Science.gov

Sample records for active input current

  1. Input-current shaped ac to dc converters

    NASA Technical Reports Server (NTRS)

    1986-01-01

    The problem of achieving near unity power factor while supplying power to a dc load from a single phase ac source of power is examined. Power processors for this application must perform three functions: input current shaping, energy storage, and output voltage regulation. The methods available for performing each of these three functions are reviewed. Input current shaping methods are either active or passive, with the active methods divided into buck-like and boost-like techniques. In addition to large reactances, energy storage methods include resonant filters, active filters, and active storage schemes. Fast voltage regulation can be achieved by post regulation or by supplementing the current shaping topology with an extra switch. Some indications of which methods are best suited for particular applications concludes the discussion.

  2. Input current shaped ac-to-dc converters

    NASA Technical Reports Server (NTRS)

    1985-01-01

    Input current shaping techniques for ac-to-dc converters were investigated. Input frequencies much higher than normal, up to 20 kHz were emphasized. Several methods of shaping the input current waveform in ac-to-dc converters were reviewed. The simplest method is the LC filter following the rectifier. The next simplest method is the resistor emulation approach in which the inductor size is determined by the converter switching frequency and not by the line input frequency. Other methods require complicated switch drive algorithms to construct the input current waveshape. For a high-frequency line input, on the order of 20 kHz, the simple LC cannot be discarded so peremptorily, since the inductor size can be compared with that for the resistor emulation method. In fact, since a dc regulator will normally be required after the filter anyway, the total component count is almost the same as for the resistor emulation method, in which the filter is effectively incorporated into the regulator.

  3. RF Input Power Couplers for High Current SRF Applications

    SciTech Connect

    Khan, V. F.; Anders, W.; Burrill, Andrew; Knobloch, Jens; Kugeler, Oliver; Neumann, Axel; Wang, Haipeng

    2014-12-01

    High current SRF technology is being explored in present day accelerator science. The bERLinPro project is presently being built at HZB to address the challenges involved in high current SRF machines with the goal of generating and accelerating a 100 mA electron beam to 50 MeV in continuous wave (cw) mode at 1.3 GHz. One of the main challenges in this project is that of handling the high input RF power required for the photo-injector as well as booster cavities where there is no energy recovery process. A high power co-axial input power coupler is being developed to be used for the photo-injector and booster cavities at the nominal beam current. The coupler is based on the KEK–cERL design and has been modified to minimise the penetration of the coupler tip in the beam pipe without compromising on beam-power coupling (Qext ~105). Herein we report on the RF design of the high power (115 kW per coupler, dual couplers per cavity) bERLinPro (BP) coupler along with initial results on thermal calculations. We summarise the RF conditioning of the TTF-III couplers (modified for cw operation) performed in the past at BESSY/HZB. A similar conditioning is envisaged in the near future for the low current SRF photo-injector and the bERLinPro main linac cryomodule.

  4. Periodontal tactile input activates the prefrontal cortex

    PubMed Central

    Higaki, Nobuaki; Goto, Takaharu; Ichikawa, Tetsuo

    2016-01-01

    The prefrontal cortex (PFC) plays a role in complex cognitive behavioural planning, decision-making, and social behaviours. However, the effects of sensory integration during motor tasks on PFC activation have not been studied to date. Therefore, we investigated the effect of peripheral sensory information and external information on PFC activation using functional near-infrared spectroscopy (fNIRS). Cerebral blood flow (CBF) was increased around bilateral Brodmann areas 46 and 10 during visual and auditory information integration during an occlusal force (biting) task. After local anesthesia, CBF values were significantly decreased, but occlusal force was similar. In conclusion, the effects of peripheral sensory information from the periodontal ligament and external information have minimal impacts on occlusal force maintenance but are important for PFC activation. PMID:27833164

  5. Somatosensory Anticipatory Alpha Activity Increases to Suppress Distracting Input

    ERIC Educational Resources Information Center

    Haegens, Saskia; Luther, Lisa; Jensen, Ole

    2012-01-01

    Effective processing of sensory input in daily life requires attentional selection and amplification of relevant input and, just as importantly, attenuation of irrelevant information. It has been proposed that top-down modulation of oscillatory alpha band activity (8-14 Hz) serves to allocate resources to various regions, depending on task…

  6. Characteristics of AZO thin films prepared at various Al target input current deposited on PET substrate

    NASA Astrophysics Data System (ADS)

    Kim, Yun-Hae; Park, Chang-Wook; Lee, Jin-Woo; Lee, Dong Myung

    2015-03-01

    Transparent conductive oxide is a thin film to be used in numerous applications throughout the industry in general. Transparent electrode materials used in these industries are in need of light transmittance with excellent high and low electrical characteristics, substances showing the most excellent physical properties while satisfying all the characteristics such as indium tin oxide film. However, reserves of indium are very small, there is an environmental pollution problem. So the study of zinc oxide (ZnO) is actively carried out in an alternative material. This study analyzed the characteristics by using a direct current (DC) magnetron sputtering system. The electric and optical properties of these films were studied by Hall measurement and optical spectroscopy, respectively. When the Al target input current is 2 mA and 4 mA, it demonstrates about 80% transmittance in the range of the visible spectrum. Also, when Al target input current was 6 mA, sheet resistance was the smallest on PET substrate. The minimum resistivity is 3.96×10-3 ohm/sq.

  7. State-dependent modulation of amygdala inputs by dopamine-induced enhancement of sodium currents in layer V entorhinal cortex.

    PubMed

    Rosenkranz, J Amiel; Johnston, Daniel

    2007-06-27

    Interaction between the entorhinal cortex (EC) and basolateral amygdala (BLA) may be a fundamental component in the consolidation of many forms of affective memory, such as inhibitory avoidance. Dopamine (DA) in the EC is necessary for, and may facilitate, this form of learning. This effect of DA on affective behaviors may be accomplished in part through modulation of amygdala inputs. Although it is known that DA can modulate neuronal activity in the EC, it is not known whether DA modulates inputs from the BLA. In this study, we used in vitro patch-clamp recordings and Ca2+ imaging of layer V neurons in the rat lateral EC to determine whether DA modulates the integration of inputs from the BLA and the mechanism for this modulation. We found that DA exerted actions that depended on the neuronal state. Near resting membrane potentials, DA suppressed integration of inputs, whereas at depolarized potentials, DA enhanced integration. DA enhanced the integration by a D2-mediated enhancement of Na+ currents, via phospholipase C. These experiments demonstrate that DA can exert actions in the EC that depend on the membrane voltage. This effect of DA may affect a wide range of inputs. Functionally, by enhancement of amygdala inputs that arrive in concert with other inputs, or during depolarized states, DA can facilitate the impact of affect on memory in a subset of conditions.

  8. Critical carbon input to maintain current soil organic carbon stocks in global wheat systems

    NASA Astrophysics Data System (ADS)

    Wang, Guocheng; Luo, Zhongkui; Han, Pengfei; Chen, Huansheng; Xu, Jingjing

    2016-01-01

    Soil organic carbon (SOC) dynamics in croplands is a crucial component of global carbon (C) cycle. Depending on local environmental conditions and management practices, typical C input is generally required to reduce or reverse C loss in agricultural soils. No studies have quantified the critical C input for maintaining SOC at global scale with high resolution. Such information will provide a baseline map for assessing soil C dynamics under potential changes in management practices and climate, and thus enable development of management strategies to reduce C footprint from farm to regional scales. We used the soil C model RothC to simulate the critical C input rates needed to maintain existing soil C level at 0.1° × 0.1° resolution in global wheat systems. On average, the critical C input was estimated to be 2.0 Mg C ha‑1 yr‑1, with large spatial variability depending on local soil and climatic conditions. Higher C inputs are required in wheat system of central United States and western Europe, mainly due to the higher current soil C stocks present in these regions. The critical C input could be effectively estimated using a summary model driven by current SOC level, mean annual temperature, precipitation, and soil clay content.

  9. Effects of Age of English Exposure, Current Input/Output, and Grade on Bilingual Language Performance

    ERIC Educational Resources Information Center

    Bedore, Lisa M.; Pena, Elizabeth D.; Griffin, Zenzi M.; Hixon, J. Gregory

    2016-01-01

    This study evaluates the effects of Age of Exposure to English (AoEE) and Current Input/Output on language performance in a cross-sectional sample of Spanish-English bilingual children. First- (N = 586) and third-graders (N = 298) who spanned a wide range of bilingual language experience participated. Parents and teachers provided information…

  10. Active control of multi-input hydraulic journal bearing system

    NASA Astrophysics Data System (ADS)

    Chuang, Jen-Chen; Chen, Chi-Yin; Tu, Jia-Ying

    2016-09-01

    Because of the advantages of high accuracy, high capacity, and low friction, the development of hydrostatic bearing for machine tool receives significant attention in the last decades. The mechanics and mechanical design of hydrostatic journal bearing with capillary restrictors has been discussed in literature. However, pragmatically, the undesired loading effects of cutting force tend to result in resonance and instability of the rotor and damage the shaft during operation. Therefore, multi-input, active flow control using state feedback design is proposed in this paper. To this purpose, the proportional pressure valves are added to the hydraulic system as active control devices, and the linearised models of the bearing and valve are discussed and identified. Simulation and experimental work is conducted to verify the proposed active control and parameter identification techniques. The results show that the unbalance responses of the rotor are reduced by the proposed state feedback controller, which is able to regulate the flow pressure effectively, thus enhancing the stability and accuracy of the hydraulic journal bearing.

  11. Exploring storm time ring current formation and response on the energy input

    NASA Astrophysics Data System (ADS)

    Ilie, Raluca

    While extensive research has been made over the last decades regarding the storm-time dynamics, there are still unanswered questions regarding the ring current formation and plasmasphere evolution, specifically about the ring current response on the energy input. Large-scale data analysis and global magnetospheric simulations provide complementary alternatives for exploring highly complex coupling of the solar wind-ionosphere-magnetosphere system. Superposed Epoch analysis of intense storms data suggests that a distinct time stamp is needed in order to resolve certain solar wind features. However, when it conies to hot proton at geosynchronous orbit, the choice of reference time primarily matters to accurately describe the size of peaks, while the presence and time evolution is unaltered by it. Examination of the role the transient spikes in the solar wind parameters play in the development of magnetic storms, reveals that changes in the energy input produce a nonlinear response of the inner magnetosphere. While initial increases in the energy input enhance the magnetospheric response, as the power transferred to the system is increased, the growth of the ring current is stalled and a saturation limits sets in. A threshold in the energy input is necessary for the ring current to develop, while the short time scale fluctuations in the solar wind parameters did not have a significant contribution. This implies the existence of an internal feedback mechanism as the magnetosphere acts as a low-pass filter of the IMF, limiting the energy flow in the magnetosphere. Further, the main characteristic in determining IMF Bz fluctuation periodicity transfer of solar wind mass and energy to the inner magnetosphere, is the peak signal to noise ratio in the power spectrum of the input parameter, suggesting that a ratio of 10 is needed in order to trigger a similar periodicity in the magnetosphere response. Theoretical and numerical modifications to an inner magnetosphere model

  12. A-current and type I/type II transition determine collective spiking from common input.

    PubMed

    Barreiro, Andrea K; Thilo, Evan L; Shea-Brown, Eric

    2012-09-01

    The mechanisms and impact of correlated, or synchronous, firing among pairs and groups of neurons are under intense investigation throughout the nervous system. A ubiquitous circuit feature that can give rise to such correlations consists of overlapping, or common, inputs to pairs and populations of cells, leading to common spike train responses. Here, we use computational tools to study how the transfer of common input currents into common spike outputs is modulated by the physiology of the recipient cells. We focus on a key conductance, g(A), for the A-type potassium current, which drives neurons between "type II" excitability (low g(A)), and "type I" excitability (high g(A)). Regardless of g(A), cells transform common input fluctuations into a tendency to spike nearly simultaneously. However, this process is more pronounced at low g(A) values. Thus, for a given level of common input, type II neurons produce spikes that are relatively more correlated over short time scales. Over long time scales, the trend reverses, with type II neurons producing relatively less correlated spike trains. This is because these cells' increased tendency for simultaneous spiking is balanced by an anticorrelation of spikes at larger time lags. These findings extend and interpret prior findings for phase oscillators to conductance-based neuron models that cover both oscillatory (superthreshold) and subthreshold firing regimes. We demonstrate a novel implication for neural signal processing: downstream cells with long time constants are selectively driven by type I cell populations upstream and those with short time constants by type II cell populations. Our results are established via high-throughput numerical simulations and explained via the cells' filtering properties and nonlinear dynamics.

  13. Sensory-evoked perturbations of locomotor activity by sparse sensory input: a computational study

    PubMed Central

    Brownstone, Robert M.

    2015-01-01

    Sensory inputs from muscle, cutaneous, and joint afferents project to the spinal cord, where they are able to affect ongoing locomotor activity. Activation of sensory input can initiate or prolong bouts of locomotor activity depending on the identity of the sensory afferent activated and the timing of the activation within the locomotor cycle. However, the mechanisms by which afferent activity modifies locomotor rhythm and the distribution of sensory afferents to the spinal locomotor networks have not been determined. Considering the many sources of sensory inputs to the spinal cord, determining this distribution would provide insights into how sensory inputs are integrated to adjust ongoing locomotor activity. We asked whether a sparsely distributed set of sensory inputs could modify ongoing locomotor activity. To address this question, several computational models of locomotor central pattern generators (CPGs) that were mechanistically diverse and generated locomotor-like rhythmic activity were developed. We show that sensory inputs restricted to a small subset of the network neurons can perturb locomotor activity in the same manner as seen experimentally. Furthermore, we show that an architecture with sparse sensory input improves the capacity to gate sensory information by selectively modulating sensory channels. These data demonstrate that sensory input to rhythm-generating networks need not be extensively distributed. PMID:25673740

  14. Input Shaping enhanced Active Disturbance Rejection Control for a twin rotor multi-input multi-output system (TRMS).

    PubMed

    Yang, Xiaoyan; Cui, Jianwei; Lao, Dazhong; Li, Donghai; Chen, Junhui

    2016-05-01

    In this paper, a composite control based on Active Disturbance Rejection Control (ADRC) and Input Shaping is presented for TRMS with two degrees of freedom (DOF). The control tasks consist of accurately tracking desired trajectories and obtaining disturbance rejection in both horizontal and vertical planes. Due to un-measurable states as well as uncertainties stemming from modeling uncertainty and unknown disturbance torques, ADRC is employed, and feed-forward Input Shaping is used to improve the dynamical response. In the proposed approach, because the coupling effects are maintained in controller derivation, there is no requirement to decouple the TRMS into horizontal and vertical subsystems, which is usually performed in the literature. Finally, the proposed method is implemented on the TRMS platform, and the results are compared with those of PID and ADRC in a similar structure. The experimental results demonstrate the effectiveness of the proposed method. The operation of the controller allows for an excellent set-point tracking behavior and disturbance rejection with system nonlinearity and complex coupling conditions.

  15. Orexin-dependent activation of layer VIb enhances cortical network activity and integration of non-specific thalamocortical inputs.

    PubMed

    Hay, Y Audrey; Andjelic, Sofija; Badr, Sammy; Lambolez, Bertrand

    2015-11-01

    Neocortical layer VI is critically involved in thalamocortical activity changes during the sleep/wake cycle. It receives dense projections from thalamic nuclei sensitive to the wake-promoting neuropeptides orexins, and its deepest part, layer VIb, is the only cortical lamina reactive to orexins. This convergence of wake-promoting inputs prompted us to investigate how layer VIb can modulate cortical arousal, using patch-clamp recordings and optogenetics in rat brain slices. We found that the majority of layer VIb neurons were excited by nicotinic agonists and orexin through the activation of nicotinic receptors containing α4-α5-β2 subunits and OX2 receptor, respectively. Specific effects of orexin on layer VIb neurons were potentiated by low nicotine concentrations and we used this paradigm to explore their intracortical projections. Co-application of nicotine and orexin increased the frequency of excitatory post-synaptic currents in the ipsilateral cortex, with maximal effect in infragranular layers and minimal effect in layer IV, as well as in the contralateral cortex. The ability of layer VIb to relay thalamocortical inputs was tested using photostimulation of channelrhodopsin-expressing fibers from the orexin-sensitive rhomboid nucleus in the parietal cortex. Photostimulation induced robust excitatory currents in layer VIa neurons that were not pre-synaptically modulated by orexin, but exhibited a delayed, orexin-dependent, component. Activation of layer VIb by orexin enhanced the reliability and spike-timing precision of layer VIa responses to rhomboid inputs. These results indicate that layer VIb acts as an orexin-gated excitatory feedforward loop that potentiates thalamocortical arousal.

  16. Noradrenergic and GABAB Receptor Activation Differentially Modulate Inputs to the Premotor Nucleus RA in Zebra Finches

    PubMed Central

    Sizemore, Max; Perkel, David J.

    2008-01-01

    Neuromodulators can rapidly modify neural circuits, altering behavior. Songbirds provide an excellent system for studying the role of neuromodulation in modifying circuits that underlie behavior because song learning and production are mediated by a discrete set of interconnected nuclei. We examined the neuromodulatory effects of noradrenergic and GABAB receptor activation on synaptic inputs to the premotor robust nucleus of the arcopallium (RA) in zebra finches using whole cell voltage-clamp recording in vitro. In adults, norepinephrine strongly reduced input from the lateral magnocellular nucleus of the anterior nidopallium (LMAN) but only slightly reduced the input from nucleus HVC (proper name), the excitatory input from axon collaterals of other RA neurons, and input from GABAergic interneurons. The effect of norepinephrine was mimicked by the α2 adrenoceptor agonist UK14,304 and blocked by the α2 antagonist yohimbine. Conversely, the GABAB receptor agonist baclofen strongly decreased HVC, collateral, and GABAergic inputs to RA neurons while causing little reduction in the LMAN input. In juveniles undergoing song learning, norepinephrine reduced the LMAN input, caused only a small reduction in the HVC input, and greatly reduced the collateral and GABAergic inputs. Baclofen caused similar results in juvenile and adult birds, reducing HVC, collateral, and GABAergic inputs significantly more than the LMAN input. Significant increases in paired-pulse ratio accompanied all reductions in synaptic transmission, suggesting a presynaptic locus. The reduction in the LMAN input by norepinephrine may be important for mediating changes in song elicited by different social contexts and is well-placed to play a role in song learning. PMID:18463188

  17. Active control of sound fields in elastic cylinders by vibrational inputs

    NASA Technical Reports Server (NTRS)

    Jones, J. D.; Fuller, C. R.

    1987-01-01

    An experiment is performed to study the mechanisms of active control of sound fields in elastic cylinders via vibrational outputs. In the present method of control, a vibrational force input was used as the secondary control input to reduce the radiated acoustic field. For the frequencies considered, the active vibration technique provided good global reduction of interior sound even though only one actuator was used.

  18. The control of preoptic aromatase activity by afferent inputs in Japanese quail.

    PubMed

    Absil, P; Baillien, M; Ball, G F; Panzica, G C; Balthazart, J

    2001-11-01

    This review summarizes current knowledge on the mechanisms that control aromatase activity in the quail preoptic area, a brain region that plays a key role in the control of reproduction. Aromatase and aromatase mRNA synthesis in the preoptic area are enhanced by testosterone and its metabolite estradiol, but estradiol receptors of the alpha subtype are not regularly colocalized with aromatase. Estradiol receptors of the beta subtype are present in the preoptic area but it is not yet known whether these receptors are colocalized with aromatase. The regulation by estrogen of aromatase activity may be, in part, trans-synaptically mediated, in a manner that is reminiscent of the ways in which steroids control the activity of gonadotropic hormone releasing hormone neurons. Aromatase-immunoreactive neurons are surrounded by dense networks of vasotocin-immunoreactive and tyrosine hydroxylase-immunoreactive fibers and punctate structures. These inputs are in part steroid-sensitive and could therefore mediate the effects of steroids on aromatase activity. In vivo pharmacological experiments indicate that catecholaminergic depletions significantly affect aromatase activity presumably by modulating aromatase transcription. In addition, in vitro studies on brain homogenates or on preoptic-hypothalamic explants show that aromatase activity can be rapidly modulated by a variety of dopaminergic compounds. These effects do not appear to be mediated by the membrane dopamine receptors and could involve changes in the phosphorylation state of the enzyme. Together, these results provide converging evidence for a direct control of aromatase activity by catecholamines consistent with the anatomical data indicating the presence of a catecholaminergic innervation of aromatase cells. These dopamine-induced changes in aromatase activity are observed after several hours or days and presumably result from changes in aromatase transcription but rapid non-genomic controls have also been

  19. The Roles of Structured Input Activities in Processing Instruction and the Kinds of Knowledge They Promote

    ERIC Educational Resources Information Center

    Marsden, Emma; Chen, Hsin-Ying

    2011-01-01

    This study aimed to isolate the effects of the two input activities in Processing Instruction: referential activities, which force learners to focus on a form and its meaning, and affective activities, which contain exemplars of the target form and require learners to process sentence meaning. One hundred and twenty 12-year-old Taiwanese learners…

  20. Ecosystem consequences of changing inputs of terrestrial dissolved organic matter to lakes: current knowledge and future challenges

    USGS Publications Warehouse

    Solomon, Christopher T.; Jones, Stuart E.; Weidel, Brian C.; Buffam, Ishi; Fork, Megan L; Karlsson, Jan; Larsen, Soren; Lennon, Jay T.; Read, Jordan S.; Sadro, Steven; Saros, Jasmine E.

    2015-01-01

    Lake ecosystems and the services that they provide to people are profoundly influenced by dissolved organic matter derived from terrestrial plant tissues. These terrestrial dissolved organic matter (tDOM) inputs to lakes have changed substantially in recent decades, and will likely continue to change. In this paper, we first briefly review the substantial literature describing tDOM effects on lakes and ongoing changes in tDOM inputs. We then identify and provide examples of four major challenges which limit predictions about the implications of tDOM change for lakes, as follows: First, it is currently difficult to forecast future tDOM inputs for particular lakes or lake regions. Second, tDOM influences ecosystems via complex, interacting, physical-chemical-biological effects and our holistic understanding of those effects is still rudimentary. Third, non-linearities and thresholds in relationships between tDOM inputs and ecosystem processes have not been well described. Fourth, much understanding of tDOM effects is built on comparative studies across space that may not capture likely responses through time. We conclude by identifying research approaches that may be important for overcoming those challenges in order to provide policy- and management-relevant predictions about the implications of changing tDOM inputs for lakes.

  1. Active integration of glutamatergic input to the inferior olive generates bidirectional postsynaptic potentials

    PubMed Central

    Garden, Derek L. F.; Rinaldi, Arianna

    2016-01-01

    Key points We establish experimental preparations for optogenetic investigation of glutamatergic input to the inferior olive.Neurones in the principal olivary nucleus receive monosynaptic extra‐somatic glutamatergic input from the neocortex.Glutamatergic inputs to neurones in the inferior olive generate bidirectional postsynaptic potentials (PSPs), with a fast excitatory component followed by a slower inhibitory component.Small conductance calcium‐activated potassium (SK) channels are required for the slow inhibitory component of glutamatergic PSPs and oppose temporal summation of inputs at intervals ≤ 20 ms.Active integration of synaptic input within the inferior olive may play a central role in control of olivo‐cerebellar climbing fibre signals. Abstract The inferior olive plays a critical role in motor coordination and learning by integrating diverse afferent signals to generate climbing fibre inputs to the cerebellar cortex. While it is well established that climbing fibre signals are important for motor coordination, the mechanisms by which neurones in the inferior olive integrate synaptic inputs and the roles of particular ion channels are unclear. Here, we test the hypothesis that neurones in the inferior olive actively integrate glutamatergic synaptic inputs. We demonstrate that optogenetically activated long‐range synaptic inputs to the inferior olive, including projections from the motor cortex, generate rapid excitatory potentials followed by slower inhibitory potentials. Synaptic projections from the motor cortex preferentially target the principal olivary nucleus. We show that inhibitory and excitatory components of the bidirectional synaptic potentials are dependent upon AMPA (GluA) receptors, are GABAA independent, and originate from the same presynaptic axons. Consistent with models that predict active integration of synaptic inputs by inferior olive neurones, we find that the inhibitory component is reduced by blocking large conductance

  2. Active processing of spatio-temporal input patterns in silicon dendrites.

    PubMed

    Wang, Yingxue; Liu, Shih-Chii

    2013-06-01

    Capturing the functionality of active dendritic processing into abstract mathematical models will help us to understand the role of complex biophysical neurons in neuronal computation and to build future useful neuromorphic analog Very Large Scale Integrated (aVLSI) neuronal devices. Previous work based on an aVLSI multi-compartmental neuron model demonstrates that the compartmental response in the presence of either of two widely studied classes of active mechanisms, is a nonlinear sigmoidal function of the degree of either input temporal synchrony OR input clustering level. Using the same silicon model, this work expounds the interaction between both active mechanisms in a compartment receiving input patterns of varying temporal AND spatial clustering structure and demonstrates that this compartmental response can be captured by a combined sigmoid and radial-basis function over both input dimensions. This paper further shows that the response to input spatio-temporal patterns in a one-dimensional multi-compartmental dendrite, can be described by a radial-basis like function of the degree of temporal synchrony between the inter-compartmental inputs.

  3. The 'window' component of the low threshold Ca2+ current produces input signal amplification and bistability in cat and rat thalamocortical neurones.

    PubMed Central

    Williams, S R; Tóth, T I; Turner, J P; Hughes, S W; Crunelli, V

    1997-01-01

    1. The mechanism underlying a novel form of input signal amplification and bistability was investigated by intracellular recording in rat and cat thalamocortical (TC) neurones maintained in slices and by computer simulation with a biophysical model of these neurones. 2. In a narrow membrane potential range centred around -60 mV, TC neurones challenged with small (10-50 pA), short (50-200 ms) current steps produced a stereotyped, large amplitude hyperpolarization (> 20 mV) terminated by the burst firing of action potentials, leading to amplification of the duration and amplitude of the input signal, that is hereafter referred to as input signal amplification. 3. In the same voltage range centred around -60 mV, single evoked EPSPs and IPSPs also produced input signal amplification, indicating that this behaviour can be triggered by physiologically relevant stimuli. In addition, a novel, intrinsic, low frequency oscillation, characterized by a peculiar voltage dependence of its frequency and by the presence of plateau potentials on the falling phase of low threshold Ca2+ potentials, was recorded. 4. Blockade of pure Na+ and K+ currents by tetrodotoxin (1 microM) and Ba2+ (0.1-2.0 mM), respectively, did not affect input signal amplification, neither did the presence of excitatory or inhibitory amino acid receptor antagonists in the perfusion medium. 5. A decrease in [Ca2+]o (from 2 to 1 mM) and an increase in [Mg2+]o (from 2 to 10 mM), or the addition of Ni2+ (2-3 mM), abolished input signal amplification, while an increase in [Ca2+]o (from 2 to 8 mM) generated this behaviour in neurones where it was absent in control conditions. These results indicate the involvement of the low threshold Ca2+ current (IT) in input signal amplification, since the other Ca2+ currents of TC neurones are activated at potentials more positive than -40 mV. 6. Blockade of the slow inward mixed cationic current (Ih) by 4-(N-ethyl-N-phenylamino)-1,2-dimethyl-6-(methylamino

  4. Higher-order correlations in common input shapes the output spiking activity of a neural population

    NASA Astrophysics Data System (ADS)

    Montangie, Lisandro; Montani, Fernando

    2017-04-01

    Recent neurophysiological experiments suggest that populations of neurons use a computational scheme in which spike timing is regulated by common non-Gaussian inputs across neurons. The presence of beyond-pairwise correlations in the neuronal inputs and the spiking outputs following a non-Gaussian statistics elicits the need of developing a new theoretical framework taking into account the complexity of synchronous activity patterns. To this end, we quantify the amount of higher-order correlations in the common neuronal inputs and outputs of a population of neurons. We provide a novel formalism, of easy numerical implementation, that can capture the subtle changes of the inputs heterogeneities. Within our approach, correlations across neurons arise from q-Gaussian inputs into threshold neurons and higher-order correlations in the spiking outputs activity are quantified by the parameter q. We present an exhaustive analysis of how input statistics are transformed in this threshold process into output statistics, and we show under which conditions higher-order correlations can lead to either bigger or smaller number of synchronized spikes in the neural population outputs.

  5. Inferring electric fields and currents from ground magnetometer data - A test with theoretically derived inputs

    NASA Technical Reports Server (NTRS)

    Wolf, R. A.; Kamide, Y.

    1983-01-01

    Advanced techniques considered by Kamide et al. (1981) seem to have the potential for providing observation-based high time resolution pictures of the global ionospheric current and electric field patterns for interesting events. However, a reliance on the proposed magnetogram-inversion schemes for the deduction of global ionospheric current and electric field patterns requires proof that reliable results are obtained. 'Theoretical' tests of the accuracy of the magnetogram inversion schemes have, therefore, been considered. The present investigation is concerned with a test, involving the developed KRM algorithm and the Rice Convection Model (RCM). The test was successful in the sense that there was overall agreement between electric fields and currents calculated by the RCM and KRM schemes.

  6. A Highly Linear and Wide Input Range Four-Quadrant CMOS Analog Multiplier Using Active Feedback

    NASA Astrophysics Data System (ADS)

    Huang, Zhangcai; Jiang, Minglu; Inoue, Yasuaki

    Analog multipliers are one of the most important building blocks in analog signal processing circuits. The performance with high linearity and wide input range is usually required for analog four-quadrant multipliers in most applications. Therefore, a highly linear and wide input range four-quadrant CMOS analog multiplier using active feedback is proposed in this paper. Firstly, a novel configuration of four-quadrant multiplier cell is presented. Its input dynamic range and linearity are improved significantly by adding two resistors compared with the conventional structure. Then based on the proposed multiplier cell configuration, a four-quadrant CMOS analog multiplier with active feedback technique is implemented by two operational amplifiers. Because of both the proposed multiplier cell and active feedback technique, the proposed multiplier achieves a much wider input range with higher linearity than conventional structures. The proposed multiplier was fabricated by a 0.6µm CMOS process. Experimental results show that the input range of the proposed multiplier can be up to 5.6Vpp with 0.159% linearity error on VX and 4.8Vpp with 0.51% linearity error on VY for ±2.5V power supply voltages, respectively.

  7. Amyloid β Peptide-Induced Changes in Prefrontal Cortex Activity and Its Response to Hippocampal Input.

    PubMed

    Flores-Martínez, Ernesto; Peña-Ortega, Fernando

    2017-01-01

    Alterations in prefrontal cortex (PFC) function and abnormalities in its interactions with other brain areas (i.e., the hippocampus) have been related to Alzheimer Disease (AD). Considering that these malfunctions correlate with the increase in the brain's amyloid beta (Aβ) peptide production, here we looked for a causal relationship between these pathognomonic signs of AD. Thus, we tested whether or not Aβ affects the activity of the PFC network and the activation of this cortex by hippocampal input stimulation in vitro. We found that Aβ application to brain slices inhibits PFC spontaneous network activity as well as PFC activation, both at the population and at the single-cell level, when the hippocampal input is stimulated. Our data suggest that Aβ can contribute to AD by disrupting PFC activity and its long-range interactions throughout the brain.

  8. Amyloid β Peptide-Induced Changes in Prefrontal Cortex Activity and Its Response to Hippocampal Input

    PubMed Central

    Flores-Martínez, Ernesto

    2017-01-01

    Alterations in prefrontal cortex (PFC) function and abnormalities in its interactions with other brain areas (i.e., the hippocampus) have been related to Alzheimer Disease (AD). Considering that these malfunctions correlate with the increase in the brain's amyloid beta (Aβ) peptide production, here we looked for a causal relationship between these pathognomonic signs of AD. Thus, we tested whether or not Aβ affects the activity of the PFC network and the activation of this cortex by hippocampal input stimulation in vitro. We found that Aβ application to brain slices inhibits PFC spontaneous network activity as well as PFC activation, both at the population and at the single-cell level, when the hippocampal input is stimulated. Our data suggest that Aβ can contribute to AD by disrupting PFC activity and its long-range interactions throughout the brain. PMID:28127312

  9. Serotonin activates catecholamine neurons in the solitary tract nucleus by increasing spontaneous glutamate inputs.

    PubMed

    Cui, Ran Ji; Roberts, Brandon L; Zhao, Huan; Zhu, Mingyan; Appleyard, Suzanne M

    2012-11-14

    Serotonin (5-HT) is a critical neurotransmitter in the control of autonomic functions. 5-HT(3) receptors participate in vagal afferent feedback to decrease food intake and regulate cardiovascular reflexes; however, the phenotype of the solitary tract nucleus (NTS) neurons involved is not known. A(2)/C(2) catecholamine (CA) neurons in the NTS are directly activated by visceral afferents and are important for the control of food intake and cardiovascular function, making them good candidates to respond to and mediate the effects of serotonin at the level of the NTS. This study examines serotonin's effects on NTS-CA neurons using patch-clamp techniques and transgenic mice expressing an enhanced green fluorescent protein driven by the tyrosine hydroxylase (TH) promoter (TH-EGFP) to identify catecholamine neurons. Serotonin increased the frequency of spontaneous glutamate excitatory postsynaptic currents (sEPSCs) in >90% of NTS-TH-EGFP neurons, an effect blocked by the 5-HT(3) receptor antagonist ondansetron and mimicked by the 5-HT(3) receptor agonists SR5227 and mCPBG. In contrast, 5-HT(3) receptor agonists increased sEPSCs on a minority (<30%) of non-TH neurons. 5-HT(3) receptor agonists increased the frequency, but not the amplitude, of mini-EPSCs, suggesting that their actions are presynaptic. 5-HT(3) receptor agonists increased the firing rate of TH-EGFP neurons, an effect dependent on the increased spontaneous glutamate inputs as it was blocked by the ionotropic glutamate antagonist NBQX, but independent of visceral afferent activation. These results demonstrate a cellular mechanism by which serotonin activates NTS-TH neurons and suggest a pathway by which it can increase catecholamine release in target regions to modulate food intake, motivation, stress, and cardiovascular function.

  10. Serotonin Activates Catecholamine Neurons in the Solitary Tract Nucleus by Increasing Spontaneous Glutamate Inputs

    PubMed Central

    Cui, Ran Ji; Roberts, Brandon L.; Zhao, Huan; Zhu, Mingyan

    2012-01-01

    Serotonin (5-HT) is a critical neurotransmitter in the control of autonomic functions. 5-HT3 receptors participate in vagal afferent feedback to decrease food intake and regulate cardiovascular reflexes; however, the phenotype of the solitary tract nucleus (NTS) neurons involved is not known. A2/C2 catecholamine (CA) neurons in the NTS are directly activated by visceral afferents and are important for the control of food intake and cardiovascular function, making them good candidates to respond to and mediate the effects of serotonin at the level of the NTS. This study examines serotonin's effects on NTS-CA neurons using patch-clamp techniques and transgenic mice expressing an enhanced green fluorescent protein driven by the tyrosine hydroxylase (TH) promoter (TH-EGFP) to identify catecholamine neurons. Serotonin increased the frequency of spontaneous glutamate excitatory postsynaptic currents (sEPSCs) in >90% of NTS-TH-EGFP neurons, an effect blocked by the 5-HT3 receptor antagonist ondansetron and mimicked by the 5-HT3 receptor agonists SR5227 and mCPBG. In contrast, 5-HT3 receptor agonists increased sEPSCs on a minority (<30%) of non-TH neurons. 5-HT3 receptor agonists increased the frequency, but not the amplitude, of mini-EPSCs, suggesting that their actions are presynaptic. 5-HT3 receptor agonists increased the firing rate of TH-EGFP neurons, an effect dependent on the increased spontaneous glutamate inputs as it was blocked by the ionotropic glutamate antagonist NBQX, but independent of visceral afferent activation. These results demonstrate a cellular mechanism by which serotonin activates NTS-TH neurons and suggest a pathway by which it can increase catecholamine release in target regions to modulate food intake, motivation, stress, and cardiovascular function. PMID:23152635

  11. Unity power factor converter based on a fuzzy controller and predictive input current.

    PubMed

    Bouafassa, Amar; Rahmani, Lazhar; Kessal, Abdelhalim; Babes, Badreddine

    2014-11-01

    This paper proposes analysis and control of a single-phase power factor corrector (PFC). The proposed control is capable of achieving a unity power factor for each DC link voltage or load fluctuation. The method under study is composed of two intelligent approaches, a fuzzy logic controller to ensure an output voltage at a suitable value and predictive current control. The fuzzy controller is used with minimum rules to attain a low cost. The method is verified and discussed through simulation on the MATLAB/Simulink platform. It presents high dynamic performance under various parameter changes. Moreover, in order to examine and evaluate the method in real-time, a test bench is built using dSPACE 1104. The implantation of the proposed method is very easy and flexible and allows for operation under parameter variations. Additionally, the obtained results are very significant.

  12. A robust interpolation procedure for producing tidal current ellipse inputs for regional and coastal ocean numerical models

    NASA Astrophysics Data System (ADS)

    Breivik, Øyvind; Alves, Jose Henrique; Greenslade, Diana; Horsburgh, Kevin; Swail, Val

    2017-03-01

    Regional and/or coastal ocean models can use tidal current harmonic forcing, together with tidal harmonic forcing along open boundaries in order to successfully simulate tides and tidal currents. These inputs can be freely generated using online open-access data, but the data produced are not always at the resolution required for regional or coastal models. Subsequent interpolation procedures can produce tidal current forcing data errors for parts of the world's coastal ocean where tidal ellipse inclinations and phases move across the invisible mathematical "boundaries" between 359° and 0° degrees (or 179° and 0°). In nature, such "boundaries" are in fact smooth transitions, but if these mathematical "boundaries" are not treated correctly during interpolation, they can produce inaccurate input data and hamper the accurate simulation of tidal currents in regional and coastal ocean models. These avoidable errors arise due to procedural shortcomings involving vector embodiment problems (i.e., how a vector is represented mathematically, for example as velocities or as coordinates). Automated solutions for producing correct tidal ellipse parameter input data are possible if a series of steps are followed correctly, including the use of Cartesian coordinates during interpolation. This note comprises the first published description of scenarios where tidal ellipse parameter interpolation errors can arise, and of a procedure to successfully avoid these errors when generating tidal inputs for regional and/or coastal ocean numerical models. We explain how a straightforward sequence of data production, format conversion, interpolation, and format reconversion steps may be used to check for the potential occurrence and avoidance of tidal ellipse interpolation and phase errors. This sequence is demonstrated via a case study of the M2 tidal constituent in the seas around Korea but is designed to be universally applicable. We also recommend employing tidal ellipse parameter

  13. 77 FR 55486 - Agency Information Collection Activities: Importer ID Input Record

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-10

    ... SECURITY U.S. Customs and Border Protection Agency Information Collection Activities: Importer ID Input Record AGENCY: U.S. Customs and Border Protection, Department of Homeland Security. ACTION: 30-Day Notice and request for comments; Extension of an existing collection of information. SUMMARY: U.S....

  14. Active sway control of a gantry crane using hybrid input shaping and PID control schemes

    NASA Astrophysics Data System (ADS)

    Mohd Tumari, M. Z.; Shabudin, L.; Zawawi, M. A.; Shah, L. H. Ahmad

    2013-12-01

    This project presents investigations into the development of hybrid input-shaping and PID control schemes for active sway control of a gantry crane system. The application of positive input shaping involves a technique that can reduce the sway by creating a common signal that cancels its own vibration and used as a feed-forward control which is for controlling the sway angle of the pendulum, while the proportional integral derivative (PID) controller is used as a feedback control which is for controlling the crane position. The PID controller was tuned using Ziegler-Nichols method to get the best performance of the system. The hybrid input-shaping and PID control schemes guarantee a fast input tracking capability, precise payload positioning and very minimal sway motion. The modeling of gantry crane is used to simulate the system using MATLAB/SIMULINK software. The results of the response with the controllers are presented in time domains and frequency domains. The performances of control schemes are examined in terms of level of input tracking capability, sway angle reduction and time response specification.

  15. Correlated activity of cortical neurons survives extensive removal of feedforward sensory input

    PubMed Central

    Shapcott, Katharine A.; Schmiedt, Joscha T.; Saunders, Richard C.; Maier, Alexander; Leopold, David A.; Schmid, Michael C.

    2016-01-01

    A fundamental property of brain function is that the spiking activity of cortical neurons is variable and that some of this variability is correlated between neurons. Correlated activity not due to the stimulus arises from shared input but the neuronal circuit mechanisms that result in these noise correlations are not fully understood. Here we tested in the visual system if correlated variability in mid-level area V4 of visual cortex is altered following extensive lesions of primary visual cortex (V1). To this end we recorded longitudinally the neuronal correlations in area V4 of two behaving macaque monkeys before and after a V1 lesion while the monkeys fixated a grey screen. We found that the correlations of neuronal activity survived the lesions in both monkeys. In one monkey, the correlation of multi-unit spiking signals was strongly increased in the first week post-lesion, while in the second monkey, correlated activity was slightly increased, but not greater than some week-by-week fluctuations observed. The typical drop-off of inter-neuronal correlations with cortical distance was preserved after the lesion. Therefore, as V4 noise correlations remain without feedforward input from V1, these results suggest instead that local and/or feedback input seem to be necessary for correlated activity. PMID:27721468

  16. Nonuniform discharge currents in active plasma lenses

    NASA Astrophysics Data System (ADS)

    van Tilborg, J.; Barber, S. K.; Tsai, H.-E.; Swanson, K. K.; Steinke, S.; Geddes, C. G. R.; Gonsalves, A. J.; Schroeder, C. B.; Esarey, E.; Bulanov, S. S.; Bobrova, N. A.; Sasorov, P. V.; Leemans, W. P.

    2017-03-01

    Active plasma lenses have attracted interest in novel accelerator applications due to their ability to provide large-field-gradient (short focal length), tunable, and radially symmetric focusing for charged particle beams. However, if the discharge current is not flowing uniformly as a function of radius, one can expect a radially varying field gradient as well as potential emittance degradation. We have investigated this experimentally for a 1-mm-diameter active plasma lens. The measured near-axis field gradient is approximately 35% larger than expected for a uniform current distribution, and at overfocusing currents ring-shaped electron beams are observed. These observations are explained by simulations.

  17. Optogenetic activation of serotonergic terminals facilitates GABAergic inhibitory input to orexin/hypocretin neurons

    PubMed Central

    Chowdhury, Srikanta; Yamanaka, Akihiro

    2016-01-01

    Orexin/hypocretin neurons play a crucial role in the regulation of sleep/wakefulness, primarily in the maintenance of wakefulness. These neurons innervate wide areas of the brain and receive diverse synaptic inputs including those from serotonergic (5-HT) neurons in the raphe nucleus. Previously we showed that pharmacological application of 5-HT directly inhibited orexin neurons via 5-HT1A receptors. However, it was still unclear how 5-HT neurons regulated orexin neurons since 5-HT neurons contain not only 5-HT but also other neurotransmitters. To reveal this, we generated new triple transgenic mice in which orexin neurons express enhanced green fluorescent protein (EGFP) and 5-HT neurons express channelrhodopsin2 (ChR2). Immunohistochemical studies show that nerve endings of ChR2-expressing 5-HT neurons are in close apposition to EGFP-expressing orexin neurons in the lateral hypothalamic area. Using these mice, we could optogenetically activate 5-HT nerve terminals and record postsynaptic effects from orexin neurons. Activation of nerve terminals of 5-HT neurons directly inhibited orexin neurons via the 5HT1A receptor, and also indirectly inhibited orexin neurons by facilitating GABAergic inhibitory inputs without affecting glutamatergic inputs. Increased GABAergic inhibitory inputs in orexin neurons were confirmed by the pharmacological application of 5-HT. These results suggest that orexin neurons are inhibited by 5-HT neurons, primarily via 5-HT, in both direct and indirect manners. PMID:27824065

  18. Asymmetrical Processing of Olfactory Input in the Piriform Cortex Mediates "Activation" of the Avian Navigation Circuitry.

    PubMed

    Jorge, Paulo E; Marques, Paulo A M; Pinto, Belmiro V; Phillips, John B

    2016-08-11

    The role of odors in the long-distance navigation of birds has elicited intense debate for more than half a century. Failure to resolve many of the issues fueling this debate is due at least in part to the absence of controls for a variety of non-specific effects that odors have on the navigational process. The present experiments were carried out to investigate whether the olfactory inputs are involved only in "activation" of neuronal circuitry involved in navigation or are also playing a role in providing directional information. Experienced adult pigeons were exposed to controlled olfactory stimuli during different segments of the journey (release site vs. displacement + release site). Protein levels of IEGs (immediate early genes used to mark synaptic activity) were analyzed in areas within the olfactory/navigation avian circuitry. The results indicate that 1) exposure to natural odors at the release site (and not before) elicit greater activation across brain regions than exposure to filtered air, artificial odors, and natural odors along the entire outward journey (from home to the release site, inclusive); 2) activation of the piriform cortex in terms of odor discrimination is lateralized; 3) activation of the navigation circuitry is achieved by means of lateralized activation of piriform cortex neurons. Altogether, the findings provide the first direct evidence that activation of the avian navigation circuitry is mediated by asymmetrical processing of olfactory input occurring in the right piriform cortex.

  19. Dynamic optimization of open-loop input signals for ramp-up current profiles in tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Ren, Zhigang; Xu, Chao; Lin, Qun; Loxton, Ryan; Teo, Kok Lay

    2016-03-01

    Establishing a good current spatial profile in tokamak fusion reactors is crucial to effective steady-state operation. The evolution of the current spatial profile is related to the evolution of the poloidal magnetic flux, which can be modeled in the normalized cylindrical coordinates using a parabolic partial differential equation (PDE) called the magnetic diffusion equation. In this paper, we consider the dynamic optimization problem of attaining the best possible current spatial profile during the ramp-up phase of the tokamak. We first use the Galerkin method to obtain a finite-dimensional ordinary differential equation (ODE) model based on the original magnetic diffusion PDE. Then, we combine the control parameterization method with a novel time-scaling transformation to obtain an approximate optimal parameter selection problem, which can be solved using gradient-based optimization techniques such as sequential quadratic programming (SQP). This control parameterization approach involves approximating the tokamak input signals by piecewise-linear functions whose slopes and break-points are decision variables to be optimized. We show that the gradient of the objective function with respect to the decision variables can be computed by solving an auxiliary dynamic system governing the state sensitivity matrix. Finally, we conclude the paper with simulation results for an example problem based on experimental data from the DIII-D tokamak in San Diego, California.

  20. Somatic versus Dendritic Resonance: Differential Filtering of Inputs through Non-Uniform Distributions of Active Conductances

    PubMed Central

    Zhuchkova, Ekaterina; Remme, Michiel W. H.; Schreiber, Susanne

    2013-01-01

    Synaptic inputs to neurons are processed in a frequency-dependent manner, with either low-pass or resonant response characteristics. These types of filtering play a key role in the frequency-specific information flow in neuronal networks. While the generation of resonance by specific ionic conductances is well investigated, less attention has been paid to the spatial distribution of the resonance-generating conductances across a neuron. In pyramidal neurons – one of the major excitatory cell-types in the mammalian brain – a steep gradient of resonance-generating h-conductances with a 60-fold increase towards distal dendrites has been demonstrated experimentally. Because the dendritic trees of these cells are large, spatial compartmentalization of resonant properties can be expected. Here, we use mathematical descriptions of spatially extended neurons to investigate the consequences of such a distal, dendritic localization of h-conductances for signal processing. While neurons with short dendrites do not exhibit a pronounced compartmentalization of resonance, i.e. the filter properties of dendrites and soma are similar, we find that neurons with longer dendrites ( space constant) can show distinct filtering of dendritic and somatic inputs due to electrotonic segregation. Moreover, we show that for such neurons, experimental classification as resonant versus nonresonant can be misleading when based on somatic recordings, because for these morphologies a dendritic resonance could easily be undetectable when using somatic input. Nevertheless, noise-driven membrane-potential oscillations caused by dendritic resonance can propagate to the soma where they can be recorded, hence contrasting with the low-pass filtering at the soma. We conclude that non-uniform distributions of active conductances can underlie differential filtering of synaptic input in neurons with spatially extended dendrites, like pyramidal neurons, bearing relevance for the localization

  1. Active control of sound transmission/radiation from elastic plates by vibration inputs. II - Experiments

    NASA Technical Reports Server (NTRS)

    Metcalf, V. L.; Fuller, C. R.; Silcox, R. J.; Brown, D. E.

    1992-01-01

    Actively controlled harmonic force inputs were applied experimentally to reduce the sound transmitted through an elastic circular plate. The control implementation used a time domain least mean square adaptive algorithm with two error sensors. The control forces were applied directly to the plate by point force vibration inputs, while the error information and performance were measured in the radiated acoustic field by microphones. Test cases were also performed in which the error sensors were accelerometers mounted on the plate. When accelerometers were used as error sensors, the controller performance was degraded; leading to the conclusion that minimizing plate motion does not necessarily lead to an associated decrease in radiated sound levels. In contrast, the results show excellent attenuation of the transmitted sound field when microphone error sensors were used. This result was consistent over a range of frequencies. In addition, the experimental results are compared to previously derived analytical results and the effect of using a point or global minimization scheme is discussed.

  2. Active control of structurally-coupled sound fields in elastic cylinders by vibrational force inputs

    NASA Technical Reports Server (NTRS)

    Jones, J. D.; Fuller, C. R.

    1990-01-01

    Active control of structurally-coupled sound fields in elastic cylinders is analytically and experimentally studied. The primary (noise) field in the cylinder model is generated by the coupled dynamic response of the shell under loading by a single exterior acoustic source. Control of the interior sound field is achieved by applying vibrational force inputs directly to the shell wall. Action of the point controllers serve to increase the input impedance of select structural modes of the shell which are well-coupled to the interior acoustic cavity, thus substantially reducing sound transmission into the cavity. Spatially-averaged noise reductions in excess of 30 dB are demonstrated for acoustic resonant conditions within the cavity. Twin controller configurations are presented which demonstrate the ability to independently control orthogonal modes of the interior acoustic space. Benefits and drawbacks of this new methodology for noise control are discussed and clearly demonstrated.

  3. Cingulate seizure-like activity reveals neuronal avalanche regulated by network excitability and thalamic inputs

    PubMed Central

    2014-01-01

    Background Cortical neurons display network-level dynamics with unique spatiotemporal patterns that construct the backbone of processing information signals and contribute to higher functions. Recent years have seen a wealth of research on the characteristics of neuronal networks that are sufficient conditions to activate or cease network functions. Local field potentials (LFPs) exhibit a scale-free and unique event size distribution (i.e., a neuronal avalanche) that has been proven in the cortex across species, including mice, rats, and humans, and may be used as an index of cortical excitability. In the present study, we induced seizure activity in the anterior cingulate cortex (ACC) with medial thalamic inputs and evaluated the impact of cortical excitability and thalamic inputs on network-level dynamics. We measured LFPs from multi-electrode recordings in mouse cortical slices and isoflurane-anesthetized rats. Results The ACC activity exhibited a neuronal avalanche with regard to avalanche size distribution, and the slope of the power-law distribution of the neuronal avalanche reflected network excitability in vitro and in vivo. We found that the slope of the neuronal avalanche in seizure-like activity significantly correlated with cortical excitability induced by γ-aminobutyric acid system manipulation. The thalamic inputs desynchronized cingulate seizures and affected the level of cortical excitability, the modulation of which could be determined by the slope of the avalanche size. Conclusions We propose that the neuronal avalanche may be a tool for analyzing cortical activity through LFPs to determine alterations in network dynamics. PMID:24387299

  4. [Changes in cortical neuron input resistance and the stimulation threshold of its electroexcitable membrane by a depolarizing current during the habituation process].

    PubMed

    Pivovarov, A S; Gusel'nikov, V I

    1979-01-01

    The habituation of neurones in the turtle visual cortex is accompanied by changes in their input resistance and in the threshold of stimulation of their electro-excitable membrane by depolarizing current. Input resistance of the neurone during monotoneous stimulation decreases throughout habituation and increases following an alien stimulus. The threshold becomes higher if the current acts as a monotoneous stimulus and gets lower if it acts as an alien stimulus. Input resistance of a habituated neurone and its threshold are restored after alien stimulation and spontaneously--after interruption. These changes are specific to the stimulation, appear during its action, and are reversible. They form postsynaptic mechanisms of habituation.

  5. Brain activation related to combinations of gaze position, visual input, and goal-directed hand movements.

    PubMed

    Bédard, Patrick; Wu, Min; Sanes, Jerome N

    2011-06-01

    Humans reach to and acquire objects by transforming visual targets into action commands. How the brain integrates goals specified in a visual framework to signals into a suitable framework for an action plan requires clarification whether visual input, per se, interacts with gaze position to formulate action plans. To further evaluate brain control of visual-motor integration, we assessed brain activation, using functional magnetic resonance imaging. Humans performed goal-directed movements toward visible or remembered targets while fixating gaze left or right from center. We dissociated movement planning from performance using a delayed-response task and manipulated target visibility by its availability throughout the delay or blanking it 500 ms after onset. We found strong effects of gaze orientation on brain activation during planning and interactive effects of target visibility and gaze orientation on movement-related activation during performance in parietal and premotor cortices (PM), cerebellum, and basal ganglia, with more activation for rightward gaze at a visible target and no gaze modulation for movements directed toward remembered targets. These results demonstrate effects of gaze position on PM and movement-related processes and provide new information how visual signals interact with gaze position in transforming visual inputs into motor goals.

  6. Characterization of sacral interneurons that mediate activation of locomotor pattern generators by sacrocaudal afferent input.

    PubMed

    Etlin, Alex; Finkel, Eran; Mor, Yoav; O'Donovan, Michael J; Anglister, Lili; Lev-Tov, Aharon

    2013-01-09

    Identification of the neural pathways involved in retraining the spinal central pattern generators (CPGs) by afferent input in the absence of descending supraspinal control is feasible in isolated rodent spinal cords where the locomotor CPGs are potently activated by sacrocaudal afferent (SCA) input. Here we study the involvement of sacral neurons projecting rostrally through the ventral funiculi (VF) in activation of the CPGs by sensory stimulation. Fluorescent labeling and immunostaining showed that VF neurons are innervated by primary afferents immunoreactive for vesicular glutamate transporters 1 and 2 and by intraspinal neurons. Calcium imaging revealed that 55% of the VF neurons were activated by SCA stimulation. The activity of VF neurons and the sacral and lumbar CPGs was abolished when non-NMDA receptors in the sacral segments were blocked by the antagonist CNQX. When sacral NMDA receptors were blocked by APV, the sacral CPGs were suppressed, VF neurons with nonrhythmic activity were recruited and a moderate-drive locomotor rhythm developed during SCA stimulation. In contrast, when the sacral CPGs were activated by SCA stimulation, rhythmic and nonrhythmic VF neurons were recruited and the locomotor rhythm was most powerful. The activity of 73 and 27% of the rhythmic VF neurons was in-phase with the ipsilateral and contralateral motor output, respectively. Collectively, our studies indicate that sacral VF neurons serve as a major link between SCA and the hindlimb CPGs and that the ability of SCA to induce stepping can be enhanced by the sacral CPGs. The nature of the ascending drive to lumbar CPGs, the identity of subpopulations of VF neurons, and their potential role in activating the locomotor rhythm are discussed.

  7. NMDA currents modulate the synaptic input-output functions of neurons in the dorsal nucleus of the lateral lemniscus in Mongolian gerbils.

    PubMed

    Porres, Christian P; Meyer, Elisabeth M M; Grothe, Benedikt; Felmy, Felix

    2011-03-23

    Neurons in the dorsal nucleus of the lateral lemniscus (DNLL) receive excitatory and inhibitory inputs from the superior olivary complex (SOC) and convey GABAergic inhibition to the contralateral DNLL and the inferior colliculi. Unlike the fast glycinergic inhibition in the SOC, this GABAergic inhibition outlasts auditory stimulation by tens of milliseconds. Two mechanisms have been postulated to explain this persistent inhibition. One, an "integration-based" mechanism, suggests that postsynaptic excitatory integration in DNLL neurons generates prolonged activity, and the other favors the synaptic time course of the DNLL output itself. The feasibility of the integration-based mechanism was tested in vitro in DNLL neurons of Mongolian gerbils by quantifying the cellular excitability and synaptic input-output functions (IO-Fs). All neurons were sustained firing and generated a near monotonic IO-F on current injections. From synaptic stimulations, we estimate that activation of approximately five fibers, each on average liberating ∼18 vesicles, is sufficient to trigger a single postsynaptic action potential. A strong single pulse of afferent fiber stimulation triggered multiple postsynaptic action potentials. The steepness of the synaptic IO-F was dependent on the synaptic NMDA component. The synaptic NMDA receptor current defines the slope of the synaptic IO-F by enhancing the temporal and spatial EPSP summation. Blocking this NMDA-dependent amplification during postsynaptic integration of train stimulations resulted into a ∼20% reduction of the decay time course of the GABAergic inhibition. Thus, our data show that the NMDA-dependent amplification of the postsynaptic activity contributes to the GABAergic persistent inhibition generated by DNLL neurons.

  8. The nature of the language input affects brain activation during learning from a natural language

    PubMed Central

    Plante, Elena; Patterson, Dianne; Gómez, Rebecca; Almryde, Kyle R.; White, Milo G.; Asbjørnsen, Arve E.

    2015-01-01

    Artificial language studies have demonstrated that learners are able to segment individual word-like units from running speech using the transitional probability information. However, this skill has rarely been examined in the context of natural languages, where stimulus parameters can be quite different. In this study, two groups of English-speaking learners were exposed to Norwegian sentences over the course of three fMRI scans. One group was provided with input in which transitional probabilities predicted the presence of target words in the sentences. This group quickly learned to identify the target words and fMRI data revealed an extensive and highly dynamic learning network. These results were markedly different from activation seen for a second group of participants. This group was provided with highly similar input that was modified so that word learning based on syllable co-occurrences was not possible. These participants showed a much more restricted network. The results demonstrate that the nature of the input strongly influenced the nature of the network that learners employ to learn the properties of words in a natural language. PMID:26257471

  9. The nature of the language input affects brain activation during learning from a natural language.

    PubMed

    Plante, Elena; Patterson, Dianne; Gómez, Rebecca; Almryde, Kyle R; White, Milo G; Asbjørnsen, Arve E

    2015-11-01

    Artificial language studies have demonstrated that learners are able to segment individual word-like units from running speech using the transitional probability information. However, this skill has rarely been examined in the context of natural languages, where stimulus parameters can be quite different. In this study, two groups of English-speaking learners were exposed to Norwegian sentences over the course of three fMRI scans. One group was provided with input in which transitional probabilities predicted the presence of target words in the sentences. This group quickly learned to identify the target words and fMRI data revealed an extensive and highly dynamic learning network. These results were markedly different from activation seen for a second group of participants. This group was provided with highly similar input that was modified so that word learning based on syllable co-occurrences was not possible. These participants showed a much more restricted network. The results demonstrate that the nature of the input strongly influenced the nature of the network that learners employ to learn the properties of words in a natural language.

  10. Thyrotropin-releasing hormone causes a tonic excitatory postsynaptic current and inhibits the phasic inspiratory inhibitory inputs in inspiratory-inhibited airway vagal preganglionic neurons.

    PubMed

    Hou, L; Zhou, X; Chen, Y; Qiu, D; Zhu, L; Wang, J

    2012-01-27

    The airway vagal preganglionic neurons (AVPNs) in the external formation of the nucleus ambiguus (eNA), which include the inspiratory-activated AVPNs (IA-AVPNs) and inspiratory-inhibited AVPNs (II-AVPNs), predominate in the control of the trachea and bronchia. The AVPNs receive particularly dense inputs from terminals containing thyrotropin-releasing hormone (TRH). TRH microinjection into the nucleus ambiguus (NA) caused constriction of the tracheal smooth muscles. However, it is unknown whether TRH affects all subtypes of the AVPNs in the eNA, and as a result affects the control of all types of target tissues in the airway (smooth muscles, submucosal glands, and blood vessels). It is also unknown how TRH affects the AVPNs at neuronal and synaptic levels. In this study, the AVPNs in the eNA were retrogradely labeled from the extrathoracic trachea, the II-AVPNs were identified in rhythmically firing brainstem slices, and the effects of TRH were examined using patch-clamp. TRH (100 nmol L(-1)) enhanced both the rhythm and the intensity of the hypoglossal bursts, and caused a tonic excitatory inward current in the II-AVPNs at a holding voltage of -80 mV. The frequency of the spontaneous excitatory postsynaptic currents (EPSCs) in the II-AVPNs, which showed no respiratory-related change in a respiratory cycle, was not significantly changed by TRH. At a holding voltage of -50 mV, the II-AVPNs showed both spontaneous and phasic inspiratory (outward) inhibitory postsynaptic currents (IPSCs). TRH had no effect on the spontaneous IPSCs but significantly attenuated the phasic inspiratory outward currents, in both the amplitude and area. After focal application of strychnine, an antagonist of glycine receptors, to the II-AVPNs, the spontaneous IPSCs were extremely scarce and the phasic inspiratory inhibitory currents were abolished; and further application of TRH had no effect on these currents. Under current clamp configuration, TRH caused a depolarization and increased the

  11. Sharp wave-associated synchronized inputs from the piriform cortex activate olfactory tubercle neurons during slow-wave sleep.

    PubMed

    Narikiyo, Kimiya; Manabe, Hiroyuki; Mori, Kensaku

    2014-01-01

    During slow-wave sleep, anterior piriform cortex neurons show highly synchronized discharges that accompany olfactory cortex sharp waves (OC-SPWs). The OC-SPW-related synchronized activity of anterior piriform cortex neurons travel down to the olfactory bulb and is thought to be involved in the reorganization of bulbar neuronal circuitry. However, influences of the OC-SPW-related activity on other regions of the central olfactory system are still unknown. Olfactory tubercle is an area of OC and part of ventral striatum that plays a key role in reward-directed motivational behaviors. In this study, we show that in freely behaving rats, olfactory tubercle receives OC-SPW-associated synchronized inputs during slow-wave sleep. Local field potentials in the olfactory tubercle showed SPW-like activities that were in synchrony with OC-SPWs. Single-unit recordings showed that a subpopulation of olfactory tubercle neurons discharged in synchrony with OC-SPWs. Furthermore, correlation analysis of spike activity of anterior piriform cortex and olfactory tubercle neurons revealed that the discharges of anterior piriform cortex neurons tended to precede those of olfactory tubercle neurons. Current source density analysis in urethane-anesthetized rats indicated that the current sink of the OC-SPW-associated input was located in layer III of the olfactory tubercle. These results indicate that OC-SPW-associated synchronized discharges of piriform cortex neurons travel to the deep layer of the olfactory tubercle and drive discharges of olfactory tubercle neurons. The entrainment of olfactory tubercle neurons in the OC-SPWs suggests that OC-SPWs coordinate reorganization of neuronal circuitry across wide areas of the central olfactory system including olfactory tubercle during slow-wave sleep.

  12. An ionic current model for neurons in the rat medial nucleus tractus solitarii receiving sensory afferent input.

    PubMed Central

    Schild, J H; Khushalani, S; Clark, J W; Andresen, M C; Kunze, D L; Yang, M

    1993-01-01

    1. Neurons from a horizontal slice of adult rat brainstem were examined using intracellular recording techniques. Investigations were restricted to a region within the nucleus tractus solitarii, medial to the solitary tract and centred on the obex (mNTS). Previous work has shown this restricted area of the NTS to contain the greatest concentration of aortic afferent baroreceptor terminal fields. Electrical stimulation of the tract elicited short-latency excitatory postsynaptic potentials in all neurons. 2. mNTS neurons were spontaneously active with firing frequencies ranging between 1 and 10 Hz, at resting potentials of -65 to -45 mV. These neurons did not exhibit spontaneous bursting activity. 3. Depolarizing current injection immediately evoked a finite, high-frequency spike discharge which rapidly declined to a lower steady-state level (i.e. spike frequency adaptation, SFA). Increasing depolarizations produced a marked increase in the peak instantaneous frequency but a much smaller increase in the steady-state firing level. 4. Conditioning with a hyperpolarizing prepulse resulted in a prolonged delay of up to 600 ms before the first action potential (i.e. delayed excitation, DE) with an attendant decrease in peak discharge rates. DE was modulated by both the magnitude and duration of the prestimulus hyperpolarization, as well as the magnitude of the depolarizing stimulus. Tetrodotoxin (TTX) eliminated spike discharge but had little effect on the ramp-like membrane depolarization characteristic of DE. 5. We have developed a mathematical model for mNTS neurons to facilitate our understanding of the interplay between the underlying ionic currents. It consists of a comprehensive membrane model of the Hodgkin-Huxley type coupled with a fluid compartment model describing cytoplasmic [Ca2+]i homeostasis. 6. The model suggests that (a) SFA is caused by an increase in [Ca2+]i which activates the outward K+ current, IK,Ca, and (b) DE results from the competitive

  13. Precise control of plant stem cell activity through parallel regulatory inputs.

    PubMed

    Bennett, Tom; van den Toorn, Albert; Willemsen, Viola; Scheres, Ben

    2014-11-01

    The regulation of columella stem cell activity in the Arabidopsis root cap by a nearby organizing centre, the quiescent centre, has been a key example of the stem cell niche paradigm in plants. Here, we investigate interactions between transcription factors that have been shown to regulate columella stem cells using a simple quantification method for stem cell activity in the root cap. Genetic and expression analyses reveal that the RETINOBLASTOMA-RELATED protein, the FEZ and SOMBRERO NAC-domain transcription factors, the ARF10 and ARF16 auxin response factors and the quiescent centre-expressed WOX5 homeodomain protein each provide independent inputs to regulate the number of columella stem cells. Given the tight control of columella development, we found that these inputs act in a surprisingly parallel manner. Nevertheless, important points of interaction exist; for example, we demonstrate the repression of SMB activity by non-autonomous action of WOX5. Our results suggest that the developmental progression of columella stem cells may be quantitatively regulated by several more broadly acting transcription factors rather than by a single intrinsic stem cell factor, which raises questions about the special nature of the stem cell state in plants.

  14. Low-frequency absorption using a two-layer system with active control of input impedance.

    PubMed

    Cobo, Pedro; Fernández, Alejandro; Doutres, Olivier

    2003-12-01

    Broadband noise absorption, including low frequencies, may be obtained by a hybrid passive-active two-layer system. A porous layer in front of an air layer provides passive absorption, at medium and high frequencies. Active control of the input impedance of the two-layer system yields absorption at low frequencies. The active control system can implement either pressure-release or impedance-matching conditions. A simple analytical model based upon plane waves propagating in a tube permits the comparison of both control strategies. The results of this simple model show that the pressure-release condition affords higher absorption than the impedance-matching condition for some combinations of geometrical and material parameters. Experimental results corroborate the good performance of the pressure-release condition under the prescribed geometrical setup.

  15. Current Activities of the ASME Subgroup NUPACK

    SciTech Connect

    Gerald M. Foster; D. Keith Morton; Paul McConnell

    2007-10-01

    Current activities of the American Society of Mechanical Engineers (ASME), Section III Subgroup on Containment Systems for Spent Fuel High-Level Waste Transport Packagings (also known as Subgroup NUPACK) are reviewed with emphasis on the recent revision of Subsection WB. Also, brief insightson new proposals for the development of rules for internal support structures and for a strain-based acceptance criteria are provided.

  16. Biased low differential input impedance current receiver/converter device and method for low noise readout from voltage-controlled detectors

    DOEpatents

    Degtiarenko, Pavel V.; Popov, Vladimir E.

    2011-03-22

    A first stage electronic system for receiving charge or current from voltage-controlled sensors or detectors that includes a low input impedance current receiver/converter device (for example, a transimpedance amplifier), which is directly coupled to the sensor output, a source of bias voltage, and the device's power supply (or supplies), which use the biased voltage point as a baseline.

  17. Saturn's Titan: Evidence for Current Cryovolcanic Activity

    NASA Astrophysics Data System (ADS)

    Nelson, Robert M.; Cassini VIMS Titan Surface Variability Group

    2009-09-01

    We report evidence suggesting current cryovolcanic activity on Titan. This is based on surface changes seen at selected locations by the Cassini Visual and Infrared Mapping Spectrometer (VIMS). Titan's surface is hard to observe because Titan's atmosphere is opaque at visual wavelengths due to methane absorption. However, VIMS is able to image the surface at selected infrared wavelengths where the methane is relatively transparent[1,2]. VIMS reported surface reflectance variability at Hotei Arcus (26S,78W) and that the variability might be due to deposition followed by coverage or dissipation of ammonia frost. Subsequently, Cassini RADAR images found that Hotei Arcus has lobate "flow” forms, consistent with the morphology of volcanic terrain [3]. Here we report the discovery of lobate "flow” patterns at Hotei Arcus in VIMS infrared images taken during Cassini close flybys during 2008-2009. These data further suggest that the brightness variability at Hotei Arcus is associated with ammonia, a compound expected in Titan's interior. This, combined with the previous evidence from VIMS and RADAR images, creates a strong case for Titan having a presently active surface, possibly due to cryovolcanism. It has not escaped our attention that gaseous ammonia, in association with methane and nitrogen in Titan's atmosphere, is similar to the terrestrial environment at the time that life first emerged. If Titan is currently active, then these results raise the following questions: What is the full extent of current geologic activity? What are the ongoing processes? Are Titan's chemical processes today supporting a prebiotic chemistry similar to that under which life evolved on Earth? This work done at JPL under contract with NASA. References: [1]R. M. Nelson et al., Icarus 199 (2009) 429-441. [2]R. M. Nelson et al., GEOPHYSICAL RESEARCH LETTERS, VOL. 36, L04202, doi:10.1029/2008GL036206, 2009. [3]S. D. Wall GEOPHYSICAL RESEARCH LETTERS, VOL. 36, L04203, doi:10.1029/2008GL

  18. Plasticity of NMDA receptor-mediated excitatory postsynaptic currents at perforant path inputs to dendrite-targeting interneurons.

    PubMed

    Harney, Sarah C; Anwyl, Roger

    2012-08-15

    Synaptic plasticity of NMDA receptors (NMDARs) has been recently described in a number of brain regions and we have previously characterised LTP and LTD of glutamatergic NMDA receptor-mediated EPSCs (NMDAR-EPSCs) in granule cells of dentate gyrus. The functional significance of NMDAR plasticity at perforant path synapses on hippocampal network activity depends on whether this is a common feature of perforant path synapses on all postsynaptic target cells or if this plasticity occurs only at synapses on principal cells. We recorded NMDAR-EPSCs at medial perforant path synapses on interneurons in dentate gyrus which had significantly slower decay kinetics compared to those recorded in granule cells. NMDAR pharmacology in interneurons was consistent with expression of both GluN2B- and GluN2D-containing receptors. In contrast to previously described high frequency stimulation-induced bidirectional plasticity of NMDAR-EPSCs in granule cells, only LTD of NMDAR-EPSCs was induced in interneurons in our standard experimental conditions. In interneurons, LTD of NMDAR-EPSCs was associated with a loss of sensitivity to a GluN2D-selective antagonist and was inhibited by the actin stabilising agent, jasplakinolide. While LTP of NMDAR-EPSCs can be readily induced in granule cells, this form of plasticity was only observed in interneurons when extracellular calcium was increased above physiological concentrations during HFS or when PKC was directly activated by phorbol ester, suggesting that opposing forms of plasticity at inputs to interneurons and principal cells may act to regulate granule cell dendritic integration and processing.

  19. Relationships between sensory input, motor output and unit activity in interpositus and red nuclei during intentional movement.

    PubMed

    Soechting, J F; Burton, J E; Onoda, N

    1978-08-18

    The relationship between unit activity in interpositus (8 units) and red nuclei (11 units) and the EMG activity of the biceps during intentional elbow flexion movements was investigated by means of cross-correlation analysis. This analysis showed that there were long-lasting (200 msec) changes in the probability of EMG activity both before and after a single spike in neurons which covaried with the motor output. The dependence of the activity of these units on sensory inputs was investigated by (1) calculating the quantitative relationship between angular displacement and unit activity and (2) recording unit activity after the sensory input from peripheral afferents had been eliminated by dorsal rhizotomy.

  20. Variation in active and passive resource inputs to experimental pools: mechanisms and possible consequences for food webs

    USGS Publications Warehouse

    Kraus, Johanna M.; Pletcher, Leanna T.; Vonesh, James R.

