Use Of Laser Raman Spectroscopy Research Articles

Review of Laser Raman Spectroscopy for Surgical Breast Cancer Detection: Stochastic Backpropagation Neural Networks.

Laser Raman spectroscopy (LRS) is a highly specific biomolecular technique which has been shown to have the ability to distinguish malignant and normal breast tissue. This paper discusses significant advancements in the use of LRS in surgical breast cancer diagnosis, with an emphasis on statistical and machine learning strategies employed for precise, transparent and real-time analysis of Raman spectra. When combined with a variety of “machine learning” techniques LRS has been increasingly employed in oncogenic diagnostics. This paper proposes that the majority of these algorithms fail to provide the two most critical pieces of information required by the practicing surgeon: a probability that the classification of a tissue is correct, and, more importantly, the expected error in that probability. Stochastic backpropagation artificial neural networks inherently provide both pieces of information for each and every tissue site examined by LRS. If the networks are trained using both human experts and an unsupervised classification algorithm as gold standards, rapid progress can be made understanding what additional contextual data is needed to improve network classification performance. Our patients expect us to not simply have an opinion about their tumor, but to know how certain we are that we are correct. Stochastic networks can provide that information.

Improvement of the fidelity of molecular DNA computations: control of DNA duplex melting using Raman spectroscopy

In this study it is demonstrated that use of laser Raman spectroscopy for monitoring biochemical reactions provides the detection and control of the processes of renaturation and denaturation of DNA strands, the determination of state of strands, and also the control of possible mutations in DNA molecules. The obtained results are very promising to improve the fidelity of DNA computations, i.e. to provide the greater convergence of the estimated and exact values.

Using Laser Raman Spectroscopy to Reduce False Positives of Autofluorescence Bronchoscopies: A Pilot Study

Preneoplastic lesions of the bronchial tree have a high probability of developing into malignant tumors. Currently, the best method for localizing them for further treatment is a combined white light bronchoscopy (WLB) and autofluorescence bronchoscopy (AFB) (WLB + AFB). The average specificity from large clinical trials for this combined detection method is approximately 60%, leading to many false positives. The object of this study is to determine whether adding point laser Raman spectroscopy (LRS) to a WLB + AFB has the potential to improve the specificity of preneoplastic lesion detection and what the implication is to the detection sensitivity. An LRS system was developed to collect real-time, in vivo lung spectra with a fiber optic catheter passed down the instrument channel of a bronchoscope. WLB + AFB imaging modalities were used to identify lesions from 26 subjects, from which 129 Raman spectra were measured. Multivariate statistical analyses were performed on the spectra with a leave-one-out crossvalidation. Clear in vivo Raman spectra were obtained in 1 second. The location of individual Raman peaks in the spectra correlated well with the known positions of Raman peaks generated by lipids, proteins, and water molecules. Preneoplastic lesions were detected with a sensitivity of 96% and a specificity of 91%. Adding point LRS analysis to WLB + AFB imaging has the ability to detect preneoplastic lesions in real time with high sensitivity and specificity. The use of LRS has great potential for substantially reducing the number of false-positive biopsies associated with WLB + AFB with very little reduction in the detection sensitivity.

Measurement of the residual macro and microstrain in strained Si/SiGe using Raman spectroscopy

ABSTRACTThe use of laser Raman spectroscopy to assess the residual strain in strained silicon/silicon germanium devices is well established. The peak shift associated with the 520cm−1 silicon peak can be used to directly measure the strain in the cap layer provided that the strained silicon peak can be deconvoluted from the more intense Si in SiGe peak which occurs at slightly lower wavenumbers. However, though peak position gives a measure of the macrostrains in the layer it is not useful for the assessment of microstrains associated with point defects which may also influence device performance; such microstrains influence the intensity of the Raman peaks and can, in principle, be monitored by this method. In this study we have undertaken a study of peak shape as a function of processing conditions for strained silicon on SiGe. Changes in peak position may be correlated with macrostrains and macrostrain relaxation around extended defects such as dislocations. Changes in peak width can be correlated with processes which lead to changes in composition (e.g. germanium build-up in the surface after etching) and microstrain. Such changes are not necessarily correlated with changes in macrostrain but indicate that microstrain could also be an important factor influencing device performance.

