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International audience; This paper focuses on the effect of different scales of fillers, from nano to macrometer, on the rheological and electrical behaviour of thermoplastic-based composites. Composites based on poly (etherimide) matrix (PEI) with multiscale reinforcement are processed by melting in a co-kneader to disperse homogeneously carbon nanotubes and glass fibers. We clearly demonstrate the strong link between the liquid-solid transition and the electrical conductivity. We show that the specific mechanical energy is a key parameter. Glass fibers allow to increase the electrical conductivity of blends based on carbon nanotubes and to obtain a lower decreasing of conductivity at the liquid transition which takes place in the same time as rheological and electrical parameters.

To systematically review the evidence of how adjustments of the electrical threshold (T) level, input dynamic range (IDR) and electrical stimulation rate impact on speech perception for cochlear implant (CI) users.Systematic review.A search of two electronic data sources yielded 32 studies, which met the inclusion criteria. A quality assessment and two evidence-based practice (EBP) review rating schemes were used to grade studies.Due to the heterogeneity of speech perception measures, CI device type and study design, comparisons were made by structured review.The quality of studies was found to be moderate to poor. Increasing T levels above behavioural threshold, or as a proportion of electrical dynamic range (EDR), has been demonstrated to improve perception of monosyllables in quiet and sentences in both quiet and in noise. Specific IIDR and IDR setting may improve perception of monosyllables in quiet and sentences in noise. However, no recommendation could be determined for setting rate of stimulation as speech perception varied significantly across rates examined. To optimise speech perception, a bespoke approach to parameter setting providing an individualised CI fitting is recommended; however, detail of how to optimise settings and the interactions between parameters is as yet unknown.

Background Migraine is a common headache disorder, with cortical spreading depolarization (CSD) considered as the underlying electrophysiological event. CSD is a slowly propagating wave of neuronal and glial depolarization. Sleep disorders are well known risk factors for migraine chronification, and changes in wake-sleep pattern such as sleep deprivation are common migraine triggers. The underlying mechanisms are unknown. As a step towards developing an animal model to study this, we test whether sleep deprivation, a modifiable migraine trigger, enhances CSD susceptibility in rodent models. Methods Acute sleep deprivation was achieved using the “gentle handling method”, chosen to minimize stress and avoid confounding bias. Sleep deprivation was started with onset of light (diurnal lighting conditions), and assessment of CSD was performed at the end of a 6 h or 12 h sleep deprivation period. The effect of chronic sleep deprivation on CSD was assessed 6 weeks or 12 weeks after lesioning of the hypothalamic ventrolateral preoptic nucleus. All experiments were done in a blinded fashion with respect to sleep status. During 60 min of continuous topical KCl application, we assessed the total number of CSDs, the direct current shift amplitude and duration of the first CSD, the average and cumulative duration of all CSDs, propagation speed, and electrical CSD threshold. Results Acute sleep deprivation of 6 h (n = 17) or 12 h (n = 11) duration significantly increased CSD frequency compared to controls (17 ± 4 and 18 ± 2, respectively, vs. 14 ± 2 CSDs/hour in controls; p = 0.003 for both), whereas other electrophysiological properties of CSD were unchanged. Acute total sleep deprivation over 12 h but not over 6 h reduced the electrical threshold of CSD compared to controls (p = 0.037 and p = 0.095, respectively). Chronic partial sleep deprivation in contrast did not affect CSD susceptibility in rats. Conclusions Acute but not chronic sleep deprivation enhances CSD susceptibility in rodents, possibly underlying its negative impact as a migraine trigger and exacerbating factor. Our findings underscore the importance of CSD as a therapeutic target in migraine and suggest that headache management should identify and treat associated sleep disorders.

Objective To identify differences in outcomes and map characteristics in pediatric bilateral cochlear implants with modiolar conforming and lateral wall arrays in opposite ears. Study design Retrospective case series. Setting Tertiary care pediatric referral center. Patients Fourteen children who received a perimodiolar array in one ear and a slim straight array in the opposite ear in sequential surgeries. Interventions None. Main outcome measures Consonant-nucleus-consonant test (CNC) word recognition score, battery life, power levels, electrical compound action potential (ECAP) thresholds, and electrical threshold and comfort charge levels. Results Speech perception outcomes were poorer in the lateral wall ears than the perimodiolar ears, and scores in the bilateral condition were better than with the lateral wall device alone. Sequential placement was a factor with differences in preoperative candidacy time correlating with greater difference in speech perception. There was no difference in charge levels between ears, in spite of higher ECAP threshold values for the lateral wall devices. Conclusion While bilateral speech perception was good, speech perception with the lateral wall device alone was poorer. This cannot be explained solely by the device, as differences in preoperative candidacy time were a significant factor. ECAP thresholds are significantly higher for lateral wall electrodes, but that did not translate in to higher psychophysical measurements.

