bluuebunny/crossref_metadata_2025 huggingface dataset:
Absorption Cross-Sections of the C—H Overtone of Volatile Organic Compounds: 2 Methyl-1,3-Butadiene (Isoprene), 1,3-Butadiene, and 2,3-Dimethyl-1,3-Butadiene
Authors: Cias Pawel , Wang Chuji , Dibble Theodore S.
Published: February 2007

Many molecules or transient radicals have well-documented absorption cross-sections in the ultraviolet (UV) region, but their absorption cross-sections in the near-infrared (NIR) region are much less often known and are difficult to measure. We propose a method to determine the unknown NIR absorption cross-sections using the known absorption cross-sections in the UV region, in which single-path UV absorption spectroscopy and NIR continuous wave cavity ringdown spectroscopy (cw-CRDS) are employed in a cross-arm reaction chamber for simultaneous measurements. Without knowing the actual sample partial pressures (or concentrations), the NIR absorption cross-sections can be accurately determined through the two sets of measurements. The method is demonstrated by measuring the NIR absorption cross-section of the first overtone of the asymmetric C–H stretch of 2-methyl-1,3-butadiene (isoprene) (3.24 (±0.16) × 10−22 cm2 molecule−1) at 1651.52 nm using the known value of the absorption cross-section at 220 nm. The diode laser wavelength was calibrated by atmospheric cavity ringdown spectra of CH4, CO2, and H2O. By comparison with sample pressure measurements, this method can also be used as a pressure calibration means for the reaction chamber, and this has been demonstrated with two additional measurements of the absorption cross-sections of 1,3-butadiene and 2,3-dimethyl-1,3-butadiene (2.50 (± 0.08) × 10−22 and 2.82 (± 0.16) × 10−22 cm2 molecule−1, respectively) at 1651.52 nm. The applicability of the method to determining absorption cross-sections using the simultaneous measurements of cw-CRDS and single-path absorption spectroscopy is discussed.
Evaluation of Disseminated Candidiasis on an Experimental Animal Model: A Fourier Transform Infrared Study
Authors: Dogan Ayca , Ergen Kivanc , Budak Fatma , Severcan Feride
Published: February 2007

Invasive candidiasis, defined as candidemia and disseminated candidiasis, is the most common fungal infection in hospitalized patients. In the current study, we used Fourier transform infrared (FT-IR) spectroscopy as a rapid, non-perturbing technique to investigate the effects of disseminated candidiasis on mouse liver tissues at the molecular level. The results revealed that the infection caused compositional changes in the tissues by decreasing the lipid content and the ratio of the saturated lipids to unsaturated lipids. An increase in the lipid/protein ratio was also observed. In addition, investigation of the olefinic band at 3014 cm−1 showed that lipid peroxidation took place in the infected samples. These results indicate that FT-IR spectroscopy is a promising technique for the evaluation and diagnosis of disseminated candidiasis.
Evaluation of Physical Properties of Human Hair by Diffuse Reflectance Near-Infrared Spectroscopy
Authors: Miyamae Yuta , Yamakawa Yumika , Ozaki Yukihiro
Published: February 2007

The objective of the present study is to develop a novel nondestructive, simple, and quick method to evaluate the friction, twist, and gloss of human hair based on near-infrared diffuse reflectance (NIR-DR) spectroscopy and chemometrics. NIR-DR spectra were measured for human hair, which was collected from eleven Japanese women (age 5–44 years), by use of an optical fiber probe. Partial least squares (PLS) regression has been applied to the NIR-DR spectra of human hair after mean centering (MC), standard normal variate (SNV), and first derivative (1d) or second derivative (2d) analysis to develop calibration models that predict the friction, twist, and gloss of human hair. We identified the most suitable wavenumber region for the evaluation of each physical property. Correlation coefficients and standard errors of calibration of the PLS calibration models for the friction, twist, and gloss of hair were calculated to be 0.96 and 0.023, 0.81 and 3.27, and 0.90 and 0.36, respectively. Thus, the calibration models have high accuracy.
Fluorescence Absorbance Inner-Filter Decomposition: The Role of Emission Shape on Estimates of Free Ca2+ Using Rhod-2
Authors: Territo Paul R. , Heil Jeremy , Bose Salil , Evans Frank J. , Balaban Robert S.
Published: February 2007

A method for decomposing complex emission spectra by correcting for known inner-filter effects is described. This approach builds on previous work using a linear combination of model emission spectra and combines the known absorption characteristics of the system to fit the composite emission spectrum. Rhod-2, which has a small Stokes shift and significant self-absorption, was used as the model system. By adding the absorption characteristics of Rhod-2 to the model, the degree of fit was significantly improved, thus minimizing residuals, and accurately predicted the spectral shape changes with increasing concentration, [Rhod-2]. More complex studies were conducted with Rhod-2 in isolated cardiac mitochondria with multiple emission and absorption elements. By including known absorbances to the spectral decomposition, the overall precision increased almost four fold. Moreover, this approach eliminated the significant [Rhod-2] dependence on the apparent K50 and therefore improved the accuracy of free [Ca2+] calculations. These data demonstrate that secondary inner-filter correction can significantly improve spectral decomposition of complex emission spectra, which are used in a variety of biological applications.
Two-Point Maximum Entropy Noise Discrimination in Spectra over a Range of Baseline Offsets and Signal-to-Noise Ratios
Authors: Schulze H. Georg , Foist Rod B. , Jirasek Andrew I. , Ivanov Andre , Turner Robin F. B.
Published: February 2007

