bluuebunny/crossref_metadata_2025 huggingface dataset:
Discrimination of Enantiomers at Microgram Level Using Liquid Crystalline Solutions
Authors: Korte E. H.
Published: September 2005

In a nematic liquid crystal a cholesteric, i.e., helical, arrangement of molecules is induced by doping with a low concentration of chiral molecules. This structure is oppositely coiled for enantiomers leading to countercurrent infrared rotatory dispersion curves. It is shown that by employing this effect, enantiomers can be discriminated even if only microgram quantities are available. The measurement of the rotatory dispersion using a normal infrared spectrometer is described, and examples to demonstrate the applicability are given.
A Molecular Orbital Treatment of the Electronic Structure and Spectra of Tautomeric Rhodanines
Authors: Hilal Rifaat , Ead H. , Osman A.
Published: September 2005

An experimental as well as theoretical investigation of the electronic structure and tautomeric equilibria of 2,4-thiazolidinedione, 4-thiazolidinone-2-thione (rhodanine), 2-thiazolidinone-4-thione (isorhodanine) and 2,4-thiazolidinedithione (thiorhodanine) has been conducted. The origin of the electronic absorption transitions and the effect of replacing oxygen by sulfur atoms on coplanarity have been discussed. The solvent and pH dependence of the electronic spectra of the studied compounds indicate that there should be a statistical distribution of the ground and excited states between all possible tautomeric structures. This has been confirmed via molecular orbital computations. The calculated pK values have been interpreted with a mechanism based on the calculated deprotonation energies. Results of the present investigation concur with the chemistry of the studied compounds and reveal that these compounds are far from complete homocyclization.
Temperature Determination on a 9.2 MHz Inductively Coupled Plasma Source Using N2+ Bands as Monitor
Authors: Zeeman P. B. , Terblanche S. P. , Visser K. , Hamm F. H.
Published: September 2005

In recent experiments with a 9.2 MHz inductively coupled plasma assembly air was used as cooling gas. The molecular N2+ band system appeared on the photographic plates taken in the first order of a 3.4 m Jarrell-Ash Ebert grating spectrograph. The rotational lines of this band system was used to evaluate the temperature of the plasma tail flame at various heights above the load coil. These varied from approximately 8000°K at 17 mm above the coil to 6400 at 41 mm.
Vibrational Assignments of Organosilanetriols. II. Crystalline Phenylsilanetriol and Phenylsilanetriol-D3
Authors: Ishida H. , Koenig J. L.
Published: September 2005

Fourier transform infrared spectra (3800 to 450 cm−1) and laser Raman spectra (4000 to 0 cm−1) of crystalline phenylsilanetriol and phenylsilanetriol-d3, and liquid state phenylsilanetriol and phenylsilanetriol-d3 are first reported. Complete band assignments are attempted. All vibrational modes of the SiOH group except for the SiC torsional mode, including the SiOH in-plane and out-of-plane bending modes, are observed. In addition to the phenylsilanetriols, infrared and laser Raman spectra of crystalline diphenylsilanediol and triphenylsilanol are also studied to aid the band assignments.
A Sample Holder for Raman Spectroscopic Studies of Crystals at Low Temperatures. Application: Phase Transition in Succinonitrile
Authors: Cavagnat R. , Cornut J. C. , Couzi M. , Daleau G. , Huong P. V.
Published: September 2005

A device to improve the thermal exchange between the cold tail, in a Raman cryostat working at liquid helium temperatures, and the crystalline sample is described and a side-reference method for the temperature measurement is used. The method is then applied to the study of the phase transition in succinonitrile.
High Temperature Absorption of the 3.39 µm He-Ne Laser Line by Small Hydrocarbons
Authors: Olson D. B. , Mallard W. G. , Gardiner W. C.
Published: September 2005

Absorptivity measurements for the 3.39 µm He-Ne laser line are reported for methane, acetylene, ethylene, ethane, propane, n-butane, and n-pentane over the temperature range 300 < T < 2000°K. Shock-heated mixtures containing formaldehyde and methyl iodide showed no absorption or transient absorption at any temperature that could be attributed to formaldehyde or methyl radicals. The temperature dependence of the absorptivities of the C2 and higher hydrocarbons was much weaker than for methane. Comparison with simple theoretical expectations and broad-band absorptivities showed that the higher hydrocarbon absorptions include quite large numbers of absorbing states.
Optoacoustic Spectrometry of Surfaces: Dielectric Coatings for Laser Mirrors
Authors: Adams M. J. , Beadle B. C. , Kirkbright G. F. , Menon K. R.
Published: September 2005

A double-beam optoacoustic spectrometer has been employed to obtain the transmission, reflectance, and absorption spectra of a number of dielectric-coated glasses used for laser mirror applications. The complementary nature of these spectra is demonstrated and, by simply reversing the sample within the optoacoustic cell, the absorption spectra of the surface coating and the substrate may be determined independently.
Vibrational Assignments of Organosilanetriols. I. Vinylsilanetriol and Vinylsilanetriol-D3 in Aqueous Solutions
Authors: Ishida H. , Koenig J. L.
Published: September 2005