Introduction This pilot study was aimed to compare pulpal pain provoked by electrical and thermal (cold) stimuli in healthy young women during various phases of menstrual cycle and postmenopausal women. Material and methods The study included 20 regularly menstruating healthy women and 20 postmenopausal women. Electrical (electrical pulp tester) and cold (refrigerant spray) stimuli were performed on mandibular central incisors, twice in regularly menstruating (menstrual and luteal phases) and once in postmenopausal women. Results were expressed as pain threshold values for electrical pulp stimulation (0-80 units) and pain intensity scores (visual numeric scale, from 0 to 10) for cold stimulation. Results In young women, higher pain electrical threshold (p=0.484) and pain sensitivity score (p=0.015) were observed in luteal in comparison to menstrual phase. In postmenopausal women, electrical pain threshold was significantly higher while pain intensity score was significantly lower than in young women, regardless of the menstrual phase and painful stimuli. Conclusion Lower responsiveness to dental pulp pain was obtained in young women in luteal phase and postmenopausal women.

Hélène LM Ruel,1,2 Ryota Watanabe,1,2 Marina C Evangelista,1,2 Guy Beauchamp,3 Paulo V Steagall1,2 1Department of Clinical Sciences, Faculty of Veterinary Medicine, Université de Montréal, Saint-Hyacinthe, QC, Canada; 2Quebec Animal Pharmacology Research Group, Faculty of Veterinary Medicine, Université de Montréal, Saint-Hyacinthe, QC, Canada; 3Faculty of Veterinary Medicine, Université de Montréal, Saint-Hyacinthe, QC, Canada Purpose: Quantitative sensory testing has been used to assess the somatosensory system. This study aimed to evaluate the feasibility and reliability of electrical (ENT), mechanical (MNT) and thermal (TNT) nociceptive testing and the effect of a conditioning stimulus on MNT. Patients and methods: Sixteen healthy client-owned dogs were included in this study. Stimulation was applied bilaterally to the dorsal and plantar aspect of the metacarpus and metatarsus respectively, using transcutaneous electrical stimulator, algometry and a cold nociceptive device in a randomized order until a behavior response was observed or a cut-off reached. Tests were performed twice (60 seconds apart) by two observers. Retesting was performed 5 hours later. The diffuse noxious inhibitory control was tested by comparing MNT pre- and post-conditioning stimuli. Sham-testing was performed for ENT and TNT. Statistical analysis included linear model and intra-class correlation coefficient (P

Electrical treeing endurance behavior of XLPE cable insulation was investigated by application of AC voltages on specimens with a pin-plane electrode system. The needle inserted has a tip radius of 10 μm, and the pin-plane distance is 2 mm. The relation between applied voltage and tree initiation time, when plotted in a log-log coordinate, could be approximated by three straight lines, and an electrical threshold stress of about 100 kV/mm was deduced from it in the low field region. The voltage endurance coefficient obtained from tree initiation time increased with higher cumulative probability in the constant voltage method, but altered little with the ramping-up rate of step voltages applied in the step-constant voltage method. The treeing breakdown time gave a smaller value of this coefficient, compared with tree initiation. The XLPE insulation of a taping mould joint was tested to be more voltage withstanding than a cable body, for its higher voltage endurance coefficient, 18.6 to 13.8, and slower tree growth, 0.53 to 0.62 mm in 20 minutes. The electrical field for cable insulation design could be connected with tree initiation stress by a field enhancement factor, and this allowed the insulation thickness of a 110 kV XLPE cable to be determined with the value of 12 to 13 mm. It is shown that the insulation design of HV XLPE cables could be safely achieved by the characteristic parameters determined from electrical treeing test.

Objective Percutaneous electrical stimulation of the motor point permits selective activation of a muscle. However, the definition and number of motor points reported for a given muscle varies. Our goal was to address these problems. Methods The area, location and number of motor points in human tibialis anterior were examined, using isometric dorsiflexion torque responses to electrical stimuli. Three methods were used: lowest electrical threshold, maximum muscle response, and approximate motor point. Results A single motor point was identified in 39/40 subjects regardless of method. The area of the site of lowest electrical threshold was smaller (median, 35mm 2 ) than those using the maximum muscle response (144mm 2 ) and approximate motor point (132mm 2 ). There was substantial, but not significant, between-subject variation in motor point location. Fifty three percent of motor points would have been missed if located only by reference to anatomical landmarks. Conclusions These results suggested that the motor point's location cannot be determined a priori and that the identification method will affect both area and location. Significance If it is important to maximally activate a single muscle in isolation, the motor point is best represented by the site producing a maximal but isolated muscle response at the lowest stimulation intensity.

