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At least 919 records · Page 51Linked to original sources
PubMed1993

Vibration analysis of the temporomandibular joints with degenerative joint disease.

The surface vibrations of 42 temporomandibular joints (TMJ) with degenerative joint disease (DJD) and/or perforation of the disk were evaluated using electrovibratography and compared to the surface vibrations of 83 joints with normal TMJ imagings and 61 joints with meniscal displacement without reduction. Through the frequency spectrum analysis, TMJs with DJD showed higher vibration energy above 350-450 Hz and TMJs with perforation showed higher vibration energy between 100-150 and 300-450 Hz. The presence of perforation did not seem to affect the characteristic of vibrations when TMJs were associated with DJD. A threshold was set for the total vibration energy as described in our previous report and used as a parameter in order to separate patients with internal derangement from a pool of TMJ dysfunction patients (diagnostic specificity = 75%, diagnostic sensitivity = 80.2%). Using this criteria, the following were correctly identified as internal derangement and/or DJD: a) 100% of the TMJs with meniscal displacement without reduction associated with DJD; b) 87.0% of the TMJs with meniscal displacement without reduction associated with perforation; c) 88.9% of the TMJs with meniscal displacement without reduction associated with DJD and perforation; and d) 100% of the TMJs with perforation.

Adolescent↗
PubMed1996

Heart rate variability in hypertensive subjects.

Hypertension is often associated with findings of sympathetic hyperactivity. Evidence shows that adrenergic receptor stimulation can induce left ventricular hypertrophy. Using an autoregressive algorithm in a power spectrum analysis of heart-rate variability in 14 subjects with mild hypertension (mean age 41 +/- 9.0 years) and 9 age-matched normotensives we compared autonomic nervous system function at baseline (rest) and during sympathetic stress (passive head-up tilt). The spectrum comprised four spectral frequency-domains: total power (0.0033-0.40 Hz), high-frequency power (0.16-0.40 Hz), low-frequency power (0.04-0.15 Hz) and very-low-frequency power (0.0033-0.04). The high-frequency spectral component predominantly reflects vagal activity, the low-frequency component sympathetic nervous system activity. The ratio between low-and high-frequency power expresses the sympathovagal balance. Results were expressed as natural logarithms of power and normalized units. In addition, we compared spectral densities obtained, with the left ventricular mass index evaluated by M-mode echocardiography. Hypertensive subjects had greater low-frequency and low-high frequency ratio values (P < 0.001) than normotensive controls. They also had a low capacity for increase after tilt. Multiple regression analysis showed that the left-ventricular mass index was independently associated with the body mass index (P < 0.0027), very-low frequency (P < 0.043), and low frequency (P < 0.0138) expressed as the natural logarithm, low-high frequency ratio (P < 0.0172) and systolic blood pressure (P < 0.0353). Our findings confirm enhanced sympathetic activity in hypertensive subjects. They also indicate a close association between the left-ventricular mass index and spectral indices of sympathetic activation.

Adult↗
PubMed2003

The thiosulfinyl group serves as a stereogenic center and shows diamagnetic anisotropy similar to that of the sulfinyl group.

The pseudotetrahedral geometry of the thiosulfinyl group (>S=S) in the thionosulfite which was prepared by treatment of cis-3,4-di-tert-butylthiolane-3,4-diol with 1,1'-thiobisbenzimidazole is stable enough to allow the isolation of two diastereomers. X-ray crystallographic analysis revealed that the configuration of the >S=S group of the major diastereomer (45% isolated yield) is syn to the thiolane ring, while that of the minor diastereomer (10% isolated yield) is anti to the thiolane ring. 1H NMR spectrum analysis clarified that the shielding and deshielding zones of the >S=S group are similar to those of the >S=O group. Chemical properties of the >S=S group toward thermolysis, hydrolysis, and oxidation were clarified. The absorptions or bands in the UV/vis, IR, and Raman spectra, which originate from the >S=S group, were assigned on the basis of the B3LYP/6-31G* level calculations.

Journal Article↗
PubMed2004

Effects of two-month vocal exercising with and without spectral biofeedback on student actors' speaking voice.

