Incidence of leukemias in people aged 0 to 24 in north Cotentin

Multifocal electroretinograms were recorded from twelve subjects on three separate days using the Visual Evoked Response Imaging System (VERIS). The subjects were 18-40 years-of-age. Each recording session was separated by an interval of between one and 16 weeks. Four electrode types were compared: the JET contact lens electrode, the gold foil electrode, the DTL thread electrode and the carbon fibre (c-glide) electrode. The b-wave amplitude density (nV/sq.deg) recorded with each electrode was measured. The mean amplitude density recorded at each session for each subject and each electrode was calculated and compared. There were no significant differences in amplitude density for the ERGs recorded with each type of electrode over the three days. The coefficient of variation for each electrode and each subject was then calculated using the results for the three days. The coefficients of variation for each electrode showed significant differences (One-way ANOVA: F = 4.51, d.f. = 3.44, P < 0.008). The c-glide electrode results had the highest variability and post hoc tests showed that its coefficient of variation was significantly different from those of the JET and gold foil electrodes but not from that of the DTL thread electrode.     

Efficacy of various surface disinfectants on an irregular surface

Skin contact electrodes require electrolyte gels between the skin and the electrode in order to ensure good electrical contact. The effect of different types of electrolyte gel on skin impedance was studied. The main types of gels used were wet gels, karaya-gum based hydrogels and synthetic copolymer-based hydrogels [2-acrylamide-2-methylpropanesulfonic acid-N,N'-methylenebis(acrylamide) copolymers]. The effect of variation in gel composition on the impedance of the skin was investigated.     

Electroretinographic testing in diabetics: a comparison study of the Burian-Allen and the Henkes corneal electrodes

A series of 57 diabetics underwent standard electroretinographic recordings for the purpose of testing the effect of insulin on the electroretinograms in diabetes mellitus, specifically on the oscillatory potential changes (Kozak et al., Jap. J. Ophthal. Suppl., 1979). Use of the speculum-type corneal electrode (Burian-Allen, Hansen Labs.,) produced 9 corneal abrasions in the first 28 patients in this series. However, when the technique of examination was altered by use of the Henkes-type bipolar electrode, only 2 abrasions were produced in the last 29 patients. These frequencies of abrasions are statistically different. The suggestion is made that electroretinographic tracings in diabetics the performed with the use of the Henkes bipolar low-vacuum corneal electrode (Medical Workshops, Holland).     

Electroretinographic findings in macular dystrophy

The flash and pattern electroretinogram were investigated in a group of families with rare forms of inherited macular dystrophy, which included Sorsby's fundus dystrophy, X-linked retinoschisis and macular dystrophy of uncertain classification and variable expression. Flash electroretinograms, under both photopic and scotopic conditions, were attenuated in both Sorsby's fundus dystrophy and X-linked retinoschisis--with some effect on implicit time being noted in the latter condition--but in the unknown group the effect was less demonstrable, only 50% having attenuated flash electroretinograms. Pattern electroretinograms were reduced in all three conditions and in almost all cases. The study demonstrates that some so-called macular dystrophies also have widespread abnormalities affecting the peripheral retina. These findings may contribute to a better understanding of the underlying pathophysiologic mechanisms in these rare forms of retinal dysfunction.     

Epoxyeicosatrienoic acids, potassium channel blockers and endothelium-dependent hyperpolarization in the guinea-pig carotid artery

PURPOSE: To record the on and off responses of the multifocal photopic electroretinogram (ERG) from the human retina and to explore how each ERG component (a-, b-, and d-waves) changes at different retinal eccentricities. METHODS: Multifocal ERGs were recorded with the visual evoked response imaging system. Sixty-one densely packed stimulus elements were square wave-modulated between stimulus on and stimulus off, according to a binary m-sequence at a rate of 4.7 Hz under a constant background illumination. The ERGs were recorded with a bipolar Burian-Allen bipolar contact lens electrode from five normal subjects. Response densities (amplitude per retinal area) were calculated for five different eccentric rings. RESULTS: The response densities for all components (a-, b-, and d-waves) decreased with increasing retinal eccentricities. The ratio of the d-wave to b-wave amplitudes was minimal in the central retina and increased toward the periphery. The ratio of a-wave to b-wave amplitudes also increased toward the peripheral retina. CONCLUSIONS: These results demonstrate that the on and off responses of the human cone ERGs have different spatial distributions across the human retina, and they suggest a change in the photopic retinal circuitry with increasing retinal eccentricities.     