Background and Objectives: Pain estimation remains a difficult medical problem. Many subjective and objective methods were tried. Subjective methods depend on personal difference to a good extent and cannot be accurate. The aim of this work was to evaluate the validity of using electrical stimulation (ES) as an objective and valid method in quantitating the pain intensity and, consequently, the intensity of needed treatment. Methods: Twenty chronic low back pain (LBP) patients with sciatica and 20 normal subjects participated, and they were compared in this study. Electrical threshold and pain tolerance were recorded from the most painful site in the study group and from the corresponding matching site in the control group. Blood analysis for β-endorphin was done to objectively determine the intensity of pain as well as the objectivity and validity of ES in the assessment of pain. Pain intensity was also recorded by the visual analogue scale for each subject. Results: Significant differences between both groups regarding the threshold and pain tolerance to electrical current were noted. A significant positive correlation was also observed between β-endorphin level as well as the threshold and pain tolerance intensity in the patient group. Non-significant correlation was also observed between the visual analogue scale and β-endorphin level. Conclusion: ES is an objective and valid method, whereas visual analogue scale is a subjective method in the assessment of pain intensity in chronic LBP patients.

Previous studies have shown large decreases in cochlear implant psychophysical detection thresholds during the weeks following the onset of electrical testing. The current study sought to determine the variables underlying these threshold decreases by examining the effects of four deafening and implantation procedures on detection thresholds and implant impedances. Thirty-two guinea pigs were divided into four matched groups. Group I was deafened and implanted Day 0 and began electrical testing Day 1. Group II was deafened and implanted Day 0 and began electrical testing Day 45. Group III was deafened Day 0, implanted Day 45 and began electrical testing Day 46. Group IV was not predeafened but was implanted Day 0 and began electrical testing Day 1. All groups showed threshold decreases over time but the magnitude of change, time course and final stable threshold levels depended on the type and time course of treatment. Impedances increased over the first two weeks following the onset of electrical testing except in Group II. Results suggest that multiple mechanisms underlie the observed threshold shifts including (1) recovery of the cochlea from a temporary pathology caused by the deafening and/or implantation procedures, (2) effects of electrical stimulation on the auditory pathway, and (3) tissue growth in the implanted cochlea. They also suggest that surviving hair cells influence electrical threshold levels.

OBJECTIVE Perimodiolar electrode arrays were developed to improve stimulation of specific neural populations and to decrease power consumption. Postoperative radiographs suggest that some arrays are more tightly coiled than others. The purpose of this study was to evaluate whether the degree of modiolar coil correlates with electrical threshold and/or performance measures postimplantation with the Nucleus CI24RCS (Contour) device. STUDY DESIGN Retrospective review. SETTING Cochlear implant center and a tertiary care hospital. PATIENTS Twenty-eight adult cochlear implant recipients with normal cochlear anatomy who underwent implantation with the Nucleus C124RCS perimodiolar electrode and are at least 1 year postimplantation. INTERVENTIONS Therapeutic. MAIN OUTCOME MEASURES Radiologic degree of perimodiolar electrode placement (determined by a computer algorithmic analysis) compared with electrical thresholds and standard speech perception outcome measures at 1 year postcochlear implantation. RESULTS No significant correlations were found between the degree of modiolar coiling of the electrode array and electrical thresholds and speech perception outcome measures at 1 year postcochlear implantation. CONCLUSIONS The degree of coiling of a modiolar hugging electrode array was not directly correlated with the level of electrical thresholds or postoperative speech perception outcome measures. Appearance of coil tightness on postoperative radiographs could reflect either differences in array placement or intrinsic variations in cochlear anatomy, and variations in speech perception performance can be influenced by other factors, including length of deafness.

Objective: This assessment evaluates the clinical utility, efficacy, and safety of quantitative sensory testing (QST). Methods: By searching MEDLINE, Current Contents, and their personal files, the authors identified 350 articles. Selected articles utilized computer operated threshold systems, manually operated threshold systems, and electrical threshold devices. The authors evaluated the use of normal values and the degree of reproducibility between the same and different systems. Articles were rated using a standard classification of evidence scheme. Results: Because of differences between systems, normal values from one system cannot be transposed to others. Reproducibility of results was also an important concern, and there is no consensus on how it should be defined. The authors identified no adequately powered class I studies demonstrating the effectiveness of QST in evaluating any particular disorder. A number of class II and III studies demonstrated that QST is probably or possibly useful in identifying small or large fiber sensory abnormalities in patients with diabetic neuropathy, small fiber neuropathies, uremic neuropathies, and demyelinating neuropathy. Conclusions: QST is a potentially useful tool for measuring sensory impairment for clinical and research studies. However, QST results should not be the sole criteria used to diagnose pathology. Because malingering and other nonorganic factors can influence the test results, QST is not currently useful for the purpose of resolving medicolegal matters. Well-designed studies comparing different QST devices and methodologies are needed and should include patients with abnormalities detected solely by QST.

