Control over phase separation and nucleation using a laser-tweezing potential

Science.gov (United States)

Walton, Finlay; Wynne, Klaas

2018-05-01

Control over the nucleation of new phases is highly desirable but elusive. Even though there is a long history of crystallization engineering by varying physicochemical parameters, controlling which polymorph crystallizes or whether a molecule crystallizes or forms an amorphous precipitate is still a poorly understood practice. Although there are now numerous examples of control using laser-induced nucleation, the absence of physical understanding is preventing progress. Here we show that the proximity of a liquid-liquid critical point or the corresponding binodal line can be used by a laser-tweezing potential to induce concentration gradients. A simple theoretical model shows that the stored electromagnetic energy of the laser beam produces a free-energy potential that forces phase separation or triggers the nucleation of a new phase. Experiments in a liquid mixture using a low-power laser diode confirm the effect. Phase separation and nucleation using a laser-tweezing potential explains the physics behind non-photochemical laser-induced nucleation and suggests new ways of manipulating matter.

Information content in spectral dependencies of optical unit volume parameters under action of He-Ne laser on blood

Science.gov (United States)

Khairullina, Alphiya Y.; Oleinik, Tatiana V.

1995-01-01

Our previous works concerned with the development of methods for studying blood and action of low-intensity laser radiation on blood and erythrocyte suspensions had shown the light- scattering methods gave a large body of information on a medium studied due to the methodological relationship between irradiation processes and techniques for investigations. Detail analysis of spectral diffuse reflectivities and transmissivities of optically thick blood layers, spectral absorptivities calculated on this basis over 600 - 900 nm, by using different approximations, for a pathological state owing to hypoxia testifies to the optical significance of not only hemoglobin derivatives but also products of hemoglobin decomposition. Laser action on blood is specific and related to an initial state of blood absorption due to different composition of chromoproteids. This work gives the interpretation of spectral observations. Analysis of spectral dependencies of the exinction coefficient e, mean cosine m of phase function, and parameter Q equals (epsilon) (1-(mu) )H/(lambda) (H - hematocrit) testifies to decreasing the relative index of refraction of erythrocytes and to morphological changes during laser action under pathology owing to hypoxia. The possibility to obtain physical and chemical information on the state of blood under laser action in vivo is shown to be based on the method proposed by us for calculating multilayered structures modeling human organs and on the technical implementation of this method.

High-power CO laser and its potential applications

International Nuclear Information System (INIS)

Sato, Shunichi; Takahashi, Kunimitsu; Shimamoto, Kojiro; Takashima, Yoichi; Matsuda, Keiichi; Kuribayashi, Shizuma; Noda, Osamu; Imatake, Shigenori; Kondo, Motoe.

1995-01-01

The R and D program for the development of a high-power CO laser and its application technologies is described. Based on a self-sustained discharge excitation scheme, the available laser output has been successfully scaled to over 20 kW. The CO laser cutting experiments for thick metals have been performed in association with the decommissioning technologies development. Other potential applications, which include those based on photo chemical process, are reviewed. Recently demonstrated high-power tunable operation and room-temperature operation are also reported. (author)

Spectroscopic studies of the energy transfer processes important to obtain holmium laser action in the Er:Tm:Ho:YLF

International Nuclear Information System (INIS)

Tarelho, Luiz Vicente Gomes

1995-01-01

There are several processes of energy transfer between Er, Tm and Ho ions in YLF crystal that could be evaluated using the Foerster-Dexter method. Energy transfer processes, important to understand Holmium laser action, were studied, specially involving the energy transfer between the first excited states of Er and Tm donors and Ho acceptor. The back-transfer processes were evaluated too in order to minimize the system losses. Another important process to understand Ho laser action in the host is the energy diffusion mechanism between donor ions due to excitation migration processes which take place before the energy transfer to Ho. The proposed model of energy transfer was developed to include the diffusion mechanism between donors in the absence and presence of the acceptors. The energy transfer probability was evaluated including the back-transfer processes besides the diffusion assistance. A laser medium model based on the fundamental spectroscopic parameters was used in order to determine the ideal donor acceptor concentrations in order to maximize the laser action of Ho at 2,1 μm. (author)

Comparison of the effect of soft-core potentials and Coulombic potentials on bremsstrahlung during laser matter interaction

Science.gov (United States)

Pandit, Rishi R.; Becker, Valerie R.; Barrington, Kasey; Thurston, Jeremy; Ramunno, Lora; Ackad, Edward

2018-04-01

An intense, short laser pulse incident on rare-gas clusters can produce nano-plasmas containing energetic electrons. As these electrons undergo scattering, from both phonons and ions, they emit bremsstrahlung radiation. Here, we compare a theory of bremsstrahlung emission appropriate for the interaction of intense lasers with matter using soft-core potentials and Coulombic potentials. A new scaling for the radiation cross-section and the radiated power via bremsstrahlung is derived for a soft-core potential (which depends on the potential depth) and compared with the Coulomb potential. Calculations using the new scaling are performed for electrons in vacuum ultraviolet, infrared and mid-infrared laser pulses. The radiation cross-section and the radiation power via bremsstrahlung are found to increase rapidly with increases in the potential depth of up to around 200 eV and then become mostly saturated for larger depths while remaining constant for the Coulomb potential. In both cases, the radiation cross-section and the radiation power of bremsstrahlung decrease with increases in the laser wavelength. The ratio of the scattering amplitude for the soft-core potential and that for the Coulombic potential decreases exponentially with an increase in momentum transfer. The bremsstrahlung emission by electrons in plasmas may provide a broadband light source for diagnostics.

Components of action potential repolarization in cerebellar parallel fibres.

Science.gov (United States)

Pekala, Dobromila; Baginskas, Armantas; Szkudlarek, Hanna J; Raastad, Morten

2014-11-15

Repolarization of the presynaptic action potential is essential for transmitter release, excitability and energy expenditure. Little is known about repolarization in thin, unmyelinated axons forming en passant synapses, which represent the most common type of axons in the mammalian brain's grey matter.We used rat cerebellar parallel fibres, an example of typical grey matter axons, to investigate the effects of K(+) channel blockers on repolarization. We show that repolarization is composed of a fast tetraethylammonium (TEA)-sensitive component, determining the width and amplitude of the spike, and a slow margatoxin (MgTX)-sensitive depolarized after-potential (DAP). These two components could be recorded at the granule cell soma as antidromic action potentials and from the axons with a newly developed miniaturized grease-gap method. A considerable proportion of fast repolarization remained in the presence of TEA, MgTX, or both. This residual was abolished by the addition of quinine. The importance of proper control of fast repolarization was demonstrated by somatic recordings of antidromic action potentials. In these experiments, the relatively broad K(+) channel blocker 4-aminopyridine reduced the fast repolarization, resulting in bursts of action potentials forming on top of the DAP. We conclude that repolarization of the action potential in parallel fibres is supported by at least three groups of K(+) channels. Differences in their temporal profiles allow relatively independent control of the spike and the DAP, whereas overlap of their temporal profiles provides robust control of axonal bursting properties.

[Loudness optimized registration of compound action potential in cochlear implant recipients].

Science.gov (United States)

Berger, Klaus; Hocke, Thomas; Hessel, Horst

2017-11-01

Background Postoperative measurements of compound action potentials are not always possible due to the insufficient acceptance of the CI-recipients. This study investigated the impact of different parameters on the acceptance of the measurements. Methods Compound action potentials of 16 CI recipients were measured with different pulse-widths. Recipients performed a loudness rating at the potential thresholds with the different sequences. Results Compound action potentials obtained with higher pulse-widths were rated softer than those obtained with smaller pulse-widths. Conclusions Compound action potentials measured with higher pulse-widths generate a gap between loudest acceptable presentation level and potential threshold. This gap contributes to a higher acceptance of postoperative measurements. Georg Thieme Verlag KG Stuttgart · New York.

Studies on the Action Potential From a Thermodynamic Perspective

DEFF Research Database (Denmark)

Wang, Tian

and nerves with ganglia. (2) Attempts have been made to measure the temperature change associated with an action potential as well as an oscillation reaction (Briggs-Rauscher reaction) that shares the adiabatic feature. It turns out that some practical issues need to be solved for the temperature measurement...... of the nerve impulses, while the measured temperature change during the oscillation reaction suggests that there are a reversible adiabatic process and a dissipative process. (3) Local anesthetic e↵ect on nerves is studied. Local anesthetic lidocaine causes a significant stimulus threshold shift of the action......Nerve impulse, also called action potential, has mostly been considered as a pure electrical phenomenon. However, changes in dimensions, e.g. thickness and length, and in temperature along with action potentials have been observed, which indicates that the nerve is a thermodynamic system. The work...

Wireless cardiac action potential transmission with ultrasonically inserted silicon microprobes

International Nuclear Information System (INIS)

Shen, C J; Ramkumar, A; Lal, A; Gilmour, R F Jr

2011-01-01

This paper reports on the integration of ultrasonically inserted horn-shaped cardiac probes with wireless transmission of 3D cardiac action potential measurement for applications in ex vivo preparations such as monitoring the onset of ventricular fibrillation. Ultrasonically inserted silicon horn probes permit reduced penetration force during insertion, allowing silicon, a brittle material, to penetrate cardiac tissue. The probes also allow recording from multiple sites that are lithographically defined. An application-specific integrated circuit has been designed with a 40 dB amplifying stage and a frequency modulating oscillator at 95 MHz to wirelessly transmit the recorded action potentials. This ultrasonically inserted microprobe wireless system demonstrates the initial results in wireless monitoring of 3D action potential propagation, and the extraction of parameters of interest including the action potential duration and diastolic interval

An Evaluation of the Cutting Potential of Different Types of High Power Lasers

DEFF Research Database (Denmark)

Olsen, Flemming Ove

2006-01-01

Laser cutting is a widespread industrial process. The boundaries for the performance of the lasers in terms of cutting capabilities is steadily moving towards higher cutting rates and thicker section cutting. In this paper the potential of different high power laser sources in cutting is evaluated...... based upon the historical development, the available cutting mechanisms understanding and the critical parameters involved in high power laser cutting. From the theoretical point of view, the new laser sources, the Disc-laser and the Fibre laser possess a potential of changing dramatically the limits...... for cutting performance. These theoretical considerations are evaluated against available cutting data....

YCOB lasers

International Nuclear Information System (INIS)

Richardson, Martin; Hammons, Dennis; Eichenholz, Jason; Chai, Bruce; Ye, Qing; Jang, Won; Shah, Lawrence

1999-01-01

We review new developments with a new laser host material, YCa 4 O(BO 3 ) 3 or YCOB. Lasers based on this host material will open new opportunities for the development of compact, high-power, frequency-agile visible and near IR laser sources, as well as sources for ultrashort pulses. Efficient diode-pumped laser action with both Nd-doped and Yb-doped YCOB has already been demonstrated. Moreover, since these materials are biaxial, and have high nonlinear optical coefficients, they have become the first laser materials available as efficient self-frequency-doubled lasers, capable of providing tunable laser emission in several regions of the visible spectrum. Self-frequency doubling eliminates the need for inclusion of a nonlinear optical element within or external to the laser resonator. These laser materials possess excellent thermal and optical properties, have high laser-damage thresholds, and can be grown to large sizes. In addition they are non-hygroscopic. They therefore possess all the characteristics necessary for laser materials required in rugged, compact systems. Here we summarize the rapid progress made in the development of this new class of lasers, and review their potential for a number of applications. (author)

Numerical investigation of action potential transmission in plants

Directory of Open Access Journals (Sweden)

Mariusz Pietruszka

2014-01-01

Full Text Available In context of a fairly concise review of recent literature and well established experimental results we reconsider the problem of action potential propagating steadily down the plant cell(s. Having adopted slightly modified Hodgkin-Huxley set of differential equations for the action potential we carried out the numerical investigation of these equations in the course of time. We argue that the Hodgkin-Huxley-Katz model for the nerve impulse can be used to describe the phenomena which take place in plants - this point of view seems to be plausible since the mechanisms involving active ionic transport across membranes from the mathematical point of view are similar. Besides, we compare in a qualitative way our theoretical outcomes with typical experimental results for the action potentials which arise as the reaction of plants to electrical, mechanical and light stimuli. Moreover, we point out the relevance of the sequence of events during the pulse with the appropriate ionic fluxes.

Perturbation analysis of spontaneous action potential initiation by stochastic ion channels

KAUST Repository

Keener, James P.; Newby, Jay M.

2011-01-01

A stochastic interpretation of spontaneous action potential initiation is developed for the Morris-Lecar equations. Initiation of a spontaneous action potential can be interpreted as the escape from one of the wells of a double well potential

Laser wakefield accelerator based light sources: potential applications and requirements

Energy Technology Data Exchange (ETDEWEB)

Albert, F. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). NIF and Photon Sciences; Thomas, A. G. [Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Nuclear Engineering and Radiological Sciences; Mangles, S. P.D. [Imperial College, London (United Kingdom). Blackett Lab.; Banerjee, S. [Univ. of Nebraska, Lincoln, NE (United States); Corde, S. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Flacco, A. [ENSTA, CNRS, Ecole Polytechnique, Palaiseau (France); Litos, M. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Neely, D. [Science and Technology Facilities Council (STFC), Oxford (United Kingdom). Rutherford Appleton Lab. (RAL). Central Laser Facility; Viera, J. [Univ. of Lisbon (Portugal). GoLP-Inst. de Plasmas e Fusao Nuclear-Lab. Associado; Najmudin, Z. [Imperial College, London (United Kingdom). Blackett Lab.; Bingham, R. [Science and Technology Facilities Council (STFC), Oxford (United Kingdom). Rutherford Appleton Lab. (RAL). Central Laser Facility; Joshi, C. [Univ. of California, Los Angeles, CA (United States). Dept. of Electrical Engineering; Katsouleas, T. [Duke Univ., Durham, NC (United States). Platt School of Engineering

2015-01-15

In this article we review the prospects of laser wakefield accelerators as next generation light sources for applications. This work arose as a result of discussions held at the 2013 Laser Plasma Accelerators Workshop. X-ray phase contrast imaging, X-ray absorption spectroscopy, and nuclear resonance fluorescence are highlighted as potential applications for laser-plasma based light sources. We discuss ongoing and future efforts to improve the properties of radiation from plasma betatron emission and Compton scattering using laser wakefield accelerators for these specific applications.

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

Science.gov (United States)

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

2012-06-03

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

Formation of microspheres under the action of femtosecond laser radiation on titanium samples in hydrocarbons

Science.gov (United States)

Kochuev, D. A.; Khorkov, K. S.; Ivashchenko, A. V.; Prokoshev, V. G.; Arakelian, S. M.

2018-01-01

This work describes the original method of laser synthesis of microspheres which contain titanium carbide. The formation of microspheres is carried out by the action of femtosecond laser radiation on the surface of titanium in the reaction medium - the ultimate hydrocarbon. The resulting microspheres have a high surface smoothness, a narrow particle size distribution, an average size of 1-3 μm. They can be used in applications of additive engineering, powder metallurgy as the main raw material, or as an alloying additive.

Active action potential propagation but not initiation in thalamic interneuron dendrites

Science.gov (United States)

Casale, Amanda E.; McCormick, David A.

2012-01-01

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

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

Science.gov (United States)

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

2014-08-25

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

High-efficiency γ-ray flash generation via multiple-laser scattering in ponderomotive potential well.

Science.gov (United States)

Gong, Z; Hu, R H; Shou, Y R; Qiao, B; Chen, C E; He, X T; Bulanov, S S; Esirkepov, T Zh; Bulanov, S V; Yan, X Q

2017-01-01

γ-ray flash generation in near-critical-density target irradiated by four symmetrical colliding laser pulses is numerically investigated. With peak intensities about 10^{23} W/cm^{2}, the laser pulses boost electron energy through direct laser acceleration, while pushing them inward with the ponderomotive force. After backscattering with counterpropagating laser, the accelerated electron is trapped in the electromagnetic standing waves or the ponderomotive potential well created by the coherent overlapping of the laser pulses, and emits γ-ray photons in a multiple-laser-scattering regime, where electrons act as a medium transferring energy from the laser to γ rays in the ponderomotive potential valley.

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

Science.gov (United States)

Muñoz, Fabián; Fuentealba, Pablo

2012-01-01

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

Preliminary detection of explosive standard components with Laser Raman Technique

International Nuclear Information System (INIS)

Botti, S.; Ciardi, R.

2008-01-01

Presently, our section is leader of the ISOTREX project (Integrated System for On-line TRace EXplosives detection in solid, liquid and vapour state), funded in the frame of the PASR 2006 action (Preparatory Action on the enhancement of the European industrial potential in the field of Security Research Preparatory Action) of the 6. EC framework. ISOTREX project will exploit the capabilities of different laser techniques as LIBS (Laser Induced Breakdown Spectroscopy), LPA (Laser Photo Acustic) and CRDS (Cavity Ring Down Spectroscopy) to monitor explosive traces. In this frame, we extended our investigation also to the laser induced Raman effect spectroscopy, in order to investigate its capabilities and possible future integration. We analysed explosive samples in bulk solid phase, diluted liquid phase and as evaporated films over suitable substrate. In the following, we present the main results obtained, outlining preliminary conclusions [it

The DBI action, higher-derivative supergravity, and flattening inflaton potentials

International Nuclear Information System (INIS)

Bielleman, Sjoerd; Ibáñez, Luis E.; Pedro, Francisco G.; Valenzuela, Irene; Wieck, Clemens

2016-01-01

In string theory compactifications it is common to find an effective Lagrangian for the scalar fields with a non-canonical kinetic term. We study the effective action of the scalar position moduli of Type II Dp-branes. In many instances the kinetic terms are in fact modified by a term proportional to the scalar potential itself. This can be linked to the appearance of higher-dimensional supersymmetric operators correcting the Kähler potential. We identify the supersymmetric dimension-eight operators describing the α"′ corrections captured by the D-brane Dirac-Born-Infeld action. Our analysis then allows an embedding of the D-brane moduli effective action into an N=1 supergravity formulation. The effects of the potential-dependent kinetic terms may be very important if one of the scalars is the inflaton, since they lead to a flattening of the scalar potential. We analyze this flattening effect in detail and compute its impact on the CMB observables for single-field inflation with monomial potentials.

Reconstruction of action potential of repolarization in patients with congenital long-QT syndrome

International Nuclear Information System (INIS)

Kandori, Akihiko; Shimizu, Wataru; Yokokawa, Miki; Kamakura, Shiro; Miyatake, Kunio; Murakami, Masahiro; Miyashita, Tsuyoshi; Ogata, Kuniomi; Tsukada, Keiji

2004-01-01

A method for reconstructing an action potential during the repolarization period was developed. This method uses a current distribution-plotted as a current-arrow map (CAM)-calculated using magnetocardiogram (MCG) signals. The current arrows are summarized during the QRS complex period and subtracted during the ST-T wave period in order to reconstruct the action-potential waveform. To ensure the similarity between a real action potential and the reconstructed action potential using CAM, a monophasic action potential (MAP) and an MCG of the same patient with type-I long-QT syndrome were measured. Although the MAP had one notch that was associated with early afterdepolarization (EAD), the reconstructed action potential had two large and small notches. The small notch timing agreed with the occurrence of the EAD in the MAP. On the other hand, the initiation time of an abnormal current distribution coincides with the appearance timing of the first large notch, and its end time coincides with that of the second small notch. These results suggest that a simple reconstruction method using a CAM based on MCG data can provide a similar action-potential waveform to a MAP waveform without having to introduce a catheter

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

Science.gov (United States)

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

2017-06-01

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

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

Science.gov (United States)

Lu, Siyuan; Madhukar, Anupam

2013-02-01

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

A phantom axon setup for validating models of action potential recordings.

Science.gov (United States)

Rossel, Olivier; Soulier, Fabien; Bernard, Serge; Guiraud, David; Cathébras, Guy

2016-08-01

Electrode designs and strategies for electroneurogram recordings are often tested first by computer simulations and then by animal models, but they are rarely implanted for long-term evaluation in humans. The models show that the amplitude of the potential at the surface of an axon is higher in front of the nodes of Ranvier than at the internodes; however, this has not been investigated through in vivo measurements. An original experimental method is presented to emulate a single fiber action potential in an infinite conductive volume, allowing the potential of an axon to be recorded at both the nodes of Ranvier and the internodes, for a wide range of electrode-to-fiber radial distances. The paper particularly investigates the differences in the action potential amplitude along the longitudinal axis of an axon. At a short radial distance, the action potential amplitude measured in front of a node of Ranvier is two times larger than in the middle of two nodes. Moreover, farther from the phantom axon, the measured action potential amplitude is almost constant along the longitudinal axis. The results of this new method confirm the computer simulations, with a correlation of 97.6 %.

Shedding light: laser physics and mechanism of action.

Science.gov (United States)

De Felice, E

2010-02-01

Lasers have affected health care in many ways. Clinical applications have been found in a number of medical and surgical specialities. In particular, applications of laser technology in phlebology has made it essential for vein physicians to obtain a fundamental knowledge of laser physics, laser operation and also to be well versed in laser safety procedures. This article reviews recommended text books and current literature to detail the basics of laser physics and its application to venous disease. Laser safety and laser side effects are also discussed.

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

Science.gov (United States)

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

2012-10-25

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

Model and trajectory optimization for an ideal laser-enhanced solar sail

OpenAIRE

Carzana (student TUDelft), Livio; Dachwald, Bernd; Noomen, R.

2017-01-01

A laser-enhanced solar sail is a solar sail that is not solely propelled by solar radiation but additionally by a laser beam that illuminates the sail. This way, the propulsive acceleration of the sail results from the combined action of the solar and the laser radiation pressure onto the sail. The potential source of the laser beam is a laser satellite that coverts solar power (in the inner solar system) or nuclear power (in the outer solar system) into laser power. Such a laser satellite (o...

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

Science.gov (United States)

Furong, Liu; Shengtian, L I

2016-05-25

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

Triangulation of the monophasic action potential causes flattening of the electrocardiographic T-wave

DEFF Research Database (Denmark)

Bhuiyan, Tanveer Ahmed; Graff, Claus; Thomsen, Morten Bækgaard

2012-01-01

of the action potential under the effect of the IKr blocker sertindole and associated these changes to concurrent changes in the morphology of electrocardiographic T-waves in dogs. We show that, under the effect of sertindole, the peak changes in the morphology of action potentials occur at time points similar......It has been proposed that triangulation on the cardiac action potential manifests as a broadened, more flat and notched T-wave on the ECG but to what extent such morphology characteristics are indicative of triangulation is more unclear. In this paper, we have analyzed the morphological changes...... to those observed for the peak changes in T-wave morphology on the ECG. We further show that the association between action potential shape and ECG shape is dose-dependent and most prominent at the time corresponding to phase 3 of the action potential....

Prolonged action potential duration in cardiac ablation of PDK1 mice.

Science.gov (United States)

Han, Zhonglin; Jiang, Yu; Yang, Zhongzhou; Cao, Kejiang; Wang, Dao W

2015-01-01

The involvement of the AGC protein kinase family in regulating arrhythmia has drawn considerable attention, but the underlying mechanisms are still not clear. The aim of this study is to explore the role of 3-phosphoinositide-dependent protein kinase-1 (PDK1), one of upstream protein kinases of the AGC protein kinase family, in the pathogenesis of dysregulated electrophysiological basis. PDK1(F/F) αMHC-Cre mice and PDK1(F/F) mice were divided into experiment group and control group. Using patch clamping technology, we explored action potential duration in both groups, and investigated the functions of transient outward potassium channel and L-type Ca(2+) channel to explain the abnormal action potential duration. Significant prolongation action potential duration was found in mice with PDK1 deletion. Further, the peak current of transient outward potassium current and L-type Ca(2+) current were decreased by 84% and 49% respectively. In addition, dysregulation of channel kinetics lead to action potential duration prolongation further. In conclusion, we have demonstrated that PDK1 participates in action potential prolongation in cardiac ablation of PDK1 mice. This effect is likely to be mediated largely through downregulation of transient outward potassium current. These findings indicate the modulation of the PDK1 pathway could provide a new mechanism for abnormal electrophysiological basis.

Fiber Optic Detection of Action Potentials in Axons

National Research Council Canada - National Science Library

Smela, Elisabeth

2006-01-01

In prior exploratory research, we had designed a fiber optic sensor utilizing a long period Bragg grating for the purpose of detecting action potentials in axons optically, through a change in index...

Random lasing actions in self-assembled perovskite nanoparticles

Science.gov (United States)

Liu, Shuai; Sun, Wenzhao; Li, Jiankai; Gu, Zhiyuan; Wang, Kaiyang; Xiao, Shumin; Song, Qinghai

2016-05-01

Solution-based perovskite nanoparticles have been intensively studied in the past few years due to their applications in both photovoltaic and optoelectronic devices. Here, based on the common ground between solution-based perovskite and random lasers, we have studied the mirrorless lasing actions in self-assembled perovskite nanoparticles. After synthesis from a solution, discrete lasing peaks have been observed from optically pumped perovskites without any well-defined cavity boundaries. We have demonstrated that the origin of the random lasing emissions is the scattering between the nanostructures in the perovskite microplates. The obtained quality (Q) factors and thresholds of random lasers are around 500 and 60 μJ/cm2, respectively. Both values are comparable to the conventional perovskite microdisk lasers with polygon-shaped cavity boundaries. From the corresponding studies on laser spectra and fluorescence microscope images, the lasing actions are considered random lasers that are generated by strong multiple scattering in random gain media. In additional to conventional single-photon excitation, due to the strong nonlinear effects of perovskites, two-photon pumped random lasers have also been demonstrated for the first time. We believe this research will find its potential applications in low-cost coherent light sources and biomedical detection.

TRH regulates action potential shape in cerebral cortex pyramidal neurons.

Science.gov (United States)

Rodríguez-Molina, Víctor; Patiño, Javier; Vargas, Yamili; Sánchez-Jaramillo, Edith; Joseph-Bravo, Patricia; Charli, Jean-Louis

2014-07-07

Thyrotropin releasing hormone (TRH) is a neuropeptide with a wide neural distribution and a variety of functions. It modulates neuronal electrophysiological properties, including resting membrane potential, as well as excitatory postsynaptic potential and spike frequencies. We explored, with whole-cell patch clamp, TRH effect on action potential shape in pyramidal neurons of the sensorimotor cortex. TRH reduced spike and after hyperpolarization amplitudes, and increased spike half-width. The effect varied with dose, time and cortical layer. In layer V, 0.5µM of TRH induced a small increase in spike half-width, while 1 and 5µM induced a strong but transient change in spike half-width, and amplitude; after hyperpolarization amplitude was modified at 5µM of TRH. Cortical layers III and VI neurons responded intensely to 0.5µM TRH; layer II neurons response was small. The effect of 1µM TRH on action potential shape in layer V neurons was blocked by G-protein inhibition. Inhibition of the activity of the TRH-degrading enzyme pyroglutamyl peptidase II (PPII) reproduced the effect of TRH, with enhanced spike half-width. Many cortical PPII mRNA+ cells were VGLUT1 mRNA+, and some GAD mRNA+. These data show that TRH regulates action potential shape in pyramidal cortical neurons, and are consistent with the hypothesis that PPII controls its action in this region. Copyright © 2014 Elsevier B.V. All rights reserved.

Osteogenic potential of laser modified and conditioned titanium zirconium surfaces

Directory of Open Access Journals (Sweden)

P David Charles

2016-01-01

Full Text Available Statement of Problem: The osseointegration of dental implant is related to their composition and surface treatment. Titanium zirconium (TiZr has been introduced as an alternative to the commercially pure titanium and its alloys as dental implant material, which is attributed to its superior mechanical and biological properties. Surface treatments of TiZr have been introduced to enhance their osseointegration ability; however, reliable, easy to use surface modification technique has not been established. Purpose: The purpose of this study was to evaluate and compare the effect of neodymium-doped yttrium aluminum garnet (Nd-YAG laser surface treatment of TiZr implant alloy on their osteogenic potential. Materials and Methods: Twenty disc-shaped samples of 5 mm diameter and 2 mm height were milled from the TiZr alloy ingot. The polished discs were ultrasonically cleaned in distilled water. Ten samples each were randomly selected as Group A control samples and Group B consisted of Nd-YAG laser surface etched and conditioned test samples. These were evaluated for cellular response. Cellular adhesion and proliferation were quantified, and the results were statistically analyzed using nonparametric analysis. Cellular morphology was observed using electron and epiflurosence microscopy. Results: Nd-YAG laser surface modified and conditioned TiZr samples increased the osteogenic potential. Conclusion: Nd-YAG laser surface modification of TiZr, improves the cellular activity, surface roughness, and wettability, thereby increasing the osteogenic potential.

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

Science.gov (United States)

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

2012-10-25

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

Membrane, action, and oscillatory potentials in simulated protocells

Science.gov (United States)

Syren, R. M.; Fox, S. W.; Przybylski, A. T.; Stratten, W. P.

1982-01-01

Electrical membrane potentials, oscillations, and action potentials are observed in proteinoid microspheres impaled with (3 M KCl) microelectrodes. Although effects are of greater magnitude when the vesicles contain glycerol and natural or synthetic lecithin, the results in the purely synthetic thermal protein structures are substantial, attaining 20 mV amplitude in some cases. The results add the property of electrical potential to the other known properties of proteinoid microspheres, in their role as models for protocells.

Introducing the Action Potential to Psychology Students

Science.gov (United States)

Simon-Dack, Stephanie L.

2014-01-01

For this simple active learning technique for teaching, students are assigned "roles" and act out the process of the action potential (AP), including the firing threshold, ion-specific channels for ions to enter and leave the cell, diffusion, and the refractory period. Pre-post test results indicated that students demonstrated increased…

Perturbation analysis of spontaneous action potential initiation by stochastic ion channels

KAUST Repository

Keener, James P.

2011-07-01

A stochastic interpretation of spontaneous action potential initiation is developed for the Morris-Lecar equations. Initiation of a spontaneous action potential can be interpreted as the escape from one of the wells of a double well potential, and we develop an asymptotic approximation of the mean exit time using a recently developed quasistationary perturbation method. Using the fact that the activating ionic channel\\'s random openings and closings are fast relative to other processes, we derive an accurate estimate for the mean time to fire an action potential (MFT), which is valid for a below-threshold applied current. Previous studies have found that for above-threshold applied current, where there is only a single stable fixed point, a diffusion approximation can be used. We also explore why different diffusion approximation techniques fail to estimate the MFT. © 2011 American Physical Society.

Action potentials in retinal ganglion cells are initiated at the site of maximal curvature of the extracellular potential.

Science.gov (United States)

Eickenscheidt, Max; Zeck, Günther

2014-06-01

The initiation of an action potential by extracellular stimulation occurs after local depolarization of the neuronal membrane above threshold. Although the technique shows remarkable clinical success, the site of action and the relevant stimulation parameters are not completely understood. Here we identify the site of action potential initiation in rabbit retinal ganglion cells (RGCs) interfaced to an array of extracellular capacitive stimulation electrodes. We determine which feature of the extracellular potential governs action potential initiation by simultaneous stimulation and recording RGCs interfaced in epiretinal configuration. Stimulation electrodes were combined to areas of different size and were presented at different positions with respect to the RGC. Based on stimulation by electrodes beneath the RGC soma and simultaneous sub-millisecond latency measurement we infer axonal initiation at the site of maximal curvature of the extracellular potential. Stimulation by electrodes at different positions along the axon reveals a nearly constant threshold current density except for a narrow region close to the cell soma. These findings are explained by the concept of the activating function modified to consider a region of lower excitability close to the cell soma. We present a framework how to estimate the site of action potential initiation and the stimulus required to cross threshold in neurons tightly interfaced to capacitive stimulation electrodes. Our results underscore the necessity of rigorous electrical characterization of the stimulation electrodes and of the interfaced neural tissue.

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

Science.gov (United States)

Crago, Patrick E; Makowski, Nathaniel S

2014-10-01

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

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

Science.gov (United States)

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

2014-01-01

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

Unmasking of an early laser evoked potential by a point localization task

DEFF Research Database (Denmark)

Valeriani, M.; Restuccia, D.; Le Pera, D.

2000-01-01

Objectives: The investigation of the CO2 laser evoked potential (LEP) modifications following a point localization task. Methods: LEPs were recorded from 10 healthy subjects in two different conditions. (1) Task condition: laser stimuli were shifted among 3 different locations on the right hand d...

Nd:Ta2O5 rib waveguide lasers

International Nuclear Information System (INIS)

Unal, Bayram; Tai, C.-Y.; Shepherd, David P.; Wilkinson, James S.; Perney, Nicolas M.B.; Netti, M. Caterina; Parker, Gregory J.

2005-01-01

Ta 2 O 5 waveguides offer great potential for high-density active photonic crystal circuits and their combination with rare-earth dopants for active devices is of interest for increasing their potential functionality. To this end, neodymium-doped Ta 2 O 5 rib waveguide lasers have been fabricated on an oxidized silicon wafer by rf sputtering and argon ion-beam milling and laser action in this material has been demonstrated. Lasing was observed at wavelenghts between 1060 and 1080 nm and an absorbed pump power threshold of 87 mW was obtained

Rosewood oil induces sedation and inhibits compound action potential in rodents.

Science.gov (United States)

de Almeida, Reinaldo Nóbrega; Araújo, Demétrius Antonio Machado; Gonçalves, Juan Carlos Ramos; Montenegro, Fabrícia Costa; de Sousa, Damião Pergentino; Leite, José Roberto; Mattei, Rita; Benedito, Marco Antonio Campana; de Carvalho, José Gilberto Barbosa; Cruz, Jader Santos; Maia, José Guilherme Soares

2009-07-30

Aniba rosaeodora is an aromatic plant which has been used in Brazil folk medicine due to its sedative effect. Therefore, the purpose of the present study was to evaluate the sedative effect of linalool-rich rosewood oil in mice. In addition we sought to investigate the linalool-rich oil effects on the isolated nerve using the single sucrose-gap technique. Sedative effect was determined by measuring the potentiation of the pentobarbital-induced sleeping time. The compound action potential amplitude was evaluated as a way to detect changes in excitability of the isolated nerve. The results showed that administration of rosewood oil at the doses of 200 and 300 mg/kg significantly decreased latency and increased the duration of sleeping time. On the other hand, the dose of 100 mg/kg potentiated significantly the pentobarbital action decreasing pentobarbital latency time and increasing pentobarbital sleeping time. In addition, the effect of linalool-rich rosewood oil on the isolated nerve of the rat was also investigated through the single sucrose-gap technique. The amplitude of the action potential decreased almost 100% when it was incubated for 30 min at 100 microg/ml. From this study, it is suggested a sedative effect of linalool-rich rosewood oil that could, at least in part, be explained by the reduction in action potential amplitude that provokes a decrease in neuronal excitability.

Improving Cardiac Action Potential Measurements: 2D and 3D Cell Culture.

Science.gov (United States)

Daily, Neil J; Yin, Yue; Kemanli, Pinar; Ip, Brian; Wakatsuki, Tetsuro

2015-11-01

Progress in the development of assays for measuring cardiac action potential is crucial for the discovery of drugs for treating cardiac disease and assessing cardiotoxicity. Recently, high-throughput methods for assessing action potential using induced pluripotent stem cell (iPSC) derived cardiomyocytes in both two-dimensional monolayer cultures and three-dimensional tissues have been developed. We describe an improved method for assessing cardiac action potential using an ultra-fast cost-effective plate reader with commercially available dyes. Our methods improve dramatically the detection of the fluorescence signal from these dyes and make way for the development of more high-throughput methods for cardiac drug discovery and cardiotoxicity.

Multiple modes of action potential initiation and propagation in mitral cell primary dendrite

DEFF Research Database (Denmark)

Chen, Wei R; Shen, Gongyu Y; Shepherd, Gordon M

2002-01-01

recordings with computational modeling to analyze action-potential initiation and propagation in the primary dendrite. In response to depolarizing current injection or distal olfactory nerve input, fast Na(+) action potentials were recorded along the entire length of the primary dendritic trunk. With weak......-to-moderate olfactory nerve input, an action potential was initiated near the soma and then back-propagated into the primary dendrite. As olfactory nerve input increased, the initiation site suddenly shifted to the distal primary dendrite. Multi-compartmental modeling indicated that this abrupt shift of the spike......-initiation site reflected an independent thresholding mechanism in the distal dendrite. When strong olfactory nerve excitation was paired with strong inhibition to the mitral cell basal secondary dendrites, a small fast prepotential was recorded at the soma, which indicated that an action potential was initiated...

Ionic channels underlying the ventricular action potential in zebrafish embryo.

Science.gov (United States)

Alday, Aintzane; Alonso, Hiart; Gallego, Monica; Urrutia, Janire; Letamendia, Ainhoa; Callol, Carles; Casis, Oscar

2014-06-01

Over the last years zebrafish has become a popular model in the study of cardiac physiology, pathology and pharmacology. Recently, the application of the 3Rs regulation and the characteristics of the embryo have reduced the use of adult zebrafish use in many studies. However, the zebrafish embryo cardiac physiology is poorly characterized since most works have used indirect techniques and direct recordings of cardiac action potential and ionic currents are scarce. In order to optimize the zebrafish embryo model, we used electrophysiological, pharmacological and immunofluorescence tools to identify the characteristics and the ionic channels involved in the ventricular action potentials of zebrafish embryos. The application of Na(+) or T-type Ca(+2) channel blockers eliminated the cardiac electrical activity, indicating that the action potential upstroke depends on Na(+) and T-type Ca(+2) currents. The plateau phase depends on L-type Ca(+2) channels since it is abolished by specific blockade. The direct channel blockade indicates that the action potential repolarization and diastolic potential depends on ERG K(+) channels. The presence in the embryonic heart of the Nav1.5, Cav1.2, Cav3.2 and ERG channels was also confirmed by immunofluorescence, while the absence of effect of specific blockers and immunostaining indicate that two K(+) repolarizing currents present in human heart, Ito and IKs, are absent in the embryonic zebrafish heart. Our results describe the ionic channels present and its role in the zebrafish embryo heart and support the use of zebrafish embryos to study human diseases and their use for drug testing. Copyright © 2014 Elsevier Ltd. All rights reserved.

Decoupling Action Potential Bias from Cortical Local Field Potentials

Directory of Open Access Journals (Sweden)

Stephen V. David

2010-01-01

Full Text Available Neurophysiologists have recently become interested in studying neuronal population activity through local field potential (LFP recordings during experiments that also record the activity of single neurons. This experimental approach differs from early LFP studies because it uses high impendence electrodes that can also isolate single neuron activity. A possible complication for such studies is that the synaptic potentials and action potentials of the small subset of isolated neurons may contribute disproportionately to the LFP signal, biasing activity in the larger nearby neuronal population to appear synchronous and cotuned with these neurons. To address this problem, we used linear filtering techniques to remove features correlated with spike events from LFP recordings. This filtering procedure can be applied for well-isolated single units or multiunit activity. We illustrate the effects of this correction in simulation and on spike data recorded from primary auditory cortex. We find that local spiking activity can explain a significant portion of LFP power at most recording sites and demonstrate that removing the spike-correlated component can affect measurements of auditory tuning of the LFP.

Warm Body Temperature Facilitates Energy Efficient Cortical Action Potentials

Science.gov (United States)

Yu, Yuguo; Hill, Adam P.; McCormick, David A.

2012-01-01

The energy efficiency of neural signal transmission is important not only as a limiting factor in brain architecture, but it also influences the interpretation of functional brain imaging signals. Action potential generation in mammalian, versus invertebrate, axons is remarkably energy efficient. Here we demonstrate that this increase in energy efficiency is due largely to a warmer body temperature. Increases in temperature result in an exponential increase in energy efficiency for single action potentials by increasing the rate of Na+ channel inactivation, resulting in a marked reduction in overlap of the inward Na+, and outward K+, currents and a shortening of action potential duration. This increase in single spike efficiency is, however, counterbalanced by a temperature-dependent decrease in the amplitude and duration of the spike afterhyperpolarization, resulting in a nonlinear increase in the spike firing rate, particularly at temperatures above approximately 35°C. Interestingly, the total energy cost, as measured by the multiplication of total Na+ entry per spike and average firing rate in response to a constant input, reaches a global minimum between 37–42°C. Our results indicate that increases in temperature result in an unexpected increase in energy efficiency, especially near normal body temperature, thus allowing the brain to utilize an energy efficient neural code. PMID:22511855

Warm body temperature facilitates energy efficient cortical action potentials.

Directory of Open Access Journals (Sweden)

Yuguo Yu

Full Text Available The energy efficiency of neural signal transmission is important not only as a limiting factor in brain architecture, but it also influences the interpretation of functional brain imaging signals. Action potential generation in mammalian, versus invertebrate, axons is remarkably energy efficient. Here we demonstrate that this increase in energy efficiency is due largely to a warmer body temperature. Increases in temperature result in an exponential increase in energy efficiency for single action potentials by increasing the rate of Na(+ channel inactivation, resulting in a marked reduction in overlap of the inward Na(+, and outward K(+, currents and a shortening of action potential duration. This increase in single spike efficiency is, however, counterbalanced by a temperature-dependent decrease in the amplitude and duration of the spike afterhyperpolarization, resulting in a nonlinear increase in the spike firing rate, particularly at temperatures above approximately 35°C. Interestingly, the total energy cost, as measured by the multiplication of total Na(+ entry per spike and average firing rate in response to a constant input, reaches a global minimum between 37-42°C. Our results indicate that increases in temperature result in an unexpected increase in energy efficiency, especially near normal body temperature, thus allowing the brain to utilize an energy efficient neural code.

Direct detection of a single evoked action potential with MRS in Lumbricus terrestris.

Science.gov (United States)

Poplawsky, Alexander J; Dingledine, Raymond; Hu, Xiaoping P

2012-01-01

Functional MRI (fMRI) measures neural activity indirectly by detecting the signal change associated with the hemodynamic response following brain activation. In order to alleviate the temporal and spatial specificity problems associated with fMRI, a number of attempts have been made to detect neural magnetic fields (NMFs) with MRI directly, but have thus far provided conflicting results. In this study, we used MR to detect axonal NMFs in the median giant fiber of the earthworm, Lumbricus terrestris, by examining the free induction decay (FID) with a sampling interval of 0.32 ms. The earthworm nerve cords were isolated from the vasculature and stimulated at the threshold of action potential generation. FIDs were acquired shortly after the stimulation, and simultaneous field potential recordings identified the presence or absence of single evoked action potentials. FIDs acquired when the stimulus did not evoke an action potential were summed as background. The phase of the background-subtracted FID exhibited a systematic change, with a peak phase difference of (-1.2 ± 0.3) × 10(-5) radians occurring at a time corresponding to the timing of the action potential. In addition, we calculated the possible changes in the FID magnitude and phase caused by a simulated action potential using a volume conductor model. The measured phase difference matched the theoretical prediction well in both amplitude and temporal characteristics. This study provides the first evidence for the direct detection of a magnetic field from an evoked action potential using MR. Copyright © 2011 John Wiley & Sons, Ltd.

A fast Na+/Ca2+-based action potential in a marine diatom.

Directory of Open Access Journals (Sweden)

Alison R Taylor

Full Text Available BACKGROUND: Electrical impulses in animals play essential roles in co-ordinating an array of physiological functions including movement, secretion, environmental sensing and development. Underpinning many of these electrical signals is a fast Na+-based action potential that has been fully characterised only in cells associated with the neuromuscular systems of multicellular animals. Such rapid action potentials are thought to have evolved with the first metazoans, with cnidarians being the earliest representatives. The present study demonstrates that a unicellular protist, the marine diatom Odontella sinensis, can also generate a fast Na+/Ca2+ based action potential that has remarkably similar biophysical and pharmacological properties to invertebrates and vertebrate cardiac and skeletal muscle cells. METHODOLOGY/PRINCIPAL FINDINGS: The kinetic, ionic and pharmacological properties of the rapid diatom action potential were examined using single electrode current and voltage clamp techniques. Overall, the characteristics of the fast diatom currents most closely resemble those of vertebrate and invertebrate muscle Na+/Ca2+ currents. CONCLUSIONS/SIGNIFICANCE: This is the first demonstration of voltage-activated Na+ channels and the capacity to generate fast Na+-based action potentials in a unicellular photosynthetic organism. The biophysical and pharmacological characteristics together with the presence of a voltage activated Na+/Ca2+ channel homologue in the recently sequenced genome of the diatom Thalassiosira pseudonana, provides direct evidence supporting the hypothesis that this rapid signalling mechanism arose in ancestral unicellular eukaryotes and has been retained in at least two phylogenetically distant lineages of eukaryotes; opisthokonts and the stramenopiles. The functional role of the fast animal-like action potential in diatoms remains to be elucidated but is likely involved in rapid environmental sensing of these widespread and

Channel sialic acids limit hERG channel activity during the ventricular action potential.

Science.gov (United States)

Norring, Sarah A; Ednie, Andrew R; Schwetz, Tara A; Du, Dongping; Yang, Hui; Bennett, Eric S

2013-02-01

Activity of human ether-a-go-go-related gene (hERG) 1 voltage-gated K(+) channels is responsible for portions of phase 2 and phase 3 repolarization of the human ventricular action potential. Here, we questioned whether and how physiologically and pathophysiologically relevant changes in surface N-glycosylation modified hERG channel function. Voltage-dependent hERG channel gating and activity were evaluated as expressed in a set of Chinese hamster ovary (CHO) cell lines under conditions of full glycosylation, no sialylation, no complex N-glycans, and following enzymatic deglycosylation of surface N-glycans. For each condition of reduced glycosylation, hERG channel steady-state activation and inactivation relationships were shifted linearly by significant depolarizing ∼9 and ∼18 mV, respectively. The hERG window current increased significantly by 50-150%, and the peak shifted by a depolarizing ∼10 mV. There was no significant change in maximum hERG current density. Deglycosylated channels were significantly more active (20-80%) than glycosylated controls during phases 2 and 3 of action potential clamp protocols. Simulations of hERG current and ventricular action potentials corroborated experimental data and predicted reduced sialylation leads to a 50-70-ms decrease in action potential duration. The data describe a novel mechanism by which hERG channel gating is modulated through physiologically and pathophysiologically relevant changes in N-glycosylation; reduced channel sialylation increases hERG channel activity during the action potential, thereby increasing the rate of action potential repolarization.

A Parametric Computational Model of the Action Potential of Pacemaker Cells.

Science.gov (United States)

Ai, Weiwei; Patel, Nitish D; Roop, Partha S; Malik, Avinash; Andalam, Sidharta; Yip, Eugene; Allen, Nathan; Trew, Mark L

2018-01-01

A flexible, efficient, and verifiable pacemaker cell model is essential to the design of real-time virtual hearts that can be used for closed-loop validation of cardiac devices. A new parametric model of pacemaker action potential is developed to address this need. The action potential phases are modeled using hybrid automaton with one piecewise-linear continuous variable. The model can capture rate-dependent dynamics, such as action potential duration restitution, conduction velocity restitution, and overdrive suppression by incorporating nonlinear update functions. Simulated dynamics of the model compared well with previous models and clinical data. The results show that the parametric model can reproduce the electrophysiological dynamics of a variety of pacemaker cells, such as sinoatrial node, atrioventricular node, and the His-Purkinje system, under varying cardiac conditions. This is an important contribution toward closed-loop validation of cardiac devices using real-time heart models.

Laser Incident Lessons Learned and Action List

Energy Technology Data Exchange (ETDEWEB)

Yarotski, Dmitry Anatolievitch [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2016-02-29

On Thursday November 19, 2015, LANL postdoc received an eye injury from a reflected, nonvisible laser beam (Class 4, pulsed, wavelength 800 nanometer). The setup is configured to split the laser output into two work areas in which qualified operators conduct research experiments. During this incident, the laser output beam was being projected to both experimental work areas, although only one experimental area was actively being used. The second laser beam directed to the second work area was blocked by an inappropriate device (Plexiglas, reflective, non-normal incidence) that reflected substantial portion of the beam toward the first setup. In preparation for the measurements, worker stepped on the stepstool and decided to remove the laser goggles to better see the micrometer readings which were difficult to see due to insufficient lighting. Immediately, he noticed a flash of light in his eye. The operator quickly replaced the laser eye-wear and then, using an infrared viewer, located a stray laser beam being reflected from the plexiglas beam block. The operator did not think he had sustained any injury and continued working. Later that day, however, he noticed a blurry spot in the vision of his left eye. He notified his supervisor on Friday morning, November 20, 2015, and was taken by CINT management to Sandia National Laboratories (SNL) medical facility for evaluation. SNL Medical did not find any abnormalities, but referred the operator to a local ophthalmologist for further evaluation. Further evaluations by the ophthalmologist on November 21 and November 23 identified a small spot of inflammation near the fovea on the retina in his left eye. The ophthalmologist stated that this spot would most likely heal on its own and that the blurry spot on the operator's vision would go away. A follow-up visit was scheduled. The employee was released back to work without restrictions.