The two-point maximum entropy method (TPMEM) is a useful method for signal-to-noise ratio enhancement and deconvolution of spectra, but its efficacy is limited under conditions of high background offsets. This means that spectra with high average background levels, regions with high background in spectra with varying background levels, and regions of high signal-to-noise ratios are smoothed less effectively than spectra or spectral regions without these conditions. We report here on the cause of this TPMEM limitation and on appropriate baseline estimation and removal procedures that effectively minimize the effects on regularization. We also present a comparative analysis of TPMEM and Savitzky–Golay filtering to facilitate selection of the best technique under a given range of conditions.
Moisture Sorption as a Potential Condition Marker for Historic Silks: Noninvasive Determination by Near-Infrared Spectroscopy
Authors: Zhang Xiaomei , Wyeth Paul
Published: February 2007

Given their ephemeral nature, the preservation of historic silks can be problematic. Rapid, on-site condition monitoring would offer significant benefits to conservators and museum curators concerned with continued access to collections. In this paper, near-infrared spectroscopy (NIR) is investigated as a noninvasive approach to the characterization of silk fabrics and particularly for determining the moisture content of silks as a potential age-related marker. Bands within the NIR spectrum of silk are assigned to contributions from water and the silk fibroin polymer. The water bands may be deconvolved to show separate contributions from bound and structural water. When silk is exposed to deuterium oxide, the water OH NIR bands are rapidly lost. The accompanying changes in the amide-related NIR absorptions reflect differential accessibility of regions within the semi-crystalline fibroin aggregate. NIR spectra were recorded while silk was maintained at a range of relative humidity; complementary gravimetry provided absolute reference data for moisture sorption. A single spectral parameter, the intensity of the water combination band, is sufficient to indicate the relative moisture content of silk and allows distinction of unaged and heat, light, and humidity aged silks. The results confirm that NIR has significant potential for on-site studies at collections in support of the preservation and access of our silk heritage.
Sequential-Pulse Laser-Induced Breakdown Spectroscopy of High-Pressure Bulk Aqueous Solutions
Authors: Lawrence-Snyder Marion , Scaffidi Jon , Angel S. Michael , Michel Anna P. M. , Chave Alan D.
Published: February 2007

Sequential-pulse (or dual-pulse) laser-induced breakdown spectroscopy (DP-LIBS) with an orthogonal spark orientation is described for elemental analysis of bulk aqueous solutions at pressures up to ∼138 × 105 Pa (138 bar). The use of sequential laser pulses for excitation, when compared to single-pulse LIBS excitation (SP-LIBS), provides significant emission intensity enhancements for a wide range of elements in bulk solution and allows additional elements to be measured using LIBS. Our current investigations of high-pressure solutions reveal that increasing solution pressure leads to a significant decrease in DP-LIBS emission enhancements for all elements examined, such that we see little or no emission enhancements for pressures above 100 bar. Observed pressure effects on DP-LIBS enhancements are thought to result from pressure effects on the laser-induced bubble formed by the first laser pulse. These results provide insight into the feasibility and limitations of DP-LIBS for in situ multi-elemental detection in high-pressure aqueous environments like the deep ocean.
Monitoring 2-Ethylhexyl-4-Methoxycinnamate Photoisomerization on Skin Using Attenuated Total Reflection Fourier Transform Infrared Spectroscopy
Authors: Pangnakorn P. , Nonthabenjawan R. , Ekgasit S. , Thammacharoen C. , Wanichwecharungruang S. Pattanaargson
Published: February 2007

Photoisomerization and photodimerization of a widely used UVB filter, 2-ethylhexy-4-methoxycinnamate (EHMC) on a ZnSe surface and baby mouse ( Mus musculus Linn.) skin were monitored using attenuated total reflection Fourier transform infrared spectroscopy (ATR-FT-IR). Differentiation between the E- and the Z-EHMC could be achieved by examining the infrared (IR) peak at 981 cm−1 (b peak), which corresponds to the CH rocking deformation vibration of Ph-CH=CH- detected only in the E configuration. By plotting the ratios of the peak area of the b peak and an internal standard peak (1060–998 cm−1) against mole percentage of Z-isomer in the E-Z mixtures, a linear calibration plot was obtained. Thus, a simple estimation of the mole percentage of each configuration in a sample was obtained. At the same UVB exposure, photostationary equilibrium of the E/Z isomerization on the surface varied with the applied amounts of EHMC. Photoisomerizations on ZnSe and on baby mouse skin were comparable. Less than 10% of E-EHMC changed configuration when the mouse skins applied with 1.0–4.0 mg/cm2 E-EHMC were exposed to sunlight for 60 min (UVB radiant exposure of ∼0.30 J/cm2). This corresponded to less than 5% loss in UV filtering efficiency. However, at a typical EHMC skin coverage (∼0.2 mg/cm2), 0.30 J/cm2 UVB exposure induced ∼50% photoisomerization resulting in 25% loss of UV filtering efficiency. No photodimerization was detected even at the extreme EHMC coverage of 4.0 mg/cm2 after a UVB exposure of 0.90 J/cm2.
Noninvasive in Vivo Measurement of Venous Blood pH during Exercise Using Near-Infrared Reflectance Spectroscopy
Authors: Yang Ye , Soyemi Olusola O. , Landry Michelle R. , Soller Babs R.
Published: February 2007

