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At least 631 records · Page 35Linked to original sources
PubMed1991

Contour mapping of the cutaneous microvasculature by computerized laser Doppler velocimetry.

A probe holder for laser Doppler velocimetry was designed to allow a narrow (1.24-mm) probe to be moved in increments of 1.04 mm, approximately the width of the probe window itself, so that four contiguous 1-mm2 spots in a 2.29 x 2.29 mm area could be sampled. An area as large as 2.48 x 2.48 cm can be measured with this device. The flux was fed into a computer by an analog/digital board, for visualization as a wave-form on the monitor, and for analysis by fast Fourier transforms and power spectrum analysis. Each spot sampled was given a unique x,y coordinate and the mean amplitude of the flux was designated as the z coordinate. With the aid of software, the values of these three coordinates were mathematically processed to produce contour graphs with shading that represented a map of the arteriolar circulation in the skin. This methodology allows for accurate movement and placement of the probe on the skin and the ability to relocate a spot within 1 mm of its original location after intervals of hours to days. Video images of the superficial plexus at the sites where the maps were made confirm the topographic appearance of these maps. Data generated by these maps raise the intriguing possibility that microcirculatory vessels may be engaged in a division of labor--some involved primarily with tissue perfusion, others with thermoregulation.

Computers↗
PubMed1985

[Gamma ray spectrum smoothing by one-pass method].

One-pass method with a piecewise cubic polynomial was used as a smoothing technique in gamma ray spectrum analysis. By this method, smoothed results of spectrum region is represented to several divided intervals each of which are fitted with a cubic polynomial calculated by least square technique, respectively. From the smoothing procedure of simulated photoelectric peaks and actual gamma ray spectra, following results were obtained. Photoelectric peaks which had more than 10 channels of FWHM (full width at half maximum) were fitted correctly and low count spectra of about 100 counts per channel could also be fitted smoothly. These smooth results can not easily be obtained by Savitzky's convolution technique. In conclusion, this one-pass method was found to be effective for gamma ray spectra, especially for photoelectric peaks of large FWHM and Compton region.

Spectrometry, Gamma↗
PubMed1999

Cyclophotocoagulation: experimental investigations of dosage problems.

BACKGROUND: During cyclophotocoagulation, transsclerally applied laser light reduces the aqueous-producing structures of the eye. One problem using this therapy is patient-specific dosage of the applied laser energy. The aim of our investigations was to obtain information about intensity and distribution of tissue destruction in the coagulation area. This may provide a basis for further on-line control of cyclophotocoagulation by ultrasound-controlled engineering of the diode laser. METHODS: To visualize the process of cyclophotocoagulation, a multifunctional measurement set-up was developed. It allowed the visualization of structural changes in the coagulation area using a common light microscope and comparison in the first set-up to the results detected by high-resolution ultrasound, applied in different working modes (B-mode, M-mode and RF signal analyses). In a second set-up an infrared thermography system showing temperature distribution on the scleral surface at the contact point of the laser probe was used. RESULTS: High resolution working in B- and M-mode was unsuitable to visualize structural changes within the therapeutic width. By analyzing RF ultrasound date, structural changes within the therapeutic width could be detected. Surface temperatures measured by infrared thermography correlated with visible structural changes when long exposure times and low laser power were applied. CONCLUSIONS: In certain cases the visualization of coagulation effects was possible with the help of either high-resolution ultrasound or infrared thermography. Spectrum analysis of RF ultrasound signals seems to be a potential method for successful control of cyclophotocoagulation.

Animals↗
PubMed1978

Quantification of EEG variability.

This paper presents a method of segmenting the EEG based on the well-known power spectrum analysis. This procedure is applied to the EEG recordings of two normal subjects in order to determine the temporal EEG variability. These results are compared with a more classical approach.

Adult↗
PubMed1978

Demonstration of segmentation techniques for EEG records.

In this paper three different techniques for segmenting EEG's are presented. The principles of these techniques (the Kalman filter approach, the power spectrum analysis and the texture matrix approach) are explained and the results obtained summarised. The segmentation is used in an interactive EEG interpretation system.

Adult↗
PubMedDate not supplied

Chemiluminescence in hypoxic brain--the second report: cerebral protective effect of mannitol, vitamin E and glucocorticoid.