Infrared and laser Raman spectra of vinylsilanetriol and vinylsilanetriol-d3 in H2O and D2O, respectively, are reported. Complete band assignments of the silanetriol group are discussed. In addition, band assignments of the vinyl group are reexamined. Most of the related bands to silanol are very broad or weak in intensity except for the SiO stretching modes which are potentially of use for structural analysis of silane coupling agents in the presence of glass surfaces.
Gas Analysis by Computer-Controlled Microwave Rotational Spectrometry
Authors: Hrubesh Lawrence W.
Published: September 2005

Microwave rotational spectrometry has inherently high resolution and is thus nearely ideal for qualitative gas mixture analysis. Quantitative gas analysis is also possible by a simplified method which utilizes the ease with which molecular rotational transitions can be saturated at low microwave power densities. This article describes a computer-controlled microwave spectrometer which is used to demonstrate for the first time a totally automated analysis of a complex gas mixture. Examples are shown for a complete qualitative and quantitative analysis, in which a search of over 100 different compounds is made in less than 7 min, with sensitivity for most compounds in the 10 to 100 ppm range. This technique is expected to find increased use in view of the reduced complexity and increased reliability of microwave spectrometers and because of new energy-related applications for analysis of mixtures of small molecules.
Infrared Spectra of Some Nonreduced Methanation Catalysts
Authors: Bradley Eugene B. , Stencel John M.
Published: September 2005

The infrared spectra (4000 to 400 cm−1) of two commercial nonreduced methanation catalysts have been recorded and interpreted. The catalysts are prepared as mixtures of (a) nickel in a silica support and (b) nickel in an alumina support. Graphite is added to these mixtures as a binder to facilitate pressing of catalyst pellets for commercial use. It is revealed in the spectra of the catalysts that although (a) is prepared to have a simple NiO/SiO2 composition the silica support is not of the form SiO2; rather the spectral characteristics are similar to those found for linear chain silicates. In (b) the Al—O vibrations are characteristic of amorphous Al2O3, and H2O is tightly bound in the pellet. The CO3= ion is present in both (a) and (b). It is not bound to Ni in either (a) or (b), but it is bound in the silicate structure of (a) and associated with Al in (b). The presence of the ion cannot be explained by only in situ generation from atmospheric CO2 and H2O, but its presence must be due to residual CO3= from the catalyst preparation.
Laser Saturation Broadening in Flame Absorption and Fluorescence Experiments
Authors: Hosch Jimmy W. , Piepmeier Edward H.
Published: September 2005

Atomic absorption and fluorescence excitation spectral profiles of Na in an air/C2H2 flame were scanned for high sample irradiances. The light source was a flash lamp pumped tuneable dye laser having a spectral bandwidth of less than 0.005 nm. The transmittance profile disappeared into the noise level of the unity transmittance line for an irradiance of 500 kW/cm2. The halfwidth of the fluorescence excitation spectral profile increased from 0.0010 to 0.0019 nm for an increase in irradiance from 0.2 to 42 kW/cm2. Exciting the 588.99 nm Na line with the laser tuned to 588.53 nm allowed baseline resolution to be achieved between the fluoresced light at 588.99 nm and the scattered light at 588.53 nm. The possibility of using such far wing excitation to improve detection limits for resonance fluorescence is discussed.
Microphotometric Errors for Photographically Recorded Spectral Lines of Nonuniform Half-Width
Authors: McGonagle L. C. , Holcombe J. A.
Published: September 2005

Various microphotometric (or densitometric) techniques for generating quantitative intensity information from photographically recorded spectral lines of time or spatially resolved sources are discussed. The impact of various parameters on the accuracy of quantitative densitometry is presented. These parameters include line widths of the calibration spectrum, source line broadening, microphotometer scan slit width and the optical density of the photographic image. Nonrandom errors associated with the use of various microphotometer slit widths for spectral lines of nonuniform half-width are presented. Spectral lines which are uniform and exhibit slit width or diffraction limited resolution can be scanned with any size microphotometer slit width as long as the calibration curve is prepared using the same scan slit width. The use of microphotometer slit widths narrower than the line width produce H and D curves with maximal γ and increased accuracy in the final intensity value. A density-to-intensity conversion accuracy with a 6% average error was determined for SA-1 plates. For sources whose line widths are larger than the spectrometer bandpass, minimal errors are generated by using a narrow line source for calibration and scanning this spectrum with a slit width less than the line width. Scanning of the broadened line of interest is accomplished using a scan slit width equal to approximately twice the spectrometer slit width. Under these conditions an average error of approximately 11% was determined experimentally for SA-1 plates.
Spectra and Structure of Silicon-Containing Compounds. X. Infrared and Raman Spectra of Methoxytrimethylsilane and Methoxy-D3-Trimethylsilane
Authors: Durig J. R. , Streusand B. J.
Published: September 2005

The infrared (20 to 3100 cm−1) and Raman (10 to 3100 cm−1) spectra of gaseous (CH3)3SiOCH3 and (CH3)3SiOCD3 have been recorded. The Raman spectra of both liquids and the infrared and Raman spectra of the “light” compound in the solid state have also been recorded. A vibrational assignment based upon depolarization ratios, frequency shifts with isotopic substitution, and group frequencies is proposed. The Si—O torsional mode was observed at 67 cm−1 which gives a barrier to internal rotation of 1.02 kcal/mol. Strong mixing of the Si—O—C bending mode with the C—Si—C bends is proposed. The CH3—O torsion was not observed.
A Practical Real-Time Fourier Transform Infrared Detector for Liquid Chromatography
Authors: Vidrine D. Warren , Mattson David R.
Published: September 2005

