Transient Potential Research Articles

Role of quantum fluctuations in a system with strong fields: Spectral properties and thermalization

In a previous work [arXiv:1009.4363], we have studied the evolution of a scalar field with a quartic coupling, driven by a classical source that initializes it to a non-perturbatively large value. At leading order in the coupling, the evolution of this system is given by classical solutions of the field equation of motion. However, this system is subject to a parametric resonance that leads to secular divergences in higher order corrections to physical observables. We have proposed a scheme that resums all the leading secular terms: this resummation leads to finite results at all times, and we have observed also that it makes the pressure tensor of the system relax to its equilibrium value. In the present paper, we continue the study of this system by looking at finer details of its dynamics. We first compute its spectral function at various stages of the evolution, and we observe that after a fairly short transient time there are well defined massive quasi-particles. We then consider the time evolution of the momentum distribution of these quasi-particles, and we show that after a stage dominated by the parametric resonance, this distribution slowly evolves to an equilibrium distribution. Interestingly, this distribution develops a transient chemical potential, signalling the fact that number changing processes are much slower than the elastic ones.

Enhancement of the accuracy of the Green element method: Application to potential problems

The 2-D formulation of the Green element method (GEM) which approximates the internal normal directional fluxes by difference expressions in terms of the field variable had been recognized to be fraught with errors that comprise its accuracy. However, this approach is computational attractive because there is only one degree of freedom at every node, the system matrix is slender, and it does require additional compatibility relationships. There have been attempts to reduce the numerical errors of this original GEM formulation by the use of flux-based formulations which essentially retain the internal fluxes but at the expense of those attractive numerical features. Here the original GEM is revisited and shown that, with difference approximation of the internal normal fluxes whose error is of the order of the square of the size of the element, its accuracy is greatly enhanced to a level comparable to the flux-based formulations. This approach is demonstrated on regular domains with rectangular elements and irregular domains with triangular elements using six examples that cover steady, transient, linear and nonlinear potential flow and heat transfer problems in homogeneous and heterogeneous media.

Effect of ramipril on the cardiac fibrosis in the left ventricle of spontaneously hypertensive rats through intervening the expression of TRPC3

Objective: To investigate the effect of ramipril on the expression of TRPC3 (canonical transient potential receptor channel 3) in the overload induced cardiac fibrosis in the left ventricle of spontaneously hypertensive rats (SHR). Methods: 12-week-old SHRs were divided into two groups: the placebo group (SHRs) and the ramipril group (Ram-SHR), the same aged Wistar Kyoto rats (WKYs) were used as control group (WKY). Four weeks after drug intervention, the left ventricle mass index (LVMI), the cardiac collagen volume fraction (CVF) and the expression of TRPC3 mRNA and protein were detected.

Characterization of capsaicin induced responses in mice vas deferens: Evidence of CGRP uptake

Calcitonin gene-related peptide (CGRP) is extensively distributed in primary afferent sensory nerves, including those innervating the genitourinary tract. Capsaicin can stimulate the release of CGRP from intracellular stores of these nerves, but this phenomenon has not been investigated in-depth in isolated preparations. The present study sets out to study and characterize the capsaicin as well as CGRP-induced responses in isolated mouse vas deferens. The effects of capsaicin and CGRP family of peptides were studied on electrically-induced twitch responses in the absence or presence of transient receptor potential cation channel vanilloid subfamily member 1 (TRPV1) antagonist and CGRP receptor antagonists. Twitch responses were attenuated by capsaicin (1 nM–30 nM) and CGRP family of peptides. The potency order was CGRP > intermedin-long (IMDL) ~ [Cys(Et) 2,7]αCGRP ~ adrenomedullin (AM) > [Cys(ACM) 2,7]αCGRP > amylin (AMY). These responses were disinhibited by the CGRP receptor antagonists and TRPV1 antagonists. The addition of CGRP receptor antagonists caused a transient potentiation of the twitch response and this potentiation was blocked by pretreatment with capsaicin and enhanced by incubation with exogenous CGRP. During the second consecutive cumulative concentration-response curve with capsaicin, the first phase of concentration-response curve disappeared and this was partially restored when the mouse vas deferens was preincubated with CGRP, suggesting the uptake of exogenous CGRP by nerves. Besides showing capsaicin-induced CGRP releases this study shows that exogenous CGRP can be taken up in vas deferens and can be re-released. CGRP uptake will add another dimension in understanding the homeostasis of this neuropeptide.

