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At least 937 records · Page 52Linked to original sources
PubMed1989

Hallucinogenic and stimulatory amphetamine derivatives: fingerprinting DOM, DOI, DOB, MDMA, and MBDB by spectral analysis of brain field potentials in the freely moving rat (Tele-Stereo-EEG).

Telemetric recordings of field potentials from frontal cortex, hippocampus, striatum and reticular formation of freely moving rats were analysed before and after injection of the enantiomeric hallucinogenic amphetamine derivatives R-DOB [(-)-1-(2,5-dimethoxy-4-bromophenyl)-2-aminopropane], R-DOM [(-)-1-(2,5-dimethoxy-4-methylphenyl)-2-amino-propane] and R-DOI [(-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane] as well as the nonhallucinogenic amphetamine derivatives S-MBDB [(+)-N-methyl-1-(1,3-benzodioxol-5-yl)butanamine] and S-MDMA [(+)-3,4-methylenedioxymethamphetamine] and S-(+)-amphetamine. The frequency analysis of the field potentials revealed a clearcut difference between them. The spectral patterns emerging after injection of the non-hallucinogens were characterized by a general decrease of power, the changes in the alpha2 and delta band being the most prominent, whereas only after the application of the hallucinogenic compounds was a contrasting increase of power observed in the alpha 1 frequency band, especially in the striatum. As increases in alpha 1 power have been correlated in the same pharmacological model to serotonergic control mechanisms, the results are in line with the hypothesis that 5-HT2 receptors, predominantly occurring in the striatum, might be involved in the hallucinogenic action of drugs.

DOM 2,5-Dimethoxy-4-Methylamphetamine↗
PubMed2005

Real-time plaque characterization and visualization with spectral analysis of intravascular ultrasound data.

Coronary artery disease is the number one cause of death in the United States and the Western world, and approximately 250,000 affected people die per year without ever being admitted to a hospital. One of the main reasons of such a high death-rate without any diagnosis is that more than 50 or heart-attacks) occur in patients with no prior history of known heart disease or symptoms. Coronary artery disease leads to the occlusion of arteries that are vital in providing nutrients to the heart muscles. The disease develops by progressive accumulation or formation of "plaque" within an artery. Certain types of plaques could occlude blood flow and yet might be "stable". These plaques usually have a high fibrous content, and are known as hard plaques. On the other hand, "unstable" or "soft" plaques might not cause much occlusion but could be vulnerable to rupture. Rupture of such plaques could lead to total or partial occlusion in arteries resulting in sudden cardiac death or heart-attack. In fact, 68 coronary arteries are less than 50.Intravascular ultrasound (IVUS) is a minimally invasive imaging modality that provides cross-section images of arteries in real-time, allowing visualization of atherosclerotic plaques in vivo. In standard IVUS gray-scale images, calcified regions of plaque and dense fibrous components generally reflect ultrasound energy well and thus appear bright and homogeneous on IVUS images. Conversely, regions of low echo reflectance in IVUS images are usually labeled "soft" or "mixed" plaque. However, this visual interpretation has been demonstrated to be very inconsistent in accurately determining plaque composition and does not allow real-time assessment of quantitative plaque constituents.Spectral analysis of the backscattered radiofrequency (RF) ultrasound signals allows detailed assessment of plaque composition. Advanced mathematical techniques can be employed to extract spectral information from these RF data to determine composition. The spectral content or signature of RF data reflected from tissue depends on density, compressibility, concentration, size, etc. A combination of spectral parameters were used to develop statistical classification schemes for analysis of in vivo IVUS data in real-time. The clinical data acquisition system is ECG gated and the analysis software developed by our group reconstructs IVUS gray-scale images from the acquired RF data. A combination of spectral parameters and active contour models is used for real-time 3D plaque segmentation followed by computation of color-coded tissue maps for each image cross-section and longitudinal views of the entire vessel. The "fly-through" mode allows one to visualize the complete length of the artery internally with the histology components at the lumen surface. In addition, vessel and plaque metrics such as areas and volumes of individual plaque components (collagen, fibro-lipid, calcium, lipid-core) are also available.

