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At least 307 records · Page 17Linked to original sources
PubMed1993

Power spectrum analysis of cardiovascular variability monitored by telemetry in conscious unrestrained rats.

Beat-to-beat variability of arterial pressure and heart period (R-R) was studied in eight conscious freely-moving adult male rats in which telemetric recordings of arterial pressure, ECG and respiratory movements were obtained under unrestrained and unstressed conditions. The beat-to-beat time series of these signals (systolic arterial pressure, diastolic arterial pressure and R-R) were analyzed, in the frequency domain, using autoregressive spectral analysis in order to detect and quantify the rhythmic components. In basal conditions, the systolic arterial pressure variability spectrum was characterized by three major spectral components which had central frequencies respectively of 0.08 +/- 0.03 Hz (very low frequency), 0.43 +/- 0.02 Hz (low frequency) and 1.36 +/- 0.19 Hz (high frequency). Similar rhythmic components were found in R-R signal variability. The very low frequency component included a higher percentage of total power in R-R variability spectrum (75.3%) than in systolic arterial pressure variability spectrum (58.4%). The low frequency component was more pronounced in both systolic and diastolic arterial pressure variability spectra. The high frequency component of R-R, systolic and diastolic arterial pressure was synchronous with respiration. Cross-spectral analysis revealed a high statistical coherence between R-R and arterial pressure variabilities in all the three frequency bands. An alpha-adrenergic blocker (phentolamine) specifically abolished the low frequency components of systolic and diastolic arterial pressure variability spectra, thus suggesting that low frequency is a marker of sympathetic modulation of vasomotor activity. The low frequency component of R-R variability spectrum was also markedly blunted. We suggest that cardiovascular variability signals, (R-R, systolic and diastolic arterial pressure) are composed almost of two main rhythms linked to respiration and vasomotor activity. These rhythms can be quantified in conscious unrestrained rats by using telemetry and spectral analysis. This approach seems to offer a new powerful tool for pharmacological studies in conscious small animals.

Animals↗
PubMed1995

The effects of emotions on short-term power spectrum analysis of heart rate variability .

In summary, this work extends previous findings by demonstrating that anger produces a sympathetically dominated power spectrum, whereas appreciation produces a power spectral shift toward MF and HF activity. Results suggest that positive emotions lead to alterations in HRV, which may be beneficial in the treatment of hypertension and in reducing the likelihood of sudden death in patients with congestive heart failure and coronary artery disease.

Adult↗
PubMed1989

Decrease in delta sleep in growth hormone deficiency assessed by a new power spectrum analysis.

Seven pituitary dwarfs between 18 and 28 years old with congenital absence of growth hormone, i.e., isolated growth hormone deficiency (IGHD), were examined with polysomnography. Power spectrum analyses of the delta band showed a significant decrease in power in the delta sleep in the IGHD patients compared with the controls. Power spectrum analyses add a new dimension to the description of sleep, as it evaluates, not only frequency of the electroencephalogram (EEG) in time but also the amplitude of the EEG signal. This means that sleep of same quantity can have different powers; for example, 15 min of stage 4 in one person can have another quality than 15 min of stage 4 in another person. An additional observation was that the power in the delta band in the normal young controls showed a correlation to age, with significant decrease within a 10-year period.

Adolescent↗
PubMed1995

[Heart rate fluctuations in the horse at rest: (1) Investigation of heart rate changes by spectrum analysis].

The heart rate fluctuations at rest were studied in order to explore the emotionality of the horses by isolating the influence of the autonomic control. This paper presents a method of spectral analysis which was used to analyse the heart rate variability in the frequency domain. The heartbeat intervals were recorded during 1 h and a series of 1,024 heartbeats was extracted to compute a power spectrum of density. This was obtained by calculating the Fourier transform of the autocorrelation function of the series. This spectral analysis was applied to heart rate recordings in order to illustrate its sensitivity. The normal heart rate fluctuations at rest were compared with those obtained after atropine and atropine+adrenaline injections. The normal power spectrum revealed several low frequency components (< 0.1 cycle/beat). The atropine injection reduced heart rate variability while the atropine+adrenaline injection increased the power of low frequency fluctuations.

Animals↗
PubMed1993

Time-variant power spectrum analysis for the detection of transient episodes in HRV signal.

A time-variant algorithm of autoregressive (AR) identification is introduced and applied to the heart rate variability (HRV) signal. The power spectrum is calculated from the AR coefficients derived from each single RR interval considered. Time-variant AR coefficients are determined through adaptive parametric identification with a forgetting factor which obtains weighed values on a running temporal window of 50 preceding measurements. Power spectrum density (PSD) is hence obtained at each cardiac cycle, making it possible to follow the dynamics of the spectral parameters on a beat-by-beat basis. These parameters are mainly the LF (low frequency) and the HF (high frequency) powers, and their ratio LF/HF. These together account for the balanced sympatho-vagal control mechanism affecting the heart rate. This method is applied to subjects suffering from transient ischemic attacks. The time variant spectral parameters suggest an early activation of LF component in the HRV power spectrum. It precedes by approximately 1.5-2 min the tachycardia and the ST displacement, generally indicative of the onset of an ischemic episode. The results suggest an arousal of sympathetic system before the acute attack.