Blood pH is an important indicator of anaerobic metabolism in exercising muscle. This paper demonstrates multivariate calibration techniques that can be used to produce a general pH model that can be applied to spectra from any new subject without significant prediction error. Tissue spectra (725∼880 nm) were acquired through the skin overlying the flexor digitorum profundus muscle on the forearms of eight healthy subjects during repetitive hand-grip exercise and referenced to the pH of venous blood drawn from a catheter placed in a vein close to the muscle. Calibration models were developed using multi-subject partial least squares (PLS) and validated using subject-out cross-validation after the subject-to-subject spectral variations were corrected by mathematical preprocessing methods. A combination of standard normal variate (SNV) scaling and principal component analysis loading correction (PCALC) successfully removed most of the subject-to-subject variations and provided the most accurate prediction results.
Variability in Surface Infrared Reflectance of Thirteen Nitrile Rubber Gloves at Key Wavelengths for Analysis of Captan
Authors: Phalen R. N. , Hee Shane S. Que
Published: February 2007

The aim of this study was to investigate the surface variability of 13 powder-free, unlined, and unsupported nitrile rubber gloves using attenuated total reflection Fourier transform infrared (ATR-FT-IR) spectrophotometry at key wavelengths for analysis of captan contamination. The within-glove, within-lot, and between-lot variability was measured at 740, 1124, 1252, and 1735 cm−1, the characteristic captan reflectance minima wavelengths. Three glove brands were assessed after conditioning overnight at relative humidity (RH) values ranging from 2 ± 1 to 87 ± 4% and temperatures ranging from −8.6 ± 0.7 to 59.2 ± 0.9 °C. For all gloves, 1735 cm−1 provided the lowest background absorbance and greatest potential sensitivity for captan analysis on the outer glove surface: absorbances ranged from 0.0074 ± 0.0005 (Microflex) to 0.0195 ± 0.0024 (SafeSkin); average within-glove coefficients of variation (CV) ranged from 2.7% (Best, range 0.9–5.3%) to 10% (SafeSkin, 1.2–17%); within-glove CVs greater than 10% were for one brand (SafeSkin); within-lot CVs ranged from 2.8% (Best N-Dex) to 28% (SafeSkin Blue); and between-lot variation was statistically significant ( p ≤ 0.05) for all but two SafeSkin lots. The RH had variable effects dependent on wavelength, being minimal at 1735, 1252, and 1124 cm−1 and highest at 3430 cm−1 (O–H stretch region). There was no significant effect of temperature conditioning. Substantial within-glove, within-lot, and between-lot variability was observed. Thus, surface analysis using ATR-FT-IR must treat glove brands and lots as different. ATR-FT-IR proved to be a useful realtime analytical tool for measuring glove variability, detecting surface humidity effects, and choosing selective and sensitive wavelengths for analysis of nonvolatile surface contaminants.
Low Temperature Infrared Absorption Spectra of Cellulosics
Authors: McCall Elizabeth R. , Morris Nancy M. , Tripp Verne W. , O'Connor Robert T.
Published: February 2007

The ir absorption spectra of Valonia ventricosa cellulose, hydrocellulose i, and hydrocellulose ii at ambient and liquid nitrogen temperatures have been compared. Some of the bands exhibit a striking increase in peak intensity at the lower temperature. On cooling, changes to lower frequencies occur in the OH stretching region and to higher frequencies in the 1800–300 cir−1 region. The changes which were observed on cooling are undoubtedly associated with hydrogen bonding effects since the positions of absorption bands in the spectra, obtained under the same conditions, of analogous specimens containing no hydroxyl groups are not affected by temperature.
Ion-Sensitive Plate Detectors in Mass Spectrometry
Authors: McCrea J. M.
Published: February 2007

The role of the ion-sensitive plate as an ion detector in contemporary mass spectrometers or spectrographs is discussed in this paper. The plates are mainly used in instruments of the Mattauch–Herzog geometry for detecting ions with mass-to-charge ratios from 1 to well over 1000. The energies of the ions detected usually lie in the range from 5 to 75 keV. The type Q2 low-gelatin plate is widely used in both organic structure studies by the electron bombardment method and elemental analysis of metals and inorganics by the spark source method. In addition to detectors with low-gelatin emulsions, those with centrifuged emulsions or vapor deposited films are also used for special applications, as are ion-to-light and ion-to-electron converters.
Infrared Spectra-Structure Correlations for Monohalogenated Monocarboxylic Acids
Authors: Katon J. E. , Carll Thomas P. , Bentley F. F.
Published: February 2007

The ir spectra of 16 monohalogenated monocarboxylic acids have been recorded over the range 4000–200 cm−1. Attempts have been made to find useful spectra structure correlations which would serve to distinguish these acids from their unsubstituted analogs. It is concluded that differentiation of halogenated acids, either from unsubstituted acids or from each other, is not possible on the basis of consistent group frequencies, which forces one to resort to reference spectra for identification of these compounds. The one exception is provided by the alpha chloro-substituted compounds, which can, tentatively, be differentiated from both unsubstituted acids and other halogen-substituted acids. In contrast to previous reports, alpha halogen-substituted acids cannot be differentiated from the others unless the halogen is chlorine.
Measurement of Magnetic Circular Dichroism Using Alternating Magnetic Fields
Authors: Abu-Shumays A. , Hooper G. E. , Duffield J. J.
Published: February 2007

