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PubMed2003

Design and responses of Butterworth and critically damped digital filters.

For many years the Butterworth lowpass filter has been used to smooth many kinds of biomechanical data, despite the fact that it is underdamped and therefore overshoots and/or undershoots data during rapid transitions. A comparison of the conventional Butterworth filter with a critically damped filter shows that the critically damped filter not only removes the undershooting and overshooting, but has a superior rise time during rapid transitions. While analog filters always create phase distortion, both the critically damped and Butterworth filters can be modified to become zero-lag filters when the data are processed in both the forward and reverse directions. In such cases little improvement is realized by applying multiple passes. The Butterworth filter has superior 'roll-off' (attenuation of noise above the cutoff frequency) than the critically damped filter, but by increasing the number of passes of the critically damped filter the same 'roll-off' can be achieved. In summary, the critically damped filter was shown to have superior performance in the time domain than the Butterworth filter, but for data that need to be double differentiated (e.g. displacement data) the Butterworth filter may still be the better choice.

Biomechanical Phenomena↗

PubMed1983

Effect of damp on isokinetic measurements.

Meaningful use of isokinetic data requires understanding potential sources of variation and error. The purpose of this study was to examine one possible source of variation: the effect of recorder damp settings on Cybex II torque tracings. The effect of damp settings 0 through 4 at speeds of 30 degrees/sec and 75 degrees/sec was assessed by dropping loads of 13.65 kg and 36.85 kg attached to a lever arm of 30.5 cm on a Cybex II. The effect of damp settings at 180 degrees/sec was examined with the same weights at damp settings 2 and 4. Increasing damp resulted in 1) a decrease in amplitude of the entire torque curve and a decreased measurement of peak torque and 2) a shift of the torque curve to the right (later in time). The data underscore the need to record and to report the damp settings used during isokinetic testing.

Electronics, Medical↗

PubMed1996

Muscle damping measured with a modified pendulum test in patients with fibromyalgia, lumbago, and cervical syndrome.

STUDY DESIGN: Muscle tension with tenderness may be localized or generalized as in fibromyalgia. Wartenberg's pendulum test might be appropriate for quantitating muscle damping, at least in generalized cases. OBJECTIVE: Damping values provide a quantitative measure of muscle tension and of the response to various treatments. SUMMARY OF THE BACKGROUND DATA: According to recent anatomic and experimental works, intrafusal muscle fibers are double-innervated by gamma motoneurons and sympathetic fibers. With electromyograph recording, the activity of extrafusal fibers and gamma motoneurons (reflexes) can be assessed and separated from the action of the sympathetic system. METHODS: An electrogoniometer registers the movements of the freely swinging leg. On the oscilloscope, the patient's nodular curve is compared with an ideal calculated dampened curve to find the damping value. Electromyograph surface electrodes from the knee extensors and flexors detect the activity of extrafusal fibers and the occurrence of reflexes. RESULTS: In longstanding severe fibromyalgia, damping values are almost always elevated, at least in one leg. Half or more of patients with chronic lumbago and cervical syndrome present with increased damping. The surface electromyograph remains silent (in contrast to spastic patients). CONCLUSION: The findings support the hypothesis that muscle tension in rheumatic patients results from overactivity of the sympathetic system (or part of it). Even in clinically localized pain syndromes, muscle damping is often increased in the legs. The test is valuable for quantitating muscle tension and the effectiveness of therapeutic methods.

Adult↗

PubMed1994

A prospective randomized comparison of defibrillation efficacy of truncated pulses and damped sine wave pulses in humans.

