Spectral Component Analysis Research Articles

Regional variations of noise-induced changes in operating range in cat AI

Regional differences in spectral integration of neurons in cat primary auditory cortex (AI) suggest that regions differ in effects of background noise on operating characteristics of neurons. Therefore, tone-response threshold, best level (peak-rate intensity), dynamic range, and sharpness of tuning in quiet and in continuous broadband noise were mapped for single neurons along the isofrequency domain of AI. Neurons did not show an excitatory response to the noise. Noise invariably increased the tone-response threshold and best levels. Consequently, the dynamic ranges and receptive fields shifted to higher intensity levels without changes of average sharpness of tuning. These shifts were linearly related to noise level and showed little inter-neuronal variability for neurons in the central, mostly sharply tuned part of AI. In more dorsal and ventral parts of AI, neurons were more variable in tone-response threshold, dynamic range and best level, and no systematic relationship between increase in noise level, threshold increase and best-level increase was observed. We conclude that linear shifts in the operating range of neurons in central AI in the presence of continuous noise backgrounds do not affect other response properties and may relate to the unaltered analysis and representation of spectral components of sounds. In contrast, neurons in dorsal and ventral AI change response properties in a non-predictable way in the presence of noise in accordance with the more complex receptive field properties in those areas.

Even slight movements disturb analysis of cardiovascular dynamics.

We hypothesized that spontaneous movements (postural adjustments and ideomotion) disturb analysis of heart rate and blood pressure variability and could explain the discrepancy between studies. We measured R-R intervals and systolic blood pressure in nine healthy sitting subjects during three protocols: 1) no movement allowed, 2) movements allowed but not standing, 3) movements and standing allowed. Heart rate and blood pressure were not altered by movements. Movements with or without standing produced a twofold or greater increase of the overall variability of R-R intervals and of the low-frequency components of spectral analysis of heart rate variability. The spectral exponent beta of heart rate variability (1. 123 at rest) was changed by movements (1.364), and the percentage of fractal noise (79% at rest) was increased by standing (91%, coarse-graining spectral analysis). Spontaneous movements could induce a plateau in the correlation dimensions of heart rate variability, but they changed its nonlinear predictability. We suggest that future studies on short-term cardiovascular variability should control spontaneous movements.

Improved NASVD smoothing of airborne gamma–ray spectra

Noise–adjusted singular value decomposition (NASVD) is a spectral component analysis procedure for the removal of noise from gamma–ray spectra. The procedure transforms observed spectra into orthogonal spectral components. The lower–order components represent the signal in the original observed spectra, and the higher–order components represent uncorrelated noise. Noise is removed from the observed spectra by rejecting noise components and reconstructing the spectra from lower–order components.A synthetic dataset has been used to obtain new insights into the NASVD method. The dataset is based on an airborne survey over the Jemalong Plains area, NSW. The estimated ground concentrations of potassium (K), uranium (U) and thorium (Th) were spatially filtered and then used to synthesise airborne spectra using simulated Poisson noise. These spectra include a background component based on typical aircraft and cosmic background, and a simple model of the distribution of atmospheric radon. The application of NASVD smoothing to this dataset gives a much greater reduction in U concentration errors than that normally experienced. Careful investigation suggests that the reason for this is that the Jemalong Plains dataset exhibits high correlation between U and Th, and because the survey was flown on a day of low and near constant atmospheric radon concentration. If the dataset is modified by either adding spectra derived from an anomalous U/Th source, or by including atmospheric radon variations typical of most airborne surveys, then the large reductions in U concentration error are no longer achieved.Tests on the synthetic data suggest that the smaller the variation in spectral shape within the input signal, the greater the noise reduction. This is used to develop an improved implementation of the NASVD method that can be applied to large survey datasets. Instead of processing the survey data by flight, the entire survey database is sorted into clusters on the basis of similarity in spectral shape, and the NASVD method is applied to these clusters. This typically halves the K, U and Th fractional errors compared with those obtained when the data are processed according to flight. This increases the amount of geological information that can be extracted from enhanced images of the processed data.