Countable Markov shifts with transient potentials

We define a simple property on an infinite directed graph 𝒢 and show that it is necessary and sufficient for the existence of a transient potential on the associated countable Markov shift.

The Ontogeny of Cardiac Regeneration

### Transient Regenerative Potential of the Neonatal Mouse Heart Porello et al Science . 2011;331:1078–1080 The regenerative capacity of adult human hearts after infarction seems vestigial at best, perhaps because of the poor proliferative capacity of terminally differentiated cardiomyocytes and desecration of the local environment that would otherwise be conducive of stem cell-mediated repair or loss of stem cells, or both. In a recent edition of the journal Science , Porello et al set a new benchmark in this field by showing that the hearts of neonatal mice have, in contrast, an impressive regenerative capacity after surgical resection, albeit one that is lost almost immediately as cardiomyocytes exit the cell cycle and mature. In a technical tour de force, Porello et al1 report that day 1 neonatal mice subjected to resection of the apex of the left ventricle (amounting to ∼15% of the ventricular myocardium) not only survive but also show complete regeneration of the myocardium and restoration of cardiac function. Furthermore, they provide evidence that the predominant mechanism involved is not differentiation of stem cells, but transient dedifferentiation and proliferation of cardiomyocytes in both the border and remote zones of the heart. In contrast, resection of a lesser amount of apical myocardium in day 7 neonates, at a time after terminal differentiation of cardiomyocytes has already taken place, resulted in markedly increased mortality and failure of myocardial regeneration, with wound repair by scar formation only. It has long been known that in adult mammals, the heart is one of the least regenerative organs in the body. As a result, repair after massive tissue injury, as occurs with myocardial infarction, is limited to replacement of the myocardium by dense collagenous scar tissue. This impairs contractile function, resulting in adverse remodelling and, in severe cases, ventricular dilation, heart failure, and death. To explore if intracardiac …

C-fibers, but not the transient potential receptor vanilloid 1 (TRPV1), play a role in experimental allergic airway inflammation

The activation of C-fibers in the airways induces coughing, mucus production and bronchoconstriction, which are also symptoms of airway diseases. In this study, we evaluated the role of the C-fibers and the TRPV1 (transient receptor potential vanilloid 1) receptor in an experimental mouse model of allergic airway inflammation. To study the role of C-fibers, we either degenerated the C-fibers persistently (capsaicin administration in neonate mice) or transiently (capsaicin administration in adult mice). No alteration was observed in eosinophil recruitment to the bronchoalveolar lavage fluid in animals treated with capsaicin in the neonatal period. However, in adult animals, capsaicin treatment after the first ovalbumin challenge (in the establishment of the inflammatory process) decreased the eosinophil numbers. This effect was more pronounced in adult animals treated with capsaicin before beginning the ovalbumin immunization (in the development of the inflammatory process). In addition, interleukin (IL)-5 and chemokine ligand 11 (CCL11) levels in the bronchoalveolar lavage fluid, as well as P-selectin expression and p65 nuclear factor κB (NF-κB) activation in the lung were also decreased. No alterations were observed in the IL-10 and IL-13 levels. Next we determined the effect of TRPV1 receptor blockade on allergic airway inflammation. SB366791 administrated in mice by intraperitoneal (500μg/kg) or intranasal (0.1, 1 or 10nmol/site) route failed to decrease eosinophil recruitment to the bronchoalveolar lavage fluid or alter any other metrics cited above. Thus, the present results confirm and extend previous data supporting the involvement of C-fibers, but not the TRPV1 receptor, in allergic airway inflammation.