    2010-01-01

    1. Cross-ecosystem movements of resources, including detritus, nutrients and living prey, can strongly influence food web dynamics in recipient habitats. Variation in resource inputs is thought to be driven by factors external to the recipient habitat (e.g. donor habitat productivity and boundary conditions). However, inputs of or by ‘active’ living resources may be strongly influenced by recipient habitat quality when organisms exhibit behavioural habitat selection when crossing ecosystem boundaries. 2. To examine whether behavioural responses to recipient habitat quality alter the relative inputs of ‘active’ living and ‘passive’ detrital resources to recipient food webs, we manipulated the presence of caged predatory fish and measured biomass, energy and organic content of inputs to outdoor experimental pools of adult aquatic insects, frog eggs, terrestrial plant matter and terrestrial arthropods. 3. Caged fish reduced the biomass, energy and organic matter donated to pools by tree frog eggs by ∼70%, but did not alter insect colonisation or passive allochthonous inputs of terrestrial arthropods and plant material. Terrestrial plant matter and adult aquatic insects provided the most energy and organic matter inputs to the pools (40–50%), while terrestrial arthropods provided the least (7%). Inputs of frog egg were relatively small but varied considerably among pools and over time (3%, range = 0–20%). Absolute and proportional amounts varied by input type. 4. Aquatic predators can strongly affect the magnitude of active, but not passive, inputs and that the effect of recipient habitat quality on active inputs is variable. Furthermore, some active inputs (i.e. aquatic insect colonists) can provide similar amounts of energy and organic matter as passive inputs of terrestrial plant matter, which are well known to be important. Because inputs differ in quality and the trophic level they subsidise, proportional changes in input type could have

  1. Opening remarks: Current and future activities

    NASA Technical Reports Server (NTRS)

    Davarian, Faramaz

    1993-01-01

    It is our custom to present the Propagation Program's recent accomplishments and future plans at the onset of a NAPEX meeting. A summary is presented. The data analysis phase of the U.S. Olympus Campaign is nearing its end. The final report will be published by Virginia Tech by midsummer 1993. The report will comprise measurement analysis for 12 months. It will include monthly and annual attenuation statistics and statistics on scintillation effects. A number of prediction models will be presented. The ACTS propagation experiment preparations are moving forward as expected. The mobile/personal channel characterization efforts continued during the last year. Data collected by the University of Texas in 1992 are being analyzed and will become available by September 1993. We have recently started a study to characterize LEO mobile/personal channels. Topics such as indoor reception, tree shadowing, blockage, and delay spread will be investigated. These results will become available in one to two years from now. We have also collected Ka-band mobile data using Olympus 20 GHz beacon transmissions. The University of Texas has already collected five years of low-elevation angle, 11GHz propagation data. The work on database for propagation models has progressed very well. The first release is ready, and the participants of this meeting will receive a copy of the software. We had an active year where CCIR is concerned. An input document on land mobile satellite system (LMSS) propagation models was submitted to the U.S. national committee and was approved and sent to Geneva.

  2. Opening remarks: Current and future activities

    NASA Astrophysics Data System (ADS)

    Davarian, Faramaz

    1993-08-01

    It is our custom to present the Propagation Program's recent accomplishments and future plans at the onset of a NAPEX meeting. A summary is presented. The data analysis phase of the U.S. Olympus Campaign is nearing its end. The final report will be published by Virginia Tech by midsummer 1993. The report will comprise measurement analysis for 12 months. It will include monthly and annual attenuation statistics and statistics on scintillation effects. A number of prediction models will be presented. The ACTS propagation experiment preparations are moving forward as expected. The mobile/personal channel characterization efforts continued during the last year. Data collected by the University of Texas in 1992 are being analyzed and will become available by September 1993. We have recently started a study to characterize LEO mobile/personal channels. Topics such as indoor reception, tree shadowing, blockage, and delay spread will be investigated. These results will become available in one to two years from now. We have also collected Ka-band mobile data using Olympus 20 GHz beacon transmissions. The University of Texas has already collected five years of low-elevation angle, 11GHz propagation data. The work on database for propagation models has progressed very well. The first release is ready, and the participants of this meeting will receive a copy of the software. We had an active year where CCIR is concerned. input document on land mobile satellite system (LMSS) propagation models was submitted to the U.S. national committee and was approved and sent to Geneva.

  3. Pederson Current Dissipation In Emerging Active Regions

    NASA Astrophysics Data System (ADS)

    Leake, James E.; Linton, M. G.

    2011-05-01

    Pederson current dissipation in emerging active regions. Certain regions of the solar atmosphere, such as the photosphere and chromosphere, as well as prominences, contain a significant amount of neutral atoms, and a complete description of the plasma requires including the effects of partial ionization. In the chromosphere the dissipation of Pederson currents is important for the evolution of emerging magnetic fields. Due to the relatively high number density in the chromosphere, the ion-neutral collision time-scale is much smaller than timescales associated with flux emergence. Hence we use a single-fluid approach to model the partially ionized plasma. Looking at both the emergence of large-scale sub-surface structures, and the emergence and reconnection of undulatory fields, we investigate the effect of Pederson current dissipation on the state of the emerging field, on magnetic reconnection and on dissipative heating of the atmosphere. Specifically we examine the effect of motions across fieldlines in the partially ionized regions, and how this can increase the free energy supplied to the corona by flux emergence. We also look at reconnection associated with flux emergence in the partially ionized atmosphere, and how this can account for observed small-scale brightenings (Ellerman Bombs).

  4. Alternating Current Influences Anaerobic Electroactive Biofilm Activity.

    PubMed

    Wang, Xin; Zhou, Lean; Lu, Lu; Lobo, Fernanda Leite; Li, Nan; Wang, Heming; Park, Jaedo; Ren, Zhiyong Jason

    2016-09-06

    Alternating current (AC) is known to inactivate microbial growth in suspension, but how AC influences anaerobic biofilm activities has not been systematically investigated. Using a Geobacter dominated anaerobic biofilm growing on the electrodes of microbial electrochemical reactors, we found that high frequency AC ranging from 1 MHz to 1 kHz (amplitude of 5 V, 30 min) showed only temporary inhibition to the biofilm activity. However, lower frequency (100 Hz, 1.2 or 5 V) treatment led to 47 ± 19% permanent decrease in limiting current on the same biofilm, which is attributed to the action of electrohydrodynamic force that caused biofilm damage and loss of intercellular electron transfer network. Confocal microscopy images show such inactivation mainly occurred at the interface between the biofilm and the electrode. Reducing the frequency further to 1 Hz led to water electrolysis, which generated gas bubbles that flushed all attached cells out of the electrode. These findings provide new references on understanding and regulating biofilm growth, which has broader implications in biofouling control, anaerobic waste treatment, energy and product recovery, and general understanding of microbial ecology and physiology.

  5. Opposing Effects of Intrinsic Conductance and Correlated Synaptic Input on Vm-Fluctuations during Network Activity

    PubMed Central

    Kolind, Jens; Hounsgaard, Jørn; Berg, Rune W.

    2012-01-01

    Neurons often receive massive concurrent bombardment of synaptic inhibition and excitation during functional network activity. This increases membrane conductance and causes fluctuations in membrane potential (Vm) and spike timing. The conductance increase is commonly attributed to synaptic conductance, but also includes the intrinsic conductances recruited during network activity. These two sources of conductance have contrasting dynamic properties at sub-threshold membrane potentials. Synaptic transmitter gated conductance changes abruptly and briefly with each presynaptic action potential. If the spikes arrive at random times the changes in synaptic conductance are therefore stochastic and rapid during intense network activity. In comparison, sub-threshold intrinsic conductances vary smoothly in time. In the present study this discrepancy is investigated using two conductance-based models: a (1) compartment model and a (2) compartment with realistic slow intrinsic conductances. We examine the effects of varying the relative contributions of non-fluctuating intrinsic conductance with fluctuating concurrent inhibitory and excitatory synaptic conductance. For given levels of correlation in the synaptic input we find that the magnitude of the membrane fluctuations uniquely determines the relative contribution of synaptic and intrinsic conductance. We also quantify how Vm-fluctuations vary with synaptic correlations for fixed ratios of synaptic and intrinsic conductance. Interestingly, the levels of Vm -fluctuations and conductance observed experimentally during functional network activity leave little room for intrinsic conductance to contribute. Even without intrinsic conductances the variance in Vm -fluctuations can only be explained by a high degree of correlated firing among presynaptic neurons. PMID:22783184

  6. Anthropogenic activities have contributed moderately to increased inputs of organic materials in marginal seas off China.

    PubMed

    Liu, Liang-Ying; Wei, Gao-Ling; Wang, Ji-Zhong; Guan, Yu-Feng; Wong, Charles S; Wu, Feng-Chang; Zeng, Eddy Y

    2013-10-15

    Sediment has been recognized as a gigantic sink of organic materials and therefore can record temporal input trends. To examine the impact of anthropogenic activities on the marginal seas off China, sediment cores were collected from the Yellow Sea, the inner shelf of the East China Sea (ECS), and the South China Sea (SCS) to investigate the sources and spatial and temporal variations of organic materials, i.e., total organic carbon (TOC) and aliphatic hydrocarbons. The concentration ranges of TOC were 0.5-1.29, 0.63-0.83, and 0.33-0.85%, while those of Σn-C14-35 (sum of n-alkanes with carbon numbers of 14-35) were 0.08-1.5, 0.13-1.97, and 0.35-0.96 μg/g dry weight in sediment cores from the Yellow Sea, ECS inner shelf, and the SCS, respectively. Terrestrial higher plants were an important source of aliphatic hydrocarbons in marine sediments off China. The spatial distribution of Σn-C14-35 concentrations and source diagnostic ratios suggested a greater load of terrestrial organic materials in the Yellow Sea than in the ECS and SCS. Temporally, TOC and Σn-C14-35 concentrations increased with time and peaked at either the surface or immediate subsurface layers. This increase was probably reflective of elevated inputs of organic materials to marginal seas off China in recent years, and attributed partly to the impacts of intensified anthropogenic activities in mainland China. Source diagnostics also suggested that aliphatic hydrocarbons were mainly derived from biogenic sources, with a minority in surface sediment layers from petroleum sources, consistent with the above-mentioned postulation.

  7. Sensory deprivation regulates the development of the hyperpolarization-activated current in auditory brainstem neurons.

    PubMed

    Hassfurth, Benjamin; Magnusson, Anna K; Grothe, Benedikt; Koch, Ursula

    2009-10-01

    Hyperpolarization-activated and cyclic nucleotide-gated (HCN) channels are highly expressed in the superior olivary complex, the primary locus for binaural information processing. This hyperpolarization-activated current (I(h)) regulates the excitability of neurons and enhances the temporally precise analysis of the binaural acoustic cues. By using the whole-cell patch-clamp technique, we examined the properties of I(h) current in neurons of the lateral superior olive (LSO) and the medial nucleus of the trapezoid body (MNTB) before and after hearing onset. Moreover, we tested the hypothesis that I(h) currents are actively regulated by sensory input activity by performing bilateral and unilateral cochlear ablations before hearing onset, resulting in a chronic auditory deprivation. The results show that after hearing onset, I(h) currents are rapidly upregulated in LSO neurons, but change only marginally in neurons of the MNTB. We also found a striking difference in maximal current density, voltage dependence and activation time constant between the LSO and the MNTB in mature-like animals. Following bilateral cochlear ablations before hearing onset, the I(h) currents were scaled up in the LSO and scaled down in the MNTB. Consequently, in the LSO this resulted in a depolarized resting membrane potential and a lower input resistance of these neurons. This type of activity-dependent homeostatic change could thus result in an augmented response to the remaining inputs.

  8. GIS interoperability: current activities and military implications

    NASA Astrophysics Data System (ADS)

    Lam, Sylvia

    1997-07-01

    Geographic information systems (GIS) are gaining importance in military operations because of their capability to spatially and visually integrate various kinds of information. In an era of limited resources, geospatial data must be shared efficiently whenever possible. The military-initiated Global Geospatial Information and Services (GGI&S) Project aims at developing the infrastructure for GIS interoperability for the military. Current activities in standardization and new technology have strong implications on the design and development of GGI&S. To facilitate data interoperability at both the national and international levels, standards and specifications in geospatial data sharing are being studied, developed and promoted. Of particular interest to the military community are the activities related to the NATO DIGEST, ISO TC/211 Geomatics standardization and the industry-led Open Geodata Interoperability Specifications (OGIS). Together with new information technology, standardization provides the infrastructure for interoperable GIS for both civilian and military environments. The first part of this paper describes the major activities in standardization. The second part presents the technologies developed at DREV in support of the GGI&S. These include the Open Geospatial Datastore Interface (OGDI) and the geospatial data warehouse. DREV has been working closely with Defence Geomatics and private industry in the research and development of new technology for the GGI&S project.

  9. Input permutation method to detect active voxels in fMRI study☆

    PubMed Central

    Lee, Sang H.; Lim, Johan; Park, DoHwan; Biswal, Bharat B.; Petkova, Eva

    2013-01-01

    Correctly identifying voxels or regions of interest (ROI) that actively respond to a given stimulus is often an important objective/step in many functional magnetic resonance imaging (fMRI) studies. In this article, we study a nonparametric method to detect active voxels, which makes minimal assumption about the distribution of blood oxygen level-dependent (BOLD) signals. Our proposal has several interesting features. It uses time lagged correlation to take into account the delay in response to the stimulus, due to hemodynamic variations. We introduce an input permutation method (IPM), a type of block permutation method, to approximate the null distribution of the test statistic. Also, we propose to pool the permutation-derived statistics of preselected voxels for a better approximation to the null distribution. Finally, we control multiple testing error rate using the local false discovery rate (FDR) by Efron [Correlation and large-scale simultaneous hypothesis testing. J Am Stat Assoc 102 (2007) 93–103] and Park et al. [Estimation of empirical null using a mixture of normals and its use in local false discovery rate. Comput Stat Data Anal 55 (2011) 2421–2432] to select the active voxels. PMID:22819177

  10. Innocuous, Not Noxious, Input Activates PKCγ Interneurons of the Spinal Dorsal Horn via Myelinated Afferent Fibers

    PubMed Central

    Braz, Joao M.; Skinner, Kate; Llewellyn-Smith, Ida J.; Basbaum, Allan I.

    2008-01-01

    Protein kinase C γ (PKCγ), which is concentrated in interneurons of the inner part of lamina II of the dorsal horn, has been implicated in injury-induced allodynia, a condition wherein pain is produced by innocuous stimuli. Although it is generally assumed that these interneurons receive input from the nonpeptidergic, IB4-positive subset of nociceptors, the fact that PKCγ cells do not express Fos in response to noxious stimulation suggests otherwise. Here, we demonstrate that the terminal field of the nonpeptidergic population of nociceptors, in fact, lies dorsal to that of PKCγ interneurons. There was also no overlap between the PKCγ-expressing interneurons and the transganglionic tracer wheat germ agglutinin which, after sciatic nerve injection, labels all unmyelinated nociceptors. However, transganglionic transport of the β-subunit of cholera toxin, which marks the medium-diameter and large-diameter myelinated afferents that transmit non-noxious information, revealed extensive overlap with the layer of PKCγ interneurons. Furthermore, expression of a transneuronal tracer in myelinated afferents resulted in labeling of PKCγ interneurons. Light and electron microscopic double labeling further showed that the VGLUT1 subtype of vesicular glutamate transmitter, which is expressed in myelinated afferents, marks synapses that are presynaptic to the PKCγ interneurons. Finally, we demonstrate that a continuous non-noxious input, generated by walking on a rotarod, induces Fos in the PKCγ interneurons. These results establish that PKCγ interneurons are activated by myelinated afferents that respond to innocuous stimuli, which suggests that injury-induced mechanical allodynia is transmitted through a circuit that involves PKCγ interneurons and non-nociceptive, VGLUT1-expressing myelinated primary afferents. PMID:18685019

  11. NMDA receptor activity and the transmission of sensory input into motor output in introverts and extraverts.

    PubMed

    Rammsayer, Thomas H

    2003-05-01

    Recent research suggests that individual differences in brain dopamine functioning may be related to the personality dimension of extraversion. The major goal of the present study was to answer the question of whether a pharmacologically induced change in glutamatergic NMDA receptor activity would also differentially affect the transmission of sensory input into motor out-put in introverts and extraverts. Therefore, in a double-blind within-subjects design, either 30 mg of the NMDA receptor antagonist memantine or placebo were administered to 48 healthy male volunteers before performing a choice reaction-time task. In introverts, memantine caused a pronounced increase in lift-off time (i.e., the time required to lift the finger from a home button) compared to that in extraverts, whereas movement time (i.e., the time required to move the finger from the home button to a response button) was decreased in both groups. The pattern of results suggests that extraversion-related differential sensitivity to pharmacologically induced changes in NMDA receptor activity is limited to functions that involve an interaction between the glutamatergic and dopaminergic systems.

  12. Removing sensory input disrupts spinal locomotor activity in the early postnatal period

    PubMed Central

    Acevedo, JeanMarie; Díaz-Ríos, Manuel

    2013-01-01

    Motor patterns driving rhythmic movements of our lower limbs during walking are generated by groups of neurons within the spinal cord, called central pattern generators (CPGs). After suffering a spinal cord injury (SCI), many descending fibers from our brain are severed or become nonfunctional which leaves the spinal CPG network without its initiating drive. Recent studies are focusing on the importance of maintaining sensory stimulation to the legs on SCI patients as a way to initiate and control the CPG locomotor network. We began assessing the role of sensory feedback to the locomotor CPG network by using a neonatal mouse spinal cord preparation were the lower limbs are still attached. Removing sensory feedback coming from the hindlimbs by way of a lower lumbar transection or by ventral root denervation revealed a positive correlation in the ability of sensory input deprivation to disrupt ongoing locomotor activity on older versus younger animals. The differences in the motor responses as a function of age could be correlated with the loss of excitatory activity from sensory afferents. Continued studies on this field could eventually provide key information that translates in the design of novel therapeutic strategies to treat patients that have suffered a SCI. PMID:24043359

  13. Suckling-induced activation of neuronal input to the dorsomedial nucleus of the hypothalamus: possible candidates for mediating the activation of DMH neuropeptide Y neurons during lactation.

    PubMed

    Chen, Peilin; Smith, M Susan

    2003-09-12

    Activation of the neuropeptide Y (NPY) neuronal system in the dorsomedial nucleus of the hypothalamus (DMH) during lactation in the rat is in part due to neural impulses arising from the suckling stimulus. However, the afferent neuronal input to the DMH that is activated during lactation and is responsible for activation of NPY neurons is currently unknown. Previously, using cFos as a marker for neuronal activation, we identified several brain areas in the lactating animals that were activated by the suckling stimulus. Thus, the objective of the present study was to determine if any of these suckling activated areas project directly to the DMH. The retrograde tracer, fluorogold (FG), was injected into the DMH on day 4 postpartum. FG-injected lactating rats were then deprived of their eight-pup litters on day 9 postpartum, and 48 h later, the pups were returned to the females to reinitiate the suckling stimulus for 90 min and induce cFos expression. The animals were then perfused and the brains were subjected to double-label immunohistochemistry to visualize both FG- and cFos-positive cells. Substantial numbers of FG/cFos double-labeled cells were found in forebrain regions, including the preoptic area, lateral septal nucleus, ventral subiculum, and supramammillary nucleus, and in brainstem regions, including the lateral parabrachial nucleus, periaqeductal gray, and ventrolateral medulla. In conclusion, these areas are potentially important candidates for mediating the activation of the NPY neuronal system in the DMH during lactation.

  14. HEAT INPUT AND POST WELD HEAT TREATMENT EFFECTS ON REDUCED-ACTIVATION FERRITIC/MARTENSITIC STEEL FRICTION STIR WELDS

    SciTech Connect

    Tang, Wei; Chen, Gaoqiang; Chen, Jian; Yu, Xinghua; Frederick, David Alan; Feng, Zhili

    2015-01-01

    Reduced-activation ferritic/martensitic (RAFM) steels are an important class of structural materials for fusion reactor internals developed in recent years because of their improved irradiation resistance. However, they can suffer from welding induced property degradations. In this paper, a solid phase joining technology friction stir welding (FSW) was adopted to join a RAFM steel Eurofer 97 and different FSW parameters/heat input were chosen to produce welds. FSW response parameters, joint microstructures and microhardness were investigated to reveal relationships among welding heat input, weld structure characterization and mechanical properties. In general, FSW heat input results in high hardness inside the stir zone mostly due to a martensitic transformation. It is possible to produce friction stir welds similar to but not with exactly the same base metal hardness when using low power input because of other hardening mechanisms. Further, post weld heat treatment (PWHT) is a very effective way to reduce FSW stir zone hardness values.

  15. Visual input controls the functional activity of goldfish Mauthner neuron through the reciprocal synaptic mechanism.

    PubMed

    Moshkov, Dmitry A; Shtanchaev, Rashid S; Mikheeva, Irina B; Bezgina, Elena N; Kokanova, Nadezhda A; Mikhailova, Gulnara Z; Tiras, Nadezhda R; Pavlik, Lyubov' L

    2013-03-01

    Goldfish are known to exhibit motor asymmetry due to functional asymmetry of their Mauthner neurons that induce the turns to the right or left during free swimming. It has been previously found that if the less active neuron is subjected to prolonged aimed visual stimulation via its ventral dendrite, the motor asymmetry of goldfish is inverted, testifying that this neuron becomes functionally dominant, while the size of the ventral dendrite under these conditions is reduced 2-3 times compared to its counterpart in mirror neuron. Earlier it has been also revealed that training optokinetic stimulation induces adaptation, a substantial resistance of both fish motor asymmetry and morphofunctional state of Mauthner neurons against prolonged optokinetic stimulation. The aim of this work was to study the cellular mechanisms of the effect of an unusual visual afferent input on goldfish motor asymmetry and Mauthner neuron function in norm and under adaptation. It was shown that serotonin applied onto Mauthner neurons greatly reduces their activity whereas its antagonist ondansetron increases it. Against the background of visual stimulation, serotonin strengthens functional asymmetry between neurons whereas ondansetron smoothes it. Taken together these data suggest the involvement of serotonergic excitatory synaptic transmission in the regulation of Mauthner neurons by vision. Ultrastructural study of the ventral dendrites after prolonged optokinetic stimulation has revealed depletions of numeral axo-axonal synapses with specific morphology, identified by means of immunogold label as serotonergic ones. These latter in turn are situated mainly on shaft boutons, which according to specific ultrastructural features are assigned to axo-dendritic inhibitory synapses. Thus, the excitatory serotonergic synapses seem to affect Mauthner neuron indirectly through inhibitory synapses. Further, it was morphometrically established that adaptation is accompanied by the significant

  16. Effects of Phonological Input as a Pre-Listening Activity on Vocabulary Learning and L2 Listening Comprehension Test Performance

    ERIC Educational Resources Information Center

    Mihara, Kei

    2015-01-01

    The purpose of the present study is twofold. The first goal is to examine the effects of phonological input on students' vocabulary learning. The second is to discuss how different pre­-listening activities affect students' second language listening comprehension. The participants were first-­year students at a Japanese university. There were two…

  17. Active Debris Removal: Current Status of Activities in CNES

    NASA Astrophysics Data System (ADS)

    Bonnal, Christophe; Ruault, Jean-Marc; Desjean, Marie-Christine

    2013-08-01

    Most of the ongoing studies led at worldwide level, mainly through IADC Actions, conclude that in order to keep a stable Low Earth Orbit environment in the coming decades, it may be necessary to retrieve some 5 to 10 large objects annually. These operations, known as Active Debris Removal (ADR), raise a huge amount of difficulties in numerous domains: political, legal, insurance, defense, financing and, last but not least, technical questions. The current paper aims at reviewing the current status of the ADR activities led by CNES both at National and Multi-lateral level. The first question which is raised is that of the high level requirements to be applied. What are the requirements coming from the operators; do we want to stabilize the environment, decrease it or could we accept some increase over the years; when do we have to act; can we baseline random reentry of such large objects or do we have to stick to controlled destructive reentries?… There may not yet be clear answers to these points, so efforts at international level are required. The second part of the paper deals with the potential solutions at system level. Numerous possibilities can be identified, depending on the size of the launcher and of the strategy selected to de-orbit the debris. Large space tugs visiting some 10 debris or small dedicated chasers launched as piggyback are among the solutions which have been traded. The currently preferred solution is described in details. The third part of the paper is devoted to the chaser-debris operations themselves, following five key functions; - the long range rendezvous, - the short range rendezvous up to contact, - the mechanical interfacing of the debris, - its control by the chaser, when required, - the de-orbiting maneuver itself. For each of these functions, the current status of available technologies is described, enabling the identification of the most critical ones requiring additional R&T effort and subsequent demonstrations. Among them

  18. Rhythmic activity of neurons in the rostral ventrolateral medulla of conscious cats: effect of removal of vestibular inputs

    PubMed Central

    Barman, Susan M.; Sugiyama, Yoichiro; Suzuki, Takeshi; Cotter, Lucy A.; DeStefino, Vincent J.; Reighard, Derek A.; Cass, Stephen P.

    2011-01-01

    Although it is well established that bulbospinal neurons located in the rostral ventrolateral medulla (RVLM) play a pivotal role in regulating sympathetic nerve activity and blood pressure, virtually all neurophysiological studies of this region have been conducted in anesthetized or decerebrate animals. In the present study, we used time- and frequency-domain analyses to characterize the naturally occurring discharges of RVLM neurons in conscious cats. Specifically, we compared their activity to fluctuations in carotid artery blood flow to identify neurons with cardiac-related (CR) activity; we then considered whether neurons with CR activity also had a higher-frequency rhythmic firing pattern. In addition, we ascertained whether the surgical removal of vestibular inputs altered the rhythmic discharge properties of RVLM neurons. Less than 10% of RVLM neurons expressed CR activity, although the likelihood of observing a neuron with CR activity in the RVLM varied between recording sessions, even when tracking occurred in a very limited area and was higher after vestibular inputs were surgically removed. Either a 10-Hz or a 20- to 30-Hz rhythmic discharge pattern coexisted with the CR discharges in some of the RVLM neurons. Additionally, the firing rate of RVLM neurons, including those with CR activity, decreased after vestibular lesions. These findings raise the prospect that RVLM neurons may or may not express rhythmic firing patterns at a particular time due to a variety of influences, including descending projections from higher brain centers and sensory inputs, such as those from the vestibular system. PMID:21734018

  19. Solutions Network Formulation Report. Improving NOAA's Tides and Currents Through Enhanced Data Inputs from NASA's Ocean Surface Topography Mission

    NASA Technical Reports Server (NTRS)

    Guest, DeNeice C.

    2006-01-01

    The Nation uses water-level data for a variety of practical purposes, including hydrography, nautical charting, maritime navigation, coastal engineering, and tsunami and storm surge warnings (NOAA, 2002; Digby et al., 1999). Long-term applications include marine boundary determinations, tidal predictions, sea-level trend monitoring, oceanographic research, and climate research. Accurate and timely information concerning sea-level height, tide, and ocean current is needed to understand their impact on coastal management, disaster management, and public health. Satellite altimeter data products are currently used by hundreds of researchers and operational users to monitor ocean circulation and to improve scientists understanding of the role of the oceans in climate and weather. The NOAA (National Oceanic and Atmospheric Administration) National Ocean Service has been monitoring sea-level variations for many years (NOAA, 2006). NOAA s Tides & Currents DST (decision support tool, managed by the Center for Operational Oceanographic Products and Services, is the portal to a vast collection of oceanographic and meteorological data (historical and real-time), predictions, and nowcasts and forecasts. This report assesses the capacity of NASA s satellite altimeter data to meet societal decision support needs through incorporation into NOAA s Tides & Currents.

  20. A Low Input Current and Wide Conversion Ratio Buck Regulator with 75% Efficiency for High-Voltage Triboelectric Nanogenerators

    NASA Astrophysics Data System (ADS)

    Luo, Li-Chuan; Bao, De-Chun; Yu, Wu-Qi; Zhang, Zhao-Hua; Ren, Tian-Ling

    2016-01-01

    It is meaningful to research the Triboelectric Nanogenerators (TENG), which can create electricity anywhere and anytime. There are many researches on the structures and materials of TENG to explain the phenomenon that the maximum voltage is stable and the current is increasing. The output voltage of the TENG is high about 180–400 V, and the output current is small about 39 μA, which the electronic devices directly integration of TENG with Li-ion batteries will result in huge energy loss due to the ultrahigh TENG impedance. A novel interface circuit with the high-voltage buck regulator for TENG is introduced firstly in this paper. The interface circuit can transfer the output signal of the TENG into the signal fit to a lithium ion battery. Through the circuit of the buck regulator, the average output voltage is about 4.0 V and the average output current is about 1.12 mA. Further, the reliability and availability for the lithium ion battery and the circuit are discussed. The interface circuit is simulated using the Cadence software and verified through PCB experiment. The buck regulator can achieve 75% efficiency for the High-Voltage TENG. This will lead to a research hot and industrialization applications.

  1. A Low Input Current and Wide Conversion Ratio Buck Regulator with 75% Efficiency for High-Voltage Triboelectric Nanogenerators

    PubMed Central

    Luo, Li-Chuan; Bao, De-Chun; Yu, Wu-Qi; Zhang, Zhao-Hua; Ren, Tian-Ling

    2016-01-01

    It is meaningful to research the Triboelectric Nanogenerators (TENG), which can create electricity anywhere and anytime. There are many researches on the structures and materials of TENG to explain the phenomenon that the maximum voltage is stable and the current is increasing. The output voltage of the TENG is high about 180–400 V, and the output current is small about 39 μA, which the electronic devices directly integration of TENG with Li-ion batteries will result in huge energy loss due to the ultrahigh TENG impedance. A novel interface circuit with the high-voltage buck regulator for TENG is introduced firstly in this paper. The interface circuit can transfer the output signal of the TENG into the signal fit to a lithium ion battery. Through the circuit of the buck regulator, the average output voltage is about 4.0 V and the average output current is about 1.12 mA. Further, the reliability and availability for the lithium ion battery and the circuit are discussed. The interface circuit is simulated using the Cadence software and verified through PCB experiment. The buck regulator can achieve 75% efficiency for the High-Voltage TENG. This will lead to a research hot and industrialization applications. PMID:26781881

  2. A Low Input Current and Wide Conversion Ratio Buck Regulator with 75% Efficiency for High-Voltage Triboelectric Nanogenerators.

    PubMed

    Luo, Li-Chuan; Bao, De-Chun; Yu, Wu-Qi; Zhang, Zhao-Hua; Ren, Tian-Ling

    2016-01-19

    It is meaningful to research the Triboelectric Nanogenerators (TENG), which can create electricity anywhere and anytime. There are many researches on the structures and materials of TENG to explain the phenomenon that the maximum voltage is stable and the current is increasing. The output voltage of the TENG is high about 180-400 V, and the output current is small about 39 μA, which the electronic devices directly integration of TENG with Li-ion batteries will result in huge energy loss due to the ultrahigh TENG impedance. A novel interface circuit with the high-voltage buck regulator for TENG is introduced firstly in this paper. The interface circuit can transfer the output signal of the TENG into the signal fit to a lithium ion battery. Through the circuit of the buck regulator, the average output voltage is about 4.0 V and the average output current is about 1.12 mA. Further, the reliability and availability for the lithium ion battery and the circuit are discussed. The interface circuit is simulated using the Cadence software and verified through PCB experiment. The buck regulator can achieve 75% efficiency for the High-Voltage TENG. This will lead to a research hot and industrialization applications.

  3. Direct Evidence for Active Suppression of Salient-but-Irrelevant Sensory Inputs.

    PubMed

    Gaspelin, Nicholas; Leonard, Carly J; Luck, Steven J

    2015-11-01

    Researchers have long debated whether attentional capture is purely stimulus driven or purely goal driven. In the current study, we tested a hybrid account, called the signal-suppression hypothesis, which posits that stimuli automatically produce a bottom-up salience signal, but that this signal can be suppressed via top-down control processes. To test this account, we used a new capture-probe paradigm in which participants searched for a target shape while ignoring an irrelevant color singleton. On occasional probe trials, letters were briefly presented inside the search shapes, and participants attempted to report these letters. Under conditions that promoted capture by the irrelevant singleton, accuracy was greater for the letter inside the singleton distractor than for letters inside nonsingleton distractors. However, when the conditions were changed to avoid capture by the singleton, accuracy for the letter inside the irrelevant singleton was reduced below the level observed for letters inside nonsingleton distractors, an indication of active suppression of processing at the singleton location.

  4. Transient sodium current at subthreshold voltages: activation by EPSP waveforms.

    PubMed

    Carter, Brett C; Giessel, Andrew J; Sabatini, Bernardo L; Bean, Bruce P

    2012-09-20

    Tetrodotoxin (TTX)-sensitive sodium channels carry large transient currents during action potentials and also "persistent" sodium current, a noninactivating TTX-sensitive current present at subthreshold voltages. We examined gating of subthreshold sodium current in dissociated cerebellar Purkinje neurons and hippocampal CA1 neurons, studied at 37°C with near-physiological ionic conditions. Unexpectedly, in both cell types small voltage steps at subthreshold voltages activated a substantial component of transient sodium current as well as persistent current. Subthreshold EPSP-like waveforms also activated a large component of transient sodium current, but IPSP-like waveforms engaged primarily persistent sodium current with only a small additional transient component. Activation of transient as well as persistent sodium current at subthreshold voltages produces amplification of EPSPs that is sensitive to the rate of depolarization and can help account for the dependence of spike threshold on depolarization rate, as previously observed in vivo.

  5. Transient sodium current at subthreshold voltages: activation by EPSP waveforms

    PubMed Central

    Carter, Brett C.; Giessel, Andrew J.; Sabatini, Bernardo L.; Bean, Bruce P.

    2012-01-01

    Summary Tetrodotoxin (TTX)-sensitive sodium channels carry large transient currents during action potentials and also “persistent” sodium current, a non-inactivating TTX-sensitive current present at subthreshold voltages. We examined gating of subthreshold sodium current in dissociated cerebellar Purkinje neurons and hippocampal CA1 neurons, studied at 37 °C with near-physiological ionic conditions. Unexpectedly, in both cell types small voltage steps at subthreshold voltages activated a substantial component of transient sodium current as well as persistent current. Subthreshold EPSP-like waveforms also activated a large component of transient sodium current, but IPSP-like waveforms engaged primarily persistent sodium current with only a small additional transient component. Activation of transient as well as persistent sodium current at subthreshold voltages produces amplification of EPSPs that is sensitive to the rate of depolarization and can help account for the dependence of spike threshold on depolarization rate, as previously observed in vivo. PMID:22998875

  6. Current and future offshore activities in Canada

    SciTech Connect

    Hnatiuk, J.

    1987-06-01

    The development of innovative exploratory drilling systems for Canada's harsh Arctic offshore areas over the past decade and future activity in these areas, including possible production concepts, are discussed. The results can be applied in other Arctic areas of the world, including offshore Alaska. This operating experience will advance technology and serve as a basis for the design of Arctic offshore production and transportation systems. Unique technology has been developed and successfully used in the discovery of major accumulations of hyrodcarbons. Continued technological advances are anticipated to have widespread Arctic applications in both exploratory and production operations.

  7. Cholinergic receptor activation induces a relative facilitation of synaptic responses in the entorhinal cortex during theta- and gamma-frequency stimulation of parasubicular inputs.

    PubMed

    Sparks, D W; Chapman, C A

    2013-01-29

    The parasubiculum sends its single major output to layer II of the entorhinal cortex, and it may therefore interact with inputs to the entorhinal cortex from other cortical areas, and help to shape the activity of layer II entorhinal cells that project to the hippocampal formation. Cholinergic inputs are thought to contribute to the generation of theta- and gamma-frequency activities in the parasubiculum and entorhinal cortex, and the present study assessed how cholinergic receptor activation affects synaptic responses of the entorhinal cortex to theta- and gamma-frequency stimulation. Depth profiles of field excitatory postsynaptic potentials (fEPSPs) in acute brain slices showed a short-latency negative fEPSP in layer II, consistent with the activation of excitatory synaptic inputs to layer II. Application of the cholinergic agonist carbachol (CCh) suppressed synaptic responses and enhanced paired-pulse facilitation. CCh also resulted in a marked relative facilitation of synaptic responses evoked during short 5-pulse trains of stimulation at both theta- and gamma-frequencies. Application of the M(1) antagonist pirenzepine, but not the M(2) antagonist methoctramine, blocked the facilitation of responses. Inhibition of the M-current or block of GABA(B) receptors had no effect, but the facilitation effect was partially blocked by the N-methyl-d-aspartate (NMDA) antagonist APV, indicating that NMDA receptors play a role. Application of ZD7288, a selective inhibitor of the hyperpolarization-activated cationic current I(h), almost completely blocked the relative facilitation of responses, and the less potent I(h)-blocker Cs(+) also resulted in a partial block. The relative facilitation of synaptic responses induced by CCh is therefore likely mediated by multiple mechanisms including the cholinergic suppression of transmitter release that enhances transmitter availability during repetitive stimulation, NMDA receptor-mediated effects on pre- or postsynaptic function, and

  8. How Effective Are Affective Activities? Relative Benefits of Two Types of Structured Input Activities as Part of a Computer-Delivered Lesson on the Spanish Subjunctive

    ERIC Educational Resources Information Center

    Henshaw, Florencia

    2012-01-01

    Proponents of Processing Instruction (VanPatten, 2005) claim that learners benefit most when presented with both referential and affective structured input activities. Following a classic pretest-posttest design, the present study investigates the role of these two types of activities on the learning of the Spanish subjunctive. Groups differed…

  9. Current and future offshore activities in Canada

    SciTech Connect

    Hnatiuk, J.

    1984-05-01

    The development of innovative exploratory drilling systems for Canada's harsh Arctic offshore areas over the past decade is described. Future activity in these areas, including possible production concepts, is also discussed. The results of the experience in Canadian waters can be applied in other Arctic areas of the world including offshore Alaska. This operating experience will serve to further advance the drilling technology and will serve as a basis for the design of Arctic offshore production and transportation systems. Artificial islands, first commenced in 1972, are still being constructed but with improved designs and equipment. A step forward has been the use of subsea berms on which concrete or steel segmented caissons have been placed. Integrated-type steel caissons have also been adapted for placement on subsea berms, one of which is half of a crude oil tanker and a second, a purpose-built steel caisson to be placed this summer.

  10. State, Parameter, and Unknown Input Estimation Problems in Active Automotive Safety Applications

    NASA Astrophysics Data System (ADS)

    Phanomchoeng, Gridsada

    A variety of driver assistance systems such as traction control, electronic stability control (ESC), rollover prevention and lane departure avoidance systems are being developed by automotive manufacturers to reduce driver burden, partially automate normal driving operations, and reduce accidents. The effectiveness of these driver assistance systems can be significant enhanced if the real-time values of several vehicle parameters and state variables, namely tire-road friction coefficient, slip angle, roll angle, and rollover index, can be known. Since there are no inexpensive sensors available to measure these variables, it is necessary to estimate them. However, due to the significant nonlinear dynamics in a vehicle, due to unknown and changing plant parameters, and due to the presence of unknown input disturbances, the design of estimation algorithms for this application is challenging. This dissertation develops a new approach to observer design for nonlinear systems in which the nonlinearity has a globally (or locally) bounded Jacobian. The developed approach utilizes a modified version of the mean value theorem to express the nonlinearity in the estimation error dynamics as a convex combination of known matrices with time varying coefficients. The observer gains are then obtained by solving linear matrix inequalities (LMIs). A number of illustrative examples are presented to show that the developed approach is less conservative and more useful than the standard Lipschitz assumption based nonlinear observer. The developed nonlinear observer is utilized for estimation of slip angle, longitudinal vehicle velocity, and vehicle roll angle. In order to predict and prevent vehicle rollovers in tripped situations, it is necessary to estimate the vertical tire forces in the presence of unknown road disturbance inputs. An approach to estimate unknown disturbance inputs in nonlinear systems using dynamic model inversion and a modified version of the mean value theorem is

  11. A synaptic input portal for a mapped clock oscillator model of neuronal electrical rhythmic activity

    NASA Astrophysics Data System (ADS)

    Zariffa, José; Ebden, Mark; Bardakjian, Berj L.

    2004-09-01

    Neuronal electrical oscillations play a central role in a variety of situations, such as epilepsy and learning. The mapped clock oscillator (MCO) model is a general model of transmembrane voltage oscillations in excitable cells. In order to be able to investigate the behaviour of neuronal oscillator populations, we present a neuronal version of the model. The neuronal MCO includes an extra input portal, the synaptic portal, which can reflect the biological relationships in a chemical synapse between the frequency of the presynaptic action potentials and the postsynaptic resting level, which in turn affects the frequency of the postsynaptic potentials. We propose that the synaptic input-output relationship must include a power function in order to be able to reproduce physiological behaviour such as resting level saturation. One linear and two power functions (Butterworth and sigmoidal) are investigated, using the case of an inhibitory synapse. The linear relation was not able to produce physiologically plausible behaviour, whereas both the power function examples were appropriate. The resulting neuronal MCO model can be tailored to a variety of neuronal cell types, and can be used to investigate complex population behaviour, such as the influence of network topology and stochastic resonance.

  12. Effects of nutritional input and diesel contamination on soil enzyme activities and microbial communities in Antarctic soils.

    PubMed

    Han, Jiwon; Jung, Jaejoon; Hyun, Seunghun; Park, Hyun; Park, Woojun

    2012-12-01

    Pollution of Antarctic soils may be attributable to increased nutritional input and diesel contamination via anthropogenic activities. To investigate the effect of these environmental changes on the Antarctic terrestrial ecosystem, soil enzyme activities and microbial communities in 3 types of Antarctic soils were evaluated. The activities of alkaline phosphomonoesterase and dehydrogenase were dramatically increased, whereas the activities of β-glucosidase, urease, arylsulfatase, and fluorescein diacetate hydrolysis were negligible. Alkaline phosphomonoesterase and dehydrogenase activities in the 3 types of soils increased 3- to 10-fold in response to nutritional input, but did not increase in the presence of diesel contamination. Consistent with the enzymatic activity data, increased copy numbers of the phoA gene, encoding an alkaline phosphomonoesterase, and the 16S rRNA gene were verified using quantitative real-time polymerase chain reaction. Interestingly, dehydrogenase activity and 16S rRNA gene copy number increased slightly after 30 days, even under diesel contamination, probably because of adaptation of the bacterial population. Intact Antarctic soils showed a predominance of Actinobacteria phylum (mostly Pseudonorcarida species) and other phyla such as Proteobacteria, Chloroflexi, Planctomycetes, Firmicutes, and Verrucomicrobia were present in successively lower proportions. Nutrient addition might act as a selective pressure on the bacterial community, resulting in the prevalence of Actinobacteria phylum (mostly Arthrobacter species). Soils contaminated by diesel showed a predominance of Proteobacteria phylum (mostly Phyllobacterium species), and other phyla such as Actinobacteria, Bacteroidetes, Planctomycetes, and Gemmatimonadetes were present in successively lower proportions. Our data reveal that nutritional input has a dramatic impact on bacterial communities in Antarctic soils and that diesel contamination is likely toxic to enzymes in this

  13. DISTRIBUTION OF ELECTRIC CURRENTS IN SOLAR ACTIVE REGIONS

    SciTech Connect

    Török, T.; Titov, V. S.; Mikić, Z.; Leake, J. E.; Archontis, V.; Linton, M. G.; Dalmasse, K.; Aulanier, G.; Kliem, B.

    2014-02-10

    There has been a long-standing debate on the question of whether or not electric currents in solar active regions are neutralized. That is, whether or not the main (or direct) coronal currents connecting the active region polarities are surrounded by shielding (or return) currents of equal total value and opposite direction. Both theory and observations are not yet fully conclusive regarding this question, and numerical simulations have, surprisingly, barely been used to address it. Here we quantify the evolution of electric currents during the formation of a bipolar active region by considering a three-dimensional magnetohydrodynamic simulation of the emergence of a sub-photospheric, current-neutralized magnetic flux rope into the solar atmosphere. We find that a strong deviation from current neutralization develops simultaneously with the onset of significant flux emergence into the corona, accompanied by the development of substantial magnetic shear along the active region's polarity inversion line. After the region has formed and flux emergence has ceased, the strong magnetic fields in the region's center are connected solely by direct currents, and the total direct current is several times larger than the total return current. These results suggest that active regions, the main sources of coronal mass ejections and flares, are born with substantial net currents, in agreement with recent observations. Furthermore, they support eruption models that employ pre-eruption magnetic fields containing such currents.

  14. Active vibration control of Flexible Joint Manipulator using Input Shaping and Adaptive Parameter Auto Disturbance Rejection Controller

    NASA Astrophysics Data System (ADS)

    Li, W. P.; Luo, B.; Huang, H.

    2016-02-01

    This paper presents a vibration control strategy for a two-link Flexible Joint Manipulator (FJM) with a Hexapod Active Manipulator (HAM). A dynamic model of the multi-body, rigid-flexible system composed of an FJM, a HAM and a spacecraft was built. A hybrid controller was proposed by combining the Input Shaping (IS) technique with an Adaptive-Parameter Auto Disturbance Rejection Controller (APADRC). The controller was used to suppress the vibration caused by external disturbances and input motions. Parameters of the APADRC were adaptively adjusted to ensure the characteristic of the closed loop system to be a given reference system, even if the configuration of the manipulator significantly changes during motion. Because precise parameters of the flexible manipulator are not required in the IS system, the operation of the controller was sufficiently robust to accommodate uncertainties in system parameters. Simulations results verified the effectiveness of the HAM scheme and controller in the vibration suppression of FJM during operation.

  15. Activation of lateral habenula inputs to the ventral midbrain promotes behavioral avoidance

    PubMed Central

    Stamatakis, Alice M.; Stuber, Garret D.

    2012-01-01

    Lateral habenula (LHb) projections to the ventral midbrain, including the rostromedial tegmental nucleus (RMTg) conveys negative reward-related information, but the behavioral ramifications of selective activation of this pathway remain unexplored. We found that exposure to aversive stimuli in mice increased LHb excitatory drive onto RMTg neurons. Further, optogenetic activation of this pathway promoted active, passive, and conditioned behavioral avoidance. These data demonstrate that activity of LHb efferents to the midbrain is aversive, but can also serve to negatively reinforce behavioral responding. PMID:22729176

  16. Variations in Solar Activity and Irradiance and Their Implications for Energy Input Into the Terrestrial Atmosphere

    NASA Astrophysics Data System (ADS)

    Parker, Daryl Gray

    This dissertation presents research into the question of how variations in the physical properties of resolved solar magnetic surface features combine to produce variations in the physical properties of the integrated Sun and the possible impacts of those variations on the terrestrial climate system. The core approach to the research was development of techniques to apply automated Bayesian statistical pattern recognition methods as implemented in the AutoClass software to magnetic and intensity-like solar images from the Mount Wilson Solar Observatory (MWO) 150 Foot Solar Telescope. The goals were to: (1) identify in an objective and quantifiable manner the solar surface features responsible for changes in solar irradiance, (2) enhance understanding of the evolution of these features and the resultant solar irradiance variations over the most recent solar cycles, (3) develop methods to identify the specific features responsible for variations in specific wavelengths, (4) use global observations of global solar irradiance indices to identify the spatially resolved features which contribute to them, (5) attempt to apply these results to specific topics of current interest in solar-stellar astronomy. Using these techniques, a method was developed to identify classes of features from thousands of MWO solar images based on the per pixel values of absolute magnetic field strength and an intensity measure known as a "ratio-gram" in MWO images. Using these classes along with observations from independent, usually satellite based, sources in different wavelengths, models were constructed of total solar irradiance (TSI) and solar UV indices. These models were able to reproduce with high correlations solar observations in a number of different solar wavelengths. These classes were also used to construct images mapping different wavelength emissions to the areas to the solar surface features from which they originated. These techniques proved able to reproduce with high

  17. Biological Ocean Margins Program. Active Microbes Responding to Inputs from the Orinoco River Plume. Final Report

    SciTech Connect

    Jorge E. Corredor

    2013-01-28

    The overall goal of the proposed work is to identify the active members of the heterotrophic community involved in C and N cycling in the perimeter of the Orinoco River Plume (ORP), assess their spatial distribution, quantify their metabolic activity, and correlate these parameters to plume properties such as salinity, organic matter content and phytoplankton biomass.

  18. Icing Branch Current Research Activities in Icing Physics

    NASA Technical Reports Server (NTRS)

    Vargas, Mario

    2009-01-01

    Current development: A grid block transformation scheme which allows the input of grids in arbitrary reference frames, the use of mirror planes, and grids with relative velocities has been developed. A simple ice crystal and sand particle bouncing scheme has been included. Added an SLD splashing model based on that developed by William Wright for the LEWICE 3.2.2 software. A new area based collection efficiency algorithm will be incorporated which calculates trajectories from inflow block boundaries to outflow block boundaries. This method will be used for calculating and passing collection efficiency data between blade rows for turbo-machinery calculations.

  19. Microbial dynamics and enzyme activities in tropical Andosols depending on land use and nutrient inputs

    NASA Astrophysics Data System (ADS)

    Mganga, Kevin; Razavi, Bahar; Kuzyakov, Yakov

    2015-04-01

    Microbial decomposition of soil organic matter is mediated by enzymes and is a key source of terrestrial CO2 emissions. Microbial and enzyme activities are necessary to understand soil biochemical functioning and identify changes in soil quality. However, little is known about land use and nutrients availability effects on enzyme activities and microbial processes, especially in tropical soils of Africa. This study was conducted to examine how microbial and enzyme activities differ between different land uses and nutrient availability. As Andosols of Mt. Kilimanjaro are limited by nutrient concentrations, we hypothesize that N and P additions will stimulate enzyme activity. N and P were added to soil samples (0-20 cm) representing common land use types in East Africa: (1) savannah, (2) maize fields, (3) lower montane forest, (4) coffee plantation, (5) grasslands and (6) traditional Chagga homegardens. Total CO2 efflux from soil, microbial biomass and activities of β-glucosidase, cellobiohydrolase, chitinase and phosphatase involved in C, N and P cycling, respectively was monitored for 60 days. Total CO2 production, microbial biomass and enzyme activities varied in the order forest soils > grassland soils > arable soils. Increased β-glucosidase and cellobiohydrolase activities after N addition of grassland soils suggest that microorganisms increased N uptake and utilization to produce C-acquiring enzymes. Low N concentration in all soils inhibited chitinase activity. Depending on land use, N and P addition had an inhibitory or neutral effect on phosphatase activity. We attribute this to the high P retention of Andosols and low impact of N and P on the labile P fractions. Enhanced CO2 production after P addition suggests that increased P availability could stimulate soil organic matter biodegradation in Andosols. In conclusion, land use and nutrients influenced soil enzyme activities and microbial dynamics and demonstrated the decline in soil quality after landuse

  20. Hypotonicity activates a native chloride current in Xenopus oocytes

    PubMed Central

    1994-01-01

    Xenopus oocytes are frequently utilized for in vivo expression of cellular proteins, especially ion channel proteins. A thorough understanding of the endogenous conductances and their regulation is paramount for proper characterization of expressed channel proteins. Here we detail a novel chloride current (ICl.swell) responsive to hypotonicity in Xenopus oocytes using the two-electrode voltage clamp technique. Reducing the extracellular osmolarity by 50% elicited a calcium-independent chloride current having an anion conductivity sequence identical with swelling-induced chloride currents observed in epithelial cells. The hypotonicity-activated current was blocked by chloride channel blockers, trivalent lanthanides, and nucleotides. G- protein, cAMP-PKA, and arachidonic acid signaling cascades were not involved in ICl.swell activation. ICl.swell is distinct from both stretch-activated nonselective cation channels and the calcium- activated chloride current in oocytes and may play a critical role in volume regulation in Xenopus oocytes. PMID:8189203

  1. Explorations of electric current system in solar active regions. I - Empirical inferences of the current flows

    NASA Technical Reports Server (NTRS)

    Ding, Y. J.; Hong, Q. F.; Hagyard, M. J.; Deloach, A. C.; Liu, X. P.

    1987-01-01

    Techniques to identify sources of electric current systems and their channels of flow in solar active regions are explored. Measured photospheric vector magnetic fields together with high-resolution white-light and H-alpha filtergrams provide the data base to derive the current systems in the photosphere and chromosphere. As an example, the techniques are then applied to infer current systems in AR 2372 in early April 1980.

  2. Optimisation of active suspension control inputs for improved vehicle handling performance

    NASA Astrophysics Data System (ADS)

    Čorić, Mirko; Deur, Joško; Kasać, Josip; Tseng, H. Eric; Hrovat, Davor

    2016-11-01

    Active suspension is commonly considered under the framework of vertical vehicle dynamics control aimed at improvements in ride comfort. This paper uses a collocation-type control variable optimisation tool to investigate to which extent the fully active suspension (FAS) application can be broaden to the task of vehicle handling/cornering control. The optimisation approach is firstly applied to solely FAS actuator configurations and three types of double lane-change manoeuvres. The obtained optimisation results are used to gain insights into different control mechanisms that are used by FAS to improve the handling performance in terms of path following error reduction. For the same manoeuvres the FAS performance is compared with the performance of different active steering and active differential actuators. The optimisation study is finally extended to combined FAS and active front- and/or rear-steering configurations to investigate if they can use their complementary control authorities (over the vertical and lateral vehicle dynamics, respectively) to further improve the handling performance.

  3. Binaral interaction and centrifugal input enhances spatial contrast in olfactory bulb activation.

    PubMed

    Singer, Benjamin H; Kim, Soyoun; Zochowski, Michal

    2007-01-01

    We used paired-pulse odorant stimulation, with a conditioning stimulus delivered either ipsilateral or contralateral to a test stimulus, to unmask the effects of centrifugal feedback on olfactory bulb responses. In reptiles and mammals there are no direct connections between the paired olfactory bulbs, and thus all information transfer between the olfactory bulbs depends on feedback from retrobulbar structures. We measured odor-induced activity in the turtle olfactory bulb using a voltage-sensitive dye and a 464-element photodiode array, which allowed us to monitor the spatial variation in activation of the olfactory bulb. We found that both contralateral and ipsilateral conditioning stimuli evoked long-lasting inhibition of olfactory bulb activation. In contrast to previous studies using local field potential recording to monitor activity at a single site, we found that this inhibition increased contrast in the spatial patterning of activation over the dorsal surface of the olfactory bulb. Inhibition was also increased when different odorants were used as conditioning and test stimuli, suggesting a role for centrifugal feedback in olfactory discrimination. These results highlight the functional importance of centrifugal feedback and information processing in a broadly distributed olfactory network.

  4. The optimization of force inputs for active structural acoustic control using a neural network

    NASA Technical Reports Server (NTRS)

    Cabell, R. H.; Lester, H. C.; Silcox, R. J.

    1992-01-01

    This paper investigates the use of a neural network to determine which force actuators, of a multi-actuator array, are best activated in order to achieve structural-acoustic control. The concept is demonstrated using a cylinder/cavity model on which the control forces, produced by piezoelectric actuators, are applied with the objective of reducing the interior noise. A two-layer neural network is employed and the back propagation solution is compared with the results calculated by a conventional, least-squares optimization analysis. The ability of the neural network to accurately and efficiently control actuator activation for interior noise reduction is demonstrated.

  5. A Newly Identified Extrinsic Input Triggers a Distinct Gastric Mill Rhythm via Activation of Modulatory Projection Neurons

    PubMed Central

    Blitz, Dawn M.; White, Rachel S.; Saideman, Shari R.; Cook, Aaron; Christie, Andrew E.; Nadim, Farzan; Nusbaum, Michael P.

    2008-01-01

    Neuronal network flexibility enables animals to respond appropriately to changes in their internal and external states. We are using the isolated crab stomatogastric nervous system to determine how extrinsic inputs contribute to network flexibility. The stomatogastric system includes the well-characterized gastric mill (chewing) and pyloric (filtering of chewed food) motor circuits in the stomatogastric ganglion. Projection neurons with somata in the commissural ganglia (CoGs) regulate these rhythms. Previous work characterized a unique gastric mill rhythm that occurred spontaneously in some preparations, but whose origin remained undetermined. This rhythm includes a distinct protractor phase activity pattern, during which all active gastric mill circuit and projection neurons fire in a pyloric rhythm-timed activity pattern instead of the tonic firing pattern exhibited by these neurons during previously studied gastric mill rhythms. Here we identify a new extrinsic input, the post-oesophageal commissure (POC) neurons, relatively brief stimulation (30 sec) of which triggers a long-lasting (tens of minutes) activation of this novel gastric mill rhythm at least in part via its lasting activation of CoG projection neurons, including the previously identified MCN1 and CPN2. Immunocytochemical and electrophysiological data suggest that the POC neurons excite MCN1 and CPN2 by release of the neuropeptide Cancer borealis tachykinin-related peptide Ia (CabTRP Ia). These data further suggest that the CoG arborization of the POC neurons comprises the previously identified anterior commissural organ (ACO), a CabTRP Ia-containing neurohemal organ. This endocrine pathway thus appears to also have paracrine actions that include activation of a novel and lasting gastric mill rhythm. PMID:18310125

  6. EVALUATION OF ESTROGENIC ACTIVITY FROM A MUNICIPAL WASTEWATER TREATMENT PLANT WITH PREDOMINANTLY DOMESTIC INPUT

    EPA Science Inventory

    The purpose of this study was to survey estrogenic releases from two primarily domestic wastewater treatment plants over three seasons (1996-1999). Mature male channel catfish were maintained at two sites within each WWTP and a reference site for 21 days. Estrogenic activity of e...

  7. Rapid and continuous activity-dependent plasticity of olfactory sensory input

    PubMed Central

    Cheetham, Claire E. J.; Park, Una; Belluscio, Leonardo

    2016-01-01

    Incorporation of new neurons enables plasticity and repair of circuits in the adult brain. Adult neurogenesis is a key feature of the mammalian olfactory system, with new olfactory sensory neurons (OSNs) wiring into highly organized olfactory bulb (OB) circuits throughout life. However, neither when new postnatally generated OSNs first form synapses nor whether OSNs retain the capacity for synaptogenesis once mature, is known. Therefore, how integration of adult-born OSNs may contribute to lifelong OB plasticity is unclear. Here, we use a combination of electron microscopy, optogenetic activation and in vivo time-lapse imaging to show that newly generated OSNs form highly dynamic synapses and are capable of eliciting robust stimulus-locked firing of neurons in the mouse OB. Furthermore, we demonstrate that mature OSN axons undergo continuous activity-dependent synaptic remodelling that persists into adulthood. OSN synaptogenesis, therefore, provides a sustained potential for OB plasticity and repair that is much faster than OSN replacement alone. PMID:26898529

  8. Brain activations associated with sign production using word and picture inputs in deaf signers.

    PubMed

    Hu, Zhiguo; Wang, Wenjing; Liu, Hongyan; Peng, Danling; Yang, Yanhui; Li, Kuncheng; Zhang, John X; Ding, Guosheng

    2011-02-01

    Effective literacy education in deaf students calls for psycholinguistic research revealing the cognitive and neural mechanisms underlying their written language processing. When learning a written language, deaf students are often instructed to sign out printed text. The present fMRI study was intended to reveal the neural substrates associated with word signing by comparing it with picture signing. Native deaf signers were asked to overtly sign in Chinese Sign Language (CSL) common objects indicated with written words or presented as pictures. Except in left inferior frontal gyrus and inferior parietal lobule where word signing elicited greater activation than picture signing, the two tasks engaged a highly overlapping set of brain regions previously implicated in sign production. The results suggest that word signing in the deaf signers relies on meaning activation from printed visual forms, followed by similar production processes from meaning to signs as in picture signing. The present study also documents the basic brain activation pattern for sign production in CSL and supports the notion of a universal core neural network for sign production across different sign languages.

  9. Convergence of inhibitory neural inputs regulate motor activity in the murine and monkey stomach.

    PubMed

    Shaylor, Lara A; Hwang, Sung Jin; Sanders, Kenton M; Ward, Sean M

    2016-11-01

    Inhibitory motor neurons regulate several gastric motility patterns including receptive relaxation, gastric peristaltic motor patterns, and pyloric sphincter opening. Nitric oxide (NO) and purines have been identified as likely candidates that mediate inhibitory neural responses. However, the contribution from each neurotransmitter has received little attention in the distal stomach. The aims of this study were to identify the roles played by NO and purines in inhibitory motor responses in the antrums of mice and monkeys. By using wild-type mice and mutants with genetically deleted neural nitric oxide synthase (Nos1(-/-)) and P2Y1 receptors (P2ry1(-/-)) we examined the roles of NO and purines in postjunctional inhibitory responses in the distal stomach and compared these responses to those in primate stomach. Activation of inhibitory motor nerves using electrical field stimulation (EFS) produced frequency-dependent inhibitory junction potentials (IJPs) that produced muscle relaxations in both species. Stimulation of inhibitory nerves during slow waves terminated pacemaker events and associated contractions. In Nos1(-/-) mice IJPs and relaxations persisted whereas in P2ry1(-/-) mice IJPs were absent but relaxations persisted. In the gastric antrum of the non-human primate model Macaca fascicularis, similar NO and purine neural components contributed to inhibition of gastric motor activity. These data support a role of convergent inhibitory neural responses in the regulation of gastric motor activity across diverse species.

  10. Human cervical spinal cord circuitry activated by tonic input can generate rhythmic arm movements.

    PubMed

    Solopova, I A; Selionov, V A; Zhvansky, D S; Gurfinkel, V S; Ivanenko, Y

    2016-02-01

    The coordination between arms and legs during human locomotion shares many features with that in quadrupeds, yet there is limited evidence for the central pattern generator for the upper limbs in humans. Here we investigated whether different types of tonic stimulation, previously used for eliciting stepping-like leg movements, may evoke nonvoluntary rhythmic arm movements. Twenty healthy subjects participated in this study. The subject was lying on the side, the trunk was fixed, and all four limbs were suspended in a gravity neutral position, allowing unrestricted low-friction limb movements in the horizontal plane. The results showed that peripheral sensory stimulation (continuous muscle vibration) and central tonic activation (postcontraction state of neuronal networks following a long-lasting isometric voluntary effort, Kohnstamm phenomenon) could evoke nonvoluntary rhythmic arm movements in most subjects. In ∼40% of subjects, tonic stimulation elicited nonvoluntary rhythmic arm movements together with rhythmic movements of suspended legs. The fact that not all participants exhibited nonvoluntary limb oscillations may reflect interindividual differences in responsiveness of spinal pattern generation circuitry to its activation. The occurrence and the characteristics of induced movements highlight the rhythmogenesis capacity of cervical neuronal circuitries, complementing the growing body of work on the quadrupedal nature of human gait.

  11. Dependence of the activity of interpositus and red nucleus neurons on sensory input data generated by movement.

    PubMed

    Burton, J E; Onoda, N

    1978-08-18

    Cats performed flexion movements of the forearm, and the discharge of interpositus and red nucleus neurons was examined for relationships to the motion and to the EMG activity of agonist and antagonist muscles. It is shown that, over a wide range in the time course of the motion, the activity of the neurons is covariant with both the EMG and the movement parameters, in particular, the velocity. Also, the discharge of the interpositus neurons is modulated in phase with the velocity of passive movement. It is concluded that during fast, intentional movements, sensory input data generated by motion is a major determinant of the output of the interpositus nucleus. Furthermore, the results are consistent with the concept that this output provides a continuous modulation of spinal segmental mechanisms by way of the red nucleus and rubrospinal tract.

  12. Inferred flows of electric currents in solar active regions

    NASA Technical Reports Server (NTRS)

    Ding, Y. J.; Hong, Q. F.; Hagyard, M. J.; Deloach, A. C.

    1985-01-01

    Techniques to identify sources of major current systems in active regions and their channels of flow are explored. Measured photospheric vector magnetic fields together with high resolution white light and H-alpha photographs provide the data base to derive the current systems in the photosphere and chromosphere of a solar active region. Simple mathematical constructions of active region fields and currents are used to interpret these data under the assumptions that the fields in the lower atmosphere (below 200 km) may not be force free but those in the chromosphere and higher are. The results obtained for the complex active region AR 2372 are: (1) Spots exhibiting significant spiral structure in the penumbral filaments were the source of vertical currents at the photospheric surface; (2) Magnetic neutral lines where the transverse magnetic field was strongly sheared were channels along which a strong current system flowed; (3) The inferred current systems produced a neutral sheet and oppositely-flowing currents in the area of the magnetic delta configuration that was the site of flaring.

  13. Eukaryotic Elongation Factor 2 Kinase Activity Is Controlled by Multiple Inputs from Oncogenic Signaling

    PubMed Central

    Wang, Xuemin; Regufe da Mota, Sergio; Liu, Rui; Moore, Claire E.; Xie, Jianling; Lanucara, Francesco; Agarwala, Usha; Pyr dit Ruys, Sébastien; Vertommen, Didier; Rider, Mark H.; Eyers, Claire E.

    2014-01-01

    Eukaryotic elongation factor 2 kinase (eEF2K), an atypical calmodulin-dependent protein kinase, phosphorylates and inhibits eEF2, slowing down translation elongation. eEF2K contains an N-terminal catalytic domain, a C-terminal α-helical region and a linker containing several regulatory phosphorylation sites. eEF2K is expressed at high levels in certain cancers, where it may act to help cell survival, e.g., during nutrient starvation. However, it is a negative regulator of protein synthesis and thus cell growth, suggesting that cancer cells may possess mechanisms to inhibit eEF2K under good growth conditions, to allow protein synthesis to proceed. We show here that the mTORC1 pathway and the oncogenic Ras/Raf/MEK/extracellular signal-regulated kinase (ERK) pathway cooperate to restrict eEF2K activity. We identify multiple sites in eEF2K whose phosphorylation is regulated by mTORC1 and/or ERK, including new ones in the linker region. We demonstrate that certain sites are phosphorylated directly by mTOR or ERK. Our data reveal that glycogen synthase kinase 3 signaling also regulates eEF2 phosphorylation. In addition, we show that phosphorylation sites remote from the N-terminal calmodulin-binding motif regulate the phosphorylation of N-terminal sites that control CaM binding. Mutations in the former sites, which occur in cancer cells, cause the activation of eEF2K. eEF2K is thus regulated by a network of oncogenic signaling pathways. PMID:25182533

  14. Voltage-activated proton current in eosinophils from human blood.

    PubMed Central

    Gordienko, D V; Tare, M; Parveen, S; Fenech, C J; Robinson, C; Bolton, T B

    1996-01-01

    1. The resting membrane potential of freshly purified normodense human eosinophils bathed in and dialysed with quasi-physiological solutions was -63 +/- 2 mV (n = 100). 2. In voltage-clamp mode with quasi-physiological internal and external solutions, voltage steps from the holding potential of -60 mV to levels positive to +20 mV resulted in development of a quasi-instantaneous outward current and a slowly developing outward current. The instantaneous current was absent when the cells were bathed in and dialysed with K(+)-free solution. 3. The slow outward current persisted following simultaneous replacement of K+, Na+ and most of the Cl- with largely impermeant ions (tetraethylammonium, N-methyl-D-glucamine and methanesulphonate) and was augmented when the cell was dialysed with a solution of increased buffering capacity for protons. The observed reversal potential of the current closely followed the hydrogen equilibrium potential over a wide range of internal-external pH combinations, indicating that the conductance underlying the slow outward current was highly selective for H+ ions. 4. Acidification of the pipette solution (increasing [H+]i) augmented the outward H+ current and shifted its activation range negatively, whilst acidification of the external solution had the opposite effect. The voltage dependence of the current is modulated by the transmembrane pH gradient so the only outward current could be activated. However, when the outward current was activated by a voltage step, rapid acidification of external solution produced an inward H+ current which rapidly deactivated. 5. The proton current was reversibly inhibited in a voltage-dependent manner by extracellular application of Zn2+. The apparent dissociation constants were 8 nM (at +40 mV), 36 nM (at +70 mV) and 200 nM (at +100 mV). 6. The proton current was augmented by exposure to 10 microM arachidonic acid. This augmentation consisted of a shift of the voltage dependence of activation to more

  15. Suppression of spontaneous epileptiform activity with applied currents.

    PubMed

    Nakagawa, M; Durand, D

    1991-12-20

    It has been well established that both applied and endogenous electric fields can modulate neuronal activity in various preparations. In this paper, we present the effects of applied currents on spontaneous epileptiform activity in the CA1 region of the rat hippocampus. A computer-controlled system was designed to detect the spontaneous abnormal activity and then apply current pulses of programmable amplitude with monopolar electrodes in the stratum pyramidale. The epileptiform activity was generated by subperfusion of the neural tissue with an elevated potassium artificial cerebrospinal fluid (CSF) solution. Extracellular recordings showed that the interictal bursts could be fully suppressed in 90% of the slices by subthreshold currents with an average amplitude of 12.5 microA. Intracellular recordings showed that the anodic currents generated hyperpolarization of the somatic membrane thereby suppressing neuronal firing. This inhibitory effect of applied current pulses is important for the understanding of electric field effects on abnormal neuronal activity and could be an effective means of preventing the spread of epileptiform activity.

  16. Optimisation of active suspension control inputs for improved vehicle ride performance

    NASA Astrophysics Data System (ADS)

    Čorić, Mirko; Deur, Joško; Xu, Li; Tseng, H. Eric; Hrovat, Davor

    2016-07-01

    A collocation-type control variable optimisation method is used in the paper to analyse to which extent the fully active suspension (FAS) can improve the vehicle ride comfort while preserving the wheel holding ability. The method is first applied for a cosine-shaped bump road disturbance of different heights, and for both quarter-car and full 10 degree-of-freedom vehicle models. A nonlinear anti-wheel hop constraint is considered, and the influence of bump preview time period is analysed. The analysis is then extended to the case of square- or cosine-shaped pothole with different lengths, and the quarter-car model. In this case, the cost function is extended with FAS energy consumption and wheel damage resilience costs. The FAS action is found to be such to provide a wheel hop over the pothole, in order to avoid or minimise the damage at the pothole trailing edge. In the case of long pothole, when the FAS cannot provide the wheel hop, the wheel is travelling over the pothole bottom and then hops over the pothole trailing edge. The numerical optimisation results are accompanied by a simplified algebraic analysis.

  17. Geomorphic change in Dingzi Bay, East China since the 1950s: impacts of human activity and fluvial input

    NASA Astrophysics Data System (ADS)

    Tian, Qing; Wang, Qing; Liu, Yalong

    2016-11-01

    This study examines the geomorphic evolution of Dingzi Bay, East China in response to human activity and variations in fluvial input since the 1950s. The analysis is based on data from multiple mathematical methods, along with information obtained from Remote Sensing, Geographic Information System and Global Position System technology. The results show that the annual runoff and sediment load discharged into Dingzi Bay display significant decreasing trends overall, and marked downward steps were observed in 1966 and 1980. Around 60%-80% of the decline is attributed to decreasing precipitation in the Wulong River Basin. The landform types in Dingzi Bay have changed significantly since the 1950s, especially over the period between 1981 and 1995. Large areas of tidal flats, swamp, salt fields, and paddy fields have been reclaimed, and aquaculture ponds have been constructed. Consequently, the patterns of erosion and deposition in the bay have changed substantially. Despite a reduction in sediment input of 65.68% after 1966, low rates of sediment deposition continued in the bay. However, deposition rates changed significantly after 1981 owing to large-scale development in the bay, with a net depositional area approximately 10 times larger than that during 1961-1981. This geomorphic evolution stabilized following the termination of large-scale human activity in the bay after 1995. Overall, Dingzi Bay has shown a tendency towards silting-up during 1952-2010, with the bay head migrating seaward, the number of channels in the tidal creek system decreasing, and the tidal inlet becoming narrower and shorter. In conclusion, largescale development and human activity in Dingzi Bay have controlled the geomorphic evolution of the bay since the 1950s.

  18. Calcium current and calcium-activated inward current in the oocyte of the starfish Leptasterias hexactis.

    PubMed Central

    Lansman, J B

    1987-01-01

    1. Inward currents in the immature oocyte of the starfish Leptasterias hexactis were studied with a two-micro-electrode voltage clamp. Experiments investigated the role of Ca2+ in the Na+-dependent plateau of the action potential. 2. Voltage steps more positive than -55 mV produced inward currents in normal sea water that activated and then decayed to a non-zero level with a double-exponential time course. Returning the voltage to the resting potential produced an inward tail current that relaxed slowly to zero with a time course of seconds. 3. Replacing Na+ with choline abolished the slowly decaying component as well as the slow tail current which followed the end of the voltage pulse. This suggested that inward current in Na+-containing sea water consisted of a rapidly decaying component that flowed through Ca2+ channels and a more slowly decaying component carried by Na+. 4. Ca2+ current was isolated in Na+-free sea water. Activation followed a sigmoidal time course that could be described with m2 kinetics. Inactivation during a maintained depolarization followed first-order kinetics and was voltage dependent. 5. When Ba2+ was substituted for Ca2+ as the divalent ion charge carrier, inward currents in Na+-containing sea water decayed along a single-exponential time course. The absence of a slowly decaying Na+ current in Ba2+-containing sea water suggested that Na+ current depended on Ca2+ influx. 6. The effects of altering Ca2+ influx on the time course of Na+ current were investigated. Na+ current decayed more rapidly as the test pulse potential was made more positive, while raising [Ca2+]o slowed the decaying phase without altering its dependence on membrane potential. 7. Tail currents measured after rapidly stepping the membrane potential back to the resting level consisted of a fast component associated with the closing of Ca2+ channels and a slow component that was abolished by removing Na+. 8. The variation of the amplitude of the slow component of tail

  19. Accessory subunit NUYM (NDUFS4) is required for stability of the electron input module and activity of mitochondrial complex I.