The broadband seismic station CAD (Túnel del cadí, eastern pyrenees): Site characteristics and background noise

Abstract This article presents the main characteristics of the broadband (BB) seismic station of Túnel del Cadí (CAD) along with an analysis of seismic noise and its correlation with regional meteorological conditions. The quality of the sensor site (in a closed cave, 80 m below surface) provides ideal conditions for the location of a BB station with the ability to detect small events. Through the analysis of noise series 30 min in length during a period of 15 months, a characterization of the level of detectability has been performed. Using one estimate of noise per day, the seasonal variation of the amplitude of the noise has been analyzed, and using four samples per day, short-period variations have been studied and compared with external meteorological conditions. Results show that the characteristics of the station are similar to a typical station placed in a hard basement rock and that there are no differences between the behavior of the three components. The analysis of several spectral components shows the relative excitation of microseisms and atmospheric disturbances that may differ more than one order of magnitude. There is a clear anticorrelation between the noise amplitude spectra and the atmospheric pressure in short-period variations, and the high-frequency noise is directly related to the external wind velocity, although there is not a direct impact to the sensor site. No correlation of the shape of the spectra (general or for specific frequencies) with any meteorological parameter is observed.

Free radicals from X-irradiated 'dry' and hydrated lyophilized DNA as studied by electron spin resonance spectroscopy: analysis of spectral components between 77K and room temperature

Purpose: To investigate the number, spectroscopic signatures and chemical structures of free radicals from X-irradiated lyophilized DNA (dry and equilibrated at 76% relative humidity) between 77K and room temperature by electron spin resonance (ESR) spectroscopy. Materials and methods: Samples were prepared by freeze drying DNA (sodium salt, salmon testes) in H2O or D2O and used as such ('dry' DNA) or after equilibration at 76% relative humidity. K3{Fe(CN)6} was co-lyophilized in some samples as an electron scavenger. X-irradiation was performed at 77K (liquid nitrogen). Data acquisition was on a Bruker ESP 380 ESR-spectrometer (X-band, 9.5 GHz) and at high magnetic fields (245 GHz, Y-band; GHMFL, Grenoble, France). Data analysis involved computer treatment of spectra. Results: There were 12 different radical components isolated from DNA in four different conditions (dry and after equilibration at 76% relative humidity in either H2O or D2O) with the additional help of high magnetic field ESR and the use of K3 {Fe(CN)6}as an electron scavenger. Several components were detected at 77K and were found to be common for both hydration conditions, although their spectral shape varied considerably. These involved reduced thymine and cytosine bases, the oxidized guanine base, probably a C1-located sugar radical, a thymine allyl radical and a secondary thymine H-addition radical. For the reduced cytosine base the amino-protonated form was observed in H2O samples, which was only partially exchanged in the D2O samples. At high water content another species, perhaps due to a sugar radical, contributes in addition even at low temperatures. All radical components anneal out with temperature, with only small secondary reactions taking place. A peroxy radical and a sharp singlet, probably due to the deprotonated radical cation from guanine, come into the balance together with the secondary thymine radical. At high doses, a further sugar radical (perhaps at the C3-position) was detected in dry DNA. The relative yields of the isolated patterns were determined by precise reconstruction of the experimental spectra. Conclusions: The comprehensive component delineation performed at 77K and upon annealing to room temperature for lyophilized DNA showed a larger diversity and a higher variance of radicals at 77K than discussed so far. Thermal annealing brings about only a few reactions to produce secondary species. Most components decay without paramagnetic successors.

健常タイプA者における長期的有酸素運動の効果に関する研究

The purpose of this study was to clarify the effects of aerobic exercise training on the cardiovascular-autonomic function and self-report evaluation in healthy Type A individuals. Seventy eight participants were first recruited by the local newspaper, and 14 male and 14 female individuals of them were chosen as subjects in this study by the Type A behabior pattern (TABP) questionnaire. Then, the subjects were randomly assigned to the 9-week aerobic exercise training (AE) and waiting-list control (WC) groups. The cardiovascular-autonomic function was assessed during the mental task by the spectral component analysis of electrocardiographic R-R interval variability for both subject groups prior to and following the training period. In addition, weight and ventilatory threshold (VT) as a physical fitness index were also compared between the pre- and post-training. Results revealed that while the AE group improved their VTs and decreased their weights following the training, the WC group didn't. The AE group showed a significantly greater power of high frequency obtained by the spectral component analysis after the 9 weeks compared to that prior to the training period, which indicated enhanced cardiovascular- parasympathetic (CP) function by the training. However, the AE group didn't show the improvement on the subscores of TABP. Some of the measures of perceived change had significantly greater scores for the AE group, relative to the WC group, after the training period. These results suggest that aerobic exercise training contributes to the enhancement of CP function and indirectly to the prevention of cardiovascular disease for Type A individuals, although it may not influence TABP itself.