TRPM2: a multifunctional ion channel for calcium signalling

The transient potential receptor melastatin-2 (TRPM2) channel has emerged as an important Ca(2+) signalling mechanism in a variety of cells, contributing to cellular functions that include cytokine production, insulin release, cell motility and cell death. Its ability to respond to reactive oxygen species has made TRPM2 a potential therapeutic target for chronic inflammation, neurodegenerative diseases, and oxidative stress-related pathologies. TRPM2 is a non-selective, calcium (Ca(2+))-permeable cation channel of the melastatin-related transient receptor potential (TRPM) ion channel subfamily. It is activated by intracellular adenosine diphosphate ribose (ADPR) through a diphosphoribose hydrolase domain in its C-terminus and regulated through a variety of factors, including synergistic facilitation by [Ca(2+)](i), cyclic ADPR, H(2)O(2), NAADP, and negative feedback regulation by AMP and permeating protons (pH). In addition to its role mediating Ca(2+) influx into the cells, TRPM2 can also function as a lysosomal Ca(2+) release channel, contributing to cell death. The physiological and pathophysiological context of ROS-mediated events makes TRPM2 a promising target for the development of therapeutic tools of inflammatory and degenerative diseases.

Adhesion Hysteresis from Interdependent Capillary and Electrostatic Forces

Adhesion hysteresis commonly occurs at the nanoscale in humid atmospheres, yet mechanisms are not entirely understood. Here, the adhesion forces between silicon (111) oxide surfaces and tungsten oxide probes have been examined using interfacial force microscopy. The results show that the adhesion forces during surface approach and separation differ not only in magnitude but also in mechanism, arising mainly from capillary and electrostatic forces, respectively. Surface contact leads to a transient intersurface potential on dewetting. This mechanism of adhesion hysteresis differs in not relying singly on hysteretic wetting. Furthermore, by biasing the surfaces, nonadditivity is demonstrated between the capillary and electrostatic forces at the onset of condensation. These results hold important implications on the interpretation of force in nanoprobe geometries in humid atmospheres.

Transient regenerative potential of the neonatal mouse heart.

Certain fish and amphibians retain a robust capacity for cardiac regeneration throughout life, but the same is not true of the adult mammalian heart. Whether the capacity for cardiac regeneration is absent in mammals or whether it exists and is switched off early after birth has been unclear. We found that the hearts of 1-day-old neonatal mice can regenerate after partial surgical resection, but this capacity is lost by 7 days of age. This regenerative response in 1-day-old mice was characterized by cardiomyocyte proliferation with minimal hypertrophy or fibrosis, thereby distinguishing it from repair processes. Genetic fate mapping indicated that the majority of cardiomyocytes within the regenerated tissue originated from preexisting cardiomyocytes. Echocardiography performed 2 months after surgery revealed that the regenerated ventricular apex had normal systolic function. Thus, for a brief period after birth, the mammalian heart appears to have the capacity to regenerate.

Rapid and Automated Analytical Methods for Redox Species Based on Potentiometric Flow Injection Analysis Using Potential Buffers

Two analytical methods, which prove the utility of a potentiometric flow injection technique for determining various redox species, based on the use of some redox potential buffers, are reviewed. The first is a potentiometric flow injection method in which a redox couple such as Fe(III)-Fe(II), Fe(CN)6 3−-Fe(CN)(CN)6 4−, and bromide-bromine and a redox electrode or a combined platinum-bromide ion selective electrode are used. The analytical principle and advantages of the method are discussed, and several examples of its application are reported. Another example is a highly sensitive potentiometric flow injection method, in which a large transient potential change due to bromine or chlorine as an intermediate, generated during the reaction of the oxidative species with an Fe(III)-Fe(II) potential buffer containing bromide or chloride, is utilized. The analytical principle and details of the proposed method are described, and examples of several applications are described. The determination of trace amounts of hydrazine, based on the detection of a transient change in potential caused by the reaction with a Ce(IV)-Ce(III) potential buffer, is also described.