Twelve student actors (6 males, 6 females) were given voice training for two months. Randomly selected, half of the students (3 males, 3 females) was trained in the traditional way, while the other half was given biofeedback with real-time spectrum analysis. The aim was a ringing voice quality with strong overtones at 3-5 kHz. Text samples read at different loudness levels were recorded before and after training. Fundamental frequency (F0), sound pressure level (SPL) and long-term-average spectrum (LTAS) analyses were made. Voice quality was evaluated by two voice trainers. Sound energy at 3-5 kHz increased by 3-4 dB (1.5-14.5 dB) across groups after training. This change, which was slightly larger for the biofeedback (BF) group, did not correlate with SPL. F0 increased slightly in the BF group and decreased in the control group. The relative dB level of fundamental decreased significantly more in the BF group probably suggesting a tighter adduction. Voice quality improved in both groups. Visual feedback seems to add some efficacy in voice training. However, there is a danger of hyperfunctional voice production if other sensory feedback is neglected.

Adult↗
PubMed2004

Advances in quantitative electroencephalogram analysis methods.

Quantitative electroencephalogram (qEEG) plays a significant role in EEG-based clinical diagnosis and studies of brain function. In past decades, various qEEG methods have been extensively studied. This article provides a detailed review of the advances in this field. qEEG methods are generally classified into linear and nonlinear approaches. The traditional qEEG approach is based on spectrum analysis, which hypothesizes that the EEG is a stationary process. EEG signals are nonstationary and nonlinear, especially in some pathological conditions. Various time-frequency representations and time-dependent measures have been proposed to address those transient and irregular events in EEG. With regard to the nonlinearity of EEG, higher order statistics and chaotic measures have been put forward. In characterizing the interactions across the cerebral cortex, an information theory-based measure such as mutual information is applied. To improve the spatial resolution, qEEG analysis has also been combined with medical imaging technology (e.g., CT, MR, and PET). With these advances, qEEG plays a very important role in basic research and clinical studies of brain injury, neurological disorders, epilepsy, sleep studies and consciousness, and brain function.

Animals↗
PubMedDate not supplied

[Use of microprocessor controllers for the analysis of Doppler signals of blood flow velocity].

Herein the approach to the design of the ultrasound Doppler constant emitters has been considered. One of its versions is the described unit, which allows one to store in its memory and display on the TV monitor curves of the blood flow being divided according the direction, to carry out the spectrum analysis of the Doppler signal in the chosen time intervals, to calculate the quantitative parameters of the blood flow.

Blood Flow Velocity↗
PubMed1998

Electroretinographic oscillatory potentials in different aged rats: an analysis in the domains of time and frequency.

OBJECTIVES: Electroretinographic Oscillatory Potentials (Ops) are considered to be the optimal parameter to study the retinal circulation disturbances the present we compared parameters of OPs between different aged rats under dark adaptation. METHODS: The scotopic ERG were performed in anaesthetized rats aged 3, 12, 24 months. According a window of collective power spectrum field of the OPs was isolated by using the FFT and IFFT of the spectrum analysis program. The parameters in the time and frequency domains were calculated. RESULTS: Results showed that the amplitudes of wavelets and the summed amplitudes of OPs declined with the increase of age. A reduction of the total power and dominated power of OPs was also found after the FFT. But implicit time of each OP and dominant frequency did not change obviously. CONCLUSIONS: The present study indicated that change of OPs of rat might be related to senile degeneration of the retina and circulative deficiency in retina in elder rats.

Aging↗
PubMed2006

Air-breathing rhythm in Clarias batrachus (Linn.): modulatory role of eyes, pineal and exogenous melatonin.