Cell-type-dependent action potentials and voltage-gated currents in mouse fungiform taste buds.

Science.gov (United States)

Kimura, Kenji; Ohtubo, Yoshitaka; Tateno, Katsumi; Takeuchi, Keita; Kumazawa, Takashi; Yoshii, Kiyonori

2014-01-01

Taste receptor cells fire action potentials in response to taste substances to trigger non-exocytotic neurotransmitter release in type II cells and exocytotic release in type III cells. We investigated possible differences between these action potentials fired by mouse taste receptor cells using in situ whole-cell recordings, and subsequently we identified their cell types immunologically with cell-type markers, an IP3 receptor (IP3 R3) for type II cells and a SNARE protein (SNAP-25) for type III cells. Cells not immunoreactive to these antibodies were examined as non-IRCs. Here, we show that type II cells and type III cells fire action potentials using different ionic mechanisms, and that non-IRCs also fire action potentials with either of the ionic mechanisms. The width of action potentials was significantly narrower and their afterhyperpolarization was deeper in type III cells than in type II cells. Na(+) current density was similar in type II cells and type III cells, but it was significantly smaller in non-IRCs than in the others. Although outwardly rectifying current density was similar between type II cells and type III cells, tetraethylammonium (TEA) preferentially suppressed the density in type III cells and the majority of non-IRCs. Our mathematical model revealed that the shape of action potentials depended on the ratio of TEA-sensitive current density and TEA-insensitive current one. The action potentials of type II cells and type III cells under physiological conditions are discussed. © 2013 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

Imaging Action Potential in Single Mammalian Neurons by Tracking the Accompanying Sub-Nanometer Mechanical Motion.

Science.gov (United States)

Yang, Yunze; Liu, Xian-Wei; Wang, Hui; Yu, Hui; Guan, Yan; Wang, Shaopeng; Tao, Nongjian

2018-03-28

Action potentials in neurons have been studied traditionally by intracellular electrophysiological recordings and more recently by the fluorescence detection methods. Here we describe a label-free optical imaging method that can measure mechanical motion in single cells with a sub-nanometer detection limit. Using the method, we have observed sub-nanometer mechanical motion accompanying the action potential in single mammalian neurons by averaging the repeated action potential spikes. The shape and width of the transient displacement are similar to those of the electrically recorded action potential, but the amplitude varies from neuron to neuron, and from one region of a neuron to another, ranging from 0.2-0.4 nm. The work indicates that action potentials may be studied noninvasively in single mammalian neurons by label-free imaging of the accompanying sub-nanometer mechanical motion.

Noise Enhances Action Potential Generation in Mouse Sensory Neurons via Stochastic Resonance.

Science.gov (United States)

Onorato, Irene; D'Alessandro, Giuseppina; Di Castro, Maria Amalia; Renzi, Massimiliano; Dobrowolny, Gabriella; Musarò, Antonio; Salvetti, Marco; Limatola, Cristina; Crisanti, Andrea; Grassi, Francesca

2016-01-01

Noise can enhance perception of tactile and proprioceptive stimuli by stochastic resonance processes. However, the mechanisms underlying this general phenomenon remain to be characterized. Here we studied how externally applied noise influences action potential firing in mouse primary sensory neurons of dorsal root ganglia, modelling a basic process in sensory perception. Since noisy mechanical stimuli may cause stochastic fluctuations in receptor potential, we examined the effects of sub-threshold depolarizing current steps with superimposed random fluctuations. We performed whole cell patch clamp recordings in cultured neurons of mouse dorsal root ganglia. Noise was added either before and during the step, or during the depolarizing step only, to focus onto the specific effects of external noise on action potential generation. In both cases, step + noise stimuli triggered significantly more action potentials than steps alone. The normalized power norm had a clear peak at intermediate noise levels, demonstrating that the phenomenon is driven by stochastic resonance. Spikes evoked in step + noise trials occur earlier and show faster rise time as compared to the occasional ones elicited by steps alone. These data suggest that external noise enhances, via stochastic resonance, the recruitment of transient voltage-gated Na channels, responsible for action potential firing in response to rapid step-wise depolarizing currents.

Cortical Interneuron Subtypes Vary in Their Axonal Action Potential Properties.

Science.gov (United States)

Casale, Amanda E; Foust, Amanda J; Bal, Thierry; McCormick, David A

2015-11-25

The role of interneurons in cortical microcircuits is strongly influenced by their passive and active electrical properties. Although different types of interneurons exhibit unique electrophysiological properties recorded at the soma, it is not yet clear whether these differences are also manifested in other neuronal compartments. To address this question, we have used voltage-sensitive dye to image the propagation of action potentials into the fine collaterals of axons and dendrites in two of the largest cortical interneuron subtypes in the mouse: fast-spiking interneurons, which are typically basket or chandelier neurons; and somatostatin containing interneurons, which are typically regular spiking Martinotti cells. We found that fast-spiking and somatostatin-expressing interneurons differed in their electrophysiological characteristics along their entire dendrosomatoaxonal extent. The action potentials generated in the somata and axons, including axon collaterals, of somatostatin-expressing interneurons are significantly broader than those generated in the same compartments of fast-spiking inhibitory interneurons. In addition, action potentials back-propagated into the dendrites of somatostatin-expressing interneurons much more readily than fast-spiking interneurons. Pharmacological investigations suggested that axonal action potential repolarization in both cell types depends critically upon Kv1 channels, whereas the axonal and somatic action potentials of somatostatin-expressing interneurons also depend on BK Ca(2+)-activated K(+) channels. These results indicate that the two broad classes of interneurons studied here have expressly different subcellular physiological properties, allowing them to perform unique computational roles in cortical circuit operations. Neurons in the cerebral cortex are of two major types: excitatory and inhibitory. The proper balance of excitation and inhibition in the brain is critical for its operation. Neurons contain three main

Re-modeling Chara action potential: II. The action potential form under salinity stress

Directory of Open Access Journals (Sweden)

Mary Jane Beilby

2017-04-01

Full Text Available In part I we established Thiel-Beilby model of the Chara action potential (AP. In part II the AP is investigated in detail at the time of saline stress. Even very short exposure of salt-sensitive Chara cells to artificial pond water with 50 mM NaCl (Saline APW modified the AP threshold and drastically altered the AP form. Detailed modeling of 14 saline APs from 3 cells established that both the Ca2+ pump and the Ca2+ channels on internal stores seem to be affected, with the changes sometimes cancelling and sometimes re-enforcing each other, leading to APs with long durations and very complex forms. The exposure to salinity offers further insights into AP mechanism and suggests future experiments. The prolonged APs lead to greater loss of chloride and potassium ions, compounding the effects of saline stress.

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

Science.gov (United States)

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

2010-01-01

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

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

Science.gov (United States)

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

2015-05-01

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

Modelling in vivo action potential propagation along a giant axon.

Science.gov (United States)

George, Stuart; Foster, Jamie M; Richardson, Giles

2015-01-01

A partial differential equation model for the three-dimensional current flow in an excitable, unmyelinated axon is considered. Where the axon radius is significantly below a critical value R(crit) (that depends upon intra- and extra-cellular conductivity and ion channel conductance) the resistance of the intracellular space is significantly higher than that of the extracellular space, such that the potential outside the axon is uniformly small whilst the intracellular potential is approximated by the transmembrane potential. In turn, since the current flow is predominantly axial, it can be shown that the transmembrane potential is approximated by a solution to the one-dimensional cable equation. It is noted that the radius of the squid giant axon, investigated by (Hodgkin and Huxley 1952e), lies close to R(crit). This motivates us to apply the three-dimensional model to the squid giant axon and compare the results thus found to those obtained using the cable equation. In the context of the in vitro experiments conducted in (Hodgkin and Huxley 1952e) we find only a small difference between the wave profiles determined using these two different approaches and little difference between the speeds of action potential propagation predicted. This suggests that the cable equation approximation is accurate in this scenario. However when applied to the it in vivo setting, in which the conductivity of the surrounding tissue is considerably lower than that of the axoplasm, there are marked differences in both wave profile and speed of action potential propagation calculated using the two approaches. In particular, the cable equation significantly over predicts the increase in the velocity of propagation as axon radius increases. The consequences of these results are discussed in terms of the evolutionary costs associated with increasing the speed of action potential propagation by increasing axon radius.

On stochastic heating of electrons by intense laser radiation in the presence of electrostatic potential well

International Nuclear Information System (INIS)

Krasheninnikov, S. I.

2014-01-01

A simple model developed by Paradkar et al. [Phys. Plasmas 19, 060703 (2012)] for the study of synergistic effects of electrostatic potential well and laser radiation is extended for the case where electric field of the well is accelerating electrons moving in the direction of the laser field propagation. It was found that in these cases, the rate of stochastic heating of energetic electrons remains virtually the same as in Paradkar et al. [Phys. Plasmas 19, 060703 (2012)], where electric field in electrostatic potential was slowing down electrons moving in the direction of the laser field propagation. However, the heating of electrons with relatively low energy can be sensitive to the orientation of the electrostatic potential well with respect to the direction of the laser radiation propagation

Potentials for progress in laser medicine

International Nuclear Information System (INIS)

Parrish, J.A.; Walsh, J.T. Jr.

1985-01-01

Lasers could come to occupy a highly important position in the armament of medicine. They are the brightest known sources of light, man-made or natural, and emit light having such properties as coherence and monochromaticity. Furthermore, lasers have the ability to deliver very brief pulses of light which can cause unique alterations in biological materials. The major obstacle to the increased use of lasers in medicine and surgery is not the availability of laser devices, but the dearth of basic information about laser-tissue interactions. We have recently demonstrated that, even in turbid tissue such as the dermis, it is possible simultaneously to induce microscopically selective thermal damage, localized to millions of selectively absorbing targets, while sparing surrounding tissues. These targets may be as small as organelles or as large as blood vessels. Such localized thermal damage is truly unique to pulsed laser exposures. The scope and medical utility of these lesions has yet to be fully understood. Thus, there is much research to be done in describing and characterizing laser-induced injury. There is, however, ample evidence that several laser therapies could be improved by using selectively absorbed, short pulses that lead to the spatial confinement of thermal injury. Treatment of port wine stains, pigmented lesions, atheromatous arterial plaques, and the fragmentation of kidney and gall stones are examples. It should also be possible to use a variety of systems to deliver exogenous laser targets on or within individual types of cells or organelles. Such chromophores may lead to new forms of cancer therapy, for example

7 CFR 1945.19 - Reporting potential natural disasters and initial actions.

Science.gov (United States)

2010-01-01

... 7 Agriculture 13 2010-01-01 2009-01-01 true Reporting potential natural disasters and initial... Assistance-General § 1945.19 Reporting potential natural disasters and initial actions. (a) Purpose. The purpose of reporting potential natural disasters is to provide a systematic procedure for rapid reporting...

INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Spectroscopic investigation of thermodynamic parameters of a plasma plume formed by the action of cw CO2 laser radiation on a metal substrate

Science.gov (United States)

Vasil'chenko, Zh V.; Azharonok, V. V.; Filatova, I. I.; Shimanovich, V. D.; Golubev, V. S.; Zabelin, A. M.

1996-09-01

Emission spectroscopy methods were used in an investigation of thermodynamic parameters of a surface plasma formed by the action of cw CO2 laser radiation of (2-5)×106 W cm-2 intensity on stainless steel in a protective He or Ar atmosphere. The spatiotemporal structure and pulsation characteristics of the plasma plume were used to determine the fields of the plasma electron density and temperature.

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

Science.gov (United States)

Rodriguez-Falces, Javier

2015-01-01

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

Action potential-independent and pharmacologically unique vesicular serotonin release from dendrites

Science.gov (United States)

Colgan, Lesley A.; Cavolo, Samantha L.; Commons, Kathryn G.; Levitan, Edwin S.

2012-01-01

Serotonin released within the dorsal raphe nucleus (DR) induces feedback inhibition of serotonin neuron activity and consequently regulates mood-controlling serotonin release throughout the forebrain. Serotonin packaged in vesicles is released in response to action potentials by the serotonin neuron soma and terminals, but the potential for release by dendrites is unknown. Here three-photon (3P) microscopy imaging of endogenous serotonin in living rat brain slice, immunofluorescence and immuno-gold electron microscopy detection of VMAT2 (vesicular monoamine transporter 2) establish the presence of vesicular serotonin within DR dendrites. Furthermore, activation of glutamate receptors is shown to induce vesicular serotonin release from dendrites. However, unlike release from the soma and terminals, dendritic serotonin release is independent of action potentials, relies on L-type Ca2+ channels, is induced preferentially by NMDA, and displays distinct sensitivity to the selective serotonin reuptake inhibitor (SSRI) antidepressant fluoxetine. The unique control of dendritic serotonin release has important implications for DR physiology and the antidepressant action of SSRIs, dihydropyridines and NMDA receptor antagonists. PMID:23136413

Miscellaneous Lasing Actions in Organo-Lead Halide Perovskite Films.

Science.gov (United States)

Duan, Zonghui; Wang, Shuai; Yi, Ningbo; Gu, Zhiyuan; Gao, Yisheng; Song, Qinghai; Xiao, Shumin

2017-06-21

Lasing actions in organo-lead halide perovskite films have been heavily studied in the past few years. However, due to the disordered nature of synthesized perovskite films, the lasing actions are usually understood as random lasers that are formed by multiple scattering. Herein, we demonstrate the miscellaneous lasing actions in organo-lead halide perovskite films. In addition to the random lasers, we show that a single or a few perovskite microparticles can generate laser emissions with their internal resonances instead of multiple scattering among them. We experimentally observed and numerically confirmed whispering gallery (WG)-like microlasers in polygon shaped and other deformed microparticles. Meanwhile, owing to the nature of total internal reflection and the novel shape of the nanoparticle, the size of the perovskite WG laser can be significantly decreased to a few hundred nanometers. Thus, wavelength-scale lead halide perovskite lasers were realized for the first time. All of these laser behaviors are complementary to typical random lasers in perovskite film and will help the understanding of lasing actions in complex lead halide perovskite systems.

The monophasic action potential upstroke: a means of characterizing local conduction.

Science.gov (United States)

Levine, J H; Moore, E N; Kadish, A H; Guarnieri, T; Spear, J F

1986-11-01

The upstrokes of monophasic action potentials (MAPs) recorded with an extracellular pressure electrode were characterized in isolated canine tissue preparations in vitro. The characteristics of the MAP upstroke were compared with those of the local action potential foot as well as with the characteristics of approaching electrical activation during uniform and asynchronous conduction. The upstroke of the MAP was exponential during uniform conduction. The time constant of rise of the MAP upstroke (TMAP) correlated with that of the action potential foot (Tfoot): TMAP + 1.01 Tfoot + 0.50; r2 = .80. Furthermore, changes in Tfoot with alterations in cycle length were associated with similar changes in TMAP: Tfoot = 1.06 TMAP - 0.11; r2 = .78. In addition, TMAP and Tfoot both deviated from exponential during asynchronous activation; the inflections that developed in the MAP upstroke correlated in time with intracellular action potential upstrokes that were asynchronous in onset in these tissues. Finally, the field of view of the MAP was determined and was found to be dependent in part on tissue architecture and the space constant. Specifically, the field of view of the MAP was found to be greater parallel compared with transverse to fiber orientation (6.02 +/- 1.74 vs 3.03 +/- 1.10 mm; p less than .01). These data suggest that the MAP upstroke may be used to define and characterize local electrical activation. The relatively large field of view of the MAP suggests that this technique may be a sensitive means to record focal membrane phenomena in vivo.

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

Science.gov (United States)

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

2013-03-01

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

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

Science.gov (United States)

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

2014-01-01

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

Calcium-Induced calcium release during action potential firing in developing inner hair cells.

Science.gov (United States)

Iosub, Radu; Avitabile, Daniele; Grant, Lisa; Tsaneva-Atanasova, Krasimira; Kennedy, Helen J

2015-03-10

In the mature auditory system, inner hair cells (IHCs) convert sound-induced vibrations into electrical signals that are relayed to the central nervous system via auditory afferents. Before the cochlea can respond to normal sound levels, developing IHCs fire calcium-based action potentials that disappear close to the onset of hearing. Action potential firing triggers transmitter release from the immature IHC that in turn generates experience-independent firing in auditory neurons. These early signaling events are thought to be essential for the organization and development of the auditory system and hair cells. A critical component of the action potential is the rise in intracellular calcium that activates both small conductance potassium channels essential during membrane repolarization, and triggers transmitter release from the cell. Whether this calcium signal is generated by calcium influx or requires calcium-induced calcium release (CICR) is not yet known. IHCs can generate CICR, but to date its physiological role has remained unclear. Here, we used high and low concentrations of ryanodine to block or enhance CICR to determine whether calcium release from intracellular stores affected action potential waveform, interspike interval, or changes in membrane capacitance during development of mouse IHCs. Blocking CICR resulted in mixed action potential waveforms with both brief and prolonged oscillations in membrane potential and intracellular calcium. This mixed behavior is captured well by our mathematical model of IHC electrical activity. We perform two-parameter bifurcation analysis of the model that predicts the dependence of IHCs firing patterns on the level of activation of two parameters, the SK2 channels activation and CICR rate. Our data show that CICR forms an important component of the calcium signal that shapes action potentials and regulates firing patterns, but is not involved directly in triggering exocytosis. These data provide important insights

Selective effects of potassium elevations on glutamate signaling and action potential conduction in hippocampus.

Science.gov (United States)

Meeks, Julian P; Mennerick, Steven

2004-01-07

High-frequency synaptic transmission is depressed by moderate rises in the extracellular potassium concentration ([K+]o). Previous reports have indicated that depression of action potential signaling may underlie the synaptic depression. Here, we investigated the specific contribution of K+-induced action potential changes to synaptic depression. We found that glutamatergic transmission in the hippocampal area CA1 was significantly depressed by 8-10 mM [K+]o, but that GABAergic transmission remained intact. Riluzole, a drug that slows recovery from inactivation of voltage-gated sodium channels (NaChs), interacts with subthreshold [K+]o to depress afferent volleys and EPSCs strongly. Thus, elevated [K+]o likely depresses synapses by slowing NaCh recovery from inactivation. It is unclear from previous studies whether [K+]o-induced action potential depression is caused by changes in initiation, reliability, or waveform. We investigated these possibilities explicitly. [K+]o-induced afferent volley depression was independent of stimulus strength, suggesting that changes in action potential initiation do not explain [K+]o-induced depression. Measurements of action potentials from single axons revealed that 8 mM [K+]o increased conduction failures in a subpopulation of fibers and depressed action potential amplitude in all fibers. Together, these changes quantitatively account for the afferent volley depression. We estimate that conduction failure explains more than half of the synaptic depression observed at 8 mM [K+]o, with the remaining depression likely explained by waveform changes. These mechanisms of selective sensitivity of glutamate release to [K+]o accumulation represent a unique neuromodulatory mechanism and a brake on runaway excitation.

Compound sensory action potential in normal and pathological human nerves

DEFF Research Database (Denmark)

Krarup, Christian

2004-01-01

The compound sensory nerve action potential (SNAP) is the result of phase summation and cancellation of single fiber potentials (SFAPs) with amplitudes that depend on fiber diameter, and the amplitude and shape of the SNAP is determined by the distribution of fiber diameters. Conduction velocitie...... effort and attention to theory and practical detail that may be time consuming....

Fusion of blastomeres in mouse embryos under the action of femtosecond laser radiation. Efficiency of blastocyst formation and embryo development

Energy Technology Data Exchange (ETDEWEB)

Osychenko, A A; Zalesskii, A D; Krivokharchenko, A S; Zhakhbazyan, A K; Nadtochenko, V A [N N Semenov Institute of Chemical Physics, Russian Academy of Sciences, Moscow (Russian Federation); Ryabova, A V [A M Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2015-05-31

Using the method of femtosecond laser surgery we study the fusion of two-cell mouse embryos under the action of tightly focused femtosecond laser radiation with the fusion efficiency reaching 60%. The detailed statistical analysis of the efficiency of blastomere fusion and development of the embryo up to the blastocyst stage after exposure of the embryos from different mice to a femtosecond pulse is presented. It is shown that the efficiency of blastocyst formation essentially depends on the biological characteristics of the embryo, namely, the strain and age of the donor mouse. The possibility of obtaining hexaploid embryonal cells using the methods of femtosecond laser surgery is demonstrated. (extreme light fields and their applications)

Optical properties of costal cartilage and their variation in the process of non-destructive action of laser radiation with the wavelength 1.56 μm

Energy Technology Data Exchange (ETDEWEB)

Yuzhakov, A V; Sviridov, A P; Shcherbakov, E M; Baum, O I; Sobol, E N [Institute on Laser and Information Technologies, Russian Academy of Sciences, Shatura, Moscow Region (Russian Federation)

2014-01-31

The optical properties of costal cartilage and their variation under the action of laser radiation with the wavelength 1.56 μm are studied. The laser action regime corresponds to that used for changing the cartilage shape. The dynamics of the passed scattered laser radiation was studied by means of the optical fibre system, and the optical properties of the cartilage tissue (on the basis of Monte Carlo modelling of light propagation) – using the setup with two integrating spheres. Under the influence of radiation, the characteristics of which corresponded to those used for the cartilage shape correction, no essential changes in the optical parameters were found. The results obtained in the course of studying the dynamics of optical signals in the process of costal cartilage irradiation can be used for developing control systems, providing the safety and efficiency of laser medical technologies. (biophotonics)

Gas dynamic lasers

International Nuclear Information System (INIS)

Hill, R.J.; Jewell, N.T.

1975-01-01

In a high powered laser system it is proposed that combustion gases be bled off from a gas turbine engine and their composition adjusted by burning extra fuel in the bleed gases or adding extra substances. Suitable aerodynamic expansion produces a population inversion resulting in laser action in the CO 2 species. Alternatively, bleed gases may be taken from the high pressure compressor of the gas turbine engine and an appropriate fuel burned therein. If required, other adjustments may also be made to the composition and the resulting gaseous mixture subjected to aerodynamic expansion to induce laser action as before. (auth)

Distributed feedback dye laser pumped with copper-vapor laser emission

Energy Technology Data Exchange (ETDEWEB)

Mirza, S Yu; Soldatov, A N; Sukhanov, V B

1983-10-01

The power-spectrum characteristics of the emission of a distributed feedback dye laser pumped with a copper vapor laser have been studied. Laser action has been observed in five dyes over a tuning range of 530-723 nm with an efficiency of 12.4%. The specfic features of the distributed feedback dye laser operating at pulse repetition rates of 4 kHz are discussed.

Dynamics of the inward rectifier K+ current during the action potential of guinea pig ventricular myocytes

OpenAIRE

Ibarra, J.; Morley, G.E.; Delmar, M.

1991-01-01

The potassium selective, inward rectifier current (IK1) is known to be responsible for maintaining the resting membrane potential of quiescent ventricular myocytes. However, the contribution of this current to the different phases of the cardiac action potential has not been adequately established. In the present study, we have used the action potential clamp (APC) technique to characterize the dynamic changes of a cesium-sensitive (i.e., Ik1) current which occur during the action potential. ...

Restitution slope is principally determined by steady-state action potential duration.

Science.gov (United States)

Shattock, Michael J; Park, Kyung Chan; Yang, Hsiang-Yu; Lee, Angela W C; Niederer, Steven; MacLeod, Kenneth T; Winter, James

2017-06-01

The steepness of the action potential duration (APD) restitution curve and local tissue refractoriness are both thought to play important roles in arrhythmogenesis. Despite this, there has been little recognition of the apparent association between steady-state APD and the slope of the restitution curve. The objective of this study was to test the hypothesis that restitution slope is determined by APD and to examine the relationship between restitution slope, refractoriness and susceptibility to VF. Experiments were conducted in isolated hearts and ventricular myocytes from adult guinea pigs and rabbits. Restitution curves were measured under control conditions and following intervention to prolong (clofilium, veratridine, bretylium, low [Ca]e, chronic transverse aortic constriction) or shorten (catecholamines, rapid pacing) ventricular APD. Despite markedly differing mechanisms of action, all interventions that prolonged the action potential led to a steepening of the restitution curve (and vice versa). Normalizing the restitution curve as a % of steady-state APD abolished the difference in restitution curves with all interventions. Effects on restitution were preserved when APD was modulated by current injection in myocytes pre-treated with the calcium chelator BAPTA-AM - to abolish the intracellular calcium transient. The non-linear relation between APD and the rate of repolarization of the action potential is shown to underpin the common influence of APD on the slope of the restitution curve. Susceptibility to VF was found to parallel changes in APD/refractoriness, rather than restitution slope. Steady-state APD is the principal determinant of the slope of the ventricular electrical restitution curve. In the absence of post-repolarization refractoriness, factors that prolong the action potential would be expected to steepen the restitution curve. However, concomitant changes in tissue refractoriness act to reduce susceptibility to sustained VF. Dependence on

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

Science.gov (United States)

Li, S N; Zhang, K Y

1992-11-01

Effects of dauricine (Dau) on the action potentials (AP), the slow action potentials (SAP), and the slow inward currents (Isi) of guinea pig ventricular papillary muscles were observed by means of intracellular microelectrode and single sucrose gap voltage clamp technique. In the early stage, Dau shortened action potential duration 100 (APD100) and effective refractory period (ERP) (ERP/APD ERP, and APD20, significantly decreased action potential amplitude (APA), maximum velocity (Vmax), and overshot (OS) (ERP/APD > 1; P SAP induced by isoprenaline (P < 0.01), and remarkably inhibited Isi (P < 0.01). The results suggested that Dau exerted an inhibitory effect on Na+, Ca2+, and K+ channels.

High power visible diode laser for the treatment of eye diseases by laser coagulation

Science.gov (United States)

Heinrich, Arne; Hagen, Clemens; Harlander, Maximilian; Nussbaumer, Bernhard

2015-03-01

We present a high power visible diode laser enabling a low-cost treatment of eye diseases by laser coagulation, including the two leading causes of blindness worldwide (diabetic retinopathy, age-related macular degeneration) as well as retinopathy of prematurely born children, intraocular tumors and retinal detachment. Laser coagulation requires the exposure of the eye to visible laser light and relies on the high absorption of the retina. The need for treatment is constantly increasing, due to the demographic trend, the increasing average life expectancy and medical care demand in developing countries. The World Health Organization reacts to this demand with global programs like the VISION 2020 "The right to sight" and the following Universal Eye Health within their Global Action Plan (2014-2019). One major point is to motivate companies and research institutes to make eye treatment cheaper and easily accessible. Therefore it becomes capital providing the ophthalmology market with cost competitive, simple and reliable technologies. Our laser is based on the direct second harmonic generation of the light emitted from a tapered laser diode and has already shown reliable optical performance. All components are produced in wafer scale processes and the resulting strong economy of scale results in a price competitive laser. In a broader perspective the technology behind our laser has a huge potential in non-medical applications like welding, cutting, marking and finally laser-illuminated projection.

Intense laser field effects on a Woods-Saxon potential quantum well

Science.gov (United States)

Restrepo, R. L.; Morales, A. L.; Akimov, V.; Tulupenko, V.; Kasapoglu, E.; Ungan, F.; Duque, C. A.

2015-11-01

This paper presents the results of the theoretical study of the effects of non-resonant intense laser field and electric and magnetic fields on the optical properties in an quantum well (QW) make with Woods-Saxon potential profile. The electric field and intense laser field are applied along the growth direction of the Woods-Saxon quantum well and the magnetic field is oriented perpendicularly. To calculate the energy and the wave functions of the electron in the Woods-Saxon quantum well, the effective mass approximation and the method of envelope wave function are used. The confinement in the Woods-Saxon quantum well is changed drastically by the application of intense laser field or either the effect of electric and magnetic fields. The optical properties are calculated using the compact density matrix.

Position-dependent patterning of spontaneous action potentials in immature cochlear inner hair cells.

Science.gov (United States)

Johnson, Stuart L; Eckrich, Tobias; Kuhn, Stephanie; Zampini, Valeria; Franz, Christoph; Ranatunga, Kishani M; Roberts, Terri P; Masetto, Sergio; Knipper, Marlies; Kros, Corné J; Marcotti, Walter

2011-06-01

Spontaneous action potential activity is crucial for mammalian sensory system development. In the auditory system, patterned firing activity has been observed in immature spiral ganglion and brain-stem neurons and is likely to depend on cochlear inner hair cell (IHC) action potentials. It remains uncertain whether spiking activity is intrinsic to developing IHCs and whether it shows patterning. We found that action potentials were intrinsically generated by immature IHCs of altricial rodents and that apical IHCs showed bursting activity as opposed to more sustained firing in basal cells. We show that the efferent neurotransmitter acetylcholine fine-tunes the IHC's resting membrane potential (V(m)), and as such is crucial for the bursting pattern in apical cells. Endogenous extracellular ATP also contributes to the V(m) of apical and basal IHCs by triggering small-conductance Ca(2+)-activated K(+) (SK2) channels. We propose that the difference in firing pattern along the cochlea instructs the tonotopic differentiation of IHCs and auditory pathway.

Position-dependent patterning of spontaneous action potentials in immature cochlear inner hair cells

Science.gov (United States)

Johnson, Stuart L.; Eckrich, Tobias; Kuhn, Stephanie; Zampini, Valeria; Franz, Christoph; Ranatunga, Kishani M.; Roberts, Terri P.; Masetto, Sergio; Knipper, Marlies; Kros, Corné J.; Marcotti, Walter

2011-01-01

Spontaneous action potential activity is crucial for mammalian sensory system development. In the auditory system, patterned firing activity has been observed in immature spiral ganglion cells and brain-stem neurons and is likely to depend on cochlear inner hair cell (IHC) action potentials. It remains uncertain whether spiking activity is intrinsic to developing IHCs and whether it shows patterning. We found that action potentials are intrinsically generated by immature IHCs of altricial rodents and that apical IHCs exhibit bursting activity as opposed to more sustained firing in basal cells. We show that the efferent neurotransmitter ACh, by fine-tuning the IHC’s resting membrane potential (Vm), is crucial for the bursting pattern in apical cells. Endogenous extracellular ATP also contributes to the Vm of apical and basal IHCs by activating SK2 channels. We hypothesize that the difference in firing pattern along the cochlea instructs the tonotopic differentiation of IHCs and auditory pathway. PMID:21572434

Effects of Acetylcholine and Noradrenalin on Action Potentials of Isolated Rabbit Sinoatrial and Atrial Myocytes

Science.gov (United States)

Verkerk, Arie O.; Geuzebroek, Guillaume S. C.; Veldkamp, Marieke W.; Wilders, Ronald

2012-01-01

The autonomic nervous system controls heart rate and contractility through sympathetic and parasympathetic inputs to the cardiac tissue, with acetylcholine (ACh) and noradrenalin (NA) as the chemical transmitters. In recent years, it has become clear that specific Regulators of G protein Signaling proteins (RGS proteins) suppress muscarinic sensitivity and parasympathetic tone, identifying RGS proteins as intriguing potential therapeutic targets. In the present study, we have identified the effects of 1 μM ACh and 1 μM NA on the intrinsic action potentials of sinoatrial (SA) nodal and atrial myocytes. Single cells were enzymatically isolated from the SA node or from the left atrium of rabbit hearts. Action potentials were recorded using the amphotericin-perforated patch-clamp technique in the absence and presence of ACh, NA, or a combination of both. In SA nodal myocytes, ACh increased cycle length and decreased diastolic depolarization rate, whereas NA decreased cycle length and increased diastolic depolarization rate. Both ACh and NA increased maximum upstroke velocity. Furthermore, ACh hyperpolarized the maximum diastolic potential. In atrial myocytes stimulated at 2 Hz, both ACh and NA hyperpolarized the maximum diastolic potential, increased the action potential amplitude, and increased the maximum upstroke velocity. Action potential duration at 50 and 90% repolarization was decreased by ACh, but increased by NA. The effects of both ACh and NA on action potential duration showed a dose dependence in the range of 1–1000 nM, while a clear-cut frequency dependence in the range of 1–4 Hz was absent. Intermediate results were obtained in the combined presence of ACh and NA in both SA nodal and atrial myocytes. Our data uncover the extent to which SA nodal and atrial action potentials are intrinsically dependent on ACh, NA, or a combination of both and may thus guide further experiments with RGS proteins. PMID:22754533

Recombinational laser employing electron transitions of diatomic molecules

Energy Technology Data Exchange (ETDEWEB)

Biriukov, A S; Prokhorov, A M; Shelepin, L A; Shirokov, N N

1974-12-01

Conditions are established for obtaining laser action in the visible and uv regions of the spectrum, using transitions between electronic states of diatomic molecules during recombination of a dissociated gas. The mechanism of population inversion was studied for the oxygen molecule, and gain estimates were obtained for laser action at a wavelength of 4881 A. The feasibility of laser action at other wavelengths was examined.

Implementing participatory action research in Lithuania: potential and challenges

Directory of Open Access Journals (Sweden)

Gabija Jarašiūnaitė

2015-12-01

Full Text Available Participatory action research is a quite new approach to research in Lithuania. The aim of an article was to disscuss the potential and challenges of participatory action research while implementing it in Lithuanian organizations. The qualitative approach was chosen for the study using the method of Focus groups. 20 researchers from social and biomedicine sciences from six institutions of High education in Lithuania participated in the study. The results of the study showed that participatory action reasearch is seen as an approach with many possibilities because of a wide range of used methods, constant interactions with research participants and the lenght of the research process. Researchers value the possibility to access organization at the begining, during research process and evaluate the effectiveness of the changes after the process. The research challenges are associated with the competence of a researcher including his/her sensitivity during process, ability to involve active participation of organization members in the ongoing process by creating safe and trusting environment. Some specific challenges associated with Lithuanian organizations are organizations‘ tiredness of researches and lack of faith of the benefits of researches because of some previous experiences. Keywords: Participatory Action Research, Organization, Lithuania.

Action of a 904-nm diode laser in orthopedics and traumatology: a clinical study on 447 cases

Science.gov (United States)

Tam, Giuseppe

2001-10-01

Objective: The evidence in medical literature is that a beneficial analgesic effect can only be obtained by employing laser radiation of relatively low power density and wavelengths which are able to penetrate tissue. For this reason the semiconductor, or laser diode (GaAs, 904 nm), is the most appropriate choice in pain-reduction therapy. Summary Background Data: Low power laser (or LLL) acts on the Prostaglandins synthesis, increases the endorphins synthesis in the Rolando gelatinous substance and in the dorsal horn of the spinal cord. The L-Arginine, which is the classic substrate of nitric oxide, carries on vasodilatory and anti- inflammatory action. Methods: Treatment was carried out on 447 cases and 435 patients (250 women and 185 men) between 20th May 1987 and 31st December 1999. The patients, whose age ranged from 25 to 70, were suffering from rheumatic, degenerative and traumatic pathologies as well as cutaneous ulcers. The majority of patients had been seen by orthopaedists and rheumatologists and had undergone x-ray, ultrasound scan, etc. All patients had previously received drug-based treatment and/or physiotherapy, with poor results. Two thirds were experiencing acute symptomatic pain, while the others presented a chronic pathology with recurrent crises. We used a pulsed IR diode laser, GaAs emitting at 904 nm. Frequency of treatment: 1 application per day for 5 consecutive days, followed by a 2-day interval. The percentage reduction in symptoms or improvement in functional status were determined on the basis of objective analysis as it happens in the Legal and Insurance Medicine field. Results: Very good results were achieved especially with cases of symptomatic osteoarthritis of the cervical vertebrae, with sport-related injuries, epicondylitis, osteoarthritis of the knee, periarthritis and with cutaneous ulcers. The beneficial action of the LLLT in the latter pathology is linked to the increase in collagen and to fibroblast proliferation. The total

RXP-E: a connexin43-binding peptide that prevents action potential propagation block

DEFF Research Database (Denmark)

Lewandowski, Rebecca; Procida, Kristina; Vaidyanathan, Ravi

2008-01-01

. Separately, RXP-E was concatenated to a cytoplasmic transduction peptide (CTP) for cytoplasmic translocation (CTP-RXP-E). The effect of RXP-E on action potential propagation was assessed by high-resolution optical mapping in monolayers of neonatal rat ventricular myocytes, containing approximately 20......% of randomly distributed myofibroblasts. In contrast to control experiments, when heptanol (2 mmol/L) was added to the superfusate of monolayers loaded with CTP-RXP-E, action potential propagation was maintained, albeit at a slower velocity. Similarly, intracellular acidification (pH(i) 6.2) caused a loss...... of action potential propagation in control monolayers; however, propagation was maintained in CTP-RXP-E-treated cells, although at a slower rate. Patch-clamp experiments revealed that RXP-E did not prevent heptanol-induced block of sodium currents, nor did it alter voltage dependence or amplitude of Kir2...

ACTION-SPACE CLUSTERING OF TIDAL STREAMS TO INFER THE GALACTIC POTENTIAL

Energy Technology Data Exchange (ETDEWEB)

Sanderson, Robyn E.; Helmi, Amina [Kapteyn Astronomical Institute, P.O. Box 800, 9700 AV Groningen (Netherlands); Hogg, David W., E-mail: robyn@astro.columbia.edu [Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003 (United States)

2015-03-10

We present a new method for constraining the Milky Way halo gravitational potential by simultaneously fitting multiple tidal streams. This method requires three-dimensional positions and velocities for all stars to be fit, but does not require identification of any specific stream or determination of stream membership for any star. We exploit the principle that the action distribution of stream stars is most clustered when the potential used to calculate the actions is closest to the true potential. Clustering is quantified with the Kullback-Leibler Divergence (KLD), which also provides conditional uncertainties for our parameter estimates. We show, for toy Gaia-like data in a spherical isochrone potential, that maximizing the KLD of the action distribution relative to a smoother distribution recovers the input potential. The precision depends on the observational errors and number of streams; using K III giants as tracers, we measure the enclosed mass at the average radius of the sample stars accurate to 3% and precise to 20%-40%. Recovery of the scale radius is precise to 25%, biased 50% high by the small galactocentric distance range of stars in our mock sample (1-25 kpc, or about three scale radii, with mean 6.5 kpc). 20-25 streams with at least 100 stars each are required for a stable confidence interval. With radial velocities (RVs) to 100 kpc, all parameters are determined with ∼10% accuracy and 20% precision (1.3% accuracy for the enclosed mass), underlining the need to complete the RV catalog for faint halo stars observed by Gaia.

Neuronal oscillations enhance stimulus discrimination by ensuring action potential precision

DEFF Research Database (Denmark)

Schaefer, Andreas T; Angelo, Kamilla; Spors, Hartwig

2006-01-01

generated membrane potential oscillations dramatically improve action potential (AP) precision by removing the membrane potential variance associated with jitter-accumulating trains of APs. This increased AP precision occurred irrespective of cell type and--at oscillation frequencies ranging from 3 to 65 Hz......Although oscillations in membrane potential are a prominent feature of sensory, motor, and cognitive function, their precise role in signal processing remains elusive. Here we show, using a combination of in vivo, in vitro, and theoretical approaches, that both synaptically and intrinsically......, membrane potential oscillations dramatically enhance the discriminatory capabilities of individual neurons and networks of cells and provide one attractive explanation for their abundance in neurophysiological systems....

Action Potential Dynamics in Fine Axons Probed with an Axonally Targeted Optical Voltage Sensor.

Science.gov (United States)

Ma, Yihe; Bayguinov, Peter O; Jackson, Meyer B

2017-01-01

The complex and malleable conduction properties of axons determine how action potentials propagate through extensive axonal arbors to reach synaptic terminals. The excitability of axonal membranes plays a major role in neural circuit function, but because most axons are too thin for conventional electrical recording, their properties remain largely unexplored. To overcome this obstacle, we used a genetically encoded hybrid voltage sensor (hVOS) harboring an axonal targeting motif. Expressing this probe in transgenic mice enabled us to monitor voltage changes optically in two populations of axons in hippocampal slices, the large axons of dentate granule cells (mossy fibers) in the stratum lucidum of the CA3 region and the much finer axons of hilar mossy cells in the inner molecular layer of the dentate gyrus. Action potentials propagated with distinct velocities in each type of axon. Repetitive firing broadened action potentials in both populations, but at an intermediate frequency the degree of broadening differed. Repetitive firing also attenuated action potential amplitudes in both mossy cell and granule cell axons. These results indicate that the features of use-dependent action potential broadening, and possible failure, observed previously in large nerve terminals also appear in much finer unmyelinated axons. Subtle differences in the frequency dependences could influence the propagation of activity through different pathways to excite different populations of neurons. The axonally targeted hVOS probe used here opens up the diverse repertoire of neuronal processes to detailed biophysical study.

The effects of Nd2O3 concentration in the laser emission of TeO2-ZnO glasses

Science.gov (United States)

Moreira, L. M.; Anjos, V.; Bell, M. J. V.; Ramos, C. A. R.; Kassab, L. R. P.; Doualan, D. J. L.; Camy, P.; Moncorgé, R.

2016-08-01

The present work reports the modification introduced by different Nd2O3 concentration on optical properties and the laser operation of Nd3+ doped (TeO2-ZnO) bulk tellurite glass. The spectroscopic data are analyzed within the Judd Ofelt formalism framework and the results are compared to the fluorescence lifetime and emission measurements to derive values for the quantum efficiency and the stimulated emission cross section of the considered 4F3/2 → 4I11/2 infrared laser transition around 1062.5 nm. Continuous-wave laser action is achieved with this bulk tellurite glass by pumping the sample inside a standard plan-concave mirror laser cavity with different output couplers. It is possible to observe coherent emission only for the lower concentration (0.5%(wt.) of Nd2 O3). Also laser action could only be observed for this sample with threshold pump power of 73 mW associated with a laser slope efficiency of 8% for an output coupler transmission of 4% indicating that TeO2-ZnO are potential materials for laser action. The results presented in this work together with those previously reported with higher concentration (1.0% (wt) of Nd2O3) determine the adequate Nd2O3 concentration for laser action and guide the correct experimental procedure for TeO2-ZnO glasses preparation.

Skin denervation does not alter cortical potentials to surface concentric electrode stimulation: A comparison with laser evoked potentials and contact heat evoked potentials.

Science.gov (United States)

La Cesa, S; Di Stefano, G; Leone, C; Pepe, A; Galosi, E; Alu, F; Fasolino, A; Cruccu, G; Valeriani, M; Truini, A

2018-01-01

In the neurophysiological assessment of patients with neuropathic pain, laser evoked potentials (LEPs), contact heat evoked potentials (CHEPs) and the evoked potentials by the intraepidermal electrical stimulation via concentric needle electrode are widely agreed as nociceptive specific responses; conversely, the nociceptive specificity of evoked potentials by surface concentric electrode (SE-PREPs) is still debated. In this neurophysiological study we aimed at verifying the nociceptive specificity of SE-PREPs. We recorded LEPs, CHEPs and SE-PREPs in eleven healthy participants, before and after epidermal denervation produced by prolonged capsaicin application. We also used skin biopsy to verify the capsaicin-induced nociceptive nerve fibre loss in the epidermis. We found that whereas LEPs and CHEPs were suppressed after capsaicin-induced epidermal denervation, the surface concentric electrode stimulation of the same denervated skin area yielded unchanged SE-PREPs. The suppression of LEPs and CHEPs after nociceptive nerve fibre loss in the epidermis indicates that these techniques are selectively mediated by nociceptive system. Conversely, the lack of SE-PREP changes suggests that SE-PREPs do not provide selective information on nociceptive system function. Capsaicin-induced epidermal denervation abolishes laser evoked potentials (LEPs) and contact heat evoked potentials (CHEPs), but leaves unaffected pain-related evoked potentials by surface concentric electrode (SE-PREPs). These findings suggest that unlike LEPs and CHEPs, SE-PREPs are not selectively mediated by nociceptive system. © 2017 European Pain Federation - EFIC®.

Arsenic Trioxide Modulates the Central Snail Neuron Action Potential

Directory of Open Access Journals (Sweden)

Guan-Ling Lu

2009-09-01

Conclusion: As2O3 at 10 mM elicits BoPs in central snail neurons and this effect may relate to the PLC activity of the neuron, rather than protein kinase A activity, or calcium influxes of the neuron. As2O3 at higher concentration irreversibly abolishes the spontaneous action potentials of the neuron.

Action potentials and ion conductances in wild-type and CALHM1-knockout type II taste cells

Science.gov (United States)

Saung, Wint Thu; Foskett, J. Kevin

2017-01-01

Taste bud type II cells fire action potentials in response to tastants, triggering nonvesicular ATP release to gustatory neurons via voltage-gated CALHM1-associated ion channels. Whereas CALHM1 regulates mouse cortical neuron excitability, its roles in regulating type II cell excitability are unknown. In this study, we compared membrane conductances and action potentials in single identified TRPM5-GFP-expressing circumvallate papillae type II cells acutely isolated from wild-type (WT) and Calhm1 knockout (KO) mice. The activation kinetics of large voltage-gated outward currents were accelerated in cells from Calhm1 KO mice, and their associated nonselective tail currents, previously shown to be highly correlated with ATP release, were completely absent in Calhm1 KO cells, suggesting that CALHM1 contributes to all of these currents. Calhm1 deletion did not significantly alter resting membrane potential or input resistance, the amplitudes and kinetics of Na+ currents either estimated from action potentials or recorded from steady-state voltage pulses, or action potential threshold, overshoot peak, afterhyperpolarization, and firing frequency. However, Calhm1 deletion reduced the half-widths of action potentials and accelerated the deactivation kinetics of transient outward currents, suggesting that the CALHM1-associated conductance becomes activated during the repolarization phase of action potentials. NEW & NOTEWORTHY CALHM1 is an essential ion channel component of the ATP neurotransmitter release mechanism in type II taste bud cells. Its contribution to type II cell resting membrane properties and excitability is unknown. Nonselective voltage-gated currents, previously associated with ATP release, were absent in cells lacking CALHM1. Calhm1 deletion was without effects on resting membrane properties or voltage-gated Na+ and K+ channels but contributed modestly to the kinetics of action potentials. PMID:28202574

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

Directory of Open Access Journals (Sweden)

Philip Gemmell

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

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

Science.gov (United States)

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

2014-01-01

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

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

NARCIS (Netherlands)

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

2012-01-01

Action potential generation and conduction requires large quantities of energy to restore Na+ and K+ ion gradients. We investigated the subcellular location and voltage dependence of this metabolic cost in rat neocortical pyramidal neurons. Using Na+/K+ charge overlap as a measure of action

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

NARCIS (Netherlands)

Hallermann, S.; de Kock, C.P.J.; Stuart, G.J.; Kole, M.H.

2012-01-01

Action potential generation and conduction requires large quantities of energy to restore Na + and K + ion gradients. We investigated the subcellular location and voltage dependence of this metabolic cost in rat neocortical pyramidal neurons. Using Na +K + charge overlap as a measure of action

Synchronisation and desynchronisation of self-modulation oscillations in a ring chip laser under the action of a periodic signal and noise

International Nuclear Information System (INIS)

Dudetskiy, V Yu; Lariontsev, E G; Chekina, S N

2014-01-01

The effect of pump noise on the synchronisation of selfmodulation oscillations in a solid-state ring laser with periodic pump modulation is studied numerically and experimentally. It is found that, in contrast to desynchronisation that usually occurs under action of noise in the case of 1/1 synchronisation of self-oscillations by a periodic signal, the effect of noise on 1/2 synchronisation may be positive, namely, at a sufficiently low intensity, pump noise is favourable for synchronisation of self-oscillations, for narrowing of their spectrum, and for increasing the signal-to-noise ratio. (lasers)

Generation of electromagnetic radiation in laser action with solids

International Nuclear Information System (INIS)

Aref'ev, K.P.; Vorob'ev, S.A.; Kuznetsov, M.F.; Mastov, Sh.R.; Pogrebnyak, A.D.

1984-01-01

A new effect of electromagnetic pulse generation in solids, exposed to laser irradiation was revealed experimentally. The ruby laser with 694.36 nm wave length was used in the experiments. Monocrystals of Si, GaAs, KCl, LiF, polycrystals of Cu, Al, metals, the rocks-calcite, marble, natural quartz, feldspar - were used as samples. The effect of electromagnetic pulse generation, which is characterized by sharp threshold dependence on the density of laser radiation power, as well as on the type of material and its characteristics was observed for each material. The possibility of using the method of electromagnetic pulse detection during laser irradiation for evaluation of defectiveness degree and strength characteristics of investigated materials was shown

Effects of pioglitazone on cardiac ion currents and action potential morphology in canine ventricular myocytes.