A practical Fourier transform infrared system for real-time liquid chromatographic detection is described. Simple flowcell detection with automatic solvent subtraction is used, and detection of 500 ng of injected paraffin oil is demonstrated. Results from several chromatographic runs illustrate the system capability to serve as a real time infrared detector and simultaneously acquire infrared spectra.
Instrumental Sources of Noise in a Pulsed Dye Laser Double Beam Spectrometer
Authors: Hosch Jimmy W. , Piepmeier Edward H.
Published: September 2005

Reducing the noise in the ratio of the signals for the two beams in a double beam spectrometer that uses a pulsed laser as a light source depends upon the ability of each beam to respond equally to all parts of the cross section of the laser beam. Optical components that are free of bulk and surface scattering sites are important. An opal glass filter placed near each detection system, in a position to fill its aperture, helps to improve the shot-to-shot reproducibility of the ratio. The best results are obtained when the spatial mode structure, or the cross section intensity pattern, of the laser is relatively reproducible.
Evaluation of Inductively Coupled Plasma Optical Emission Spectrometry as a Method for the Elemental Analysis of Organic Compounds
Authors: Windsor David L. , Denton M. Bonner
Published: September 2005

The application of inductively coupled plasma optical emission spectrometry (ICP-OES) to the elemental analysis of organic compounds is evaluated successfully for seven nonmetallic elements. A comparison of this method with previously reported microwave techniques shows that, while both methods are sensitive (detection limits in the low nanogram region), ICP-OES has fewer complications and appears to be less prone to interferences than the analogous microwave techniques. The results of these studies suggest that ICP-OES should be applicable to the simultaneous multielement analysis of the gaseous effluents from a gas chromatograph.
A High Resolution Interferometric Accessory for Raman Spectrometers
Authors: Silberman E. , Springer J.
Published: September 2005

Increases in the resolution and light throughput of a Raman spectrometer can be obtained by coupling it to a scanning Fabry-Perot interferometer. A relatively inexpensive accessory that will not interfere with the normal use of the spectrometer is described. A test run with naphthalene at 77°K showed errors in the current interpretation of the spectrum.
PROBE — Profile Resolution Obtained by Excitation
Authors: Measures R. M.
Published: September 2005

A new approach for evaluating, with spatial resolution, the line of sight properties of a specific constituent is proposed. This PROBE (profile resolution obtained by excitation) concept involves the use of two counter-propagating laser pulses; a pump pulse to condition the medium and a probe pulse to interrogate the medium where the pulses overlap. In this way, information regarding the spatial distribution of a species is transformed into temporal information in the form of a change in the amplitude of a returned probe pulse. For certain situations the PROBE technique offers several advantages over scattering or laser induced fluorescence methods. A theoretical formulation of the concept clearly indicates the importance of the lifetime of the pumped state.
Coupled Resonance Raman, Visible Absorption and Electrochemistry—Applications of a Novel Circulating Cell to Multispectral and Redox Investigations of the Heme Proteins Carboxyhemoglobin and Cytochrome c
Authors: Anderson James L. , Kincaid James R.
Published: September 2005

A small volume, self-contained, anaerobic circulating flow cell has been developed and applied to the resonance Raman investigation of two heme proteins: carboxyhemoglobin and cytochrome c. The cell has been demonstrated to be effective in reducing photodissociation of light-sensitive compounds. The flow performance is competitive with several alternative approaches. Electrochemical methods have been coupled with visible absorption and resonance Raman spectroscopy to titrate and determine potentiometrically the formal reduction potential of cytochrome c. Agreement between the results of visible and Raman spectral data demonstrates the feasibility of utilizing quantitative resonance Raman spectroscopy as a probe of formal reduction potentials of enzyme components.
Sensitivity of a Fourier Transform Infrared Spectrometer
Authors: Mattson David R.
Published: September 2005

The theoretical sensitivity of a Fourier transform infrared spectrometer as measured by the signal/noise ratio of a 100% line is calculated. This theoretically expected sensitivity is shown to be in excellent agreement with experimental values observed for a particular spectrometer configuration. The experimental method used to quantify the performance level of the spectrometer may also be applied as a general systems test for Fourier transform infrared spectrometers.
Infrared Spectra of Aluminum Hydroxide Chlorides
Authors: Riesgraf Diane A. , May Mary L.
Published: September 2005

Infrared spectra of aluminum chloride and aluminum hydroxide chloride solute species were determined using a Fourier transform infrared spectrometer. The solutions which were examined contained: aluminum chloride; an aluminum hydroxide chloride with an OH/A1 ratio of 2.4, prepared by dissolving freshly prepared aluminum hydroxide gel in an aluminum chloride solution; and an aluminum hydroxide chloride with an OH/A1 ratio of 2.5, prepared by reacting aluminum metal with an AlCl3 solution. Significant differences in the infrared spectra were observed. All solute spectra contained bands in the 2500 to 3100 cm−1 region for the stretch of water coordinated to aluminum, with the bands for aluminum chloride solutions most intense. In the bending region for Al—O—H, bands were observed at 970 to 1080 cm−1. The polymeric solute species also had absorption bands, although at different frequencies, in the OH stretch region, 3300 to 3700 cm−1, and in the frequency region from 600 to 800 cm−1.
Establishment of Compromise Conditions for Multielement Analysis by Inductively Coupled Plasma Emission Spectrometry: A Preliminary Report
Authors: Berman S. S. , McLaren J. W.
Published: September 2005