Analysis of the dentin–resin interface by use of laser Raman spectroscopy

Objectives. Adhesion of resin-bonding agents to dentin is currently believed to result from impregnation of adhesive resin into superficially demineralized dentin. The purpose of this study was to investigate the chemical composition of the resin-impregnated dentin (hybrid) layer using a micro-Raman spectroscopy. Methods. Resin composites were bonded to bovine dentin with the two-step bonding systems, and specimens were sectioned parallel to dentinal tubules. These surfaces were then polished down to 1 μm diamond pastes. Raman spectra were successively recorded along a line perpendicular to the dentin–adhesive interface by steps of 0.2 μm on a computer controlled X– Y stage. The relative amounts of hydroxyapatite (960 cm −1, P–O), adhesive resin (640 cm −1, aromatic ring), and organic substrate (1450 cm −1, C–H) in the dentin–adhesive bonding area were calculated. Results. From the Raman spectroscopy results, the hybrid layer represents a gradual transition in the relative amount of adhesive from the resin side to dentin side. Evidence of poor saturation of the adhesive resin in the demineralized dentin with the one-bottle adhesive system was detected. Significance. From the results of this study, inhomogeneity of the hybrid layer composition was detected, and the degree of resin impregnation was found to be different between the bonding systems tested.

Pyroelectric characteristics of thin PbTiO3 and la-modified PbTiO3 films on platinum films for infrared sensors

In this work, we grew lead titanate (PbTiO3) and La-modified PbTiO3 thin films on platinized silicon (Si(100)) substrates under controlled substrate temperature and ambient by a modified jet-vapor deposition (JVD) process described in this paper. The x-ray diffraction patterns obtained from these films showed a single-phase perovskite structure. We examined locally homogeneity and thickness of these films through the comparative use of laser Raman spectroscopy. We also collected Raman and x-ray data on pure PbTiO3, as well as prepared lead zirconate titanate (PZT) (54/46), and PZT (50/50) films using the JVD process. This paper discusses the temperature variations of the pyroelectric and dielectric properties of three compositions of La-modified PbTiO3 films containing 5.2% to 15% of La, respectively, with a view toward studying the effect of La in place of Pb on these electrical properties. We detected significant pyroelectric currents on all three La-modified PbTiO3 films before performing poling treatments, and observed pyroelectric coefficeints as high as 84 nC/cm2·°C in the poled La-doped PbTiO3 films containing 5.2% La. The pyroelectric coefficient and dielectric constant varied significantly with La content. We compared the calculated figures of merit, which were based on the measured physical properties, with pure PbTiO3 as well as PZT and lead lanthanide zirconate titanate (PLZT) films. These properties just described illustrate that these films would be suitable for IR detectors.

Structural studies of bean pod mottle virus, capsid and RNA in crystal and solution states by laser Raman spectroscopy

Structures of protein and RNA components of bean pod mottle virus (BPMV) have been investigated by use of laser Raman spectroscopy. Raman spectra were collected from both aqueous solutions and single crystals of BPMV capsids (top component) and virions (middle and bottom components, which package, respectively, small and large RNA molecules). Analysis of the data permits the assignment of conformation-sensitive Raman bands to viral protein and RNA constituents and observation of structural similarities and differences between solution and crystalline states of BPMV components. The Raman results show that the protein subunits of the empty capsid contain between 45% and 55% beta-strand and beta-turn secondary structure, in agreement with the recently determined X-ray crystal structure, and that this total beta-strand content undergoes a small increase (approximately 5%) with packaging of RNA. The subunits are relatively deficient in alpha-helix secondary structure, estimated at less than 25%, and therefore must contain extensive amounts (greater than 20%) of loops and irregular chain conformations. The Raman spectra also show the following: (1) The molecular environments of as many as four tryptophan residues per subunit are altered upon packaging RNA, resulting in stronger 1N-H hydrogen bonding for two Trp residues and more hydrophobic environments for two indole rings. (2) Hydrogen-bonding states of the seven Tyr residues per subunit do not change detectably when RNA is packaged. At least five tyrosine OH groups are involved exclusively as strong hydrogen bond donors to protein acceptor groups, which suggests restricted access of solvent H2O molecules to these parahydroxyls.(ABSTRACT TRUNCATED AT 250 WORDS)

