bluuebunny/crossref_metadata_2025 huggingface dataset:
Error Tabulation by Text Searching of Large Chemical Data Base Compilations—Application to the ASTM Infrared Spectral Index
Authors: de Haseth J. A. , Woodruff H. B. , Isenhour T. L.
Published: October 2005

A text search method has been developed with which errors within large data base compilations may be located if the citations contain redundant information. This study has been applied to the ASTM Infrared Spectral Index of 91 875 spectra. Each citation within the data base contains some redundant information. If the citation is correct, the redundant information is the same; if the information differs, the citation is incorrect and an error has been located. The overall error was found to be between 3 and 5% within the limits of this study. The error search is general and can be applied to most chemical data base compilations.
Measurement of Excitation, Ionization, and Electron Temperatures and Positive Ion Concentrations in a 144 MHz Inductively Coupled Radiofrequency Plasma
Authors: Walters P. E. , Chester T. L. , Winefordner J. D.
Published: October 2005

Diagnostic measurements of 144 MHz radiofrequency inductively coupled plasmas at pressures between 0.5 and 14 Torr have been made. Other variables studied included the gas type (Ar or Ne) and material in plasma (Ti or Tl). Parameters measured included excitation temperatures via the atomic Boltzmann plot and the two-line method, ionization temperatures via the Saha expression, electron temperatures via double electric floating probes, and ion densities via the same electric probes. Excitation temperatures increased as the pressure of Ar or Ne plasmas decreased and reached a maximum of ∼9000°K in the latter case and ∼6700°K in the former case; Tl in the Ar plasma resulted in a smaller rate of decrease of excitation temperature with increase of pressure of Ar. The ionization temperatures were lower than the excitation temperatures and were similar for both the Ar and Ne plasmas. Electron temperatures were about 10 times higher than the excitation temperatures indicating non-LTE behavior. Again, the electron temperatures in Ne were considerably higher than in Ar. With the presence of metals, the electron temperatures with a metal in the Ar plasma were higher than in the absence. Positive ion concentrations were also measured for the various plasmas and were found to be similar (∼1018 m−3) in both the Ar and Ne plasmas. The presence of metals caused significant increase in the positive ion concentrations. From the results obtained, the optimum Ar pressure for Tl electrodeless discharge lamps operated at 144 MHz would be between 2 and 4 Torr.
Atomic Absorption Determination of Lead, Bismuth, Selenium, Tellurium, Thallium and Tin in Complex Alloys Using Direct Atomization from Metal Chips in the Graphite Furnace
Authors: Marks J. Y. , Welcher G. G. , Spellman R. J.
Published: October 2005

Atomic absorption spectrometry utilizing electrothermal atomization devices has proven to be the best technique available for the analysis of complex alloys for trace elements of metallurgical interest. The determination of lead, bismuth, selenium, tellurium, thallium, and tin was successfully demonstrated by direct atomization from complex, nickel-base alloy chips with commercial atomic absorption furnace equipment. The determination was carried out by first milling metal chips from the bulk sample. The sample was transferred directly to the furnace and atomized immediately with no preatomization heating cycle. A series of cast alloy standards containing the trace elements were prepared by additions to a nickel-base alloy, then subsequently analyzed by established analytical methods. Of the three commercial atomizers studied, the Perkin-Elmer model HGA 2100 proved to be the most suitable for direct determination of the trace elements of interest. The coefficient of variation of absorbance measurements varied from 7% for bismuth which is easily atomized to 25% for tin which is more difficult to atomize.
Nuclear Spin Relaxation Spectroscopy
Authors: Netzel Daniel A. , Miknis Francis P.
Published: October 2005

From the time dependence of the nuclear spin relaxation phenomena, molecular structure, conformation, motions, interactions, diffusion, and adsorption can readily be studied. Aside from the studies at the molecular level, nuclear spin relaxation phenomena have been applied to qualitative and quantitative analysis in the areas of polymer research, agriculture and food research, petroleum research, and medical research. This article presents an introduction to the theory, techniques, and applications of nuclear spin spectroscopy.
A Study of Inductively Coupled Plasma Torch Configurations
Authors: Allemand Charly D. , Barnes Ramon M.
Published: October 2005