Protocol for microneurography with concentric needle electrodes

In 1968, the method of human percutaneous microneurography with solid tungsten electrodes was introduced. Since then many investigators used this technique to study peripheral mechanisms in the somatosensory, motor and autonomic systems of conscious humans. Although some modifications of the method were described, the basic construction of the recording electrode has remained the same over the years. In the present protocol we describe in detail the procedures of microneurography using a thin diameter concentric needle electrode. There are some advantages with the concentric electrodes in comparison with the tungsten needles: (1) the electrical and mechanical properties of the electrode are stable which allows repeated use, (2) its restricted and one-dimensionally directed recording area provides the possibility to study topographical aspects within even a part of a peripheral nerve fascicle, and (3) multi-channel recordings can be achieved by adding more recording surfaces to the electrode. Based on recent investigations evaluating the recording properties of concentric electrodes we propose a novel procedure for signal analysis where template matching is incorporated. The analyses described in this protocol might also be applicable for extracellular recordings from muscle or elsewhere within the nervous system.     

锂离子电芯用电极对温度与SOC的敏感性

采用阻抗谱技术,对2.8 A·h 18650电芯进行拆解解析,单独分析正负极电极在不同温度下(25、10和-5℃),不同荷电状态下的阻抗变化.结果表明:在不同温度下,在20%~100%荷电状态下,负极作为控制电极,其反应电化学阻抗是正极的数倍,尤其是在-5℃,达到了4倍,负极是电芯一致性问题中动力学因素的控制主因;在0~20%荷电状态下,在10和25℃下,正极的反应电化学阻抗要远远大于负极,正极成为控制端.结合目前电动车上动力电池的实用荷电状态一般在20%~95%,针对该2.8 A·h 18650电芯,提高负极电极的一致性是核心所在.同理,对其他类型电芯而言,在电芯设计过程中,在综合考虑成本的前提下,需要更有针对性地提高正负极的一致性标准,从而更为有效地改善整个电芯产品的一致性.      

Novel popout with nonsense strings: effects of predictability of string length and spatial location

The implanted system was composed of four silver ball electrodes placed in the burr hole of the skull, a reference placed subcutaneously near the nose, two electrodes for EMG, and a ground. The dural attachment was 0.1 mm in diameter. A cassette connector was placed on the back. Implanted cables between the cassette connector and all electrodes consist of twisted fine wires placed in a silicone tube 0.5 mm in diameter. The implanted electrode system weighed 0.8 g. The outlet cables were of the same materials used for implanted cables and placed in a silicone tube 1.5 mm in diameter. The impedance matching between these cables was successful and assured the minimum contamination of artifacts in the EEG recording of freely moving mice. Long-term (4-5 weeks) recording, thus, became possible without damage to the implanted materials. Monopolar recordings demonstrated the localized paroxysmal discharges during general tonic clonic convulsion in El mice. Several artifacts are presented.     

Single unit recording capabilities of a 100 microelectrode array

We have developed a three-dimensional silicon electrode array which provides 100 separate channels for neural recording in cortex. The device is manufactured using silicon micromachining techniques, and we have conducted acute recording experiments in cat striate cortex to evaluate the recording capabilities of the array. In a series of five acute experiments, 58.6% of the electrodes in the array were found to be capable of recording visually evoked responses. In the most recent acute study, the average signal-to-noise ratio for recordings obtained from 56 of the electrodes in the array was calculated to be 5.5:1. Using standard window discrimination techniques, an average of 3.4 separable spikes were identified for each of these electrodes. In order to compare the two-dimensional mapping capabilities of the array with those derived from other technologies, orientation preference and ocular dominance maps were generated for each of the evoked responses. Histological evaluation of the implant site indicates some localized tissue insult, but this is likely due to the perfusion procedure since high signal-to-noise ratio neural responses were recorded. The recording capabilities of the Utah Intracortical Electrode Array in combination with the large number of electrodes available for recording make the array a tool well suited for investigations into the parallel processing mechanisms in cortex.     

