but considerable variability is seen between ECAP thresholds and HiRes programming levels.

Maxillary and mandibular anterior crown width/height ratio and its relation to various arch perimeters, arch length, and arch width groups

PubMed Central

Shahid, Fazal; Alam, Mohammad Khursheed; Khamis, Mohd Fadhli

2015-01-01

Objective: To investigate the maxillary and mandibular anterior crown width/height ratio and its relation to various arch perimeters, arch length, and arch width (intercanine, interpremolar, and intermolar) groups. Materials and Methods: The calculated sample size was 128 subjects. The crown width/height, arch length, arch perimeter, and arch width of the maxilla and mandible were obtained via digital calliper (Mitutoyo, Japan). A total of 4325 variables were measured. The sex differences in the crown width and height were evaluated. Analysis of variance was applied to evaluate the differences between arch length, arch perimeter, and arch width groups. Results: Males had significantly larger mean values for crown width and height than females (P ≤ 0.05) for maxillary and mandibular arches, both. There were no significant differences observed for the crown width/height ratio in various arch length, arch perimeter, and arch width (intercanine, interpremolar, and intermolar) groups (P ≤ 0.05) in maxilla and mandible, both. Conclusions: Our results indicate sexual disparities in the crown width and height. Crown width and height has no significant relation to various arch length, arch perimeter, and arch width groups of maxilla and mandible. Thus, it may be helpful for orthodontic and prosthodontic case investigations and comprehensive management. PMID:26929686

Variability of surface and center position radiation dose in MDCT: Monte Carlo simulations using CTDI and anthropomorphic phantoms

PubMed Central

Zhang, Di; Savandi, Ali S.; Demarco, John J.; Cagnon, Chris H.; Angel, Erin; Turner, Adam C.; Cody, Dianna D.; Stevens, Donna M.; Primak, Andrew N.; McCollough, Cynthia H.; McNitt-Gray, Michael F.

2009-01-01

The larger coverage afforded by wider z-axis beams in multidetector CT (MDCT) creates larger cone angles and greater beam divergence, which results in substantial surface dose variation for helical and contiguous axial scans. This study evaluates the variation of absorbed radiation dose in both cylindrical and anthropomorphic phantoms when performing helical or contiguous axial scans. The approach used here was to perform Monte Carlo simulations of a 64 slice MDCT. Simulations were performed with different radiation profiles (simulated beam widths) for a given collimation setting (nominal beam width) and for different pitch values and tube start angles. The magnitude of variation at the surface was evaluated under four different conditions: (a) a homogeneous CTDI phantom with different combinations of pitch and simulated beam widths, (b) a heterogeneous anthropomorphic phantom with one measured beam collimation and various pitch values, (c) a homogeneous CTDI phantom with fixed beam collimation and pitch, but with different tube start angles, and (d) pitch values that should minimize variations of surface dose—evaluated for both homogeneous and heterogeneous phantoms. For the CTDI phantom simulations, peripheral dose patterns showed variation with percent ripple as high as 65% when pitch is 1.5 and simulated beam width is equal to the nominal collimation. For the anterior surface dose on an anthropomorphic phantom, the percent ripple was as high as 40% when the pitch is 1.5 and simulated beam width is equal to the measured beam width. Low pitch values were shown to cause beam overlaps which created new peaks. Different x-ray tube start angles create shifts of the peripheral dose profiles. The start angle simulations showed that for a given table position, the surface dose could vary dramatically with minimum values that were 40% of the peak when all conditions are held constant except for the start angle. The last group of simulations showed that an “ideal” pitch value can be determined which reduces surface dose variations, but this pitch value must take into account the measured beam width. These results reveal the complexity of estimating surface dose and demonstrate a range of dose variability at surface positions for both homogeneous cylindrical and heterogeneous anthropomorphic phantoms. These findings have potential implications for small-sized dosimeter measurements in phantoms, such as with TLDs or small Farmer chambers. PMID:19378763

A device for emulating cuff recordings of action potentials propagating along peripheral nerves.

PubMed

Rieger, Robert; Schuettler, Martin; Chuang, Sheng-Chih

2014-09-01

This paper describes a device that emulates propagation of action potentials along a peripheral nerve, suitable for reproducible testing of bio-potential recording systems using nerve cuff electrodes. The system is a microcontroller-based stand-alone instrument which uses established nerve and electrode models to represent neural activity of real nerves recorded with a nerve cuff interface, taking into consideration electrode impedance, voltages picked up by the electrodes, and action potential propagation characteristics. The system emulates different scenarios including compound action potentials with selectable propagation velocities and naturally occurring nerve traffic from different velocity fiber populations. Measured results from a prototype implementation are reported and compared with in vitro recordings from Xenopus Laevis frog sciatic nerve, demonstrating that the electrophysiological setting is represented to a satisfactory degree, useful for the development, optimization and characterization of future recording systems.

Nerve Impulses in Plants

ERIC Educational Resources Information Center

Blatt, F. J.

1974-01-01

Summarizes research done on the resting and action potential of nerve impulses, electrical excitation of nerve cells, electrical properties of Nitella, and temperature effects on action potential. (GS)

Predissociation of tif by tunneling

NASA Astrophysics Data System (ADS)

Wolf, U.; Tiemann, E.

1987-01-01

The UV spectra of the B 3Π 1-X 1Σ + transition in TIF were recorded applying frequency-doubled laser radiation and fluorescence or direct absorption detection. The observed J' -dependent predissociation in the upper levels v' = 2 and v' = 3 is explained quantitatively by invoking tunneling through a potential hump. The line positions and widths are fitted to a potential curve of the B 3Π 1 state using the semiclassical approximation for bound and quasibound levels.

Central Nervous System-Toxic Lidocaine Concentrations Unmask L-Type Ca²⁺ Current-Mediated Action Potentials in Rat Thalamocortical Neurons: An In Vitro Mechanism of Action Study.

PubMed

Putrenko, Igor; Ghavanini, Amer A; Meyer Schöniger, Katrin S; Schwarz, Stephan K W

2016-05-01

High systemic lidocaine concentrations exert well-known toxic effects on the central nervous system (CNS), including seizures, coma, and death. The underlying mechanisms are still largely obscure, and the actions of lidocaine on supraspinal neurons have received comparatively little study. We recently found that lidocaine at clinically neurotoxic concentrations increases excitability mediated by Na-independent, high-threshold (HT) action potential spikes in rat thalamocortical neurons. Our goal in this study was to characterize these spikes and test the hypothesis that they are generated by HT Ca currents, previously implicated in neurotoxicity. We also sought to identify and isolate the specific underlying subtype of Ca current. We investigated the actions of lidocaine in the CNS-toxic concentration range (100 μM-1 mM) on ventrobasal thalamocortical neurons in rat brain slices in vitro, using whole-cell patch-clamp recordings aided by differential interference contrast infrared videomicroscopy. Drugs were bath applied; action potentials were generated using current clamp protocols, and underlying currents were identified and isolated with ion channel blockers and electrolyte substitution. Lidocaine (100 μM-1 mM) abolished Na-dependent tonic firing in all neurons tested (n = 46). However, in 39 of 46 (85%) neurons, lidocaine unmasked evoked HT action potentials with lower amplitudes and rates of de-/repolarization compared with control. These HT action potentials remained during the application of tetrodotoxin (600 nM), were blocked by Cd (50 μM), and disappeared after superfusion with an extracellular solution deprived of Ca. These features implied that the unmasked potentials were generated by high-voltage-activated Ca channels and not by Na channels. Application of the L-type Ca channel blocker, nifedipine (5 μM), completely blocked the HT potentials, whereas the N-type Ca channel blocker, ω-conotoxin GVIA (1 μM), had little effect. At clinically CNS-toxic concentrations, lidocaine unmasked in thalamocortical neurons evoked HT action potentials mediated by the L-type Ca current while substantially suppressing Na-dependent excitability. On the basis of the known role of an increase in intracellular Ca in the pathogenesis of local anesthetic neurotoxicity, this novel action represents a plausible contributing candidate mechanism for lidocaine's CNS toxicity in vivo.

An intracellular analysis of the visual responses of neurones in cat visual cortex.

PubMed Central

Douglas, R J; Martin, K A; Whitteridge, D

1991-01-01

1. Extracellular and intracellular recordings were made from neurones in the visual cortex of the cat in order to compare the subthreshold membrane potentials, reflecting the input to the neurone, with the output from the neurone seen as action potentials. 2. Moving bars and edges, generated under computer control, were used to stimulate the neurones. The membrane potential was digitized and averaged for a number of trials after stripping the action potentials. Comparison of extracellular and intracellular discharge patterns indicated that the intracellular impalement did not alter the neurones' properties. Input resistance of the neurone altered little during stable intracellular recordings (30 min-2 h 50 min). 3. Intracellular recordings showed two distinct patterns of membrane potential changes during optimal visual stimulation. The patterns corresponded closely to the division of S-type (simple) and C-type (complex) receptive fields. Simple cells had a complex pattern of membrane potential fluctuations, involving depolarizations alternating with hyperpolarizations. Complex cells had a simple single sustained plateau of depolarization that was often followed but not preceded by a hyperpolarization. In both simple and complex cells the depolarizations led to action potential discharges. The hyperpolarizations were associated with inhibition of action potential discharge. 4. Stimulating simple cells with non-optimal directions of motion produced little or no hyperpolarization of the membrane in most cases, despite a lack of action potential output. Directional complex cells always produced a single plateau of depolarization leading to action potential discharge in both the optimal and non-optimal directions of motion. The directionality could not be predicted on the basis of the position of the hyperpolarizing inhibitory potentials found in the optimal direction. 5. Stimulation of simple cells with non-optimal orientations occasionally produced slight hyperpolarizations and inhibition of action potential discharge. Complex cells, which had broader orientation tuning than simple cells, could show marked hyperpolarization for non-optimal orientations, but this was not generally the case. 6. The data do not support models of directionality and orientation that rely solely on strong inhibitory mechanisms to produce stimulus selectivity. PMID:1804981

Hyperpolarization-activated current (I(h)) in vestibular calyx terminals: characterization and role in shaping postsynaptic events.