Objective Myofascial trigger points contribute significantly to musculoskeletal pain and motor dysfunction and may be associated with accelerated muscle fatiguability. The aim of this study was to investigate the electrically induced force and fatigue characteristics of muscle taut bands in rats. Methods Muscle taut bands were dissected out and subjected to trains of electrical stimulation. The electrical threshold intensity for muscle contraction and maximum contraction force (MCF), electrical intensity dependent fatigue and electrical frequency dependent fatigue characteristics were assessed in three different sessions (n=10 each) and compared with non-taut bands in the biceps femoris muscle. Results The threshold intensity for muscle contraction and MCF at the 10th, 15th and 20th intensity dependent fatigue stimuli of taut bands were significantly lower than those of non-taut bands (all pConclusions The present study demonstrates that the muscle taut band itself was more excitable to electrical stimulation and significantly less fatigue resistant than normal muscle fibres.

A phase-change material of Sb/sub 65/Se/sub 35/ was newly proposed for the nonvolatile memory applications. The fabricated phase-change memory device using Sb/sub 65/Se/sub 35/ showed a good electrical threshold switching characteristic in the dc current-voltage (I-V) measurement. The programming time for set operation of the memory device decreased from 1 /spl mu/s to 250 ns when Sb/sub 65/Se/sub 35/ was introduced in place of the conventionally employed Ge/sub 2/Sb/sub 2/Te/sub 5/ (GST). The reset current of Sb/sub 65/Se/sub 35/ device also dramatically reduced from 15 mA to 1.6 mA, compared with that of GST device. These results are attributed to the low melting temperature and high crystallization speed of Sb/sub 65/Se/sub 35/ and will contribute to lower power and higher speed operations of a phase-change nonvolatile memory.

Background Nanotechnology has made inroads over time within surgery and medicine. Translational medical devices and therapies based on nanotechnology are being developed and put into practice. In plastic surgery, it is anticipated that this new technology may be instrumental in the future. Microelectromechanical systems are one form of nanotechnology that offers the ability to develop miniaturized implants for use in the treatment of numerous clinical conditions. The authors summarize their published preliminary findings regarding a microelectromechanical systems-based electrochemical stimulation method through modulation of ions around the nerve that is potentially implantable and clinically efficacious, and expand upon current and potential usages of nanotechnology in plastic surgery. Methods Sciatic nerves (n = 100) of 50 American bullfrogs were placed on a microfabricated planar gold electrode array and stimulated electrically. Using Ca(2+)-selective membranes, ion concentrations were modulated around the nerve environment in situ. In addition, a comprehensive review of the literature was performed to identify all available data pertaining to the use of nanotechnology in medicine. Results A 40 percent reduction of the electrical threshold value was observed using the Ca(2+) ion-selective membrane. The uses of nanotechnology specifically applicable to plastic surgery are detailed. Conclusions Nanotechnology may likely lead to advancements in the art and science of plastic surgery. Using microelectromechanical systems nanotechnology, the authors have demonstrated a novel means of modulating the activation of nerve impulses. These findings have potentially significant implications for the design of special nano-enhanced materials that can be used to promote healing, control infection, restore function, and aid nerve regeneration and rehabilitation.

In the paper, life models, are collected valid for solid insulating materials subjected to electrical and multiple thermal-electrical stresses whose life lines show a tendency to reach an electrical threshold. Their fit is investigated with reference to several sets of data derived from accelerated life tests performed on different insulating materials (XLPE, composite Nomex-Mylar-Nomex, epoxy bisphenolic resin, polyimide). In particular, two phenomenological life models, characterized by four parameters and based on exponential and inverse-power relationships, are compared with three-parameter life models taken from the literature and derived considering different aging and breakdown mechanisms. Discussion of the ability of these models to provide significant parameters for insulation endurance evaluation and electrical system design closes the paper.

Direct cortical stimulation in commonly used for the accurate localization of the motor cortex but the electrical threshold stimulation parameters with this technique had not been fully established.A retrospective review of 15 cases of pediatric surgical cases were performed. The patients consisted of nine male patients and six female patients with age range from 2 to 18 years (mean: 10.8 years; median: 14 years). The most common pathology was cortical dysplasia (nine cases). Stimulation was performed with a train of five stimulations (range five-seven stimulations;5% of stimulations required more than five stimulations) applied, each train of 50 micros pulse duration, with an interstimulus interval of 1.1 msec. Stimulation intensity commenced at 25 V and this was increased at 5-10 V increments until motor evoked potentials waveforms of sufficient duration and morphology were consistently generated.Monopolar electrical stimulation threshold for intraoperative motor cortical mapping were found to be more consistent in the upper limb compared to lower limb and facial muscles. Evoked responses from the extensor digitorium communis had the highest recorded rate (83.7%) and required the lowest stimulation voltage (36.0 V). The stimulation voltage was found to be statistically significant compared to threshold values for abductor hallucis, tibialis anterior, deltoid, and orbicularis oris with respective p values of 0.006, 0.021, 0,027, and 0.015. There was also a distinct trend that patients with cortical dysplasia/tuberous sclerosis have higher stimulation thresholds when compared to other pathology (p = 0.067).Monopolar electrical stimulation threshold for intraoperative motor cortical mapping were more consistent in the upper limb compared to lower limb and facial muscles. Evoked responses from the extensor digitorium communis had the highest recorded rate and required the lowest stimulation voltage. There was also a distinct trend that patients with cortical dysplasia/tuberous sclerosis have higher stimulation thresholds.