Electron spin resonance spectroscopic detection of oxygen-centred radicals in human serum following exhaustive exercise

The purpose of the study contained herein was to determine the usefulness of electrical impedance for measurement of bladder volume in spinal cord-injured patients, with an assessment of the relationship between electrical impedance and bladder volume exclusively. The study was performed during urodynamic studies to match the exact bladder volume. Thirteen patients with complete spinal cord injuries were recruited. We used silver-silver chloride compound electrodes composed of one pair of current and amplitude electrodes to minimize the influence of superficial skin impedance. Each compound electrode was attached on the lower abdomen bilaterally after skin cleansing. Constant current (60 kHz-1.0 mA), converted from 9 V of direct current, was applied, and corresponding electrical impedance (omega) was measured at "pre" (before urodynamic empty bladder), "full" (with a urodynamic filled bladder), and "post" (after urodynamic empty bladder) status. Electrical impedance at the full status was definitely lower than that at the pre and post statuses in all subjects, with a statistically significant difference (P < 0. 001). The correlation between electrical impedance and bladder volume was negative (r = -0.7988), and the fact of how much the variation in electrical impedance could be explained by variation in bladder volume was estimated (r2 = 0.6381). From these findings, we have determined that the electrical impedance analysis technique can be an alternative measure of bladder volume indirectly.     

A quantitative technical quality assay method for electrocardiograms

A method is presented for quantitative assessment of ECG technical quality to permit sensitive detection of performance trends of individual technicians or entire ECG laboratories. The common flaws in ECG recording technic are those which introduce ultra-low frequency artifact or baseline shift, powerline artifact, myographic and intermediate frequency artifact, clipping of waveforms, disconnection or reversal of electrodes and general faults of protocol adherence. Procedures for quantitating these attributes are presented and explained in order to arrive at a mean figure of merit for each ECG recording. Use of such a method can aid ECG technicians' understanding of the important features of tracing quality and provide an objective basis for the recognition of outstanding performance, on one hand, or the need for remedial training, on the other.     

丝网印刷制备银/氯化银电极研究与应用进展

随着电化学传感器、生物传感器以及医用电极应用环境的发展,对银/氯化银参比电极和银/氯化银医用电极的可设计性、柔韧性、适应工业大批量生产等方面有了新要求.采用丝网印刷工艺制备再经低温固化成型的银/氯化银电极作为一种具备以上优点的低成本电极,已经成为了传感检测领域研究与应用的热点.从3个方面综述了丝网印刷制备银/氯化银电极...     

Motor evoked potentials: appropriate positioning of recording electrodes for diagnosis of spinal disorders

The interpretation of normal and pathological findings of motor evoked potential obtained by the use of transcranial magnetic stimulation depends on adequate examination technique, including the appropriate positioning of the recording electrodes over the muscle. On the basis of knowing the location of the motor end plate zones in muscles, magnetic stimulation of the motor cortex of 30 healthy adults was performed in order to explore the influence of the position of the surface recording electrodes on potential parameters and to establish the standard location of the recording electrodes over the biceps brachii, medial vastus, anterior tibial and abductor hallucis muscles for diagnostic use in spine disorders. The cortical latencies and peak-to-peak amplitudes of the evoked potentials were analysed by varying the location of the recording electrodes and the stimulus intensities. The latencies were significantly shorter when the different electrode lay more proximally over the muscle belly. Reproducible potentials with sharp negative onset and maximum amplitude were recorded with a separation of 5-7.5 cm between the different electrode, located over the motor end plate area, and the different electrode, located over the distal myotendinous junction. This implies that the parameters of evoked potentials depend on the position and separation distance of the recording electrodes over the muscles and that it is possible to record the potentials using a lower stimulus intensity and, above all, on relaxed muscles, which may prove to be applicable for intraoperative monitoring of the spinal cord using magnetic stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Fiber fracture during processing of continuous fiber,metal-matrix composites using the foil/fiber/foil technique