PubMed

Meredith, Frances L; Benke, Tim A; Rennie, Katherine J

2012-12-01

Calyx afferent terminals engulf the basolateral region of type I vestibular hair cells, and synaptic transmission across the vestibular type I hair cell/calyx is not well understood. Calyces express several ionic conductances, which may shape postsynaptic potentials. These include previously described tetrodotoxin-sensitive inward Na(+) currents, voltage-dependent outward K(+) currents and a K(Ca) current. Here, we characterize an inwardly rectifying conductance in gerbil semicircular canal calyx terminals (postnatal days 3-45), sensitive to voltage and to cyclic nucleotides. Using whole-cell patch clamp, we recorded from isolated calyx terminals still attached to their type I hair cells. A slowly activating, noninactivating current (I(h)) was seen with hyperpolarizing voltage steps negative to the resting potential. External Cs(+) (1-5 mM) and ZD7288 (100 μM) blocked the inward current by 97 and 83 %, respectively, confirming that I(h) was carried by hyperpolarization-activated, cyclic nucleotide gated channels. Mean half-activation voltage of I(h) was -123 mV, which shifted to -114 mV in the presence of cAMP. Activation of I(h) was well described with a third order exponential fit to the current (mean time constant of activation, τ, was 190 ms at -139 mV). Activation speeded up significantly (τ=136 and 127 ms, respectively) when intracellular cAMP and cGMP were present, suggesting that in vivo I(h) could be subject to efferent modulation via cyclic nucleotide-dependent mechanisms. In current clamp, hyperpolarizing current steps produced a time-dependent depolarizing sag followed by either a rebound afterdepolarization or an action potential. Spontaneous excitatory postsynaptic potentials (EPSPs) became larger and wider when I(h) was blocked with ZD7288. In a three-dimensional mathematical model of the calyx terminal based on Hodgkin-Huxley type ionic conductances, removal of I(h) similarly increased the EPSP, whereas cAMP slightly decreased simulated EPSP size and width.

Staff Handbook on Natural Gas.

ERIC Educational Resources Information Center

Gorges, H. A., Ed.; Raine, L. P., Ed.

The Department of Commerce created a Natural Gas Action Group early in the fall of 1975 to assist industrial firms and the communities they serve to cope with the effects of potentially severe and crippling curtailment situations. This action group was trained to assess a specific local situation, review the potential for remedial action and…

75 FR 43072 - Trichoderma Hamatum Isolate 382; Exemption from the Requirement of a Tolerance

Federal Register 2010, 2011, 2012, 2013, 2014

2010-07-23

... Information A. Does this Action Apply to Me? You may be potentially affected by this action if you are an agricultural producer, food manufacturer, or pesticide manufacturer. Potentially affected entities may include... exhaustive, but rather provides a guide for readers regarding entities likely to be affected by this action...

Remodelling of action potential and intracellular calcium cycling dynamics during subacute myocardial infarction promotes ventricular arrhythmias in Langendorff-perfused rabbit hearts

PubMed Central

Chou, Chung-Chuan; Zhou, Shengmei; Hayashi, Hideki; Nihei, Motoki; Liu, Yen-Bin; Wen, Ming-Shien; Yeh, San-Jou; Fishbein, Michael C; Weiss, James N; Lin, Shien-Fong; Wu, Delon; Chen, Peng-Sheng

2007-01-01

We hypothesize that remodelling of action potential and intracellular calcium (Cai) dynamics in the peri-infarct zone contributes to ventricular arrhythmogenesis in the postmyocardial infarction setting. To test this hypothesis, we performed simultaneous optical mapping of Cai and membrane potential (Vm) in the left ventricle in 15 rabbit hearts with myocardial infarction for 1 week. Ventricular premature beats frequently originated from the peri-infarct zone, and 37% showed elevation of Cai prior to Vm depolarization, suggesting reverse excitation–contraction coupling as their aetiology. During electrically induced ventricular fibrillation, the highest dominant frequency was in the peri-infarct zone in 61 of 70 episodes. The site of highest dominant frequency had steeper action potential duration restitution and was more susceptible to pacing-induced Cai alternans than sites remote from infarct. Wavebreaks during ventricular fibrillation tended to occur at sites of persistently elevated Cai. Infusion of propranolol flattened action potential duration restitution, reduced wavebreaks and converted ventricular fibrillation to ventricular tachycardia. We conclude that in the subacute phase of myocardial infarction, the peri-infarct zone exhibits regions with steep action potential duration restitution slope and unstable Cai dynamics. These changes may promote ventricular extrasystoles and increase the incidence of wavebreaks during ventricular fibrillation. Whereas increased tissue heterogeneity after subacute myocardial infarction creates a highly arrhythmogenic substrate, dynamic action potential and Cai cycling remodelling also contribute to the initiation and maintenance of ventricular fibrillation in this setting. PMID:17272354

Effects of pioglitazone on cardiac ion currents and action potential morphology in canine ventricular myocytes.

PubMed

Kistamás, Kornél; Szentandrássy, Norbert; Hegyi, Bence; Ruzsnavszky, Ferenc; Váczi, Krisztina; Bárándi, László; Horváth, Balázs; Szebeni, Andrea; Magyar, János; Bányász, Tamás; Kecskeméti, Valéria; Nánási, Péter P

2013-06-15

Despite its widespread therapeutical use there is little information on the cellular cardiac effects of the antidiabetic drug pioglitazone in larger mammals. In the present study, therefore, the concentration-dependent effects of pioglitazone on ion currents and action potential configuration were studied in isolated canine ventricular myocytes using standard microelectrode, conventional whole cell patch clamp, and action potential voltage clamp techniques. Pioglitazone decreased the maximum velocity of depolarization and the amplitude of phase-1 repolarization at concentrations ≥3 μM. Action potentials were shortened by pioglitazone at concentrations ≥10 μM, which effect was accompanied with significant reduction of beat-to-beat variability of action potential duration. Several transmembrane ion currents, including the transient outward K(+) current (Ito), the L-type Ca(2+) current (ICa), the rapid and slow components of the delayed rectifier K(+) current (IKr and IKs, respectively), and the inward rectifier K(+) current (IK1) were inhibited by pioglitazone under conventional voltage clamp conditions. Ito was blocked significantly at concentrations ≥3 μM, ICa, IKr, IKs at concentrations ≥10 μM, while IK1 at concentrations ≥30 μM. Suppression of Ito, ICa, IKr, and IK1 has been confirmed also under action potential voltage clamp conditions. ATP-sensitive K(+) current, when activated by lemakalim, was effectively blocked by pioglitazone. Accordingly, action potentials were prolonged by 10 μM pioglitazone when the drug was applied in the presence of lemakalim. All these effects developed rapidly and were readily reversible upon washout. In conclusion, pioglitazone seems to be a harmless agent at usual therapeutic concentrations. Copyright © 2013 Elsevier B.V. All rights reserved.

Activation of cannabinoid CB1 receptors modulates evoked action potentials in rat retinal ganglion cells.

PubMed

Jiang, Shu-Xia; Li, Qian; Wang, Xiao-Han; Li, Fang; Wang, Zhong-Feng

2013-08-25

Activation of cannabinoid CB1 receptors (CB1Rs) regulates a variety of physiological functions in the vertebrate retina through modulating various types of ion channels. The aim of the present study was to investigate the effects of this receptor on cell excitability of rat retinal ganglion cells (RGCs) in retinal slices using whole-cell patch-clamp techniques. The results showed that under current-clamped condition perfusing WIN55212-2 (WIN, 5 μmol/L), a CB1R agonist, did not significantly change the spontaneous firing frequency and resting membrane potential of RGCs. In the presence of cocktail synaptic blockers, including excitatory postsynaptic receptor blockers CNQX and D-APV, and inhibitory receptor blockers bicuculline and strychnine, perfusion of WIN (5 μmol/L) hardly changed the frequencies of evoked action potentials by a series of positive current injection (from +10 to +100 pA). Phase-plane plot analysis showed that both average threshold voltage for triggering action potential and delay time to reach threshold voltage were not affected by WIN. However, WIN significantly decreased +dV/dtmax and -dV/dtmax of action potentials, suggestive of reduced rising and descending velocities of action potentials. The effects of WIN were reversed by co-application of SR141716, a CB1R selective antagonist. Moreover, WIN did not influence resting membrane potential of RGCs with synaptic inputs being blocked. These results suggest that activation of CB1Rs may regulate intrinsic excitability of rat RGCs through modulating evoked action potentials.

Cardiac structural changes and electrical remodeling in a thiamine-deficiency model in rats.

PubMed

Roman-Campos, D; Campos, A C; Gioda, C R; Campos, P P; Medeiros, M A A; Cruz, J S

2009-06-05

Thiamine is an important cofactor present in many biochemical reactions, and its deprivation can lead to heart dysfunction. Little is known about the influence of thiamine deprivation on the electrophysiological behavior of the isolated heart cells and information about thiamine deficiency in heart morphology is controversial. Thus, we decided to investigate the major repolarizing conductances and their influence in the action potential (AP) waveform as well as the changes in the heart structure in a set of thiamine deficiency in rats. Using the patch-clamp technique, we investigated inward (I(K1)) and outward K(+) currents (I(to)), T-type and L-type Ca(2+) currents and APs. To evaluate heart morphology we used hematoxylin and eosin in transversal heart sections. Thiamine deficiency caused a marked decrease in left ventricle thickness, cardiomyocyte number, cell length and width, and membrane capacitance. When evaluating I(to) we did not find difference in current amplitude; however an acceleration of I(to) inactivation was observed. I(K1) showed a reduction in the amplitude and slope conductance, which implicated a less negative resting membrane potential in cardiac myocytes isolated from thiamine-deficient rats. We did not find any difference in L-type Ca(2+) current density. T-type Ca(2+) current was not observed. In addition, we did not observe significant changes in AP repolarization. Based on our study we can conclude that thiamine deficiency causes heart hypotrophy and not heart hypertrophy. Moreover, we provided evidence that there is no major electrical remodeling during thiamine deficiency, a feature of heart failure models.

Nicotine inhibits potassium currents in Aplysia bag cell neurons

PubMed Central

White, Sean H.; Sturgeon, Raymond M.

2016-01-01

Acetylcholine and the archetypal cholinergic agonist, nicotine, are typically associated with the opening of ionotropic receptors. In the bag cell neurons, which govern the reproductive behavior of the marine snail, Aplysia californica, there are two cholinergic responses: a relatively large acetylcholine-induced current and a relatively small nicotine-induced current. Both currents are readily apparent at resting membrane potential and result from the opening of distinct ionotropic receptors. We now report a separate current response elicited by applying nicotine to cultured bag cell neurons under whole cell voltage-clamp. This current was ostensibly inward, best resolved at depolarized voltages, presented a noncooperative dose-response with a half-maximal concentration near 1.5 mM, and associated with a decrease in membrane conductance. The unique nicotine-evoked response was not altered by intracellular perfusion with the G protein blocker GDPβS or exposure to classical nicotinic antagonists but was occluded by replacing intracellular K+ with Cs+. Consistent with an underlying mechanism of direct inhibition of one or more K+ channels, nicotine was found to rapidly reduce the fast-inactivating A-type K+ current as well as both components of the delayed-rectifier K+ current. Finally, nicotine increased bag cell neuron excitability, which manifested as reduction in spike threshold, greater action potential height and width, and markedly more spiking to continuous depolarizing current injection. In contrast to conventional transient activation of nicotinic ionotropic receptors, block of K+ channels could represent a nonstandard means for nicotine to profoundly alter the electrical properties of neurons over prolonged periods of time. PMID:26864763

Selective and graded recruitment of cat hamstring muscles with intrafascicular stimulation.