Laser Raman studies of α–bromoacrylamide reactive dyes and wool

The use of laser Raman spectroscopy in the investigation of interactions in α–bromoacrylamide reactive dye–wool fibre systems has been established. The spectra obtained (in particular using C. I. Reactive Red 84) provide some evidence to support the proposal that the dye reacts via addition at the double bond of the reactive group, followed by ring closure through nucleophilic substitution. Furthermore, preliminary studies of the effect of the commercial levelling assistant Albegal B on the aqueous dye environment have been made using C. I. Reactive Yellow 39. The results show that, whilst the primary interaction between the dye and auxiliary may be via the water–solubilising sulphonate groups of the dye, hydrophobic interactions are also important.

The use of laser Raman spectroscopy to study the degradation of poly(vinyl chloride)

The results of natural weathering tests carried out on plasticised poly(vinyl chloride) in three different locations representing cool/wet, hot/wet and hot/dry climates are detailed. The value of laser-Raman spectroscopy for determining dehydrochlorination levels of naturally weathered samples is demonstrated. The results indicate that plasticisers can play a significant role in this dehydrochlorination process. Results of studies on the effects of thermal stabilisers and amines, particularly those used as catalysts for polyurethane foam formation, on the stability on poly(vinyl chloride) are also reported.

ChemInform Abstract: A Mechanistic Investigation on the Formation of Molybdophosphate Complexes in Aqueous Solution by the Use of Laser Raman Spectroscopy.

AbstractTwo distinct reaction rates are observed for the formation of (PMo12O40)3‐ (I) depending on the formation procedure: mixing an acidic molybdate solution with an acidic phosphate solution exhibits a very slow reaction rate (formation of (I) is completed after ∼ 10 min), whereas acidification of the mixed molybdate‐phosphate solution rapidly produces 80% of (I) (30 s).

A mechanistic investigation on the formation of molybdophosphate complexes in aqueous solution by the use of laser Raman spectroscopy

Two distinct reaction rates were found in the formation of 12-molybdophosphate complex. These differences in the formation processes were understood by the use of laser Raman spectroscopy. The reaction of isopolymolybdate (MoO 4) 2−(MoO 3) 11 with phosphate PO 4 ⋯- proceeds slowly via formation of 11- molybdophosphate then to produce 12-molybdophosphate taken for 8 min. This reaction mechanism is considered to undergo first the replacement between MoO 4 2− and PO 4 3− then the transformation reaction from 11-molybdophosphate into 12-molybdophosphate. On the other hand, the acidification of the mixed solution of molybdate and phosphate rapidly produces 80% of 12-molybdophosphate within 30 s.

In Situ Resonance Raman Spectroscopic Characterization of Electrogenerated Methyl Viologen Radical Cation on Carbon Electrode

In situ Raman spectroscopic characterization of solution and surface species on a carbon electrode is reported. An optical flow-through cell has been designed for the characterization of electrode surfaces and electrogenerated solution species during an electrochemical reaction. The electrogeneration of the methyl viologen (1,1′-dimethyl-4,4′-bipyridine) radical cation (MV+) at a carbon electrode in aqueous chloride solution has been studied with the use of laser Raman spectroscopy. In the case of the radical ion, resonance enhancement of the order of 25–30 was observed with 514.5 nm excitation. The effect of concentration, potential, and flow rate on the observed spectrum is discussed. Time-dependent studies with optical multichannel analyzer detection suggest the formation of a multilayer film on the electrode.