Effects of enucleation followed by pinealectomy and administration of exogenous melatonin on air-breathing activity rhythm in a fresh water catfish, C. batrachus maintained at LD 12:12 and laboratary temperature during its prepratory phase, were examined. Results of cosinor analysis clearly reveal that most of the intact individuals exhibited circadian rhythm in their air-breathing activity and such rhythm persists even after enucleation followed by pinealectomy and then melatonin administration. However, the period (tau) of the activity obtained by power spectrum analysis was prominent 24 hr in most of the intact individuals, but it was increased (tau > 24 hr) after enucleation in most of the individuals. In most of the enucleated + pinealectomized individuals tau was less than 24 hr, and after receiving melatonin treatment tau was shifted to prominent 24 hr in most of the individuals. In addition, visual analysis of the actograms depicted that in intact individuals air-breathing activity is entrained with the timings of lights on/off with elevation of activity during dark period and decreased activity during light hours. However, enucleated and enucleated + pinealectomized individuals showed free run in their activity rhythm. The treatment of melatonin reestablished the entrainment of activity at least with the timing of lights off, in most of the studied individuals. Further, daily mean of the air-breathing activity was decreased in enucleated + pinealectomized individuals as compared with other studied groups (intact, enucleated, enucleated + pinealectomized + melatonin receiving). It could be speculated that there may be existence of extraretinal and extrapineal photoreceptors in C. batrachus. However, eyes play an important role in regulating air-breathing activity rhythm in such species. In addition, exogenous melatonin may also have some modulatory effect on such rhythm.

Animals↗
PubMed1990

Effects of transdermal scopolamine on heart rate variability in normal subjects.

A decrease in cardiac parasympathetic tone is a recognized finding in patients with ischemic heart disease, sudden cardiac death and heart failure, correlating closely with disease severity and overall survival. To study the clinical potential of vagomimetic intervention, the effect of transdermal scopolamine on fluctuations in heart rate was studied in 32 healthy adult subjects using both time-domain (mean RR interval, standard deviation of the mean RR interval, mean of the differences between consecutive RR intervals) and frequency-domain measures (spectrum analysis of 128 consecutive RR intervals) of heart rate variability. After an exposure of 24 hours, transdermal scopolamine resulted in a significant increase in all indexes tested. The increase was most pronounced in the 0.25-Hz respiratory peak of the RR interval power spectrum, compatible with a strong vagomimetic mode of action of transdermal scopolamine. Results indicate that transdermal scopolamine may have potential merit as a selective vagotonic agent in certain patients with myocardial infarction, heart failure or ventricular arrhythmias.

Administration, Cutaneous↗
PubMed1989

Age-dependent ECoG spectrum power alterations are reduced by phosphatidylserine in rats.

The present experiments were carried out in order to characterize the changes in ECoG spectrum power occurring in old compared with young rats. In addition, it was planned to ascertain whether chronic treatment with phosphatidylserine affected possible ECoG changes occurring in aged animals. In comparison to 3 months-old rats, the ECoG activity of 13-15 months-old rats showed spontaneous single or bursts of monophasic and biphasic spikes. In addition, spectrum analysis revealed a significant increase in the power of the lowest frequency band (0.25-3 Hz), accompanied by a decrease in 6-9, 9-12 and 12-16 Hz power. Chronic oral or parenteral treatment with phosphatidylserine gradually reversed the changes in ECoG spectrum power occurring in old rats and produced, at the ECoG level, a distribution pattern of single frequency, bands similar to that observed in young animals.

Age Factors↗
PubMedDate not supplied

The maintained discharge of neurons in the cat lateral geniculate nucleus: spectral analysis and computational modeling.

The maintained discharge of neurons along the early visual pathway in mammals constitutes the "noise" from which the visual signal must be discriminated. The statistics of this background noise in cat retinal ganglion cells (RGCs) have been shown to conform to that of a gamma-distributed renewal process (Kuffler et al., 1957; Barlow & Levick, 1969), and power spectrum analysis reveals that this property allows for low noise levels at the temporal-frequency range (0-10 Hz) most important for visual performance (Troy & Robson, 1992). In this study, we compare the statistics of the maintained discharge of cat lateral geniculate neurons with those of its RGC input by simultaneous recordings of spikes and S-potentials in single relay cells of the cat lateral geniculate nucleus (LGN). We demonstrate that, during primarily tonic spiking activity, the LGN maintained discharge preserves the renewal process statistics of its RGC input and also generates relatively little noise at the temporal frequencies important for vision. However, during burst spiking activity, the renewal process model breaks down and increased noise is generated at 2-10 Hz. This suggests that optimization of the visual signal/noise ratio is not a prime consideration in the behavioral states associated with bursting activity in the LGN. The occurrence of burst spikes in LGN relay cells is dependent on the activity of T-type calcium channels in their plasma membranes (Jahnsen & Llinas, 1984a,b). We show that a computational model of LGN relay cells that incorporates T-channel kinetics (Mukherjee & Kaplan, 1995) can correctly simulate LGN maintained discharge statistics during both tonic and bursty firing conditions, and indicates an essential role for this ion channel in determining the dynamic noise properties of the LGN. We also use the computational model to predict how the burstiness of the LGN maintained discharge is affected by the statistics of its RGC input.

