Analysis Of Intensity Ratios Research Articles

Optical diagnosis of cervical cancer by fluorescence spectroscopy technique

In the present work, we examine normal and malignant stage IIIB cervical tissue by laser induced fluorescence, with 2 different objectives. (i) Development of the fluorescence spectroscopy technique as a standard optical method for discrimination of normal and malignant tissue samples and, (ii) Optimization of the technique by the method of matching of a sample spectrum with calibration sets of spectra of pathologically certified samples. Laser-induced fluorescence spectra were measured using samples from 62 subjects at different excitation wavelengths. Principal component analysis (PCA) of spectra and intensity ratios of curve-resolved fluorescence peaks were tested for discrimination. It was found that PCA of total fluorescence at 325 nm excitation gives specificity and sensitivity over 95%. Use of calibration sets of spectra of histo-pathologically certified samples combined with PCA for matching and pass/fail classification of test samples is shown to have high sensitivity/specificity for routine diagnostic purposes as well as for possible staging of the disease. Further, the multi-component origin of the fluorescence spectra is illustrated by curve resolution and fluorescence spectra of separated proteins of tissue homogenates.

Vapor-phase oxidation during pulsed laser deposition of SrBi2Ta2O9

Time-integrated optical emission spectroscopy has been used to observe the plume produced during pulsed laser deposition (PLD) in oxygen of the ferroelectric oxide SrBi2Ta2O9 (SBTO). Line emission from atomic and singly ionized target material was observed, together with emission from atomic oxygen. Band emission from strontium oxide was also observed. Spatially resolved analysis of oxide emission and atomic emission together with the assumption of an optically thin plasma plume distant from the point of ablation indicated that oxidation occurred most readily at the interface between the visible plume and the background gas. The oxide content in the visible plume was seen to increase as the plume passed through the background gas. Analysis of line intensity ratios and widths allowed the plasma electron temperature and density of the plume to be measured, with peak values of 7300 K and 1.2×1017 cm−3, respectively, measured at the laser spot. These results are of interest for the fabrication of SBTO thin fi...

Particle size dependent molecular rearrangements during the dehydration of trehalose dihydrate in situ FT-Raman spectroscopy.

(1) To characterise the different phases of trehalose using FT-Raman spectroscopy. (2) To monitor the changes in the structure of trehalose dihydrate on isothermal heating at 80 degrees C. Different phases of trehalose were prepared and FT-Raman spectra obtained. Trehalose dihydrate was sieved to < 45 microns and > 425 microns particle size fractions and FT-Raman spectra were obtained at various time intervals during heating at 80 degrees C. During heating at this temperature, the spectra of a < 45 microns particle size fraction showed a loss of peak resolution with time and after 210 minutes resembled the spectrum of amorphous trehalose prepared by lyophilisation, indicating that the material was rendered amorphous by heating. In contrast, spectra obtained from a > 425 micron particle size fraction altered with time and became characteristic of the crystalline anhydrate. The approximate kinetics of this transformation to the anhydrate were monitored by analysis of peak intensity ratios with time. A two state rearrangement was indicated; some functional groups appeared to manoeuvre into the spatial arrangement found in the anhydrate initially before the rest of the ring structure relaxed into this conformation. This may be due to some parts of the molecule being immediately affected by the loss of the water molecules on dehydration prior to the subsequent reorientation of the entire molecule into the anhydrate crystal lattice. The < 45 micron particle size fraction becomes disordered on dehydration induced by heating at 80 degrees C whilst the > 425 micron particle size fraction crystallises to the anhydrate under the same conditions.

Laser-induced fluorescence: III. Quantitative analysis of atherosclerotic plaque content.

Laser-induced fluorescence (LF) spectroscopic analysis of the chemical composition of atherosclerotic plaque was examined. The intima of 18 dog aortas was injected with chemical compounds found in atherosclerotic plaque. Spectra were recorded in air prior to and after injection of collagens I, III and IV, elastin, cholesterol, triglyceride, and beta-nicotinamide adenine dinucleotide (NADH). Significant changes in LF intensity were detected after injection of collagens I and III, cholesterol and elastin in thoracic aorta (P < 0.001), but not with triglyceride or NADH. Minor changes were detected in abdominal aorta. Multiple regression analysis of LF intensity ratios demonstrated a clear correlation with the quantity of injected collagens I (R2 = 0.90-0.99) and III (R2 = 0.84-1.0), cholesterol (R2 = 0.72-0.76), and triglyceride (R2 = 0.68-0.80) in both thoracic and abdominal aorta. The correlation between LF and atherosclerotic plaque composition was confirmed in a rooster model of atherosclerosis where multiple regression analysis predicted the measured aortic cholesterol (R2 = 0.78) and triglyceride content (R2 = 0.96). (1) Fluorescence spectra recorded from dog aorta were significantly altered by injection of collagens I and III, cholesterol, and elastin. (2) LF may allow quantitative assessment of plaque chemical content.