PubMed

Dowden, Brett R; Wilder, Andrew M; Hiatt, Scott D; Normann, Richard A; Brown, Nicholas A T; Clark, Gregory A

2009-12-01

The muscles of the hamstring group can produce different combinations of hip and knee torque. Thus, the ability to activate the different hamstring muscles selectively is of particular importance in eliciting functional movements such as stance and gait in a person with spinal cord injury. We investigated the ability of intrafascicular stimulation of the muscular branch of the sciatic nerve to recruit the feline hamstring muscles in a selective and graded fashion. A Utah Slanted Electrode Array, consisting of 100 penetrating microelectrodes, was implanted into the muscular branch of the sciatic nerve in six cats. Muscle twitches were evoked in the three compartments of biceps femoris (anterior, middle, and posterior), as well as semitendinosus and semimembranosus, using pulse-width modulated constant-voltage pulses. The resultant compound muscle action potentials were recorded using intramuscular fine-wire electrodes. 74% of the electrodes per implant were able to evoke a threshold response in these muscles, and these electrodes were evenly distributed among the instrumented muscles. Of the five muscles instrumented, on average 2.5 could be selectively activated to 90% of maximum EMG, and 3.5 could be selectively activated to 50% of maximum EMG. The muscles were recruited selectively with a mean stimulus dynamic range of 4.14 +/- 5.05 dB between threshold and either spillover to another muscle or a plateau in the response. This selective and graded activation afforded by intrafascicular stimulation of the muscular branch of the sciatic nerve suggests that it is a potentially useful stimulation paradigm for eliciting distinct forces in the hamstring muscle group in motor neuroprosthetic applications.

Does small-bodied salmon spawning activity enhance streambed mobility?

NASA Astrophysics Data System (ADS)

Hassan, Marwan A.; Tonina, Daniele; Buxton, Todd H.

2015-09-01

Female salmonids bury and lay their eggs in streambeds by digging a pit, which is then covered with sediment from a second pit that is dug immediately upstream. The spawning process alters streambed topography, winnows fine sediment, and mixes sediment in the active layer. The resulting egg nests (redds) contain coarser and looser sediments than those of unspawned streambed areas, and display a dune-like shape with an amplitude and length that vary with fish size, substrate conditions, and flow conditions. Redds increase local bed surface roughness (<10-1 channel width, W), but may reduce the size of macro bedforms by eroding reach-scale topography (100-101W). Research has suggested that spawning may increase flow resistance due to redd form drag, resulting in lower grain shear stress and less particle mobility. Spawning, also prevents streambed armoring by mixing surface and subsurface material, potentially increasing particle mobility. Here we use two-dimensional hydraulic modeling with detailed prespawning and postspawning bathymetries and field observations to test the effect of spawning by small-bodied salmonids on sediment transport. Our results show that topographical roughness from small salmon redds has negligible effects on shear stress at the reach-unit scale, and limited effects at the local scale. Conversely, results indicate sediment mixing reduces armoring and enhances sediment mobility, which increases potential bed load transport by subsequent floods. River restoration in fish-bearing streams should take into consideration the effects of redd excavation on channel stability. This is particularly important for streams that historically supported salmonids and are the focus of habitat restoration actions.

Rotational Dynamics of the Methyl Radical in Superfluid 4He Nanodroplets

DOE PAGES

Morrison, Alexander M.; Raston, Paul L.; Douberly, Gary E.

2012-12-07

Here, we report the ro-vibrational spectrum of the ν 3(e') band of the methyl radical (CH 3) solvated in superfluid 4He nanodroplets. Five allowed transitions produce population in the N K = 0 0, 1 1, 1 0, 2 2 and 2 0 rotational levels. The observed transitions exhibit variable Lorentzian line shapes, consistent with state specific homogeneous broadening effects. Population relaxation of the 00 and 11 levels is only allowed through vibrationally inelastic decay channels, and the PP 1(1) and RR 0(0) transitions accessing these levels have 4.12(1) and 4.66(1) GHz full-width at half-maximum line widths, respectively. The linemore » widths of the PR 1(1) and RR 1(1) transitions are comparatively broader (8.6(1) and 57.0(6) GHz, respectively), consistent with rotational relaxation of the 2 0 and 2 2 levels within the vibrationally excited manifold. The nuclear spin symmetry allowed rotational relaxation channel for the excited 1 0 level has an energy difference similar to those associated with the 2 0 and 2 2 levels. However, the PQ 1(1) transition that accesses the 1 0 level is 2.3 and 15.1 times narrower than the PR 1(1) and RR 1(1) lines, respectively. The relative line widths of these transitions are rationalized in terms of the anisotropy in the He-CH 3 potential energy surface, which couples the molecule rotation to the collective modes of the droplet.« less

Effect of temperature and ridge-width on the lasing characteristics of InAs/InP quantum-dash lasers: A thermal analysis view

NASA Astrophysics Data System (ADS)

Alkhazraji, E.; Khan, M. T. A.; Ragheb, A. M.; Fathallah, H.; Qureshi, K. K.; Alshebeili, S.; Khan, M. Z. M.

2018-01-01

We investigate the thermal characteristics of multi-stack chirped barrier thickness InAs/InGaAlAs/InP quantum-dash-in-a-well lasers of different ridge widths 2, 3, 4 and 15 μm. The effect of varying this geometrical parameter on the extracted thermal resistance and characteristic temperature, and their stability with temperature are examined. The results show an inverse relation of ridge-width with junction temperature with 2 μm device exhibiting the largest junction temperature buildup owing to an associated high thermal resistance of ∼45 °C/W. Under the light of this thermal analysis, lasing behavior of different ridge-width quantum-dash (Qdash) lasers with injection currents and operating temperatures, is investigated. Thermionic carrier escape and phonon-assisted tunneling are found to be the dominant carrier transport mechanisms resulting in wide thermal spread of carriers across the available transition states of the chirped active region. An emission coverage of ∼75 nm and 3 dB bandwidth of ∼55 nm is exhibited by the 2 μm device, thus possibly exploiting the inhomogeneous optical transitions to the fullest. Furthermore, successful external modulation of a single Qdash Fabry-Perot laser mode via injection locking is demonstrated with eye diagrams at bit rates of 2-12 Gbit/s incorporating various modulation schemes. These devices are being considered as potential light sources for future high-speed wavelength-division multiplexed optical communication systems.

Shape optimization of electrostatically driven microcantilevers using simulated annealing to enhance static travel range

NASA Astrophysics Data System (ADS)

Trivedi, R. R.; Joglekar, M. M.; Shimpi, R. P.; Pawaskar, D. N.

2013-12-01

The objective of this paper is to present a systematic development of the generic shape optimization of elec- trostatically actuated microcantilever beams for extending their static travel range. Electrostatic actuators are widely used in micro electro mechanical system (MEMS) devices because of low power density and ease of fab- rication. However, their useful travel range is often restricted by a phenomenon known as pull-in instability. The Rayleigh- Ritz energy method is used for computation of pull-in parameters which includes electrostatic potential and fringing field effect. Appropriate width function and linear thickness functions are employed along the length of the non-prismatic beam to achieve enhanced travel range. Parameters used for varying the thick- ness and width functions are optimized using simulated annealing with pattern search method towards the end to refine the results. Appropriate penalties are imposed on the violation of volume, width, thickness and area constraints. Nine test cases are considered for demonstration of the said optimization method. Our results indicate that around 26% increase in the travel range of a non-prismatic beam can be achieved after optimiza- tion compared to that in a prismatic beam having the same volume. Our results also show an improvement in the pull-in displacement of around 5% compared to that of a variable width constant thickness actuator. We show that simulated annealing is an effective and flexible method to carry out design optimization of structural elements under electrostatic loading.

On the Detectability of Oxygen X-Ray Fluorescence and Its Use as a Solar Photospheric Abundance Diagnostic

NASA Astrophysics Data System (ADS)

Drake, Jeremy J.; Ercolano, Barbara

2008-08-01

Monte Carlo calculations of the O Kα line fluoresced by coronal X-rays and emitted just above the temperature minimum region of the solar atmosphere have been employed to investigate the use of this feature as an abundance diagnostic. While they are quite weak, we estimate line equivalent widths in the range 0.02-0.2 Å, depending on the X-ray plasma temperature. The line remains essentially uncontaminated by blends for coronal temperatures T <= 3 × 106 K and should be quite observable, with a flux gtrsim2 photons s-1 arcmin-2. Model calculations for solar chemical mixtures with an O abundance adjusted up and down by a factor of 2 indicate 35%-60% changes in O Kα line equivalent width, providing a potentially useful O abundance diagnostic. Sensitivity of equivalent width to differences between recently recommended chemical compositions with "high" and "low" complements of the CNO trio important for interpreting helioseismological observations is less acute, amounting to 20%-26% at coronal temperatures T <= 2 × 106 K. While still feasible for discriminating between these two mixtures, uncertainties in measured line equivalent widths and in the models used for interpretation would need to be significantly less than 20%. Provided a sensitive X-ray spectrometer with resolving power >=1000 and suitably well-behaved instrumental profile can be built, X-ray fluorescence presents a viable means for resolving the solar "oxygen crisis."

Strategies for improving neural signal detection using a neural-electronic interface.

PubMed

Szlavik, Robert B

2003-03-01

There have been various theoretical and experimental studies presented in the literature that focus on interfacing neurons with discrete electronic devices, such as transistors. From both a theoretical and experimental perspective, these studies have emphasized the variability in the characteristics of the detected action potential from the nerve cell. The demonstrated lack of reproducible fidelity of the nerve cell action potential at the device junction would make it impractical to implement these devices in any neural prosthetic application where reliable detection of the action potential was a prerequisite. In this study, the effects of several different physical parameters on the fidelity of the detected action potential at the device junction are investigated and discussed. The impact of variations in the extracellular resistivity, which directly affects the junction seal resistance, is studied along with the impact of variable nerve cell membrane capacitance and variations in the injected charge. These parameters are discussed in the context of their suitability to design manipulation for the purpose of improving the fidelity of the detected neural action potential. In addition to investigating the effects of variations in these parameters, the applicability of the linear equivalent circuit approach to calculating the junction potential is investigated.

Simulation of action potentials from metabolically impaired cardiac myocytes. Role of ATP-sensitive K+ current.