We previously described the ability to induce adult-like, coordinated airstepping following electrical stimulation of the brainstem in the hindlimb-attached, in vitro brainstem-spinal cord preparation. These findings suggest the presence at birth of supraspinal systems capable of activating and modulating spinal locomotor mechanisms, which presumably also are present at birth. The current study employed the hindlimb-attached in vitro brainstem-spinal cord preparation from 0- to 4-day-old rats maintained in oxygenated artificial cerebrospinal fluid. After the control threshold-frequency relationship for eliciting airstepping was established, the dorsal roots to the attached limbs were severed and the procedure was repeated. No changes in electrical threshold or major differences in the elicited locomotor pattern were observed after deafferentation, although the amplitude of the electromyograms decreased. The mean frequency of alternation at threshold before deafferentation was similar to that after deafferentation. However, the maximum mean frequency induced by suprathreshold stimulation was significantly higher after deafferentation than that before deafferentation. These results suggest that (1) the supraspinal modulation of spinal locomotor mechanisms is not entirely dependent on afferent input; (2) intrinsic spinal locomotor mechanisms are present in the spinal cord at birth; and (3) afferent input may limit the maximum frequency of alternation of the limbs early in development.

Publisher Summary This chapter reviews physiological and biophysical aspects of the three most widely used techniques—namely electrical, contact heat, and laser pulsed stimulation. Standard neurophysiological techniques used for somatosensory assessment use low-intensity electrical stimuli, and therefore excite preferentially large-diameter, fast-conducting afferents, which have an electrical threshold lower than that of small-size, nociceptive fibers. Although increasing the intensity of electrical stimulation induces a growing aversive pain response, nociceptive afferents are excited “simultaneously” with non-nociceptive fibers, hence precluding the recording of specifically “nociceptive” evoked potentials (EPs). Standard thermodes such as those used in functional imaging studies do not allow temperature changes rapid enough to evoke EPs. New generations of fast-acting heat foil-thermodes allow temperature rise times up to 70°C/s and can evoke cortical responses. Radiant heat stimulation can circumvent most of the difficulties inherent in electrical or contact-heat stimuli, by providing selective activation of A-δ and C-thermosensitive nociceptors in the hairy skin, without concomitant activation of mechanoreceptors and A-β fibers.

Dc space-charge measurements, performed by PEA, are used to estimate the electrical threshold in XLPE and modified XLPE-based materials. In addition to threshold, a quantity is proposed for the characterization of a material, in relation to its expected voltage endurance. This quantity is associated to the slope of the charge vs field plot coming from space-charge measurements. The different behavior as regards space-charge accumulation in the tested materials and its relevance to insulation endurance is discussed. The quantities presented in this paper are thought useful for electrical characterization of insulating materials candidate for DC high-field applications.

Cross-linked polyethylene (XLPE) cable models obtained by a steam curing process have been investigated. These models were subjected to life tests with electrical, thermal, and multiple thermal-electrical stresses. The tests were performed by means of the progressive-censoring procedure in order to obtain information on both failure time percentiles and aging mechanisms by the study of significant properties related to breakdown. The results of multiple-stress tests are presented, and the behavior of such properties as density, melting enthalpy, and DC electrical conductivity is investigated as a function of aging conditions, and is related to the failure times obtained from each life test. It is shown that changes occur in the material during aging under multiple stresses which are not detected at the same aging times when electrical and thermal stresses are applied singly. Moreover, failure times are strongly reduced when stresses are combined, so that the electrical threshold decreases as temperature grows and seems to disappear at temperatures higher than 100 degrees C. The appearance of heterogeneous regions in the bulk of cable models aged under multiple stresses and the time behavior of the investigated properties suggest that the breakdown is mainly due to localized phenomena, even if bulk degradation processes occur in the insulation. >

Additives have been introduced in the conventional high-voltage grade XLPE, with the purpose to modify the electrical threshold level. The electrical threshold is estimated through the steady-state current-voltage characteristic obtained from dc charging current measurements performed at different voltage levels. Space-charge distribution observations are carried out, by PEA, in order to confirm the threshold values detected by charging-current measurements, having associated the threshold to the limit value above which space charges are steadily trapped in insulation. Significant variations of the electrical threshold levels is actually observed in the two tested additivated compounds, with respect to the reference XLPE. The conduction mechanism, phenomenologically attributed to space-charge limited current (SCLC), is rediscussed on the basis of space-charge distribution observations which show deviations from the SCLC theory.