The effect of vitamin E, betamethasone and mannitol upon a series of pathological free radical reactions within hypoxic brain tissue was evaluated by the chemiluminescence method. Hypoxia was induced by arterial hypoxemia (PaO2 17-22 mmHg) with normocapnia (PaCO2 28-38 mmHg) and normotension (MABP 100-140 mmHg). 4% O2-96% N2 mixed gas was used to obtain the lowered PaO2. In the untreated group, increased chemiluminescence was measured in the hypoxic state and the early stage of the initial post-hypoxic state. In the groups administered vitamin E, betamethasone, mannitol and a combination of them reduced chemiluminescence was detected. To explore the reaction stage at which the drugs act in lipid peroxidation, chemiluminescence spectra was analyzed using the brain homogenate with the drugs added. Intensity peaks of the spectra were around at 480, 520-530, 570, 620-640, 680-700 nm before addition of the drugs. All the intensity peaks diminished after addition of vitamin E and betamethasone, but very little decrease occurred after mannitol. The lowered chemiluminescence value may indicate the free radical scavenging action of vitamin E, betamethasone and mannitol in vivo. Chemiluminescence spectrum analysis shows that vitamin E and betamethasone act on the late chain reaction following hydroperoxide and mannitol acts on the early reaction--generation of active oxygens.

Animals↗
PubMed2004

Extraction of extracellular polymeric substances from the photosynthetic bacterium Rhodopseudomonas acidophila.

Among the four methods for extracting extracellular polymeric substances (EPS) from Rhodopseudomonas acidophila (EDTA, NaOH, H(2)SO(4), heating/centrifugation), EDTA extraction was found to be the most effective. The contents of the major components of EPS from R. acidophila, i.e., carbohydrate, protein and nucleic acid, were 6.5, 58.4 and 5.4 mg g(-1) dry cells, respectively. The optimum extraction time was 1-3 h and the EDTA dosage was approximately 2.8 g g(-1) dry cells. Under these conditions, no cell lysis was observed. The EPS content and the percentage of the three main components were greatly dependent on the extraction method. The intensity of absorption peaks for photosynthetic pigments in the UV-visible spectrum of bacteria remained unchanged prior to and after EDTA extraction; and no pigment peaks appeared in the EPS spectrum. This suggests that few cells were destroyed and lysis did not occur. UV-visible spectrum analysis, an easy and rapid technique, could be used to monitor cell lysis during EPS extraction from R. acidophila.

Bacterial Proteins↗
PubMed1996

Quantitative EEG analysis as a supplement to the clinical coma scale RLS85.

BACKGROUND: The aim of the study was to investigate the correlation between EEG indicators and clinical scores based on the RLS85 (Reaction Level Scale 85) in comatose patients. The results of a simple visual assessment of the EEG, using an arbitrary scale with typical EEG patterns, were compared with those obtained by quantitative electroencephalography (qEEG). METHOD: The RLS85 scores were examined in 34 patients with impaired consciousness due to brain tumours, vascular lesions or head injuries. The EEG was recorded shortly before or after the clinical examination. The semiquantitative assessment was made by visual inspection of the tracings, using an arbitrary scale where 12 EEG patterns with increasing proportion of slow activity were displayed. Parallel to the visual analysis, the EEGs were processed by means of EEG spectrum analysis and the power/amplitude in slow frequency bands was used as an indicator. The results were based on correlation between various types of EEG variables and the RLS scores which were obtained in the same patients. RESULTS: The correlation between the visual EEG indicators and coma scores ranged between 0.53 and 0.57 (P < 0.01). As regards the computerised EEG analysis, the correlation between the clinical scores and various EEG spectrum values did not exceed 0.45 (P < 0.01). A higher correlation could be obtained by combining eight EEG variables; the multiple correlation coefficient was then 0.68. CONCLUSIONS: The amount of EEG slow activity is significantly correlated to the RLS85 score. This means that the EEG also provides information on the level and not only on the changes of the coma degree. Surprisingly, the indicators based on quantitative EEG, as used in commercially available instruments, did not give better results than the visual assessment. However, the results of the computerised analysis could be improved using multivariate statistical methods. The study also showed a way to improve communication between the neurophysiologist and clinician by presenting the EEG findings in terms similar to those used in the clinical scales. However, the clinician should be aware of the fact that the "EEG score" and the clinical score is not the same: the intention is to supplement rather than to simulate the clinical observation.

Adolescent↗
PubMed1987

Noninvasive differentiation of carotid artery occlusion from high-grade stenosis.

The differentiation of high-grade carotid artery stenosis from occlusion can be a difficult but important diagnostic dilemma. The authors used a combination of duplex scanning, pulsed spectrum analysis, audible analysis of continuous wave doppler signal, and peri-orbital doppler compressions to accurately differentiate high-grade stenosis from occlusion in a series of 24 patients.

Arterial Occlusive Diseases↗
PubMed1985

[Trace element content in the blood and tissues of patients with precancerous and precursor diseases of the female genitalia].