Spherical plasma oscillations in a reversed-polarity inertial-electrostatic confinement device

A pulsed reversed-polarity inertial-electrostatic confinement device has been investigated experimentally using voltage and spectroscopic diagnostics. Large-amplitude oscillations were observed in the floating potential of the plasma immediately following the initiation of the discharge. It is postulated that the observations were the result of coherent ion oscillations within a harmonic potential well formed by a uniform electron density in the center of the device. A simple model of the system predicts the depth of this transient potential well to be approximately 100 V. Observations of the relative occupation of the third and fourth energy levels of hydrogen in the plasma indicated the formation of a Maxwellian electron energy distribution after 20 μs. The results suggest a promising avenue toward a net fusion power gain by utilizing these oscillations to periodically compress and heat the plasma to thermonuclear densities and energies.

Endocannabinoid-Dependent LTD in a Nociceptive Synapse Requires Activation of a Presynaptic TRPV-Like Receptor

Recent studies have found that some forms of endocannabinoid-dependent synaptic plasticity in the hippocampus are mediated through activation of transient potential receptor vanilloid (TRPV) receptors instead of cannabinoid receptors CB1 or CB2. The potential role for synaptic localization of TRPV receptors during endocannabinoid modulation of nociceptive synapses was examined in the leech CNS where it is possible to record from the same pair of neurons from one preparation to the next. Long-term depression (LTD) in the monosynaptic connection between the nociceptive (N) sensory neuron and the longitudinal (L) motor neuron was found to be endocannabinoid-dependent given that this depression was blocked by RHC-80267, an inhibitor of DAG lipase that is required for 2-arachidonoyl glycerol (2AG) synthesis. Intracellular injection of a second DAG lipase inhibitor, tetrahyrdolipstatin (THL) was also able to block this endocannabinoid-dependent LTD (ecLTD) when injected postsynaptically but not presynaptically. N-to-L ecLTD was also inhibited by the TRPV1 antagonists capsazepine and SB 366791. Bath application of 2AG or the TRPV1 agonists capsaicin and resiniferatoxin mimicked LTD and both capsaicin- and 2AG-induced depression were blocked by capsazepine. In addition, pretreatment with 2AG or capsaicin occluded subsequent expression of LTD induced by repetitive activity. Presynaptic, but not postsynaptic, intracellular injection of capsazepine blocked both activity- and 2AG-induced ecLTD, suggesting that a presynaptic TRPV-like receptor in the leech mediated this form of synaptic plasticity. These findings potentially extend the role ecLTD to nociceptive synapses and suggest that invertebrate synapses, which are thought to lack CB1/CB2 receptor orthologues, utilize a TRPV-like protein as an endocannabinoid receptor.

Manifestation of ocular-muscle EMG contamination in human intracranial recordings

It is widely assumed that intracranial recordings from the brain are only minimally affected by contamination due to ocular-muscle electromyogram (oEMG). Here we show that this is not always the case. In intracranial recordings from five surgical epilepsy patients we observed that eye movements caused a transient biphasic potential at the onset of a saccade, resembling the saccadic spike potential commonly seen in scalp EEG, accompanied by an increase in broadband power between 20 and 200Hz. Using concurrently recorded eye movements and high-density intracranial EEG (iEEG) we developed a detailed overview of the spatial distribution and temporal characteristics of the saccade-related oculomotor signal within recordings from ventral, medial and lateral temporal cortex. The occurrence of the saccadic spike was not explained solely by reference contact location, and was observed near the temporal pole for small (<2deg) amplitude saccades and over a broad area for larger saccades. We further examined the influence of saccade-related oEMG contamination on measurements of spectral power and interchannel coherence. Contamination manifested in both spectral power and coherence measurements, in particular, over the anterior half of the ventral and medial temporal lobe. Next, we compared methods for removing the contaminating signal and found that nearest-neighbor bipolar re-referencing and ICA filtering were effective for suppressing oEMG at locations far from the orbits, but tended to leave some residual contamination at the temporal pole. Finally, we show that genuine cortical broadband gamma responses observed in averaged data from ventral temporal cortex can bear a striking similarity in time course and band-width to oEMG contamination recorded at more anterior locations. We conclude that eye movement-related contamination should be ruled out when reporting high gamma responses in human intracranial recordings, especially those obtained near anterior and medial temporal lobe.