Plasma torch design and shapes were studied to facilitate ignition, to concentrate the sample into a narrow central channel, to raise the sample to excitation temperatures with optimized efficiency, and to avoid clogging by organic samples such as residual oil. Observation of the influence of the torch configuration on ignition emphasized the importance of the shape and rate of the gas flows. Operating conditions of torches with diameters from 7 to 18 mm were calculated using a computer model, and predicted operation of small diameter torches requires high magnetic flux density. Experimental verification of an improved torch design demonstrated a higher efficiency, a lower gas consumption, and an easier ignition than conventional configurations.
A Theoretical Discussion of the Comparative Performances of Dispersion and Fourier-Transform Interferometric Spectrometers for the Infrared Region
Authors: Sheppard N. , Greenler R. G. , Griffiths P. R.
Published: October 2005

A summary is given of the theoretical factors that determine the performances of dispersion and Fourier-transform (interferometric) infrared spectrometers in terms of the signal/noise ratio obtainable in relation to the time spent in signal measurement for a given spectral resolution. It is assumed that, as is normal in the infrared region of the spectrum, the performances of the spectrometers are limited by detector noise. “Trading rules” are given relating the spectral resolution to the time of spectral measurement or the signal/noise ratio for each type of instrument. It is shown that, for a given pair of dispersion and interferometric spectrometers, the latter operating with matched-throughput, the relative performance of the interferometer improves by a factor of √2 in signal/noise ratio (or 2 in time) when the resolution interval, Δ, is halved.
Spectral Absorption Pattern Detection and Estimation. II. System Applications and Design Procedures
Authors: Morgan D. R.
Published: October 2005

In Part I of this paper, a number of analytical techniques were developed for the detection and estimation of spectral absorption patterns. In this second part, these techniques are applied to the design of practical systems and several examples of actual problems are given. Laser systems, multichannel broadband systems, a modified absorption cell technique, and adaptive processing are among the topics considered.
Spectral Absorption Pattern Detection and Estimation. I. Analytical Techniques
Authors: Morgan D. R.
Published: October 2005

Spectroscopic techniques have been widely employed in the middle infrared and other regions of the electromagnetic spectrum for the identification and concentration measurement of atmospheric constituents. A principal consideration in such applications is the discrimination of target gas effects from a whole background of interference effects, especially from other known or unknown gases that are present. The primary results presented in this paper concern the development of a unified theory and optimum signal processing techniques that specifically address this problem. Both active and passive, narrowband (laser), and broadband systems are treated simultaneously by adopting a vector space formalism whereby Euclidian coordinates represent appropriate spectral samples. Linear hypothesis testing and LMS estimation theory are then applied in order to derive mathematical expressions for optimum linear weights under various constraints. Both single and multiple targets are considered and a systematic approach to linear weight design is developed.
The Application of Fourier Transform Spectroscopy to the Remote Identification of Solids in the Solar System
Authors: Larson Harold P. , Fink Uwe
Published: October 2005

The techniques of Fourier transform spectroscopy combined with large aperture telescopes and advances in detector technology now permit infrared (λ > 1 µ) observations of the surfaces of small solar system objects such as asteroids and satellites. The results demonstrate that this activity can produce important new compositional information related to the origin and evolution of the solar system. The detection of water ice in Saturn's rings and on some of the satellites of Jupiter and Saturn confirm expectations that ices are important mineralogical components in the chemistry of the outer solar system. More recent studies of the mineralogical composition of the surfaces of asteroids provide a new observational link to the origin of meteorites and the early thermal history of the solar system. These results have been dependent upon supporting laboratory studies of the spectral behavior of ices and minerals to define the potential, and limitations, of the method. Since many of the astronomical observations have been exploratory in nature, prospects are good that continued refinement of the techniques will lead to additional insights.
Theoretical Calculation of Optical Collisional Cross Sections and α-Parameter Values for Transitions of Interest in Atomic Absorption Spectrometry
Authors: Lovett R. J. , Parsons M. L.
Published: October 2005

A method has been developed for calculating optical collisional cross sections and subsequent a-parameter values for spectral transitions of interest to analytical atomic spectroscopists. A combination of classical and semiclassical line broadening theory is used. The calculated values compare well (±20% or less) with values determined experimentally for elements without extensive hyperfine structure. If hyperfine structure is significant, the calculated a-parameter can be used to calculate the full width at half maximum of the spectral transition, but not the actual shape. The cross section values are found to correlate well with the proximity of the energy of the excited state of the atom to the ionization energy and to the orbitals involved in the electronic transition (e.g., s-p). A method of converting a values to different flame conditions has also been developed. Cross sections and a-parameter values for a total of 114 transitions from 52 elements have been calculated for the air-acetylene flame.
On the Analysis of Raman Spectra by Curve Resolution
Authors: Gans Peter , Gill J. Bernard
Published: October 2005