A new method for the detection of the ac electrical threshold for space charge injection in polymeric materials is presented in this paper. The ac charge injection-extraction dynamic in discussed, and experimental procedures are proposed to establish the electrical field for charge injection. These procedures are based on the observation of the space charge profiles obtained by the Pulsed Electroacoustic technique. The ac threshold data provided by the two tested materials i.e. LDPE and XLPE, are compared with dc threshold results, showing that the r.m.s. ac injection threshold values are very close to, but slightly smaller than, the dc ones.

We describe the electrically enhanced growth of needle crystals from the vapor phase, for which there exists a morphological instability above a threshold applied potential. Our improved theoretical treatment of this phenomenon shows that the instability is present in both polar and non-polar systems, and we provide an extension of solvability theory to include electrical effects. We present extensive experimental data for ice needle growth above the electrical threshold, where at $T=-5$C high-velocity shape-preserving growth is observed. These data indicate that the needle tip assumes an effective radius} $R^{\ast}$ which is nearly independent of both supersaturation and the applied potential. The small scale of $R^{\ast}$ and its response to chemical additives suggest that the needle growth rate is being limited primarily by structural instabilities, possibly related to surface melting. We also demonstrate experimentally that non-polar systems exhibit this same electrically induced morphological instability.

We report the dielectric response (100mHz-1MHz) of the spin density wave (SDW) in (TMTSF) 2 PF 6 and (TMTSF) 2 AsF 6 between 1.4K–4.2K. The relaxation gradually slows down in PF 6 , while in AsF 6 it shows a tendency of divergence hinting the appearance of a glassy transition. The latter correlates with the important increase of the electrical threshold field for the SDW sliding found in AsF 6 , but not observed in PF 6 compound.

In this paper a general life model, valid for any type of insulating materials, with or without evidence of an electrical threshold at room temperature, is proposed. First of all, the old definition of threshold or no-threshold materials is changed and the behavior of materials is considered, as a threshold or as a no-threshold material, according to the value of applied stresses. The electrical gradient-temperature graph is examined, showing the relationships between electrical and thermal thresholds. The various life models for electrical and thermal stress used by researchers are examined and discussed; the old combined-stress life model for threshold materials is improved by adding to the denominator a cross term which gives rise to a threshold line which is curved instead of straight. Since for no-threshold materials the denominator should be equal to 1, this is raised to an exponent β, a function of the ratios between the applied stresses and thresholds, which becomes 0 when the stresses are higher than the thresholds (no-threshold behavior) and is, instead, > 0 if at least one of the stresses is lower than the corresponding threshold (threshold behavior). In such a way, the improved model assumes general validity. Application of the model is outlined and compared with experimental data obtained for several insulating materials. © 1993 IEEE

The sensory threshold was determined for 50 teeth in 31 patients using constant-current stimuli of 0.1, 1.0 and 10 ms duration at 10 Hz through both monopolar and bipolar electrodes. The teeth were also tested with a cold stimulus (ethyl chloride on cotton wool), then extracted, processed and examined by light microscopy. Histologically, 38 teeth were vital and 7 non-vital. The best prediction of vitality was from ethyl chloride (80% correct) or bipolar stimuli of 10 ms duration and up to 200 microA (73% correct). The remaining 5 teeth had vital radicular pulps and necrotic tissue coronally, but a comparison between the results of monopolar and bipolar stimulation did not permit the detection of this group. There was no correlation between the electrical threshold and presence of caries, restorations, pulp stones or diffuse pulpal mineralization.

Whether long-term intracochlear implantation and direct electrical stimulation of the acoustic nerve will induce intracochlear bone growth or cause further degeneration of a severely compromised auditory system is an important clinical consideration. Thin-section CT evaluations of the cochleas of six subjects who have used their cochlear implant devices on a daily basis for 3 or more years demonstrated no evidence of osteoneogenesis of the cochlea in the vicinity of the active electrode. No corrosion of the electrode or insulation material was noted on electron microscopy of an explanted electrode system. Electrical threshold and dynamic range measurements have remained stable or even improved during the period of observation. Performance measures using a variety of audiologic tests and speech-tracking scores have demonstrated stability of performance.

It was shown that disturbances of the heart electrical stability in postinfarction cardiosclerosis manifested in a fall of the electrical threshold of the heart fibrillation and the development of extrasystoles during the vagus stimulation. These disturbances were effectively eliminated by administration of GABA in the brain.