INTRODUCTION: Damped sine wave pulses have been used for nearly 50 years in transthoracic defibrillation systems. The purpose of this study was to determine whether damped sine wave pulses have a role in implantable defibrillators. METHODS AND RESULTS: In 21 survivors of cardiac arrest, we prospectively compared defibrillation efficacy of a standard truncated capacitor (RC) monophasic pulse with a damped sine wave inductor-capacitor (LRC) pulse using a right ventricular-left ventricular epicardial patch-patch electrode system. The RC pulse was a standard 65% tilt monophasic waveform generated from a 120 mu F capacitor. The LRC pulse was designed to simulate the waveform currently used in transthoracic defibrillators and was generated by passing the charge stored on a 40 mu F capacitor through a 37-mH inductor. Capacitor voltage, peak delivered voltage, peak delivered current, discharge pathway resistance, delivered energy, and stored energy were compared for the two waveforms at the defibrillation threshold. There was no difference in defibrillation efficacy for the two waveforms. Peak delivered voltage was similar at the defibrillation threshold: 313 +/- 101 V for the RC pulse and 342 +/- 119 V for the LRC pulse (P = 0.16). Similarly, no differences were found in defibrillation threshold peak delivered current: 8.6 +/- 2.5 (RC) versus 9.3 +/- 2.7 (LRC) amperes (A) (P = 0.20); discharge pathway resistance: 37 +/- 11 (RC) versus 38 +/- 13 (LRC) omega (P = 0.71); delivered energy: 7.0 +/- 4.5 (RC) versus 7.0 +/- 4.0 (LRC) joules (J) (P = 0.88); and stored energy: 8.7 +/- 5.7 (RC) versus 9.8 +/- 5.4 (LRC) J (P = 0.35). Although both waveforms performed the same, it was necessary to use substantially higher stored voltages with the damped sine wave delivery system than with the truncated waveform delivery system: 356 +/- 110 V for the RC pulse and 675 +/- 192 V for the LRC pulse (P < 0.0001). CONCLUSION: This study demonstrates that RC monophasic pulses provide equally effective epicardial defibrillation as LRC pulses with respect to delivered voltage and current and stored and delivered energy. However, in order for LRC pulses to provide comparable delivered voltage, current, and energy to that of RC pulses, nearly twice the voltage must be stored on the capacitor to accomplish the same task. These findings suggest that despite the nearly 50-year experience with damped sine wave pulses with transthoracic defibrillators, there is no need to begin using damped sine wave pulses for implantable defibrillators. Moreover, these data raise a question regarding the need for inductors in transthoracic defibrillators.

Aged↗

PubMed1986

Formation of a covalent complex between the terminal protein of pneumococcal bacteriophage Cp-1 and 5'-dAMP.

Incubation of extracts of Cp-1-infected Streptococcus pneumoniae with [alpha-32P]dATP produced a labeled treatment with micrococcal nuclease and sensitive to treatment with proteinase K. Incubation of the 32P-labeled protein with 5 M piperidine for 4 h at 50 degrees C released 5'-dAMP, indicating that a covalent complex between the terminal protein and 5'-dAMP was formed in vitro. When the four deoxynucleoside triphosphates were included in the reaction mixture, a labeled complex of slower electrophoretic mobility in sodium dodecyl sulfate-polyacrylamide gels than the terminal protein-dAMP complex was also found, indicating that the Cp-1 terminal protein-dAMP complex can be elongated and, therefore, that it is an initiation complex. Treatment of the 32P-labeled terminal protein-dAMP complex with 5.8 M HCl at 110 degrees C for 2 h yielded phosphothreonine. These results, together with the resistance of the terminal protein-DNA linkage to hydroxylamine, suggest that the Cp-1 terminal protein is covalently linked to the DNA through a phosphoester bond between L-threonine and 5'-dAMP, namely, a O-5'-deoxyadenylyl-L-threonine bond.

Bacteriophages↗

PubMed2000

An epidemiological study of the relative importance of damp housing in relation to adult health.

