To see the other types of publications on this topic, follow the link: Thermode de contact.
Journal articles on the topic 'Thermode de contact'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'Thermode de contact.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Rasmussen, Vibe Maria, Catarina Ellehuus-Hilmersson, Per Rotbøll-Nielsen, and Mads Utke Werner. "Spatial summation of thermal stimuli assessed by a standardized, randomized, single-blinded technique." Scandinavian Journal of Pain 9, no. 1 (October 1, 2015): 81–86. http://dx.doi.org/10.1016/j.sjpain.2014.12.001.
Full textAbstract:
AbstractBackground and aimsQuantitative sensory testing of thermal perception (QTT) is a valuable method in clinical and experimental assessment of the function of small nerve fibres. Previous studies have indicated existence of spatial summation for warmth, cool and heat pain stimulation, but study designs and assessment methods have not always been mutually consistent. The aims of this study were, first, to examine spatial summation of QTT by differently sized contact thermodes, and, second, to evaluate if these differences are significant from a clinical and scientific perspective.MethodsSixteen healthy subjects were included. Warmth detection (WDT), cool detection (CDT) and heat pain (HPT) thresholds were assessed in random order, with the stimulation areas of the contact thermodes of 3.0, 6.3 and 12.5 cm2, blinded to the subjects. Assessments were made bilaterally at volar part of the distal arm and medial part of the lower leg. Data analyses were by a mixed model with random effect for subject and fixed-effects for the variables, site (arm/leg), thermode area (ln thermode area) and side (dominant/non-dominant), in addition to conventional pairwise non-parametric comparisons.ResultsData from 2 subjects were excluded. In the remaining 14 subjects only 4 subjects were able to identify the correct sequence of thermode sizes. The model demonstrated highly statistical significant relationships regarding main effects: thermode area (P < 0.0001) and stimulation site (P < 0.0001; except for CDT P = 0.011). The only significant interaction was between thermode area*site (P = 0.005) for CDT. The study demonstrated in 17 of 18 possible comparisons between thermode size and stimulation site, a significant spatial summation for WDT, CDT and HPT.ConclusionThis randomized, single-blind study of thermal thresholds demonstrated spatial summation and that considerable deviations may occur if values obtained with differing thermode sizes are used uncritically.ImplicationsData from the present study enable interpolation of thermal thresholds with differing thermode sizes, facilitating comparisons across studies.
2
Vierck, Charles J., Richard L. Cannon, Gentry Fry, William Maixner, and Barry L. Whitsel. "Characteristics of Temporal Summation of Second Pain Sensations Elicited by Brief Contact of Glabrous Skin by a Preheated Thermode." Journal of Neurophysiology 78, no. 2 (August 1, 1997): 992–1002. http://dx.doi.org/10.1152/jn.1997.78.2.992.
Full textAbstract:
Vierck, Charles J., Jr., Richard L. Cannon, Gentry Fry, William Maixner, and Barry L. Whitsel. Characteristics of temporal summation of second pain sensations elicited by brief contact of glabrous skin by a preheated thermode. J. Neurophysiol. 78: 992–1002, 1997. Temporal summation of sensory intensity was investigated in normal subjects using novel methods of thermal stimulation. A Peltier thermode was heated and then applied in a series of brief (700 ms) contacts to different sites on the glabrous skin of either hand. Repetitive contacts on the thenar or hypothenar eminence, at interstimulus intervals (ISIs) of 3 s, progressively increased the perceived intensity of a thermal sensation that followed each contact at an onset latency >2 s. Temporal summation of these delayed (late) sensations was proportional to thermode temperature over a range of 45–53°C, progressing from a nonpainful level (warmth) to painful sensations that could be rated as very strong after 10 contacts. Short-latency pain sensations rarely were evoked by such stimuli and never attained levels substantially above pain threshold for the sequences and temperatures presented. Temporal summation produced by brief contacts was greater in rate and amount than increases in sensory intensity resulting from repetitive ramping to the same temperature by a thermode in constant contact with the skin. Variation of the interval between contacts revealed a dependence of sensory intensity on interstimulus interval that is similar to physiological demonstrations of windup, where increasing frequencies of spike train activity are evoked from spinal neurons by repetitive activation of unmyelinated nociceptors. However, substantial summation at repetition rates of ≥0.33 Hz was observed for temperatures that produced only late sensations of warmth when presented at frequencies <0.16 Hz. Measurements of subepidermal skin temperature from anesthetized monkeys revealed different time courses for storage and dissipation of heat by the skin than for temporal summation and decay of sensory intensity for the human subjects. For example, negligible heat loss occurred during a 6-s interval between two trials of 10 contacts at 0.33 Hz, but ratings of sensory magnitude decreased from very strong levels of pain to sensations of warmth during the same interval. Evidence that temporal summation of sensory intensity during series of brief contacts relies on central integration, rather than a sensitization of peripheral receptors, was obtained using two approaches. In the first, a moderate degree of temporal summation was observed during alternating stimulation of adjacent but nonoverlapping skin sites at 0.33 Hz. Second, temporal summation was significantly attenuated by prior administration of dextromethorphan, a N-methyl-d-aspartate receptor antagonist.
3
Tousignant-Laflamme, Yannick, and Serge Marchand. "Aging Independently of the Hormonal Status Changes Pain Responses in Young Postmenopausal Women." Pain Research and Treatment 2012 (October 3, 2012): 1–7. http://dx.doi.org/10.1155/2012/693912.
Full textAbstract:
Both aging and hormonal status have an effect on pain perception. The goal of this study was to isolate as much as possible the effect of aging in postmenopausal women. Thirty-two women with regular menstrual cycles (RMW) and 18 postmenopausal women (PMW) underwent a 2-minute cold pressor test (CPT) to activate DNIC with a series of tonic heat pain stimulations with a contact thermode to assess ascending pain pathways. We found that this procedure induced much less pain during the first 15 seconds of stimulation the PMW group (P=0.03), while the mean thermode pain ratings, pain tolerance, pain threshold, and DNIC analgesia were similar for both groups (P>0.05). The absence of the peak pain in the PMW was probably due to reduced function of the myelinated Aδ fibers that naturally occurs with age.
4
Mauderli, Andre P., Charles J. Vierck, Richard L. Cannon, Anthony Rodrigues, and Chiayi Shen. "Relationships Between Skin Temperature and Temporal Summation of Heat and Cold Pain." Journal of Neurophysiology 90, no. 1 (July 2003): 100–109. http://dx.doi.org/10.1152/jn.01066.2002.
Full textAbstract:
Temporal summation of heat pain during repetitive stimulation is dependent on C nociceptor activation of central N-methyl-d-aspartate (NMDA) receptor mechanisms. Moderate temporal summation is produced by sequential triangular ramps of stimulation that control skin temperature between heat pulses but do not elicit distinct first and second pain sensations. Dramatic summation of second pain is produced by repeated contact of the skin with a preheated thermode, but skin temperature between taps is not controlled by this procedure. Therefore relationships between recordings of skin temperature and psychophysical ratings of heat pain were evaluated during series of repeated skin contacts. Surface and subcutaneous recordings of skin temperatures revealed efficient thermoregulatory compensation for heat stimulation at interstimulus intervals (ISIs) ranging from 2 to 8 s. Temporal summation of heat pain was strongly influenced by the ISIs and cannot be explained by small increases in skin temperature between taps or by heat storage throughout a stimulus series. Repetitive brief contact with a precooled thermode was utilized to evaluate whether temporal summation of cold pain occurs, and if so, whether it is influenced by skin temperature. Surface and subcutaneous recordings of skin temperature revealed a sluggish thermoregulatory compensation for repetitive cold stimulation. In contrast to heat stimulation, skin temperature did not recover between cold stimuli throughout ISIs of 3–8 s. Psychophysically, repetitive cold stimulation produced an aching pain sensation that progressed gradually and radiated beyond the site of stimulation. The magnitude of aching pain was well related to skin temperature and thus appeared to be established primarily by peripheral factors.
5
Craig, A. D., and D. Andrew. "Responses of Spinothalamic Lamina I Neurons to Repeated Brief Contact Heat Stimulation in the Cat." Journal of Neurophysiology 87, no. 4 (April 1, 2002): 1902–14. http://dx.doi.org/10.1152/jn.00578.2001.
Full textAbstract:
It was recently shown that repeated heat stimulation, using brief contacts (<1 s) with a preheated thermode at sufficiently short interstimulus intervals (ISIs <5 s) and high temperatures (≥51°C), will elicit in humans a sensation of rapidly augmenting “second” (burning) pain with only a weak “first” (sharp) pain sensation. Most strikingly, at short intertrial intervals (ITIs >5 s) such summation will reset, or begin again at baseline. In the present experiments, the responses of nociceptive lamina I spinothalamic (STT) neurons in the lumbosacral dorsal horn of barbiturate-anesthetized cats were examined using this repeated brief contact heat paradigm. The neurons were classified as nociceptive-specific (NS, n = 8) or polymodal nociceptive (HPC, n = 8) based on their responses to quantitative thermal stimuli; all had receptive fields on the glabrous ventral hindpaw. A pneumatic piston was used to apply a thermode preheated to 34, 46, 49, 53, or 58°C with a contact dwell time of ∼0.7 s to the ventral hindpaw repeatedly (15 times) at ISIs of 2, 3, and 5 s, with 3–5 min between trials. The mean responses of the 16 nociceptive lamina I STT cells showed rapid temporal summation that was directly dependent on temperature and inversely dependent on ISI, with the greatest increases occurring between the 3rd and 10th contacts. The temporal profiles of this family of curves correspond with the psychophysical data on human sensation. Further analysis showed that this summation was due to the HPC cells, which all showed strong summation; in contrast, the NS cells showed little, if any. The HPC responses to the repeated heat stimuli lagged each contact by ∼1 s, consistent with the strong, monosynaptic C-fiber input that is characteristic of HPC cells and also with the dependence of second pain on C-fiber nociceptors. HPC cells also displayed the reset phenomenon at short ITIs, again in correspondence with the psychophysical data. The summation and the reset displayed by HPC cells were not related to skin temperature. Thus the results presented in this study, together with those in the preceding article, demonstrate a double dissociation indicating that NS and HPC lamina I STT cells can subserve the qualitatively distinct sensations of first (sharp) and second (burning) pain, respectively. These findings support the concept that the lamina I STT projection comprises several discrete sensory channels that are integrated in the forebrain to generate distinct sensations.
6
Springborg, Anders Deichmann, Caitlin Rae Wessel, Lars Peter Kloster Andersen, and Mads Utke Werner. "Methodology and applicability of the human contact burn injury model: A systematic review." PLOS ONE 16, no. 7 (July 30, 2021): e0254790. http://dx.doi.org/10.1371/journal.pone.0254790.