PubMed

Ferrero, J M; Sáiz, J; Ferrero, J M; Thakor, N V

1996-08-01

The role of the ATP-sensitive K+ current (IK-ATP) and its contribution to electrophysiological changes that occur during metabolic impairment in cardiac ventricular myocytes is still being discussed. The aim of this work was to quantitatively study this issue by using computer modeling. A model of IK-ATP is formulated and incorporated into the Luo-Rudy ionic model of the ventricular action potential. Action potentials under different degrees of activation of IK-ATP are simulated. Our results show that in normal ionic concentrations, only approximately 0.6% of the KATP channels, when open, should account for a 50% reduction in action potential duration. However, increased levels of intracellular Mg2+ counteract this shortening. Under conditions of high [K+]0, such as those found in early ischemia, the activation of only approximately 0.4% of the KATP channels could account for a 50% reduction in action potential duration. Thus, our results suggest that opening of IK-ATP channels should play a significant role in action potential shortening during hypoxic/ischemic episodes, with the fraction of open channels involved being very low ( < 1%). However, the results of the model suggest that activation of IK-ATP alone does not quantitatively account for the observed K+ efflux in metabolically impaired cardiac myocytes. Mechanisms other than KATP channel activation should be responsible for a significant part of the K+ efflux measured in hypoxic/ischemic situations.

Peripheral nerve recruitment curve using near-infrared stimulation

NASA Astrophysics Data System (ADS)

Dautrebande, Marie; Doguet, Pascal; Gorza, Simon-Pierre; Delbeke, Jean; Nonclercq, Antoine

2018-02-01

In the context of near-infrared neurostimulation, we report on an experimental hybrid electrode allowing for simultaneous photonic or electrical neurostimulation and for electrical recording of evoked action potentials. The electrode includes three contacts and one optrode. The optrode is an opening in the cuff through which the tip of an optical fibre is held close to the epineurium. Two contacts provide action potential recording. The remaining contact, together with a remote subcutaneous electrode, is used for electric stimulation which allows periodical assessment of the viability of the nerve during the experiment. A 1470 nm light source was used to stimulate a mouse sciatic nerve. Neural action potentials were not successfully recorded because of the electrical noise so muscular activity was used to reflect the motor fibres stimulation. A recruitment curve was obtained by stimulating with photonic pulses of same power and increasing duration and recording the evoked muscular action potentials. Motor fibres can be recruited with radiant exposures between 0.05 and 0.23 J/cm2 for pulses in the 100 to 500 μs range. Successful stimulation at short duration and at a commercial wavelength is encouraging in the prospect of miniaturisation and practical applications. Motor fibres recruitment curve is a first step in an ongoing research work. Neural action potential acquisition will be improved, with aim to shed light on the mechanism of action potential initiation under photonic stimulation.

Spectral singularities of complex scattering potentials and infinite reflection and transmission coefficients at real energies.

PubMed

Mostafazadeh, Ali

2009-06-05

Spectral singularities are spectral points that spoil the completeness of the eigenfunctions of certain non-Hermitian Hamiltonian operators. We identify spectral singularities of complex scattering potentials with the real energies at which the reflection and transmission coefficients tend to infinity, i.e., they correspond to resonances having a zero width. We show that a waveguide modeled using such a potential operates like a resonator at the frequencies of spectral singularities. As a concrete example, we explore the spectral singularities of an imaginary PT-symmetric barrier potential and demonstrate the above resonance phenomenon for a certain electromagnetic waveguide.

Spectral Singularities of Complex Scattering Potentials and Infinite Reflection and Transmission Coefficients at Real Energies

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

Mostafazadeh, Ali

2009-06-05

Spectral singularities are spectral points that spoil the completeness of the eigenfunctions of certain non-Hermitian Hamiltonian operators. We identify spectral singularities of complex scattering potentials with the real energies at which the reflection and transmission coefficients tend to infinity, i.e., they correspond to resonances having a zero width. We show that a waveguide modeled using such a potential operates like a resonator at the frequencies of spectral singularities. As a concrete example, we explore the spectral singularities of an imaginary PT-symmetric barrier potential and demonstrate the above resonance phenomenon for a certain electromagnetic waveguide.

Three dimensional α-tunneling in intense laser fields

NASA Astrophysics Data System (ADS)

Kis, Daniel P.; Szilvasi, Reka

2018-04-01

The width and life-time of the quasibound state of the α cluster in intense monochromatic electromagnetic (laser) field are discussed in details. The laser modified three dimensional potential barrier felt by the α particle is investigated analytically in long wave approximation and zero-order approximations with some different nuclear models: Coulomb potential with rectangular well, and with Woods-Saxon type potential. We show that the circularly polarized electromagnetic field and the special parameters of the nuclear potentials determine an enhancement of the decay probability, so the life-time of the quasibound state decreases in few times compared to the case of free field.

75 FR 33659 - Agency Information Collection Activities: Request for Comments for a New Information Collection

Federal Register 2010, 2011, 2012, 2013, 2014

2010-06-14

... tunnel construction completed; traffic data, including posted speed, design speed, current average daily... vertical clearance; minimum cross- sectional width; lane width(s); shoulder width(s); and pavement type. (3...

Fundamental Tactical Principles of Soccer: A Comparison of Different Age Groups

PubMed Central

Guilherme, José; Rechenchosky, Leandro; da Costa, Luciane Cristina Arantes; Rinadi, Wilson

2017-01-01

Abstract The fundamental tactical principles of the game of soccer represent a set of action rules that guide behaviours related to the management of game space. The aim of this study was to compare the performance of fundamental offensive and defensive tactical principles among youth soccer players from 12 to 17 years old. The sample consisted of 3689 tactical actions performed by 48 soccer players in three age categories: under 13 (U-13), under 15 (U-15), and under 17 (U-17). Tactical performance was measured using the System of Tactical Assessment in Soccer (FUT-SAT). The Kruskal Wallis, Mann-Whitney U, Friedman, Wilcoxon, and Cohen’s Kappa tests were used in the study analysis. The results showed that the principles of “offensive coverage” (p = 0.01) and “concentration” (p = 0.04) were performed more frequently by the U-17 players than the U-13 players. The tactical principles “width and length” (p < 0.05) and “defensive unit” (p < 0.05) were executed more frequently by younger soccer players. It can be concluded that the frequency with which fundamental tactical principles are performed varies between the gaming categories, which implies that there is valuation of defensive security and a progressive increase in “offensive coverage” caused by increased confidence and security in offensive actions. PMID:28828091

Fundamental Tactical Principles of Soccer: A Comparison of Different Age Groups.

PubMed

Borges, Paulo Henrique; Guilherme, José; Rechenchosky, Leandro; da Costa, Luciane Cristina Arantes; Rinadi, Wilson

2017-09-01

The fundamental tactical principles of the game of soccer represent a set of action rules that guide behaviours related to the management of game space. The aim of this study was to compare the performance of fundamental offensive and defensive tactical principles among youth soccer players from 12 to 17 years old. The sample consisted of 3689 tactical actions performed by 48 soccer players in three age categories: under 13 (U-13), under 15 (U-15), and under 17 (U-17). Tactical performance was measured using the System of Tactical Assessment in Soccer (FUT-SAT). The Kruskal Wallis, Mann-Whitney U, Friedman, Wilcoxon, and Cohen's Kappa tests were used in the study analysis. The results showed that the principles of "offensive coverage" (p = 0.01) and "concentration" (p = 0.04) were performed more frequently by the U-17 players than the U-13 players. The tactical principles "width and length" (p < 0.05) and "defensive unit" (p < 0.05) were executed more frequently by younger soccer players. It can be concluded that the frequency with which fundamental tactical principles are performed varies between the gaming categories, which implies that there is valuation of defensive security and a progressive increase in "offensive coverage" caused by increased confidence and security in offensive actions.

Second virial coefficient of a generalized Lennard-Jones potential.

PubMed

González-Calderón, Alfredo; Rocha-Ichante, Adrián

2015-01-21

We present an exact analytical solution for the second virial coefficient of a generalized Lennard-Jones type of pair potential model. The potential can be reduced to the Lennard-Jones, hard-sphere, and sticky hard-sphere models by tuning the potential parameters corresponding to the width and depth of the well. Thus, the second virial solution can also regain the aforementioned cases. Moreover, the obtained expression strongly resembles the one corresponding to the Kihara potential. In fact, the Fk functions are the same. Furthermore, for these functions, the complete expansions at low and high temperature are given. Additionally, we propose an alternative stickiness parameter based on the obtained second virial coefficient.

Characterizing Physical Habitat of a Mixed-Land Use Stream of the Central U.S.

NASA Astrophysics Data System (ADS)

Hooper, L. W.; Hubbart, J. A.; Hosmer, G. W.; Hogan, M. L.

2014-12-01

Land use altered flow regime impacts on aquatic biological habitat can be quantified by means of a physical habitat assessment (PHA). PHA metrics include (but are not limited to) channel substrate, width and wetted width, bank slope, and bank height. Hinkson Creek, located in Boone County, Missouri, was placed on the Missouri Department of Natural Resources list of impaired waters (Section 303d) of the Clean Water Act in 1998. A physical habitat assessment of Hinkson Creek in 2014 provides quantitative data characterizing the current potential of Hinkson Creek to fully support aquatic life, specifically macroinvertebrates (a goal for delisting). The PHA was conducted every 100m of Hinkson Creek (56km). Results from the lower 87.9% (contiguous) of the drainage indicate channel width ranged from a maximum of 70m to a minimum of 4.6m, with a mean width of 17m and standard deviation (SD) of 7.4m. Bankfull width ranged from a maximum of 74m to a minimum of 8.8m (mean = 26.1m, SD = 8.2). Bank height ranged from a maximum of 5.8m to a minimum of 0.4m (mean = 2.9m, SD = 1m). Mean bank angle for the left and right banks was nearly equivalent (left = 33.8°, right = 34.6°). Bank height and bankfull width increased with increasing drainage distance. Trench pools were the dominant channel unit at 71.4% of the sample transects, while riffles were present at 16.6%. Analysis of stream channel bed composition was conducted using a modified Wolman pebble count survey at each site and Thalweg profile between sites. Size class results were quantified as follows: 56.1% fines (16mm or less), 36.2% intermediate (16mm to 1000mm, plus vegetation and wood), 8.7% large/bedrock (greater than 1000mm, riprap and bedrock). Study results provide science-based information to better equip land planners in Hinkson Creek watershed and similar multi-use watersheds of the central United States for future management decisions and development scenarios.

