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At least 1,657 records · Page 92Linked to original sources
PubMed2005

[Preparation and infrared spectral analysis of nanoporous silica thin film].

Crack-free homogeneous nanoporous silica films on silicon wafer have been synthesized via supercritical drying of wet gel films obtained by spin-coating the polymeric silica sol, which was prepared using sol-gel method with tetraethoxysilane (TEOS) as precursor. The film is amorphous and nanoporous, and three-dimensional network, cross-linked by the primary particles whose sizes distribute between 10-20 nm showed respectively by XRD and SEM micrograph. The structure of the nanoporous SiO2 thin film was studied by FTIR spectra. The SiO2 thin film was composed of Si-O-Si and Si-OR, and was hydrophobic. The film contained Si-OH and became hydrophilic after being heat-treated at 250 degrees C or above in air. The heat-treated SiO2 thin film becomes hydrophobic by reacting with trimethylchlorosilane(TMCS). The TMCS-modified SiO2 thin film remains hydrophobic and can keep its nanoporous structure at a temperature lower than 450 degrees C in nitrogen.

Hot Temperature↗
PubMed2006

[Spectral analysis and photoluminescence properties of 1,5-naphthalene diamine derivative].

In the present paper, 1,5-bis[N-(1-naphthyl)-N-phenyl] naphthalene diamine (NPN) with high purity was synthesized by liquid-phase Ullmann reaction, and high quality film of NPN was formed on cleaned glass substrates by vacuum evaporation. Photoluminescence properties were studied by solvent effects on UV-Vis absorption spectra and fluorescence spectra. In addition the structure of energy band of NPN was studied by cyclic voltammetry, UV-Vis absorption spectra, and fluorescence spectra. The results indicate that the fluorescence emitting is attributed to the charge transfer transition from nitrogen to aromatic ring. The molecules of NPN in its film form "J-aggregate". The HOMO energy and optical gap of NPN are -5.74 and 2.79 eV respectively. NPN film could emit intense blue fluorescence with a peak wavelength at 448.6 nm and a bandwidth of 72.6 nm under UV-Vis excitation at 365 nm.

English Abstract↗
PubMed2006

[Spectral analysis and study of the microsome cytochrome P450 aromatase of Thais clavigera].

The microsomes were prepared from the viscera masses of Thais clavigeras. It is well known that there are some main components in microsome cytochrome P450 aroamtase, including cytochrome P450, cytochrome b5 and NADPH-cytochrome P450 reductase. So the contents of cytochrome P450 and cytochrome b5, and the activity of NADPH-cytochrome P450 reductase were determined by Shimadzu UV Visible spectrophotometer. And the microsomal proteins were analysed by SDS-PAGE. All the results indicated that there exists P450 arom in the T. clavigeras.

Animals↗
PubMed2006

[Spectral analysis of transient species of quinoline degradation].

Quinoline's degradation was studied by pulse radiolysis. It was found that hydrated electron, hydrogen radical, hydroxyl radical and SO4*- can react with quinoline. The absorption spectra of the transient species of quinoline were obtained, and related constants were determined, but it was found that the species of Br2*- and N3*- can't react with quinoline. The results give us some advices for studing the degradation of quinoline.

Electrons↗
PubMed1991

Spectral analysis of the renal sympathetic neurogram during left ventricular assistance.

To assess the effect of left ventricular assistance on cardiac-related sympathetic nerve activity, renal sympathetic nerve activity was analysed using power spectrum and coherence function. Our TH-7B pneumatically driven sac type Ventricular Assist Device (VAD) was used in the acute experiment of 7 adult mongrel dogs. VAD were inserted between the left atrium and the descending aorta as left heart bypass. RSNA was detected by use of the bipolar electrodes attached to the left renal sympathetic nerve. Values of squared coherence between the arterial pulse wave and RSNA were measured at the cardiac rhythm and VAD pumping rhythm. Before the left ventricular assistance, coherence at the cardiac rhythm and the pumping rhythm were 0.62 +/- 0.15, 0.23 +/- 0.18 (mean +/- SD), respectively. With the VAD pumping, these values became 0.09 +/- 0.05, 0.53 +/- 0.20, respectively. These results indicate that arterial pressure wave which was created by the VAD assistance contributed to the post ganglionic sympathetic activity.

Animals↗
PubMed1991

[Correlation between the results of Doppler velocimetry with spectral analysis and the viscosity of cord blood].