Conventional systems for the measurement of magnetic circular dichroism (MCD) employ a dc magnet in the sample space of a circular dichroism spectropolarimeter, where the state of polarization of the light beam is modulated between left and right circular. The photometric system of the instrument measures the difference between sample absorbances for the two states of polarization of the light beam. The method described in this paper uses a fixed state of polarization of the light beam, left or right circular, an alternating or pulsed magnetic field, and otherwise the same photometric system as the conventional method. The two methods are shown to be mathematically and physically equivalent. The proposed method offers two fundamental advantages: (1) Only the magnetically induced circular dichroism is measured, even in the presence of natural optical activity, and (2) the method is capable of extension to spectral regions where polarization modulation is difficult to achieve. Experimental apparatus using the two methods are described and their relative merits are discussed.
Diffuse Reflectance Spectra of Some Compounds of Elements of IV a Group
Authors: Tandon S. P. , Gupta J. P.
Published: February 2007

Diffuse reflectance spectra of lead halides, lead oxide, and stannic oxide have been studied in the region 1.2–6.20 eV. Four bands at 2.52, 3.10, 3.90, and 5.93 eV have been observed in pure samples of lead iodide while only three bands have been observed at 3.48, 4.08, and 5.17 eV and 4.30, 4.72 and, 5.90 eV, respectively, in samples of lead bromide and lead chloride. The assignment of these bands has been discussed in the light of band structure of lead halides. Two bands at 3.54 and 5.61 eV and one band at 5.64 eV have been observed in pure samples of lead oxide and stannic oxide, respectively. These bands have been assigned to band-to-band transitions.
Investigation of the Hollow Cathode Discharge as an Atomic Absorption Medium
Authors: Gandrud B. W. , Skogerboe R. K.
Published: February 2007

A hollow cathode discharge has been studied as a means for vaporizing and atomizing samples for atomic absorption. The design and operational characteristics of the cell are presented with detection limits and precision data for Ag, As, Ca, Cd, Hg, Pb, Se, and Zn. In general, detection limits between 1 and 10 ng were obtained. The present limitation of the method due to the sample holder blank is discussed.
The Infrared Spectra of Amino Acids and Some Simple Polypeptides to 33 cm−1 at Room and Liquid Nitrogen Temperatures
Authors: Feairheller William R. , Miller J. T.
Published: February 2007

The ir spectra of a number of amino acids have been studied and the absorption bands in the 400–33 cm−1 region are reported. Spectra were recorded at both room and liquid nitrogen temperatures. It was observed that recording at low temperatures is a useful method for obtaining additional analytical information when the amino acids are in the zwitterion form. Low temperature is also useful in determining the assignment of several of the low frequency bands.
Hydrogen Rearrangements in the Mass Spectra of Alkylbenzenes
Authors: Lightner David A. , Quistad Gary B. , Irwin Elizabeth
Published: February 2007

By means of extensive deuterium labeling, the γ-carbon has been shown to be the principal site of transferred hydrogen (deuterium) regardless whether the hydrogen (deuterium) is primary, secondary, or tertiary. Although a significant transfer is also observed from the β, δ, ε, and more remote (to θ) carbons of the alkyl chain, such transfer is not attended by C–C cleavage (fragmentation) and is interpreted as an exchange between the aromatic ring ( ortho-hydrogen atoms) and the alkyl chain hydrogen atoms (deuterium atoms). The data herein also set small upper limits 011 the formation of m/ e 91 (C7H7+) from m/ e 92 (C7Hs+−) at both high and low ionizing voltages as well as in long and short alkyl chains.
Determination of Metals in Paint and Vinyl Additives by Atomic Absorption Spectrophotometry
Authors: Eider Norman G.
Published: February 2007

A method is described for determining the metal content of paint and vinyl additives by atomic absorption spectrophotometry. The chief advantage of this technique is the ability to analyze multielement metallo-organic compounds and complex mixtures without prior chemical separation at a considerable savings in time, compared to wet chemical methods. Accuracy of better than 1% relative error, and precision equivalent to wet chemical analysis were obtained.
Pulsed NMR Sulfur-33 Investigations with a Superconducting Solenoid
Authors: Schultz Harry D. , Karr Clarence , Vickers G. D.
Published: February 2007

There is much interest in examining the structure of sulfur compounds because of the role of sulfur as a principal contributor to environmental pollution. By a pulsed NMR technique, the extremely weak free induction decay signal of 33S in several liquid compounds was detected. Using the relatively easy to detect carbon disulfide resonance as a reference model, a method is discussed for studying sulfur compounds which takes into consideration the symmetry and spin relaxation parameters ( T1 and T2). Consideration is given to the instrumental parameters which can be varied to enhance 33S pulsed NMR resonances.
A Simple Monochromatorless Atomic Fluorescence Flame Spectrometer
Authors: Elser R. C. , Winefordner J. D.
Published: February 2007

A novel design for a monochromatorless atomic fluorescence spectrometer is presented. The instrument was used to measure the atomic fluorescence of Cd, Hg, and Zn. Analytical curves obtained agreed with theoretical predictions. Limits of detection and scatter experiments demonstrated the sensitivity and selectivity of the instrument.
Internal Standardization in Mössbauer Spectrometry
Authors: Pella P. A. , DeVoe J. R.
Published: February 2007

The concept of internal standardization is applied to Mössbauer spectrometry using SnO2 and β-Sn as analyte and internal standard absorbers, respectively. One of the difficulties encountered in using the Mössbauer technique for assay work is that the Mössbauer gamma ray is accompanied by background radiation. Through simultaneous measurement of the analyte and internal standard absorbers, the background contribution can be eliminated.
Machine Intelligence Applied to Chemical Systems: A Graph Theoretical and Learning Machine Study of Second-Order Effects in Low Resolution Mass Spectra
Authors: Jurs Peter C.
Published: February 2007