Residual timber values within Piedmont streamside management zones of different widths and harvest levels

Treesearch

William A. Lakel; Wallace Aust; C. Andrew Dolloff; Patrick D. Keyser

2015-01-01

Forested streamside management zones (SMZs) provide numerous societal benefits including protection of water quality and enhancement of in-stream and riparian habitats. However, values of residual timber in SMZs are often ignored, yet maintenance of unnecessarily wide SMZs can potentially reduce merchantable timber. Therefore, forestland owners, managers, and logging...

Electromagnetic banana kinetic equation and its applications in tokamaks

NASA Astrophysics Data System (ADS)

Shaing, K. C.; Chu, M. S.; Sabbagh, S. A.; Seol, J.

2018-03-01

A banana kinetic equation in tokamaks that includes effects of the finite banana width is derived for the electromagnetic waves with frequencies lower than the gyro-frequency and the bounce frequency of the trapped particles. The radial wavelengths are assumed to be either comparable to or shorter than the banana width, but much wider than the gyro-radius. One of the consequences of the banana kinetics is that the parallel component of the vector potential is not annihilated by the orbit averaging process and appears in the banana kinetic equation. The equation is solved to calculate the neoclassical quasilinear transport fluxes in the superbanana plateau regime caused by electromagnetic waves. The transport fluxes can be used to model electromagnetic wave and the chaotic magnetic field induced thermal particle or energetic alpha particle losses in tokamaks. It is shown that the parallel component of the vector potential enhances losses when it is the sole transport mechanism. In particular, the fact that the drift resonance can cause significant transport losses in the chaotic magnetic field in the hitherto unknown low collisionality regimes is emphasized.

Oscillation of Branching Ratios Between the D(2s)+D(1s) and the D(2p)+D(1s) Channels in Direct Photodissociation of D_{2}.

PubMed

Wang, Jie; Meng, Qingnan; Mo, Yuxiang

2017-08-04

The direct photodissociation of D_{2} at excitation energies above 14.76 eV occurs via two channels, D(2s)+D(1s) and D(2p)+D(1s). The branching ratios between the two have been measured from the dissociation threshold to 3200 cm^{-1} above it, and it is found that they show cosine oscillations as a function of the fragment wave vector magnitudes. The oscillation is due to an interference effect and can be simulated using the phase difference between the wave functions of the two channels, analogous to Young's double-slit experiment. By fitting the measured branching ratios, we have determined the depths and widths of the effective spherical potential wells related to the two channels, which are in agreement with the effective depths and widths of the ab initio interaction potentials. The results of this Letter illustrate the importance of the relative phase between the fragments in controlling the branching ratios of the photodissociation channels.

Study on ion energy distribution in low-frequency oscillation time scale of Hall thrusters

NASA Astrophysics Data System (ADS)

Wei, Liqiu; Li, Wenbo; Ding, Yongjie; Han, Liang; Yu, Daren; Cao, Yong

2017-11-01

This paper reports on the dynamic characteristics of the distribution of ion energy during Hall thruster discharge in the low-frequency oscillation time scale through experimental studies, and a statistical analysis of the time-varying peak and width of ion energy and the ratio of high-energy ions during the low-frequency oscillation. The results show that the ion energy distribution exhibits a periodic change during the low-frequency oscillation. Moreover, the variation in the ion energy peak is opposite to that of the discharge current, and the variations in width of the ion energy distribution and the ratio of high-energy ions are consistent with that of the discharge current. The variation characteristics of the ion density and discharge potential were simulated by one-dimensional hybrid-direct kinetic simulations; the simulation results and analysis indicate that the periodic change in the distribution of ion energy during the low-frequency oscillation depends on the relationship between the ionization source term and discharge potential distribution during ionization in the discharge channel.

Addressing uncertainty in atomistic machine learning.

PubMed

Peterson, Andrew A; Christensen, Rune; Khorshidi, Alireza

2017-05-10

Machine-learning regression has been demonstrated to precisely emulate the potential energy and forces that are output from more expensive electronic-structure calculations. However, to predict new regions of the potential energy surface, an assessment must be made of the credibility of the predictions. In this perspective, we address the types of errors that might arise in atomistic machine learning, the unique aspects of atomistic simulations that make machine-learning challenging, and highlight how uncertainty analysis can be used to assess the validity of machine-learning predictions. We suggest this will allow researchers to more fully use machine learning for the routine acceleration of large, high-accuracy, or extended-time simulations. In our demonstrations, we use a bootstrap ensemble of neural network-based calculators, and show that the width of the ensemble can provide an estimate of the uncertainty when the width is comparable to that in the training data. Intriguingly, we also show that the uncertainty can be localized to specific atoms in the simulation, which may offer hints for the generation of training data to strategically improve the machine-learned representation.

Oscillation of Branching Ratios Between the D (2 s )+D (1 s ) and the D (2 p )+D (1 s ) Channels in Direct Photodissociation of D2

NASA Astrophysics Data System (ADS)

Wang, Jie; Meng, Qingnan; Mo, Yuxiang

2017-08-01

The direct photodissociation of D2 at excitation energies above 14.76 eV occurs via two channels, D (2 s )+D (1 s ) and D (2 p )+D (1 s ) . The branching ratios between the two have been measured from the dissociation threshold to 3200 cm-1 above it, and it is found that they show cosine oscillations as a function of the fragment wave vector magnitudes. The oscillation is due to an interference effect and can be simulated using the phase difference between the wave functions of the two channels, analogous to Young's double-slit experiment. By fitting the measured branching ratios, we have determined the depths and widths of the effective spherical potential wells related to the two channels, which are in agreement with the effective depths and widths of the ab initio interaction potentials. The results of this Letter illustrate the importance of the relative phase between the fragments in controlling the branching ratios of the photodissociation channels.

Exact exchange plane-wave-pseudopotential calculations for slabs: Extending the width of the vacuum

NASA Astrophysics Data System (ADS)

Engel, Eberhard

2018-04-01

Standard plane-wave pseudopotential (PWPP) calculations for slabs such as graphene become extremely demanding, as soon as the exact exchange (EXX) of density functional theory is applied. Even if the Krieger-Li-Iafrate (KLI) approximation for the EXX potential is utilized, such EXX-PWPP calculations suffer from the fact that an accurate representation of the occupied states throughout the complete vacuum between the replicas of the slab is required. In this contribution, a robust and efficient extension scheme for the PWPP states is introduced, which ensures the correct exponential decay of the slab states in the vacuum for standard cutoff energies and therefore facilitates EXX-PWPP calculations for very wide vacua and rather thick slabs. Using this scheme, it is explicitly verified that the Slater component of the EXX/KLI potential decays as -1 /z over an extended region sufficiently far from the surface (assumed to be perpendicular to the z direction) and from the middle of the vacuum, thus reproducing the asymptotic behavior of the exact EXX potential of a single slab. The calculations also reveal that the orbital-shift component of the EXX/KLI potential is quite sizable in the asymptotic region. In spite of the long-range exchange potential, the replicas of the slab decouple rather quickly with increasing width of the vacuum. Relying on the identity of the work function with the Fermi energy obtained with a suitably normalized total potential, the present EXX/KLI calculations predict work functions for both graphene and the Si(111) surface which are substantially larger than the corresponding experimental data. Together with the size of the orbital-shift potential in the asymptotic region, the very large EXX/KLI work functions indicate a failure of the KLI approximation for nonmetallic slabs.

Nutrition and growth: assessing the impact of regional nutritional intake on childhood development and metacarpal parameters.

PubMed

Moro, Christian; Covino, Jessica

2018-03-01

Measuring skeletal development throughout juvenile growth can provide a greater understanding into the health, hormonal function and genetics of children. The metacarpals have been of interest for their potential to provide insights into healthy juvenile skeletal development. This study investigated the growth patterns of developing females from isolated communities who had varied diets. Anthropometrical measurements and hand-wrist X-rays were taken of 353 juvenile females from three populations: Pari Coastal Village and Bundi Highlands Village, Papua New Guinea (PNG); and Brisbane, Australia between 1968 to 1983. Radiographs were digitized, and the length and width of the second and third metacarpals compared to each subject's height and weight. As subject heights increased, metacarpal length and width increased. However, stature and second metacarpal length indicated the strongest correlation ( P <0.01), compared to third metacarpal length ( P <0.01) or width. From 11 to 13 years of age, Brisbane subjects were significantly heavier and taller in comparison to subjects from PNG, and coastal females were heavier and taller than the highland females. A prominent difference between the two PNG populations was the regional intake of protein in their diets. The second metacarpal presents particularly accurate measurements when determining the height or development of a child. Nutritional intake appears to have a major influence normal childhood growth, with a potential for protein deficiency to strongly inhibit growth. Any delayed growth is particularly evident in the child's stature, as well as in the development of the metacarpal long bones of the hand.

Molecular Dynamics of a Water-Lipid Bilayer Interface

NASA Technical Reports Server (NTRS)

Wilson, Michael A.; Pohorille, Andrew

1994-01-01

We present results of molecular dynamics simulations of a glycerol 1-monooleate bilayer in water. The total length of analyzed trajectories is 5ns. The calculated width of the bilayer agrees well with the experimentally measured value. The interior of the membrane is in a highly disordered fluid state. Atomic density profile, orientational and conformational distribution functions, and order parameters indicate that disorder increases toward the center of the bilayer. Analysis of out-of-plane thermal fluctuations of the bilayer surfaces occurring at the time scale of the present calculations reveals that the distribution of modes agrees with predictions of the capillary wave model. Fluctuations of both bilayer surfaces are uncorrelated, yielding Gaussian distribution of instantaneous widths of the membrane. Fluctuations of the width produce transient thinning defects in the bilayer which occasionally span almost half of the membrane. The leading mechanism of these fluctuations is the orientational and conformational motion of head groups rather than vertical motion of the whole molecules. Water considerably penetrates the head group region of the bilayer but not its hydrocarbon core. The total net excess dipole moment of the interfacial water points toward the aqueous phase, but the water polarization profile is non-monotonic. Both water and head groups significantly contribute to the surface potential across the interface. The calculated sign of the surface potential is in agreement with that from experimental measurements, but the value is markedly overestimated. The structural and electrical properties of the water-bilayer system are discussed in relation to membrane functions, in particular transport of ions and nonelectrolytes across membranes.