Algorithms↗
PubMed2002

Detection of periodicity in eukaryotic genomes on the basis of power spectrum analysis.

In the present study, we identified periodic patterns in nucleotide sequence, and characterized nucleotide sequences that confer periodicities to Arabidopsis thaliana and Drosophila melanogaster on the basis of a power spectrum method and frequency of nucleotide sequences. To assign regions that contribute to each periodicity we calculated periodic nucleotide distributions by a parameter proposed in the paper. In A. thaliana, we obtained three periodicities (248 bp-, 167 bp-, and 126 bp) in chromosome 3, three peaks (174 bp-, 88 bp-, and 59 bp-period) in chromosome 4, and four periodicities (356 bp, 174 bp, 88 bp, and 59 bp) in chromosome 5. These are relation to ORF that consists of Gly-rich amino acid sequences including histone protein that consists of Gly-, Ser-, and Ala-rich amino acids residues. For D. melanogaster genome we found that G or C spectral curves have flat region at middle frequency range from f = 10(-4) to 10(-5) (corresponding to cyclic size 1 kb-5 kb), which may be associated with randomness of base sequence composition. This property has not been observed in Saccharomyces cerevisiae, Caenorhabditis elegans, and Homo sapiens yet.

Animals↗
PubMed2005

[Spectrum analysis of erythrocyte intracellular hemoglobin with a novel fast multi-channel micro-spectrophotometry].

With the application of a novel fast multi-channel micro-spectrophotometry (MMSP), the absorption spectrum of intracellular hemoglobin molecule in a human single living red blood cell was monitored under the altered physiological environments (pH, temperature, partial pressure of oxygen, and osmotic pressure). It was found that on the absorption spectrum curve of hemoglobin the spike, the height and the position of the characteristic absorption peaks at 540 and 575 nm were altered obviously with the changes in physiological conditions, indicating that the concentration, structure and function of the hemoglobin in the red blood cell may be closely associated with the physiological environments.

Algorithms↗
PubMed2001

[Determination of content and specific activity of radioactive elements in phosphate slag by spectral and energy spectrum analysis].

Phosphate slag is the slag discarded after phosphate ore is smelted. The content and specific activity of radioactive elements in slag must be determined accurately for environmental protection and comprehensive utilization. This paper discusses how IR spectrum and X-ray diffraction method are used to study its components. The main phase composition is glassy slag. The samples are decomposed with HF-HNO3-HClO4. After anion-exchange separation, arsenazo III is used to determine the content of uranium and thorium in slag. The average content of U is 32.11 micrograms.g-1 and 8.5 micrograms.g-1 for Th. gamma spectrum is used to determine the specific activity of radioactive nuclear elements in it. The specific activities of 226Ra, 232Th and 40K are 112 +/- 2.0% Bq.kg-1, 18.8 +/- 6.4% Bq.kg-1 and 77.6 +/- 3.7% Bq.kg-1, respectively. The values are calculated as follow: M(Ra) = 0.6 Bq.kg-1, M gamma = 0.5 Bq.kg-1. The results show that the values are below 1.0 Bq.kg-1, which is stipulated by national GB6566-86 standard for radioactivity of building materials. The slag is therefore can be utilized to produce slag cement. This provides theoretical basis for the treatment of it.

Elements, Radioactive↗
PubMed1997

[The spectrum analysis of high performance liquid chromatographic peak by ultraviolet-visible spectrophotometric detectors].

In the analysis of high performance liquid chromatography (HPLC), the qualification of chromatographic peak can be carried out by the methods of adding standard, comparing retention time and absorption spectrum etc. This paper reports a simple and practical method for measurement of absorption spectrum of HPLC peak by ultraviolet and visible variable wavelength detector. A BASIC program was edited with Shimadzu C-R4A data processor. Stopping the pump at the retention time we use the program to analyse absorption spectrum of the peak and the absorption spectrum of standard (Cr, PU, UA) by Shimadzu UV-2201 UV-VIS recording spectrophotometer and the absorption spectrum of standard (-S) with sample (-T) by this method are presented. The figure shows that the absorption spectra of the samples of Cr, PU and UA almost completely overlapped with those of the standards. The results showed that this method is reliable.

English Abstract↗
PubMed1995

Subclass approach for mutational spectrum analysis.