Science.gov (United States)

Kistamás, Kornél; Szentandrássy, Norbert; Hegyi, Bence; Ruzsnavszky, Ferenc; Váczi, Krisztina; Bárándi, László; Horváth, Balázs; Szebeni, Andrea; Magyar, János; Bányász, Tamás; Kecskeméti, Valéria; Nánási, Péter P

2013-06-15

Despite its widespread therapeutical use there is little information on the cellular cardiac effects of the antidiabetic drug pioglitazone in larger mammals. In the present study, therefore, the concentration-dependent effects of pioglitazone on ion currents and action potential configuration were studied in isolated canine ventricular myocytes using standard microelectrode, conventional whole cell patch clamp, and action potential voltage clamp techniques. Pioglitazone decreased the maximum velocity of depolarization and the amplitude of phase-1 repolarization at concentrations ≥3 μM. Action potentials were shortened by pioglitazone at concentrations ≥10 μM, which effect was accompanied with significant reduction of beat-to-beat variability of action potential duration. Several transmembrane ion currents, including the transient outward K(+) current (Ito), the L-type Ca(2+) current (ICa), the rapid and slow components of the delayed rectifier K(+) current (IKr and IKs, respectively), and the inward rectifier K(+) current (IK1) were inhibited by pioglitazone under conventional voltage clamp conditions. Ito was blocked significantly at concentrations ≥3 μM, ICa, IKr, IKs at concentrations ≥10 μM, while IK1 at concentrations ≥30 μM. Suppression of Ito, ICa, IKr, and IK1 has been confirmed also under action potential voltage clamp conditions. ATP-sensitive K(+) current, when activated by lemakalim, was effectively blocked by pioglitazone. Accordingly, action potentials were prolonged by 10 μM pioglitazone when the drug was applied in the presence of lemakalim. All these effects developed rapidly and were readily reversible upon washout. In conclusion, pioglitazone seems to be a harmless agent at usual therapeutic concentrations. Copyright © 2013 Elsevier B.V. All rights reserved.

Conduction velocity of action potentials measured from unidimensional latency-topography in human and frog skeletal muscle fibers.

Science.gov (United States)

Homma, S; Nakajima, Y; Hayashi, K; Toma, S

1986-01-01

Conduction of an action potential along skeletal muscle fibers was graphically displayed by unidimensional latency-topography, UDLT. Since the slopes of the equipotential line were linear and the width of the line was constant, it was possible to calculate conduction velocity from the slope. To determine conduction direction of the muscle action potential elicited by electric stimulation applied directly to the muscle, surface recording electrodes were placed on a two-dimensional plane over a human muscle. Thus a bi-dimensional topography was obtained. Then, twelve or sixteen surface electrodes were placed linearly along the longitudinal direction of the action potential conduction which was disclosed by the bi-dimensional topography. Thus conduction velocity of muscle action potential in man, calculated from the slope, was for m. brachioradialis, 3.9 +/- 0.4 m/s; for m. biceps brachii, 3.6 +/- 0.2 m/s; for m. sternocleidomastoideus, 3.6 +/- 0.4 m/s. By using a tungsten microelectrode to stimulate the motor axons, a convex-like equipotential line of an action potential in UDLT was obtained from human muscle fibers. Since a similar pattern of UDLT was obtained from experiments on isolated frog muscles, in which the muscle action potential was elicited by stimulating the motor axon, it was assumed that the maximum of the curve corresponds to the end-plate region, and that the slopes on both sides indicate bi-directional conduction of the action potential.

Fish oil curtails the human action potential dome in a heterogeneous manner: Implication for arrhythmogenesis

NARCIS (Netherlands)

Verkerk, Arie O.; den Ruijter, Hester M.; de Jonge, Nicolaas; Coronel, Ruben

2009-01-01

Omega-3 polyunsaturated fatty acids (omega3-PUFAs) from fish oil modulate various ion channels, including the L-type calcium current (I(Ca,L)). As a result, fish oil shortens the cardiac action potential and may cause a loss of the dome of the action potential (AP). Under conditions of increased

Cardiac action potential repolarization revisited: early repolarization shows all-or-none behaviour.

Science.gov (United States)

Trenor, Beatriz; Cardona, Karen; Saiz, Javier; Noble, Denis; Giles, Wayne

2017-11-01

In healthy mammalian hearts the action potential (AP) waveform initiates and modulates each contraction, or heartbeat. As a result, AP height and duration are key physiological variables. In addition, rate-dependent changes in ventricular AP duration (APD), and variations in APD at a fixed heart rate are both reliable biomarkers of electrophysiological stability. Present guidelines for the likelihood that candidate drugs will increase arrhythmias rely on small changes in APD and Q-T intervals as criteria for safety pharmacology decisions. However, both of these measurements correspond to the final repolarization of the AP. Emerging clinical evidence draws attention to the early repolarization phase of the action potential (and the J-wave of the ECG) as an additional important biomarker for arrhythmogenesis. Here we provide a mechanistic background to this early repolarization syndrome by summarizing the evidence that both the initial depolarization and repolarization phases of the cardiac action potential can exhibit distinct time- and voltage-dependent thresholds, and also demonstrating that both can show regenerative all-or-none behaviour. An important consequence of this is that not all of the dynamics of action potential repolarization in human ventricle can be captured by data from single myocytes when these results are expressed as 'repolarization reserve'. For example, the complex pattern of cell-to-cell current flow that is responsible for AP conduction (propagation) within the mammalian myocardium can change APD and the Q-T interval of the electrocardiogram alter APD stability, and modulate responsiveness to pharmacological agents (such as Class III anti-arrhythmic drugs). © 2017 The Authors. The Journal of Physiology © 2017 The Physiological Society.

Post-evaluation of the neurophaties treatment post-trauma with therapeutic laser. Model in sciatic nerve of frog

International Nuclear Information System (INIS)

Escobar, Antonio S.; Ocampo, Arcelia F. M.; Hernandez, Maria G. H.; Jasso, Jose L. C.; Lira, Maricela O. F.; Flores, Mariana A.; Balderrama, Vicente L.

2010-01-01

The purpose of this study was to evaluate the compound nerve action potential amplitude and latency measured to determine the degree of myelination and the number of fibers stimulated in a model of stimulated frog sciatic nerve laser at 810 nm as perioperative treatment after injury. It used 30 bullfrogs (Rana catesbeiana) to obtain 60 sciatic nerves forming four groups, groups 1 and 2 worked with nerves in vitro, were dissected in humid chambers for placing isolated organ, was recorded on compound nerve action potential, the second group laser was applied at 24, 48, 72, 96 and 120 hours and at the same time were placed in 10% formalin. Groups 3 and 4 are worked in vivo localizing the nerve and causing damage through compression, occurred over the compound nerve action potential to assess the degree of myelination and the number of fibers stimulated, the group 4 was applied to 810 nm laser (500 Hz, 10 J, 200 mW) after injury, after 48 hours, three frogs were sacrificed by introducing the nerves in 10% formalin. The latency recorded by stimulating the sciatic nerve of frog to 0.5 mA and 100 ms in groups 1 and 2 show significant differences (p 000), as to the extent, if any statistically significant difference. (p<0.001 and p<0.000). The laser produces a favorable response in the treatment of paresthesia (post-traumatic neuropathy).

Differential effects of thioridazine enantiomers on action potential duration in rabbit papillary muscle

DEFF Research Database (Denmark)

Jensen, Ask Schou; Pennisi, Cristian Pablo; Sevcencu, Cristian

2015-01-01

with (+)-thioridazine. In this study we for the first time investigate the cardiotoxicity of the isolated thioridazine enantiomers and show their effects on ventricular repolarization. The effects of (+)-thioridazine, (-)-thioridazine, and racemate on the rabbit ventricular action potential duration (APD) were...... investigated in a randomized controlled blinded experiment. Action potentials were measured in papillary muscles isolated from 21 female rabbits, and the drug effect on 90% APD in comparison with control (DeltaDelta-APD90) was evaluated. Increasing concentrations of (+)-thioridazine and the racemate caused...

Inhibition of HSV-1 replication by laser diode-irradiation: possible mechanism of action.

Science.gov (United States)

Donnarumma, G; De Gregorio, V; Fusco, A; Farina, E; Baroni, A; Esposito, V; Contaldo, M; Petruzzi, M; Pannone, G; Serpico, R

2010-01-01

Herpes labialis are the most frequent clinical manifestations of HSV-1 infection. Epithelial cells are able to respond to HSV-1 presence inducing the expression of IL-6, IL-1, TNF-α and IL-8. These proinflammatory cytokines have a function in the acute-phase response mediation, chemotaxis, inflammatory cell activation and antigen-presenting cells. In the human epithelial cell models, it has been demonstrated that, after an early induction of proinflammatory host response, HSV-1 down-modulates the proinflammatory cytokine production through the accumulation of two viral proteins, ICP4 and ICP27, whose transcription is induced by tegument protein VP16. These viral proteins, through the decreasing of stabilizing the mRNAs of proinflammatory genes, delay cytokine production to an extent that allows the virus to replicate. Moreover, viral transactivating proteins, ICP-0 and VP-16 induce IL-10 expression. The conventional treatment of herpes labialis involves the topical and systemic use of antiviral drugs but it is necessary to find new therapies that can act in a selective and non-cytotoxic manner in viral infection. Laser diode therapy has been considered as a non-invasive alternative treatment to the conventional treatment of herpes labialis in pain therapy, in modulation of inflammation and in wound healing. This study aims to report a possible mechanism of action of laser diode irradiation in prevention and reduction of severity of labial manifestations of herpes labialis virus. We investigated, in an in vitro model of epithelial cells HaCat, the laser-effect on HSV-1 replication and we evaluated the modulation of expression of certain proinflammatory cytokines (TNF-α, IL-1β and IL-6), antimicrobial peptide HBD2, chemokine IL-8 and the immunosuppressive cytokine, IL-10. Our results lead us to hypothesize that LD-irradiation acts in the final stage of HSV-1 replication by limiting viral spread from cell to cell and that laser therapy acts also on the host immune

Recovery of Action Potentials and Twitches after K-contractures in Frog Skeletal Muscle(Physiology)

OpenAIRE

Atsuko, Suzuki; Ibuki, Shirakawa; Kazunari, Noguchi; Hirohiko, Kishi; Haruo, Sugi; Department of Physiology, School of Medicine, Teikyo University:(Present office)Department of Physical Therapy, Health Science University; Department of Physiology, School of Medicine, Teikyo University; Department of Physiology, School of Medicine, Teikyo University; Department of Physiology, School of Medicine, Teikyo University; Department of Physiology, School of Medicine, Teikyo University

2004-01-01

To give information about intracellular Ca^ translocation during and after K-contractures in vertebrate skeletal muscle fibers, we examined recovery of action potentials and twitches after interruption and spontaneous relaxation of K-contractures at low temperature (3℃) that greatly reduced the rate of Ca^ reuptake by the sarcoplasmic reticulum. On membrane repolarization interrupting K-contractures, the amplitude of both action potentials and twitches recovered quickly, while the falling pha...

Surface deformation during an action potential in pearled cells

Science.gov (United States)

Mussel, Matan; Fillafer, Christian; Ben-Porath, Gal; Schneider, Matthias F.

2017-11-01

Electric pulses in biological cells (action potentials) have been reported to be accompanied by a propagating cell-surface deformation with a nanoscale amplitude. Typically, this cell surface is covered by external layers of polymer material (extracellular matrix, cell wall material, etc.). It was recently demonstrated in excitable plant cells (Chara braunii) that the rigid external layer (cell wall) hinders the underlying deformation. When the cell membrane was separated from the cell wall by osmosis, a mechanical deformation, in the micrometer range, was observed upon excitation of the cell. The underlying mechanism of this mechanical pulse has, to date, remained elusive. Herein we report that Chara cells can undergo a pearling instability, and when the pearled fragments were excited even larger and more regular cell shape changes were observed (˜10 -100 μ m in amplitude). These transient cellular deformations were captured by a curvature model that is based on three parameters: surface tension, bending rigidity, and pressure difference across the surface. In this paper these parameters are extracted by curve-fitting to the experimental cellular shapes at rest and during excitation. This is a necessary step to identify the mechanical parameters that change during an action potential.

Onset Dynamics of Action Potentials in Rat Neocortical Neurons and Identified Snail Neurons: Quantification of the Difference

OpenAIRE

Volgushev, Maxim; Malyshev, Aleksey; Balaban, Pavel; Chistiakova, Marina; Volgushev, Stanislav; Wolf, Fred

2008-01-01

The generation of action potentials (APs) is a key process in the operation of nerve cells and the communication between neurons. Action potentials in mammalian central neurons are characterized by an exceptionally fast onset dynamics, which differs from the typically slow and gradual onset dynamics seen in identified snail neurons. Here we describe a novel method of analysis which provides a quantitative measure of the onset dynamics of action potentials. This method captures the...

Future prospects of laser diodes and fiber lasers

International Nuclear Information System (INIS)

Ueda, Ken-ichi

2000-01-01

For the next century we should develop new concepts for coherent control of light generation and propagation. Owing to the recent development of ultra fine structures in semiconductor lasers, fiber lasers, and various kinds of waveguide structure, we can make optical devices which control the light propagation artificially. But, the phase locking and phase control of multiple laser oscillators are one of the most important directions of laser science and technology. The coherent summation has been a dream of laser since 1960. Is it possible to solve this old and quite challenging problem for laser science? This is also a very basic concept because the laser action based on the stimulated emission is the process of coherent summation of huge number of photons emitted from individual atoms. In this paper, I discuss the fundamental direction of laser research in the next ten or twenty years. The active optics and laser technology should be combined intrinsically in near future. (author)

Potential of solar-simulator-pumped alexandrite lasers

Science.gov (United States)

Deyoung, Russell J.

1990-01-01

An attempt was made to pump an alexandrite laser rod using a Tamarak solar simulator and also a tungsten-halogen lamp. A very low optical laser cavity was used to achieve the threshold minimum pumping-power requirement. Lasing was not achieved. The laser threshold optical-power requirement was calculated to be approximately 626 W/sq cm for a gain length of 7.6 cm, whereas the Tamarak simulator produces 1150 W/sq cm over a gain length of 3.3 cm, which is less than the 1442 W/sq cm required to reach laser threshold. The rod was optically pulsed with 200 msec pulses, which allowed the alexandrite rod to operate at near room temperature. The optical intensity-gain-length product to achieve laser threshold should be approximately 35,244 solar constants-cm. In the present setup, this product was 28,111 solar constants-cm.

Scaling of the quark-antiquark potential and improved actions in SU(2) lattice gauge theory

International Nuclear Information System (INIS)

Montvay, I.; Gutbrod, F.

1983-11-01

The scaling behaviour of the quark-antiquark potential is investigated by a high statistics Monte Carlo calculation in SU(2) lattice gauge theory. Besides the standard one-plaquette action we also use Symanzik's tree-level improved action and Wilson's block-spin improved action. No significant differences between Symanzik's action and the standard action have been observed. For small β Wilson's action scales differently. The string tension value chi extracted from the data corresponds to Λsub(latt) = (0.018 +- 0.001) √chi for the one-plaquette action. (orig.)

Formation of a fine-dispersed liquid-metal target under the action of femto- and picosecond laser pulses for a laser-plasma radiation source in the extreme ultraviolet range

Energy Technology Data Exchange (ETDEWEB)

Vinokhodov, A Yu; Krivokorytov, M S [EUV Labs, Ltd., Troitsk, Moscow (Russian Federation); Koshelev, K N; Krivtsun, V M; Sidelnikov, Yu V; Medvedev, V V; Kompanets, V O; Melnikov, A A; Chekalin, S V [Institute of Spectroscopy, Russian Academy of Sciences, Troitsk, Moscow (Russian Federation)

2016-01-31

We report the results of studying the dynamics of deformation and fragmentation of liquid-metal droplets under the action of ultrashort laser pulses. The experiments have been performed to optimise the shape of the droplet target used in extreme ultraviolet (EUV) radiation sources based on the laser-produced plasma using the pre-pulse technology. The pre-pulse is generated by a system incorporating a master Ti : sapphire oscillator and a regenerative amplifier, allowing one to vary the pulse duration from 50 fs to 50 ps. The power density of laser radiation at the droplet target, averaged over the pulse duration and spatial coordinates, has reached 3 × 10{sup 15} W cm{sup -2}. The production of liquid-metal droplets has been implemented by means of a droplet generator based on a nozzle with a ring piezoceramic actuator. The droplet material is the eutectic indium – tin alloy. The droplet generator could operate in the droplet and jet regime with a maximal rate of stable operation 5 and 150 kHz, respectively. The spatial stability of droplet position σ = 1% – 2% of its diameter is achieved. The size of the droplets varied within 30 – 70 μm, their velocity was 2 – 8 m s{sup -1} depending on the operation regime. (interaction of laser radiation with matter. laser plasma)

On X-ray laser

International Nuclear Information System (INIS)

Durrani, I.R.; Bhatti, Z.R.

2000-01-01

Although considerable efforts have been invested in the area of short wavelength lasers at the conceptual and theoretical level for approaching thirty years now it is only with in last two decades that significant progress has been made. The philosophy behind the preparation of this paper has been to indicate to the nonspecialist the fundamental requirements and associated difficulties of achieving laser action. Although we can look to inner shell transitions in neutral or weakly ionized action in this instance the discussion is restricted to the latter possibility. This is mainly because of successful experiments demonstrating amplification using laser produced plasma as a source of lasant ion species. (author)

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

Science.gov (United States)

Yang, Li-Zhen; Zhu, Yi-Chun

2015-07-05

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

Automated grouping of action potentials of human embryonic stem cell-derived cardiomyocytes.

Science.gov (United States)

Gorospe, Giann; Zhu, Renjun; Millrod, Michal A; Zambidis, Elias T; Tung, Leslie; Vidal, Rene

2014-09-01

Methods for obtaining cardiomyocytes from human embryonic stem cells (hESCs) are improving at a significant rate. However, the characterization of these cardiomyocytes (CMs) is evolving at a relatively slower rate. In particular, there is still uncertainty in classifying the phenotype (ventricular-like, atrial-like, nodal-like, etc.) of an hESC-derived cardiomyocyte (hESC-CM). While previous studies identified the phenotype of a CM based on electrophysiological features of its action potential, the criteria for classification were typically subjective and differed across studies. In this paper, we use techniques from signal processing and machine learning to develop an automated approach to discriminate the electrophysiological differences between hESC-CMs. Specifically, we propose a spectral grouping-based algorithm to separate a population of CMs into distinct groups based on the similarity of their action potential shapes. We applied this method to a dataset of optical maps of cardiac cell clusters dissected from human embryoid bodies. While some of the nine cell clusters in the dataset are presented with just one phenotype, the majority of the cell clusters are presented with multiple phenotypes. The proposed algorithm is generally applicable to other action potential datasets and could prove useful in investigating the purification of specific types of CMs from an electrophysiological perspective.

Free-Free Transitions in the Presence of Laser Fields and Debye Potential at Very Low Incident Electron Energies

Science.gov (United States)

Bhatia, Anand

2012-01-01

We study the free-free transition in electron-helium ion in the ground state and embedded in a Debye potential in the presence of an external laser field at very low incident electron energies. The laser field is treated classically while the collision dynamics is treated quantum mechanically. The laser field is chosen as monochromatic, linearly polarized and homogeneous. The incident electron is considered to be dressed by the laser field in a nonperturbative manner by choosing Volkov wave function for it. The scattering wave function for the incident electron on the target embedded in a Debye potential is solved numerically by taking into account the effect of electron exchange. We calculate the laser-assisted differential and total cross sections for free-free transition for absorption/emission of a single photon or no photon exchange. The results will be presented at the conference.

Laser action benzimidazoles in various aggregate states

Science.gov (United States)

Gruzinskii, V. V.; Degtiarenko, K. M.; Shalaev, V. K.; Kopylova, T. N.; Verkhovskii, V. S.; Tarasenko, V. F.; Melchenko, S. V.

1983-04-01

Lasing has been obtained in solutions of benzimidazole (Bi) derivatives: 2-phenyl-Bi (with the band maximum lambda-r-max = 341-347 nm), 2-n-tolyl-Bi (344 nm), and 2-(4'-biphenilyl) Bi (366-374 nm). It is found that compounds of this class provide a basis for laser radiation covering a wide region of the spectrum. Lasing has been obtained on the vapors of 2-(4'-biphenilyl) Bi (361.2 nm) and 2-(n-tolyl) Bi (336.5 nm) with a pentane stabilizer of the excited states. High volatility, photostability, and lasing in wide ranges of concentration determine the efficiency of using this new class of compounds (chain arylbenzimidazoles) in lasers using the vapors of complex molecules.

Laser action benzimidazoles in various aggregate states

Energy Technology Data Exchange (ETDEWEB)

Gruzinskii, V V; Degtiarenko, K M; Shalaev, V K; Kopylova, T N; Verkhovskii, V S; Tarasenko, V F; Melchenko, S V

1983-04-01

Lasing has been obtained in solutions of benzimidazole (Bi) derivatives: 2-phenyl-Bi (with the band maximum lambda-r-max 341-347 nm), 2-n-tolyl-Bi (344 nm), and 2-(4'-biphenilyl) Bi (366-374 nm). It is found that compounds of this class provide a basis for laser radiation covering a wide region of the spectrum. Lasing has been obtained on the vapors of 2-(4'-biphenilyl) Bi (361.2 nm) and 2-(n-tolyl) Bi (336.5 nm) with a pentane stabilizer of the excited states. High volatility, photostability, and lasing in wide ranges of concentration determine the efficiency of using this new class of compounds (chain arylbenzimidazoles) in lasers using the vapors of complex molecules.

Efficiencies of laser dyes for atomic vapor laser isotope separation

International Nuclear Information System (INIS)

Maeda, Mitsuo; Oki, Yuji; Uchiumi, Michihiro; Takao, Takayuki; Igarashi, Kaoru; Shimamoto, Kojiro.

1995-01-01

Efficiencies of 30 laser dyes for the atomic vapor laser isotope separation (AVLIS) are experimentally evaluated with a dye laser pumped by a frequency-doubled Nd:YAG laser. On the other hand, a simulation code is developed to describe the laser action of Rhodamine 6G, and the dependence of the laser efficiency on the pump wavelength is calculated. Following conclusions are obtained by these considerations:space: 1) Pyrromethene 567 showed 16% higher laser efficiency than Rhodamine 6G by 532 nm pumping, and Pyrromethene 556 has an ability to provide better efficiency by green light pumping with a Cu vapor laser; 2) Kiton red 620 and Rhodamine 640, whose efficiencies were almost the same as Rhodamine 6G by 532 nm pumping, will show better efficiencies by two-wavelength pumping with a Cu vapor laser. (author)

Laser vaccine adjuvants

Science.gov (United States)

Kashiwagi, Satoshi; Brauns, Timothy; Gelfand, Jeffrey; Poznansky, Mark C

2014-01-01

Immunologic adjuvants are essential for current vaccines to maximize their efficacy. Unfortunately, few have been found to be sufficiently effective and safe for regulatory authorities to permit their use in vaccines for humans and none have been approved for use with intradermal vaccines. The development of new adjuvants with the potential to be both efficacious and safe constitutes a significant need in modern vaccine practice. The use of non-damaging laser light represents a markedly different approach to enhancing immune responses to a vaccine antigen, particularly with intradermal vaccination. This approach, which was initially explored in Russia and further developed in the US, appears to significantly improve responses to both prophylactic and therapeutic vaccines administered to the laser-exposed tissue, particularly the skin. Although different types of lasers have been used for this purpose and the precise molecular mechanism(s) of action remain unknown, several approaches appear to modulate dendritic cell trafficking and/or activation at the irradiation site via the release of specific signaling molecules from epithelial cells. The most recent study, performed by the authors of this review, utilized a continuous wave near-infrared laser that may open the path for the development of a safe, effective, low-cost, simple-to-use laser vaccine adjuvant that could be used in lieu of conventional adjuvants, particularly with intradermal vaccines. In this review, we summarize the initial Russian studies that have given rise to this approach and comment upon recent advances in the use of non-tissue damaging lasers as novel physical adjuvants for vaccines. PMID:25424797

The different intracellular action potentials of fast and slow muscle fibres = Différences entre les potentiels d'action intracellulaires de fibres musculaires rapides et lentes

NARCIS (Netherlands)

Wallinga, W.; Gielen, Frans L.H.; Wirtz, Peter; de Jong, Paul; Broenink, Johannes F.

1985-01-01

The time course of the intracellular action potential was studied quantitatively, because it is an important factor in the generation of electromyographic signals. In in vivo preparations of the m. EDL and m. soleus of the rat single motor units were stimulated and intracellular action potentials

The Potential of Deweyan-Inspired Action Research

Science.gov (United States)

Stark, Jody L.

2014-01-01

In its broadest sense, pragmatism could be said to be the philosophical orientation of all action research. Action research is characterized by research, action, and participation grounded in democratic principles and guided by the aim of social improvement. Furthermore, action research is an active process of inquiry that does not admit…

Laser-activated solid protein bands for peripheral nerve repair: an vivo study.

Science.gov (United States)

Lauto, A; Trickett, R; Malik, R; Dawes, J M; Owen, E R

1997-01-01

Severed tibial nerves in rats were repaired using a novel technique, utilizing a semiconductor diode-laser-activated protein solder applied longitudinally across the join. Welding was produced by selective laser denaturation of solid solder bands containing the dye indocyanine green. An in vivo study, using 48 adult male Wistar rats, compared conventional microsuture-repaired tibial nerves with laser solder-repaired nerves. Nerve repairs were characterised immediately after surgery and after 3 months. Successful regeneration with average compound muscle action potentials of 2.5 +/- 0.5 mV and 2.7 +/- 0.3 mV (mean and standard deviation) was demonstrated for the laser-soldered nerves and the sutured nerves, respectively. Histopathology confirmed comparable regeneration of axons in laser- and suture-operated nerves. The laser-based nerve repair technique was easier and faster than microsuture repair, minimising manipulation damage to the nerve.

Inhibition by TRPA1 agonists of compound action potentials in the frog sciatic nerve

Energy Technology Data Exchange (ETDEWEB)

Matsushita, Akitomo; Ohtsubo, Sena; Fujita, Tsugumi; Kumamoto, Eiichi, E-mail: kumamote@cc.saga-u.ac.jp

2013-04-26

Highlights: •TRPA1 agonists inhibited compound action potentials in frog sciatic nerves. •This inhibition was not mediated by TRPA1 channels. •This efficacy was comparable to those of lidocaine and cocaine. •We found for the first time an ability of TRPA1 agonists to inhibit nerve conduction. -- Abstract: Although TRPV1 and TRPM8 agonists (vanilloid capsaicin and menthol, respectively) at high concentrations inhibit action potential conduction, it remains to be unknown whether TRPA1 agonists have a similar action. The present study examined the actions of TRPA1 agonists, cinnamaldehyde (CA) and allyl isothiocyanate (AITC), which differ in chemical structure from each other, on compound action potentials (CAPs) recorded from the frog sciatic nerve by using the air-gap method. CA and AITC concentration-dependently reduced the peak amplitude of the CAP with the IC{sub 50} values of 1.2 and 1.5 mM, respectively; these activities were resistant to a non-selective TRP antagonist ruthenium red or a selective TRPA1 antagonist HC-030031. The CA and AITC actions were distinct in property; the latter but not former action was delayed in onset and partially reversible, and CA but not AITC increased thresholds to elicit CAPs. A CAP inhibition was seen by hydroxy-α-sanshool (by 60% at 0.05 mM), which activates both TRPA1 and TRPV1 channels, a non-vanilloid TRPV1 agonist piperine (by 20% at 0.07 mM) and tetrahydrolavandulol (where the six-membered ring of menthol is opened; IC{sub 50} = 0.38 mM). It is suggested that TRPA1 agonists as well as TRPV1 and TRPM8 agonists have an ability to inhibit nerve conduction without TRP activation, although their agonists are quite different in chemical structure from each other.

Post-evaluation of the neurophaties treatment post-trauma with therapeutic laser. Model in sciatic nerve of frog

Science.gov (United States)

Escobar, Antonio S.; Ocampo, Arcelia F. M.; Hernández, María G. H.; Jasso, José L. C.; Lira, Maricela O. F.; Flores, Mariana A.; Balderrama, Vicente L.

2010-05-01

The purpose of this study was to evaluate the compound nerve action potential amplitude and latency measured to determine the degree of myelination and the number of fibers stimulated in a model of stimulated frog sciatic nerve laser at 810 nm as perioperative treatment after injury. It used 30 bullfrogs (Rana catesbeiana) to obtain 60 sciatic nerves forming four groups, groups 1 and 2 worked with nerves in vitro, were dissected in humid chambers for placing isolated organ, was recorded on compound nerve action potential, the second group laser was applied at 24, 48, 72, 96 and 120 hours and at the same time were placed in 10% formalin. Groups 3 and 4 are worked in vivo localizing the nerve and causing damage through compression, occurred over the compound nerve action potential to assess the degree of myelination and the number of fibers stimulated, the group 4 was applied to 810 nm laser (500 Hz, 10 J, 200 mW) after injury, after 48 hours, three frogs were sacrificed by introducing the nerves in 10% formalin. The latency recorded by stimulating the sciatic nerve of frog to 0.5 mA and 100 ms in groups 1 and 2 show significant differences (p000), as to the extent, if any statistically significant difference. (pparesthesia (post-traumatic neuropathy).

Off-shell properties of the second-order Born approximation for laser-assisted potential scattering

International Nuclear Information System (INIS)

Trombetta, F.

1991-01-01

A formal method is presented to evaluate the second-order Born approximation of the laser-assisted potential scattering. It is an implicit closure technique that includes intermediate virtual-state transitions and enables one to find the exact explicit expression of the transition amplitude. This is of interest from two standpoints: first, one can deal with ranges of parameters in which the first-order Born approximation is a poor one; second, one can set limits of on-shell approximations that are also widely used to analyze recent laser-assisted experiments. The off-shell character yields new terms in the exact amplitude, and in particular, it is shown to play a crucial role in forward scattering from a long-range potential

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

Science.gov (United States)

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

2012-01-01

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

Incorporated fish oil fatty acids prevent action potential shortening induced by circulating fish oil fatty acids

Directory of Open Access Journals (Sweden)

Hester M Den Ruijter

2010-11-01

Full Text Available Increased consumption of fatty fish, rich in omega-3 polyunsaturated fatty acids (3-PUFAs reduces the severity and number of arrhythmias. Long term 3-PUFA-intake modulates the activity of several cardiac ion channels leading to cardiac action potential shortening. Circulating 3-PUFAs in the bloodstream and incorporated 3-PUFAs in the cardiac membrane have a different mechanism to shorten the action potential. It is, however, unknown whether circulating 3-PUFAs in the bloodstream enhance or diminish the effects of incorporated 3-PUFAs. In the present study, we address this issue. Rabbits were fed a diet rich in fish oil (3 or sunflower oil (9, as control for 3 weeks. Ventricular myocytes were isolated by enzymatic dissociation and action potentials were measured using the perforated patch clamp technique in the absence and presence of acutely administered 3-PUFAs. Plasma of 3 fed rabbits contained more free eicosapentaenoic acid (EPA and isolated myocytes of 3 fed rabbits contained higher amounts of both EPA and docosahexaenoic acid (DHA in their sarcolemma compared to control. In the absence of acutely administered fatty acids, 3 myocytes had a shorter action potential with a more negative plateau than 9 myocytes. In the 9 myocytes, but not in the 3 myocytes, acute administration of a mixture of EPA+DHA shortened the action potential significantly. From these data we conclude that incorporated 3-PUFAs into the sarcolemma and acutely administered 3 fatty acids do not have a cumulative effect on action potential duration and morphology. As a consequence, patients with a high cardiac 3-PUFA status will probably not benefit from short term 3 supplementation as an antiarrhythmic therapy.

Experience With Laser Safety In The USA--A Review

Science.gov (United States)

Sliney, David H.

1986-10-01

Following several research programs in the 1960's aimed at studying the adverse biological effects of lasers and other optical radiation sources, laser occupational exposure limits were set and general safety standards were developed. Today, the experience from laser accidents and the development of new lasers and new applications have altered the format of the exposure limits and the safety procedures. It is critically important to distinguish between different biological injury mechanisms. The biological effects of ultraviolet radiation upon the skin and eye are additive over a period of at least one workday, and require different safety procedures. The scattered UV irradiance from excimer lasers may be quite hazardous, depending upon wavelength and action spectra. Since laser technology is young, the exposure of an individual in natural sunlight must be studied to evaluate the potential for chronic effects. The safety measures necessary in the use of lasers depend upon a hazard evaluation. The appropriate control measures and alternate means of enclosure, baffling, and operational control measures are presented. Present laser safety standards are explained briefly. Eye protective techniques and eyewear are considered for a variety of sources. The optical properties of enclosure materials are also discussed.

Yb3+:Sr5(VO4)3F: Crystal growth, spectroscopic characterization and laser development

International Nuclear Information System (INIS)

Bustamante, Andrea Nora Pino

1999-01-01

Crystal growth, spectroscopic characterization and laser development of Yb 3+ :SVAP [Sr 5 (VO 4 ) 3 F] was performed to demonstrate for the first time, operation of tunable laser emission centered at 1120 nm. Initially, SVAP crystals were grown with high dopant concentrations, up to 6.0 mol % of Yb 2 O 3 in the melt, in order to investigate the material for potential laser operation at a new laser wavelength. Additional research was performed to alleviate highly doped SVAP crystals of defects previously observed. Basic spectroscopic characterization including absorption and luminescent properties were measured to better understand the behavior of Yb 3+ ions in SVAP. Based upon these studies, discussion of the 1120 nm laser transition is presented as it arises from a ground state vibrational level. Investigations of the charge compensation process and the optical parameters as a function of dopant concentration are also presented. The laser development of Yb 3+ :SVAP included continuous and pulsed modes of operation of the 1044 nm and 1120 nm transitions. Initial laser action of the 1044 nm transition was achieved using a Yi: Saphire laser pump source in order to compare with previously results. Further development of a diode-pumped Yb 3+ :SVAP laser system demonstrated continuously tunable laser operation from 1103 nm for the first time. The laser investigations also proved that this high gain media does provide continuous wave laser action at 1044 nm and 1120 simultaneously without significant gain depletion. (author)

Excimer Pumped Pulsed Tunable Dye Laser

Science.gov (United States)

Littman, Michael G.

1988-06-01

It has been recently shown and reported for the first time at this meeting, that Excimer pumping of a single-mode, short-cavity, grazing-incidence, longitudinally-pumped pulsed dye laser is feasible. In this paper the key concepts upon which this latest development is based are presented and are in a somewhat unusual form. This manuscript describes five specific dye laser examples. The five examples represent a progression from the simplest type of dye laser to the single-mode version mentioned above. The examples thus serve as a tutorial introduction to potential users of dye lasers. The article is organized into five sections or STEPS, each of which describes a different pulsed dye laser. Since the subtle points about dye lasers are best appreciated only after one actually attempts to build a working model, a PROCEDURES category is included in which details about the construction of the particular form of laser are given. As one reads through this category, think of it as looking over the shoulder of the laser builder. The NOTES category which follows is a brief but essential discussion explaining why various components and procedures are used, as well as how laser performance specifications are obtained. This subsection can he viewed as a discussion with the laser builder concerning the reasons for specific actions and choices made in the assembly of the example laser. The last category contains COMMENTS which provide additional related information pertaining to the example laser that goes beyond the earlier annotated discussion. If you like, these are the narrator's comments. At the end of the article, after the five sequential forms of the laser have been presented, there is a brief summation.

ER Stress-Mediated Signaling: Action Potential and Ca(2+) as Key Players.

Science.gov (United States)

Bahar, Entaz; Kim, Hyongsuk; Yoon, Hyonok

2016-09-15

The proper functioning of the endoplasmic reticulum (ER) is crucial for multiple cellular activities and survival. Disturbances in the normal ER functions lead to the accumulation and aggregation of unfolded proteins, which initiates an adaptive response, the unfolded protein response (UPR), in order to regain normal ER functions. Failure to activate the adaptive response initiates the process of programmed cell death or apoptosis. Apoptosis plays an important role in cell elimination, which is essential for embryogenesis, development, and tissue homeostasis. Impaired apoptosis can lead to the development of various pathological conditions, such as neurodegenerative and autoimmune diseases, cancer, or acquired immune deficiency syndrome (AIDS). Calcium (Ca(2+)) is one of the key regulators of cell survival and it can induce ER stress-mediated apoptosis in response to various conditions. Ca(2+) regulates cell death both at the early and late stages of apoptosis. Severe Ca(2+) dysregulation can promote cell death through apoptosis. Action potential, an electrical signal transmitted along the neurons and muscle fibers, is important for conveying information to, from, and within the brain. Upon the initiation of the action potential, increased levels of cytosolic Ca(2+) (depolarization) lead to the activation of the ER stress response involved in the initiation of apoptosis. In this review, we discuss the involvement of Ca(2+) and action potential in ER stress-mediated apoptosis.

Potentialities of a new sigma(+)-sigma(-)laser configuration for radiative cooling and trapping

Energy Technology Data Exchange (ETDEWEB)

Dalibard, J; Reynaud, S; Cohen-Tannoudji, C

1984-11-28

In the process of cooling and trapping neutral atoms, a new laser configuration is investigated which consists of two counterpropagating laser beams with orthogonal sigma(+) and sigma(-)polarizations. It is shown that such a configuration looks more promising than an ordinary standing wave (where the two counterpropagating waves have the same polarization), and this result is explained as being due to angular momentum conservation which prevents any coherent redistribution of photons between the two waves. The present conclusions are based on a quantitative calculation of the various parameters (potential depth, friction coefficient, diffusion coefficient) describing the mean value and the fluctuations of the radiative forces experienced, in such a laser configuration, by an atom with a J 0 ground state and a J 1 excited state. 30 references.

Antibacterial free fatty acids: activities, mechanisms of action and biotechnological potential.

Science.gov (United States)

Desbois, Andrew P; Smith, Valerie J

2010-02-01

Amongst the diverse and potent biological activities of free fatty acids (FFAs) is the ability to kill or inhibit the growth of bacteria. The antibacterial properties of FFAs are used by many organisms to defend against parasitic or pathogenic bacteria. Whilst their antibacterial mode of action is still poorly understood, the prime target of FFA action is the cell membrane, where FFAs disrupt the electron transport chain and oxidative phosphorylation. Besides interfering with cellular energy production, FFA action may also result from the inhibition of enzyme activity, impairment of nutrient uptake, generation of peroxidation and auto-oxidation degradation products or direct lysis of bacterial cells. Their broad spectrum of activity, non-specific mode of action and safety makes them attractive as antibacterial agents for various applications in medicine, agriculture and food preservation, especially where the use of conventional antibiotics is undesirable or prohibited. Moreover, the evolution of inducible FFA-resistant phenotypes is less problematic than with conventional antibiotics. The potential for commercial or biomedical exploitation of antibacterial FFAs, especially for those from natural sources, is discussed.

Amphetamine elevates nucleus accumbens dopamine via an action potential-dependent mechanism that is modulated by endocannabinoids

Science.gov (United States)

Covey, Dan P.; Bunner, Kendra D.; Schuweiler, Douglas R.; Cheer, Joseph F.; Garris, Paul A.

2018-01-01

The reinforcing effects of abused drugs are mediated by their ability to elevate nucleus accumbens dopamine. Amphetamine (AMPH) was historically thought to increase dopamine by an action potential-independent, non-exocytotic type of release called efflux, involving reversal of dopamine transporter function and driven by vesicular dopamine depletion. Growing evidence suggests that AMPH also acts by an action potential-dependent mechanism. Indeed, fast-scan cyclic voltammetry demonstrates that AMPH activates dopamine transients, reward-related phasic signals generated by burst firing of dopamine neurons and dependent on intact vesicular dopamine. Not established for AMPH but indicating a shared mechanism, endocannabinoids facilitate this activation of dopamine transients by broad classes of abused drugs. Here, using fast-scan cyclic voltammetry coupled to pharmacological manipulations in awake rats, we investigated the action potential and endocannabinoid dependence of AMPH-induced elevations in nucleus accumbens dopamine. AMPH increased the frequency, amplitude and duration of transients, which were observed riding on top of slower dopamine increases. Surprisingly, silencing dopamine neuron firing abolished all AMPH-induced dopamine elevations, identifying an action potential-dependent origin. Blocking cannabinoid type 1 receptors prevented AMPH from increasing transient frequency, similar to reported effects on other abused drugs, but not from increasing transient duration and inhibiting dopamine uptake. Thus, AMPH elevates nucleus accumbens dopamine by eliciting transients via cannabinoid type 1 receptors and promoting the summation of temporally coincident transients, made more numerous, larger and wider by AMPH. Collectively, these findings are inconsistent with AMPH eliciting action potential-independent dopamine efflux and vesicular dopamine depletion, and support endocannabinoids facilitating phasic dopamine signalling as a common action in drug reinforcement

Amphetamine elevates nucleus accumbens dopamine via an action potential-dependent mechanism that is modulated by endocannabinoids.

Science.gov (United States)

Covey, Dan P; Bunner, Kendra D; Schuweiler, Douglas R; Cheer, Joseph F; Garris, Paul A

2016-06-01

The reinforcing effects of abused drugs are mediated by their ability to elevate nucleus accumbens dopamine. Amphetamine (AMPH) was historically thought to increase dopamine by an action potential-independent, non-exocytotic type of release called efflux, involving reversal of dopamine transporter function and driven by vesicular dopamine depletion. Growing evidence suggests that AMPH also acts by an action potential-dependent mechanism. Indeed, fast-scan cyclic voltammetry demonstrates that AMPH activates dopamine transients, reward-related phasic signals generated by burst firing of dopamine neurons and dependent on intact vesicular dopamine. Not established for AMPH but indicating a shared mechanism, endocannabinoids facilitate this activation of dopamine transients by broad classes of abused drugs. Here, using fast-scan cyclic voltammetry coupled to pharmacological manipulations in awake rats, we investigated the action potential and endocannabinoid dependence of AMPH-induced elevations in nucleus accumbens dopamine. AMPH increased the frequency, amplitude and duration of transients, which were observed riding on top of slower dopamine increases. Surprisingly, silencing dopamine neuron firing abolished all AMPH-induced dopamine elevations, identifying an action potential-dependent origin. Blocking cannabinoid type 1 receptors prevented AMPH from increasing transient frequency, similar to reported effects on other abused drugs, but not from increasing transient duration and inhibiting dopamine uptake. Thus, AMPH elevates nucleus accumbens dopamine by eliciting transients via cannabinoid type 1 receptors and promoting the summation of temporally coincident transients, made more numerous, larger and wider by AMPH. Collectively, these findings are inconsistent with AMPH eliciting action potential-independent dopamine efflux and vesicular dopamine depletion, and support endocannabinoids facilitating phasic dopamine signalling as a common action in drug reinforcement

Fokker-action principle for a system of particles interacting through a linear potential

International Nuclear Information System (INIS)

Rivacoba, A.

1984-01-01

A Fokker-action principle for a system of scalar particles interacting through their time-symmetric relativistic generalization of linear potential is obtained. From this action, motion equations and conservation laws for the total energy and angular momentum of the system, in which field contributions are included, are derived. These equations are exactly applied to the problem suggested by Schild of two particles moving in circular concentric orbits

Axon initial segment Kv1 channels control axonal action potential waveform and synaptic efficacy

NARCIS (Netherlands)

Kole, Maarten H. P.; Letzkus, Johannes J.; Stuart, Greg J.

2007-01-01

Action potentials are binary signals that transmit information via their rate and temporal pattern. In this context, the axon is thought of as a transmission line, devoid of a role in neuronal computation. Here, we show a highly localized role of axonal Kv1 potassium channels in shaping the action

Laser-activated protein solder for peripheral nerve repair

Science.gov (United States)

Trickett, Rodney I.; Lauto, Antonio; Dawes, Judith M.; Owen, Earl R.

1995-05-01

A 100 micrometers core optical fiber-coupled 75 mW diode laser operating at a wavelength of 800 nm has been used in conjunction with a protein solder to stripe weld severed rat tibial nerves, reducing the long operating time required for microsurgical nerve repair. Welding is produced by selective laser denaturation of the albumin based solder which contains the dye indocyanine green. Operating time for laser soldering was 10 +/- 5 min. (n equals 20) compared to 23 +/- 9 min. (n equals 10) for microsuturing. The laser solder technique resulted in patent welds with a tensile strength of 15 +/- 5 g, while microsutured nerves had a tensile strength of 40 +/- 10 g. Histopathology of the laser soldered nerves, conducted immediately after surgery, displayed solder adhesion to the outer membrane with minimal damage to the inner axons of the nerves. An in vivo study is under way comparing laser solder repaired tibial nerves to conventional microsuture repair. At the time of submission 15 laser soldered nerves and 7 sutured nerves were characterized at 3 months and showed successful regeneration with compound muscle action potentials of 27 +/- 8 mV and 29 +/- 8 mW respectively. A faster, less damaging and long lasting laser based anastomotic technique is presented.

Application of Emergency Action Levels from Potential Release at Research Reactor HANARO

International Nuclear Information System (INIS)

Kim, Jongsoo; Lee, Goan Yub; Lee, Hae Choi; Kim, Bong Suk

2014-01-01

Execution of the protective action promptly is possible that Emergency Action Levels (EALs) must be established for a radiological release from nuclear facility. The EALs for electric power reactor are already developed and applied to recognize an emergency situation rapidly. Recently the IAEA published the safety report including the EALs for research reactor. This paper describes the EALs to apply for a potential release pathway at the research reactor HANARO. The results of table 1 and 2 will be higher than actual because the weather condition in real situation is difference. However, the EALs applying the potential stack release, ground release and site can be useful for research reactor HANARO making the emergency declaration. The EALs at the site boundary of the table 3 can be applied to protect the off-site public

Dynamic Action Potential Restitution Contributes to Mechanical Restitution in Right Ventricular Myocytes From Pulmonary Hypertensive Rats.

Science.gov (United States)

Hardy, Matthew E L; Pervolaraki, Eleftheria; Bernus, Olivier; White, Ed

2018-01-01

We investigated the steepened dynamic action potential duration (APD) restitution of rats with pulmonary artery hypertension (PAH) and right ventricular (RV) failure and tested whether the observed APD restitution properties were responsible for negative mechanical restitution in these myocytes. PAH and RV failure were provoked in male Wistar rats by a single injection of monocrotaline (MCT) and compared with saline-injected animals (CON). Action potentials were recorded from isolated RV myocytes at stimulation frequencies between 1 and 9 Hz. Action potential waveforms recorded at 1 Hz were used as voltage clamp profiles (action potential clamp) at stimulation frequencies between 1 and 7 Hz to evoke rate-dependent currents. Voltage clamp profiles mimicking typical CON and MCT APD restitution were applied and cell shortening simultaneously monitored. Compared with CON myocytes, MCT myocytes were hypertrophied; had less polarized diastolic membrane potentials; had action potentials that were triggered by decreased positive current density and shortened by decreased negative current density; APD was longer and APD restitution steeper. APD90 restitution was unchanged by exposure to the late Na + -channel blocker (5 μM) ranolazine or the intracellular Ca 2+ buffer BAPTA. Under AP clamp, stimulation frequency-dependent inward currents were smaller in MCT myocytes and were abolished by BAPTA. In MCT myocytes, increasing stimulation frequency decreased contraction amplitude when depolarization duration was shortened, to mimic APD restitution, but not when depolarization duration was maintained. We present new evidence that the membrane potential of PAH myocytes is less stable than normal myocytes, being more easily perturbed by external currents. These observations can explain increased susceptibility to arrhythmias. We also present novel evidence that negative APD restitution is at least in part responsible for the negative mechanical restitution in PAH myocytes. Thus

Potential of high-average-power solid state lasers

International Nuclear Information System (INIS)

Emmett, J.L.; Krupke, W.F.; Sooy, W.R.

1984-01-01

We discuss the possibility of extending solid state laser technology to high average power and of improving the efficiency of such lasers sufficiently to make them reasonable candidates for a number of demanding applications. A variety of new design concepts, materials, and techniques have emerged over the past decade that, collectively, suggest that the traditional technical limitations on power (a few hundred watts or less) and efficiency (less than 1%) can be removed. The core idea is configuring the laser medium in relatively thin, large-area plates, rather than using the traditional low-aspect-ratio rods or blocks. This presents a large surface area for cooling, and assures that deposited heat is relatively close to a cooled surface. It also minimizes the laser volume distorted by edge effects. The feasibility of such configurations is supported by recent developments in materials, fabrication processes, and optical pumps. Two types of lasers can, in principle, utilize this sheet-like gain configuration in such a way that phase and gain profiles are uniformly sampled and, to first order, yield high-quality (undistorted) beams. The zig-zag laser does this with a single plate, and should be capable of power levels up to several kilowatts. The disk laser is designed around a large number of plates, and should be capable of scaling to arbitrarily high power levels

Diode laser-pumped Ho:YLF laser

International Nuclear Information System (INIS)

Hemmati, H.