Shining a light on star formation driven outflows: the physical conditions within galactic outflows

NASA Astrophysics Data System (ADS)

Chisholm, John P.; Tremonti, Christina A.; Leitherer, Claus; Wofford, Aida; Chen, Yanmei

2016-01-01

Stellar feedback drives energy and momentum into the surrounding gas, which drives gas and metals out of galaxies through a galactic outflow. Unfortunately, galactic outflows are difficult to observe and characterize because they are extremely diffuse, and contain gas at many different temperatures. Here we present results from a sample of 37 nearby (z < 0.27) star forming galaxies observed in the ultraviolet with the Cosmic Origins Spectrograph on the Hubble Space Telescope. The sample covers over three decades in stellar mass and star formation rate, probing different morphologies such as dwarf irregulars and high-mass merging systems. Using four different UV absorption lines (O I, Si II, Si III and Si IV) that trace a wide range of temperatures (ionization potentials between 13.6 eV and 45 eV), we find shallow correlations between the outflow velocity or the equivalent width of absorption lines with stellar mass or star formation rate. Absorption lines probing different temperature phases have similar centroid velocities and line widths, indicating that they are comoving. Using the equivalent width ratios of the four different transitions, we find the ratios to be consistent with photo-ionized outflows, with moderately strong ionization parameters. By constraining the ionization mechanism we model the ionization fractions for each transition, but find the ionization fractions depend crucially on input model parameters. The shallow velocity scalings imply that low-mass galaxies launch outflows capable of escaping their galactic potential, while higher mass galaxies retain all of their gas, unless they undergo a merger.

Proposal of a defense application for a chemical oxygen laser

NASA Astrophysics Data System (ADS)

Takehisa, K.

2015-05-01

Defense application for a chemical oxygen laser (COL) is explained. Although a COL has not yet been successful in lasing, the oscillator was estimated to produce a giant pulse with the full width at half maximum (FWHM) of ~0.05ms which makes the damage threshold for the mirrors several-order higher than that for a typical solid-state laser with a ~10ns pulse width. Therefore it has a potential to produce MJ class output considering the simple scalability of being a chemical laser. Since within 0.05ms a supersonic aircraft can move only a few centimeters which is roughly equal to the spot size of the focused beam at ~10km away using a large-diameter focusing mirror, a COL has a potential to make a damage to an enemy aircraft by a single shot without beam tracking. But since the extracted beam can propagate up to a few kilometers due to the absorption in the air, it may be suitable to use in space. While a chemical oxygen-iodine laser (COIL) can give a pulsed output with a width of ~2 ms using a high-pressure singlet oxygen generator (SOG). Therefore a pulsed COIL may also not require beam tracking if a target aircraft is approaching. Another advantage for these pulsed high-energy lasers (HELs) is that, in case of propagating in cloud or fog, much less energy is required for a laser for aerosol vaporization (LAV) than that of a LAV for a CW HEL. Considerations to use a COL as a directed energy weapon (DEW) in a point defense system are shown.

Action Learning: Avoiding Conflict or Enabling Action

ERIC Educational Resources Information Center

Corley, Aileen; Thorne, Ann

2006-01-01

Action learning is based on the premise that action and learning are inextricably entwined and it is this potential, to enable action, which has contributed to the growth of action learning within education and management development programmes. However has this growth in action learning lead to an evolution or a dilution of Revan's classical…

Action Learning: Potential for Inner City Youth

ERIC Educational Resources Information Center

Epps, Edgar G.

1974-01-01

Working class and minority participation in action-learning poses potential problems likely to be overlooked by program planners. This presentation reveals the trouble spots and offers constructive suggestions. (Editor)

Onset dynamics of action potentials in rat neocortical neurons and identified snail neurons: quantification of the difference.

PubMed

Volgushev, Maxim; Malyshev, Aleksey; Balaban, Pavel; Chistiakova, Marina; Volgushev, Stanislav; Wolf, Fred

2008-04-09

The generation of action potentials (APs) is a key process in the operation of nerve cells and the communication between neurons. Action potentials in mammalian central neurons are characterized by an exceptionally fast onset dynamics, which differs from the typically slow and gradual onset dynamics seen in identified snail neurons. Here we describe a novel method of analysis which provides a quantitative measure of the onset dynamics of action potentials. This method captures the difference between the fast, step-like onset of APs in rat neocortical neurons and the gradual, exponential-like AP onset in identified snail neurons. The quantitative measure of the AP onset dynamics, provided by the method, allows us to perform quantitative analyses of factors influencing the dynamics.

Onset Dynamics of Action Potentials in Rat Neocortical Neurons and Identified Snail Neurons: Quantification of the Difference

PubMed Central

Volgushev, Maxim; Malyshev, Aleksey; Balaban, Pavel; Chistiakova, Marina; Volgushev, Stanislav; Wolf, Fred

2008-01-01

The generation of action potentials (APs) is a key process in the operation of nerve cells and the communication between neurons. Action potentials in mammalian central neurons are characterized by an exceptionally fast onset dynamics, which differs from the typically slow and gradual onset dynamics seen in identified snail neurons. Here we describe a novel method of analysis which provides a quantitative measure of the onset dynamics of action potentials. This method captures the difference between the fast, step-like onset of APs in rat neocortical neurons and the gradual, exponential-like AP onset in identified snail neurons. The quantitative measure of the AP onset dynamics, provided by the method, allows us to perform quantitative analyses of factors influencing the dynamics. PMID:18398478

Electroosmotic flow and ionic conductance in a pH-regulated rectangular nanochannel

NASA Astrophysics Data System (ADS)

Sadeghi, Morteza; Saidi, Mohammad Hassan; Sadeghi, Arman

2017-06-01

Infinite series solutions are obtained for electrical potential, electroosmotic velocity, ionic conductance, and surface physicochemical properties of long pH-regulated rectangular nanochannels of low surface potential utilizing the double finite Fourier transform method. Closed form expressions are also obtained for channels of large height to width ratio for which the depthwise variations vanish. Neglecting the Stern layer impact, the effects of EDL (Electric Double Layer) overlap, multiple ionic species, and association/dissociation reactions on the surface are all taken into account. Moreover, finite-element-based numerical simulations are conducted to account for the end effects as well as to validate the analytical solutions. We show that, with the exception of the migratory ionic conductivity, all the physicochemical parameters are strong functions of the channel aspect ratio. Accordingly, a slit geometry is not a good representative of a rectangular channel when the width is comparable to the height. It is also observed that the distribution of the electrical potential is not uniform over the surface of a charge-regulated channel. In addition, unlike ordinary channels for which an increase in the background salt concentration is always accompanied by higher flow rates, quite the opposite may be true for a pH-regulated duct at higher salt concentrations.

Multi-hump potentials for efficient wave absorption in the numerical solution of the time-dependent Schrödinger equation

NASA Astrophysics Data System (ADS)

Silaev, A. A.; Romanov, A. A.; Vvedenskii, N. V.

2018-03-01

In the numerical solution of the time-dependent Schrödinger equation by grid methods, an important problem is the reflection and wrap-around of the wave packets at the grid boundaries. Non-optimal absorption of the wave function leads to possible large artifacts in the results of numerical simulations. We propose a new method for the construction of the complex absorbing potentials for wave suppression at the grid boundaries. The method is based on the use of the multi-hump imaginary potential which contains a sequence of smooth and symmetric humps whose widths and amplitudes are optimized for wave absorption in different spectral intervals. We show that this can ensure a high efficiency of absorption in a wide range of de Broglie wavelengths, which includes wavelengths comparable to the width of the absorbing layer. Therefore, this method can be used for high-precision simulations of various phenomena where strong spreading of the wave function takes place, including the phenomena accompanying the interaction of strong fields with atoms and molecules. The efficiency of the proposed method is demonstrated in the calculation of the spectrum of high-order harmonics generated during the interaction of hydrogen atoms with an intense infrared laser pulse.

Effect of Detergent on Electrical Properties of Squid Axon Membrane

PubMed Central

Kishimoto, Uichiro; Adelman, William J.

1964-01-01

The effects of detergents on squid giant axon action and resting potentials as well as membrane conductances in the voltage clamp have been studied. Anionic detergents (sodium lauryl sulfate, 0.1 to 1.0 mM; dimethyl benzene sulfonate, 1 to 20 mM, pH 7.6) cause a temporary increase and a later decrease of action potential height and the value of the resting potential. Cationic detergent (cetyl trimethyl ammonium chloride, 6 x 10-5 M or more, pH 7.6) generally brings about immediate and irreversible decreases in the action and resting potentials. Non-ionic detergent (tween 80, 0.1 M, pH 7.6) causes a slight reversible reduction of action potential height without affecting the value of the resting potential. Both anionic and cationic detergents generally decrease the sodium and potassium conductances irreversibly. The effect of non-ionic detergent is to decrease the sodium conductance reversibly, leaving the potassium conductance almost unchanged. PMID:14158665

The influence of action observation on action execution: Dissociating the contribution of action on perception, perception on action, and resolving conflict.

PubMed

Deschrijver, Eliane; Wiersema, Jan R; Brass, Marcel

2017-04-01

For more than 15 years, motor interference paradigms have been used to investigate the influence of action observation on action execution. Most research on so-called automatic imitation has focused on variables that play a modulating role or investigated potential confounding factors. Interestingly, furthermore, a number of functional magnetic resonance imaging (fMRI) studies have tried to shed light on the functional mechanisms and neural correlates involved in imitation inhibition. However, these fMRI studies, presumably due to poor temporal resolution, have primarily focused on high-level processes and have neglected the potential role of low-level motor and perceptual processes. In the current EEG study, we therefore aimed to disentangle the influence of low-level perceptual and motoric mechanisms from high-level cognitive mechanisms. We focused on potential congruency differences in the visual N190 - a component related to the processing of biological motion, the Readiness Potential - a component related to motor preparation, and the high-level P3 component. Interestingly, we detected congruency effects in each of these components, suggesting that the interference effect in an automatic imitation paradigm is not only related to high-level processes such as self-other distinction but also to more low-level influences of perception on action and action on perception. Moreover, we documented relationships of the neural effects with (autistic) behavior.

Fabrication of cylindrical micro-parts using synchronous rotary scan-projection lithography and chemical etching

NASA Astrophysics Data System (ADS)

Ito, Kaiki; Suzuki, Yuta; Horiuchi, Toshiyuki

2017-07-01

Lithographical patterning on the surface of a fine pipe with a thin wall is required for fabricating three-dimensional micro-parts. For this reason, a new exposure system for printing patterns on a cylindrical pipe by synchronous rotary scan-projection exposure was developed. Using the exposure system, stent-like resist patterns with a width of 251 μm were printed on a surface of stainless-steel pipe with an outer diameter of 2 mm. The exposure time was 30 s. Next, the patterned pipe was chemically etched. As a result, a stent-like mesh pipe with a line width of 230 μm was fabricated. It was demonstrated that the new method had a potential to be applied to fabrications of stent and other cylindrical micro-parts.