Emission spectrum analysis was used for measuring the levels of such trace elements as copper, manganese, zinc, nickel and silver in blood serum and tissues of the diseased organs in female patients with certain precancerous and precursor lesions of genital tract. It was found that such changes as an increase in serum copper, a decrease in zinc concentration in blood cells and a rise in the levels of zinc and silver in the affected tissues were more pronounced in cases of precancerous lesions than in those of precursor pathology.

Cervix Uteri↗
PubMed2004

Determination of Cu environments in the cyanobacterium Anabaena flos-aquae by X-ray absorption spectroscopy.

Whole cells and peptidoglycan isolated from cell walls of the cyanobacterium Anabaena flos-aquae were lyophilized and used at pH 2 and pH 5 in Cu(II) binding studies. X-ray absorption spectra measured at the Cu K-edge were used to determine the oxidation states and chemical environments of Cu species in the whole-cell and peptidoglycan samples. In the whole-cell samples, most of the Cu retained at both pH values was coordinated by phosphate ligands. The whole-cell fractions contained significant concentrations of Cu(I) as well as Cu(II). An X-ray absorption near-edge spectrum analysis suggested that Cu(I) was coordinated by amine and thiol ligands. An analysis of the peptidoglycan fractions found that more Cu was adsorbed by the peptidoglycan fraction prepared at pH 5, due to increased chelation by amine and carboxyl ligands. The peptidoglycan fractions, also referred to as the cell wall fractions, contained little or no Cu(I). The Cu loading level was 30 times higher in the cell wall sample prepared at pH 5 than in the sample prepared at pH 2. Amine and bidentate carboxyl ligands had similar relative levels of importance in cell wall peptidoglycan samples prepared at both pH values, but phosphate coordination was insignificant.

Anabaena↗
PubMed2002

A computer-aided detection of EEG seizures in infants: a singular-spectrum approach and performance comparison.

This paper presents a scalp electroencephalogram (EEG) seizure detection scheme based on singular spectrum analysis (SSA) and Rissanen minimum description length (MDL) model-order selection (SSA-MDL). Preprocessing of the signals allows for the drastic reduction of the number of false alarms. Statistical performance comparison with seizure detection schemes of Gotman et al. and Liu et al. is performed on both synthetic data and real EEG seizures. Monte Carlo simulations based on synthetic infant EEG seizure data reveals some detection drawbacks on a large variety of seizure waveforms. Detection using both Monte Carlo and four real infant scalp EEG signals shows the superiority of the SSA-MDL method with an average good detection rate of >93% and false detection rate <4%.

Computer Simulation↗
PubMed2000

[Application of spectral analysis on atmosphere corrosion research].

This paper applied two methods of spectrum analysis to measure the rusty layer of samples atmosphere corrosion from Qingdao and Chengdu. The main component elements and rust phase of rusty layer are obtained. It showed that the relative content of the elements and rust phase varies with the change of corroded environment and time. The result, relative content of each rust phase of A3(1) rusty layer sample have following relation: gamma-Fe00H > alpha-Fe00H > delta-Fe00H, and, relative content of other rusty layer samples have relation: gamma-Fe00H > delta-Fe00H > alpha-Fe00H, in the rusty layer of low-alloy steel, there are the alloy elements of rest body.

English Abstract↗
PubMed2000

Semi-interpenetrating polymer networks composed of biocompatible phospholipid polymer and segmented polyurethane.

2-Methacryloyloxyethyl phosphorylcholine (MPC) polymers, which have excellent biocompatibility, have been receiving increasing attention in biomedical and bioengineering fields; however, the mechanical strength of the hydrated MPC polymers is not sufficient for use in these fields as a bulk material. Therefore, we hypothesized that a novel material might be realized by reinforcing the MPC polymer network with segmented polyurethane (SPU). Semi-interpenetrating polymer networks (IPNs) composed of crosslinked MPC polymer and SPU were prepared. The mechanical properties of the IPN membrane were significantly improved compared with those of the MPC polymer membrane. Three-dimensional polymer networks of the MPC polymer in the IPNs were observed after solvent extraction of SPU. An X-ray photoelectron spectrum analysis revealed that the MPC units were exposed on the IPN surface. When the IPN was alternately soaked in water and ethanol, the swelling ratio was found to be completely reversible and no disintegration of the network structure was observed. The permeation coefficient of 1, 4-di(2-hydroxyethoxy)benzene through the IPN membrane was 1.11 x 10(-7) cm(-2)s(-1). The amount of adsorbed protein and the number of adherent platelets on the IPN membrane were effectively reduced compared with those on SPU. We concluded that IPNs composed of the MPC polymer and SPU are a new bulk biomaterial, which possesses both blood compatibility and good mechanical properties.

Absorption↗
PubMed2006

Magnetic fields of induction heaters in the framework of directive 2004/40/EC of the European Parliament and of the Council.