Raman spectra obtained during studies of solution equilibria are subjected to analysis using a combination of a small, manually controlled, digital minicomputer and a large digital computer. The shape-function of the bands is regarded as an empirical parameter, and the majority of bands are found to have Lorentzian shape. Simultaneous determination of shape-function and curved baseline is shown to be unsatisfactory. The possibility that components of a multiplet have different shape-functions is considered, and a probable example of such a case is given. Finally, it is shown that the ν3 region of the Raman spectrum of sodium nitrate in liquid ammonia probably contains three component bands, but uncertainty regarding shape-function introduces large uncertainty into the areas and positions of the bands.
The Use of Some Metal Photocathodes for Absolute Intensity Measurements in the Soft X-ray-Vacuum Ultraviolet
Authors: Burns Erskine J. T. , Thurston John F.
Published: October 2005

The total electron emission of better than 99.9% bulk purity aluminum, titanium, iron, and copper has been measured for six photon energies impinging at near normal incidence (90 ± 0.8°) to the electron emitting surface. Six nearly monochromatic photon energies between 0.109 and 1.49 keV were used. Surface smoothness, oxygen, and carbon contaminants were found to strongly influence the electron emission from these devices.
Selective Volatilization in the dc Arc Determined with a Direct-Reading Spectrometer
Authors: Cain Doug , Barnett Paul R.
Published: October 2005

The volatilization behavior of 22 elements in a 12-A dc arc has been determined using a direct-reading spectrometer and is presented as intensity-time curves. The curves are generally complex in shape, often having more than one peak. An order of volatilization has also been determined using the same data. The order of volatilization is similar to others already published, but significant differences exist. The irregular curve shapes may be due to volatilization of more than one compound of a given element from the electrode. This phenomenon may be caused by reactions that occur in the electrode. Because of a lack of data, it was impossible to correlate specific peaks on the intensity-time curves with physical constants of the possible compounds present. Both the presence of graphite powder and the concentration of the volatilizing element have an effect on the volatilization curves.
Subsurface Layer Studies by Attenuated Total Reflection Fourier Transform Spectroscopy
Authors: Hirschfeld Tomas
Published: October 2005

In total reflection spectroscopy the effective sampled depth increases as the angle of incidence approaches the critical one. At each angle of incidence, successive layers within the sample are weighed differently in the overall spectrum, and the manner of this weighing changes with angle. It is thus possible in principle to deconvolute a set of spectra taken at different angles into spectra corresponding to successive depth invervals. As this angular effect is particularly marked near the critical angle, where attenuated total reflection spectra are severely distorted, the spectra usually require inversion into optical constant spectra. This has been done by a new technique that measures spectra twice at each angle with different prism materials to give the necessary data sets. Examples of such subsurface spectra are shown.
Optimized Sampling in the Gas Chromatography-Infrared Spectroscopy Interface
Authors: Griffiths Peter R.
Published: October 2005

The optimum volume for a flow-through gas cell used in the gas chromatography-infrared spectroscopy interface (GC-ir) is shown to be equal to the volume of carrier gas between the half-width points of the GC peak. The optimum length and diameter for light-pipe gas cells for GC fractions separated using 1/8 in. packed columns and support-coated open tubular columns has been calculated for infrared measurements made using a rapid-scanning Fourier transform infrared spectrometer with either a triglycine sulfate or a mercury cadmium telluride detector. A sampling trigger actuated by the inflection points of the GC peak has been shown to be superior to the more usual threshold type of trigger. Expressions for the delay time between actuation of the trigger and initiation of data collection are also derived.
Slitless Optical-Fiber Laser-Raman Spectrometer Employing a Concave Holographic Grating
Authors: Walrafen George E.
Published: October 2005

