Relevant Spectral Regions Research Articles

IR spectrum of H2SO4 species trapped in low temperature solid CO and in CO containing matrices

The IR spectrum of the vapors above neat sulfuric acid trapped in CO enriched argon matrices was studied and compared to their IR spectra in pure CO matrices. We assigned vibrational modes of (OC)·(H2SO4), (OC)·(H2O)·(H2SO4), (OC)2·(H2SO4) and (OC)·(SO3) species isolated in argon matrices in all relevant spectral regions. Bonding between the moieties of the mixed complexes is indicated. These species are formed by surface diffusion within the deposited layer and do not represent a vapor phase equilibrium. No spectral evidence was found for any binary (H2O)m·(SO3)n or ternary (CO)l·(H2O)m·(SO3)n complexes or of ionic species, to indicate a proton transfer below 30 K between the H2SO4 and H2O moieties in either CO enriched or pure CO matrices.

A knowledge-controlled method for sequential wavelength-dispersive X-ray spectrometry: a feasibility study

A knowledge-based method for obtaining sequential wavelength-dispersive X-ray fluorescence intensities is proposed. The method aims at maximum precision in minimal time. Time reduction is established by measuring only relevant spectral regions. These regions are identified by on-line interpretation of the measured data. For identification and quantification a curve fit procedure is used. Curve fitting makes it possible to determine peak heights with less sampling points than in traditional methods. The feasibility of the strategy is shown by means of an off-line version based on premeasured X-ray spectra.

Classification of 1H MR spectra of human brain neoplasms: the influence of preprocessing and computerized consensus diagnosis on classification accuracy.

We study how classification accuracy can be improved when both different data preprocessing methods and computerized consensus diagnosis (CCD) are applied to 1H magnetic resonance (MR) spectra of astrocytomas, meningiomas, and epileptic brain tissue. The MR spectra (360 MHz, 37 degrees C) of tissue specimens (biopsies) from subjects with meningiomas (95; 26 cases), astrocytomas (74; 26 cases), and epilepsy (37; 8 cases) were preprocessed by several methods. Each data set was partitioned into training and validation sets. Robust classification was carried out via linear discriminant analysis (LDA), artificial neural nets (NN), and CCD, and the results were compared with histopathological diagnosis of the MR specimens. Normalization of the relevant spectral regions affects classification accuracy significantly. The spectra-based average three-class classification accuracies of LDA and NN increased from 81.7% (unnormalized data sets) to 89.9% (normalized). CCD increased the classification accuracy of the normalized sets to an average of 91.8%. CCD invariably decreases the fraction of unclassifiable spectra. The same trends prevail, with improved results, for case-based classification. Preprocessing the 1H MR spectra is essential for accurate and reliable classification of astrocytomas, meningiomas, and nontumorous epileptic brain tissue. CCD improves classification accuracy, with an attendant decrease in the fraction of unclassifiable spectra or cases.

Phonon density of states in Pb2Sr2(Ca,Y)Cu3O8.

The phonon density of states of the high-${T}_{c}$ superconductor ${\mathrm{Pb}}_{2}$${\mathrm{Sr}}_{2}$${\mathrm{Ca}}_{0.5}$${\mathrm{Y}}_{0.5}$ ${\mathrm{Cu}}_{3}$${\mathrm{O}}_{8}$ has been measured by the neutron time-of-flight technique. Comparison with the undoped nonsuperconducting compound ${\mathrm{Pb}}_{2}$${\mathrm{Sr}}_{2}$${\mathrm{YCu}}_{3}$${\mathrm{O}}_{8}$ shows small differences near 35 and 67 meV. Available lattice-dynamical results suggest the relevant spectral regions correspond to Sr and O(3) bond-bending modes in the first case, and O(1), O(2) bond-stretching modes in the second case. The results are discussed in the light of comparable results on other high-${T}_{c}$ superconductors.