As a first step in the establishment of compromise conditions for multielement analysis by inductively coupled plasma (ICP) emission spectrometry, the effects of three critical ICP operating parameters on atomic and ionic emission of elements of interest were investigated in detail. The line/background ratios for both atom and ion lines were found to be very sensitive to (1) the aerosol Ar flow rate, (2) the observation height, and (3) the power, and optimum conditions for ion lines were often quite different from those for atom lines. In addition to assisting in the eventual choice of compromise ICP operating conditions for simultaneous multielement analysis, the results emphasize the importance of precise control of these critical parameters in analytical applications of the ICP.
Infrared Emission Spectroscopy Applied to the Oxidation of Molybdenum
Authors: Gratton L. M. , Paglia S. , Scattaglia F. , Cavallini M.
Published: September 2005

The present work points out the utility of infrared emission spectroscopy as applied to the study of the oxidation of metal surfaces. It is shown that good results can be achieved even with standard dispersion spectrophotometers. The work shows emission spectra obtained at a temperature of only 133°C from samples of about 380 A thickness and 2 cm2 area. The molybdenum oxides are particularly useful to test the capability of the infrared emission spectroscopy technique. The study of the behavior of the emission bands and the differences between the emission and absorption spectra show that this technique cannot only be an alternative to absorption spectroscopy, but also can give different data from those which can be achieved by the absorption technique. Spectra are recorded directly on the oxidizing sample. The increase in intensity and the change in the shape of the bands are monitored while the oxidation is performed. It is noted that with infrared emission spectroscopy, sample preparation is greatly simplified.
Raman Microprobe Characterization of Residual Carbonaceous Material Associated with Urban Airborne Particulates
Authors: Blaha J. J. , Rosasco G. J. , Etz E. S.
Published: September 2005

Analyses of individual urban airborne particulates were conducted in the Raman microprobe. In addition to the spectral features characteristic of the particle, two features at ∼1350 and ∼1600 cm−1 have been observed. The appearance of these bands is found to vary a function of the laser irradiance. By modeling experiments, it is demonstrated that these two bands can be explained by the presence of carbon in a form analogous to polycrystalline graphite. In air particulates the source of the carbon can be either “graphitic soot” or an organic “contaminant” which converts to polycrystalline graphite upon exposure to the laser beam.
Application of X-ray Photoelectron Spectroscopy to the Study of Fly Ash
Authors: Campbell James A. , Smith Richard D. , Davis L. E.
Published: September 2005

X-ray photoelectron spectroscopy has been used to identify and determine the oxidation states of a number of major and minor elements present on the surface of fly ash particles. With the use of a sputtering-etching procedure, relative concentrations as a function of depth were obtained for Si, Al, Fe, Ca, Na, C, O, and S. The concentrations of Na, C, O, and S were found to decrease and Si, Al, and Fe were found to increase upon sputtering to a depth of approximately 50 Å.
Infrared Spectroscopy in Supersonic Molecular Beams: ν3 Band of SF6 at 10.6 µm
Authors: Kim K. C. , Holland R. F. , Filip H.
Published: September 2005

A band contour analysis is shown for the ν3 absorption of the flow-cooled SF6. Temperature dependence of the absorption feature is simulated. The possible utility of this technique as a temperature probe of flow-cooled gas mixtures is discussed.
The Vibrational Spectra and Structure of Mucochloric and Mucobromic Acids
Authors: Moore R. D. , Katon J. E.
Published: September 2005

The infrared spectra of mucochloric acid (2,3-dichloro-4-oxo-2-butenoic acid), mucochloric acid-d1, and mucobromic acid (2,3-di-bromo-4-oxo-2-butenoic acid) have been recorded in the solid and liquid phases in the region 4000 to 50 cm −1. The solid phase Raman spectral data of mucochloric and mucobromic acids are also reported. It has been found that mucochloric acid exists in the solid and liquid phases in the hydroxylactone configuration (2,3-dichloro-4-hydroxybut-2-enelactone) rather than the chain configuration indicated by the name.
Absorbance Ratio Calculations from the Infrared Spectra of Thick Liquid Films
Authors: Cleverley Barry , Dolby Rex
Published: September 2005

Thick liquid films have been used for determining low concentrations of a component of a liquid mixture by the infrared absorbance ratio method. The major component must be represented by absorption bands that would be insignificant in the spectrum of a thinner sample.
An Auger Electron Spectroscopic Study of the Diffusion of Sulfur, Carbon, and Chlorine in Powdered Titanium
Authors: Lofton C. P. , Swartz W. E.
Published: September 2005

Auger electron spectroscopy has been employed to study the diffusion of sulfur, carbon, and chlorine in powdered α-titanium. Arrhenius analysis of the diffusion rates indicates that the activation energies are 15.5, 6.2, and 9.8 kcal/mol for sulfur, carbon, and chlorine, respectively. These activation energies are consistent with diffusion along grain boundaries within the α-titanium.
Aerosols, Aerodynamics, and Atomic Analysis
Authors: Skogerboe R. K. , Olson K. W.
Published: September 2005