1987-01-01

The author reports laser action in Ho:YLF at 2.06 μm following optical pumping with a cw diode laser array. Diode laser-pumped Nd-YAG and Ho:YAG have been reported recently. Lasers with a wavelength of 2 μm have medical and optical communication applications. The diode laser light is focused with a 60-mm focal length lens onto the YLF crystal. A high-reflectivity mirror with 100-mm radius of curvature was used as the output coupler. The lasing threshold was at 5 mWof incident power. This is higher than expected considering that a high reflector was used as the output coupler. However, a more uniform cooling of the crystal is expected to lower the lasing threshold. With 100 mW of pump power coupled into the crystal, --20 mW of 2-μm radiation was observed from this unoptimized setup. The 2-μm laser output is highly sensitive to output coupler alignment, YLF crystal temperature, and pump laser wavelength. The 20% optical conversion efficiency achieved in his preliminary measurements is expected to be improved by better crystal cooling, proper matching of laser wavelength to crystal absorption, variations in the concentration of Ho and sensitizers and use of a proper output coupler. A study of the parameters mentioned above and the effect of crystal temperature on the laser output is under way

Potential of CO2 lasers (10.6 µm associated with fluorides in inhibiting human enamel erosion

Directory of Open Access Journals (Sweden)

Thayanne Monteiro RAMOS-OLIVEIRA

2014-01-01

Full Text Available This in vitro study aimed to investigate the potential of CO2 lasers associated with different fluoride agents in inhibiting enamel erosion. Human enamel samples were randomly divided into 9 groups (n = 12: G1-eroded enamel; G2-APF gel; G3-AmF/NaF gel; G4-AmF/SnF2 solution; G5-CO2 laser (λ = 10.6 µm+APF gel; G6-CO2 laser+AmF/NaF gel; G7-CO2laser+AmF/SnF2solution; G8-CO2 laser; and G9-sound enamel. The CO2 laser parameters were: 0.45 J/cm2; 6 μs; and 128 Hz. After surface treatment, the samples (except from G9 were immersed in 1% citric acid (pH 4.0, 3 min. Surface microhardness was measured at baseline and after surface softening. The data were statistically analyzed by one-way ANOVA and Tukey’s tests (p < 0.05. G2 (407.6 ± 37.3 presented the highest mean SMH after softening, followed by G3 (407.5 ± 29.8 and G5 (399.7 ± 32.9. Within the fluoride-treated groups, G4 (309.0 ± 24.4 had a significantly lower mean SMH than G3 and G2, which were statistically similar to each other. AmF/NaF and APF application showed potential to protect and control erosion progression in dental enamel, and CO2 laser irradiation at 0.45J/cm2 did not influence its efficacy. CO2 laser irradiation alone under the same conditions could also significantly decrease enamel erosive mineral loss, although at lower levels.

Sensitivity to structure in action sequences: An infant event-related potential study.

Science.gov (United States)

Monroy, Claire D; Gerson, Sarah A; Domínguez-Martínez, Estefanía; Kaduk, Katharina; Hunnius, Sabine; Reid, Vincent

2017-05-06

Infants are sensitive to structure and patterns within continuous streams of sensory input. This sensitivity relies on statistical learning, the ability to detect predictable regularities in spatial and temporal sequences. Recent evidence has shown that infants can detect statistical regularities in action sequences they observe, but little is known about the neural process that give rise to this ability. In the current experiment, we combined electroencephalography (EEG) with eye-tracking to identify electrophysiological markers that indicate whether 8-11-month-old infants detect violations to learned regularities in action sequences, and to relate these markers to behavioral measures of anticipation during learning. In a learning phase, infants observed an actor performing a sequence featuring two deterministic pairs embedded within an otherwise random sequence. Thus, the first action of each pair was predictive of what would occur next. One of the pairs caused an action-effect, whereas the second did not. In a subsequent test phase, infants observed another sequence that included deviant pairs, violating the previously observed action pairs. Event-related potential (ERP) responses were analyzed and compared between the deviant and the original action pairs. Findings reveal that infants demonstrated a greater Negative central (Nc) ERP response to the deviant actions for the pair that caused the action-effect, which was consistent with their visual anticipations during the learning phase. Findings are discussed in terms of the neural and behavioral processes underlying perception and learning of structured action sequences. Copyright © 2017 Elsevier Ltd. All rights reserved.

Emitting recombination of BCl molecules with chlorine atoms, resulting from dissociation of boron trichloride molecules under action of pulse CO2-laser radiation

International Nuclear Information System (INIS)

Nikonorov, A.P.; Moskvitina, E.N.; Kuzyakov, Yu.Ya.; Stepanov, P.I.

1983-01-01

Luminescence in BCl 3 is investigated. The results of measurements of gas temperature, BCl molecules concentration, and luminescence absolute intensity at boron trichloride presure of 40 mm pH and density of laser pulse energy from 1.7 up to 4.0 J/cm 2 are obtained. Nature of uninterrupted spectrum is considered. It is established that luminescence appearing in the BCl 3 under action of pulse CO 2 -laser is caused by reaction of emitting recombination of BCl molecules with chlorine atoms. Rate constant of this reaction in the range of 2300-3100 K is determined

Laser-diode pumped Nd:YAG lasers; Laser diode reiki Nd:YAG lasear

Energy Technology Data Exchange (ETDEWEB)

Yuasa, H.; Akiyama, Y.; Nakayama, M. [Toshiba Corp., Tokyo (Japan)

2000-04-01

Laser-diode pumped Nd:YAG lasers are expected to be applied to laser processing fields such as welding, cutting, drilling, and marking due to their potential for high efficiency and compactness. We are designing and developing laser-diode pumped Nd:YAG lasers using numerical analysis simulation techniques such as ray tracing and thermal analysis. We have succeeded in achieving a laser power of more than 3 kW with 20% efficiency, which is the best ever obtained. In addition, we have developed a laser-diode pumped green laser by second harmonic generation, for precision machining on silicon wafers. (author)

Activation of Mechanosensitive Transient Receptor Potential/Piezo Channels in Odontoblasts Generates Action Potentials in Cocultured Isolectin B4-negative Medium-sized Trigeminal Ganglion Neurons.

Science.gov (United States)

Sato, Masaki; Ogura, Kazuhiro; Kimura, Maki; Nishi, Koichi; Ando, Masayuki; Tazaki, Masakazu; Shibukawa, Yoshiyuki

2018-04-27

Various stimuli to the dentin surface elicit dentinal pain by inducing dentinal fluid movement causing cellular deformation in odontoblasts. Although odontoblasts detect deformation by the activation of mechanosensitive ionic channels, it is still unclear whether odontoblasts are capable of establishing neurotransmission with myelinated A delta (Aδ) neurons. Additionally, it is still unclear whether these neurons evoke action potentials by neurotransmitters from odontoblasts to mediate sensory transduction in dentin. Thus, we investigated evoked inward currents and evoked action potentials form trigeminal ganglion (TG) neurons after odontoblast mechanical stimulation. We used patch clamp recordings to identify electrophysiological properties and record evoked responses in TG neurons. We classified TG cells into small-sized and medium-sized neurons. In both types of neurons, we observed voltage-dependent inward currents. The currents from medium-sized neurons showed fast inactivation kinetics. When mechanical stimuli were applied to odontoblasts, evoked inward currents were recorded from medium-sized neurons. Antagonists for the ionotropic adenosine triphosphate receptor (P2X 3 ), transient receptor potential channel subfamilies, and Piezo1 channel significantly inhibited these inward currents. Mechanical stimulation to odontoblasts also generated action potentials in the isolectin B 4 -negative medium-sized neurons. Action potentials in these isolectin B 4 -negative medium-sized neurons showed a short duration. Overall, electrophysiological properties of neurons indicate that the TG neurons with recorded evoked responses after odontoblast mechanical stimulation were myelinated Aδ neurons. Odontoblasts established neurotransmission with myelinated Aδ neurons via P2X 3 receptor activation. The results also indicated that mechanosensitive TRP/Piezo1 channels were functionally expressed in odontoblasts. The activation of P2X 3 receptors induced an action potential

Stretchable Random Lasers with Tunable Coherent Loops.

Science.gov (United States)

Sun, Tzu-Min; Wang, Cih-Su; Liao, Chi-Shiun; Lin, Shih-Yao; Perumal, Packiyaraj; Chiang, Chia-Wei; Chen, Yang-Fang

2015-12-22

Stretchability represents a key feature for the emerging world of realistic applications in areas, including wearable gadgets, health monitors, and robotic skins. Many optical and electronic technologies that can respond to large strain deformations have been developed. Laser plays a very important role in our daily life since it was discovered, which is highly desirable for the development of stretchable devices. Herein, stretchable random lasers with tunable coherent loops are designed, fabricated, and demonstrated. To illustrate our working principle, the stretchable random laser is made possible by transferring unique ZnO nanobrushes on top of polydimethylsiloxane (PDMS) elastomer substrate. Apart from the traditional gain material of ZnO nanorods, ZnO nanobrushes were used as optical gain materials so they can serve as scattering centers and provide the Fabry-Perot cavity to enhance laser action. The stretchable PDMS substrate gives the degree of freedom to mechanically tune the coherent loops of the random laser action by changing the density of ZnO nanobrushes. It is found that the number of laser modes increases with increasing external strain applied on the PDMS substrate due to the enhanced possibility for the formation of coherent loops. The device can be stretched by up to 30% strain and subjected to more than 100 cycles without loss in laser action. The result shows a major advance for the further development of man-made smart stretchable devices.

The potential for optical beam shaping of UV laser sources for mass scale quarantine disinfection applications

Science.gov (United States)

Lizotte, Todd

2010-08-01

Recent events concerning H1N1 "swine flu", have demonstrated to the world the significant potential of rapid increases in death and illness among all age groups and even among the healthy population [1] when a highly infectious influenza virus is introduced. In terms of mass casualties due to a pandemic, preparedness and response planning must be done. One course of action to prevent a pandemic outbreak or reduce the impact of a bioterrorist event is the use of isolation or quarantine facilities. The first level of isolation or quarantine is within the personal residence of the person exposed or infected. In the case where, the specific virus is extremely contagious and its onset of symptoms is rapid and severe, there will be a need for the deployment and setup of larger self contained quarantine facilities. Such facilities are used to house infectious individuals to minimize the exposure of susceptible individuals to contagious individuals, especially when specialized care or treatment is required and during the viral shedding period (5 to 7 days). These types of facilities require non-shared air conditioning, heating and ventilating systems where 100% of air is vented to the outside through a series of disinfection systems and staged filters. Although chemical disinfection is possible, there is a desire to incorporate intense UV radiation as a means to deactivate and disinfect airborne virus within hospital settings and isolated mass scale quarantine facilities. UV radiation is also being considered for disinfection of contaminated surfaces, such as table tops, walls and floors in hospitals and temporary quarantine facilities. In such applications the use of UV bulb technology can create many problems, for instance bulb technology requires numerous bulbs to treat a large volume of air, generates significant heat, uses significant power and does not produce large fluxes of UV light efficiently. This paper provides several methods of creating quarantine level

Conduction velocity of the human spinothalamic tract as assessed by laser evoked potentials

DEFF Research Database (Denmark)

Cruccu, G.; Iannetti, G. D.; Agostino, R.

2000-01-01

To study the conduction velocity of the spinothalamic tract (STT) we delivered CO2 laser pulses, evoking pinprick sensations, to the skin overlying the vertebral spinous processes at different spinal levels from C5 to T10 and recorded evoked potentials (LEPs) in 15 healthy human subjects...

76 FR 21938 - Potential Environmental Impacts of the Proposed Runway 13 Extension and Associated Actions for...

Science.gov (United States)

2011-04-19

... DEPARTMENT OF TRANSPORTATION Federal Aviation Administration Potential Environmental Impacts of the Proposed Runway 13 Extension and Associated Actions for the Devils Lake Regional Airport in Devils Lake, ND AGENCY: Federal Aviation Administration (FAA), Department of Transportation (DOT). ACTION...

Determination of Nerve Fiber Diameter Distribution From Compound Action Potential: A Continuous Approach.

Science.gov (United States)

Un, M Kerem; Kaghazchi, Hamed

2018-01-01

When a signal is initiated in the nerve, it is transmitted along each nerve fiber via an action potential (called single fiber action potential (SFAP)) which travels with a velocity that is related with the diameter of the fiber. The additive superposition of SFAPs constitutes the compound action potential (CAP) of the nerve. The fiber diameter distribution (FDD) in the nerve can be computed from the CAP data by solving an inverse problem. This is usually achieved by dividing the fibers into a finite number of diameter groups and solve a corresponding linear system to optimize FDD. However, number of fibers in a nerve can be measured sometimes in thousands and it is possible to assume a continuous distribution for the fiber diameters which leads to a gradient optimization problem. In this paper, we have evaluated this continuous approach to the solution of the inverse problem. We have utilized an analytical function for SFAP and an assumed a polynomial form for FDD. The inverse problem involves the optimization of polynomial coefficients to obtain the best estimate for the FDD. We have observed that an eighth order polynomial for FDD can capture both unimodal and bimodal fiber distributions present in vivo, even in case of noisy CAP data. The assumed FDD distribution regularizes the ill-conditioned inverse problem and produces good results.

Quantitative analysis of single muscle fibre action potentials recorded at known distances

NARCIS (Netherlands)

Albers, B.A.; Put, J.H.M.; Wallinga, W.; Wirtz, P.

1989-01-01

In vivo records of single fibre action potentials (SFAPs) have always been obtained at unknown distance from the active muscle fibre. A new experimental method has been developed enabling the derivation of the recording distance in animal experiments. A single fibre is stimulated with an

Excited State Assignment and Laser Action in π-Conjugated Polymers

Science.gov (United States)

Vardeny, Z. V.

1998-03-01

degenerate and nondegenerate ground states, respectively. In addition, due to strong electron-phonon coupling, the unrelaxed 1B_u, the relaxed 1B_u, the excited 1Ag and the ground 1Ag form an ideal four-level laser system( S.V. Frolov, W. Gellermann, M. Ozaki, K. Yoshino, and Z.V. Vardeny, Phys. Rev. Lett). 78, 729 (1997). with population inversion that is very easy to achieve due to the intrachain exciton confinement in the polymer film. If η gtorder 10%, the excitonic PA does not overlap with the main PL band and long-lived photoexcitation density is small, then laser action may be achieved. This is in the form of cooperative emission or superfluorescence (SF) in poorly prepared films,^3 amplified spontaneous emission (ASE) in solutions and superior films where wave guiding is dominant,( S.V. Frolov, Z.V. Vardeny, and K. Yoshino, Phys. Rev). B (in press) and lasing in μ-cavities.(S.V. Frolov, M. Shkunov, Z.V. Vardeny, and K. Yoshino, Phys. Rev). B56, R4363 (1997) New time-resolved nonlinear emission data will be shown where delay time statistics, characteristics of SF was measured. We will also report on single laser-line emission, of less than 1Ålinewidth and threshold of 100 pJ, which was achieved in miniature cylindrical DOO-PPV μ-cavities of both ring and disk-type geometries.

Outcome producing potential influences twelve-month-olds' interpretation of a novel action as goal-directed.

Science.gov (United States)

Biro, Szilvia; Verschoor, Stephan; Coalter, Esther; Leslie, Alan M

2014-11-01

Learning about a novel, goal-directed action is a complex process. It requires identifying the outcome of the action and linking the action to its outcome for later use in new situations to predict the action or to anticipate its outcome. We investigated the hypothesis that linking a novel action to a salient change in the environment is critical for infants to assign a goal to the novel action. We report a study in which we show that 12-month-old infants, who were provided with prior experience with a novel action accompanied with a salient visible outcome in one context, can interpret the same action as goal-directed even in the absence of the outcome in another context. Our control condition shows that prior experience with the action, but without the salient effect, does not lead to goal-directed interpretation of the novel action. We also found that, for the case of 9-month-olds infants, prior experience with the outcome producing potential of the novel action does not facilitate a goal-directed interpretation of the action. However, this failure was possibly due to difficulties with generalizing the learnt association to another context rather than with linking the action to its outcome. Copyright © 2014 Elsevier Inc. All rights reserved.

On the potential of laser driven isotope generation at ELI-NP for positron emission tomography

Science.gov (United States)

Cucoanes, A. S.; Balabanski, D. L.; Canova, F.; Cuong, P.; Negoita, F.; Puicea, F.; Tanaka, K. A.

2017-05-01

The huge progress made in the laser driven ion acceleration had open the possibility of using ions generated in high power laser interactions with solid targets for the production of medical isotopes. Indeed, lasers could provide several key features with respect to the traditional method where the target activation is produced by particle beams delivered by cyclotrons. The price and the dimensions of high power lasers are on a descendant slope and the quality of the produced ion beams is continuously increasing. However, in order to compete with cyclotrons, the average proton current intensity has to be increased for example by increasing the frequency of the laser pulses. In our contribution, we review the general ideas of the laser-based radioisotope production and we present our analysis on the potential of the medical isotope generation at ELI-NP with a focus on 18F. We use estimations of the proton beam parameters and a code implemented in Geant4 for computing the yield of the main production channel taking into account the experimental conditions available soon at ELI-NP. The obtained results are compatible with previous studies and will be verified by experiments foreseen at the future ELI-NP facility, under construction now in Magurele, Romania.

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

Science.gov (United States)

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

2012-10-01

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

Yb{sup 3+}:Sr{sub 5}(VO{sub 4}){sub 3}F: Crystal growth, spectroscopic characterization and laser development; Yb{sup 3+}:Sr{sub 5}(VO{sub 4}){sub 3}F: Crescimento, caracterizacao espectroscopica e desenvolvimento do laser

Energy Technology Data Exchange (ETDEWEB)

Bustamante, Andrea Nora Pino

1999-07-01

Crystal growth, spectroscopic characterization and laser development of Yb{sup 3+}:SVAP [Sr{sub 5}(VO{sub 4}){sub 3}F] was performed to demonstrate for the first time, operation of tunable laser emission centered at 1120 nm. Initially, SVAP crystals were grown with high dopant concentrations, up to 6.0 mol % of Yb{sub 2} O{sub 3} in the melt, in order to investigate the material for potential laser operation at a new laser wavelength. Additional research was performed to alleviate highly doped SVAP crystals of defects previously observed. Basic spectroscopic characterization including absorption and luminescent properties were measured to better understand the behavior of Yb{sup 3+} ions in SVAP. Based upon these studies, discussion of the 1120 nm laser transition is presented as it arises from a ground state vibrational level. Investigations of the charge compensation process and the optical parameters as a function of dopant concentration are also presented. The laser development of Yb{sup 3+}:SVAP included continuous and pulsed modes of operation of the 1044 nm and 1120 nm transitions. Initial laser action of the 1044 nm transition was achieved using a Yi: Saphire laser pump source in order to compare with previously results. Further development of a diode-pumped Yb{sup 3+}:SVAP laser system demonstrated continuously tunable laser operation from 1103 nm for the first time. The laser investigations also proved that this high gain media does provide continuous wave laser action at 1044 nm and 1120 simultaneously without significant gain depletion. (author)

A dual potassium channel activator improves repolarization reserve and normalizes ventricular action potentials

DEFF Research Database (Denmark)

Calloe, Kirstine; Di Diego, José M; Hansen, Rie Schultz

2016-01-01

in cultured canine cardiac myocytes and determined whether a dual K(+) current activator can normalize K(+) currents and restore action potential (AP) configuration. METHODS AND RESULTS: Ventricular myocytes were isolated and cultured for up to 48h. Current and voltage clamp recordings were made using patch...... of EADs. Our results suggest a potential benefit of K(+) current activators under conditions of reduced repolarization reserve including heart failure....

Action potential propagation recorded from single axonal arbors using multi-electrode arrays.

Science.gov (United States)

Tovar, Kenneth R; Bridges, Daniel C; Wu, Bian; Randall, Connor; Audouard, Morgane; Jang, Jiwon; Hansma, Paul K; Kosik, Kenneth S

2018-04-11

We report the presence of co-occurring extracellular action potentials (eAPs) from cultured mouse hippocampal neurons among groups of planar electrodes on multi-electrode arrays (MEAs). The invariant sequences of eAPs among co-active electrode groups, repeated co-occurrences and short inter-electrode latencies are consistent with action potential propagation in unmyelinated axons. Repeated eAP co-detection by multiple electrodes was widespread in all our data records. Co-detection of eAPs confirms they result from the same neuron and allows these eAPs to be isolated from all other spikes independently of spike sorting algorithms. We averaged co-occurring events and revealed additional electrodes with eAPs that would otherwise be below detection threshold. We used these eAP cohorts to explore the temperature sensitivity of action potential propagation and the relationship between voltage-gated sodium channel density and propagation velocity. The sequence of eAPs among co-active electrodes 'fingerprints' neurons giving rise to these events and identifies them within neuronal ensembles. We used this property and the non-invasive nature of extracellular recording to monitor changes in excitability at multiple points in single axonal arbors simultaneously over several hours, demonstrating independence of axonal segments. Over several weeks, we recorded changes in inter-electrode propagation latencies and ongoing changes in excitability in different regions of single axonal arbors. Our work illustrates how repeated eAP co-occurrences can be used to extract physiological data from single axons with low electrode density MEAs. However, repeated eAP co-occurrences leads to over-sampling spikes from single neurons and thus can confound traditional spike-train analysis.

Improving executive function using transcranial infrared laser stimulation.

Science.gov (United States)

Blanco, Nathaniel J; Maddox, W Todd; Gonzalez-Lima, Francisco

2017-03-01

Transcranial infrared laser stimulation is a new non-invasive form of low-level light therapy that may have a wide range of neuropsychological applications. It entails using low-power and high-energy-density infrared light from lasers to increase metabolic energy. Preclinical work showed that this intervention can increase cortical metabolic energy, thereby improving frontal cortex-based memory function in rats. Barrett and Gonzalez-Lima (2013, Neuroscience, 230, 13) discovered that transcranial laser stimulation can enhance sustained attention and short-term memory in humans. We extend this line of work to executive function. Specifically, we ask whether transcranial laser stimulation enhances performance in the Wisconsin Card Sorting Task that is considered the gold standard of executive function and is compromised in normal ageing and a number of neuropsychological disorders. We used a laser of a specific wavelength (1,064 nm) that photostimulates cytochrome oxidase - the enzyme catalysing oxygen consumption for metabolic energy production. Increased cytochrome oxidase activity is considered the primary mechanism of action of this intervention. Participants who received laser treatment made fewer errors and showed improved set-shifting ability relative to placebo controls. These results suggest that transcranial laser stimulation improves executive function and may have exciting potential for treating or preventing deficits resulting from neuropsychological disorders or normal ageing. © 2015 The British Psychological Society.

Laser Processing and Chemistry

CERN Document Server

Bäuerle, Dieter

2011-01-01

This book gives an overview of the fundamentals and applications of laser-matter interactions, in particular with regard to laser material processing. Special attention is given to laser-induced physical and chemical processes at gas-solid, liquid-solid, and solid-solid interfaces. Starting with the background physics, the book proceeds to examine applications of lasers in “standard” laser machining and laser chemical processing (LCP), including the patterning, coating, and modification of material surfaces. This fourth edition has been enlarged to cover the rapid advances in the understanding of the dynamics of materials under the action of ultrashort laser pulses, and to include a number of new topics, in particular the increasing importance of lasers in various different fields of surface functionalizations and nanotechnology. In two additional chapters, recent developments in biotechnology, medicine, art conservation and restoration are summarized. Graduate students, physicists, chemists, engineers, a...

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

Science.gov (United States)

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

2015-08-01

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

Anti-addiction Drug Ibogaine Prolongs the Action Potential in Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes.

Science.gov (United States)

Rubi, Lena; Eckert, Daniel; Boehm, Stefan; Hilber, Karlheinz; Koenig, Xaver

2017-04-01

Ibogaine is a plant alkaloid used as anti-addiction drug in dozens of alternative medicine clinics worldwide. Recently, alarming reports of life-threatening cardiac arrhythmias and cases of sudden death associated with the ingestion of ibogaine have accumulated. Using whole-cell patch clamp recordings, we assessed the effects of ibogaine and its main metabolite noribogaine on action potentials in human ventricular-like cardiomyocytes derived from induced pluripotent stem cells. Therapeutic concentrations of ibogaine and its long-lived active metabolite noribogaine significantly retarded action potential repolarization in human cardiomyocytes. These findings represent the first experimental proof that ibogaine application entails a cardiac arrhythmia risk for humans. In addition, they explain the clinically observed delayed incidence of cardiac adverse events several days after ibogaine intake. We conclude that therapeutic concentrations of ibogaine retard action potential repolarization in the human heart. This may give rise to a prolongation of the QT interval in the electrocardiogram and cardiac arrhythmias.

Towards a spectroscopically accurate set of potentials for heavy hydride laser cooling candidates: Effective core potential calculations of BaH

Energy Technology Data Exchange (ETDEWEB)

Moore, Keith; McLaughlin, Brendan M.; Lane, Ian C., E-mail: i.lane@qub.ac.uk [School of Chemistry and Chemical Engineering, Queen’s University Belfast, Stranmillis Road, Belfast BT9 5AG (United Kingdom)

2016-04-14

BaH (and its isotopomers) is an attractive molecular candidate for laser cooling to ultracold temperatures and a potential precursor for the production of ultracold gases of hydrogen and deuterium. The theoretical challenge is to simulate the laser cooling cycle as reliably as possible and this paper addresses the generation of a highly accurate ab initio {sup 2}Σ{sup +} potential for such studies. The performance of various basis sets within the multi-reference configuration-interaction (MRCI) approximation with the Davidson correction is tested and taken to the Complete Basis Set (CBS) limit. It is shown that the calculated molecular constants using a 46 electron effective core-potential and even-tempered augmented polarized core-valence basis sets (aug-pCVnZ-PP, n = 4 and 5) but only including three active electrons in the MRCI calculation are in excellent agreement with the available experimental values. The predicted dissociation energy D{sub e} for the X{sup 2}Σ{sup +} state (extrapolated to the CBS limit) is 16 895.12 cm{sup −1} (2.094 eV), which agrees within 0.1% of a revised experimental value of <16 910.6 cm{sup −1}, while the calculated r{sub e} is within 0.03 pm of the experimental result.

Action Research’s Potential to Foster Institutional Change for Urban Water Management

Directory of Open Access Journals (Sweden)

Dimitrios Zikos

2013-04-01

Full Text Available The paper discusses the potential of action research to meet the challenges entailed in institutional design for urban water management. Our overall aim is to briefly present action research and discuss its methodological merits with regard to the challenges posed by the different conceptual bases for extrapolating the effects of institutional design on institutional change. Thus, our aim is to explore how Action Research meets the challenge of scoping the field in an open fashion for determining the appropriate mechanisms of institutional change and supporting the emerging of new water institutions. To accomplish this aim, we select the Water Framework Directive (WFD as an illustrative driving force requiring changes in water management practices and implying the need for the emergence of new institutions. We employ a case of urban water management in the Volos Metropolitan Area, part of the Thessaly region in Greece, where a Pilot River Basin Plan was implemented. By applying action research and being involved in a long process of interaction between stakeholders, we examine the emergence of new institutions dealing with urban water management under the general principles of the major driving force for change: the WFD.

Event-related potential effects of superior action anticipation in professional badminton players.

Science.gov (United States)

Jin, Hua; Xu, Guiping; Zhang, John X; Gao, Hongwei; Ye, Zuoer; Wang, Pin; Lin, Huiyan; Mo, Lei; Lin, Chong-De

2011-04-04

The ability to predict the trajectory of a ball based on the opponent's body kinematics has been shown to be critical to high-performing athletes in many sports. However, little is known about the neural correlates underlying such superior ability in action anticipation. The present event-related potential study compared brain responses from professional badminton players and non-player controls when they watched video clips of badminton games and predicted a ball's landing position. Replicating literature findings, the players made significantly more accurate judgments than the controls and showed better action anticipation. Correspondingly, they showed enlarged amplitudes of two ERP components, a P300 peaking around 350ms post-stimulus with a parietal scalp distribution and a P2 peaking around 250ms with a posterior-occipital distribution. The P300 effect was interpreted to reflect primed access and/or directing of attention to game-related memory representations in the players facilitating their online judgment of related actions. The P2 effect was suggested to reflect some generic learning effects. The results identify clear neural responses that differentiate between different levels of action anticipation associated with sports expertise. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Extraction of Vertical Walls from Mobile Laser Scanning Data for Solar Potential Assessment

Directory of Open Access Journals (Sweden)

Martin Rutzinger

2011-03-01

Full Text Available In recent years there has been an increasing demand among home owners for cost effective sustainable energy production such as solar energy to provide heating and electricity. A lot of research has focused on the assessment of the incoming solar radiation on roof planes acquired by, e.g., Airborne Laser Scanning (ALS. However, solar panels can also be mounted on building facades in order to increase renewable energy supply. Due to limited reflections of points from vertical walls, ALS data is not suitable to perform solar potential assessment of vertical building facades. This paper focuses on a new method for automatic solar radiation modeling of facades acquired by Mobile Laser Scanning (MLS and uses the full 3D information of the point cloud for both the extraction of vertical walls covered by the survey and solar potential analysis. Furthermore, a new method isintroduced determining the interior and exterior face, respectively, of each detected wall in order to calculate its slope and aspect angles that are of crucial importance for solar potential assessment. Shadowing effects of nearby objects are considered by computing the 3D horizon of each point of a facade segment within the 3D point cloud.

Effects of external trigeminal nerve stimulation (eTNS) on laser evoked cortical potentials (LEP): A pilot study in migraine patients and controls.

Science.gov (United States)

Vecchio, Eleonora; Gentile, Eleonora; Franco, Giovanni; Ricci, Katia; de Tommaso, Marina

2017-01-01

Background Transcutaneous external supraorbital nerve stimulation has emerged as a treatment option for primary headache disorders, though its action mechanism is still unclear. Study aim In this randomized, sham-controlled pilot study we aimed to test the effects of a single external transcutaneous nerve stimulation session on pain perception and cortical responses induced by painful laser stimuli delivered to the right forehead and the right hand in a cohort of migraine without aura patients and healthy controls. Methods Seventeen migraine without aura patients and 21 age- and sex-matched controls were selected and randomly assigned to a real or sham external transcutaneous nerve stimulation single stimulation session. The external transcutaneous nerve stimulation was delivered with a self-adhesive electrode placed on the forehead and generating a 60 Hz pulse at 16 mA intensity for 20 minutes. For sham stimulation, we used 2 mA intensity. Laser evoked responses were recorded from 21 scalp electrodes in basal condition (T0), during external transcutaneous nerve stimulation and sham stimulation (T1), and immediately after these (T2). The laser evoked responses were analyzed by LORETA software. Results The real external transcutaneous nerve stimulation reduced the trigeminal N2P2 amplitude in migraine and control groups significantly in respect to placebo. The real stimulation was associated with lower activity in the anterior cingulate cortex under trigeminal laser stimuli. The pattern of LEP-reduced habituation was reverted by real and sham transcutaneous stimulation in migraine patients. Conclusions The present results could suggest that the external transcutaneous nerve stimulation may interfere with the threshold and the extent of trigeminal system activation, with a mechanism of potential utility in the resolution and prevention of migraine attacks.

Analysis of electrically evoked compound action potential of the auditory nerve in children with bilateral cochlear implants.

Science.gov (United States)

Caldas, Fernanda Ferreira; Cardoso, Carolina Costa; Barreto, Monique Antunes de Souza Chelminski; Teixeira, Marina Santos; Hilgenberg, Anacléia Melo da Silva; Serra, Lucieny Silva Martins; Bahmad Junior, Fayez

2016-01-01

The cochlear implant device has the capacity to measure the electrically evoked compound action potential of the auditory nerve. The neural response telemetry is used in order to measure the electrically evoked compound action potential of the auditory nerve. To analyze the electrically evoked compound action potential, through the neural response telemetry, in children with bilateral cochlear implants. This is an analytical, prospective, longitudinal, historical cohort study. Six children, aged 1-4 years, with bilateral cochlear implant were assessed at five different intervals during their first year of cochlear implant use. There were significant differences in follow-up time (p=0.0082) and electrode position (p=0.0019) in the T-NRT measure. There was a significant difference in the interaction between time of follow-up and electrode position (p=0.0143) when measuring the N1-P1 wave amplitude between the three electrodes at each time of follow-up. The electrically evoked compound action potential measurement using neural response telemetry in children with bilateral cochlear implants during the first year of follow-up was effective in demonstrating the synchronized bilateral development of the peripheral auditory pathways in the studied population. Copyright © 2015 Associação Brasileira de Otorrinolaringologia e Cirurgia Cérvico-Facial. Published by Elsevier Editora Ltda. All rights reserved.

Action Learning: Avoiding Conflict or Enabling Action

Science.gov (United States)

Corley, Aileen; Thorne, Ann

2006-01-01

Action learning is based on the premise that action and learning are inextricably entwined and it is this potential, to enable action, which has contributed to the growth of action learning within education and management development programmes. However has this growth in action learning lead to an evolution or a dilution of Revan's classical…

Preparation of conjugated poly(ethyl acetylene carboxylate) as optical limiter of laser radiation

International Nuclear Information System (INIS)

Allaf, A. W.; Al-Zier, A.; Al-Naima, D.

2009-03-01

The optical limiting action of poly (ethylacetylene carboxylate) dissolved in dichloroethane were investigated under irradiation with 8 ns laser pulses at 532 nm. The optical limiting measurements were performed at a series of concentrations. The threshold limiting fluence was observed for high concentrations at 5 J/cm 2 with a transmission of about 20 %. No optical limiting action was observed at very low concentration of the prepared polymer in the dichloroethane solvent. The observed data show that poly (ethylacetylene carboxylate) has the potential for the use as optical limiting material for future applications. (author)

Beat-to-beat variability of cardiac action potential duration: underlying mechanism and clinical implications.

Science.gov (United States)

Nánási, Péter P; Magyar, János; Varró, András; Ördög, Balázs

2017-10-01

Beat-to-beat variability of cardiac action potential duration (short-term variability, SV) is a common feature of various cardiac preparations, including the human heart. Although it is believed to be one of the best arrhythmia predictors, the underlying mechanisms are not fully understood at present. The magnitude of SV is basically determined by the intensity of cell-to-cell coupling in multicellular preparations and by the duration of the action potential (APD). To compensate for the APD-dependent nature of SV, the concept of relative SV (RSV) has been introduced by normalizing the changes of SV to the concomitant changes in APD. RSV is reduced by I Ca , I Kr , and I Ks while increased by I Na , suggesting that ion currents involved in the negative feedback regulation of APD tend to keep RSV at a low level. RSV is also influenced by intracellular calcium concentration and tissue redox potential. The clinical implications of APD variability is discussed in detail.

INTERACTION OF LASER RADIATION WITH MATTER AND OTHER LASER APPLICATIONS: Changes in the emission properties of metal targets during pulse-periodic laser irradiation

Science.gov (United States)

Konov, Vitalii I.; Pimenov, S. M.; Prokhorov, A. M.; Chapliev, N. I.

1988-02-01

A scanning electron microscope was used with a pulse-periodic CO2 laser to discover the laws governing the correlation of the modified microrelief of metal surfaces, subjected to the action of multiple laser pulses, with the emission of charged particles and the luminescence of the irradiated zone. It was established that the influence of sorption and laser-induced desorption on the emission signals may be manifested differently depending on the regime of current generation in the "target-vacuum chamber" circuit.

Identification of New Potential Scientific and Technology Areas for DoD Application. Summary of Activities

Science.gov (United States)

1983-08-02

of Southern California (USC). Following Dr. Bass’s briefing, Dr. Elsa Garmire, also of USC, discussed the use of high-power laser diodes as pumps for...remaining portion of the light is imaged with a lens (not snown). 26 LJI-R-82-217 -vPOTENTIAL OF VERY LARGE ARRAYS OF SEMICONDUCTOR LASER SOURCES ELSA ...semiconductors, surface physics, and the action of catalysts which are not accessible to synchrotron light sources. Such a promising new development certainly

Compound sensory action potential in normal and pathological human nerves

DEFF Research Database (Denmark)

Krarup, Christian

2004-01-01

The compound sensory nerve action potential (SNAP) is the result of phase summation and cancellation of single fiber potentials (SFAPs) with amplitudes that depend on fiber diameter, and the amplitude and shape of the SNAP is determined by the distribution of fiber diameters. Conduction velocities...... dispersion over increasing conduction distance is greater for the SNAP than CMAP, and demonstration of conduction block is therefore difficult. In addition, the effect of temporal dispersion on amplitude and shape is strongly dependent on the number of conducting fibers and their distribution, and......, with fiber loss or increased conduction velocity variability changes of the SNAP may be smaller than expected from normal nerve. The biophysical characteristics of sensory and motor fibers differ, and this may to some extent determine divergent pathophysiological changes in sensory and motor fibers...

Laser-activated protein bands for peripheral nerve repair

Science.gov (United States)

Lauto, Antonio; Trickett, Rodney I.; Malik, Richard; Dawes, Judith M.; Owen, Earl R.

1996-01-01

A 100 micrometer core optical fiber-coupled 75 mW diode laser operating at a wavelength of 800 nm has been used in conjunction with a protein solder to stripe weld severed rat tibial nerves, reducing the long operating time required for microsurgical nerve repair. Welding is produced by selective laser denaturation of the protein based solder which contains the dye indocyanine green. Operating time for laser soldering was 10 plus or minus 5 min. (n equals 24) compared to 23 plus or minus 9 min (n equals 13) for microsuturing. The laser solder technique resulted in patent welds with a tensile strength of 15 plus or minus 5 g, while microsutured nerves had a tensile strength of 40 plus or minus 10 g. Histopathology of the laser soldered nerves, conducted immediately after surgery, displayed solder adhesion to the outer membrane with minimal damage to the inner axons of the nerves. An in vivo study, with a total of fifty-seven adult male wistar rats, compared laser solder repaired tibial nerves to conventional microsuture repair. Twenty-four laser soldered nerves and thirteen sutured nerves were characterized at three months and showed successful regeneration with average compound muscle action potentials (CMAP) of 2.4 plus or minus 0.7 mV and 2.7 plus or minus 0.8 mV respectively. Histopathology of the in vivo study, confirmed the comparable regeneration of axons in laser and suture operated nerves. A faster, less damaging and long lasting laser based anastomotic technique is presented.

Effect of an Educational Game on University Students' Learning about Action Potentials

Science.gov (United States)

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

2017-01-01

The aim of this study was to evaluate the effect of an educational game that is used for teaching the mechanisms of the action potentials in cell membranes. The game was composed of pieces representing the intracellular and extracellular environments, ions, ion channels, and the Na+-K+-ATPase pump. During the game activity, the students arranged…

Action potential conduction between a ventricular cell model and an isolated ventricular cell

NARCIS (Netherlands)

Wilders, R.; Kumar, R.; Joyner, R. W.; Jongsma, H. J.; Verheijck, E. E.; Golod, D.; van Ginneken, A. C.; Goolsby, W. N.

1996-01-01

We used the Luo and Rudy (LR) mathematical model of the guinea pig ventricular cell coupled to experimentally recorded guinea pig ventricular cells to investigate the effects of geometrical asymmetry on action potential propagation. The overall correspondence of the LR cell model with the recorded

Laser materials processing with diode lasers

OpenAIRE

Li, Lin; Lawrence, Jonathan; Spencer, Julian T.

1996-01-01

Laser materials processing is currently dominated by CO2, Nd-YAG and Excimer lasers. Continuous advances in semiconductor laser technology over the last decade have increased the average power output of the devices annualy by two fold, resulting in the commercial availability of the diode lasers today with delivery output powers in excess of 60W in CW mode and 5kW in qasi-CW mode. The advantages of compactness, high reliability, high efficiency and potential low cost, due to the mass producti...

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

Science.gov (United States)

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

2017-11-01

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

Teachers in Action Research: Assumptions and Potentials

Science.gov (United States)

Li, Yuen-Ling

2008-01-01

Research literature has long indicated that action research may stimulate practitioners themselves to actively evaluate the quality of their practice. This study is designed to report the use of action research for the development of early years professional practice by analyzing the pre-project and the post-project video-filmed teaching events.…

An Excel‐based implementation of the spectral method of action potential alternans analysis

Science.gov (United States)

Pearman, Charles M.

2014-01-01

Abstract Action potential (AP) alternans has been well established as a mechanism of arrhythmogenesis and sudden cardiac death. Proper interpretation of AP alternans requires a robust method of alternans quantification. Traditional methods of alternans analysis neglect higher order periodicities that may have greater pro‐arrhythmic potential than classical 2:1 alternans. The spectral method of alternans analysis, already widely used in the related study of microvolt T‐wave alternans, has also been used to study AP alternans. Software to meet the specific needs of AP alternans analysis is not currently available in the public domain. An AP analysis tool is implemented here, written in Visual Basic for Applications and using Microsoft Excel as a shell. This performs a sophisticated analysis of alternans behavior allowing reliable distinction of alternans from random fluctuations, quantification of alternans magnitude, and identification of which phases of the AP are most affected. In addition, the spectral method has been adapted to allow detection and quantification of higher order regular oscillations. Analysis of action potential morphology is also performed. A simple user interface enables easy import, analysis, and export of collated results. PMID:25501439

Diverse effects of a 445 nm diode laser on isometric contraction of the rat aorta

Science.gov (United States)

Park, Sang Woong; Shin, Kyung Chul; Park, Hyun Ji; Lee, In Wha; Kim, Hyung-Sik; Chung, Soon-Cheol; Kim, Ji-Sun; Jun, Jae-Hoon; Kim, Bokyung; Bae, Young Min

2015-01-01

The usefulness of visible lasers in treating vascular diseases is controversial. It is probable that multiple effects of visible lasers on blood vessels and their unclear mechanisms have hampered the usefulness of this therapy. Therefore, elucidating the precise actions and mechanisms of the effects of lasers on blood vessels would provide insight into potential biomedical applications. Here, using organ chamber isometric contraction measurements, western blotting, patch-clamp, and en face immunohistochemistry, we showed that a 445 nm diode laser contracted rat aortic rings, both by activating endothelial nitric oxide synthase and by increasing oxidative stress. In addition to the effects on the endothelium, the laser also directly relaxed and contracted vascular smooth muscle by inhibiting L-type Ca2+ channels and by activating protein tyrosine kinases, respectively. Thus, we conclude that exposure to 445 nm laser might contract and dilate blood vessels in the endothelium and smooth muscle via distinct mechanisms. PMID:26417517

Ventricular filling slows epicardial conduction and increases action potential duration in an optical mapping study of the isolated rabbit heart

Science.gov (United States)

Sung, Derrick; Mills, Robert W.; Schettler, Jan; Narayan, Sanjiv M.; Omens, Jeffrey H.; McCulloch, Andrew D.; McCullough, A. D. (Principal Investigator)

2003-01-01

INTRODUCTION: Mechanical stimulation can induce electrophysiologic changes in cardiac myocytes, but how mechanoelectric feedback in the intact heart affects action potential propagation remains unclear. METHODS AND RESULTS: Changes in action potential propagation and repolarization with increased left ventricular end-diastolic pressure from 0 to 30 mmHg were investigated using optical mapping in isolated perfused rabbit hearts. With respect to 0 mmHg, epicardial strain at 30 mmHg in the anterior left ventricle averaged 0.040 +/- 0.004 in the muscle fiber direction and 0.032 +/- 0.006 in the cross-fiber direction. An increase in ventricular loading increased average epicardial activation time by 25%+/- 3% (P action potential duration at 20% repolarization (APD20) but did at 80% repolarization (APD80), from 179 +/- 7 msec to 207 +/- 5 msec (P action potential duration by a load-dependent mechanism that may not involve stretch-activated channels.

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

Directory of Open Access Journals (Sweden)

Snezana Levic

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

High efficiency laser action in mildly doped Yb:LuYAG ceramics

Czech Academy of Sciences Publication Activity Database

Pirri, A.; Toci, G.; Li, J.; Xie, T.; Pan, Y.; Babin, Vladimir; Beitlerová, Alena; Nikl, Martin; Vannini, M.

2017-01-01

Roč. 73, Nov (2017), s. 312-318 ISSN 0925-3467 Institutional support: RVO:68378271 Keywords : laser ceramic s * Yb laser * mixed garnets * LuYAG Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 2.238, year: 2016

Voltage Gated Calcium Channel Activation by Backpropagating Action Potentials Downregulates NMDAR Function

Directory of Open Access Journals (Sweden)

Anne-Kathrin Theis

2018-04-01

Full Text Available The majority of excitatory synapses are located on dendritic spines of cortical glutamatergic neurons. In spines, compartmentalized Ca2+ signals transduce electrical activity into specific long-term biochemical and structural changes. Action potentials (APs propagate back into the dendritic tree and activate voltage gated Ca2+ channels (VGCCs. For spines, this global mode of spine Ca2+ signaling is a direct biochemical feedback of suprathreshold neuronal activity. We previously demonstrated that backpropagating action potentials (bAPs result in long-term enhancement of spine VGCCs. This activity-dependent VGCC plasticity results in a large interspine variability of VGCC Ca2+ influx. Here, we investigate how spine VGCCs affect glutamatergic synaptic transmission. We combined electrophysiology, two-photon Ca2+ imaging and two-photon glutamate uncaging in acute brain slices from rats. T- and R-type VGCCs were the dominant depolarization-associated Ca2+conductances in dendritic spines of excitatory layer 2 neurons and do not affect synaptic excitatory postsynaptic potentials (EPSPs measured at the soma. Using two-photon glutamate uncaging, we compared the properties of glutamatergic synapses of single spines that express different levels of VGCCs. While VGCCs contributed to EPSP mediated Ca2+ influx, the amount of EPSP mediated Ca2+ influx is not determined by spine VGCC expression. On a longer timescale, the activation of VGCCs by bAP bursts results in downregulation of spine NMDAR function.

Differential roles of two delayed rectifier potassium currents in regulation of ventricular action potential duration and arrhythmia susceptibility.

Science.gov (United States)

Devenyi, Ryan A; Ortega, Francis A; Groenendaal, Willemijn; Krogh-Madsen, Trine; Christini, David J; Sobie, Eric A

2017-04-01

Arrhythmias result from disruptions to cardiac electrical activity, although the factors that control cellular action potentials are incompletely understood. We combined mathematical modelling with experiments in heart cells from guinea pigs to determine how cellular electrical activity is regulated. A mismatch between modelling predictions and the experimental results allowed us to construct an improved, more predictive mathematical model. The balance between two particular potassium currents dictates how heart cells respond to perturbations and their susceptibility to arrhythmias. Imbalances of ionic currents can destabilize the cardiac action potential and potentially trigger lethal cardiac arrhythmias. In the present study, we combined mathematical modelling with information-rich dynamic clamp experiments to determine the regulation of action potential morphology in guinea pig ventricular myocytes. Parameter sensitivity analysis was used to predict how changes in ionic currents alter action potential duration, and these were tested experimentally using dynamic clamp, a technique that allows for multiple perturbations to be tested in each cell. Surprisingly, we found that a leading mathematical model, developed with traditional approaches, systematically underestimated experimental responses to dynamic clamp perturbations. We then re-parameterized the model using a genetic algorithm, which allowed us to estimate ionic current levels in each of the cells studied. This unbiased model adjustment consistently predicted an increase in the rapid delayed rectifier K + current and a drastic decrease in the slow delayed rectifier K + current, and this prediction was validated experimentally. Subsequent simulations with the adjusted model generated the clinically relevant prediction that the slow delayed rectifier is better able to stabilize the action potential and suppress pro-arrhythmic events than the rapid delayed rectifier. In summary, iterative coupling of

Pulsed chemical laser

International Nuclear Information System (INIS)

Jacobson, T.V.; Kimbell, G.H.

1975-01-01

A hydrogen fluoride laser capable of operating super radiantly and at atmospheric pressure is described. A transverse electrical discharge is utilized to energize the reaction of a hydrogen donor to provide hydrogen fluoride in a metastable energy state which reverts to a stable state by laser action. A large range of hydrogen and fluorine donors is disclosed. A preferred pair of donors is sulphur hexafluoride and propane. Helium is frequently added to the gas mix to act as a buffer. (U.S.)

[Theory of lasers and lamps].

Science.gov (United States)

Mordon, S; Michaud, T

2009-10-01

Lasers emit a coherent and monochromatic light beam, whereas pulsed lights produce a polychromatic light whose bandwidth is selected by adapted filters. The skin's chromophores are made up of water, hemoglobin, and melanin, to which must be added the exogenous pigments of tattoos. Each chromophore has its specific absorption spectrum. Lasers' main mechanisms of action are the photothermal effect and the photomechanical effect.

An Excel-based implementation of the spectral method of action potential alternans analysis.

