Search results for "SPECTRA"
showing 10 items of 3542 documents
An interpretation of EPR spectra of azide ligated superoxide dismutase from Propionibacterium shermanii
1995
A self-consistent description of the EPR spectra of the azide ligated SOD is obtained by taking into account the general configuration of the crystal field splitting in the crystal field Hamiltonian. The spread in the rhombicity parameter due to the presence of different conformational substates is introduced.
1H 2D-NMR characterization of Ni(II)-substituted azurin fromPseudomonas aeruginosa
1993
1 H two-dimemional NMR experiments on nickel(II)-substituted azurin have been succesfully applied. Despite the short relaxation time of the hyperfine-shifted resonances, the combined use of NOESY and COSY spectra allowed the alignment of 15 resonances belonging to the metal-coordinated residues Gly-45, His-46, His-117 and Met-121. Even in the case of the two broad and furthest downfield resonances, the NOESY spectra were successful in assigning these signals to the β-CH 2 protons of Cys-112. The protons of the non-coordinated residues Met-13, Phe-15 and Trp-48 were also assigned via NOESY, COSY and TOCSY experiments
The active center of superoxide dismutase from Propionibacterium shermanii
1996
A self-consistent description of the EPR spectra and of the Mossbauer spectra of the natural superoxide dismutase from Propionibacterium shermanii with ferric iron as an active centre is presented. The spectra were measured at pH 6.5, 7.8 and 9.4. The theoretical approach is based on the use of the complete crystal field Hamiltonian for the high-spin ferric complexes with due regard for the terms of the fourth power of the electronic spin. It is shown that a SOD molecule can exist in two conformations. The low-pH conformation has predominantly trigonal symmetry, while the high-pH conformation has the symmetry close to the «extreme rhombic». This interpretation is in full agreement with EXAF…
Trichromatic color vision in the salamander (Salamandra salamandra)
1995
Spectral sensitivity functions were measured between 334 nm and 683 nm in Salamandra salamandra by utilizing two behavioral reactions: the negative phototactic response, and the prey catching behavior elicited by a moving worm dummy. The action spectrum of the negative phototactic response revealed 3 pronounced maxima: at 360–400 nm, at 520–540 nm, and at 600–640 nm. In the range around 450 nm, there was a “reaction gap” where sensitivity could not be measured. The action spectrum of the prey catching behavior was entirely different: maximal sensitivity was found at 500 nm and at 570 nm. Between 500 nm and 334 nm sensitivity decreased continuously for about 1 log unit (Fig. 6).
Comparison of aerosol optical thickness retrieval from spectroradiometer measurements and from two radiative transfer models
2000
Abstract The spectral values of the aerosol optical thickness τ a λ in the 400–670 nm band have been determined from 500 solar direct irradiance spectra at normal incidence registered at Valencia (Spain) in the period from July 1993 to March 1997. The τ a λ values obtained from experimental measurements have been compared with the boundary layer aerosol models implemented in the radiative transfer codes ZD-LOA and LOWTRAN 7. For the ZD-LOA code, the continental and maritime models have been considered and for the LOWTRAN 7 code the rural, maritime, urban and tropospheric models have been used. The obtained results show that the aerosol model that best represents the average turbidity of the…
Phantoms Used for Mapping of Skin Chromophores by Multi-spectral Imaging
2014
Skin phantoms can be used for better understanding of diffuse reflectance imaging of skin. In this study, skin phantoms of hemoglobin, bilirubin and melanin were developed and studied for possibilities to calibrate chromophore concentration values.
Recognition of Chip Forms by Means of Dynamic Force Spectrum Analysis
1993
In this study the ability to identify chip forms occurrs in the turning of austenitic stainless steel using dynamic force spectrum analysis has been tested. For this purpose the frequency spectra obtained from various metal cutting tests were recorded along with the static cutting forces. A dual channel analysis, based on the Fast Fourier Transform (FFT), was adopted to help identify the continuous/discontinuous (favourable/unfavourable) chip forming boundary. The results showed an acceptable correlation between the types of the frequency spectra and the types of chip forms. Finally, an original classification of the spectra obtained during turning of AISI 304 (DIN 1.4301) stainless steel i…
A sun-induced vegetation fluorescence retrieval method from top of atmosphere radiance for the FLEX/Sentinel-3 TanDEM mission
2015
A new fluorescence retrieval method is proposed to support ESA's 8th Earth Explorer FLuorescence EXplorer/Sentinel-3 (FLEX-S3) candidate tandem mission. FLEX is the first mission specially dedicated to measure the Sun-Induced vegetation chlorophyll fluorescence (SIF) strongly related with the vegetation photosynthetic activity. Most hyperspectral fluorescence retrieval algorithms available in the literature are very sensitive to true reflectance modelization and/or they assume the atmospheric status as known. The proposed algorithm delivers the retrieval of full fluorescence spectrum at canopy level by using only Top Of Atmosphere (TOA) radiances from S3 and FLEX as input. Once the spatial …
Raman and optical reflection spectra of germanate and silicate glasses
2005
Abstract Germanate and phosphosilicate glasses made in oxygen surplus conditions were studied by Raman and optical reflection methods. We found that the optical reflection spectra of the germanate glasses are quite similar to the one those of a GeO 2 crystal with the α-quartz structure. The reflection of phosphosilicate glasses is very close to silica glass-related spectra. Hence, the determining influence of the tetrahedral structure on reflection spectra is revealed. The Raman spectra of germanate samples are similar to those reported the one known in the literature. Octahedral entities, namely bands similar to stishovite vibration modes, were difficult to detect in phosphosilicate glasse…
Análisis tiempo-frecuencia de la fibrilación ventricular. Estudio experimental
2006
Introduction and objectives. The analysis of frequency variability during ventricular fibrillation has yielded inconsistent results. We used an experimental model of ventricular fibrillation, with a short timescale, to analyze variations in frequency and their associated spatial distribution. Methods. Epicardial recordings of ventricular fibrillation were made in 10 perfused isolated rabbit heart preparations using a multiple electrode system (i.e., 240 unipolar electrodes). Both spectral and time-frequency analysis were used to derive the dominant frequency in the anterolateral wall of the left ventricle. Results. Linear regression analysis showed that there was a good correlation between …