The role of processes with a high threshold energy in the physics of the upper atmospheres of the planets

2005 ◽  
Vol 72 (8) ◽  
pp. 602 ◽  
Author(s):  
S. V. Avakyan
Keyword(s):  
Threshold Energy ◽  
High Threshold

scholarly journals Electrophysiological Properties of Inferior Olive Neurons: A Compartmental Model

1999 ◽  
Vol 82 (2) ◽  
pp. 804-817 ◽  
Author(s):  
Nicolas Schweighofer ◽  
Kenji Doya ◽  
Mitsuo Kawato
Keyword(s):  
Calcium Current ◽  
Potassium Current ◽  
Inferior Olive ◽  
Sodium Current ◽  
Electrical Coupling ◽  
Biophysical Model ◽  
Delayed Rectifier ◽  
High Threshold ◽  
Electrophysiological Properties

As a step in exploring the functions of the inferior olive, we constructed a biophysical model of the olivary neurons to examine their unique electrophysiological properties. The model consists of two compartments to represent the known distribution of ionic currents across the cell membrane, as well as the dendritic location of the gap junctions and synaptic inputs. The somatic compartment includes a low-threshold calcium current ( I Ca_l), an anomalous inward rectifier current ( I h), a sodium current ( I Na), and a delayed rectifier potassium current ( I K_dr). The dendritic compartment contains a high-threshold calcium current ( I Ca_h), a calcium-dependent potassium current ( I K_Ca), and a current flowing into other cells through electrical coupling ( I c). First, kinetic parameters for these currents were set according to previously reported experimental data. Next, the remaining free parameters were determined to account for both static and spiking properties of single olivary neurons in vitro. We then performed a series of simulated pharmacological experiments using bifurcation analysis and extensive two-parameter searches. Consistent with previous studies, we quantitatively demonstrated the major role of I Ca_l in spiking excitability. In addition, I h had an important modulatory role in the spike generation and period of oscillations, as previously suggested by Bal and McCormick. Finally, we investigated the role of electrical coupling in two coupled spiking cells. Depending on the coupling strength, the hyperpolarization level, and the I Ca_l and I hmodulation, the coupled cells had four different synchronization modes: the cells could be in-phase, phase-shifted, or anti-phase or could exhibit a complex desynchronized spiking mode. Hence these simulation results support the counterintuitive hypothesis that electrical coupling can desynchronize coupled inferior olive cells.

Comparison of Responses of Primate Spinothalamic Tract Neurons to Pruritic and Algogenic Stimuli

2004 ◽  
Vol 91 (1) ◽  
pp. 213-222 ◽  
Author(s):  
Donald A. Simone ◽  
Xijing Zhang ◽  
Jun Li ◽  
Jun-Ming Zhang ◽  
Christopher N. Honda ◽  
...  
Keyword(s):  
Dynamic Range ◽  
Intradermal Injection ◽  
High Threshold ◽  
Mechanical Stimuli ◽  
Spinothalamic Tract ◽  
Wide Dynamic Range ◽  
Antidromic Activation ◽  
Lateral Nucleus ◽  
Maximal Time

We investigated the role of mechanosensitive spinothalamic tract (STT) neurons in mediating 1) the itch evoked by intradermal injection of histamine, 2) the enhanced sense of itch evoked by innocuous stroking (alloknesis), and 3) the enhanced pain evoked by punctate stimulation (hyperalgesia) of the skin surrounding the injection site. Responses to intradermal injections of histamine and capsaicin were compared in STT neurons recorded in either the superficial or the deep dorsal horn of the anesthetized monkey. Each neuron was identified by antidromic activation from the ventral posterior lateral nucleus of thalamus and classified by its initial responses to mechanical stimuli as wide dynamic range (WDR) or high-threshold (HT). Approximately half of the WDRs and one of the HTs responded weakly to histamine, some with a duration > 5 min, the maximal time allotted. WDRs but not HTs exhibited a significant increase in response to punctate stimulation after histamine consistent with their possible role in mediating histamine-induced hyperalgesia. Neither type of neuron exhibited significant changes in response to stroking, consistent with their unlikely role in mediating alloknesis. Furthermore, nearly all STT neurons exhibited vigorous and persistent responses to capsaicin, after which they became sensitized to stroking and to punctate stimulation. We conclude that the STT neurons in our sample are more likely to contribute to pain, allodynia, and hyperalgesia than to itch and alloknesis.