Full textAbstract:
The contact burn injury model is an experimental contact thermode-based physiological pain model primarily applied in research of drug efficacy in humans. The employment of the contact burn injury model across studies has been inconsistent regarding essential methodological variables, challenging the validity of the model. This systematic review analyzes methodologies, outcomes, and research applications of the contact burn injury model. Based on these results, we propose an improved contact burn injury testing paradigm. A literature search was conducted (15-JUL-2020) using PubMed, EMBASE, Web of Science, and Google Scholar. Sixty-four studies were included. The contact burn injury model induced consistent levels of primary and secondary hyperalgesia. However, the analyses revealed variations in the methodology of the contact burn injury heating paradigm and the post-burn application of test stimuli. The contact burn injury model had limited testing sensitivity in demonstrating analgesic efficacy. There was a weak correlation between experimental and clinical pain intensity variables. The data analysis was limited by the methodological heterogenicity of the different studies and a high risk of bias across the studies. In conclusion, although the contact burn injury model provides robust hyperalgesia, it has limited efficacy in testing analgesic drug response. Recommendations for future use of the model are being provided, but further research is needed to improve the sensitivity of the contact burn injury method. The protocol for this review has been published in PROSPERO (ID: CRD42019133734).
7
Micus, Sebastian, Ivan Kirsten, Michael Haupt, and Götz T. Gresser. "Analysis of Hot Bar Soldering, Insulation Displacement Connections (IDC), and Anisotropic Conductive Adhesives (ACA), for the Automated Production of Smart Textiles." Sensors 20, no. 1 (December 18, 2019): 5. http://dx.doi.org/10.3390/s20010005.
Full textAbstract:
Despite all the growth forecasts of the smart textiles market, there is no stable automated manufacturing process for attaching classic electronics to textiles. The great amount of manual production steps causes high prices, which slow down market growth. During the production process, the contacting step offers the greatest potential to reduce manual manufacturing steps. For this reason, we have analyzed various contacting methods for electronic parts on conductive yarns that have a high potential for automation. The chosen methods were thermode soldering, insulation–displacement connectors and anisotropic conductive adhesives. In order to ensure reliable mechanical contacting, the samples were tested in a peeling experiment. The examination of the contact resistances took place in the context of a resistance test using four-wire measuring technology.
8
Ruscheweyh, Ruth, Frederike Stumpenhorst, Stefan Knecht, and Martin Marziniak. "Comparison of the Cold Pressor Test and Contact Thermode-Delivered Cold Stimuli for the Assessment of Cold Pain Sensitivity." Journal of Pain 11, no. 8 (August 2010): 728–36. http://dx.doi.org/10.1016/j.jpain.2009.10.016.
Full text
9
Moulton, E. A., M. L. Keaser, R. P. Gullapalli, and J. D. Greenspan. "Regional Intensive and Temporal Patterns of Functional MRI Activation Distinguishing Noxious and Innocuous Contact Heat." Journal of Neurophysiology 93, no. 4 (April 2005): 2183–93. http://dx.doi.org/10.1152/jn.01025.2004.
Full textAbstract:
Cortical responses to painful and nonpainful heat were measured using functional magnetic resonance imaging (fMRI) region of interest analysis (ROI) of primary somatosensory cortex (S1), secondary somatosensory cortex (S2), anterior cingulate (ACC), supplementary motor area (SMA), insula, and inferior frontal gyrus (IFG). Previous studies indicated that innocuous and noxious stimuli of different modalities produce responses with different time courses in S1 and S2. The aim of this study was to 1) determine whether temporally distinct nociceptive blood oxygen level–dependent (BOLD) responses are evoked in multiple somatosensory processing cortical areas and 2) whether these responses discriminate small noxious stimulus intensity differences. Thirty-three subjects underwent fMRI scanning while receiving three intensities of thermal stimuli, ranging from innocuous warm (41°C) to 1°C below tolerance, applied to the dorsum of the left foot. Innocuous and noxious responses were distinguishable in contralateral S1, the mid-ACC, and SMA. The peak of the nociceptive response was temporally delayed from the innocuous response peak by 6–8 s. Responses to noxious but not to innocuous stimuli were observed in contralateral posterior insula. Responses to innocuous and noxious stimuli were not statistically different in contralateral S2. In contralateral S1 only, the nociceptive response could differentiate heat stimuli separated by 1°C. These results show that 1) multiple cortical areas have temporally distinguishable innocuous and noxious responses evoked by a painfully hot thermode, 2) the nociceptive processing properties vary across cortical regions, and 3) nociceptive responses in S1 discriminate between painful temperatures at a level unmatched in other cortical areas.
10
Knezevic, Aleksandar, Milena Kovacevic, Ljiljana Klicov, Magdalena Pantic, Jana Vasin, and Tijana Spasojevic. "Conditioned pain modulation assessment using contact heat as conditioning stimulus and two different test stimuli." Medical review 72, no. 3-4 (2019): 66–71. http://dx.doi.org/10.2298/mpns1904066k:.
Full textAbstract:
Introduction. The objective of the study was to determine the potentials and reliability of conditioned pain modulation effect in healthy population by application of a conditioning contact heat stimulus, and heat and pressure applied to the low back region as a test stimulus. Material and Methods. The study included 33 healthy subjects (average age 25.73 ? 5.35 years). Pressure and heat pain thresholds were examined on the paravertebral musculature of the lower back as test stimuli. Contact heat was used on the contralateral forearm as a conditioning stimulus. Conditioned pain modulation was calculated as the difference between pain thresholds after and before conditioning stimulus application. To assess the reliability, identical testing was performed 14 ? 2 days later. Results. The pressure and heat pain thresholds, after the conditioning stimulus, were significantly higher compared to pain thresholds obtained before the conditioning stimulus (101,63 N/cm2 ? 45,21N/cm2 vs 82,15 N/cm2 ? 36,15 N/cm2, t = -7,528, p < 0,001 and 47,08?C ? 2,19o C vs 45,00 ? 3,05?C, t = -6,644, p < 0,001, respectively). The reli?ability of the same protocol, measured 14 ? 2 days after the previous testing, showed good reliability of the pressure pain threshold (intraclass correlation coefficient = 0,636, 95% confidence interval 0,240 - 0,825), and fair of the heat pain threshold (intraclass cor?relation coefficient = 0,435, 95% confidence interval - 0,070 - 0,713). Conclusion. Conditioned pain modulation was successfully induced by contact heat applied via a thermode, a conditioning stimulus. The reliability of this method of testing proved to be fair when it comes to the heat pain threshold and good when it comes to the pressure pain threshold.
11
Lejeune, N., and A. Mouraux. "Investiguer la relation entre douleur et conscience : une approche lésionnelle au moyen de l’électroencéphalographie." Douleur et Analgésie 32, no. 1 (March 2019): 69–70. http://dx.doi.org/10.3166/dea-2019-0054.
Full textAbstract:
La douleur est une expérience subjective et dès lors probablement consciente. Les patients en état de conscience altérée (en état végétatif ou en état de conscience minimale) constituent un modèle pathologique de choix afin d’étudier les liens entre expérience de la douleur et conscience. Pour ce faire, étudier les réponses électroencéphalographiques de ces patients, générées par des stimulations empruntant soit la voie spinothalamique, soit la voie lemniscale, est une méthode de choix. De manière spécifique, l’étude des potentiels évoqués cérébraux générés par des stimuli froids est particulièrement intéressante, puisque les réponses observées sont convoyées au cerveau par la voie spinothalamique, tout en présentant l’avantage d’évoquer, du moins chez le sujet sain, des sensations non douloureuses. Techniquement, il est nécessaire d’utiliser une thermode capable de générer de manière très phasique des stimuli froids au contact de la peau. Un tel dispositif est disponible depuis peu, ayant par ailleurs le grand avantage d’être utilisable au chevet des patients. Les résultats de ces analyses pourraient avoir un impact éthique et clinique important dans la prise en charge des patients sévèrement cérébrolésés, incapables de communiquer leurs expériences sensorielles, y compris la douleur.
12
Duschek, Stefan, Heike Heiss, Boriana Buechner, and Rainer Schandry. "Reduction in Pain Sensitivity from Pharmacological Elevation of Blood Pressure in Persons with Chronically Low Blood Pressure." Journal of Psychophysiology 23, no. 3 (January 2009): 104–12. http://dx.doi.org/10.1027/0269-8803.23.3.104.
Full textAbstract:
Recent studies have revealed evidence for increased pain sensitivity in individuals with chronically low blood pressure. The present trial explored whether pain sensitivity can be reduced by pharmacological elevation of blood pressure. Effects of the sympathomimetic midodrine on threshold and tolerance to heat pain were examined in 52 hypotensive persons (mean blood pressure 96/61 mmHg) based on a randomized, placebo-controlled, double-blind design. Heat stimuli were applied to the forearm via a contact thermode. Confounding of drug effects on pain perception with changes in skin temperature, temperature sensitivity, and mood were statistically controlled for. Compared to placebo, higher pain threshold and tolerance, increased blood pressure, as well as reduced heart rate were observed under the sympathomimetic condition. Increases in systolic blood pressure between points of measurement correlated positively with increases in pain threshold and tolerance, and decreases in heart rate were associated with increases in pain threshold. The findings underline the causal role of hypotension in the augmented pain sensitivity related to this condition. Pain reduction as a function of heart rate decrease suggests involvement of a baroreceptor-related mechanism in the pain attrition. The increased proneness of persons with chronic hypotension toward clinical pain is discussed.
13
Hofbauer, Robert K., Pierre Fiset, Gilles Plourde, Steven B. Backman, and M. Catherine Bushnell. "Dose-dependent Effects of Propofol on the Central Processing of Thermal Pain." Anesthesiology 100, no. 2 (February 1, 2004): 386–94. http://dx.doi.org/10.1097/00000542-200402000-00031.
Full textAbstract:
Background Anatomic and physiologic data show that multiple regions of the forebrain are activated by pain. However, the effect of anesthetic level on nociceptive input to these regions is not well understood. Methods The authors used positron emission tomography to measure the effect of various concentrations of propofol on pain-evoked changes in regional cerebral blood flow. Fifteen volunteers were scanned while warm and painful heat stimuli were presented to the volar forearm using a contact thermode during administration of target propofol concentrations of 0.0 microg/ml (alert control), 0.5 microg/ml (mild sedation), 1.5 microg/ml (moderate sedation), and 3.5 microg/ml (unconsciousness). Results During the 0.5-microg/ml target propofol concentration (mild sedation), the subjects' pain ratings increased relative to the alert control condition; correspondingly, pain-evoked regional cerebral blood flow increased in the thalamus and the anterior cingulate cortex. In contrast, when subjects lost consciousness (3.5 microg/ml), pain-evoked responses in the thalamus and the anterior cingulate cortex were no longer observed, whereas significant pain-evoked activation remained in the insular cortex. Conclusion These data show that propofol has a dose-dependent effect on thalamocortical transfer of nociceptive information but that some pain-evoked cortical activity remains after loss of consciousness.