Power Spectral Components Analysis of Heart Rate Variability during Propofol-O2-N2O Anesthesia

Power Spectral Components Analysis of Heart Rate Variability during Propofol-O2-N2O Anesthesia

Equatorial Atmospheric Waves and Their Association to Convection

Equatorial wave systems and their relationships with convective activity are analyzed in the western and central Pacific regions during the Coupled Ocean‐Atmosphere Response Experiment (COARE) intensive observation periods. The study uses Geostationary Meteorological Satellite infrared temperature observations and the operational European Centre for Medium-Range Weather Forecasts analyses supplemented with COARE observations. Spectral and complex principal component analysis are applied to the data. Using the linear theory of equatorially trapped waves as a guideline, the existence of three types of waves is detected. In the 7‐10-day period range, n 5 1 Rossby waves are found to the east of the date line, in a region of weak convective activity. Over the western equatorial Pacific, where intense convection occurs, the 7‐10-day waves do not possess the general characteristics of linear Rossby waves, but they are strongly linked to the active phases of westerly wind bursts and of convection. Analysis of the meridional wind reveals intense mixed Rossby‐gravity waves with a mean 5-day period and westward phase and eastward group velocities. Over the western Pacific, the convection is found to be strongly correlated with the antisymmetric structure of the divergent field, as predicted by the linear theory. In the 200-hPa divergence field,n 5 1 gravity waves are visible, having periods shorter than 2.5 days. They rapidly propagate (about 25 m s21) both westward and eastward, and have strong correlations with convective clusters.

Spectral analysis of AC and DC components of the pulse photoplethysmograph at rest and during induction of anaesthesia.

We examined spectral components of beat to beat variability in AC and DC signals of the reflectance photoplethysmograph at finger and earlobe sites in 20 resting volunteers and 20 patients during propofol, alfentanil, isoflurane, nitrous oxide anaesthesia. We observed that at rest, the majority of spectral power at both sites and in both signals was in the low 'thermoregulatory' frequency band (0.01-0.08 Hz). These fluctuations were greater in the finger than in the earlobe and in the AC signal compared to the DC. With anaesthesia, low as well as mid (0.08-0.15 Hz) frequency variability decreased at both sites and in both signals whereas high frequency 'ventilatory' power (0.15-0.45 Hz) was maintained. During anaesthesia we found no significant differences between the spectral components of the AC or DC signals or between the finger and the earlobe sites. At all frequencies, the fluctuations in the AC and DC signals were out of phase with each other.

Carotenogenic and abscisic acid biosynthesizing activity in a cell‐free system

Abscisic acid is considered an apocarotenoid formed by cleavage of a C‐40 precursor and subsequent oxidation of xanthoxin and abscisic aldehyde. Confirmation of this reaction sequence is still awaited, and might best be achieved using a cell‐free system capable of both carotenoid and abscisic acid biosynthesis. An abscisic acid biosynthesizing cell‐free system, prepared from flavedo of mature orange fruits, was used to demonstrate conversion of farnesyl pyrophosphate, geranylgeranyl pyrophosphate and all‐trans‐β‐carotene into a range of β,β‐xanthophylls, xanthoxin, xanthoxin acid, 1′,4′‐trans‐abscisic acid diol and abscisic acid. Identification of product carotenoids was achieved by high‐performance liquid chromatography and on‐line spectral analysis of individual components together with co‐chromatography. Putative C‐15 intermediates and product abscisic acid were identified by combined capillary gas chroma‐tography‐mass spectrometry. Kinetic studies revealed that β‐carotene, formed from either famesyl pyrophosphate or geranylgeranyl pyrophosphate, reached a maximum within 30 min of initiation of the reaction. Thereafter, β‐carotene levels declined exponentially. Catabolism of substrate β‐carotene into xanthophylls, putative abscisic acid precursors and product abscisic acid was restricted to the all‐trans‐isomer. However, when a combination of all‐trans‐ and 9‐cis‐β‐carotene in the ratio 1:1 was used as substrate, formation of abscisic acid and related metabolites was enhanced. Biosyn‐thetically prepared [14C]‐all‐trans‐violaxanthin, [14C]‐all‐trans‐neoxanthin and [14C]‐9′‐cis‐neoxanthin were used as substrates to confirm the metabolic interrelationship between carotenoids and abscisic acid. The results are consistent with 9′‐cis‐neoxan‐thin being the immediate carotenoid precursor to ABA, which is oxidatively cleaved to produce xanthoxin. Formation of abscisic aldehyde was not observed. Rather, xanthoxin appeared to be converted to abscisic acid via xanthoxin acid and 1′,4′‐trans‐abscisic acid diol. An alternative pathway for abscisic acid biosynthesis is therefore proposed.