Analysis and comparison of mutational spectra represents a burning question in molecular biology. We report an algorithm based upon the SEM subclass approach (SEM--stochastique, estimations, maximizations). Any real mutational spectrum is regarded as a mixture of standard binomial distributions. The separation procedure is run by rounds. Each iteration includes simulation, maximization and estimation. The algorithm has been checked on random spectra with the preset parameters and on real mutational spectra. As has been shown, any real mutational spectrum can be represented as a mixture of two and more binomial distributions, of which one contains hotspots of mutation.

Algorithms↗
PubMed1985

Flow cytometric fluorescence emission spectrum analysis of Hoechst-33342-stained DNA in chicken thymocytes.

Hoechst-33342-stained chicken thymocytes were analysed simultaneously on two fluorescence wavelength bands (green and violet) in our custom-built flow cytometer, and two major subsets were identified. In one subset (33% of the total) the emission spectrum remained constant with time, with little change in the respective green and violet fluorescence intensities. In the other subset (42% of the total) the green fluorescence increased during staining, resulting in a considerable change in the green-to-violet ratio, due to a change in the "shape" of the fluorescence emission with time. The data indicate that two binding sites, or two types of binding at the same site, exist in DNA for this dye and that these have different binding energies and, consequently, different fluorescence emission properties.

Animals↗
PubMed1994

Experimental assessment of spectrum analysis of ultrasonic echoes as a method for estimating scatterer properties.

In vitro experiments using weak scatterers ranging in size from mean longest diameter of 26.9 to 83.0 microns were performed to test the validity of theoretical predictions for scatterer size and concentration derived from normalized power spectrum parameters of ultrasonic backscatterer echoes. Scatterers consisting of cell clusters were suspended in collagen gel and scanned by a 10 MHz transducer system. Optical measurements validated theoretical predictions that (1) slope value is a function solely of scatterer size; (2) intercept value is a function of scatterer size and concentration; and (3) midband fit value increases as scatterer concentration increases, and, to a lesser extent, as size increases. These results were obtained under relatively ideal conditions of minimal attenuation and scatterer spacing (not closer than two scatterer diameters) and were consistent with the assumptions underlying the scattering theory.

Humans↗
PubMed1993

Power spectrum analysis of the fetal heart rate during noradrenaline infusion and acute hypoxemia in the chronic fetal lamb preparation.

In a chronically instrumented fetal lamb the effect on heart rate variability of noradrenaline as well as hypoxemia is studied by the use of power spectral analysis. Subsequent to both noradrenaline infusion and hypoxemia the very low frequency components of the variability are markedly decreased as compared with control conditions. After hypoxemia also a high frequency peak appears in the spectrum.

Acute Disease↗
PubMed2000

Broad spectrum analysis of 109 priority compounds listed in the 76/464/CEE Council Directive using solid-phase extraction and GC/EI/MS

A single multiresidue method was developed to determine 109 priority organic compounds included in the 76/464/EEC Council Directive on Pollution of the European Union. Such Directive includes 132 priority pollutants with a broad spectrum of polarities to be analyzed in drinking and surface waters, with the aim to protect water quality. From this list, the compounds analyzed included benzidines, chloroanilines, chloronitrobenzenes, chloronitrotoluenes, chlorophenols, chloronitrotoluidines, PAHs, PCBs, pesticides, phenylurea, and triazine herbicides. The method was developed in four steps. First, automated off-line solid-phase extraction using polymeric sorbent Oasis 60 mg cartridges was optimized to trap 109 compounds. Second, gas chromatography coupled to mass spectrometry with electron impact ionization (GC/EI/MS) was used in selected ion monitoring (SIM) mode for tentative identification of target analytes. Third, GC/EI/MS under full scan conditions was used for spectrum identification and analyte confirmation. Last, quantification was performed from SIM chromatogram using surrogates and internal standard. This method offered excellent sensitivity and selectivity, and the preconcentration of 200 mL permitted the achievement of limits of detection at the low nanogram/liter level and recoveries between 70 and 120%. Such methodology was applied to determine 109 organic compounds in French surface waters, and several pollutants were detected at levels from ppt to ppb. This multiresidue method developed was highly reproducible and robust and permitted a high sample throughput.

Journal Article↗
PubMed1986

Resolution of steroid binding heterogeneity by Fourier-derived affinity spectrum analysis (FASA).