The spectrum and the polarization of the magnetic flux density (B-field) of 6 induction heaters and 1 arc oven were measured by means of a PMM (Italy) spectrum analyser. The spectrum analysis showed that no substantial harmonics were observed while the polarization analysis revealed that the operator's exposure was non-homogeneous within a distance of 1.5 m from the heater. When the distance was larger, the body was homogeneously exposed. In general we can state that the B-field strongly varied between heaters and that exposure exceeded the occupational reference levels recommended by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) (1998) and European Directive 2004/40/EC in 5 of the 7 heaters. Within the framework of the Directive some protection actions should be taken. Whereas mitigation of existing/old induction ovens is difficult, the design of new induction heaters and their housing should be based, among others, on electromagnetic reducing engineering concepts.

Electromagnetic Fields↗
PubMed2004

Copper selectively triggers beta-sheet assembly of an N-terminally truncated amyloid beta-peptide beginning with Glu3.

Metal ions have been suggested to induce aggregation of amyloid beta-peptide (Abeta), which is a key event in Alzheimer's disease. However, direct evidence that specific metal-peptide interactions are responsible for the amyloid formation has not previously been provided. Here we present the first example of the metal-induced amyloid formation by an Abeta fragment, which exhibits a clear-cut dependence on the amino acid sequence. A heptapeptide, EFRHDSG, corresponding to the amino acid residues 3-9 of Abeta (Abeta(3-9)) undergoes a conformational transition from irregular to beta-sheet and self-associates into insoluble aggregates upon Cu(II) binding. A Raman spectrum analysis of the Cu(II)-Abeta(3-9) complex and aggregation assays of mutated Abeta(3-9) peptides demonstrated that a concerted Cu(II) coordination of the imidazole side chain of His6, the carboxyl groups of Glu3 and Asp7, and the amino group at the N-terminus is essential for the amyloid formation. Although Abeta(1-9) and Abeta(2-9) also contain the metal binding sites, neither of these peptides forms amyloid depositions in the presence of Cu(II). The results of this study may not only provide new insight into the mechanism of amyloid formation, but also be important as a step toward the construction of proteinaceous materials with a specific function under the control of Cu(II).

Amino Acid Sequence↗
PubMed1978

Photic EEG-driving responses in thalamotomized and medicated cases of Parkinson's disease.

EEG-driving responses to visual stimulation were studied using EEG Interval Spectrum Analysis (EISA) before and after stereotaxic thalamotomy and Nacom (L--Carbidopa and Levodopa) treatment of 67 Parkinson patients. Five types of photic-driving responses were distinguished in the EISA results: (1) all-band response, (2) Beta-dominant, (3) Alpha-Beta-dominant, (4) Alpha-Theta-dominant, (5) non-response. Twenty patients received a daily dose of 750--1000 mg of Nacom orally, and 47 patients 1000--1500 mg for a period of 3 to 4 weeks. In most cases the medication produced no change in photic-driving and EEG patterns. The photic-driving response showed no significant correlation with clinical signs and background EEG. Unilateral thalamotomy was performed in ten Parkinson patients. In two of these patients the EEG-driving response diminished in the first post-operative week for low frequency stimuli but increased after the second week.

Adult↗
PubMed1991

Omega-oxidized leukotriene B4 detected in the broncho-alveolar lavage fluid of patients with non-cardiogenic pulmonary edema, but not in those with cardiogenic edema.

Leukotriene (LT) generation has been implicated in the pathogenesis of the acute respiratory distress syndrome, ARDS. In the present study, we analysed broncho-alveolar lavage fluids of patients on mechanical ventilation because of ARDS (17 samples taken from 9 patients) or because of cardiogenic edema (8 samples taken from 6 patients) and of healthy volunteers (10 samples from different donors). LTs were separated as methylated and non-methylated compounds using different HPLC procedures, and were identified by chromatographic mobility, on-line UV-spectrum analysis and post HPLC immunoreactivity. In the lavage samples of the healthy volunteers and the patients with cardiogenic edema, no LTs were detected by these techniques (detection limit congruent to 0.1-0.2 ng/ml lavage fluid). By contrast, in 15 out of 17 samples from patients with ARDS LTB4 or its metabolites 20-OH-LTB4 and 20-COOH-LTB4 were detected. The endproduct of omega-oxidation, 20-COOH-LTB4, represented the quantitatively predominant compound, detected in the range of 0.3-2.6 ng/ml perfusate. We conclude that the chemotactic agent LTB4 may be involved in the amplification of inflammatory events encountered in ARDS, and that the oxidized metabolites of LTB4 are particularly suitable for monitoring lung leukotriene generation under conditions of neutrophil efflux and oxidative stress.

Adult↗