Science.gov (United States)

Pearman, Charles M

2014-12-01

Action potential (AP) alternans has been well established as a mechanism of arrhythmogenesis and sudden cardiac death. Proper interpretation of AP alternans requires a robust method of alternans quantification. Traditional methods of alternans analysis neglect higher order periodicities that may have greater pro-arrhythmic potential than classical 2:1 alternans. The spectral method of alternans analysis, already widely used in the related study of microvolt T-wave alternans, has also been used to study AP alternans. Software to meet the specific needs of AP alternans analysis is not currently available in the public domain. An AP analysis tool is implemented here, written in Visual Basic for Applications and using Microsoft Excel as a shell. This performs a sophisticated analysis of alternans behavior allowing reliable distinction of alternans from random fluctuations, quantification of alternans magnitude, and identification of which phases of the AP are most affected. In addition, the spectral method has been adapted to allow detection and quantification of higher order regular oscillations. Analysis of action potential morphology is also performed. A simple user interface enables easy import, analysis, and export of collated results. © 2014 The Author. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society.

Tapered diode laser pumped 946 nm Nd:YAG laser

DEFF Research Database (Denmark)

Cheng, Haynes Pak Hay; Jensen, Ole Bjarlin; Petersen, Paul Michael

2009-01-01

We successfully implemented a 946 nm Nd:YAG laser based on a 808 nm tapered diode pump laser. The tapered diode is developed at the Ferdinand-Braun-Institute fur Hochstfrequenztechnik in Germany. Figure 2 shows the experimental setup and results of each pump source coupled into a 1.5 mm crystal...... laser, we show that tapered diode laser pumping potentially increase the power of 946 nm lasers by a factor of two and reduce the threshold by a factor of three....

Investigating a Potential Auxin-Related Mode of Hormetic/Inhibitory Action of the Phytotoxin Parthenin.

Science.gov (United States)

Belz, Regina G

2016-01-01

Parthenin is a metabolite of Parthenium hysterophorus and is believed to contribute to the weed's invasiveness via allelopathy. Despite the potential of parthenin to suppress competitors, low doses stimulate plant growth. This biphasic action was hypothesized to be auxin-like and, therefore, an auxin-related mode of parthenin action was investigated using two approaches: joint action experiments with Lactuca sativa, and dose-response experiments with auxin/antiauxin-resistant Arabidopsis thaliana genotypes. The joint action approach comprised binary mixtures of subinhibitory doses of the auxin 3-indoleacetic acid (IAA) mixed with parthenin or one of three reference compounds [indole-3-butyric acid (IBA), 2,3,5-triiodobenzoic acid (TIBA), 2-(p-chlorophenoxy)-2-methylpropionic acid (PCIB)]. The reference compounds significantly interacted with IAA at all doses, but parthenin interacted only at low doses indicating that parthenin hormesis may be auxin-related, in contrast to its inhibitory action. The genetic approach investigated the response of four auxin/antiauxin-resistant mutants and a wildtype to parthenin or two reference compounds (IAA, PCIB). The responses of mutant plants to the reference compounds confirmed previous reports, but differed from the responses observed for parthenin. Parthenin stimulated and inhibited all mutants independent of resistance. This provided no indication for an auxin-related action of parthenin. Therefore, the hypothesis of an auxin-related inhibitory action of parthenin was rejected in two independent experimental approaches, while the hypothesis of an auxin-related stimulatory effect could not be rejected.

Physical basics of endovenous laser treatment and potential of innovative developments

Science.gov (United States)

Sroka, R.; Esipova, A.; Schmedt, C. G.

2017-04-01

During the last decade, endoluminal laser treatment (ELT) has been rapidly developing. Protocols using radially emitting ELT fibres in combination with infrared laser light show clinical advantages over the bare-fibre technique and near infrared irradiation. Although the clinical response rate is high several side effects occurred. Innovative light application systems and feedback systems are therefore being under development to potentially improve the clinical situation. The irradiation patterns of bare fibres and radially emitting 1-ring and 2-ring fibres were measured using the goniometer technique. The device robustness, device handling and tissue effects were investigated using the established ox-foot-model. Furthermore, temperature measurements were performed either intraluminal within the irradiation field using a tiny temperature sensor and on the outer surface of the vessel wall by means of a thermocamera. All fibres showed sufficient mechanical and thermal robustness. The destruction threshold is far beyond the light powers employed during clinical application. The 1-ring fibre showed very high peak temperatures for a short time, while the 2-ring-fibre hold its somewhat lower maximum temperature for a longer time. Both forms of energy application resulted in the desired shrinkage and destruction effect. In this regard, the handling of the 2-ring fibre appears subjectively more convenient with reduced sticking-related problems. Acute tissue effects could be investigated to improve the understanding especially of the interaction between handling, maneuvers and tissue effects. The 2-ring radially emitting fibre in combination with IR laser light and specific application parameters showed improved handling and safety features.

Recent developments in laser glasses

International Nuclear Information System (INIS)

Weber, M.J.

1983-01-01

The past decade has witnessed a proliferation of new glass-forming compositions including oxides, halides, oxyhalides, and chalcogenides. Many of these glasses are applicable to lasers and have greatly expanded the range of optical properties and spectroscopic parameters available to the laser designer. Our knowledge and understanding of many properties of interest for laser action - transparency, linear and nonlinear refractive indices, and damage threshold of the host glass and the absorption spectrum, radiative and nonradiative transition probabilities, fluorescence wavelength, stimulated emission cross section, and spectroscopic inhomogeneities of the lasing ion Nd 3 + - are reviewed

Laser wakefield acceleration with high-power, few-cycle mid-IR lasers

OpenAIRE

Papp, Daniel; Wood, Jonathan C.; Gruson, Vincent; Bionta, Mina; Gruse, Jan-Niclas; Cormier, Eric; Najmudin, Zulfikar; Légaré, François; Kamperidis, Christos

2018-01-01

The study of laser wakefield electron acceleration (LWFA) using mid-IR laser drivers is a promising path for future laser driven electronaccelerators, when compared to traditional near-IR laser drivers uperating at 0.8-1 {\\mu}m central wavelength ({\\lambda}laser), as the necessary vector potential a_0 for electron injection can be achieved with smaller laser powers due to the linear dependence on {\\lambda}laser. In this work, we perform 2D PIC simulations on LWFA using few-cycle high power (5...

Traditional Japanese medicines inhibit compound action potentials in the frog sciatic nerve.

Science.gov (United States)

Matsushita, Akitomo; Fujita, Tsugumi; Ohtsubo, Sena; Kumamoto, Eiichi

2016-02-03

Traditional Japanese (Kampo) medicines have a variety of clinical effects including pain alleviation, but evidence for a mechanism for their pain relief has not yet been elucidated fully. Considering that Kampo medicine contains many plant-derived chemicals having an ability to inhibit nerve action potential conduction, it is possible that this medicine inhibits nerve conduction. The purpose of the present study was to know how various Kampo medicines affect nerve conduction. We examined the effects of Kampo and crude medicines on compound action potentials (CAPs) recorded from the frog sciatic nerve by using the air-gap method. Daikenchuto, rikkosan, kikyoto, rikkunshito, shakuyakukanzoto and kakkonto concentration-dependently reduced the peak amplitude of the CAP. Among the Kampo medicines, daikenchuto was the most effective in inhibiting CAPs. Daikenchuto is composed of three kinds of crude medicine, Japanese pepper, processed ginger and ginseng radix. When the crude medicines were tested, Japanese pepper and processed ginger reduced CAP peak amplitudes, while ginseng radix hardly affected CAPs. Moreover, there was an interaction between the Japanese pepper and processed ginger activities in such that one medicine at low but not high concentrations increased the extent of the inhibition by the other one that was co-applied. Kampo medicines have an ability to inhibit nerve conduction. This action of daikenchuto is due to Japanese pepper and processed ginger but not ginseng radix, probably through an interaction between Japanese pepper and processed ginger in a manner dependent on their concentrations. Nerve conduction inhibition could contribute to at least a part of Kampo medicine's clinical effects such as pain alleviation. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Development of a solid state laser of Nd:YLF

International Nuclear Information System (INIS)

Amaral Neto, R. do.

1984-01-01

The CW laser action was obtained at room temperature of a Nd:YLF crystal in an astigmatically compensated cavity, pumped by an argon laser. This laser was completely projected, constructed and characterized in our laboratories, thus having a high degree of nationalization. It initiates a broader project on lasers development that will have several applications like nuclear fusion, industry, medicine, telemetry, etc.... Throught the study of the optical properties of the Nd:YLF crystal, laser operation was predicted using a small volume gain medium on the mentioned cavity, pumped by an Ar 514,5 nm laser line. To obtain the laser action at polarizations σ (1,053 μm) and π (1,047 μm) an active medium was prepared which was a cristalline plate with a convenient crystalographic orientation. The laser characterization is in reasonable agreement with the initial predictions. For a 3.5% output mirror transmission, the oscillation threshold is about 0.15 W incident on the crystal, depending upon the sample used. For 1 W of incident pump light, the output power is estimated to be 12 mW, which corresponds to almost 1.5% slope efficiency. The versatile arrangement is applicable to almost all optically pumped solid state laser materials. (Author) [pt

Action potential generation requires a high sodium channel density in the axon initial segment

NARCIS (Netherlands)

Kole, Maarten H. P.; Ilschner, Susanne U.; Kampa, Björn M.; Williams, Stephen R.; Ruben, Peter C.; Stuart, Greg J.

2008-01-01

The axon initial segment ( AIS) is a specialized region in neurons where action potentials are initiated. It is commonly assumed that this process requires a high density of voltage-gated sodium ( Na(+)) channels. Paradoxically, the results of patch-clamp studies suggest that the Na(+) channel

Influence of ionizing radiation on optical hardness of transparent dielectrics to action of huge intensity laser light

International Nuclear Information System (INIS)

Bedilov, M.R.; Khalilov, R.A.

2006-01-01

of plasma. Significant growth of total number of ions of all frequency rates of charge N Σ reduction of maximal energy E max and frequency rates of a charge Z max ions are observed. Correlation between parameters of superficial damage - threshold q s and the size of damage d and characteristics of ion plasma - N Σ , Z max and E max are also observed. Damages, as microscopic researches have shown, looked like the micro crater representing the fused layer with a flat bottom and melted edges. Such structure of craters is consequences of the thermal action accompanying damages by plasma. With growth of a doze γ -irradiations of investigated glasses the sizes of damage grow considerably with the increase in diameter d of formed the craters received at the same values q. It is shown that the increase in intensity of a laser radiation up to 1000 GWt/cm 2 leads to the catastrophic damage of the surface leading to breaking of glass. Results of microscopic researches show that the damage of surface and volume of the investigated non- irradiated glasses begins locally in the separate from each other small size parts where the congestion of the absorbing defects breaking the structure of glass was formed. Those are initially present in structure of glass alien impurity inclusions, dislocations and vacancies, bubbles and pores and others of heterogeneity. Concentration of absorbing defects in glass considerably increases due to formation of the radiating defects caused by γ - irradiation. This leads to an additional power consumption of a laser radiation on heating and evaporation of substance of a target, and consequently to reduction of a part of laser radiation, too, which is spent for heating and ionization of plasma. This seems to be a reason for reduction Z max and E max of emitted ion by plasma and strong growth of output of ions from plasma of γ - irradiated glass connected with recombined processes taking place in plasma. (author)

Laser vapor phase deposition of semiconductors

Energy Technology Data Exchange (ETDEWEB)

Karlov, N.V.; Luk' ianchuk, B.S.; Sisakian, E.V.; Shafeev, G.A.

1987-06-01

The pyrolytic effect of IR laser radiation is investigated with reference to the initiation and control of the vapor phase deposition of semiconductor films. By selecting the gas mixture composition and laser emission parameters, it is possible to control the deposition and crystal formation processes on the surface of semiconductors, with the main control action achieved due to the nonadiabatic kinetics of reactions in the gas phase and high temperatures in the laser heating zone. This control mechanism is demonstrated experimentally during the laser vapor deposition of germanium and silicon films from tetrachlorides on single-crystal Si and Ge substrates. 5 references.

Potentiating action of propofol at GABAA receptors of retinal bipolar cells

DEFF Research Database (Denmark)

Yue, Lan; Xie, An; Bruzik, Karol S

2011-01-01

Purpose. Propofol (2,6-diisopropyl phenol), a widely used systemic anesthetic, is known to potentiate GABA(A) receptor activity in a number of CNS neurons and to produce changes in electroretinographically recorded responses of the retina. However, little is known about propofol's effects...... on specific retinal neurons. The authors investigated the action of propofol on GABA-elicited membrane current responses of retinal bipolar cells, which have both GABA(A) and GABA(C) receptors. Methods. Single, enzymatically dissociated bipolar cells obtained from rat retina were treated with propofol...... + propofol) led to a progressive increase in peak response amplitude and, at higher propofol concentrations, additional changes that included a prolonged time course of response recovery. Pre-exposure of the cell to perfusing propofol typically enhanced the rate of development of potentiation produced...

Melatonin potentiates the anticonvulsant action of phenobarbital in neonatal rats.

Science.gov (United States)

Forcelli, Patrick A; Soper, Colin; Duckles, Anne; Gale, Karen; Kondratyev, Alexei

2013-12-01

Phenobarbital is the most commonly utilized drug for neonatal seizures. However, questions regarding safety and efficacy of this drug make it particularly compelling to identify adjunct therapies that could boost therapeutic benefit. One potential adjunct therapy is melatonin. Melatonin is used clinically in neonatal and pediatric populations, and moreover, it exerts anticonvulsant actions in adult rats. However, it has not been previously evaluated for anticonvulsant effects in neonatal rats. Here, we tested the hypothesis that melatonin would exert anticonvulsant effects, either alone, or in combination with phenobarbital. Postnatal day (P)7 rats were treated with phenobarbital (0-40mg/kg) and/or melatonin (0-80mg/kg) prior to chemoconvulsant challenge with pentylenetetrazole (100mg/kg). We found that melatonin significantly potentiated the anticonvulsant efficacy of phenobarbital, but did not exert anticonvulsant effects on its own. These data provide additional evidence for the further examination of melatonin as an adjunct therapy in neonatal/pediatric epilepsy. Copyright © 2013 Elsevier B.V. All rights reserved.

Measurement of the first ionization potential of astatine by laser ionization spectroscopy

Science.gov (United States)

Rothe, S.; Andreyev, A. N.; Antalic, S.; Borschevsky, A.; Capponi, L.; Cocolios, T. E.; De Witte, H.; Eliav, E.; Fedorov, D. V.; Fedosseev, V. N.; Fink, D. A.; Fritzsche, S.; Ghys, L.; Huyse, M.; Imai, N.; Kaldor, U.; Kudryavtsev, Yuri; Köster, U.; Lane, J. F. W.; Lassen, J.; Liberati, V.; Lynch, K. M.; Marsh, B. A.; Nishio, K.; Pauwels, D.; Pershina, V.; Popescu, L.; Procter, T. J.; Radulov, D.; Raeder, S.; Rajabali, M. M.; Rapisarda, E.; Rossel, R. E.; Sandhu, K.; Seliverstov, M. D.; Sjödin, A. M.; Van den Bergh, P.; Van Duppen, P.; Venhart, M.; Wakabayashi, Y.; Wendt, K. D. A.

2013-01-01

The radioactive element astatine exists only in trace amounts in nature. Its properties can therefore only be explored by study of the minute quantities of artificially produced isotopes or by performing theoretical calculations. One of the most important properties influencing the chemical behaviour is the energy required to remove one electron from the valence shell, referred to as the ionization potential. Here we use laser spectroscopy to probe the optical spectrum of astatine near the ionization threshold. The observed series of Rydberg states enabled the first determination of the ionization potential of the astatine atom, 9.31751(8) eV. New ab initio calculations are performed to support the experimental result. The measured value serves as a benchmark for quantum chemistry calculations of the properties of astatine as well as for the theoretical prediction of the ionization potential of superheavy element 117, the heaviest homologue of astatine. PMID:23673620

Investigations on the potential of a low power diode pumped Er:YAG laser system for oral surgery

Science.gov (United States)

Stock, Karl; Wurm, Holger; Hausladen, Florian; Wagner, Sophia; Hibst, Raimund

2015-02-01

Flash lamp pumped Er:YAG-lasers are used in clinical practice for dental applications successfully. As an alternative, several diode pumped Er:YAG laser systems (Pantec Engineering AG) become available, with mean laser power of 2W, 15W, and 30W. The aim of the presented study is to investigate the potential of the 2W Er:YAG laser system for oral surgery. At first an appropriate experimental set-up was realized with a beam delivery and both, a focusing unit for non-contact tissue cutting and a fiber tip for tissue cutting in contact mode. In order to produce reproducible cuts, the samples (porcine gingiva) were moved by a computer controlled translation stage. On the fresh samples cutting depth and quality were determined by light microscopy. Afterwards histological sections were prepared and microscopically analyzed regarding cutting depth and thermal damage zone. The experiments show that low laser power ≤ 2W is sufficient to perform efficient oral soft tissue cutting with cut depth up to 2mm (sample movement 2mm/s). The width of the thermal damage zone can be controlled by the irradiation parameters within a range of about 50μm to 110μm. In general, thermal injury is more pronounced using fiber tips in contact mode compared to the focused laser beam. In conclusion the results reveal that even the low power diode pumped Er:YAG laser is an appropriate tool for oral surgery.

Changes in time and frequency related aspects of motor unit action potentials during fatigue

NARCIS (Netherlands)

Wallinga, W.; Bouwens, Jeroen S.; Baten, Christian T.M.

1996-01-01

During fatigue the shape of motor unit action potentials (MUAPs) change. Characteristics of the MUAPs described before concern several time related aspects. No attention has been given to the frequency spectrum changes of MUAPS. The median frequency of MUAPS has now been determined for motor units

Map-based model of the cardiac action potential

International Nuclear Information System (INIS)

Pavlov, Evgeny A.; Osipov, Grigory V.; Chan, C.K.; Suykens, Johan A.K.

2011-01-01

A simple computationally efficient model which is capable of replicating the basic features of cardiac cell action potential is proposed. The model is a four-dimensional map and demonstrates good correspondence with real cardiac cells. Various regimes of cardiac activity, which can be reproduced by the proposed model, are shown. Bifurcation mechanisms of these regimes transitions are explained using phase space analysis. The dynamics of 1D and 2D lattices of coupled maps which model the behavior of electrically connected cells is discussed in the context of synchronization theory. -- Highlights: → Recent experimental-data based models are complicated for analysis and simulation. → The simplified map-based model of the cardiac cell is constructed. → The model is capable for replication of different types of cardiac activity. → The spatio-temporal dynamics of ensembles of coupled maps are investigated. → Received data are analyzed in context of biophysical processes in the myocardium.

Map-based model of the cardiac action potential

Energy Technology Data Exchange (ETDEWEB)

Pavlov, Evgeny A., E-mail: genie.pavlov@gmail.com [Department of Computational Mathematics and Cybernetics, Nizhny Novgorod State University, 23, Gagarin Avenue, 603950 Nizhny Novgorod (Russian Federation); Osipov, Grigory V. [Department of Computational Mathematics and Cybernetics, Nizhny Novgorod State University, 23, Gagarin Avenue, 603950 Nizhny Novgorod (Russian Federation); Chan, C.K. [Institute of Physics, Academia Sinica, 128 Sec. 2, Academia Road, Nankang, Taipei 115, Taiwan (China); Suykens, Johan A.K. [K.U. Leuven, ESAT-SCD/SISTA, Kasteelpark Arenberg 10, B-3001 Leuven (Heverlee) (Belgium)

2011-07-25

A simple computationally efficient model which is capable of replicating the basic features of cardiac cell action potential is proposed. The model is a four-dimensional map and demonstrates good correspondence with real cardiac cells. Various regimes of cardiac activity, which can be reproduced by the proposed model, are shown. Bifurcation mechanisms of these regimes transitions are explained using phase space analysis. The dynamics of 1D and 2D lattices of coupled maps which model the behavior of electrically connected cells is discussed in the context of synchronization theory. -- Highlights: → Recent experimental-data based models are complicated for analysis and simulation. → The simplified map-based model of the cardiac cell is constructed. → The model is capable for replication of different types of cardiac activity. → The spatio-temporal dynamics of ensembles of coupled maps are investigated. → Received data are analyzed in context of biophysical processes in the myocardium.

The Influence of Glutamate on Axonal Compound Action Potential In Vitro.

Science.gov (United States)

Abouelela, Ahmed; Wieraszko, Andrzej

2016-01-01

Background  Our previous experiments demonstrated modulation of the amplitude of the axonal compound action potential (CAP) by electrical stimulation. To verify assumption that glutamate released from axons could be involved in this phenomenon, the modification of the axonal CAP induced by glutamate was investigated. Objectives  The major objective of this research is to verify the hypothesis that axonal activity would trigger the release of glutamate, which in turn would interact with specific axonal receptors modifying the amplitude of the action potential. Methods  Segments of the sciatic nerve were exposed to exogenous glutamate in vitro, and CAP was recorded before and after glutamate application. In some experiments, the release of radioactive glutamate analog from the sciatic nerve exposed to exogenous glutamate was also evaluated. Results  The glutamate-induced increase in CAP was blocked by different glutamate receptor antagonists. The effect of glutamate was not observed in Ca-free medium, and was blocked by antagonists of calcium channels. Exogenous glutamate, applied to the segments of sciatic nerve, induced the release of radioactive glutamate analog, demonstrating glutamate-induced glutamate release. Immunohistochemical examination revealed that axolemma contains components necessary for glutamatergic neurotransmission. Conclusion  The proteins of the axonal membrane can under the influence of electrical stimulation or exogenous glutamate change membrane permeability and ionic conductance, leading to a change in the amplitude of CAP. We suggest that increased axonal activity leads to the release of glutamate that results in changes in the amplitude of CAPs.

Oxidative shift in tissue redox potential increases beat-to-beat variability of action potential duration.

Science.gov (United States)

Kistamás, Kornél; Hegyi, Bence; Váczi, Krisztina; Horváth, Balázs; Bányász, Tamás; Magyar, János; Szentandrássy, Norbert; Nánási, Péter P

2015-07-01

Profound changes in tissue redox potential occur in the heart under conditions of oxidative stress frequently associated with cardiac arrhythmias. Since beat-to-beat variability (short term variability, SV) of action potential duration (APD) is a good indicator of arrhythmia incidence, the aim of this work was to study the influence of redox changes on SV in isolated canine ventricular cardiomyocytes using a conventional microelectrode technique. The redox potential was shifted toward a reduced state using a reductive cocktail (containing dithiothreitol, glutathione, and ascorbic acid) while oxidative changes were initiated by superfusion with H2O2. Redox effects were evaluated as changes in "relative SV" determined by comparing SV changes with the concomitant APD changes. Exposure of myocytes to the reductive cocktail decreased SV significantly without any detectable effect on APD. Application of H2O2 increased both SV and APD, but the enhancement of SV was the greater, so relative SV increased. Longer exposure to H2O2 resulted in the development of early afterdepolarizations accompanied by tremendously increased SV. Pretreatment with the reductive cocktail prevented both elevation in relative SV and the development of afterdepolarizations. The results suggest that the increased beat-to-beat variability during an oxidative stress contributes to the generation of cardiac arrhythmias.

[Study of enhancement effect of laser-induced crater on plasma radiation].

Science.gov (United States)

Chen, Jin-Zhong; Zhang, Xiao-Ping; Guo, Qing-Lin; Su, Hong-Xin; Li, Guang

2009-02-01

Single pulses exported from high-energy neodymium glass laser were used to act on the same position of soil sample surface repeatedly, and the plasma emission spectra generated from sequential laser pulse action were collected by spectral recording system. The experimental results show that the laser-induced soil plasma radiation was enhanced continuously under the confinement effect of the crater walls, and the line intensities and signal-to-background ratios both had different improvements along with increasing the number of acting pulses. The photographs of the plasma image and crater appearance were taken to study the plasma shape, laser-induced crater appearance, and the mass of the ablated sample. The internal mechanism behind that laser-induced crater enhanced plasma radiation was researched. Under the sequential laser pulse action, the forming plasma as a result enlarges gradually first, leading to distortion at the trail of plasma plume, and then, its volume diminishes slowly. And also, the color of the plasma changes from buff to white gradually, which implies that the temperature increases constantly. The laser-induced crater had a regular shape, that is, the diameter increased from its bottom to top gradually, thus forming a taper. The mass of the laser-ablated substance descends along with increasing the amount of action pulse. Atomization degree of vaporized substance was improved in virtue of the crater confinement effect, Fresnel absorption produced from the crater walls reflection, and the inverse bremsstrahlung, and the plasma radiation intensity was enhanced as a result.

Tunability of optofluidic distributed feedback dye lasers

DEFF Research Database (Denmark)

Gersborg-Hansen, Morten; Kristensen, Anders

2007-01-01

We investigate the tunability of optofluidic distributed feedback (DFB) dye lasers. The lasers rely on light-confinement in a nano-structured polymer film where an array of nanofluidic channels constitutes a third order Bragg grating DFB laser resonator with a central phase-shift. The lasers...... are operated by filling the DFB laser resonator with a dye solution by capillary action and optical pumping with a frequency doubled Nd: YAG laser. The low reflection order of the DFB laser resonator yields low out-of-plane scattering losses as well as a large free spectral range (FSR), and low threshold...... fluences down to similar to 7 mu J/mm2 are observed. The large FSR facilitates wavelength tuning over the full gain spectrum of the chosen laser dye and we demonstrate 45 nm tunability using a single laser dye by changing the grating period and dye solution refractive index. The lasers are straight...

Heteromeric Kv7.2/7.3 channels differentially regulate action potential initiation and conduction in neocortical myelinated axons.

Science.gov (United States)

Battefeld, Arne; Tran, Baouyen T; Gavrilis, Jason; Cooper, Edward C; Kole, Maarten H P

2014-03-05

Rapid energy-efficient signaling along vertebrate axons is achieved through intricate subcellular arrangements of voltage-gated ion channels and myelination. One recently appreciated example is the tight colocalization of K(v)7 potassium channels and voltage-gated sodium (Na(v)) channels in the axonal initial segment and nodes of Ranvier. The local biophysical properties of these K(v)7 channels and the functional impact of colocalization with Na(v) channels remain poorly understood. Here, we quantitatively examined K(v)7 channels in myelinated axons of rat neocortical pyramidal neurons using high-resolution confocal imaging and patch-clamp recording. K(v)7.2 and 7.3 immunoreactivity steeply increased within the distal two-thirds of the axon initial segment and was mirrored by the conductance density estimates, which increased from ~12 (proximal) to 150 pS μm(-2) (distal). The axonal initial segment and nodal M-currents were similar in voltage dependence and kinetics, carried by K(v)7.2/7.3 heterotetramers, 4% activated at the resting membrane potential and rapidly activated with single-exponential time constants (~15 ms at 28 mV). Experiments and computational modeling showed that while somatodendritic K(v)7 channels are strongly activated by the backpropagating action potential to attenuate the afterdepolarization and repetitive firing, axonal K(v)7 channels are minimally recruited by the forward-propagating action potential. Instead, in nodal domains K(v)7.2/7.3 channels were found to increase Na(v) channel availability and action potential amplitude by stabilizing the resting membrane potential. Thus, K(v)7 clustering near axonal Na(v) channels serves specific and context-dependent roles, both restraining initiation and enhancing conduction of the action potential.

Laser-Induced Evoked Potentials in the Brain after Nonperceptible Optical Stimulation at the Neiguan Acupoint: A Preliminary Report

Directory of Open Access Journals (Sweden)

Gerhard Litscher

2012-01-01

Full Text Available We report on small but reproducible human cerebral evoked potentials after bilateral nonperceptible laser needle (658 nm, 40 mW, 500 μm, 1 Hz irradiation of the Neiguan acupoint (PC6. The results which are unique in scientific literature were obtained in a 26-year-old female healthy volunteer within a joint study between the Medical University of Graz, the Karl-Franzens University of Graz, and the Graz University of Technology. The findings of the 32-channel evoked potential analysis indicate that exposure to laser needle stimulation with a frequency of 1 Hz can modulate the ascending reticular activating system. Further studies are absolutely necessary to confirm or refute the preliminary findings.

Nd:YAG laser combined with gold nanorods for potential application in port-wine stains: an in vivo study

Science.gov (United States)

Xing, Linzhuang; Chen, Bin; Li, Dong; Wu, Wenjuan; Wang, Guoxiang

2017-11-01

Neodymium:yttrium aluminum garnet (Nd:YAG) lasers exhibit considerable potential for treating deeply buried port-wine stains. However, the application of Nd:YAG laser is limited by its weak absorption to blood. This in vivo study tested the efficacy and safety of utilizing thiol-terminated methoxypolyethylene glycol-modified gold nanorods (PEG-GNRs) to enhance the absorption of Nd:YAG laser to blood. Mouse mesentery and dorsal skinfold chamber (DSC) model were prepared to analyze the thermal responses of a single venule without anatomic structures, as well as blood vessels in the complex structure of the skin, to laser light. After the injection of 0.44 mg of PEG-GNRs, the required threshold density of laser energy for blood coagulation and complete vasoconstriction decreased from 24 to 18 J/cm2 in the mesentery model and from 36 to 31 J/cm2 in the DSC model. The laser pulse required for blood coagulation and complete vasoconstriction decreased by 67.75% and 62.25% on average in the mesentery model and by 67.55% and 54.45% on average in the DSC model. Histological and histochemical results confirmed that PEG-GNRs are nontoxic in the entire mouse life span. Therefore, combining PEG-GNRs with Nd:YAG laser may be effective and safe for inducing an obvious thermal response of blood vessels under low energy density and minimal pulse conditions.

Analysis of the stress raising action of flaws in laser clad deposits

International Nuclear Information System (INIS)

Alam, M.M.; Kaplan, A.F.H.; Tuominen, J.; Vuoristo, P.; Miettinen, J.; Poutala, J.; Näkki, J.; Junkala, J.; Peltola, T.; Barsoum, Z.

2013-01-01

Highlights: ► Laser clad defects are 0D-pores/inclusions, 1D-clad waviness or 2D-planar defects. ► Surface pore of laser clad bar initiates fatigue cracks. ► Side edge surface pores are more critical than in-clad surface pores. ► Smaller notch radius and angle of as-laser clad surface raises stress significantly. ► Planar inner defects grow faster towards surface. - Abstract: Fatigue cracking of laser clad cylindrical and square section bars depends upon a variety of factors. This paper presents Finite Element Analysis (FEA) of the different macro stress fields generated as well as stress raisers created by laser cladding defects for four different fatigue load conditions. As important as the defect types are their locations and orientations, categorized into zero-, one- and two-dimensional defects. Pores and inclusions become critical close to surfaces. The performance of as-clad surfaces can be governed by the sharpness of surface notches and planar defects like hot cracks or lack-of-fusion (LOF) are most critical if oriented vertically, transverse to the bar axis. The combination of the macro stress field with the defect type and its position and orientation determines whether it is the most critical stress raiser. Based on calculated cases, quantitative and qualitative charts were developed as guidelines to visualize the trends of different combinations

Comparison of tissue damage caused by various laser systems with tissue tolerable plasma by light and laser scan microscopy

International Nuclear Information System (INIS)

Vandersee, Staffan; Lademann, Jürgen; Richter, Heike; Patzelt, Alexa; Lange-Asschenfeldt, Bernhard

2013-01-01

Tissue tolerable plasma (TTP) represents a novel therapeutic method with promising capabilities in the field of dermatological interventions, in particular disinfection but also wound antisepsis and regeneration. The energy transfer by plasma into living tissue is not easily educible, as a variety of features such as the medium’s actual molecule-stream, the ions, electrons and free radicals involved, as well as the emission of ultraviolet, visible and infrared light contribute to its increasingly well characterized effects. Thus, relating possible adversary effects, especially of prolonged exposure to a single component of the plasma’s mode of action, is difficult. Until now, severe adverse events connected to plasma exposure have not been reported when conducted according to existing therapeutic protocols. In this study, we have compared the tissue damage-potential of CO 2 and dye lasers with TTP in a porcine model. After exposure of pig ear skin to the three treatment modalities, all specimens were examined histologically and by means of laser scan microscopy (LSM). Light microscopical tissue damage could only be shown in the case of the CO 2 laser, whereas dye laser and plasma treatment resulted in no detectable impairment of the specimens. In the case of TTP, LSM examination revealed only an impairment of the uppermost corneal layers of the skin, thus stressing its safety when used in vivo. (letter)

Intra-oral orthosis vs amitriptyline in chronic tension-type headache: a clinical and laser evoked potentials study

Directory of Open Access Journals (Sweden)

Sardaro Michele

2006-05-01

Full Text Available Abstract Background In the present study, we examined clinical and laser-evoked potentials (LEP features in two groups of chronic tension-type headache (CTTH patients treated with two different approaches: intra-oral appliance of prosthesis, aiming to reduce muscular tenderness, and 10 mg daily amitriptyline. Methods Eighteen patients with diagnosed CTTH participated in this open label, controlled study. A baseline evaluation was performed for clinical features, Total Tenderness Score (TTS and a topographic analysis of LEPs obtained manually and the pericranial points stimulation in all patients vs. healthy subjects. Thereafter, patients were randomly assigned to a two-month treatment by either amitriptyline or intra-oral appliance. Results and discussion Both the intra-oral appliance and amitriptyline significantly reduced headache frequency. The TTS was significantly reduced in the group treated with the appliance. The amplitude of P2 response elicited by stimulation of pericranial zones showed a reduction after amitriptyline treatment. Both therapies were effective in reducing headache severity, the appliance with a prevalent action on the pericranial muscular tenderness, amitriptyline reducing the activity of the central cortical structures subtending pain elaboration Conclusion The results of this study may suggest that in CTTH both the interventions at the peripheral and central levels improve the outcome of headache.

Distributed Feedback Laser Based on Single Crystal Perovskite

Science.gov (United States)

Sun, Shang; Xiao, Shumin; Song, Qinghai

2017-06-01

We demonstrate a single crystal perovskite based, with grating-structured photoresist on top, highly polarized distributed feedback laser. A lower laser threshold than the Fabry-Perot mode lasers from the same single crystal CH3NH3PbBr3 microplate was obtained. Single crystal CH3NH3PbBr3 microplates was synthesized with one-step solution processed precipitation method. Once the photoresist on top of the microplate was patterned with electron beam, the device was realized. This one-step fabrication process utilized the advantage of single crystal to the greatest extend. The ultra-low defect density in single crystalline microplate offer an opportunity for lower threshold lasing action compare with poly-crystal perovskite films. In the experiment, the lasing action based on the distributed feedback grating design was found with lower threshold and higher intensity than the Fabry-Perot mode lasers supported by the flat facets of the same microplate.

Comment on "Penetration of Action Potentials During Collision in the Median and Lateral Giant Axons of Invertebrates"

DEFF Research Database (Denmark)

Berg, Rune W.; Stauning, Marius Tving; Sorensen, Jakob Balslev

2017-01-01

The action potential (AP) is an electrical impulse elicited by depolarization of the neuronal membrane from the resting membrane potential (around − 70 mV). It propagates along the axon, allowing for rapid and distant communication. Recently, it was claimed that two APs traveling in opposite...

Long-lived CO/sub 2/ lasers with distributed heterogeneous catalysis

Energy Technology Data Exchange (ETDEWEB)

Browne, P G; Smith, A L.S.

1974-12-11

In a sealed CO/sub 2/-N/sub 2/-He system with a clean discharge tube the degree of dissociation of the CO/sub 2/ is greater than 80 percent (with no hydrogen present), and laser action cannot be obtained. If Pt is distributed along the discharge tube walls as a discontinuous film it catalyses back-reactions reforming CO/sub 2/. The degree of dissociation is then less than 40 percent, and efficient laser action at 10.6 ..mu.. is obtained. Using such distributed heterogeneous catalysis, a CO/sub 2/-N/sub 2/-He-Xe laser has operated for more than 3000 h. In this system, both H/sub 2/ and D/sub 2/ are undesirable additives because they decrease the excitation rate of the upper laser level. (auth)

Spatial and frequency domain ring source models for the single muscle fiber action potential

DEFF Research Database (Denmark)

Henneberg, Kaj-åge; R., Plonsey

1994-01-01

In the paper, single-fibre models for the extracellular action potential are developed that will allow the potential to the evaluated at an arbitrary field point in the extracellular space. Fourier-domain models are restricted in that they evaluate potentials at equidistant points along a line...... parallel to the fibre axis. Consequently, they cannot easily evaluate the potential at the boundary nodes of a boundary-element electrode model. The Fourier-domain models employ axial-symmetric ring source models, and thereby provide higher accuracy that the line source model, where the source is lumped...... including anisotropy show that the spatial models require extreme care in the integration procedure owing to the singularity in the weighting functions. With adequate sampling, the spatial models can evaluate extracellular potentials with high accuracy....

Motion of the plasma critical layer during relativistic-electron laser interaction with immobile and comoving ion plasma for ion acceleration

International Nuclear Information System (INIS)

Sahai, Aakash A.

2014-01-01

We analyze the motion of the plasma critical layer by two different processes in the relativistic-electron laser-plasma interaction regime (a 0 >1). The differences are highlighted when the critical layer ions are stationary in contrast to when they move with it. Controlling the speed of the plasma critical layer in this regime is essential for creating low-β traveling acceleration structures of sufficient laser-excited potential for laser ion accelerators. In Relativistically Induced Transparency Acceleration (RITA) scheme, the heavy plasma-ions are fixed and only trace-density light-ions are accelerated. The relativistic critical layer and the acceleration structure move longitudinally forward by laser inducing transparency through apparent relativistic increase in electron mass. In the Radiation Pressure Acceleration (RPA) scheme, the whole plasma is longitudinally pushed forward under the action of the laser radiation pressure, possible only when plasma ions co-propagate with the laser front. In RPA, the acceleration structure velocity critically depends upon plasma-ion mass in addition to the laser intensity and plasma density. In RITA, mass of the heavy immobile plasma-ions does not affect the speed of the critical layer. Inertia of the bared immobile ions in RITA excites the charge separation potential, whereas RPA is not possible when ions are stationary

Coupled iterated map models of action potential dynamics in a one-dimensional cable of cardiac cells

International Nuclear Information System (INIS)

Wang Shihong; Xie Yuanfang; Qu Zhilin

2008-01-01

Low-dimensional iterated map models have been widely used to study action potential dynamics in isolated cardiac cells. Coupled iterated map models have also been widely used to investigate action potential propagation dynamics in one-dimensional (1D) coupled cardiac cells, however, these models are usually empirical and not carefully validated. In this study, we first developed two coupled iterated map models which are the standard forms of diffusively coupled maps and overcome the limitations of the previous models. We then determined the coupling strength and space constant by quantitatively comparing the 1D action potential duration profile from the coupled cardiac cell model described by differential equations with that of the coupled iterated map models. To further validate the coupled iterated map models, we compared the stability conditions of the spatially uniform state of the coupled iterated maps and those of the 1D ionic model and showed that the coupled iterated map model could well recapitulate the stability conditions, i.e. the spatially uniform state is stable unless the state is chaotic. Finally, we combined conduction into the developed coupled iterated map model to study the effects of coupling strength on wave stabilities and showed that the diffusive coupling between cardiac cells tends to suppress instabilities during reentry in a 1D ring and the onset of discordant alternans in a periodically paced 1D cable

The real-time link between person perception and action: brain potential evidence for dynamic continuity.

Science.gov (United States)

Freeman, Jonathan B; Ambady, Nalini; Midgley, Katherine J; Holcomb, Phillip J

2011-01-01

Using event-related potentials, we investigated how the brain extracts information from another's face and translates it into relevant action in real time. In Study 1, participants made between-hand sex categorizations of sex-typical and sex-atypical faces. Sex-atypical faces evoked negativity between 250 and 550 ms (N300/N400 effects), reflecting the integration of accumulating sex-category knowledge into a coherent sex-category interpretation. Additionally, the lateralized readiness potential revealed that the motor cortex began preparing for a correct hand response while social category knowledge was still gradually evolving in parallel. In Study 2, participants made between-hand eye-color categorizations as part of go/no-go trials that were contingent on a target's sex. On no-go trials, although the hand did not actually move, information about eye color partially prepared the motor cortex to move the hand before perception of sex had finalized. Together, these findings demonstrate the dynamic continuity between person perception and action, such that ongoing results from face processing are immediately and continuously cascaded into the motor system over time. The preparation of action begins based on tentative perceptions of another's face before perceivers have finished interpreting what they just saw. © 2010 Psychology Press, an imprint of the Taylor & Francis Group, an Informa business

Laser dentistry: A new application of excimer laser in root canal therapy

International Nuclear Information System (INIS)

Pini, R.; Salimbeni, R.; Vannini, M.; Barone, R.; Clauser, C.

1989-01-01

We report the first study of the application of excimer lasers in dentistry for the treatment of dental root canals. High-energy ultraviolet (UV) radiation emitted by an XeCl excimer laser (308 nm) and delivered through suitable optical fibers can be used to remove residual organic tissue from the canals. To this aim, UV ablation thresholds of dental tissues have been measured, showing a preferential etching of infiltrated dentin in respect to healthy dentin, at laser fluences of 0.5-1.5 J/cm 2 . This technique has been tested on extracted tooth samples, simulating a clinical procedure. Fibers of decreasing core diameters have been used to treat different sections of the root canal down to its apical portion, resulting in an effective, easy, and fast cleaning action. Possible advantages of excimer laser clinical applications in respect to usual procedures are also discussed

Morphological Characterization of the Action Potential Initiation Segment in GnRH Neuron Dendrites and Axons of Male Mice.

Science.gov (United States)

Herde, Michel K; Herbison, Allan E

2015-11-01

GnRH neurons are the final output neurons of the hypothalamic network controlling fertility in mammals. In the present study, we used ankyrin G immunohistochemistry and neurobiotin filling of live GnRH neurons in brain slices from GnRH-green fluorescent protein transgenic male mice to examine in detail the location of action potential initiation in GnRH neurons with somata residing at different locations in the basal forebrain. We found that the vast majority of GnRH neurons are bipolar in morphology, elaborating a thick (primary) and thinner (secondary) dendrite from opposite poles of the soma. In addition, an axon-like process arising predominantly from a proximal dendrite was observed in a subpopulation of GnRH neurons. Ankyrin G immunohistochemistry revealed the presence of a single action potential initiation zone ∼27 μm in length primarily in the secondary dendrite of GnRH neurons and located 30 to 140 μm distant from the cell soma, depending on the type of process and location of the cell body. In addition to dendrites, the GnRH neurons with cell bodies located close to hypothalamic circumventricular organs often elaborated ankyrin G-positive axon-like structures. Almost all GnRH neurons (>90%) had their action potential initiation site in a process that initially, or ultimately after a hairpin loop, was coursing in the direction of the median eminence. These studies indicate that action potentials are initiated in different dendritic and axonal compartments of the GnRH neuron in a manner that is dependent partly on the neuroanatomical location of the cell body.

Laser cleaning of pulsed laser deposited rhodium films for fusion diagnostic mirrors

International Nuclear Information System (INIS)

Uccello, A.; Maffini, A.; Dellasega, D.; Passoni, M.

2013-01-01

Highlights: ► Pulsed laser deposition is exploited to produce Rh films for first mirrors. ► Pulsed laser deposition is exploited to produce tokamak-like C contaminants. ► Rh laser damage threshold has been evaluated for infrared pulses. ► Laser cleaning of C contaminated Rh films gives promising results. -- Abstract: In this paper an experimental investigation on the laser cleaning process of rhodium films, potentially candidates to be used as tokamak first mirrors (FMs), from redeposited carbon contaminants is presented. A relevant issue that lowers mirror's performance during tokamak operations is the redeposition of sputtered material from the first wall on their surface. Among all the possible techniques, laser cleaning, in which a train of laser pulses is launched to the surface that has to be treated, is a method to potentially mitigate this problem. The same laser system (Q-switched Nd:YAG laser with a fundamental wavelength of 1064-nm and 7-ns pulses) has been employed with three aims: (i) production by pulsed laser deposition (PLD) of Rh film mirrors, (ii) production by PLD of C deposits with controlled morphology, and (iii) investigation of the laser cleaning method onto C contaminated Rh samples. The evaluation of Rh films laser damage threshold, as a function of fluence and number of pulses, is discussed. Then, the C/Rh films have been cleaned by the laser beam. The exposed zones have been characterized by visual inspection and scanning electron microscopy (SEM), showing promising results

Laser colouring on titanium alloys: characterisation and potential applications

OpenAIRE

Franceschini, Federica; Demir, Ali Gökhan; Dowding, Colin; Previtali, Barbara; Griffiths, Jonathan David

2014-01-01

Oxides of titanium exhibit vivid colours that can be generated naturally or manipulated through controlled oxidation processes. The application of a laser beam for colouring titanium permits flexible manipulation of the oxidized geometry with high spatial resolution. The laser-based procedure can be applied in an ambient atmosphere to generate long-lasting coloured marks. Today, these properties are largely exploited in artistic applications such as jewellery, eyewear frames, watch components...

Powder neodymium laser with nanometric granulation

International Nuclear Information System (INIS)

Vieira, Renato Juliani Ribamar

2010-01-01

In the past few years, the interest in random lasers, which refer to lasing in disordered media where strong multiple scattering plays a constructive role instead of being only a loss factor, have received considerable attention due to its unique properties and its potential applications, such as emission at new, extremely low gain lines, simultaneous emission of several very different wavelengths at the same time, strong light localization and miniaturization. Single and multiple particle light scattering, backscattering intensity, light diffusion with gain and the energy level diagram of Neodymium will be presented in this current work, alongside with a parallel from the typical emission lines obtained experimentally with theory. The demonstration of random laser action in Nd:YVO 4 nanopowder, by analyzing the spectral and temporal behavior from the 4 F 3/2 →4I 11/2 (1064 nm) transition is presented. A method that analyzes the decay kinetics after long-pulse excitation is used to determine the laser characteristics, allowing measuring the fractional contribution of spontaneous and stimulated emission in the samples backscattering cone, with is in agreement to the smoothing linewidth narrowing as a function of pump power typical from random lasers. Also the visible emission along a method to determine quantitatively the ETU (energy-transfer up conversion) rate is presented, which is particularly interesting, as is a mechanism that introduces a loss channel for devices emitting in the infrared region. At last, the coherent laser emission and light localization will be evaluated by using the CBS (coherent backscattering) technique in this diffusive media, in which the results are compared with simulation. (author)

Nd:YAG laser combined with gold nanorods for potential application in port-wine stains: an in vivo study.

Science.gov (United States)

Xing, Linzhuang; Chen, Bin; Li, Dong; Wu, Wenjuan; Wang, Guoxiang

2017-11-01

Neodymium:yttrium aluminum garnet (Nd:YAG) lasers exhibit considerable potential for treating deeply buried port-wine stains. However, the application of Nd:YAG laser is limited by its weak absorption to blood. This in vivo study tested the efficacy and safety of utilizing thiol-terminated methoxypolyethylene glycol-modified gold nanorods (PEG-GNRs) to enhance the absorption of Nd:YAG laser to blood. Mouse mesentery and dorsal skinfold chamber (DSC) model were prepared to analyze the thermal responses of a single venule without anatomic structures, as well as blood vessels in the complex structure of the skin, to laser light. After the injection of 0.44 mg of PEG-GNRs, the required threshold density of laser energy for blood coagulation and complete vasoconstriction decreased from 24 to 18  J/cm2 in the mesentery model and from 36 to 31  J/cm2 in the DSC model. The laser pulse required for blood coagulation and complete vasoconstriction decreased by 67.75% and 62.25% on average in the mesentery model and by 67.55% and 54.45% on average in the DSC model. Histological and histochemical results confirmed that PEG-GNRs are nontoxic in the entire mouse life span. Therefore, combining PEG-GNRs with Nd:YAG laser may be effective and safe for inducing an obvious thermal response of blood vessels under low energy density and minimal pulse conditions. (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

Potential of a novel airborne hydrographic laser scanner for capturing shallow water bodies

Science.gov (United States)

Mandlburger, G.; Pfennigbauer, M.; Steinbacher, F.; Pfeifer, N.

2012-04-01

In this paper, we present the general design of a hydrographic laser scanner (prototype instrument) manufactured by the company Riegl Laser Measurement Systems in cooperation with the University of Innsbruck, Unit of Hydraulic Engineering. The instrument utilizes very short laser pulses (1 ns) in the green wavelength domain (λ=532 nm) capable of penetrating the water column. The backscattered signal is digitized in a waveform recorder at high frequency enabling sophisticated waveform processing, both, online during the flight and in post processing. In combination with a traditional topographic airborne laser scanner (λ=1500 nm) mounted on the same platform a complete hydrographic and topographic survey of the riparian foreland, the water surface and river bed can be carried out in a single campaign. In contrast to existing bathymetric LiDAR systems, the presented system uses only medium pulse energy but a high pulse repetition rate of up to 250 kHz and, thus, focuses on a detailed description of shallow water bodies under clear water conditions. Different potential fields of applications of the instrument (hydraulic modelling, hydro-morphology, hydro-biology, ecology, river restoration and monitoring) are discussed and the results of first real-world test flights in Austria and Germany are presented. It is shown that: (i) the high pulse repetition rate enables a point density on the ground of the water body of 10-20 pts/m2, (ii) the short laser pulses together with waveform processing enable a discrimination between water and ground reflections at a water depth of less than 25 cm, (iii) the combination of a topographic and hydrographic laser scanner enable the acquisition of the geometry data for hydraulic modeling in a single survey, thus, providing a much more homogeneous data basis compared to traditional techniques, and (iv) the high point density and the ranging accuracy of less than 10 cm enable a detailed and precise description of the river bed

Factors affecting potential market penetration of laser fusion power plants

International Nuclear Information System (INIS)

Deonigi, D.E.; Fraley, D.W.