The suppression of atomic excitation in a microwave-induced plasma due to the presence of sodium has been studied for three different nebulization systems. Evaluation of the factors affecting this effect has shown that its occurrence depends on the nature of the analytical aerosol introduced and the aerodynamic features of the sample nebulization system. The results indicate that the sodium suppression effects observed can be largely accounted for by reductions in the analyte transport efficiency due to changes in the aerodynamic characteristics of the aerosol resulting from variations in the salt content of the nebulized solutions. It is further shown that these effects may be generally predicted on the basis of fluid mechanical principles and that these may be used to design systems to eliminate the interferences. The study underscores the essentiality of considering aerodynamic factors in formulating mechanistic explanations for interference effects in flames and plasmas.
The Determination of Total Iron in Venezuelan Laterites: The Investigation of Interferences of Aluminum and Silicon on the Determination of Iron in the Fluoboric-Boric Acid Matrix by Atomic Absorption
Authors: Brecque J. J. La , Mendelovici E. , Villalba R. E. , Bellorin C. C.
Published: September 2005

An interference-free atomic absorption method for the determination of total iron in geological samples has been adopted. The method is based on the conventional standard curve technique employing the 386 nm atomic absorption line in the fluoboric-boric acid matrix. The use of the 386 nm line instead of the 248.3 nm line is discussed, as well as the advantages of the hydrofluoric acid dissolution of the sample. A comparison of different methods is given in search of one for routine determinations in this laboratory. Interference studies of aluminum and/or silicon on the iron determination conclude that these interferences do not exist under the conditions of this method. The literature on such interferences is reviewed and they are discussed. The proposed method was used to determine total iron in six reference materials and the results were in good agreement with the reported values. Finally, total iron was determined in a preliminary profile of Venezuelan laterites (ferrouginous bauxites).
Infrared Spectrophotometric Determination of Trace Water in Selected Organic Solvents
Authors: Barbetta Angelo , Edgell Walter
Published: September 2005

A spectrophotometric method of trace water analysis in organic solvents is reported. It is based on the water fundamental at 2.8 µ and has been applied to hexamethylphosphoramide, nitromethane, acetonitrile, oxetane, dimethylsulfoxide, 1,1-dimethoxyethane, dimethylformamide, tetrahydrofuran, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydropyran, 1,2-dimethoxyethane, n-butylmethylether, and pyridine. Methods for dealing with solvent absorption and water pickup by samples, and the preparation of water-free samples for reference are discussed. Some comments are made on drying these solvents with molecular sieves.
A Modular Michelson Interferometer for Fourier Transform Spectrochemical Measurements from the Mid-Infrared to the Ultraviolet
Authors: Horlick Gary , Yuen W. K.
Published: September 2005

A versatile Michelson interferometer system capable of Fourier transform spectrochemical measurements from the uv to the mid-ir has been developed in our laboratory. Laser fringe referencing is used in the interferometer system to sequence digitization and the velocity of the air bearing mirror drive system is controlled with the laser fringe signal using phase-locked loop techniques. Interferograms can be time averaged under white light interferogram control. The modular design of the interferometer is such that the detector, beamsplitter, and source can all be changed and the interferometer realigned in a matter of a few minutes. Interferograms are acquired and transformed with a PDP 11 minicomputer. This system is described in detail and its application to spectrochemical measurements in the mid-ir and uv-visible is briefly illustrated.
A Critical Evaluation of Fabrication Details and Operating Conditions Influencing Microwave-Excited Electrodeless Discharge Lamps
Authors: Goode Scott R. , Otto David C.
Published: September 2005

Results are presented for a detailed study of how the fabrication and excitation conditions influence the optical performance of microwave-excited electrodeless discharge lamps. The shape of the lamp is shown to be a critical parameter. The proper choice of experimental conditions yields a source which is up to 2000 times more intense, has a signal/noise ratio 50 times greater, and has a greater spectral overlap with the absorption line than a conventional hollow cathode discharge lamp. Analytical data are presented, and the improvement in sensitivity is shown to be appreciable.
Detection of Water Pollutants by Laser Excited Resonance Raman Spectroscopy; Pesticides and Fungicides
Authors: Thibeau Richard J. , van Haverbeke Laurent , Brown Chris W.
Published: September 2005

The feasibility of resonance Raman spectroscopy in the detection of hazardous chemicals in water has been tested on some nitrophenol-based pesticides and fungicides. In most cases, detection limits below the parts per million level were obtained. The method was also tested on an artifically polluted river water sample.
An Evaluation of the Practical Performance of a Digilab FTS-14 Fourier Transform Infrared Interferometer Working in the Region of 4000 to 400 cm−1
Authors: Chenery D. H. , Sheppard N.
Published: September 2005