    PubMed

    Kahlhöfer, Flora; Kmita, Katarzyna; Wittig, Ilka; Zwicker, Klaus; Zickermann, Volker

    2017-02-01

    Mitochondrial complex I is an intricate 1MDa membrane protein complex with a central role in aerobic energy metabolism. The minimal form of complex I consists of fourteen central subunits that are conserved from bacteria to man. In addition, eukaryotic complex I comprises some 30 accessory subunits of largely unknown function. The gene for the accessory NDUFS4 subunit of human complex I is a hot spot for fatal pathogenic mutations in humans. We have deleted the gene for the orthologous NUYM subunit in the aerobic yeast Yarrowia lipolytica, an established model system to study eukaryotic complex I and complex I linked diseases. We observed assembly of complex I which lacked only subunit NUYM and retained weak interaction with assembly factor N7BML (human NDUFAF2). Absence of NUYM caused distortion of iron sulfur clusters of the electron input domain leading to decreased complex I activity and increased release of reactive oxygen species. We conclude that NUYM has an important stabilizing function for the electron input module of complex I and is essential for proper complex I function.

  20. HBT-EP Program: MHD Dynamics and Active Control through 3D Fields and Currents

    NASA Astrophysics Data System (ADS)

    Navratil, G. A.; Abler, M. C.; Bialek, J.; Brooks, J. W.; Byrne, P. J.; Desanto, S.; Hughes, P. E.; Levesque, J. P.; Mauel, M. E.; Rhodes, D. J.; Hansen, C. J.

    2016-10-01

    The HBT-EP active mode control research program aims to: (i) advance understanding of the effects of 3D shaping on advanced tokamak fusion performance, (ii) resolve important MHD issues associated with disruptions, and (iii) measure and mitigate the effects of 3D scrape-off layer (SOL) currents through active and passive control of the plasma edge and conducting boundary structures. A GPU-based low latency control system uses 96 inputs and 64 outputs to control the plasma boundary. An in-vessel adjustable ferritic wall is used to study ferritic RWMs with increased growth rates, RMP response, and disruptivity. A quasi-linear sharp-boundary model is developed to study effects of toroidal curvature and plasma shaping on beta limits with resistive plasmas and walls. Measurement of currents between vessel sections reveals currents running from the plasma to the wall during wall-touching kink modes and disruptions. Asymmetries in plasma current are observed using segmented Rogowski coils. Biased electrodes in the plasma are used to control rotation of external kinks and drive currents in the SOL. An extensive array of SOL current monitors and edge drive electrodes will be installed for pioneering studies of helical edge current control. Supported by U.S. DOE Grant DE-FG02-86ER53222.

  1. THE ORIGIN OF NET ELECTRIC CURRENTS IN SOLAR ACTIVE REGIONS

    SciTech Connect

    Dalmasse, K.; Kliem, B.; Török, T.

    2015-09-01

    There is a recurring question in solar physics regarding whether or not electric currents are neutralized in active regions (ARs). This question was recently revisited using three-dimensional (3D) magnetohydrodynamic (MHD) numerical simulations of magnetic flux emergence into the solar atmosphere. Such simulations showed that flux emergence can generate a substantial net current in ARs. Other sources of AR currents are photospheric horizontal flows. Our aim is to determine the conditions for the occurrence of net versus neutralized currents with this second mechanism. Using 3D MHD simulations, we systematically impose line-tied, quasi-static, photospheric twisting and shearing motions to a bipolar potential magnetic field. We find that such flows: (1) produce both direct and return currents, (2) induce very weak compression currents—not observed in 2.5D—in the ambient field present in the close vicinity of the current-carrying field, and (3) can generate force-free magnetic fields with a net current. We demonstrate that neutralized currents are in general produced only in the absence of magnetic shear at the photospheric polarity inversion line—a special condition that is rarely observed. We conclude that  photospheric flows, as magnetic flux emergence, can build up net currents in the solar atmosphere, in agreement with recent observations. These results thus provide support for eruption models based on pre-eruption magnetic fields that possess a net coronal current.

  2. Pacemaker activity and ionic currents in mouse atrioventricular node cells.

    PubMed

    Marger, Laurine; Mesirca, Pietro; Alig, Jacqueline; Torrente, Angelo; Dubel, Stefan; Engeland, Birgit; Kanani, Sandra; Fontanaud, Pierre; Striessnig, Jörg; Shin, Hee-Sup; Isbrandt, Dirk; Ehmke, Heimo; Nargeot, Joël; Mangoni, Matteo E

    2011-01-01

    It is well established that Pacemaker activity of the sino-atrial node (SAN) initiates the heartbeat. However, the atrioventricular node (AVN) can generate viable pacemaker activity in case of SAN failure, but we have limited knowledge of the ionic bases of AVN automaticity. We characterized pacemaker activity and ionic currents in automatic myocytes of the mouse AVN. Pacemaking of AVN cells (AVNCs) was lower than that of SAN pacemaker cells (SANCs), both in control conditions and upon perfusion of isoproterenol (ISO). Block of I(Na) by tetrodotoxin (TTX) or of I(Ca,L) by isradipine abolished AVNCs pacemaker activity. TTX-resistant (I(Nar)) and TTX-sensitive (I(Nas)) Na(+) currents were recorded in mouse AVNCs, as well as T-(I(Ca,T)) and L-type (I(Ca,L)) Ca(2+) currents I(Ca,L) density was lower than in SANCs (51%). The density of the hyperpolarization-activated current, (I(f)) and that of the fast component of the delayed rectifier current (I(Kr)) were, respectively, lower (52%) and higher (53%) in AVNCs than in SANCs. Pharmacological inhibition of I(f) by 3 µM ZD-7228 reduced pacemaker activity by 16%, suggesting a relevant role for I(f) in AVNCs automaticity. Some AVNCs expressed also moderate densities of the transient outward K(+) current (I(to)). In contrast, no detectable slow component of the delayed rectifier current (I(Ks)) could be recorded in AVNCs. The lower densities of I(f) and I(Ca,L), as well as higher expression of I(Kr) in AVNCs than in SANCs may contribute to the intrinsically slower AVNCs pacemaking than that of SANCs.

  3. Distinct Spatiotemporal Activation Patterns of the Perirhinal-Entorhinal Network in Response to Cortical and Amygdala Input

    PubMed Central

    Willems, Janske G. P.; Wadman, Wytse J.; Cappaert, Natalie L. M.

    2016-01-01

    The perirhinal (PER) and entorhinal cortex (EC) receive input from the agranular insular cortex (AiP) and the subcortical lateral amygdala (LA) and the main output area is the hippocampus. Information transfer through the PER/EC network however, is not always guaranteed. It is hypothesized that this network actively regulates the (sub)cortical activity transfer to the hippocampal network and that the inhibitory system is involved in this function. This study determined the recruitment by the AiP and LA afferents in PER/EC network with the use of voltage sensitive dye (VSD) imaging in horizontal mouse brain slices. Electrical stimulation (500 μA) of the AiP induced activity that gradually propagated predominantly in the rostro-caudal direction: from the PER to the lateral EC (LEC). In the presence of 1 μM of the competitive γ-aminobutyric acid (GABAA) receptor antagonist bicuculline, AiP stimulation recruited the medial EC (MEC) as well. In contrast, LA stimulation (500 μA) only induced activity in the deep layers of the PER. In the presence of bicuculline, the initial population activity in the PER propagated further towards the superficial layers and the EC after a delay. The latency of evoked responses decreased with increasing stimulus intensities (50–500 μA) for both the AiP and LA stimuli. The stimulation threshold for evoking responses in the PER/EC network was higher for the LA than for the AiP. This study showed that the extent of the PER/EC network activation depends on release of inhibition. When GABAA dependent inhibition is reduced, both the AiP and the LA activate spatially overlapping regions, although in a distinct spatiotemporal fashion. It is therefore hypothesized that the inhibitory network regulates excitatory activity from both cortical and subcortical areas that has to be transmitted through the PER/EC network. PMID:27378860

  4. Genetic Feedback Regulation of Frontal Cortical Neuronal Ensembles Through Activity-Dependent Arc Expression and Dopaminergic Input

    PubMed Central

    Mastwal, Surjeet; Cao, Vania; Wang, Kuan Hong

    2016-01-01

    Mental functions involve coordinated activities of specific neuronal ensembles that are embedded in complex brain circuits. Aberrant neuronal ensemble dynamics is thought to form the neurobiological basis of mental disorders. A major challenge in mental health research is to identify these cellular ensembles and determine what molecular mechanisms constrain their emergence and consolidation during development and learning. Here, we provide a perspective based on recent studies that use activity-dependent gene Arc/Arg3.1 as a cellular marker to identify neuronal ensembles and a molecular probe to modulate circuit functions. These studies have demonstrated that the transcription of Arc is activated in selective groups of frontal cortical neurons in response to specific behavioral tasks. Arc expression regulates the persistent firing of individual neurons and predicts the consolidation of neuronal ensembles during repeated learning. Therefore, the Arc pathway represents a prototypical example of activity-dependent genetic feedback regulation of neuronal ensembles. The activation of this pathway in the frontal cortex starts during early postnatal development and requires dopaminergic (DA) input. Conversely, genetic disruption of Arc leads to a hypoactive mesofrontal dopamine circuit and its related cognitive deficit. This mutual interaction suggests an auto-regulatory mechanism to amplify the impact of neuromodulators and activity-regulated genes during postnatal development. Such a mechanism may contribute to the association of mutations in dopamine and Arc pathways with neurodevelopmental psychiatric disorders. As the mesofrontal dopamine circuit shows extensive activity-dependent developmental plasticity, activity-guided modulation of DA projections or Arc ensembles during development may help to repair circuit deficits related to neuropsychiatric disorders. PMID:27999532

  5. Genetic Feedback Regulation of Frontal Cortical Neuronal Ensembles Through Activity-Dependent Arc Expression and Dopaminergic Input.

    PubMed

    Mastwal, Surjeet; Cao, Vania; Wang, Kuan Hong

    2016-01-01

    Mental functions involve coordinated activities of specific neuronal ensembles that are embedded in complex brain circuits. Aberrant neuronal ensemble dynamics is thought to form the neurobiological basis of mental disorders. A major challenge in mental health research is to identify these cellular ensembles and determine what molecular mechanisms constrain their emergence and consolidation during development and learning. Here, we provide a perspective based on recent studies that use activity-dependent gene Arc/Arg3.1 as a cellular marker to identify neuronal ensembles and a molecular probe to modulate circuit functions. These studies have demonstrated that the transcription of Arc is activated in selective groups of frontal cortical neurons in response to specific behavioral tasks. Arc expression regulates the persistent firing of individual neurons and predicts the consolidation of neuronal ensembles during repeated learning. Therefore, the Arc pathway represents a prototypical example of activity-dependent genetic feedback regulation of neuronal ensembles. The activation of this pathway in the frontal cortex starts during early postnatal development and requires dopaminergic (DA) input. Conversely, genetic disruption of Arc leads to a hypoactive mesofrontal dopamine circuit and its related cognitive deficit. This mutual interaction suggests an auto-regulatory mechanism to amplify the impact of neuromodulators and activity-regulated genes during postnatal development. Such a mechanism may contribute to the association of mutations in dopamine and Arc pathways with neurodevelopmental psychiatric disorders. As the mesofrontal dopamine circuit shows extensive activity-dependent developmental plasticity, activity-guided modulation of DA projections or Arc ensembles during development may help to repair circuit deficits related to neuropsychiatric disorders.

  6. CURRENT AND KINETIC HELICITY OF LONG-LIVED ACTIVITY COMPLEXES

    SciTech Connect

    Komm, Rudolf; Gosain, Sanjay

    2015-01-01

    We study long-lived activity complexes and their current helicity at the solar surface and their kinetic helicity below the surface. The current helicity has been determined from synoptic vector magnetograms from the NSO/SOLIS facility, and the kinetic helicity of subsurface flows has been determined with ring-diagram analysis applied to full-disk Dopplergrams from NSO/GONG and SDO/HMI. Current and kinetic helicity of activity complexes follow the hemispheric helicity rule with mainly positive values (78%; 78%, respectively, with a 95% confidence level of 31%) in the southern hemisphere and negative ones (80%; 93%, respectively, with a 95% confidence level of 22% and 14%, respectively) in the northern hemisphere. The locations with the dominant sign of kinetic helicity derived from Global Oscillation Network Group (GONG) and SDO/HMI data are more organized than those of the secondary sign even if they are not part of an activity complex, while locations with the secondary sign are more fragmented. This is the case for both hemispheres even for the northern one where it is not as obvious visually due to the large amount of magnetic activity present as compared to the southern hemisphere. The current helicity shows a similar behavior. The dominant sign of current helicity is the same as that of kinetic helicity for the majority of the activity complexes (83% with a 95% confidence level of 15%). During the 24 Carrington rotations analyzed here, there is at least one longitude in each hemisphere where activity complexes occur repeatedly throughout the epoch. These ''active'' longitudes are identifiable as locations of strong current and kinetic helicity of the same sign.

  7. Electric currents and coronal heating in NOAA active region 6952

    NASA Technical Reports Server (NTRS)

    Metcalf, T. R.; Canfield, R. C.; Hudson, H. S.; Mickey, D. L.; Wulser, J. -P.; Martens, P. C. H.; Tsuneta, S.

    1994-01-01

    We examine the spatial and temporal relationship between coronal structures observed with the soft X-ray telescope (SXT) on board the Yohkoh spacecraft and the vertical electric current density derived from photospheric vector magnetograms obtained using the Stokes Polarimeter at the Mees Solar Observatory. We focus on a single active region: AR 6952 which we observed on 7 days during 1991 December. For 11 independent maps of the vertical electric current density co-aligned with non-flaring X-ray images, we search for a morphological relationship between sites of high vertical current density in the photosphere and enhanced X-ray emission in the overlying corona. We find no compelling spatial or temporal correlation between the sites of vertical current and the bright X-ray structures in this active region.

  8. Voltage and Current Unbalance Compensation Using a Parallel Active Filter

    SciTech Connect

    Xu, Yan; Tolbert, Leon M; Kueck, John D; Rizy, D Tom

    2007-01-01

    A three-phase insulated gate bipolar transistor (IGBT)-based parallel active filter is used for current and/or voltage unbalance compensation. An instantaneous power theory is adopted for real-time calculation and control. Three control schemes, current control, voltage control, and integrated control are proposed to compensate the unbalance of current, voltage, or both. The compensation results of the different control schemes in unbalance cases (load unbalance or voltage source unbalance) are compared and analyzed. The simulation and experimental results show that the control schemes can compensate the unbalance in load current or in the voltage source. Different compensation objectives can be achieved, i.e., balanced and unity power factor source current, balanced and regulated voltage, or both, by choosing appropriate control schemes.

  9. Changes in muscle activation patterns in response to enhanced sensory input during treadmill stepping in infants born with myelomeningocele

    PubMed Central

    Pantall, Annette; Teulier, Caroline; Ulrich, Beverly D.

    2013-01-01

    Infants with myelomeningocele (MMC) increase step frequency in response to modifications to the treadmill surface. The aim was to investigate how these modifications impacted the electromyographic (EMG) patterns. We analyzed EMG from 19 infants aged 2–10 months, with MMC at the lumbosacral level. We supported infants upright on the treadmill for 12 trials, each 30 seconds long. Modifications included visual flow, unloading, weights, Velcro and lcriction. Surface electrodes recorded EMG from tibialis anterior, lateral gastrocnemius, rectus femoris and biceps femoris. We determined muscle bursts for each stride cycle and from these calculated various parameters. Results indicated that each of the five sensory conditions generated different motor patterns. Visual flow and friction which we previously reported increased step frequency impacted lateral gastrocnemius most. Weights, which significantly decreased step frequency increased burst duration and co-activity of the proximal muscles. We also observed an age effect, with all conditions increasing muscle activity in younger infants whereas in older infants visual flow and unloading stimulated most activity. In conclusion, we have demonstrated that infants with myelomeningocele at levels which impact the myotomes of major locomotor muscles find ways to respond and adapt their motor output to changes in sensory input. PMID:23158017

  10. Antiepileptic Activity of Preferential Inhibitors of Persistent Sodium Current

    PubMed Central

    Anderson, Lyndsey L.; Thompson, Christopher H.; Hawkins, Nicole A.; Nath, Ravi D.; Petersohn, Adam A.; Rajamani, Sridharan; Bush, William S.; Frankel, Wayne N.; Vanoye, Carlos G.; Kearney, Jennifer A.; George, Alfred L.

    2014-01-01

    Objective Evidence from basic neurophysiology and molecular genetics has implicated persistent sodium current conducted by voltage-gated sodium (NaV) channels as a contributor to the pathogenesis of epilepsy. Many antiepileptic drugs target NaV channels and modulate neuronal excitability mainly by a use-dependent block of transient sodium current, although suppression of persistent current may also contribute to the efficacy of these drugs. We hypothesized that a drug or compound capable of preferential inhibition of persistent sodium current would have antiepileptic activity. Methods We examined the antiepileptic activity of two selective persistent sodium current blockers ranolazine, an FDA-approved drug for treatment of angina pectoris, and GS967, a novel compound with more potent effects on persistent current, in the epileptic Scn2aQ54 mouse model. We also examined the effect of GS967 in the maximal electroshock model and evaluated effects of the compound on neuronal excitability, propensity for hilar neuron loss, development of mossy fiber sprouting and survival of Scn2aQ54 mice. Results We found that ranolazine was capable of reducing seizure frequency by ~50% in Scn2aQ54 mice. The more potent persistent current blocker GS967 reduced seizure frequency by greater than 90% in Scn2aQ54 mice and protected against induced seizures in the maximal electroshock model. GS967 greatly attenuated abnormal spontaneous action potential firing in pyramidal neurons acutely isolated from Scn2aQ54 mice. In addition to seizure suppression in vivo, GS967 treatment greatly improved the survival of Scn2aQ54 mice, prevented hilar neuron loss, and suppressed the development of hippocampal mossy fiber sprouting. Significance Our findings indicate that the selective persistent sodium current blocker GS967 has potent antiepileptic activity and this compound could inform development of new agents. PMID:24862204

  11. Current Activity of the U.S. ASTER Science Team

    NASA Technical Reports Server (NTRS)

    Kahle, A. B.; Abrams, M. J.; Hook, S. J.; Pieri, D. C.; Ramsey, M.; Rowan, L. C.; Schmugge, T.; Wessels, R.

    2001-01-01

    The U.S. ASTER Science Team is currently engaged in numerous ASTER related activities, many of them jointly with our Japanese colleagues. These include vicarious instrument calibration, algorithm development and validation for higher level data products, assistance to ERSDAC for scheduling activities (primarily for U.S. users), assistance to data users other than Science Team members, and science applications of ASTER data, notably in the areas of glacial monitoring, volcanic monitoring, heat balance determinations, geologic mapping, and cloud studies.

  12. IS THE CURRENT LACK OF SOLAR ACTIVITY ONLY SKIN DEEP?

    SciTech Connect

    Broomhall, A.-M.; Chaplin, W. J.; Elsworth, Y.; Fletcher, S. T.; New, R. E-mail: wjc@bison.ph.bham.ac.uk E-mail: S.Fletcher@shu.ac.uk

    2009-08-01

    The Sun is a variable star whose magnetic activity and total irradiance vary on a timescale of approximately 11 years. The current activity minimum has attracted considerable interest because of its unusual duration and depth. This raises the question: what might be happening beneath the surface where the magnetic activity ultimately originates? The surface activity can be linked to the conditions in the solar interior by the observation and analysis of the frequencies of the Sun's natural seismic modes of oscillation-the p modes. These seismic frequencies respond to changes in activity and are probes of conditions within the Sun. The Birmingham Solar-Oscillations Network (BiSON) has made measurements of p-mode frequencies over the last three solar activity cycles, and so is in a unique position to explore the current unusual and extended solar minimum. We show that the BiSON data reveal significant variations of the p-mode frequencies during the current minimum. This is in marked contrast to the surface activity observations, which show little variation over the same period. The level of the minimum is significantly deeper in the p-mode frequencies than in the surface observations. We observe a quasi-biennial signal in the p-mode frequencies, which has not previously been observed at mid- and low-activity levels. The stark differences in the behavior of the frequencies and the surface activity measures point to activity-related processes occurring in the solar interior, which are yet to reach the surface, where they may be attenuated.

  13. Modulation of divalent cation-activated chloride ion currents.

    PubMed

    Scott, R H; McGuirk, S M; Dolphin, A C

    1988-07-01

    1. Voltage-sensitive calcium channel currents carried by Ca2+ (ICa) or Ba2+ (IBa) were followed by tail currents carried by Cl- ions in approximately 45% of cultured dorsal root ganglion neurones. 2. Extracellular application of (-)-baclofen (100 microM) inhibited IBa and ICl(Ba). Bay K 8644 (5 microM) potentiated both currents. 3. Intracellular GTP-gamma-S increased the proportion of neurones in which ICl(Ba) was recorded. In addition, the activation by GTP-gamma-S of a pertussis toxin-sensitive GTP binding (G)-protein resulted in a steady increase in the Cl- tail current with time, despite a concurrent reduction in IBa. 4. Extracellular application of 10mM caffeine selectively reduced ICl(Ba) without significant change in IBa. When Ca2+ was the charge carrier, caffeine had little effect on ICl(Ca), and increased the inactivation of ICa. 5. We conclude that, in addition to being regulated by divalent cation entry through Ca2+ channels, the Cl- current is also regulated by G-protein activation. The mechanism of activation of ICl(Ba) may involve Ca2+ release from intracellular stores.

  14. Transnational Higher Education: A Stock Take of Current Activity

    ERIC Educational Resources Information Center

    Naidoo, Vik

    2009-01-01

    Transnational higher education (TNHE) development is not an entirely new international activity in the education services sector. The nature and scale of the global expansion of contemporary TNHE developments are, however, changing substantially. An understanding of this growth is currently largely lacking because of a dearth of comprehensive…

  15. The Current State of Marketing Activity among Higher Education Institutions.

    ERIC Educational Resources Information Center

    Newman, Cynthia M.

    2002-01-01

    Investigated the current state of marketing, marketing research, and planning practices at four-year higher education institutions. Builds upon previous studies by Blackburn (1979) and Goldgehn (1982 and 1989). Determined whether the use and apparent understanding of marketing and its attendant activities by admissions and enrollment management…

  16. Fast Delayed Rectifier Potassium Current Required for Circadian Neural Activity

    PubMed Central

    JN, Itri; S, Michel; MJ, Vansteensel; JH, Meijer; CS, Colwell

    2005-01-01

    In mammals, the precise circadian timing of many biological processes depends on the generation of oscillations in neural activity of pacemaker cells in the suprachiasmatic nucleus (SCN). The ionic mechanisms underlying these rhythms are largely unknown. Using the mouse brain slice preparation, we demonstrate that the magnitude of fast delayed rectifier potassium currents exhibits a diurnal rhythm that peaks during the day. Importantly, this rhythm continues in constant darkness, providing the first demonstration of the circadian regulation of an intrinsic voltage–gated current in mammalian cells. Blocking this current prevented the daily rhythm in firing rate in SCN neurons. Kv3.1b and Kv3.2 potassium channels were found to be widely distributed within the SCN with higher expression during the day. We conclude that the fast delayed rectifier is necessary for the circadian modulation of electrical activity in SCN neurons, and represents an important part of the ionic basis for the generation of rhythmic output. PMID:15852012

  17. Pharmacological characterization of BDNF promoters I, II and IV reveals that serotonin and norepinephrine input is sufficient for transcription activation.

    PubMed

    Musazzi, L; Rimland, J M; Ieraci, A; Racagni, G; Domenici, E; Popoli, M

    2014-05-01

    Compelling evidence has shown that the effects of antidepressants, increasing extracellular serotonin and noradrenaline as a primary mechanism of action, involve neuroplastic and neurotrophic mechanisms. Brain-derived neurotrophic factor (BDNF) has been shown to play a key role in neuroplasticity and synaptic function, as well as in the pathophysiology of neuropsychiatric disorders and the mechanism of action of antidepressants. The expression of BDNF is mediated by the transcription of different mRNAs derived by the splicing of one of the eight 5' non-coding exons with the 3' coding exon (in rats). The transcription of each non-coding exon is driven by unique and different promoters. We generated a gene reporter system based on hippocampal and cortical neuronal cultures, in which the transcription of luciferase is regulated by BDNF promoters I, II, IV or by cAMP response element (CRE), to investigate the activation of selected promoters induced by monoaminergic antidepressants and by serotonin or noradrenaline agonists. We found that incubation with fluoxetine or reboxetine failed to induce any activation of BDNF promoters or CRE. On the other hand, the incubation of cultures with selective agonists of serotonin or noradrenaline receptors induced a specific and distinct profile of activation of BDNF promoters I, II, IV and CRE, suggesting that the monoaminergic input, absent in dissociated cultures, is essential for the modulation of BDNF expression. In summary, we applied a rapidly detectable and highly sensitive reporter gene assay to characterize the selective activation profile of BDNF and CRE promoters, through specific and different pharmacological stimuli.

  18. Parallel input parallel output high voltage bi-directional converters for driving dielectric electro active polymer actuators

    NASA Astrophysics Data System (ADS)

    Thummala, P.; Zhang, Z.; Andersen, M. A. E.; Rahimullah, S.

    2014-03-01

    Dielectric electroactive polymer (DEAP) actuators are capacitive devices which provide mechanical motions when charged electrically. The charging characteristics of a DEAP actuator depends on its size, voltage applied to its electrodes, and its operating frequency. The main idea of this paper is to design and implement driving circuits for the DEAP actuators for their use in various applications. This paper presents implementation of parallel input, parallel output, high voltage (~2.5 kV) bi-directional DC-DC converters for driving the DEAP actuators. The topology is a bidirectional flyback DC-DC converter incorporating commercially available high voltage MOSFETs (4 kV) and high voltage diodes (5 kV). Although the average current of the aforementioned devices is limited to 300 mA and 150 mA, respectively, connecting the outputs of multiple converters in parallel can provide a scalable design. This enables operating the DEAP actuators in various static and dynamic applications e.g. positioning, vibration generation or damping, and pumps. The proposed idea is experimentally verified by connecting three high voltage converters in parallel to operate a single DEAP actuator. The experimental results with both film capacitive load and the DEAP actuator are shown for a maximum charging voltage of 2 kV.

  19. Current concepts of active vasodilation in human skin

    PubMed Central

    Wong, Brett J.; Hollowed, Casey G.

    2017-01-01

    ABSTRACT In humans, an increase in internal core temperature elicits large increases in skin blood flow and sweating. The increase in skin blood flow serves to transfer heat via convection from the body core to the skin surface while sweating results in evaporative cooling of the skin. Cutaneous vasodilation and sudomotor activity are controlled by a sympathetic cholinergic active vasodilator system that is hypothesized to operate through a co-transmission mechanism. To date, mechanisms of cutaneous active vasodilation remain equivocal despite many years of research by several productive laboratory groups. The purpose of this review is to highlight recent advancements in the field of cutaneous active vasodilation framed in the context of some of the historical findings that laid the groundwork for our current understanding of cutaneous active vasodilation. PMID:28349094

  20. Activation of outward K+ currents: effect of VIP in oesophagus

    PubMed Central

    Jury, Jennifer; Daniel, Edwin E

    1999-01-01

    Electrical field stimulations (EFS) of the opossum and canine lower oesophageal sphincters (OLOS and CLOS respectively) and opossum oesophageal body circular muscle (OOBCM) induce non-adrenergic, non-cholinergic (NANC) relaxations of any active tension and NO-mediated hyperpolarization. VIP relaxes the OLOS and CLOS and any tone in OOBCM without major electrophysiological effects. These relaxations are not blocked by NOS inhibitors. Using isolated smooth muscle cells, we tested whether VIP acted through myogenic NO production.Outward currents were similar in OOBCM and OLOS and NO increased them regardless of pipette Ca2+i, from 50–8000 nM. L-NAME or L-NOARG did not block outward currents in OLOS at 200 nM pipette Ca2+.Outward currents in CLOS cells decreased at 200 nM pipette Ca2+ or less but NO donors still increased them. VIP had no effect on outward currents in cells from OOBCM, OLOS or CLOS under conditions of pipette Ca2+ at which NO donors increased outward K+ currents.We conclude, VIP does not mimic electrophysiological effects of NO donors on isolated cells of OOBCM, OLOS or CLOS. VIP relaxes the OLOS and CLOS and inhibits contraction of OOBCM by a mechanism unrelated to release of myogenic NO or an increase in outward current.Also, the different dependence of outward currents of OOBCM and OLOS on pipette Ca2+ from those of CLOS suggests that different K+ channels are involved and that myogenic NO production contributes to K+ channel activity in CLOS but not in OLOS or OOBCM. PMID:10385258

  1. Current Research Activities of the Department of Oceanography.

    DTIC Science & Technology

    1981-04-01

    cores indicate that concentrations of both chemical The goal of this continuing classes have increased by up to a research is to assemble a unified...ofOeaorah 0 EvhmtL .. - CURRENT RESEARCH ACTIVITIES / OF THE DEPARTMENT OF OCEANOGRAPHY University of Washington Seattle, Washington 98195 Reference: A81-3...Production control mechanisms of the subarctic Pacific Oceano.............7 Subarctic Pacific ecosystem research : a planning project

  2. Repeating Spatial-Temporal Motifs of CA3 Activity Dependent on Engineered Inputs from Dentate Gyrus Neurons in Live Hippocampal Networks

    PubMed Central

    Bhattacharya, Aparajita; Desai, Harsh; DeMarse, Thomas B.; Wheeler, Bruce C.; Brewer, Gregory J.

    2016-01-01

    Anatomical and behavioral studies, and in vivo and slice electrophysiology of the hippocampus suggest specific functions of the dentate gyrus (DG) and the CA3 subregions, but the underlying activity dynamics and repeatability of information processing remains poorly understood. To approach this problem, we engineered separate living networks of the DG and CA3 neurons that develop connections through 51 tunnels for axonal communication. Growing these networks on top of an electrode array enabled us to determine whether the subregion dynamics were separable and repeatable. We found spontaneous development of polarized propagation of 80% of the activity in the native direction from DG to CA3 and different spike and burst dynamics for these subregions. Spatial-temporal differences emerged when the relationships of target CA3 activity were categorized with to the number and timing of inputs from the apposing network. Compared to times of CA3 activity when there was no recorded tunnel input, DG input led to CA3 activity bursts that were 7× more frequent, increased in amplitude and extended in temporal envelope. Logistic regression indicated that a high number of tunnel inputs predict CA3 activity with 90% sensitivity and 70% specificity. Compared to no tunnel input, patterns of >80% tunnel inputs from DG specified different patterns of first-to-fire neurons in the CA3 target well. Clustering dendrograms revealed repeating motifs of three or more patterns at up to 17 sites in CA3 that were importantly associated with specific spatial-temporal patterns of tunnel activity. The number of these motifs recorded in 3 min was significantly higher than shuffled spike activity and not seen above chance in control networks in which CA3 was apposed to CA3 or DG to DG. Together, these results demonstrate spontaneous input-dependent repeatable coding of distributed activity in CA3 networks driven by engineered inputs from DG networks. These functional configurations at measured times

  3. Predicting the activity phase of a follower neuron with A-current in an inhibitory network.

    PubMed

    Zhang, Yu; Bose, Amitabha; Nadim, Farzan

    2008-09-01

    The transient potassium A-current is present in most neurons and plays an important role in determining the timing of action potentials. We examine the role of the A-current in the activity phase of a follower neuron in a rhythmic feed-forward inhibitory network with a reduced three-variable model and conduct experiments to verify the usefulness of our model. Using geometric analysis of dynamical systems, we explore the factors that determine the onset of activity in a follower neuron following release from inhibition. We first analyze the behavior of the follower neuron in a single cycle and find that the phase plane structure of the model can be used to predict the potential behaviors of the follower neuron following release from inhibition. We show that, depending on the relative scales of the inactivation time constant of the A-current and the time constant of the recovery variable, the follower neuron may or may not reach its active state following inhibition. Our simple model is used to derive a recursive set of equations to predict the contribution of the A-current parameters in determining the activity phase of a follower neuron as a function of the duration and frequency of the inhibitory input it receives. These equations can be used to demonstrate the dependence of activity phase on the period and duty cycle of the periodic inhibition, as seen by comparing the predictions of the model with the activity of the pyloric constrictor (PY) neurons in the crustacean pyloric network.

  4. Design, experimental verification, and analysis of a 1.8-V-input-range voltage-to-current converter using source degeneration for low-noise multimodal CMOS biosensor array

    NASA Astrophysics Data System (ADS)

    Niitsu, Kiichi; Ikeda, Kei; Muto, Keita; Nakazato, Kazuo

    2017-01-01

    A multimodal complementary metal-oxide semiconductor (CMOS) biosensor array manufactured using measurement methods such as potentiometry, amperometry, and impedimetry improves its cost competitiveness and measurement accuracy. In addition, it provides a wider range of application because it can obtain signals from multiple aspects. To develop high-signal-to-noise ratio (SNR) multimodal biosensor arrays, time-domain current integration was proposed in the literature and found to be effective. In addition to amperometry and impedimetry, it is possible to perform current integration using the potentiometry output by employing a voltage-to-current converter (VCC). However, a conventional VCC with a fixed transconductance mode does not provide a sufficient input range (<0.6 V) and its noise property has not been investigated. In this work, we investigate the design and noise property of a newly proposed VCC with source degeneration that enhances the input range. For evaluating the proposed method, a test chip was fabricated in a 0.6 µm CMOS. The measured results successfully demonstrate that the input range was enhanced from 0.6 to 1.8 V. Autonomous current limitation was also confirmed. The measured total input-referred noise was 0.445 mV (from 10 Hz to 10 kHz, assuming current integration at every 1 ms).

  5. Spatiotemporal order and emergent edge currents in active spinner materials

    PubMed Central

    van Zuiden, Benjamin C.; Paulose, Jayson; Irvine, William T. M.; Bartolo, Denis; Vitelli, Vincenzo

    2016-01-01

    Collections of interacting, self-propelled particles have been extensively studied as minimal models of many living and synthetic systems from bird flocks to active colloids. However, the influence of active rotations in the absence of self-propulsion (i.e., spinning without walking) remains less explored. Here, we numerically and theoretically investigate the behavior of ensembles of self-spinning dimers. We find that geometric frustration of dimer rotation by interactions yields spatiotemporal order and active melting with no equilibrium counterparts. At low density, the spinning dimers self-assemble into a triangular lattice with their orientations phase-locked into spatially periodic phases. The phase-locked patterns form dynamical analogs of the ground states of various spin models, transitioning from the three-state Potts antiferromagnet at low densities to the striped herringbone phase of planar quadrupoles at higher densities. As the density is raised further, the competition between active rotations and interactions leads to melting of the active spinner crystal. Emergent edge currents, whose direction is set by the chirality of the active spinning, arise as a nonequilibrium signature of the transition to the active spinner liquid and vanish when the system eventually undergoes kinetic arrest at very high densities. Our findings may be realized in systems ranging from liquid crystal and colloidal experiments to tabletop realizations using macroscopic chiral grains. PMID:27803323

  6. Hyperpolarization-Activated Currents and Subthreshold Resonance in Granule Cells of the Olfactory Bulb

    PubMed Central

    Hu, Ruilong; Ferguson, Katie A.; Meijer, Dimphna H.

    2016-01-01

    Abstract An important contribution to neural circuit oscillatory dynamics is the ongoing activation and inactivation of hyperpolarization-activated currents (Ih). Network synchrony dynamics play an important role in the initial processing of odor signals by the main olfactory bulb (MOB) and accessory olfactory bulb (AOB). In the mouse olfactory bulb, we show that Ih is present in granule cells (GCs), the most prominent inhibitory neuron in the olfactory bulb, and that Ih underlies subthreshold resonance in GCs. In accord with the properties of Ih, the currents exhibited sensitivity to changes in extracellular K+ concentration and ZD7288 (4-ethylphenylamino-1,2-dimethyl-6-methylaminopyrimidin chloride), a blocker of Ih. ZD7288 also caused GCs to hyperpolarize and increase their input resistance, suggesting that Ih is active at rest in GCs. The inclusion of cAMP in the intracellular solution shifted the activation of Ih to less negative potentials in the MOB, but not in the AOB, suggesting that channels with different subunit composition mediate Ih in these regions. Furthermore, we show that mature GCs exhibit Ih-dependent subthreshold resonance in the theta frequency range (4–12 Hz). Another inhibitory subtype in the MOB, the periglomerular cells, exhibited Ih-dependent subthreshold resonance in the delta range (1–4 Hz), while principal neurons, the mitral cells, do not exhibit Ih-dependent subthreshold resonance. Importantly, Ih size, as well as the strength and frequency of resonance in GCs, exhibited a postnatal developmental progression, suggesting that this development of Ih in GCs may differentially contribute to their integration of sensory input and contribution to oscillatory circuit dynamics. PMID:27844056

  7. Current status on tissue factor activation of factor VIIa.

    PubMed

    Persson, Egon; Olsen, Ole H

    2010-04-01

    Free factor VIIa displays a zymogen-like behavior with low intrinsic activity. Formation of a complex between factor VIIa and tissue factor is necessary to enhance the procoagulant activity of factor VIIa, not only by providing membrane localization, substrate exosites and positioning the active site at an appropriate distance above the surface but also by allosteric enhancement of the enzymatic activity, and this event signals initiation of blood coagulation. The interaction is of high affinity and all the domains are engaged at the interface. The crosstalk between the protease domain of factor VIIa, in particular residue Met-306, and the N-terminal domain of tissue factor provides the starting point for the allosteric activation of factor VIIa. The pathway(s) of conformational transitions in factor VIIa ensuing tissue factor binding has not been entirely mapped. The present paper is a brief compilation of our current knowledge of the allosteric mechanism by which tissue factor induces and stabilizes the active conformation of factor VIIa.

  8. Improved Active Harmonic Current Elimination Based on Voltage Detection.

    PubMed

    Tan, Tianyuan; Dong, Shuan; Huang, Yingwei; Liu, Jian; Le, Jian; Liu, Kaipei

    2016-01-01

    With the increasing penetration of power electronic equipment in modern residential distribution systems, harmonics mitigation through the distributed generation (DG) interfacing converters has received significant attention. Among recently proposed methods, the so-called active resonance damper (ARD) and harmonic voltage compensator (HVC) based on voltage detection can effectively reduce the harmonic distortions in selected areas of distribution systems. However, it is found out that when traditional ARD algorithm is used to eliminate harmonic current injected by non-linear loads, its performance is constrained by stability problems and can at most eliminate half of the load harmonic currents. Thus, inspired by the duality between ARD and HVC, this paper presents a novel improved resistive active power filter (R-APF) algorithm based on integral-decoupling control. The design guideline for its parameters is then investigated through carefully analyzing the closed-loop poles' trajectory. Computer studies demonstrate that the proposed algorithm can effectively mitigate the load harmonic currents and its performance is much better than traditional ARD based on proportional control.

  9. Improved Active Harmonic Current Elimination Based on Voltage Detection

    PubMed Central

    Tan, Tianyuan; Dong, Shuan; Huang, Yingwei; Liu, Jian; Le, Jian; Liu, Kaipei

    2016-01-01

    With the increasing penetration of power electronic equipment in modern residential distribution systems, harmonics mitigation through the distributed generation (DG) interfacing converters has received significant attention. Among recently proposed methods, the so-called active resonance damper (ARD) and harmonic voltage compensator (HVC) based on voltage detection can effectively reduce the harmonic distortions in selected areas of distribution systems. However, it is found out that when traditional ARD algorithm is used to eliminate harmonic current injected by non-linear loads, its performance is constrained by stability problems and can at most eliminate half of the load harmonic currents. Thus, inspired by the duality between ARD and HVC, this paper presents a novel improved resistive active power filter (R-APF) algorithm based on integral-decoupling control. The design guideline for its parameters is then investigated through carefully analyzing the closed-loop poles’ trajectory. Computer studies demonstrate that the proposed algorithm can effectively mitigate the load harmonic currents and its performance is much better than traditional ARD based on proportional control. PMID:27295213

  10. Adaptive Current Control Method for Hybrid Active Power Filter

    NASA Astrophysics Data System (ADS)

    Chau, Minh Thuyen

    2016-09-01

    This paper proposes an adaptive current control method for Hybrid Active Power Filter (HAPF). It consists of a fuzzy-neural controller, identification and prediction model and cost function. The fuzzy-neural controller parameters are adjusted according to the cost function minimum criteria. For this reason, the proposed control method has a capability on-line control clings to variation of the load harmonic currents. Compared to the single fuzzy logic control method, the proposed control method shows the advantages of better dynamic response, compensation error in steady-state is smaller, able to online control is better and harmonics cancelling is more effective. Simulation and experimental results have demonstrated the effectiveness of the proposed control method.

  11. Current water resources activities in Alabama, fiscal year 1986

    USGS Publications Warehouse

    Slack, L.J.; Meadows, E.A.

    1986-01-01

    The purpose of this report is to describe the current (as of 1986) water resources activities of the U.S. Geological Survey in Alabama. The responsibilities and objectives of the Survey; organization of the Alabama District; sources of funding; current projects; hydrologic data program; and a selected bibliography of hydrologic reports are presented. Water resources projects are undertaken usually at the request of and with partial funding from another agency, provided: they are high priority problems and generally identified to fall within the mission of the Water Resources Division and they are consistent with the Program Management Plan developed by the Water Resources Division in Alabama to meet the long range plan for hydrologic data in the State. (USGS)

  12. Voltage Dependence of a Neuromodulator-Activated Ionic Current123

    PubMed Central

    2016-01-01

    Abstract The neuromodulatory inward current (IMI) generated by crab Cancer borealis stomatogastric ganglion neurons is an inward current whose voltage dependence has been shown to be crucial in the activation of oscillatory activity of the pyloric network of this system. It has been previously shown that IMI loses its voltage dependence in conditions of low extracellular calcium, but that this effect appears to be regulated by intracellular calmodulin. Voltage dependence is only rarely regulated by intracellular signaling mechanisms. Here we address the hypothesis that the voltage dependence of IMI is mediated by intracellular signaling pathways activated by extracellular calcium. We demonstrate that calmodulin inhibitors and a ryanodine antagonist can reduce IMI voltage dependence in normal Ca2+, but that, in conditions of low Ca2+, calmodulin activators do not restore IMI voltage dependence. Further, we show evidence that CaMKII alters IMI voltage dependence. These results suggest that calmodulin is necessary but not sufficient for IMI voltage dependence. We therefore hypothesize that the Ca2+/calmodulin requirement for IMI voltage dependence is due to an active sensing of extracellular calcium by a GPCR family calcium-sensing receptor (CaSR) and that the reduction in IMI voltage dependence by a calmodulin inhibitor is due to CaSR endocytosis. Supporting this, preincubation with an endocytosis inhibitor prevented W7 (N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride)-induced loss of IMI voltage dependence, and a CaSR antagonist reduced IMI voltage dependence. Additionally, myosin light chain kinase, which is known to act downstream of the CaSR, seems to play a role in regulating IMI voltage dependence. Finally, a Gβγ-subunit inhibitor also affects IMI voltage dependence, in support of the hypothesis that this process is regulated by a G-protein-coupled CaSR. PMID:27257619

  13. Voltage Dependence of a Neuromodulator-Activated Ionic Current.

    PubMed

    Gray, Michael; Golowasch, Jorge

    2016-01-01

    The neuromodulatory inward current (IMI) generated by crab Cancer borealis stomatogastric ganglion neurons is an inward current whose voltage dependence has been shown to be crucial in the activation of oscillatory activity of the pyloric network of this system. It has been previously shown that IMI loses its voltage dependence in conditions of low extracellular calcium, but that this effect appears to be regulated by intracellular calmodulin. Voltage dependence is only rarely regulated by intracellular signaling mechanisms. Here we address the hypothesis that the voltage dependence of IMI is mediated by intracellular signaling pathways activated by extracellular calcium. We demonstrate that calmodulin inhibitors and a ryanodine antagonist can reduce IMI voltage dependence in normal Ca(2+), but that, in conditions of low Ca(2+), calmodulin activators do not restore IMI voltage dependence. Further, we show evidence that CaMKII alters IMI voltage dependence. These results suggest that calmodulin is necessary but not sufficient for IMI voltage dependence. We therefore hypothesize that the Ca(2+)/calmodulin requirement for IMI voltage dependence is due to an active sensing of extracellular calcium by a GPCR family calcium-sensing receptor (CaSR) and that the reduction in IMI voltage dependence by a calmodulin inhibitor is due to CaSR endocytosis. Supporting this, preincubation with an endocytosis inhibitor prevented W7 (N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride)-induced loss of IMI voltage dependence, and a CaSR antagonist reduced IMI voltage dependence. Additionally, myosin light chain kinase, which is known to act downstream of the CaSR, seems to play a role in regulating IMI voltage dependence. Finally, a Gβγ-subunit inhibitor also affects IMI voltage dependence, in support of the hypothesis that this process is regulated by a G-protein-coupled CaSR.

  14. Arginine Vasopressin Alters Both Spontaneous and Phase-Locked Synaptic Inputs to Airway Vagal Preganglionic Neuron via Activation of V1a Receptor: Insights into Stress-Related Airway Vagal Excitation

    PubMed Central

    Yan, Xianxia; Chen, Xingxin; Guo, Yuhong; He, Ding; Chen, Yonghua; Xia, Chunmei; Wang, Jijiang

    2017-01-01

    postsynaptic currents (mEPSCs), miniature inhibitory postsynaptic currents (mIPSCs) and membrane input resistance of either type of AVPNs. These results demonstrate that AVP, via activation of V1a receptors, enhanced the spontaneous excitatory and inhibitory inputs similarly in the two types of AVPNs, but differentially altered their phase-locked inspiratory excitatory and inhibitory inputs. The overall effects of AVP are excitatory in both types AVPNs. These results suggest that increased central AVP release may be involved in the stress-induced augmentation of airway vagal activity, and, consequently, the induction or exacerbation of some airway diseases. PMID:28210214

  15. Data Mining Activities for Bone Discipline - Current Status

    NASA Technical Reports Server (NTRS)

    Sibonga, J. D.; Pietrzyk, R. A.; Johnston, S. L.; Arnaud, S. B.

    2008-01-01

    The disciplinary goals of the Human Research Program are broadly discussed. There is a critical need to identify gaps in the evidence that would substantiate a skeletal health risk during and after spaceflight missions. As a result, data mining activities will be engaged to gather reviews of medical data and flight analog data and to propose additional measures and specific analyses. Several studies are briefly reviewed which have topics that partially address these gaps in knowledge, including bone strength recovery with recovery of bone mass density, current renal stone formation knowledge, herniated discs, and a review of bed rest studies conducted at Ames Human Research Facility.

  16. The effect of Peltier heat during current activated densification

    NASA Astrophysics Data System (ADS)

    Becker, A.; Angst, S.; Schmitz, A.; Engenhorst, M.; Stoetzel, J.; Gautam, D.; Wiggers, H.; Wolf, D. E.; Schierning, G.; Schmechel, R.

    2012-07-01

    It is shown that current-activated pressure-assisted densification (CAPAD) is sensitive to the Peltier effect. Under CAPAD, the Peltier effect leads to a significant redistribution of heat within the sample during the densification. The densification of highly p-doped silicon nanoparticles during CAPAD and the properties of the obtained samples are investigated experimentally and by computer simulation. Both, simulation and experiments, indicate clearly a higher temperature on the cathode side and a decreasing temperature from the center to the outer shell. Furthermore, computer simulations provide additional insights into the temperature profile which explain the anisotropic properties of the measured sample.

  17. Input Specificity and Dependence of Spike Timing–Dependent Plasticity on Preceding Postsynaptic Activity at Unitary Connections between Neocortical Layer 2/3 Pyramidal Cells

    PubMed Central

    Holmgren, Carl; Shemer, Isaac; Silberberg, Gilad; Grillner, Sten; Harkany, Tibor

    2009-01-01

    Layer 2/3 (L2/3) pyramidal cells receive excitatory afferent input both from neighbouring pyramidal cells and from cortical and subcortical regions. The efficacy of these excitatory synaptic inputs is modulated by spike timing–dependent plasticity (STDP). Here we report that synaptic connections between L2/3 pyramidal cell pairs are located proximal to the soma, at sites overlapping those of excitatory inputs from other cortical layers. Nevertheless, STDP at L2/3 pyramidal to pyramidal cell connections showed fundamental differences from known STDP rules at these neighbouring contacts. Coincident low-frequency pre- and postsynaptic activation evoked only LTD, independent of the order of the pre- and postsynaptic cell firing. This symmetric anti-Hebbian STDP switched to a typical Hebbian learning rule if a postsynaptic action potential train occurred prior to the presynaptic stimulation. Receptor dependence of LTD and LTP induction and their pre- or postsynaptic loci also differed from those at other L2/3 pyramidal cell excitatory inputs. Overall, we demonstrate a novel means to switch between STDP rules dependent on the history of postsynaptic activity. We also highlight differences in STDP at excitatory synapses onto L2/3 pyramidal cells which allow for input specific modulation of synaptic gain. PMID:19193711

  18. Measuring Input Thresholds on an Existing Board

    NASA Technical Reports Server (NTRS)

    Kuperman, Igor; Gutrich, Daniel G.; Berkun, Andrew C.

    2011-01-01

    A critical PECL (positive emitter-coupled logic) interface to Xilinx interface needed to be changed on an existing flight board. The new Xilinx input interface used a CMOS (complementary metal-oxide semiconductor) type of input, and the driver could meet its thresholds typically, but not in worst-case, according to the data sheet. The previous interface had been based on comparison with an external reference, but the CMOS input is based on comparison with an internal divider from the power supply. A way to measure what the exact input threshold was for this device for 64 inputs on a flight board was needed. The measurement technique allowed an accurate measurement of the voltage required to switch a Xilinx input from high to low for each of the 64 lines, while only probing two of them. Directly driving an external voltage was considered too risky, and tests done on any other unit could not be used to qualify the flight board. The two lines directly probed gave an absolute voltage threshold calibration, while data collected on the remaining 62 lines without probing gave relative measurements that could be used to identify any outliers. The PECL interface was forced to a long-period square wave by driving a saturated square wave into the ADC (analog to digital converter). The active pull-down circuit was turned off, causing each line to rise rapidly and fall slowly according to the input s weak pull-down circuitry. The fall time shows up as a change in the pulse width of the signal ready by the Xilinx. This change in pulse width is a function of capacitance, pulldown current, and input threshold. Capacitance was known from the different trace lengths, plus a gate input capacitance, which is the same for all inputs. The pull-down current is the same for all inputs including the two that are probed directly. The data was combined, and the Excel solver tool was used to find input thresholds for the 62 lines. This was repeated over different supply voltages and

  19. Systems and methods for reconfiguring input devices

    NASA Technical Reports Server (NTRS)

    Lancaster, Jeff (Inventor); De Mers, Robert E. (Inventor)

    2012-01-01

    A system includes an input device having first and second input members configured to be activated by a user. The input device is configured to generate activation signals associated with activation of the first and second input members, and each of the first and second input members are associated with an input function. A processor is coupled to the input device and configured to receive the activation signals. A memory coupled to the processor, and includes a reconfiguration module configured to store the input functions assigned to the first and second input members and, upon execution of the processor, to reconfigure the input functions assigned to the input members when the first input member is inoperable.

  20. Active debris removal: Recent progress and current trends

    NASA Astrophysics Data System (ADS)

    Bonnal, Christophe; Ruault, Jean-Marc; Desjean, Marie-Christine

    2013-04-01

    According to all available findings at international level, the Kessler syndrome, increase of the number of space debris in Low Earth Orbits due to mutual collisions, appears now to be a fact, triggered mainly by several major break-ups in orbit which occurred since 2007. The time may have come to study how to clean this fundamentally useful orbital region in an active way. CNES has studied potential solutions for more than 12 years! The paper aims at reviewing the current status of these activities. The high level requirements are fundamental, and have to be properly justified. The working basis, as confirmed through IADC studies consists in the removal of 5-10 integer objects from the overcrowded orbits, spent upper stages or old satellites, as identified by NASA. The logic of CNES activities consider a stepped approach aiming at progressively gaining the required Technological Readiness Level on the features required for Active Debris Removal which have not yet been demonstrated in orbit. The rendezvous with a non-cooperative, un-prepared, tumbling debris is essential. Following maturation gained with Research and Technology programs, a set of small orbital demonstrators could enable a confidence high enough to perform a full end to end demonstration performing the de-orbiting of a large debris and paving the way for the development of a first generation operational de-orbiter. The internal CNES studies, led together by the Toulouse Space Centre and the Paris Launcher Directorate, have started in 2008 and led to a detailed System Requirements Document used for the Industrial studies. Three industrial teams did work under CNES contract during 2011, led by Thales Alenia Space, Bertin Technologies and Astrium Space Transportation, with numerous sub-contractors. Their approaches were very rich, complementary, and innovative. The second phase of studies began mid-2012. Some key questions nevertheless have to be resolved, and correspond generally to current IADC

  1. The hyperpolarization-activated non-specific cation current (In ) adjusts the membrane properties, excitability, and activity pattern of the giant cells in the rat dorsal cochlear nucleus.

    PubMed

    Rusznák, Zoltán; Pál, Balázs; Kőszeghy, Aron; Fu, Yuhong; Szücs, Géza; Paxinos, George

    2013-03-01

    Giant cells of the cochlear nucleus are thought to integrate multimodal sensory inputs and participate in monaural sound source localization. Our aim was to explore the significance of a hyperpolarization-activated current in determining the activity of giant neurones in slices prepared from 10 to 14-day-old rats. When subjected to hyperpolarizing stimuli, giant cells produced a 4-(N-ethyl-N-phenylamino)-1,2-dimethyl-6-(methylamino) pyridinium chloride (ZD7288)-sensitive inward current with a reversal potential and half-activation voltage of -36 and -88 mV, respectively. Consequently, the current was identified as the hyperpolarization-activated non-specific cationic current (Ih ). At the resting membrane potential, 3.5% of the maximum Ih conductance was available. Immunohistochemistry experiments suggested that hyperpolarization-activated, cyclic nucleotide-gated, cation non-selective (HCN)1, HCN2, and HCN4 subunits contribute to the assembly of the functional channels. Inhibition of Ih hyperpolarized the membrane by 6 mV and impeded spontaneous firing. The frequencies of spontaneous inhibitory and excitatory postsynaptic currents reaching the giant cell bodies were reduced but no significant change was observed when evoked postsynaptic currents were recorded. Giant cells are affected by biphasic postsynaptic currents consisting of an excitatory and a subsequent inhibitory component. Inhibition of Ih reduced the frequency of these biphasic events by 65% and increased the decay time constants of the inhibitory component. We conclude that Ih adjusts the resting membrane potential, contributes to spontaneous action potential firing, and may participate in the dendritic integration of the synaptic inputs of the giant neurones. Because its amplitude was higher in young than in adult rats, Ih of the giant cells may be especially important during the postnatal maturation of the auditory system.

  2. Current Reactor Physics Benchmark Activities at the Idaho National Laboratory

    SciTech Connect

    John D. Bess; Margaret A. Marshall; Mackenzie L. Gorham; Joseph Christensen; James C. Turnbull; Kim Clark

    2011-11-01

    The International Reactor Physics Experiment Evaluation Project (IRPhEP) [1] and the International Criticality Safety Benchmark Evaluation Project (ICSBEP) [2] were established to preserve integral reactor physics and criticality experiment data for present and future research. These valuable assets provide the basis for recording, developing, and validating our integral nuclear data, and experimental and computational methods. These projects are managed through the Idaho National Laboratory (INL) and the Organisation for Economic Co-operation and Development Nuclear Energy Agency (OECD-NEA). Staff and students at the Department of Energy - Idaho (DOE-ID) and INL are engaged in the development of benchmarks to support ongoing research activities. These benchmarks include reactors or assemblies that support Next Generation Nuclear Plant (NGNP) research, space nuclear Fission Surface Power System (FSPS) design validation, and currently operational facilities in Southeastern Idaho.

  3. Current activities handbook: formerly utilized sites remedial action program

    SciTech Connect

    1981-02-27

    This volume is one of a series produced under contract with the DOE, by Politech Corporation to develop a legislative and regulatory data base to assist the FUSRAP management in addressing the institutional and socioeconomic issues involved in carrying out the Formerly Utilized Sites Remedial Action Program. This Information Handbook series contains information about all relevant government agencies at the Federal and state levels, the pertinent programs they administer, each affected state legislature, and current Federal and state legislative and regulatory initiatives. This volume is a compilation of information about the activities each of the thirteen state legislatures potentially affected by the Formerly Utilized Sites Remedial Action Program. It contains a description of the state legislative procedural rules and a schedule of each legislative session; a summary of pending relevant legislation; the name and telephone number of legislative and state agency contacts; and the full text of all bills identified.

  4. Simulation of current-activated pressure-assisted densification

    NASA Astrophysics Data System (ADS)

    Wolf, Dietrich; Angst, Sebastian; Schierning, Gabi

    2013-03-01

    Cohesive particles usually form very porous agglomerates. They support loads up to a consolidation pressure, which increases with decreasing particle size. Compaction of nano-powders can therefore be very costly and time consuming. If the particles are electrically conducting, which is the case e.g. for novel nano-structured thermoelectric materials, the technique of current-activated pressure-assisted densification (CAPAD) turns out to have many advantages. Electrical power deposited locally as Joule heat lowers the consolidation pressure such that particles fill nearby pores. This process leads to fast, scalable densification without much coarsening. Simulations are presented which address the influence of correlations on density and conductivity. They also take thermal conductivity and Peltier coefficient into account. Funded by DFG within the Priority Programme SPP 1386 (Nanostructured Thermoelectrics).

  5. Serbia National Poison Control Centre: organization and current activities.

    PubMed

    Jovanović, Dugan; Joksović, Dragan; Vucinić, Savica; Todorović, Veljko; Segrt, Zoran; Kilibarda, Vesna; Bokonjić, Dubravko

    2005-01-01

    Ministry of Health of the former Federal Republic of Yugoslavia established the National Poison Control Centre in 1995. However, that was only the formally solution since clinical, analytical and experimental services in toxicology had worked independently for at least 40 years. Besides the Headquarters, NPCC has currently 2 main units, the Clinic of Emergency and Clinical Toxicology and Pharmacology and the Institute of Toxicology and Pharmacology. The latter is consisted of Toxicological Information Department, Department of Analytical Toxicology and Department of Experimental Toxicology and Pharmacology. The Mobile Toxicological Chemical Unit is a separate department that is activated from personnel of the NPCC in a case of chemical accidents and/or disasters. Clinical, information and analytical parts of NPCC have a 365-day/24-hour working service. The Clinic of Emergency and Clinical Toxicology and Pharmacology is a place where the intoxicated patients are treated, including those that need the intensive care measures. Toxicological Information Department uses the data from a self-made computer Database for different information purposes. Department of Analytical Toxicology is equipped with a lot of contemporary analytical equipment that is giving the opportunity of identification and quantification of chemicals/metabolites/degradation products in biological material, food, water, air and soil. Basic pharmacological and toxicological research of chemicals and pre-clinical investigations of antidotes are realized in the Department of Experimental Toxicology and Pharmacology. In terms of medical prevention and rational treatment of human poison exposures in Serbia, the current organization of NPCC has so far proven to be effective.

  6. Continuous Registration of Membrane Input Resistances of Small Plant Cells Using a Double-Pulse Current Clamp Technique for Single-Electrode Impalements 12

    PubMed Central

    Schefczik, Kurt; Simonis, Wilhelm; Schiebe, Michael

    1983-01-01

    To measure the cell input resistance in Elodea leaf cells, a new single-microelectrode method was explored by comparing the results with conventional two-microelectrode experiments. The new method takes advantage of the difference in the frequency response curves between electrode and cell impedances. By application of electrical stimuli, which contain specific frequency bands, the different impedances can be analyzed separately. To get a distinct separation in the frequency response of cell and electrode, respectively, the electrode capacitance has to be compensated during the impalement. Different time constants of the cell membrane can be accounted for by adjustment of the stimulus length. It is shown that both the single- and the double-electrode method yield the same results, even if the cell input resistances change considerably during the course of the experiment. This demonstrates the usefulness of the new single-electrode method for continuous measurements of cell membrane resistances, especially in cells so small that the double-electrode method is no longer applicable. Images Fig. 4 Fig. 2 PMID:16663008

  7. Hyperpolarization-activated current (I(h)) in ganglion-cell photoreceptors.

    PubMed

    Van Hook, Matthew J; Berson, David M

    2010-12-20

    Intrinsically photosensitive retinal ganglion cells (ipRGCs) express the photopigment melanopsin and serve as the primary retinal drivers of non-image-forming visual functions such as circadian photoentrainment, the pupillary light reflex, and suppression of melatonin production in the pineal. Past electrophysiological studies of these cells have focused on their intrinsic photosensitivity and synaptic inputs. Much less is known about their voltage-gated channels and how these might shape their output to non-image-forming visual centers. Here, we show that rat ipRGCs retrolabeled from the suprachiasmatic nucleus (SCN) express a hyperpolarization-activated inwardly-rectifying current (I(h)). This current is blocked by the known I(h) blockers ZD7288 and extracellular cesium. As in other systems, including other retinal ganglion cells, I(h) in ipRGCs is characterized by slow kinetics and a slightly greater permeability for K(+) than for Na(+). Unlike in other systems, however, I(h) in ipRGCs apparently does not actively contribute to resting membrane potential. We also explore non-specific effects of the common I(h) blocker ZD7288 on rebound depolarization and evoked spiking and discuss possible functional roles of I(h) in non-image-forming vision. This study is the first to characterize I(h) in a well-defined population of retinal ganglion cells, namely SCN-projecting ipRGCs.

  8. Sea surface temperatures from the southern Benguela region from the Pliocene and Pleistocene: tracking Agulhas Current input into the SE Atlantic

    NASA Astrophysics Data System (ADS)

    Petrick, B. F.; McClymont, E.; Felder, S.; Lloyd, J. M.; Leng, M. J.

    2011-12-01

    The Pliocene and-Pleistocene epochs provide a way to understand the effect of past climate changes on key ocean currents. Here, we show results from ODP Site1087 (31.28'S, 15.19'E, 1374m water depth) to investigate changes in ocean circulation over the period of the mid-Pliocene warm period 3.0-3.5 Ma and compare these to the time of the 100 kyr Pleistocene glacial cycles. ODP 1087 is located in the South-eastern Atlantic Ocean, outside of the Benguela upwelling region; reconstructing the temperature history of the site will therefore provide an important data set from a part of the ocean that has few orbital-scale and continuous Pliocene temperature reconstructions. ODP 1087 can be used to investigate the history of the heat and salt transfer to the Atlantic Ocean from the Indian Ocean via the Agulhas Retroflection, which plays an important part in the global thermohaline circulation (Lutjeharms, 2007). Climate models and reconstructions for the most recent glacial-interglacial cycles have shown that changes to the strength of the heat transfer may cause major climatic changes and may play a role in transitions from glacial to interglacial events (Knorr & Lohmann, 2003). It is unknown how this transfer reacted to generally warmer global temperatures during the mid-Pliocene. Because the mid-Pliocene is seen as a model for future climate change it might provide a model for ocean circulations in a warmer world. Our approach is to apply several organic geochemistry proxies and foraminiferal analyses to reconstruct the history of ODP 1087. The UK37' index records differences in the unsaturated bonds in the C37 alkenones to reconstruct sea surface temperatures (Brassell et al., 1986). We present SSTs generated for the mid-Pliocene Warm period with a resolution of 4000 years. We compare this data to the time of the 100 kyr glacial cycles during the late Pleistocene. Even though ODP 1087 is located outside the Benguela upwelling system, it has lower Pliocene temperatures

  9. Nanostimulation: manipulation of single neuron activity by juxtacellular current injection.

    PubMed

    Houweling, Arthur R; Doron, Guy; Voigt, Birgit C; Herfst, Lucas J; Brecht, Michael

    2010-03-01

    In the mammalian brain, many thousands of single-neuron recording studies have been performed but less than 10 single-cell stimulation studies. This paucity of single-cell stimulation data reflects a lack of easily applicable single-cell stimulation techniques. We provide a detailed description of the procedures involved in nanostimulation, a single-cell stimulation method derived from the juxtacellular labeling technique. Nanostimulation is easy to apply and can be directed to a wide variety of identifiable neurons in anesthetized and awake animals. We describe the recording approach and the parameters of the electric configuration underlying nanostimulation. We use glass pipettes with a DC resistance of 4-7 Mohms. Obtaining the juxtacellular configuration requires a close contact between pipette tip and neuron and is associated with a several-fold increase in resistance to values > or = 20 Mohms. The recorded action potential (AP) amplitude grows to > or = 2 mV, and neurons can be activated with currents in the nanoampere range--hence the term nanostimulation. While exact AP timing has not been achieved, AP frequency and AP number can be parametrically controlled. We demonstrate that nanostimulation can also be used to selectively inhibit sensory responses in identifiable neurons. Nanostimulation is biophysically similar to electroporation, and based on this assumption, we argue that nanostimulation operates on membranes in the micrometer area directly below the pipette tip, where membrane pores are induced by high transmembrane voltage. There is strong evidence to suggest that nanostimulation selectively activates single neurons and that the evoked effects are cell-specific. Nanostimulation therefore holds great potential for elucidating how single neurons contribute to behavior.

  10. Intermediate inputs and economic productivity.

    PubMed

    Baptist, Simon; Hepburn, Cameron

    2013-03-13

    Many models of economic growth exclude materials, energy and other intermediate inputs from the production function. Growing environmental pressures and resource prices suggest that this may be increasingly inappropriate. This paper explores the relationship between intermediate input intensity, productivity and national accounts using a panel dataset of manufacturing subsectors in the USA over 47 years. The first contribution is to identify sectoral production functions that incorporate intermediate inputs, while allowing for heterogeneity in both technology and productivity. The second contribution is that the paper finds a negative correlation between intermediate input intensity and total factor productivity (TFP)--sectors that are less intensive in their use of intermediate inputs have higher productivity. This finding is replicated at the firm level. We propose tentative hypotheses to explain this association, but testing and further disaggregation of intermediate inputs is left for further work. Further work could also explore more directly the relationship between material inputs and economic growth--given the high proportion of materials in intermediate inputs, the results in this paper are suggestive of further work on material efficiency. Depending upon the nature of the mechanism linking a reduction in intermediate input intensity to an increase in TFP, the implications could be significant. A third contribution is to suggest that an empirical bias in productivity, as measured in national accounts, may arise due to the exclusion of intermediate inputs. Current conventions of measuring productivity in national accounts may overstate the productivity of resource-intensive sectors relative to other sectors.

  11. Terrestrial Reference Systems and Frames. A review of current activities

    NASA Astrophysics Data System (ADS)

    Boucher, C. C.

    2009-12-01

    Terrestrial Reference Systems (TRS) refer to an important domain of Geodesy, involving both theoretical and applied aspects, as well as deep connections with Astronomy, Earth Sciences and Geo-information. The concept of TRS implies several visions : - An astronomical vision, using TRS to study translational and rotational motion of the Earth in inertial space - An Earth Science vision, using TRS to build physical models of the Earth system, and its various components (solid earth, oceans, atmosphere, hydrosphere) - A metrological vision, using TRS together with suitable coordinate systems (geographical coordinates, map projections…) to define geographical position of objects in the Earth’s vicinity A survey of current activities in this area is presented, referring to works done by the International Association of Geodesy (IAG) and more specifically its Commission 1, GGOS and IERS. A focus is done on concepts and terminology, as well as progresses to get a wide acceptance on the International Terrestrial Reference System (ITRS) and its system of realizations through global, regional and national frames, as well as through specific systems such as satellite navigation systems.

  12. Activation of Ih and TTX-sensitive sodium current at subthreshold voltages during CA1 pyramidal neuron firing.

    PubMed

    Yamada-Hanff, Jason; Bean, Bruce P

    2015-10-01

    We used dynamic clamp and action potential clamp techniques to explore how currents carried by tetrodotoxin-sensitive sodium channels and HCN channels (Ih) regulate the behavior of CA1 pyramidal neurons at resting and subthreshold voltages. Recording from rat CA1 pyramidal neurons in hippocampal slices, we found that the apparent input resistance and membrane time constant were strongly affected by both conductances, with Ih acting to decrease apparent input resistance and time constant and sodium current acting to increase both. We found that both Ih and sodium current were active during subthreshold summation of artificial excitatory postsynaptic potentials (EPSPs) generated by dynamic clamp, with Ih dominating at less depolarized voltages and sodium current at more depolarized voltages. Subthreshold sodium current-which amplifies EPSPs-was most effectively recruited by rapid voltage changes, while Ih-which blunts EPSPs-was maximal for slow voltage changes. The combined effect is to selectively amplify rapid EPSPs. We did similar experiments in mouse CA1 pyramidal neurons, doing voltage-clamp experiments using experimental records of action potential firing of CA1 neurons previously recorded in awake, behaving animals as command voltages to quantify flow of Ih and sodium current at subthreshold voltages. Subthreshold sodium current was larger and subthreshold Ih was smaller in mouse neurons than in rat neurons. Overall, the results show opposing effects of subthreshold sodium current and Ih in regulating subthreshold behavior of CA1 neurons, with subthreshold sodium current prominent in both rat and mouse CA1 pyramidal neurons and additional regulation by Ih in rat neurons.

  13. The magnitudes of hyperpolarization-activated and low-voltage-activated potassium currents co-vary in neurons of the ventral cochlear nucleus.

    PubMed

    Cao, Xiao-Jie; Oertel, Donata

    2011-08-01

    In the ventral cochlear nucleus (VCN), neurons have hyperpolarization-activated conductances, which in some cells are enormous, that contribute to the ability of neurons to convey acoustic information in the timing of their firing by decreasing the input resistance and speeding-up voltage changes. Comparisons of the electrophysiological properties of neurons in the VCN of mutant mice that lack the hyperpolarization-activated cyclic nucleotide-gated channel α subunit 1 (HCN1(-/-)) (Nolan et al. 2003) with wild-type controls (HCN1(+/+)) and with outbred ICR mice reveal that octopus, T stellate, and bushy cells maintain their electrophysiological distinctions in all strains. Hyperpolarization-activated (I(h)) currents were smaller and slower, input resistances were higher, and membrane time constants were longer in HCN1(-/-) than in HCN1(+/+) in octopus, bushy, and T stellate cells. There were significant differences in the average magnitudes of I(h), input resistances, and time constants between HCN1(+/+) and ICR mice, but the resting potentials did not differ between strains. I(h) is opposed by a low-voltage-activated potassium (I(KL)) current in bushy and octopus cells, whose magnitudes varied widely between neuronal types and between strains. The magnitudes of I(h) and I(KL) were correlated across neuronal types and across mouse strains. Furthermore, these currents balanced one another at the resting potential in individual cells. The magnitude of I(h) and I(KL) is linked in bushy and octopus cells and varies not only between HCN1(-/-) and HCN1(+/+) but also between "wild-type" strains of mice, raising the question to what extent the wild-type strains reflect normal mice.

  14. The magnitudes of hyperpolarization-activated and low-voltage-activated potassium currents co-vary in neurons of the ventral cochlear nucleus

    PubMed Central

    Cao, Xiao-Jie

    2011-01-01

    In the ventral cochlear nucleus (VCN), neurons have hyperpolarization-activated conductances, which in some cells are enormous, that contribute to the ability of neurons to convey acoustic information in the timing of their firing by decreasing the input resistance and speeding-up voltage changes. Comparisons of the electrophysiological properties of neurons in the VCN of mutant mice that lack the hyperpolarization-activated cyclic nucleotide-gated channel α subunit 1 (HCN1−/−) (Nolan et al. 2003) with wild-type controls (HCN1+/+) and with outbred ICR mice reveal that octopus, T stellate, and bushy cells maintain their electrophysiological distinctions in all strains. Hyperpolarization-activated (Ih) currents were smaller and slower, input resistances were higher, and membrane time constants were longer in HCN1−/− than in HCN1+/+ in octopus, bushy, and T stellate cells. There were significant differences in the average magnitudes of Ih, input resistances, and time constants between HCN1+/+ and ICR mice, but the resting potentials did not differ between strains. Ih is opposed by a low-voltage-activated potassium (IKL) current in bushy and octopus cells, whose magnitudes varied widely between neuronal types and between strains. The magnitudes of Ih and IKL were correlated across neuronal types and across mouse strains. Furthermore, these currents balanced one another at the resting potential in individual cells. The magnitude of Ih and IKL is linked in bushy and octopus cells and varies not only between HCN1−/− and HCN1+/+ but also between “wild-type” strains of mice, raising the question to what extent the wild-type strains reflect normal mice. PMID:21562186

  15. Current radar responsive tag development activities at Sandia National Laboratories.

    SciTech Connect

    Plummer, Kenneth W.; Ormesher, Richard C.