1979-08-01

A mini-model has been constructed to estimate the optimal size of laser fusion power plants and to estimate the allowable cost of the first such plant in relation to the next best alternative. In estimating the costs of laser fusion, the mini-model incorporates such factors as market penetration, learning, economies of scale, system size, transmission costs, reserve requirements, development and licensing costs and site costs. The results of the mini-model simulations indicate that the optimal laser fusion plant size is approximately 3 GWe; risk considerations unincorporated in the mini-model suggest an optimal size closer to 2.5 GWe

Microelectrode array measurement of potassium ion channel remodeling on the field action potential duration in rapid atrial pacing rabbits model.

Science.gov (United States)

Sun, Juan; Yan, Huang; Wugeti, Najina; Guo, Yujun; Zhang, Ling; Ma, Mei; Guo, Xingui; Jiao, Changan; Xu, Wenli; Li, Tianqi

2015-01-01

Atrial fibrillation (AF) arises from abnormalities in atrial structure and electrical activity. Microelectrode arrays (MEA) is a real-time, nondestructive measurement of the resting and action potential signal, from myocardial cells, to the peripheral circuit of electrophysiological activity. This study examined the field action potential duration (fAPD) of the right atrial appendage (RAA) by MEA in rapid atrial pacing (RAP) in the right atrium of rabbits. In addition, this study also investigated the effect of potassium ion channel blockers on fAPD. 40 New Zealand white rabbits of either sex were randomly divided into 3 groups: 1) the control, 2) potassium ion channel blocker (TEA, 4-Ap and BaCl2), and 3) amiodarone groups. The hearts were quickly removed and right atrial appendage sectioned (slice thickness 500 μm). Each slice was perfused with Tyrode's solution and continuously stimulated for 30 minutes. Sections from the control group were superfused with Tyrode's solution for 10 minutes, while the blocker groups and amiodarone were both treated with their respective compounds for 10 minutes each. The fAPD of RAA and action field action potential morphology were measured using MEA. In non-pace (control) groups, fAPD was 188.33 ± 18.29 ms after Tyrode's solution superfusion, and 173.91 ± 6.83 ms after RAP. In pace/potassium ion channel groups, TEA and BaCl2 superfusion prolonged atrial field action potential (fAPD) (control vs blocker: 176.67 ± 8.66 ms vs 196.11 ± 10.76 ms, 182.22 ± 12.87 ms vs 191.11 ± 13.09 ms with TEA and BaCl2 superfusion, respectively, P action potential in animal heart slices. After superfusing potassium ion channel blockers, fAPD was prolonged. These results suggest that Ito, IKur and IK1 remodel and mediate RAP-induced atrial electrical remodeling. Amiodarone alter potassium ion channel activity (Ito, IKur, IK1 and IKs), shortening fAPD.

Diatomic infrared gas-dynamic laser

International Nuclear Information System (INIS)

Mckenzie, R.L.

1971-01-01

A laser is provided which utilizes the infrared vibration rotation transitions of a diatomic gas such as carbon monoxide. The laser action is produced by an active diatomic gas such as carbon monoxide mixed with a vibrationally resonant pumping gas such as nitrogen. In addition, a noble gas such as argon may be employed as a third gas in the mixture. The gas mixture contains from 1 to 80 vol percent of the active gas based on the pumping gas, and the third gas, if used, can constitute up to 90 percent of the total gas volume. A number of significantly different wavelengths can be produced by the laser. A single laser may contain several optical resonators at different locations, so that the desired wave length can be selected at will

Model and trajectory optimization for an ideal laser-enhanced solar sail

NARCIS (Netherlands)

Carzana (student TUDelft), Livio; Dachwald, Bernd; Noomen, R.

2017-01-01

A laser-enhanced solar sail is a solar sail that is not solely propelled by solar radiation but additionally by a laser beam that illuminates the sail. This way, the propulsive acceleration of the sail results from the combined action of the solar and the laser radiation pressure onto the sail. The

Multi-temporal terrestrial laser scanning for identifying rockslide modifications: potentialities and problems

Science.gov (United States)

Castagnetti, Cristina; Bertacchini, Eleonora; Capra, Alessandro; Rivola, Riccardo

2013-04-01

The heart of this research is to provide an efficient methodology for a reliable acquisition and interpretation of Terrestrial Laser Scanner (TLS) data in the application field of landslide monitoring. In particular, rockslides, which are characterized by vertical walls of rock and by a complex morphology, are of great concern in the study. In these cases the airborne laser scanning is not able to provide useful and reliable description and the terrestrial laser scanning might be the only possible choice to obtain a good and reliable description of the geomorphology or to identify the changes occurred over time. The last purpose is still a challenging task when long distances are involved because the accurate and punctual identification of displacements is not possible due to the laser beam divergence. The final purpose of the research is a proposal of a methodology which is based on TLS technology for identifying displacements and extracting geomorphological changes. The approach is clearly based on a multi-temporal analysis which is computed on several repetitions of TLS surveys performed on the area of interest. To achieve best results and optimize the processing strategy, different methods about point clouds alignment have been tested together with algorithms both for filtering and post-processing. The case study is the Collagna Landslide that is located in the North Appennines (Reggio Emilia, Italy) on the right flank of Biola torrent. The large scale composite landslide area is made both by a wide rock slide sector and a more limited earth slide sector that, after high precipitation rates, disrupted the National Road 63 in December 2008. An integrated monitoring system is installed since 2009 and comprises both point-based technologies such as extensometers, total station and global positioning system, and also area-based technologies such as airborne laser scanner, long-range TLS and ground-based radar. This choice allows to couple the advantages of both

Potential of advanced ceramics elaborated from laser-synthetized powders

International Nuclear Information System (INIS)

Lihrmann, J.M.; Luce, M.; Croix, O.; Cauchetier, M.

1987-01-01

Use of ultrafine powders obtained by pyrolysis of gaseous reagents with a CO 2 laser gives high tech ceramics. Initiated by Haggerty from MIT, this new method is in use at the CEA since 1985. Conditions for synthesis with a 1KW laser are presented. Lab production is nearly 40g/hr of SiC with yields of 99%. Methods for powder treatment and results of mechanical and chemical properties of the compact materials obtained are given [fr

Laser-Compton Scattering as a Potential Electron Beam Monitor

International Nuclear Information System (INIS)

Chouffani, K.; Wells, D.; Harmon, F.; Lancaster, G.; Jones, J.

2002-01-01

LCS experiments were carried out at the Idaho Accelerator Center (IAC); sharp monochromatic x-ray lines were observed. These are produced using the so-called inverse Compton effect, whereby optical laser photons are collided with a relativistic electron beam. The back-scattered photons are then kinematically boosted to keV x-ray energies. We have first demonstrated these beams using a 20 MeV electron beam collided with a 100 MW, 7 ns Nd; YAG laser. We observed narrow LCS x-ray spectral peaks resulting from the interaction of the electron beam with the Nd; YAG laser second harmonic (532 nm). The LCS x-ray energy lines and energy deviations were measured as a function of the electron beam energy and energy-spread respectively. The results showed good agreement with the predicted valves. LCS could provide an excellent probe of electron beam energy, energy spread, transverse and longitudinal distribution and direction

Optical coherence tomography characterization of femtosecond laser manufactured microfluidic circuits

Science.gov (United States)

De Pretto, Lucas Ramos; Samad, Ricardo Elgul; de Rossi, Wagner; de Freitas, Anderson Zanardi

2018-02-01

Dimensional characterization of microfluidic circuits were performed using three-dimensional models constructed from OCT images of such circuits. Were fabricated microchannels on the same BK7 glass plate, under different laser ablation conditions and substrate displacement velocity in relation to laser beam. Were used the following combination of energy, from 30 μJ to 60 μJ and velocity from 588 mm/min to 1176 mm/min, at 1 kHz laser repetition rate and 40 fs of pulse duration (FWHM). For OCT imaging we used an OCP930SR (Thorlabs System Inc) with 930 nm central wavelength, 6 μm of lateral and axial resolution, and image of 500 x 512 pixel corresponding to 2.0 mm x 1.6 mm of lateral and axial scans respectively at 8 frames per second. We also characterized devices like, micropumps, microvalves and microreactors. It was possible register the micropumps and valves in action in real time. Using the OCT images analyses was possible to select the best combination of laser pulse energy and substrate velocity. All the devices were made in raster protocol, where laser beam pass through the same path in a controlled number of times, and with each iteration more material is removed and deeper the channels remain. We found a deformation at the edge of fabricated structures, due to velocity reduction of substrate in relation to laser beam, which causes more laser pulses superposition in these regions, and more material is ablated. The technique was thus evaluated as a potential tool to aid in the inspection of microchannels.

Generation of radicals in hard biological tissues under the action of laser radiation

Science.gov (United States)

Sviridov, Alexander P.; Bagratashvili, Victor N.; Sobol, Emil N.; Omelchenko, Alexander I.; Lunina, Elena V.; Zhitnev, Yurii N.; Markaryan, Galina L.; Lunin, Valerii V.

2002-07-01

The formation of radicals upon UV and IR laser irradiation of some biological tissues and their components was studied by the EPR technique. The radical decay kinetics in body tissue specimens after their irradiation with UV light were described by various models. By the spin trapping technique, it was shown that radicals were not produced during IR laser irradiation of cartilaginous tissue. A change in optical absorption spectra and the dynamics of optical density of cartilaginous tissue, fish scale, and a collagen film under exposure to laser radiation in an air, oxygen, and nitrogen atmosphere was studied.

[Effects of 2-(p-dimethylaminostyryl) pyridine methycholide (DSPM-Ci) on ECG, left atrium contractivity and on papillary muscle action potentials].

Science.gov (United States)

Jiang, X Y; Zhou, C M; Li, D M; Zhang, K J

1996-01-01

The effects of DSPM-Cl on ECG in rats, on the dose-effect curve in guinea pig left atria and on the fast action potential (AP), high-K+ depolarized slow action potential (SAP) in guinea pigs papillary muscle were examined electrophysiologically. DSPM-Cl (2 mg.kg-1) showed significant nagative frequency, negative conductivity effect, and prolonged the PP and PR interval. DSPM-CI (30-50 mumol.L-1) was shown to inhibit left atria contractility and shift the concentration-response curve of Iso and CaCl2 to the right with PD2' values of 4.60 and 4.13, respectively. In addition, DSPM-Cl was found to prolong the duration of action potential 90 (APD90) and effective refractory period (ERP), and decrease the maximal upstroke velocity (Vmax) in K(+)-depolarized guinea pigs papillary muscles. The results suggest that, like verpamil, DSPM-Cl might be a calcium antagonist.

The Transformative Potential of Action Research and ICT in the Second Language (L2) Classroom

Science.gov (United States)

Farren, Margaret; Crotty, Yvonne; Kilboy, Laura

2015-01-01

This study shows the transformative potential of action research and information and communications technology (ICT) in the second language (L2) classroom. Two enquiries from teacher-researchers are detailed in the article. Their engagement in a collaborative professional development Masters programme was pivotal in designing and implementing ICT…

A simulation of T-wave alternans vectocardiographic representation performed by changing the ventricular heart cells action potential duration.

Science.gov (United States)

Janusek, D; Kania, M; Zaczek, R; Zavala-Fernandez, H; Maniewski, R

2014-04-01

The presence of T wave alternans (TWA) in the surface ECG signals has been recognized as a marker of electrical instability, and is hypothesized to be related to patients at increased risk for ventricular arrhythmias. In this paper we present a TWA simulation study. The TWA phenomenon was simulated by changing the duration of the ventricular heart cells action potential. The magnitude was calculated in the surface ECG with the use of the time domain method. The spatially concordant TWA, where during one heart beat all ventricular cells display a short-duration action potential and during the next beat they exhibit a long-duration action potential, as well as the discordant TWA, where at least one region is out of phase, was simulated. The vectocardiographic representation was employed. The obtained results showed a high level of T-loop pattern and location disturbances connected to the discordant TWA simulation in contrast to the concordant one. This result may be explained by the spatial heterogeneity of the ventricular repolarization process, which could be higher for the discordant TWA than for the concordant TWA. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Backpropagating Action Potentials Enable Detection of Extrasynaptic Glutamate by NMDA Receptors

Directory of Open Access Journals (Sweden)

Yu-Wei Wu

2012-05-01

Full Text Available Synaptic NMDA receptors (NMDARs are crucial for neural coding and plasticity. However, little is known about the adaptive function of extrasynaptic NMDARs occurring mainly on dendritic shafts. Here, we find that in CA1 pyramidal neurons, backpropagating action potentials (bAPs recruit shaft NMDARs exposed to ambient glutamate. In contrast, spine NMDARs are “protected,” under baseline conditions, from such glutamate influences by perisynaptic transporters: we detect bAP-evoked Ca2+ entry through these receptors upon local synaptic or photolytic glutamate release. During theta-burst firing, NMDAR-dependent Ca2+ entry either downregulates or upregulates an h-channel conductance (Gh of the cell depending on whether synaptic glutamate release is intact or blocked. Thus, the balance between activation of synaptic and extrasynaptic NMDARs can determine the sign of Gh plasticity. Gh plasticity in turn regulates dendritic input probed by local glutamate uncaging. These results uncover a metaplasticity mechanism potentially important for neural coding and memory formation.

High energy HF pulsed lasers

International Nuclear Information System (INIS)

Patterson, E.L.; Gerber, R.A.

1976-01-01

Recent experiments show that pulsed HF lasers are capable of producing high energy with good efficiency. Preliminary experiments show that the laser radiation from the high-gain medium can be controlled with a low-power probe laser beam or with low-level feedback. These results indicate that the HF laser may have potential for second-generation laser fusion experiments

Recent studies of laser science in paintings conservation and research.

Science.gov (United States)

Pouli, Paraskevi; Selimis, Alexandros; Georgiou, Savas; Fotakis, Costas

2010-06-15

The removal of aged and deteriorated molecular overlayers from the surface of paintings is a delicate and critical intervention in Cultural Heritage (CH) conservation. This irreversible action gets particularly complicated given the multitude of materials that may be present within a painted work of art (often in ultrathin layers or traces), as well as the exceptional sensitivity of the original surfaces to environmental conditions such as heat, light, and so on. Lasers hold an important role among the available cleaning methodologies, as they enable high control and accuracy, material selectivity, and immediate feedback. Still, prior to their implementation, it is imperative to optimize the cleaning parameters, so to ensure that any potential implications to the remaining materials are minimal and well understood. Toward this aim, research at IESL-FORTH is focused on both refining and continuously updating the laser-cleaning protocols (by introducing novel laser technologies into the field, i.e., ultrashort laser pulses), as well as on investigating and studying the nature and extent of laser-induced physicochemical alterations to the involved materials. In this Account, extended work for the understanding of ultraviolet (UV) laser ablation of polymers is presented. Emphasis is placed on the use of model systems (polymers doped with chromophores of known photochemistry) to examine the in-depth laser-induced modifications at the processed surfaces and thus to illustrate the dependence of their nature and extent on laser parameters and material properties. Furthermore, studies for the potential use of femtosecond UV pulses to overcome certain limitations involved with the nanosecond ablation of molecular overlayers from CH surfaces are highlighted. In particular, it is demonstrated that in the femtosecond regime any chemical modifications are, qualitatively and quantitatively, highly defined, limited and nearly independent of the material properties, such as the

Increased transient Na+ conductance and action potential output in layer 2/3 prefrontal cortex neurons of the fmr1-/y mouse.

Science.gov (United States)

Routh, Brandy N; Rathour, Rahul K; Baumgardner, Michael E; Kalmbach, Brian E; Johnston, Daniel; Brager, Darrin H

2017-07-01

Layer 2/3 neurons of the prefrontal cortex display higher gain of somatic excitability, responding with a higher number of action potentials for a given stimulus, in fmr1 -/y mice. In fmr1 -/y L2/3 neurons, action potentials are taller, faster and narrower. Outside-out patch clamp recordings revealed that the maximum Na + conductance density is higher in fmr1 -/y L2/3 neurons. Measurements of three biophysically distinct K + currents revealed a depolarizing shift in the activation of a rapidly inactivating (A-type) K + conductance. Realistic neuronal simulations of the biophysical observations recapitulated the elevated action potential and repetitive firing phenotype. Fragile X syndrome is the most common form of inherited mental impairment and autism. The prefrontal cortex is responsible for higher order cognitive processing, and prefrontal dysfunction is believed to underlie many of the cognitive and behavioural phenotypes associated with fragile X syndrome. We recently demonstrated that somatic and dendritic excitability of layer (L) 5 pyramidal neurons in the prefrontal cortex of the fmr1 -/y mouse is significantly altered due to changes in several voltage-gated ion channels. In addition to L5 pyramidal neurons, L2/3 pyramidal neurons play an important role in prefrontal circuitry, integrating inputs from both lower brain regions and the contralateral cortex. Using whole-cell current clamp recording, we found that L2/3 pyramidal neurons in prefrontal cortex of fmr1 -/y mouse fired more action potentials for a given stimulus compared with wild-type neurons. In addition, action potentials in fmr1 -/y neurons were significantly larger, faster and narrower. Voltage clamp of outside-out patches from L2/3 neurons revealed that the transient Na + current was significantly larger in fmr1 -/y neurons. Furthermore, the activation curve of somatic A-type K + current was depolarized. Realistic conductance-based simulations revealed that these biophysical changes in Na

Potentiation of E-4031-induced torsade de pointes by HMR1556 or ATX-II is not predicted by action potential short-term variability or triangulation.

Science.gov (United States)

Michael, G; Dempster, J; Kane, K A; Coker, S J

2007-12-01

Torsade de pointes (TdP) can be induced by a reduction in cardiac repolarizing capacity. The aim of this study was to assess whether IKs blockade or enhancement of INa could potentiate TdP induced by IKr blockade and to investigate whether short-term variability (STV) or triangulation of action potentials preceded TdP. Experiments were performed in open-chest, pentobarbital-anaesthetized, alpha 1-adrenoceptor-stimulated, male New Zealand White rabbits, which received three consecutive i.v. infusions of either the IKr blocker E-4031 (1, 3 and 10 nmol kg(-1) min(-1)), the IKs blocker HMR1556 (25, 75 and 250 nmol kg(-1) min(-1)) or E-4031 and HMR1556 combined. In a second study rabbits received either the same doses of E-4031, the INa enhancer, ATX-II (0.4, 1.2 and 4.0 nmol kg(-1)) or both of these drugs. ECGs and epicardial monophasic action potentials were recorded. HMR1556 alone did not cause TdP but increased E-4031-induced TdP from 25 to 80%. ATX-II alone caused TdP in 38% of rabbits, as did E-4031; 75% of rabbits receiving both drugs had TdP. QT intervals were prolonged by all drugs but the extent of QT prolongation was not related to the occurrence of TdP. No changes in STV were detected and triangulation was only increased after TdP occurred. Giving modulators of ion channels in combination substantially increased TdP but, in this model, neither STV nor triangulation of action potentials could predict TdP.

Effects of Near-Infrared Laser on Neural Cell Activity

International Nuclear Information System (INIS)

Mochizuki-Oda, Noriko; Kataoka, Yosky; Yamada, Hisao; Awazu, Kunio

2004-01-01

Near-infrared laser has been used to relieve patients from various kinds of pain caused by postherpetic neuralgesia, myofascial dysfunction, surgical and traumatic wound, cancer, and rheumatoid arthritis. Clinically, He-Ne (λ=632.8 nm, 780 nm) and Ga-Al-As (805 ± 25 nm) lasers are used to irradiate trigger points or nerve ganglion. However the precise mechanisms of such biological actions of the laser have not yet been resolved. Since laser therapy is often effective to suppress the pain caused by hyperactive excitation of sensory neurons, interactions with laser light and neural cells are suggested. As neural excitation requires large amount of energy liberated from adenosine triphosphate (ATP), we examined the effect of 830-nm laser irradiation on the energy metabolism of the rat central nervous system and isolated mitochondria from brain. The diode laser was applied for 15 min with irradiance of 4.8 W/cm2 on a 2 mm-diameter spot at the brain surface. Tissue ATP content of the irradiated area in the cerebral cortex was 19% higher than that of the non-treated area (opposite side of the cortex), whereas the ADP content showed no significant difference. Irradiation at another wavelength (652 nm) had no effect on either ATP or ADP contents. The temperature of the brain tissue was increased 4.5-5.0 deg. C during the irradiation of both 830-nm and 652-nm laser light. Direct irradiation of the mitochondrial suspension did not show any wavelength-dependent acceleration of respiration rate nor ATP synthesis. These results suggest that the increase in tissue ATP content did not result from the thermal effect, but from specific effect of the laser operated at 830 nm. Electrophysiological studies showed the hyperpolarization of membrane potential of isolated neurons and decrease in membrane resistance with irradiation of the laser, suggesting an activation of potassium channels. Intracellular ATP is reported to regulate some kinds of potassium channels. Possible mechanisms

Real time estimation of generation, extinction and flow of muscle fibre action potentials in high density surface EMG.

Science.gov (United States)

Mesin, Luca

2015-02-01

Developing a real time method to estimate generation, extinction and propagation of muscle fibre action potentials from bi-dimensional and high density surface electromyogram (EMG). A multi-frame generalization of an optical flow technique including a source term is considered. A model describing generation, extinction and propagation of action potentials is fit to epochs of surface EMG. The algorithm is tested on simulations of high density surface EMG (inter-electrode distance equal to 5mm) from finite length fibres generated using a multi-layer volume conductor model. The flow and source term estimated from interference EMG reflect the anatomy of the muscle, i.e. the direction of the fibres (2° of average estimation error) and the positions of innervation zone and tendons under the electrode grid (mean errors of about 1 and 2mm, respectively). The global conduction velocity of the action potentials from motor units under the detection system is also obtained from the estimated flow. The processing time is about 1 ms per channel for an epoch of EMG of duration 150 ms. A new real time image processing algorithm is proposed to investigate muscle anatomy and activity. Potential applications are proposed in prosthesis control, automatic detection of optimal channels for EMG index extraction and biofeedback. Copyright © 2014 Elsevier Ltd. All rights reserved.

First-principles assessment of potential ultrafast laser-induced structural transition in Ni

Energy Technology Data Exchange (ETDEWEB)

Bévillon, E.; Colombier, J.P., E-mail: jean.philippe.colombier@univ-st-etienne.fr; Stoian, R.

2016-06-30

Highlights: • First-principles theory calculations in nonequilibrium conditions. • Electronic temperatures fully and consistently taken into account. • Evaluation of an ultrafast laser-induced solid-to-solid transition in Ni. • Relative energies, phonon spectra and energy path are evaluated. • Discussion on the generation of non-thermal forces in metals. - Abstract: The possibility to trigger ultrafast solid-to-solid transitions in transition metals under femtosecond laser irradiation is investigated by means of first-principles calculations. Electronic heating can drastically modify screening, charge distribution and atomic binding features, potentially determining new structural relaxation paths in the solid phase, before thermodynamic solid-to-liquid transformations set in. Consequently, we evaluate here the effect of electronic excitation on structural stability and conditions for structural transitions. Ni is chosen as a case study for the probability of a solid transition, and the stability of its FCC phase is compared to the non-standard HCP structure while accounting for the heating of the electronic subsystem. From a phonon spectra analysis, we show that the thermodynamic stability order reverses at an electronic temperature of around 10{sup 4} K. Both structures exhibit a dynamic stability, indicating they present a metastability depending on the heating. However, the general hardening of phonon modes with the increase of the electronic temperature points out that no transformation will occur, as confirmed by the study of a typical FCC to HCP diffusionless transformation path, showing an increasing energy barrier. Finally, based on electronic density of states interpretation, the tendency of different metal categories to undergo or not an ultrafast laser-induced structural transition is discussed.

Lasers in chemical processing

International Nuclear Information System (INIS)

Davis, J.I.

1982-01-01

The high cost of laser energy is the crucial issue in any potential laser-processing application. It is expensive relative to other forms of energy and to most bulk chemicals. We show those factors that have previously frustrated attempts to find commercially viable laser-induced processes for the production of materials. Having identified the general criteria to be satisfied by an economically successful laser process and shown how these imply the laser-system requirements, we present a status report on the uranium laser isotope separation (LIS) program at the Lawrence Livermore National Laboratory

Compound muscle action potential duration in critical illness neuromyopathy.

Science.gov (United States)

Kramer, Christopher L; Boon, Andrea J; Harper, C Michel; Goodman, Brent P

2018-03-01

We sought to determine the specificity of compound muscle action potential (CMAP) durations and amplitudes in a large critical illness neuromyopathy (CINM) cohort relative to controls with other neuromuscular conditions. Fifty-eight patients with CINM who had been seen over a 17-year period were retrospectively studied. Electrodiagnostic findings of the CINM cohort were compared with patients with axonal peripheral neuropathy and myopathy due to other causes. Mean CMAP durations were prolonged, and mean CMAP amplitudes were severely reduced both proximally and distally in all nerves studied in the CINM cohort relative to the control groups. The specificity of prolonged CMAP durations for CINM approached 100% if they were encountered in more than 1 nerve. Prolonged, low-amplitude CMAPs occur more frequently and with greater severity in CINM patients than in neuromuscular controls with myopathy and axonal neuropathy and are highly specific for the diagnosis of CINM. Muscle Nerve 57: 395-400, 2018. © 2017 Wiley Periodicals, Inc.

Evolution of Wigner function in laser process under the action of linear resonance force and its application

Science.gov (United States)

Dao-ming, Lu

2018-05-01

The negativity of Wigner function (WF) is one of the important symbols of non-classical properties of light field. Therefore, it is of great significance to study the evolution of WF in dissipative process. The evolution formula of WF in laser process under the action of linear resonance force is given by virtue of thermo entangled state representation and the technique of integration within an ordered product of operator. As its application, the evolution of WF of thermal field and that of single-photon-added coherent state are discussed. The results show that the WF of thermal field maintains its original character. On the other hand, the negative region size and the depth of negativity of WF of single- photon-added coherent state decrease until it vanishes with dissipation. This shows that the non-classical property of single-photon-added coherent state is weakened, until it disappears with dissipation time increasing.

Preconditioning With Low-Level Laser Irradiation Enhances the Therapeutic Potential of Human Adipose-derived Stem Cells in a Mouse Model of Photoaged Skin.

Science.gov (United States)

Liao, Xuan; Li, Sheng-Hong; Xie, Guang-Hui; Xie, Shan; Xiao, Li-Ling; Song, Jian-Xing; Liu, Hong-Wei

2018-02-19

This study was conducted to explore the therapeutic potential of human adipose-derived stem cells (ADSCs) irradiated with a low-level laser (LLL). Cultured ADSCs were treated with 650-nm GaAlAs laser irradiation at 2, 4 and 8 J cm -2 . Cell proliferation was quantified by MTT assays, cytokine secretion was determined by enzyme-linked immunosorbent assays, and adipogenic differentiation was examined by oil red O staining. Additionally, the expression profiles of putative ADSC surface markers were analyzed by quantitative real-time PCR. In addition, a mouse photoaged skin model was established by UVB irradiation. Effects of GaAlAs laser-treated ADSCs on the thicknesses of the epidermis and dermis were analyzed by hematoxylin and eosin staining. The results showed that GaAlAs laser treatment of cells at a radiant exposure of 4 J cm -2 enhanced ADSC proliferation and adipogenic differentiation and increased secretion of growth factors. Furthermore, GaAlAs laser irradiation upregulated the expression of putative ADSC surface markers. In the mouse model of photoaged skin, ADSCs treated with GaAlAs laser irradiation had markedly decreased the epidermal thickness and increased the dermal thickness of photoaged mouse skin. Our data indicate that LLL irradiation is an effective biostimulator of ADSCs and might enhance the therapeutic potential of ADSCs for clinical use. © 2018 The American Society of Photobiology.

Bacterial action of carbon dioxide laser radiation in experimental dental root canals

International Nuclear Information System (INIS)

Zakariasen, K.L.; Dederich, D.N.; Tulip, John; DeCoste, Sandra; Jensen, S.E.; Pickard, M.A.

1986-01-01

The ability of a carbon dioxide laser to sterilize the root canal of human teeth has been investigated. Three oral bacteria, Streptococcus sanguis, Streptococcus mutans, and Actinomyces viscosus, and three other bacteria, Bacillus cereus, Staphyloccus aureus, and Pseudomonoas aeruginosa were used as experimental organisms. Exposure of cells on glass slides to laser radiation showed there was little difference in the exposure required to kill these six organisms. Complete recovery of bacteria from the root canal was initially a problem and was only achieved when bacterial manipulations and removal were carried out in rapid succession, within 5 min of inoculation. However, the geometry of the instrumented canal and the laser alignment were major factors in achieving consistent cell death of oral bacteria in the root canals. Using sets of 10 teeth, four repeated exposures of 10 W for 1 s was found to sterilize 4 or more of the teeth

Sensitivity of the amplitude of the single muscle fibre action potential to microscopic volume conduction parameters

NARCIS (Netherlands)

Alberts, B.A.; Rutten, Wim; Wallinga, W.; Boom, H.B.K.

1988-01-01

A microscopic model of volume conduction was applied to examine the sensitivity of the single muscle fibre action potential to variations in parameters of the source and of the volume conductor, such as conduction velocity, intracellular conductivity and intracellular volume fraction. The model

Youth Participatory Action Research and Educational Transformation: The Potential of Intertextuality as a Methodological Tool

Science.gov (United States)

Bertrand, Melanie

2016-01-01

In this article, Melanie Bertrand explores the potential of using the concept of intertextuality--which captures the way snippets of written or spoken text from one source become incorporated into other sources--in the study and practice of youth participatory action research (YPAR). Though this collective and youth-centered form of research…

Biomedical effects of low-power laser controlled by electroacupuncture

Science.gov (United States)

Kalenchits, Nadezhda I.; Nicolaenko, Andrej A.; Shpilevoj, Boris N.

1997-12-01

The methods and technical facilities of testing the biomedical effects caused by the influence of low-power laser radiation in the process of laser therapy are presented. Described studies have been conducted by means of the complex of fireware facilities consisting of the system of electroacupuncture diagnostics (EA) and a system of laser therapy on the basis of multichannel laser and magneto-laser devices. The task of laser therapy was concluded in undertaking acupuncture anaesthetization, achievement of antioedemic and dispersional actions, raising tone of musculus and nervous system, normalization of immunity factors under the control of system EA. The 82 percent to 95 percent agreement of the result of an electroacupuncture diagnostics with clinical diagnoses were achieved.

Confocal Laser Endomicroscopy in Neurosurgery: A New Technique with Much Potential

Directory of Open Access Journals (Sweden)

David Breuskin

2013-01-01

Full Text Available Technical innovations in brain tumour diagnostic and therapy have led to significant improvements of patient outcome and recurrence free interval. The use of technical devices such as surgical microscopes as well as neuronavigational systems have helped localising tumours as much as fluorescent agents, such as 5-aminolaevulinic acid, have helped visualizing pathologically altered tissue. Nonetheless, intraoperative instantaneous frozen sections and histological diagnosis remain the only method of gaining certainty of the nature of the resected tissue. This technique is time consuming and does not provide close-to-real-time information. In gastroenterology, confocal endoscopy closed the gap between tissue resection and histological examination, providing an almost real-time histological diagnosis. The potential of this technique using a confocal laser endoscope EndoMAG1 by Karl Storz Company was evaluated by our group on pig brains, tumour tissue cell cultures, and fresh human tumour specimen. Here, the authors report for the first time on the results of applying this new technique and provide first confocal endoscopic images of various brain and tumour structures. In all, the technique harbours a very promising potential to provide almost real-time intraoperative diagnosis, but further studies are needed to provide evidence for the technique’s potential.

BK channels regulate spontaneous action potential rhythmicity in the suprachiasmatic nucleus.

Directory of Open Access Journals (Sweden)

Jack Kent

Full Text Available BACKGROUND: Circadian ( approximately 24 hr rhythms are generated by the central pacemaker localized to the suprachiasmatic nucleus (SCN of the hypothalamus. Although the basis for intrinsic rhythmicity is generally understood to rely on transcription factors encoded by "clock genes", less is known about the daily regulation of SCN neuronal activity patterns that communicate a circadian time signal to downstream behaviors and physiological systems. Action potentials in the SCN are necessary for the circadian timing of behavior, and individual SCN neurons modulate their spontaneous firing rate (SFR over the daily cycle, suggesting that the circadian patterning of neuronal activity is necessary for normal behavioral rhythm expression. The BK K(+ channel plays an important role in suppressing spontaneous firing at night in SCN neurons. Deletion of the Kcnma1 gene, encoding the BK channel, causes degradation of circadian behavioral and physiological rhythms. METHODOLOGY/PRINCIPAL FINDINGS: To test the hypothesis that loss of robust behavioral rhythmicity in Kcnma1(-/- mice is due to the disruption of SFR rhythms in the SCN, we used multi-electrode arrays to record extracellular action potentials from acute wild-type (WT and Kcnma1(-/- slices. Patterns of activity in the SCN were tracked simultaneously for up to 3 days, and the phase, period, and synchronization of SFR rhythms were examined. Loss of BK channels increased arrhythmicity but also altered the amplitude and period of rhythmic activity. Unexpectedly, Kcnma1(-/- SCNs showed increased variability in the timing of the daily SFR peak. CONCLUSIONS/SIGNIFICANCE: These results suggest that BK channels regulate multiple aspects of the circadian patterning of neuronal activity in the SCN. In addition, these data illustrate the characteristics of a disrupted SCN rhythm downstream of clock gene-mediated timekeeping and its relationship to behavioral rhythms.

New-laser research and development

International Nuclear Information System (INIS)

Anon.

1978-01-01

Two new-laser research efforts were initiated during the reporting period; the chemically pumped iodine laser and HgXe exciplex excitation by electric discharge. The chemically pumped iodine laser was recently discovered by personnel at the Air Force Weapons Laboratory. The laser offers exciting possibilities as an ICF driver because it does not require a capital-intensive pulse power source to drive it, and up to 10% efficiency may be possible. Modeling studies of the laser are in progress and its potential as a high-average power laser seems to be very favorable at this time. The HgXe exciplex radiates in a band centered at 265 nm. This system is being studied because it could be used to pump an iodine laser. Its potential as a high-power laser candidate will be assessed. An advanced oscillator system based upon a microprocessor-controlled Nd:YAG-pumped pulsed dye laser is being developed so that it can be used as the front end of new laser-fusion lasers and utilized in testing and making germane laser amplifier measurements of candidate laser systems for the wavelength region of 4000 A to 8000 A and extended range with frequency doubling and mixing. The operating requirements of the oscillator system include long-term stability, high reliability, absolute wavelength calibration and control, tunability, hands-off operation, and variable pulse width generation in the nanosecond regime

The effect of recording site on extracted features of motor unit action potential.

Science.gov (United States)

Artuğ, N Tuğrul; Goker, Imran; Bolat, Bülent; Osman, Onur; Kocasoy Orhan, Elif; Baslo, M Baris

2016-06-01

Motor unit action potential (MUAP), which consists of individual muscle fiber action potentials (MFAPs), represents the electrical activity of the motor unit. The values of the MUAP features are changed by denervation and reinnervation in neurogenic involvement as well as muscle fiber loss with increased diameter variability in myopathic diseases. The present study is designed to investigate how increased muscle fiber diameter variability affects MUAP parameters in simulated motor units. In order to detect this variation, simulated MUAPs were calculated both at the innervation zone where the MFAPs are more synchronized, and near the tendon, where they show increased temporal dispersion. Reinnervation in neurogenic state increases MUAP amplitude for the recordings at both the innervation zone and near the tendon. However, MUAP duration and the number of peaks significantly increased in a case of myopathy for recordings near the tendon. Furthermore, of the new features, "number of peaks×spike duration" was found as the strongest indicator of MFAP dispersion in myopathy. MUAPs were also recorded from healthy participants in order to investigate the biological counterpart of the simulation data. MUAPs which were recorded near to tendon revealed significantly prolonged duration and decreased amplitude. Although the number of peaks was increased by moving the needle near to tendon, this was not significant. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Control of clustered action potential firing in a mathematical model of entorhinal cortex stellate cells.

Science.gov (United States)

Tait, Luke; Wedgwood, Kyle; Tsaneva-Atanasova, Krasimira; Brown, Jon T; Goodfellow, Marc

2018-07-14

The entorhinal cortex is a crucial component of our memory and spatial navigation systems and is one of the first areas to be affected in dementias featuring tau pathology, such as Alzheimer's disease and frontotemporal dementia. Electrophysiological recordings from principle cells of medial entorhinal cortex (layer II stellate cells, mEC-SCs) demonstrate a number of key identifying properties including subthreshold oscillations in the theta (4-12 Hz) range and clustered action potential firing. These single cell properties are correlated with network activity such as grid firing and coupling between theta and gamma rhythms, suggesting they are important for spatial memory. As such, experimental models of dementia have revealed disruption of organised dorsoventral gradients in clustered action potential firing. To better understand the mechanisms underpinning these different dynamics, we study a conductance based model of mEC-SCs. We demonstrate that the model, driven by extrinsic noise, can capture quantitative differences in clustered action potential firing patterns recorded from experimental models of tau pathology and healthy animals. The differential equation formulation of our model allows us to perform numerical bifurcation analyses in order to uncover the dynamic mechanisms underlying these patterns. We show that clustered dynamics can be understood as subcritical Hopf/homoclinic bursting in a fast-slow system where the slow sub-system is governed by activation of the persistent sodium current and inactivation of the slow A-type potassium current. In the full system, we demonstrate that clustered firing arises via flip bifurcations as conductance parameters are varied. Our model analyses confirm the experimentally suggested hypothesis that the breakdown of clustered dynamics in disease occurs via increases in AHP conductance. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

Rotational Coherence Encoded in an “Air-Laser” Spectrum of Nitrogen Molecular Ions in an Intense Laser Field

Directory of Open Access Journals (Sweden)

Haisu Zhang

2013-10-01

Full Text Available We investigate lasing action in aligned nitrogen molecular ions (N_{2}^{+} produced in an intense laser field. We find that, besides the population inversion between the B^{2}Σ_{u}^{+}-X^{2}Σ_{g}^{+} states, which is responsible for the observed simulated amplification of a seed pulse, a rotational wave packet in the ground vibrational state (v=0 of the excited electronic B^{2}Σ_{u}^{+} state has been created in N_{2}^{+}. The rotational coherence can faithfully encode its characteristics into the amplified seed pulses, enabling reconstruction of rotational wave packets of molecules in a single-shot detection manner from the frequency-resolved laser spectrum. Our results suggest that the air laser can potentially provide a promising tool for remote characterization of coherent molecular rotational wave packets.

Power stabilized CO2 gas transport laser

International Nuclear Information System (INIS)

Foster, J.D.; Kirk, R.F.; Moreno, F.E.; Ahmed, S.A.

1975-01-01

The output power of a high power (1 kW or more) CO 2 gas transport laser is stabilized by flowing the gas mixture over copper plated baffles in the gas channel during operation of the laser. Several other metals may be used instead of copper, for example, nickel, manganese, palladium, platinum, silver and gold. The presence of copper in the laser gas circuit stabilizes output power by what is believed to be a compensation of the chemical changes in the gas due to the cracking action of the electrical discharge which has the effect of diminishing the capactiy of the carbon dioxide gas mixture to maintain the rated power output of the laser. (U.S.)

Ionization from short-range potential under action of electromagnetic field of complex configuration

CERN Document Server

Rodionov, V N; Kravtsova, G A

2002-01-01

The transcendental equation for the complex energy is obtained on the basis of the exactly solvable 3D model of the short-acting potential and the Green time function in the intensive electromagnetic field, constituting the combination of the constant magnetic field and the circular-polarization wave field. The electron quasistationary states parameters in the delta-potential with an account of the action of the intensive external field of complex configuration are calculated. The problem on the possibility of stabilizing the bound states decay of the spinor and scalar particles through the intensive magnetic field is clarified. It is established that the obtained results regime the reexamination of the accepted notion on the stabilizing role of the strong magnetic field by the atoms ionization

One-dimensional "atom" with zero-range potential perturbed by finite sequence of zero-duration laser pulses

Science.gov (United States)

Gusev, A. A.; Chuluunbaatar, O.; Popov, Yu. V.; Vinitsky, S. I.; Derbov, V. L.; Lovetskiy, K. P.

2018-04-01

The exactly soluble model of a train of zero-duration electromagnetic pulses interacting with a 1D atom with short-range interaction potential modelled by a δ-function is considered. The model is related to the up-to-date laser techniques providing the duration of pulses as short as a few attoseconds and the intensities higher than 1014 W/cm2.

Action of low-power laser irradiation on the proliferation of human gingival fibroblasts in vitro

Science.gov (United States)

Almeida-Lopes, Luciana; Jaeger, Marcia M. M.; Brugnera, Aldo, Jr.; Rigau, Josepa

1998-04-01

The low level power laser has been used in dental treatments aiming to improve tissue healing. An in vitro study was performed to analyze the laser influence on gingival fibroblast. A human gingival fibroblast culture (LMF) was produced in DME medium with 10% bovine fetal serum (BFS) cells (LMF) were allocated in Petri plates and cultured in different SFB concentrations (0%, 5% e 10%). After 48 hours the plates were divided in 9 groups: 3 control: 3 irradiated by 635 nm laser; and 3 irradiated by 780 nm laser. The cultured cells received 4 applications, in 12 hours intervals, with energy dosage of 2 joules for each plate, by means of a punctual technique. The growth curves showed that the growth levels were lower in low BFS concentrations. The irradiation with laser accelerated the growth rate in all groups. Additionally, the number of cells developed in low BFS concentration (5%) and irradiated was similar to the number of control cells developed in ideal conditions (10% BFS). There was no statistically significant differences between the effects of the two types of laser studied.

Small-conductance calcium-activated potassium (SK) channels contribute to action potential repolarization in human atria

DEFF Research Database (Denmark)

Skibsbye, Lasse; Poulet, Claire; Diness, Jonas Goldin

2014-01-01

(+) currents by ∼15% and prolonged action potential duration (APD), but no effect was observed in myocytes from AF patients. In trabeculae muscle strips from right atrial appendages of SR patients, both compounds increased APD and effective refractory period, and depolarized the resting membrane potential......, while only NS8593 induced these effects in tissue from AF patients. SK channel inhibition did not alter any electrophysiological parameter in human interventricular septum tissue. CONCLUSIONS: SK channels are present in human atria where they participate in repolarization. SK2 and SK3 were down...

Regulation of gap junction conductance by calcineurin through Cx43 phosphorylation: implications for action potential conduction.

Science.gov (United States)

Jabr, Rita I; Hatch, Fiona S; Salvage, Samantha C; Orlowski, Alejandro; Lampe, Paul D; Fry, Christopher H

2016-11-01

Cardiac arrhythmias are associated with raised intracellular [Ca 2+ ] and slowed action potential conduction caused by reduced gap junction (GJ) electrical conductance (Gj). Ventricular GJs are composed of connexin proteins (Cx43), with Gj determined by Cx43 phosphorylation status. Connexin phosphorylation is an interplay between protein kinases and phosphatases but the precise pathways are unknown. We aimed to identify key Ca 2+ -dependent phosphorylation sites on Cx43 that regulate cardiac gap junction conductance and action potential conduction velocity. We investigated the role of the Ca 2+ -dependent phosphatase, calcineurin. Intracellular [Ca 2+ ] was raised in guinea-pig myocardium by a low-Na solution or increased stimulation. Conduction velocity and Gj were measured in multicellular strips. Phosphorylation of Cx43 serine residues (S365 and S368) and of the intermediary regulator I1 at threonine35 was measured by Western blot. Measurements were made in the presence and absence of inhibitors to calcineurin, I1 or protein phosphatase-1 and phosphatase-2.Raised [Ca 2 + ] i decreased Gj, reduced Cx43 phosphorylation at S365 and increased it at S368; these changes were reversed by calcineurin inhibitors. Cx43-S368 phosphorylation was reversed by the protein kinase C inhibitor chelerythrine. Raised [Ca 2+ ] i also decreased I1 phosphorylation, also prevented by calcineurin inhibitors, to increase activity of the Ca 2+ -independent phosphatase, PPI. The PP1 inhibitor, tautomycin, prevented Cx43-365 dephosphorylation, Cx43-S368 phosphorylation and Gj reduction in raised [Ca 2+ ] i . PP2A had no role. Conduction velocity was reduced by raised [Ca 2+ ] i and reversed by calcineurin inhibitors. Reduced action potential conduction and Gj in raised [Ca 2+ ] are regulated by calcineurin-dependent Cx43-S365 phosphorylation, leading to Cx43-S368 dephosphorylation. The calcineurin action is indirect, via I1 dephosphorylation and subsequent activation of PP1.

High power lasers

CERN Document Server

Niku-Lari, A

1989-01-01

The use of lasers for the working and treatment of materials is becoming increasingly common in industry. However, certain laser applications, for example, in welding, cutting and drilling, are more widely exploited than others. Whilst the potential of lasers for the surface treatment of metals is well recognised, in practice, this particular application is a relative newcomer. The 24 papers in this volume present the latest research and engineering developments in the use of lasers for processes such as surface melting, surface alloying and cladding, and machining, as well as discussing th

Laser acceleration... now with added fibre

CERN Multimedia

Katarina Anthony

2012-01-01

Laser acceleration technology is plagued by two main issues: efficiency and repetition rates. In other words, lasers consume too much power and cannot sustain accelerating particles long enough to produce collisions. ICAN, a new EU-funded project, is examining how fibre lasers may help physicists tackle these issues.   A diode-pumped fibre laser. (Image courtesy of Laser Zentrum Hannover.) The International Coherent Amplification Network (ICAN) is studying the potential of lasers for collision physics. CERN is a beneficiary of the project and will collaborate with 15 other institutes from around the world, including KEK in Japan, Fermilab in the USA, and DESY in Germany. “The network is looking into existing fibre laser technology, which we believe has fantastic potential for accelerators,” says Gerard Mourou, ICAN co-ordinator at the École Polytechnique in France. “The hope is to make laser acceleration competitive with traditional radio-fre...

The potential of laser cutting and snake arm robots in aspects of nuclear decommissioning

International Nuclear Information System (INIS)

Hilton, Paul; Khan, Ali

2013-01-01

This paper will describe recent work conducted in the UK to highlight the potential of applying high power laser cutting to aspects of decommissioning and dismantling in the nuclear sector. A major driver for this activity is size reduction of metallic structures, vessels and tubing, with the objective of efficient stacking of the cut parts for future long term storage. TWI have used a standard 5 kW multi-mode laser with fibre optic delivery of the beam, to demonstrate techniques for cutting stainless steel tubing, at diameters up to 150 mm and wall thicknesses up to 7 mm, and various thicknesses of plate materials. Using specially developed cutting heads, employing long focal length lenses to form the beam, techniques were developed to allow the cutting of tubes from one side only and without changing the focal position of the laser beam with respect to the diameter of the tube perpendicular to the incident beam. The latter means that remote programming of the cutting path becomes much simpler. For cutting plate materials, special gas nozzle dynamics have produced great tolerance of the cutting process to stand-off distance (the distance between the surface of the material being cut and the exit of the cutting nozzle). One particularly interesting method of remote deployment of these cutting techniques is to use 'snake arm' robots. These robots, by nature of their construction, can access areas un-accessible using other techniques. This of course makes them particularly suited to aspects of nuclear decommissioning, particularly in what are termed 'un-structured environments', where the exact disposition of items encountered is not known. The paper will also describe the first time a laser cutting head has been installed on the end of a snake arm robot and the combination used in a simulated nuclear cutting application. (author)

Photobiomodulation with non-thermal lasers: Mechanisms of action and therapeutic uses in dermatology and aesthetic medicine.