A new mathematical method of analyzing radioreceptor assay data is presented. When there are many binding classes with different affinities, the probability-density function B(p) is described by the equation B(p) = (integral negative infinity to infinity) q(k)f(p-k)dk, where q(k) is the affinity spectrum (density of a particular binding class as a function of affinity) and f(p-k) is a probability function (probability that dissociation constants will fall between k and p-k, where p is the free ligand concentration). This equation is solved for q(k) and evaluated explicitly by Fourier transformation, namely, q(w) = b(w)/f(w), where w is frequency. Since division by f(w) can amplify and high frequency noise present in the experimental data, a Gaussian smoothing function is introduced thus: qs(w) = q(w)e(-w/W0)2, where W0 is a constant. This produces an affinity spectrum defined as a plot of the number of binding sites, qs(k), versus their respective dissociation constants, k. Using a FORTRAN computer program, we verify this algorithm using simulated data. We also apply the procedure to resolve heterogeneous populations of estrogen binders in human endometrium using [3H]estradiol as ligand. Two estrogen binder classes are revealed with dissociation constants approximately 2.5 natural logarithmic units apart. We identify one high-affinity (Kd = 0.18 nM)-low density (70 pM [or 72 fmol/mg protein]) subpopulation and one low affinity (Kd = 2.5 nM)-high density (101 pM [or 102 fmol/mg protein]) subpopulation of estradiol binders. The management of experimental error, sampling limitations, and nonspecific binding are discussed. This method directly transforms experimental data into an easily interpretable representation without mathematical modeling or statistical procedures.

Endometrium↗
PubMed1998

The subclass approach for mutational spectrum analysis: application of the SEM algorithm.

Analysis and comparison of mutational spectra represents an important problem in molecular biology. To analyse a mutational spectra we apply an algorithm based on the SEM subclass approach (Simulation, Expectation, Maximization). The algorithm tries to classify the mutational sites according to different mutation probabilities, and each site should belong to one class. Each class is approximated by binomial distribution and thus any real mutational spectrum is regarded as a mixture of binomial distributions. The separation process runs iteratively. Each iteration includes the simulation, maximization and estimation procedures. To evaluate the quality of the classification results, the X2 test is used. The algorithm has been checked on random spectra with preset parameters and on real mutational spectra. As has been shown, 17 out of 19 analysed real mutational spectra can be divided into two or more classes of sites, of which one contains hotspots of mutation. For the G:C-->A:T mutational spectra induced by Sn1 alkylating mutagenes (11 spectra) the classification accuracy was 0.95. To test different site volumes, each Sn1-induced spectrum was divided into the G-->A and C-->T spectra. The classification accuracy for these spectra was 0.96. From the analysis of classification errors it is possible to suggest that at least part of them cannot be ascribed to the faults of the algorithm but are caused by some special features of the mutagenesis itself. The results of the real data are in good relation with existing knowledge. The approach we present is an attempt to formalize the concept of a "mutational hotspot". The program implementing the SEM algorithm is available on the Web server (http:/(/)www.itba.mi.cnr.it/webmutation).

Algorithms↗
PubMed1994

[Spectrum analysis of cat si neurone discharges].

Spontaneous firing and the discharges evoked by A- and/or C-fiber inputs (A-ED, C-ED, AC-ED) of saphenous nerve were recorded in the somatosensory cortical (SI) neurons (n = 128) of the cats anesthetized with chloralose and paralysed by gallamine. Normalized power spectrum density function (NPSDF) was used to analyse the neuron discharges. The results showed that 1) all the NPSDFs for the spontaneous discharges were single-peak with a peak frequency of 3.91 +/- 1.63 Hz (spontaneous rhythm) and a peak value of 0.0154 +/- 0.0045; 2) the NPSDFs of A-ED showed a single peak (peak value 0.021 +/- 0.0054) and an overlapped double-peak (with spontaneous discharge) or a separate multi-peak (without spontaneous discharge); 3) the NPSDFs of C-ED showed a single peak (peak value 0.020 +/- 0.007) or a separate double-peak; 4) the NPSDFs of AC-ED have two patterns: a single peak (peak value 0.023 +/- 0.004) and an overlapped multi-peak. It is suggested that A-fiber input can potentiate the rhythms of the spontaneous discharge and induce specific rhythm; that C-fiber input can potentiate the spontaneous rhythm and induce characteristic C-rhythm. It is also observed that both spontaneous rhythm and evoked rhythm affect each other; that the evoked rhythms by A-fiber and C-fiber inputs also affect each other.

Animals↗
PubMed1988

Spectrum analysis of turbulence in the canine ascending aorta measured with a hot-film anemometer.

We measured turbulence velocity in the canine ascending aorta using a hot-film anemometer. Blood flow velocity was measured at various points across the ascending aorta approximately 1.5-2 times the diameter downstream from the aortic valve. The turbulence spectrum was calculated and its characteristics were examined in connection with the mean Reynolds number and/or measuring positions. In the higher wave number range the values of the turbulence spectra were higher at larger mean Reynolds number. In the higher wave number range, the values of the turbulence spectra were higher at points closer to the centerline of the aorta, when the mean Reynolds number was relatively large. The patterns of the turbulence spectra at various points outside the boundary layer on the aortic wall were similar.

Animals↗