Volterra series analysis of spectral components in quasi-resonant d.c.–d.c. converters

The Volterra series method is used to predict the spectral components of a d.c.–d.c. quasi-resonant converter output wave-form. The Volterra kernels computed for quasi-resonant converters are based on their small-signal non-linear model. Illustrative analytic and simulation results are presented for several quasi-resonant converter topologies and are shown to match very closely. © 1997 by John Wiley & Sons, Ltd.

Retention in Situ and Spectral Analysis of Fluorescent Vacuole Components in Sections of Plant Tissues

The contents of plant vacuoles vary in different organs and with the health of the plant, but little is known of the cell-to-cell distribution of soluble organic compounds within plant tissues. Soluble fluorescent phenolic compounds can be immobilized in plant tissues using an anhydrous freeze-substitution and resin embedment process. The vacuolar fluorescence can be characterized in fluorescence photomicrographs for variations in color and intensity, or more quantitatively with spectra obtained using a microspectrofluorometer. This is demonstrated here in freeze-substituted roots and leaves of soybean. Excitation and emission spectra of individual vacuoles can be compared with spectra of pure compounds to form profiles of the varied phenolic contents of plant vacuoles. Such analyses will add an important anatomical dimension to the study of plant defense and stress responses.

Effects of isoflurane on cardiovascular system and sympathovagal balance in New Zealand white rabbits.

We investigated the effects of isoflurane on the rabbit cardiovascular system at several end-tidal concentrations. Furthermore, because isoflurane has been reported to produce tachycardia while reducing sympathetic nervous activity and baroreflex function, we evaluated whether the chronotropic effects of isoflurane could be due to a vagal withdrawal. ECG, mean arterial pressure (MAP), and heart rate (HR) were obtained in rabbits the conscious, unsedated state and during isoflurane anesthesia by telemetric device. Measurements of pH, oxygen, carbon dioxide, plasma catecholamines, baroreflex sensitivity, and spectral analysis of HR variability were made in nonanesthetized and anesthetized animals. Isoflurane caused an increase in HR at 0.5, 1, and 1.5 minimum alveolar concentration (MAC) and a decrease in systolic and diastolic blood pressure (SBP, DBP) and MAP at 1 and 1.5 MAC. Biochemical analysis showed that isoflurane-mediated cardiovascular effects were not accompanied by any significant changes in plasma norepinephrine (NE) and epinephrine (Epi) levels. Neither were any significant differences in plasma catecholamine levels noted between anesthetized and awake animals. The analysis of spectral components of HR variability and baroreflex function indicated that isoflurane induced a marked reduction in the low- and high-frequency spectral power of HR variability and in baroreflex sensitivity. Tachycardia under isoflurane was suppressed dose dependently by the administration of clonidine or atenolol and was not influenced by bilateral vagotomy. Collectively, our results indicate that cardiovascular effects induced by isoflurane in smaller animals such as rabbits are similar to those observed in humans and other animal species. We showed that isoflurane-induced tachycardia is mainly the result of vagal withdrawal rather than a baroreflex response, even though a marginal role of baroreflex in heart response to higher concentrations of isoflurane cannot be excluded.