Coronary Artery Disease↗
PubMed2000

Application of periodogram and AR spectral analysis to EEG signals.

In this study, in order to analyze the EEG signal, the conventional and modern spectral methods were investigated. Interpretation and performance of these methods were detected for clinical applications. For this purpose EEG data obtained from different persons were processed by PC computer using periodogram and AR model algorithms. Periodogram and AR modeling approaches were compared for their resolution and interpretation performance. It was determined that the AR approach is better for the use in clinical and research areas, because of the clear spectra that are obtained by it.

Algorithms↗
PubMed2006

Existence of conformers revealed by spectral analysis of single molecules of perylene orange in thin sol-gel films.

This paper reports on the spectral dynamics of perylene orange in thin sol-gel films. The studies are performed at the single molecule level to retrieve local information on such samples. The fluorescence spectrum of a molecule depends on the properties of the molecule itself and especially on its conformation in the ground state and in the state reached after excitation. Studies have been performed at room temperature and at a lower temperature, around 173 K. A large number of the recorded spectra reflect dual fluorescence. It is the rule at room temperature. However, at low temperature, single molecules either are relatively free to change conformation or are caught in a rigid environment. In the latter case, they present the spectrum of a rigid dye and we have identified the signature of several conformers of perylene orange in the ground state.

Journal Article↗
PubMed1995

Spectral analysis of body weight, food and water consumption and spontaneous motor activity in male Sprague-Dawley rats.

Spectral analyses by maximum entropy method were performed on the time-series data of body weight, food and water consumption and spontaneous motor activity in Sprague-Dawley rats. These parameters were recorded by a monitoring system collected every 30 min for 10 days. All the parameters had circadian (24 +/- 4 hr) and ultradian (less than 20 hr) rhythms. From the logarithmic transformation of spectral frequencies and their power spectral densities, the characteristics of the spectrum of body weight showed 1/f fluctuation and those of food and water consumption were white noises. The spectrum of the spontaneous motor activity showed complex characters. The range of frequencies lower than 0.1 Hz showed white noise while the range of those higher than 0.1 Hz were 1/f or 1/f2 fluctuations, especially in the range between 0.5 and 1.0 Hz (1-2 hours cycle). The auto-correlation coefficients of body weight did not declined suggesting that 24 hours cycle is only periodic phenomenon in body weight changes. Though the auto-correlation coefficients of food and water consumption also did not declined, they had not enough auto-correlations. This was consistent with the appearance of white noise in spectral analyses. The auto-correlation coefficients of spontaneous motor activity declined remarkably, and this suggests that there are various periodic changes in spontaneous motor activity including one to two hours cycles. These results suggest that the possibility of further extension of research is expected by using rhythmicity. It is also indicated that the time of measurement of body weight must be taken into consideration in experiments because of the presence of the circadian rhythmic changes.

Animals↗
PubMed2001

Reassessment of childhood B-lineage lymphoblastic leukemia karyotypes using spectral analysis.

We studied a stratified cohort of 51 childhood B-lineage acute lymphoblastic leukemias (B-ALLs) to evaluate the efficiency of spectral karyotyping (SKY) in the detection of chromosome aberrations previously diagnosed using chromosome banding and/or reverse transcriptase polymerase chain reaction. Despite the small number of cases analyzed, several important features emerge from the study: (a) The result of banding analysis was revised in two-thirds of the cases. Eighty-three chromosome anomalies previously undetected or not characterized using chromosome banding were identified by spectral karyotyping, even in patients with apparently normal karyotypes. (b) All hyperdiploidy cases showed one or more extra copies of chromosomes X, 14, and 21. (c) Two hidden rearrangements, a t(7;12)(?p12;p13), and a new translocation, a t(9;12)(q31;p13), both involving the TEL gene, were characterized. (d) Some cryptic rearrangements, such as the der(21) t(12;21) translocation, remained undetected. (e) No new recurrent chromosome anomalies were discovered with this technique. In conclusion, the present study confirms the efficiency of the SKY technique in resolving and characterizing many complex chromosome anomalies seen in childhood B-ALLs, but it raises questions about the ability of this technique to detect cryptic rearrangements, such as the t(12;21) translocation.