Plasma/Corona Treatment of Silicones

2005 ◽  
Vol 58 (6) ◽  
pp. 433 ◽  
Author(s):  
Michael J. Owen
Keyword(s):  
Threshold Energy ◽  
Low Molecular Weight ◽  
Atmospheric Pressure Glow Discharge ◽  
Pressure Glow Discharge ◽  
Plasma Corona ◽  
Hydrophobic Recovery ◽  
Fresh Insight ◽  
Corona Treatment

There is considerable current interest in plasma and corona treatment of silicones. It is well established that a thin, silica-like layer is created on the surface by such treatments. Much fresh insight has emerged concerning the role of low-molecular-weight materials in the hydrophobic recovery of treated elastomers. Even if these diffusible species are removed before treatment, hydrophobic recovery still occurs above a threshold energy implying that they are produced in situ by the treatment. A particularly significant new direction in the plasma treatment field is plasma polymerization of organosilicon monomers using atmospheric pressure glow discharge (APGD).

The role of high-threshold calcium channels in spinal neuron hyperexcitability induced by knee inflammation

2000 ◽  
pp. 173-190 ◽  
Author(s):  
Hans-Georg Schaible ◽  
Johannes Nebe ◽  
Volker Neugebauer ◽  
Andrea Ebersberger ◽  
Horacio Vanegas
Keyword(s):  
Calcium Channels ◽  
Spinal Neuron ◽  
High Threshold

scholarly journals Anoctamin 2-chloride channels reduce simple spike activity and mediate inhibition at elevated calcium concentration in cerebellar Purkinje cells

PLoS ONE ◽  
2021 ◽  
Vol 16 (3) ◽  
pp. e0247801
Author(s):  
Friederike Auer ◽  
Eliana Franco Taveras ◽  
Uli Klein ◽  
Céline Kesenheimer ◽  
Dana Fleischhauer ◽  
...  
Keyword(s):  
Purkinje Cells ◽  
Spike Activity ◽  
Chloride Channels ◽  
Cell Activity ◽  
High Threshold ◽  
Chloride Currents ◽  
Simple Spike ◽  
Cerebellar Purkinje Cells ◽  
Inferior Olivary

Modulation of neuronal excitability is a prominent way of shaping the activity of neuronal networks. Recent studies highlight the role of calcium-activated chloride currents in this context, as they can both increase or decrease excitability. The calcium-activated chloride channel Anoctamin 2 (ANO2 alias TMEM16B) has been described in several regions of the mouse brain, including the olivo-cerebellar system. In inferior olivary neurons, ANO2 was proposed to increase excitability by facilitating the generation of high-threshold calcium spikes. An expression of ANO2 in cerebellar Purkinje cells was suggested, but its role in these neurons remains unclear. In the present study, we confirmed the expression of Ano2 mRNA in Purkinje cells and performed electrophysiological recordings to examine the influence of ANO2-chloride channels on the excitability of Purkinje cells by comparing wildtype mice to mice lacking ANO2. Recordings were performed in acute cerebellar slices of adult mice, which provided the possibility to study the role of ANO2 within the cerebellar cortex. Purkinje cells were uncoupled from climbing fiber input to assess specifically the effect of ANO2 channels on Purkinje cell activity. We identified an attenuating effect of ANO2-mediated chloride currents on the instantaneous simple spike activity both during strong current injections and during current injections close to the simple spike threshold. Moreover, we report a reduction of inhibitory currents from GABAergic interneurons upon depolarization, lasting for several seconds. Together with the role of ANO2-chloride channels in inferior olivary neurons, our data extend the evidence for a role of chloride-dependent modulation in the olivo-cerebellar system that might be important for proper cerebellum-dependent motor coordination and learning.