Science.gov (United States)

Nestor, Mark; Andriessen, Anneke; Berman, Brian; Katz, Bruce E; Gilbert, Dore; Goldberg, David J; Gold, Michael H; Kirsner, Robert S; Lorenc, Paul Z

2017-08-01

Non-thermal laser therapy in dermatology, is a growing field in medical technology by which therapeutic effects are achieved by exposing tissues to specific wavelengths of light. The purpose of this review was to gain a better understanding of the science behind non-thermal laser and the evidence supporting its use in dermatology. A group of dermatologists and surgeons recently convened to review the evidence supporting the use of non-thermal laser for body sculpting, improving the appearance of cellulite, and treating onychomycosis. The use of non-thermal laser for body sculpting is supported by three randomized, double-blind, sham-controlled studies (N = 161), one prospective open-label study (N = 54), and two retrospective studies (N = 775). Non-thermal laser application for improving the appearance of cellulite is supported by one randomized, double-blind, sham-controlled study (N = 38). The use of non-thermal laser for the treatment of onychomycosis is supported by an analysis of three non-randomized, open-label studies demonstrating clinical improvement of nails (N = 292). Non-thermal laser is steadily moving into mainstream medical practice, such as dermatology. Although present studies have demonstrated the safety and efficacy of non-thermal laser for body sculpting, cellulite reduction and onychomycosis treatment, studies demonstrating the efficacy of non-thermal laser as a stand-alone procedure are still inadequate.

Human dental enamel and dentin structural effects after Er:YAG laser irradiation.

Science.gov (United States)

Lima, Darlon Martíns; Tonetto, Mateus Rodrigues; de Mendonça, Adriano Augusto Melo; Elossais, André Afif; Saad, José Roberto Cury; de Andrade, Marcelo Ferrarezi; Pinto, Shelon Cristina Souza; Bandéca, Matheus Coelho

2014-05-01

Ideally projected to be applied on soft tissues, infrared lasers were improved by restorative dentistry to be used in hard dental tissues cavity preparations--namely enamel and dentin. This paper evidentiates the relevant aspects of infrared Erbium laser's action mechanism and its effects, and characterizes the different effects deriving from the laser's beams emission. The criteria for use and selection of optimal parameters for the correct application of laser systems and influence of supporting factors on the process, such as water amount and its presence in the ablation process, protection exerted by the plasma shielding and structural factors, which are indispensable in dental tissues cavity preparation related to restorative technique, are subordinated to optical modifications caused by the interaction of the energy dissipated by these laser light emission systems in the targeted tissue substrate. Differences in the action of infrared Erbium laser system in regard to the nature of the ablation process and variations on the morphological aspects observed in the superficial structure of the target tissue irradiated, may be correlated to the structural optical modifications of the substrate produced by an interaction of the energy propagated by laser systems.

The use of laser beams for plasma diagnostics

International Nuclear Information System (INIS)

Gex, J.P.; Jolas, A.; Launspach, J.; Schirmann, D.

1975-01-01

The optical properties of lasers allow them to be a promising source for plasma diagnosis. The Q-switched lasers provide the opportunity to make observations in a very short time interval down to a few picoseconds. The laser space and time coherence properties allow interferometric measurements of plasma electron densities. Thus in the experiments of laser-matter interactions, the radiation obtained by frequency conversion of the Nd: glass laser emission is used for density measurements (up to 10 20 cm -3 ) in small scale plasmas (approximately equal to 1mm). Owing to the monochromaticity and high intensity of the Q-switched laser radiation, density fluctuations and microscopic instabilities of the plasma can be studied by Thompson scattering measurements. Finally, some statistically isotropic media become birefringent under the action of the strong electrical field of the laser beam radiation. This effect can be used for laser pulse duration measurements in a range not exceeding a few picoseconds [fr

Cross-relaxation solid state lasers

International Nuclear Information System (INIS)

Antipenko, B.M.

1989-01-01

Cross-relaxation functional diagrams provide a high quantum efficiency for pumping bands of solid state laser media and a low waste heat. A large number of the cross-relaxation mechanisms for decay rare earth excited states in crystals have been investigated. These investigations have been a starting-point for development of the cross-relaxation solid state lasers. For example, the cross-relaxation interactions, have been used for the laser action development of LiYF 4 :Gd-Tb. These interactions are important elements of the functional diagrams of the 2 μm Ho-doped media sensitized with Er and Tm and the 3 μm Er-doped media. Recently, new efficient 2 μm laser media with cross-relaxation pumping diagrams have been developed. Physical aspects of these media are the subject of this paper. A new concept of the Er-doped medium, sensitized with Yb, is illustrated

Hard rock drilling: from conventional technologies to the potential use of laser; Perfuracao em rochas duras: das tecnologias convencionais ate o potencial uso do laser

Energy Technology Data Exchange (ETDEWEB)

Amaro, Renato; Lomba, Rosana Fatima Teixieira [Petroleo Brasileiro S.A. (PETROBRAS), Rio de Janeiro, RJ (Brazil); Perez, Maria Angelica Acosta; Valente, Luiz Carlos Guedes; Braga, Arthur Martins Barbosa [Pontificia Universidade Catolica do Rio de Janeiro (PUC-Rio), RJ (Brazil)

2012-07-01

One of the biggest challenges in the drilling of the carbonate rocks of the Pre-salt is to overcome the low penetration rates that have been obtained in the drilling of the reservoir rock in the vertical and directional wells. To overcome this challenge, a great effort is being developed in several lines of research, both in developing new concepts in drill bits and in the selection of a drilling system that together with appropriate type of bit provide an expected improvement in performance. To achieve these results, procedures are being prioritized and drilling systems with lower vibration levels are being used, since this phenomenon of vibration reduces the performance of penetration rate also affecting the lifetime of the equipment and consequently causes a reduction in reliability of all system and raises the cost per meter of drilling. Thus, new drill bit technology and new drilling systems are under development and, among these technologies we can distinguish those that promote improvements in conventional technologies and innovative technologies frankly which uses new mechanisms to cut or weaken the rock. This paper presents an overview of the conventional technology of drilling systems and drill bits, and provides information about the researches that have been developed with the use of innovative technologies which is presented as highly promising, among these innovative technologies, laser drilling and the drilling itself assisted by laser. In this process the laser beam has the main function to weaken the rock improving the rate of penetration. This paper presents a summary of studies and analyzes which are underway to investigate the potential of laser technology, also presents some results of laboratory tests already carried out. The drilling fluid in which the laser will have to pass through in the future applications is analyzed on the approach of their physicochemical properties. Thus, a better understanding of the interaction with the drilling

Principles of laser surgery. Advantages and disadvantages.

Science.gov (United States)

Ballow, E B

1992-07-01

An attempt has been made in this article to present an honest and accurate state-of-art narrative of laser surgery for pedal conditions. The theory of operation, physiologic effects and procedural comparisons have been presented regarding those procedures and lasers that are available for use by podiatric surgeons and others treating the foot and leg. Although some information described within this article is anecdotal, it is elaborated with representative expert material from the scientific literature. Overall, a sound theoretic understanding of the mode of action of lasers and extensive training and experience is encouraged when engaging in this exciting discipline of surgery.

Laser Propulsion - Is it another myth or a real potential?

International Nuclear Information System (INIS)

Cook, Joung R.

2008-01-01

This paper discusses different principles of inducing propulsive power using lasers and examines the performance limits along with pros and cons with respect to different space propulsion applications: satellite launching, orbital transfer, space debris clearing, satellite propulsion, and space travels. It concludes that a use of electrical propulsion, in conjunction with laser power beaming, is the most feasible application with technological and economic advantages for commercial use within the next decades

Investigations into a potential laser-NASP transport technology

Science.gov (United States)

1990-01-01

Laser propelled flight/transport technology is surveyed. A detailed conceptual design is presented for an on-place Mercury-Lightcraft: other designs are briefly explored for larger, 15-place Executive Lightcraft, and 150 to 350 passenger Jumbo Lightcraft.

Laser technologies for laser accelerators. Annual report

International Nuclear Information System (INIS)

1985-01-01

The primary result of the work reported is the determination of laser system architectures that satsify the requirements of high luminosity, high energy (about 1 TeV), electron accelerators. It has been found that high laser efficiency is a very hard driver for these accelerators as the total average laser output optical power is likely to fall above 10 MW. The luminosity requires rep rates in the kHz range, and individual pulse lengths in the 1-10 psec range are required to satisfy acceleration gradient goals. CO 2 and KrF lasers were chosen for study because of their potential to simultaneously satisfy the given requirements. Accelerator luminosity is reviewed, and requirements on laser system average power and rep rate are determined as a function of electron beam bunch parameters. Laser technologies are reviewed, including CO 2 , excimers, solid state, and free electron lasers. The proposed accelerator mechanisms are summarized briefly. Work on optical transport geometries for near and far field accelerators are presented. Possible exploitation of the CO 2 and DrF laser technology to generate the required pulse lengths, rep rates, and projected efficiencies is illustrated and needed development work is suggested. Initial efforts at developing a 50 GeV benchmark conceptual design and a 100 MeV demonstration experiment conceptual design are presented

Flexible Laser Metal Cutting

DEFF Research Database (Denmark)

Villumsen, Sigurd; Jørgensen, Steffen Nordahl; Kristiansen, Morten

2014-01-01

This paper describes a new flexible and fast approach to laser cutting called ROBOCUT. Combined with CAD/CAM technology, laser cutting of metal provides the flexibility to perform one-of-a-kind cutting and hereby realises mass production of customised products. Today’s laser cutting techniques...... possess, despite their wide use in industry, limitations regarding speed and geometry. Research trends point towards remote laser cutting techniques which can improve speed and geometrical freedom and hereby the competitiveness of laser cutting compared to fixed-tool-based cutting technology...... such as punching. This paper presents the concepts and preliminary test results of the ROBOCUT laser cutting technology, a technology which potentially can revolutionise laser cutting....

Single K ATP channel opening in response to action potential firing in mouse dentate granule neurons.

Science.gov (United States)

Tanner, Geoffrey R; Lutas, Andrew; Martínez-François, Juan Ramón; Yellen, Gary

2011-06-08

ATP-sensitive potassium channels (K(ATP) channels) are important sensors of cellular metabolic state that link metabolism and excitability in neuroendocrine cells, but their role in nonglucosensing central neurons is less well understood. To examine a possible role for K(ATP) channels in modulating excitability in hippocampal circuits, we recorded the activity of single K(ATP) channels in cell-attached patches of granule cells in the mouse dentate gyrus during bursts of action potentials generated by antidromic stimulation of the mossy fibers. Ensemble averages of the open probability (p(open)) of single K(ATP) channels over repeated trials of stimulated spike activity showed a transient increase in p(open) in response to action potential firing. Channel currents were identified as K(ATP) channels through blockade with glibenclamide and by comparison with recordings from Kir6.2 knock-out mice. The transient elevation in K(ATP) p(open) may arise from submembrane ATP depletion by the Na(+)-K(+) ATPase, as the pump blocker strophanthidin reduced the magnitude of the elevation. Both the steady-state and stimulus-elevated p(open) of the recorded channels were higher in the presence of the ketone body R-β-hydroxybutyrate, consistent with earlier findings that ketone bodies can affect K(ATP) activity. Using perforated-patch recording, we also found that K(ATP) channels contribute to the slow afterhyperpolarization following an evoked burst of action potentials. We propose that activity-dependent opening of K(ATP) channels may help granule cells act as a seizure gate in the hippocampus and that ketone-body-mediated augmentation of the activity-dependent opening could in part explain the effect of the ketogenic diet in reducing epileptic seizures.

The Effects of Action Potential Stimulation on Pain, Swelling and Function of Patients with Knee Osteoarthritis

Directory of Open Access Journals (Sweden)

Razieh Sepehri

2012-06-01

Full Text Available Background: Knee osteoarthritis (OA is one of the most prevalent joint diseases. Electrical muscle stimulation is effective to improve its symptoms. Today, action potential stimulation (APS with various currents and periods is used to treat OA. This study aims at analyzing the effect of action potential stimulation in improving knee OA symptoms. Materials and Methods: In this clinical trial, patients with mild to moderate knee OA divided randomly in two groups each had 15 people. Along with the conventional exercises of physiotherapy, one group received 16 minutes action potential stimulation with the lowest intensity (sensible; but the other group besides receiving the conventional exercises of physiotherapy was connected into a plugged off machine for 16 minutes. Certain variables were measured and recorded four times. Results: Comparing the variables before and after intervention did not show any meaningful difference between the two groups. But within group, pain with p=0.0001 showed a meaningful decrease. Decreasing of swelling (inflammation in group 1 and 2 was meaningful with p<0.001 and p<0.001, respectively. For group 1, knee flexion range was improved meaningfully between first and fourth times as p<0.031, but it was not meaningful for group 2. Duration of 50 meters walking and step up and down from three steps significantly decreased in both groups. Conclusion: Although there was no significant difference in variables between two groups, but within both groups’ pain and swelling decreased and functional ability increased, thus, it can be concluded that type of APS does not play a key role in treating knee OA.

[Magneto-laser therapy of chronic gastritis in children and adolescents].

Science.gov (United States)

Zviagin, A A; Nikolaenko, E A

2008-01-01

The efficiency of transcutaneous magneto-laser treatment as a component of combined therapy of chronic gastritis in children and adolescents (aged 5-17 years) was compared with that of pharmacotherapy and low-intensity laser therapy. The patients were allocated to three groups of 25 persons each. Patients of group 1 were given only drug therapy, those in group 2 were treated with pharmaceuticals and low-intensity laser therapy. The patients comprising group 3 were subjected to the action of magneto-laser radiation. Magneto-laser therapy was shown to result in a significantly more expressed improvement of clinical and morphological characteristics of the patients compared with pharmacotherapy alone. There was no significant difference between effects of magneto-laser and low-intensity laser radiation.

Nuclear activated cw chemical laser

International Nuclear Information System (INIS)

Roberts, T.G.

1982-01-01

A cw chemical laser which uses processed radioactive waste to produce active atoms from a chemically inactive gas before being mixed with another molecule such as hydrogen or deuterium is disclosed. This laser uses no toxic or corrosive fuels and does not require any electrical or other type of auxiliary power supply. The energy released by the radioactive material is used to produce the active atoms such as fluorine. This is accomplished by using the radiation products from processed radioactive waste to dissociate the inert gas in the plenum of the laser. The radioactive material is held in the passageway walls of a device similar to a heat exchanger. The exchanger device may be located in the gas generator section of a chemical laser. The inactive gas is passed through the exchanger device and while passing through it the radiation from the radioactive material dissociates the gas, producing a concentration of free active atoms. This active atom generator then feeds the nozzle bank or mixing section of a laser to produce a lasing action

In vitro terahertz monitoring of muscle tissue dehydration under the action of hyperosmotic agents

Energy Technology Data Exchange (ETDEWEB)

Kolesnikov, A S; Kolesnikova, E A; Popov, A P; Tuchin, V V [N.G. Chernyshevsky Saratov State University, Saratov (Russian Federation); Nazarov, M M [Institute on Laser and Information Technologies, Russian Academy of Sciences, Shatura, Moscow Region (Russian Federation); Shkurinov, A P [International Laser Center, M. V. Lomonosov Moscow State University, Moscow (Russian Federation)

2014-07-31

Dehydration of muscle tissue in vitro under the action of biologically compatible hyperosmotic agents is studied using a laser terahertz spectrometer in the frequency range from 0.25 to 2.5 THz. Broadband terahertz absorption and reflection spectra of the bovine skeletal muscle tissue were obtained under the action of glycerol, polyethylene glycol with the molecular weight 600 (PEG-600), and propylene glycol. The presented results are proposed for application in developing the methods of image contrast enhancement and increasing the depth of biological tissue probing with terahertz radiation. (laser biophotonics)

ISOLDE gets a new laser system

CERN Multimedia

Anaïs Schaeffer

2011-01-01

It's action stations at ISOLDE, the On-Line Isotope Mass Separator at CERN. The Laboratory is preparing to add a second laser ion source system to its arsenal. By alternating between two laser systems, the ISOLDE team will be able to switch from one type of beam to another in record time.   Bruce Marsh, from the EN-STI Group, with one of the lasers from ISOLDE's current system. The first laser source for producing radioactive ion beams (see box) was installed in the ISOLDE hall in the 1990s. This method, which was highly innovative for its time, has since been adopted by several laboratories all over the world. "This laser system allows us to control the ionisation wavelength with precision and thus to select specific atoms in order to produce very pure radioactive ion beams," explains Valentin Fedosseev of the EN Department. "These beams are then used for various experiments, in nuclear astrophysics and biology, for example. With two laser systems we will be able to do ...

High potential oxidation-reduction titration of absorbance changes induced by pulsed laser and continuous light in chromatophores of photosynthesizing bacteria Rhodospirillum rubrum and Ectothiorhodospira shaposhnikovii

International Nuclear Information System (INIS)

Remennikov, S.M.; Chamorovsky, S.K.; Kononenko, A.A.; Venediktov, P.S.; Rubin, A.B.

1975-01-01

The photoreactions, activated both by pulsed laser and continuous light were studied in the membranes of isolated bacterial chromatophores poised at different oxidation-reduction potentials over a range of +200 mV to +500 mV. In Rhodospirillum rubrum a midpoint potential of oxidation-reduction curves for the laser-induced positive absorbance changes centred around 430 nm and carotenoid red shifts coincides with that for continuous light-induced absorbance changes, bleaching at 865 nm and blue shift at 800 nm, of the photosynthetic reaction centre bacteriochlorophyll. In Ectothiorhodospira shaposhnikovii the photosynthetic reaction centre bacteriochlorophyll, its photooxidation can be seen as light-induced absorbance changes, bleaching at 890 nm, blue shift at 800 nm and broad band appearance near 440 nm, has a midpoint oxidation-reduction potential of +390 mV at pH 7.4. The analysis of the oxidation-reduction titration curves for the high-potential c-type cytochrome absorbance changes induced both by pulsed laser and continuous light allowed to show that at least two haems of this cytochrome with a midpoint potential of +290 mV (pH 7.4), associated with each reaction centre bacteriochlorophyll, can donate electrons to the oxidized pigment directly

Sympathetic Nervous Regulation of Calcium and Action Potential Alternans in the Intact Heart.

Science.gov (United States)

Winter, James; Bishop, Martin J; Wilder, Catherine D E; O'Shea, Christopher; Pavlovic, Davor; Shattock, Michael J

2018-01-01

Rationale: Arrhythmogenic cardiac alternans are thought to be an important determinant for the initiation of ventricular fibrillation. There is limited information on the effects of sympathetic nerve stimulation (SNS) on alternans in the intact heart and the conclusions of existing studies, focused on investigating electrical alternans, are conflicted. Meanwhile, several lines of evidence implicate instabilities in Ca handling, not electrical restitution, as the primary mechanism underpinning alternans. Despite this, there have been no studies on Ca alternans and SNS in the intact heart. The present study sought to address this, by application of voltage and Ca optical mapping for the simultaneous study of APD and Ca alternans in the intact guinea pig heart during direct SNS. Objective : To determine the effects of SNS on APD and Ca alternans in the intact guinea pig heart and to examine the mechanism(s) by which the effects of SNS are mediated. Methods and Results : Studies utilized simultaneous voltage and Ca optical mapping in isolated guinea pig hearts with intact innervation. Alternans were induced using a rapid dynamic pacing protocol. SNS was associated with rate-independent shortening of action potential duration (APD) and the suppression of APD and Ca alternans, as indicated by a shift in the alternans threshold to faster pacing rates. Qualitatively similar results were observed with exogenous noradrenaline perfusion. In contrast with previous reports, both SNS and noradrenaline acted to flatten the slope of the electrical restitution curve. Pharmacological block of the slow delayed rectifying potassium current (I Ks ), sufficient to abolish I Ks -mediated APD-adaptation, partially reversed the effects of SNS on pacing-induced alternans. Treatment with cyclopiazonic acid, an inhibitor of the sarco(endo)plasmic reticulum ATPase, had opposite effects to that of SNS, acting to increase susceptibility to alternans, and suggesting that accelerated Ca reuptake

Biophysical basis of low-power-laser effects

Science.gov (United States)

Karu, Tiina I.

1996-06-01

Biological responses of cells to visible and near IR (laser) radiation occur due to physical and/or chemical changes in photoacceptor molecules, components of respiratory chains (cyt a/a3 in mitochondria). As a result of the photoexcitation of electronic states, the following physical and/or chemical changes can occur: alteration of redox properties and acceleration of electron transfer, changes in biochemical activity due to local transient heating of chromophores, one-electron auto-oxidation and O2- production, and photodynamic action and 1O2 production. Different reaction channels can be activated to achieve the photobiological macroeffect. The primary physical and/or chemical changes induced by light in photoacceptor molecules are followed by a cascade of biochemical reactions in the cell that do not need further light activation and occur in the dark (photosignal transduction and amplification chains). These actions are connected with changes in cellular homeostasis parameters. The crucial step here is thought to be an alteration of the cellular redox state: a shift towards oxidation is associated with stimulation of cellular vitality, and a shift towards reduction is linked to inhibition. Cells with a lower than normal pH, where the redox state is shifted in the reduced direction, are considered to be more sensitive to the stimulative action of light than those with the respective parameters being optimal or near optimal. This circumstance explains the possible variations in observed magnitudes of low-power laser effects. Light action on the redox state of a cell via the respiratory chain also explains the diversity of low-power laser effects. Beside explaining many controversies in the field of low-power laser effects (i.e., the diversity of effects, the variable magnitude or absence of effects in certain studies), the proposed redox-regulation mechanism may be a fundamental explanation for some clinical effects of irradiation, for example the positive

Biphasic response of action potential duration to metabolic inhibition in rabbit and human ventricular myocytes: role of transient outward current and ATP-regulated potassium current

NARCIS (Netherlands)

Verkerk, A. O.; Veldkamp, M. W.; van Ginneken, A. C.; Bouman, L. N.

1996-01-01

Inhibition of cell metabolism is associated with significant changes in action potential duration. The aim of this study was to investigate the time course of the changes in action potential duration during metabolic inhibition and to determine what changes in membrane currents are responsible. The

Expansion of a Bose-Einstein condensate formed on a joint harmonic and one-dimensional optical-lattice potential

International Nuclear Information System (INIS)

Adhikari, Sadhan K

2003-01-01

We study the expansion of a Bose-Einstein condensate trapped in a combined optical-lattice and axially-symmetric harmonic potential using the numerical solution of the mean-field Gross-Pitaevskii equation. First, we consider the expansion of such a condensate under the action of the optical-lattice potential alone. In this case the result of numerical simulation for the axial and radial sizes during expansion is in agreement with two experiments by Morsch et al (2002 Phys. Rev. A 66 021601(R) and 2003 Laser Phys. 13 594). Finally, we consider the expansion under the action of the harmonic potential alone. In this case the oscillation, and the disappearance and revival of the resultant interference pattern is in agreement with the experiment by Mueller et al (2003 J. Opt. B: Quantum Semiclass. Opt. 5 S38)

UV Photodissociation Action Spectroscopy of Haloanilinium Ions in a Linear Quadrupole Ion Trap Mass Spectrometer

Science.gov (United States)

Hansen, Christopher S.; Kirk, Benjamin B.; Blanksby, Stephen J.; O'Hair, Richard. A. J.; Trevitt, Adam J.

2013-06-01

UV-vis photodissociation action spectroscopy is becoming increasingly prevalent because of advances in, and commercial availability of, ion trapping technologies and tunable laser sources. This study outlines in detail an instrumental arrangement, combining a commercial ion-trap mass spectrometer and tunable nanosecond pulsed laser source, for performing fully automated photodissociation action spectroscopy on gas-phase ions. The components of the instrumentation are outlined, including the optical and electronic interfacing, in addition to the control software for automating the experiment and performing online analysis of the spectra. To demonstrate the utility of this ensemble, the photodissociation action spectra of 4-chloroanilinium, 4-bromoanilinium, and 4-iodoanilinium cations are presented and discussed. Multiple photoproducts are detected in each case and the photoproduct yields are followed as a function of laser wavelength. It is shown that the wavelength-dependent partitioning of the halide loss, H loss, and NH3 loss channels can be broadly rationalized in terms of the relative carbon-halide bond dissociation energies and processes of energy redistribution. The photodissociation action spectrum of (phenyl)Ag2 + is compared with a literature spectrum as a further benchmark.

Iodine laser - A new candidat for laser fusion - Generalities - Working principles - technological aspects

International Nuclear Information System (INIS)

Friart, Daniel.

1979-10-01

The first part of this report deals with theoretical problems concerning atomic iodine as a 1,315 μm amplifying medium. One can find a brief description of levels and lines in atomic iodine, of the influence of pressure on stimulated cross-section, of the kinetic of the amplifying medium and of its action on the gain, the saturated energy and the stored energy. An important paragraph deals with the pumping of the laser medium, especially using flash lamps. It considers the influence of the shock-waves resulting from this kind of pumping and improvements that would increase the laser efficiency up to one percent [fr

Optofluidic lens actuated by laser-induced solutocapillary forces

Science.gov (United States)

Malyuk, A. Yu.; Ivanova, N. A.

2017-06-01

We demonstrate an adaptive liquid lens controlled by laser-induced solutocapillary forces. The liquid droplet serving as a lens is formed in a thin layer of binary liquid mixture by surface tension driven flows caused by the thermal action of laser irradiation. The shape of droplet, its aperture and the focal length are reversibly changed without hysteresis by varying the intensity of the laser beam. The focal length variation range of the droplet-lens lies in between infinity (a flat layer) to 15 mm (a curved interface). The droplet-lens is capable to adjust the in-plane lateral position in response to a displacement of the laser beam. The proposed laser controlled droplet-lens will enable to develop smart liquid optical devices, which can imitate the accommodation reflex and pupillary light reflex of the eye.

Organic solid-state lasers

CERN Document Server

Forget, Sébastien

2013-01-01

Organic lasers are broadly tunable coherent sources, potentially compact, convenient and manufactured at low-costs. Appeared in the mid 60’s as solid-state alternatives for liquid dye lasers, they recently gained a new dimension after the demonstration of organic semiconductor lasers in the 90's. More recently, new perspectives appeared at the nanoscale, with organic polariton and surface plasmon lasers. After a brief reminder to laser physics, a first chapter exposes what makes organic solid-state organic lasers specific. The laser architectures used in organic lasers are then reviewed, with a state-of-the-art review of the performances of devices with regard to output power, threshold, lifetime, beam quality etc. A survey of the recent trends in the field is given, highlighting the latest developments with a special focus on the challenges remaining for achieving direct electrical pumping of organic semiconductor lasers. A last chapter covers the applications of organic solid-state lasers.

Direct pumping of ultrashort Ti:sapphire lasers by a frequency doubled diode laser

DEFF Research Database (Denmark)

Müller, André; Jensen, Ole Bjarlin; Unterhuber, Angelika

2011-01-01

electro-optical efficiency of the diode laser. Autocorrelation measurements show that pulse widths of less than 20 fs can be expected with an average power of 52 mW when using our laser. These results indicate the high potential of direct diode laser pumped Ti: sapphire lasers to be used in applications....... When using our diode laser system, the optical conversion efficiencies from green to near-infrared light reduces to 75 % of the values achieved with the commercial pump laser. Despite this reduction the overall efficiency of the Ti: sapphire laser is still increased by a factor > 2 due to the superior...... like retinal optical coherence tomography (OCT) or pumping of photonic crystal fibers for CARS (coherent anti-stokes Raman spectroscopy) microscopy....

Picosecond laser ablation of porcine sclera

Science.gov (United States)

Góra, Wojciech S.; Harvey, Eleanor M.; Dhillon, Baljean; Parson, Simon H.; Maier, Robert R. J.; Hand, Duncan P.; Shephard, Jonathan D.

2013-03-01

Lasers have been shown to be successful in certain medical procedures and they have been identified as potentially making a major contribution to the development of minimally invasive procedures. However, the uptake is not as widespread and there is scope for many other applications where laser devices may offer a significant advantage in comparison to the traditional surgical tools. The purpose of this research is to assess the potential of using a picosecond laser for minimally invasive laser sclerostomy. Experiments were carried out on porcine scleral samples due to the comparable properties to human tissue. Samples were prepared with a 5mm diameter trephine and were stored in lactated Ringer's solution. After laser machining, the samples were fixed in 3% glutaraldehyde, then dried and investigated under SEM. The laser used in the experiments is an industrial picosecond TRUMPF TruMicro laser operating at a wavelength of 1030nm, pulse length of 6ps, repetition rate of 1 kHz and a focused spot diameter of 30μm. The laser beam was scanned across the samples with the use of a galvanometer scan head and various ablation patterns were investigated. Processing parameters (pulse energy, spot and line separation) which allow for the most efficient laser ablation of scleral tissue without introducing any collateral damage were investigated. The potential to create various shapes, such as linear incisions, square cavities and circular cavities was demonstrated.

Does ozone enhance the remineralizing potential of nanohydroxyapatite on artificially demineralized enamel? A laser induced fluorescence study

Science.gov (United States)

Srinivasan, Samuelraj; Prabhu, Vijendra; Chandra, Subhash; Koshy, Shalini; Acharya, Shashidhar; Mahato, Krishna K.

2014-02-01

The present era of minimal invasive dentistry emphasizes the early detection and remineralization of initial enamel caries. Ozone has been shown to reverse the initial demineralization before the integrity of the enamel surface is lost. Nano-hydroxyapatite is a proven remineralizing agent for early enamel caries. In the present study, the effect of ozone in enhancing the remineralizing potential of nano-hydroxyapatite on artificially demineralized enamel was investigated using laser induced fluorescence. Thirty five sound human premolars were collected from healthy subjects undergoing orthodontic treatment. Fluorescence was recorded by exciting the mesial surfaces using 325 nm He-Cd laser with 2 mW power. Tooth specimens were subjected to demineralization to create initial enamel caries. Following which the specimens were divided into three groups, i.e ozone (ozonated water for 2 min), without ozone and artificial saliva. Remineralization regimen was followed for 3 weeks. The fluorescence spectra of the specimens were recorded from all the three experimental groups at baseline, after demineralization and remineralization. The average spectrum for each experimental group was used for statistical analysis. Fluorescence intensities of Ozone treated specimens following remineralization were higher than that of artificial saliva, and this difference was found to be statistically significant (P<0.0001). In a nutshell, ozone enhanced the remineralizing potential of nanohydroxyapatite, and laser induced fluorescence was found to be effective in assessing the surface mineral changes in enamel. Ozone can be considered an effective agent in reversing the initial enamel caries there by preventing the tooth from entering into the repetitive restorative cycle.

Low level laser therapy/photobiomodulation in the management of side effects of chemoradiation therapy in head and neck cancer: part 1: mechanisms of action, dosimetric, and safety considerations

Science.gov (United States)

Zecha, Judith A. E. M.; Raber-Durlacher, Judith E.; Nair, Raj G.; Epstein, Joel B.; Sonis, Stephen T.; Elad, Sharon; Hamblin, Michael R.; Barasch, Andrei; Migliorati, Cesar A.; Milstein, Dan M. J.; Genot, Marie-Thérèse; Lansaat, Liset; van der Brink, Ron; Arnabat-Dominguez, Josep; van der Molen, Lisette; Jacobi, Irene; van Diessen, Judi; de Lange, Jan; Smeele, Ludi E.; Schubert, Mark M.

2016-01-01

Purpose There is a large body of evidence supporting the efficacy of low level laser therapy (LLLT), more recently termed photobiomodulation (PBM), for the management of oral mucositis (OM) in patients undergoing radiotherapy for head and neck cancer (HNC). Recent advances in PBM technology, together with a better understanding of mechanisms involved, may expand the applications for PBM in the management of other complications associated with HNC treatment. This article (part 1) describes PBM mechanisms of action, dosimetry, and safety aspects and, in doing so, provides a basis for a companion paper (part 2) which describes the potential breadth of potential applications of PBM in the management of side-effects of (chemo)radiation therapy in patients being treated for HNC and proposes PBM parameters. Methods This study is a narrative non-systematic review. Results We review PBM mechanisms of action and dosimetric considerations. Virtually, all conditions modulated by PBM (e.g., ulceration, inflammation, lymphedema, pain, fibrosis, neurological and muscular injury) are thought to be involved in the pathogenesis of (chemo)radiation therapy-induced complications in patients treated for HNC. The impact of PBM on tumor behavior and tumor response to treatment has been insufficiently studied. In vitro studies assessing the effect of PBM on tumor cells report conflicting results, perhaps attributable to inconsistencies of PBM power and dose. Nonetheless, the biological bases for the broad clinical activities ascribed to PBM have also been noted to be similar to those activities and pathways associated with negative tumor behaviors and impeded response to treatment. While there are no anecdotal descriptions of poor tumor outcomes in patients treated with PBM, confirming its neutrality with respect to cancer responsiveness is a critical priority. Conclusion Based on its therapeutic effects, PBM may have utility in a broad range of oral, oropharyngeal, facial, and neck

INTERACTION OF LASER RADIATION WITH MATTER: Influence of surface breakdown on the process of drilling metals with pulsed CO2 laser radiation

Science.gov (United States)

Arutyunyan, R. V.; Baranov, V. Yu; Bobkov, I. V.; Bol'shov, Leonid A.; Dolgov, V. A.; Kanevskiĭ, M. F.; Malyuta, D. D.; Mezhevov, V. S.

1988-03-01

A report is given of the influence of low-threshold surface optical breakdown, occurring under the action of short (~ 5-μs) radiation pulses from a CO2 laser, on the process of the laser drilling of metals. Data are given on the difference between the interaction of radiation pulses having the same duration but differing in shape. A study was made of the influence of the pressure of the atmosphere surrounding a target on the results of laser drilling of metals. A theoretical explanation is given of the experimental results.

Prediction of Thorough QT study results using action potential simulations based on ion channel screens.

Science.gov (United States)

Mirams, Gary R; Davies, Mark R; Brough, Stephen J; Bridgland-Taylor, Matthew H; Cui, Yi; Gavaghan, David J; Abi-Gerges, Najah

2014-01-01

Detection of drug-induced pro-arrhythmic risk is a primary concern for pharmaceutical companies and regulators. Increased risk is linked to prolongation of the QT interval on the body surface ECG. Recent studies have shown that multiple ion channel interactions can be required to predict changes in ventricular repolarisation and therefore QT intervals. In this study we attempt to predict the result of the human clinical Thorough QT (TQT) study, using multiple ion channel screening which is available early in drug development. Ion current reduction was measured, in the presence of marketed drugs which have had a TQT study, for channels encoded by hERG, CaV1.2, NaV1.5, KCNQ1/MinK, and Kv4.3/KChIP2.2. The screen was performed on two platforms - IonWorks Quattro (all 5 channels, 34 compounds), and IonWorks Barracuda (hERG & CaV1.2, 26 compounds). Concentration-effect curves were fitted to the resulting data, and used to calculate a percentage reduction in each current at a given concentration. Action potential simulations were then performed using the ten Tusscher and Panfilov (2006), Grandi et al. (2010) and O'Hara et al. (2011) human ventricular action potential models, pacing at 1Hz and running to steady state, for a range of concentrations. We compared simulated action potential duration predictions with the QT prolongation observed in the TQT studies. At the estimated concentrations, simulations tended to underestimate any observed QT prolongation. When considering a wider range of concentrations, and conventional patch clamp rather than screening data for hERG, prolongation of ≥5ms was predicted with up to 79% sensitivity and 100% specificity. This study provides a proof-of-principle for the prediction of human TQT study results using data available early in drug development. We highlight a number of areas that need refinement to improve the method's predictive power, but the results suggest that such approaches will provide a useful tool in cardiac safety

Integrated Broadband Quantum Cascade Laser

Science.gov (United States)

Mansour, Kamjou (Inventor); Soibel, Alexander (Inventor)

2016-01-01

A broadband, integrated quantum cascade laser is disclosed, comprising ridge waveguide quantum cascade lasers formed by applying standard semiconductor process techniques to a monolithic structure of alternating layers of claddings and active region layers. The resulting ridge waveguide quantum cascade lasers may be individually controlled by independent voltage potentials, resulting in control of the overall spectrum of the integrated quantum cascade laser source. Other embodiments are described and claimed.

Effectiveness of laser sources for contactless sampling of explosives

Science.gov (United States)

Akmalov, Artem E.; Chistyakov, Alexander A.; Kotkovskii, Gennadii E.

2016-05-01

A mass-spectrometric study of photo processes initiated by ultraviolet (UV) laser radiation in explosives adsorbed on metal and dielectric substrates has been performed. A calibrated quadrupole mass spectrometer was used to determine a value of activation energy of desorption and a quantity of explosives desorbed by laser radiation. A special vacuumoptical module was elaborated and integrated into a vacuum mass-spectrometric system to focus the laser beam on a sample. It has been shown that the action of nanosecond laser radiation set at q= 107 - 108 W/cm2, λ=266 nm on adsorbed layers of molecules of trinitrotoluene (TNT ) and pentaerytritoltetranitrate (PETN) leads not only to an effective desorption, but also to the non-equilibrium dissociation of molecules with the formation of nitrogen oxide NO. The cyclotrimethylenetrinitramine (RDX) dissociation products are observed only at high laser intensities (q> 109 W/cm2) thus indicating the thermal nature of dissociation, whereas desorption of RDX is observed even at q> 107 W/cm2 from all substrates. Desorption is not observed for cyclotetramethylenetetranitramine (HMX) under single pulse action: the dissociation products NO and NO2 are registered only, whereas irradiation at 10Hz is quite effective for HMX desorption. The results clearly demonstrate a high efficiency of nanosecond laser radiation with λ = 266 nm, q ~ 107 - 108 W/cm2, Epulse= 1mJ for desorption of molecules of explosives from various surfaces.

Nanoelectronics-biology frontier: From nanoscopic probes for action potential recording in live cells to three-dimensional cyborg tissues

OpenAIRE

Duan, Xiaojie; Fu, Tian-Ming; Liu, Jia; Lieber, Charles M.

2013-01-01

Semiconductor nanowires configured as the active channels of field-effect transistors (FETs) have been used as detectors for high-resolution electrical recording from single live cells, cell networks, tissues and organs. Extracellular measurements with substrate supported silicon nanowire (SiNW) FETs, which have projected active areas orders of magnitude smaller than conventional microfabricated multielectrode arrays (MEAs) and planar FETs, recorded action potential and field potential signa...

Effects of He-Ne laser beam on mechanical, heat, chemical and superficial wounds

International Nuclear Information System (INIS)

Kakai, S.F.K.; Albarwari, S.E.; Alsenawi, T.A.

1988-02-01

This study summarizes the effects of low-doses of He-Ne laser radiation (λ = 6328 A), on healing of four types of wounds, including mechanical, heat, chemical and superficial wounds. The results revealed that variations between complete wound-closure in irradiated samples and that of control groups were statistically significant. Moreover, the results suggest that the stimulative action of laser is an accumulative phenomenon, that affects factors involved in the course of wound healing. The results also indicate that the skin epithelium is a highly responsive tissue towards this sort of radiation, which suggests that the stimulative action of He-Ne laser could be assayed easily by using such tissues as a test target. (author). 11 refs, 2 tabs

Electrophysiological properties of computational human ventricular cell action potential models under acute ischemic conditions.

Science.gov (United States)

Dutta, Sara; Mincholé, Ana; Quinn, T Alexander; Rodriguez, Blanca

2017-10-01

Acute myocardial ischemia is one of the main causes of sudden cardiac death. The mechanisms have been investigated primarily in experimental and computational studies using different animal species, but human studies remain scarce. In this study, we assess the ability of four human ventricular action potential models (ten Tusscher and Panfilov, 2006; Grandi et al., 2010; Carro et al., 2011; O'Hara et al., 2011) to simulate key electrophysiological consequences of acute myocardial ischemia in single cell and tissue simulations. We specifically focus on evaluating the effect of extracellular potassium concentration and activation of the ATP-sensitive inward-rectifying potassium current on action potential duration, post-repolarization refractoriness, and conduction velocity, as the most critical factors in determining reentry vulnerability during ischemia. Our results show that the Grandi and O'Hara models required modifications to reproduce expected ischemic changes, specifically modifying the intracellular potassium concentration in the Grandi model and the sodium current in the O'Hara model. With these modifications, the four human ventricular cell AP models analyzed in this study reproduce the electrophysiological alterations in repolarization, refractoriness, and conduction velocity caused by acute myocardial ischemia. However, quantitative differences are observed between the models and overall, the ten Tusscher and modified O'Hara models show closest agreement to experimental data. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Advanced lasers for fusion

International Nuclear Information System (INIS)

Krupke, W.F.; George, E.V.; Haas, R.A.

1979-01-01

Laser drive systems' performance requirements for fusion reactors are developed following a review of the principles of inertial confinement fusion and of the technical status of fusion research lasers (Nd:glass; CO 2 , iodine). These requirements are analyzed in the context of energy-storing laser media with respect to laser systems design issues: optical damage and breakdown, medium excitation, parasitics and superfluorescence depumping, energy extraction physics, medium optical quality, and gas flow. Three types of energy-storing laser media of potential utility are identified and singled out for detailed review: (1) Group VI atomic lasers, (2) rare earth solid state hybrid lasers, and (3) rare earth molecular vapor lasers. The use of highly-radiative laser media, particularly the rare-gas monohalide excimers, are discussed in the context of short pulse fusion applications. The concept of backward wave Raman pulse compression is considered as an attractive technique for this purpose. The basic physics and device parameters of these four laser systems are reviewed and conceptual designs for high energy laser systems are presented. Preliminary estimates for systems efficiencies are given. (Auth.)

Feature-Specific Event-Related Potential Effects to Action- and Sound-Related Verbs during Visual Word Recognition.

Science.gov (United States)

Popp, Margot; Trumpp, Natalie M; Kiefer, Markus

2016-01-01

Grounded cognition theories suggest that conceptual representations essentially depend on modality-specific sensory and motor systems. Feature-specific brain activation across different feature types such as action or audition has been intensively investigated in nouns, while feature-specific conceptual category differences in verbs mainly focused on body part specific effects. The present work aimed at assessing whether feature-specific event-related potential (ERP) differences between action and sound concepts, as previously observed in nouns, can also be found within the word class of verbs. In Experiment 1, participants were visually presented with carefully matched sound and action verbs within a lexical decision task, which provides implicit access to word meaning and minimizes strategic access to semantic word features. Experiment 2 tested whether pre-activating the verb concept in a context phase, in which the verb is presented with a related context noun, modulates subsequent feature-specific action vs. sound verb processing within the lexical decision task. In Experiment 1, ERP analyses revealed a differential ERP polarity pattern for action and sound verbs at parietal and central electrodes similar to previous results in nouns. Pre-activation of the meaning of verbs in the preceding context phase in Experiment 2 resulted in a polarity-reversal of feature-specific ERP effects in the lexical decision task compared with Experiment 1. This parallels analogous earlier findings for primed action and sound related nouns. In line with grounded cognitions theories, our ERP study provides evidence for a differential processing of action and sound verbs similar to earlier observation for concrete nouns. Although the localizational value of ERPs must be viewed with caution, our results indicate that the meaning of verbs is linked to different neural circuits depending on conceptual feature relevance.

Pathophysiological Mechanisms of Laser Correction in Critical Conditions

Directory of Open Access Journals (Sweden)

V. L. Kozhura

2006-01-01

Full Text Available The paper provides the generalized results of studies dealing with the use of low-intensive laser irradiation in blood loss-induced critical conditions in an experiment and in patients with severe mechanical injury. In the light of recent data and the data available in the literature, the authors consider some pathophysiological mechanisms of action of laser radiation at all living matter organization levels: molecular, cellular, organ, and systemic. The feasibilities of laser correction of hemostastic disorders are defined in relation to the volume of blood loss and the functional state of compensatory systems. 

Solar-pumped solid state Nd lasers

Science.gov (United States)

Williams, M. D.; Zapata, L.

1985-01-01

Solid state neodymium lasers are considered candidates for space-based polar-pumped laser for continuous power transmission. Laser performance for three different slab laser configurations has been computed to show the excellent power capability of such systems if heat problems can be solved. Ideas involving geometries and materials are offered as potential solutions to the heat problem.

Boron-doped nanocrystalline diamond microelectrode arrays monitor cardiac action potentials.

Science.gov (United States)

Maybeck, Vanessa; Edgington, Robert; Bongrain, Alexandre; Welch, Joseph O; Scorsone, Emanuel; Bergonzo, Philippe; Jackman, Richard B; Offenhäusser, Andreas

2014-02-01

The expansion of diamond-based electronics in the area of biological interfacing has not been as thoroughly explored as applications in electrochemical sensing. However, the biocompatibility of diamond, large safe electrochemical window, stability, and tunable electronic properties provide opportunities to develop new devices for interfacing with electrogenic cells. Here, the fabrication of microelectrode arrays (MEAs) with boron-doped nanocrystalline diamond (BNCD) electrodes and their interfacing with cardiomyocyte-like HL-1 cells to detect cardiac action potentials are presented. A nonreductive means of structuring doped and undoped diamond on the same substrate is shown. The resulting BNCD electrodes show high stability under mechanical stress generated by the cells. It is shown that by fabricating the entire surface of the MEA with NCD, in patterns of conductive doped, and isolating undoped regions, signal detection may be improved up to four-fold over BNCD electrodes passivated with traditional isolators. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The potential to characterize ecological data with terrestrial laser scanning in Harvard Forest, MA

Science.gov (United States)

Boucher, P.; Saenz, E.; Li, Z.

2018-01-01

Contemporary terrestrial laser scanning (TLS) is being used widely in forest ecology applications to examine ecosystem properties at increasing spatial and temporal scales. Harvard Forest (HF) in Petersham, MA, USA, is a long-term ecological research (LTER) site, a National Ecological Observatory Network (NEON) location and contains a 35 ha plot which is part of Smithsonian Institution's Forest Global Earth Observatory (ForestGEO). The combination of long-term field plots, eddy flux towers and the detailed past historical records has made HF very appealing for a variety of remote sensing studies. Terrestrial laser scanners, including three pioneering research instruments: the Echidna Validation Instrument, the Dual-Wavelength Echidna Lidar and the Compact Biomass Lidar, have already been used both independently and in conjunction with airborne laser scanning data and forest census data to characterize forest dynamics. TLS approaches include three-dimensional reconstructions of a plot over time, establishing the impact of ice storm damage on forest canopy structure, and characterizing eastern hemlock (Tsuga canadensis) canopy health affected by an invasive insect, the hemlock woolly adelgid (Adelges tsugae). Efforts such as those deployed at HF are demonstrating the power of TLS as a tool for monitoring ecological dynamics, identifying emerging forest health issues, measuring forest biomass and capturing ecological data relevant to other disciplines. This paper highlights various aspects of the ForestGEO plot that are important to current TLS work, the potential for exchange between forest ecology and TLS, and emphasizes the strength of combining TLS data with long-term ecological field data to create emerging opportunities for scientific study. PMID:29503723

The potential to characterize ecological data with terrestrial laser scanning in Harvard Forest, MA.

Science.gov (United States)

Orwig, D A; Boucher, P; Paynter, I; Saenz, E; Li, Z; Schaaf, C

2018-04-06

Contemporary terrestrial laser scanning (TLS) is being used widely in forest ecology applications to examine ecosystem properties at increasing spatial and temporal scales. Harvard Forest (HF) in Petersham, MA, USA, is a long-term ecological research (LTER) site, a National Ecological Observatory Network (NEON) location and contains a 35 ha plot which is part of Smithsonian Institution's Forest Global Earth Observatory (ForestGEO). The combination of long-term field plots, eddy flux towers and the detailed past historical records has made HF very appealing for a variety of remote sensing studies. Terrestrial laser scanners, including three pioneering research instruments: the Echidna Validation Instrument, the Dual-Wavelength Echidna Lidar and the Compact Biomass Lidar, have already been used both independently and in conjunction with airborne laser scanning data and forest census data to characterize forest dynamics. TLS approaches include three-dimensional reconstructions of a plot over time, establishing the impact of ice storm damage on forest canopy structure, and characterizing eastern hemlock ( Tsuga canadensis ) canopy health affected by an invasive insect, the hemlock woolly adelgid ( Adelges tsugae ). Efforts such as those deployed at HF are demonstrating the power of TLS as a tool for monitoring ecological dynamics, identifying emerging forest health issues, measuring forest biomass and capturing ecological data relevant to other disciplines. This paper highlights various aspects of the ForestGEO plot that are important to current TLS work, the potential for exchange between forest ecology and TLS, and emphasizes the strength of combining TLS data with long-term ecological field data to create emerging opportunities for scientific study.

Loop-mirror laser neural network using a fast liquid-crystal display

NARCIS (Netherlands)

Mos, E.C.; Schleipen, J.J.H.B.; Waardt, de H.; Khoe, G.D.

1999-01-01

In our laser neural network (LNN) all-optical threshold action is obtained by application of controlled optical feedback to a laser diode. Here an extended experimental LNN is presented with as many as 32 neurons and 12 inputs. In the setup we use a fast liquid-crystal display to implement an

Computer controlling of writing beam in laser microfabrication of diffractive optics

OpenAIRE

Korolkov, V.; Shimansky, R.; Cherkashin, V.; Denk, D.

2003-01-01

Laser microfabrication of diffractive optics with continuous relief is based on the direct local action of focused laser radiation on the recording material. Control of writing beam parameters (beam power, spot size, waist position) is one of the main tasks in microfabrication using laser writing systems. Method of the control defines the correspondence between the fabricated microrelief of the diffractive optical element and a designed one. Complexity of this task consists in the necessity t...