Burkitt Lymphoma↗
PubMed1982

Spectral analysis of impulse noise for hearing conservation purposes.

Damage-risk criteria for impulse noise does not presently take the spectrum of the impulse into account; however, it is known that the human auditory system is spectrally tuned. The present paper advocates the extension to impulse noise of the noise dose concept which is widely used for continuous noise. This approach is based upon sound exposure instead of sound pressure. An A-weighting filter or an octave band analysis can then be used to take the spectral content of the impulses into account. The equipment needed for applying these procedures for impulse noise is an integrating sound level meter or a digital Fourier processor. Generalized spectral methods have been evaluated by means of an impulse simulation applied to a mathematical model of the human hearing mechanism. The results of this simulation agree with the most recent experiments on impulse noise and fully support the proposed rating methods. This conclusion must be emphasized as it leads the derivation of a uniform procedure for predicting loudness and damage risk for hearing which is applicable for continuous noise as well as for impulse noise.

Environmental Exposure↗
PubMed1992

Spectral analysis of heart rate variability in bronchial asthma.

Sympathetic and parasympathetic activity was evaluated in ten healthy controls, nine asymptomatic, untreated asthmatic subjects and ten asthmatic patients during treatment for acute asthma, by measurement of the variation in resting heart rate using frequency spectrum analysis. Heart rate was recorded by ECG and respiratory rate by impedance plethysmography. Spectral density of the beat-to-beat heart rate was measured within the low frequency band 0.04 to 0.10 Hz (low frequency power) modulated by sympathetic and parasympathetic activity, and within a 0.12 Hz band width at the respiratory frequency mode (respiratory frequency power) modulated by parasympathetic activity. Acute asthmatics had higher heart rates than either of the other two groups; this was probably related to the effects of beta-adrenoceptor agonist medication. Sympathetically mediated heart rate variability (normalized low frequency power) was significantly lower in both asymptomatic (p less than 0.002) and acute (p less than 0.02) asthma subjects compared to controls. This is consistent with altered sympathetic/parasympathetic regulation of heart rate in subjects with bronchial asthma.

Adult↗
PubMed1997

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.

Adult↗
PubMed1994

Spectral analysis of the cardiac cycle of signal-averaged Frank leads from patients with ventricular tachycardia.

Identification of the spectral features in electrocardiograms that distinguish patients prone to ventricular tachycardia (VT) is a prerequisite to increasing the diagnostic power of the signal-averaged electrocardiogram (SAECG). To determine distinguishing features of the magnitude spectrum, the spectra of SAECGs of sinus beats were analyzed over the entire cardiac cycle from 32 patients with VT, 30 without VT, and 10 normal control subjects. The magnitude spectra of the Frank SAECGs separated patients with VT from those without VT over the band from 7 to 140 Hz with a P value of .000000047. To determine distinguishing features of phase and group-delay spectra, SAECGs of sinus beats over the entire cardiac cycle were analyzed from 57 patients with VT, 65 without VT, and 20 normal control subjects. Unwrapped phase spectra from SAECGs of the entire cardiac cycle were calculated with respect to the onset of the Q wave. Phase spectra of SAECGs from patients with VT differed from those from non-VT patients at frequencies of 60 Hz or greater (P = .00085). Average group delays in SAECGs from patients with and without VT differed (P = .00000069) from 14 to 24 Hz. Group delays in the VT patients in the 14-24-Hz band were on average 9 ms and 5 ms longer than those of the non-VTs and normal subjects, respectively. Time-domain reconstructions demonstrated that distinguishing frequency bands were detectable throughout the QRS complex, ST-segment, and T wave in SAECGs from each group. Thus, the spectra of SAECGs over the cardiac cycle contain features that together with temporal features from throughout the cardiac cycle are essential in improving methods for stratifying risk of VT.

Electrocardiography↗
PubMed1999

Broad-band spectral analysis of 24 h continuous finger blood pressure: comparison with intra-arterial recordings.