The minimum current and energy (threshold values) required for direct ventricular defibrillation in dogs was measured before and after acute myocardial infarction produced by ligation of the interventricular descending branch of the left coronary artery. The current waveform employed was a single 8.33 msec. duration halfsinusoidal pulse. Myocardial infarction markedly increased the strength of electric countershock required for ventricular defibrillation in each of the fourteen subjects. The average current threshold increase was 55 per cent, whereas the average energy threshold increase was 155 per cent. The maximum increase in current and energy occurred during the first 30 minutes after infarction and gradually decreased toward control values over the following 90 minutes.

Preoperative appreciation of the future clinical results of the multichannel cochlear implant is important to assess in the case of pre- or post-lingual total deafness, in order to improve the patients selection. The psychological status of the future implanted is one of the main concerns because the post-operative reeducation efficacity depends on the patient's motivation. The Round Window electrical stimulation test supplies us with important and measurable data (electrical threshold level, tone decay test). The age of the patient, the age and the etiology of the deafness, the vestibular status and the cochlear tomodensitometry only offer non-decisive informations. The patient's socialisation level is a considerable factor. But per-operative observations are sometimes and surprisingly determinant (electrode impedances, ossified cochlea). Moreover immediate post-operative electrical and psychophysic data must also be considered.

After surgical and antibiotic destruction of guinea pig cochleas non specific lesions appear which seem more due to this destruction than to the electrode implantation or chronic stimulation. Moreover, despite these lesions, the electrical threshold level value necessary to elicit brain stem evoked responses in these implanted animals does not vary in time. The electrical chronic stimulation of the newborn deafened guinea pigs cochlea prevents the cochlear nucleus atrophy observed in the non stimulated animals. In man the implanted material tolerance is perfect provided this material is covered by a Silastic or teflon sheet and is located far from the skin incision. Degradation of isolating material occurred only in case of chronic movements. For this reason device and electrodes must be placed above and behind the ear. The waterproofness of the implanted receptor is indispensable to avoid physiological liquid penetration inside the electronic device. High level voltage stimulation may involve bubble form...

Two stimulating microelectrodes were inserted 0.5 mm apart in the rat's nucleus raphe magnus (NRM), giving a joint electrical threshold for suppression of the heat-evoked tail-flick reflex. Synchronous stimulation often required more current than predicted by consideration of each site's solitary threshold. Asynchronous stimulation required yet more current. We postulate that some NRM cells, perhaps corresponding to the ‘on-cells’ found previously by microelectrode recording, facilitate flexion and become relatively more influential at higher stimulus currents. We also postulate that the dominating cells that suppress flexion, possibly ‘off-cells’, operate optimally when firing simultaneously.

This paper presents an extensive study of the fundamental characteristics of InGaAsP/InP double-heterojunction (DH) lasers with a wavelength of 1.3 μm. The confinement properties of injected carriers in the quaternary active region, the electrical properties such as leakage current and diode current versus voltage, the threshold characteristics, and the threshold temperature characteristics are determined through an analysis of the heterojunction energy band structure. The threshold temperature characteristics and the carrier leakage from the active region into the confining layers are examined in detail. To clarify the dependence of carrier leakage on lasing wavelength in InGaAsP/InP DH lasers and to explain the difference between GaAlAs/GaAs DH and InGaAsP/InP DH lasers, the barrier heights required to effectively confine the injected carriers and the effective carrier masses in the active region are discussed. Various possible explanations for the observed threshold temperature characteristics are considered.

Behavioural responses to electrical stimulation of mechanosensory neurones were characterized in two species of leeches, Hirudo medicinalis and Macrobdella decora. Depending upon the site and intensity of stimulation, the stimuli elicited one or a combination of five different responses: local bending, curling, shortening, whole-body bending or swimming. The electrical threshold for activating identified mechanosensory neurones, T (touch) cells and P (pressure) cells, was the same in all regions of the body. The voltage range over which the electrical stimuli produced progressively more mechanosensory impulses was the same as the range that produced different behavioural responses. These results suggest that the T and P mechanosensory neurones provide the entire sensory input for all the behavioural responses. The production of different behavioural responses to stimuli of different intensities at the same location are attributable to different firing rates of the same sensory cells, and different responses to the same stimulus at different locations suggest different interneuronal targets for the T and P cells in different body regions.

Observations of earlier workers on the chromatic responses to local heating or cooling of the skin of Phoxinus have been confirmed. They have also been found to hold true for anaesthetized fish, in which finer control and observation are possible. The results of a series of nerve-section experiments are held to exclude any possibility that the responses of the intact fish are mediated by a nervous reflex from thermoreceptors in the skin. The responses of melanophores following section of the chromatic motor tracts, or when isolated from the body, are considered to be independent cellular responses. Normal responses in the intact fish show clear temperature thresholds and are completely dependent upon continuation of the respiratory rhythm. Possible physiological mechanisms for mediating these non-adaptive responses are discussed and a new hypothesis is put forward.