STUDY OBJECTIVE: To examine the association between damp housing and adult health, taking into account a wide range of other factors that may influence health and could confound this relation. PARTICIPANTS AND SETTING: A general population sample of adults, aged 18-64, from Oxfordshire, Buckinghamshire, Berkshire and Northamptonshire. DESIGN: Secondary analysis of responses to a postal questionnaire survey carried out in 1997 with a 64% response rate (8889 of 13 800). Housing dampness was assessed by self report. Health was measured by responses to a series of questions including presence of asthma and longstanding illness generally, use of health services and perceived health status (the SF-36). The effect of damp was examined using the chi(2) test and one way analysis of variance. Significant associations with the various health outcomes were further explored taking into account 35 other housing, demographic, psychosocial and lifestyle variables using stepwise logistic and linear regression. MAIN RESULTS: Bivariate analyses indicated that damp was associated with the majority of health outcomes. Regression modelling however, found that being unable to keep the home warm enough in winter was a more important explanatory variable. Worry about pressure at work and to a lesser extent about money, showed an independent association with perceived health status equal to or greater than that of the housing environment, including cold housing, and that of health related lifestyles. CONCLUSIONS: This study shows that being unable to keep the home warm enough in winter is more strongly associated with health outcomes than is damp housing. However, as cold and damp housing are closely related, it is likely that their combined effects are shown in these results. The importance of worry as an independent predictor of health status needs testing in other studies. Its prevalence and relative importance suggest that it may be a significant determinant of public health.

Adolescent↗

PubMed2005

Genomic expression for rat model of damp obstruction in Chinese medicine: application of microarray technology.

Damp obstruction refers to the stagnation of vital energy (qi) caused by dampness resulting in dysfunction of body and limbs movement, as well as impairment of spleen and stomach digestive function. Damp obstruction is the dampness-induced imbalance of five elements; thus it serves as an ideal model for genomic study using cDNA microarray. We have performed microarray analyses to major organs of damp-obstructed rats. Cluster analysis for the expression profiles of major organs indicated that spleen, stomach, and kidney respond to dampness differently from heart, liver, lung, and brain. Gene expression profile specific to each element or group of elements was also identified. Our results are consistent with the philosophy of Chinese medicine that the five elements, metal (lung), wood (liver), water (kidney), fire (heart), and earth (spleen and stomach) coordinate by subjugation or restriction to maintain a healthy, physiological state. This is the first time that a powerful genomic tool was applied to probe the ancient theory of Chinese medicine.

Alanine Transaminase↗

PubMed2006

Functional and molecular characterization for the damp-obstructed rat model in Chinese medicine.

Functional and molecular characterization was performed on the major organs of damp-obstructed rats by applying expression datasets of microarray experiments and real-time RT-PCR. Gene ontology repertoires, i.e. cellular component, molecular function, and biological process were used to classify differentially expressed genes in the major organs of rats upon treatment of dampness. As to the cellular component, over-expression of genes associated with the plasma membrane was observed in the stomach, spleen, kidney, heart, liver, and lung. Genes associated with translational machinery, endoplasmic reticulum membrane, Golgi apparatus, and nuclear envelope were down-regulated in the stomach. Concerning the molecular function, genes associated with oxidoreductase activity were up-regulated in the stomach, spleen, kidney, lung, and brain. Channel activity, membrane receptor, and electron transporter activity were up-regulated in stomach, kidney, and lung. Regarding the biological process, genes associated with signal transduction were up-regulated in the stomach, while genes associated with biosynthesis and ATP metabolism were down-regulated. In the spleen, melanin biosynthesis was up-regulated while hormone-related activities were down-regulated. In the kidney, genes associated with nucleotide biosynthesis and ATP metabolism were depressed. In the heart and liver, apoptosis was up-regulated while immune response and RAS signal transduction were down-regulated. Interestingly, genes associated with oncogenesis were up-regulated in the stomach and kidney. Functional fingerprints indicated that dampness weakened membrane structures, depressed metabolic activity (especially ATP metabolism), damaged matrix proteins, enhanced signal transduction, and revealed a positive association with oncogenesis. To quantify the functional impact at the molecular level, mRNA levels of key genes were determined by real-time RT-PCR. The results indicated that ATP storage in kidney, spleen, and stomach was depleted in damp-obstructed rats. We propose that oxidative stress, membrane integrity, melanin biosynthesis, ion channel activity, and ATP metabolism might be hallmarks for damp-obstructed rats. Our results also suggested dampness as a pathogenic factor in rats which is possibly associated with enhanced liabilities of cancer.