The present study compares the spectral characteristics of 24-h blood pressure variability estimated invasively at the brachial artery level with those estimated by measurement of blood pressure at the finger artery using the non-invasive Portapres device. Broad-band spectra (from 3x10(-5) to 0.5 Hz) were derived from both finger and intra-brachial pressures recorded simultaneously for 24 h in eight normotensive and twelve hypertensive ambulant subjects. At frequencies lower than 0.07 Hz, higher spectral estimates were obtained by Portapres than by intra-brachial measurements. The maximum overestimation occurred in systolic pressure at around 10(-2) Hz, where the amplitude of the oscillations was two times greater when measured by Portapres. A less pronounced overestimation was found for diastolic pressures. The maximum overestimation was greater during daytime than during night-time. At around 0.1 Hz, invasive and non-invasive spectra were similar. At the respiratory frequencies (0.15-0.50 Hz), the power spectra were overestimated by Portapres during daytime, and underestimated at night. These results provide reference information for the correct interpretation of Portapres data in the estimation of 24-h blood pressure spectral power.

Adult↗
PubMed2000

High resolution spectral analysis of 13CH3OH in the excited torsional states.

In this work, we have extended our previous analysis of the Hamiltonian of 13C substituted methanol to include a large number of spectral lines involving the second excited torsional state using an improved model. The data set consisted of 2529 Fourier transform and microwave transitions with the rotational angular momentum J < or = 10, K < or = 6 and n < or = 2 (with 336 MW lines). The data set was fitted with the new Hamiltonian model to derive the molecular parameters. The results indicate that the model developed for the other methanol species (CH3OH, CH3(18)OH and CH3OD) is also valid for the C-13 substituted species. The results will allow the energy levels of the molecule to be calculated for higher torsional levels above the internal rotational barrier with improved precision and allow the analysis to be carried out for more excited torsional states.

Carbon Isotopes↗
PubMed1993

High-frequency ultrasound imaging and spectral analysis in traumatic hyphema.

PURPOSE: High-frequency (50-MHz) ultrasound allows high-resolution imaging of anterior ocular structures. Spectrum analysis of acoustic backscatter is sensitive to the concentration, size, and density of tissue inhomogeneities. The authors sought to determine whether acoustic imaging and spectrum analysis of hyphema would allow them to distinguish organized from fluid hyphema and recent from old hemorrhage in the eye. METHODS: Trauma-induced hyphemas were followed by slit-lamp photography and high-frequency ultrasonography in six New Zealand white rabbits. The blood collections were analyzed using the normalized power spectra of the digitized radio frequency ultrasound data and compared with in vitro references. RESULTS: The 50-MHz acoustic images permitted differentiation between fluid (diffuse) and clotted (organized) blood. Spectrum analysis allowed quantitative characterization of the degree of blood organization. Significant changes were observed in spectral properties during the time course of absorption both for initial and after-rebleeding hemorrhages. The characteristics of a human postsurgical hyphema also were examined and found to be similar to those seen in the experimental model. CONCLUSION: Spectrum analysis of high-frequency ultrasound data was able to distinguish organized from recent hemorrhage, which is clinically helpful for planning hyphema therapy.

Animals↗
PubMed2005

Spectral analysis of heart rate variability: interchangeability between autoregressive analysis and fast Fourier transform.

Interchangeability between fast Fourier transform (FFT) and autoregressive (AR) analysis was assessed on series of 256 R-R intervals recorded in 56 seated subjects and in 15 men performing an orthostatic test. Low- (LF) and high-frequency (HF) components were calculated and expressed both in absolute (square milliseconds) and normalized units (NU). During orthostatic stress, the same upward trend for LF square milliseconds and LF/HF ratio and downward trend for HF square milliseconds and HF NU were observed with FFT and AR analysis. However, the values for HF square milliseconds were significantly greater with FFT, as compared with AR analysis in standing position (P < .05). Moreover, Bland & Altman method highlighted a large discrepancy between the results of FFT and AR analysis for all heart rate variability indices in the 3 conditions. Therefore, parametric and nonparametric spectral analyses could not be considered as interchangeable at rest in healthy subjects even if they give same qualitative results.