The performance of a Digilab FTS-14 Fourier transform infrared interferometric spectrometer has been evaluated in terms of (1) sensitivity and signal/noise ratio (in comparison with a high quality infrared grating instrument), (2) the attainment of very high absolute signal/noise ratios by use of double-precision arithmetic, (3) photometric accuracy, (4) wavenumber accuracy, (5) resolution, (6a) water vapor cancellation and double-beam operation, (6b) ratioing facilities against stored reference spectra, (7) the measurement of very high optical densities, and (8) miscellaneous other operational considerations. It is shown that, compared with a diffraction grating spectrometer of good performance, over most of the spectral region the interferometer enables the attainment of more than an order of magnitude improvement in signal/noise ratio (S/N) for a given time of scan and resolution. This improvement in S/N was found to reach a maximum of about 40 times at 2000 cm−1 when the full wavenumber range (3600 cm−1) is measured with the highest resolution (0.5 cm−1). This corresponds to the measurement of 7200 spectral elements, n. The S/N improvement is proportional to n and is correspondingly reduced for more limited ranges of spectral measurement or for more limited resolutions. The enhanced S/N can alternatively be traded for rapid scanning. The performance of the interferometer is shown to be very good in relation to the other operational parameters listed above. Substantial additional advantages – particularly in relation to automated operation, ratioing of related spectra, and flexibility in modes of plotting wavenumber or intensities – occur from the use of a dedicated minicomputer with, or as part of, a spectrometer.
Development of a Drift-Correction Procedure for a Photoelectric Spectrometer
Authors: Chapman Gilbert B. , Gordon William A.
Published: September 2005

This procedure provides automatic correction for drifts in the radiometric sensitivity of each detector channel in a direct-reading emission spectrometer. Such drifts are customarily controlled by the regular analyses of standards, which provide corrections for changes in the excitational, optical, and electronic components of the instrument. This standardization procedure, however, corrects for the optical and electronic drifts, thus minimizing the time, effort, and cost of regularly processing standards. This method of radiometric drift correction uses a 1000-W tungsten-halogen reference lamp to illuminate each detector through the same optical path as that traversed during sample analysis. The responses of the detector channels to this reference light are regularly compared with channel responses to the same light intensity at the time of analytical calibration in order to determine and correct for drift. The coefficients of variation of these drift corrections average less than 1%. Except for placing the lamp in position, the procedure is fully automated and compensates for changes in spectral intensity due to variations in lamp current. A discussion of the implementation of this drift-correction system is included.
Trace Analysis by Infrared Spectroscopy Using Preconcentration, Separation, and Computer Techniques
Authors: Hannah Robert W. , Pattacini S. C. , Grasselli Jeanette G. , Mocadlo Suzanne E.
Published: September 2005

The use of infrared spectroscopy in trace analysis can be greatly aided by employing preconcentration and/or separation techniques for appropriate samples. In some cases, classical infrared difference spectroscopy or computer treatment of data will be sufficient to identify qualitatively or to quantitate a trace component in a complex mixture. Analysis of aromatic isomers, gasoline additives, drugs, and polymer additives will be described to illustrate the methods.
The Characteristic Pattern of Thioamides in Infrared and Raman Spectra
Authors: Desseyn H. O. , van der Veken B. J. , Herman M. A.
Published: September 2005

A number of simple products, containing the thioamide functional groups, have been investigated in infrared and Raman spectra; from the average appearance and potential energy distribution values, a pattern characteristic for the thioamide groups has been given.
Hyperhomocysteinemia and macromolecule modifications in uremic patients
Authors: Perna Alessandra F. , Capasso Rosanna , Lombardi Cinzia , Acanfora Filomena , Satta Ersilia , Ingrosso Diego
Published: September 2005

Hyperhomocysteinemia is present in the majority of well-nourished chronic renal failure and uremic patients. Most observations reported in the literature come from studies carried out in end-stage renal disease patients treated with hemodialysis. The underlying mechanisms of the toxic effects of homocysteine in uremia related to cardiovascular disease and other disturbances are still under scrutiny. As a consequence, macromolecules (i.e., proteins and DNA) have been found to be altered to various extents. One of the mechanisms of homocysteine toxicity is related to the action of its metabolic precursor, S-adenosylhomocysteine, a powerful methyltransferase competitive inhibitor. Disruption of DNA methylation has been demonstrated to occur as a result of hyperhomocysteinemia, and/or is associated with vascular damage. DNA hypomethylation has been found in the mononuclear cell fraction of uremic patients with hyperhomocysteinemia. Proteins are also targets of homocysteine-dependent molecular damage. The formation of oxidative products with free cysteinyl residue thiol groups has been demonstrated to occur in blood. The latter also represents a mechanism for the transport of homocysteine in plasma. In addition, homocysteine thiolactone has been shown to react with free amino groups in proteins to form isopeptide bonds, in particular at the lysine residue level. Another type of isopeptide bond in proteins may result from the deamidation and isomerization of asparaginyl residues, yielding abnormal isoaspartyl residues, which have been demonstrated to be increased in uremic patients. Folate treatment exerts a partial, but significant, homocysteine-lowering effect in uremic patients and has been shown to improve the changes in macromolecules induced by high homocysteine levels. In conclusion, both DNA and proteins are structurally modified in uremia as a consequence of high homocysteine levels. The role of these macromolecule changes in inducing the clinical complications of hyperhomocysteinemia in these patients, although still conjectural in some respects, is at present sustained by several pieces of evidence.
Homocysteine – a newly recognised risk factor for osteoporosis
Authors: Herrmann Markus , Widmann Thomas , Herrmann Wolfgang
Published: September 2005