14
Khan, Pathan Fayaz, S. Sengottuvel, Rajesh Patel, K. Gireesan, R. Baskaran, and Awadhesh Mani. "Design and Implementation of a Discrete-Time Proportional Integral (PI) Controller for the Temperature Control of a Heating Pad." SLAS TECHNOLOGY: Translating Life Sciences Innovation 23, no. 6 (May 10, 2018): 614–23. http://dx.doi.org/10.1177/2472630318773697.
Full textAbstract:
Contact heat evoked potentials (CHEPs) are recorded from the brain by giving thermal stimulations through heating pads kept on the surface of the skin. CHEP signals have crucial diagnostic implications in human pain activation studies. This work proposes a novel design of a digital proportional integral (PI) controller based on Arduino microcontroller with a view to explore the suitability of an electric heating pad for use as a thermode in a custom-made, cost-effective CHEP stimulator. The purpose of PI controller is to set, regulate, and deliver desired temperatures on the surface of the heating pad in a user-defined pattern. The transfer function of the heating system has been deduced using the parametric system identification method, and the design parameters of the controller have been identified using the root locus technique. The efficiency of the proposed PI controller in circumventing the well-known integrator windup problem (error in the integral term builds excessively, leading to large transients in the controller output) in tracking the reference input and the controller effort (CE) in rejecting output disturbances to maintain the set temperature of the heating pad have been found to be superior compared with the conventional PI controller and two of the existing anti-windup models.
15
Kenshalo, D. R., F. Anton, and R. Dubner. "The detection and perceived intensity of noxious thermal stimuli in monkey and in human." Journal of Neurophysiology 62, no. 2 (August 1, 1989): 429–36. http://dx.doi.org/10.1152/jn.1989.62.2.429.
Full textAbstract:
1. The magnitude of the sensations produced by small increases in thermal stimuli superimposed on noxious levels of heat stimulation was studied by the use of a simple reaction-time task. Noxious thermal stimuli were presented on the face of three monkeys, the forearm volar surface of three monkeys, and the face of four human subjects. The subject, either monkey or human, initiated a trial by pressing an illuminated button. Subsequently, a contact thermode increased in temperature from a base line of 38 degree C to temperatures of 44, 45, 46, or 47 degrees C (T1). After a variable time period lasting between 4 and 10 s, the thermode temperature increased an additional 0.1, 0.2, 0.4, 0.6, or 0.8 degrees C (T2). The subject was required to release the button as soon as the T2 stimulus was detected. Detection latency, expressed as its reciprocal, detection speed, was defined as the time interval between the onset of T2 and the release of the button. 2. The monkeys' detection speed to stimuli presented on the upper lip was dependent on the intensity of both T1 and T2. Increases in the intensity of T2 between 0.1 and 0.8 degrees C produced faster detection speeds. In general, as the intensity of T1 increased, the detection speed increased to identical T2 stimuli. The monkeys' T2-detection threshold was also dependent on the intensity of T1. 3. The psychophysical functions obtained from stimulation of the monkey's face were compared with those obtained from the volar surface of the monkey's forearm. Whereas the T2 thresholds obtained from stimulation of the monkey's forearm and face were similar, the psychophysical functions obtained from stimulation of the face were significantly steeper than those obtained from stimulation of the forearm. 4. The humans' detection speed of T2 stimuli presented on the face was monotonically related to the intensity of T2 and was dependent on the level of T1. The psychophysical functions obtained from the human's face were equivalent to those obtained from the monkey's faces. 5. A cross-modality matching procedure was used to examine the perceived intensity of pain sensation produced by T2 stimuli in human subjects. The magnitude estimates of these stimuli were dependent on the level of T1, as well as the intensity of T2. Detection speed, plotted as a function of the estimated magnitude of pain, independent of T1 and T2 temperature, was best fit by a logarithmic function.(ABSTRACT TRUNCATED AT 400 WORDS)
16
Price, D. D., J. G. McHaffie, and M. A. Larson. "Spatial summation of heat-induced pain: influence of stimulus area and spatial separation of stimuli on perceived pain sensation intensity and unpleasantness." Journal of Neurophysiology 62, no. 6 (December 1, 1989): 1270–79. http://dx.doi.org/10.1152/jn.1989.62.6.1270.
Full textAbstract:
1. Psychophysical experiments were initiated to determine the possible influence of increasing stimulus size on perceived pain intensity. Six trained human subjects (5 male, 1 female) made visual analogue scale (VAS) ratings for pain-sensation intensity and unpleasantness in response to nociceptive thermal stimuli. Test stimuli consisted of 5-s duration heat pulses (45-50 degrees C in 1 degrees increments) delivered by one, two, or three contact thermal probes (1 cm2 each) applied to the medial aspect of the anterior forearm. 2. The area of skin receiving noxious thermal stimuli was changed by randomly varying the number of thermodes activated. The effects of varying the distance between the thermal probes also were evaluated. In the first series of experiments, thermal-probe separation was kept close to 0; in subsequent experimental series, the thermodes were separated by either 5 or 10 cm. 3. In each experimental series, considerable spatial summation occurred in both pain-sensation intensity and unpleasantness dimensions of pain. This summation occurred throughout the nociceptive thermal range of 45-50 degrees C and was larger at suprathreshold temperatures (greater than or equal to 47 degrees C) than those near threshold (less than or equal to 46 degrees C). Unlike spatial summation of perceived warmth, that of pain was not characterized by systematic changes in power-function exponents but as approximately upward parallel displacements in double-logarithmic coordinates. 4. Thermal-probe separation over a range of 0-10 cm had no effects on spatial summation of pain-sensation intensity or pain unpleasantness. In contrast, increasing thermal-probe separation increased the subjects' ability to discriminate differences in stimulus size and their ability to detect correctly the number of thermal probes activated. 5. Because affective VAS ratings of unpleasantness were linearly related to, but distinctly and systematically less than, VAS ratings of pain-sensation intensity, it was clear that subjects responded quite differently to these two pain dimensions. Affective judgements were not additionally influenced by thermal probe separation and hence by the ability to perceive stimulus size or number of thermal probes activated. 6. The results indicate that powerful spatial-summation mechanisms exist for heat-induced pain. Spatial summation of pain is likely to be subserved both by local integration mechanisms at the level of single spinothalamic-tract neurons and by recruitment of central nociceptive neurons, because spatial summation of pain occurred to approximately equal extents under conditions of thermode separations over a distance of at least 20 cm.
17
Werner, Mads U., Preben Duun, and Henrik Kehlet. "Prediction of Postoperative Pain by Preoperative Nociceptive Responses to Heat Stimulation." Anesthesiology 100, no. 1 (January 1, 2004): 115–19. http://dx.doi.org/10.1097/00000542-200401000-00020.
Full textAbstract:
Background Despite major advances in the understanding of the neurobiologic mechanisms of pain, the wide variation in acute pain experience has not been well explained. Therefore, the authors investigated the potential of a preoperatively induced heat injury to predict subsequent postoperative pain ratings in patients undergoing knee surgery. Methods Twenty patients were studied. The burn injury was induced 6 days before surgery with a contact thermode (12.5 cm2, 47 degrees C for 7 min). The sensory testing, before and 1 h after the injury, included pain score during induction of the burn, secondary hyperalgesia area, thermal and mechanical pain perception, and pain thresholds. Postoperative analgesia consisted of ibuprofen and acetaminophen. Pain ratings (visual analog scale) at rest and during limb movement were followed for 10 days after surgery. Results The burn injury was associated with development of significant hyperalgesia. There was a significant correlation between preoperative pain ratings during the burn injury and early (0-2 days, area under the curve) and late (3-10 days, area under the curve) postoperative dynamic pain ratings during limb movement. Conclusion The results of this study suggest that the pain response to a preoperative heat injury may be useful in research in predicting the intensity of postoperative pain. These findings may have important implications to identify patients at risk for development of chronic pain and to stratify individuals for investigations of new analgesics.
18
Tousignant-Laflamme, Yannick, Marilyne Brochu, Cynthia Dupuis-Michaud, Catherine Pagé, Draga Popovic, and Marie-Eve Simard. "Duration of Analgesia Induced by Acupuncture-Like TENS on Experimental Heat Pain." ISRN Pain 2013 (April 7, 2013): 1–6. http://dx.doi.org/10.1155/2013/792383.
Full textAbstract:
Background. Acupuncture-like TENS (AL-TENS) is a treatment modality that can be used to temporarily reduce pain. However, there is no clear data in the literature regarding the specific duration of analgesia induced by AL-TENS. Objectives. To describe and quantify the duration and magnitude of AL-TENS analgesia on experimental heat pain in healthy subjects and verify if the duration or magnitude of analgesia induced by the AL-TENS was influenced by the duration of the application of the AL-TENS (15 versus 30 minutes). Methods. A repeated-measures, intrasubject randomized experimental design was used, where each participant was his/her own control. 22 healthy volunteers underwent heat pain stimulations with a contact thermode before (pretest) and after (posttest) AL-TENS application (15 and 30 minutes). Outcome measures included subjective pain during AL-TENS, duration, and magnitude of AL-TENS-induced analgesia. Results. Survival analysis showed that the median duration of AL-TENS analgesia was 10 minutes following the application of either 15 or 30 minutes of AL-TENS. The magnitude of analgesia following either application was comparable at all points in time (P values > 0.05) and ranged between −20% and −36% pain reduction. Conclusion. Only half of the participants still had heat-pain analgesia induced by the AL-TENS at 15 minutes postapplication.
19
Dubner, R., D. R. Kenshalo, W. Maixner, M. C. Bushnell, and J. L. Oliveras. "The correlation of monkey medullary dorsal horn neuronal activity and the perceived intensity of noxious heat stimuli." Journal of Neurophysiology 62, no. 2 (August 1, 1989): 450–57. http://dx.doi.org/10.1152/jn.1989.62.2.450.