    2003-09-01

    Over the past ten years, Sandia has developed RF radar responsive tag systems and supporting technologies for various government agencies and industry partners. RF tags can function as RF transmitters or radar transponders that enable tagging, tracking, and location determination functions. Expertise in tag architecture, microwave and radar design, signal analysis and processing techniques, digital design, modeling and simulation, and testing have been directly applicable to these tag programs. In general, the radar responsive tag designs have emphasized low power, small package size, and the ability to be detected by the radar at long ranges. Recently, there has been an interest in using radar responsive tags for Blue Force tracking and Combat ID (CID). The main reason for this interest is to allow airborne surveillance radars to easily distinguish U.S. assets from those of opposing forces. A Blue Force tracking capability would add materially to situational awareness. Combat ID is also an issue, as evidenced by the fact that approximately one-quarter of all U.S. casualties in the Gulf War took the form of ground troops killed by friendly fire. Because the evolution of warfare in the intervening decade has made asymmetric warfare the norm rather than the exception, swarming engagements in which U.S. forces will be freely intermixed with opposing forces is a situation that must be anticipated. Increasing utilization of precision munitions can be expected to drive fires progressively closer to engaged allied troops at times when visual de-confliction is not an option. In view of these trends, it becomes increasingly important that U.S. ground forces have a widely proliferated all-weather radar responsive tag that communicates to all-weather surveillance. The purpose of this paper is to provide an overview of the recent, current, and future radar responsive research and development activities at Sandia National Laboratories that support both the Blue Force Tracking

  16. Noradrenergic and serotonergic modulation of a hyperpolarization-activated cation current in thalamic relay neurones.

    PubMed Central

    McCormick, D A; Pape, H C

    1990-01-01

    1. Modulation of the hyperpolarization-activated cation current, Ih, by noradrenaline (NA) and serotonin (5-HT) was examined in guinea-pig and cat medial and lateral geniculate relay neurones using the in vitro slice technique. 2. In the absence of pharmacological antagonists, local application of NA resulted in a slow depolarization and decrease in apparent input conductance, a response which was blocked by local or bath application of the alpha 1-adrenoceptor antagonist prazosin. Application of NA after pharmacological block of alpha 1- and alpha 2-adrenoceptors, or application of 5-HT in all conditions, induced a 1-3 mV slow depolarization which was associated with a pronounced increase in apparent input conductance. This response to NA and 5-HT persisted during blocked synaptic transmission and was present in both the guinea-pig and cat medial and lateral geniculate nuclei. 3. The increase in membrane conductance elicited by NA was mimicked by the beta-specific agonist isoprenaline and blocked by the beta-antagonists propranolol and atenolol, indicating that it is mediated by beta-adrenoceptors. The response to 5-HT was blocked by the 5-HT1 and 5-HT2 antagonist methysergide, but not by the 5-HT2 antagonist ritanserin. Applications of either the 5-HT1A agonist ipsapirone or the partial agonist 8-hydroxy-dipropylaminotetralin (8-OHDPAT) were without effect. 4. Current versus voltage relationships obtained under voltage clamp revealed NA and 5-HT to cause a voltage-dependent inward shift at membrane potentials negative to approximately -60 mV. This response appeared to be shared by NA and 5-HT since maximal application of 5-HT greatly reduced or abolished the response to NA. 5. Application of NA and/or 5-HT during hyperpolarizing voltage steps in voltage clamp resulted in a marked increase in amplitude of the hyperpolarization-activated cation current, Ih. In addition, the rate of activation of Ih was strongly increased during activation of beta-adrenoceptors. 6

  17. Noradrenergic and serotonergic modulation of a hyperpolarization-activated cation current in thalamic relay neurones.

    PubMed

    McCormick, D A; Pape, H C

    1990-12-01

    1. Modulation of the hyperpolarization-activated cation current, Ih, by noradrenaline (NA) and serotonin (5-HT) was examined in guinea-pig and cat medial and lateral geniculate relay neurones using the in vitro slice technique. 2. In the absence of pharmacological antagonists, local application of NA resulted in a slow depolarization and decrease in apparent input conductance, a response which was blocked by local or bath application of the alpha 1-adrenoceptor antagonist prazosin. Application of NA after pharmacological block of alpha 1- and alpha 2-adrenoceptors, or application of 5-HT in all conditions, induced a 1-3 mV slow depolarization which was associated with a pronounced increase in apparent input conductance. This response to NA and 5-HT persisted during blocked synaptic transmission and was present in both the guinea-pig and cat medial and lateral geniculate nuclei. 3. The increase in membrane conductance elicited by NA was mimicked by the beta-specific agonist isoprenaline and blocked by the beta-antagonists propranolol and atenolol, indicating that it is mediated by beta-adrenoceptors. The response to 5-HT was blocked by the 5-HT1 and 5-HT2 antagonist methysergide, but not by the 5-HT2 antagonist ritanserin. Applications of either the 5-HT1A agonist ipsapirone or the partial agonist 8-hydroxy-dipropylaminotetralin (8-OHDPAT) were without effect. 4. Current versus voltage relationships obtained under voltage clamp revealed NA and 5-HT to cause a voltage-dependent inward shift at membrane potentials negative to approximately -60 mV. This response appeared to be shared by NA and 5-HT since maximal application of 5-HT greatly reduced or abolished the response to NA. 5. Application of NA and/or 5-HT during hyperpolarizing voltage steps in voltage clamp resulted in a marked increase in amplitude of the hyperpolarization-activated cation current, Ih. In addition, the rate of activation of Ih was strongly increased during activation of beta-adrenoceptors. 6

  18. Activation of Ih and TTX-sensitive sodium current at subthreshold voltages during CA1 pyramidal neuron firing

    PubMed Central

    Yamada-Hanff, Jason

    2015-01-01

    We used dynamic clamp and action potential clamp techniques to explore how currents carried by tetrodotoxin-sensitive sodium channels and HCN channels (Ih) regulate the behavior of CA1 pyramidal neurons at resting and subthreshold voltages. Recording from rat CA1 pyramidal neurons in hippocampal slices, we found that the apparent input resistance and membrane time constant were strongly affected by both conductances, with Ih acting to decrease apparent input resistance and time constant and sodium current acting to increase both. We found that both Ih and sodium current were active during subthreshold summation of artificial excitatory postsynaptic potentials (EPSPs) generated by dynamic clamp, with Ih dominating at less depolarized voltages and sodium current at more depolarized voltages. Subthreshold sodium current—which amplifies EPSPs—was most effectively recruited by rapid voltage changes, while Ih—which blunts EPSPs—was maximal for slow voltage changes. The combined effect is to selectively amplify rapid EPSPs. We did similar experiments in mouse CA1 pyramidal neurons, doing voltage-clamp experiments using experimental records of action potential firing of CA1 neurons previously recorded in awake, behaving animals as command voltages to quantify flow of Ih and sodium current at subthreshold voltages. Subthreshold sodium current was larger and subthreshold Ih was smaller in mouse neurons than in rat neurons. Overall, the results show opposing effects of subthreshold sodium current and Ih in regulating subthreshold behavior of CA1 neurons, with subthreshold sodium current prominent in both rat and mouse CA1 pyramidal neurons and additional regulation by Ih in rat neurons. PMID:26289465

  19. Cortical hyperpolarization-activated depolarizing current takes part in the generation of focal paroxysmal activities

    PubMed Central

    Timofeev, Igor; Bazhenov, Maxim; Sejnowski, Terrence; Steriade, Mircea

    2002-01-01

    During paroxysmal neocortical oscillations, sudden depolarization leading to the next cycle occurs when the majority of cortical neurons are hyperpolarized. Both the Ca2+-dependent K+ currents (IK(Ca)) and disfacilitation play critical roles in the generation of hyperpolarizing potentials. In vivo experiments and computational models are used here to investigate whether the hyperpolarization-activated depolarizing current (Ih) in cortical neurons also contributes to the generation of paroxysmal onsets. Hyperpolarizing current pulses revealed a depolarizing sag in ≈20% of cortical neurons. Intracellular recordings from glial cells indirectly indicated an increase in extracellular potassium concentration ([K+]o) during paroxysmal activities, leading to a positive shift in the reversal potential of K+-mediated currents, including Ih. In the paroxysmal neocortex, ≈20% of neurons show repolarizing potentials originating from hyperpolarizations associated with depth-electroencephalogram positive waves of spike-wave complexes. The onset of these repolarizing potentials corresponds to maximal [K+]o as estimated from dual simultaneous impalements from neurons and glial cells. Computational models showed how, after the increased [K+]o, the interplay between Ih, IK(Ca), and a persistent Na+ current, INa(P), could organize paroxysmal oscillations at a frequency of 2–3 Hz. PMID:12089324

  20. Wastewater and Saltwater: Studying the Biogeochemistry and Microbial Activity Associated with Wastewater Inputs to San Francisco Bay

    NASA Astrophysics Data System (ADS)

    Challenor, T.; Menendez, A. D.; Damashek, J.; Francis, C. A.; Casciotti, K. L.

    2014-12-01

    Nitrification is the process of converting ammonium (NH­­4+) into nitrate (NO3-), and is a crucial step in removing nitrogen (N) from aquatic ecosystems. This process is governed by ammonia-oxidizing bacteria (AOB) and archaea (AOA) that utilize the ammonia monooxygenase gene (amoA). Studying the rates of nitrification and the abundances of ammonia-oxidizing microorganisms in south San Francisco Bay's Artesian Slough, which receives treated effluent from the massive San Jose-Santa Clara Regional Wastewater Facility, are important for understanding the cycling of nutrients in this small but complex estuary. Wastewater inputs can have negative environmental impacts, such as the release of nitrous oxide, a byproduct of nitrification and a powerful greenhouse gas. Nutrient inputs can also increase productivity and sometimes lead to oxygen depletion. Assessing the relative abundance and diversity of AOA and AOB, along with measuring nitrification rates gives vital information about the biology and biogeochemistry of this important N-cycling process. To calculate nitrification rates, water samples were spiked with 15N-labeled ammonium and incubated in triplicate for 24 hours. Four time-points were extracted across the incubation and the "denitrifier" method was used to measure the isotopic ratio of nitrate in the samples over time. In order to determine relative ratios of AOB to AOA, DNA was extracted from water samples and used in clade-specific amoA PCR assays. Nitrification rates were detectable in all locations sampled and were higher than in other regions of the bay, as were concentrations of nitrate and ammonium. Rates were highest in the regions of Artesian Slough most directly affected by wastewater effluent. AOB vastly outnumbered AOA, which is consistent with other studies showing that AOB prefer high nutrient environments. AOB diversity includes clades of Nitrosospira and Nitrosomonas prevalent in estuarine settings. Many of the sequenced genes are related

  1. Complementary Postsynaptic Activity Patterns Elicited in Olfactory Bulb by Stimulation of Mitral/Tufted and Centrifugal Fiber Inputs to Granule Cells

    PubMed Central

    Laaris, Nora; Puche, Adam; Ennis, Matthew

    2009-01-01

    Main olfactory bulb (MOB) granule cells receive spatially segregated glutamatergic synaptic inputs from the dendrites of mitral/tufted cells as well as from the axons of centrifugal fibers (CFFs) originating in olfactory cortical areas. Dendrodendritic synapses from mitral/tufted cells occur on granule cell distal dendrites in the external plexiform layer (EPL), whereas CFFs preferentially target the somata/proximal dendrites of granule cells in the granule cell layer (GCL). In the present study, tract tracing, and recordings of field potentials and voltage-sensitive dye optical signals were used to map activity patterns elicited by activation of these two inputs to granule cells in mouse olfactory bulb slices. Stimulation of the lateral olfactory tract (LOT) produced a negative field potential in the EPL and a positivity in the GCL. CFF stimulation produced field potentials of opposite polarity in the EPL and GCL to those elicited by LOT. LOT-evoked optical signals appeared in the EPL and spread subsequently to deeper layers, whereas CFF-evoked responses appeared in the GCL and then spread superficially. Evoked responses were reduced by N-methyl-d-aspartate (NMDA) receptor antagonists and completely suppressed by AMPA receptor antagonists. Reduction of extracellular Mg2+ enhanced the strength and spatiotemporal extent of the evoked responses. These and additional findings indicate that LOT- and CFF-evoked field potentials and optical signals reflect postsynaptic activity in granule cells, with moderate NMDA and dominant AMPA receptor components. Taken together, these results demonstrate that LOT and CFF stimulation in MOB slices selectively activate glutamatergic inputs to the distal dendrites versus somata/proximal dendrites of granule cells. PMID:17035366

  2. Akt-mTORC1 signaling regulates Acly to integrate metabolic input to control of macrophage activation

    PubMed Central

    Covarrubias, Anthony J; Aksoylar, Halil Ibrahim; Yu, Jiujiu; Snyder, Nathaniel W; Worth, Andrew J; Iyer, Shankar S; Wang, Jiawei; Ben-Sahra, Issam; Byles, Vanessa; Polynne-Stapornkul, Tiffany; Espinosa, Erika C; Lamming, Dudley; Manning, Brendan D; Zhang, Yijing; Blair, Ian A; Horng, Tiffany

    2016-01-01

    Macrophage activation/polarization to distinct functional states is critically supported by metabolic shifts. How polarizing signals coordinate metabolic and functional reprogramming, and the potential implications for control of macrophage activation, remains poorly understood. Here we show that IL-4 signaling co-opts the Akt-mTORC1 pathway to regulate Acly, a key enzyme in Ac-CoA synthesis, leading to increased histone acetylation and M2 gene induction. Only a subset of M2 genes is controlled in this way, including those regulating cellular proliferation and chemokine production. Moreover, metabolic signals impinge on the Akt-mTORC1 axis for such control of M2 activation. We propose that Akt-mTORC1 signaling calibrates metabolic state to energetically demanding aspects of M2 activation, which may define a new role for metabolism in supporting macrophage activation. DOI: http://dx.doi.org/10.7554/eLife.11612.001 PMID:26894960

  3. Akt-mTORC1 signaling regulates Acly to integrate metabolic input to control of macrophage activation.

    PubMed

    Covarrubias, Anthony J; Aksoylar, Halil Ibrahim; Yu, Jiujiu; Snyder, Nathaniel W; Worth, Andrew J; Iyer, Shankar S; Wang, Jiawei; Ben-Sahra, Issam; Byles, Vanessa; Polynne-Stapornkul, Tiffany; Espinosa, Erika C; Lamming, Dudley; Manning, Brendan D; Zhang, Yijing; Blair, Ian A; Horng, Tiffany

    2016-02-19

    Macrophage activation/polarization to distinct functional states is critically supported by metabolic shifts. How polarizing signals coordinate metabolic and functional reprogramming, and the potential implications for control of macrophage activation, remains poorly understood. Here we show that IL-4 signaling co-opts the Akt-mTORC1 pathway to regulate Acly, a key enzyme in Ac-CoA synthesis, leading to increased histone acetylation and M2 gene induction. Only a subset of M2 genes is controlled in this way, including those regulating cellular proliferation and chemokine production. Moreover, metabolic signals impinge on the Akt-mTORC1 axis for such control of M2 activation. We propose that Akt-mTORC1 signaling calibrates metabolic state to energetically demanding aspects of M2 activation, which may define a new role for metabolism in supporting macrophage activation.

  4. Past challenges faced: An overview of current educational activities of IUTOX

    SciTech Connect

    Dybing, Erik . E-mail: erik.dybing@fhi.no; MacGregor, Judith; Malmfors, Torbjoern; Chipman, J. Kevin; Wright, Paul

    2005-09-01

    Over the past decade, educational programmes have been the main focus of the activities of the International Union of Toxicology (IUTOX). The IUTOX educational programmes are dynamic and have been growing in scope and frequency each year. It is envisaged that this growth will continue with guidance from our member societies and the continuing support of our sponsors. Presently, IUTOX is engaged in the following educational programmes: (1) International congresses that provide the opportunity for direct communication of current toxicological information. Fellowships are sponsored to facilitate attendance at these congresses for toxicologists in need. (2) Workshops that permit interaction on a more localised level of topics of more regional interest. Workshops have served to help stimulate formation of toxicology societies by bringing together sufficient scientists to facilitate these discussions. (3) Continuing educational (CE) programmes at member society meetings. Topics are prioritised based on input received from the local societies. Programmes often are those from CE courses given at meetings, such as conferences of the US Society of Toxicology (US SOT) and EUROTOX from the previous year. (4) Biennial Risk Assessment Summer School (RASS), an intensive week-long interaction between senior toxicologists who serve as faculty with attendees providing individual training. (5) Dissemination of donated printed toxicological books from publishers and syllabi from continuing education courses to regional locations. (6) Web-based interactive training programmes in regions where formal toxicological educational programmes are limited or lacking. (7) Preparation and distribution of monographs on selected topics of very current interest. Monographs on environmental oestrogens and genetically-modified foods have been published. The recent activities in each of these programmes are reviewed in this paper.

  5. Root carbon inputs to the rhizosphere stimulate extracellular enzyme activity and increase nitrogen availability in temperate forest soils

    NASA Astrophysics Data System (ADS)

    Brzostek, E. R.; Phillips, R.; Dragoni, D.; Drake, J. E.; Finzi, A. C.

    2011-12-01

    The mobilization of nitrogen (N) from soil organic matter in temperate forest soils is controlled by the microbial production and activity of extracellular enzymes. The exudation of carbon (C) by tree roots into the rhizosphere may subsidize the microbial production of extracellular enzymes in the rhizosphere and increase the access of roots to N. The objective of this research was to investigate whether rates of root exudation and the resulting stimulation of extracellular enzyme activity in the rhizosphere (i.e., rhizosphere effect) differs between tree species that form associations with ectomycorrhizal (ECM) or arbuscular mycorrhizal (AM) fungi. This research was conducted at two temperate forest sites, the Harvard Forest (HF) in Central MA and the Morgan Monroe State Forest (MMSF) in Southern IN. At the HF, we measured rates of root exudation and the rhizosphere effects on enzyme activity, N cycling, and C mineralization in AM and ECM soils. At the MMSF, we recently girdled AM and ECM dominated plots to examine the impact of severing belowground C allocation on rhizosphere processes. At both sites, the rhizosphere effect on proteolytic, chitinolytic and ligninolytic enzyme activities was greater in ECM soils than in AM soils. In particular, higher rates of proteolytic enzyme activity increased the availability of amino acid-N in ECM rhizospheres relative to the bulk soils. Further, this stimulation of enzyme activity was directly correlated with higher rates of C mineralization in the rhizosphere than in the bulk soil. Although not significantly different between species, root exudation of C comprised 3-10% of annual gross primary production at the HF. At the MMSF, experimental girdling led to a larger decline in soil respiration and enzyme activity in ECM plots than in AM plots. In both ECM and AM soils, however, girdling resulted in equivalent rates of enzyme activity in rhizosphere and corresponding bulk soils. The results of this study contribute to the

  6. Voltage-activated Calcium Currents in Octopus Cells of the Mouse Cochlear Nucleus

    PubMed Central

    Bal, Ramazan

    2007-01-01

    Octopus cells, neurons in the most posterior and dorsal part of the mammalian ventral cochlear nucleus, convey the timing of synchronous firing of auditory nerve fibers to targets in the contralateral superior paraolivary nucleus and ventral nucleus of the lateral lemniscus. The low input resistances and short time constants at rest that arise from the partial activation of a large, low-voltage-activated K+ conductance (gKL) and a large mixed-cation, hyperpolarization-activated conductance (gh) enable octopus cells to detect coincident firing of auditory nerve fibers with exceptional temporal precision. Octopus cells fire conventional, Na+ action potentials but a voltage-sensitive Ca2+ conductance was also detected. In this study, we explore the nature of that calcium conductance under voltage-clamp. Currents, carried by Ca2+ or Ba2+ and blocked by 0.4 mM Cd2+, were activated by depolarizations positive to −50 mV and peaked at −23 mV. At −23 mV they reached 1.1 ± 0.1 nA in the presence of 5 mM Ca2+ and 1.6 ± 0.1 nA in 5 mM Ba2+. Ten micromolar BAY K 8644, an agonist of high-voltage-activated L-type channels, enhanced IBa by 63 ± 11% (n = 8) and 150 μM nifedipine, an antagonist of L-type channels, reduced the IBa by 65 ± 5% (n = 5). Meanwhile, 0.5 μM ω-Agatoxin IVA, an antagonist of P/Q-type channels, or 1 μM ω-conotoxin GVIA, an antagonist of N-type channels, suppressed IBa by 15 ± 4% (n = 5) and 9 ± 4% (n = 5), respectively. On average 16% of the current remained in the presence of the cocktail of blockers, indicative of the presence of R-type channels. Together these experiments show that octopus cells have a depolarization-sensitive gCa that is largely formed from L-type Ca2+ channels and that P/Q-, N-, and R-type channels are expressed at lower levels in octopus cells. PMID:17710492

  7. A Laboratory Activity on the Eddy Current Brake

    ERIC Educational Resources Information Center

    Molina-Bolivar, J. A.; Abella-Palacios, A. J.

    2012-01-01

    The aim of this paper is to introduce a simple and low-cost experimental setup that can be used to study the eddy current brake, which considers the motion of a sliding magnet on an inclined conducting plane in terms of basic physical principles. We present a set of quantitative experiments performed to study the influence of the geometrical and…

  8. A National Perspective on the Current Evaluation Activities in Extension

    ERIC Educational Resources Information Center

    Lamm, Alexa J.; Israel, Glenn D.; Diehl, David

    2013-01-01

    In order to enhance Extension evaluation efforts it is important to understand current practices. The study reported here researched the evaluation behaviors of county-based Extension professionals. Extension professionals from eight states (n = 1,173) responded to a survey regarding their evaluation data collection, analysis, and reporting…

  9. Active current gating in electrically biased conical nanopores

    NASA Astrophysics Data System (ADS)

    Bearden, Samuel; Simpanen, Erik; Zhang, Guigen

    2015-05-01

    We observed that the ionic current through a gold/silicon nitride (Si3N4) nanopore could be modulated and gated by electrically biasing the gold layer. Rather than employing chemical modification to alter device behavior, we achieved control of conductance directly by electrically biasing the gold portion of the nanopore. By stepping through a range of bias potentials under a constant trans-pore electric field, we observed a gating phenomenon in the trans-pore current response in a variety of solutions including potassium chloride (KCl), sodium chloride (NaCl), and potassium iodide (KI). A computational model with a conical nanopore was developed to examine the effect of the Gouy-Chapman-Stern electrical double layer along with nanopore geometry, work function potentials, and applied electrical bias on the ionic current. The numerical results indicated that the observed modulation and gating behavior was due to dynamic reorganization of the electrical double layer in response to changes in the electrical bias. Specifically, in the conducting state, the nanopore conductance (both numerical and experimental) is linearly proportional to the applied bias due to accumulation of charge in the diffuse layer. The gating effect occurs due to the asymmetric charge distribution in the fluid induced by the distribution of potentials at the nanopore surface. Time dependent changes in current due to restructuring of the electrical double layer occur when the electrostatic bias is instantaneously changed. The nanopore device demonstrates direct external control over nanopore behavior via modulation of the electrical double layer by electrostatic biasing.

  10. Re-Mediating Current Activity for the Future

    ERIC Educational Resources Information Center

    Gutierrez, Kris D.

    2012-01-01

    The growing poverty and inequity in America should create a sense of urgency in researchers to leverage what they know for the public good--to intervene more productively and vigorously in an ever more fragile public educational system and to address the increasing vulnerability of far too many youth in the United States. The current worldwide…

  11. Get Current: Switch on Clean Energy Activity Book

    SciTech Connect

    2014-06-01

    Switching on clean energy technologies means strengthening the economy while protecting the environment. This activity book for all ages promotes energy awareness, with facts on different types of energy and a variety of puzzles in an energy theme.

  12. Ca2+ current and Ca(2+)-activated chloride current in isolated smooth muscle cells of the sheep urethra.

    PubMed Central

    Cotton, K D; Hollywood, M A; McHale, N G; Thornbury, K D

    1997-01-01

    1. Isolated sheep urethral cells were studied using the perforated patch clamp technique (T = 37 degrees C). Depolarizing steps ranging from -40 to -10 mV evoked an inward current that peaked within 10 ms and a slower inward current. Stepping back to the holding potential of -80 mV evoked large inward tail currents. All three currents were abolished by nifedipine (1 microM). Substitution of external Ca2+ with Ba2+ resulted in potentiation of the fast inward current and blockade of the slow current and tails. 2. Changing the chloride equilibrium potential (ECl) from 0 to +27 mV shifted the reversal potential of the tail currents from 1 +/- 1 to 27 +/- 1 mV (number of cells, n = 5). Chloride channel blockers, niflumic acid (10 microM) and anthracene-9-carboxylic acid (9AC, 1 mM), reduced the slow current and tails suggesting that these were Ca(2+)-activated Cl- currents, ICl(Ca). 4. Caffeine (10 mM) induced currents that reversed at ECl and were blocked by niflumic acid (10 microM). 5. In current clamp mode, some cells developed spontaneous transient depolarizations (STDs) and action potentials. Short exposure to nifedipine blocked the action potentials and unmasked STDs. In contrast, 9AC and niflumic acid reduced the amplitude of the STDs and blocked the action potentials. 6. In conclusion, these cells have both L-type ICa and ICl(Ca). The former appears to be responsible for the upstroke of the action potential, while the latter may act as a pacemaker current. PMID:9409476

  13. The hyperpolarization-activated current (Ih) and its contribution to pacemaker activity in rat CA1 hippocampal stratum oriens-alveus interneurones.

    PubMed Central

    Maccaferri, G; McBain, C J

    1996-01-01

    1. The hyperpolarization-activated current (Ih) and its role in pacemaking activity in rat hippocampal stratum oriens-alveus interneurones was studied using whole-cell and perforated patch-clamp configurations. 2. Voltage-clamp recordings revealed Ih as a slowly activating, inward current, activated by hyperpolarizing steps (holding potential, Vh = -40 mV), with a reversal potential close to -30 mV. Its activation curve ranged from approximately -50 to -120 mV with a mid-activation point of -84.1 mV. 3. Ih was blocked by external application of Cs+ (2-5 mM) and ZD7288 (100 microM), but not by Ba2+ (1 mM). 4. Ih was potentiated by both noradrenaline and isoprenaline by a mechanism consistent with a shift in the Ih activation curve. 5. Under current-clamp conditions (Vh = -60 mV), ZD7288 induced a membrane hyperpolarization concomitant with an increase in the membrane input resistance and abolished the voltage sag generated by hyperpolarizing current injection. 6. Analysis of the current-discharge relationship revealed that block of Ih differentially increased the firing frequency of spikes occurring early in the train compared with those occurring late in the discharge. 7. When applied to spontaneously firing cells, ZD7288 reduced the firing frequency by selectively altering the time course of the interspike interval, while minimally affecting other action potential characteristics. Similarly, isoprenaline increased the spontaneous firing frequency by an effect exclusively on the after-hyperpolarization and interspike interval. 8. These results provide evidence for the involvement of Ih in the excitability and generation of spontaneous firing in hippocampal stratum oriens-alveus interneurones. PMID:8951716

  14. Distribution of vestibulospinal synaptic input to cat triceps surae motoneurons.

    PubMed

    Westcott, S L; Powers, R K; Robinson, F R; Binder, M D

    1995-01-01

    We applied supramaximal, repetitive stimulation to the lateral vestibular nucleus (Deiters' nucleus, DN) at 200 Hz to evoke stead-state synaptic potentials in ipsilateral triceps surae motoneurons of the cat. The effective synaptic currents underlying these potentials were measured using a modified voltage-clamp technique. The steady-state effective synaptic currents evoked by activating DN were generally small and depolarizing (mean 2.5 +/- 2.6 nA). DN stimulation generated hyperpolarizing synaptic currents in 2 of the 34 triceps motoneurons studied. The effective synaptic currents from DN tended to be larger in putative type F motoneurons than in putative type S cells (type F mean 3.0 +/- 3.1 nA; type S mean 1.8 +/- 1.0 nA). There was a statistically significant difference between the inputs to putative type FF and putative type S motoneurons (mean difference 2.8 nA, t = 2.87, P < 0.01). The synaptic input from DN to medial gastrocnemius motoneurons had approximately the same amplitude as that from homonymous Ia afferent fibers. However, the distribution of DN input with respect to putative motor unit type was the opposite of that previously reported for Ia afferent input. Thus, the synaptic input from DN might act to compress the range of recruitment thresholds within the motoneuron pool and thereby increase the gain of its input-output function.

  15. ASSESSING AND MANAGING MERCURY FROM HISTORIC AND CURRENT MINING ACTIVITIES

    EPA Science Inventory

    Mining activities in the US (not counting coal) produce between one and two billion tons of mine waste annually. Since many of the ore mines involve sulfide minerals, the production of acid mine drainage (AMD) is a common problem from these abandoned mine sites. The combination o...

  16. Teacher Feedback during Active Learning: Current Practices in Primary Schools

    ERIC Educational Resources Information Center

    van den Bergh, Linda; Ros, Anje; Beijaard, Douwe

    2013-01-01

    Background: Feedback is one of the most powerful tools, which teachers can use to enhance student learning. It appears dif?cult for teachers to give qualitatively good feedback, especially during active learning. In this context, teachers should provide facilitative feedback that is focused on the development of meta-cognition and social learning.…

  17. Using Ecological Momentary Assessment to Evaluate Current Physical Activity

    PubMed Central

    Marszalek, Jolanta; Morgulec-Adamowicz, Natalia; Rutkowska, Izabela; Kosmol, Andrzej

    2014-01-01

    Objective. The purpose of this study was to assess the value of ecological momentary assessment in evaluating physical activity among children, adolescents, and adults. It also determines whether ecological momentary assessment fulfills the criteria of validity, reliability, objectivity, norms, and standardization applied to the tools used for the evaluation of physical activity. Methods. The EBSCO-CINHAL, Medline, PsycINFO, PubMed, and SPORTDiscuss databases were reviewed in December 2012 for articles associated with EMA. Results. Of the 20 articles examined, half (10) used electronic methods for data collection, although various methods were used, ranging from pen and paper to smartphone applications. Ten studies used objective monitoring equipment. Nineteen studies were performed over 4 days. While the validity of the EMA method was discussed in 18 studies, only four found it to be objective. In all cases, the EMA procedures were precisely documented and confirmed to be feasible. Conclusions. Ecological momentary assessment is a valid, reliable, and feasible approach to evaluate activity and sedentary behavior. Researchers should be aware that while ecological momentary assessment offers many benefits, it simultaneously imposes many limitations which should be considered when studying physical activity. PMID:25126580

  18. Calcium-activated conductance in skate electroreceptors: current clamp experiments.

    PubMed

    Clusin, W T; Bennett, M V

    1977-02-01

    When current clamped, skate electroreceptor epithelium produces large action potentials in response to stimuli that depolarize the lumenal faces of the receptor cells. With increasing stimulus strength these action potentials become prolonged. When the peak voltage exceeds about 140 mV the repolarizing phase is blocked until the end of the stimulus. Perfusion experiments show that the rising phase of the action potential results from an increase in calcium permeability in the lumenal membranes. Perfusion of the lumen with cobalt or with a zero calcium solution containing EGTA blocks the action potential. Perfusion of the lumen with a solution containing 10 mM Ca and 20 mM EGTA initially slows the repolarizing process at all voltages and lowers the potential at which it is blocked. With prolonged perfusion, repolarization is blocked at all voltages. When excitability is abolished by perfusion with cobalt, or with a zero calcium solution containing EGTA, no delayed rectification occurs. We suggest that repolarization during the action potential depends on an influx of calcium into the cytoplasm, and that the rate of repolarization depends on the magnitude of the inward calcium current. Increasingly large stimuli reduce the rate of repolarization by reducing the driving force for calcium, and then block repolarization by causing the lumenal membrane potential to exceed ECa. Changes in extracellular calcium affect repolarization in a manner consistent with the resulting change in ECa.

  19. Impact of organic and mineral inputs onto soil biological and metabolic activities under a long-term rice-wheat cropping system in sub-tropical Indian Inceptisols.

    PubMed

    Basak, Nirmalendu; Datta, Ashim; Mitran, Tarik; Mandal, Biswapati; Mani, P K

    2016-01-01

    Long-term use of organic and mineral inputs has an overriding impact on soil biological and metabolic activities and crop management. Farm yard manure (FYM), paddy straw (PS) and green manure (GM, Sesbania sesban L.) were used for 24- years old rice (Oyza sativa L.) -wheat (Triticum aestivum L.) cropping system in sub-tropical India to predict whether the screened soil biological and metabolic activities are correlated with system yield. The integrated approaches viz., NPK + FYM, NPK + PS and NPK + GM significantly increased both rice and wheat yield together by 67.5, 44.4 and 55.4%, respectively over control. However, for a few exceptions both soil microbial activity and metabolic activity were remarkably enhanced under integrated treatment NPK + FYM followed by NPK + PS, and NPK + GM, respectively. Among the studied attributes fluorescein diacetate hydrolyzing, dehydrogenase, β-glucosidase activity (β-glu) and microbial biomass C (C(mic)) were screened through principal component (PCA) and discriminate analysis (DA) that explained nearly 89% of total variations of the entire data set. Among the four identified attributes, only β-glu assay value could predict system yield (R2 = 0.65). Further, estimation of β-glu activity in soil can predict other soil biological properties (R2 = 0.96).

  20. The cytochrome ba3 oxygen reductase from Thermus thermophilus uses a single input channel for proton delivery to the active site and for proton pumping.

    PubMed

    Chang, Hsin-Yang; Hemp, James; Chen, Ying; Fee, James A; Gennis, Robert B

    2009-09-22

    The heme-copper oxygen reductases are redox-driven proton pumps that generate a proton motive force in both prokaryotes and mitochondria. These enzymes have been divided into 3 evolutionarily related groups: the A-, B- and C-families. Most experimental work on proton-pumping mechanisms has been performed with members of the A-family. These enzymes require 2 proton input pathways (D- and K-channels) to transfer protons used for oxygen reduction chemistry and for proton pumping, with the D-channel transporting all pumped protons. In this work we use site-directed mutagenesis to demonstrate that the ba(3) oxygen reductase from Thermus thermophilus, a representative of the B-family, does not contain a D-channel. Rather, it utilizes only 1 proton input channel, analogous to that of the A-family K-channel, and it delivers protons to the active site for both O2 chemistry and proton pumping. Comparison of available subunit I sequences reveals that the only structural elements conserved within the oxygen reductase families that could perform these functions are active-site components, namely the covalently linked histidine-tyrosine, the Cu(B) and its ligands, and the active-site heme and its ligands. Therefore, our data suggest that all oxygen reductases perform the same chemical reactions for oxygen reduction and comprise the essential elements of the proton-pumping mechanism (e.g., the proton-loading and kinetic-gating sites). These sites, however, cannot be located within the D-channel. These results along with structural considerations point to the A-propionate region of the active-site heme and surrounding water molecules as the proton-loading site.

  1. Geothermal materials development: FY 1990 accomplishments and current activities

    SciTech Connect

    Kukacka, L.E.

    1991-01-01

    Advances in the development of hydrothermally stable materials, the commercial availabilities of which are considered essential for the attainment of the Geothermal Division's (GD) Hydrothermal Category Objectives, continue to be made. Fiscal year 1990 R D was focused on reducing well drilling and completion costs, energy conversion costs, and on mitigating corrosion in well casing. Activities on lost circulation control materials, CO{sub 2}-resistant lightweight cements and thermally conductive corrosion and scale-resistant linear systems have reached the final development stages. In addition, field tests to determine the feasibility for the use of polymer cement liners to mitigate HCl-induced corrosion at the Geysers were performed. Technology transfer efforts on high temperature elastomers for use in drilling tools such as drillpipe protectors and rotating head seals were continued under Geothermal Drilling Organization sponsorship. Recent accomplishments and ongoing work on each of these activities are described in the paper. 8 refs.

  2. Current status of pyrazole and its biological activities

    PubMed Central

    Naim, Mohd Javed; Alam, Ozair; Nawaz, Farah; Alam, Md. Jahangir; Alam, Perwaiz

    2016-01-01

    Pyrazole are potent medicinal scaffolds and exhibit a full spectrum of biological activities. This review throws light on the detailed synthetic approaches which have been applied for the synthesis of pyrazole. This has been followed by an in depth analysis of the pyrazole with respect to their medical significance. This follow-up may help the medicinal chemists to generate new leads possessing pyrazole nucleus with high efficacy. PMID:26957862

  3. Current status of pyrazole and its biological activities.

    PubMed

    Naim, Mohd Javed; Alam, Ozair; Nawaz, Farah; Alam, Md Jahangir; Alam, Perwaiz

    2016-01-01

    Pyrazole are potent medicinal scaffolds and exhibit a full spectrum of biological activities. This review throws light on the detailed synthetic approaches which have been applied for the synthesis of pyrazole. This has been followed by an in depth analysis of the pyrazole with respect to their medical significance. This follow-up may help the medicinal chemists to generate new leads possessing pyrazole nucleus with high efficacy.

  4. Proton currents constrain structural models of voltage sensor activation

    PubMed Central

    Randolph, Aaron L; Mokrab, Younes; Bennett, Ashley L; Sansom, Mark SP; Ramsey, Ian Scott

    2016-01-01

    The Hv1 proton channel is evidently unique among voltage sensor domain proteins in mediating an intrinsic ‘aqueous’ H+ conductance (GAQ). Mutation of a highly conserved ‘gating charge’ residue in the S4 helix (R1H) confers a resting-state H+ ‘shuttle’ conductance (GSH) in VGCs and Ci VSP, and we now report that R1H is sufficient to reconstitute GSH in Hv1 without abrogating GAQ. Second-site mutations in S3 (D185A/H) and S4 (N4R) experimentally separate GSH and GAQ gating, which report thermodynamically distinct initial and final steps, respectively, in the Hv1 activation pathway. The effects of Hv1 mutations on GSH and GAQ are used to constrain the positions of key side chains in resting- and activated-state VS model structures, providing new insights into the structural basis of VS activation and H+ transfer mechanisms in Hv1. DOI: http://dx.doi.org/10.7554/eLife.18017.001 PMID:27572256

  5. A laboratory activity on the eddy current brake

    NASA Astrophysics Data System (ADS)

    Molina-Bolívar, J. A.; Abella-Palacios, A. J.

    2012-05-01

    The aim of this paper is to introduce a simple and low-cost experimental setup that can be used to study the eddy current brake, which considers the motion of a sliding magnet on an inclined conducting plane in terms of basic physical principles. We present a set of quantitative experiments performed to study the influence of the geometrical and electromagnetic properties of the magnet on the magnetic drag force. This video-based experiment is ideal for the study of kinematic graphs and the application of Newton's laws. Video motion analysis software enables students to make precise measurements of the magnet's position at incremental times during its motion, thus allowing them to quantify electromagnetic induction phenomena. The equipment needed for this experiment and data collection software are present in most physics teaching laboratories or are inexpensive and available.

  6. 75 FR 14185 - Agency Information Collection Activities: Extension of a Currently Approved Collection: Comments...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-24

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF JUSTICE Office of Justice Programs Agency Information Collection Activities: Extension of a Currently Approved... currently approved collection. Bureau of Justice Assistance Application Form: Public Safety...

  7. Activation of Transient Receptor Potential Vanilloid 4 Increases NMDA-Activated Current in Hippocampal Pyramidal Neurons

    PubMed Central

    Li, Lin; Qu, Weijun; Zhou, Libin; Lu, Zihong; Jie, Pinghui; Chen, Lei; Chen, Ling

    2013-01-01

    The glutamate excitotoxicity, mediated through N-methyl-d-aspartate receptors (NMDARs), plays an important role in cerebral ischemia injury. Transient receptor potential vanilloid 4 (TRPV4) can be activated by multiple stimuli that may happen during stroke. The present study evaluated the effect of TRPV4 activation on NMDA-activated current (INMDA) and that of blocking TRPV4 on brain injury after focal cerebral ischemia in mice. We herein report that activation of TRPV4 by 4α-PDD and hypotonic stimulation increased INMDA in hippocampal CA1 pyramidal neurons, which was sensitive to TRPV4 antagonist HC-067047 and NMDAR antagonist AP-5, indicating that TRPV4 activation potentiates NMDAR response. In addition, the increase in INMDA by hypotonicity was sensitive to the antagonist of NMDAR NR2B subunit, but not of NR2A subunit. Furthermore, antagonists of calcium/calmodulin-dependent protein kinase II (CaMKII) significantly attenuated hypotonicity-induced increase in INMDA, while antagonists of protein kinase C or casein kinase II had no such effect, indicating that phosphorylation of NR2B subunit by CaMKII is responsible for TRPV4-potentiated NMDAR response. Finally, we found that intracerebroventricular injection of HC-067047 after 60 min middle cerebral artery occlusion reduced the cerebral infarction with at least a 12 h efficacious time-window. These findings indicate that activation of TRPV4 increases NMDAR function, which may facilitate glutamate excitotoxicity. Closing TRPV4 may exert potent neuroprotection against cerebral ischemia injury through many mechanisms at least including the prevention of NMDAR-mediated glutamate excitotoxicity. PMID:23459987

  8. WATERSHEED NUTRIENT INPUTS, PHYTOPLANKTON ACCUMULATION, AND C STOCKS IN CHESAPEAKE BAY

    EPA Science Inventory

    Inputs of N and P to Chesapeake Bay have been enhanced by anthropogenic activities. Fertilizers, developed areas, N emissions, and industrial effluents contribute to point and diffuse sources currently 2-20X higher than those from undisturbed watersheds. Enhanced nutrient inputs ...

  9. [Active teaching-learning methodologies in health education: current debates].

    PubMed

    Mitre, Sandra Minardi; Siqueira-Batista, Rodrigo; Girardi-de-Mendonça, José Márcio; de Morais-Pinto, Neila Maria; Meirelles, Cynthia de Almeida Brandão; Pinto-Porto, Cláudia; Moreira, Tânia; Hoffmann, Leandro Marcial Amaral

    2008-12-01

    The vertiginous transformations of the contemporary societies have been raising questions concerning aspects of professional education. Such questions have been raised in a more and more incisive way. This debate gains a new shape when applied to health work, where theory and practice cannot be dissociated, and where the development of an integral vision of the human being and the amplification of the concept care are essential for a proper performance. Based on these considerations, this article aims to discuss the main methodological transformations in the education process of health professionals, with emphasis to active teaching-learning methodologies.

  10. Effect of electric current frequency on the activation kinetics of raw charcoal

    SciTech Connect

    Shevchenko, A.O.; Ivakhnyuk, G.K.; Fedorov, N.F.

    1993-12-10

    The effect of electric current frequency on the kinetics of raw charcoal activation with water vapor has been investigated. It was established that under the effect of alternating current the rate constant increases under otherwise equal conditions. A dependence of the reaction rate on the current frequency was found. It was discovered that under the effect of alternating current the activation energy of interaction with water vapor diminishes.

  11. The magnitude of alpha7 nicotinic receptor currents in rat hippocampal neurons is dependent upon GABAergic activity and depolarization.

    PubMed

    Santos, Hélio R; Ribeiro, Helizane S; Setti-Perdigão, Pedro; Albuquerque, Edson X; Castro, Newton G

    2006-10-01

    Hippocampal alpha7(*) nicotinic acetylcholine receptors modulate the release of GABA and glutamate. The control of functional receptor pools by cell firing or synaptic activity could therefore allow for a local adjustment of the sensitivity to cholinergic input upon changes in neuronal activity. We first investigated whether tonic depolarization or cell firing affected the function of alpha7(*). The amplitude of alpha7(*)-gated whole-cell currents in cultured rat hippocampal neurons exposed to high-extracellular K(+) (40 mM KCl) for 24 to 48 h increased 1.3 to 5.5 times. The proportion of alpha7(*)-responsive neurons (99%), the potency of acetylcholine, and the sensitivity to nicotinic antagonists were all unaffected. In contrast, block of spontaneous cell firing with tetrodotoxin for 24 h led to a 37% reduction in mean current amplitude. Reduced alpha7(*) responses were seen after a 24-h blockade of N-type calcium channels but not of L-type calcium channels, N-methyl-d-aspartate (NMDA), or non-NMDA receptor channels, protein kinase C, or calcium-calmodulin kinases II and IV. The N-type or L-type calcium channel antagonists omega-conotoxin GVIA and nifedipine did not prevent the current-potentiating effect of KCl. The GABA(A) antagonist picrotoxin led to a 44% reduction of the currents, despite increasing action potential firing, and also reversed the potentiating effect of KCl. Treatment with GABA, midazolam, or a GABA uptake blocker led to increased currents. These data indicate that alpha7(*)-gated currents in hippocampal neurons are regulated by GABAergic activity and suggest that depolarization-induced GABA release may underlie the effect of increased extracellular KCl.

  12. Voltage-activated currents recorded from rabbit pigmented ciliary body epithelial cells in culture.

    PubMed Central

    Fain, G L; Farahbakhsh, N A

    1989-01-01

    1. The whole-cell recording mode of the patch-clamp technique was used to investigate the presence of voltage-activated currents in the isolated pigmented cells from the rabbit ciliary body epithelium grown in culture. 2. In Ringer solution with composition similar to that of the rabbit aqueous humour, depolarizing voltage steps activated a transient inward current and a delayed outward current, while hyperpolarization elicited an inwardly rectified current. 3. The depolarization-activated inward current was mainly carried by Na+ and was blocked by submicromolar concentrations of tetrodotoxin. This current in many cells was sufficiently large to produce a regenerative Na+ spike. 4. The depolarization-activated outward current was carried by K+ and blocked by external TEA and Ba2+. Its activation appeared to be Ca2(+)-independent. 5. The hyperpolarization-activated inward current was almost exclusively carried by K+ and was blocked by Ba2+ and Cs+. For large hyperpolarizations below -120 mV, this current exhibited a biphasic activation with a fast transient peak followed by a slower sag, that appeared to be due to K+ depletion. 6. The voltage-dependent K+ conductances probably act to stabilize the cell membrane resting potential and may also play a role in ion transport. The function of the Na(+)-dependent inward current is unclear, but it may permit the electrically coupled epithelial cells of the ciliary body to conduct propagated action potentials. Images Fig. 2 PMID:2621623

  13. The Current Case of Quinolones: Synthetic Approaches and Antibacterial Activity.

    PubMed

    Naeem, Abdul; Badshah, Syed Lal; Muska, Mairman; Ahmad, Nasir; Khan, Khalid

    2016-03-28

    Quinolones are broad-spectrum synthetic antibacterial drugs first obtained during the synthesis of chloroquine. Nalidixic acid, the prototype of quinolones, first became available for clinical consumption in 1962 and was used mainly for urinary tract infections caused by Escherichia coli and other pathogenic Gram-negative bacteria. Recently, significant work has been carried out to synthesize novel quinolone analogues with enhanced activity and potential usage for the treatment of different bacterial diseases. These novel analogues are made by substitution at different sites--the variation at the C-6 and C-8 positions gives more effective drugs. Substitution of a fluorine atom at the C-6 position produces fluroquinolones, which account for a large proportion of the quinolones in clinical use. Among others, substitution of piperazine or methylpiperazine, pyrrolidinyl and piperidinyl rings also yields effective analogues. A total of twenty six analogues are reported in this review. The targets of quinolones are two bacterial enzymes of the class II topoisomerase family, namely gyrase and topoisomerase IV. Quinolones increase the concentration of drug-enzyme-DNA cleavage complexes and convert them into cellular toxins; as a result they are bactericidal. High bioavailability, relative low toxicity and favorable pharmacokinetics have resulted in the clinical success of fluoroquinolones and quinolones. Due to these superior properties, quinolones have been extensively utilized and this increased usage has resulted in some quinolone-resistant bacterial strains. Bacteria become resistant to quinolones by three mechanisms: (1) mutation in the target site (gyrase and/or topoisomerase IV) of quinolones; (2) plasmid-mediated resistance; and (3) chromosome-mediated quinolone resistance. In plasmid-mediated resistance, the efflux of quinolones is increased along with a decrease in the interaction of the drug with gyrase (topoisomerase IV). In the case of chromosome

  14. Results of community deliberation about social impacts of ecological restoration: comparing public input of self-selected versus actively engaged community members.

    PubMed

    Harris, Charles C; Nielsen, Erik A; Becker, Dennis R; Blahna, Dale J; McLaughlin, William J

    2012-08-01

    Participatory processes for obtaining residents' input about community impacts of proposed environmental management actions have long raised concerns about who participates in public involvement efforts and whose interests they represent. This study explored methods of broad-based involvement and the role of deliberation in social impact assessment. Interactive community forums were conducted in 27 communities to solicit public input on proposed alternatives for recovering wild salmon in the Pacific Northwest US. Individuals identified by fellow residents as most active and involved in community affairs ("AE residents") were invited to participate in deliberations about likely social impacts of proposed engineering and ecological actions such as dam removal. Judgments of these AE participants about community impacts were compared with the judgments of residents motivated to attend a forum out of personal interest, who were designated as self-selected ("SS") participants. While the magnitude of impacts rated by SS participants across all communities differed significantly from AE participants' ratings, in-depth analysis of results from two community case studies found that both AE and SS participants identified a large and diverse set of unique impacts, as well as many of the same kinds of impacts. Thus, inclusion of both kinds of residents resulted in a greater range of impacts for consideration in the environmental impact study. The case study results also found that the extent to which similar kinds of impacts are specified by AE and SS group members can differ by type of community. Study results caution against simplistic conclusions drawn from this approach to community-wide public participation. Nonetheless, the results affirm that deliberative methods for community-based impact assessment involving both AE and SS residents can provide a more complete picture of perceived impacts of proposed restoration activities.

  15. Cyclic-nucleotide–gated cation current and Ca2+-activated Cl current elicited by odorant in vertebrate olfactory receptor neurons

    PubMed Central

    Li, Rong-Chang; Ben-Chaim, Yair; Yau, King-Wai; Lin, Chih-Chun

    2016-01-01

    Olfactory transduction in vertebrate olfactory receptor neurons (ORNs) involves primarily a cAMP-signaling cascade that leads to the opening of cyclic-nucleotide–gated (CNG), nonselective cation channels. The consequent Ca2+ influx triggers adaptation but also signal amplification, the latter by opening a Ca2+-activated Cl channel (ANO2) to elicit, unusually, an inward Cl current. Hence the olfactory response has inward CNG and Cl components that are in rapid succession and not easily separable. We report here success in quantitatively separating these two currents with respect to amplitude and time course over a broad range of odorant strengths. Importantly, we found that the Cl current is the predominant component throughout the olfactory dose–response relation, down to the threshold of signaling to the brain. This observation is very surprising given a recent report by others that the olfactory-signal amplification effected by the Ca2+-activated Cl current does not influence the behavioral olfactory threshold in mice. PMID:27647918

  16. Habitat management affects soil chemistry and allochthonous organic inputs mediating microbial structure and exo-enzyme activity in Wadden Sea salt-marsh soils

    NASA Astrophysics Data System (ADS)

    Mueller, Peter; Granse, Dirk; Thi Do, Hai; Weingartner, Magdalena; Nolte, Stefanie; Hoth, Stefan; Jensen, Kai

    2016-04-01

    The Wadden Sea (WS) region is Europe's largest wetland and home to approximately 20% of its salt marsh area. Mainland salt marshes of the WS are anthropogenically influenced systems and have traditionally been used for livestock grazing in wide parts. After foundation of WS National Parks in the late 1980s and early 1990s, artificial drainage has been abandoned; however, livestock grazing is still common in many areas of the National Parks and is under ongoing discussion as a habitat-management practice. While studies so far focused on effects of livestock grazing on biodiversity, little is known about how biogeochemical processes, element cycling, and particularly carbon sequestration are affected. Here, we present data from a recent field study focusing on grazing effects on soil properties, microbial exo-enzyme activity, microbial abundance and structure. Exo-enzyme activity was studied conducting digestive enzyme assays for various enzymes involved in C- and N cycling. Microbial abundance and structure was assessed measuring specific gene abundance of fungi and bacteria using quantitative PCR. Soil compaction induced by grazing led to higher bulk density and decreases in soil redox (∆ >100 mV). Soil pH was significantly lower in grazed parts. Further, the proportion of allochthonous organic matter (marine input) was significantly smaller in grazed vs. ungrazed sites, likely caused by a higher sediment trapping capacity of the taller vegetation in the ungrazed sites. Grazing induced changes in bulk density, pH and redox resulted in reduced activity of enzymes involved in microbial C acquisition; however, there was no grazing effect on enzymes involved in N acquisition. While changes in pH, bulk density or redox did not affect microbial abundance and structure, the relative amount of marine organic matter significantly reduced the relative abundance of fungi (F:B ratio). We conclude that livestock grazing directly affects microbial exo-enzyme activity, thus

  17. Activation processes on GaAs photocathode by different currents of oxygen source

    NASA Astrophysics Data System (ADS)

    Miao, Zhuang; Shi, Feng; Cheng, Hongchang; Wang, Shufei; Zhang, Xiaohui; Yuan, Yuan; Chen, Chang

    2015-04-01

    In order to know the influence of activation processes on GaAs photocathodes, three GaAs samples were activated by a fixed current of cesium source and different currents of oxygen source. The current of caesium source is same during activation to ensure initial adsorption of caesium quantum is similar, which is the base to show the difference during alternation activation of caesium and oxygen. Analysed with the activation data, it is indicated that Cs-to-O current ratio of 1.07 is the optimum ratio to obtain higher sensitivity and better stability. According to double dipole model, stable and uniform double dipole layers of GaAs-O-Cs:Cs-O-Cs are formed and negative electron affinity is achieved on GaAs surface by activation with cesium and oxygen. The analytical result is just coincident with the model. Thus there is an efficient technological method to improve sensitivity and stability of GaAs photocathode.

  18. Ionic currents during sustained pacemaker activity in rabbit sino-atrial myocytes.

    PubMed Central

    Zaza, A; Micheletti, M; Brioschi, A; Rocchetti, M

    1997-01-01

    1. The contribution of various ionic currents to diastolic depolarization (DD) in rabbit sinoatrial myocytes was evaluated by the action potential clamp technique. Individual currents were identified, during sustained pacemaking activity reproduced under voltage clamp conditions, according to their sensitivity to specific channel blockers. 2. The current sensitive to dihydropyridines (DHPs), blockers of L-type Ca2+ current (ICa,L), was small and outward during most of DD. Diastolic DHP-sensitive current was affected by changes in the driving force for K+, but it was insensitive to E-4031, which blocks the current termed IK,r; it was abolished by cell dialysis with a Ca2+ chelator. 3. The current sensitive to 2 mM Cs+ (ICs), a blocker of hyperpolarization-activated current (I(f)), was inward during the whole DD and it was substantially larger than the net inward current flowing during this phase. However, diastolic IK,r, identified in the same cells as the current sensitive to the blocker E-4031, exceeded ICs 2-fold. 4. These findings suggest that: (a) Ca2+ influx during the pacemaker cycle increases a K+ conductance, thus inverting the direction of the net current generated by L-type Ca2+ channel activity during DD; (b) the magnitude of I(f) would be adequate to account fully for DD; however, the coexistence of a larger IK,r suggests that other channels besides I(f) contribute inward current during this phase. PMID:9457645

  19. Photonic Network R&D Activities in Japan-Current Activities and Future Perspectives

    NASA Astrophysics Data System (ADS)

    Kitayama, Ken-Ichi; Miki, Tetsuya; Morioka, Toshio; Tsushima, Hideaki; Koga, Masafumi; Mori, Kazuyuki; Araki, Soichiro; Sato, Ken-Ichi; Onaka, Hiroshi; Namiki, Shu; Aoyama, Tomonori

    2005-10-01

    R&D activities on photonic networks in Japan are presented. First, milestones in current ongoing R&D programs supported by Japanese government agencies are introduced, including long-distance and wavelength division multiplexing (WDM) fiber transmission, wavelength routing, optical burst switching (OBS), and control-plane technology for IP backbone networks. Their goal was set to evolve a legacy telecommunications network to IP-over-WDM networks by introducing technologies for WDM and wavelength routing. We then discuss the perspectives of so-called PHASE II R&D programs for photonic networks over the next 5 years until 2010, by focusing on the report that has been recently issued by the Photonic Internet Forum (PIF), a consortium that has major carriers, telecom vendors, and Japanese academics as members. The PHASE II R&D programs should serve to establish a photonic platform to provide abundant bandwidth on demand, at any time on a real-time basis, through the customer's initiative to promote bandwidth-rich applications, such as grid computing, real-time digital-cinema streaming, medical and educational applications, and network storage in e-commerce.

  20. Cutaneous inputs from the back abolish locomotor-like activity and reduce spastic-like activity in the adult cat following complete spinal cord injury.

    PubMed

    Frigon, Alain; Thibaudier, Yann; Johnson, Michael D; Heckman, C J; Hurteau, Marie-France

    2012-06-01

    Spasticity is a condition that can include increased muscle tone, clonus, spasms, and hyperreflexia. In this study, we report the effect of manually stimulating the dorsal lumbosacral skin on spontaneous locomotor-like activity and on a variety of reflex responses in 5 decerebrate chronic spinal cats treated with clonidine. Cats were spinalized 1 month before the terminal experiment. Stretch reflexes were evoked by stretching the left triceps surae muscles. Crossed reflexes were elicited by electrically stimulating the right tibial or superficial peroneal nerves. Wind-up of reflex responses was evoked by electrically stimulating the left tibial or superficial peroneal nerves. We found that pinching the skin of the back abolished spontaneous locomotor-like activity. We also found that back pinch abolished the rhythmic activity observed during reflex testing without eliminating the reflex responses. Some of the rhythmic episodes of activity observed during reflex testing were consistent with clonus with an oscillation frequency greater than 3 Hz. Pinching the skin of the back effectively abolished rhythmic activity occurring spontaneously or evoked during reflex testing, irrespective of oscillation frequency. The results are consistent with the hypothesis that locomotion and clonus are produced by common central pattern-generators. Stimulating the skin of the back could prove helpful in managing undesired rhythmic activity in spinal cord-injured humans.

  1. Principal component analysis of Birkeland currents determined by the Active Magnetosphere and Planetary Electrodynamics Response Experiment

    NASA Astrophysics Data System (ADS)

    Milan, S. E.; Carter, J. A.; Korth, H.; Anderson, B. J.

    2015-12-01

    Principal component analysis is performed on Birkeland or field-aligned current (FAC) measurements from the Active Magnetosphere and Planetary Electrodynamics Response Experiment. Principal component analysis (PCA) identifies the patterns in the FACs that respond coherently to different aspects of geomagnetic activity. The regions 1 and 2 current system is shown to be the most reproducible feature of the currents, followed by cusp currents associated with magnetic tension forces on newly reconnected field lines. The cusp currents are strongly modulated by season, indicating that their strength is regulated by the ionospheric conductance at the foot of the field lines. PCA does not identify a pattern that is clearly characteristic of a substorm current wedge. Rather, a superposed epoch analysis of the currents associated with substorms demonstrates that there is not a single mode of response, but a complicated and subtle mixture of different patterns.

  2. Principle Component Analysis of Birkeland Currents Determined by the Active Magnetosphere and Planetary Electrodynamics Response Experiment

    NASA Astrophysics Data System (ADS)

    Milan, S. E.; Carter, J. A.; Korth, H.; Anderson, B. J.

    2015-12-01

    Principle Component Analysis is performed on northern and southern hemisphere Birkeland or field-aligned current (FAC) measurements from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE). PCA identifies the patterns in the FACs that respond coherently to different aspects of geomagnetic activity. The region 1 and 2 current system is shown to be the most reproducible feature of the currents, followed by cusp currents associated with magnetic tension forces on newly-reconnected field lines. The cusp currents are strongly modulated by season, indicating that their strength is regulated by the ionospheric conductance at the foot of the field lines. PCA does not identify a pattern that is clearly characteristic of a substorm current wedge. Rather, a superposed epoch analysis of the currents associated with substorms demonstrates that there is not a single mode of response, but a complicated and subtle mixture of different patterns. Other interhemispheric differences are discussed.

  3. Physical activity (PA) among middle-aged women: initial and current influences and patterns of participation.

    PubMed

    Codina, Nuria; Pestana, José V; Armadans, Immaculada

    2013-01-01

    This study investigated the initial and current influences for doing physical activity (PA), current levels of PA participation, and future plans for it. Participants were 200 women aged 45 to 64 years old. Factor loadings of influences were explored using Principal Components Analysis. Pearson bivariate correlations, t-test, and ANOVA were used to show the differences among the influences, sociodemographic characteristics, and present/future PA participation. Personal fulfillment was the main initial influence, while health benefits/self-care, and outdoor/family activities were the most important current influences. The results highlight the factors that best explain present PA participation and also plans for activity in the future.

  4. Ca(2+)-activated K current in the ARC muscle of Aplysia.

    PubMed

    Brezina, V; Weiss, K R

    1995-03-01

    1. This work continues our examination of the electrophysiology and contractions of single, functionally intact fibers dissociated from a widely studied molluscan muscle, the accessory radula closer (ARC) muscle of Aplysia californica, aimed at understanding its excitation-contraction mechanisms and their modulation. Extensive previous work has characterized a number of ion currents in the fibers. 2. Here we describe an additional major current that could not be studied earlier because, unlike all of the other currents in the ARC muscle fibers, it becomes prominent only during contraction of the fiber. It is a Ca(2+)-activated K current, associated with contraction most likely because both are activated by the same elevation in intracellular free Ca2+. 3. We used several manipulations to elicit the Ca(2+)-activated K current and contraction: depolarizing voltage steps in the presence of extracellular Ca2+, application of caffeine in the presence or absence of extracellular Ca2+ (and thus presumably working by releasing Ca2+ from intracellular stores), application of the Ca(2+)-ionophore A23187, and direct iontophoretic injection of Ca2+ into the fiber. 4. The Ca(2+)-activated K current reversed around -70 mV, not far from EK, and the reversal potential shifted substantially with elevated extracellular K+. Activation of the current was not only Ca2+ dependent, but also quite strongly voltage dependent, promoted by depolarization. The current was well blocked by tetraethylammonium (KD approximately 2 mM), but not blocked by even 10 mM 4-aminopyridine or low concentrations of the K-current blocking toxins charybdotoxin and apamin. 5. After a depolarizing voltage step in Ca(2+)-containing solution, the Ca(2+)-activated K current appeared, often with some delay, as a large peak of current that soon disintegrated into a prolonged period of individual oscillatory transients of Ca(2+)-activated K current, sometimes correlated with transient contractions. Similar transients

  5. Pathological impact of hyperpolarization-activated chloride current peculiar to rat pulmonary vein cardiomyocytes.

    PubMed

    Okamoto, Yosuke; Kawamura, Koichi; Nakamura, Yuta; Ono, Kyoichi

    2014-01-01

    Pulmonary veins (PVs) are believed to be a crucial origin of atrial fibrillation. We recently reported that rat PV cardiomyocytes exhibit arrhythmogenic automaticity in response to norepinephrine. Herein, we further characterized the electrophysiological properties underlying the potential arrhythmogenicity of PV cardiomyocytes. Patch clamping studies revealed a time dependent hyperpolarization-activated inward current in rat PV cardiomyocytes, but not in left atrial (LA) myocytes. The current was Cs(+) resistant, and was not affected by removal of external Na(+) or K(+). The current was inhibited with Cd(2+), and the reversal potential was sensitive to changes in [Cl(-)] on either side of the membrane in a manner consistent with a Cl(-) selective channel. Cl(-) channel blockers attenuated the current, and slowed or completely inhibited the norepinephrine-induced automaticity. The biophysical properties of the hyperpolarization-activated Cl(-) current in rat PVs were different from those of ClC-2 currents previously reported: (i) the voltage-dependent activation of the Cl(-) current in rat PVs was shifted to negative potentials as [Cl(-)]i increased, (ii) the Cl(-) current was enhanced by extracellular acidification, and (iii) extracellular hyper-osmotic stress increased the current, whereas hypo-osmotic cell swelling suppressed the current. qPCR analysis revealed negligible ClC-2 mRNA expression in the rat PV. These findings suggest that rat PV cardiomyocytes possess a peculiar voltage-dependent Cl(-) channel, and that the channel may play a functional role in norepinephrine-induced automaticity.

  6. Selective regulation of current densities underlies spontaneous changes in the activity of cultured neurons.

    PubMed

    Turrigiano, G; LeMasson, G; Marder, E

    1995-05-01

    We study the electrical activity patterns and the expression of conductances in adult stomatogastric ganglion (STG) neurons as a function of time in primary cell culture. When first plated in culture, these neurons had few active properties. After 1 d in culture they produced small action potentials that rapidly inactivated during maintained depolarization. After 2 d in culture they fired large action potentials tonically when depolarized, and their properties resembled very closely the properties of STG neurons pharmacologically isolated in the ganglion. After 3-4 d in culture, however, their electrical properties changed and they fired in bursts when depolarized. We characterized the currents expressed by these neurons in culture. They included two TTX-sensitive sodium currents, a calcium current, a delayed-rectifier-like current, a calcium-dependent potassium current, and two A-type currents. The changes in firing properties with time in culture were accompanied by an increase in inward and decrease in outward current densities. A single-compartment conductance-based model of an STG neuron was constructed by fitting the currents measured in the biological neurons. When the current densities in the model neuron were matched to those measured for the biological neurons in each activity state, the model neuron closely reproduced each state, indicating that the changes in current densities are sufficient to account for the changes in intrinsic properties. These data indicate that STG neurons isolated in culture change their intrinsic electrical properties by selectively adjusting the magnitudes of their ionic conductances.

  7. High input impedance amplifier

    NASA Technical Reports Server (NTRS)

    Kleinberg, Leonard L.

    1995-01-01

    High input impedance amplifiers are provided which reduce the input impedance solely to a capacitive reactance, or, in a somewhat more complex design, provide an extremely high essentially infinite, capacitive reactance. In one embodiment, where the input impedance is reduced in essence, to solely a capacitive reactance, an operational amplifier in a follower configuration is driven at its non-inverting input and a resistor with a predetermined magnitude is connected between the inverting and non-inverting inputs. A second embodiment eliminates the capacitance from the input by adding a second stage to the first embodiment. The second stage is a second operational amplifier in a non-inverting gain-stage configuration where the output of the first follower stage drives the non-inverting input of the second stage and the output of the second stage is fed back to the non-inverting input of the first stage through a capacitor of a predetermined magnitude. These amplifiers, while generally useful, are very useful as sensor buffer amplifiers that may eliminate significant sources of error.

  8. MDS MIC Catalog Inputs

    NASA Technical Reports Server (NTRS)

    Johnson-Throop, Kathy A.; Vowell, C. W.; Smith, Byron; Darcy, Jeannette

    2006-01-01

    This viewgraph presentation reviews the inputs to the MDS Medical Information Communique (MIC) catalog. The purpose of the group is to provide input for updating the MDS MIC Catalog and to request that MMOP assign Action Item to other working groups and FSs to support the MITWG Process for developing MIC-DDs.

  9. Talking Speech Input.

    ERIC Educational Resources Information Center

    Berliss-Vincent, Jane; Whitford, Gigi

    2002-01-01

    This article presents both the factors involved in successful speech input use and the potential barriers that may suggest that other access technologies could be more appropriate for a given individual. Speech input options that are available are reviewed and strategies for optimizing use of speech recognition technology are discussed. (Contains…

  10. Dynamic Input Conductances Shape Neuronal Spiking(1,2).

    PubMed

    Drion, Guillaume; Franci, Alessio; Dethier, Julie; Sepulchre, Rodolphe

    2015-01-01

    Assessing the role of biophysical parameter variations in neuronal activity is critical to the understanding of modulation, robustness, and homeostasis of neuronal signalling. The paper proposes that this question can be addressed through the analysis of dynamic input conductances. Those voltage-dependent curves aggregate the concomitant activity of all ion channels in distinct timescales. They are shown to shape the current-voltage dynamical relationships that determine neuronal spiking. We propose an experimental protocol to measure dynamic input conductances in neurons. In addition, we provide a computational method to extract dynamic input conductances from arbitrary conductance-based models and to analyze their sensitivity to arbitrary parameters. We illustrate the relevance of the proposed approach for modulation, compensation, and robustness studies in a published neuron model based on data of the stomatogastric ganglion of the crab Cancer borealis.

  11. Continuous Active Sonar for Undersea Vehicles Final Report: Input of Factor Graphs into the Detection, Classification, and Localization Chain and Continuous Active SONAR in Undersea Vehicles

    DTIC Science & Technology

    2015-12-31

    simply adding the two branches. Equation 50 gives the final step before substituting the previously found covanances. (50) where G ~ (v3 + crvz( c [) H ... H can be compared to c since they both are matrices relating the measurement to the state. The variable R in the Kalman filter is the covariance...Wakayama, C . (2013). Multistatic Tracking for Continuous Active Sonar using Doppler-Bearing Measurements. 16th International Conference on Information

  12. Large-conductance calcium-activated potassium current modulates excitability in isolated canine intracardiac neurons

    PubMed Central

    Pérez, Guillermo J.; Desai, Mayurika; Anderson, Seth

    2013-01-01

    We studied principal neurons from canine intracardiac (IC) ganglia to determine whether large-conductance calcium-activated potassium (BK) channels play a role in their excitability. We performed whole cell recordings in voltage- and current-clamp modes to measure ion currents and changes in membrane potential from isolated canine IC neurons. Whole cell currents from these neurons showed fast- and slow-activated outward components. Both current components decreased in the absence of calcium and following 1–2 mM tetraethylammonium (TEA) or paxilline. These results suggest that BK channels underlie these current components. Single-channel analysis showed that BK channels from IC neurons do not inactivate in a time-dependent manner, suggesting that the dynamic of the decay of the fast current component is akin to that of intracellular calcium. Immunohistochemical studies showed that BK channels and type 2 ryanodine receptors are coexpressed in IC principal neurons. We tested whether BK current activation in these neurons occurred via a calcium-induced calcium release mechanism. We found that the outward currents of these neurons were not affected by the calcium depletion of intracellular stores with 10 mM caffeine and 10 μM cyclopiazonic acid. Thus, in canine intracardiac neurons, BK currents are directly activated by calcium influx. Membrane potential changes elicited by long (400 ms) current injections showed a tonic firing response that was decreased by TEA or paxilline. These data strongly suggest that the BK current present in canine intracardiac neurons regulates action potential activity and could increase these neurons excitability. PMID:23195072

  13. 75 FR 40840 - Agency Information Collection Activities; Proposed Collection; Comment Request; Current Good...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-14

    ... HUMAN SERVICES Food and Drug Administration Agency Information Collection Activities; Proposed Collection; Comment Request; Current Good Manufacturing Practice in Manufacturing, Packaging, Labeling, or Holding Operations for Dietary Supplements AGENCY: Food and Drug Administration, HHS. ACTION:...

  14. 76 FR 31342 - Agency Information Collection Activities; Proposed Collection; Comment Request; Current Good...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-31

    ... HUMAN SERVICES Food and Drug Administration Agency Information Collection Activities; Proposed Collection; Comment Request; Current Good Manufacturing Practice Regulations for Finished Pharmaceuticals AGENCY: Food and Drug Administration, HHS. ACTION: Notice. SUMMARY: The Food and Drug Administration...

  15. 75 FR 11621 - Agency Information Collection Activities: Notice of Request for Extension of Currently Approved...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-11

    ... information; and (4) ways that the burden could be minimized, including the use of electronic technology... Federal Highway Administration Agency Information Collection Activities: Notice of Request for Extension of Currently Approved Information Collection AGENCY: Federal Highway Administration (FHWA),...

  16. 78 FR 19333 - Agency Information Collection Activities: Renewal of Currently Approved Collection; Comment Request

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-29

    ... TRANSPARENCY BOARD Agency Information Collection Activities: Renewal of Currently Approved Collection; Comment Request AGENCY: Recovery Accountability and Transparency Board. ACTION: Notice and request for comments. SUMMARY: The Recovery Accountability and Transparency Board (Board) invites comments on the...

  17. 75 FR 4612 - Agency Information Collection Activities: Notice of Request for Extension of Currently Approved...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-28

    ... construction time and traffic congestion; C. The development of engineering design criteria for innovative... Federal Highway Administration Agency Information Collection Activities: Notice of Request for Extension of Currently Approved Information Collection AGENCY: Federal Highway Administration (FHWA),...

  18. 78 FR 13932 - Agency Information Collection Activities; Approval of a Currently Approved Information Collection...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-01

    ... Federal Motor Carrier Safety Administration Agency Information Collection Activities; Approval of a Currently Approved Information Collection Request: Financial Responsibility for Motor Carriers of Passengers... tura.gatling@dot.gov and gerald.folsom@dot.gov . SUPPLEMENTARY INFORMATION: Title:...