Action Potentials↗
PubMed1999

Infradian rhythm of paroxysmal atrial fibrillation. A case report.

To examine the circadian and infradian rhythms of paroxysmal atrial fibrillation, the time and date of 85 arrhythmic attacks occurring over a period of 4 years were analyzed in a patient with reliable symptoms. In the hourly analysis, a remarkable circadian rhythm similar to the reported population circadian rhythm was observed. On a day basis, the distribution of the intervals between 2 successive episodes showed a significant departure from the exponential distribution, indicating the arrhythmia was not a simple probabilistic phenomenon. Spectrum analysis revealed a prominent peak occurring at about 0.3 cycles/day, suggesting a possible circasemiseptan rhythm. Thus, in this patient, paroxysmal atrial fibrillation was not a random event when observed not only from an hour incremental perspective but also from a day incremental perspective, suggesting the circadian and infradian rhythms of this arrhythmia.

Atrial Fibrillation↗
PubMed2001

Moleculary imprinted polymers with metalloporphyrin-based molecular recognition sites coassembled with methacrylic acid.

A diastereoselective molecularly imprinted polymer (MIP) for (-)-cinchonidine, PPM(CD), was prepared by the combined use of methacrylic acid and vinyl-substituted zinc(II) porphyrin as functional monomers. Compared to MIPs using only methacrylic acid or zinc porphyrin as a functional monomer, PM(CD) and PP(CD), respectively, PPM(CD) showed higher binding ability for (-)-cinchonidine in chromatographic tests using the MIP-packed columns. Scatchard analysis gave a higher association constant of PPM(CD) for (-)-cinchonidine (1.14 x 10(7) M(-1)) than those of PP(CD) (1.45 x 10(6) M(-1)) and PM(CD) (6.78 x 10(6) M(-1)). The affinity distribution of binding sites estimated by affinity spectrum analysis showed a higher percentage of high-affinity sites and a lower percentage of low-affinity sites in PPM(CD). The MIPs containing a zinc(II) porphyrin in the binding sites, PPM(CD) and PP(CD), showed fluorescence quenching according to the binding of (-)-cinchonidine, and the quenching was significant in the low-concentration range, suggesting that the high-affinity binding sites contain the porphyrin residue. The correlation of the relative fluorescence intensity against log of (-)-cinchonidine concentrations showed a linear relationship. These results revealed that the MIP having highly specific binding sites was assembled by the two functional monomers, vinyl-substituted zinc(II) porphyrin and methacrylic acid, and they cooperatively worked to yield the specific binding. In addition, the zinc(II) porphyrin-based MIPs appeared to act as fluorescence sensor selectively responded by binding events of the template molecule.

Binding Sites↗
PubMed2005

Analysis of charge-transfer absorption and emission spectra on an absolute scale: evaluation of free energies, matrix elements, and reorganization energies.

The relationship between the absorption and emission spectra of the charge-transfer complexes formed between a series of methyl-substituted benzene donors with 1,2,4,5-tetracyanobenzene as acceptor in 1,2-dichloroethane was examined in detail. The association constants for charge-transfer complex formation and the emission quantum yields for these complexes were used to place the experimental absorption and emission spectra on absolute scales. The simultaneous analysis of these spectra is valid only when the Mulliken two-state model is justified. For several of the complexes included in this study the electron-transfer parameters, including the electronic coupling matrix elements, obtained from the analysis of the individual absorption and emission spectra are in close agreement. The simultaneous analysis of the combined absorption and emission spectra leads to a well-defined set of electron-transfer parameters for these complexes. In other complexes, where the two-state model does not apply because of the influence of localized excited states on the absorption spectrum, analysis of the absorption and emission spectra led to significantly different sets of electron-transfer parameters. It is demonstrated that the electronic coupling matrix elements are a very sensitive indicator of the influence of localized excited states on these spectra.