Full textAbstract:
1. We examined the relationship between the activity of medullary dorsal horn nociceptive neurons and the monkeys' ability to detect noxious heat stimuli. In two different detection tasks, the temperature of a contact thermode positioned on the monkey's face increased from 38 degrees C to temperatures between 44 and 48 degrees C (T1). After a variable time period, the thermode temperature increased an additional 0.2-1.5 degrees C (T2), and the monkeys' detection speed from the onset of T2 was determined. We previously have established that detection speed is a measure of the perceived intensity of noxious thermal stimuli. Nociceptive neurons were classified as wide-dynamic-range (WDR, responsive to innocuous mechanical stimuli with greater responses to noxious mechanical stimuli) and nociceptive-specific (NS, responsive only to noxious stimuli). WDR neurons were subclassified as WDR1 and WDR2 based on the higher slope values of the stimulus-response functions of WDR1 neurons. The monkeys were trained to detect small increases in noxious heat, and their detection speeds were correlated with the responses of WDR1, WDR2, and NS neurons. 2. Detection speeds to T2 temperatures of 1.0 degrees C from preceding T1 temperatures of 45 and 46 degrees C were faster during a preceding ascending series of stimuli than during a descending series. Similarly, the peak discharge frequencies of WDR1 neurons in response to the same stimuli were greater during the ascending series of T2 temperatures. In contrast, the responses of WDR2 and NS neurons showed no significant differences during the ascending and descending series of stimuli. 3. Detection speeds following 0.4, 0.6, and 0.8 degrees C T2 stimuli were higher when the preceding T1 temperature was 46 degrees C as compared with detection speeds to the identical stimuli when the preceding T1 temperature was 45 degrees C. WDR1 neurons also exhibited a significant increase in peak discharge frequency to these same T2 stimuli when the preceding T1 temperature was 46 degrees C. In contrast, the neuronal activity of WDR2 and NS neurons did not differ on 45 and 46 degrees C T1 trials. 4. The relationship between detection speed and neuronal peak discharge frequency was examined in response to different pairs of T1 and T2 stimuli when T1 was either 45 or 46 degrees C. There was a significant correlation between detection speed and neuronal discharge for WDR1 and WDR2 neurons. No correlation was observed for NS neurons. 5. The magnitude of neuronal activity on correctly detected and nondetected trials was compared when T1 was 46 degrees C and T2 was 0.2 degree C.(ABSTRACT TRUNCATED AT 400 WORDS)
20
Opsommer, E., E. Masquelier, and L. Plaghki. "Determination of nerve conduction velocity of C-fibres in humans from thermal thresholds to contact heat (thermode) and from evoked brain potentials to radiant heat (CO2 laser)." Neurophysiologie Clinique/Clinical Neurophysiology 29, no. 5 (October 1999): 411–22. http://dx.doi.org/10.1016/s0987-7053(00)87265-2.
Full text
21
Fardo, Francesca, Mikkel C. Vinding, Micah Allen, Troels Staehelin Jensen, and Nanna Brix Finnerup. "Delta and gamma oscillations in operculo-insular cortex underlie innocuous cold thermosensation." Journal of Neurophysiology 117, no. 5 (May 1, 2017): 1959–68. http://dx.doi.org/10.1152/jn.00843.2016.
Full textAbstract:
Cold-sensitive and nociceptive neural pathways interact to shape the quality and intensity of thermal and pain perception. Yet the central processing of cold thermosensation in the human brain has not been extensively studied. Here, we used magnetoencephalography and EEG in healthy volunteers to investigate the time course (evoked fields and potentials) and oscillatory activity associated with the perception of cold temperature changes. Nonnoxious cold stimuli consisting of Δ3°C and Δ5°C decrements from an adapting temperature of 35°C were delivered on the dorsum of the left hand via a contact thermode. Cold-evoked fields peaked at around 240 and 500 ms, at peak latencies similar to the N1 and P2 cold-evoked potentials. Importantly, cold-related changes in oscillatory power indicated that innocuous thermosensation is mediated by oscillatory activity in the range of delta (1–4 Hz) and gamma (55–90 Hz) rhythms, originating in operculo-insular cortical regions. We suggest that delta rhythms coordinate functional integration between operculo-insular and frontoparietal regions, while gamma rhythms reflect local sensory processing in operculo-insular areas. NEW & NOTEWORTHY Using magnetoencephalography, we identified spatiotemporal features of central cold processing, with respect to the time course, oscillatory profile, and neural generators of cold-evoked responses in healthy human volunteers. Cold thermosensation was associated with low- and high-frequency oscillatory rhythms, both originating in operculo-insular regions. These results support further investigations of central cold processing using magnetoencephalography or EEG and the clinical utility of cold-evoked potentials for neurophysiological assessment of cold-related small-fiber function and damage.
22
Werner, Mads U., Preben Duun, Otto Kraemer, Birgit Lassen, and Henrik Kehlet. "Arthroscopic Knee Surgery Does Not Modify Hyperalgesic Responses to Heat Injury." Anesthesiology 99, no. 5 (November 1, 2003): 1152–57. http://dx.doi.org/10.1097/00000542-200311000-00023.
Full textAbstract:
Background Experimental studies suggest that surgical injury may up- or down-regulate nociceptive function. Therefore, the aim of this clinical study was to evaluate the effect of elective arthroscopically assisted knee surgery on nociceptive responses to a heat injury. Methods Seventeen patients scheduled to undergo repair of the anterior cruciate ligament and 16 healthy controls were studied. The first burn injury was induced 6 days before surgery, and the second burn was induced 1 day after surgery with a contact thermode (12.5 cm2, 47 degrees C for 7 min) placed on the medial aspect of the calf contralateral to the surgical side. Ibuprofen and acetaminophen were given for 2 days before the first burn injury and again from the time of surgery. In the controls, the two burn injuries were separated by 7 days. Sensory variables included cumulated pain score during induction of the burn (visual analog scale), secondary hyperalgesia area, and mechanical and thermal pain perception and pain thresholds assessed before and 1 h after the burn injury. Results The heat injuries induced significant increases in pain perception (P < 0.001) and decreases in pain thresholds (P < 0.02). Baseline heat pain thresholds were higher during the second burn injury in patients (P < 0.001) and controls (P < 0.01). However, there were no significant differences in pain to heat injury (P > 0.8), secondary hyperalgesia areas (P > 0.1), mechanical and thermal pain perception (P > 0.1), or mechanical and thermal pain thresholds (P > 0.08) in the burn area before surgery compared to after surgery. Conclusion Arthroscopic knee surgery did not modify nociceptive responses to a contralaterally applied experimental burn injury.
23
Hobson, Anthony R., Boris Chizh, Kirsty Hicks, Qasim Aziz, Sian Worthen, Philip Lawrence, Odile Dewit, Yvonne Boyle, and George Dukes. "Neurophysiological evaluation of convergent afferents innervating the human esophagus and area of referred pain on the anterior chest wall." American Journal of Physiology-Gastrointestinal and Liver Physiology 298, no. 1 (January 2010): G31—G36. http://dx.doi.org/10.1152/ajpgi.00288.2009.
Full textAbstract:
Noxious stimuli in the esophagus cause pain that is referred to the anterior chest wall because of convergence of visceral and somatic afferents within the spinal cord. We sought to characterize the neurophysiological responses of these convergent spinal pain pathways in humans by studying 12 healthy subjects over three visits (V1, V2, and V3). Esophageal pain thresholds (Eso-PT) were assessed by electrical stimulation and anterior chest wall pain thresholds (ACW-PT) by use of a contact heat thermode. Esophageal evoked potentials (EEP) were recorded from the vertex following 200 electrical stimuli, and anterior chest wall evoked potentials (ACWEP) were recorded following 40 heat pulses. The fear of pain questionnaire (FPQ) was administered on V1. Statistical data are shown as point estimates of difference ± 95% confidence interval. Pain thresholds increased between V1 and V3 [Eso-PT: V1-V3 = −17.9 mA (−27.9, −7.9) P < 0.001; ACW-PT: V1-V3 = −3.38°C (−5.33, −1.42) P = 0.001]. The morphology of cortical responses from both sites was consistent and equivalent [P1, N1, P2, N2 complex, where P1 and P2 are is the first and second positive (downward) components of the CEP waveform, respectively, and N1 and N2 are the first and second negative (upward) components, respectively], indicating activation of similar cortical networks. For EEP, N1 and P2 latencies decreased between V1 and V3 [N1: V1-V3 = 13.7 (1.8, 25.4) P = 0.02; P2: V1-V3 = 32.5 (11.7, 53.2) P = 0.003], whereas amplitudes did not differ. For ACWEP, P2 latency increased between V1 and V3 [−35.9 (−60, −11.8) P = 0.005] and amplitudes decreased [P1-N1: V1-V3 = 5.4 (2.4, 8.4) P = 0.01; P2-N2: 6.8 (3.4, 10.3) P < 0.001]. The mean P1 latency of EEP over three visits was 126.6 ms and that of ACWEP was 101.6 ms, reflecting afferent transmission via Aδ fibers. There was a significant negative correlation between FPQ scores and Eso-PT on V1 ( r = −0.57, P = 0.05). These data provide the first neurophysiological evidence of convergent esophageal and somatic pain pathways in humans.
24
Strigo, Irina A., Franco Carli, and M. Catherine Bushnell. "Effect of Ambient Temperature on Human Pain and Temperature Perception." Anesthesiology 92, no. 3 (March 1, 2000): 699–707. http://dx.doi.org/10.1097/00000542-200003000-00014.
Full textAbstract:
Background Animal studies show reduced nociceptive responses to noxious heat stimuli and increases in endogenous beta-endorphin levels in cold environments, suggesting that human pain perception may be dependent on ambient temperature. However, studies of changes in local skin temperature on human pain perception have yielded variable results. This study examines the effect of both warm and cool ambient temperature on the perception of noxious and innocuous mechanical and thermal stimuli. Methods Ten subjects (7 men and 3 women, aged 20-23 yr) used visual analog scales to rate the stimulus intensity, pain intensity, and unpleasantness of thermal (0-50 degrees C) and mechanical (1.2-28.9 g) stimuli applied on the volar forearm with a 1-cm2 contact thermode and von Frey filaments, respectively. Mean skin temperatures were measured throughout the experiment by infrared pyrometer. Each subject was tested in ambient temperatures of 15 degrees C (cool), 25 degrees C (neutral), and 35 degrees C (warm) on separate days, after a 30-min acclimation to the environment. Studies began in the morning after an 8-h fast. Results Mean skin temperature was altered by ambient temperature (cool room: 30.1 degrees C; neutral room: 33.4 degrees C; warm room: 34.5 degrees C; P < 0.0001). Ambient temperature affected both heat (44-50 degrees C) and cold (25-0 degrees C) perception (P < 0.01). Stimulus intensity ratings tended to be lower in the cool than in the neutral environment (P < 0.07) but were not different between the neutral and warm environments. Unpleasantness ratings revealed that cold stimuli were more unpleasant than hot stimuli in the cool room and that noxious heat stimuli were more unpleasant in a warm environment. Environmental temperature did not alter ratings of warm (37 and 40 degrees C) or mechanical stimuli. Conclusions These results indicate that, in humans, a decrease in skin temperature following exposure to cool environments reduces thermal pain. Suppression of Adelta primary afferent cold fiber activity has been shown to increase cold pain produced by skin cooling. Our current findings may represent the reverse phenomenon, i.e., a reduction in thermal nociceptive transmission by the activation of Adelta cutaneous cold fibers.