  19. Genetic activation of BK currents in vivo generates bidirectional effects on neuronal excitability

    PubMed Central

    Montgomery, Jenna R.; Meredith, Andrea L.

    2012-01-01

    Large-conductance calcium-activated potassium channels (BK) are potent negative regulators of excitability in neurons and muscle, and increasing BK current is a novel therapeutic strategy for neuro- and cardioprotection, disorders of smooth muscle hyperactivity, and several psychiatric diseases. However, in some neurons, enhanced BK current is linked with seizures and paradoxical increases in excitability, potentially complicating the clinical use of agonists. The mechanisms that switch BK influence from inhibitory to excitatory are not well defined. Here we investigate this dichotomy using a gain-of-function subunit (BKR207Q) to enhance BK currents. Heterologous expression of BKR207Q generated currents that activated at physiologically relevant voltages in lower intracellular Ca2+, activated faster, and deactivated slower than wild-type currents. We then used BKR207Q expression to broadly augment endogenous BK currents in vivo, generating a transgenic mouse from a circadian clock-controlled Period1 gene fragment (Tg-BKR207Q). The specific impact on excitability was assessed in neurons of the suprachiasmatic nucleus (SCN) in the hypothalamus, a cell type where BK currents regulate spontaneous firing under distinct day and night conditions that are defined by different complements of ionic currents. In the SCN, Tg-BKR207Q expression converted the endogenous BK current to fast-activating, while maintaining similar current-voltage properties between day and night. Alteration of BK currents in Tg-BKR207Q SCN neurons increased firing at night but decreased firing during the day, demonstrating that BK currents generate bidirectional effects on neuronal firing under distinct conditions. PMID:23112153

  20. 76 FR 63320 - Agency Information Collection Activities: Form N-470, Revision of a Currently Approved...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-12

    ... Agency Information Collection Activities: Form N-470, Revision of a Currently Approved Information Collection; Comment Request ACTION: 60-Day Notice of Information Collection Under Review: Form N- 470... revision of Form N-470 instead of extending the current edition. USCIS invites members of the public...

  1. 40 CFR 1611.7 - Testimony by current CSB employees regarding prior activity.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Testimony by current CSB employees regarding prior activity. 1611.7 Section 1611.7 Protection of Environment CHEMICAL SAFETY AND HAZARD INVESTIGATION BOARD TESTIMONY BY EMPLOYEES IN LEGAL PROCEEDINGS § 1611.7 Testimony by current CSB...

  2. Planar fuel cell utilizing nail current collectors for increased active surface area

    DOEpatents

    George, Thomas J.; Meacham, G. B. Kirby

    2002-03-26

    A plurality of nail current collector members are useful in the gas flow passages of an electrochemical device to optimize the active surfaces of the device and to provide structural support. In addition, the thicknesses of cathode and anode layers within the electrochemical device are varied according to current flow through the device to reduce resistance and increase operating efficiency.

  3. 76 FR 68786 - Agency Information Collection Activities: Extension of a Currently Approved Collection; Annual...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-07

    ... annual progress report is 2,556 hours. If additional information is required contact: Jerri Murray... Activities: Extension of a Currently Approved Collection; Annual Progress Report for the STOP Formula Grants... Information Collection: Extension of a currently approved collection. (2) Title of the Form/Collection:...

  4. Planar fuel cell utilizing nail current collectors for increased active surface area

    SciTech Connect

    George, Thomas J.; Meacham, G.B. Kirby

    1999-11-26

    A plurality of nail current collector members are useful in the gas flow passages of an electrochemical device to optimize the active surfaces of the device and to provide structural support. In addition, the thicknesses of cathode and anode layers within the electrochemical device are varied according to current flow through the device to reduce resistance and increase operating efficiency.

  5. Duration differences of corticostriatal responses in striatal projection neurons depend on calcium activated potassium currents

    PubMed Central

    Arias-García, Mario A.; Tapia, Dagoberto; Flores-Barrera, Edén; Pérez-Ortega, Jesús E.; Bargas, José; Galarraga, Elvira

    2013-01-01

    The firing of striatal projection neurons (SPNs) exhibits afterhyperpolarizing potentials (AHPs) that determine discharge frequency. They are in part generated by Ca2+-activated K+-currents involving BK and SK components. It has previously been shown that suprathreshold corticostriatal responses are more prolonged and evoke more action potentials in direct pathway SPNs (dSPNs) than in indirect pathway SPNs (iSPNs). In contrast, iSPNs generate dendritic autoregenerative responses. Using whole cell recordings in brain slices, we asked whether the participation of Ca2+-activated K+-currents plays a role in these responses. Secondly, we asked if these currents may explain some differences in synaptic integration between dSPNs and iSPNs. Neurons obtained from BAC D1 and D2 GFP mice were recorded. We used charybdotoxin and apamin to block BK and SK channels, respectively. Both antagonists increased the depolarization and delayed the repolarization of suprathreshold corticostriatal responses in both neuron classes. We also used NS 1619 and NS 309 (CyPPA), to enhance BK and SK channels, respectively. Current enhancers hyperpolarized and accelerated the repolarization of corticostriatal responses in both neuron classes. Nevertheless, these drugs made evident that the contribution of Ca2+-activated K+-currents was different in dSPNs as compared to iSPNs: in dSPNs their activation was slower as though calcium took a diffusion delay to activate them. In contrast, their activation was fast and then sustained in iSPNs as though calcium flux activates them at the moment of entry. The blockade of Ca2+-activated K+-currents made iSPNs to look as dSPNs. Conversely, their enhancement made dSPNs to look as iSPNs. It is concluded that Ca2+-activated K+-currents are a main intrinsic determinant causing the differences in synaptic integration between corticostriatal polysynaptic responses between dSPNs and iSPNs. PMID:24109439

  6. THE EVOLUTION OF THE ELECTRIC CURRENT DURING THE FORMATION AND ERUPTION OF ACTIVE-REGION FILAMENTS

    SciTech Connect

    Wang, Jincheng; Yan, Xiaoli; Qu, Zhongquan; Xue, Zhike; Xiang, Yongyuan; Li, Hao

    2016-02-01

    We present a comprehensive study of the electric current related to the formation and eruption of active region filaments in NOAA AR 11884. The vertical current on the solar surface was investigated by using vector magnetograms (VMs) observed by HMI on board the Solar Dynamics Observatory. To obtain the electric current along the filament's axis, we reconstructed the magnetic fields above the photosphere by using nonlinear force-free field extrapolation based on photospheric VMs. Spatio-temporal evolutions of the vertical current on the photospheric surface and the horizontal current along the filament's axis were studied during the long-term evolution and eruption-related period, respectively. The results show that the vertical currents of the entire active region behaved with a decreasing trend and the magnetic fields also kept decreasing during the long-term evolution. For the eruption-related evolution, the mean transverse field strengths decreased before two eruptions and increased sharply after two eruptions in the vicinity of the polarity inversion lines underneath the filament. The related vertical current showed different behaviors in two of the eruptions. On the other hand, a very interesting feature was found: opposite horizontal currents with respect to the current of the filament's axis appeared and increased under the filament before the eruptions and disappeared after the eruptions. We suggest that these opposite currents were carried by the new flux emerging from the photosphere bottom and might be the trigger mechanism for these filament eruptions.

  7. Negative-shift activation, current reduction and resurgent currents induced by β-toxins from Centruroides scorpions in sodium channels.

    PubMed

    Schiavon, Emanuele; Pedraza-Escalona, Martha; Gurrola, Georgina B; Olamendi-Portugal, Timoteo; Corzo, Gerardo; Wanke, Enzo; Possani, Lourival D

    2012-02-01

    The β-toxins purified from the New World scorpion venoms of the Centruroides species affect several voltage-gated sodium channels (VGSCs) and thus are essential tools not only for the discrimination of different channel sub-types but also for studying the structure-function relationship between channels and toxins. This communication reports the results obtained with four different peptides purified from three species of Centruroides scorpions and assayed on seven distinct isoforms of VGSC (Na(v)1.1-Na(v)1.7) by specific functional analysis conducted through single cell electrophysiology. The toxins studied were CssII from Centruroides suffusus suffusus, Cll1 and Cll2 from Centruroides limpidus limpidus and a novel toxin from Centruroides noxius, which was characterized for the first time here. It has 67 amino acid residues and four disulfide bridges with a molecular mass of 7626 Da. Three different functional features were identified: current reduction of macroscopic conductance, left shift of the voltage-dependent activation and induction of resurgent currents at negative voltages following brief, strong depolarizations. The isoforms which revealed to be more affected resulted to be Na(v)1.6 > 1.1 > 1.2 and, for the first time, a β-toxin is here shown to induce resurgent current also in isoforms different from Na(v)1.6. Additionally, these results were analyzed with molecular modelling. In conclusion, although the four toxins have a high degree of identity, they display tri-modal function, each of which shows selectivity among the different sub-types of Na+ -channels. Thus, they are invaluable as tools for structure-function studies of β-toxins and offer a basis for the design of novel ion channel-specific drugs.

  8. Ocean Currents: Marine Science Activities for Grades 5-8. Teacher's Guide.

    ERIC Educational Resources Information Center

    Halversen, Catherine; Beals, Kevin; Strang, Craig

    This teacher's guide attempts to answer questions such as: What causes ocean currents? What impact do they have on Earth's environment? and How have they influenced human history? Seven innovative activities are provided in which students can gain fascinating insights into the earth as the ocean planet. Activities focus on how wind, temperature,…

  9. Sailing toward Understanding Surface Currents: A Science and Geography Integration Activity for Upper-Elementary Students

    ERIC Educational Resources Information Center

    Eidietis, Laura; Rutherford, Sandra

    2009-01-01

    In the activities presented in this article, students mimic real scientists while constructing predictions and scientific explanations about surface currents. The activities are inspired by and couched within true scientific inquiries regarding the ocean and the North American Great Lakes. Students engage in a classroom inquiry and use map-reading…

  10. Glycine-activated currents are changed by coincident membrane depolarization in developing rat auditory brainstem neurones

    PubMed Central

    Backus, Kurt H; Deitmer, Joachim W; Friauf, Eckhard

    1998-01-01

    During early ontogeny, glycine receptors (GlyRs) exert depolarizing responses which may be of developmental relevance. We have used the gramicidin-perforated patch technique to elucidate the mechanism of glycine-activated currents in developing neurones of the rat lateral superior olive (LSO). When the holding potential was set to −60 mV, perforated-patch recordings revealed glycine-induced inward currents in 59%, outward currents in 5% and biphasic currents in 34% of the LSO neurones tested (n = 44). The biphasic currents were characterized by a transient outward phase which was followed by an inward phase. Ion substitution experiments showed that both Cl− and HCO3− contributed to the glycine- induced biphasic current responses. In the biphasic responses, the reversal potential of the glycine-induced current (Egly) depended on the response phase. A strong shift of Egly from a mean of −72 mV during the outward phase of the glycine response to a mean of −51 mV during the inward phase was observed, suggesting a shift of an ion gradient. When the membrane potential was depolarized, ‘tail’ currents were induced in the presence of glycine. An increased duration or amplitude of the evoked depolarizations resulted in a proportional enlargement of these tail currents, indicating that they were produced by a shift of an ion gradient. Since changes of the HCO3− gradient are negligible, because of the carbonic anhydrase activity, we suggest that these tail currents were caused by a shift of the Cl− gradient. We conclude that Cl− accumulates intracellularly during the activation of GlyRs and, consequently, Egly moves towards more positive values. Coincident depolarizing stimuli enhanced intracellular Cl− accumulation and the shift of Egly, thereby switching hyperpolarizing to depolarizing action. This change could assist in an activity-dependent strengthening and refinement of glycinergic synapses during the maturation of inhibitory connectivity. PMID

  11. Activation of group I metabotropic glutamate receptors enhances persistent sodium current and rhythmic bursting in main olfactory bulb external tufted cells

    PubMed Central

    Ennis, Matthew

    2013-01-01

    Rhythmically bursting olfactory bulb external tufted (ET) cells are thought to play a key role in synchronizing glomerular network activity to respiratory-driven sensory input. Whereas spontaneous bursting in these cells is intrinsically generated by interplay of several voltage-dependent currents, bursting strength and frequency can be modified by local intrinsic and centrifugal synaptic input. Activation of metabotropic glutamate receptors (mGluRs) engages a calcium-dependent cation current (ICAN) that increases rhythmic bursting, but mGluRs may also modulate intrinsic mechanisms involved in bursting. Here, we used patch-clamp electrophysiology in rat olfactory bulb slices to investigate whether mGluRs modulate two key intrinsic currents involved in ET cell burst initiation: persistent sodium (INaP) and hyperpolarization-activated cation (Ih) currents. Using a BAPTA-based internal solution to block ICAN, we found that the mGluR1/5 agonist DHPG enhanced INaP but did not alter Ih. INaP enhancement consisted of increased current at membrane potentials between −60 and −50 mV and a hyperpolarizing shift in activation threshold. Both effects would be predicted to shorten the interburst interval. In agreement, DHPG modestly depolarized (∼3.5 mV) ET cells and increased burst frequency without effect on other major burst parameters. This increase was inversely proportional to the basal burst rate such that slower ET cells exhibited the largest increases. This may enable ET cells with slow intrinsic burst rates to pace with faster sniff rates. Taken with other findings, these results indicate that multiple neurotransmitter mechanisms are engaged to fine-tune rhythmic ET cell bursting to context- and state-dependent changes in sniffing frequency. PMID:24225539

  12. A methodology for fast assessments to the electrical activity of barrel fields in vivo: from population inputs to single unit outputs

    PubMed Central

    Riera, Jorge J.; Goto, Takakuni; Kawashima, Ryuta

    2014-01-01

    Here we propose a methodology to analyze volumetric electrical activity of neuronal masses in the somatosensory barrel field of Wistar rats. The key elements of the proposed methodology are a three-dimensional microelectrode array, which was customized by our group to observe extracellular recordings from an extended area of the barrel field, and a novel method for the current source density analysis. By means of this methodology, we were able to localize single barrels from their event-related responses to single whisker deflection. It was also possible to assess the spatiotemporal dynamics of neuronal aggregates in several barrels at the same time with the resolution of single neurons. We used simulations to study the robustness of our methodology to unavoidable physiological noise and electrode configuration. We compared the accuracy to reconstruct neocortical current sources with that obtained with a previous method. This constitutes a type of electrophysiological microscopy with high spatial and temporal resolution, which could change the way we analyze the activity of cortical neurons in the future. PMID:24550785

  13. In-vitro activity of sparfloxacin in comparison with currently available antimicrobials against respiratory tract pathogens.

    PubMed

    Baquero, F; Cantón, R

    1996-05-01

    Bacterial resistance to antimicrobial agents is an ever-increasing problem. The in-vitro activity of sparfloxacin compared with that of currently available antimicrobial agents against pathogens implicated in respiratory tract infections is reviewed. Sparfloxacin is a fluoroquinolone active against both penicillin-susceptible and -resistant strains of Streptococcus pneumoniae. It is also active against many other respiratory tract pathogens and may be a suitable alternative for empirical therapy of community-acquired respiratory tract infections.

  14. Choline chloride activates time-dependent and time-independent K+ currents in dog atrial myocytes.

    PubMed

    Fermini, B; Nattel, S

    1994-01-01

    Using the whole cell configuration of the patch-clamp technique, we studied the effect of isotonic replacement of bath sodium chloride (NaCl) by choline chloride (ChCl) in dog atrial myocytes. Our results show that ChCl triggered 1) activation of a time-independent background current, characterized by a shift of the holding current in the outward direction at potentials positive to the K+ equilibrium potential (EK), and 2) activation of a time- and voltage-dependent outward current, following depolarizing voltage steps positive to EK. Because the choline-induced current obtained by depolarizing steps exhibited properties similar to the delayed rectifier K+ current (IK), we named it IKCh. The amplitude of IKCh was determined by extracellular ChCl concentration, and this current was generally undetectable in the absence of ChCl. IKCh was not activated by acetylcholine (0.001-1.0 mM) or carbachol (10 microM) and could not be recorded in the absence of ChCl or when external NaCl was replaced by sucrose or tetramethylammonium chloride. IKCh was inhibited by atropine (0.01-1.0 microM) but not by the M1 antagonist pirenzepine (up to 10 microM). This current was carried mainly by K+ and was inhibited by CsCl (120 mM, in the pipette) or barium (1 mM, in the bath). We conclude that in dog atrial myocytes, ChCl activates a background conductance comparable to ACh-dependent K+ current, together with a time-dependent K+ current showing properties similar to IK.

  15. Niflumic acid reduces the hyperpolarization-activated current (I(h)) in rod photoreceptor cells.

    PubMed

    Satoh, T O; Yamada, M

    2001-08-01

    We examined the effects of niflumic acid (NFA), a chloride channel blocker, on the hyperpolarization-activated current (I(h)) in newt rod photoreceptors. At 100 microM, NFA delayed the activation of I(h) induced by hyperpolarizing voltage pulses to -83 mV from a holding potential of -43 mV, and reduced the steady-state current. However, reduction by NFA was weakened when I(h) was activated by hyperpolarizing steps to -123 mV, suggesting that these effects were voltage-dependent. The suppressive effects of NFA on I(h) were accompanied by a negative shift in activation voltage. NFA also delayed the relaxation of I(h) tail currents, showing that this drug also inhibited deactivation of the current. The reversal potential and the fully activated conductance were not affected. These observations suggest that NFA reduces I(h) by modifying the gating kinetics of the underlying channels. The suppressive actions of NFA remained when intracellular Ca2+ was strongly chelated, and the failure of suppression by NFA in inside-out patches suggests that the agent may act on the I(h) channel from the extracellular side. These results, obtained in rod photoreceptors, are consistent with similar effects of NFA on I(f) in cardiac myocytes, suggesting that both currents share similar pharmacological properties.

  16. Characterization of the maitotoxin-activated cationic current from human skin fibroblasts

    PubMed Central

    Martínez-François, Juan Ramón; Morales-Tlalpan, Verónica; Vaca, Luis

    2002-01-01

    The maitotoxin (MTX)-induced cationic current (Imtx) from human skin fibroblasts was characterized using the patch-clamp technique in whole-cell configuration. Under resting conditions (absence of MTX), the main current observed is produced by an outwardly rectifying K+ channel which is inhibited by 1 mm TEA. The current reversal potential was −86 mV (n = 12). MTX (500 pm) activated a current with a linear current–voltage relationship and a reversal potential of −10 mV (n = 10). Replacing the extracellular Na+ and K+ with N-methyl-d-glucamine (NMDG) caused a shift of the reversal potential to a value below −100 mV, indicating that Na+ and K+, but not NMDG, carry Imtx. Further ion selectivity experiments showed that Ca2+ carries Imtx also. The resulting permeability sequence obtained with the Goldman–Hodgkin–Katz equation yielded Na+ (1) ≈ K+ (1) > Ca2+ (0.87). The Imtx activation time course reflected the changes in intracellular Ca2+ and Na+ measured with the fluorescent indicators fura-2 and SBFI, respectively, suggesting that the activation of Imtx brings about an increment in intracellular Ca2+ and Na+. Reducing the extracellular Ca2+ concentration below 1.8 mm prevented the activation of Imtx and the increment in intracellular Na+ induced by MTX. Mn2+ and Mg2+ could not replace Ca2+, but Ba2+ could replace Ca2+. MTX activation of current in 10 mm Ba2+ was approximately 50 % of that induced in the presence of 1.8 mm Ca2+. When 5 mm of the Ca2+ chelator BAPTA was included in the patch pipette, MTX either failed to activate the current or induced a small current (less than 15 % of the control), indicating that intracellular Ca2+ is also required for the activation of Imtx. Intracellular Ba2+ can replace Ca2+ as an activator of Imtx. However, in the presence of 10 mm Ba2+ the activation by MTX of the current was 50 % less than the activation with nm concentrations of free intracellular Ca2+. PMID:11773318

  17. Three-dimensional ventricular activation imaging by means of equivalent current source modeling and estimation.

    PubMed

    Liu, Z; Liu, C; He, B

    2006-01-01

    This paper presents a novel electrocardiographic inverse approach for imaging the 3-D ventricular activation sequence based on the modeling and estimation of the equivalent current density throughout the entire myocardial volume. The spatio-temporal coherence of the ventricular excitation process is utilized to derive the activation time from the estimated time course of the equivalent current density. At each time instant during the period of ventricular activation, the distributed equivalent current density is noninvasively estimated from body surface potential maps (BSPM) using a weighted minimum norm approach with a spatio-temporal regularization strategy based on the singular value decomposition of the BSPMs. The activation time at any given location within the ventricular myocardium is determined as the time point with the maximum local current density estimate. Computer simulation has been performed to evaluate the capability of this approach to image the 3-D ventricular activation sequence initiated from a single pacing site in a physiologically realistic cellular automaton heart model. The simulation results demonstrate that the simulated "true" activation sequence can be accurately reconstructed with an average correlation coefficient of 0.90, relative error of 0.19, and the origin of ventricular excitation can be localized with an average localization error of 5.5 mm for 12 different pacing sites distributed throughout the ventricles.

  18. Paralleling power MOSFETs in their active region: Extended range of passively forced current sharing

    NASA Technical Reports Server (NTRS)

    Niedra, Janis M.

    1989-01-01

    A simple passive circuit that improves current balance in parallelled power MOSFETs that are not precisely matched and that are operated in their active region from a common gate drive are exhibited. A nonlinear circuit consisting of diodes and resistors generates the differential gate potential required to correct for unbalance while maintaining low losses over a range of current. Also application of a thin tape wound magnetic core to effect dynamic current balance is reviewed, and a simple theory is presented showing that for operation in the active region the branch currents tend to revert to their normal unbalanced values even if the core is not driven into saturation. Results of several comparative experiments are given.

  19. FCCP depolarizes plasma membrane potential by activating proton and Na+ currents in bovine aortic endothelial cells.

    PubMed

    Park, Kyu-Sang; Jo, Inho; Pak, Kim; Bae, Sung-Won; Rhim, Hyewhon; Suh, Suk-Hyo; Park, Jin; Zhu, Hong; So, Insuk; Kim, Ki Whan

    2002-01-01

    We investigated the effects of carbonylcyanide p-trifluoromethoxyphenylhydrazone (FCCP), a protonophore and uncoupler of mitochondrial oxidative phosphorylation in mitochondria, on plasma membrane potential and ionic currents in bovine aortic endothelial cells (BAECs). The membrane potential and ionic currents of BAECs were recorded using the patch-clamp technique in current-clamp and voltage-clamp modes, respectively. FCCP activated ionic currents and depolarized the plasma membrane potential in a dose-dependent manner. Neither the removal of extracellular Ca2+ nor pretreatment with BAPTA/AM affected the FCCP-induced currents, implying that the currents are not associated with the FCCP-induced intracellular [Ca2+]i increase. FCCP-induced currents were significantly influenced by the changes in extracellular or intracellular pH; the increased proton gradient produced by lowering the extracellular pH or intracellular alkalinization augmented the changes in membrane potential and ionic currents caused by FCCP. FCCP-induced currents were significantly reduced under extracellular Na+-free conditions. The reversal potentials of FCCP-induced currents under Na+-free conditions were well fitted to the calculated equilibrium potential for protons. Interestingly, FCCP-induced Na+ transport (subtracted currents, I(control)- I(Na+-free) was closely dependent on extracellular pH, whereas FCCP-induced H+transport was not significantly affected by the absence of Na+. These results suggest that the FCCP-induced ionic currents and depolarization, which are strongly dependent on the plasmalemmal proton gradient, are likely to be mediated by both H+ and Na+ currents across the plasma membrane. The relationship between H+ and Na+ transport still needs to be determined.

  20. Activation of muscarinic K+ current in guinea-pig atrial myocytes by a serum factor.

    PubMed Central

    Banach, K; Hüser, J; Lipp, P; Wellner, M C; Pott, L

    1993-01-01

    1. Atrial myocytes obtained by enzymatic perfusion of hearts from adult guinea-pigs and cultured for 0-14 days were studied using the whole-cell voltage-clamp technique. 2. Superfusion of the myocytes with diluted sera (1:100 to 1:10,000) from different species (human, horse, guinea-pig) evoked an inward rectifying K+ current. The voltage-dependent properties of this current were identical to those of the K+ current activated by acetylcholine (IK(ACh)). Current density in the presence of horse serum (1:100) approximately corresponded to the non-desensitizing fraction of IK(ACh) during superfusion with 1-2 x 10(-6) M ACh. 3. During a maximal serum-evoked current, application of ACh (10(-6) M) failed to evoke additional K+ current. After switching superfusion from serum-containing to serum-free solution, the K+ current decayed 1-2 orders of magnitude slower than ACh-activated IK(ACh). During the decay of the serum-evoked current, a proportional increase in responsiveness to ACh was recorded. During submaximal activation of K+ current by serum, a saturating concentration of ACh resulted in a total current that was identical to the current evoked by ACh alone minus the desensitizing component. Thus, activation of K+ current by serum caused desensitization of IK(ACh). From these results it is concluded that sera contain a factor that activates the same population of K+ channels as ACh. 4. Irreversible activation of IK(ACh) by ACh in myocytes dialysed with the GTP-analogue GTP-gamma-S abolished sensitivity to serum and vice versa. 5. The effect of serum was not modified by atropine (10(-6) M) which completely blocked the response to 2 x 10(-6) M ACh. Furthermore, theophylline (1 mM), which completely inhibited IK(ACh) activation by adenosine (100 microM), failed to inhibit the effect of serum. Thus, neither muscarinic nor purinergic (A1) receptors are involved. 6. The peptide somatostatin (10(-6) M) and the alpha 1-agonist phenylephrine (1 microM) which previously have

  1. Input and Input Processing in Second Language Acquisition.

    ERIC Educational Resources Information Center

    Alcon, Eva

    1998-01-01

    Analyzes second-language learners' processing of linguistic data within the target language, focusing on input and intake in second-language acquisition and factors and cognitive processes that affect input processing. Input factors include input simplification, input enhancement, and interactional modifications. Individual learner differences…

  2. A Palladium-Binding Deltarhodopsin for Light-Activated Conversion of Protonic to Electronic Currents.

    PubMed

    Soto-Rodríguez, Jessica; Hemmatian, Zahra; Josberger, Erik E; Rolandi, Marco; Baneyx, François

    2016-08-01

    Fusion of a palladium-binding peptide to an archaeal rhodopsin promotes intimate integration of the lipid-embedded membrane protein with a palladium hydride protonic contact. Devices fabricated with the palladium-binding deltarhodopsin enable light-activated conversion of protonic currents to electronic currents with on/off responses complete in seconds and a nearly tenfold increase in electrical signal relative to those made with the wild-type protein.

  3. Activation of Ca(2+)-dependent K+ current by acetylcholine and histamine in a human gastric epithelial cell line

    PubMed Central

    1993-01-01

    The effects of acetylcholine (ACh) and histamine (His) on the membrane potential and current were examined in JR-1 cells, a mucin-producing epithelial cell line derived from human gastric signet ring cell carcinoma. The tight-seal, whole cell clamp technique was used. The resting membrane potential, the input resistance, and the capacitance of the cells were approximately -12 mV, 1.4 G ohms, and 50 pF, respectively. Under the voltage-clamp condition, no voltage-dependent currents were evoked. ACh or His added to the bathing solution hyperpolarized the membrane by activating a time- and voltage- independent K+ current. The ACh-induced hyperpolarization and K+ current persisted, while the His response desensitized quickly (< 1 min). These effects of ACh and His were mediated predominantly by m3- muscarinic and H1-His receptors, respectively. The K+ current induced by ACh and His was inhibited by charybdotoxin, suggesting that it is a Ca(2+)-activated K+ channel current (IK.Ca). The measurement of intracellular Ca2+ ([Ca2+]i) using Indo-1 revealed that both agents increased [Ca2+]i with similar time courses as they increased IK.Ca. When EGTA in the pipette solution was increased from 0.15 to 10 mM, the induction of IK.Ca by ACh and His was abolished. Thus, both ACh and His activate IK.Ca by increasing [Ca2+]i in JR-1 cells. In the Ca(2+)-free bathing solution (0.15 mM EGTA in the pipette), ACh evoked IK.Ca transiently. Addition of Ca2+ (1.8 mM) to the bath immediately restored the sustained IK.Ca. These results suggest that the ACh response is due to at least two different mechanisms; i.e., the Ca2+ release-related initial transient activation and the Ca2+ influx-related sustained activation of IK.Ca. Probably because of desensitization, the Ca2+ influx-related component of the His response could not be identified. Intracellularly applied inositol 1,4,5-trisphosphate (IP3), with and without inositol 1,3,4,5-tetrakisphosphate (IP4), mimicked the ACh response. IP4 alone

  4. Tools to Develop or Convert MOVES Inputs

    EPA Pesticide Factsheets

    The following tools are designed to help users develop inputs to MOVES and post-process the output. With the release of MOVES2014, EPA strongly encourages state and local agencies to develop local inputs based on MOVES fleet and activity categories.

  5. Effects of SDPNFLRF-amide (PF1) on voltage-activated currents in Ascaris suum muscle.

    PubMed

    Verma, S; Robertson, A P; Martin, R J

    2009-02-01

    Helminth infections are of significant concern in veterinary and human medicine. The drugs available for chemotherapy are limited in number and the extensive use of these drugs has led to the development of resistance in parasites of animals and humans (Geerts and Gryseels, 2000; Kaplan, 2004; Osei-Atweneboana et al., 2007). The cyclooctadepsipeptide, emodepside, belongs to a new class of anthelmintic that has been released for animal use in recent years. Emodepside has been proposed to mimic the effects of the neuropeptide PF1 on membrane hyperpolarization and membrane conductance (Willson et al., 2003). We investigated the effects of PF1 on voltage-activated currents in Ascaris suum muscle cells. The whole cell voltage-clamp technique was employed to study these currents. Here we report two types of voltage-activated inward calcium currents: transient peak (I(peak)) and a steady-state (I(ss)). We found that 1microM PF1 inhibited the two calcium currents. The I(peak) decreased from -146nA to -99nA (P=0.0007) and the I(ss) decreased from -45nA to -12nA (P=0.002). We also found that PF1 in the presence of calcium increased the voltage-activated outward potassium current (from 521nA to 628nA (P=0.004)). The effect on the potassium current was abolished when calcium was removed and replaced with cobalt; it was also reduced at a higher concentration of PF1 (10microM). These studies demonstrate a mechanism by which PF1 decreases the excitability of the neuromuscular system by modulating calcium currents in nematodes. PF1 inhibits voltage-activated calcium currents and potentiates the voltage-activated calcium-dependent potassium current. The effect on a calcium-activated-potassium channel appears to be common to both PF1 and emodepside (Guest et al., 2007). It will be of interest to investigate the actions of emodepside on calcium currents to further elucidate the mechanism of action.

  6. Current steering to activate targeted neural pathways during deep brain stimulation of the subthalamic region

    PubMed Central

    Chaturvedi, Ashutosh; Foutz, Thomas J.; McIntyre, Cameron C.

    2012-01-01

    Deep brain stimulation (DBS) has steadily evolved into an established surgical therapy for numerous neurological disorders, most notably Parkinson’s disease (PD). Traditional DBS technology relies on voltage-controlled stimulation with a single source; however, recent engineering advances are providing current-controlled devices with multiple independent sources. These new stimulators deliver constant current to the brain tissue, irrespective of impedance changes that occur around the electrode, and enable more specific steering of current towards targeted regions of interest. In this study, we examined the impact of current steering between multiple electrode contacts to directly activate three distinct neural populations in the subthalamic region commonly stimulated for the treatment of PD: projection neurons of the subthalamic nucleus (STN), globus pallidus internus (GPi) fibers of the lenticular fasiculus, and internal capsule (IC) fibers of passage. We used three-dimensional finite element electric field models, along with detailed multi-compartment cable models of the three neural populations to determine their activations using a wide range of stimulation parameter settings. Our results indicate that selective activation of neural populations largely depends on the location of the active electrode(s). Greater activation of the GPi and STN populations (without activating any side-effect related IC fibers) was achieved by current steering with multiple independent sources, compared to a single current source. Despite this potential advantage, it remains to be seen if these theoretical predictions result in a measurable clinical effect that outweighs the added complexity of the expanded stimulation parameter search space generated by the more flexible technology. PMID:22277548

  7. Input Decimated Ensembles

    NASA Technical Reports Server (NTRS)

    Tumer, Kagan; Oza, Nikunj C.; Clancy, Daniel (Technical Monitor)

    2001-01-01

    Using an ensemble of classifiers instead of a single classifier has been shown to improve generalization performance in many pattern recognition problems. However, the extent of such improvement depends greatly on the amount of correlation among the errors of the base classifiers. Therefore, reducing those correlations while keeping the classifiers' performance levels high is an important area of research. In this article, we explore input decimation (ID), a method which selects feature subsets for their ability to discriminate among the classes and uses them to decouple the base classifiers. We provide a summary of the theoretical benefits of correlation reduction, along with results of our method on two underwater sonar data sets, three benchmarks from the Probenl/UCI repositories, and two synthetic data sets. The results indicate that input decimated ensembles (IDEs) outperform ensembles whose base classifiers use all the input features; randomly selected subsets of features; and features created using principal components analysis, on a wide range of domains.

  8. CURRENT HELICITY OF ACTIVE REGIONS AS A TRACER OF LARGE-SCALE SOLAR MAGNETIC HELICITY

    SciTech Connect

    Zhang, H.; Gao, Y.; Xu, H.; Moss, D.; Kleeorin, N.; Rogachevskii, I.; Kuzanyan, K.; Sokoloff, D.

    2012-05-20

    We demonstrate that the current helicity observed in solar active regions traces the magnetic helicity of the large-scale dynamo generated field. We use an advanced two-dimensional mean-field dynamo model with dynamo saturation based on the evolution of the magnetic helicity and algebraic quenching. For comparison, we also studied a more basic two-dimensional mean-field dynamo model with simple algebraic alpha-quenching only. Using these numerical models we obtained butterfly diagrams both for the small-scale current helicity and also for the large-scale magnetic helicity, and compared them with the butterfly diagram for the current helicity in active regions obtained from observations. This comparison shows that the current helicity of active regions, as estimated by -A {center_dot} B evaluated at the depth from which the active region arises, resembles the observational data much better than the small-scale current helicity calculated directly from the helicity evolution equation. Here B and A are, respectively, the dynamo generated mean magnetic field and its vector potential. A theoretical interpretation of these results is given.

  9. Reduction, Analysis, and Properties of Electric Current Systems in Solar Active Regions

    NASA Technical Reports Server (NTRS)

    Gary, G. Allen; Demoulin, Pascal

    1995-01-01

    The specific attraction and, in large part, the significance of solar vector magnetograms lie in the fact that they give the most important data on the electric currents and the nonpotentiality of active regions. Using the vector magnetograms from the Marshall Space Flight Center (MSFC), we employ a unique technique in the area of data analysis for resolving the 180 degree ambiguity in order to calculate the spatial structure of the vertical electric current density. The 180 degree ambiguity is resolved by applying concepts from the nonlinear multivariable optimization theory. The technique is shown to be of particular importance in very nonpotential active regions. The characterization of the vertical electric current density for a set of vector magnetograms using this method then gives the spatial scale, locations, and magnitude of these current systems. The method, which employs an intermediate parametric function which covers the magnetogram and which defines the local "preferred" direction, minimizes a specific functional of the observed transverse magnetic field. The specific functional that is successful is the integral of the square of the vertical current density. We find that the vertical electric current densities have common characteristics for the extended bipolar beta gamma delta-regions studied. The largest current systems have j(sub z)'s which maximizes around 30 mA per square meter and have a linear decreasing distribution to a diameter of 30 Mm.

  10. Reduction, analysis, and properties of electric current systems in solar active regions

    NASA Technical Reports Server (NTRS)

    Gary, G. Allen; Demoulin, Pascal

    1995-01-01

    The specific attraction and, in large part, the significance of solar magnetograms lie in the fact that they give the most important data on the electric currents and the nonpotentiality of active regions. Using the vector magnetograms from the Marshall Space Flight Center (MSFC), we employ a unique technique in the area of data analysis for resolving the 180 deg ambiguity in order to calculate the spatial structure of the vertical electric current density. The 180 deg ambiguity is resolved by applying concepts from the nonlinear multivariable optimization theory. The technique is shown to be of particular importance in very nonpotential active regions. The characterization of the vertical electric current density for a set of vector magnetograms using this method then gives the spatial scale, locations, and magnitude of these current systems. The method, which employs an intermediate parametric function which covers the magnetogram and which defines the local `preferred' direction, minimizes a specific functional of the observed transverse magnetic field. The specific functional that is successful is the integral of the square of the vertical current density. We find that the vertical electric current densities have common characteristics for the extended bipolar (beta) (gamma) (delta)-regions studied. The largest current systems have j(sub z)'s which maximizes around 30 mA/sq m and have a linear decreasing distribution to a diameter of 30 Mn.

  11. Current Research Activities in Drive System Technology in Support of the NASA Rotorcraft Program

    NASA Technical Reports Server (NTRS)

    Handschuh, Robert F.; Zakrajsek, James J.

    2006-01-01

    Drive system technology is a key area for improving rotorcraft performance, noise/vibration reduction, and reducing operational and manufacturing costs. An overview of current research areas that support the NASA Rotorcraft Program will be provided. Work in drive system technology is mainly focused within three research areas: advanced components, thermal behavior/emergency lubrication system operation, and diagnostics/prognostics (also known as Health and Usage Monitoring Systems (HUMS)). Current research activities in each of these activities will be presented. Also, an overview of the conceptual drive system requirements and possible arrangements for the Heavy Lift Rotorcraft program will be reviewed.

  12. Current and Future Research in Active Control of Lightweight, Flexible Structures Using the X-56 Aircraft

    NASA Technical Reports Server (NTRS)

    Ryan, John J.; Bosworth, John T.; Burken, John J.; Suh, Peter M.

    2014-01-01

    The X-56 Multi-Utility Technology Testbed aircraft system is a versatile experimental research flight platform. The system was primarily designed to investigate active control of lightweight flexible structures, but is reconfigurable and capable of hosting a wide breadth of research. Current research includes flight experimentation of a Lockheed Martin designed active control flutter suppression system. Future research plans continue experimentation with alternative control systems, explore the use of novel sensor systems, and experiments with the use of novel control effectors. This paper describes the aircraft system, current research efforts designed around the system, and future planned research efforts that will be hosted on the aircraft system.

  13. Calcium-activated chloride currents in olfactory sensory neurons from mice lacking bestrophin-2.

    PubMed

    Pifferi, Simone; Dibattista, Michele; Sagheddu, Claudia; Boccaccio, Anna; Al Qteishat, Ahmed; Ghirardi, Filippo; Tirindelli, Roberto; Menini, Anna

    2009-09-01

    Olfactory sensory neurons use a chloride-based signal amplification mechanism to detect odorants. The binding of odorants to receptors in the cilia of olfactory sensory neurons activates a transduction cascade that involves the opening of cyclic nucleotide-gated channels and the entry of Ca(2+) into the cilia. Ca(2+) activates a Cl(-) current that produces an efflux of Cl(-) ions and amplifies the depolarization. The molecular identity of Ca(2+)-activated Cl(-) channels is still elusive, although some bestrophins have been shown to function as Ca(2+)-activated Cl(-) channels when expressed in heterologous systems. In the olfactory epithelium, bestrophin-2 (Best2) has been indicated as a candidate for being a molecular component of the olfactory Ca(2+)-activated Cl(-) channel. In this study, we have analysed mice lacking Best2. We compared the electrophysiological responses of the olfactory epithelium to odorant stimulation, as well as the properties of Ca(2+)-activated Cl(-) currents in wild-type (WT) and knockout (KO) mice for Best2. Our results confirm that Best2 is expressed in the cilia of olfactory sensory neurons, while odorant responses and Ca(2+)-activated Cl(-) currents were not significantly different between WT and KO mice. Thus, Best2 does not appear to be the main molecular component of the olfactory channel. Further studies are required to determine the function of Best2 in the cilia of olfactory sensory neurons.

  14. Calcium-activated chloride currents in olfactory sensory neurons from mice lacking bestrophin-2

    PubMed Central

    Pifferi, Simone; Dibattista, Michele; Sagheddu, Claudia; Boccaccio, Anna; Al Qteishat, Ahmed; Ghirardi, Filippo; Tirindelli, Roberto; Menini, Anna

    2009-01-01

    Olfactory sensory neurons use a chloride-based signal amplification mechanism to detect odorants. The binding of odorants to receptors in the cilia of olfactory sensory neurons activates a transduction cascade that involves the opening of cyclic nucleotide-gated channels and the entry of Ca2+ into the cilia. Ca2+ activates a Cl− current that produces an efflux of Cl− ions and amplifies the depolarization. The molecular identity of Ca2+-activated Cl− channels is still elusive, although some bestrophins have been shown to function as Ca2+-activated Cl− channels when expressed in heterologous systems. In the olfactory epithelium, bestrophin-2 (Best2) has been indicated as a candidate for being a molecular component of the olfactory Ca2+-activated Cl− channel. In this study, we have analysed mice lacking Best2. We compared the electrophysiological responses of the olfactory epithelium to odorant stimulation, as well as the properties of Ca2+-activated Cl− currents in wild-type (WT) and knockout (KO) mice for Best2. Our results confirm that Best2 is expressed in the cilia of olfactory sensory neurons, while odorant responses and Ca2+-activated Cl− currents were not significantly different between WT and KO mice. Thus, Best2 does not appear to be the main molecular component of the olfactory channel. Further studies are required to determine the function of Best2 in the cilia of olfactory sensory neurons. PMID:19622610

  15. Epac activator critically regulates action potential duration by decreasing potassium current in rat adult ventricle.

    PubMed

    Brette, Fabien; Blandin, Erick; Simard, Christophe; Guinamard, Romain; Sallé, Laurent

    2013-04-01

    Sympathetic stimulation is an important modulator of cardiac function via the classic cAMP-dependent signaling pathway, PKA. Recently, this paradigm has been challenged by the discovery of a family of guanine nucleotide exchange proteins directly activated by cAMP (Epac), acting in parallel to the classic signaling pathway. In cardiac myocytes, Epac activation is known to modulate Ca(2+) cycling yet their actions on cardiac ionic currents remain poorly characterized. This study attempts to address this paucity of information using the patch clamp technique to record action potential (AP) and ionic currents on rat ventricular myocytes. Epac was selectively activated by 8-CPT-AM (acetoxymethyl ester form of 8-CPT). AP amplitude, maximum depolarization rate and resting membrane amplitude were unaltered by 8-CPT-AM, strongly suggesting that Na(+) current and inward rectifier K(+) current are not regulated by Epac. In contrast, AP duration was significantly increased by 8-CPT-AM (prolongation of duration at 50% and 90% of repolarization by 41±10% and 43±8% respectively, n=11). L-type Ca(2+) current density was unaltered by 8-CPT-AM (n=16) so this cannot explain the action potential lengthening. However, the steady state component of K(+) current was significantly inhibited by 8-CPT-AM (-38±6%, n=15), while the transient outward K(+) current was unaffected by 8-CPT-AM. These effects were PKA-independent since they were observed in the presence of PKA inhibitor KT5720. Isoprenaline (100nM) induced a significant prolongation of AP duration, even in the presence of KT5720. This study provides the first evidence that the cAMP-binding protein Epac critically modulates cardiac AP duration by decreasing steady state K(+) current. These observations may be relevant to diseases in which Epac is upregulated, like cardiac hypertrophy.

  16. Acidosis inhibits spontaneous activity and membrane currents in myocytes isolated from the rabbit atrioventricular node.

    PubMed

    Cheng, Hongwei; Smith, Godfrey L; Orchard, Clive H; Hancox, Jules C

    2009-01-01

    Recent evidence from intact hearts suggests that the function of cardiac nodal tissue may be particularly susceptible to acidosis. Little is currently known, however, about the effects of acidosis on the cellular electrophysiology of the atrioventricular node (AVN). This study was conducted, therefore, to determine the effect of acidosis on the spontaneous activity and membrane currents of myocytes isolated from the rabbit AVN, recorded at 35-37 degrees C using whole-cell patch-clamp. Reduction of extracellular pH (pH(e); from 7.4 to 6.8 or 6.3) produced pH-dependent slowing of spontaneous action potential rate and upstroke velocity, and reductions in maximum diastolic potential and action potential amplitude. Ionic current recordings under voltage-clamp indicated that acidosis (pH(e) 6.3) decreased L-type Ca current (I(Ca,L)), without significant changes in voltage-dependent activation or inactivation. Acidosis reduced the E-4031-sensitive, rapid delayed rectifier current (I(Kr)) tail amplitude at -40 mV following command pulses to between -30 and +50 mV, and accelerated tail-current deactivation. In contrast, the time-dependent hyperpolarisation-activated current, I(f), was unaffected by acidosis. Background current insensitive to E-4031 and nifedipine was reduced by acidosis. Measurement of intracellular pH (pH(i)) from undialysed cells using BCECF showed a reduction in mean pH(i) from 7.24 to 6.45 (n=17) when pH(e) was lowered from 7.4 to 6.3. We conclude that I(f) is unlikely to be involved in the response of the AVN to acidosis, whilst inhibition of I(Ca,L) and I(Kr) by acidosis are likely to play a significant role in effects on AVN cellular electrophysiology.

  17. Adenosine-activated potassium current in smooth muscle cells isolated from the pig coronary artery.

    PubMed Central

    Dart, C; Standen, N B

    1993-01-01

    1. The perforated patch technique with nystatin or amphotericin was used to record whole cell currents activated by adenosine in smooth muscle cells isolated enzymatically from pig coronary arteries. 2. Adenosine (5-40 microM) activated an outward current at a holding potential of 0 mV in 5 mM [K+]o and an inward current at -60 mV in 143 mM [K+]o. The dependence of the reversal potential for the adenosine-activated current on [K+]o suggests that it flows through K+ channels, while its current-voltage relation is consistent with the channels showing little voltage dependence. 3. The adenosine-activated current was inhibited by the sulphonylurea glibenclamide (5 microM) and by phencyclidine (5 microM). It was unaffected by charybdotoxin (50 nM) or apamin (100 nM), blockers of large and small conductance Ca(2+)-activated K+ channels respectively. 4. At -60 mV in 143 mM K+ solution, openings of single channels passing a current of just over -2 pA could sometimes be detected in the absence of adenosine. Openings became more frequent after the application of adenosine, with several levels then being detected. Openings of channels with a larger conductance were sometimes also seen in the presence of adenosine. Fluctuation analysis gave somewhat lower estimates of unitary current than did direct measurements. 5. The effect of adenosine could be mimicked by the A1 receptor agonist CCPA (2-chloro-N6-cyclopentyladenosine), while the A2 agonist CGS 21680 (2-p-(2-carboxethyl)phenethylamino-5'-N-ethylcarboxamido adenosine hydrochloride) was without effect. The response to adenosine was inhibited by the A1 antagonist DPCPX (8-cyclopentyl-1,3-dipropylxanthine), but was unaffected by the A2 antagonist CGS 15943A (5-amino-9-chloro-2-(2-furanyl)-1,2,4- triazolo[1,5-C]quinazoline monomethanesulphonate). 6. Our results suggest that adenosine acts at an A1 receptor to activate K+ channels. We consider it most likely that these are ATP-dependent K+ channels. We discuss the mechanism by

  18. Induction of self awareness in dreams through frontal low current stimulation of gamma activity.

    PubMed

    Voss, Ursula; Holzmann, Romain; Hobson, Allan; Paulus, Walter; Koppehele-Gossel, Judith; Klimke, Ansgar; Nitsche, Michael A

    2014-06-01

    Recent findings link fronto-temporal gamma electroencephalographic (EEG) activity to conscious awareness in dreams, but a causal relationship has not yet been established. We found that current stimulation in the lower gamma band during REM sleep influences ongoing brain activity and induces self-reflective awareness in dreams. Other stimulation frequencies were not effective, suggesting that higher order consciousness is indeed related to synchronous oscillations around 25 and 40 Hz.

  19. Antibacterial efficacy and cytotoxicity of low intensity direct current activated silver-titanium implant system prototype.

    PubMed

    Tan, Zhuo; Havell, Edward A; Orndorff, Paul E; Shirwaiker, Rohan A

    2017-02-01

    Silver-based devices activated by electric current are of interest in biomedicine because of their broad-spectrum antimicrobial activity. This study investigates the in vitro antibacterial efficacy and cytotoxicity of a low intensity direct current (LIDC)-activated silver-titanium implant system prototype designed for localized generation and delivery of silver ions at the implantation site. First, the antibacterial efficacy of the system was assessed against methicillin-resistant Staphylococcus aureus (MRSA) over 48 h at current levels of 3 and 6 µA in Mueller-Hinton broth. The cytotoxicity of the system was then evaluated over 48 h in two phases using an in vitro model with in which the activated electrodes were suspended in growth medium in a cell-seeded tissue culture plate. In phase-1, the system was tested on human osteosarcoma (MG-63) cell line and compared to titanium controls. In phase-2, the cytotoxicity characteristics were validated with normal human diploid osteoblast cells. The LIDC-activated system demonstrated high antimicrobial efficacy against MRSA, but was also toxic to human cells immediately surrounding the electrodes. The statistical analysis showed that the cytotoxicity was a result of the presence of silver, and the electric activation did not make it worse.

  20. Temperature dependence of rapidly adapting mechanically activated currents in rat dorsal root ganglion neurons.

    PubMed

    Jia, Zhanfeng; Ling, Jennifer; Gu, Jianguo G

    2012-08-01

    Rapidly adapting mechanically activated channels (RA) are expressed on somatosensory neurons and thought to play a role in mechanical transduction. Because mechanical sensations can be significantly affected by temperatures, we examined thermal sensitivity of RA currents in cultured dorsal root ganglion (DRG) neurons to see if RA channel activity is highly temperature-dependent. RA currents were evoked from DRG neurons by membrane displacements and recorded by the whole-cell patch-clamp recording technique. We found that RA currents were significantly enhanced by warming temperatures from 22 to 32 °C and reduced by cooling temperatures from 24 to 14 °C. RA channel activation exhibited steep temperature-dependence with a large temperature coefficient (Q10>5) and a high activation energy (Ea>30 kcal/mol). We further showed that RA channel activation by mechanical stimulation led to membrane depolarization, which could result in action potential firing at 22 °C or 32 °C but not at 14 °C. Taken together, our results provide the measurements of thermal dynamics and activation energy of RA channels, and suggest that a high energy barrier is present for RA channels to open. These findings are in agreement with temperature sensitivity of mechanical sensations in mammals.

  1. Magnetic current sensor

    NASA Technical Reports Server (NTRS)

    Black, Jr., William C. (Inventor); Hermann, Theodore M. (Inventor)

    1998-01-01

    A current determiner having an output at which representations of input currents are provided having an input conductor for the input current and a current sensor supported on a substrate electrically isolated from one another but with the sensor positioned in the magnetic fields arising about the input conductor due to any input currents. The sensor extends along the substrate in a direction primarily perpendicular to the extent of the input conductor and is formed of at least a pair of thin-film ferromagnetic layers separated by a non-magnetic conductive layer. The sensor can be electrically connected to a electronic circuitry formed in the substrate including a nonlinearity adaptation circuit to provide representations of the input currents of increased accuracy despite nonlinearities in the current sensor, and can include further current sensors in bridge circuits.

  2. The morphology of flare phenomena, magnetic fields, and electric currents in active regions. III - NOAA active region 6233 (1990 August)

    NASA Technical Reports Server (NTRS)

    De La Beaujardiere, J.-F.; Canfield, Richard C.; Leka, K. D.

    1993-01-01

    We investigate the spatial relationship between vertical electric currents and flare phenomena in NOAA Active Region 6233, which was observed 1990, August 28-31 at Mees Solar Observatory. The two flares studied are the 1N/M1.8 flare on August 28, 22:30 UT and the 1N/M1.6 flare on August 29, 20:35 UT. Using Stokes polarimetry we make magnetograms of the region and compute the vertical current density. Using H-alpha imaging spectroscopy we identify sites of intense nonthermal electron precipitation or of high coronal pressure. The precipitation in these flares is barely strong enough to be detectable. We find that both precipitation and high pressure tend to occur near vertical currents, but that neither phenomenon is cospatial with current maxima. In contrast with the conclusion of other authors, we argue that these observations do not support a current-interruption model for flares, unless the relevant currents are primarily horizontal. The magnetic morphology and temporal evolution of these flares suggest that an erupting filament model may be relevant, but this model does not explicitly predict the relationship between precipitation, high pressure, and vertical currents.

  3. Metabolic inhibition enhances Ca(2+)-activated K+ current in smooth muscle cells of rabbit portal vein.

    PubMed

    Miller, A L; Morales, E; Leblanc, N R; Cole, W C

    1993-12-01

    The effect of metabolic inhibition on macroscopic and single-channel K+ currents in isolated rabbit portal vein myocytes was investigated by patch-clamp technique. Depression of adenosine triphosphate synthesis was produced by 2-deoxy-D-glucose (10 mM) and either cyanide (2 mM) or dinitrophenol (50 microM). Outward quasi-steady-state current evoked by a ramp protocol and outward time-dependent current during step depolarizations were increased during metabolic inhibition. The reversal potential for quasi-steady-state current shifted negatively toward equilibrium potential of K+ during treatment consistent with a role for K+ conductance and hyperpolarization of membrane potential. The macroscopic K+ current affected was 1) voltage dependent, 2) inhibited by intracellular Ca2+ chelation and low tetraethylammonium ion (1 mM) but unaffected by 4-aminopyridine (2 mM), and 3) associated with a rise in intracellular Ca2+ assessed by indo 1. Metabolic inhibition caused an increase in voltage-dependent large-conductance K+ channel (120-130 pS) activity in cell-attached patches of myocytes bathed in physiological solution (140 mM K+ in pipette). The channels were blocked in a flickery fashion by tetraethylammonium ion (0.5 mM) and inhibited with charybdotoxin (100 nM). We conclude that metabolic inhibition increases the activity of large-conductance Ca(2+)-activated K+ channels in vascular smooth muscle.

  4. Osteoclast spreading kinetics are correlated with an oscillatory activation of a calcium-dependent potassium current.

    PubMed

    Espinosa, Leon; Paret, Laurent; Ojeda, Carlos; Tourneur, Yves; Delmas, Pierre D; Chenu, Chantal

    2002-10-01

    Cell movement and spreading involve calcium-dependent processes and ionic channel activation. During bone resorption, osteoclasts alternate between spread, motile and resorptive phases. We investigated whether the electrical membrane properties of osteoclasts were linked to their membrane morphological changes. Rabbit osteoclasts were recorded by time-lapse videomicroscopy performed simultaneously with patch-clamp whole cell and single channel recordings. Original image analysis methods were developed and used to demonstrate for the first time an oscillatory activation of a spontaneous membrane current in osteoclasts, which is directly correlated to the membrane movement rate. This current was identified as a calcium-dependent potassium current (IK(Ca)) that is sensitive to both charybdotoxin and apamin and was generated by a channel with unitary conductance of approximately 25+/-2 pS. Blockade of this current also decreased osteoclast spreading and inhibited bone resorption in vitro, demonstrating a physiological role for this current in osteoclast activity. These results establish for the first time a temporal correlation between lamellipodia formation kinetics and spontaneous peaks of IK(Ca), which are both involved in the control of osteoclast spreading and bone resorption.

  5. NSAIDs modulate GABA-activated currents via Ca2+-activated Cl− channels in rat dorsal root ganglion neurons

    PubMed Central

    ZHAO, LEI; LI, LI; MA, KE-TAO; WANG, YANG; LI, JING; SHI, WEN-YAN; ZHU, HE; ZHANG, ZHONG-SHUANG; SI, JUN-QIANG

    2016-01-01

    The ability of non-steroidal anti-inflammatory drugs (NSAIDs) to modulate γ-aminobutyrate (GABA)-activated currents via Ca2+-activated Cl− channels in rat dorsal root ganglion neurons (DRG), was examined in the present study. During the preparation of DRG neurons harvested from Sprague-Dawley rats, the whole-cell recording technique was used to record the effect of NSAIDs on GABA-activated inward currents, and the expression levels of the TMEM16A and TMEM16B subunits were revealed. In the event that DRG neurons were pre-incubated for 20 sec with niflumic acid (NFA) and 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) prior to the administration of GABA, the GABA-induced inward currents were diminished markedly in the majority of neurons examined (96.3%). The inward currents induced by 100 µmol/l GABA were attenuated by (0±0.09%; neurons = 4), (5.32±3.51%; neurons = 6), (21.3±4.00%; neurons = 5), (33.8±5.20%; neurons = 17), (52.2±5.10%; neurons = 4) and (61.1±4.12%; neurons = 12) by 0.1, 1, 3, 10, 30 and 100 µmol/l NFA, respectively. The inward currents induced by 100 µmol/l GABA were attenuated by (13.8±6%; neurons = 6), (23.2±14.7%; neurons = 6) and (29.7±9.1%; neurons = 9) by 3, 10 and 30 µmol/l NPPB, respectively. NFA and NPPB dose-dependently inhibited GABA-activated currents with half maximal inhibitory concentration (IC50) values of 6.7 and 11 µmol/l, respectively. The inhibitory effect of 100 µmol/l NFA on the GABA-evoked inward current were also strongly inhibited by nitrendipine (NTDP; an L-type calcium channel blocker), 1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid tetrakis (a highly selective calcium chelating reagent), caffeine (a widely available Ca2+ consuming drug) and calcium-free extracellular fluid, in a concentration-dependent manner. Immunofluorescent staining indicated that TMEM16A and TMEM16B expression was widely distributed in DRG neurons. The results suggest that NSAIDs may be able to regulate Ca2

  6. Cesium blockade of delayed outward currents and electrically induced pacemaker activity in mammalian ventricular myocardium.

    PubMed

    Meier, C F; Katzung, B G

    1981-05-01

    The effects of Cs+, 5-25 mM, were studied in cat and guinea pig papillary muscles using voltage clamp and current clamp techniques. In solutions containing normal K+, the major effects of Cs+ were depolarization of the resting potential and reduction of the delayed outward current (ixl) between -80 and -20 mV. Both inward and outward portions of the isochronal current voltage relation (l-s clamps) were reduced by extracellular Cs+. This resulted in a substantial reduction of inward rectification and, by subtraction from the normal I-V relationship, the definition of a Cs+-sensitive component of current. Under current clamp conditions, 5-10 mM Cs+ produced a dose-dependent slowing of repetitive firing induced by depolarization. At higher concentrations (25 mM) the resting potential was depolarized and repetitive activity could not be induced by further depolarization. However, release of hyperpolarizing pulses was followed by prolonged bursts of repetitive action potentials, suggesting partial reversal of blockade or participation of another pacemaker process. The experimental results and a numerical simulation show that under readily attainable conditions, reduction in an outward pacemaker current may slow pacemaker activity.

  7. 78 FR 4175 - Agency Information Collection Activities: Renewal of Currently Approved Collection; Comment Request

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-18

    ... From the Federal Register Online via the Government Publishing Office RECOVERY ACCOUNTABILITY AND TRANSPARENCY BOARD Agency Information Collection Activities: Renewal of Currently Approved Collection; Comment Request Correction In notice document 2012-30952, appearing on page 76097, in the issue of...

  8. Video: Animals; Electric Current; Force; Science Activities. Learning in Science Project. Working Papers 51-54.

    ERIC Educational Resources Information Center

    Bell, Beverley; And Others

    Four papers to be used in conjunction with video-tapes developed by the Learning in Science Project are presented. Topic areas of the papers focus on: (1) animals; (2) electric current; (3) force; and (4) science activities. The first paper presents transcripts of class discussions focusing on the scientific meaning of the word animal. The second…

  9. 78 FR 12789 - Agency Information Collection Activities; Extension of a Currently Approved Collection: Office on...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-25

    ... Information Collection Activities; Extension of a Currently Approved Collection: Office on Violence Against Women Solicitation Template ACTION: 60-Day Notice. The Department of Justice, Office on Violence Against... Cathy Poston, Office on Violence Against Women, at 202-514-5430. Written comments and suggestions...

  10. 78 FR 14402 - Agency Information Collection Activities; Extension of a Currently Approved Collection: Driver...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-05

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  11. 76 FR 38207 - Agency Information Collection Activities: Extension of a Currently Approved Information Collection

    Federal Register 2010, 2011, 2012, 2013, 2014

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    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-19

    ... TRANSPARENCY BOARD Agency Information Collection Activities: Renewal of Currently Approved Collection; Comment.... SUMMARY: The Recovery Accountability and Transparency Board (Board) is giving public notice that it will... comments to Sharon Mar, Desk Officer for the Recovery Accountability and Transparency Board, Office...

  13. 78 FR 40522 - Agency Information Collection Activities: Renewal of Currently Approved Collection; Comment Request

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-05

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  14. 76 FR 37151 - Agency Information Collection Activities; Extension of Currently Approved Collection; Comments...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-24

    ... Information Collection Activities; Extension of Currently Approved Collection; Comments Requested; Semi-Annual Progress Report for the Grants to Indian Tribal Governments Program ACTION: 30-Day Notice of Information...-Annual Progress Report for Grants to Indian Tribal Governments Program. ] (3) Agency form number, if...

  15. 78 FR 66953 - Agency Information Collection Activities: Extension of a Currently Approved Collection; Annual...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-11-07

    ... Information Collection Activities: Extension of a Currently Approved Collection; Annual Progress Report for... approved collection. (2) Title of the Form/Collection: Annual Progress Report for the STOP Formula Grants...\\ to complete the relevant portion of the annual progress report. The Annual Progress Report for...

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    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-22

    ... Information Collection Activities: Extension of a Currently Approved Collection Semi-Annual Progress Report... Approved Collection. (2) Title of the Form/Collection: Semi-Annual Progress Report for Grantees from the... progress report. The semi-annual progress report is divided into sections that pertain to the...

  17. 77 FR 48540 - Agency Information Collection Activities: Extension of a Currently Approved Collection; Semi...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-08-14

    ... Information Collection Activities: Extension of a Currently Approved Collection; Semi-Annual Progress Report.../Collection: Semi-Annual Progress Report for Grantees from the Semi-Annual Progress Report for the Sexual... one hour to complete a semi-annual progress report. The semi-annual progress report is divided......

  18. Summary of Current and Future MSFC International Space Station Environmental Control and Life Support System Activities

    NASA Technical Reports Server (NTRS)

    Ray, Charles D.; Carrasquillo, Robyn L.; Minton-Summers, Silvia

    1997-01-01

    This paper provides a summary of current work accomplished under technical task agreement (TTA) by the Marshall Space Flight Center (MSFC) regarding the Environmental Control and Life Support System (ECLSS) as well as future planning activities in support of the International Space Station (ISS). Current activities include ECLSS computer model development, component design and development, subsystem integrated system testing, life testing, and government furnished equipment delivered to the ISS program. A long range plan for the MSFC ECLSS test facility is described whereby the current facility would be upgraded to support integrated station ECLSS operations. ECLSS technology development efforts proposed to be performed under the Advanced Engineering Technology Development (AETD) program are also discussed.

  19. Soil Moisture Active Passive (SMAP) Calibration and Validation Plan and Current Activities

    NASA Technical Reports Server (NTRS)

    Jackson, T. J.; Cosh, M.; Bindlish, R.; Crow, W.; Colliander, A.; Njoku, E.; McDonald, K.; Kimball, J.; Belair, S.; Walker, J.; Entekhabi, P.; O'Neill, P.

    2010-01-01

    The primary objective of the SMAP calibration and validation (Cal/Val) program is demonstrating that the science requirements (product accuracy and bias) have been met over the mission life. This begins during pre-launch with activities that contribute to high quality products and establishing post-launch validation infrastructure and continues through the mission life. However, the major focus is on a relatively short Cal/Val period following launch. The general approach and elements of the SMAP Cal/Val plan will be described and along with details on several ongoing or recent field experiments designed to address both near- and long-term Cal/Val.

  20. Application of active quenching of second generation wire for current limiting

    SciTech Connect

    Solovyov, Vyacheslav F.; Li, Qiang

    2015-10-19

    Superconducting fault current limiters (SFCL's) are increasingly implemented in the power grid as a protection of substation equipment from fault currents. Resistive SFCL's are compact and light, however they are passively triggered and thus may not be sufficiently sensitive to respond to faults in the distribution grid. Here, we explore the prospect of adding an active management feature to a traditional resistive SFCL. A flexible radio-frequency coil, which is an integral part of the switching structure, acts as a triggering device. We show that the application of a short, 10 ms, burst of ac magnetic field during the fault triggers a uniform quench of the wire and significantly reduces the reaction time of the wire at low currents. The ac field burst generates a high density of normal zones, which merge into a continuous resistive region at a rate much faster than that of sparse normal zones created by the transport current alone.

  1. Application of active quenching of second generation wire for current limiting

    DOE PAGES

    Solovyov, Vyacheslav F.; Li, Qiang

    2015-10-19

    Superconducting fault current limiters (SFCL's) are increasingly implemented in the power grid as a protection of substation equipment from fault currents. Resistive SFCL's are compact and light, however they are passively triggered and thus may not be sufficiently sensitive to respond to faults in the distribution grid. Here, we explore the prospect of adding an active management feature to a traditional resistive SFCL. A flexible radio-frequency coil, which is an integral part of the switching structure, acts as a triggering device. We show that the application of a short, 10 ms, burst of ac magnetic field during the fault triggersmore » a uniform quench of the wire and significantly reduces the reaction time of the wire at low currents. The ac field burst generates a high density of normal zones, which merge into a continuous resistive region at a rate much faster than that of sparse normal zones created by the transport current alone.« less

  2. Application of active quenching of second generation wire for current limiting

    NASA Astrophysics Data System (ADS)

    Solovyov, Vyacheslav F.; Li, Qiang

    2015-12-01

    Superconducting fault current limiters (SFCLs) are increasingly implemented in the power grid as a protection of substation equipment from fault currents. Resistive SFCLs are compact and light, however they are passively triggered and thus may not be sufficiently sensitive to respond to faults in the distribution grid. Here, we explore the prospect of adding an active management feature to a traditional resistive SFCL. A flexible radio-frequency coil, which is an integral part of the switching structure, acts as a triggering device. We show that the application of a short, 10 ms, burst of ac magnetic field during the fault triggers a uniform quench of the wire and significantly reduces the reaction time of the wire at low currents. The ac field burst generates a high density of normal zones, which merge into a continuous resistive region at a rate much faster than that of sparse normal zones created by the transport current alone.

  3. Inhibition of the hyperpolarization-activated current (if) of rabbit SA node myocytes by niflumic acid.

    PubMed

    Accili, E A; DiFrancesco, D

    1996-03-01

    The effects of the amphiphilic substance niflumic acid (NFA) were examined in myocytes isolated from the sino-atrial node of the rabbit heart. NFA (50 and 500 microM), for 30-60 s, produced a reversible negative chronotropic effect by reducing the rate of diastolic depolarization, suggesting an inhibitory effect on the hyperpolarization-activated pacemaker current (if). NFA (from 0.05 to 500 microM) inhibited if by modifying the current kinetics, without alteration of the conductance. This was shown by evidence indicating that: (1) NFA inhibited if during hyperpolarizing pulses to the mid-point of if activation but not at fully activating voltages; (2) the slope and reversal potential of the fully activated current/voltage (I/V) relation were not altered by NFA, indicating no change in slope conductance or ion selectivity; and (3) hyperpolarizing ramp protocols confirmed the lack of action of 50 microM NFA on the fully activated current and a shift of approximately -8 mV. Although similar to inhibition by acetylcholine (ACh), inhibition by NFA was only partly additive with the action of ACh and was not altered by atropine or pertussis toxin, both of which eliminated the action of ACh. The effect of NFA was present after stimulation of adenylate cyclase by forskolin and after inhibition of phosphodiesterase by isobutylmethylxanthine (IBMX). In cell-attached patch measurements, NFA applied externally did not affect if measured in the patch. Finally, application of NFA to the cytoplasmic side of excised patches did not alter the current in the absence or presence of adenosine 3',5'-cyclic monophosphate (cAMP). These results suggest an external, membrane-delimited action of NFA on if.

  4. Current Steering to Control the Volume of Tissue Activated During Deep Brain Stimulation

    PubMed Central

    Butson, Christopher R.; McIntyre, Cameron C.

    2009-01-01

    Background Over the last two decades, deep brain stimulation (DBS) has become a recognized and effective clinical therapy for numerous neurological conditions. Since its inception, clinical DBS technology has progressed at a relatively slow rate; however, advances in neural engineering research have the potential to improve DBS systems. One such advance is the concept of current steering, or the use of multiple stimulation sources to direct current flow through targeted regions of brain tissue. Objective The goals of this study were to develop a theoretical understanding of the effects of current steering in the context of DBS, and use that information to evaluate the potential utility of current steering during stimulation of the subthalamic nucleus. Methods We used finite element electric field models, coupled to multi-compartment cable axon models, to predict the volume of tissue activated (VTA) by DBS as a function of the stimulation parameter settings. Results Balancing current flow through adjacent cathodes increased the VTA magnitude, relative to monopolar stimulation, and current steering enabled us to sculpt the shape of the VTA to fit a given anatomical target. Conclusions These results provide motivation for the integration of current steering technology into clinical DBS systems, thereby expanding opportunities to customize DBS to individual patients, and potentially enhancing therapeutic efficacy. PMID:19142235

  5. Sodium-activated potassium channels are functionally coupled to persistent sodium currents.

    PubMed

    Hage, Travis A; Salkoff, Lawrence

    2012-02-22

    We report a novel coupled system of sodium-activated potassium currents (I(KNa)) and persistent sodium currents (I(NaP)), the components of which are widely distributed throughout the brain. Its existence and importance has not been previously recognized. Although I(KNa) was known to exist in many cell types, the source of Na(+) which activates I(KNa) remained a mystery. We now show in single membrane patches generated from the somas of rat neurons that sodium influx through I(NaP) is sufficient for activation of K(Na) channels, without substantial contribution from the transient sodium current or bulk [Na(+)](i). I(NaP) was found to be active at cell membrane resting potentials, a finding that may explain why I(KNa) can be evoked from negative holding potentials. These results show an unanticipated role for I(NaP) in activating a negative feedback system countering the excitable effects I(NaP); the interrelatedness of I(NaP) and I(KNa) suggests new ways neurons can tune their excitability.

  6. Current standards, variations, and pitfalls for the determination of constitutive TSHR activity in vitro.

    PubMed

    Mueller, Sandra; Jaeschke, Holger; Paschke, Ralf

    2010-01-01

    Constitutively activating mutations of the TSHR are the major cause for nonautoimmune hyperthyroidism, which is based on ligand independent, permanent receptor activation. Several reports have highlighted the difficulties to determine whether a TSHR mutation is constitutively active or not especially for borderline cases with only a slight increase of the basal cAMP activity. Current methods to precisely classify such mutants as constitutively active or not, are limited. In some cases, in vitro characterization of TSHR mutants has led to false positive conclusions regarding constitutive TSHR activity and subsequently the molecular origin of hyperthyroidism. For characterization of constitutive TSHR activity, a particular point to consider is that basal receptor activity tightly correlates with the receptor number expressed on the cell surface. Therefore, a comparison of the receptors basal activity in relation to the wild type is only possible with determination of the receptor cell surface expression. Thus, the experimental approaches to determine constitutive TSHR activity should consider the receptor's cell surface expression. We here provide a description of three methods for the determination of constitutive TSHR activity: (A) the evaluation of constitutive TSHR activity under conditions of equal receptor expression; (B) computation of the specific constitutive activity; and (C) the linear regression analysis (LRA). To date, LRA is the best experimental approach to characterize the mutant's basal activity as a function of TSHR cell surface expression. This approach utilizes a parallel measurement of basal cAMP values and receptor cell surface expression and therefore provides a more reliable decision with respect to the presence or absence of constitutive activity.

  7. Coronal Hole-Active Region-Current Sheet (CHARCS) Association with Intense Interplanetary and Geomagnetic Activity

    NASA Technical Reports Server (NTRS)

    Gonzalez, W. D.; Tsurutani, B. T.; McIntosh, P. S.; Gonzalez, A. L.

    1996-01-01

    Intense geomagnetic storms (Dstactive regions(flares and/or filament eruptions) ocurring close to the streamer belt and to growing low altitude coronal holes. It is also shown that such type of coronal holes had a dual-peak solar cycle distribution during solar cycle 21, similar to that previously reported for the above mentioned interplanetary and geomagnetic phenomena.