Osteoporosis is a widespread problem, which frequently has devastating health consequences through its association with fragility fractures. The total number of fractures, and hence the cost to society, will increase dramatically over the next 50years as a result of demographic changes in the number of elderly people. Thus, prevention of osteoporosis by identifying risk factors or risk indicators, as well as the development of new treatment strategies, are major issues. Recent data suggest that homocysteine (Hcy), folate, vitamin B
Elevated levels of asymmetric dimethylarginine (ADMA) as a marker of cardiovascular disease and mortality
Authors: Böger Rainer H. , Maas Renke , Schulze Friedrich , Schwedhelm Edzard
Published: September 2005

The endothelium plays a crucial role in the maintenance of vascular tone and structure by releasing the endothelium-derived vasoactive mediator, nitric oxide (NO). NO is formed in healthy vascular endothelium from the amino acid precursor L-arginine. Endothelial dysfunction is caused by various cardiovascular risk factors, metabolic diseases, and systemic or local inflammation. One mechanism that explains the occurrence of endothelial dysfunction is the presence of elevated blood levels of asymmetric dimethylarginine (ADMA) – an L-arginine analogue that inhibits NO formation and thereby can impair vascular function. Accumulating evidence from prospective clinical studies suggests that elevated plasma or serum levels of ADMA are associated with an increased risk of major adverse cardiovascular events. This article gives an updated overview of the currently available literature on ADMA and cardiovascular disease from prospective clinical trials. Recently, advances have been made in the development of analytical methods that are reliable and fast enough to allow determination of ADMA in clinical routine.
The potential cocarcinogenic effect of vitamin B12 deficiency
Authors: Friso Simonetta , Choi Sang-Woon
Published: September 2005

Since vitamin B
The vegetarian lifestyle and DNA methylation
Authors: Geisel Jürgen , Schorr Heike , Bodis Marion , Isber Sonia , Hübner Ulrich , Knapp Jean-Pierre , Obeid Rima , Herrmann Wolfgang
Published: September 2005

Vegetarians have a lower intake of vitamin B
Measurement of Transcutaneous Hemoglobin Concentration by Noninvasive White-Light Spectroscopy in Infants
Authors: Rabe Heike , Stupp Natascha , Özgün Murat , Harms Erik , Jungmann Holger
Published: September 2005

Objective. To compare transcutaneously spectroscopically measured hemoglobin values with venous hemoglobin values in infants.

Study Design. Prospective study in healthy preterm and term infants who were breathing spontaneously.

Results. Recordings were obtained from 85 stable infants (median gestational age at measurement: 36 weeks [range: 34–43 weeks]; median body weight: 1890 g [range: 1095–4360 g]). The spectroscopic hemoglobin values were corrected for inhomogeneous distribution of hemoglobin in the tissue. The venous and spectroscopic hemoglobin values were then compared by using the Bland-Altman method, which gave an error of <5%.

Conclusions. This pilot study could illustrate a good relation between the 2 methods for measuring hemoglobin. Larger studies are required to validate the spectroscopic method in those with conditions that affect the skin microcirculation (eg, septicemia).
Explaining the Poor Bacteriologic Eradication Rate of Single-Dose Ceftriaxone in Group A Streptococcal Tonsillopharyngitis: A Reverse Engineering Solution Using Pharmacodynamic Modeling
Authors: Blumer Jeffrey L. , Reed Michael D. , Kaplan Edward L. , Drusano George L.
Published: September 2005

Objective. To explore pharmacokinetic factors underlying the poor bacteriologic eradication rate with a single 500-mg dose of ceftriaxone for streptococcal tonsillopharyngitis and to identify the minimum ceftriaxone dose required for effective treatment.

Methods. Population modeling techniques were applied to pharmacokinetic data derived from paired plasma and tonsil samples from 153 children to assess the contribution of pharmacokinetic variability to patients' responses to ceftriaxone. In addition, a Monte Carlo simulation was performed to determine (1) the amount of time that free ceftriaxone concentrations must exceed the minimum inhibitory concentration (MIC) of group A Streptococcus to achieve bacteriologic eradication and (2) the ceftriaxone dose required to maintain free drug concentrations above the target MIC for the requisite amount of time. Ceftriaxone MICs for group A Streptococcus were obtained from a previous trial, in which all MICs (n = 115) were ≤0.064 mg/L; 33.9% were susceptible at ≤0.016 mg/L, 66.4% were susceptible at 0.032 mg/L, and 1.7% were susceptible at 0.064 mg/L.

Results. Mean population pharmacokinetic parameters and their variances reflected substantial variability of clearance and half-life in the target population. Tonsillar ceftriaxone protein binding was 89.1%. The proportions of 1000 simulated patients with free ceftriaxone concentrations that exceeded MICs of 0.016 mg/L, 0.032 mg/L, and 0.064 mg/L at 24 hours were 71.7%, 65.4%, and 57.2%, respectively, and at 48 hours were 41.8%, 35.8%, and 28.6%, respectively. The amount of time that free ceftriaxone concentrations need to exceed MIC to achieve bacteriologic success was estimated to be 36 hours. Using this time criterion, two 500-mg doses of ceftriaxone separated by 18 hours should achieve a bacteriologic cure rate of ∼95%.