25
Tommerdahl, M., K. A. Delemos, O. V. Favorov, C. B. Metz, C. J. Vierck, and B. L. Whitsel. "Response of Anterior Parietal Cortex to Different Modes of Same-Site Skin Stimulation." Journal of Neurophysiology 80, no. 6 (December 1, 1998): 3272–83. http://dx.doi.org/10.1152/jn.1998.80.6.3272.
Full textAbstract:
Tommerdahl, M., K. A. Delemos, O. V. Favorov, C. B. Metz, C. J. Viereck, Jr., and B. L. Whitsel. Response of anterior parietal cortex to different modes of same-site skin stimulation. J. Neurophysiol. 80: 3272–3283, 1998. Intrinsic optical signal (IOS) imaging was used to study responses of the anterior parietal cortical hindlimb region (1 subject) and forelimb region (3 subjects) to repetitive skin stimulation. Subjects were four squirrel monkeys anesthetized with a halothane/nitrous oxide/oxygen gas mixtures. Cutaneous flutter of 25 Hz evoked a reflectance decrease in the sectors of cytoarchitectonic areas 3b and/or 1 that receive input from the stimulated skin site. The intrinsic signal evoked by 25-Hz flutter attained maximal intensity ≤2.5–3.5 s after stimulus onset, remained well maintained as long as stimulation was continued, and disappeared rapidly (usually ≤2–5 s) after stimulus termination. Repetitive skin heating stimuli were delivered via a probe/thermode in stationary contact with the skin (6 temperature ramps/trial; within-trial ramp frequency 0.42 Hz; intertrial interval 180 s; initial temperature 32–36°C; maximal temperature 48–52°C; rate of temperature change 19°C/s). Skin heating led to a large-amplitude reflectance decrease within a zone of area 3a, which neighbored the region in areas 3b/1 that emitted an intrinsic signal in response to same-site 25-Hz flutter in the same subject. In three of four subjects a lower-amplitude decrease in reflectance also occurred in a region of area 4 continuous with the area 3a region that responded maximally to same-site skin heating. The reflectance decrease evoked in areas 3a/4 by skin heating consistently exceeded in both intensity and spatial extent the decrease in reflectance evoked in areas 3b/1 by same-site 25-Hz cutaneous flutter. These findings are viewed as consistent with the proposal that area 3a plays a leading role in the anterior parietal cortical processing of the afferent drive evoked by skin-heating stimuli perceived as painful. In all four subjects the reflectance decrease evoked in areas 3a/4 by skin heating was accompanied by a simultaneous but opposite change in reflectance (a reflectance increase) within a large territory located immediately posterior to the regions that responded with a decrease in reflectance—an observation that raised the possibility that skin heating evoked opposing influences on the activity of area 3a and 3b/1 regions that receive input from the stimulated skin site. This was evaluated with the method of correlation mapping. The observations obtained with correlation mapping appear consistent with demonstrations by others that skin-heating stimuli perceived as painful by conscious subjects suppress/inhibit the anterior parietal response to innocuous mechanical skin stimulation. The opposing (relative to the response of area 3a) optical response of area 1 and/or area 3b during skin heating stimulation is attributed to suppression/inhibition of area 1 and/or area 3b neuron activity.
26
Casey, K. L., S. Minoshima, T. J. Morrow, and R. A. Koeppe. "Comparison of human cerebral activation pattern during cutaneous warmth, heat pain, and deep cold pain." Journal of Neurophysiology 76, no. 1 (July 1, 1996): 571–81. http://dx.doi.org/10.1152/jn.1996.76.1.571.
Full textAbstract:
1. We wished to determine whether there are differences in the spatial pattern and intensity of synaptic activity within the conscious human forebrain when different forms and intensities of innocuous and noxious thermal stimuli are experienced. Accordingly, positron emission tomography (PET) with intravenous injection of H2(15)O was used to detect increases in regional cerebral blood flow (rCBF) in normal humans as they discriminated differences in the intensity of noxious and innocuous thermal stimulation applied to the nondominant (left) arm. After stereotactic registration, subtraction images were formed from each subject by subtracting counts of emissions obtained during lower-intensity stimulation from those obtained during stimulation at higher intensities. A statistical summation analysis (Z score) of individual voxels was performed. In addition, volumes of interest were chosen on the basis of a priori hypotheses and the results of previously published PET studies. In both types of analysis, statistical thresholds were established with corrections for multiple comparisons. 2. Twenty-seven subjects were divided into three groups of nine subjects each for the three phases of this investigation. For studies in which repetitive contact heat stimuli were used, each subject was instructed in magnitude estimation on the basis of a scale for which 0 indicated "no heat sensation," 7 "just barely painful," and 10 "just barely tolerable." For the study of pain elicited by immersion of the hand in cold water, subjects were instructed to use a scale in which 0 represented "no pain" and 10 represented just barely tolerable pain. 3. In the warm-discrimination study, two intensities of innocuous heat (36 and 43 degrees C) were applied with a thermode as repetitive 5-s contacts to the volar forearm for a total of approximately 100 s, 8 stimuli before and 12 during each scan. Each temperature was applied on alternate scans for a total of four scans per subject. Neither stimulus was rated painful. All subjects discriminated the 43 degrees C stimulus (average rating 5.90 +/- 1.43, mean +/- SD) from the 36 degrees C stimulus (1.96 +/- 1.08, mean +/- SD; t = 13.19, P < 0.0001). Significant increases in rCBF to the 43 degrees C stimuli were found in the contralateral ventral posterior thalamus, lenticular nucleus, medial prefrontal cortex (Brodmann's areas 10 and 32), and cerebellar vermis. 4. The procedure for discriminating between noxious and innocuous heat stimuli was identical to that used for warm discrimination except that the stimulation temperatures were 40 and 50 degrees C. All subjects rated the 50 degrees C stimuli as painful (average rating 8.9 +/- 0.9, mean +/- SD) and the 40 degrees C stimuli as warm, but not painful (2.1 +/- 1.0). Significant rCBF increases to 50 degrees C stimuli were found contralaterally in the thalamus, anterior cingulate cortex, premotor cortex, and secondary somatosensory (S2) and posterior insular cortices. Significant activity also appeared within the region of the contralateral anterior insula and lenticular nucleus. The ipsilateral premotor cortex and thalamus, and the medial dorsal midbrain and cerebellar vermis, also showed significant rCBF increases. Cerebral blood flow (CBF) increases just below the threshold for statistical significance were seen in the contralateral sensorimotor cortex [primary motor cortex (M1)/primary somatosensory cortex (S1)]. 5. For discrimination between tonic innocuous cold and tonic cold pain, the left hand was immersed to the wrist, throughout each of six scans, in water kept at an average temperature of either 20.5 +/- 1.15 degrees C (mean +/- SD) or 6.02 +/- 1.18 degrees C (mean +/- SD) on alternate scans. All subjects rated the intensity of the stimuli on a scale in which 0 indicated no pain and 10 represented barely tolerable pain. Subjects rated the 20 degrees C water immersion as painless (average rating 0.18 +/- 0.48, mean +/- SD), but gave ratings indicating i
27
Haffane, N., T. Benameur, and J. M. Vergnaud. "Hardness variation of a thermoset in contact with a liquid." Polymer Testing 16, no. 3 (June 1997): 259–70. http://dx.doi.org/10.1016/s0142-9418(96)00046-3.
Full text
28
Jiang, Guo Zhan, and Stephen J. Pickering. "Recycled Carbon Fibres: Contact Angles and Interfacial Bonding with Thermoset Resins." Materials Science Forum 714 (March 2012): 255–61. http://dx.doi.org/10.4028/www.scientific.net/msf.714.255.
Full textAbstract:
Recycled T800S carbon fibre from a polymer composite using a pyrolysis process was compared with virgin T800S fibre and the contact angle and interfacial shear strength with epoxy and vinyl ester resins were measured. The contact angles were measured using drop length-height method, and the interfacial shear strengths were measured using micro-bond method. For the same type of resin, the recycled T800S carbon fibre had a greater contact angle and lower interfacial shear strength than those of the virgin fibre.
29
Simone, Donald A., and Keith C. Kajander. "Responses of Cutaneous A-Fiber Nociceptors to Noxious Cold." Journal of Neurophysiology 77, no. 4 (April 1, 1997): 2049–60. http://dx.doi.org/10.1152/jn.1997.77.4.2049.
Full textAbstract:
Simone, Donald A. and Keith C. Kajander. Responses of cutaneous A fiber nociceptors to noxious cold. J. Neurophysiol. 77: 2049–2060, 1997. Responses of cutaneous nociceptors to natural stimuli, particularly mechanical and heat stimuli, have been well documented. Although nociceptors are excited by noxious cold stimuli, there have been few studies of their stimulus-response functions for cold stimuli over a wide range of stimulus temperatures. Furthermore, the proportion of nociceptors excited by noxious cold is not clear. In the present study, we examined responses of mechanosensitive Aδ-nociceptors and low-threshold mechanoreceptors to a wide range of cold stimuli that included stimulus temperatures <0°C. Electrophysiological recordings were made from single primary afferent fibers in the saphenous nerves of anesthetized rats. Cutaneous sensory receptors were classed according to their conduction velocity and subgrouped functionally according to their responses evoked by mechanical, heat, and cold stimuli (0°C). Responses evoked by a wide range of cold stimulus intensities that included stimuli considered innocuous and noxious (painful) were then assessed. Stimuli of 20 to −20°C were delivered to the receptive field via a 1-cm2 contact thermode from a base temperature of 32°C. Stimuli were applied in descending order of 2°C decrements. Stimulus ramp rate was 5°C/s, and stimulus temperatures were applied for a duration of 10 s. A total of 90 A fibers was studied, of which 61 were nociceptors and had conduction velocity in the Aδ-range (2–30 m/s). Nociceptors were classed initially as mechanical, mechanoheat, and mechanocold nociceptors. The remaining 29 fibers were low-threshold mechanoreceptors with conduction velocity in the Aδ- or Aβ-range (>30 m/s). These were subgrouped according to their adaptive properties as slowly or rapidly adapting, and according to whether they were excited by hair movement (hair follicle afferent fibers). All nociceptors were excited by noxious cold. Only 30% of nociceptors were considered sensitive to cold on initial classification with the use of a cold stimulus of 0°C. However, all nociceptors were excited by stimulus intensities <0°C. Response thresholds for cold ranged from 14 to −18°C (−4.6 ± 1.07°C, mean ± SE). The total number of impulses, discharge rate, and peak discharge increased monotonically as intensity of cold stimuli increased. Power functions were used to determine the rate at which the number of impulses increased as stimulus intensity increased. The slopes of power functions ranged from 0.12 to 2.28 (mean 1.07 ± 0.13). Most mechanoreceptors were not excited by cold stimuli. The only types of mechanoreceptors that responded reliably to cold stimuli were the slowly adapting mechanoreceptors. Responses usually occurred during the temperature ramp when the skin temperature was decreasing. There was no evidence that mechanoreceptors encoded the intensity of cold stimuli at intensities above or below 0°C, because evoked responses did not increase with intensity of cold stimuli. It is concluded that the proportion of cutaneous Aδ-nociceptors excited by noxious cold stimuli has been underestimated in previous studies. All nociceptors were excited by stimulus temperatures <0°C and encoded the intensity of cold stimuli. It is therefore likely that cutaneous Aδ-nociceptors contribute to the sensation of cold pain, particularly pain produced by stimulus temperatures <0°C.