Benzene Derivatives↗
PubMedDate not supplied

[Spectrographic study of voice disorders: subharmonics].

The presence of subharmonics in abnormal adult voices (polyps, polypoid degeneration, plicae ventricularis) was investigated. Subharmonics are low-frequency modulations located between two consecutive harmonics in the spectrum. Spectrum analysis was performed on 115 abnormal voices, of which 36 (31%) had subharmonics. Thirteen of the 36 voices with subharmonics had normal jitter and shimmer, so the rough voice was characterized acoustically not only by jitter and shimmer but by the presence of subharmonics in the spectrum. Subharmonics may correspond to a qualitative change in the behavior of the vibratory system.

Adult↗
PubMed2004

Spectral analysis of burst periods in EEG from healthy and post-asphyctic full-term neonates.

OBJECTIVE: To investigate whether the periodic EEG patterns seen in healthy and sick full term neonates (trace alternant and burst suppression, respectively) have different frequency characteristics. METHODS: Burst episodes were selected from the EEGs of 9 healthy and 9 post-asphyctic full-term neonates and subjected to power spectrum analysis. Powers in two bands were estimated; 0-4 and 4-30 Hz, designated low- and high-frequency activity, respectively (LFA, HFA). The spectral edge frequency (SEF) was also assessed. RESULTS: In bursts, the LFA power was lower in periods of burst suppression as compared to those of trace alternant. The parameter that best discriminated between the groups was the relative amount of low- and high-frequency activity. The SEF parameter had a low sensitivity to the group differences. In healthy neonates, the LFA power was higher over the posterior right as compared to the posterior left region. CONCLUSIONS: Spectral power of low frequencies differs significantly between the burst episodes of healthy and sick neonates. SIGNIFICANCE: These results can be used when monitoring cerebral function in neonates.

Asphyxia Neonatorum↗
PubMed2006

Non-random fluctuations in power output during self-paced exercise.

OBJECTIVES: To analyse the power output measured during a self-paced 20-km cycling time trial, during which power output was free to vary, in order to assess the level and characteristics of the variability in power output that occurred during the exercise bout. METHODS: Eleven well-trained cyclists performed a 20-km cycling time trial, during which power output was sampled every 200 m. Power spectrum analysis was performed on the power output data, and a fractal dimension was calculated for each trial using the Higuchi method. RESULTS: In all subjects, power output was maintained throughout the trial until the final kilometre, when it increased significantly, indicating the presence of a global pacing strategy. The power spectrum revealed the presence of 1/f-like scaling of power output and multiple frequency peaks during each trial, with the values of the frequency peaks changing over the course of the trial. The fractal dimension (D-score) was similar for all subjects over the 20-km trial and ranged between 1.5 and 1.9. CONCLUSIONS: The presence of an end spurt in all subjects, 1/f-like scaling and multiple frequency peaks in the power output data indicate that the measured oscillations in power output during cycling exercise activity may not be system noise, but may rather be associated with system control mechanisms that are similar in different individuals.

Adult↗
PubMed2001

EEG abnormalities in dementia reflect the parietal lobe syndrome.

The aim of this study was to investigate to what extent the examination of regional syndromes can improve EEG diagnostics in dementia. The study was based on 77 patients, aged between 47 and 83 years, with a dementia disease in accordance with the DSM-III-R criteria. The clinical examination was refined using a so-called stepwise clinical status analysis to estimate the occurrence and intensity of the parietal lobe syndrome, the frontal lobe syndrome, the subcortical syndrome and the less-regionalised global syndrome. In the same time period, the patients were examined electroencephalographically and the recordings were assessed both visually and by means of spectrum analysis. It was found that the intensity of the parietal lobe syndrome was correlated more strongly to the EEG slow activity as compared to the other regional syndromes. Thus, it can be expected that the EEG will be most valuable in the early-onset type of Alzheimer's disease, in which the parietal syndrome is dominant, giving information regarding the degree of dementia and suggesting a possible interference with depression. The results of the study can probably explain some discrepancies between the EEG findings and the results of clinical examination in other forms of dementia.

Aged↗