Low resolution mass spectra can be usefully classified using pattern classifiers based on linear threshold logic units. These systems are linear in that they use the mass spectrometry peaks independently of one another. However, the theory of mass spectrometry as well as pattern classification considerations suggests that second-order interactions (cross terms which consider relationships between peaks) could be used to advantage in performing such classifications. A similarity measure has been used to develop two types of cross terms (intraset and interset cross terms) from low resolution mass spectra. It is shown that the interset cross terms thereby derived have a high probability of being correlated with the molecular features which define the categories of classification. The method has been implemented with threshold logic unit pattern classifiers working with several sets of mass spectrometry data. The cross terms are shown to increase the power of the pattern classification systems by speeding up convergence and/or raising their predictive ability.
The Spectrographic Determination of Traces of Tellurium
Authors: Marks J. , Cone R. , Leao E.
Published: February 2007

A spectrographic method for the determination of as little as 0.3 µg tellurium in nickel-base alloys has been developed. The method utilizes a preliminary separation and concentration of tellurium by precipitation of the metal with stannous chloride. The precipitate is then filtered and the filter paper ashed in the spectrographic electrode. Tellurium is measured by a dc arc technique.
The Technique of Raman Spectroscopy: A State-of-the-Art Comparison to Infrared
Authors: Sloane Howard J.
Published: February 2007

This paper in a tabulated summary format discusses the state-of-the-art of Raman spectroscopy for commercially available instrumentation. A comparison to infrared is made in terms of (I) instrumentation, (II) sample handling, and (III) applications. Although the two techniques yield similar and often complementary information, they are quite different from the point of view of instrumentation and sampling procedures. This leads to various advantages and disadvantages or limitations for each. These are discussed as well as the future outlook.
Vibrational Spectroscopic Study of 0,0-Dimethyl 0-(2,4,5-Trichlorophenyl)Phosphorothioate
Authors: Nyquist R. A. , Muelder W. W.
Published: February 2007

Pertinent spectral features of 0,0-dimethyl 0-(2,4,5-trichlorophenyl)phosphorothioate have been assigned on the basis of comparison with the vibrational spectra of the 0,0-dimethyl- d6 analog, the P = O analog, the 0,0-dimethyl- d6 P = O analog, and by comparison with vibrational assignments for 0,0-dimethyl phosphorochloridothioate, 0,0-dimethyl- d6 phosphorochloridothioate, and 1-fluoro-2,4,5-trichlorobenzene.
Reproducibility of Integrated Infrared Intensity Measurements
Authors: Brownlee R. T. C. , Cameron D. G. , Ternai B. , Topsom R. D.
Published: February 2007

Careful control of instrument parameters and the use of a computer program for integration gives a reproducibility of <±2% between intensity measurements of reasonably isolated absorptions on different grating spectrometers in different laboratories.
Variation of the Electronic Transition Moment and the Effective Vibrational Temperature in 4800–6700-Å System of MnO Molecule
Authors: Dube Prem Shankar , Chaudhry A. K. , Baruah G. D. , Rai D. K.
Published: February 2007

The 4800–6700-Å system of MnO has been excited in an arc. Using the photographic photometry, the relative band intensities have been measured. The data were interpreted with the aid of Franck-Condon factors and r centroids. The electronic transition moment is found to vary according to the relation Re(r) = const (1- 3.192 r + 1.99 r2), where 1.736≤ r≤ 1.90 Å. The slope of the straight line plot of log ∑ v″ I/v4 against G'(ν') for ν' progression gives an estimate of effective vibrational temperature to be 3860 K.
The Applications of Light Scattering
Authors: Gravatt C. C.
Published: February 2007

Light scattering provides information concerning the size, shape, number, and time dependence of the physical nonuniformities of a system. Measurements of the scattered intensity as a function of both scattering angle and wavelength describe static properties, whereas the spectral distribution of the scattered radiation is related to time dependent phenomena. The applications of light scattering are discussed, including critical phenomena, molecular weight determination, air pollution analysis, and diffusion phenomena.
The Characterization of Rhenium by Atomic-Absorption Spectroscopy in Nitrous Oxide-Acetylene Flames: The Analysis of Organorhenium Compounds
Authors: Tomkins David F. , Frank C. W.
Published: February 2007

This investigation of the atomic-absorption characteristics of rhenium included studies of optimum operating conditions, detection limits, interferences from various inorganic acids, and the effect of organic-solvent ratios on absorption. Atomic-absorption analysis of some organorhenium complexes are also described.
Computer-Plotted Soft X-Ray Spectra to Facilitate Chemical Combination Studies with the Electron Microbeam Probe
Authors: Solomon J. S. , Baun W. L.
Published: February 2007

A dual-function plotter-printer terminal linked to a commercial time-share computer system was used to process electron microprobe soft x-ray spectral data and produce plots of soft x-ray spectra. This system is fast, highly reliable, and minimizes measurement time and errors. It provides the means of practical application of chemical combination effects on soft x-ray spectra to qualitative and quantitative electron microprobe analyses. The instrumentation and software operations are described, examples of plotted spectra are presented, and applications are shown.
Slit-Function Corrections Applied to Laser-Excited Raman Bands of Liquids
Authors: Frenzel C. A. , Bradley E. B. , Mathur M. S.
Published: February 2007