A slitless optical-fiber laser-Raman spectrometer has been developed that employs a single f/3 concave holographic diffraction grating. The exit end of an optical fiber is positioned at the grating focus, and the divergent excitation and Raman radiation are then dispersed and refocussed. Detection is accomplished by translating an exit slit and photomultiplier tube along the focal line. A moveable solid-core optical fiber that transmits light to a fixed photomultiplier tube may also be used. The holographic grating produces a straight focal line, instead of a curve, resulting in accurate focussing from 480 to 650 nm, with linear scanning. The low f-number grating was used to accommodate high numerical aperture optical fibers without loss of light. A comparison between the present spectrometer with a 55 m fused silica fiber and a Jarrell-Ash Czerny-Turner single monochromator using a 1-cm bulk sample indicates a signal/noise improvement by a factor of 137 for the very weak two-phonon band from fused silica near 1600 cm−1.
An Infrared Solution Method for the Analysis of Trapped Atmospheric Contaminants Desorbed from Charcoal Tubes
Authors: Diaz-Rueda J. , Sloane H. J. , Obremski R. J.
Published: October 2005

An infrared analysis of toxic gases and vapors trapped in charcoal tubes is described. A minimum volume infrared liquid cell, optimized for sensitivity, is described and design compromises are discussed. The C2 extraction methodology was examined and recommendations are made to increase the extraction efficiency. Ten compounds on the OSHA list of toxic gases and vapors were studied; in all cases, good spectra useful for qualitative identification were obtained at less than the threshold limit value. Quantitative limits below threshold limit value levels are also reported for the compounds selected.
Dc Plasma Arcs for Elemental Analysis
Authors: Keirs Christopher D. , Vickers Thomas J.
Published: October 2005

The development of plasma arc devices as replacements for chemical combustion flames in trace element analyses by emission spectrometry is traced with particular emphasis on those devices in which the spectrometric observation is made in the non-current-carrying portion of the discharge or “plume.” The question of local thermal equilibrium in both the arc column and plasma plume is discussed and the dependence of temperature on experimental variables is considered in terms of a model. In addition to the temperature attained, the performance of various gas stabilized arcs and plasma jets is discussed with reference to interferences, background emission, limits of detection, and precision. Particular attention is paid to the problem of sample aerosol introduction into the high temperature plasma. The dc plasma arc at its present level of development is compared with the inductively coupled plasma for use as a source in emission spectroscopy.
A Review of the Theory and Application of Coherent Anti-Stokes Raman Spectroscopy (CARS)
Authors: Tolles W. M. , Nibler J. W. , McDonald J. R. , Harvey A. B.
Published: October 2005

Coherent anti-Stokes Raman spectroscopy (CARS) is a relatively new kind of Raman spectroscopy which is based on a nonlinear conversion of two laser beams into a coherent, laser-like Raman beam of high intensity in the anti-Stokes region. The emission is often many orders of magnitude greater than normal Raman scattering and, because of the coherent and anti-Stokes character of radiation, the method is very useful for obtaining Raman spectra of fluorescing samples, gases in discharges, plasmas, combustion, atmospheric chemistry. In this paper we outline the basic theory behind CARS and describe its unusual effects and drawbacks. We review the research to date on various materials, and indicate the possible future direction, utility and applications of CARS such as surface studies, fluctuation phenomena, reaction dynamics, photochemistry, kinetics, relaxation, and energy transfer.
Comparison of Pulsed Source with Continuous Wave Source Excitation in Atomic and Molecular Luminescence Spectrometry via Signal/Noise Ratio Calculations
Authors: Boutilier G. D. , Bradshaw J. D. , Weeks S. J. , Winefordner J. D.
Published: October 2005

Pulsed source excitation-gated detection (with or without time resolution) and cw excitation-cw detection are compared theoretically with respect to signal/noise (S/N) ratios in atomic and molecular luminescence spectrometry. The calculations indicate that in those cases where there is no loss in flux due to pulsing, pulsed source excitation with delayed gated detection results in a considerable improvement in S/N as long as the major noise sources are either not related to the source decay or, if related to the source decay or luminescence decay of impurities, the delay time between excitation and detection is greater than the corresponding source or impurity decay times. In general, pulsed source excitation-gated detection and modulated source lock-in detection do not provide significant S/N advantages over cw excitation and cw detection unless the major source of noise is related to either the detector or to non-source-induced background. Calculations of S/N ratio are given for a variety of analytically useful situations in atomic fluorescence spectrometry, molecular fluorescence spectrometry of gas phase and condensed phase species, and molecular phosphorescence spectrometry.
The Ratio Method for Analyzing Infrared Spectra of Mixtures
Authors: Koenig J. L. , D'Esposito L. , Antoon M. K.
Published: October 2005