Interaction of Endocannabinoid Receptors with Biological Membranes

Cellular signaling is regulated by several biochemical reactions, whose dynamics depends on changes in the fluxes of specific ligands through the containment barriers that are the biological membranes. The regulation of this complex dynamic equilibrium is mainly due to the activity of border proteins, that must be able to interact simultaneously with the lipid bilayer and the extracellular milieu. Endocannabinoid receptors, that include type-1 and type-2 cannabinoid receptors, the transient vanilloid potential receptors and the peroxisome proliferator-activated receptors, represent one of the most intriguing examples of "border" proteins. They have also been identified as important drug discovery targets with potential therapeutic applications, from antiemesis, appetite enhancement, analgesia, glaucoma treatment, and immune suppression. However, as yet the molecular details of endocannabinoid receptor regulation remain elusive. In this review we summarize the most relevant aspects of the structural/functional characterization of these receptors, with a focus on the active role played by biological membranes (in particular lipid rafts) in the modulation of their accessibility and mode of ligand binding. Based on available evidence, we propose that endocannabinoid receptors can be regulated by the rate of interlayer exchange and lateral diffusion of endocannabinoid/cholesterol complexes within lipid bilayers, thus suggesting innovative approaches for the therapeutic exploitation of the membrane component of endocannabinoid signaling.

Transient formation of internal potentials in solid electrolytes

Electrode effects can play an important role in ion-conducting polymers in which a space charge polarization of mobile internal ions prevails. The ions are shifted in an external field and they are attracted to the electrodes due to Coulomb forces caused by their own image charges. These image charges influence the static and dynamic charge distribution. This can be proved experimentally by measurements of the transient surface potential with the scanning Kelvin probe using polyethylene oxide doped with lithium perchlorate (PEO-LiClO4). Simulations performed with a three-dimensional hopping model coincide with the experimental results qualitatively.

TRP'Ing on QPatch in Multi-Hole Mode

Transient receptor potential (TRP) channels are non-selective cationic channels that are widely distributed in mammalian tissues. Their specific physiological functions are largely unknown. Proposed functions include responses to pain, temperature, touch, osmolarity, pheromones, and taste. But due to the lack of specific blockers and the full understanding of their mechanisms of activation studies of TRP channels have been difficult and unexpectedly slow.The emergence of automated patch clamp (APC) systems has increased the number of new targets available for ion channel drug development and has augmented throughput.In order to facilitate tests of large compounds libraries on e.g. TRP targets, we have recently developed two multi-hole APC systems: QPatch HTX and QPatch 16X. The multi-hole technology allows the simultaneous recording of 10 cells in parallel per recording site thereby increasing the signal to noise ratio and the success rate.In this study, we have validated several TRP channels for their activation by their appropriate agonist e.g. Menthol, Capsaicin and temperature. We have found that using the QPatch in multi-hole mode significantly increased the volume of electrophysiology data that can be generated. Our results demonstrate that the QPatch multi-hole systems are capable of generating high quality data from a wide range of the channels belonging to the TRP family of receptors.We believe that the combination of high throughput and high quality data in a single system has more than a “transient potential” to advance the understanding of the complex mechanisms of action exhibited by difficult targets such as the TRP channels.