PASS, an extended-range Ge spectrometer for radionuclide analysis via L X-, γ-ray spectrometry

PASS (Photon Analysis Spectrometer System) is a pulser-equipped, extended range, thin-window, Ge detector spectrometer that is capable of automatically measuring radionuclide activity concentrations in up to 100 samples per day at remediation sites. No operator intervention is required after the counting queue for the sample changer has been setup. Actinides are measured from L X-rays following α decay such as A Pu → A−4 U and 241Am → 237Np and from low-energy γ-rays by spectral component analysis. Activation, fission products and a few actinides (e.g., 241Am) are measured from their characteristic γ-ray emission by fitting the associated peaks. Pulses from a precision, dual-energy pulser can be used to determine the energy scale, provide documentation of the data quality, and provide a correction for pulse pileup. Soil, smear, and air particulate samples can be counted. For an 11-g sample counted for 15 min the lower-limits-of-detection are 50, 1, and 5 pCi/g for plutonium, americium, and several γ-ray emitting radionuclides, respectively.

Determination of proper frequency bandwidth for 3D topography measurement using spectral analysis. Part I: isotropic surfaces

Areal spectral analysis is applied to achieve proper frequency bandwidth for topography measurements from machined surfaces. The effect of aliasing on the spectrum of surface features due to a large sample spacing is evaluated. The characteristics of low-frequency components of a surface are also investigated. The low-frequency limit of measurement for obtaining the genuine features of a surface can be decided from the spectral analysis of low-frequency components of the surface. The guidelines for topography measurement are proposed for selecting an appropriate sampling bandwidth of surfaces with due consideration of limited computer memory. The guidelines developed are applied to study the general patterns of spectra from a range of isotropic engineering surfaces. An example is given to demonstrate the selection of a temporary sample spacing for a further measurement searching for the low-frequency cut-off of a surface, which may be in turn used to determine the high-frequency limit with an estimate of aliasing influence. In spectral analysis, circular spectra and/or accumulation spectra have been shown to be suitable for the analysis of sample surfaces from isotropic machining processes.

Changes in frequency domain measures of heart rate variability in relation to the onset of ventricular tachycardia in acute myocardial infarction

The imbalance of the autonomic nervous function has been shown to contribute to the genesis of ventricular arrhythmias. Power spectral analysis of components of heart rate variability has the potential to quantify the cardiac autonomic tone during ambulatory electrocardiographic recording. We analysed the power spectral components of total power, very low frequency power (0.0033–0.04 Hz), low frequency (0.04–0.15 Hz) and high frequency (0.15–0.40 Hz) power in 12 consecutive patients accompanied with 27 episodes of ventricular tachycardia in acute myocardial infarction. The spectral areas were measured in 5-min periods preceding the onset of ventricular tachycardias. The total power of heart rate variability increased progressively before the onset of ventricular tachycardia episodes ( P < 0.05). The increase of total power was mainly due to higher, very low frequency power at the onset rather than before the onset of ventricular tachycardia ( P < 0.05). The trend towards adrenergic predominance at the onset of ventricular tachycardia was observed by an increase of average heart rate ( P < 0.05) without concomitant increase in high frequency power. Thus, the occurrence of ventricular tachycardia is associated with changes in the power spectrum of heart rate variability suggesting alterations in autonomic tone at the onset of ventricular tachycardia in acute myocardial infarction.

Relationship between spectral measures of heart rate variability and ventricular ectopic activity in patients with idiopathic ventricular tachycardia.

This study examines the relationship of hourly spectral measures of heart rate variability (HRV) to the occurrence of ventricular ectopic (VE) activity in 20 patients with idiopathic ventricular tachycardia and frequent VE's. Spectral measures of HRV were obtained from 24-hour Holter recordings from the patients in a drug free state and included the total energies in the spectrum, the low frequency components (L) (0.04-0.15 Hz) representing predominantly sympathetic tone with some contribution from the parasympathetic and high frequency components (H) (0.15-0.4 Hz) representing mainly parasympathetic tone. A high H component (parasympathetic) was defined as area > 12 msec and high L components (sympathetic) as area > 30 msec. On an hourly analysis of spectral components in relation to VE activity, VE's occurred significantly more frequently during periods of low H and low L (F = 20.5, DF = 3, P < 0.0001). The number of VE's did not differ statistically in the other combinations of H and L components (low H, low L = 612.8 (50.1); high H, low L = 180.1 (36.8); low H, high L = 338.4 (58.9); high H, high L = 204.9 (17.7) VE's/hr (SEM). The results suggest that VE's are more frequent during periods of low H and low L and are diminished when either H or L are increased in patients with idiopathic ventricular tachycardia. The results would be consistent with the hypothesis that the parasympathetic nervous system has an electrophysiologically stabilizing effect on the myocardium.