The use of small spectral slitwidths complicates Raman intensity measurements of laser-excited spectra. The nature of the slit-function correction in medium-resolution laser-Raman instruments is discussed and some effects of asymmetric slit functions on asymmetric and symmetric Raman bands are explored. Corrections to bandwidth and band shape for nonideal slit functions are obtained from the concept of an intermediate standard which represents the pure slit function at some limiting spectral slitwidth. The corrections are applied to the contours of the Raman bands of CCl4 at 458 cm−1 and CH3OH at 1028 cm−1, and the corrected contour of the 1028-cm−1 band is compared to that obtained for the same band on a high-resolution laser-Raman spectrometer. A codification of Raman band shapes by means of two shape parameters is discussed.
The Design and Operation of a High-Resolution Infrared Spectrometer
Authors: Robertson Charles W. , Hunt Robert H. , Plyler Earle K.
Published: February 2007

A high-resolution grating spectrometer has been designed and built for use in the infrared region between 0.8 and 6 µ. A Littrow optical system is employed and a 3-m focal length spherical mirror is utilized as the collimator. By the use of a four-pass optical system and a 17.5-cm grating with 400 lines/mm, a spectral slitwidth of 0.013 cm−1 is obtained in the region of 3.4 µ. Details of the design and operation of the instrument are given and the precision which can be obtained with the mechanical drive system is discussed.
Background Elimination in Spectra Generated by Fourier Transform Spectrometers
Authors: Mark H. , Low M. J. D.
Published: February 2007

Two methods are described for reducing or eliminating the background of single-beam spectra obtained by Fourier transform spectrometers incorporating analog data-reduction systems. One method simply involves increasing the amplifier gain so that the central spike of the interferogram is clipped. The second method involves the use of an electronic device which eliminates the central part of the interferogram. Both methods lead to spectra having flat backgrounds, but distortion of the spectrum may also be caused.
Direct Nebulization of Metal Samples for Flame Atomic-Emission and Absorption Spectroscopy
Authors: Winge Royce K. , Fassel Velmer A. , Kniseley Richard N.
Published: February 2007

A device for transforming solid-metal samples into an aerosol of fine metal particles has been combined with a flame spectroscopic method for the determination of trace impurities and alloying elements in steels. The aerosol generator is a simple apparatus in which the sample serves as the cathode of a low-current dc-arc discharge. Constant movement of the cathode spot results in uniform sampling of a relatively large area. A flowing gas stream transports the aerosol particles from the arc discharge to the nitrous oxide–acetylene flame. Analytical curves for the determination of chromium, manganese, and nickel in steel are shown. The method provides a very rapid means of determining trace elements and alloy constituents in metals without the complications attendant to dissolution procedures.
Raman Spectra of Polyacrylonitrile
Authors: Huang Y. S. , Koenig J. L.
Published: February 2007

The polarized Raman spectra of polyacrylonitrile have been obtained and compared with ir spectra. On the basis of the selection rules, various proposed structural models are compared with the experimental results. The spectra suggest a syndiotactic rich composition with a planar structure. The blocks of syndiotactic placements are disrupted by short sequences of isotactic or atactic placements.
A Comparison Study of Detection Limits Using Flame-Emission Spectroscopy with the Nitrous Oxide—Acetylene Flame and Atomic-Absorption Spectroscopy
Authors: Christian Gary D. , Feldman Fredric J.
Published: February 2007

The minimum detection limits using flame-emission spectroscopy with the nitrous oxide–acetylene flame and using atomic-absorption spectroscopy were determined under optimum instrumental and flame-operating conditions for 68 elements, using the same nebulizer system, the same instrument, and signal integration techniques. Based on these studies, 27 elements show equal detectability by the two methods, 15 are more sensitive by flame emission, and 26 are more sensitive by atomic absorption. Results are compared and discussed with respect to theoretical prediction.
The Determination of Trace Elements in Brine by Atomic Absorption
Authors: Galle O. Karmie
Published: February 2007

A method for the determination of Mn, Fe, Co, Ni, Cu, Zn, and Pb in oil field brines is described. The elements are concentrated by passing 200 ml of the brine through a column of Dowex A-1 chelating resin. The pH of the resin is adjusted to 4.5 with ammonium chloride. At this pH, the trace metals are retained on the resin and the sodium and other alkali metals allowed to pass through. The metals are then eluted with 1 N HCl to a final volume of 50 ml and the concentration of the elements determined by atomic absorption. The method is compared with the standard additions method and coefficients of variation calculated for both methods. The advantages and disadvantages of both methods are discussed. A similar method is described for the extraction and analysis of Ca, Mg, and Sr. Six oil field brines were analyzed using the described method and the results tabulated.
Candidate Genetic Risk Factors of Stroke: Results of a Multilocus Genotyping Assay
Authors: Lalouschek Wolfgang , Endler Georg , Schillinger Martin , Hsieh Kety , Lang Wilfried , Cheng Suzanne , Bauer Peter , Wagner Oswald , Mannhalter Christine
Published: February 2007

Background: Epidemiological studies indicate that genetic factors play a role in the risk of stroke, particularly in younger individuals, but the role of single-nucleotide polymorphisms (SNPs) is controversial. We tested the possible association of a number of previously described SNPs with stroke risk.

Methods: We investigated the prevalence of 60 polymorphisms located in 35 genes in 450 white patients who suffered an acute stroke or transient ischemic attack before the age of 60 years and in 817 healthy control individuals by a multilocus PCR-based assay. The controls were randomly selected from attendees of a health service program. Genetic variations were detected by hybridization to nylon strips (Roche Molecular Systems) containing detection oligonucleotides for the SNPs. We used P values of <0.05 for confirmatory analysis of the SNPs in the genes for APOE (allele 4), angiotensin converting enzyme, factor V, prothrombin, and methylenetetrahydrofolate reductase. To account for multiple testing we defined a P value of <0.001 as statistically significant for all exploratory tests. The genes represented in the test panel by more than 1 SNP were also evaluated by haplotype analysis.