Wave Energy Prize - 1/20th Testing - Sea Potential

DOE Data Explorer

Scharmen, Wesley

2016-09-23

Data from the 1/20th scale testing data completed on the Wave Energy Prize for the Sea Potential team, including the 1/20th scale test plan, raw test data, video, photos, and data analysis results. The top level objective of the 1/20th scale device testing is to obtain the necessary measurements required for determining Average Climate Capture Width per Characteristic Capital Expenditure (ACE) and the Hydrodynamic Performance Quality (HPQ), key metrics for determining the Wave Energy Prize (WEP) winners.

Associative, Bidirectional Changes in Neural Signaling Utilizing NMDA Receptor- and Endocannabinoid-Dependent Mechanisms

ERIC Educational Resources Information Center

Li, Qin; Burrell, Brian D.

2011-01-01

Persistent, bidirectional changes in synaptic signaling (that is, potentiation and depression of the synapse) can be induced by the precise timing of individual pre- and postsynaptic action potentials. However, far less attention has been paid to the ability of paired trains of action potentials to elicit persistent potentiation or depression. We…

Final Environmental Assessment: Addressing An Army and Air Force Exchange Service (AAFES) Lifestyle Center at Eglin Air Force Base, Florida

DTIC Science & Technology

2008-11-01

the proposed site has the potential for adverse effects on surface water bodies in the event of a spill or uncontrolled erosion. Implementation of...inclusion of a No Action Alternative against which potential effects can be compared. While the No Action Alternative would not satisfy the purpose... potential effects on project site and adjacent land uses. The foremost factor affecting a proposed action in terms of land use is its compliance

Localization of effective actions in open superstring field theory

NASA Astrophysics Data System (ADS)

Maccaferri, Carlo; Merlano, Alberto

2018-03-01

We consider the construction of the algebraic part of D-branes tree-level effective action from Berkovits open superstring field theory. Applying this construction to the quartic potential of massless fields carrying a specific worldsheet charge, we show that the full contribution to the potential localizes at the boundary of moduli space, reducing to elementary two-point functions. As examples of this general mechanism, we show how the Yang-Mills quartic potential and the instanton effective action of a Dp/D( p - 4) system are reproduced.

Ultraviolet random lasing action from highly disordered n-AlN/p-GaN heterojunction.

PubMed

Yang, H Y; Yu, S F; Wong, J I; Cen, Z H; Liang, H K; Chen, T P

2011-05-01

Room-temperature random lasing is achieved from an n-AlN/p-GaN heterojunction. The highly disordered n-AlN layer, which was deposited on p-GaN:Mg layer via radio frequency magnetron sputtering, acts as a scattering medium to sustain coherent optical feedback. The p-GaN:Mg layer grown on sapphire provides optical amplification to the scattered light propagating along the heterojunction. Hence, lasing peaks of line width less than 0.4 nm are emerged from the emission spectra at round 370 nm for the heterojunction under forward bias larger than 5.1 V. Lasing characteristics of the heterojunction are in agreement with the behavior of random lasers.

Developing easy to perform routine MRI measurements as potential surrogates for cognitive impairment in MS.

PubMed

Morrow, Sarah A; Menon, Suresh; Rosehart, Heather; Sharma, Manas

2017-02-01

One of the most frequently disabling symptoms in Multiple Sclerosis (MS) is cognitive impairment which is often insidious in onset and therefore difficult to recognize in the early stages, for both persons with MS and clinicians. A biomarker that would help identify those at risk of cognitive impairment, or with only mild impairment, would be a useful tool for clinicians. Using MRI, already an integral tool in the diagnosis and monitoring of disease activity in MS, would be ideal. Thus, this study aimed to determine if simple measures on routine MRI could serve as potential biomarkers for cognitive impairment in MS. We retrospectively identified 51 persons with MS who had a cognitive assessment and MRI within six months of the MRI. Simple linear measurements of the hippocampi, bifrontral and third ventricular width, bicaudate width and the anterior, mid and posterior corpus callosum were made. Pearson's correlations examined the relationship between these MRI measures and cognitive tests, and MRI measures were compared in persons with MS who were either normal or cognitively impaired on objective cognitive tests using Analysis of Covariance (ANCOVA). Bicaudate span and third ventricular width were both negatively correlated, while corpus callosal measures were positive correlated with cognitive test performance. After controlling for potential confounders, bicaudate span was significant different on measures of immediate recall. Both anterior and posterior corpus collosal measure were significantly different on measures of verbal fluency, immediate recall and higher executive function; while the anterior corpus callosum was also significantly different on processing speed. The middle corpus collosal measure was significantly different on immediate recall and higher executive function. This study presents data demonstrating that simple to apply MRI measures of atrophy may serve as biomarkers for cognitive impairment in persons with MS. Further prospective studies are needed to validate these findings. Copyright © 2016 Elsevier B.V. All rights reserved.

Ion concentrations and velocity profiles in nanochannel electroosmotic flows

NASA Astrophysics Data System (ADS)

Qiao, R.; Aluru, N. R.

2003-03-01

Ion distributions and velocity profiles for electroosmotic flow in nanochannels of different widths are studied in this paper using molecular dynamics and continuum theory. For the various channel widths studied in this paper, the ion distribution near the channel wall is strongly influenced by the finite size of the ions and the discreteness of the solvent molecules. The classical Poisson-Boltzmann equation fails to predict the ion distribution near the channel wall as it does not account for the molecular aspects of the ion-wall and ion-solvent interactions. A modified Poisson-Boltzmann equation based on electrochemical potential correction is introduced to account for ion-wall and ion-solvent interactions. The electrochemical potential correction term is extracted from the ion distribution in a smaller channel using molecular dynamics. Using the electrochemical potential correction term extracted from molecular dynamics (MD) simulation of electroosmotic flow in a 2.22 nm channel, the modified Poisson-Boltzmann equation predicts the ion distribution in larger channel widths (e.g., 3.49 and 10.00 nm) with good accuracy. Detailed studies on the velocity profile in electro-osmotic flow indicate that the continuum flow theory can be used to predict bulk fluid flow in channels as small as 2.22 nm provided that the viscosity variation near the channel wall is taken into account. We propose a technique to embed the velocity near the channel wall obtained from MD simulation of electroosmotic flow in a narrow channel (e.g., 2.22 nm wide channel) into simulation of electroosmotic flow in larger channels. Simulation results indicate that such an approach can predict the velocity profile in larger channels (e.g., 3.49 and 10.00 nm) very well. Finally, simulation of electroosmotic flow in a 0.95 nm channel indicates that viscosity cannot be described by a local, linear constitutive relationship that the continuum flow theory is built upon and thus the continuum flow theory is not applicable for electroosmotic flow in such small channels.

77 FR 45535 - Aldicarb; Proposed Tolerance Actions

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-01

... Aldicarb; Proposed Tolerance Actions AGENCY: Environmental Protection Agency (EPA). ACTION: Proposed rule... Information A. Does this action apply to me? You may be potentially affected by this action if you are an... exhaustive, but rather provides a guide for readers regarding entities likely to be affected by this action...

Sodium and potassium conductance changes during a membrane action potential.

PubMed

Bezanilla, F; Rojas, E; Taylor, R E

1970-12-01

1. A method for turning a membrane potential control system on and off in less than 10 musec is described. This method was used to record membrane currents in perfused giant axons from Dosidicus gigas and Loligo forbesi after turning on the voltage clamp system at various times during the course of a membrane action potential.2. The membrane current measured just after the capacity charging transient was found to have an almost linear relation to the controlled membrane potential.3. The total membrane conductance taken from these current-voltage curves was found to have a time course during the action potential similar to that found by Cole & Curtis (1939).4. The instantaneous current voltage curves were linear enough to make it possible to obtain a good estimate of the individual sodium and potassium channel conductances, either algebraically or by clamping to the sodium, or potassium, reversal potentials. Good general agreement was obtained with the predictions of the Hodgkin-Huxley equations.5. We consider these results to constitute the first direct experimental demonstration of the conductance changes to sodium and potassium during the course of an action potential.

Calcium-Induced Calcium Release during Action Potential Firing in Developing Inner Hair Cells

PubMed Central

Iosub, Radu; Avitabile, Daniele; Grant, Lisa; Tsaneva-Atanasova, Krasimira; Kennedy, Helen J.

2015-01-01

In the mature auditory system, inner hair cells (IHCs) convert sound-induced vibrations into electrical signals that are relayed to the central nervous system via auditory afferents. Before the cochlea can respond to normal sound levels, developing IHCs fire calcium-based action potentials that disappear close to the onset of hearing. Action potential firing triggers transmitter release from the immature IHC that in turn generates experience-independent firing in auditory neurons. These early signaling events are thought to be essential for the organization and development of the auditory system and hair cells. A critical component of the action potential is the rise in intracellular calcium that activates both small conductance potassium channels essential during membrane repolarization, and triggers transmitter release from the cell. Whether this calcium signal is generated by calcium influx or requires calcium-induced calcium release (CICR) is not yet known. IHCs can generate CICR, but to date its physiological role has remained unclear. Here, we used high and low concentrations of ryanodine to block or enhance CICR to determine whether calcium release from intracellular stores affected action potential waveform, interspike interval, or changes in membrane capacitance during development of mouse IHCs. Blocking CICR resulted in mixed action potential waveforms with both brief and prolonged oscillations in membrane potential and intracellular calcium. This mixed behavior is captured well by our mathematical model of IHC electrical activity. We perform two-parameter bifurcation analysis of the model that predicts the dependence of IHCs firing patterns on the level of activation of two parameters, the SK2 channels activation and CICR rate. Our data show that CICR forms an important component of the calcium signal that shapes action potentials and regulates firing patterns, but is not involved directly in triggering exocytosis. These data provide important insights into the calcium signaling mechanisms involved in early developmental processes. PMID:25762313

Calcium-Induced calcium release during action potential firing in developing inner hair cells.

PubMed

Iosub, Radu; Avitabile, Daniele; Grant, Lisa; Tsaneva-Atanasova, Krasimira; Kennedy, Helen J

2015-03-10

In the mature auditory system, inner hair cells (IHCs) convert sound-induced vibrations into electrical signals that are relayed to the central nervous system via auditory afferents. Before the cochlea can respond to normal sound levels, developing IHCs fire calcium-based action potentials that disappear close to the onset of hearing. Action potential firing triggers transmitter release from the immature IHC that in turn generates experience-independent firing in auditory neurons. These early signaling events are thought to be essential for the organization and development of the auditory system and hair cells. A critical component of the action potential is the rise in intracellular calcium that activates both small conductance potassium channels essential during membrane repolarization, and triggers transmitter release from the cell. Whether this calcium signal is generated by calcium influx or requires calcium-induced calcium release (CICR) is not yet known. IHCs can generate CICR, but to date its physiological role has remained unclear. Here, we used high and low concentrations of ryanodine to block or enhance CICR to determine whether calcium release from intracellular stores affected action potential waveform, interspike interval, or changes in membrane capacitance during development of mouse IHCs. Blocking CICR resulted in mixed action potential waveforms with both brief and prolonged oscillations in membrane potential and intracellular calcium. This mixed behavior is captured well by our mathematical model of IHC electrical activity. We perform two-parameter bifurcation analysis of the model that predicts the dependence of IHCs firing patterns on the level of activation of two parameters, the SK2 channels activation and CICR rate. Our data show that CICR forms an important component of the calcium signal that shapes action potentials and regulates firing patterns, but is not involved directly in triggering exocytosis. These data provide important insights into the calcium signaling mechanisms involved in early developmental processes. Copyright © 2015 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Power-Law Dynamics of Membrane Conductances Increase Spiking Diversity in a Hodgkin-Huxley Model.