The fracture of continuous fibers during processing of foil/fiber/foil (F/F/F) metal-matrix composites (MMCs) has been investigated both experimentally and theoretically. Experimental observations revealed that fiber fracture occurs during the heat-up portion of the consolidation cycle primarily in a bending mode in regions where cross-weave wires are present. Based on these observations, a general model that describes fiber fracture as a function of the processing stress and fiber mat geometry was developed. Model results showed that fiber stresses and, hence, the propensity for fracture are very sensitive to the distance between cross-weave wires in adjacent fiber mats; analytical expressions that allow the definition of a critical distance between such cross-weave wires were derived. The model relations demonstrated that fiber fracture is more likely in areas of a composite in which the fibers are arranged in a rectangular, rather than a triangular, pattern. The experimental and theoretical results were used to develop guide-lines for the design of F/F/F layups to avoid fiber fracture during processing. Formerly Graduate Student, Department of Materials Science and Engineering, Carnegie Mellon University     

Obstetric and gynaecological patients in an intensive care unit: a 1 year review

BACKGROUND: Pathophysiologic events in biological tissue are characterized by a shift of the electrical impedance spectra of the tissue under study. OBJECTIVE: To discuss studies on experimental skin reactions with an improved impedance spectrometer. The instrumentation is related to noninvasive techniques based on other physical principles. METHODS: The results from studies on patients with allergic contact reactions (n = 8), prick tests (n = 10), and irritant contact reactions (benzalkonium chloride [n = 14], sodium lauryl sulfate [n = 12], and nonanoic acid [n = 14]), and an appropriate number of controls are reviewed. RESULTS: Results show statistically significant changes of the impedance parameters when compared with relevant controls, at different types of experimental cutaneous reactions, both allergic and irritant type. Each reaction type had a specific impedance index pattern. CONCLUSIONS: Current data indicate that the improved impedance technique offers a possible noninvasive alternative for characterization and perhaps differentiation, not only between the skin responses induced by either an allergen or an irritant, but also a capability to distinguish responses induced by chemically different irritants. The assumption that the impedance method is capable to distinguish allergic from irritant contact reactions has not been proven yet in direct comparative studies.     

Formation processes,structure, and properties of spark coatings of armco iron obtained with the use of nanostructured and microstructured WC-Co electrodes

Nanostructured and microstructured electrode materials of the composition 92%WC-8%Co were used for deposition of spark coatings on Armco iron upon variation in the energy of pulsed discharges in the range from 0.01 to 1.2 J. Physicochemical processes on contact surfaces are considered during operation by both types of electrode pairs, namely, in the forming coating of the cathode substrate and in the secondary structure of the anode electrode. It is found that the main phases in coatings are the amorphous phase and tungsten semicarbide W₂C. In the case of a nanostructured electrode, an increase in the energy mode above a certain threshold value leads to an increase in the fraction of crystalline phases and to the formation of a structure consisting of submicron W₂C/WC grains surrounded by an amorphous binder. With the use of a microstructured electrode, the fraction of the amorphous phase in coatings prevails in all energy modes. The use of nanostructured electrodes in the technology of spark treatment of substrates made from Armco iron is expedient only at a pulse energy of <0.23 J.     

Integration of excitatory postsynaptic potentials in dendrites of motoneurons of rat spinal cord slice cultures

We examined the attenuation and integration of spontaneous excitatory postsynaptic potentials (sEPSPs) in the dendrites of presumed motoneurons (MNs) of organotypic rat spinal cord cultures. Simultaneous whole cell recordings in current-clamp mode were made from either the soma and a dendrite or from two dendrites. Direct comparison of the two voltage recordings revealed that the membrane potentials at the two recording sites followed each other very closely except for the fast-rising phases of the EPSPs. The dendritic recording represented a low-pass filtered version of the somatic recording and vice versa. A computer-assisted method was developed to fit the sEPSPs with a generalized alpha-function for measuring their amplitudes and rise times (10-90%). The mean EPSP peak attenuation between the two recording electrodes was determined by a maximum likelihood analysis that extracted populations of similar amplitude ratios from the fitted events at each electrode. For each pair of recordings, the amplitude attenuation ratio for EPSP traveling from dendrite to soma was larger than that traveling from soma to dendrite. The linear relation between mean ln attenuation and distance between recording electrodes was used to map 1/e attenuations into units of distance (micron). For EPSPs with typical time course traveling from the somatic to the dendritic recording electrode, the mean 1/e attenuation corresponded to 714 micron for EPSPs traveling in the opposite direction, the mean 1/e attenuation corresponded to 263 micron. As predicted from cable analysis, fast EPSPs attenuated more in both the somatofugal and somatopetal direction than did slow EPSPs. For EPSPs with rise times shorter than approximately 2.0 ms, the attenuation factor increased steeply. Compartmental computer modeling of the experiments with biocytin-filled and reconstructed MNs that used passive membrane properties revealed amplitude attenuation ratios of the EPSP traveling in both the somatofugal and somatopetal direction that were comparable to those observed in real experiments. The modeling of a barrage of sEPSPs further confirmed that the somato-dendritic compartments of a MN are virtually isopotential except for the fast-rising phase of EPSPs. Large, transient differences in membrane potential are locally confined to the site of EPSP generation. Comparing the modeling results with the experiments suggests that the observed attenuation ratios are adequately explained by passive membrane properties alone.     