Results: Frequencies of all 60 tested SNPs among patients and controls were very similar. No SNP reached an odds ratio of 2, and no association with stroke risk was statistically significant.

Conclusions: Our results do not indicate a clinically relevant role of any of the investigated SNPs for stroke risk in individuals hospitalized for ischemic stroke/transient ischemic attack before or at 60 years of age. These results are in accordance with previous metaanalyses showing at most a very modest or no significant effect of these SNPs on stroke risk.
LC-MS/MS Quantification of Zn-α2 Glycoprotein: A Potential Serum Biomarker for Prostate Cancer
Authors: Bondar Olga P , Barnidge David R , Klee Eric W , Davis Brian J , Klee George G
Published: February 2007

Background: Zn-α2 glycoprotein (ZAG) is a relatively abundant glycoprotein that has potential as a biomarker for prostate cancer. We present a high-flow liquid chromatography–tandem mass spectrometry (LC-MS/MS) method for measuring serum ZAG concentrations by proteolytic cleavage of the protein and quantification of a unique peptide.

Methods: We selected the ZAG tryptic peptide 147EIPAWVPEDPAAQITK162 as the intact protein for quantification and used a stable isotope-labeled synthetic peptide with this sequence as an internal standard. Standards using recombinant ZAG in bovine serum albumin, 50 g/L, and a pilot series of patient sera were denatured, reduced, alkylated, and digested with trypsin. The concentration of ZAG was calculated from a dose–response curve of the ratio of the relative abundance of the ZAG tryptic peptide to internal standard.

Results: The limit of detection for ZAG in serum was 0.08 mg/L, and the limit of quantification was 0.32 mg/L with a linear dynamic range of 0.32 to 10.2 mg/L. Replicate digests from pooled sera run during a period of 3 consecutive days showed intraassay imprecision (CV) of 5.0% to 6.3% and interassay imprecision of 4.4% to 5.9%. Mean (SD) ZAG was higher in 25 men with prostate cancer [7.59 (2.45) mg/L] than in 20 men with nonmalignant prostate disease [6.21 (1.65) mg/L, P = 0.037] and 6 healthy men [3.65 (0.71) mg/L, P = 0.0007].

Conclusions: This LC-MS/MS assay is reproducible and can be used to evaluate the clinical utility of ZAG as a cancer biomarker.
Asymmetric Dimethylarginine, Smoking, and Risk of Coronary Heart Disease in Apparently Healthy Men: Prospective Analysis from the Population-Based Monitoring of Trends and Determinants in Cardiovascular Disease/Kooperative Gesundheitsforschung in der Region Augsburg Study and Experimental Data
Authors: Maas Renke , Schulze Friedrich , Baumert Jens , Löwel Hannelore , Hamraz Khatera , Schwedhelm Edzard , Koenig Wolfgang , Böger Rainer H
Published: February 2007

Background: An increased plasma concentration of the endogenous nitric oxide synthase inhibitor asymmetric dimethylarginine (ADMA) predicts adverse clinical outcome in patients with coronary heart disease. We investigated the association between plasma concentrations of ADMA and risk in initially healthy smoking and nonsmoking men.

Methods: Participants for this nested case-control study came from the population-based Monitoring of Trends and Determinants in Cardiovascular Disease/Kooperative Gesundheitsforschung in der Region Augsburg study. ADMA was measured by liquid chromatography–tandem mass spectrometry in 88 men with incident coronary events (fatal and nonfatal myocardial infarction and sudden cardiac death) and 254 age-matched controls, with a median (interquartile range) follow-up of 6.2 (3.3–7.9) years.

Results: After adjustment for potential confounders, the relative risk for a future coronary event was 2.00 [95% confidence interval (CI) 1.27–3.16; P = 0.003] for smokers compared with nonsmokers and 1.35 (95% CI 0.78–2.33; P = 0.282) for the top vs the bottom tertile of the ADMA distribution. In cases and controls, lower ADMA plasma concentrations were observed in smokers. Analysis of ADMA-associated risk in smokers and nonsmokers separately revealed substantial differences: the adjusted relative risk for future coronary events (top vs bottom tertile of the ADMA distribution) was 0.48 (95% CI 0.16–1.46; P = 0.198) in smokers and 2.40 (95% CI 1.14–5.08; P = 0.021) in nonsmokers. Exposure of human endothelium-derived EAhy 926 cells to tobacco smoke enhanced expression of the ADMA metabolizing enzyme dimethylarginine dimethylaminohydrolase 2 and reduced ADMA concentration.

Conclusions: In apparently healthy men, increased ADMA predicts the risk for coronary events in nonsmokers, but not in smokers. This may be explained in part by an alteration of ADMA metabolism by tobacco smoke.
Statins and the Risk of Pneumonia: A Population‐Based, Nested Case‐Control Study
Authors: Schlienger Raymond G. , Fedson David S. , Jick Susan S. , Jick Hershel , Meier Christoph R.
Published: February 2007

Study Objective. To determine if the use of statins affects pneumonia‐related outpatient visits, hospitalizations with survival, and deaths.

Design. Population‐based, retrospective, nested case‐control analysis.

Data Source. United Kingdom‐based General Practice Research Database.

Participants. The study population (134,262 patients aged > 30 yrs) consisted of 55,118 patients who took statins and/or fibrates, 29,144 patients with hyperlipidemia not taking lipid‐lowering agents, and 50,000 randomly selected patients without hyperlipidemia and without lipid‐lowering treatment.