PubMed

Teka, Wondimu; Stockton, David; Santamaria, Fidel

2016-03-01

We studied the effects of non-Markovian power-law voltage dependent conductances on the generation of action potentials and spiking patterns in a Hodgkin-Huxley model. To implement slow-adapting power-law dynamics of the gating variables of the potassium, n, and sodium, m and h, conductances we used fractional derivatives of order η≤1. The fractional derivatives were used to solve the kinetic equations of each gate. We systematically classified the properties of each gate as a function of η. We then tested if the full model could generate action potentials with the different power-law behaving gates. Finally, we studied the patterns of action potential that emerged in each case. Our results show the model produces a wide range of action potential shapes and spiking patterns in response to constant current stimulation as a function of η. In comparison with the classical model, the action potential shapes for power-law behaving potassium conductance (n gate) showed a longer peak and shallow hyperpolarization; for power-law activation of the sodium conductance (m gate), the action potentials had a sharp rise time; and for power-law inactivation of the sodium conductance (h gate) the spikes had wider peak that for low values of η replicated pituitary- and cardiac-type action potentials. With all physiological parameters fixed a wide range of spiking patterns emerged as a function of the value of the constant input current and η, such as square wave bursting, mixed mode oscillations, and pseudo-plateau potentials. Our analyses show that the intrinsic memory trace of the fractional derivative provides a negative feedback mechanism between the voltage trace and the activity of the power-law behaving gate variable. As a consequence, power-law behaving conductances result in an increase in the number of spiking patterns a neuron can generate and, we propose, expand the computational capacity of the neuron.

Reexamining cluster radioactivity in trans-lead nuclei with consideration of specific density distributions in daughter nuclei and clusters

NASA Astrophysics Data System (ADS)

Qian, Yibin; Ren, Zhongzhou; Ni, Dongdong

2016-08-01

We further investigate the cluster emission from heavy nuclei beyond the lead region in the framework of the preformed cluster model. The refined cluster-core potential is constructed by the double-folding integral of the density distributions of the daughter nucleus and the emitted cluster, where the radius or the diffuseness parameter in the Fermi density distribution formula is determined according to the available experimental data on the charge radii and the neutron skin thickness. The Schrödinger equation of the cluster-daughter relative motion is then solved within the outgoing Coulomb wave-function boundary conditions to obtain the decay width. It is found that the present decay width of cluster emitters is clearly enhanced as compared to that in the previous case, which involved the fixed parametrization for the density distributions of daughter nuclei and clusters. Among the whole procedure, the nuclear deformation of clusters is also introduced into the calculations, and the degree of its influence on the final decay half-life is checked to some extent. Moreover, the effect from the bubble density distribution of clusters on the final decay width is carefully discussed by using the central depressed distribution.

Effect of nonsinusoidal bias waveforms on ion energy distributions and fluorocarbon plasma etch selectivity

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

Agarwal, Ankur; Kushner, Mark J.; Iowa State University, Department of Electrical and Computer Engineering, 104 Marston Hall, Ames, Iowa 50011-2151

2005-09-15

The distributions of ion energies incident on the wafer significantly influence feature profiles and selectivity during plasma etching. Control of ion energies is typically obtained by varying the amplitude or frequency of a radio frequency sinusoidal bias voltage applied to the substrate. The resulting ion energy distribution (IED), though, is generally broad. Controlling the width and shape of the IED can potentially improve etch selectivity by distinguishing between threshold energies of surface processes. In this article, control of the IED was computationally investigated by applying a tailored, nonsinusoidal bias waveform to the substrate of an inductively coupled plasma. The waveformmore » we investigated, a quasi-dc negative bias having a short positive pulse each cycle, produced a narrow IED whose width was controllable based on the length of the positive spike and frequency. We found that the selectivity between etching Si and SiO{sub 2} in fluorocarbon plasmas could be controlled by adjusting the width and energy of the IED. Control of the energy of a narrow IED enables etching recipes that transition between speed and selectivity without change of gas mixture.« less

On the use of space photography for identifying transportation routes: A summary of problems

NASA Technical Reports Server (NTRS)

Simonett, D. S.; Henderson, F. M.; Egbert, D. D.

1970-01-01

It has been widely suggested that space photography may be used for updating maps of transportation networks. Proponents of the argument have suggested that color space photographs of the resolution obtained with Hasselblad 80 mm lenses (about 300 feet) contain enough useful information to update the extensions of major U. S. highways. The present study systematically documents for the Dallas-Fort Worth area the potential of such space photography in detecting, and to a lesser degree identifying, the existing road networks. Color separation plates and an enlargement of the color photograph were produced and all visible roads traced onto transparencies for study. Major roads and roads under construction were the most visible while lower class roads and roads in urban areas had the poorest return. Road width and classification were found to be the major determinant in visibility, varying from 100 per cent visible for divided highways to 15 per cent visible of bladed earth roads. In summary, space photographs of this resolution proved to be difficult to use for accurate road delineation. Only super highways in rural areas with the greatest road-width were completely identifiable, the width being about 1/3 that of the resolution cell.

Quasi-stationary states of an electron with linearly dependent effective mass in an open nanostructure within transmission coefficient and S-matrix methods

NASA Astrophysics Data System (ADS)

Seti, Julia; Tkach, Mykola; Voitsekhivska, Oxana

2018-03-01

The exact solutions of the Schrödinger equation for a double-barrier open semiconductor plane nanostructure are obtained by using two different approaches, within the model of the rectangular potential profile and the continuous position-dependent effective mass of the electron. The transmission coefficient and scattering matrix are calculated for the double-barrier nanostructure. The resonance energies and resonance widths of the electron quasi-stationary states are analyzed as a function of the size of the near-interface region between wells and barriers, where the effective mass linearly depends on the coordinate. It is established that, in both methods, the increasing size affects in a qualitatively similar way the spectral characteristics of the states, shifting the resonance energies into the low- or high-energy region and increasing the resonance widths. It is shown that the relative difference of resonance energies and widths of a certain state, obtained in the model of position-dependent effective mass and in the widespread abrupt model in physically correct range of near-interface sizes, does not exceed 0.5% and 5%, respectively, independently of the other geometrical characteristics of the structure.

Properties of interfaces and transport across them.

PubMed

Cabezas, H

2000-01-01

Much of the biological activity in cell cytoplasm occurs in compartments some of which may be formed, as suggested in this book, by phase separation, and many of the functions of such compartments depend on the transport or exchange of molecules across interfaces. Thus a fundamentally based discussion of the properties of phases, interfaces, and diffusive transport across interfaces has been given to further elucidate these phenomena. An operational criterion for the width of interfaces is given in terms of molecular and physical arguments, and the properties of molecules inside phases and interfaces are discussed in terms of molecular arguments. In general, the properties of the interface become important when the molecules diffusing across are smaller than the width of the interface. Equilibrium partitioning, Donnan phenomena, and electrochemical potentials at interfaces are also discussed in detail. The mathematical expressions for modeling transport across interfaces are discussed in detail. These describe a practical and detailed model for transport across interfaces. For molecules smaller than the width of the interface, this includes a detailed model for diffusion inside the interface. Last, the question of the time scale for phase formation and equilibration in biological systems is discussed.

[Dendroclimatic potentials for the tree rings of Huangshan pine (Pinus taiwanensis ) at Xiaolinhai in the western Dabie Mountains, China].

PubMed

Peng, Jian-Feng; Li, Guo-Dong; Li, Ling-Ling

2014-07-01

By using the dendrochronology research methods, this paper developed the 1915-2011 tree ring-width standard chronology of the Huangshan pine (Pinus taiwanesis) at the north slope of western Dabie Mountains in the junction of Hubei, Henan and Anhui provinces. High mean sensitivity (MS) indicated that there was conspicuous high-frequency climate signals and high first-order autocorrelation (AC) showed there were significant lag-effects of tree previous growth. The higher signal-to-noise ratio (SNR) and expressed population signal (EPS) indicated that the trees had high levels of common climate signals. Correlations between the tree ring-width standard chronology and climatic factors (1959-2011) revealed the significant influences of temperature, precipitation and relative humidity on the tree width growth of Huangshan pine by the end of growing season (September and October). Significant positive correlations were found between the tree-ring indices and the Palmer drought severity index (PDSI) of current September and October. In conclusion, the combination of water and heat of September and October is the major effect factor for the growth of Huangshan pine in western Dabie Mountains.

Comparison of the large muscle group widths of the pelvic limb in seven breeds of dogs.

PubMed

Sabanci, Seyyid Said; Ocal, Mehmet Kamil

2018-05-14

Orthopaedic diseases are common in the pelvic limbs of dogs, and reference values for large muscle groups of the pelvic limb may aid in diagnosis such diseases. As such, the objective of this study was to compare the large muscle groups of the pelvic limb in seven breeds of dogs. A total of 126 dogs from different breeds were included, and the widths of the quadriceps, hamstring and gastrocnemius muscles were measured from images of the lateral radiographies. The width of the quadriceps was not different between the breeds, but the widths of the hamstring and gastrocnemius muscles were significantly different between the breeds. The widest hamstring and gastrocnemius muscles were seen in the Rottweilers and the Boxers, respectively. The narrowest hamstring and gastrocnemius muscles were seen in the Belgian Malinois and the Golden retrievers, respectively. All ratios between the measured muscles differed significantly between the breeds. Doberman pinschers and Belgian Malinois had the highest ratio of gastrocnemius width:hamstring width. Doberman pinschers had also the highest ratio of quadriceps width:hamstring width. German shepherds had the highest ratio of gastrocnemius width:quadriceps width. The lowest ratios of quadriceps width:hamstring width were determined in the German shepherds. The ratios of the muscle widths may be used as reference values to assess muscular atrophy or hypertrophy in cases of bilateral or unilateral orthopaedic diseases of the pelvic limbs. Further studies are required to determine the widths and ratios of the large muscle groups of the pelvic limbs in other dog breeds. © 2018 Blackwell Verlag GmbH.