Power spectral analysis of heart rate variability in type As during solo and competitive mental arithmetic task

It has been reported that there are differences in autonomic balance between Type As and Type Bs. This study evaluated the sympathovagal interaction in Type A ( N = 10) and Type B ( N = 10) male students during mental arithmetic task in a solo and a competitive condition by the spectral component analysis of heart rate variability (HRV). The low-frequency (LF) component to high-frequency (HF) component ratio was significantly greater in Type As than in Type Bs, though no significant differences were found in task performance, heart rate change, and blood pressure between the two subject groups in both conditions. The present findings indicate that there was a significant difference in sympathovagal balance between Type As and Type Bs, and that Type As showed dominant sympathetic activity. The results suggest that the power spectral analysis of HRV, which is convenient and non-invasive, has enough sensitivity to discriminate differences in autonomic balance between Type A subjects and Type B subjects, not only during the solo and competitive task period but also during the resting period.

Vegetation indices in crop assessments

Vegetation indices (VI), such as greenness (GVI), perpendicular (PVI), transformed soil adjusted (TSAVI), and normalized difference (NDVI), measure the photosynthetic size of plant canopies and portend yields. A set of equations, called spectral components analysis (SCA), that interrelates VI or cumulative seasonal VI (∑ VI), leaf area index (I), fractional photosynthetically active radiation (FPAR, dimensionless), cumulative daily PAR energy absorbed (∑ APAR, MJ/ m 2), above-ground dry photomass (DM, g/m 2), and economic yield (Y, g /m 2) are presented and used to analyze data from two studies conducted in 1989. In one study we made boll counts and percent plant cover measurements in a salt-affected cotton field on 60 m grid intervals and calculated GVI, PVI, TSAVI, and NDVI at the grid intersections for SPOT-1 HRV and videography scenes. The four VI from SPOT accounted for more of the variation in the lint yield estimated from the boll counts (75–76%) than those from videography (61–63%), but VI from the different systems each accounted for 67% of the variation in plant cover. All relations were linear. In the other study, reflectance factors and FPAR were measured periodically during the season in corn planted at three densities (7.7, 5.4, and 3.1 plants/m 2). FPAR could be estimated from NDVI and PVI, respectively, by FPAR = −0.344 + 0.229 exp (1.95 NDVI) ( r 2 = 0.973) and FPAR = 0.015 + 0.036( PVI) ( r 2 = 0.956). Methods of obtaining FPAR and their effect on the efficiency of conversion of APAR to DM are illustrated and discussed. The data demonstrate how SCA unifies and strengthens the scientific basis of VI interpretations.

Signal processing and data analysis in middle atmosphere radar

Use of signal‐processing and data analysis methods in radar studies of middle atmospheric motions is examined. Detection of weak Doppler‐shifted signals from thin atmospheric regions in a noise background requires an optimum receiver. It is noted that the optimum receiver is implemented in successive stages using matched‐filter and correlator structures for locating targets distributed in range and a filter bank for estimating their Doppler shifts. Effectiveness of coherent integration in reducing high data rates, and as an efficient but crude low‐pass filter, is discussed. Use of noiselike binary phase codes and decoding in improving range resolution is outlined. Spectral analysis of radar signals using a time‐averaged periodogram and the autoregressive model is briefly reviewed. Methods of reducing undesirable artifacts in spectral analysis of nonstationary signal components, using windows and trend removal, are delineated. Estimation of signal parameters through spectral moments and least squares estimation is summarized. Finally, simple ad hoc data‐editing methods for suppressing outliers and interference are outlined.