30
JANKŮ, Rostislav, and Vladimír HORÁK. "THERMO-ANEMOMETRIC DETERMINATION OF LIQUID WATER CONTENT IN WET AIRSTREAM." SCIENTIFIC RESEARCH AND EDUCATION IN THE AIR FORCE 18, no. 1 (June 24, 2016): 331–36. http://dx.doi.org/10.19062/2247-3173.2016.18.1.45.
Full text
31
Li, Guoqiang, and Amir Shojaei. "A viscoplastic theory of shape memory polymer fibres with application to self-healing materials." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 468, no. 2144 (April 11, 2012): 2319–46. http://dx.doi.org/10.1098/rspa.2011.0628.
Full textAbstract:
The difficulty in healing structural damage is that most existing schemes need external help to bring the fractured surfaces in contact before healing can occur. To facilitate the existing schemes to heal macroscopic cracks, we envision that the cracked surfaces can be brought in contact through constrained shape recovery of a shape memory polymer (SMP) fibre-reinforced grid skeleton that is embedded in thermoset polymer matrix, similar to stitch a cut in the human skin by suture. In this study, we show that polyurethane SMP fibres can be hardened through cyclic cold-drawing programming, which makes them suitable for reinforcement and healing in thermoset polymer composites. We characterized the microstructure of the SMP fibres, which provides fundamental understanding of the effect of programming on the degree of crystallinity and molecular orientation. Then, a micromechanical multiscale viscoplastic theory is developed to predict the thermomechanical behaviours of the SMP fibres, including the cyclic hardening and stress recovery responses. The proposed theory takes into account the stress-induced crystallization process and the evolution of the morphological texture based on the applied stresses. The cyclic loading and the thermomechanical responses of the SMP fibres confirm the capabilities of the proposed model in capturing these phenomena.
32
Wang, Chunhong, Zilong Ren, Shan Li, and Xiaosu Yi. "Effect of Ramie Fabric Chemical Treatments on the Physical Properties of Thermoset Polylactic Acid (PLA) Composites." Aerospace 5, no. 3 (September 2, 2018): 93. http://dx.doi.org/10.3390/aerospace5030093.
Full textAbstract:
Ramie fabric-reinforced thermoset polylactic acid (PLA) composites were prepared by using heat pressing technology. Fabrics were treated with alkali, silane, and alkali–silane respectively, expecting an improvement of the interface between the fabric and the matrix. Scanning electron microscopy (SEM) results indicated that after alkali treatment, impurities on the fiber surface were removed and its diameter became finer. After the silane, and alkali–silane treatments, the contact angles of the ramie fibers increased by 14.26%, and 33.12%, respectively. The contact angle of the alkali–silane treated fiber reached 76.41°; this is beneficial for the adhesion between ramie fiber and the PLA. The research revealed that the tensile strength of the fiber increased after the alkali and silane treatments. A slight decrease was noticed on the tensile strength of fibers treated with alkali–silane. After all, three chemical treatments were done, the flexure strength of the ramie fabric-reinforced PLA composites, improved in all cases. Among the three treatments, the alkali–silane treatment demonstrated the best result, as far as the flexure strength and modulus of the fabricated composites were concerned. On the other hand, water absorption of the related composites decreased by 23.70%, which might contribute to the closer contact between the ramie fiber and the matrix. The ramie fabric-reinforced PLA composites, prepared in this study, can meet the standard requirements of aircraft interior structures and have favorable application foreground.
33
Takács, László, and Ferenc Szabó. "Experimental and Numerical Failure Analysis of Adhesive Joint of Glass Fiber Reinforced Polymer Composite." Periodica Polytechnica Mechanical Engineering 64, no. 1 (December 17, 2019): 88–95. http://dx.doi.org/10.3311/ppme.15106.
Full textAbstract:
The adhesive joint is the most widely used joining technique of thermoset composite structures. Analysis of the failure of adhesive joints of composite structures has a high importance due to its significance in industrial applications such as automobile or autobus bodies. In this paper we performed experimental and numerical analysis of a glass fiber reinforced, vinyl-ester matrix composite bonded with a methacrylate adhesive. The critical energy release rate in normal loading direction obtained from standard double cantilever beam test is used as input data in finite element simulations, in which the failure process is modeled by using cohesive zone material. Results of interface elements with exponential and standard contact elements with bilinear cohesive behavior are compared. The use of interface elements is numerically robust, convergence is reached faster, but identical mesh between the parts is needed. It can be a good alternative when simulating sub-models. When using standard contact elements, the robustness needs contact stabilization, however this method does not need identical mesh and it also allows the use of shell elements, therefore it can be used on a full-structure scale with high efficiency.
34
Kharrat, Mohamed, Abdelkader Krichen, and Antoine Chateauminois. "Analysis of the Fretting Conditions in a Contact Between an Epoxy Thermoset and a Glass Counterface." Tribology Transactions 42, no. 2 (January 1999): 377–84. http://dx.doi.org/10.1080/10402009908982231.
Full text
35
Pasco, Corentin, Muhammad Khan, Jaipal Gupta, and Kenneth Kendall. "Experimental investigation on interply friction properties of thermoset prepreg systems." Journal of Composite Materials 53, no. 2 (June 9, 2018): 227–43. http://dx.doi.org/10.1177/0021998318781706.
Full textAbstract:
A comprehensive novel investigation into the characterisation of interply friction behaviour of thermoset prepregs for high-volume manufacturing was conducted. High interply slipping rate and normal pressure typically used for high-volume manufacturing present challenges when preforming carbon fibre reinforced plastics. The study involved multiple reinforcement architectures (woven and unidirectional with the same rapid-cure resin system) which were characterised using a bespoke interply friction test rig used to simulate processing conditions representative to press forming and double diaphragm forming. Under prescribed conditions, woven and unidirectional prepregs exhibit significantly different frictional behaviour. Results demonstrated the unidirectional material obeys a hydrodynamic lubrication mode. For the woven material, a rate-dependent friction behaviour was found at low normal pressure. At higher normal pressure however, the woven material exhibited a friction behaviour similar to that of a dry reinforcement and significant tow displacement was observed. Post-characterisation analysis of test-specimens showed significant resin migration towards the outer edges of the plies, leaving a relatively resin-starved contact interface. The findings generate new knowledge on interply friction properties of thermoset prepreg for high-volume manufacturing applications, yet reveal a lack of understanding of the influence of tow tensions as well as the pre-impregnation level for a range of processing conditions.
36
Pransky, Joanne. "Geoff Howe, senior vice president, Howe and Howe, Inc., a subsidiary of Textron Systems; co-pioneer of robotic firefighting technologies, including Thermite™ firefighting robots." Industrial Robot: the international journal of robotics research and application 48, no. 2 (June 19, 2021): 169–73. http://dx.doi.org/10.1108/ir-12-2020-0266.
Full textAbstract:
Purpose The purpose of this paper is to provide a “Q&A interview” conducted by Joanne Pransky of Industrial Robot Journal as a method to impart the combined technological, business and personal experience of a prominent, industry engineer-turned entrepreneur regarding his pioneering efforts in bringing a robotic invention to market. This paper aims to discuss these issues. Design/methodology/approach The interviewee is Geoff Howe, Senior Vice President of Howe & Howe, Inc., a subsidiary of Textron Systems and a leader in advanced robotic platform solutions and applications built and proven for the most extreme conditions in the world. Geoff and Michael Howe founded Howe & Howe Technologies in 2001 and was acquired by Textron Systems in 2018. In 2010, Howe and Howe developed one of the world’s first robotic fire-fighting solutions. Geoff Howe describes the evolution of the Thermite robotic firefighter’s commercial development, along with the challenges of breaking ground in this new industry. Findings Geoff and his identical twin brother, Michael Howe, are inventors, military contractors, actors and entrepreneurial businessmen famous for their philanthropic drive to give back to their community. When Geoff and Mike were just six years old, they were known as “Howe and Howe Construction.” At the age of eight, Mike and Geoff built their own one room log cabin with the power tools their mom had given them for their birthday. At 16 years old, they started tinkering with vehicles before they even had their drivers’ licenses. They both graduated from Maine high school and colleges with honors. The company’s portfolio includes the RIPSAW® , Thermite, the Badger, Subterranean Rover and other extreme vehicles used for numerous applications. In 2010, Howe and Howe completed three new vehicles. First was the Thermite™ which entered the unmanned ground vehicle (UGV) market as the USA’s first firefighting UGV. The second vehicle was Ripchair™, the development of an off-road wheelchair for those that have become disabled and are unable to walk. The third vehicle was Riptide, the amphibious version of the RIPSAW. Year 2015 saw the commercial development of the Big Dog Extreme 4x4 fire truck and the Thermite RS1 and RS3 firefighting robots. The Big Dog is an off-road truck and also serves as an all-terrain multi-use firetruck. The Thermite provides firefighters and first responders immediate eyes inside the fire as well the ability to safely attack industrial, chemical and HAZMAT fires from their core. The Thermite robot provides safety and inside access on containing and defeating fires of any magnitude. Originality/value Howe & Howe Technologies first gained notoriety in 2001, with the development of the world’s fastest tank, the RIPSAW. Successful demonstrations soon followed, which eventually allowed the Howes, at the age of 31, to be named among the youngest in history to ever receive a multi-million dollar military contract from the USA. Soon after, in 2010, Howe & Howe received a Guinness World Record for developing the world’s smallest armored vehicle, the Badger. By the time the Howes were 36, they had one world record, multiple patents pending for their product developments, as well as military contracts. The Howes also had their own reality television show on a major US network. In 2010, they completed the Thermite, Fire Fighting Unmanned Ground Vehicle. In 2012, the Howes founded “Outdoors Again,” a nonprofit 501c3 organization that holds outdoor events and social activities for those who require the use of a wheelchair.