A critical review of Electric Earthquake Precursors

The generation of transient electric potential prior to rupture has been demonstrated in a number of laboratory experiments involving both dry and wet rock specimens. Several different electrification effects are responsible for these observations, but how these may scale up co-operatively in large heterogeneous rock volumes, to produce observable macroscopic signals, is still incompletely understood. Accordingly, the nature and properties of possible Electric Earthquake Precursors (EEP) are still inadequately understood. For a long time observations have been fragmentary, narrow band and oligo-parametric (for instance, the magnetic field was not routinely measured). In general, the discrimination of purported EEP signals relied on experience and ad hoc empirical rules that could be shown unable to guarantee the validity of the data. In consequence, experimental studies have produced a prolific variety of signal shape, complexity and duration but no explanation for the apparently indefinite diversity. A set of inconsistent or conflicting ideas attempted to explain such observations, including different concepts about the EEP source region (near the observer or at the earthquake focus) and propagation (frequently assumed to be guided by peculiar geoelectric structure). Statistics was also applied to establish the beyond chance association between presumed EEP signals and earthquakes. In the absence of well constrained data, this approach ended up with intense debate and controversy but no useful results. The response of the geophysical community was scepticism and by the mid-90's, the very existence of EEP was debated. At that time, a major re-thinking of EEP research began to take place, with reformulation of its queries and objectives and refocusing on the exploration of fundamental concepts, less on field experiments. The first encouraging results began to appear in the last two years of the 20th century. Observation technologies are mature and can guarantee reliable electric field measurements, although improvements are still possible with new generation electrodes and smart measurement schemes facilitating noise suppression. It is increasingly apparent that simultaneous electric and magnetic measurements are indispensable and conducted in most new experiments. There is also an emerging trend towards multi-parametric, broadband observations that should provide far better data and constraints on the source processes. The physics of electrification mechanisms are beginning to clarify, as also is the potential of solid state effects: charge and current densities under controlled conditions are such, that if scaled up to the size of seismogenic zones, they would yield observable EEP. However, there are still many unknowns, requiring careful experimentation and theoretical development. Research is also directed towards decoding the physics of stress/strain changes that cause electrification, exploiting properties such as are the fractal nature of faulting and Self-Organised Criticality (SOC). The first evidence of possible electromagnetic precursors due to a SOC system has been published recently. Modelling of the source processes from first principles is stepping up and certain classes of observed signals can now be predicted by theory, providing new and more rigorous means of data authentication; such models have also established the feasibility of long range EEP signals. Although progress is apparent, the knowledge is still grossly incomplete and EEP data are not indisputable, if tested with the full rigour of scientific verification methods. The new research philosophy requires time and vigilance before it begins to pay off, but it appears to have taken a more promising course.

The erosion of EB-PVD thermal barrier coatings: The competition between mechanisms

The normal impact of thermal barrier coatings by spherical particles is analysed by the finite element method in order to determine the transient stress state and potential for erosion. During the impact event, the deformation response can progress from elasto-dynamic to quasi-static elastic and then plastic. The precise sequence depends upon the size and velocity of the impacting particle, and upon the geometric and mechanical properties of the coating. Each deformation mechanism involves transient tensile stresses at characteristic depths within the coating, and these can lead to fracture of the columns from pre-existing flaws. Analytical solutions are presented that describe the transient stress state within the coating for each deformation mechanism; the analytical models are validated by independent finite element simulations in order to evaluate independent parameters. The analytical framework is used to construct deformation mechanism maps for the erosion of the thermal barrier coatings. It is concluded that erosion is a consequence of a set of potentially active deformation mechanisms.

Understanding ac–dc–ac accelerated test results

The ac–dc–ac accelerated testing method is an unconventional method that involves subjecting organic coatings on metallic substrates to cycles of cathodic potential. The ac–dc–ac degradation associated with a standard Army epoxy primer on a steel substrate is reported. The ac–dc–ac procedure was modified to include wetting and drying stages. Experimental results demonstrated the influence that the method had on the barrier property, the diffusion of water, and saturated condition of the primer. A quantitative analysis of the transient potential profile that followed the cathodic potential was performed to address processes of charge transfer, transport, and coating relaxation during this step.