scholarly journals The role of annealing in determining the yielding behavior of glasses under cyclic shear deformation

2021 ◽  
Vol 118 (16) ◽  
pp. e2100227118
Author(s):  
Himangsu Bhaumik ◽  
Giuseppe Foffi ◽  
Srikanth Sastry
Keyword(s):  
Shear Deformation ◽  
Strain Amplitude ◽  
Threshold Energy ◽  
Cyclic Shear ◽  
Annealing Regime ◽  
Uniform Shear ◽  
High Annealing ◽  
Wide Range ◽  
Yielding Behavior

Yielding behavior in amorphous solids has been investigated in computer simulations using uniform and cyclic shear deformation. Recent results characterize yielding as a discontinuous transition, with the degree of annealing of glasses being a significant parameter. Under uniform shear, discontinuous changes in stresses at yielding occur in the high annealing regime, separated from the poor annealing regime in which yielding is gradual. In cyclic shear simulations, relatively poorly annealed glasses become progressively better annealed as the yielding point is approached, with a relatively modest but clear discontinuous change at yielding. To understand better the role of annealing on yielding characteristics, we perform athermal quasistatic cyclic shear simulations of glasses prepared with a wide range of annealing in two qualitatively different systems—a model of silica (a network glass) and an atomic binary mixture glass. Two strikingly different regimes of behavior emerge. Energies of poorly annealed samples evolve toward a unique threshold energy as the strain amplitude increases, before yielding takes place. Well-annealed samples, in contrast, show no significant energy change with strain amplitude until they yield, accompanied by discontinuous energy changes that increase with the degree of annealing. Significantly, the threshold energy for both systems corresponds to dynamical cross-over temperatures associated with changes in the character of the energy landscape sampled by glass-forming liquids.

scholarly journals Ion-Enhanced Etching Characteristics of sp2-Rich Hydrogenated Amorphous Carbons in CF4 Plasmas and O2 Plasmas

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2941
Author(s):  
Jie Li ◽  
Yongjae Kim ◽  
Seunghun Han ◽  
Heeyeop Chae
Keyword(s):  
Etch Rate ◽  
Semiconductor Device ◽  
Threshold Energy ◽  
Device Fabrication ◽  
High Threshold ◽  
Ion Density ◽  
Bias Power ◽  
Ion Energy ◽  
Etch Rates ◽  
Hydrogenated Amorphous

The sp2-rich hydrogenated amorphous carbon (a-C:H) is widely adopted as hard masks in semiconductor-device fabrication processes. The ion-enhanced etch characteristics of sp2-rich a-C:H films on ion density and ion energy were investigated in CF4 plasmas and O2 plasmas in this work. The etch rate of sp2-rich a-C:H films in O2 plasmas increased linearly with ion density when no bias power was applied, while the fluorocarbon deposition was observed in CF4 plasmas instead of etching without bias power. The etch rate was found to be dependent on the half-order curve of ion energy in both CF4 plasmas and O2 plasmas when bias power was applied. An ion-enhanced etching model was suggested to fit the etch rates of a-C:H in CF4 plasmas and O2 plasmas. Then, the etch yield and the threshold energy for etching were determined based on this model from experimental etch rates in CF4 plasma and O2 plasma. The etch yield of 3.45 was observed in CF4 plasmas, while 12.3 was obtained in O2 plasmas, owing to the high reactivity of O radicals with carbon atoms. The threshold energy of 12 eV for a-C:H etching was obtained in O2 plasmas, while the high threshold energy of 156 eV was observed in CF4 plasmas. This high threshold energy is attributed to the formation of a fluorocarbon layer that protects the a-C:H films from ion-enhanced etching.