Adolescent↗
PubMed1995

Age, race, and sex differences in autonomic cardiac function measured by spectral analysis of heart rate variability--the ARIC study. Atherosclerosis Risk in Communities.

To investigate the distribution of heart rate variability (HRV) spectral power in an unselected sample of the population, and to ascertain the population correlates of HRV, we examined 1,984 healthy persons, aged 45 to 64 years, randomly selected from the Atherosclerosis Risk in Communities (ARIC) study cohort. Resting, supine, 2-minute, beat-to-beat heart rate data were collected between 7 A.M. and 12 noon. The race- and sex-adjusted geometric means of low-frequency component (LF, 0.025 to 0.15 Hz) were 4.00 and 3.13 (beats/min)2; of high-frequency component (HF, 0.16 to 0.35 Hz), 1.65 and 1.21 (beats/min)2; and of the HF/LF ratio, 0.41 and 0.39, for 45-to-54 and 55-to-64 years age groups, respectively (test of mean difference by age, p < 0.01, p < 0.01, and p = 0.11 for LF, HF, and HF/LF ratio, respectively). Comparing black with white examinees, the age- and sex-adjusted geometric means of LF were 3.06 and 3.70 (beats/min)2; of HF, 1.66 and 1.36 (beats/min)2; of HF/LF, 0.54 and 0.37, respectively (test of mean difference by race, p < 0.01, p < 0.01, and p < 0.01). The age- and race-adjusted geometric means of LF for women and men were 3.12 and 4.10 (beats/min)2; of HF, 1.46 and 1.38 (beats/min)2; and of HF/LF, 0.47 and 0.34, respectively (test of mean difference, p < 0.01, p = 0.34, and p < 0.01). We conclude that HRV spectral indexes are associated with age, race, and sex. With increasing age, the parasympathetic and sympathetic spectral power components decrease.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1996

Heart rate power spectral analysis in patients before and 6 weeks after coronary artery bypass grafting.

Decreased cardiac vagal activity is a known risk factor in coronary artery disease. The aim of our study was to determine the effect of coronary artery bypass grafting (CABG) on heart rate variability (HRV) before and 6 weeks after CABG. The study group consisted of 34 patients (4 women, 30 men, mean age 56 +/- 9 years). ECGs were recorded in 10 minutes periods in both supine and standing position with controlled breathing rate (0.25Hz). The analysis of HRV power spectrum was done by means of fast Fourier transformation. The total spectral power (TPS), power in very low frequency band (VLF: < 0.05 Hz), low frequency band (LF:0.05-0.15Hz), high frequency band (HF:0.15-0.5Hz), LF/HF ratio and percentage fraction of total power in these frequency bands (%VLF, %LF, %HF) were analysed. Significant attenuation of all spectral components of HRV were found during orthostatic load before CABG (p < 0.05). TPS, VLF, LF, %HF decreased in standing position to about half of their level in supine position, HF decreased to as little as one fourth, while LF/HF ratio and %LF increased significantly (p < 0.05). After the CABG these changes were not significant. We have found significant increase of HF (p < 0.05) and %HF (p < 0.01) in standing position after the CABG. The results suggest that CABG causes an improvement in cardiac vagal activity especially in standing position.

Coronary Artery Bypass↗
PubMed1992

NMR spectral analysis of cytotoxic ether lipids.

Several cytotoxic ether lipid analogs of platelet activating factor exhibit a wide range of interesting pharmacological properties. Furthermore, at least two members of this family of lipids have progressed to phase I clinical trials as potential cancer chemotherapeutic agents. In spite of the promise that these compounds hold as anticancer drugs, they remain poorly characterized. We report herein the first complete 1H NMR analysis of several palmityl-based ether lipids. In addition, we report the 13C NMR spectral assignments for these lipids, which are based, in part, on both the presence and magnitude of 31P-13C and 14N-13C coupling constants.

Antineoplastic Agents↗