A method is described for determining the spectra of the pure components from spectra of the mixtures. A computer simulation of the method demonstrates its feasibility and outlines possible sources of error. Application of the method to several polymer systems yielded satisfactory spectra of their pure components.
A Study of the Optical Emission from an rf Plasma during Semiconductor Etching
Authors: Harshbarger W. R. , Porter R. A. , Miller T. A. , Norton P.
Published: October 2005

Spectroscopic analysis of optical emission during rf plasma etching of semiconductor materials has been used to gain a better understanding of the plasma chemistry involved in these systems. The emission was studied principally in CF4-O2 gas mixtures, but other gases were observed as well. It is known that the addition of a relatively small percentage of O2 to CF4 yields a much faster etching rate for silicon and silicon nitride. With the addition of 02 to CF4 discharges we have studied emission from atomic O and molecular CO with a large increase in the emission of atomic F. When the plasma is actively etching silicon or silicon nitride, the emission intensities of both F and O atoms are significantly lower. The etching process can be monitored by observing the intensities of these lines. Analysis of the emission features has also been used to determine abnormal conditions which can adversely affect the etching process.
Strategy and Tactics in the Raman Spectroscopy of Biomolecules
Authors: Lord Richard C.
Published: October 2005

The strategic bases for the application of Raman spectroscopy to the problems of molecular biology and the tactics used in exploiting them are examined and discussed with the help of specific examples. The correlation of vibrational frequencies and intensities with molecular geometry is illustrated by several group frequencies of importance in the analysis of the Raman spectra of proteins, including those of the disulfide and amide groups. A new correlation between the amide-III frequency and peptide geometry is proposed and utilized to follow the reversible thermal denaturation of the enzyme ribonuclease. How other physical techniques may be combined with Raman methods is shown by the comparison of the Raman spectrum of a crystalline transfer ribonucleic acid, whose molecular structure is known from x-ray diffraction, with the spectra of the same substance in aqueous solution under different conditions of ionic strength, pH, and temperature. From the quantitative variation of the spectra the structural changes produced by temperature are evaluated. Possible improvements and new developments in the strategy and tactics of Raman spectroscopy are considered briefly.
A Fourier Transform Infrared Method of Studying Elastomers Filled with Carbon Black
Authors: Hart W. W. , Painter P. C. , Koenig J. L. , Coleman M. M.
Published: October 2005

Infrared spectra have been obtained of carbon black filled polybutadiene using a Fourier transform infrared spectrometer. Transmission and reflection techniques were employed. Polybutadiene was compounded with three fillers: Silene, general purpose furnace black, and Austin black. Subtle changes were observed in the vibrations of polybutadiene upon the addition of fillers. Transmission sampling through dilution with KBr gave better spectra than attenuated total reflection techniques in ease of data acquisition, and was therefore chosen as the principal method for further studies.
Application of Computer-Simulated Infrared Solar Spectra to the Detection of Atmospheric Fluorocarbon-12
Authors: Nordstrom Robert J. , Shaw John H. , Skinner Wilbert R. , Chan Walter H. , Calvert Jack G. , Uselman William M.
Published: October 2005

Fluorocarbon-12 (CCl2F2) has been detected in the atmosphere by observation of infrared solar spectra in two spectral regions of the 8 to 12 µm atmospheric transmission window. The solar spectra were compared with laboratory spectra of CCl2F2 and also with computer synthesized spectra which were generated from the most recent Air Force Cambridge Research Laboratories line parameters listing. Water vapor lines interfere with strong Q-branch absorption features of CCl2F2 in the spectral region near 923 cm−1. The region near 1161 cm−1 is free from water vapor absorption and has the strongest Q-branch feature of CCl2F2. Many laboratory spectra of CCl2F2 were studied and this absorption feature was found to be independent of N2 broadening pressure. No change in the half-width was found as the N2 pressure was varied from 0 to 700 Torr. Furthermore, assuming a Lorentz line shape for this CCl2F2 absorption feature, an intensity of 3.8 × 1018 cm·molecule−1 and a half-width of 0.026 cm−1 were found. Using these parameters, synthetic solar spectra were computed which included the CCl2F2 absorption feature. Results of this computer generation of solar spectra indicate a ground level concentration of 110 parts per trillion of CCl2F2 in our solar spectra.
The Vibrational Spectra of VPO5 Crystal Phases and Related Glasses
Authors: Bhargava R. N. , Condrate R. A.
Published: October 2005