Animals↗

PubMed2004

[Application of the theory of damp-heat in spleen and stomach in treatment of kidney diseases].

There exists close relationship between the damp-heat and the occurrence, development, treatment and prognosis of kidney diseases. The occurrence of damp-heat is based on water and wetness, which may come from outside or may be caused by internal damage. The water and wetness can change into heat if they are stored in the body for a long period, and the combination of water and wetness and heat may cause damp-heat syndrome. The function of spleen and stomach plays the most important role in the water metabolism of sanjiao. Kidney diseases are mainly caused by damp-heat of spleen and stomach resulted from internal damage of spleen and stomach, and symptoms of damp-heat of middle-jiao are commonly seen in most patients of chronic kidney diseases. During the development from renal function damage to renal failure, the remaining of damp-heat in san-jiao can affect the function of spleen and stomach for transportation, transformation and digestion, resulting in the symptoms of dysfunction of spleen and stomach. Regulating the function of spleen and stomach is one of the most important therapeutic methods for kidney diseases.

Hot Temperature↗

PubMed2000

Deficits in attention, motor control and perception (DAMP): a simplified school entry examination.

OBJECTIVE: To suggest an empirically based school entry screening examination for the detection of deficits in attention, motor control and perception (DAMP) in 6-y-old children. MATERIAL AND METHODS: A population-based cohort of 113 children, 6-7 y of age (62 with and 51 without DAMP), compared on measures of attention, motor functions, language and cognition. RESULTS: Attention deficits were convincingly identified by both parents and paediatrician. The motor function tests clearly distinguished between the two groups. Linguistic and meta-linguistic tests demonstrated greater phonological processing difficulties in the DAMP group. The cognitive test revealed an overall lower IQ but no consistent characteristic pattern in the DAMP group. CONCLUSIONS: A simplified paediatric school entry examination test is suggested. Four motor tests (standing on one foot, Fog test, design copying and diadochokinesis) administered by the paediatrician, combined with a brief structured clinical observation and a structured parent interview, identified 80% of children with DAMP-and all those with severe DAMP-as well as a small number of false positives.

Attention Deficit Disorder with Hyperactivity↗

PubMed2000

Asthma symptoms in relation to measured building dampness in upper concrete floor construction, and 2-ethyl-1-hexanol in indoor air.

SETTING: Asthma symptoms in adults in relation to the indoor environment. OBJECTIVES: To study the relationships between current asthma symptoms (wheeze or attacks of breathlessness) and the indoor environment and dampness in hospitals. DESIGN: A study among personnel (n = 87) in four geriatric hospitals in winter. Indoor air pollutants, dampness in the concrete floor, and allergens in settled dust were measured. Multiple logistic regression analysis was applied, adjusting for age, sex, atopy, and dampness in the participants' own dwellings. RESULTS: Current asthma symptoms were reported by 17%, and 8% had doctor's diagnosed asthma. Asthma symptoms were more common (adjusted odds ratio = 8.6; 95% confidence interval 1.3-56.7) in two buildings with signs of dampness-related degradation of di(ethylhexyl)-phthalate (DEHP) in polyvinyl chloride (PVC) floor material, detected as presence of 2-ethyl-1-hexanol (2-32 microg/m3) in indoor air (CAS nr 104-76-7). Asthma symptoms were related to higher relative humidity in the upper concrete floor construction, and ammonia in the floor. The newest hospital, built by an anthroposophic society, had low levels of dampness and few asthma symptoms (4%). Cat (Fel d1) and dog allergens (Can f1) were found in dust from all buildings (geometric mean 340 ng/g and 2490 ng/g, respectively). House dust mite allergens (Derp1, Derf1, or Derm1) were found in 75% of all samples (geometric mean 130 ng/g). There was no relationship between allergen levels and asthma symptoms. CONCLUSIONS: Asthma symptoms may be related to increased humidity in concrete floor constructions and emission of 2-ethyl-1-hexanol, an indicator of dampness-related alkaline degradation of plasticiser DEHP. Moreover, geriatric hospitals can be contaminated by significant amounts of cat, dog and mite allergens.