Power scaling of laser diode pumped Pr3+:LiYF4 cw lasers: efficient laser operation at 522.6 nm, 545.9 nm, 607.2 nm, and 639.5 nm.

Science.gov (United States)

Gün, Teoman; Metz, Philip; Huber, Günter

2011-03-15

We report efficient cw laser operation of laser diode pumped Pr(3+)-doped LiYF4 crystals in the visible spectral region. Using two InGaN laser diodes emitting at λ(P)=443.9 nm with maximum output power of 1 W each and a 2.9-mm-long crystal with a doping concentration of 0.5%, output powers of 938 mW, 418 mW, 384 mW, and 773 mW were achieved for the laser wavelengths 639.5 nm, 607.2 nm, 545.9 nm, and 522.6 nm, respectively. The maximum absorbed pump powers were approximately 1.5 W, resulting in slope efficiencies of 63.6%, 32.0%, 52.1%, and 61.5%, as well as electro-optical efficiencies of 9.4%, 4.2%, 3.8%, and 7.7%, respectively. Within these experiments, laser diode-pumped laser action at 545.9 nm was demonstrated for what is believed to be the first time.

Action Potential Modulation of Neural Spin Networks Suggests Possible Role of Spin

CERN Document Server

Hu, H P

2004-01-01

In this paper we show that nuclear spin networks in neural membranes are modulated by action potentials through J-coupling, dipolar coupling and chemical shielding tensors and perturbed by microscopically strong and fluctuating internal magnetic fields produced largely by paramagnetic oxygen. We suggest that these spin networks could be involved in brain functions since said modulation inputs information carried by the neural spike trains into them, said perturbation activates various dynamics within them and the combination of the two likely produce stochastic resonance thus synchronizing said dynamics to the neural firings. Although quantum coherence is desirable and may indeed exist, it is not required for these spin networks to serve as the subatomic components for the conventional neural networks.

Interference of laser-induced resonances in the continuous structures of a helium atom

International Nuclear Information System (INIS)

Magunov, A I; Strakhova, S I

2003-01-01

Coherent effects in the interference of overlapping laser-induced resonances in helium atoms are considered. The simultaneous action of single-mode radiation of the 294-nm second harmonic of a cw dye laser and a 1064-nm Nd:YAG laser on helium atoms provides the overlap of two resonances induced by transitions from the 1s2s 1 S and 1s4s 1 S helium levels. The shape of the overlapping laser-induced resonances in the rotating-wave approximation is described by analytic expressions, which depend on the laser radiation intensities and the ratio of laser frequencies. (nonlinear optical phenomena)

Nanosecond laser pulse stimulation of spiral ganglion neurons and model cells.

Science.gov (United States)

Rettenmaier, Alexander; Lenarz, Thomas; Reuter, Günter

2014-04-01

Optical stimulation of the inner ear has recently attracted attention, suggesting a higher frequency resolution compared to electrical cochlear implants due to its high spatial stimulation selectivity. Although the feasibility of the effect is shown in multiple in vivo experiments, the stimulation mechanism remains open to discussion. Here we investigate in single-cell measurements the reaction of spiral ganglion neurons and model cells to irradiation with a nanosecond-pulsed laser beam over a broad wavelength range from 420 nm up to 1950 nm using the patch clamp technique. Cell reactions were wavelength- and pulse-energy-dependent but too small to elicit action potentials in the investigated spiral ganglion neurons. As the applied radiant exposure was much higher than the reported threshold for in vivo experiments in the same laser regime, we conclude that in a stimulation paradigm with nanosecond-pulses, direct neuronal stimulation is not the main cause of optical cochlea stimulation.

Nonablative laser treatment of facial rhytides

Science.gov (United States)

Lask, Gary P.; Lee, Patrick K.; Seyfzadeh, Manouchehr; Nelson, J. Stuart; Milner, Thomas E.; Anvari, Bahman; Dave, Digant P.; Geronemus, Roy G.; Bernstein, Leonard J.; Mittelman, Harry; Ridener, Laurie A.; Coulson, Walter F.; Sand, Bruce; Baumgarder, Jon; Hennings, David R.; Menefee, Richard F.; Berry, Michael J.

1997-05-01

The purpose of this study is to evaluate the safety and effectiveness of the New Star Model 130 neodymium:yttrium aluminum garnet (Nd:YAG) laser system for nonablative laser treatment of facial rhytides (e.g., periorbital wrinkles). Facial rhytides are treated with 1.32 micrometer wavelength laser light delivered through a fiberoptic handpiece into a 5 mm diameter spot using three 300 microsecond duration pulses at 100 Hz pulse repetition frequency and pulse radiant exposures extending up to 12 J/cm2. Dynamic cooling is used to cool the epidermis selectively prior to laser treatment; animal histology experiments confirm that dynamic cooling combined with nonablative laser heating protects the epidermis and selectively injures the dermis. In the human clinical study, immediately post-treatment, treated sites exhibit mild erythema and, in a few cases, edema or small blisters. There are no long-term complications such as marked dyspigmentation and persistent erythema that are commonly observed following ablative laser skin resurfacing. Preliminary results indicate that the severity of facial rhytides has been reduced, but long-term follow-up examinations are needed to quantify the reduction. The mechanism of action of this nonablative laser treatment modality may involve dermal wound healing that leads to long- term synthesis of new collagen and extracellular matrix material.

Study of the use of methanol-filled Er-doped suspended-core fibres in a temperature-sensing ring laser system

International Nuclear Information System (INIS)

Martín, J C; Berdejo, V; Vallés, J A; Sánchez-Martín, J A; Díez, A; Andrés, M V

2013-01-01

We report on an experimental/numerical investigation into the use of methanol-filled Er-doped suspended-core fibres (SCFs) in temperature-sensing ring laser systems. We have adopted a ring laser configuration that includes an Er-doped SCF as a temperature-dependent attenuator (TDA) with a step-index Er-doped fibre (EDF) as the laser active medium. The laser performance dependence on the temperature was measured both in continuous wave (CW) and transient regimes. CW laser output power and build-up time values are compared with those of similar laser systems based on other types of Er-doped PCFs or using other laser configurations. A notable variation of 0.73% °C −1 was achieved in CW operation. Then, by means of parameters obtained by numerically fitting the experimental results, the potential sensing performance of the laser configuration with an SCF as a TDA is studied. Moreover, two ring cavity laser configurations (with the SCF acting basically as an attenuator or also as the active media) are compared and the influence of the position of the coupler inside the ring cavity and the contribution of the erbium doping to improve the sensor features are analysed. The longer interaction lengths compatible with laser action using the Er-doped SCF as a TDA could provide variations of laser output power up to 8.6% °C −1 for 90 mW pump power and a 1 m methanol-filled SCF. (paper)

Experimental aspects concerning the laser action on the living tissue

Science.gov (United States)

Ciuchita, Tavi; Antipa, Ciprian; Stanescu, Constantin S.; Anghel, Sorin; Calugareanu, Mircea

2001-06-01

The paper presents some experimental methods of the treatment and investigation aspects and results concerning the interaction of the low energy laser (LEL) with living tissue in the treatment of some skin diseases: lichen ruber planus (LP) and infectious finger pulpits (IFP), scalp alopecia (SA) and crural ulcers (CU). We concluded that LEL therapy is a useful complementary method in the treatments of these skin diseases .

Nd:YAG laser in urogenital surgery of the dog and cat

NARCIS (Netherlands)

van Nimwegen, S.A.

2008-01-01

It was hypothesized that the fiber-guided Nd:YAG laser with its incisional and hemostatic action, could be useful for meticulous tissue dissection in a subcapsular partial prostatectomy in dogs, and in laparoscopic surgery of dogs and cats. Prior to clinical use, its action was investigated in

An all-solid state laser system for the laser ion sources RILIS and in-source laser spectroscopy of astatine at ISOLDE/CERN

International Nuclear Information System (INIS)

Rothe, Sebastian

2012-01-01

This doctoral thesis describes the extension of the resonance ionization laser ion source RILIS at CERN/ISOLDE by the addition of an all-solid state tunable titanium:sapphire (Ti:Sa) laser system to complement the well-established system of dye lasers. Synchronous operation of the so called Dual RILIS system of Ti:Sa and dye lasers was investigated and the potential for increased ion beam intensity, reliability, and reduced setup time has been demonstrated. In-source resonance ionization spectroscopy was performed at ISOLDE/CERN and at ISAC/TRIUMF radioactive ion beam facilities to develop an efficient and selective three-colour ionization scheme for the purely radioactive element astatine. A LabVIEW based monitoring, control and measurement system was conceived which enabled, in conjunction with Dual RILIS operation, the spectroscopy of high lying Rydberg states, from which the ionization potential of the astatine atom was determined for the first time experimentally.

An all-solid state laser system for the laser ion source RILIS and in-source laser spectroscopy of astatine at ISOLDE, CERN

CERN Document Server

Rothe, Sebastian; Nörtershäuser, W

This doctoral thesis describes the extension of the resonance ionization laser ion source RILIS at ISOLDE, CERN, by the addition of an all-solid state tuneable titanium: sapphire (Ti:Sa) laser system to complement the well-established system of dye lasers. Synchronous operation of the so called Dual RILIS system of Ti:Sa and dye lasers was investigated and the potential for increased ion beam intensity, reliability, and reduced setup time has been demonstrated. In-source resonance ionization spectroscopy was performed at ISOLDE, CERN, and at ISAC, TRIUMF, radioactive ion beam facilities to develop an efficient and selective three-colour ionization scheme for the purely radioactive element astatine. A LabVIEW based monitoring, control and measurement system was conceived which enabled, in conjunction with Dual RILIS operation, the spectroscopy of high lying Rydberg states, from which the ionization potential of the astatine atom was determined for the first time experimentally.

An all-solid state laser system for the laser ion sources RILIS and in-source laser spectroscopy of astatine at ISOLDE/CERN

Energy Technology Data Exchange (ETDEWEB)

Rothe, Sebastian

2012-09-24

This doctoral thesis describes the extension of the resonance ionization laser ion source RILIS at CERN/ISOLDE by the addition of an all-solid state tunable titanium:sapphire (Ti:Sa) laser system to complement the well-established system of dye lasers. Synchronous operation of the so called Dual RILIS system of Ti:Sa and dye lasers was investigated and the potential for increased ion beam intensity, reliability, and reduced setup time has been demonstrated. In-source resonance ionization spectroscopy was performed at ISOLDE/CERN and at ISAC/TRIUMF radioactive ion beam facilities to develop an efficient and selective three-colour ionization scheme for the purely radioactive element astatine. A LabVIEW based monitoring, control and measurement system was conceived which enabled, in conjunction with Dual RILIS operation, the spectroscopy of high lying Rydberg states, from which the ionization potential of the astatine atom was determined for the first time experimentally.

New developments on ChemCam laser transmitter and potential applications for other planetology programs

Science.gov (United States)

Faure, Benoît; Durand, Eric; Maurice, Sylvestre; Bruneau, Didier; Montmessin, Franck

2017-11-01

ChemCam is a LIBS Instrument mounted on the MSL 2011 NASA mission. The laser transmitter of this Instrument has been developed by the French society Thales Optronique (former Thales Laser) with a strong technical support from CNES. The paper will first rapidly present the performance of this laser and will then describe the postChemCam developments realized on and around this laser for new planetology programs.

Free-electron laser driven by the LBNL laser-plasma accelerator

International Nuclear Information System (INIS)

Schroeder, C.B.; Fawley, W.M.; Gruner, F.; Bakeman, M.; Nakamura, K.; Robinson, K.E.; Toth, Cs.; Esarey, E.; Leemans, W.P.

2008-01-01

A design of a compact free-electron laser (FEL), generating ultra-fast, high-peak flux, XUV pulses is presented. The FEL is driven by ahigh-current, 0.5 GeV electron beam from the Lawrence Berkeley National Laboratory (LBNL) laser-plasma accelerator, whose active acceleration length is only a few centimeters. The proposed ultra-fast source (∼10 fs) would be intrinsically temporally synchronized to the drive laser pulse, enabling pump-probe studies in ultra-fast science. Owing to the high current (>10 kA) of the laser-plasma-accelerated electron beams, saturated output fluxes are potentially greater than 10 13 photons/pulse. Devices based both on self-amplified spontaneous emission and high-harmonic generated input seeds, to reduce undulator length and fluctuations, are considered.

Nano lasers in photonic VLSI

NARCIS (Netherlands)

Hill, M.T.; Oei, Y.S.; Smit, M.K.

2007-01-01

We examine the use of micro and nano lasers to form digital photonic VLSI building blocks. Problems such as isolation and cascading of building blocks are addressed, and the potential of future nano lasers explored.

Continuous-wave diode-pumped Yb 3+:LYSO tunable laser

Science.gov (United States)

Du, Juan; Liang, Xiaoyan; Xu, Yi; Li, Ruxin; Yan, Chengfeng; Zhao, Guangjun; Su, Liangbi; Xu, Jun; Xu, Zhizhan

2007-01-01

A new alloyed crystal, Yb:LYSO, has been grown by the Czochralski method in our institute for the first time, and its effective diode-pumped cw tunable laser action was demonstrated. The alloyed crystal retains excellent laser properties of LSO with reduced growth cost, as well as the favorable growth properties of YSO. With a 5-at.% Yb:LYSO sample, we achieved 2.84 W output power at 1085 nm and a slope efficiency of 63.5%. And its laser wavelength could be tuned over a range broader than 80nm, from 1030nm to 1111 nm. This is the broadest tunable range achieved for Yb:LYSO laser, as far as we know.

Induced Compton scattering of a laser in an inhomogeneous plasma

International Nuclear Information System (INIS)

Liu, C.S.; Tripathi, V. K.

2003-01-01

A laser propagating through a high temperature low density plasma undergoes induced Compton backscattering involving the coupling of the laser pump and the scattered electromagnetic wave via the resonant electrons or the resistive quasimode. The region of nonlinear interaction is localized due to plasma inhomogeneity. At short density scale lengths when the interaction region is strongly localized and resonant electrons quickly move out of it, the electron distribution function remains Maxwellian and Compton reflectivity is significant at laser intensity >10 16 W/cm 2 . In gentle density gradients the resonant electrons are trapped in the ponderomotive and self-consistent potential well of the quasimode as they enter the interaction region. The ones with velocity v z p (v p being the phase velocity of the ponderomotive wave propagating along z direction) are accelerated to v p while those with v z >v p are retarded to v p . Since the number of the former is more than that of the latter there is a net momentum transfer to electrons. Momentum and action conservation lead to a reflectivity, R, that initially goes as the square of pump intensity, then rises gradually at higher intensity. R decreases rapidly with v th /v p , where v th is the thermal velocity of electrons

Overexpression of the Large-Conductance, Ca2+-Activated K+ (BK) Channel Shortens Action Potential Duration in HL-1 Cardiomyocytes.

Science.gov (United States)

Stimers, Joseph R; Song, Li; Rusch, Nancy J; Rhee, Sung W

2015-01-01

Long QT syndrome is characterized by a prolongation of the interval between the Q wave and the T wave on the electrocardiogram. This abnormality reflects a prolongation of the ventricular action potential caused by a number of genetic mutations or a variety of drugs. Since effective treatments are unavailable, we explored the possibility of using cardiac expression of the large-conductance, Ca2+-activated K+ (BK) channel to shorten action potential duration (APD). We hypothesized that expression of the pore-forming α subunit of human BK channels (hBKα) in HL-1 cells would shorten action potential duration in this mouse atrial cell line. Expression of hBKα had minimal effects on expression levels of other ion channels with the exception of a small but significant reduction in Kv11.1. Patch-clamped hBKα expressing HL-1 cells exhibited an outward voltage- and Ca2+-sensitive K+ current, which was inhibited by the BK channel blocker iberiotoxin (100 nM). This BK current phenotype was not detected in untransfected HL-1 cells or in HL-1 null cells sham-transfected with an empty vector. Importantly, APD in hBKα-expressing HL-1 cells averaged 14.3 ± 2.8 ms (n = 10), which represented a 53% reduction in APD compared to HL-1 null cells lacking BKα expression. APD in the latter cells averaged 31.0 ± 5.1 ms (n = 13). The shortened APD in hBKα-expressing cells was restored to normal duration by 100 nM iberiotoxin, suggesting that a repolarizing K+ current attributed to BK channels accounted for action potential shortening. These findings provide initial proof-of-concept that the introduction of hBKα channels into a cardiac cell line can shorten APD, and raise the possibility that gene-based interventions to increase hBKα channels in cardiac cells may hold promise as a therapeutic strategy for long QT syndrome.

Critical Utopian Action Research

DEFF Research Database (Denmark)

Nielsen, Birger Steen; Nielsen, Kurt Aagaard

2016-01-01

The specific concept of critical utopian action research is presented and discussed, as to its origin, use and potentials. The inspiration from Robert Jungk and his future creating workshops is elaborated.......The specific concept of critical utopian action research is presented and discussed, as to its origin, use and potentials. The inspiration from Robert Jungk and his future creating workshops is elaborated....

X-ray emission as a potential hazard during ultrashort pulse laser material processing

Science.gov (United States)

Legall, Herbert; Schwanke, Christoph; Pentzien, Simone; Dittmar, Günter; Bonse, Jörn; Krüger, Jörg

2018-06-01

In laser machining with ultrashort laser pulses unwanted X-ray radiation in the keV range can be generated when a critical laser intensity is exceeded. Even if the emitted X-ray dose per pulse is low, high laser repetition rates can lead to an accumulation of X-ray doses beyond exposure safety limits. For 925 fs pulse duration at a center wavelength of 1030 nm, the X-ray emission was investigated up to an intensity of 2.6 × 1014 W/cm2. The experiments were performed in air with a thin disk laser at a repetition rate of 400 kHz. X-ray spectra and doses were measured for various planar target materials covering a wide range of the periodic table from aluminum to tungsten. Without radiation shielding, the measured radiation doses at this high repetition rate clearly exceed the regulatory limits. Estimations for an adequate radiation shielding are provided.

Isosteviol prevents the prolongation of action potential in hypertrophied cardiomyoctyes by regulating transient outward potassium and L-type calcium channels.

Science.gov (United States)

Fan, Zhuo; Lv, Nanying; Luo, Xiao; Tan, Wen

2017-10-01

Cardiac hypertrophy is a thickening of the heart muscle that is associated with cardiovascular diseases such as hypertension and myocardial infarction. It occurs initially as an adaptive process against increased workloads and often leads to sudden arrhythmic deaths. Studies suggest that the lethal arrhythmia is attributed to hypertrophy-induced destabilization of cardiac electrical activity, especially the prolongation of the action potential. The reduced activity of I to is demonstrated to be responsible for the ionic mechanism of prolonged action potential duration and arrhythmogeneity. Isosteviol (STV), a derivative of stevioside, plays a protective role in a variety of stress-induced cardiac diseases. Here we report effects of STV on rat ISO-induced hypertrophic cardiomyocytes. STV alleviated ISO-induced hypertrophy of cardiomyocytes by decreasing cell area of hypertrophied cardiomyocytes. STV application prevented the prolongation of action potential which was prominent in hypertrophied cells. The decrease and increase of current densities for I to and I CaL observed in hypertrophied myocytes were both prevented by STV application. In addition, the results of qRT-PCR suggested that the changes of electrophysiological activity of I to and I CaL are correlated to the alterations of the mRNA transcription level. Copyright © 2017. Published by Elsevier B.V.

Excited argon 1s5 production in micro-hollow cathode discharges for use as potential rare gas laser sources

Science.gov (United States)

Peterson, Richard D.; Eshel, Ben; Rice, Christopher A.; Perram, Glen P.

2018-02-01

The diode-pumped rare gas laser (DPRGL) has been suggested as a potential high-gain, high-energy laser which requires densities on the order of 1013 cm-3 at pressures around 1 atmosphere for efficient operation. Argon 1s5 number densities have been measured in micro-hollow cathode discharges with electrode gaps of 127 and 254 μm and hole diameters from 100-400 μm. The dependency of the metastable argon (1s5) density on total gas pressure, electrode gap distance and hole diameter were explored. The measured densities were all in the range of 0.5 - 2 × 1013 cm-3 with the 400 μm hole diameters being the lowest.

Lasers in materials processing

International Nuclear Information System (INIS)

Davis, J.I.; Rockower, E.B.

1981-01-01

A status report on the uranium Laser Isotope Separation (LIS) Program at the Lawrence Livermore National Laboratory is presented. Prior to this status report, process economic analysis is presented so as to understand how the unique properties of laser photons can be best utilized in the production of materials and components despite the high cost of laser energy. The characteristics of potential applications that are necessary for success are identified, and those factors that have up to now frustrated attempts to find commercially viable laser induced chemical and physical process for the production of new or existing materials are pointed out

Laser-driven acceleration with Bessel beam

International Nuclear Information System (INIS)

Imasaki, Kazuo; Li, Dazhi

2005-01-01

A new approach of laser-driven acceleration with Bessel beam is described. Bessel beam, in contrast to the Gaussian beam, shows diffraction-free'' characteristics in its propagation, which implies potential in laser-driven acceleration. But a normal laser, even if the Bessel beam, laser can not accelerate charged particle efficiently because the difference of velocity between the particle and photon makes cyclic acceleration and deceleration phase. We proposed a Bessel beam truncated by a set of annular slits those makes several special regions in its travelling path, where the laser field becomes very weak and the accelerated particles are possible to receive no deceleration as they undergo decelerating phase. Thus, multistage acceleration is realizable with high gradient. In a numerical computation, we have shown the potential of multistage acceleration based on a three-stage model. (author)

Quantum tunneling time of a Bose-Einstein condensate traversing through a laser-induced potential barrier

International Nuclear Information System (INIS)

Duan Zhenglu; Fan Bixuan; Yuan Chunhua; Zhang Weiping; Cheng Jing; Zhu Shiyao

2010-01-01

We theoretically study the effect of atomic nonlinearity on the tunneling time in the case of an atomic Bose-Einstein condensate (BEC) traversing the laser-induced potential barrier. The atomic nonlinearity is controlled to appear only in the region of the barrier by employing the Feshbach resonance technique to tune interatomic interaction in the tunneling process. Numerical simulation shows that the atomic nonlinear effect dramatically changes the tunneling behavior of the BEC matter wave packet and results in the violation of the Hartman effect and the occurrence of negative tunneling time.

Electrons and atoms in intense laser fields

International Nuclear Information System (INIS)

Davidovich, L.

1982-11-01

Several non-linear effects that show up when electrons and atoms interact with strong laser fields are considered. Thomson scattering, electron potential scattering in the presence of a laser beam, atomic ionization by strong laser fields, the refraction of electrons by laser beams and the Kapitza-Dirac effect are discussed. (Author) [pt

Electrons and atoms in intense laser fields

International Nuclear Information System (INIS)

Davidovich, L.

1982-01-01

Several non-linear effects that show up when electrons and atoms interact with strong laser fields are considered. Thomson scattering, electron potential scattering in the presence of a laser beam, atomic ionization by strong laser fields, the refraction of electrons by laser beams and the Kapitza-Dirac effect are discussed. (Author) [pt

Investigation of local optical inhomogeneities in flashlamp photolysis lasers

Energy Technology Data Exchange (ETDEWEB)

Alekhin, B V; Borovkov, V V; Lazhintsev, B V; Nor-Arenian, V A; Sukhanov, L V; Ustinenko, V A

1979-09-01

Local changes in the refractive index which occur in the active medium under flashlamp-excited photolysis laser action are examined experimentally. Under conditions of the inverse population storage and suppression of the laser action by a strong quencher, local inhomogeneities have been absent. It is shown that the stimulated emission is inhomogeneous over the active medium and features regular character with the radiation density modulation within 20-30 percent and with typical size of inhomogeneities of not greater than 0.5 mm. On the basis of experimental results and estimation, a conclusion is drawn that the local optical inhomogeneities are caused by gasdynamic displacements of the gas due to different heat evolutions in the regions of the radiation density maximum and minimum.

Single-Photon Ionization Soft-X-Ray Laser Mass Spectrometry of Potential Hydrogen Storage Materials

Science.gov (United States)

Dong, F.; Bernstein, E. R.; Rocca, J. J.

A desk-top size capillary discharge 46.9 nm lasear is applied in the gas phase study of nanoclusters. The high photon energy allows for single-photon ionization mass spectrometry with reduced cluster fragmentation. In the present studies, neutral Al m C n and Al m C n H x cluster are investigation for the first time. Single photon ionization through 46.9 nm, 118 nm, 193 nm lasers is used to detect neutral cluster distributions through time of flight mass spectrometry. Al m C n clusters are generated through laser ablation of a mixture of Al and C powders pressed into a disk. An oscillation of the vertical ionization energies (VIEs) of Al m C n clusters is observed in the experiments. The VIEs of Al m C n clusters changes as a function of the numbers of Al and C atoms in the clusters. Al m C n H x clusters are generated through an Al ablation plasma-hydrocarbon reaction, an Al-C ablation plasma reacting with H2 gas, or through cold Al m C n clusters reacting with H2 gas in a fast flow reactor. DFT and ab inito calculations are carried out to explore the structures, IEs, and electronic structures of Al m C n H x clusters. C=C bonds are favored for the lowest energy structures for Al m C n clusters. Be m C n H x are generated through a beryllium ablation plasma-hydrocarbon reaction and detected by single photon ionization of 193 nm laser. Both Al m C n H x and Be m C n H x are considered as potential hydrogen storage materials.

Effects of acoustic noise on the auditory nerve compound action potentials evoked by electric pulse trains.

Science.gov (United States)

Nourski, Kirill V; Abbas, Paul J; Miller, Charles A; Robinson, Barbara K; Jeng, Fuh-Cherng

2005-04-01

This study investigated the effects of acoustic noise on the auditory nerve compound action potentials in response to electric pulse trains. Subjects were adult guinea pigs, implanted with a minimally invasive electrode to preserve acoustic sensitivity. Electrically evoked compound action potentials (ECAP) were recorded from the auditory nerve trunk in response to electric pulse trains both during and after the presentation of acoustic white noise. Simultaneously presented acoustic noise produced a decrease in ECAP amplitude. The effect of the acoustic masker on the electric probe was greatest at the onset of the acoustic stimulus and it was followed by a partial recovery of the ECAP amplitude. Following cessation of the acoustic noise, ECAP amplitude recovered over a period of approximately 100-200 ms. The effects of the acoustic noise were more prominent at lower electric pulse rates (interpulse intervals of 3 ms and higher). At higher pulse rates, the ECAP adaptation to the electric pulse train alone was larger and the acoustic noise, when presented, produced little additional effect. The observed effects of noise on ECAP were the greatest at high electric stimulus levels and, for a particular electric stimulus level, at high acoustic noise levels.

Molecular motions that shape the cardiac action potential: Insights from voltage clamp fluorometry.

Science.gov (United States)

Zhu, Wandi; Varga, Zoltan; Silva, Jonathan R

2016-01-01

Very recently, voltage-clamp fluorometry (VCF) protocols have been developed to observe the membrane proteins responsible for carrying the ventricular ionic currents that form the action potential (AP), including those carried by the cardiac Na(+) channel, NaV1.5, the L-type Ca(2+) channel, CaV1.2, the Na(+)/K(+) ATPase, and the rapid and slow components of the delayed rectifier, KV11.1 and KV7.1. This development is significant, because VCF enables simultaneous observation of ionic current kinetics with conformational changes occurring within specific channel domains. The ability gained from VCF, to connect nanoscale molecular movement to ion channel function has revealed how the voltage-sensing domains (VSDs) control ion flux through channel pores, mechanisms of post-translational regulation and the molecular pathology of inherited mutations. In the future, we expect that this data will be of great use for the creation of multi-scale computational AP models that explicitly represent ion channel conformations, connecting molecular, cell and tissue electrophysiology. Here, we review the VCF protocol, recent results, and discuss potential future developments, including potential use of these experimental findings to create novel computational models. Copyright © 2015 Elsevier Ltd. All rights reserved.

Modulation of KCNQ1 alternative splicing regulates cardiac IKs and action potential repolarization.

Science.gov (United States)

Lee, Hsiang-Chun; Rudy, Yoram; Po-Yuan, Phd; Sheu, Sheng-Hsiung; Chang, Jan-Gowth; Cui, Jianmin

2013-08-01

Slow delayed-rectifier potassium current (IKs) channels, made of the pore-forming KCNQ1 and auxiliary KCNE1 subunits, play a key role in determining action potential duration (APD) in cardiac myocytes. The consequences of drug-induced KCNQ1 splice alteration remain unknown. To study the modulation of KCNQ1 alternative splicing by amiloride and the consequent changes in IKs and action potentials (APs) in ventricular myocytes. Canine endocardial, midmyocardial, and epicardial ventricular myocytes were isolated. Levels of KCNQ1a and KCNQ1b as well as a series of splicing factors were quantified by using the reverse transcriptase-polymerase chain reaction and Western blot. The effect of amiloride-induced changes in the KCNQ1b/total KCNQ1 ratio on AP was measured by using whole-cell patch clamp with and without isoproterenol. With 50 μmol/L of amiloride for 6 hours, KCNQ1a at transcriptional and translational levels increased in midmyocardial myocytes but decreased in endo- and epicardial myocytes. Likewise, changes in splicing factors in midmyocardial were opposite to that in endo- and epicardial myocytes. In midmyocardial myocytes amiloride shortened APD and decreased isoproterenol-induced early afterdepolarizations significantly. The same amiloride-induced effects were demonstrated by using human ventricular myocyte model for AP simulations under beta-adrenergic stimulation. Moreover, amiloride reduced the transmural dispersion of repolarization in pseudo-electrocardiogram. Amiloride regulates IKs and APs with transmural differences and reduces arrhythmogenicity through the modulation of KCNQ1 splicing. We suggested that the modulation of KCNQ1 splicing may help prevent arrhythmia. Copyright © 2013 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

Nanowire Lasers

Directory of Open Access Journals (Sweden)

Couteau C.

2015-05-01

Full Text Available We review principles and trends in the use of semiconductor nanowires as gain media for stimulated emission and lasing. Semiconductor nanowires have recently been widely studied for use in integrated optoelectronic devices, such as light-emitting diodes (LEDs, solar cells, and transistors. Intensive research has also been conducted in the use of nanowires for subwavelength laser systems that take advantage of their quasione- dimensional (1D nature, flexibility in material choice and combination, and intrinsic optoelectronic properties. First, we provide an overview on using quasi-1D nanowire systems to realize subwavelength lasers with efficient, directional, and low-threshold emission. We then describe the state of the art for nanowire lasers in terms of materials, geometry, andwavelength tunability.Next,we present the basics of lasing in semiconductor nanowires, define the key parameters for stimulated emission, and introduce the properties of nanowires. We then review advanced nanowire laser designs from the literature. Finally, we present interesting perspectives for low-threshold nanoscale light sources and optical interconnects. We intend to illustrate the potential of nanolasers inmany applications, such as nanophotonic devices that integrate electronics and photonics for next-generation optoelectronic devices. For instance, these building blocks for nanoscale photonics can be used for data storage and biomedical applications when coupled to on-chip characterization tools. These nanoscale monochromatic laser light sources promise breakthroughs in nanophotonics, as they can operate at room temperature, can potentially be electrically driven, and can yield a better understanding of intrinsic nanomaterial properties and surface-state effects in lowdimensional semiconductor systems.

Laser physics and a review of laser applications in dentistry for children.

Science.gov (United States)

Martens, L C

2011-04-01

The aim of this introduction to this special laser issue is to describe some basic laser physics and to delineate the potential of laser-assisted dentistry in children. A brief review of the available laser literature was performed within the scope of paediatric dentistry. Attention was paid to soft tissue surgery, caries prevention and diagnosis, cavity preparation, comfort of the patient, effect on bacteria, long term pulpal vitality, endodontics in primary teeth, dental traumatology and low level laser therapy. Although there is a lack of sufficient evidence taking into account the highest standards for evidence-based dentistry, it is clear that laser application in a number of different aetiologies for soft tissue surgery in children has proven to be successful. Lasers provide a refined diagnosis of caries combined with the appropriate preventive adhesive dentistry after cavity preparation. This will further lead to a new wave of micro-dentistry based on 'filling without drilling'. It has become clear from a review of the literature that specific laser applications in paediatric dentistry have gained increasing importance. It can be concluded that children should be considered as amongst the first patients for receiving laser-assisted dentistry.

Talk and Action

DEFF Research Database (Denmark)

Christensen, Lars Thøger; Morsing, Mette; Thyssen, Ole

The aim of this paper is to analyze the relationship between organizational talk and action. Focusing in particular on the temporal dimension of this relationship, that is, the potential for talk to become action over time, we put forward ideal types of organizational strategies for possible talk...

The evolution of the laser: A systems perspective on science, technology and society

Science.gov (United States)

Deruiter, Willem

The evolution of laser technology is addressed, and an attempt is made to correlate this evolution to the macrosociological theory of Juergen Habermas. The economic and social consequences of innovations are evaluated. Different laser applications are described. The evolution of the semiconductor laser is discussed. The evolution of optical telecommunication systems is outlined. The Habermas theory of communicative action, focussing on the theoretical distinction between 'system' and 'lifeworld,' is treated. The modified theory of Habermas is applied to the evolution of the laser. The embedding of a number of laser applications in the social context is discussed: laser isotope separation, compact disc players, and the Strategic Defense Initiative.

Intense isolated attosecond pulse generation from relativistic laser plasmas using few-cycle laser pulses

International Nuclear Information System (INIS)

Ma, Guangjin; Dallari, William; Borot, Antonin; Tsakiris, George D.; Veisz, Laszlo; Krausz, Ferenc; Yu, Wei

2015-01-01

We have performed a systematic study through particle-in-cell simulations to investigate the generation of attosecond pulse from relativistic laser plasmas when laser pulse duration approaches the few-cycle regime. A significant enhancement of attosecond pulse energy has been found to depend on laser pulse duration, carrier envelope phase, and plasma scale length. Based on the results obtained in this work, the potential of attaining isolated attosecond pulses with ∼100 μJ energy for photons >16 eV using state-of-the-art laser technology appears to be within reach

Channeling of electrons in a crossed laser field

Directory of Open Access Journals (Sweden)

S. B. Dabagov

2015-06-01

Full Text Available In this article a new analytical description of the effective interaction potential for a charged particle with the field of two interfering laser beams is presented. The potential dependence on the lasers intensities, orientation and parameters of the particle entering the considered system is analyzed. For the first time the phenomenon of effective potential inversion (or “relativistic reversal” is described for arbitrary lasers crossing angle. Threshold electron velocity values for the phenomenon are introduced and its extended illustration based on numerical simulations for two laser beams polarizations is presented. In addition the projectile radiation spectral distribution is given and general estimations on the expected beam radiation yield are outlined.

Laser Cutting of Different Materials

Directory of Open Access Journals (Sweden)

Kadir ÇAVDAR

2013-08-01

Full Text Available In this paper; in general potential developments and trends of a particular machining field by extensively evaluating present studies of laser beam machining have been discussed. As it is indicated below, technical literatures have been subsumed under five major headlines: Experimental studies, reviews, optimization researches of the cutting parameters, theoretical modelling studies of laser beam cutting and academic studies relating to laser cutting

Application of optical action potentials in human induced pluripotent stem cells-derived cardiomyocytes to predict drug-induced cardiac arrhythmias.

Science.gov (United States)

Lu, H R; Hortigon-Vinagre, M P; Zamora, V; Kopljar, I; De Bondt, A; Gallacher, D J; Smith, G

2017-09-01

Human induced pluripotent stem cell-derived cardiomyocytes (hiPS-CMs) are emerging as new and human-relevant source in vitro model for cardiac safety assessment that allow us to investigate a set of 20 reference drugs for predicting cardiac arrhythmogenic liability using optical action potential (oAP) assay. Here, we describe our examination of the oAP measurement using a voltage sensitive dye (Di-4-ANEPPS) to predict adverse compound effects using hiPS-CMs and 20 cardioactive reference compounds. Fluorescence signals were digitized at 10kHz and the records subsequently analyzed off-line. Cells were exposed to 30min incubation to vehicle or compound (n=5/dose, 4 doses/compound) that were blinded to the investigating laboratory. Action potential parameters were measured, including rise time (T rise ) of the optical action potential duration (oAPD). Significant effects on oAPD were sensitively detected with 11 QT-prolonging drugs, while oAPD shortening was observed with I Ca -antagonists, I Kr -activator or ATP-sensitive K + channel (K ATP )-opener. Additionally, the assay detected varied effects induced by 6 different sodium channel blockers. The detection threshold for these drug effects was at or below the published values of free effective therapeutic plasma levels or effective concentrations by other studies. The results of this blinded study indicate that OAP is a sensitive method to accurately detect drug-induced effects (i.e., duration/QT-prolongation, shortening, beat rate, and incidence of early after depolarizations) in hiPS-CMs; therefore, this technique will potentially be useful in predicting drug-induced arrhythmogenic liabilities in early de-risking within the drug discovery phase. Copyright © 2017 Elsevier Inc. All rights reserved.

New infrared solid state laser materials for CALIOPE

International Nuclear Information System (INIS)

DeLoach, L.D.; Page, R.H.; Wilke, G.D.

1994-01-01

Tunable infrared laser light may serve as a useful means by which to detect the presence of the targeted effluents. Since optical parametric oscillators (OPOs) have proven to be a versatile method of generating coherent light from the ultraviolet to the mid-infrared, this technology is a promising choice by which to service the CALIOPE applications. In addition, since some uncertainty remains regarding the precise wavelengths and molecules that will be targeted, the deployment of OPOs retains the greatest amount of wavelength flexibility. Another approach that the authors are considering is that of generating tunable infrared radiation directly with a diode-pumped solid state laser (DPSSL). One important advantage of a DPSSL is that it offers flexible pulse format modes that can be tailored to meet the needs of a particular application and target molecule. On the other hand, direct generation by a tunable DPSSL will generally be able to cover a more limited wavelength range than is possible with OPO technology. In support of the CALIOPE objectives the authors are exploring the potential for laser action among a class of materials comprised of transition metal-doped zinc chalcogenide crystals (i.e., ZnS, ZnSe and ZnTe). The Cr 2+ , Co 2+ and Ni 2+ dopants were selected as the most favorable candidates, on the basis of their documented spectral properties in the scientific literature. Thus far, the authors have characterized the absorption and emission properties of these ions in the ZnS and ZnSe crystals. The absorption spectra are used to determine the preferred wavelength at which the crystal should be pumped, while the emission spectra reveal the extent of the tuning range potentially offered by the material. In addition, measurements of the emission lifetime as a function of temperature turn out to be quite useful, since this data is suggestive of the room temperature emission yield

Femtosecond Laser Filamentation

CERN Document Server

Chin, See Leang

2010-01-01

Femtosecond Laser Filamentation gives a comprehensive review of the physics of propagation of intense femtosecond laser pulses in optical media (principally air) and the applications and challenges of this new technique. This book presents the modern understanding of the physics of femtosecond laser pulse propagation, including unusual new effects such as the self-transformation of the pulse into a white light laser pulse, intensity clamping, the physics of multiple filamentation and competition, and how filaments’ ability to melt glass leads to wave guide writing. The potential applications of laser filamentation in atmospheric sensing and the generation of other electromagnetic pulses from the UV to the radio frequency are treated, together with possible future challenges in the excitation of super-excited states of molecules. Exciting new phenomena such as filament induced ultrafast birefringence and the excitation of molecular rotational wave packets and their multiple revivals in air (gases) will also ...

Applications of laser-driven particle acceleration

CERN Document Server

Parodi, Katia; Schreiber, Jorg

2018-01-01

The first book of its kind to highlight the unique capabilities of laser-driven acceleration and its diverse potential, Applications of Laser-Driven Particle Acceleration presents the basic understanding of acceleration concepts and envisioned prospects for selected applications. As the main focus, this new book explores exciting and diverse application possibilities, with emphasis on those uniquely enabled by the laser driver that can also be meaningful and realistic for potential users. A key aim of the book is to inform multiple, interdisciplinary research communities of the new possibilities available and to inspire them to engage with laser-driven acceleration, further motivating and advancing this developing field. Material is presented in a thorough yet accessible manner, making it a valuable reference text for general scientific and engineering researchers who are not necessarily subject matter experts. Applications of Laser-Driven Particle Acceleration is edited by Professors Paul R. Bolton, Katia ...

Optofluidic third order distributed feedback dye laser

DEFF Research Database (Denmark)

Gersborg-Hansen, Morten; Kristensen, Anders

2006-01-01

which has a refractive index lower than that of the polymer. In combination with a third order DFB grating, formed by the array of nanofluidic channels, this yields a low threshold for lasing. The laser is straightforward to integrate on lab-on-a-chip microsystems where coherent, tunable light......This letter describes the design and operation of a polymer-based third order distributed feedback (DFB) microfluidic dye laser. The device relies on light confinement in a nanostructured polymer film where an array of nanofluidic channels is filled by capillary action with a liquid dye solution...

Advances in solid state laser technology for space and medical applications

Science.gov (United States)

Byvik, C. E.; Buoncristiani, A. M.

1988-01-01

Recent developments in laser technology and their potential for medical applications are discussed. Gas discharge lasers, dye lasers, excimer lasers, Nd:YAG lasers, HF and DF lasers, and other commonly used lasers are briefly addressed. Emerging laser technology is examined, including diode-pumped lasers and other solid state lasers.

Recent advances in laser-driven neutron sources

Science.gov (United States)

Alejo, A.; Ahmed, H.; Green, A.; Mirfayzi, S. R.; Borghesi, M.; Kar, S.

2016-11-01

Due to the limited number and high cost of large-scale neutron facilities, there has been a growing interest in compact accelerator-driven sources. In this context, several potential schemes of laser-driven neutron sources are being intensively studied employing laser-accelerated electron and ion beams. In addition to the potential of delivering neutron beams with high brilliance, directionality and ultra-short burst duration, a laser-driven neutron source would offer further advantages in terms of cost-effectiveness, compactness and radiation confinement by closed-coupled experiments. Some of the recent advances in this field are discussed, showing improvements in the directionality and flux of the laser-driven neutron beams.

Laser puncture therapy of nervous system disorders

Energy Technology Data Exchange (ETDEWEB)

Anishchenko, G.; Kochetkov, V.

1984-08-29

The authors discuss experience with treatment of nervous system disorders by means of laser-puncture therapy. Commenting on the background of the selection of this type of treatment, they explain that once researchers determined the biological action of laser light on specific nerve receptors of the skin, development of laser apparatus capable of concentrating the beam in the millimeter band was undertaken. The devices that are being used for laser-puncture are said to operate in the red helium-neon band of light. The authors identify beam parameters that have been selected for different groups of acupuncture points of the skin, and the courses of treatment (in seconds of radiation) and their time intervals. They go on to discuss the results of treatment of over 800 patients categorized in a group with disorders of the peripheral nervous system and a second group with disorders of the central nervous system.

[Hardware Implementation of Numerical Simulation Function of Hodgkin-Huxley Model Neurons Action Potential Based on Field Programmable Gate Array].

Science.gov (United States)

Wang, Jinlong; Lu, Mai; Hu, Yanwen; Chen, Xiaoqiang; Pan, Qiangqiang

2015-12-01

Neuron is the basic unit of the biological neural system. The Hodgkin-Huxley (HH) model is one of the most realistic neuron models on the electrophysiological characteristic description of neuron. Hardware implementation of neuron could provide new research ideas to clinical treatment of spinal cord injury, bionics and artificial intelligence. Based on the HH model neuron and the DSP Builder technology, in the present study, a single HH model neuron hardware implementation was completed in Field Programmable Gate Array (FPGA). The neuron implemented in FPGA was stimulated by different types of current, the action potential response characteristics were analyzed, and the correlation coefficient between numerical simulation result and hardware implementation result were calculated. The results showed that neuronal action potential response of FPGA was highly consistent with numerical simulation result. This work lays the foundation for hardware implementation of neural network.

Efficient laser-diode end-pumped Nd:GGG lasers at 1054 and 1067 nm.

Science.gov (United States)

Xu, Bin; Xu, Huiying; Cai, Zhiping; Camy, P; Doualan, J L; Moncorgé, R

2014-10-10

Efficient and compact laser-diode end-pumped Nd:GGG simultaneous multiwavelength continuous-wave lasers at ∼1059, ∼1060 and ∼1062  nm were first demonstrated in a free-running 30 mm plano-concave laser cavity. The maximum output power was up to 3.92 W with a slope efficiency of about 53.6% with respect to the absorbed pump power. By inserting a 0.1 mm optical glass plate acting as a Fabry-Pérot etalon, a single-wavelength laser at ∼1067  nm with a maximum output power of 1.95 W and a slope efficiency of 28.5% can be obtained. Multiwavelength lasers, including those at ∼1054 or ∼1067  nm, were also achievable by suitably tilting the glass etalon. These simultaneous multiwavelength lasers provide a potential source for terahertz wave generation.

Excitation mechanisms for XUV and X-ray lasers

International Nuclear Information System (INIS)

El-Sherbini, T.M.; Arrubban, M.M.

1992-01-01

Two excitation mechanisms leading to lasing action in the extreme ultraviolet and soft X-ray spectral regions are proposed. Boron- like ions of Mg VIII, Al IX and Si X plasmas are used as the active laser material. The upper laser level is the metastable 1s 2 2s 2 4p( 2 p) state while the lower level is the short lived 1s 2 2s 2 3d( 2 D) state. (author). 10 refs, 1 fig., 3 tabs

Bone ingrowth potential of electron beam and selective laser melting produced trabecular-like implant surfaces with and without a biomimetic coating

NARCIS (Netherlands)

Biemond, J.E.; Hannink, G.; Verdonschot, Nicolaas Jacobus Joseph; Buma, P.

2013-01-01

The bone ingrowth potential of trabecular-like implant surfaces produced by either selective laser melting (SLM) or electron beam melting (EBM), with or without a biomimetic calciumphosphate coating, was examined in goats. For histological analysis and histomorphometry of bone ingrowth depth and

Biophysical foundations for the study of the electrical excitability and action potential propagation in myocardium

International Nuclear Information System (INIS)

Suarez Antola, R.

1991-01-01

The electric current flow in the heterogeneous and anysotropic volume conductor of the myocardium is studied. The equations of bidomain theory are derived using an approach framed in the theory of averaged fields, introducing microscopic, mesoscopic and macroscopic spatial scales. However, the procedure, compatible with the histological and the anatomical details of the organ, is different from the multiple scale asymptotic expansions usually applied in homogeneization problems. A probabilistic approach framed in large numbers theorems is used to derive the equation for membrane ionic current from the stochastic activity of the channels at the microscopic level. An operational procedure suitable to define a sharp bidomain boundary from the fuzzy distribution of structural details and physical properties at the histological level is given. The problem of threshold is studied. The sizes and shapes of critical masses of cardiac cells that must be depolarized above threshold in order to produce a propagated action potential are determined by an approximate analytical procedure. The concept of family of threshold patterns for the emergence of action potentials in the heart is introduced. This concept is applied to discuss the conditions of emergence of ectopic focus. Analytical formulae are derived, for the time constant and the rheobase for electrical stimulation of the myocardium. These formulae are in good agreement with known experimental results. New experiments that could be done to confirm or reject them are suggested

Acute effects of ethanol on action potential and intracellular Ca2+ transient in cardiac ventricular cells: a simulation study

Czech Academy of Sciences Publication Activity Database

Pásek, Michal; Bébarová, M.; Christé, G.; Šimurdová, M.; Šimurda, J.

2016-01-01

Roč. 54, č. 5 (2016), s. 753-762 ISSN 0140-0118 Institutional support: RVO:61388998 Keywords : ethanol * cardiomyocyte * action potential * rat ventricular cell model * human ventricular cell model Subject RIV: BO - Biophysics Impact factor: 1.916, year: 2016

The Belem Framework for Action: Harnessing the Power and Potential of Adult Learning and Education for a Viable Future

Science.gov (United States)

Adult Learning, 2012

2012-01-01

This article presents the Belem Framework for Action. This framework focuses on harnessing the power and potential of adult learning and education for a viable future. This framework begins with a preamble on adult education and towards lifelong learning.

Ultraviolet-laser ablation of skin

Energy Technology Data Exchange (ETDEWEB)

Lane, R.J.; Linsker, R.; Wynne, J.J.; Torres, A.; Geronemus, R.G.

1985-05-01

The authors report on the use of pulsed ultraviolet-laser irradiation at 193 nm from an argon-fluoride laser and at 248 nm from a krypton-fluoride laser to ablate skin. In vitro, both wavelengths performed comparably, removing tissue precisely and cleanly, and leaving minimal thermal damage to the surrounding tissue. In vivo, the 193-nm laser radiation failed to remove tissue after bleeding began. The 248-nm radiation, however, continued to remove tissue despite bleeding and left a clean incision with only minimal thermal damage. The krypton-fluoride excimer laser beam at 248 nm, which should be deliverable through a quartz optical fiber, has great potential as a surgical instrument.