Infrared and Raman spectra were measured and interpreted for two crystalline VPO5 phases (α- and β-VPO5) and several related vanadium phosphate glasses. The spectral results for the crystalline phases were consistent with those predicted by factor group analysis using the previously determined space groups. Empirical band assignments were made for the observed bands on the basis of the bands observed earlier for related phosphate and oxyvanadium compounds. Also, the band assignments made for the infrared spectra of the glasses were consistent with the assignments for crystalline V2O5 and the two crystalline VPO5 phases. No Raman spectra were observed for the glasses because processes involving adsorption and Rayleigh scattering dominated over Raman scattering. The infrared spectra of vanadium phosphate glasses with high P2O5 concentrations possessed many features resembling those observed in the infrared spectra of α-VPO5, suggesting similarities in the short range order for the two materials. Analyses of the vibrational spectra of hydrated α-VPO5 samples suggests that the water molecules are adsorbed in the interlamellar spaces of the crystals, complexing to vanadium ions. Initial steps in the hydration of vanadium phosphate glasses apparently involve physical adsorption of water on their surfaces. No water adsorption could be detected for β-VPO5 under normal conditions from its infrared and Raman spectra.
A Nonlinear Least Squares Method of Determining Line Intensities and Half-Widths
Authors: Chang Y. S. , Shaw J. H.
Published: October 2005

A nonlinear least squares method of retrieving line intensities and half-widths from spectra degraded by a finite instrumental resolving power is discussed. Examples of the applications of this technique to obtain the parameters of a single isolated line and of an overlapping pair of lines are presented.
An Auger Electron Spectroscopic Study of the Diffusion of Sulfur and Carbon in α-Iron
Authors: Swartz W. E. , Holloway D. M.
Published: October 2005

Auger electron spectroscopy has been employed to study the diffusion of sulfur and carbon in α-iron. In the temperature range 25 to 500°C carbon preferentially segregates to the surface. From 400 to 700°C sulfur segregates to the surface while carbon is thermally desorbed. An Arrhenius analysis of the sulfur diffusion data yields an activation energy of 14.5 kcal/mol, which is consistent with a grain boundary diffusion process. The kinetics of carbon migration is complicated by the thermal desorption which makes Arrhenius analysis impossible.
Flame Diagnostics: Local Temperature Profiles and Atomic Fluorescence Intensity Profiles in Air-Acetylene Flames
Authors: Haraguchi H. , Winefordner J. D.
Published: October 2005

Temperature profiles of the “premixed” air-acetylene and argon-separated air-acetylene flames, produced with a capillary burner, have been investigated by a two-line atomic fluorescence method. The temperatures were obtained at a volume resolution of 0.3 × 2 × 5 mm3 in the flames. In an unseparated air-acetylene flame, temperature ranges from ca. 2600 to ca. 1900°K; the highest temperature (2650°K) was found 3 mm from the burner center and 60 mm above the burner head. In an argon-separated air-acetylene flame, temperature is in the range ca. 2500 to 1300°K; the temperature is the highest at the center and decreases rapidly towards the fringe of the flame (outer cone) due to the cooling effect of argon gas. In order to elucidate the analytical usefulness of the temperature profiles obtained, atomic fluorescence intensity profiles of Mg, Cu, In, and Cr have been also measured and discussed in detail.
Infrared Spectra of Diacid and Triacid Triglycerides
Authors: De Ruig W. G.
Published: October 2005

Seven diacid and five triacid saturated triglycerides have been investigated by infrared spectroscopy. The majority of absorption bands could be assigned with the help of the concept “diathesis.” A diathesis is a (part of a) molecule acting as a separate vibration unit. The spectra have practical value for identification purposes. It is demonstrated that from the spectra can be concluded: (1) the polymorphic form of the investigated sample (α, β‘, β); (2) the chain lengths of the three fatty acid moieties, i.e., the composition of the triglyceride; and (3) the position of these fatty acid moieties in the molecule, i.e., the isomer. Aided by tables with appropriate data, given here, unknown samples can be identified in most cases.
Infrared Spectra of Crystalline Acetic Acid, a Hydrogen-Bonded Polymer
Authors: Krause P. F. , Katon J. E. , Rogers J. M. , Phillips D. B.
Published: October 2005