Air Pollution, Indoor↗

PubMed2003

Mechanical characteristics of rat vibrissae: resonant frequencies and damping in isolated whiskers and in the awake behaving animal.

We investigated the natural resonance properties and damping characteristics of rat macrovibrissae (whiskers). Isolated whiskers rigidly fixed at the base showed first-mode resonance peaks between 27 and 260 Hz, principally depending on whisker length. These experimentally measured resonant frequencies were matched using a theoretical model of the whisker as a conical cantilever beam, with Young's modulus as the only free parameter. The best estimate for Young's modulus was approximately 3-4 GPa. Results of both vibration and impulse experiments showed that the whiskers are strongly damped, with damping ratios between 0.11 and 0.17. In the behaving animal, whiskers that deflected past an object were observed to resonate but were damped significantly more than isolated whiskers. The time course of damping varied depending on the individual whisker and the phase of the whisking cycle, which suggests that the rat may modulate biomechanical parameters that affect damping. No resonances were observed for whiskers that did not contact the object or during free whisking in air. Finally, whiskers on the same side of the face were sometimes observed to move in opposite directions over the full duration of a whisk. We discuss the potential roles of resonance during natural exploratory behavior and specifically suggest that resonant oscillations may be important in the rat's tactile detection of object boundaries.

Animals↗

PubMed2005

Reaction of selected soybean cultivars to Rhizoctonia root rot and other damping-off disease agents.

Eight soybean cultivars; Giza 21. Giza 22, Giza 35, Giza 82, Giza 83, Crawford, Holladay and Toamo were evaluated to Rhizoctonia root rot using agar plate and potted plant techniques. Data cleared that, in agar plate assay all soybean cultivars were moderately susceptible (MS), although the differences between them were significant (P=0.05). Generally, in potted assay, the reactions were resistant (R) or moderately resistant (MR) to root rots. Also, the differences between cultivars were significant (P=0.05). These cultivars were inoculated under greenhouse conditions with Fusarium solani, Macrophomina phaseolina, Rhizoctonia solani and Sclerotium rolfsii Generally, G21 had the least pre-emergence damping-off followed by Giza 35, Crawford and Giza 83 with averages of 19.0, 20.0, 20.5 and 21.5%, respectively. In case of post-emergence, Giza 35 had the least values, followed by Giza 21, Crawford and Giza 82 with averages 3.95, 4.10, 4.10 and 4.25%, respectively. Under naturally infested soil in the field conditions the reactions of the same cultivars to damping-off were evaluated in two successive seasons. In 2002 season, G35 had the least pre-emergence damping-off % followed by Giza 21 and Giza 22 with averages of 22.61, 24.33 and 29.33%, respectively. Also, G35 had the least post-emergence damping-off % followed by Toamo and Giza 21 with averages of 9.40, 10.33 and 10.41%, respectively. In 2003 season, the same trend was appeared with light grade where Giza 35 had the least pre-emergence damping of % followed by Giza 22 and Giza 21 with averages of 30.67, 31.00 and 36.67%, respectively and Giza 35 was the most resistant cultivar against post-emergence damping-off, followed by Giza 21 and Giza 22 with averages of 10.91, 11.32 and 11.80%, respectively. Generally, Giza 21 significantly surpassed the other cultivars in plant height, number of pods per plant and 100-seed weight. Moreover, also it had second grade with the other traits.

Colony Count, Microbial↗

PubMed1983

CNDO/2 molecular orbital calculations on the antifolate DAMP and some related species: structural geometries, ring distortions, change distributions and conformational characteristics.