  8. Changes of extracellular potassium activity induced by electric current through brain tissue in the rat.

    PubMed Central

    Gardner-Medwin, A R; Nicholson, C

    1983-01-01

    Ion-selective micro-electrodes have been used to measure K+ and Ca2+ activity changes in extracellular space beneath the surface of the neocortex and cerebellar cortex during current flow across the tissue surface in anaesthetized rats. Inward currents produced decreases of [K+]o and outward currents produced increases, with insignificant changes in [Ca2+]o. Changes of [K+]o were largest just under the surface of the tissue, but were detectable down to depths of ca. 1 mm. With appropriate sitting of electrodes in the cerebellar cortex, currents of 22 microA mm-2 for 400 sec produced changes averaging -42% for inward current and +66% for outward current. The [K+]o changes near the surface were most rapid immediately after the onset of current and more gradual after some tens of seconds. Deeper within the tissue the rate of change was more uniform and after the end of stimulation the return to base line was slower. The amplitude, depth dependence and time course of the [K+]o changes were in reasonable agreement with the results calculated for a model in which K+ moves partly through extracellular space but primarily through membranes and cytoplasm within the tissue. The [K+]o changes were not attributable to variations in neuronal activity, although unit activity could be modified by current, since alternating currents failed to produce [K+]o changes and neither 0.1 mM-tetrodotoxin nor 5 mM-Mn2+ abolished the changes. The [K+]o changes were not abolished by topically applied ouabain (4 X 10(-4) M), 2,4-dinitrophenol (20 mM) or iodoacetate (10 mM), or by asphyxiation. Consequently the [K+]o changes are not dependent on metabolism. The data suggest that there is a selective mechanism for passive K+ transport in an electrochemical gradient within brain tissue that results in higher K+ fluxes than could be supported by ionic mobility in the extracellular fluid. This mechanism exists not only at the surface but within the brain parenchyma and may involve current flow

  9. Modulation by different GABAB receptor types of voltage-activated calcium currents in rat thalamocortical neurones.

    PubMed Central

    Guyon, A; Leresche, N

    1995-01-01

    1. The effects of the GABAB receptor agonist baclofen on the voltage-dependent Ca2+ currents were studied in rat thalamocortical neurones with the use of whole cell voltage-clamp recordings in brain slices. 2. The contribution of N-, L- and P-types of Ca2+ channels to the total high voltage-activated Ca2+ (HVA Ca2+) current was assessed by the use of omega-conotoxin, nifedipine and omega-agatoxin IVA, respectively. No P-type current could be detected. Thus, the HVA Ca2+ current contained an N- and an L-type current (23 and 15% of the total current, respectively) and a residual current, which will be referred to as the 'R' component. 3. Baclofen (1-50 microM) had no effect on the low voltage-activated (LVA) Ca2+ current (IT). 4. At low concentrations (0.5-10 microM), baclofen decreased the HVA Ca2+ currents by about 10-20% without a marked modification on the kinetics, whereas 50 microM baclofen decreased the HVA Ca2+ currents by about 40% with a pronounced slowing down of the kinetics. 5. The 10-20% decrease of the total HVA Ca2+ currents produced by the low concentrations of baclofen occurred as the result of a 30% block of the 'R' component. The additional decrease observed with the dose of 50 microM was due to a full block of the N-type current. The L-type was unaffected by baclofen. 6. The effect of baclofen on the total HVA Ca2+ current was partially blocked by GABAB receptor antagonists indicating that it occurred through stimulation of GABAB receptors. 7. The effect of baclofen on the N-type current was abolished by CGP 35348 (100 microM) and CGP 55845A (100 nM). The effect on the 'R' component was also antagonized by CGP 55845A (100 nM) although with a lower potency, but was not blocked by CGP 35348 (100 microM). 8. We conclude that the effects of baclofen on the various components of the HVA Ca2+ currents occur through different types of GABAB receptors. One receptor has a high affinity for baclofen (i.e. saturated by concentrations as low as 0.5 micro

  10. Hyperpolarization-Activated Current Induces Period-Doubling Cascades and Chaos in a Cold Thermoreceptor Model.

    PubMed

    Xu, Kesheng; Maidana, Jean P; Caviedes, Mauricio; Quero, Daniel; Aguirre, Pablo; Orio, Patricio

    2017-01-01

    In this article, we describe and analyze the chaotic behavior of a conductance-based neuronal bursting model. This is a model with a reduced number of variables, yet it retains biophysical plausibility. Inspired by the activity of cold thermoreceptors, the model contains a persistent Sodium current, a Calcium-activated Potassium current and a hyperpolarization-activated current (Ih) that drive a slow subthreshold oscillation. Driven by this oscillation, a fast subsystem (fast Sodium and Potassium currents) fires action potentials in a periodic fashion. Depending on the parameters, this model can generate a variety of firing patterns that includes bursting, regular tonic and polymodal firing. Here we show that the transitions between different firing patterns are often accompanied by a range of chaotic firing, as suggested by an irregular, non-periodic firing pattern. To confirm this, we measure the maximum Lyapunov exponent of the voltage trajectories, and the Lyapunov exponent and Lempel-Ziv's complexity of the ISI time series. The four-variable slow system (without spiking) also generates chaotic behavior, and bifurcation analysis shows that this is often originated by period doubling cascades. Either with or without spikes, chaos is no longer generated when the Ih is removed from the system. As the model is biologically plausible with biophysically meaningful parameters, we propose it as a useful tool to understand chaotic dynamics in neurons.

  11. cAMP-activated chloride currents in amphibian retinal pigment epithelial cells.

    PubMed Central

    Hughes, B A; Segawa, Y

    1993-01-01

    1. The effect of cAMP on whole-cell currents in isolated retinal pigment epithelial (RPE) cells of the bullfrog and marine toad was investigated by means of the perforated patch clamp technique. 2. Superfusing cells with either cAMP or forskolin led to the development of a time-independent current that had a linear current-voltage (I-V) relationship. The reversal potential of (Vrev) of the cAMP-activated current was unaffected by the removal of either Na+ or HCO3- from the external and internal solutions or by the addition of extracellular barium, but it was near the Cl- equilibrium potential (ECl) over a wide range of extracellular Cl- concentrations, suggesting the presence of a Cl(-)-selective channel. 3. The anion permeability sequence of the cAMP-activated conductance calculated from biionic reversal potentials was NO3- = I- > Br- > Cl- >> HCO3- > methanesulphonate. 4. The conductance was blocked by a variety of Cl- transport inhibitors, including 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS), 4,4'-dinitro-2,2'- stilbene disulphonic acid (DNDS), frusemide, N-phenylanthranilic acid (DPC) and niflumic acid. 5. The present study demonstrates that cAMP activates a Cl(-)-selective channel that most probably resides in the basolateral membrane. PMID:8410715

  12. Hyperpolarization-Activated Current Induces Period-Doubling Cascades and Chaos in a Cold Thermoreceptor Model

    PubMed Central

    Xu, Kesheng; Maidana, Jean P.; Caviedes, Mauricio; Quero, Daniel; Aguirre, Pablo; Orio, Patricio

    2017-01-01

    In this article, we describe and analyze the chaotic behavior of a conductance-based neuronal bursting model. This is a model with a reduced number of variables, yet it retains biophysical plausibility. Inspired by the activity of cold thermoreceptors, the model contains a persistent Sodium current, a Calcium-activated Potassium current and a hyperpolarization-activated current (Ih) that drive a slow subthreshold oscillation. Driven by this oscillation, a fast subsystem (fast Sodium and Potassium currents) fires action potentials in a periodic fashion. Depending on the parameters, this model can generate a variety of firing patterns that includes bursting, regular tonic and polymodal firing. Here we show that the transitions between different firing patterns are often accompanied by a range of chaotic firing, as suggested by an irregular, non-periodic firing pattern. To confirm this, we measure the maximum Lyapunov exponent of the voltage trajectories, and the Lyapunov exponent and Lempel-Ziv's complexity of the ISI time series. The four-variable slow system (without spiking) also generates chaotic behavior, and bifurcation analysis shows that this is often originated by period doubling cascades. Either with or without spikes, chaos is no longer generated when the Ih is removed from the system. As the model is biologically plausible with biophysically meaningful parameters, we propose it as a useful tool to understand chaotic dynamics in neurons. PMID:28344550

  13. Characteristics of chloride currents activated by noradrenaline in rabbit ear artery cells.

    PubMed

    Amédée, T; Large, W A; Wang, Q

    1990-09-01

    1. Responses to noradrenaline were studied in isolated rabbit ear artery cells with the nystatin method of whole-cell patch-clamp recording. With this technique it was possible to obtain reproducible responses to noradrenaline which was not possible with traditional whole-cell recording. 2. With NaCl as the major constituent of the bathing solution (potassium-free pipette and external solutions) the reversal potential (Er) of the noradrenaline-evoked current was about 0 mV. When external chloride was replaced by thiocyanate, iodide, nitrate and bromide, Er was shifted to more negative potentials which indicates that a chloride conductance increase contributes to the current activated by noradrenaline. 3. When sodium was substituted by Tris, N-methyl-D-glucamine, choline or barium, Er of the noradrenaline-evoked current did not alter. This result suggests that a cation conductance is not implicated in the response to noradrenaline recorded with the nystatin method of whole-cell recording. 4. The chloride current activated by noradrenaline was blocked by the selective alpha 1-adrenoceptor antagonist prazosin but was not affected by the alpha 2-adrenoceptor antagonist yohimbine. 5. When cells were exposed to zero calcium bathing solutions the amplitude of the current elicited by noradrenaline was unaffected when measured within 1-2 min in zero calcium conditions. Continued exposure to 0 Ca + 1 mM-EGTA solution reversibly abolished the chloride current to noradrenaline. 6. In the presence of caffeine, which releases Ca2+ from internal stores and itself induced an inward current (at a holding potential of -50 mV), noradrenaline did not elicit a current. These data suggest that the chloride current evoked by noradrenaline results from an increase in intracellular concentration of calcium derived from internal stores. 7. The chloride channel blocking agents 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS; 0.5 mM) and furosemide (0.5 mM) produced partial

  14. The Effect of Water on the Flow of Stress-Activated Electric Currents through Rocks

    NASA Astrophysics Data System (ADS)

    Jahoda, A. M.; Cyr, G. G.; Dahlgren, R.; Freund, F. T.

    2011-12-01

    When igneous or high-grade metamorphic rocks are subjected to deviatoric stresses, dormant defects in the matrix of common rock-forming minerals become activated. These defects consist of pairs of oxygen anions in the 1- valence state, e.g. peroxy links such as O3Si-OO-SiO3. When a peroxy bond breaks, O3Si-O:O-SiO3, an electron is transferred from a neighboring O2- causing the donor oxygen, now O-, to turn into a defect electron, also known as a positive hole, that can propagate as a highly mobile positive charge through the rocks1. The current outflow is driven by the battery potential that builds up during this process. The question is how this electric current through rocks is affected by water. When positive holes flow into bulk water, they oxidize H2O to H2O2 and are thereby consumed2. This electrochemical reaction is driven by the potential drop across the rock-water interface. However, no such potential drop occurs across water that fills pores inside the rocks along the path of the electronic charge carriers. We present evidence that the presence of water in the pore space does indeed not "kill" the current flow. This observation leads to the conclusion that stress-activated positive hole currents should be able to flow through water-saturated rocks maybe as well as, possibly even better than through dry rocks. 1 Freund, F. T., et al.: Electric currents streaming out of stressed igneous rocks - A step towards understanding pre-earthquake low frequency EM emissions, Phys. Chem. Earth, 2006, 31, 389-396. 2 Balk, M., et al.: Oxidation of water to hydrogen peroxide at the rock-water interface due to stress-activated electric currents in rocks, Earth Planet. Sci. Lett. 2009, 283, 87-92

  15. The morphology of flare phenomena, magnetic fields, and electric currents in active regions. II - NOAA active region 5747 (1989 October)

    NASA Technical Reports Server (NTRS)

    Leka, K. D.; Canfield, Richard C.; Mcclymont, A. N.; De La Beaujardiere, J.-F.; Fan, Yuhong; Tang, F.

    1993-01-01

    The paper describes October 1989 observations in NOAA Active Region 5747 of the morphology of energetic electron precipitation and high-pressure coronal flare plasmas of three flares and their relation to the vector magnetic field and vertical electric currents. The H-alpha spectroheliograms were coaligned with the vector magnetograms using continuum images of sunspots, enabling positional accuracy of a few arcsec. It was found that, during the gradual phase, the regions of the H-alpha flare that show the effects of enhanced pressure in the overlying corona often encompass extrema of the vertical current density, consistent with earlier work showing a close relationship between H-alpha emission and line-of-sight currents. The data are also consistent with the overall morphology and evolution described by erupting-filament models such as those of Kopp and Pneuman (1976) and Sturrock (1989).

  16. Preface: Special Session SpS7 The impact hazard: current activities and future plans

    NASA Astrophysics Data System (ADS)

    Montmerle, Thierry

    2015-03-01

    In 2012, at the time of the Beijing GA, two decades had passed since the publication of the Spaceguard Report. Time has not passed in vain for the subject of NEO-related hazards, and we are currently in a totally different situation than in the early nineties. The amount of work done, and the level of awareness of the underlying problems, have both risen to such a level that a re-assessment by the astronomical community of its rôle and involvement was in order, and the GA Special Session 7 ``The impact hazard: current activities and future plans'' was aimed exactly at that.

  17. A Metabolic Biofuel Cell: Conversion of Human Leukocyte Metabolic Activity to Electrical Currents

    PubMed Central

    2011-01-01

    An investigation of the electrochemical activity of human white blood cells (WBC) for biofuel cell (BFC) applications is described. WBCs isolated from whole human blood were suspended in PBS and introduced into the anode compartment of a proton exchange membrane (PEM) fuel cell. The cathode compartment contained a 50 mM potassium ferricyanide solution. Average current densities between 0.9 and 1.6 μA cm-2 and open circuit potentials (Voc) between 83 and 102 mV were obtained, which were both higher than control values. Cyclic voltammetry was used to investigate the electrochemical activity of the activated WBCs in an attempt to elucidate the mechanism of electron transfer between the cells and electrode. Voltammograms were obtained for the WBCs, including peripheral blood mononuclear cells (PBMCs - a lymphocyte-monocyte mixture isolated on a Ficoll gradient), a B lymphoblastoid cell line (BLCL), and two leukemia cell lines, namely K562 and Jurkat. An oxidation peak at about 363 mV vs. SCE for the PMA (phorbol ester) activated primary cells, with a notable absence of a reduction peak was observed. Oxidation peaks were not observed for the BLCL, K562 or Jurkat cell lines. HPLC confirmed the release of serotonin (5-HT) from the PMA activated primary cells. It is believed that serotonin, among other biochemical species released by the activated cells, contributes to the observed BFC currents. PMID:21569243

  18. Volunteering and overseas placements in the NHS: a survey of current activity

    PubMed Central

    Chatwin, John; Ackers, Louise

    2016-01-01

    Objective The study aimed to establish current levels of overseas volunteering and placement activity across all staff grades within the National Health Service (NHS) in the North West of England. Design Cross-sectional survey. Instrument Descriptive statistics. Setting 4 main regional hospitals in the North West of England, and additional NHS staff training events. Participants Convenience sample of NHS staff (n=911). Results 911 NHS staff took part in the survey. The medical and dental staff group returned the highest number of responses (32.1%). 42% of staff reported some form of overseas volunteering or placement experience. Most staff took an international placement as students (33.6% men; 40.6% women). Medium-term placements were undertaken by 46.7% of men, and 52.5% of women. Settlement stays (ie, over 1 year) were reported by 7.6% men, and 8.3% women). The majority of respondents engaged in international placement were from the age groups incorporating ‘below 25’ to ‘41–50’ (74%). Multiple placement experiences were uncommon: 2.5% of respondents reported three periods of overseas activity, and 1.5% reported four. All those with multiple placement experience came from the staff groups incorporating midwife/nurse/health visitor, and medical and dental. Conclusions This survey captured a snapshot of current levels of volunteering and overseas placement activity across NHS staff grades in the North West. Owing to relatively homogenous organisational structures, findings are likely to broadly represent the position across the organisation as a whole. Although some degree of overseas placement activity is undertaken by a relatively high proportion of NHS staff, such activity is currently heavily skewed towards higher clinical staff grades. Significant numbers of allied health professionals and equivalent non-clinical cadres also report overseas experience, and we anticipate that the numbers will continue to rise if current policy initiatives gain

  19. Current limitations and recommendations to improve testing for the environmental assessment of endocrine active substances.

    PubMed

    Coady, Katherine K; Biever, Ronald C; Denslow, Nancy D; Gross, Melanie; Guiney, Patrick D; Holbech, Henrik; Karouna-Renier, Natalie K; Katsiadaki, Ioanna; Krueger, Hank; Levine, Steven L; Maack, Gerd; Williams, Mike; Wolf, Jeffrey C; Ankley, Gerald T

    2017-03-01

    In the present study, existing regulatory frameworks and test systems for assessing potential endocrine active chemicals are described, and associated challenges are discussed, along with proposed approaches to address these challenges. Regulatory frameworks vary somewhat across geographies, but all basically evaluate whether a chemical possesses endocrine activity and whether this activity can result in adverse outcomes either to humans or to the environment. Current test systems include in silico, in vitro, and in vivo techniques focused on detecting potential endocrine activity, and in vivo tests that collect apical data to detect possible adverse effects. These test systems are currently designed to robustly assess endocrine activity and/or adverse effects in the estrogen, androgen, and thyroid hormone signaling pathways; however, there are some limitations of current test systems for evaluating endocrine hazard and risk. These limitations include a lack of certainty regarding: 1) adequately sensitive species and life stages; 2) mechanistic endpoints that are diagnostic for endocrine pathways of concern; and 3) the linkage between mechanistic responses and apical, adverse outcomes. Furthermore, some existing test methods are resource intensive with regard to time, cost, and use of animals. However, based on recent experiences, there are opportunities to improve approaches to and guidance for existing test methods and to reduce uncertainty. For example, in vitro high-throughput screening could be used to prioritize chemicals for testing and provide insights as to the most appropriate assays for characterizing hazard and risk. Other recommendations include adding endpoints for elucidating connections between mechanistic effects and adverse outcomes, identifying potentially sensitive taxa for which test methods currently do not exist, and addressing key endocrine pathways of possible concern in addition to those associated with estrogen, androgen, and thyroid

  20. A self-sensing active magnetic bearing based on a direct current measurement approach.

    PubMed

    Niemann, Andries C; van Schoor, George; du Rand, Carel P

    2013-09-11

    Active magnetic bearings (AMBs) have become a key technology in various industrial applications. Self-sensing AMBs provide an integrated sensorless solution for position estimation, consolidating the sensing and actuating functions into a single electromagnetic transducer. The approach aims to reduce possible hardware failure points, production costs, and system complexity. Despite these advantages, self-sensing methods must address various technical challenges to maximize the performance thereof. This paper presents the direct current measurement (DCM) approach for self-sensing AMBs, denoting the direct measurement of the current ripple component. In AMB systems, switching power amplifiers (PAs) modulate the rotor position information onto the current waveform. Demodulation self-sensing techniques then use bandpass and lowpass filters to estimate the rotor position from the voltage and current signals. However, the additional phase-shift introduced by these filters results in lower stability margins. The DCM approach utilizes a novel PA switching method that directly measures the current ripple to obtain duty-cycle invariant position estimates. Demodulation filters are largely excluded to minimize additional phase-shift in the position estimates. Basic functionality and performance of the proposed self-sensing approach are demonstrated via a transient simulation model as well as a high current (10 A) experimental system. A digital implementation of amplitude modulation self-sensing serves as a comparative estimator.

  1. Alpha-2 noradrenergic receptor activation inhibits the hyperpolarization-activated cation current (Ih ) in neurons of the ventral tegmental area

    PubMed Central

    Inyushin, Mikhail U.; Arencibia-Albite, Francisco; Vázquez-Torres, Rafael; Vélez-Hernández, María E.; Jiménez-Rivera, Carlos A.

    2010-01-01

    The ventral tegmental area (VTA) is the source of dopaminergic projections innervating cortical structures and ventral forebrain. Dysfunction of this mesocorticolimbic system is critically involved in psychiatric disorders such as addiction and schizophrenia. Changes in VTA dopamine (DA) neuronal activity can alter neurotransmitter release at target regions which modify information processing in the reward circuit. Here we studied the effect of α-2 noradrenergic receptor activation on the hyperpolarization-activated cation current (Ih ) in DA neurons of the rat VTA. Brain slice preparations using whole-cell current and voltage-clamp techniques were employed. Clonidine and UK14304 (α-2 receptor selective agonists) were found to decrease Ih amplitude and to slow its rate of activation indicating a negative shift in the current’s voltage dependence. Two non-subtype-selective α-2 receptor antagonists, yohimbine and RS79948, prevented the effects of α-2 receptor activation. RX821002, a noradrenergic antagonist specific for α-2A and α-2D did not prevent Ih inhibition. This result suggests that clonidine might be acting via an α-2C subtype since this receptor is the most abundant variant in the VTA. Analysis of a second messenger system associated with the α-2 receptor revealed that Ih inhibition is independent of cyclic adenosine monophosphate (cAMP) and resulted from the activation of protein kinase C. It is suggested that the α-2 mediated hyperpolarizing shift in Ih voltage dependence can facilitate the transition from pacemaker firing to afferent-driven burst activity. This transition may play a key role on the changes in synaptic plasticity that occurs in the mesocorticolimbic system under pathological conditions. PMID:20122999

  2. Quantum-classical transition and quantum activation of ratchet currents in the parameter space.

    PubMed

    Beims, M W; Schlesinger, M; Manchein, C; Celestino, A; Pernice, A; Strunz, W T

    2015-05-01

    The quantum ratchet current is studied in the parameter space of the dissipative kicked rotor model coupled to a zero-temperature quantum environment. We show that vacuum fluctuations blur the generic isoperiodic stable structures found in the classical case. Such structures tend to survive when a measure of statistical dependence between the quantum and classical currents are displayed in the parameter space. In addition, we show that quantum fluctuations can be used to overcome transport barriers in the phase space. Related quantum ratchet current activation regions are spotted in the parameter space. Results are discussed based on quantum, semiclassical, and classical calculations. While the semiclassical dynamics involves vacuum fluctuations, the classical map is driven by thermal noise.

  3. Modulation of membrane currents and mechanical activity by niflumic acid in rat vascular smooth muscle.

    PubMed

    Kirkup, A J; Edwards, G; Green, M E; Miller, M; Walker, S D; Weston, A H

    1996-12-12

    The effects of niflumic acid on whole-cell membrane currents and mechanical activity were examined in the rat portal vein. In freshly dispersed portal vein cells clamped at -60 mV in caesium (Cs+)-containing solutions, niflumic acid (1-100 microM) inhibited calcium (Ca2+)-activated chloride currents (IC1(Ca)) induced by caffeine (10 mM) and by noradrenaline (10 microM). In a potassium (K+)-containing solution and at a holding potential of - 10 mV, niflumic acid (10-100 microM) induced an outward K+ current (IK(ATP)) which was sensitive to glibenclamide (10-30 microM). At concentrations < 30 microM and at a holding potential of -2 mV, niflumic acid had no effect on the magnitude of the caffeine- or noradrenaline-stimulated current (IBK(Ca)) carried by the large conductance, Ca(2+)-sensitive K+ channel (BKCa). However, at a concentration of 100 microM, niflumic acid significantly inhibited IBK(Ca)) evoked by caffeine (10 mM) but not by NS1619 (1-(2'-hydroxy-5'-trifluoromethylphenyl)-5-trifluoromethyl-2(3 H) benzimidazolone; 20 microM). In Cs(+)-containing solutions, niflumic acid (10-100 microM) did not inhibit voltage-sensitive Ca2+ currents. In intact portal veins, niflumic acid (1-300 microM) inhibited spontaneous mechanical activity, an action which was partially antagonised by glibenclamide (1-10 microM), and contractions produced by noradrenaline (10 microM), an effect which was glibenclamide-insensitive. It is concluded that inhibition of ICl(Ca) and stimulation of IK(ATP) both contribute to the mechano-inhibitory actions of niflumic acid in the rat portal vein.

  4. Active to sterile neutrino mixing limits from neutral-current interactions in MINOS.

    PubMed

    Adamson, P; Auty, D J; Ayres, D S; Backhouse, C; Barr, G; Bishai, M; Blake, A; Bock, G J; Boehnlein, D J; Bogert, D; Cavanaugh, S; Cherdack, D; Childress, S; Coelho, J A B; Coleman, S J; Corwin, L; Cronin-Hennessy, D; Danko, I Z; de Jong, J K; Devenish, N E; Diwan, M V; Dorman, M; Escobar, C O; Evans, J J; Falk, E; Feldman, G J; Frohne, M V; Gallagher, H R; Gomes, R A; Goodman, M C; Gouffon, P; Graf, N; Gran, R; Grant, N; Grzelak, K; Habig, A; Harris, D; Hartnell, J; Hatcher, R; Himmel, A; Holin, A; Huang, X; Hylen, J; Ilic, J; Irwin, G M; Isvan, Z; Jaffe, D E; James, C; Jensen, D; Kafka, T; Kasahara, S M S; Koizumi, G; Kopp, S; Kordosky, M; Kreymer, A; Lang, K; Lefeuvre, G; Ling, J; Litchfield, P J; Loiacono, L; Lucas, P; Mann, W A; Marshak, M L; Mayer, N; McGowan, A M; Mehdiyev, R; Meier, J R; Messier, M D; Miller, W H; Mishra, S R; Mitchell, J; Moore, C D; Morfín, J; Mualem, L; Mufson, S; Musser, J; Naples, D; Nelson, J K; Newman, H B; Nichol, R J; Nicholls, T C; Nowak, J A; Oliver, W P; Orchanian, M; Paley, J; Patterson, R B; Pawloski, G; Pearce, G F; Petyt, D A; Phan-Budd, S; Pittam, R; Plunkett, R K; Qiu, X; Ratchford, J; Raufer, T M; Rebel, B; Rodrigues, P A; Rosenfeld, C; Rubin, H A; Sanchez, M C; Schneps, J; Schreiner, P; Sharma, R; Shanahan, P; Sousa, A; Stamoulis, P; Strait, M; Tagg, N; Talaga, R L; Tetteh-Lartey, E; Thomas, J; Thomson, M A; Tinti, G; Toner, R; Torretta, D; Tzanakos, G; Urheim, J; Vahle, P; Viren, B; Walding, J J; Weber, A; Webb, R C; White, C; Whitehead, L; Wojcicki, S G; Zwaska, R

    2011-07-01

    Results are reported from a search for active to sterile neutrino oscillations in the MINOS long-baseline experiment, based on the observation of neutral-current neutrino interactions, from an exposure to the NuMI neutrino beam of 7.07×10(20) protons on target. A total of 802 neutral-current event candidates is observed in the Far Detector, compared to an expected number of 754 ± 28(stat) ± 37(syst) for oscillations among three active flavors. The fraction f(s) of disappearing ν(μ) that may transition to ν(s) is found to be less than 22% at the 90% C.L.

  5. Activation of protein kinase C inhibits potassium currents in cultured endothelial cells.

    PubMed

    Zhang, H; Weir, B; Daniel, E E

    1995-04-01

    The effect of protein kinase C on potassium channels in cultured endothelial cells was investigated by using whole-cell patch-clamp techniques. Activation of protein kinase C by phorbol 12-myristate 13-acetate (PMA) and phorbol 12,13-dibutyrate (PDBu), but not phorbol 12-monomyristate (PMM), an inactive analogue of phorbol esters, depressed an outward calcium-dependent potassium current. The inhibitory actions of PMA and PDBu could be reversed by the kinase inhibitor H-7. Cyclopiazonic acid, an inhibitor of the sarcoplasmic reticulum calcium pump, and LP-805, a novel vasodilator which also releases endothelium-derived relaxing factors, activated the outward calcium-dependent potassium conductance. PMA and PDBu, but not PMM, reduced the outward conductance induced by cyclopiazonic acid and LP-805. These effects of PMA and PDBu on potassium currents may be mediated either by phosphorylation of ion channels, or by decreasing intracellular calcium concentration.

  6. Phorbol ester activation of chloride current in guinea-pig ventricular myocytes.

    PubMed Central

    Shuba, L. M.; Asai, T.; McDonald, T. F.

    1996-01-01

    1. Although earlier studies with phorbol esters indicate that protein kinase C (PKC) may be an important regulator of Cl- current (Icl) in cardiac cells, there is a need for additional quantitative data and investigation of conflicting findings. Our objectives were to measure the magnitude, time course, and concentration-dependence of Icl activated in guinea-pig ventricular myocytes by phorbol 12-myristate 13-acetate (PMA), evaluate its PKC dependence, and examine its modification by external and internal ions. 2. The whole-cell patch clamp technique was used to apply short depolarizing and hyperpolarizing pulses to myocytes superfused with Na(+)-, K(+)-, Ca(2+)-free solution (36 degrees C) and dialysed with Cs+ solution. Stimulation of membrane currents by PMA (threshold < or = 1nM, EC50 approximately equal to 14 nM, maximal 40% increase with > or = 100 nM) plateaued within 6-10 min. 3. PMA-activated current was time-independent, and suppressed by l mM 9-anthracenecarboxylic acid (9-AC). Its reversal potential (Erev) was sensitive to changes in the Cl- gradient, and outward rectification of the current-voltage (I-V) relationship was more pronounced with 30 mM than 140 mM Cl- dialysate. 4. The relative permeability of PMA-activated channels estimated from Erev measurements was I- > Cl- > > aspartate. Channel activation was independent of external Na+. 5. PMA failed to activate Icl in myocytes pretreated with 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7) or dialysed with pCa 10.5 solution. Lack of response to 4 alpha-phorbol 12, 13-didecanoate (alpha PDD) was a further indication of mediation by PKC. 6. Icl induced by 2 microM forskolin was far larger than that induced by PMA, suggesting that endogenous protein kinase A is a much stronger Cl- channel activator than endogenous PKC in these myocytes. 7. The macroscopic properties of PMA-induced Icl appear to be indistinguishable from those of PKA-activated Icl. We discount stimulation of PKA by PMA as an

  7. Effect of Direct-Current Electric Field on Enzymatic Activity and the Concentration of Laccase.

    PubMed

    Wang, Chunxing; Zhang, Huiling; Ren, Dajun; Li, Qian; Zhang, Shuqin; Feng, Tao

    2015-09-01

    This work investigates the effect of direct-current electric field on the extracellular enzymatic activity, concentration and other experimental parameters of laccase from Trametes versicolor. The results showed that laccase could significantly contribute to the change of pH at the end of graphite electrode. In addition, it increased the electrical conductivity of the water. In the experiment, the optimum pH and catalytic pH range for laccase activity were 3.0 and pH 2.5-4.0. The application of 6 V direct current showed significant effects on the laccase enzyme activity. The activity of laccase was enhanced in the anodic region, but at the same time was strongly inhibited at the cathode. The electric charge characteristics of laccase were changed when exposed to electric field, and some laccases molecules moved to the anode, which produced a slight migration phenomenon. This study is the basis of combination of laccase and electrical technology, at the same time, providing a new direction of enhancing laccase activity. Compared to immobilization, using electric field is simple, no chemical additives, and great potential.

  8. Atmospheric input of inorganic nitrogen to Delaware Bay

    SciTech Connect

    Scudlark, J.R.; Church, T.M. )

    1993-12-01

    The coastal waters of the mid-Atlantic region of the United States receive inputs of atmospheric pollutants as a consequence of being located downwind from major industrial and urban emission. These inputs are potentially the largest received by any marine area of the country. Of current interest is the atmospheric input of dissolved inorganic nitrogen (DIN = NO[sub 3][sup [minus

  9. Control of spontaneous firing patterns by the selective coupling of calcium currents to calcium-activated potassium currents in striatal cholinergic interneurons.

    PubMed

    Goldberg, Joshua A; Wilson, Charles J

    2005-11-02

    The spontaneous firing patterns of striatal cholinergic interneurons are sculpted by potassium currents that give rise to prominent afterhyperpolarizations (AHPs). Large-conductance calcium-activated potassium (BK) channel currents contribute to action potential (AP) repolarization; small-conductance calcium-activated potassium channel currents generate an apamin-sensitive medium AHP (mAHP) after each AP; and bursts of APs generate long-lasting slow AHPs (sAHPs) attributable to apamin-insensitive currents. Because all these currents are calcium dependent, we conducted voltage- and current-clamp whole-cell recordings while pharmacologically manipulating calcium channels of the plasma membrane and intracellular stores to determine what sources of calcium activate the currents underlying AP repolarization and the AHPs. The Cav2.2 (N-type) blocker omega-conotoxin GVIA (1 microM) was the only blocker that significantly reduced the mAHP, and it induced a transition to rhythmic bursting in one-third of the cells tested. Cav1 (L-type) blockers (10 microM dihydropyridines) were the only ones that significantly reduced the sAHP. When applied to cells induced to burst with apamin, dihydropyridines reduced the sAHPs and abolished bursting. Depletion of intracellular stores with 10 mM caffeine also significantly reduced the sAHP current and reversibly regularized firing. Application of 1 microM omega-conotoxin MVIIC (a Cav2.1/2.2 blocker) broadened APs but had a negligible effect on APs in cells in which BK channels were already blocked by submillimolar tetraethylammonium chloride, indicating that Cav2.1 (Q-type) channels provide the calcium to activate BK channels that repolarize the AP. Thus, calcium currents are selectively coupled to the calcium-dependent potassium currents underlying the AHPs, thereby creating mechanisms for control of the spontaneous firing patterns of these neurons.

  10. Polarographic study of hydrogen peroxide anodic current and its application to antioxidant activity determination.

    PubMed

    Sužnjević, Desanka Ž; Pastor, Ferenc T; Gorjanović, Stanislava Ž

    2011-09-15

    Behavior of hydrogen peroxide in alkaline medium has been studied by direct current (DC) polarography with dropping mercury electrode (DME) aiming to apply it in antioxidant (AO) activity determination. Development of a peroxide anodic current having form of a peak, instead of common polarographic wave, has been investigated. As a base for this investigation the interaction of H(2)O(2) with anodically dissolved mercury was followed. Formation of mercury complex [Hg(O(2)H)(OH)] has been confirmed. The relevant experimental conditions, such as temperature, concentration and pH dependence, as well as time stability of hydrogen peroxide anodic current, have been assessed. Development of an AO assay based on decrease of anodic current of hydrogen peroxide in the presence of antioxidants (AOs) has been described. Under optimized working conditions, a series of benzoic acids along with corresponding cinnamate analogues have been tested for hydrogen peroxide scavenging activity. In addition, the assay versatility has been confirmed on various complex samples.

  11. A Mathematical Model of Neonatal Rat Atrial Monolayers with Constitutively Active Acetylcholine-Mediated K+ Current

    PubMed Central

    Majumder, Rupamanjari; Jangsangthong, Wanchana; Feola, Iolanda; Ypey, Dirk L.; Pijnappels, Daniël A.; Panfilov, Alexander V.

    2016-01-01

    Atrial fibrillation (AF) is the most frequent form of arrhythmia occurring in the industrialized world. Because of its complex nature, each identified form of AF requires specialized treatment. Thus, an in-depth understanding of the bases of these arrhythmias is essential for therapeutic development. A variety of experimental studies aimed at understanding the mechanisms of AF are performed using primary cultures of neonatal rat atrial cardiomyocytes (NRAMs). Previously, we have shown that the distinct advantage of NRAM cultures is that they allow standardized, systematic, robust re-entry induction in the presence of a constitutively-active acetylcholine-mediated K+ current (IKACh-c). Experimental studies dedicated to mechanistic explorations of AF, using these cultures, often use computer models for detailed electrophysiological investigations. However, currently, no mathematical model for NRAMs is available. Therefore, in the present study we propose the first model for the action potential (AP) of a NRAM with constitutively-active acetylcholine-mediated K+ current (IKACh-c). The descriptions of the ionic currents were based on patch-clamp data obtained from neonatal rats. Our monolayer model closely mimics the action potential duration (APD) restitution and conduction velocity (CV) restitution curves presented in our previous in vitro studies. In addition, the model reproduces the experimentally observed dynamics of spiral wave rotation, in the absence and in the presence of drug interventions, and in the presence of localized myofibroblast heterogeneities. PMID:27332890

  12. Photospheric electric current and transition region brightness within an active region

    NASA Technical Reports Server (NTRS)

    Deloach, A. C.; Hagyard, M. J.; Rabin, D.; Moore, R. L.; Smith, B. J., Jr.; West, E. A.; Tandberg-Hanssen, E.

    1984-01-01

    Distributions of vertical electrical current density J(z) calculated from vector measurements of the photospheric magnetic field are compared with ultraviolet spectroheliograms to investigate whether resistive heating is an important source of enhanced emission in the transition region. The photospheric magnetic fields in Active Region 2372 were measured on April 6 and 7, 1980 with the Marshall Space Flight Center vector magnetograph; ultraviolet wavelength spectroheliograms (L-alpha and N V 1239 A) were obtained with the UV Spectrometer and Polarimeter experiment aboard the Solar Maximum Mission satellite. Spatial registration of the J(z) (5 arcsec resolution) and UV (3 arcsec resolution) maps indicates that the maximum current density is cospatial with a minor but persistent UV enhancement, but there is little detected current associated with other nearby bright areas. It is concluded that, although resistive heating may be important in the transition region, the currents responsible for the heating are largely unresolved in the present measurements and have no simple correlation with the residual current measured on 5-arcsec scales.

  13. Predictive current control of permanent magnet synchronous motor based on linear active disturbance rejection control

    NASA Astrophysics Data System (ADS)

    Li, Kunpeng

    2017-01-01

    The compatibility problem between rapidity and overshooting in the traditional predictive current control structure is inevitable and difficult to solve by reason of using PI controller. A novel predictive current control (PCC) algorithm for permanent magnet synchronous motor (PMSM) based on linear active disturbance rejection control (LADRC) is presented in this paper. In order to displace PI controller, the LADRC strategy which consisted of linear state error feedback (LSEF) control algorithm and linear extended state observer (LESO), is designed based on the mathematic model of PMSM. The purpose of LSEF is to make sure fast response to load mutation and system uncertainties, and LESO is designed to estimate the uncertain disturbances. The principal structures of the proposed system are speed outer loop based on LADRC and current inner loop based on predictive current control. Especially, the instruction value of qaxis current in inner loop is derived from the control quantity which is designed in speed outer loop. The simulation is carried out in Matlab/Simulink software, and the results illustrate that the dynamic and static performances of proposed system are satisfied. Moreover the robust against model parameters mismatch is enhanced obviously.

  14. Lasting modulation of in vitro oscillatory activity with weak direct current stimulation

    PubMed Central

    Bikson, Marom; Parra, Lucas C.

    2014-01-01

    Transcranial direct current stimulation (tDCS) is emerging as a versatile tool to affect brain function. While the acute neurophysiological effects of stimulation are well understood, little is know about the long-term effects. One hypothesis is that stimulation modulates ongoing neural activity, which then translates into lasting effects via physiological plasticity. Here we used carbachol-induced gamma oscillations in hippocampal rat slices to establish whether prolonged constant current stimulation has a lasting effect on endogenous neural activity. During 10 min of stimulation, the power and frequency of gamma oscillations, as well as multiunit activity, were modulated in a polarity specific manner. Remarkably, the effects on power and multiunit activity persisted for more than 10 min after stimulation terminated. Using a computational model we propose that altered synaptic efficacy in excitatory and inhibitory pathways could be the source of these lasting effects. Future experimental studies using this novel in vitro preparation may be able to confirm or refute the proposed hypothesis. PMID:25505103

  15. A-Type potassium currents active at subthreshold potentials in mouse cerebellar purkinje cells

    PubMed Central

    Sacco, Tiziana; Tempia, Filippo

    2002-01-01

    Voltage-dependent and calcium-independent K+ currents were whole-cell recorded from cerebellar Purkinje cells in slices. Tetraethylammonium (TEA, 4 mm) application isolated an A-type K+ current (Ik(a)) with a peak amplitude, at +20 mV, of about one third of the total voltage-dependent and calcium-independent K+ current. The Ik(a) activated at about −60 mV, had a V0.5 of activation of −24.9 mV and a V0.5 of inactivation of −69.2 mV. The deactivation time constant at −70 mV was 3.4 ± 0.4 ms, while the activation time constant at +20 mV was 0.9 ± 0.2 ms. The inactivation kinetics was weakly voltage dependent, with two time constants; those at +20 mV were 19.3 ± 3.1 and 97.6 ± 9.8 ms. The recovery from inactivation had two time constants of 60.8 ms (78.4%) and 962.3 ms (21.6%). The Ik(a) was blocked by 4-aminopyridine with an IC50 of 67.6 μM. Agitoxin-2 (2 nm) blocked 17.4 ± 2.1% of the Ik(a). Flecainide completely blocked the Ik(a) with a biphasic effect with IC50 values of 4.4 and 183.2 μM. In current-clamp recordings the duration of evoked action potentials was affected neither by agitoxin-2 (2 nm) nor by flecainide (3 μM), but action potentials that were already broadened by TEA were further prolonged by 4-aminopyridine (100 μM). The amplitude of the hyperpolarisation at the end of depolarising steps was reduced by all these blockers. PMID:12205185

  16. Activation of ganglion cells in wild-type and rd1 mouse retinas with monophasic and biphasic current pulses

    NASA Astrophysics Data System (ADS)

    Jensen, Ralph J.; Rizzo, Joseph F. III

    2009-06-01

    We and other research groups are designing an electronic retinal prosthesis to provide vision for patients who are blind due to photoreceptor degeneration. In this study, we examined the effect of stimulus waveform on the amount of current needed to activate retinal ganglion cells (RGCs) when the retinal neural network is stimulated. Isolated retinas of wild-type and rd1 mice were stimulated with cathodal and anodal monophasic current pulses of 1 ms duration and symmetric biphasic current pulses (1 ms per phase) delivered through an electrode that was located subretinally. For both wild-type and rd1 mouse retinas, cathodal current pulses were least effective in activating most RGCs. The median threshold current for a cathodal current pulse was 2.0-4.4 fold higher than the median threshold current for either an anodal or a biphasic current pulse. In wild-type mouse retinas, the median threshold current for activating RGCs with anodal current pulses was 23% lower than that with biphasic current pulses. In rd1 mouse retinas, the median threshold currents for anodal and biphasic current pulses were about the same. However, the variance in thresholds of rd1 RGCs for biphasic pulse stimulation was much smaller than for anodal pulse stimulation. Thus, a symmetric biphasic current pulse may be the best stimulus for activating the greatest number of RGCs in retinas devoid of photoreceptors.

  17. TRPA1 contributes to specific mechanically activated currents and sensory neuron mechanical hypersensitivity.

    PubMed

    Brierley, Stuart M; Castro, Joel; Harrington, Andrea M; Hughes, Patrick A; Page, Amanda J; Rychkov, Grigori Y; Blackshaw, L Ashley

    2011-07-15

    The mechanosensory role of TRPA1 and its contribution to mechanical hypersensitivity in sensory neurons remains enigmatic. We elucidated this role by recording mechanically activated currents in conjunction with TRPA1 over- and under-expression and selective pharmacology. First, we established that TRPA1 transcript, protein and functional expression are more abundant in smaller-diameter neurons than larger-diameter neurons, allowing comparison of two different neuronal populations. Utilising whole cell patch clamping, we applied calibrated displacements to neurites of dorsal root ganglion (DRG) neurons in short-term culture and recorded mechanically activated currents termed intermediately (IAMCs), rapidly (RAMCs) or slowly adapting (SAMCs). Trpa1 deletion (–/–) significantly reduced maximum IAMC amplitude by 43% in small-diameter neurons compared with wild-type (+/+) neurons. All other mechanically activated currents in small- and large-diameter Trpa1−/− neurons were unaltered. Seventy-three per cent of Trpa1+/+ small-diameter neurons responding to the TRPA1 agonist allyl-isothiocyanate (AITC) displayed IAMCs to neurite displacement, which were significantly enhanced after AITC addition. The TRPA1 antagonist HC-030031 significantly decreased Trpa1+/+ IAMC amplitudes, but only in AITC responsive neurons. Using a transfection system we also showed TRPA1 over-expression in Trpa1+/+ small-diameter neurons increases IAMC amplitude, an effect reversed by HC-030031. Furthermore, TRPA1 introduction into Trpa1−/− small-diameter neurons restored IAMC amplitudes to Trpa1+/+ levels, which was subsequently reversed by HC-030031. In summary our data demonstrate TRPA1 makes a contribution to normal mechanosensation in a specific subset of DRG neurons. Furthermore, they also provide new evidence illustrating mechanisms by which sensitisation or over-expression of TRPA1 enhances nociceptor mechanosensitivity. Overall, these findings suggest TRPA1 has the capacity to

  18. TRPA1 contributes to specific mechanically activated currents and sensory neuron mechanical hypersensitivity

    PubMed Central

    Brierley, Stuart M; Castro, Joel; Harrington, Andrea M; Hughes, Patrick A; Page, Amanda J; Rychkov, Grigori Y; Blackshaw, L Ashley

    2011-01-01

    Abstract The mechanosensory role of TRPA1 and its contribution to mechanical hypersensitivity in sensory neurons remains enigmatic. We elucidated this role by recording mechanically activated currents in conjunction with TRPA1 over- and under-expression and selective pharmacology. First, we established that TRPA1 transcript, protein and functional expression are more abundant in smaller-diameter neurons than larger-diameter neurons, allowing comparison of two different neuronal populations. Utilising whole cell patch clamping, we applied calibrated displacements to neurites of dorsal root ganglion (DRG) neurons in short-term culture and recorded mechanically activated currents termed intermediately (IAMCs), rapidly (RAMCs) or slowly adapting (SAMCs). Trpa1 deletion (–/–) significantly reduced maximum IAMC amplitude by 43% in small-diameter neurons compared with wild-type (+/+) neurons. All other mechanically activated currents in small- and large-diameter Trpa1−/− neurons were unaltered. Seventy-three per cent of Trpa1+/+ small-diameter neurons responding to the TRPA1 agonist allyl-isothiocyanate (AITC) displayed IAMCs to neurite displacement, which were significantly enhanced after AITC addition. The TRPA1 antagonist HC-030031 significantly decreased Trpa1+/+ IAMC amplitudes, but only in AITC responsive neurons. Using a transfection system we also showed TRPA1 over-expression in Trpa1+/+ small-diameter neurons increases IAMC amplitude, an effect reversed by HC-030031. Furthermore, TRPA1 introduction into Trpa1−/− small-diameter neurons restored IAMC amplitudes to Trpa1+/+ levels, which was subsequently reversed by HC-030031. In summary our data demonstrate TRPA1 makes a contribution to normal mechanosensation in a specific subset of DRG neurons. Furthermore, they also provide new evidence illustrating mechanisms by which sensitisation or over-expression of TRPA1 enhances nociceptor mechanosensitivity. Overall, these findings suggest TRPA1 has the

  19. Characteristics and physiological role of hyperpolarization activated currents in mouse cold thermoreceptors

    PubMed Central

    Orio, Patricio; Madrid, Rodolfo; de la Peña, Elvira; Parra, Andrés; Meseguer, Víctor; Bayliss, Douglas A; Belmonte, Carlos; Viana, Félix

    2009-01-01

    Hyperpolarization-activated currents (Ih) are mediated by the expression of combinations of hyperpolarization-activated, cyclic nucleotide-gated (HCN) channel subunits (HCN1–4). These cation currents are key regulators of cellular excitability in the heart and many neurons in the nervous system. Subunit composition determines the gating properties and cAMP sensitivity of native Ih currents. We investigated the functional properties of Ih in adult mouse cold thermoreceptor neurons from the trigeminal ganglion, identified by their high sensitivity to moderate cooling and responsiveness to menthol. All cultured cold-sensitive (CS) neurons expressed a fast activating Ih, which was fully blocked by extracellular Cs+ or ZD7288 and had biophysical properties consistent with those of heteromeric HCN1–HCN2 channels. In CS neurons from HCN1(−/−) animals, Ih was greatly reduced but not abolished. We find that Ih activity is not essential for the transduction of cold stimuli in CS neurons. Nevertheless, Ih has the potential to shape the excitability of CS neurons. First, Ih blockade caused a membrane hyperpolarization in CS neurons of about 5 mV. Furthermore, impedance power analysis showed that all CS neurons had a prominent subthreshold membrane resonance in the 5–7 Hz range, completely abolished upon blockade of Ih and absent in HCN1 null mice. This frequency range matches the spontaneous firing frequency of cold thermoreceptor terminals in vivo. Behavioural responses to cooling were reduced in HCN1 null mice and after peripheral pharmacological blockade of Ih with ZD7288, suggesting that Ih plays an important role in peripheral sensitivity to cold. PMID:19273581

  20. Calcium-activated chloride current expression in axotomized sensory neurons: what for?

    PubMed Central

    Boudes, Mathieu; Scamps, Frédérique

    2012-01-01

    Calcium-activated chloride currents (CaCCs) are activated by an increase in intracellular calcium concentration. Peripheral nerve injury induces the expression of CaCCs in a subset of adult sensory neurons in primary culture including mechano- and proprioceptors, though not nociceptors. Functional screenings of potential candidate genes established that Best1 is a molecular determinant for CaCC expression among axotomized sensory neurons, while Tmem16a is acutely activated by inflammatory mediators in nociceptors. In nociceptors, such CaCCs are preferentially activated under receptor-induced calcium mobilization contributing to cell excitability and pain. In axotomized mechano- and proprioceptors, CaCC activation does not promote electrical activity and prevents firing, a finding consistent with electrical silencing for growth competence of adult sensory neurons. In favor of a role in the process of neurite growth, CaCC expression is temporally correlated to neurons displaying a regenerative mode of growth. This perspective focuses on the molecular identity and role of CaCC in axotomized sensory neurons and the future directions to decipher the cellular mechanisms regulating CaCC during neurite (re)growth. PMID:22461766

  1. Somatostatinergic modulation of firing pattern and calcium-activated potassium currents in medium spiny neostriatal neurons.

    PubMed

    Galarraga, E; Vilchis, C; Tkatch, T; Salgado, H; Tecuapetla, F; Perez-Rosello, T; Perez-Garci, E; Hernandez-Echeagaray, E; Surmeier, D J; Bargas, J

    2007-05-11

    Somatostatin is synthesized and released by aspiny GABAergic interneurons of the neostriatum, some of them identified as low threshold spike generating neurons (LTS-interneurons). These neurons make synaptic contacts with spiny neostriatal projection neurons. However, very few somatostatin actions on projection neurons have been described. The present work reports that somatostatin modulates the Ca(2+) activated K(+) currents (K(Ca) currents) expressed by projection cells. These actions contribute in designing the firing pattern of the spiny projection neuron; which is the output of the neostriatum. Small conductance (SK) and large conductance (BK) K(Ca) currents represent between 30% and 50% of the sustained outward current in spiny cells. Somatostatin reduces SK-type K(+) currents and at the same time enhances BK-type K(+) currents. This dual effect enhances the fast component of the after hyperpolarizing potential while reducing the slow component. Somatostatin then modifies the firing pattern of spiny neurons which changed from a tonic regular pattern to an interrupted "stuttering"-like pattern. Semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) tissue expression analysis of dorsal striatal somatostatinergic receptors (SSTR) mRNA revealed that all five SSTR mRNAs are present. However, single cell RT-PCR profiling suggests that the most probable receptor in charge of this modulation is the SSTR2 receptor. Interestingly, aspiny interneurons may exhibit a "stuttering"-like firing pattern. Therefore, somatostatin actions appear to be the entrainment of projection neurons to the rhythms generated by some interneurons. Somatostatin is then capable of modifying the processing and output of the neostriatum.

  2. Ca2+-activated K+ currents regulate odor adaptation by modulating spike encoding of olfactory receptor cells.

    PubMed Central

    Kawai, Fusao

    2002-01-01

    The olfactory system is thought to accomplish odor adaptation through the ciliary transduction machinery in olfactory receptor cells (ORCs). However, ORCs that have lost their cilia can exhibit spike frequency accommodation in which the action potential frequency decreases with time despite a steady depolarizing stimulus. This raises the possibility that somatic ionic channels in ORCs might serve for odor adaptation at the level of spike encoding, because spiking responses in ORCs encode the odor information. Here I investigate the adaptational mechanism at the somatic membrane using conventional and dynamic patch-clamp recording techniques, which enable the ciliary mechanism to be bypassed. A conditioning stimulus with an odorant-induced current markedly shifted the response range of action potentials induced by the same test stimulus to higher concentrations of the odorant, indicating odor adaptation. This effect was inhibited by charybdotoxin and iberiotoxin, Ca2+-activated K+ channel blockers, suggesting that somatic Ca2+-activated K+ currents regulate odor adaptation by modulating spike encoding. I conclude that not only the ciliary machinery but also the somatic membrane currents are crucial to odor adaptation. PMID:11916858

  3. Pharmacological modulations of cardiac ultra-rapid and slowly activating delayed rectifier currents: potential antiarrhythmic approaches.

    PubMed

    Islam, Mohammed A

    2010-01-01

    Despite the emerging new insights into our understandings of the cellular mechanisms underlying cardiac arrhythmia, medical therapy for this disease remains unsatisfactory. Atrial fibrillation (AF), the most prevalent arrhythmia, is responsible for significant morbidity and mortality. On the other hand, ventricular fibrillation results in sudden cardiac deaths in many instances. Prolongation of cardiac action potential (AP) is a proven principle of antiarrhythmic therapy. Class III antiarrhythmic agents prolong AP and QT interval by blocking rapidly activating delayed rectifier current (I(Kr)). However, I(Kr) blocking drugs carry the risk of life-threatening proarrhythmia. Recently, modulation of atrial-selective ultra-rapid delayed rectifier current (I(Kur)), has emerged as a novel therapeutic approach to treat AF. A number of I(Kur) blockers are being evaluated for the treatment of AF. The inhibition of slowly activating delayed rectifier current (I(Ks)) has also been proposed as an effective and safer antiarrhythmic approach because of its distinguishing characteristics that differ in remarkable ways from other selective class III agents. Selective I(Ks) block may prolong AP duration (APD) at rapid rates without leading to proarrhythmia. This article reviews the pathophysiological roles of I(Kur) and I(Ks) in cardiac repolarization and the implications of newly developed I(Kur) and I(Ks) blocking agents as promising antiarrhythmic approaches. Several recent patents pertinent to antiarrhythmic drug development have been discussed. Further research will be required to evaluate the efficacy and safety of these agents in the clinical setting.

  4. The effect of transcranial Direct Current Stimulation on gamma activity and working memory in schizophrenia.

    PubMed

    Hoy, Kate E; Bailey, Neil W; Arnold, Sara L; Fitzgerald, Paul B

    2015-08-15

    Working memory impairments in schizophrenia have been strongly associated with abnormalities in gamma oscillations within the dorsolateral prefrontal cortex (DLFPC). We recently published the first ever study showing that anodal transcranial Direct Current Stimulation (tDCS) to the left DLPFC was able to significantly improve working memory performance in schizophrenia. In the current paper we present a secondary analysis from this study, specifically looking at the effect of tDCS on gamma activity and its relationship to working memory. In a repeated measures design we assessed the impact of anodal tDCS (1mA, 2mA, sham) on gamma activity in the left DLPFC at three time-points post-stimulation (0min, 20min, 40min). EEG data was available for 16 participants in the 2mA condition, 13 in the 1mA condition and 12 in the sham condition. Following 2mA stimulation we found a significant increase in gamma event-related synchronisation in the left DLPFC, this was in the context of a significantly improved working memory performance. There was also a significant decrease in gamma event-related synchronisation, with no changes in working memory, following sham stimulation. The current study provides preliminary evidence that tDCS may enhance working memory in schizophrenia by restoring normal gamma oscillatory function.

  5. Effects of cytochrome P450 inhibitors on potassium currents and mechanical activity in rat portal vein.

    PubMed Central

    Edwards, G.; Zygmunt, P. M.; Högestätt, E. D.; Weston, A. H.

    1996-01-01

    1. The effects of the cytochrome P450 inhibitors, proadifen, clotrimazole and 17-octadecynoic acid (17-ODYA) on K-currents in freshly-isolated single cells derived from rat portal vein and on mechanical activity in whole veins were studied. 2. When cells were stepped from -90 mV to a series of test potentials (from -80 to +50 mV), a delayed rectifier current (IK(V)) and an A-type current (IK(A)) could be identified. Proadifen (10 microM), clotrimazole (30 microM) and 17-ODYA (5 microM) each inhibited IK(V) but had little effect on IK(A). 3. When cells were held at -10 mV to inactivate the time-dependent K-currents, IK(V) and IK(A), levcromakalim (3 microM) induced a time-independent outward K-current (IK(ATP)) which was totally inhibited by clotrimazole (30 microM) and almost fully inhibited by proadifen (10 microM). 17-ODYA (5 microM) had no effect on IK(ATP) and exerted only a minor inhibitory action on this current at 20 microM. 4. 17-ODYA (5 microM) potentiated current flow through the large conductance, Ca-sensitive K-channel (BKCa). In contrast, proadifen (10 microM) had no effect on IBK(Ca) whereas clotrimazole (30 microM) exerted a small but significant inhibitory action. 5. Proadifen (10 microM) and clotrimazole (30 microM) each inhibited the magnitude but increased the frequency of spontaneous contractions in whole portal veins. 17-ODYA (5 microM) had no effect on spontaneous contractions but these were inhibited when the concentration of 17-ODYA was increased to 50 microM. 6. The spasmolytic effect of levcromakalim on spontaneous contractions was antagonized by proadifen (10-30 microM) in a concentration-dependent manner but 17-ODYA (up to 50 microM) was without effect. 7. These results in portal vein show that cytochrome P450 inhibitors exert profound effects on a variety of K-channel subtypes. This suggests that enzymes dependent on this cofactor may be important regulators of K-channel activity in smooth muscle. The relevance of these findings for the

  6. TASSRAP Input Module

    DTIC Science & Technology

    1977-07-29

    retrieve data necessary for the other modules to function. Initially there are 13 inputs, with the CRT dis - playing the information to be entered...id 46aý .0sso somma % 4bt--f. ft Aa W #4t - lQ *a - 4 c ,0 45 40 aK 43 ’ C = 04 ZSC 0 de *020.4 %- li’l ~ ~ ~ ~ ~ ~ & 1&.1 gol~ -,.-’ ow. -6 -N*4••1L...tv Z (𔃽 - C- ft %- ftb 0*4 *- -1 *4* (30 w ag &h 𔃾 0 a _6a .N I 0 A. 6.2 IL ILN ’ S MS 6C 0 to ~ 0 " di a S 0 m J *- -j f’ md op9 -9 $-. -6 = -A U .Af

  7. Dynamic properties of calcium-activated chloride currents in Xenopus laevis oocytes.

    PubMed

    M De la Fuente, Ildefonso; Malaina, Iker; Pérez-Samartín, Alberto; Boyano, María Dolores; Pérez-Yarza, Gorka; Bringas, Carlos; Villarroel, Álvaro; Fedetz, María; Arellano, Rogelio; Cortes, Jesus M; Martínez, Luis

    2017-02-13

    Chloride is the most abundant permeable anion in the cell, and numerous studies in the last two decades highlight the great importance and broad physiological role of chloride currents mediated anion transport. They participate in a multiplicity of key processes, as for instance, the regulation of electrical excitability, apoptosis, cell cycle, epithelial secretion and neuronal excitability. In addition, dysfunction of Cl(-) channels is involved in a variety of human diseases such as epilepsy, osteoporosis and different cancer types. Historically, chloride channels have been of less interest than the cation channels. In fact, there seems to be practically no quantitative studies of the dynamics of chloride currents. Here, for the first time, we have quantitatively studied experimental calcium-activated chloride fluxes belonging to Xenopus laevis oocytes, and the main results show that the experimental Cl(-) currents present an informational structure characterized by highly organized data sequences, long-term memory properties and inherent "crossover" dynamics in which persistent correlations arise at short time intervals, while anti-persistent behaviors become dominant in long time intervals. Our work sheds some light on the understanding of the informational properties of ion currents, a key element to elucidate the physiological functional coupling with the integrative dynamics of metabolic processes.

  8. Dynamic properties of calcium-activated chloride currents in Xenopus laevis oocytes

    PubMed Central

    M. De la Fuente, Ildefonso; Malaina, Iker; Pérez-Samartín, Alberto; Boyano, María Dolores; Pérez-Yarza, Gorka; Bringas, Carlos; Villarroel, Álvaro; Fedetz, María; Arellano, Rogelio; Cortes, Jesus M.; Martínez, Luis

    2017-01-01

    Chloride is the most abundant permeable anion in the cell, and numerous studies in the last two decades highlight the great importance and broad physiological role of chloride currents mediated anion transport. They participate in a multiplicity of key processes, as for instance, the regulation of electrical excitability, apoptosis, cell cycle, epithelial secretion and neuronal excitability. In addition, dysfunction of Cl− channels is involved in a variety of human diseases such as epilepsy, osteoporosis and different cancer types. Historically, chloride channels have been of less interest than the cation channels. In fact, there seems to be practically no quantitative studies of the dynamics of chloride currents. Here, for the first time, we have quantitatively studied experimental calcium-activated chloride fluxes belonging to Xenopus laevis oocytes, and the main results show that the experimental Cl− currents present an informational structure characterized by highly organized data sequences, long-term memory properties and inherent “crossover” dynamics in which persistent correlations arise at short time intervals, while anti-persistent behaviors become dominant in long time intervals. Our work sheds some light on the understanding of the informational properties of ion currents, a key element to elucidate the physiological functional coupling with the integrative dynamics of metabolic processes. PMID:28198817

  9. Electrophysiological characterization of Grueneberg ganglion olfactory neurons: spontaneous firing, sodium conductance, and hyperpolarization-activated currents.

    PubMed

    Liu, Cambrian Y; Xiao, Cheng; Fraser, Scott E; Lester, Henry A; Koos, David S

    2012-09-01

    Mammals rely on their acute olfactory sense for their survival. The most anterior olfactory subsystem in the nose, the Grueneberg ganglion (GG), plays a role in detecting alarm pheromone, cold, and urinary compounds. GG neurons respond homogeneously to these stimuli with increases in intracellular [Ca(2+)] or transcription of immediate-early genes. In this electrophysiological study, we used patch-clamp techniques to characterize the membrane properties of GG neurons. Our results offer evidence of functional heterogeneity in the GG. GG neurons fire spontaneously and independently in several stable patterns, including phasic and repetitive single-spike modes of discharge. Whole cell recordings demonstrated two distinct voltage-gated fast-inactivating Na(+) currents with different steady-state voltage dependencies and different sensitivities to tetrodotoxin. Hodgkin-Huxley simulations showed that these Na(+) currents confer dual mechanisms of action potential generation and contribute to different firing patterns. Additionally, GG neurons exhibited hyperpolarization-activated inward currents that modulated spontaneous firing in vitro. Thus, in GG neurons, the heterogeneity of firing patterns is linked to the unusual repertoire of ionic currents. The membrane properties described here will aid the interpretation of chemosensory function in the GG.

  10. Distinct modifications of convergent excitatory and inhibitory inputs in developing olfactory circuits.

    PubMed

    Ma, T-F; Chen, P-H; Hu, X-Q; Zhao, X-L; Tian, T; Lu, W

    2014-06-06

    The interaction between excitatory and inhibitory inputs is critical to neuronal signal processing. However, little is known about this fundamental property, largely due to the inability to clearly isolate the respective inputs. Here we took advantage of the characteristic stereotypical architecture of synaptic connections in the main olfactory bulb, which enabled us to entirely separate excitatory and inhibitory inputs. Using paired stimulation of two glomeruli located apart at different intensities, we separately elicited excitatory and inhibitory inputs and mimicked stimulation of competing mitral cells (MCs) with different odorants. We performed dual whole-cell patch recording of evoked excitatory postsynaptic responses (EPSPs) and inhibitory postsynaptic responses (IPSPs) in current-clamp mode from two competitive MCs that are connected to the two stimulated glomeruli in slices of the main olfactory bulb in 2-3-week-old rats. We deliberately held the recorded cells at a relative hyperpolarized potential. This manipulation not only suppressed action potential generation but also excluded the possible contamination of inhibitory components in excitatory inputs. We found that in weakly activated MCs repetitive EPSP-IPSP interactions (5 Hz, 180 times) induced long-term potentiation (LTP) and long-term depression (LTD) in convergent excitatory and inhibitory inputs, respectively. Unexpectedly, these forms of plasticity depend on activity of somatic (mainly non-synaptic) NMDA receptors (NMDARs). In contrast, the same repetitive stimulation induced the LTP of excitatory inputs in strongly activated MCs (MC2) that require activity of synaptic NMDARs. These distinct forms of plasticity in the developing olfactory circuit may represent a novel rule of modification in convergent inputs that leads to decorrelation of inputs and facilitates odor discrimination.

  11. The activity intensities reached when playing active tennis gaming relative to sedentary gaming, tennis game-play, and current activity recommendations in young adults.

    PubMed

    Scanlan, Aaron T; Arkinstall, Hayley; Dalbo, Vincent J; Humphries, Brendan J; Jennings, Cameron T; Kingsley, Michael I C

    2013-09-01

    Although active gaming is popular and can increase energy expenditure in young adults, its efficacy as a prescriptive exercise tool is not well understood. This study aimed to: (a) compare the activity intensities experienced by young adults while playing active tennis gaming with conventional sedentary gaming, tennis game-play, and current activity recommendations for health; and (b) identify changes in activity intensities across playing time. After habitualization, 10 active young adults (age: 20.2 ± 0.4 years; stature: 1.74 ± 0.03 m; body mass: 67.7 ± 3.3 kg) completed 3 experimental trials (sedentary gaming, active tennis gaming, and tennis game-play) on separate days in a randomized order. Heart rate (HR) and metabolic equivalents (METs) were averaged across 5 minutes and 10 minutes intervals, and the entire 20 minutes bout within each condition. Active gaming produced greater intensities across 5-10, 10-15, and 15-20 minutes time intervals compared with sedentary gaming (p < 0.01). Tennis game-play elicited greater HR (67 ± 5% HR(max)) and METs (5.0 ± 0.2) responses than both sedentary (40 ± 2% HR(max), 1.1 ± 0.1 METs) and active gaming (45 ± 2% HR(max), 1.4 ± 0.1 METs) (p < 0.001). Only tennis game-play produced activity intensities meeting current recommendations for health benefit. Lower HR intensities were reached across 0-5 minutes than during later time intervals during active gaming (6%) and tennis game-play (9%) (p < 0.01). Activity intensities elicited by active gaming were greater than sedentary gaming but less than tennis game-play and insufficient to contribute toward promoting and maintaining good health in young adults. These data suggest that active tennis gaming should not be recommended by exercise professionals as a substitute for actual sports participation in young adults.

  12. Ultrasound Current Source Density Imaging of the Cardiac Activation Wave Using a Clinical Cardiac Catheter

    PubMed Central

    Qin, Yexian; Li, Qian; Ingram, Pier; Barber, Christy; Liu, Zhonglin

    2015-01-01

    Ultrasound current source density imaging (UCSDI), based on the acoustoelectric (AE) effect, is a noninvasive method for mapping electrical current in 4-D (space + time). This technique potentially overcomes limitations with conventional electrical mapping procedures typically used during treatment of sustained arrhythmias. However, the weak AE signal associated with the electrocardiogram is a major challenge for advancing this technology. In this study, we examined the effects of the electrode configuration and ultrasound frequency on the magnitude of the AE signal and quality of UCSDI using a rabbit Langendorff heart preparation. The AE signal was much stronger at 0.5 MHz (2.99 μV/MPa) than 1.0 MHz (0.42 μV/MPa). Also, a clinical lasso catheter placed on the epicardium exhibited excellent sensitivity without penetrating the tissue. We also present, for the first time, 3-D cardiac activation maps of the live rabbit heart using only one pair of recording electrodes. Activation maps were used to calculate the cardiac conduction velocity for atrial (1.31 m/s) and apical (0.67 m/s) pacing. This study demonstrated that UCSDI is potentially capable of real-time 3-D cardiac activation wave mapping, which would greatly facilitate ablation procedures for treatment of arrhythmias. PMID:25122512

  13. RGS4 regulates partial agonism of the M2 muscarinic receptor-activated K+ currents

    PubMed Central

    Chen, I-Shan; Furutani, Kazuharu; Inanobe, Atsushi; Kurachi, Yoshihisa

    2014-01-01

    Partial agonists are used clinically to avoid overstimulation of receptor-mediated signalling, as they produce a submaximal response even at 100% receptor occupancy. The submaximal efficacy of partial agonists is due to conformational change of the agonist–receptor complex, which reduces effector activation. In addition to signalling activators, several regulators help control intracellular signal transductions. However, it remains unclear whether these signalling regulators contribute to partial agonism. Here we show that regulator of G-protein signalling (RGS) 4 is a determinant for partial agonism of the M2 muscarinic receptor (M2R). In rat atrial myocytes, pilocarpine evoked smaller G-protein-gated K+ inwardly rectifying (KG) currents than those evoked by ACh. In a Xenopus oocyte expression system, pilocarpine acted as a partial agonist in the presence of RGS4 as it did in atrial myocytes, while it acted like a full agonist in the absence of RGS4. Functional couplings within the agonist–receptor complex/G-protein/RGS4 system controlled the efficacy of pilocarpine relative to ACh. The pilocarpine–M2R complex suppressed G-protein-mediated activation of KG currents via RGS4. Our results demonstrate that partial agonism of M2R is regulated by the RGS4-mediated inhibition of G-protein signalling. This finding helps us to understand the molecular components and mechanism underlying the partial agonism of M2R-mediated physiological responses. PMID:24421355

  14. Oscillatory membrane currents paradoxically induced via NO-activated pathways in detrusor cells.

    PubMed

    Kajioka, Shunichi; Nakayama, Shinsuke; Seki, Narihito; Naito, Seiji; Brading, Alison F

    2008-08-01

    Oscillatory inward membrane currents (I(oscil-in)) reflecting intracellular Ca(2+) ([Ca(2+)](i)) activity in detrusor cells, are thought to play an important role in producing tonic bladder contractions during micturition. The present patch clamp study revealed a new activation mechanism: sodium nitroprusside (SNP), a nitric oxide (NO) donor induced I(oscil-in) in a subpopulation of detrusor cells. The inhibitory effect of niflumic acid on SNP-induced I(oscil-in) suggests that Ca(2+)-activated Cl(-) channels are responsible for this current. In addition, SNP-induced I(oscil-in) required the cooperation of Ca(2+) influx through SK&F96365-sensitive channels and intracellular Ca(2+) release channels sensitive to ryanodine but insensitive to xestospongin C (XeC). This is also true for muscarinic agonist (carbachol: CCh)-induced I(oscil-in). However, 1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), a guanylyl cyclase inhibitor, suppressed SNP-induced I(oscil-in) but not CCh-induced I(oscil-in). The results suggest that a subpopulation of detrusor cells employ the NO/cGMP cascade to potentiate bladder contraction. Mechanisms underlying NO-induced I(oscil-in) are likely to contribute not only to the physiology but also to the pathophysiology of the lower urinary tract.

  15. Voltage-activated sodium current is inhibited by capsaicin in rat atrial myocytes.

    PubMed

    Milesi, V; Rebolledo, A; Alvis, A G; Raingo, J; Grassi de Gende, A O

    2001-04-13

    The effects of capsaicin, the active principle of hot pepper genus Capsicum, were studied on voltage-activated, tetrodotoxin-sensitive Na+ currents in isolated rat atrial cells using the patch clamp technique in the whole-cell configuration. 0.4 and 4 microM of capsaicin produced a significant tonic block on voltage-activated Na+ current (I(Na)) evoked by a depolarizing step to -40 mV from a holding potential of -100 mV (49 +/- 7% n = 11, P < 0.05 and 72 +/- 13% n = 4, P < 0.05 respectively). We didn't observe any use-dependent block of capsaicin in our experimental conditions. Capsaicin slowed the time decay of inactivation of I(Na), and increased the time constant of the recovery of inactivation. Capsaicin and tetrodotoxin (TTX) depressed contractility of isolated electrically driven left rat atria, being the depression of maximal velocity of force development (dF/dt(max)) with respect to control values of 19 +/- 3% at 1 microM of capsaicin and 22 +/- 2% at 1 microM of TTX. These results show an inhibitory effect of capsaicin on I(Na) in isolated atrial cells that may modify the electrical and contractile function of the rat heart.

  16. New hybrid active power filter for harmonic current suppression and reactive power compensation

    NASA Astrophysics Data System (ADS)

    Biricik, Samet; Cemal Ozerdem, Ozgur; Redif, Soydan; Sezai Dincer, Mustafa

    2016-08-01

    In the case of undistorted and balanced grid voltages, low ratio shunt active power filters (APFs) can give unity power factors and achieve current harmonic cancellation. However, this is not possible when source voltages are distorted and unbalanced. In this study, the cost-effective hybrid active power filter (HAPF) topology for satisfying the requirements of harmonic current suppression and non-active power compensation for industry is presented. An effective strategy is developed to observe the effect of the placement of power capacitors and LC filters with the shunt APF. A new method for alleviating the negative effects of a nonideal grid voltage is proposed that uses a self-tuning filter algorithm with instantaneous reactive power theory. The real-time control of the studied system was achieved with a field-programmable gate array (FPGA) architecture, which was developed using the OPAL-RT system. The performance result of the proposed HAPF system is tested and presented under nonideal supply voltage conditions.