Impedance recordings to determine change in extracellular volume in the brain following cardiac arrest in broiler chickens

The present study describes a method to determine the onset and development of brain damage in broiler chickens. Exsanguination disrupts the brain metabolism and causes the brain to become ischemic. Energy-requiring systems in the cell membrane fail, which results in an ionic shift over the membrane, accompanied by a water influx into the cell. This cellular edema decreases the extracellular volume of brain tissue. In mammals, this brain damage has been measured by recording brain impedance. We adapted this approach for use with poultry. Five to six-week-old commercial broilers were equipped with impedance recording electrodes in the striatum area of the brain. Cardiac arrest was induced by means of an intravenous injection of MgCl2 and brain impedance was recorded for 30 min. The resulting curves showed a high similarity to those obtained in rats. No effects of 12 h antemortem feed deprivation on the size and rate of change in brain impedance could be found. Both in anesthetized and conscious birds, a change in brain impedance was found. We conclude that brain impedance can be used to determine the development of ischemic brain damage in broiler chickens.     

Scalp-recorded, ictal focal DC shift in a patient with tonic seizure

PURPOSE: We recorded focal ictal DC shifts from scalp electrodes in a 9-year-old boy with intractable, clinically generalized tonic seizures. The patient had a high intensity signal abnormality of the left temporal cortex with thickening of the gyri on T2-weighted MRI. METHODS: Scalp digital EEGs were recorded using electrodes made of silver/silver chloride. The low frequency filter (LFF) was set at 0.016 Hz. Recorded seizures were subsequently analyzed with LFF settings of 1.0, 0.016 and 0.03 Hz. RESULTS: All recorded seizures initially showed diffuse, low voltage, high frequency activity (electrodecremental pattern) followed 10-20 s later by quasirhythmic activity over the left frontotemporal region. In two seizures, LFF of 0.016-0.03 Hz revealed a slow negative shift over the left frontotemporal area simultaneously with onset of the bilateral electrodecremental pattern. However, in the other seizures, this initial slow negative shift was obscured by artifacts. Subsequent electrocorticography (ECoG) delineated frequent epileptiform discharges in the left temporal as well as frontal cortex. CONCLUSIONS: Scalp-recorded ictal DC shifts may help identify focal epileptogenic brain area in patients with clinically generalized seizures although the technique is vulnerable to artifact.     

The electrical resistivity of cytoplasm

The apparent cytoplasmic resistivity of two different giant cells has been measured using an extension of a previously developed single microelectrode technique. Each cell is penetrated by a metal microelectrode whose complex impedance is measured as a function of frequency between 500 kHz and 5.7 MHz. By plotting the measured impedance data on the complex Z plane and extrapolating the data to infinite frequency, the substantial effects of electrode polarization can be overcome. For Aplysia giant neurons and muscle fibers of the giant barnacle, the extrapolated cytoplasmic specific resistivities are 40 and 74 omega-cm, respectively, at infinite frequency. The barnacle data are in excellent agreement with sarcoplasmic resistivity values derived from the measured cable properties of other marine organisms, and from high frequency conductivity cell measurements in intact barnacle muscle tissue. In the Aplysia neurons, the frequency-dependent part of the electrode impedance is larger when the electrode is in a cell than when it is in an electrolyte solution with the same specific resistivity as the aqueous cytoplasm; however, the phase angle of the frequency-dependent component of the electrode impedance is the same in both cases. This suggests that the high apparent values of cytoplasmic resistivity found using the single microelectrode technique at lower frequencies probably reflect an artifact caused by reduction of the effective surface area of the electrode by intracellular membranes, with a corresponding increase in its polarization impedance.