37
Гершман, Евгений, Evgeniy Gershman, Иосиф Гершман, Iosif Gershman, Александр Миронов, and Aleksandr Mironov. "USE OF NON-EQUILIBRIUM THERMODYNAMICS AND THEORY OF SELF-ORGANIZATION FOR TRIBOSYSTEMS DESCRIPTION AND WEAR-RESISTANT MATERIALS DEVELOPMENT." Bulletin of Bryansk state technical university 2016, no. 4 (December 28, 2016): 32–38. http://dx.doi.org/10.12737/23159.
Full textAbstract:
In the paper there is presented a practical use of the non-equilibrium thermodynamics and theory of self-organization in tribology with obtaining certain results particularly at the development of new wear-resistant materials. Wear intensity decreases with the decrease of manufacturing entropy. There are shown the results of the applied investigations of non-equilibrium thermody-namics and the theory of self-organization conformably to friction. Possible states of a body of friction with equal power imparted to a body from the point of view of en-tropy are considered. There are shown practical examples of wear intensity decrease by the example of sliding electrical contacts and antifriction alloys for sliding bearings. The results of the development of antifriction aluminum alloys made simultaneously on the basis of seven-nine alloying elements are considered. Besides, in experimental alloys there were added silicon, magnesium, zinc, titanium, that allowed decreasing wear intensity by about two times and decreasing tin content in an alloy by 1.5 – 2 times.
38
Yu, Chunpei, Wei Ren, Ganggang Wu, Wenchao Zhang, Bin Hu, Debin Ni, Zilong Zheng, Kefeng Ma, Jiahai Ye, and Chenguang Zhu. "A Facile Preparation and Energetic Characteristics of the Core/Shell CoFe2O4/Al Nanowires Thermite Film." Micromachines 11, no. 5 (May 20, 2020): 516. http://dx.doi.org/10.3390/mi11050516.
Full textAbstract:
In this study, CoFe2O4 is selected for the first time to synthesize CoFe2O4/Al nanothermite films via an integration of nano-Al with CoFe2O4 nanowires (NWs), which can be prepared through a facile hydrothermal-annealing route. The resulting nanothermite film demonstrates a homogeneous structure and an intense contact between the Al and CoFe2O4 NWs at the nanoscale. In addition, both thermal analysis and laser ignition test reveal the superb energetic performances of the prepared CoFe2O4/Al NWs nanothermite film. Within different thicknesses of nano-Al for the CoFe2O4/Al NWs nanothermite films investigated here, the maximum heat output has reached as great as 2100 J·g−1 at the optimal thickness of 400 nm for deposited Al. Moreover, the fabrication strategy for CoFe2O4/Al NWs is also easy and suitable for diverse thermite systems based upon other composite metal oxides, such as MnCo2O4 and NiCo2O4. Importantly, this method has the featured advantages of simple operation and compatibility with microsystems, both of which may further facilitate potential applications for functional energetic chips.
39
Vecchio, Kenneth S. "Electron microscopy study of shock synthesis of silicides." Proceedings, annual meeting, Electron Microscopy Society of America 51 (August 1, 1993): 1162–63. http://dx.doi.org/10.1017/s0424820100151647.
Full textAbstract:
Shock-induced reactions (or shock synthesis) have been studied since the 1960’s but are still poorly understood, partly due to the fact that the reaction kinetics are very fast making experimental analysis of the reaction difficult. Shock synthesis is closely related to combustion synthesis, and occurs in the same systems that undergo exothermic gasless combustion reactions. The thermite reaction (Fe2O3 + 2Al -> 2Fe + Al2O3) is prototypical of this class of reactions. The effects of shock-wave passage through porous (powder) materials are complex, because intense and non-uniform plastic deformation is coupled with the shock-wave effects. Thus, the particle interiors experience primarily the effects of shock waves, while the surfaces undergo intense plastic deformation which can often result in interfacial melting. Shock synthesis of compounds from powders is triggered by the extraordinarily high energy deposition rate at the surfaces of the powders, forcing them in close contact, activating them by introducing defects, and heating them close to or even above their melting temperatures.
40
Alves, Carine, Janete Oliveira, Alberto Tannus, Alessandra Tarpani, and José Tarpani. "Detection and Imaging of Damages and Defects in Fibre-Reinforced Composites by Magnetic Resonance Technique." Materials 14, no. 4 (February 19, 2021): 977. http://dx.doi.org/10.3390/ma14040977.
Full textAbstract:
Defectively manufactured and deliberately damaged composite laminates fabricated with different continuous reinforcing fibres (respectively, carbon and glass) and polymer matrices (respectively, thermoset and thermoplastic) were inspected in magnetic resonance imaging equipment. Two pulse sequences were evaluated during non-destructive examination conducted in saline solution-immersed samples to simulate load-bearing orthopaedic implants permanently in contact with biofluids. The orientation, positioning, shape, and especially the size of translaminar and delamination fractures were determined according to stringent structural assessment criteria. The spatial distribution, shape, and contours of water-filled voids were sufficiently delineated to infer the amount of absorbed water if thinner image slices than this study were used. The surface texture of composite specimens featuring roughness, waviness, indentation, crushing, and scratches was outlined, with fortuitous artefacts not impairing the image quality and interpretation. Low electromagnetic shielding glass fibres delivered the highest, while electrically conductive carbon fibres produced the poorest quality images, particularly when blended with thermoplastic polymer, though reliable image interpretation was still attainable.
41
Dempsey, Daniel, Sean McDonald, Davide Masato, and Carol Barry. "Characterization of Stereolithography Printed Soft Tooling for Micro Injection Molding." Micromachines 11, no. 9 (August 28, 2020): 819. http://dx.doi.org/10.3390/mi11090819.
Full textAbstract:
The use of microfeature-enabled devices, such as microfluidic platforms and anti-fouling surfaces, has grown in both potential and application in recent years. Injection molding is an attractive method of manufacturing these devices due to its excellent process throughput and commodity-priced raw materials. Still, the manufacture of micro-structured tooling remains a slow and expensive endeavor. This work investigated the feasibility of utilizing additive manufacturing, specifically a Digital Light Processing (DLP)-based inverted stereolithography process, to produce thermoset polymer-based tooling for micro injection molding. Inserts were created with an array of 100-μm wide micro-features, having different heights and thus aspect ratios. These inserts were molded with high flow polypropylene to investigate print process resolution capabilities, channel replication abilities, and insert wear and longevity. Samples were characterized using contact profilometry as well as optical and scanning electron microscopies. Overall, the inserts exhibited a maximum lifetime of 78 molding cycles and failed by cracking of the entire insert. Damage was observed for the higher aspect ratio features but not the lower aspect ratio features. The effect of the tool material on mold temperature distribution was modeled to analyze the impact of processing and mold design.
42
Compton, David A. C., Stephen L. Hill, Norman A. Wright, Mark A. Druy, Joseph Piche, William A. Stevenson, and D. Warren Vidrine. "In Situ FT-IR Analysis of a Composite Curing Reaction Using a Mid-Infrared Transmitting Optical Fiber." Applied Spectroscopy 42, no. 6 (August 1988): 972–79. http://dx.doi.org/10.1366/0003702884430317.
Full textAbstract:
The use of a mid-infrared transmitting fiber to carry the infrared beam of an FT-IR spectrometer outside of the optical bench is reported. In addition it is demonstrated that it is possible to analyze samples using the fiber as an internal reflection element. The fiber is covered with a protective coating which can be removed for a short region, to allow contact with the sample over a controlled length. Two examples of the use of an optical fiber for remote sampling are discussed. The first shows that a spectrum of a liquid sample (2-butanone) can be easily measured, and the second shows how a fiber can be used to monitor the progress of curing reactions in thermoset composite materials. The spectrum of a resin was recorded before the cure by embedding the optical fiber in the graphite fiber/polyimide matrix resin prepreg, and then the progress of the cure was monitored during the curing process. This type of remote sampling shows tremendous potential for opening totally new areas of usage for FT-IR spectrometry, including the studies of hazardous materials, enclosed reactions, and processes that do not allow samples to be taken inside the spectrometer.
43
Peron, Mael, Vincent Sobotka, Nicolas Boyard, and Steven Le Corre. "Thermomechanical Effects in PVTα Measurements." Key Engineering Materials 611-612 (May 2014): 1584–91. http://dx.doi.org/10.4028/www.scientific.net/kem.611-612.1584.
Full textAbstract:
Knowledge of the different properties of thermoset composite materials is of great importance for the manufacturing of high quality composite parts. The resin bulk modulus is one of them and is essential to define the composite parts compressive behaviour under uniform compression. The evolution of this property with temperature and conversion degree of reaction is a challenging task and has been tentatively measured with a home-made apparatus, named PVTα, on which temperature, volume change and degree of cure are simultaneously recorded. But as the sample is contained in a non-reactive and deformable capsule, which mechanical behaviour may interfere with the measurement, a validation is required. The aim of this work is to develop a finite element model of the problem in order to simulate the thermal mechanical behaviour of the sample and the capsule, and so to validate the measurement process. The multiphysical numerical model accounts for phase change kinetics and non-linear thermal properties as well as thermo-dependent elastic properties, all problems being solved through a strong iterative coupling scheme. Mechanical contact problems between the capsule and the resin sample are handled through a penalization method contact algorithm which enables to capture the effects of chemical and thermal shrinkage in the sample and the capsule. The heterogeneous stress state generated by the material transformation is assumed to induce heterogeneous strain states which may lead to misinterpretations of macroscopic measurements. This model is a first approach and will be improved using a more sophisticated rheological model. Nevertheless, results show that the usual experimental analysis method can be used as long as the gel point is not reached. After a certain conversion degree, the measured bulk modulus is different from the effective one so corrections have to be brought.
44
Martin, Isabel, Diego Saenz del Castillo, Antonio Fernandez, and Alfredo Güemes. "Advanced Thermoplastic Composite Manufacturing by In-Situ Consolidation: A Review." Journal of Composites Science 4, no. 4 (October 13, 2020): 149. http://dx.doi.org/10.3390/jcs4040149.