  17. Control of Spontaneous Firing Patterns by the Selective Coupling of Calcium Currents to Calcium Activated Potassium Currents in Striatal Cholinergic Interneurons

    PubMed Central

    Goldberg, Joshua A.; Wilson, Charles J.

    2005-01-01

    The spontaneous firing patterns of striatal cholinergic interneurons are sculpted by potassium currents that give rise to prominent afterhyperpolarizations (AHPs): BK currents contribute to action potential (AP) repolarization; SK currents generate an apamin-sensitive medium AHP (mAHP) following each AP; and bursts of APs generate long-lasting slow AHPs (sAHPs) due to apamin-insensitive currents. As all these currents are calcium-dependent, we conducted voltage- and current-clamp whole-cell recordings while pharmacologically manipulating calcium channels of the plasma membrane and intracellular stores to determine what sources of calcium activate the currents underlying AP repolarization and the AHPs. The Cav2.2 (N type) blocker, omega-conotoxin GVIA (1 μM), was the only blocker that significantly reduced the mAHP, and it induced a transition to rhythmic bursting in a third of the cells tested. Cav1 (L type) blockers (10 μM dihydropyridines) were the only ones that significantly reduced the sAHP. When applied to cells induced to burst with apamin, dihydropyridines reduced the sAHPs and abolished bursting. Depletion of intracellular stores with 10 mM caffeine also significantly reduced the sAHP current, and reversibly regularized firing. Application of 1 μM omega-conotoxin MVIIC (a Cav2.1/2.2 blocker) broadened APs, but had a negligible effect on APs in cells whose BK channels were already blocked by submillimolar tetraethylammonium chloride, indicating that Cav2.1 (Q type) channels provide the calcium to activate BK channels that repolarize the AP. Thus, calcium currents are selectively coupled to the calcium-dependent potassium currents underlying the AHPs thereby creating mechanisms for control of these neurons’ spontaneous firing patterns. PMID:16267230

  18. EVOLUTION OF RELATIVE MAGNETIC HELICITY AND CURRENT HELICITY IN NOAA ACTIVE REGION 11158

    SciTech Connect

    Jing, Ju; Liu, Chang; Lee, Jeongwoo; Xu, Yan; Deng, Na; Wang, Haimin; Park, Sung-Hong; Wiegelmann, Thomas E-mail: chang.liu@njit.edu E-mail: na.deng@njit.edu E-mail: freemler@kasi.re.kr E-mail: wiegelmann@linmpi.mpg.de

    2012-06-10

    Both magnetic and current helicities are crucial ingredients for describing the complexity of active-region magnetic structure. In this Letter, we present the temporal evolution of these helicities contained in NOAA active region 11158 during five days from 2011 February 12 to 16. The photospheric vector magnetograms of the Helioseismic and Magnetic Imager on board the Solar Dynamic Observatory were used as the boundary conditions for the coronal field extrapolation under the assumption of nonlinear force-free field, from which we calculated both relative magnetic helicity and current helicity. We construct a time-altitude diagram in which altitude distribution of the magnitude of current helicity density is displayed as a function of time. This diagram clearly shows a pattern of upwardly propagating current helicity density over two days prior to the X2.2 flare on February 15 with an average propagation speed of {approx}36 m s{sup -1}. The propagation is synchronous with the emergence of magnetic flux into the photosphere, and indicative of a gradual energy buildup for the X2.2 flare. The time profile of the relative magnetic helicity shows a monotonically increasing trend most of the time, but a pattern of increasing and decreasing magnetic helicity above the monotonic variation appears prior to each of two major flares, M6.6 and X2.2, respectively. The physics underlying this bump pattern is not fully understood. However, the fact that this pattern is apparent in the magnetic helicity evolution but not in the magnetic flux evolution makes it a useful indicator in forecasting major flares.

  19. Time-resolved rhodopsin activation currents in a unicellular expression system.

    PubMed Central

    Sullivan, J M; Shukla, P

    1999-01-01

    The early receptor current (ERC) is the charge redistribution occurring in plasma membrane rhodopsin during light activation of photoreceptors. Both the molecular mechanism of the ERC and its relationship to rhodopsin conformational activation are unknown. To investigate whether the ERC could be a time-resolved assay of rhodopsin structure-function relationships, the distinct sensitivity of modern electrophysiological tools was employed to test for flash-activated ERC signals in cells stably expressing normal human rod opsin after regeneration with 11-cis-retinal. ERCs are similar in waveform and kinetics to those found in photoreceptors. The action spectrum of the major R(2) charge motion is consistent with a rhodopsin photopigment. The R(1) phase is not kinetically resolvable and the R(2) phase, which overlaps metarhodopsin-II formation, has a rapid risetime and complex multiexponential decay. These experiments demonstrate, for the first time, kinetically resolved electrical state transitions during activation of expressed visual pigment in a unicellular environment (single or fused giant cells) containing only 6 x 10(6)-8 x 10(7) molecules of rhodopsin. This method improves measurement sensitivity 7 to 8 orders of magnitude compared to other time-resolved techniques applied to rhodopsin to study the role particular amino acids play in conformational activation and the forces that govern those transitions. PMID:10465746

  20. Transcranial direct-current stimulation modulates offline visual oscillatory activity: A magnetoencephalography study.

    PubMed

    Heinrichs-Graham, Elizabeth; McDermott, Timothy J; Mills, Mackenzie S; Coolidge, Nathan M; Wilson, Tony W

    2017-03-01

    Transcranial direct-current stimulation (tDCS) is a noninvasive neuromodulatory method that involves delivering low amplitude, direct current to specific regions of the brain. While a wealth of literature shows changes in behavior and cognition following tDCS administration, the underlying neuronal mechanisms remain largely unknown. Neuroimaging studies have generally used fMRI and shown only limited consensus to date, while the few electrophysiological studies have reported mostly null or counterintuitive findings. The goal of the current investigation was to quantify tDCS-induced alterations in the oscillatory dynamics of visual processing. To this end, we performed either active or sham tDCS using an occipital-frontal electrode configuration, and then recorded magnetoencephalography (MEG) offline during a visual entrainment task. Significant oscillatory responses were imaged in the time-frequency domain using beamforming, and the effects of tDCS on absolute and relative power were assessed. The results indicated significantly increased basal alpha levels in the occipital cortex following anodal tDCS, as well as reduced occipital synchronization at the second harmonic of the stimulus-flicker frequency relative to sham stimulation. In addition, we found reduced power in brain regions near the cathode (e.g., right inferior frontal gyrus [IFG]) following active tDCS, which was absent in the sham group. Taken together, these results suggest that anodal tDCS of the occipital cortices differentially modulates spontaneous and induced activity, and may interfere with the entrainment of neuronal populations by a visual-flicker stimulus. These findings also demonstrate the importance of electrode configuration on whole-brain dynamics, and highlight the deceptively complicated nature of tDCS in the context of neurophysiology.

  1. Current research activities at the NASA-sponsored Illinois Computing Laboratory of Aerospace Systems and Software

    NASA Technical Reports Server (NTRS)

    Smith, Kathryn A.

    1994-01-01

    The Illinois Computing Laboratory of Aerospace Systems and Software (ICLASS) was established to: (1) pursue research in the areas of aerospace computing systems, software and applications of critical importance to NASA, and (2) to develop and maintain close contacts between researchers at ICLASS and at various NASA centers to stimulate interaction and cooperation, and facilitate technology transfer. Current ICLASS activities are in the areas of parallel architectures and algorithms, reliable and fault tolerant computing, real time systems, distributed systems, software engineering and artificial intelligence.

  2. Intracellular Na(+) modulates large conductance Ca(2+)-activated K (+) currents in human umbilical vein endothelial cells.

    PubMed

    Liang, Guo Hua; Kim, Moon Young; Park, Seonghee; Kim, Ji Aee; Choi, Shinkyu; Suh, Suk Hyo

    2008-10-01

    We studied the effects of Na(+) influx on large-conductance Ca(2+)-activated K(+) (BK(Ca)) channels in cultured human umbilical vein endothelial cells (HUVECs) by means of patch clamp and SBFI microfluorescence measurements. In current-clamped HUVECs, extracellular Na(+) replacement by NMDG(+) or mannitol hyperpolarized cells. In voltage-clamped HUVECs, changing membrane potential from 0 mV to negative potentials increased intracellular Na(+) concentration ([Na(+)](i)) and vice versa. In addition, extracellular Na(+) depletion decreased [Na(+)](i). In voltage-clamped cells, BK(Ca) currents were markedly increased by extracellular Na(+) depletion. In inside-out patches, increasing [Na(+)](i) from 0 to 20 or 40 mM reduced single channel conductance but not open probability (NPo) of BK(Ca) channels and decreasing intracellular K(+) concentration ([K(+)](i)) gradually from 140 to 70 mM reduced both single channel conductance and NPo. Furthermore, increasing [Na(+)](i) gradually from 0 to 70 mM, by replacing K(+), markedly reduced single channel conductance and NPo. The Na(+)-Ca(2+) exchange blocker Ni(2+) or KB-R7943 decreased [Na(+)](i) and increased BK(Ca) currents simultaneously, and the Na(+) ionophore monensin completely inhibited BK(Ca) currents. BK(Ca) currents were significantly augmented by increasing extracellular K(+) concentration ([K(+)](o)) from 6 to 12 mM and significantly reduced by decreasing [K(+)](o) from 12 or 6 to 0 mM or applying the Na(+)-K(+) pump inhibitor ouabain. These results suggest that intracellular Na(+) inhibit single channel conductance of BK(Ca) channels and that intracellular K(+) increases single channel conductance and NPo.

  3. Pronase acutely modifies high voltage-activated calcium currents and cell properties of Lymnaea neurons.

    PubMed

    Hermann, P M; Lukowiak, K; Wildering, W C; Bulloch, A G

    1997-12-01

    Pronase E ('pronase') is one of the proteolytic enzymes that are used in preparative procedures such as cell isolation and to soften the sheath of invertebrate ganglia. Although several effects of proteolytic enzymes on the physiology of non-neuronal tissues have been described, the effects of these enzymes on central neurons have received little attention. We examined the effects of bath-applied pronase on neurons in the Lymnaea central nervous system and in vitro. Pronase caused action potential broadening in neurons that exhibit a shoulder on the repolarization phase of their action potentials. This effect of pronase was accompanied by, although unrelated to, a depolarization and decrease in action potential interval. Some, but not all, effects of pronase in the central nervous system were reversible. For example, the decreases in membrane potential and action potential interval were both reversed after approximately 1 h of washing with saline. However, the effect of pronase on the action potential duration was not reversed after a period of 90 min. The modulation of action potential width prompted us to examine Ca2+ currents. Exposure to pronase resulted in an increase in both peak and late high voltage-activated Ca2+ currents in isolated neurons. Pronase neither changed the inactivation rate nor caused a shift in the current-voltage relationship of the current. The changes in action potential duration could be prevented by application of 0.1 mM Cd2+, indicating that the action potential broadening caused by pronase depends on Ca2+ influx. This is the first systematic study of the acute and direct actions of pronase on Ca2+ currents and cell properties both in the CNS and in vitro.

  4. Input Multiplicities in Process Control.

    ERIC Educational Resources Information Center

    Koppel, Lowell B.

    1983-01-01

    Describes research investigating potential effect of input multiplicity on multivariable chemical process control systems. Several simple processes are shown to exhibit the possibility of theoretical developments on input multiplicity and closely related phenomena are discussed. (JN)

  5. Modeling and generating input processes

    SciTech Connect

    Johnson, M.E.

    1987-01-01

    This tutorial paper provides information relevant to the selection and generation of stochastic inputs to simulation studies. The primary area considered is multivariate but much of the philosophy at least is relevant to univariate inputs as well. 14 refs.

  6. What are the implications of rapid global warming for landslide-triggered turbidity current activity?

    NASA Astrophysics Data System (ADS)

    Clare, Michael; Peter, Talling; James, Hunt

    2014-05-01

    A geologically short-lived (~170kyr) episode of global warming occurred at ~55Ma, termed the Initial Eocene Thermal Maximum (IETM). Global temperatures rose by up to 8oC over only ~10kyr and a massive perturbation of the global carbon cycle occurred; creating a negative carbon isotopic (~-4% δ13C) excursion in sedimentary records. This interval has relevance to study of future climate change and its influence on geohazards including submarine landslides and turbidity currents. We analyse the recurrence frequency of turbidity currents, potentially initiated from large-volume slope failures. The study focuses on two sedimentary intervals that straddle the IETM and we discuss implications for turbidity current triggering. We present the results of statistical analyses (regression, generalised linear model, and proportional hazards model) for extensive turbidite records from an outcrop at Zumaia in NE Spain (N=285; 54.0 to 56.5 Ma) and based on ODP site 1068 on the Iberian Margin (N=1571; 48.2 to 67.6 Ma). The sedimentary sequences provide clear differentiation between hemipelagic and turbiditic mud with only negligible evidence of erosion. We infer dates for turbidites by converting hemipelagic bed thicknesses to time using interval-averaged accumulation rates. Multi-proxy dating techniques provide good age constraint. The background trend for the Zumaia record shows a near-exponential distribution of turbidite recurrence intervals, while the Iberian Margin shows a log-normal response. This is interpreted to be related to regional time-independence (exponential) and the effects of additive processes (log-normal). We discuss how a log-normal response may actually be generated over geological timescales from multiple shorter periods of random turbidite recurrence. The IETM interval shows a dramatic departure from both these background trends, however. This is marked by prolonged hiatuses (0.1 and 0.6 Myr duration) in turbidity current activity in contrast to the

  7. Strategic Classification and Examination of the Development of Current Airline Alliance Activities

    NASA Technical Reports Server (NTRS)

    Wang, Zhi H.; Evans, Michael

    2002-01-01

    Previous research argues that despite the fact that strategic alliances have become an important feature of the world airline industry, little rigorous analysis has been done on the effects of these alliances. This is partially because there is a lack of precise definitions to specify different types of airline alliances in the literature. This research identifies several categories of airline alliances through a strategic classification of the current alliance activities involving the major airlines for the period 1989 to 1999. The classification enables this research to examine how strategic alliance activities are evolving, particularly to compare how airlines in North America, the European Union and the Asia Pacific region have committed to different alliances. Findings show that there is a significant difference between the number and scope of alliances adopted in the three aviation markets. These findings facilitate research to further analyse the impact of market liberalization on various formations of strategic airline alliances.

  8. An overview of current activities at the National Solar Thermal Test Facility

    NASA Astrophysics Data System (ADS)

    Cameron, C. P.; Klimas, P. C.

    This paper is a description of the United States Department of Energy's National Solar Thermal Test Facility, highlighting current test programs. In the central receiver area, research underway supports commercialization of molten nitrate salt technology, including receivers, thermal energy transport, and corrosion experiments. Concentrator research includes large-area, glass-metal heliostats and stretched-membrane heliostats and dishes. Test activities in support of dish-Stirling systems with reflux receivers are described. Research on parabolic troughs includes characterization of several receiver configurations. Other test facility activities include solar detoxification experiments, design assistance testing of commercially-available solar hardware, and non-DOE-funded work, including thermal exposure tests and testing of volumetric and PV central receiver concepts.

  9. Low-Power Magnetic Current Sensor

    NASA Technical Reports Server (NTRS)

    Mclyman, W. T.

    1989-01-01

    Direct current sensed via saturable-core reactor. Transducer senses direct current magnetically, providing isolation between input and output. Detecting-and-isolating element saturable reactor, where input current passes through one-turn control coil. Provides output of 0 to 3 Vdc for input current of 0 to 15 Adc and consumes power of 22 mW at 10 Adc input. Input sensed magnetically, output electrically isolated from input.

  10. Input-Based Incremental Vocabulary Instruction

    ERIC Educational Resources Information Center

    Barcroft, Joe

    2012-01-01

    This fascinating presentation of current research undoes numerous myths about how we most effectively learn new words in a second language. In clear, reader-friendly text, the author details the successful approach of IBI vocabulary instruction, which emphasizes the presentation of target vocabulary as input early on and the incremental (gradual)…

  11. Photospheric and chromospheric magnetic activity of seismic solar analogs. Observational inputs on the solar-stellar connection from Kepler and Hermes

    NASA Astrophysics Data System (ADS)

    Salabert, D.; García, R. A.; Beck, P. G.; Egeland, R.; Pallé, P. L.; Mathur, S.; Metcalfe, T. S.; do Nascimento, J.-D., Jr.; Ceillier, T.; Andersen, M. F.; Triviño Hage, A.

    2016-11-01

    We identify a set of 18 solar analogs among the seismic sample of solar-like stars observed by the Kepler satellite rotating between 10 and 40 days. This set is constructed using the asteroseismic stellar properties derived using either the global oscillation properties or the individual acoustic frequencies. We measure the magnetic activity properties of these stars using observations collected by the photometric Kepler satellite and by the ground-based, high-resolution Hermes spectrograph mounted on the Mercator telescope. The photospheric (Sph) and chromospheric (S index) magnetic activity levels of these seismic solar analogs are estimated and compared in relation to the solar activity. We show that the activity of the Sun is comparable to the activity of the seismic solar analogs, within the maximum-to-minimum temporal variations of the 11-yr solar activity cycle 23. In agreement with previous studies, the youngest stars and fastest rotators in our sample are actually the most active. The activity of stars older than the Sun seems to not evolve much with age. Furthermore, the comparison of the photospheric, Sph, with the well-established chromospheric, S index, indicates that the Sph index can be used to provide a suitable magnetic activity proxy which can be easily estimated for a large number of stars from space photometric observations. Based on observations collected by the NASA Kepler space telescope and the Hermes spectrograph mounted on the 1.2 m Mercator telescope at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.

  12. High-frequency matrix converter with square wave input

    DOEpatents

    Carr, Joseph Alexander; Balda, Juan Carlos

    2015-03-31

    A device for producing an alternating current output voltage from a high-frequency, square-wave input voltage comprising, high-frequency, square-wave input a matrix converter and a control system. The matrix converter comprises a plurality of electrical switches. The high-frequency input and the matrix converter are electrically connected to each other. The control system is connected to each switch of the matrix converter. The control system is electrically connected to the input of the matrix converter. The control system is configured to operate each electrical switch of the matrix converter converting a high-frequency, square-wave input voltage across the first input port of the matrix converter and the second input port of the matrix converter to an alternating current output voltage at the output of the matrix converter.

  13. Current topics in active and intelligent food packaging for preservation of fresh foods.

    PubMed

    Lee, Seung Yuan; Lee, Seung Jae; Choi, Dong Soo; Hur, Sun Jin

    2015-11-01

    The purpose of this review is to provide an overview of current packaging systems, e.g. active packaging and intelligent packaging, for various foods. Active packaging, such as modified atmosphere packaging (MAP), extends the shelf life of fresh produce, provides a high-quality product, reduces economic losses, including those caused by delay of ripening, and improves appearance. However, in active packaging, several variables must be considered, such as temperature control and different gas formulations with different product types and microorganisms. Active packaging refers to the incorporation of additive agents into packaging materials with the purpose of maintaining or extending food product quality and shelf life. Intelligent packaging is emerging as a potential advantage in food processing and is an especially useful tool for tracking product information and monitoring product conditions. Moreover, intelligent packaging facilitates data access and information exchange by altering conditions inside or outside the packaging and product. In spite of these advantages, few of these packaging systems are commercialized because of high cost, strict safety and hygiene regulations or limited consumer acceptance. Therefore more research is needed to develop cheaper, more easily applicable and effective packaging systems for various foods.

  14. Calcium entry via TRPC1 channels activates chloride currents in human glioma cells

    PubMed Central

    Cuddapah, Vishnu Anand; Turner, Kathryn L.; Sontheimer, Harald

    2012-01-01

    Malignant gliomas are highly-invasive brain cancers that carry a dismal prognosis. Recent studies indicate that Cl− channels facilitate glioma cell invasion by promoting hydrodynamic cell shape and volume changes. Here we asked how Cl− channels are regulated in the context of migration. Using patch-clamp recordings we show Cl− currents are activated by physiological increases of [Ca2+]i to 65 and 180 nM. Cl− currents appear to be mediated by ClC-3, a voltage-gated, CaMKII-regulated Cl− channel highly expressed by glioma cells. ClC-3 channels colocalized with TRPC1 on caveolar lipid rafts on glioma cell processes. Using perforated-patch electrophysiological recordings, we demonstrate that inducible knockdown of TRPC1 expression with shRNA significantly inhibited glioma Cl− currents in a Ca2+-dependent fashion, placing Cl− channels under the regulation of Ca2+ entry via TRPC1. In chemotaxis assays epidermal growth factor (EGF)-induced invasion was inhibition by TRPC1 knockdown to the same extent as pharmacological block of Cl− channels. Thus endogenous glioma Cl− channels are regulated by TRPC1. Cl− channels could be an important downstream target of TRPC1 in many other cells types, coupling elevations in [Ca2+]i to the shape and volume changes associated with migrating cells. PMID:23261316

  15. A hyperpolarization-activated inward current alters swim frequency of the pteropod mollusk Clione limacina.

    PubMed

    Pirtle, Thomas J; Willingham, Kyle; Satterlie, Richard A

    2010-12-01

    The pteropod mollusk, Clione limacina, exhibits behaviorally relevant swim speed changes that occur within the context of the animal's ecology. Modulation of C. limacina swimming speed involves changes that occur at the network and cellular levels. Intracellular recordings from interneurons of the swim central pattern generator show the presence of a sag potential that is indicative of the hyperpolarization-activated inward current (I(h)). Here we provide evidence that I(h) in primary swim interneurons plays a role in C. limacina swimming speed control and may be a modulatory target. Recordings from central pattern generator swim interneurons show that hyperpolarizing current injection produces a sag potential that lasts for the duration of the hyperpolarization, a characteristic of cells possessing I(h). Following the hyperpolarizing current injection, swim interneurons also exhibit postinhibitory rebound (PIR). Serotonin enhances the sag potential of C. limacina swim interneurons while the I(h) blocker, ZD7288, reduces the sag potential. Furthermore, a negative correlation was found between the amplitude of the sag potential and latency to PIR. Because latency to PIR was previously shown to influence swimming speed, we hypothesize that I(h) has an effect on swimming speed. The I(h) blocker, ZD7288, suppresses swimming in C. limacina and inhibits serotonin-induced acceleration, evidence that supports our hypothesis.

  16. Effects of Current Velocity, Particle Size, and Substrate Heterogeneity on Crayfish (Orconectes propinquus) Activity

    NASA Astrophysics Data System (ADS)

    Clark, J. M.; Kershner, M. W.

    2005-05-01

    The use of flow refugia (e.g., substrate) by lotic invertebrates often increases their likelihood of survival during flood events. Movement to potential refugia becomes risky as velocities increase, and the range of velocities that benthic invertebrates can withstand is variable. In this study, activity time and slip velocities of small [carapace length (CL)=10-20 mm] and large (CL=20-30 mm) Orconectes propinquus were measured in an artificial flume across ranges of current velocity and substrate heterogeneity. Particle sizes included small pebbles (16-32 mm), large pebbles (32-64 mm), and small cobble (64-128 mm). Water velocity was increased by 0.1 m/s increments from 0.1-1.5 m/s at 5-minute intervals or until the crayfish was dislodged from the substrate. As current velocity increased, the probability of slipping increased for all crayfish. Regardless of the degree of substrate heterogeneity, small crayfish held their position at higher velocities than large crayfish and were also less active. Slip rates were generally lower for both sizes as substrate heterogeneity increased. Essentially, the availability and probability of finding refugia increased with increased habitat heterogeneity and allowed crayfish to avoid being swept into the drift.

  17. Revealing the activation pathway for TMEM16A chloride channels from macroscopic currents and kinetic models.

    PubMed

    Contreras-Vite, Juan A; Cruz-Rangel, Silvia; De Jesús-Pérez, José J; Figueroa, Iván A Aréchiga; Rodríguez-Menchaca, Aldo A; Pérez-Cornejo, Patricia; Hartzell, H Criss; Arreola, Jorge

    2016-07-01

    TMEM16A (ANO1), the pore-forming subunit of calcium-activated chloride channels, regulates several physiological and pathophysiological processes such as smooth muscle contraction, cardiac and neuronal excitability, salivary secretion, tumour growth and cancer progression. Gating of TMEM16A is complex because it involves the interplay between increases in intracellular calcium concentration ([Ca(2+)]i), membrane depolarization, extracellular Cl(-) or permeant anions and intracellular protons. Our goal here was to understand how these variables regulate TMEM16A gating and to explain four observations. (a) TMEM16A is activated by voltage in the absence of intracellular Ca(2+). (b) The Cl(-) conductance is decreased after reducing extracellular Cl(-) concentration ([Cl(-)]o). (c) ICl is regulated by physiological concentrations of [Cl(-)]o. (d) In cells dialyzed with 0.2 μM [Ca(2+)]i, Cl(-) has a bimodal effect: at [Cl(-)]o <30 mM TMEM16A current activates with a monoexponential time course, but above 30 mM, [Cl(-)]o ICl activation displays fast and slow kinetics. To explain the contribution of Vm, Ca(2+) and Cl(-) to gating, we developed a 12-state Markov chain model. This model explains TMEM16A activation as a sequential, direct, and Vm-dependent binding of two Ca(2+) ions coupled to a Vm-dependent binding of an external Cl(-) ion, with Vm-dependent transitions between states. Our model predicts that extracellular Cl(-) does not alter the apparent Ca(2+) affinity of TMEM16A, which we corroborated experimentally. Rather, extracellular Cl(-) acts by stabilizing the open configuration induced by Ca(2+) and by contributing to the Vm dependence of activation.

  18. Calcium‐activated chloride current determines action potential morphology during calcium alternans in atrial myocytes

    PubMed Central

    Kanaporis, Giedrius

    2016-01-01

    Key points Cardiac alternans – periodic beat‐to‐beat alternations in contraction, action potential (AP) morphology or cytosolic calcium transient (CaT) amplitude – is a high risk indicator for cardiac arrhythmias and sudden cardiac death. However, it remains an unresolved issue whether beat‐to‐beat alternations in intracellular Ca2+ ([Ca2+]i) or AP morphology are the primary cause of pro‐arrhythmic alternans.Here we show that in atria AP alternans occurs secondary to CaT alternans.CaT alternans leads to complex beat‐to‐beat changes in Ca2+‐regulated ion currents that determine alternans of AP morphology.We report the novel finding that alternans of AP morphology is largely sustained by the activity of Ca2+‐activated Cl− channels (CaCCs). Suppression of the CaCCs significantly reduces AP alternans, while CaT alternans remains unaffected.The demonstration of a major role of CaCCs in the development of AP alternans opens new possibilities for atrial alternans and arrhythmia prevention. Abstract Cardiac alternans, described as periodic beat‐to‐beat alternations in contraction, action potential (AP) morphology or cytosolic Ca transient (CaT) amplitude, is a high risk indicator for cardiac arrhythmias and sudden cardiac death. We investigated mechanisms of cardiac alternans in single rabbit atrial myocytes. CaTs were monitored simultaneously with membrane currents or APs recorded with the patch clamp technique. Beat‐to‐beat alternations of AP morphology and CaT amplitude revealed a strong quantitative correlation. Application of voltage clamp protocols in the form of pre‐recorded APs (AP‐clamp) during pacing‐induced CaT alternans revealed a Ca2+‐dependent current consisting of a large outward component (4.78 ± 0.58 pA pF–1 in amplitude) coinciding with AP phases 1 and 2 that was followed by an inward current (−0.42 ± 0.03 pA pF–1; n = 21) during AP repolarization. Approximately 90% of the initial outward current

  19. Electric Current Activated Combustion Synthesis and Chemical Ovens Under Terrestrial and Reduced Gravity Conditions

    NASA Technical Reports Server (NTRS)

    Unuvar, C.; Fredrick, D.; Anselmi-Tamburini, U.; Manerbino, A.; Guigne, J. Y.; Munir, Z. A.; Shaw, B. D.

    2004-01-01

    Combustion synthesis (CS) generally involves mixing reactants together (e.g., metal powders) and igniting the mixture. Typically, a reaction wave will pass through the sample. In field activated combustion synthesis (FACS), the addition of an electric field has a marked effect on the dynamics of wave propagation and on the nature, composition, and homogeneity of the product as well as capillary flow, mass-transport in porous media, and Marangoni flows, which are influenced by gravity. The objective is to understand the role of an electric field in CS reactions under conditions where gravity-related effects are suppressed or altered. The systems being studied are Ti+Al and Ti+3Al. Two different ignition orientations have been used to observe effects of gravity when one of the reactants becomes molten. This consequentially influences the position and concentration of the electric current, which in turn influences the entire process. Experiments have also been performed in microgravity conditions. This process has been named Microgravity Field Activated Combustion Synthesis (MFACS). Effects of gravity have been demonstrated, where the reaction wave temperature and velocity demonstrate considerable differences besides the changes of combustion mechanisms with the different high currents applied. Also the threshold for the formation of a stable reaction wave is increased under zero gravity conditions. Electric current was also utilized with a chemical oven technique, where inserts of aluminum with minute amounts of tungsten and tantalum were used to allow observation of effects of settling of the higher density solid particles in liquid aluminum at the present temperature profile and wave velocity of the reaction.

  20. Shallow Lunar Seismic Activity and the Current Stress State of the Moon

    NASA Technical Reports Server (NTRS)

    Watters, T. R.; Weber, R. C.; Collins, G. C.; Johnson, C. L.

    2017-01-01

    A vast, global network of more than 3200 lobate thrust fault scarps has been revealed in high resolution Lunar Reconnaissance Orbiter Camera (LROC) images. The fault scarps very young, less than 50 Ma, based on their small scale and crisp appearance, crosscutting relations with small-diameter impact craters, and rates of infilling of associated small, shallow graben and may be actively forming today. The population of young thrust fault scarps provides a window into the recent stress state of the Moon and offers insight into the origin of global lunar stresses. The distribution of orientations of the fault scarps is non-random, inconsistent with isotropic stresses from late-stage global contraction as the sole source of stress Modeling shows that tidal stresses contribute significantly to the current stress state of the lunar crust. Tidal stresses (orbital recession and diurnal tides) superimposed on stresses from global contraction result in non-isotropic compressional stress and thrust faults consistent with lobate scarp orientations. Stresses due to orbital recession do not change with orbital position, thus it is with the addition of diurnal stresses that peak stresses are reached. At apogee, diurnal and recession stresses are most compressive near the tidal axis, while at perigee they are most compressive 90 degrees away from the tidal axis. Coseismic slip events on currently active thrust faults are expected to be triggered when peak stresses are reached. Analysis of the timing of the 28 the shallow moonquakes recorded by the Apollo seismic network shows that 19 indeed occur when the Moon is closer to apogee, while only 9 shallow events occur when the Moon is closer to perigee. Here we show the results of relocating the shallow moonquake using an algorithm designed for sparse networks to better constrain their epicentral locations in order to compare them with stress models. The model for the current stress state of the Moon is refined by investigating the

  1. Shallow Lunar Seismic Activity and the Current Stress State of the Moon

    NASA Technical Reports Server (NTRS)

    Watters, Thomas R.; Weber, Renee C.; Collins, Geoffrey C.; Johnson, Catherine L.

    2017-01-01

    A vast, global network of more than 3200 lobate thrust fault scarps has been revealed in high resolution Lunar Reconnaissance Orbiter Camera (LROC) images. The fault scarps are very young, less than 50 Ma, based on their small scale and crisp appearance, crosscutting relations with small-diameter impact craters, and rates of infilling of associated small, shallow graben and may be actively forming today. The population of young thrust fault scarps provides a window into the recent stress state of the Moon and offers insight into the origin of global lunar stresses. The distribution of orientations of the fault scarps is non-random, inconsistent with isotropic stresses from late-stage global contraction as the sole source of stress. Modeling shows that tidal stresses contribute significantly to the current stress state of the lunar crust. Tidal stresses (orbital recession and diurnal tides) superimposed on stresses from global contraction result in non-isotropic compressional stress and may produce thrust faults consistent with lobate scarp orientations. At any particular point on the lunar surface, peak compressive stress will be reached at a certain time in the diurnal cycle. Coseismic slip events on currently active thrust faults are expected to be triggered when peak stresses are reached. Analysis of the timing of the 28 the shallow moonquakes recorded by the Apollo seismic network shows that 19 indeed occur when the Moon is closer to apogee, while only 9 shallow events occur when the Moon is closer to perigee. Here we report efforts to refine the model for the current stress state of the Moon by investigating the contribution of polar wander. Progress on relocating the epicentral locations of the shallow moonquakes using an algorithm designed for sparse networks is also reported.

  2. Rapidly inactivating and non-inactivating calcium-activated potassium currents in frog saccular hair cells

    PubMed Central

    Armstrong, Cecilia E; Roberts, William M

    2001-01-01

    Using a semi-intact epithelial preparation we examined the Ca2+-activated K+ (KCa) currents of frog (Rana pipiens) saccular hair cells. After blocking voltage-dependent K+ (KV) currents with 4-aminopyridine (4-AP) an outward current containing inactivating (Itransient) and non-inactivating (Isteady) components remained.The contribution of each varied greatly from cell to cell, with Itransient contributing from 14 to 90 % of the total outward current. Inactivation of Itransient was rapid (τ≈ 2–3 ms) and occurred within the physiological range of membrane potentials (V1/2=−63 mV). Recovery from inactivation was also rapid (τ≈ 10 ms).Suppression of both Itransient and Isteady by depolarizations that approached the Ca2+ equilibrium potential and by treatments that blocked Ca2+ influx (application Ca2+-free saline or Cd2+), suggest both are Ca2+ dependent. Both were blocked by iberiotoxin, a specific blocker of large-conductance KCa channels (BK), but not by apamin, a specific blocker of small-conductance KCa channels.Ensemble-variance analysis showed that Itransient and Isteady flow through two distinct populations of channels, both of which have a large single-channel conductance (∼100 pS in non-symmetrical conditions). Together, these data indicate that both Itransient and Isteady are carried through BK channels, one of which undergoes rapid inactivation while the other does not.Inactivation of Itransient could be removed by extracellular papain and could later be restored by intracellular application of the ‘ball’ domain of the auxiliary subunit (β2) thought to mediate BK channel inactivation in rat chromaffin cells. We hypothesize that Itransient results from the association of a similar β subunit with some of the BK channels and that papain removes inactivation by cleaving extracellular sites required for this association. PMID:11579156

  3. Mouse SGLT3a generates proton-activated currents but does not transport sugar.

    PubMed

    Barcelona, Stephanie; Menegaz, Danusa; Díez-Sampedro, Ana

    2012-04-15

    Sodium-glucose cotransporters (SGLTs) are secondary active transporters belonging to the SLC5 gene family. SGLT1, a well-characterized member of this family, electrogenically transports glucose and galactose. Human SGLT3 (hSGLT3), despite sharing a high amino acid identity with human SGLT1 (hSGLT1), does not transport sugar, although functions as a sugar sensor. In contrast to humans, two different genes in mice and rats code for two different SGLT3 proteins, SGLT3a and SGLT3b. We previously cloned and characterized mouse SGLT3b (mSGLT3b) and showed that, while it does transport sugar like SGLT1, it likely functions as a physiological sugar sensor like hSGLT3. In this study, we cloned mouse SGLT3a (mSGLT3a) and characterized it by expressing it in Xenopus laevis oocytes and performing electrophysiology and sugar transport assays. mSGLT3a did not transport sugar, and sugars did not induce currents at pH 7.4, though acidic pH induced inward currents that increased in the presence of sugar. Moreover, mutation of residue 457 from glutamate to glutamine resulted in a Na(+)-dependent transport of sugar that was inhibited by phlorizin. To corroborate our results in oocytes, we expressed and characterized mSGLT3a in mammalian cells and confirmed our findings. In addition, we cloned, expressed, and characterized rat SGLT3a in oocytes and found characteristics similar to mSGLT3a. In summary, acidic pH induces currents in mSGLT3a, and sugar-induced currents are increased at acidic pH, but wild-type SGLT3a does not transport sugar.

  4. Persistence and storage of activity patterns in spiking recurrent cortical networks: modulation of sigmoid signals by after-hyperpolarization currents and acetylcholine

    PubMed Central

    Palma, Jesse; Grossberg, Stephen; Versace, Massimiliano

    2012-01-01

    Many cortical networks contain recurrent architectures that transform input patterns before storing them in short-term memory (STM). Theorems in the 1970's showed how feedback signal functions in rate-based recurrent on-center off-surround networks control this process. A sigmoid signal function induces a quenching threshold below which inputs are suppressed as noise and above which they are contrast-enhanced before pattern storage. This article describes how changes in feedback signaling, neuromodulation, and recurrent connectivity may alter pattern processing in recurrent on-center off-surround networks of spiking neurons. In spiking neurons, fast, medium, and slow after-hyperpolarization (AHP) currents control sigmoid signal threshold and slope. Modulation of AHP currents by acetylcholine (ACh) can change sigmoid shape and, with it, network dynamics. For example, decreasing signal function threshold and increasing slope can lengthen the persistence of a partially contrast-enhanced pattern, increase the number of active cells stored in STM, or, if connectivity is distance-dependent, cause cell activities to cluster. These results clarify how cholinergic modulation by the basal forebrain may alter the vigilance of category learning circuits, and thus their sensitivity to predictive mismatches, thereby controlling whether learned categories code concrete or abstract features, as predicted by Adaptive Resonance Theory. The analysis includes global, distance-dependent, and interneuron-mediated circuits. With an appropriate degree of recurrent excitation and inhibition, spiking networks maintain a partially contrast-enhanced pattern for 800 ms or longer after stimuli offset, then resolve to no stored pattern, or to winner-take-all (WTA) stored patterns with one or multiple winners. Strengthening inhibition prolongs a partially contrast-enhanced pattern by slowing the transition to stability, while strengthening excitation causes more winners when the network

  5. The Kepler Input Catalog

    NASA Astrophysics Data System (ADS)

    Latham, D. W.; Brown, T. M.; Monet, D. G.; Everett, M.; Esquerdo, G. A.; Hergenrother, C. W.

    2005-12-01

    The Kepler mission will monitor 170,000 planet-search targets during the first year, and 100,000 after that. The Kepler Input Catalog (KIC) will be used to select optimum targets for the search for habitable earth-like transiting planets. The KIC will include all known catalogued stars in an area of about 177 square degrees centered at RA 19:22:40 and Dec +44:30 (l=76.3 and b=+13.5). 2MASS photometry will be supplemented with new ground-based photometry obtained in the SDSS g, r, i, and z bands plus a custom filter centered on the Mg b lines, using KeplerCam on the 48-inch telescope at the Whipple Observatory on Mount Hopkins, Arizona. The photometry will be used to estimate stellar characteristics for all stars brighter than K 14.5 mag. The KIC will include effective temperature, surface gravity, metallicity, reddening, distance, and radius estimates for these stars. The CCD images are pipeline processed to produce instrumental magnitudes at PSI. The photometry is then archived and transformed to the SDSS system at HAO, where the astrophysical analysis of the stellar characteristics is carried out. The results are then merged with catalogued data at the USNOFS to produce the KIC. High dispersion spectroscopy with Hectochelle on the MMT will be used to supplement the information for many of the most interesting targets. The KIC will be released before launch for use by the astronomical community and will be available for queries over the internet. Support from the Kepler mission is gratefully acknowledged.

  6. Asynchronous activation of calcium and potassium currents by isoproterenol in canine ventricular myocytes.

    PubMed

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

    2014-05-01

    Adrenergic activation of L-type Ca(2+) and various K(+) currents is a crucial mechanism of cardiac adaptation; however, it may carry a substantial proarrhythmic risk as well. The aim of the present work was to study the timing of activation of Ca(2+) and K(+) currents in isolated canine ventricular cells in response to exposure to isoproterenol (ISO). Whole cell configuration of the patch-clamp technique in either conventional voltage clamp or action potential voltage clamp modes were used to monitor I(Ca), I(Ks), and I(Kr), while action potentials were recorded using sharp microelectrodes. ISO (10 nM) elevated the plateau potential and shortened action potential duration (APD) in subepicardial and mid-myocardial cells, which effects were associated with multifold enhancement of I(Ca) and I(Ks) and moderate stimulation of I(Kr). The ISO-induced plateau shift and I(Ca) increase developed faster than the shortening of APD and stimulation of I(Ks) and I(Kr). Blockade of β1-adrenoceptors (using 300 nM CGP-20712A) converted the ISO-induced shortening of APD to lengthening, decreased its latency, and reduced the plateau shift. In contrast, blockade of β2-adrenoceptors (by 50 nM ICI 118,551) augmented the APD-shortening effect and increased the latency of plateau shift without altering its magnitude. All effects of ISO were prevented by simultaneous blockade of both receptor types. Inhibition of phosphodiesterases decreased the differences observed in the turn on of the ISO-induced plateau shift and APD shortening. ISO-induced activation of I(Ca) is turned on faster than the stimulation of I(Ks) and I(Kr) in canine ventricular cells due to the involvement of different adrenergic pathways and compartmentalization.

  7. Diethylcarbamazine Increases Activation of Voltage-Activated Potassium (SLO-1) Currents in Ascaris suum and Potentiates Effects of Emodepside

    PubMed Central

    Buxton, Samuel K.; Robertson, Alan P.; Martin, Richard J.

    2014-01-01

    Diethylcarbamazine is a drug that is used for the treatment of filariasis in humans and animals; it also has effects on intestinal nematodes, but its mechanism of action remains unclear. Emodepside is a resistance-busting anthelmintic approved for treating intestinal parasitic nematodes in animals. The novel mode of action and resistance-breaking properties of emodepside has led to its use against intestinal nematodes of animals, and as a candidate drug for treating filarial parasites. We have previously demonstrated effects of emodepside on SLO-1 K+-like currents in Ascaris suum. Here, we demonstrate that diethylcarbamazine, which has been proposed to work through host mediated effects, has direct effects on a nematode parasite, Ascaris suum. It increases activation of SLO-1 K+ currents and potentiates effects of emodepside. Our results suggest consideration of the combination of emodepside and diethylcarbamazine for therapy, which is predicted to be synergistic. The mode of action of diethylcarbamazine may involve effects on parasite signaling pathways (including nitric oxide) as well as effects mediated by host inflammatory mediators. PMID:25411836

  8. Diethylcarbamazine increases activation of voltage-activated potassium (SLO-1) currents in Ascaris suum and potentiates effects of emodepside.

    PubMed

    Buxton, Samuel K; Robertson, Alan P; Martin, Richard J

    2014-01-01

    Diethylcarbamazine is a drug that is used for the treatment of filariasis in humans and animals; it also has effects on intestinal nematodes, but its mechanism of action remains unclear. Emodepside is a resistance-busting anthelmintic approved for treating intestinal parasitic nematodes in animals. The novel mode of action and resistance-breaking properties of emodepside has led to its use against intestinal nematodes of animals, and as a candidate drug for treating filarial parasites. We have previously demonstrated effects of emodepside on SLO-1 K+-like currents in Ascaris suum. Here, we demonstrate that diethylcarbamazine, which has been proposed to work through host mediated effects, has direct effects on a nematode parasite, Ascaris suum. It increases activation of SLO-1 K+ currents and potentiates effects of emodepside. Our results suggest consideration of the combination of emodepside and diethylcarbamazine for therapy, which is predicted to be synergistic. The mode of action of diethylcarbamazine may involve effects on parasite signaling pathways (including nitric oxide) as well as effects mediated by host inflammatory mediators.

  9. A biophysical model examining the role of low-voltage-activated potassium currents in shaping the responses of vestibular ganglion neurons.

    PubMed

    Hight, Ariel E; Kalluri, Radha

    2016-08-01

    The vestibular nerve is characterized by two broad groups of neurons that differ in the timing of their interspike intervals; some fire at highly regular intervals, whereas others fire at highly irregular intervals. Heterogeneity in ion channel properties has been proposed as shaping these firing patterns (Highstein SM, Politoff AL. Brain Res 150: 182-187, 1978; Smith CE, Goldberg JM. Biol Cybern 54: 41-51, 1986). Kalluri et al. (J Neurophysiol 104: 2034-2051, 2010) proposed that regularity is controlled by the density of low-voltage-activated potassium currents (IKL). To examine the impact of IKL on spike timing regularity, we implemented a single-compartment model with three conductances known to be present in the vestibular ganglion: transient sodium (gNa), low-voltage-activated potassium (gKL), and high-voltage-activated potassium (gKH). Consistent with in vitro observations, removing gKL depolarized resting potential, increased input resistance and membrane time constant, and converted current step-evoked firing patterns from transient (1 spike at current onset) to sustained (many spikes). Modeled neurons were driven with a time-varying synaptic conductance that captured the random arrival times and amplitudes of glutamate-driven synaptic events. In the presence of gKL, spiking occurred only in response to large events with fast onsets. Models without gKL exhibited greater integration by responding to the superposition of rapidly arriving events. Three synaptic conductance were modeled, each with different kinetics to represent a variety of different synaptic processes. In response to all three types of synaptic conductance, models containing gKL produced spike trains with irregular interspike intervals. Only models lacking gKL when driven by rapidly arriving small excitatory postsynaptic currents were capable of generating regular spiking.

  10. SAS2H input for computing core activities of 4.5, 5.0, and 5.5 weight % {sup 235}U fuel for Sequoyah Nuclear Plant

    SciTech Connect

    Hermann, O.W.

    1994-08-01

    Sequoyah Nuclear Plant core activities at initial fuel enrichments of 4.5, 5.0, and 5.5 wt% {sup 235}U, required in nuclear safety evaluations, were computed by the SAS2H analysis sequence and the ORIGEN-S code within the SCALE-4.2 code system.

  11. ASYMMETRIC SUNSPOT ACTIVITY AND THE SOUTHWARD DISPLACEMENT OF THE HELIOSPHERIC CURRENT SHEET

    SciTech Connect

    Wang, Y.-M.; Robbrecht, E. E-mail: eva.robbrecht@oma.be

    2011-08-01

    Observations of the interplanetary magnetic field (IMF) have suggested a statistical tendency for the heliospheric current sheet (HCS) to be shifted a few degrees southward of the heliographic equator during the period 1965-2010, particularly in the years near sunspot minimum. Using potential-field source-surface extrapolations and photospheric flux-transport simulations, we demonstrate that this southward displacement follows from Joy's law and the observed hemispheric asymmetry in the sunspot numbers, with activity being stronger in the southern (northern) hemisphere during the declining (rising) phase of cycles 20-23. The hemispheric asymmetry gives rise to an axisymmetric quadrupole field, whose equatorial zone has the sign of the leading-polarity flux in the dominant hemisphere; during the last four cycles, the polarity of the IMF around the equator thus tended to match that of the north polar field both before and after polar field reversal. However, large fluctuations are introduced by the nonaxisymmetric field components, which depend on the longitudinal distribution of sunspot activity in either hemisphere. Consistent with this model, the HCS showed an average northward displacement during cycle 19, when the 'usual' alternation was reversed and the northern hemisphere became far more active than the southern hemisphere during the declining phase of the cycle. We propose a new method for determining the north-south displacement of the HCS from coronal streamer observations.

  12. Nutrition and Physical Activity Strategies for Cancer Prevention in Current National Comprehensive Cancer Control Program Plans.

    PubMed

    Puckett, Mary; Neri, Antonio; Underwood, J Michael; Stewart, Sherri L

    2016-10-01

    Obesity, diet and physical inactivity are risk factors for some cancers. Grantees of the National Comprehensive Cancer Control Program (NCCCP) in US states, tribes, and territories develop plans to coordinate funding and activities for cancer prevention and control. Including information and goals related to nutrition and physical activity (NPA) is a key opportunity for primary cancer prevention, but it is currently unclear to what extent NCCCP plans address these issues. We reviewed 69 NCCCP plans and searched for terms related to NPA. Plans were coded as (1) knowledge of NPA and cancer link; (2) goals to improve NPA behaviors; and (3) strategies to increase healthy NPA activities, environments, or systems changes. NPA content was consistently included in all cancer plans examined across all years. Only 4 (6 %) outlined only the relationship between NPA and cancer without goals or strategies. Fifty-nine plans (89 %) contained goals or strategies related to NPA, with 53 (82 %) including both. However, numbers of goals, strategies, and detail provided varied widely. All programs recognized the importance of NPA in cancer prevention. Most plans included NPA goals and strategies. Increasing the presence of NPA strategies that can be modified or adapted appropriately locally could help with more widespread implementation and measurement of NPA interventions.

  13. Effect of Monophasic Pulsed Current on Heel Pain and Functional Activities caused by Plantar Fasciitis

    PubMed Central

    Alotaibi, Abdullah K.; Petrofsky, Jerrold S.; Daher, Noha S.; Lohman, Everett; Laymon, Michael; Syed, Hasan M.

    2015-01-01

    Background Plantar fasciitis (PF) is a soft tissue disorder considered to be one of the most common causes of inferior heel pain. The aim of this study was to investigate the effect of monophasic pulsed current (MPC) and MPC coupled with plantar fascia-specific stretching exercises (SE) on the treatment of PF. Material/Methods Forty-four participants (22 women and 22 men, with a mean age of 49 years) diagnosed with PF were randomly assigned to receive MPC (n=22) or MPC coupled with plantar fascia-specific SE (n=22). Prior to and after 4 weeks of treatment, participants underwent baseline evaluation; heel pain was evaluated using a visual analogue scale (VAS), heel tenderness threshold was quantified using a handheld pressure algometer (PA), and functional activities level was assessed using the Activities of Daily Living subscale of the Foot and Ankle Ability Measure (ADL/FAAM). Results Heel pain scores showed a significant reduction in both groups compared to baseline VAS scores (P<0.001). Heel tenderness improved significantly in both groups compared with baseline PA scores (P<0.001). Functional activity level improved significantly in both groups compared with baseline (ADL/FAAM) scores (P<0.001). However, no significant differences existed between the 2 treatment groups in all post-intervention outcome measures. Conclusions This trial showed that MPC is useful in treating inferior heel symptoms caused by PF. PMID:25791231

  14. Depression of activities of dorsal horn convergent neurones by propriospinal mechanisms triggered by noxious inputs; comparison with diffuse noxious inhibitory controls (DNIC).

    PubMed

    Cadden, S W; Villanueva, L; Chitour, D; Le Bars, D

    1983-09-19

    The ability of heterotopic noxious stimuli to inhibit the activity of dorsal horn convergent neurones was investigated in both intact anesthetized, and spinal unanesthetized rats. Forty-four convergent neurones in lumbar dorsal horn were recognized by their ability to respond to both noxious and non-noxious natural stimuli and by their characteristic responses corresponding to A- and C-fibre activity following electrical stimulation of their cutaneous excitatory receptive fields on the ipsilateral hindpaw. The application of a sustained pinch to the excitatory receptive field resulted in an initial phasic activation of the neurone, which adapted to a stable tonic level of activity (mean 31.8 +/- 2.2 spikes/s). The levels of activity produced in this fashion were not appreciably different between the two types of preparation. In the intact anesthetized rat, the tonic activity produced by the sustained pinch could be strongly depressed by noxious conditioning stimuli applied to various parts of the body for all 10 neurones studied: heating the tail or pinching the contralateral hindpaw, the tail or a forepaw during 30 s each resulted in comparable inhibitions which had mean values in the order of 80% and which were always marked by post-effects lasting for upwards of 30 s. These inhibitory effects have been called Diffuse Noxious Inhibitory Controls (DNIC). In the spinal unanesthetized rat, the tonic activity was depressed to some extent by the same conditioning stimuli, for only 16/34 neurones studied. By comparison with the intact animals these inhibitions were weak, adapted to base-line levels within 30 s and were more marked for conditioning stimuli applied to structures proximal (tail, contralateral hindpaw) to the excitatory receptive field than for stimuli applied more distally (forepaws). The differences between the inhibitions found in the intact and spinal preparations were subsequently confirmed in a series of experiments in which single convergent

  15. On the Modeling of Electrical Effects Experienced by Space Explorers During Extra Vehicular Activities: Intracorporal Currents, Resistances, and Electric Fields

    NASA Technical Reports Server (NTRS)

    Cela, Carlos J.; Loizos, Kyle; Lazzi, Gianluca; Hamilton, Douglas; Lee, Raphael C.

    2011-01-01

    Recent research has shown that space explorers engaged in Extra Vehicular Activities (EVAs) may be exposed, under certain conditions, to undesired electrical currents. This work focuses on determining whether these undesired induced electrical currents could be responsible for involuntary neuromuscular activity in the subjects, possibly caused by either large diameter peripheral nerve activation or reflex activity from cutaneous afferent stimulation. An efficient multiresolution variant of the admittance method along with a millimeter-resolution model of a male human body were used to calculate induced electric fields, resistance between contact electrodes used to simulate the potential exposure condition, and currents induced in the human body model. Results show that, under realistic exposure conditions using a 15V source, current density magnitudes and total current injected are well above previously reported startle reaction thresholds. This indicates that, under the considered conditions, the subjects could experience involuntary motor response.

  16. Serial Input Output

    SciTech Connect

    Waite, Anthony; /SLAC

    2011-09-07

    Serial Input/Output (SIO) is designed to be a long term storage format of a sophistication somewhere between simple ASCII files and the techniques provided by inter alia Objectivity and Root. The former tend to be low density, information lossy (floating point numbers lose precision) and inflexible. The latter require abstract descriptions of the data with all that that implies in terms of extra complexity. The basic building blocks of SIO are streams, records and blocks. Streams provide the connections between the program and files. The user can define an arbitrary list of streams as required. A given stream must be opened for either reading or writing. SIO does not support read/write streams. If a stream is closed during the execution of a program, it can be reopened in either read or write mode to the same or a different file. Records represent a coherent grouping of data. Records consist of a collection of blocks (see next paragraph). The user can define a variety of records (headers, events, error logs, etc.) and request that any of them be written to any stream. When SIO reads a file, it first decodes the record name and if that record has been defined and unpacking has been requested for it, SIO proceeds to unpack the blocks. Blocks are user provided objects which do the real work of reading/writing the data. The user is responsible for writing the code for these blocks and for identifying these blocks to SIO at run time. To write a collection of blocks, the user must first connect them to a record. The record can then be written to a stream as described above. Note that the same block can be connected to many different records. When SIO reads a record, it scans through the blocks written and calls the corresponding block object (if it has been defined) to decode it. Undefined blocks are skipped. Each of these categories (streams, records and blocks) have some characteristics in common. Every stream, record and block has a name with the condition that each

  17. SDR Input Power Estimation Algorithms

    NASA Technical Reports Server (NTRS)

    Nappier, Jennifer M.; Briones, Janette C.

    2013-01-01

    The General Dynamics (GD) S-Band software defined radio (SDR) in the Space Communications and Navigation (SCAN) Testbed on the International Space Station (ISS) provides experimenters an opportunity to develop and demonstrate experimental waveforms in space. The SDR has an analog and a digital automatic gain control (AGC) and the response of the AGCs to changes in SDR input power and temperature was characterized prior to the launch and installation of the SCAN Testbed on the ISS. The AGCs were used to estimate the SDR input power and SNR of the received signal and the characterization results showed a nonlinear response to SDR input power and temperature. In order to estimate the SDR input from the AGCs, three algorithms were developed and implemented on the ground software of the SCAN Testbed. The algorithms include a linear straight line estimator, which used the digital AGC and the temperature to estimate the SDR input power over a narrower section of the SDR input power range. There is a linear adaptive filter algorithm that uses both AGCs and the temperature to estimate the SDR input power over a wide input power range. Finally, an algorithm that uses neural networks was designed to estimate the input power over a wide range. This paper describes the algorithms in detail and their associated performance in estimating the SDR input power.

  18. Optogenetic Activation of Accessory Olfactory Bulb Input to the Forebrain Differentially Modulates Investigation of Opposite versus Same-Sex Urinary Chemosignals and Stimulates Mating in Male Mice.

    PubMed

    Kunkhyen, Tenzin; McCarthy, Elizabeth A; Korzan, Wayne J; Doctor, Danielle; Han, Xue; Baum, Michael J; Cherry, James A

    2017-01-01

    Surgical or genetic disruption of vomeronasal organ (VNO)-accessory olfactory bulb (AOB) function previously eliminated the ability of male mice to processes pheromones that elicit territorial behavior and aggression. By contrast, neither disruption significantly affected mating behaviors, although VNO lesions reduced males' investigation of nonvolatile female pheromones. We explored the contribution of VNO-AOB pheromonal processing to male courtship using optogenetic activation of AOB projections to the forebrain. Protocadherin-Cre male transgenic mice received bilateral AOB infections with channelrhodopsin2 (ChR2) viral vectors, and an optical fiber was implanted above the AOB. In olfactory choice tests, males preferred estrous female urine (EFU) over water; however, this preference was eliminated when diluted (5%) EFU was substituted for 100% EFU. Optogenetic AOB activation concurrent with nasal contact significantly augmented males' investigation compared to 5% EFU alone. Conversely, concurrent optogenetic AOB activation significantly reduced males' nasal investigation of diluted urine from gonadally intact males (5% IMU) compared to 5% IMU alone. These divergent effects of AOB optogenetic activation were lost when males were prevented from making direct nasal contact. Optogenetic AOB stimulation also failed to augment males' nasal investigation of deionized water or of food odors. Finally, during mating tests, optogenetic AOB stimulation delivered for 30 s when the male was in physical contact with an estrous female significantly facilitated the occurrence of penile intromission. Our results suggest that VNO-AOB signaling differentially modifies males' motivation to seek out female vs male urinary pheromones while augmenting males' sexual arousal leading to intromission and improved reproductive performance.

  19. Optogenetic Activation of Accessory Olfactory Bulb Input to the Forebrain Differentially Modulates Investigation of Opposite versus Same-Sex Urinary Chemosignals and Stimulates Mating in Male Mice

    PubMed Central

    McCarthy, Elizabeth A.; Korzan, Wayne J.; Doctor, Danielle; Han, Xue; Baum, Michael J.

    2017-01-01

    Abstract Surgical or genetic disruption of vomeronasal organ (VNO)-accessory olfactory bulb (AOB) function previously eliminated the ability of male mice to processes pheromones that elicit territorial behavior and aggression. By contrast, neither disruption significantly affected mating behaviors, although VNO lesions reduced males’ investigation of nonvolatile female pheromones. We explored the contribution of VNO-AOB pheromonal processing to male courtship using optogenetic activation of AOB projections to the forebrain. Protocadherin-Cre male transgenic mice received bilateral AOB infections with channelrhodopsin2 (ChR2) viral vectors, and an optical fiber was implanted above the AOB. In olfactory choice tests, males preferred estrous female urine (EFU) over water; however, this preference was eliminated when diluted (5%) EFU was substituted for 100% EFU. Optogenetic AOB activation concurrent with nasal contact significantly augmented males’ investigation compared to 5% EFU alone. Conversely, concurrent optogenetic AOB activation significantly reduced males’ nasal investigation of diluted urine from gonadally intact males (5% IMU) compared to 5% IMU alone. These divergent effects of AOB optogenetic activation were lost when males were prevented from making direct nasal contact. Optogenetic AOB stimulation also failed to augment males’ nasal investigation of deionized water or of food odors. Finally, during mating tests, optogenetic AOB stimulation delivered for 30 s when the male was in physical contact with an estrous female significantly facilitated the occurrence of penile intromission. Our results suggest that VNO-AOB signaling differentially modifies males’ motivation to seek out female vs male urinary pheromones while augmenting males’ sexual arousal leading to intromission and improved reproductive performance. PMID:28374006

  20. Current environmental, health, safety, and socioeconomic research activities related to oil shale: draft

    SciTech Connect

    Not Available

    1980-09-01

    This document was prepared for DOE Resource Applications. It provides a compilation of information on current environmental, health, safety and socioeconomic research activities related to oil shale. The information is the most recent available through August 29, 1980. Included are the following: (1) project title; (2) adminstering agency; (3) contractor; (4) project status; (5) funding level; (6) project schedule; (7) deliverable; and (8) key personnel. The data contained in these reports can be used in environmental impact analyses relating oil shale to various incentives given in the Alternative Fuels Bill. The information provided was obtained from computer search printouts, review of respective agency documents and communication with agency personnel. A complete list of references is provided. The sponsoring organizations include the Department of Energy, the Environmental Protection Agency, the Department of Agriculture, and the Department of Interior.

  1. Vaccines, adjuvants and dendritic cell activatorsCurrent Status and Future Challenges

    PubMed Central

    Obeid, Joseph M.; Hu, Yinin; Slingluff, Craig L.

    2015-01-01

    Cancer vaccines offer a low-toxicity approach to induce anticancer immune responses. They have shown promise for clinical benefit with one cancer vaccine approved in the U.S. for advanced prostate cancer. As other immune therapies are now clearly effective for treatment of advanced cancers of many histologies, there is renewed enthusiasm for optimizing cancer vaccines for use to prevent recurrence in early stage cancers and/or to combine with other immune therapies for therapy of advanced cancers. Future advancements in vaccine therapy will involve the identification and selection of effective antigen formulations, optimization of adjuvants, dendritic cell activation, and combination therapies. In this summary we present the current practice, the broad collection of challenges, and the promising future directions of vaccine therapy for cancer. PMID:26320060

  2. Autowaves in an active two-wire line with exponential current-voltage characteristics

    SciTech Connect

    Zhuravlev, V. M.

    2006-03-15

    Nonlinear wave processes in two-wire lines containing an active element with an exponential current-voltage characteristic (CVC) similar to that of a p-n junction are investigated. These lines are models of systems that are encountered in various physical and biological applications, such as biological membranes and semiconductor devices. It is shown that such systems may operate in different modes each of which has different dispersion and dissipation properties and, as a consequence, is described by autowave processes of different types. The behavior of a system in all basic modes is analyzed. For each mode, exact solutions to relevant equations are found and their differential conservation laws and intrinsic symmetries are investigated. One of common properties of such equations is the presence of a special superposition principle that describes the discrete structure of excitations in a line that consist of individual elementary excitations. It is shown that autopulses may be generated in such systems.

  3. Current research activities and installation status of the X-ray imaging crystal spectrometer for KSTAR

    NASA Astrophysics Data System (ADS)

    Lee, S. G.; Bak, J. G.; Nam, U. W.; Moon, M. K.; Cheon, J. K.; Bitter, M.; Hill, K.

    2008-11-01

    An X-ray imaging crystal spectrometer (XICS) for KSTAR utilizing a four-segmented position-sensitive two dimensional (2D) multi-wire proportional counter and time-to-digital converter (TDC) based delay-line readout data acquisition system has been fabricated. The XICS provides spatially and temporally resolved measurements of the ion and electron temperatures, toroidal rotation velocity, impurity charge-state distributions, and ionization equilibrium. The four-segmented 2D detector with supporting electronics successfully demonstrated to improve the photon count-rate capability of the XICS system and a position resolution of the detector showed about 0.35 mm. A spectral resolution of the fabricated spectrometer has been measured using an X-ray tube before installation in the KSTAR tokamak. The current research activities and installation status of the spectrometer will be presented.

  4. 78 FR 69134 - Agency Information Collection Activities; Submission for OMB Review; Comment Request; Current...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-11-18

    ...; Current Population Survey--Displaced Worker, Job Tenure, and Occupational Mobility Supplement ACTION...) sponsored information collection request (ICR) titled, ``Current Population Survey--Displaced Worker, Job... approved ] information collection. The BLS conducts the Current Population Survey Displaced Worker,...

  5. 75 FR 73101 - Agency Information Collection Activities; Proposed Collection; Comment Request; Current Good...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-29

    ... Collection; Comment Request; Current Good Manufacturing Practice Regulations for Medicated Feeds AGENCY: Food... appropriate, and other forms of information technology. Current Good Manufacturing Practice Regulations for... current good manufacturing practice (cGMP) regulations for drugs, including medicated feeds....

  6. 77 FR 4366 - Agency Information Collection Activities; Submission for OMB Review; Comment Request; Current...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-27

    ...; Current Population Survey Disability Supplement ACTION: Notice. SUMMARY: The Department of Labor (DOL) is... titled, ``Current Population Survey Disability Supplement,'' to the Office of Management and Budget (OMB..._PRA_PUBLIC@dol.gov . SUPPLEMENTARY INFORMATION: The Current Population Survey (CPS)...

  7. Transcranial Direct Current Stimulation Modulates Cortical Neuronal Activity in Alzheimer's Disease.

    PubMed

    Marceglia, Sara; Mrakic-Sposta, Simona; Rosa, Manuela; Ferrucci, Roberta; Mameli, Francesca; Vergari, Maurizio; Arlotti, Mattia; Ruggiero, Fabiana; Scarpini, Elio; Galimberti, Daniela; Barbieri, Sergio; Priori, Alberto

    2016-01-01

    Quantitative electroencephalography (qEEG) showed that Alzheimer's disease (AD) is characterized by increased theta power, decreased alpha and beta power, and decreased coherence in the alpha and theta band in posterior regions. These abnormalities are thought to be associated with functional disconnections among cortical areas, death of cortical neurons, axonal pathology, and cholinergic deficits. Since transcranial Direct Current Stimulation (tDCS) over the temporo-parietal area is thought to have beneficial effects in patients with AD, in this study we aimed to investigate whether tDCS benefits are related to tDCS-induced changes in cortical activity, as represented by qEEG. A weak anodal current (1.5 mA, 15 min) was delivered bilaterally over the temporal-parietal lobe to seven subjects with probable AD (Mini-Mental State Examination, MMSE score >20). EEG (21 electrodes, 10-20 international system) was recorded for 5 min with eyes closed before (baseline, t0) and 30 min after anodal and cathodal tDCS ended (t1). At the same time points, patients performed a Word Recognition Task (WRT) to assess working memory functions. The spectral power and the inter- and intra-hemispheric EEG coherence in different frequency bands (e.g., low frequencies, including delta and theta; high frequencies, including alpha and beta) were calculated for each subject at t0 and t1. tDCS-induced changes in EEG neurophysiological markers were correlated with the performance of patients at the WRT. At baseline, qEEG features in AD patients confirmed that the decreased high frequency power was correlated with lower MMSE. After anodal tDCS, we observed an increase in the high-frequency power in the temporo-parietal area and an increase in the temporo-parieto-occipital coherence that correlated with the improvement at the WRT. In addition, cathodal tDCS produced a non-specific effect of decreased theta power all over the scalp that was not correlated with the clinical observation at the WRT

  8. Transcranial Direct Current Stimulation Modulates Cortical Neuronal Activity in Alzheimer's Disease

    PubMed Central

    Marceglia, Sara; Mrakic-Sposta, Simona; Rosa, Manuela; Ferrucci, Roberta; Mameli, Francesca; Vergari, Maurizio; Arlotti, Mattia; Ruggiero, Fabiana; Scarpini, Elio; Galimberti, Daniela; Barbieri, Sergio; Priori, Alberto

    2016-01-01

    Quantitative electroencephalography (qEEG) showed that Alzheimer's disease (AD) is characterized by increased theta power, decreased alpha and beta power, and decreased coherence in the alpha and theta band in posterior regions. These abnormalities are thought to be associated with functional disconnections among cortical areas, death of cortical neurons, axonal pathology, and cholinergic deficits. Since transcranial Direct Current Stimulation (tDCS) over the temporo-parietal area is thought to have beneficial effects in patients with AD, in this study we aimed to investigate whether tDCS benefits are related to tDCS-induced changes in cortical activity, as represented by qEEG. A weak anodal current (1.5 mA, 15 min) was delivered bilaterally over the temporal-parietal lobe to seven subjects with probable AD (Mini-Mental State Examination, MMSE score >20). EEG (21 electrodes, 10–20 international system) was recorded for 5 min with eyes closed before (baseline, t0) and 30 min after anodal and cathodal tDCS ended (t1). At the same time points, patients performed a Word Recognition Task (WRT) to assess working memory functions. The spectral power and the inter- and intra-hemispheric EEG coherence in different frequency bands (e.g., low frequencies, including delta and theta; high frequencies, including alpha and beta) were calculated for each subject at t0 and t1. tDCS-induced changes in EEG neurophysiological markers were correlated with the performance of patients at the WRT. At baseline, qEEG features in AD patients confirmed that the decreased high frequency power was correlated with lower MMSE. After anodal tDCS, we observed an increase in the high-frequency power in the temporo-parietal area and an increase in the temporo-parieto-occipital coherence that correlated with the improvement at the WRT. In addition, cathodal tDCS produced a non-specific effect of decreased theta power all over the scalp that was not correlated with the clinical observation at the WRT

  9. The enhanced cortical activation induced by transcranial direct current stimulation during hand movements.

    PubMed

    Kwon, Yong Hyun; Jang, Sung Ho

    2011-04-01

    The aim of this study is to evaluate whether tDCS applied on the primary motor cortex (M1) in company with hand movements could enhance cortical activation, using functional MRI (fMRI). Twelve right-handed normal subjects were recruited. Real tDCS and sham tDCS with hand movements were applied during fMRI scanning. Subjects performed grasp-release hand movements at a metronome-guided frequency of 1Hz, while direct current with 1.0mA was delivered to the primary motor cortex. The averaged cortical map and the intensity index were compared between real tDCS with hand movements and sham tDCS with hand movements. Our result showed that cortical activation on the primary sensorimotor cortex was observed under both of two conditions; real tDCS with hand movements and sham tDCS with hand movements. Voxel count and peak intensity were 365.10±227.23 and 5.66±1.97, respectively, in the left primary sensorimotor cortex during real tDCS with right hand movements; in contrast, those were 182.20±117.88 and 4.12±0.88, respectively, during sham tDCS with right hand movements. Significant differences in voxel count and peak intensity were observed between real tDCS and sham tDCS (p<0.05). We found that anodal tDCS application during motor task enhanced cortical activation on the underlying targeted motor cortex, compared with the same motor task without tDCS. Therefore, it seemed that tDCS induced more cortical activity and modulated brain function when concurrently applied with motor task.

  10. The PRISM data/model co-operative: current modelling activities, future plans and data requirements

    NASA Astrophysics Data System (ADS)

    Haywood, Alan

    2010-05-01

    Here we review current activities and future model and data requirements associated with the palaeoclimate modelling arm of the PRISM data/model co-operative. The talk will begin with a description of modelling focussed on understanding the behaviour of climate phenomena that are responsible for generating significant regional decadal and sub-decadal climate variability (ENSO and NAO), and the challenges associated with linking such predictions to mid-Piacenzian palaeoenvironmental data. Secondly, we will examine current efforts to understand the role of changing sea-surface temperatures, in relation to other important boundary conditions, in driving global and regional climate/environmental shifts recognised in the proxy data. Thirdly, we will examine initial results from coupled climate and ice sheet modelling examining the response of the Greenland and East Antarctic Ice Sheets to orbital variations and how these predicted changes relate to current estimates of mid-Piacenzian mean sea level and sea level variability. Our future plans centre on (a) the development of the Pliocene Model Intercomparison Project, (b) understanding uncertainty in climate model predictions of mid-Piacenzian climates and (c) moving towards an Earth System Modelling framework for the PRISM interval. With the 4th iteration of the PRISM palaeoenvironmental data set under construction we briefly outline how the demands of modern climate and earth system models will partly shape PRISM4, as well as the new scientific opportunities that will stem from it (e.g. the advent of isotope enabled models, higher resolution boundary conditions, river routing schemes and palaeobathymetry).