Laser-Raman remote temperature sensing in liquids

A feasibility study has been conducted on the use of laser-Raman spectroscopy as a remote temperature sensing technique for liquids. Empirical relations between the temperature and parameters describing Raman band intensities were determined over a temperature range of 15 to 65 °C in carbon tetrachloride, benzene, ethylene glycol, aqueous sodium nitrate (5 M), and water. Using a 2-W argon ion laser and two 0.25-m monochromators in tandem, it was possible to measure temperatures in water to within 2 °C and, in ethylene glycol, to within 4 °C.

Studies on polynuclear molybdates in the aqueous solution by laser Raman spectroscopy

Polynuclear molybdates in the aqueous solution were investigated by the use of laser Raman spectroscopy. It was found from Raman measurements and chemical analysis of salts that two species of Mo 6O 2− 19 and Mo 12O 2− 37, except for Mo 7O 6− 24 and Mo 8O 4− 26 to be known, exist in the weakly acidic solutions. These species play an important role in the formation of heteropolymolybdate such as 12-molybdophosphate. The intensity in the Raman spectra was normalized by using an internal standard of sodium nitrate. This normalization made it possible to investigate some chemical equilibria of polynuclear species in detail. The formation constant of Mo 7O 6− 24 to be determined from this procedure agrees with that to be previously reported by the use of potentiometry.

Studies on yellow and colourless molybdophosphate complexes in the aqueous solution by laser raman spectroscopy

Yellow and colourless complexes of molybdophosphate were investigated by the use of laser Raman spectroscopy. Two kinds of yellow molybdophosphates were identified in the weakly acidic solutions: 12-molybdophosphoric and 11-molybdophosphoric acid which are in equilibrium in solution at pH 1-2. When excess phosphate is present, the colourless molybdophosphate is formed. This complex exists in the solutions of pH 4-1 under the condition of excess phosphate ([P]/[Mo] > 2). This complex was confirmed to be P 2Mo 5O 6− 23 and is so stable that the yellow molybdophosphate is converted into the colourless by excess phosphate.

Detection of molybdate impurity in chemical pure reagent of ammonium paramolybdate by laser Raman spectroscopy

A simple detection method of molybdate impurity in chemical pure reagents of ammonium paramolybdate by the use of laser Raman spectroscopy is proposed. Ammonium dimolybdate (NH4)2O·2MoO3 was found to be present as impurity in commercial powder ammonium paramolybdate by comparison of the Raman spectra.Since the Raman band at 905cm-1 of the impurity is very strong and paramolybdate ion has no band at this wavenumber, the presence of the impurity in less than 1% could easily be detected by this method.

Automated, photon-counting Raman spectrometer

Current research directed towards establishing the use of laser Raman spectroscopy as an effective means of making rapid determinations of isotope abundance ratios in at least nitrogen, carbon, oxygen, and hydrogen has necessitated the construction of a spectrometer of unique capabilities. The instrument, an automated, photon-counting Raman spectrometer contains as many state-of-the-art components as is feasible. The spectrometer is described along with the automatic data retrieval system, which offers the unique capability of unlimited integration time while running unattended. A concrete example of its performance, the resolution of the Q branch of 16O16O, is presented.

Untersuchungen über Isopolychromate

The infra-red absorption spectrum and laser raman spectrum of crystalline potassium trichromate are reported and compared with the corresponding spectra of potassium dichromate. It is shown that the state of aggregation of acid and concentrated aqueous chromate solutions can be investigated by use of laser raman spectroscopy. Trichromate ions are found to exist in acid dichromate solutions having concentrations ≧ 3 M and acidity pH ≪ 0, and in aqueous solutions of chromium trioxide provided concenrations are ≧ 2 M.