Geometry-optimized CNDO/2 molecular orbital calculations were carried out on 2, 4-diamino-5-(1-adamantyl 1)-6-methyl pyrimidine (DAMP), a potent inhibitor of mammalian dihydrofolate reductase which is now in clinical trials, and on its inactive 5-(1-naphthyl) analogue (DNMP-1). Crystallographic data show that DAMP (as the ethylsulfonate salt) has a severely distorted, N1 protonated, pyrimidine ring and has steric crowding of the 6-methyl and adamantyl hydrogens whereas DNMP-2 (as a methanol complex) has a planar, nonprotonated pyrimidine ring that is nearly perpendicular to the naphthalene ring. The CNDO/2 results largely reproduce the crystal structure geometry and show that the ring distortions in DAMP are initiated by steric conflicts between the adamantyl group and the 4- and 6-substituents on the ring. In DNMP-1, the non-interfering naphthyl ring induces little strain within the pyrimidine ring and the effect of protonation is negligible. Rotation about the bond joining the two ring groups is restricted in DAMP by a broad barrier of ca. 8.0 kcal mol-1, and no conformation was successful in relieving steric conflicts and hence reducing the ring distortions. In DNMP-1, rotation is less hindered overall with a broad region of accessible conformational space and a maximum barrier of ca. 7.2 kcal mol-1 for the coplanar conformation. The electronic charge distributions of DAMP and DNMP-1 are almost identical and protonation is preferred at N1 rather than at N3 by ca. 3.7 kcal mol-1 for both DAMP and DNMP-1. The calculations establish that the present methodology can be useful as a predictive tool with regard to the structure and conformational characteristics of these and related species.

Adamantane↗

PubMed1984

Synthesis of nucleotides with specific radiolabels in ribose. Primary 14C and secondary 3H kinetic isotope effects on acid-catalyzed glycosidic bond hydrolysis of AMP, dAMP, and inosine.

Adenosine 5'-phosphate was synthesized with 3H or 14C label specifically located as [1'-3H]AMP, [1'-14C] AMP, [5'-3H]AMP, and [5'-14C]AMP. The synthesis was accomplished from adenine and glucose or adenine and ribose using enzymes from the pentose pathway and/or from the purine salvage pathways. Structural analysis of the compounds confirmed the locations of the radiolabels. The methods provide a general scheme for the efficient synthesis of adenine nucleotides of high purity with 3H or 14C at any stable position on the ribose ring. Synthesis of [5'-14C]dAMP and [1'-3H] dAMP from the corresponding ribonucleotides was accomplished with ribonucleotide reductase. Labeled inosine was prepared by enzymatic dephosphorylation and deamination of labeled AMP. These compounds have been used to measure the secondary kinetic isotope effects on the acid-catalyzed hydrolysis of the N-glycosidic bond of AMP, dAMP, and inosine and the corresponding primary kinetic isotope effects with AMP. Acid hydrolysis in 0.1 or 0.2 N HCl at 50 degrees C gave 1H/3H secondary kinetic isotope effects of 1.23 +/- 0.01, 1.26 +/- 0.01, and 1.230 +/- 0.003 for AMP, dAMP, and inosine, respectively. The primary kinetic isotope effect for 12C/14C was 1.049 +/- 0.010 for AMP. The apparent rate constants for hydrolysis under these conditions were similar for inosine and AMP and were in the range 10(-6)-10(-5)s-1. Acid hydrolysis of dAMP is approximately 1000-fold faster than AMP but gives a similar 1H/3H kinetic isotope effect. The results of secondary isotope effects indicate that the transition states for the acid-catalyzed hydrolysis of the N-glycosidic bonds of inosine, AMP, and dAMP have similar bonding to 1'-3H in the transition state and have considerable carboxonium character. Results with [1'-14C]AMP demonstrate that a significant primary isotope effect can be measured in the acid solvolysis of the N-glycosidic bond of AMP.

Adenosine Monophosphate↗

PubMed1993

Heterogeneity of guinea-pig lung muscarinic receptors revealed by [3H]4-DAMP-binding.