Conclusions. Pharmacokinetic variability and high ceftriaxone tonsillar protein binding explain the high microbiologic failure rate for a single 500-mg dose of ceftriaxone in group A streptococcal tonsillopharyngitis. Monte Carlo simulation suggests that a second dose administered 18 hours after the first will be required to achieve an acceptable bacteriologic cure rate.
The Association Between Television Viewing and Irregular Sleep Schedules Among Children Less Than 3 Years of Age
Authors: Thompson Darcy A. , Christakis Dimitri A.
Published: September 2005

Background. Regular sleep schedules are an important part of healthy sleep habits. Although television viewing is associated with altered sleep patterns and sleep disorders among children and adolescents, the effect of television viewing on the sleep patterns of infants and toddlers is not known.

Objective. To test the hypothesis that television viewing by infants and toddlers is associated with having irregular naptime and bedtime schedules.

Methods. We used data from the National Survey of Early Childhood Health, a nationally representative, cross-sectional study of the health and health care of children 4 to 35 months of age. Our main outcome measures were whether children had irregular naptime and bedtime schedules. Our main predictor was hours of television watched on a daily basis. We performed multivariate logistic regression analyses, adjusting for a variety of factors including demographic information, measures of maternal mental health, and measures of family interactions, to test the independent association of television viewing and irregular naptime and bedtime schedules.

Results. Data were available for 2068 children. Thirty-four percent of all children had irregular naptime schedules, and 27% had irregular bedtime schedules. Mean hours of television viewing per day were as follows: 0.9 hours/day (95% confidence interval [CI]: 0.8–1.0 hours/day) for children <12 months of age, 1.6 hours/day (95% CI: 1.4–1.8 hours/day) for children 12 to 23 months of age, and 2.3 hours/day (95% CI: 2.1–2.5 hours/day) for children 24 to 35 months of age. In our logistic regression model, the number of hours of television watched per day was associated with both an irregular naptime schedule (odds ratio: 1.09; 95% CI: 1.01–1.18) and an irregular bedtime schedule (odds ratio: 1.13; 95% CI: 1.04–1.24).

Conclusions. Television viewing among infants and toddlers is associated with irregular sleep schedules. More research is warranted to determine whether this association is causal.
Fragmented Care for Inner-City Minority Children With Attention-Deficit/Hyperactivity Disorder
Authors: Guevara James P. , Feudtner Chris , Romer Daniel , Power Thomas , Eiraldi Ricardo , Nihtianova Snejana , Rosales Aracely , Ohene-Frempong Janet , Schwarz Donald F.
Published: September 2005

Objectives. To identify systematic problems in coordinating care for inner-city minority youths with attention-deficit/hyperactivity disorder.

Methods. We recruited participants from inner-city minority communities in a single metropolitan area for a focus group study. We held separate meetings for pediatricians, mental health therapists, school staff, and parents (both black and Latino). We audiotaped and transcribed the meetings. We identified themes by consensus and used root cause analysis as a conceptual framework to guide our analysis.

Results. We held 13 focus group meetings. Participants uniformly perceived insufficient communication and coordination of care. Five themes representing system and human factors that contributed to this fragmentation in care emerged: (1) a lack of consensus about who should oversee care; (2) changes in health care providers or teachers; (3) uncertainty in the diagnosis, insufficient training, and few resources; (4) distrust and blame that emerged when relationships among people who care for the child were absent or otherwise inadequate; and (5) lack of support from employers, friends, and family to engage in collaborative care.

Conclusions. Using a root cause analysis framework, we identified system- and human-level factors that were perceived to impede communication and coordination of care for this population of children with attention-deficit/hyperactivity disorder. These results suggest that better organizational policies that define provider responsibilities and accountability, support the coordination of care, bridge relationships between agencies, and provide additional education and resources may improve collaboration. Additional study is needed to assess the generalizability of these finding to other settings.
Early Analgesia for Children With Acute Abdominal Pain
Authors: Green Robert , Bulloch Blake , Kabani Amin , Hancock Betty Jean , Tenenbein Milton
Published: September 2005

Objectives. The objectives of this study were to determine whether the administration of morphine to children with acute abdominal pain would impede the diagnosis of appendicitis and to determine the efficacy of morphine in relieving the pain.

Methods. This was a double-blind, randomized, placebo-controlled trial involving 5- to 16-year-old children who presented to the emergency department of a children’s hospital with a chief complaint of acute abdominal pain that was thought by the pediatric emergency attending physician to require a surgical consultation. Subjects were randomized to receive intravenously administered morphine or normal saline solution. Clinical data and the emergency physician’s confidence in his or her clinical diagnosis (0–100%) were recorded systematically with a standardized form. This was repeated 15 minutes after administration of the study medication. The surgeon assessed the child within 1 hour and completed a similar data collection sheet. Pain was assessed, with a color analog scale, before and after study medication administration. Each subject was monitored for 2 weeks after enrollment.

Results. One hundred eight children were enrolled; 52 received morphine and 56 received a placebo saline solution. There were no differences between groups in demographic variables or the degree of pain. There were no differences between groups in the diagnoses of appendicitis or perforated appendicitis or the number of children who were observed and then underwent laparotomy. The reduction in the mean pain score was significantly greater in the morphine group (2.2 vs 1.2 cm). The emergency physicians’ and surgeons’ confidence in their diagnoses was not affected by the administration of morphine.

Conclusions. Our data show that morphine effectively reduces the intensity of pain among children with acute abdominal pain and morphine does not seem to impede the diagnosis of appendicitis.