Surface segregation in Mo0.75Re0.25(001) studied by low-energy alkali-ion scattering.

${\mathrm{Mo}}_{0.75}$${\mathrm{Re}}_{0.25}$(001) has been studied by low-energy alkali-ion scattering. Using a method based upon analysis of ion-scattering intensity ratios, the Re atom fractions in the first and second layers of this surface have been determined to be 0.040\ifmmode\pm\else\textpm\fi{}0.005 and 0.52\ifmmode\pm\else\textpm\fi{}0.05, respectively. From analysis of the critical edges the first interlayer spacing is found to be contracted by about 9%. These results are in excellent agreement with recent low-energy-electron-diffraction experiments. The results are described in terms of various theories of surface segregation, and are found to be in quite good agreement with the simplest models if the surface coordination is adjusted to that associated with a smoother, higher coordination surface.

Magnetization transfer of hepatic lesions: evaluation of a novel contrast technique in the abdomen.

The authors evaluated the technique of magnetization transfer to determine if it could enable distinction of benign from malignant liver lesions. Thirteen patients with 27 hemangiomas or cysts and 13 patients with 31 malignant liver lesions underwent magnetic resonance imaging. Hepatic malignancies demonstrated magnetization transfer similar to that of the liver. However, hemangiomas and cysts showed significantly less magnetization transfer than malignant liver lesions. Gradient-recalled-echo imaging with the off-resonance saturation pulse showed increased lesion contrast compared with the liver for hemangiomas and cysts but not for malignancies. On the basis of signal intensity measurements alone (ie, ignoring morphologic criteria), the magnetization transfer studies showed an area under the receiver operating characteristic curve of 0.96 for distinguishing benign from malignant liver lesions. Though the separation of these two groups was imperfect, it was comparable with that achieved with qualitative analysis of signal intensity ratios at spin-echo imaging.

Distinction of hepatic cavernous hemangioma from hepatic metastases with MR imaging.

Twenty-four hepatic cavernous hemangiomas and 91 metastases from a variety of hypovascular and hypervascular primary neoplasms were prospectively studied with magnetic resonance (MR) imaging. In addition to qualitative analysis, quantitative analysis of signal intensity ratios of lesion to normal liver was performed with images obtained with 500/28-30 (repetition time msec/echo time msec) and 2,000/28-150 sequences. Quantitative data did not improve the ability to distinguish hemangiomas from metastases in our series compared with qualitative analysis. Hypovascular metastases, such as colon carcinoma, could be differentiated from hemangioma more frequently (97.5%) than hypervascular endocrine metastases, such as islet cell tumor, carcinoid, and pheochromocytoma (61%). These findings indicate that the utility of MR imaging in differentiating hemangiomas from metastases is dependent on the histologic type of the primary neoplasm.

A model for the quantitative analysis of ESCA intensity ratios for supported catalysts with partial surface segregation

A model for the quantitative analysis of ESCA intensity ratios for supported catalysts with partial surface segregation

19F nuclear magnetic resonance in CdF2–ErF3

The 19F NMR of a single crystal of CdF2:≃ 10% ErF3 has been investigated at 8 and 16 MHz. Weak NMR lines were observed whose shifts relative to the main CdF2 peak were found to be field dependent. These shifts showed axial symmetry about the [111] crystallographic directions with (Δ H/H)∥=−8.73 ± 0.01) × 10−3 and (Δ H/H)⊥=+(5.83 ± 0.10) × 10−3. The small NMR lines are attributed to those lattice fluorides which have one nearest neighbor Er3+ occupying a normal Cd2+ site. The anisotropic portion of the shift is shown to be due to the dipolar contribution of spin on the erbium ion with no unpaired spin in the fluorine p orbitals. Analysis of intensity ratios supports a random distribution of Er3+ among Cd2+ sites with no preferential formation of clusters.