Muscarinic receptors present in guinea-pig lung were characterized using the M3 selective radioligand [3H]4-diphenylacetoxy-N-methyl-piperidine methiodide ([3H]4-DAMP). In saturation studies, [3H]4-DAMP identified two populations of binding sites with approximately 4% of the sites displaying high affinity (Kd = 0.21 nM and Bmax = 10 fmol/mg prot.) while the remaining sites were low affinity ones (Kd = 18.11 nM and Bmax = 269 fmol/mg prot.). In competition studies with [3H]4-DAMP (0.35 nM), methoctramine and hexahydro-siladifenidol (HHSiD) identified 50 and 70% of high affinity binding sites displaying the pharmacological profile of the M2 and the M3 receptors, respectively. No evidence was found for high affinity [3H]pirenzepine binding sites in guinea-pig lung. However, pirenzepine/[3H]4-DAMP competition experiments suggested that pirenzepine recognized an equal proportion of [3H]4-DAMP binding sites with intermediate and low affinity binding constants. The intermediate affinity binding constant was inconsistent with the presence of M1 receptors and reflected more the presence of M4 or a mixture of M3 and M4 receptors. The low affinity pirenzepine binding sites may represent M2 receptors. These results provide further evidence for the occurrence of M2 and M3 receptors and suggest the presence of the M4 muscarinic receptor subtype in guinea-pig lung.

Animals↗

PubMed1998

Analysis of event-related potentials (ERP) by damped sinusoids.

Several researchers propose that event-related potentials (ERPs) can be explained by a superposition of transient oscillations at certain frequency bands in response to external or internal events. The transient nature of the ERP is more suitable to be modelled as a sum of damped sinusoids. These damped sinusoids can be completely characterized by four sets of parameters, namely the amplitude, the damping coefficient, the phase and the frequency. The Prony method is used to estimate these parameters. In this study, the long-latency auditory-evoked potentials (AEP) and the auditory oddball responses (P300) of 10 healthy subjects are analysed by this method. It is shown that the original waveforms can be reconstructed by summing a small number of damped sinusoids. This allows for a parsimonious representation of the ERPs. Furthermore, the method shows that the oddball target responses contain higher amplitude, slower delta and slower damped theta components than those of the AEPs. With this technique, we show that the differentiation of sensory and cognitive potentials are not inherent in their overall frequency content but in their frequency components at certain bands.

Evoked Potentials, Auditory↗

PubMed1978

The role of action reflexes in the damping of mechanical oscillations.

Reflex responses measured during voluntary contraction of the muscle being stretched are known to differ markedly from reflex responses elicited from passive muscle. The term 'action tonic stretch reflex' or 'action TSR' has been used previously to describe a reflex response to continuous stretch, separated from voluntary activity by means of a cross-correlational and spectrographic analysis. In this paper it is proposed that the action TSR play a functional role during voluntary movement by damping the transient oscillations associated with the natural resonant frequencies of the limbs. It is suggested that oscillations excite an action TSR force response with phase lead ahead of muscle stretch. This force response can be resolved into two force components, one of which has a 90 degree phase lead ahead of muscle stretch and behaves like a viscous friction reaction force causing damping of oscillations. Three experiments which support this proposition are described. (1) Analog computer model stimulation studies of a muscle supporting a mass-spring load reveal that damping only occurs when the force response has a phase lead ahead of muscle stretch. When the force response has a phage lag behind muscle stretch, the system is unstable and the amplitude of oscillation increases with time. (2) It is demonstrated that when a mass-spring load is supported as rigidly as possible by the human arm, reaction forces from the arm damp and mass-spring oscillations more rapidly than when the mass-spring is rigidly supported. Electromyogram (EMG) recordings reveal that mass-spring oscillations excite action TSR responses with phase lead ahead of muscle stretch. (3) Recordings of elbow angle and biceps EMG during rapid forearm flexion or extension movements followed by sudden stops reveal critically damped oscillations in the elbow angle signal (i.e. no more than one or two small overshoots), which are accompanied by EMG action TSR responses with phase lead ahead of muscle stretch.

Arm↗