The electrical threshold of the eye was measured by the alternating current of 20 c. p. s. with flicker sensation caused by it as an index under various adaptation states. 1. The threshold-time curve during complete dark adaptation following light adaptation of 10 minutes to illumination of 9, 800 lux shows the following course: At first the threshold remained low for about 8 minutes, and then increased rapidly to attain a constant level in about 15 minutes. Thus, the curve showed an inflection at about 8 minutes. 2. The curve suffered from a modification when the retina was constantly exposed to a small point of light of 40' in visual angle following the same light adaptation as above. The inflection at the middle stage became more obscure and the final level lower as local illumination was moved farther towards the periphery of the retina. 3. The effect of similar local illumination was investigated with colored lights. When blue, green and red lights were used for local illumination, it was found that the red light showed an effect similar to white light confined to the fovea, but that the green and blue light acted as white light illuminating the periphery of the retina. 4. Next the effect of exposure to broad illumination was investigated upon the curve following the same light adaptation as above. The curves by illumination of 0.1 lux, 1 lux and 10 lux were low and almost steady, but those by 100 and 1, 000 lux were generally much higher. From these experiments it is likely that the threshold as determined by the A. C. of 20 c. p. s. is lowered when visual cells, especially rods are excited to some extent.

In an earlier report (3), the authors have provided experimental evidence that, under certain circumstances, the configuration of the induction takes its form in accordance with what a subject perceives in the visual field. If the pre-illuminating patterns I, II, III and a point in IV of Fig. 1 are presented in succession and fixation is shifted from the left mark to the right one between the presentation of III and that of IV, the indirect induction of Y (yellow) in I is observed at the points 1 and 4 etc. in IV and the neutralization, i.e., the arrival of the induction initiated by B (blue) in II is demonstrated at the point 2 (the pattern P in Fig. 2). Let us consider the moment when IV is presented. The region of the retina that is pre-illuminated by I, II and III, if projected to the plane where the pre-illuminating patterns are presented, is given by the dotted figure in Fig. 2, whereas the full lined figure indicates the place where I, II and III are presented, i.e., where these patterns are perceived in the visual field. Hence, the only possible interpretation may be as follows. In so far as I, II, III and IV are presented, the configuration of the induction does not exist around the pre-illuminated region of the retina, but it does take its form around the region in the visual field where the pre-illuminating patterns are perceived. This is what we named the P-result and the discovery was so unexpected that the need of its confirmation from every possible angle was pressing.In a series of experiments described in this article, the pre-illuminating patterns, the shift of fixation, the delivery of the electrical pulse to the eye, the definition of the induction (contrast effect, CE) etc. were exactly the same as those employed in the previous experiments (3). However, the psychophysical method to obtain the electrical threshold for evoking the phosphene was changed. Namely, in place of the method of limits in the descending series, the one in the ascending series was employed in Experiment 3 (Fig. 3), and the constant method in Experiment 4 (Fig. 6). And it became clear, irrespective of the method, the P-result was always obtained under the conditions mentioned above. In passing, the goodness of fit of the φ(γ) function to the data in the case of the constant method was satisfactory as shown in Fig. 4 and in Fig. 5.So far, the interval of time between the cessation of IV and the delivery of the electrical pulse was fixed at 1.5sec. since only existence or non-existence of the induction of Y was at issue. In Experiment 5, however, the interval was changed from 1 to 3sec. for the purpose of obtaining the so-called ζ-time curve. The P-result was also ascertained because two distinctively different types of curves appeared as shown in Fig. 7. The one (at the points 1 and 4) is of typical type for existence of the induction and the other (at the point 2) for occurrence of the neutralization.

A method based on electrophysiological principles is described for evaluating actions of analgesic agents in controlled tests using electrical stimulation of the dental pulp. Some of the tests depended upon use of subjects who were selected according to an objective criterion of responsiveness to painful stimuli, characterized by digital plethysmography. Other subjects were selected on the basis of an observed correlation between the plethysmographic findings and the subjective reactions of different individuals to the electrical stimuli. About 25% of the individuals tested were rejected because of erratic plethysmographic records, erratic threshold to electrical stimulation in a preliminary test, or both. None of the individuals chosen by either criterion for subsequent testing reacted to administration of placebo. About two-thirds of the group responded with marked elevations of electrical threshold to orally administered acetylsalicylic acid (1.8 gm) or codeine (30 mg). The elevations caused by codeine were about three times as large as those induced by the acetylsalicylic acid. One-third of the subjects tested, or about 25% of the total population examined, proved refractory to 1.8 gm acetylsalicylic acid, and those subjects of this group who were also tested with 30 mg codeine also failed to respond to this analgesic drug. The present findings are in accord with clinical experience, but are discrepant with statistical evaluations using clinical material. Possible sources of error in the latter procedures are discussed.