  11. Input of UAV, DTM photo-interpretation and SAR interferometry on active tectonics applied on the Southern Coastal Range (SE Taiwan)

    NASA Astrophysics Data System (ADS)

    Deffontaines, Benoit; Chang, Kuo-Jen; Champenois, Johann; Magalhaes, Samuel; Serries, Gregory

    2016-04-01

    Taiwan is an excellent geomorphic laboratory where both extreme climatic events and high active tectonics compete. Moreover many Earth Sciences and Environmental data bases exist nowadays that help to better constrain both structural geology and active deformations. The latter unfortunately is still poorly known in the Cosatal Range of E.Taiwan in terms of geology due to access difficulties, high relief, paucity of roads, tropical vegetation and high climatic events (typhoons and heavy rainfall) and so on. Indirect methods such as photogrammetric survey using UAV's helps a lot to get high resolution topographic DEM and DTM, better than 10cm in planimetry, that helps a lot to get through careful photo-interpretation, a bird's eye view of the geology. Therefore we were able to much update the famous pre-existing geological maps (Wang and Chen, 1993). Moreover, by combining our high resolution topographic results with those of SAR interferometry (database of Champenois et al, EPSL, 2012), we were able to identify, characterise and quantify the differential active features toward the LOS of the Coastal Range (eastern Taiwan). In order to synthetise and to model the deformation of that famous place, we herein constructed more than 500 parallel projected profiles in order to locate, characterize and quantify the active tectonic features and compare them to the topography and the updated photo-interpreted geology (this work). We then were able to reconstruct the structural geometry of the Coastal Range and the Longitudinal Valley in SE Taiwan. Among our results, we reveal and prove : 1. the whole 2cm differential surrection of the Coastal Range ; 2. the differential displacement between both Central and Coastal Ranges ; 3. we explain the location of the Pinantashi river situated within the Lichi melange that correspond to the maximum surrection of the Coastal Range ; 4. we reveal the different units and their relative displacement within the Coastal Range itself ; 5. we

  12. Dopamine and baclofen inhibit the hyperpolarization-activated cation current in rat ventral tegmental neurones.

    PubMed Central

    Jiang, Z G; Pessia, M; North, R A

    1993-01-01

    1. Whole-cell patch-clamp recordings were made from dopamine-containing ventral tegmental area neurones in slices of rat midbrain. An inward current (Ih) was activated by hyperpolarization from -60 mV. 2. Dopamine (30 microM) reduced the amplitude of Ih by 10-30% at potentials from -70 to -120 mV. The effect was concentration dependent, mimicked by the D2 agonist quinpirole, and prevented by the D2 antagonist (-)-sulpiride. Baclofen (0.3-3 microM) also inhibited Ih; this action was antagonized by 2-hydroxysaclofen but not by (-)-sulpiride. The decrease in Ih resulted from a reduction in the maximal current with no change in the voltage dependence. 3. The action of dopamine was unaffected by cadmium (200 microM), forskolin (10 microM), the adenylyl cyclase inhibitor 2',3'-dideoxyadenosine (100 microM), or by intracellular solution containing cyclic AMP (2 mM). 4. Ih was progressively reduced during the first 5-10 min of recording with electrodes containing guanosine 5'-O-(3-thiotriphosphate); after this time, dopamine had no further effect. 5. It is concluded that agonists acting at D2 receptors and GABAB receptors reduce Ih in ventral tegmental neurones. PMID:8392580

  13. Cutaneous retinal activation and neural entrainment in transcranial alternating current stimulation: A systematic review.

    PubMed

    Schutter, Dennis J L G

    2016-10-15

    Transcranial alternating current stimulation (tACS) applies exogenous oscillatory electric field potentials to entrain neural rhythms and is used to investigate brain-function relationships and its potential to enhance perceptual and cognitive performance. However, due to current spread tACS can cause cutaneous activation of the retina and phosphenes. Several lines of evidence suggest that retinal phosphenes are capable of inducing neural entrainment, making the contributions of central and peripheral stimulation to the effects in the brain difficult to disentangle. In this literature review, the importance of this issue is further illustrated by the fact that photic stimulation can have a direct impact on perceptual and cognitive performance. This leaves open the possibility that peripheral photic stimulation can at least in part explain the central effects that are attributed to tACS. The extent to which phosphene perception contributes to the effects of exogenous oscillatory electric fields in the brain and influence perception and cognitive performance needs to be examined to understand the working mechanisms of tACS in neurophysiology and behaviour.

  14. Enhanced Sensitivity to Rapid Input Fluctuations by Nonlinear Threshold Dynamics in Neocortical Pyramidal Neurons.

    PubMed

    Mensi, Skander; Hagens, Olivier; Gerstner, Wulfram; Pozzorini, Christian

    2016-02-01

    The way in which single neurons transform input into output spike trains has fundamental consequences for network coding. Theories and modeling studies based on standard Integrate-and-Fire models implicitly assume that, in response to increasingly strong inputs, neurons modify their coding strategy by progressively reducing their selective sensitivity to rapid input fluctuations. Combining mathematical modeling with in vitro experiments, we demonstrate that, in L5 pyramidal neurons, the firing threshold dynamics adaptively adjust the effective timescale of somatic integration in order to preserve sensitivity to rapid signals over a broad range of input statistics. For that, a new Generalized Integrate-and-Fire model featuring nonlinear firing threshold dynamics and conductance-based adaptation is introduced that outperforms state-of-the-art neuron models in predicting the spiking activity of neurons responding to a variety of in vivo-like fluctuating currents. Our model allows for efficient parameter extraction and can be analytically mapped to a Generalized Linear Model in which both the input filter--describing somatic integration--and the spike-history filter--accounting for spike-frequency adaptation--dynamically adapt to the input statistics, as experimentally observed. Overall, our results provide new insights on the computational role of different biophysical processes known to underlie adaptive coding in single neurons and support previous theoretical findings indicating that the nonlinear dynamics of the firing threshold due to Na+-channel inactivation regulate the sensitivity to rapid input fluctuations.

  15. Enhanced Sensitivity to Rapid Input Fluctuations by Nonlinear Threshold Dynamics in Neocortical Pyramidal Neurons

    PubMed Central

    Mensi, Skander; Hagens, Olivier; Gerstner, Wulfram; Pozzorini, Christian

    2016-01-01

    The way in which single neurons transform input into output spike trains has fundamental consequences for network coding. Theories and modeling studies based on standard Integrate-and-Fire models implicitly assume that, in response to increasingly strong inputs, neurons modify their coding strategy by progressively reducing their selective sensitivity to rapid input fluctuations. Combining mathematical modeling with in vitro experiments, we demonstrate that, in L5 pyramidal neurons, the firing threshold dynamics adaptively adjust the effective timescale of somatic integration in order to preserve sensitivity to rapid signals over a broad range of input statistics. For that, a new Generalized Integrate-and-Fire model featuring nonlinear firing threshold dynamics and conductance-based adaptation is introduced that outperforms state-of-the-art neuron models in predicting the spiking activity of neurons responding to a variety of in vivo-like fluctuating currents. Our model allows for efficient parameter extraction and can be analytically mapped to a Generalized Linear Model in which both the input filter—describing somatic integration—and the spike-history filter—accounting for spike-frequency adaptation—dynamically adapt to the input statistics, as experimentally observed. Overall, our results provide new insights on the computational role of different biophysical processes known to underlie adaptive coding in single neurons and support previous theoretical findings indicating that the nonlinear dynamics of the firing threshold due to Na+-channel inactivation regulate the sensitivity to rapid input fluctuations. PMID:26907675

  16. Evaluation of the pharmacological activity of the major mexiletine metabolites on skeletal muscle sodium currents

    PubMed Central

    De Bellis, M; De Luca, A; Rana, F; Cavalluzzi, M M; Catalano, A; Lentini, G; Franchini, C; Tortorella, V; Conte Camerino, D

    2006-01-01

    Background and purpose: Mexiletine (Mex), an orally effective antiarrhythmic agent used to treat ventricular arrhythmias, has also been found to be effective for myotonia and neuropathic pain. It is extensively metabolized in humans but little information exists about the pharmacodynamic properties of its metabolites. Experimental approach: To determine their contribution to the clinical activity of Mex, p-hydroxy-mexiletine (PHM), hydroxy-methyl-mexiletine (HMM), N-hydroxy-mexiletine (NHM) (phase I reaction products) and N-carbonyloxy β-D-glucuronide (NMG) (phase II reaction product) were tested on sodium currents (INa) of frog skeletal muscle fibres. Sodium currents were elicited with depolarizing pulses from different holding potentials (HP=−140, −100, −70 mV) and stimulation frequencies (0.25, 0.5, 1, 2, 5, 10 Hz) using the vaseline-gap voltage-clamp method. Key results: All the hydroxylated derivatives blocked the sodium channel in a voltage- and use-dependent manner. The PHM, HMM and NHM metabolites were up to 10-fold less effective than the parent compound. However, HMM showed a greater use-dependent behaviour (10 Hz), compared to Mex and the other metabolites. Similar to Mex, these products behaved as inactivating channel blockers. Conjugation with glucuronic acid (NMG) resulted in almost complete abolition of the pharmacological activity of the parent compound. Conclusions and Implications: Thus, although less potent, the phase I metabolites tested demonstrated similar pharmacological behaviour to Mex and might contribute to its clinical profile. PMID:16921388

  17. Fe, O, and C Charge States Associated with Quiescent Versus Active Current Sheets in the Solar Wind

    NASA Technical Reports Server (NTRS)

    Suess, S. T.; Ko, Y.-K.; vonSteiger, R.

    2008-01-01

    Ulysses MAG data were used to locate the heliospheric current sheet in data from 1991 through 2006. The purpose was to characterize typical charge states for Fe, O, and C in the vicinity of the current sheet and provide insight into the physical sources for these charge states in the corona. A study of He/H around the current sheets has led to a clear distinction between quiescent current sheets at times of low solar activity and active current sheets associated with magnetic clouds (and, presumably, ICMES). It has been shown that high ionization state Fe is produced in the corona in current sheets associated with CMEs through spectroscopic observations of the corona and through in situ detection at Ulysses. Here we show that the ionization state of Fe is typically only enhanced around active current sheets while the ionization states of O and C are commonly enhanced around both quiescent and active current sheets. This is consistent with UV coronal spectroscopy, which has shown that reconnection in current sheets behind CMEs leads to high temperatures not typically seen above quiet streamers.

  18. The Effect of Input-Based Instruction Type on the Acquisition of Spanish Accusative Clitics

    ERIC Educational Resources Information Center

    White, Justin

    2015-01-01

    The purpose of this paper is to compare structured input (SI) with other input-based instructional treatments. The input-based instructional types include: input flood (IF), text enhancement (TE), SI activities, and focused input (FI; SI without implicit negative feedback). Participants included 145 adult learners enrolled in an intermediate…

  19. The slow Ca(2+)-activated K+ current, IAHP, in the rat sympathetic neurone.

    PubMed Central

    Sacchi, O; Rossi, M L; Canella, R

    1995-01-01

    1. Adult and intact sympathetic neurones of the rat superior cervical ganglion maintained in vitro at 37 degrees C were analysed using the two-electrode voltage-clamp technique in order to investigate the slow component of the Ca(2+)-dependent K+ current, IAHP. 2. The relationship between the after-hyperpolarization (AHP) conductance, gAHP, and estimated Ca2+ influx resulting from short-duration calcium currents evoked at various voltages proved to be linear over a wide range of injected Ca2+ charge. An inflow of about 1.7 x 10(7) Ca2+ ions was required before significant activation of gAHP occurred. After priming, the gAHP sensitivity was about 0.3 nS pC-1 of Ca2+ inward charge. 3. IAHP was repeatedly measured at different membrane potentials; its amplitude decreased linearly with membrane hyperpolarization and was mostly abolished close to the K+ reversal potential, EK (-93 mV). The monoexponential decay rate of IAHP was a linear function of total Ca2+ entry and was not significantly altered by membrane potential in the -40 to -80 mV range. 4. Voltage-clamp tracings of IAHP could be modelled as a difference between two exponentials with tau on approximately 5 ms and tau off = 50-250 ms. 5. Sympathetic neurones discharged only once at the onset of a long-lasting depolarizing step. If IAHP was selectively blocked by apamin or D-tubocurarine treatments, accommodation was abolished and an unusual repetitive firing appeared. 6. Summation of IAHP was demonstrated under voltage-clamp conditions when the depolarizing steps were repeated sufficiently close to one another. Under current-clamp conditions the threshold depolarizing charge for action potential discharge significantly increased with progressive pulse numbers in the train, suggesting that an opposing conductance was accumulating with repetitive firing. This frequency-dependent spike firing ability was eliminated by pharmacological inhibition of the slow IAHP. 7. The IAHP was significantly activated by a single

  20. TRT, a Vertebrate and Protozoan Tc1-Like Transposon: Current Activity and Horizontal Transfer.

    PubMed

    Zhang, Hua-Hao; Li, Guo-Yin; Xiong, Xiao-Min; Han, Min-Jin; Zhang, Xiao-Gu; Dai, Fang-Yin

    2016-10-05

    We report a Danio rerio transposon named DrTRT, for D. rerio Transposon Related to Tc1 The complete sequence of the DrTRT transposon is 1,563 base pairs (bp) in length, and its transposase putatively encodes a 338-amino acid protein that harbors a DD37E motif in its catalytic domain. We present evidence based on searches of publicly available genomes that TRT elements commonly occur in vertebrates and protozoa. Phylogenetic and functional domain comparisons confirm that TRT constitutes a new subfamily within the Tc1 family. Hallmark features of having no premature termination codons within the transposase, the presence of all expected functional domains, and its occurrence in the bony fish transcriptome suggest that TRT might have current or recent activity in these species. Further analysis showed that the activity of TRT elements in these species might have arisen about between 4 and 19 Ma. Interestingly, our results also implied that the widespread distribution of TRT among fishes, frog, and snakes is the result of multiple independent HT events, probably from bony fishes to snakes or frog. Finally, the mechanisms underlying horizontal transfer of TRT elements are discussed.

  1. Implementation of an active instructional design for teaching the concepts of current, voltage and resistance

    NASA Astrophysics Data System (ADS)

    Orlaineta-Agüero, S.; Del Sol-Fernández, S.; Sánchez-Guzmán, D.; García-Salcedo, R.

    2017-01-01

    In the present work we show the implementation of a learning sequence based on an active learning methodology for teaching Physics, this proposal tends to promote a better learning in high school students with the use of a comic book and it combines the use of different low-cost experimental activities for teaching the electrical concepts of Current, Resistance and Voltage. We consider that this kind of strategy can be easily extrapolated to higher-education levels like Engineering-college/university level and other disciplines of Science. To evaluate this proposal, we used some conceptual questions from the Electric Circuits Concept Evaluation survey developed by Sokoloff and the results from this survey was analysed with the Normalized Conceptual Gain proposed by Hake and the Concentration Factor that was proposed by Bao and Redish, to identify the effectiveness of the methodology and the models that the students presented after and before the instruction, respectively. We found that this methodology was more effective than only the implementation of traditional lectures, we consider that these results cannot be generalized but gave us the opportunity to view many important approaches in Physics Education; finally, we will continue to apply the same experiment with more students, in the same and upper levels of education, to confirm and validate the effectiveness of this methodology proposal.

  2. Current status of information transfer activity on food irradiation and consumer attitudes in Japan

    NASA Astrophysics Data System (ADS)

    Furuta, Masakazu

    2004-09-01

    For the purpose of public education of radiation and radiation-related technology towards school kids and their parents through efficient information transfer, ''RADIATION FAIR—the relationship between daily life and radiation" has been successfully held at Kintetsu Department Store, one of the major departmental stores in downtown Osaka, the second largest city in Japan during summer vacation in every August for 19 years. Currently various irradiated products available in our daily life including irradiated potatoes and spices were displayed together with explanatory panels and attractions. The number of participants has increased every year and constantly exceeded 20,000 in recent years. This activity has become a good medium for the consumer to recognize the quality of the irradiated potatoes which has been distributed in the market since 1974, and irradiated spices, the next candidate for the clearance under examination by Japanese government. Taking advantage of this opportunity, we have demonstrated toward the participants that irradiation-decontaminated spices are superior to conventional heat-treated ones in aromatic quality as well as conducting survey of the visitor's feeling on radiation and irradiated foods. These activities would be potentially effective to facilitate public acceptance of irradiation decontamination of spices.

  3. Purification of Active Myrosinase from Plants by Aqueous Two-Phase Counter-Current Chromatography

    PubMed Central

    Wade, Kristina L.; Ito, Yoichiro; Ramarathnam, Aarthi; Holtzclaw, W. David; Fahey, Jed W.

    2014-01-01

    Introduction Myrosinase (thioglucoside glucohydrolase; E.C. 3.2.1.147), is a plant enzyme of increasing interest and importance to the biomedical community. Myrosinase catalyses the formation of isothiocyanates such as sulforaphane (frombroccoli) and 4-(α-l-rhamnopyranosyloxy)benzyl isothiocyanate (from moringa), which are potent inducers of the cytoprotective phase-2 response in humans, by hydrolysis of their abundant glucosinolate (β-thioglucoside N-hydroxysulphate) precursors. Objective To develop an aqueous two-phase counter-current chromatography (CCC) system for the rapid, three-step purification of catalytically active myrosinase. Methods A high-concentration potassium phosphate and polyethylene glycol biphasic aqueous two-phase system (ATPS) is used with a newly developed CCC configuration that utilises spiral-wound, flat-twisted tubing (with an ovoid cross-section). Results Making the initial crude plant extract directly in the ATPS and injecting only the lower phase permitted highly selective partitioning of the myrosinase complex before a short chromatography on a spiral disk CCC. Optimum phase retention and separation of myrosinase from other plant proteins afforded a 60-fold purification. Conclusion Catalytically active myrosinase is purified from 3-day broccoli sprouts, 7-day daikon sprouts, mustard seeds and the leaves of field-grown moringa trees, in a CCC system that is predictably scalable. PMID:25130502

  4. Bestrophin-Encoded Ca2+-Activated Cl− Channels Underlie a Current with Properties Similar to the Native Current in the Moth Spodoptera littoralis Olfactory Receptor Neurons

    PubMed Central

    Demondion, Elodie; Bozzolan, Françoise; Debernard, Stéphane; Lucas, Philippe

    2012-01-01

    Responses of insect olfactory receptor neurons (ORNs) involve an entry of Ca2+ through olfactory heterodimeric receptor complexes. In moths, the termination of ORN responses was found to strongly depend on the external Ca2+ concentration through the activation of unknown Ca2+-dependent Cl− channels. We thus investigated the molecular identity of these Cl− channels. There is compelling evidence that bestrophins form Cl− channels when expressed in heterologous systems. Here we provide evidence that antennae of the moth Spodoptera littoralis express three transcripts encoding proteins with hallmarks of bestrophins. One of these transcripts, SlitBest1b, is expressed in ORNs. The heterologous expression of SlitBest1b protein in CHO-K1 cells yielded a Ca2+-activated Cl− current that shares electrophysiological properties with the native Ca2+-activated Cl− current of ORNs. Both currents are anionic, present similar dependence on the intracellular Ca2+ concentration, partly inactivate over time, have the same anion permeability sequence, the same sequence of inhibitory efficiency of blockers, the same almost linear I–V relationships and finally both currents do not depend on the cell volume. Therefore, our data suggest that SlitBest1b is a good candidate for being a molecular component of the olfactory Ca2+-activated Cl− channel and is likely to constitute part of the insect olfactory transduction pathway. A different function (e.g. regulation of other proteins, maintenance of the anionic homeostasis in the sensillar lymph) and a different role (e.g. involvement in the olfactory system development) cannot be excluded however. PMID:23300744

  5. Lithium ions in nanomolar concentration modulate glycine-activated chloride current in rat hippocampal neurons.

    PubMed

    Solntseva, E I; Bukanova, J V; Kondratenko, R V; Skrebitsky, V G

    2016-03-01

    Lithium salts are successfully used to treat bipolar disorder. At the same time, according to recent data lithium may be considered as a candidate medication for the treatment of neurodegenerative disorders. The mechanisms of therapeutic action of lithium have not been fully elucidated. In particular, in the literature there are no data on the effect of lithium on the glycine receptors. In the present study we investigated the effect of Li(+) on glycine-activated chloride current (IGly) in rat isolated pyramidal hippocampal neurons using patch-clamp technique. The effects of Li(+) were studied with two glycine concentrations: 100 μM (EC50) and 500 μM (nearly saturating). Li(+) was applied to the cell in two ways: first, by 600 ms co-application with glycine through micropipette (short application), and, second, by addition to an extracellular perfusate for 10 min (longer application). Li(+) was used in the range of concentrations of 1 nM-1 mM. Short application of Li(+) caused two effects: (1) an acceleration of desensitization (a decrease in the time of half-decay, or "τ") of IGly induced by both 100 μM and 500 μM glycine, and (2) a reduction of the peak amplitude of the IGly, induced by 100 μM, but not by 500 μM glycine. Both effects were not voltage-dependent. Dose-response curves for both effects were N-shaped with two maximums at 100 nM and 1 mM of Li(+) and a minimum at 1 μM of Li(+). This complex form of dose-response may indicate that the process activated by high concentrations of lithium inhibits the process that is sensitive to low concentrations of lithium. Longer application of Li(+)caused similar effects, but in this case 1 μM lithium was effective and the dose-effect curves were not N-shaped. The inhibitory effect of lithium ions on glycine-activated current suggests that lithium in low concentrations is able to modulate tonic inhibition in the hippocampus. This important property of lithium should be considered when using this drug as a

  6. Active Landslide Erosion of Mars' North Polar Cliffs: Current Rates, Causes, and Implications

    NASA Astrophysics Data System (ADS)

    Russell, P. S.; Byrne, S.; Pathare, A.

    2014-12-01

    While the North Polar Layered Deposits (NPLD) have long been considered Mars' best climate record, only recently have some of the processes governing the evolution of the NPLD to their current form been discovered and even directly observed. MOC revealed outcrops of an interbedded ice and dark-sand "basal unit" (BU) below steep NPLD scarps. Some bright markings on the BU were suggested to be talus deposits of mass-wasted NPLD ice, caused by undercutting via removal of easily erodible BU sand. In previous work with HiRISE images that confirmed the origin of these deposits, we: detailed their meter-scale morphology, constituent features, and variability; identified fractures of BU ice layers and NPLD scarps as additional mass-wasting facilitators; and, based on inter- and inter-annual monitoring, discovered that new deposits appear over time, thereby establishing mass wasting (of both BU and NPLD ice) as a currently active process. Here, we advance from qualitative descriptions of new, active processes to quantification of the rates at which they are occurring. From ~4 years of HiRISE observations, we cataloged the location, volume, source, and timing constraints of >160 landslide events along ~ 20 km of BU-NPLD scarp. Average rates are ~44 events/yr and ~2000 m3/yr, although 7 large events account for ~3/4 of the volume; this is a very geologically dynamic environment. BU events are more frequent and smaller than NPLD events, reflecting the relative thickness of ice source deposits but also perhaps differing proportions of two causal mechanisms: sand-removal undercutting and thermal-stress induced expansion, contraction, and fracturing. BU events prefer summer over spring; NPLD events strongly prefer fall-winter over spring-summer. We compare this observational data with 1) thermal stress models of the ice scarp to assess consistency in timing of activity, and 2) sublimation models of the ice scarp to assess the relative contributions to scarp retreat - our

  7. Limitations of short range Mexican hat connection for driving target selection in a 2D neural field: activity suppression and deviation from input stimuli

    PubMed Central

    Mégardon, Geoffrey; Tandonnet, Christophe; Sumner, Petroc; Guillaume, Alain

    2015-01-01

    Dynamic Neural Field models (DNF) often use a kernel of connection with short range excitation and long range inhibition. This organization has been suggested as a model for brain structures or for artificial systems involved in winner-take-all processes such as saliency localization, perceptual decision or target/action selection. A good example of such a DNF is the superior colliculus (SC), a key structure for eye movements. Recent results suggest that the superficial layers of the SC (SCs) exhibit relatively short range inhibition with a longer time constant than excitation. The aim of the present study was to further examine the properties of a DNF with such an inhibition pattern in the context of target selection. First we tested the effects of stimulus size and shape on when and where self-maintained clusters of firing neurons appeared, using three variants of the model. In each model variant, small stimuli led to rapid formation of a spiking cluster, a range of medium sizes led to the suppression of any activity on the network and hence to no target selection, while larger sizes led to delayed selection of multiple loci. Second, we tested the model with two stimuli separated by a varying distance. Again single, none, or multiple spiking clusters could occur, depending on distance and relative stimulus strength. For short distances, activity attracted toward the strongest stimulus, reminiscent of well-known behavioral data for saccadic eye movements, while for larger distances repulsion away from the second stimulus occurred. All these properties predicted by the model suggest that the SCs, or any other neural structure thought to implement a short range MH, is an imperfect winner-take-all system. Although, those properties call for systematic testing, the discussion gathers neurophysiological and behavioral data suggesting that such properties are indeed present in target selection for saccadic eye movements. PMID:26539103

  8. Preschooler's Use of Microcomputers and Input Devices.

    ERIC Educational Resources Information Center

    King, John; Alloway, Nola

    1992-01-01

    Describes a study that measured preschoolers' use of microcomputers in the following areas: (1) efficiency of use of input devices, including the keyboard, the joystick, and the mouse; (2) use during free-play activities, including interaction with the microcomputer and with each other; and (3) gender differences. (40 references) (LRW)

  9. Sickle cell disease: current activities, public health implications, and future directions.

    PubMed

    Creary, Melissa; Williamson, Dhelia; Kulkarni, Roshni

    2007-06-01

    Sickle cell disease (SCD) is a genetic blood disorder caused by abnormal hemoglobin that damages and deforms red blood cells (RBCs). The abnormal red cells break down, causing anemia, and obstruct blood vessels, leading to recurrent episodes of severe pain and multiorgan ischemic damage. SCD affects millions of people throughout the world and is particularly common among people whose ancestors come from sub-Saharan Africa. Sickle cell trait (SCT) is an inherited condition in which both normal hemoglobin and sickle hemoglobin are produced in the RBCs. SCT is not a type of sickle cell disease. People with SCT are generally healthy. In SCD, clinical severity varies, ranging from mild and sometimes asymptomatic states to severe symptoms requiring hospitalization. Symptomatic treatments exist, but there is no cure for SCD. Although there has been extensive clinical and basic science research in SCD, many public health issues, such as blood safety surveillance, compliance with immunizations, follow-up of newborns with positive screening tests, stroke prevention, pregnancy complications, pain prevention, quality of life, and thrombosis, in people with SCT remain unaddressed. Currently, efforts are under way to strengthen SCD-related activities within the Centers for Disease Control and Prevention (CDC). To date, several activities are being or have been conducted by centers within CDC, including quality assurance of newborn screening tests for SCD, morbidity and mortality studies, genetic studies, and studies focusing on the protective effects of SCT for malaria. This paper discusses the public health implications of SCD, summarizes SCD-related activities within CDC, and points to future directions that the agency can take to begin to address some of these issues.

  10. Novel blockers of hyperpolarization-activated current with isoform selectivity in recombinant cells and native tissue.

    PubMed

    Del Lungo, Martina; Melchiorre, Michele; Guandalini, Luca; Sartiani, Laura; Mugelli, Alessandro; Koncz, Istvan; Szel, Tamas; Varro, Andras; Romanelli, Maria Novella; Cerbai, Elisabetta

    2012-05-01

    BACKGROUND AND PURPOSE Selective hyperpolarization activated, cyclic nucleotide-gated channel (HCN) blockers represent an important therapeutic goal due to the wide distribution and multiple functions of these proteins, representing the molecular correlate of f- and h-current (I(f) or I(h) ). Recently, new compounds able to block differentially the homomeric HCN isoforms expressed in HEK293 have been synthesized. In the present work, the electrophysiological and pharmacological properties of these new HCN blockers were characterized and their activities evaluated on native channels. EXPERIMENTAL APPROACH HEK293 cells expressing mHCN1, mHCN2 and hHCN4 isoforms were used to verify channel blockade. Selected compounds were tested on native guinea pig sinoatrial node cells and neurons from mouse dorsal root ganglion (DRG) by patch-clamp recordings and on dog Purkinje fibres by intracellular recordings. KEY RESULTS In HEK293 cells, EC18 was found to be significantly selective for HCN4 and MEL57A for HCN1 at physiological membrane potential. When tested on guinea pig sinoatrial node cells, EC18 (10 µM) maintained its activity, reducing I(f) by 67% at -120 mV, while MEL57A (3 µM) reduced I(f) by 18%. In contrast, in mouse DRG neurons, only MEL57A (30 and 100 µM) significantly reduced I(h) by 60% at -80 mV. In dog cardiac Purkinje fibres, EC18, but not MEL57A, reduced the amplitude and slowed the slope of the spontaneous diastolic depolarization. CONCLUSIONS Our results have identified novel and highly selective HCN isoform blockers, EC18 and MEL57A; the selectivity found in recombinant system was maintained in various tissues expressing different HCN isoforms.

  11. Small Conductance Calcium-Activated Potassium Current is Important in Transmural Repolarization of Failing Human Ventricles

    PubMed Central

    Yu, Chih-Chieh; Corr, Christopher; Shen, Changyu; Shelton, Richard; Yadava, Mrinal; Rhea, Isaac; Straka, Susan; Fishbein, Michael C.; Chen, Zhenhui; Lin, Shien-Fong; Lopshire, John C.; Chen, Peng-Sheng

    2015-01-01

    Background The transmural distribution of apamin-sensitive small conductance Ca2+-activated K+ (SK) current (IKAS) in failing human ventricles remains unclear. Methods and Results We optically mapped left ventricular wedge preparations from 12 failing native hearts and 2 rejected cardiac allografts explanted during transplant surgery. We determined transmural action potential duration (APD) before and after 100 nM apamin administration in all wedges and after sequential administration of apamin, chromanol and E4031 in 4 wedges. Apamin prolonged APD from 363 ms [95% confidence interval (CI), 341 to 385] to 409 [CI, 385 to 434] (p<0.001) in all hearts, and reduced the transmural conduction velocity from 36 cm/s [CI, 30 to 42] to 32 cm/s [CI, 27 to 37] (p=0.001) in 12 native failing hearts at 1000 ms pacing cycle length (PCL). The percent APD prolongation is negatively correlated with baseline APD and positively correlated with PCL. Only one wedge had M-cell islands. The percentages of APD prolongation in the last 4 hearts at 2000 ms PCL after apamin, chromanol and E4031 were 9.1% [CI, 3.9 to 14.2], 17.3% [CI, 3.1 to 31.5] and 35.9% [CI, 15.7 to 56.1], respectively. Immunohistochemical staining of subtype 2 of SK (SK2) protein showed increased expression in intercalated discs of myocytes. Conclusions SK current is important in the transmural repolarization in failing human ventricles. The magnitude of IKAS is positively correlated with the PCL, but negatively correlated with APD when PCL is fixed. There is abundant SK2 protein in the intercalated discs of myocytes. PMID:25908692

  12. Use of Yohkoh SXT in Measuring the Net Current and CME Productivity of Active Regions

    NASA Technical Reports Server (NTRS)

    Falconer, D. A.; Moore, R. L.; Gary, G. A.; Six, N. Frank (Technical Monitor)

    2001-01-01

    In our investigation of the correlation of global nonpotentiality of active regions to their CME productivity (Falconer, D.A. 2001, JGR, in press, and Falconer, Moore, & Gary, 2000, EOS 82, 20 S323), we use Yohkoh SXT images for two purposes. The first use is to help resolve the 180 degree ambiguity in the direction of the observed transverse magnetic field. Resolution of the 180 degree ambiguity is important, since the net current, one of our measures of global nonpotentiality, is derived from integrating the dot product of the transverse field around a contour (I(sub N)=(integral)BT(raised dot)dl). The ambiguity results from the observed transverse field being determined from the linear polarization, which gives the plane of the direction, but leaves a 180 degrees ambiguity. Automated methods to resolve the ambiguity ranging from the simple acute angle rule (Falconer, D.A. 2001) to the more sophisticated annealing method (Metcalf T.R. 1994). For many active regions, especially ones that are nearly potential these methods work well. But for very nonpotential active regions where the shear angle (the angle between the observed and potential transverse field) is near 90 degrees throughout large swaths along the main neutral line, both methods can resolve the ambiguity incorrectly for long segments of the neutral line. By determining from coronal images, such as those from Yohkoh/SXT, the sense of shear along the main neutral line in the active region, these cases can be identified and corrected by a modification of the acute angle rule described here. The second use of Yohkoh/SXT in this study is to check for the cusped coronal arcades of long-duration eruptive flares. This signature is an excellent proxy for CMEs, and was used by Canfield, Hudson, and McKenzie (1999 GRL V26, 6, 627-630). This work is funded by NSF through the Space Weather Program and by NASA through the Solar Physics Supporting Research and Technology Program.

  13. REL - English Bulk Data Input.

    ERIC Educational Resources Information Center

    Bigelow, Richard Henry

    A bulk data input processor which is available for the Rapidly Extensible Language (REL) English versions is described. In REL English versions, statements that declare names of data items and their interrelationships normally are lines from a terminal or cards in a batch input stream. These statements provide a convenient means of declaring some…

  14. Inputs for L2 Acquisition.

    ERIC Educational Resources Information Center

    Saleemi, Anjum P.

    1989-01-01

    Major approaches of describing or examining linguistic data from a potential target language (input) are analyzed for adequacy in addressing the concerns of second language learning theory. Suggestions are made for making the best of these varied concepts of input and for reformulation of a unified concept. (MSE)

  15. Input in Second Language Acquisition.

    ERIC Educational Resources Information Center

    Gass, Susan M., Ed.; Madden, Carolyn G., Ed.

    This collection of conference papers includes: "When Does Teacher Talk Work as Input?"; "Cultural Input in Second Language Learning"; "Skilled Variation in a Kindergarten Teacher's Use of Foreigner Talk"; "Teacher-Pupil Interaction in Second Language Development"; "Foreigner Talk in the University…

  16. Current Magmato-Tectonic Activity in the Asal-Ghoubbet Rift (Afar Depression, Republic of Djibouti)

    NASA Astrophysics Data System (ADS)

    Doubre, C.; Doubre, C.; Dorbath, L.; Manighetti, I.; Jacques, E.; Geoffroy, L.

    2001-12-01

    The Asal-Ghoubbet rift, the most active, emerged segment of the Aden ridge, opens at 16+/-2 mm/yr. Although normal faulting operates in the rift, it does not accommodate the entire extension, so that dyking must occur at depth. In order to investigate the current relationship between tectonics and magmatism, we installed 11 seismometers (3 3C + one broad band; plus 6 permanent stations) in the northeastern part of the rift, site of the most active faults and of the Fieale volcano caldera, and monitored the seismic activity during 5 months. About 200 small-magnitude (time, <= 3) events could be accurately ( ~ 300m) localized in the emerged part of the rift, using an appropriate velocity model. All fall within the temporary network, forming three major clusters. Nine % of the events spread in the outermost part of the rift northern shoulder, where clear active faults and volcanic structures are lacking. All seem to nucleate at a similar depth, of 6-8 km. Seven % of the events nucleate at a shallow depth ( ~1 km) in the northern Disa Le Mallo subrift, zone of intense active faulting and fissuring. Finally, the majority of events (70%) cluster below the Fieale caldera, at a mean depth of 3 km, hence just above the inferred magma chamber. The analysis of the broader-scale seismological data acquired in the rift over the last 20 years, points to a similar distribution. Thirty five out of 50 focal mechanisms we calculated using P wave polarities, are consistent with a double-couple source model, and reveal predominant normal faulting on NW-SE-striking planes parallel to the faults which structure the rift. Fifteen events, however, show non-double couple radiation pattern, particularly in the Fieale area. These particular events may result from magmatic activity (filling or collapse of the magma chamber) and/or geothermal processes. In the other two areas, where they are also found, their origin is possibly related to fissuring or dyking. One seismic sequence also occurred

  17. Eruptive history, current activity and risk estimation using geospatial information in the Colima volcano, Mexico

    NASA Astrophysics Data System (ADS)

    Suarez-Plascencia, C.; Camarena-Garcia, M.; Nunez-Cornu, F. J.; Flores-Peña, S.

    2013-12-01

    avocado orchards and fruits like blueberries, raspberries, and blackberries within the radius of 15 km from the crater. The population dynamics in the Colima volcano area had a population of 552,954 inhabitants in 2010, and a growth at an annual rate of 1.6 percent of the total population. 60 percent of the populations live in 105 towns with a population less than 250 inhabitants. Also, the region showed an increase in vulnerability for the development of economic activities, supported by the highway, railway, natural gas pipelines and electrical infrastructure that connect to the Port of Manzanillo to Guadalajara city. With the use of geospatial information quantify the vulnerability, together with the hazard maps and exposure, enabled us to build the following volcanic risk maps: a) Exclusion areas and moderate hazard for explosive events (ballistic) and pyroclastic flows, b) Hazard map of lahars and debris flow, and c) Hazard map of ash-fall. The geospatial database, a GIS mapping and current volcano monitoring, are the basis of the Operational Plan Colima Volcano. Civil Protection by the state of Jalisco and the updating of urban development plans of municipalities converge on the volcano. These instruments of land planning will help reduce volcanic risk in the region.

  18. Stress-Activated Electric Currents in the Earth Crust: How they Can and Cannot Flow (Invited)

    NASA Astrophysics Data System (ADS)

    Freund, F. T.; Bleier, T. E.; Bortnik, J.; Dahlgren, R.

    2010-12-01

    Dormant electronic charge carriers exist in rocks. They “wake up” when stresses are applied: electrons e’ and positive holes, h., the latter being defect electrons in the oxygen anion sublattice of minerals [1, 2]. The h. can flow out of the stressed subvolume. They can spread into the unstressed surrounding, turning the rocks into p-type semiconductors. They travel fast and far using energy levels at the upper edge of the valence bands. Contrary to the h., the co-activated electrons e’ cannot flow out and propagate through unstressed rocks: they are stuck in the activation volume. The situation is akin to that in an electrochemical battery except that, in the “rock battery”, the positive charge carriers are not cations but positive holes h.. In the laboratory it is easy to close the battery circuit by offering the electrons a metal contact and connecting the stressed and unstressed rock with a metal wire. This is useful to demonstrate the functioning of the “rock battery”. In the field the h. outflow from a stressed rock volume is restricted as long as there is no return path. This is an important point when we try to understand why pre-earthquake EM emission is widely considered “unreliable” [3, 4]. However, there are at least three conditions, under which circuit closure can be achieved in the field under realistic pre-earthquake situations: (i) via n-type conducting rocks; (ii) via electrolytic conductivity of water; and (iii) via the air when the air above the epicentral region becomes highly ionized. We report on examples where these three conditions might have allowed large currents to flow and strong EM signals to be emitted. [1] Freund, F.T. et al.: Electric currents streaming out of stressed igneous rocks - A step towards understanding pre-earthquake low frequency EM emissions, Phys. Chem. Earth 31, 389-396 (2006). [2] Freund, F.T.: Charge generation and propagation in rocks, J. Geodyn. 33, 545-572 (2002). [3] Johnston, M.J.S. and

  19. Glycine input induces the synaptic facilitation in salamander rod photoreceptors.

    PubMed

    Shen, Wen; Jiang, Zheng; Li, Baoqin

    2008-11-01

    Glycinergic synapses in photoreceptors are made by centrifugal feedback neurons in the network, but the function of the synapses is largely unknown. Here we report that glycinergic input enhances photoreceptor synapses in amphibian retinas. Using specific antibodies against a glycine transporter (GlyT2) and glycine receptor beta subunit, we identified the morphology of glycinergic input in photoreceptor terminals. Electrophysiological recordings indicated that 10 muM glycine depolarized rods and activated voltage-gated Ca(2+) channels in the neurons. The effects facilitated glutamate vesicle release in photoreceptors, meanwhile increased the spontaneous excitatory postsynaptic currents in Off-bipolar cells. Endogenous glycine feedback also enhanced glutamate transmission in photoreceptors. Additionally, inhibition of a Cl(-) uptake transporter NKCC1 with bumetanid effectively eliminated glycine-evoked a weak depolarization in rods, suggesting that NKCC1 maintains a high Cl(-) level in rods, which causes to depolarize in responding to glycine input. This study reveals a new function of glycine in retinal synaptic transmission.

  20. High temperature current mirror amplifier

    DOEpatents

    Patterson, III, Raymond B.

    1984-05-22

    A high temperature current mirror amplifier having biasing means in the transdiode connection of the input transistor for producing a voltage to maintain the base-collector junction reversed-biased and a current means for maintaining a current through the biasing means at high temperatures so that the base-collector junction of the input transistor remained reversed-biased. For accuracy, a second current mirror is provided with a biasing means and current means on the input leg.

  1. Multivariate autoregressive models with exogenous inputs for intracerebral responses to direct electrical stimulation of the human brain

    PubMed Central

    Chang, Jui-Yang; Pigorini, Andrea; Massimini, Marcello; Tononi, Giulio; Nobili, Lino; Van Veen, Barry D.

    2012-01-01

    A multivariate autoregressive (MVAR) model with exogenous inputs (MVARX) is developed for describing the cortical interactions excited by direct electrical current stimulation of the cortex. Current stimulation is challenging to model because it excites neurons in multiple locations both near and distant to the stimulation site. The approach presented here models these effects using an exogenous input that is passed through a bank of filters, one for each channel. The filtered input and a random input excite a MVAR system describing the interactions between cortical activity at the recording sites. The exogenous input filter coefficients, the autoregressive coefficients, and random input characteristics are estimated from the measured activity due to current stimulation. The effectiveness of the approach is demonstrated using intracranial recordings from three surgical epilepsy patients. We evaluate models for wakefulness and NREM sleep in these patients with two stimulation levels in one patient and two stimulation sites in another resulting in a total of 10 datasets. Excellent agreement between measured and model-predicted evoked responses is obtained across all datasets. Furthermore, one-step prediction is used to show that the model also describes dynamics in pre-stimulus and evoked recordings. We also compare integrated information—a measure of intracortical communication thought to reflect the capacity for consciousness—associated with the network model in wakefulness and sleep. As predicted, higher information integration is found in wakefulness than in sleep for all five cases. PMID:23226122

  2. Transcranial Direct Current Stimulation Modulates Neuronal Activity and Learning in Pilot Training

    PubMed Central

    Choe, Jaehoon; Coffman, Brian A.; Bergstedt, Dylan T.; Ziegler, Matthias D.; Phillips, Matthew E.

    2016-01-01

    Skill acquisition requires distributed learning both within (online) and across (offline) days to consolidate experiences into newly learned abilities. In particular, piloting an aircraft requires skills developed from extensive training and practice. Here, we tested the hypothesis that transcranial direct current stimulation (tDCS) can modulate neuronal function to improve skill learning and performance during flight simulator training of aircraft landing procedures. Thirty-two right-handed participants consented to participate in four consecutive daily sessions of flight simulation training and received sham or anodal high-definition-tDCS to the right dorsolateral prefrontal cortex (DLPFC) or left motor cortex (M1) in a randomized, double-blind experiment. Continuous electroencephalography (EEG) and functional near infrared spectroscopy (fNIRS) were collected during flight simulation, n-back working memory, and resting-state assessments. tDCS of the right DLPFC increased midline-frontal theta-band activity in flight and n-back working memory training, confirming tDCS-related modulation of brain processes involved in executive function. This modulation corresponded to a significantly different online and offline learning rates for working memory accuracy and decreased inter-subject behavioral variability in flight and n-back tasks in the DLPFC stimulation group. Additionally, tDCS of left M1 increased parietal alpha power during flight tasks and tDCS to the right DLPFC increased midline frontal theta-band power during n-back and flight tasks. These results demonstrate a modulation of group variance in skill acquisition through an increasing in learned skill consistency in cognitive and real-world tasks with tDCS. Further, tDCS performance improvements corresponded to changes in electrophysiological and blood-oxygenation activity of the DLPFC and motor cortices, providing a stronger link between modulated neuronal function and behavior. PMID:26903841

  3. Normal and Mutant Rhodopsin Activation Measured with the Early Receptor Current in a Unicellular Expression System

    PubMed Central

    Shukla, Pragati; Sullivan, Jack M.

    1999-01-01

    The early receptor current (ERC) represents molecular charge movement during rhodopsin conformational dynamics. To determine whether this time-resolved assay can probe various aspects of structure–function relationships in rhodopsin, we first measured properties of expressed normal human rhodopsin with ERC recordings. These studies were conducted in single fused giant cells containing on the order of a picogram of regenerated pigment. The action spectrum of the ERC of normal human opsin regenerated with 11-cis-retinal was fit by the human rhodopsin absorbance spectrum. Successive flashes extinguished ERC signals consistent with bleaching of a rhodopsin photopigment with a normal range of photosensitivity. ERC signals followed the univariance principle since millisecond-order relaxation kinetics were independent of the wavelength of the flash stimulus. After signal extinction, dark adaptation without added 11-cis-retinal resulted in spontaneous pigment regeneration from an intracellular store of chromophore remaining from earlier loading. After the ERC was extinguished, 350-nm flashes overlapping metarhodopsin-II absorption promoted immediate recovery of ERC charge motions identified by subsequent 500-nm flashes. Small inverted R2 signals were seen in response to some 350-nm flashes. These results indicate that the ERC can be photoregenerated from the metarhodopsin-II state. Regeneration with 9-cis-retinal permits recording of ERC signals consistent with flash activation of isorhodopsin. We initiated structure–function studies by measuring ERC signals in cells expressing the D83N and E134Q mutant human rhodopsin pigments. D83N ERCs were simplified in comparison with normal rhodopsin, while E134Q ERCs had only the early phase of charge motion. This study demonstrates that properties of normal rhodopsin can be accurately measured with the ERC assay and that a structure–function investigation of rapid activation processes in analogue and mutant visual pigments is

  4. 76 FR 26338 - Agency Information Collection Activities; Renewal Without Change of a Current Collection; Comment...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-06

    ... Current Collection; Comment Request ACTION: Notice and request for comments. SUMMARY: In order to comply... for such foreign bank (31 CFR 1010.630(e)). Current Action: Renewal without change to the...

  5. Intracellular Ca2+ release from endoplasmic reticulum regulates slow wave currents and pacemaker activity of interstitial cells of Cajal

    PubMed Central

    Zhu, Mei Hong; Sung, Tae Sik; O'Driscoll, Kate; Koh, Sang Don

    2015-01-01

    Interstitial cells of Cajal (ICC) provide pacemaker activity in gastrointestinal muscles that underlies segmental and peristaltic contractions. ICC generate electrical slow waves that are due to large-amplitude inward currents resulting from anoctamin 1 (ANO1) channels, which are Ca2+-activated Cl− channels. We investigated the hypothesis that the Ca2+ responsible for the stochastic activation of ANO1 channels during spontaneous transient inward currents (STICs) and synchronized activation of ANO1 channels during slow wave currents comes from intracellular Ca2+ stores. ICC, obtained from the small intestine of Kit+/copGFP mice, were studied under voltage and current clamp to determine the effects of blocking Ca2+ uptake into stores and release of Ca2+ via inositol 1,4,5-trisphosphate (IP3)-dependent and ryanodine-sensitive channels. Cyclocpiazonic acid, thapsigargin, 2-APB, and xestospongin C inhibited STICs and slow wave currents. Ryanodine and tetracaine also inhibited STICs and slow wave currents. Store-active compounds had no direct effects on ANO1 channels expressed in human embryonic kidney-293 cells. Under current clamp, store-active drugs caused significant depolarization of ICC and reduced spontaneous transient depolarizations (STDs). After block of ryanodine receptors with ryanodine and tetracaine, repolarization did not restore STDs. ANO1 expressed in ICC has limited access to cytoplasmic Ca2+ concentration, suggesting that pacemaker activity depends on Ca2+ dynamics in restricted microdomains. Our data from studies of isolated ICC differ somewhat from studies on intact muscles and suggest that release of Ca2+ from both IP3 and ryanodine receptors is important in generating pacemaker activity in ICC. PMID:25631870

  6. Modulation of physiological mirror activity with transcranial direct current stimulation over dorsal premotor cortex.

    PubMed

    Beaulé, Vincent; Tremblay, Sara; Lafleur, Louis-Philippe; Ferland, Marie C; Lepage, Jean-François; Théoret, Hugo

    2016-11-01

    Humans have a natural tendency towards symmetrical movements, which rely on a distributed cortical network that allows for complex unimanual movements. Studies on healthy humans using rTMS have shown that disruption of this network, and particularly the dorsal premotor cortex (dPMC), can result in increased physiological mirror movements. The aim of the present set of experiments was to further investigate the role of dPMC in restricting motor output to the contralateral hand and determine whether physiological mirror movements could be decreased in healthy individuals. Physiological mirror movements were assessed before and after transcranial direct current stimulation (tDCS) over right and left dPMC in three conditions: bilateral, unilateral left and unilateral right stimulation. Mirror EMG activity was assessed immediately before, 0, 10 and 20 min after tDCS. Results show that physiological mirroring increased significantly in the hand ipsilateral to cathodal stimulation during bilateral stimulation of the dPMC, 10 and 20 min after stimulation compared to baseline. There was no significant modulation of physiological mirroring in the hand ipsilateral to anodal stimulation in the bilateral condition or following unilateral anodal or unilateral cathodal stimulation. The present data further implicate the dPMC in the control of unimanual hand movements and show that physiological mirroring can be increased but not decreased with dPMC tDCS.

  7. Modulating activity in the orbitofrontal cortex changes trustees' cooperation: A transcranial direct current stimulation study.

    PubMed

    Wang, Guangrong; Li, Jianbiao; Yin, Xile; Li, Shuaiqi; Wei, Mengxing

    2016-04-15

    Trust is one of the most important factors in human society, as it pervades almost all domains of the society. The trusting behavior of trustors is dependent on the belief about the cooperative (reciprocal) level of trustees. Thence what are the motives underlying the cooperative behavior? An important explanation is that guilt aversion can motivate cooperative behavior. The right orbitofrontal cortex (OFC) is the guilt-specific region, while there is little understanding on the causal effect of this network. We explored the causal effect of the OFC on cooperative behavior using transcranial direct current stimulation (tDCS). Sixty participants played the trust game as trustees, and they received either anodal tDCS over the right OFC and simultaneously cathodal electrode over the right dorsolateral prefrontal cortex (DLPFC), or sham stimulation. Experimental results showed that participants as trustees transferred back more money in the tDCS treatment than sham stimulation. This suggests that the activity of the right OFC has causal effects on cooperative behavior.

  8. TOPICAL REVIEW: Electric current activated/assisted sintering (ECAS): a review of patents 1906-2008

    NASA Astrophysics Data System (ADS)

    Grasso, Salvatore; Sakka, Yoshio; Maizza, Giovanni

    2009-10-01

    The electric current activated/assisted sintering (ECAS) is an ever growing class of versatile techniques for sintering particulate materials. Despite the tremendous advances over the last two decades in ECASed materials and products there is a lack of comprehensive reviews on ECAS apparatuses and methods. This paper fills the gap by tracing the progress of ECAS technology from 1906 to 2008 and surveys 642 ECAS patents published over more than a century. It is found that the ECAS technology was pioneered by Bloxam (1906 GB Patent No. 9020) who developed the first resistive sintering apparatus. The patents were searched by keywords or by cross-links and were withdrawn from the Japanese Patent Office (342 patents), the United States Patent and Trademark Office (175 patents), the Chinese State Intellectual Property Office of P.R.C. (69 patents) and the World Intellectual Property Organization (12 patents). A subset of 119 (out of 642) ECAS patents on methods and apparatuses was selected and described in detail with respect to their fundamental concepts, physical principles and importance in either present ECAS apparatuses or future ECAS technologies for enhancing efficiency, reliability, repeatability, controllability and productivity. The paper is divided into two parts, the first deals with the basic concepts, features and definitions of basic ECAS and the second analyzes the auxiliary devices/peripherals. The basic ECAS is classified with reference to discharge time (fast and ultrafast ECAS). The fundamental principles and definitions of ECAS are outlined in accordance with the scientific and patent literature.

  9. Cytotoxicity, Bactericidal, and Antioxidant Activity of Sodium Alginate Hydrosols Treated with Direct Electric Current

    PubMed Central

    Król, Żaneta; Marycz, Krzysztof; Kulig, Dominika; Marędziak, Monika; Jarmoluk, Andrzej

    2017-01-01

    The aim of the study was to investigate the effect of using direct electric current (DC) of 0, 200, and 400 mA for five minutes on the physiochemical properties, cytotoxicity, antibacterial, and antioxidant activity of sodium alginate hydrosols with different sodium chloride concentrations. The pH, oxidation-reduction potential (ORP), electrical conductivity (EC), and available chlorine concentration (ACC) were measured. The effect of sodium alginate hydrosols treated with DC on Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus, Micrococcus luteus, Escherichia coli, Salmonella enteritidis, Yersinia enterocolitica, Pseudomonas fluorescence, and RAW 264.7 and L929 cells was investigated. Subsequently, the antioxidant properties of hydrosols were evaluated by determining the scavenging ability of 1,1-diphenyl-2-picrylhydrazyl free radical (DPPH) and ferric reducing antioxidant power (FRAP). The results have shown that after applying 400 mA in hydrosol samples with 0.1% and 0.2% NaCl all tested bacteria were inactivated. The ACC concentration of C400 samples with NaCl was equal to 13.95 and 19.71 mg/L, respectively. The cytotoxicity analysis revealed that optimized electric field conditions and the addition of sodium chloride allow for the avoidance of toxicity effects on normal cells without disturbing the antibacterial effects. Due to the presence of oxidizing substances, the DPPH of variants treated with DC was lower than the DPPH of control samples. PMID:28327520

  10. Control of plasma properties in a short direct-current glow discharge with active boundaries

    SciTech Connect

    Adams, S. F.; Demidov, V. I.; Bogdanov, E. A.; Kudryavtsev, A. A.; Koepke, M. E.; Kurlyandskaya, I. P.

    2016-02-15

    To demonstrate controlling electron/metastable density ratio and electron temperature by applying negative voltages to the active (conducting) discharge wall in a low-pressure plasma with nonlocal electron energy distribution function, modeling has been performed in a short (lacking the positive-column region) direct-current glow discharge with a cold cathode. The applied negative voltage can modify the trapping of the low-energy part of the energetic electrons that are emitted from the cathode sheath and that arise from the atomic and molecular processes in the plasma within the device volume. These electrons are responsible for heating the slow, thermal electrons, while production of slow electrons (ions) and metastable atoms is mostly due to the energetic electrons with higher energies. Increasing electron temperature results in increasing decay rate of slow, thermal electrons (ions), while decay rate of metastable atoms and production rates of slow electrons (ions) and metastable atoms practically are unchanged. The result is in the variation of electron/metastable density ratio and electron temperature with the variation of the wall negative voltage.

  11. ISRU: An Overview of NASA'S Current Development Activities and Long-Term Goals

    NASA Technical Reports Server (NTRS)

    Sanders, Gerald B.; Nicholson, Leonard S. (Technical Monitor)

    2000-01-01

    The concept of "living off the land" by utilizing the indigenous resources of the Moon, Mars, or other potential sites of robotic and human exploration has been termed In-Situ Resource Utilization (ISRU). It is fundamental to any program of extended human presence and operation on other extraterrestrial bodies that we learn how to utilize the indigenous resources. The chief benefits of ISRU are that it can reduce the mass, cost, and risk of robotic and human exploration while providing capabilities that enable the commercial development of space. In January 1997, the American Institute of Aeronautics and Astronautics (AIAA) Space Processing Technical Committee released a position paper entitled, "Need for A NASA Indigenous Space Resource Utilization (ISRU) Program". Besides outlining some of the potential advantages of incorporating ISRU into Lunar and Mars human mission plans and providing an overview of technologies and processes of interest, the position paper concluded with a list of seven recommendations to NASA. This paper will examine the seven recommendations proposed and provide an overview of NASA's current ISRU development activities and possible long term goals with respect to these recommendations.

  12. Electric current activated/assisted sintering (ECAS): a review of patents 1906–2008

    PubMed Central

    Grasso, Salvatore; Sakka, Yoshio; Maizza, Giovanni

    2009-01-01

    The electric current activated/assisted sintering (ECAS) is an ever growing class of versatile techniques for sintering particulate materials. Despite the tremendous advances over the last two decades in ECASed materials and products there is a lack of comprehensive reviews on ECAS apparatuses and methods. This paper fills the gap by tracing the progress of ECAS technology from 1906 to 2008 and surveys 642 ECAS patents published over more than a century. It is found that the ECAS technology was pioneered by Bloxam (1906 GB Patent No. 9020) who developed the first resistive sintering apparatus. The patents were searched by keywords or by cross-links and were withdrawn from the Japanese Patent Office (342 patents), the United States Patent and Trademark Office (175 patents), the Chinese State Intellectual Property Office of P.R.C. (69 patents) and the World Intellectual Property Organization (12 patents). A subset of 119 (out of 642) ECAS patents on methods and apparatuses was selected and described in detail with respect to their fundamental concepts, physical principles and importance in either present ECAS apparatuses or future ECAS technologies for enhancing efficiency, reliability, repeatability, controllability and productivity. The paper is divided into two parts, the first deals with the basic concepts, features and definitions of basic ECAS and the second analyzes the auxiliary devices/peripherals. The basic ECAS is classified with reference to discharge time (fast and ultrafast ECAS). The fundamental principles and definitions of ECAS are outlined in accordance with the scientific and patent literature. PMID:27877308

  13. Current perspectives on physical activity and exercise recommendations for children and adolescents with autism spectrum disorders.

    PubMed

    Srinivasan, Sudha M; Pescatello, Linda S; Bhat, Anjana N

    2014-06-01

    Recent evidence suggests that childhood obesity is increasing in children who are developing typically as well as in children with developmental disabilities such as autism spectrum disorders (ASDs). Impairments specific to autism as well as general environmental factors could lead to an imbalance between the intake and expenditure of energy, leading to obesity. In this article, we describe the mechanisms by which autism-specific impairments contribute to obesity. The evidence on exercise interventions to improve physical fitness, address obesity, and reduce autism-specific impairments in children and adolescents with ASDs is discussed. Limited evidence is currently available for exercise interventions in individuals with ASDs. Therefore, literature on other pediatric developmental disabilities and children who are developing typically was reviewed to provide recommendations for clinicians to assess physical activity levels, to promote physical fitness, and to reduce obesity in children and adolescents with ASDs. There is a clear need for further systematic research to develop sensitive assessment tools and holistic multisystem and multifactorial obesity interventions that accommodate the social communication, motor, and behavioral impairments of individuals with ASDs.

  14. Current Perspectives on Physical Activity and Exercise Recommendations for Children and Adolescents With Autism Spectrum Disorders

    PubMed Central

    Srinivasan, Sudha M.; Pescatello, Linda S.

    2014-01-01

    Recent evidence suggests that childhood obesity is increasing in children who are developing typically as well as in children with developmental disabilities such as autism spectrum disorders (ASDs). Impairments specific to autism as well as general environmental factors could lead to an imbalance between the intake and expenditure of energy, leading to obesity. In this article, we describe the mechanisms by which autism-specific impairments contribute to obesity. The evidence on exercise interventions to improve physical fitness, address obesity, and reduce autism-specific impairments in children and adolescents with ASDs is discussed. Limited evidence is currently available for exercise interventions in individuals with ASDs. Therefore, literature on other pediatric developmental disabilities and children who are developing typically was reviewed to provide recommendations for clinicians to assess physical activity levels, to promote physical fitness, and to reduce obesity in children and adolescents with ASDs. There is a clear need for further systematic research to develop sensitive assessment tools and holistic multisystem and multifactorial obesity interventions that accommodate the social communication, motor, and behavioral impairments of individuals with ASDs. PMID:24525861

  15. 76 FR 44608 - Agency Information Collection Activities; Submission for OMB Review; Comment Request; Current...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-26

    ...; Current Population Survey Volunteer Supplement ACTION: Notice. SUMMARY: The Department of Labor (DOL) is..., ``Current Population Survey Volunteer Supplement,'' to the Office of Management and Budget (OMB) for review..._PRA_PUBLIC@dol.gov . SUPPLEMENTARY INFORMATION: The Volunteer Supplement to the Current...

  16. Regulation by second messengers of the slowly activating, voltage-dependent potassium current expressed in Xenopus oocytes.

    PubMed Central

    Busch, A E; Kavanaugh, M P; Varnum, M D; Adelman, J P; North, R A

    1992-01-01

    1. Voltage-clamp recordings of membrane current were made from Xenopus oocytes that had been injected with RNA which had been transcribed in vitro from a cloned complementary DNA. 2. Depolarization from -80 mV evoked outward potassium currents that developed very slowly. At -20 mV the time constant for activation was about 50 s, and at +40 mV about 6 s. 3. The potassium current was increased by the calcium ionophore A23187 or by intracellular injection of inositol 1,4,5-trisphosphate (IP3), each of which should increase the intracellular calcium concentration ([Ca2+]i). The current was decreased by injection of BAPTA (1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid). The current was also reduced by phorbol esters; this effect was blocked by staurosporine. 4. In oocytes that had also been injected with RNA encoding the 5-hydroxytryptamine (5-HT2) receptor, 5-HT increased the potassium current. After caffeine pretreatment, to block the release of intracellular calcium, 5-HT decreased the current; this decrease was prevented by staurosporine. 5. It is concluded that the slowly activating, voltage-dependent potassium current expressed in Xenopus oocytes is increased by increases in [Ca2+]i and is decreased by activation of protein kinase C. Stimulation of 5-HT2 receptors can have both these effects, but the former normally predominates. Images Fig. 4 PMID:1432714

  17. Predicting body temperature and activity of adult Polyommatus icarus using neural network models under current and projected climate scenarios.

    PubMed

    Howe, P D; Bryant, S R; Shreeve, T G

    2007-10-01

    We use field observations in two geographic regions within the British Isles and regression and neural network models to examine the relationship between microhabitat use, thoracic temperatures and activity in a widespread lycaenid butterfly, Polyommatus icarus. We also make predictions for future activity under climate change scenarios. Individuals from a univoltine northern population initiated flight with significantly lower thoracic temperatures than individuals from a bivoltine southern population. Activity is dependent on body temperature and neural network models of body temperature are better at predicting body temperature than generalized linear models. Neural network models of activity with a sole input of predicted body temperature (using weather and microclimate variables) are good predictors of observed activity and were better predictors than generalized linear models. By modelling activity under climate change scenarios for 2080 we predict differences in activity in relation to both regional differences of climate change and differing body temperature requirements for activity in different populations. Under average conditions for low-emission scenarios there will be little change in the activity of individuals from central-southern Britain and a reduction in northwest Scotland from 2003 activity levels. Under high-emission scenarios, flight-dependent activity in northwest Scotland will increase the greatest, despite smaller predicted increases in temperature and decreases in cloud cover. We suggest that neural network models are an effective way of predicting future activity in changing climates for microhabitat-specialist butterflies and that regional differences in the thermoregulatory response of populations will have profound effects on how they respond to climate change.

  18. A novel slow hyperpolarization-activated potassium current (IK(SHA)) from a mouse hippocampal cell line.

    PubMed Central

    Wischmeyer, E; Karschin, A

    1997-01-01

    1. A slow hyperpolarization-activated inwardly rectifying K+ current (IK(SHA)) with novel characteristics was identified from the mouse embryonic hippocampus x neuroblastoma cell line HN9.10e. 2. The non-inactivating current activated negative to a membrane potential of -80 mV with slow and complex activation kinetics (tau act approximately 1-7 s) and a characteristic delay of 1-10 s (-80 to -140 mV) that was linearly dependent on the membrane potential. 3. Tail currents and instantaneous open channel currents determined through fast voltage ramps reversed at the K+ equilibrium potential (EK) indicating that primarily K+, but not Na+, permeated the channels. 4. IK(SHA) was unaffected by altering the intracellular Ca2+ concentration between approximately 0 and 10 microM, but was susceptible to block by 5 mM extracellular Ca2+, Ba2+ (Ki = 0.42 mM), and Cs+ (Ki = 2.77 mM) 5. In cells stably transformed with M2 muscarinic receptors, IK(SHA) was rapidly, but reversibly, suppressed by application of micromolar concentrations of muscarine. 6. At the single channel level K(SHA) channel openings were observed with the characteristic delay upon membrane hyperpolarization. Analysis of unitary currents revealed an inwardly rectifying I-V profile and a channel slope conductance of 7 pS. Channel activity persisted in the inside-out configuration for many minutes. 7. It is concluded that IK(SHA) in HN9.10e cells represents a novel K+ current, which is activated upon membrane hyperpolarization. It is functionally different from both classic inwardly rectifying IKir currents and other cationic hyperpolarization-activated IH currents that have been previously described in neuronal or glial cells. Images Figure 1 Figure 2 Figure 6 Figure 7 Figure 8 PMID:9401967

  19. A novel large-conductance Ca(2+)-activated potassium channel and current in nerve terminals of the rat neurohypophysis.

    PubMed Central

    Wang, G; Thorn, P; Lemos, J R

    1992-01-01

    1. Nerve terminals of the rat posterior pituitary were acutely dissociated and identified using a combination of morphological and immunohistochemical techniques. Terminal membrane currents were studied using the 'whole-cell' patch clamp technique and channels were studied using inside-out and outside-out patches. 2. In physiological solutions, but with 7 mM 4-aminopyridine (4-AP), depolarizing voltage clamp steps from different holding potentials (-90 or -50 mV) elicited a fast, inward current followed by a slow, sustained, outward current. This outward current did not appear to show any steady-state inactivation. 3. The threshold for activation of the outward current was -30 mV and the current-voltage relation was 'bell-shaped'. The amplitude increased with increasingly depolarized potential steps. The outward current reversal potential was measured using tail current analysis and was consistent with that of a potassium current. 4. The sustained potassium current was determined to be dependent on the concentration of intracellular calcium. Extracellular Cd2+ (80 microM), a calcium channel blocker, also reversibly abolished the outward current. 5. The current was delayed in onset and was sustained over the length of a 150 ms-duration depolarizing pulse. The outward current reached a peak plateau and then decayed slowly. The decay was fitted by a single exponential with a time constant of 9.0 +/- 2.2 s. The decay constants did not show a dependence on voltage but rather on intracellular Ca2+. The time course of recovery from this decay was complex with full recovery taking > 190 s. 6. 4-AP (7 mM), dendrotoxin (100 nM), apamin (40-80 nM), and charybdotoxin (10-100 nM) had no effect on the sustained outward current. In contrast Ba2+ (200 microM) and tetraethylammonium inhibited the current, the latter in a dose-dependent manner (apparent concentration giving 50% of maximal inhibition (IC50) = 0.51 mM). 7. The neurohypophysial terminal outward current recorded here

  20. A TTX-sensitive inward sodium current contributes to spontaneous activity in newborn rabbit sino-atrial node cells.

    PubMed Central

    Baruscotti, M; DiFrancesco, D; Robinson, R B

    1996-01-01

    1. Single cells were isolated from the sinus node region of rabbits (2 days old to adult) to study the age-dependent contribution of the sodium current (iNa) to pacemaker activity. 2. Experiments were conducted in 50 mM Na(+)-Ca(2+)-free solution. All newborn cells (2-19 days) exhibited a TTX-sensitive, Mn(2+)-insensitive fast inward Na+ current (peak current density 115.5 +/- 11.9 pA pF-1 at 0 mV). Fifty per cent of young cells (20-40 days) possessed the current, but only one in ten adult cells. Current density decreased with development independently of cell capacitance. 3. Newborn cells exhibited a noticeable window current. With development, the position of the activation curve was shifted in the positive direction, while the inactivation was unaltered, resulting in reduced overlap of the two curves and hence less window current. 4. In newborn cells, 3 microM TTX significantly reduced all measured parameters of spontaneous action potentials, slowing rate by 63%. In contrast, there was no significant effect of TTX on rate or most of the same parameters in adult cells. 5. These results indicate that cells of the sinus node region exhibit a substantial TTX-sensitive current at birth. With development, both the density and frequency of occurrence of this current within the sinus node decrease, as does its contribution to automaticity. PMID:8730579

  1. Histamine H1 receptor activation blocks two classes of potassium current, IK(rest) and IAHP, to excite ferret vagal afferents.

    PubMed Central

    Jafri, M S; Moore, K A; Taylor, G E; Weinreich, D

    1997-01-01

    1. Intracellular recordings were made in intact and acutely dissociated vagal afferent neurones (nodose ganglion cells) of the ferret to investigate the membrane effects of histamine. 2. In current-clamp or voltage-clamp recordings, histamine (10 microM) depolarized the membrane potential (10 +/- 0.8 mV; mean +/- S.E.M.; n = 27) or produced an inward current of 1.6 +/- 0.35 nA (n = 27) in approximately 80% of the neurones. 3. Histamine (10 microM) also blocked the post-spike slow after-hyperpolarization (AHP slow) present in 80% of these neurones (95 +/- 3.2%; n = 5). All neurones possessing AHPslow in ferret nodose were C fibre neurones; all AHPslow neurones had conduction velocities < or = 1 m s-1 (n = 7). 4. Both the histamine-induced inward current and the block of AHPslow were concentration dependent and each had an estimated EC50 value of 2 microM. These histamine-induced effects were mimicked by the histamine H1 receptor agonist 2-(2-aminoethyl) thiazole dihydrochloride (10 microM) and blocked by the H1 antagonists pyrilamine (100 nM) or diphenhydramine (100 nM). Schild plot analysis of the effect of pyrilamine on the histamine-induced inward current revealed a pA2 value of 9.7, consistent with that expected for an H1 receptor. Neither impromidine (10 microM) nor R(-)-alpha-methylhistamine (10 microM), selective H2 or H3 agonists, respectively, significantly affected the membrane potential, input resistance or AHPslow. 5. The reversal potential (Vrev) for the histamine-induced inward current was -84 +/- 2.1 mV (n = 4). The Vrev for the histamine response shifted in a Nernstian manner with changes in the extracellular potassium concentration. Alterations in the extracellular chloride concentration had no significant effect on the Vrev of the histamine response (n = 3). The Vrev for the AHPslow was -85 +/- 1.7 mV (n = 4). 6. These results indicate that histamine increases the excitability of ferret vagal afferent somata by interfering with two classes of

  2. Input management of production systems.

    PubMed

    Odum, E P

    1989-01-13

    Nonpoint sources of pollution, which are largely responsible for stressing regional and global life-supporting atmosphere, soil, and water, can only be reduced (and ultimately controlled) by input management that involves increasing the efficiency of production systems and reducing the inputs of environmentally damaging materials. Input management requires a major change, an about-face, in the approach to management of agriculture, power plants, and industries because the focus is on waste reduction and recycling rather than on waste disposal. For large-scale ecosystem-level situations a top-down hierarchical approach is suggested and illustrated by recent research in agroecology and landscape ecology.

  3. PREVIMER : Meteorological inputs and outputs

    NASA Astrophysics Data System (ADS)

    Ravenel, H.; Lecornu, F.; Kerléguer, L.

    2009-09-01

    PREVIMER is a pre-operational system aiming to provide a wide range of users, from private individuals to professionals, with short-term forecasts about the coastal environment along the French coastlines bordering the English Channel, the Atlantic Ocean, and the Mediterranean Sea. Observation data and digital modelling tools first provide 48-hour (probably 96-hour by summer 2009) forecasts of sea states, currents, sea water levels and temperatures. The follow-up of an increasing number of biological parameters will, in time, complete this overview of coastal environment. Working in partnership with the French Naval Hydrographic and Oceanographic Service (Service Hydrographique et Océanographique de la Marine, SHOM), the French National Weather Service (Météo-France), the French public science and technology research institute (Institut de Recherche pour le Développement, IRD), the European Institute of Marine Studies (Institut Universitaire Européen de la Mer, IUEM) and many others, IFREMER (the French public institute fo marine research) is supplying the technologies needed to ensure this pertinent information, available daily on Internet at http://www.previmer.org, and stored at the Operational Coastal Oceanographic Data Centre. Since 2006, PREVIMER publishes the results of demonstrators assigned to limited geographic areas and to specific applications. This system remains experimental. The following topics are covered : Hydrodynamic circulation, sea states, follow-up of passive tracers, conservative or non-conservative (specifically of microbiological origin), biogeochemical state, primary production. Lastly, PREVIMER provides researchers and R&D departments with modelling tools and access to the database, in which the observation data and the modelling results are stored, to undertake environmental studies on new sites. The communication will focus on meteorological inputs to and outputs from PREVIMER. It will draw the lessons from almost 3 years during

  4. Glycinergic synaptic inputs to bipolar cells in the salamander retina

    PubMed Central

    Maple, Bruce R; Wu, Samuel M

    1998-01-01

    Glycine activated strychnine-sensitive chloride conductances at both the dendrites and the axonal telodendria of most bipolar cells in the salamander retina. The chloride equilibrium potential of bipolar cells was found to be negative to -50 mV, indicating that glycinergic synapses on bipolar cells are inhibitory. Some bipolar cells exhibited discrete, strychnine-sensitive, chloride-mediated inhibitory postsynaptic currents (IPSCs). These were elicited by focal application of glutamate at the inner plexiform layer (IPL). Glycinergic synapses were localized using simultaneous focal application of calcium to retinal slices bathed in calcium-free media. Both dendritic and telodendritic glycinergic IPSCs were observed. The decay of the telodendritic IPSCs was well fitted by a single exponential with a time constant of 17.7 ± 8.7 ms. Similar kinetics were observed for dendritic IPSCs in some cells, but in one class of on-centre bipolar cell the decay of the dendritic IPSCs was better fitted by a sum of two exponentials with time constants 9.9 ± 4.3 and 51.3 ± 24.3 ms. The dendritic IPSCs were best driven by application of glutamate at the distal IPL (the off sublamina), while the telodendritic IPSCs were driven best by application near the telodendria. These results suggest that bipolar cell dendrites receive inhibitory glycinergic inputs from interplexiform cells that are excited by off-centre bipolar cells, whereas bipolar cell telodendria receive glycinergic amacrine cell inputs that are antagonistic to the photoreceptor inputs. Both inputs could be elicited in the presence of tetrodotoxin (TTX), but the dendritic IPSCs were sometimes abolished by TTX, suggesting that sodium-dependent spikes play an i