Full textAbstract:
This article provides an overview of the evolution of the in-situ consolidation (ISC) process over time. This evolution is intimately linked with the advancements in each of the steps of the ISC manufacturing process, is additive in nature, and is limited by the orthotropic nature of composite materials and the physicochemical behavior of the thermoplastic matrix. This review covers four key topics: (a) Thermal models—simulation tools are critical to understand a process with such large spatial gradients and fast changes. Heating systems once marked a turning point in the development of industrial ISC systems. Today, lasers are the most recent trend, and there are three key issues being studied: The absorption of energy of light by the material, the laser profile, and the laser focusing. Several approaches have been proposed for the distributed temperature measurements, given the strong temperature gradients. (b) Adhesion—this refers to two subsequent mechanisms. In the first place, the process of intimate contact is one by which two surfaces of thermoplastic pre-impregnated composite materials are brought into contact under pressure and temperature. This enables closure of the existing gaps between the two microscopic irregular surfaces. This process is then followed by the healing or diffusion of polymer molecules across the interface. (c) Crystallinity—mostly influenced by the cooling rate, and strongly affects the mechanical properties. (d) Degradation—this refers to the potential irreversible changes in the polymer structure caused by the high temperatures required for the process. Degradation can be avoided through adequate control of the process parameters. The end goal of the ISC manufacturing process is to achieve a high product quality with a high deposition rate through an industrial process competitive with the current manufacturing process for thermoset composites.
45
Pedersen, Juri L., Tina S. Galle, and Henrik Kehlet. "Peripheral Analgesic Effects of Ketamine in Acute Inflammatory Pain." Anesthesiology 89, no. 1 (July 1, 1998): 58–66. http://dx.doi.org/10.1097/00000542-199807000-00011.
Full textAbstract:
Unlabelled BACKGROUND. This study examined the analgesic effect of local ketamine infiltration, compared with placebo and systemic ketamine, in a human model of inflammatory pain. Methods Inflammatory pain was induced by a burn (at 47 degrees C for 7 min; wound size, 2.5 x 5 cm) on the calf in 15 volunteers on 3 separate days with 7-day intervals. They received either (1) subcutaneous infiltration with ketamine in the burn area (local treatment) and contralateral placebo injections, or (2) subcutaneous ketamine contralateral to the burn (systemic treatment) and placebo in the burn area, or (3) placebo on both sides. The study was double-blinded and the order of the treatments was randomized. Hyperalgesia to mechanical and heat stimuli was examined by von Frey hairs and contact thermodes (3.75 and 12.5 cm2), and pain was rated using a visual analog scale (0-100). Results The burns produced significant hyperalgesia. Local ketamine infiltration reduced pain during the burn injury compared with systemic treatment and placebo (P < 0.01). Heat pain thresholds were increased by local ketamine treatment compared with placebo immediately after injection (P < 0.03), and so were the mechanical pain thresholds (P = 0.02). Secondary hyperalgesia and suprathreshold pain responses to heat and mechanical stimuli were not significantly affected by local ketamine. No difference between local ketamine and placebo could be detected 1 h and 2 h after the burn. Conclusions Ketamine infiltration had brief local analgesic effects, but several measures of pain and hyperalgesia were unaffected. Therefore, a clinically relevant effect of peripheral ketamine in acute pain seems unlikely.
46
Samyn, Pieter. "Reciprocating sliding of polyester textile fabric composites along different fabric orientations." Journal of Composite Materials 51, no. 2 (July 28, 2016): 221–40. http://dx.doi.org/10.1177/0021998316642830.
Full textAbstract:
The coefficients of friction and wear rates of thermoset polyester matrix composites with plain woven polyester fabric reinforcement were studied during reciprocating sliding under adhesive line contact at 50 to 200 N normal loads and 0.3 to 1.2 m/s sliding velocities. The samples were prepared along different orientations of the fabric relatively to the sliding surface and sliding directions, including 0°, 30°, 45°, 60° and 90° in-plane directions and thickness z direction. The coefficients of friction and wear rates were maximum along 90° and minimum along 45° for pure and polytetrafluoroethylene-filled composites. For the latter, overload conditions were minimized, and friction and wear became low for perpendicular fabric orientations. Although sliding is controlled by solid lubrication of polytetrafluoroethylene, the fiber orientations remain dominating the friction under mild sliding conditions. The differences between friction properties along weft and warp orientations could be correlated with mechanical properties along those directions. However, a systematic study in parallel with interpretation of the thermal heating could provide better insights in dry sliding properties. By considering the effects of thermal heating, thermo-mechanical sliding conditions in the interface controlled self-lubricating properties of polytetrafluoroethylene. The wear mechanisms along 0° and 90° directions were mainly determined by the fabric reinforcement, and the sliding along off-axis 45° and thickness directions was mainly controlled by the matrix and polytetrafluoroethylene deposits.
47
Madsen, Caspar Skau, Nanna Brix Finnerup, and Ulf Baumgärtner. "Assessment of small fibers using evoked potentials." Scandinavian Journal of Pain 5, no. 2 (April 1, 2014): 111–18. http://dx.doi.org/10.1016/j.sjpain.2013.11.007.
Full textAbstract:
AbstractBackground and purposeConventional neurophysiological techniques do not assess the function of nociceptive pathways and are inadequate to detect abnormalities in patients with small-fiber damage. This overview aims to give an update on the methods and techniques used to assess small fiber (Aδ- and C-fibers) function using evoked potentials in research and clinical settings.MethodsNoxious radiant or contact heat allows the recording of heat-evoked brain potentials commonly referred to as laser evoked potentials (LEPs) and contact heat-evoked potentials (CHEPs). Both methods reliably assess the loss of Aδ-fiber function by means of reduced amplitude and increased latency of late responses, whereas other methods have been developed to record ultra-late C-fiber-related potentials. Methodological considerations with the use of LEPs and CHEPs include fixed versus variable stimulation site, application pressure, and attentional factors. While the amplitude of LEPs and CHEPs often correlates with the reported intensity of the stimulation, these factors may also be dissociated. It is suggested that the magnitude of the response may be related to the saliency of the noxious stimulus (the ability of the stimulus to stand out from the background) rather than the pain perception.ResultsLEPs and CHEPs are increasingly used as objective laboratory tests to assess the pathways mediating thermal pain, but new methods have recently been developed to evaluate other small-fiber pathways. Pain-related electrically evoked potentials with a low-intensity electrical simulation have been proposed as an alternative method to selectively activate Aδ-nociceptors. A new technique using a flat tip mechanical stimulator has been shown to elicit brain potentials following activation of Type I A mechano-heat (AMH) fibers. These pinprick-evoked potentials (PEP) have a morphology resembling those of heat-evoked potentials following activation of Type II AMH fibers, but with a shorter latency. Cool-evoked potentials can be used for recording the non-nociceptive pathways for cooling. At present, the use of cool-evoked potentials is still in the experimental state. Contact thermodes designed to generate steep heat ramps may be programmed differently to generate cool ramps from a baseline of 35◦C down to 32◦C or 30◦C. Small-fiber evoked potentials are valuable tools for assessment of small-fiber function in sensory neuropathy, central nervous system lesion, and for the diagnosis of neuropathic pain. Recent studies suggest that both CHEPs and pinprick-evoked potentials may also be convenient tools to assess sensitization of the nociceptive system.ConclusionsIn future studies, small-fiber evoked potentials may also be used in studies that aim to understand pain mechanisms including different neuropathic pain phenotypes, such as cold- or touch-evoked allodynia, and to identify predictors of response to pharmacological pain treatment.ImplicationsFuture studies are needed for some of the newly developed methods.
48
Kumar, Vipin, Sukanta Das, and Tomohiro Yokozeki. "Frequency independent AC electrical conductivity and dielectric properties of polyaniline-based conductive thermosetting composite." Journal of Polymer Engineering 38, no. 10 (November 27, 2018): 955–61. http://dx.doi.org/10.1515/polyeng-2018-0031.
Full textAbstract:
Abstract Electrical impedance characteristics of polyaniline (PANI)-dodecylbenzenesulfonic acid (DBSA)/divinylbenzene (DVB) composite were evaluated as a function of PANI content in the frequency range of 102–108 Hz. Polymer composites were prepared by a one-step thermal process where doping of the PANI and curing of the polymer matrix DVB have occurred simultaneously in the presence of a strong protonic acid, i.e. DBSA. The alternating current (AC) conductivity value with respect to frequency of the PANI-DBSA/DVB composite shows a direct current (DC) plateau up to an extensive frequency range. Almost metal-like behavior is obtained with such highly conductive plastic material. In all frequency regions, composites with higher PANI concentration showed a frequency independent behavior, while in the case of neat composites without PANI, a frequency dependent behavior is observed. A plot of the real part of complex impedance vs. frequency and a plot of AC conductivity of the composites indicate that the high electrical conductivity in high PANI concentration composites is because of the direct contacts between filler PANI particles. In this work, AC conductivity behavior and dielectric properties of very highly conductive thermoset composites are presented, and it is shown that conductivity is frequency independent for a very high frequency range (up to 108 Hz).
49
Barletta, M., A. Gisario, and G. Rubino. "Scratch response of high-performance thermoset and thermoplastic powders deposited by the electrostatic spray and ‘hot dipping’ fluidised bed coating methods: The role of the contact condition." Surface and Coatings Technology 205, no. 21-22 (August 2011): 5186–98. http://dx.doi.org/10.1016/j.surfcoat.2011.05.032.
Full text
50
SVIRIDOV, ALEKSEI S., and RAISA A. ALEKHINA. "SELECTION OF MATERIALS USED FOR MANUFACTURING DIAPHRAGMS OF DIAPHRAGM-PISTON PUMPS IN AGGRESSIVE ENVIRONMENT." Agricultural engineering, no. 1 (2021): 52–57. http://dx.doi.org/10.26897/2687-1149-2020-6-52-57.
Full textAbstract:
Abstract. Wear of the diaphragm-piston pump may occur due to a reduction in the cross-section of the suction circuit (caused by an unsuitable pipe diameter, a dirty fi lter, pumping of high-viscosity liquids, etc.), the use of very aggressive chemicals, high operating temperature, abrasive particles, and high pressure in the pneumatic line. The paper considers various types of materials used for the manufacture of diaphragm piston pumps: rubbers, thermoplastic elastomers, thermoplastics and thermoset materials. The physical and mechanical, technological and operational characteristics of materials and the corresponding requirements for chemical resistance, temperature range of operation and abrasiveness were taken into account using an example of soybean cultivation. It was found that the optimal material that meets the above criteria is cast polyurethane. It has high physical and mechanical characteristics, a wide range of hardness (from 30 A to 90 В by Shore), low shrinkage, which implies long-term use of the material. Polyurethane products are manufactured by free casting, in which the liquid polymer composition is cured in a form that does not require complex and expensive injection molding rigs, unlike thermoplastics and elastomers. Injection polyurethane has suffi cient chemical resistance in contact with the pump’s working fl uids and features wear resistance when pumping abrasive media. Therefore it is suitable for working in the climatic conditions of the Central region of Russia, and is also aff ordable, cheap and technologically advanced.