The contribution of rheological factors to be impedance of blood flow in the umbilical artery as determined by continuous wave Doppler ultrasound was investigated. Of the 51 pregnancies recruited, six were complicated by pre-eclampsia, 10 by intrauterine growth retardation, 15 by both pre-eclampsia and fetal growth retardation, and there were 20 controls. A significant correlation was demonstrated between both plasma viscosity and gestational age and the resistance index used to characterize the Doppler waveform. Multiple regression analysis demonstrated that changes in plasma viscosity explained 55 p. cent of the variance seen in the resistance index and that this was statistically significant. This finding is, however, unlikely to be of clinical significance as whole blood viscosity had an insignificant effect on the impedance in the umbilical artery. We postulate that vascular factors such as the number and calibre of the placenta arterioles are a more important determinant of umbilical artery impedance.

Blood Flow Velocity↗
PubMedDate not supplied

The weight of the cortical inflow against medullary reflexes as enlightened by spectral analysis of HR and SP waves.

Components of the autonomic drive to the heart were studied in 5 young normals subjected to: 1. sustained lung inflation (SLI) in various postures; 2. mental loading by concentration of attention; 3. face immersion (FI) in cold water under SLI or snorkel breathing, when sitting; 4. superpositions of 1-3 experimental interventions. Recorded were: cardiotachogram (CTG as RR interval) and T-wave amplitude from ECG, ear-lobe photo-plethysmogram, digital impedance rheogram, thermistor pneumogram (PNG). Heart rate (HR) and systolic pressure (SP) data were treated using the Fourier analysis on a M118B microcomputer. Preliminary data-exploration, reported in a previous paper, has verified the capability of the Fourier spectrum to spot in short quasistationary data-series known marks of single interventions and has pointed to the amphotrop nature of SLI and FI maneuvers. Present work approaches the same data from the point of view of the competition between various regulatory menus under combined interventions. The "cortico-cardiac reflex"--HR stabilizing under mental loading versus rest based upon balanced reduction in both respiratory and vasomotor sinus arrhythmia (RSA and VSA, respectively)--appeared now as a middle size actor upon medullary areas; it is overridden, yet not put to silence by the powerful orthostatic reflex; it is comparable (SLI) or major (FI) vis-a-vis of synergic vagal reflexes whose more easily approachable mechanisms could offer it meaningful models. Capacitating this "reflex" in the containment of intricated arrhythmias with extrinsic involvement or in "educating" the benefic vagal prevalence upon the heart should observe these precisions.

Adult↗
PubMedDate not supplied

Monitoring sedation levels by EEG spectral analysis.

Real-time electroencephalographic power spectra were obtained for a group of 37 volunteers undergoing sedation with enflurane at different concentrations in air. In part one, 17 subjects were given 0.5%, 0.75%, and 1.0% for 4 min at each level, and recovery after 5 min was assessed by the Trieger method. There was considerable variation in subject response to the different doses, but adequate sedation was indicated by the presence of a strong alpha rhythm (9-11 Hz) and suppression of frequencies below 5 Hz. Overdose was indicated by an initial shift in the alpha frequency to a lower value (6-7 Hz) followed by the appearance of delta waves (0.5-4 Hz) and loss of alpha waves. In part two, 20 volunteers inhaled enflurane at 0.5% for 10 min to allow adequate absorption, followed by a 10-min recovery period. Equal numbers showed sedation or a failure to respond to enflurane at this concentration. In the responders, sedation was accompanied by a marked shift in the ratio of the power in two frequency bands: 1-4 Hz and 8-12 Hz. Progress of the frequency band power ratio followed closely the state of the subject into sedation, overdose, and recovery. This measure was further improved by the use of multivariate analysis, which showed good discrimination of the alert, sedated, and overdosed states of the subject.

Adult↗
PubMedDate not supplied

Local venous lactate changes and spectral analysis of surface EMG during fatiguing isometric efforts in intrinsic hand muscles.

In this study relationships between local venous lactate concentrations and power spectrum changes in surface EMG due to fatiguing isometric contractions were investigated. Two different isometric efforts of the opponents pollicis muscle, 25% and 50% of maximum voluntary contraction, were examined. In 25% of maximum voluntary contraction no changes in local venous lactate were observed, whereas mean power frequency values of surface EMG shifted significantly towards lower frequencies. On the contrary, in 50% of maximum voluntary contraction lactate significantly increased and was related to the mean power frequency shifts of the surface EMG. These data suggest that lactate plays a role in muscle fatigue only in a limited intensity range of isometric muscle contractions.

Adult↗