Measurements and Main Results. We identified 1253 patients with pneumonia and matched them with 4838 control subjects based on age, sex, general practice, and index date. After adjusting for comorbidity and frequency of visits to general practitioners, we calculated the risks (odds ratios with 95% confidence intervals) of uncomplicated pneumonia, hospitalization for pneumonia with survival, and fatal pneumonia in participants who used statins compared with those who did not. Current statin users had a significantly reduced risk of fatal pneumonia (adjusted odds ratio 0.47, 95% confidence interval 0.25–0.88) and slightly but not significantly reduced risks of uncomplicated pneumonia and pneumonia hospitalization with survival. Recent or past statin use and fibrate use at any time were not associated with a reduced risk of pneumonia.
Adjunctive Dexmedetomidine Therapy in the Intensive Care Unit: A Retrospective Assessment of Impact on Sedative and Analgesic Requirements, Levels of Sedation and Analgesia, and Ventilatory and Hemodynamic Parameters
Authors: MacLaren Robert , Forrest Laurel K. , Kiser Tyree H.
Published: February 2007

Study Objective. To determine if adjunctive dexmedetomidine therapy in intensive care patients alters requirements for and levels of sedation and analgesia, and to describe hemodynamic and ventilatory parameters.

Design. Retrospective, noncontrolled, descriptive study of clinical practice.

Setting. Four intensive care units (ICUs; medical, surgical, neurosurgical, or burn) in a university‐affiliated medical center.

Patients. Forty patients who were already receiving sustained use of propofol, lorazepam, or fentanyl when dexmedetomidine was started.

Measurements and Main Results. Medical records were identified by searching the pharmacy database for patients who had received continuous‐infusion dexmedetomidine from January 2000‐January 2003 while in one of the four ICUs. Primary end points were discontinuation or dosage reduction of other sedatives or fentanyl from the hour before to 6 hours after starting dexmedetomidine. Other outcomes included levels of sedation and analgesia before and after dexmedetomidine and description of ventilatory and hemodynamic parameters. The initial dexmedetomidine rate of 0.4 ± 0.25 μg/kg/hour changed minimally through 47.4 ±61.1 infusion hours. At 6 hours, 11 of 13 patients receiving propofol, 14 of 23 receiving lorazepam, and 4 of 30 receiving fentanyl had the respective agent discontinued. With dexmedetomidine, the hourly rates and cumulative daily doses were reduced only for propofol. Adequate sedation occurred at rates of 64.6% and 47.9% during the 24‐hour periods before and after dexmedetomidine was started, respectively (p=0.001). Four and 12 patients had severe agitation before and after, respectively (p=0.05). One and 12 patients had severe pain before and after, respectively (p=0.02). Nine patients experienced hypotension or bradycardia. Twenty‐two patients were successfully extubated within 24 hours of starting dexmedetomidine.

Conclusions. Adjunctive dexmedetomidine reduces sedative requirements but does not alter analgesic requirements. However, dexmedetomidine was associated with enhanced agitation, severe pain, and hemodynamic compromise. Transitioning to dexmedetomidine from other sedatives and analgesics may not provide optimal sedation and analgesia. Future studies are needed to evaluate dexmedetomidine as a bridge to extubation.
Amiodarone Prophylaxis for Atrial Fibrillation After Cardiac Surgery: Meta‐Analysis of Dose Response and Timing of Initiation
Authors: Buckley Mitchell S. , Nolan Paul E. , Slack Marion K. , Tisdale James E. , Hilleman Daniel E. , Copeland Jack G.
Published: February 2007

Study Objective. To investigate a possible dose‐response relationship between amiodarone and reduction in incidence of postoperative atrial fibrillation, and to determine whether pre‐ or postoperative initiation of amiodarone is superior.

Design. Meta‐analysis of randomized controlled trials.

Data Source. MEDLINE and EMBASE databases and the Cochrane Central Register of Controlled Trials for English‐language reports published between 1966 and December 2005.

Measurements and Main Results. Of 23 identified randomized controlled trials of amiodarone prophylaxis of postoperative atrial fibrillation, 14 were included in the final analysis. These studies enrolled a total of 2864 patients. For each study, the total administered amiodarone dose—categorized as low (< 3000 mg), medium (3000–5000 mg), or high (> 5000 mg)—and preoperative versus postoperative initiation were aggregated by using meta‐analytic techniques. The incidence of postoperative atrial fibrillation was significantly reduced by amiodarone compared with placebo (p<0.001). Although the odds of developing atrial fibrillation appeared to be somewhat higher in the low‐dose group, no significant differences were noted in the odds ratios (ORs) of developing atrial fibrillation among the low‐, medium‐, and high‐dose groups: OR 0.58, 95% confidence interval (CI) 0.44–0.77; OR 0.45, 95% CI 0.30–0.69; and OR 0.44, 95% CI 0.33–0.58; respectively (p=0.238). In addition, the ORs for atrial fibrillation development associated with preoperative and postoperative initiation of amiodarone were not significantly different (OR 0.50, 95% CI 0.39–0.63; and OR 0.48, 95% CI 0.37–0.63; respectively, p=0.862).

Conclusion. Total amiodarone doses of 3000 mg or higher may be more effective than lower doses in reducing the rate of postoperative atrial fibrillation after cardiac surgery. Preoperative initiation of amiodarone appears to be unnecessary. These findings require confirmation in prospective, randomized trials.