scholarly journals Role of Intrinsic Properties in Drosophila Motoneuron Recruitment During Fictive Crawling

2010 ◽  
Vol 104 (3) ◽  
pp. 1257-1266 ◽  
Author(s):  
Jennifer E. Schaefer ◽  
Jason W. Worrell ◽  
Richard B. Levine
Keyword(s):  
Resting Membrane Potential ◽  
High Threshold ◽  
Intrinsic Properties ◽  
Whole Cell ◽  
Whole Cell Patch Clamp ◽  
Drosophila Larvae ◽  
Low Threshold ◽  
Evoked Activity

Motoneurons in most organisms conserve a division into low-threshold and high-threshold types that are responsible for generating powerful and precise movements. Drosophila 1b and 1s motoneurons may be analogous to low-threshold and high-threshold neurons, respectively, based on data obtained at the neuromuscular junction, although there is little information available on intrinsic properties or recruitment during behavior. Therefore in situ whole cell patch-clamp recordings were used to compare parameters of 1b and 1s motoneurons in Drosophila larvae. We find that resting membrane potential, voltage threshold, and delay-to-spike distinguish 1b from 1s motoneurons. The longer delay-to-spike in 1s motoneurons is a result of the shal-encoded A-type K+ current. Functional differences between 1b and 1s motoneurons are behaviorally relevant because a higher threshold and longer delay-to-spike are observed in MNISN-1s in pairwise whole cell recordings of synaptically evoked activity during bouts of fictive locomotion.

Muscarinic modulation of voltage-dependent Ca2+ channels in insulin-secreting HIT-T15 cells

1998 ◽  
Vol 274 (2) ◽  
pp. G397-G405 ◽  
Author(s):  
Jeffrey A. Love ◽  
Neil W. Richards ◽  
Chung Owyang ◽  
David C. Dawson
Keyword(s):  
High Threshold ◽  
Muscarinic Agonist ◽  
Kinase C ◽  
Open Time ◽  
Voltage Dependent ◽  
The Mean ◽  
Mean Current ◽  
Muscarinic Modulation ◽  
Ca2 Channels

Potentiation of insulin secretion from pancreatic β-cells by acetylcholine requires ongoing cyclic electrical activity initiated by other depolarizing secretagogues. Patch-clamp recordings in glucose-free solutions were made from the clonal β-cell line HIT-T15 to determine whether the muscarinic agonist bethanechol (BCh) modulated voltage-dependent Ca2+ channels independent of effects on membrane potential. Only high-threshold, dihydropyridine-sensitive (L-type) Ca2+ channels with a mean conductance of 26 pS were observed in cell-attached patches. BCh (100 μM) caused a two- to threefold increase in both fractional open time and mean current of single Ca2+channels. These changes resulted from a 44% decrease in the longer of two apparent mean closed times and a 25% increase in the mean open time. Similar BCh-stimulated increases in macroscopic Ca2+ currents were recorded in whole cell, perforated-patch recordings. The role of protein kinase C (PKC) in the muscarinic activation of Ca2+ channels was tested using a variety of PKC activators and inhibitors. Acute application of either the active phorbol ester phorbol 12-myristate 13-acetate (PMA) or the membrane-permeable diacylglycerol analog 1,2-didecanoyl- rac-glycerol mimicked the effects of BCh, whereas an inactive phorbol (4α) had no effect. Depletion of PKC activity by chronic exposure to PMA or acute application of the PKC inhibitor staurosporine greatly reduced or abolished muscarinic activation of Ca2+ channels. These results are consistent with muscarinic activation of L-type, voltage-dependent Ca2+ channels mediated in large part by PKC.

Sign in / Sign up

Export Citation Format

Share Document