The polarized infrared spectra of crystalline acetic acid and two of its deuterated derivatives, CH3COOD and CD3COOD, have been recorded from 400 to 4000 cm−1 at cryogenic temperatures. The spectroscopic results have been interpreted on the basis of a factor group analysis based on two structural models: a crystallographic cell composed of four interacting monomer units some of whose vibrational modes are highly perturbed by hydrogen bonding and a unit cell composed of two noninteracting acetic acid chains. The results are discussed in terms of possible interactions between the hydrogen-bonded acetic acid polymeric chains.
Spectroscopic Study of Radiofrequency Oxygen Plasma Stripping of Negative Photoresists. II. Visible Spectrum
Authors: Griffiths J. E. , Degenkolb E. O.
Published: October 2005

The rf O2 plasma-induced stripping of negative photoresists from semiconductor surfaces has been detected and monitored using the optical emission from electronically excited CO product molecules at 483.5 and 519.8 nm. The active species producing the stripping has been identified as electronically excited oxygen atoms. The end point of the stripping process is easily identified as is the final cleanup of the semiconductor surface. The dependence of the stripping time as a function of flow rate and oxygen pressure has also been determined.
Fluorescence Interferences in Raman Scattering from Combustion Products
Authors: Setchell R. E. , Aeschliman D. P.
Published: October 2005

Spectral interferences to Raman bands due to laser-induced fluorescence are examined in exhaust gases from an internal combustion engine operating on different fuels and fuel/air mixtures. A broadband fluorescence spectrum is observed in all cases, but the relative fluorescence intensity depends strongly on the particular engine operating condition. Elimination of the fluorescence background by various exhaust conditioning devices confirmed the fact that aerosols of hydrocarbons or other organic compounds are the principal source.
Microsampling in the Infrared — Use of Special Techniques
Authors: Sloane Howard J. , Obremski Robert J.
Published: October 2005

The examination of microsamples by infrared spectroscopy is best accomplished by reduction of beam area with small apertures. However, this technique produces energy losses and aperturing effects which distort the baseline. Methods of dealing with energy losses and correcting baseline distortions by mechanical and digital means are examined.
Interferometers vs Monochromators: Separating the Optical and Digital Advantages
Authors: Griffiths Peter R. , Sloane Howard J. , Hannah Robert W.
Published: October 2005

Fourier transform (FT) and grating infrared spectrophotometers are compared from a theoretical viewpoint in terms of the multiplex advantage of FT spectrometers, the relative optical throughputs, the comparative performance of the detectors used with each type of system, and other more minor parameters. The signal/noise ratios of spectra measured using commercial FT and grating spectrophotometers are compared. The relative performance varies with wavenumber in the manner forecast theoretically, although the experimental performance of the FT spectrometer is slightly worse than we predicted. Optimum applications for each type of instrument are discussed in terms of these results.
Dimethylnitrosamine Detection and Measurement Using Laser Raman Spectroscopy
Authors: Thomas Dwaine M.
Published: October 2005

The Raman spectra of various concentrations of dimethylnitrosamine in water have been measured. The lowest concentration detected was 10 mg/l. Instrumental parameters were varied to optimize the signal response.
Direct Determination of Manganese in Gasoline by Atomic Absorption Spectrometry in the Nitrous Oxide-Hydrogen Flame
Authors: Lukasiewicz R. J. , Buell B. E.
Published: October 2005

The nitrous oxide-hydrogen flame provides efficient combustion of aspirated gasoline without the formation of luminescent unburned carbon particles. Direct aspiration of gasoline into this flame is practical even at very high nebulizer uptake rates and is thus the basis for rapid direct determination of manganese by atomic absorption spectrometry. The atomic absorption spectrophotometer, however, must be calibrated by using standards prepared from the same organometallic manganese compound present in the samples. Atomic absorption response for manganese naphthenate, manganese octoate, and methylcyclopentadienylmanganese tricarbonyl (MMT) can differ by as much as 45% relative depending on the nebulizer uptake rate. At the optimum nebulizer uptake rate used, 6 ml/min, the difference between absorption response of the most sensitive compound, manganese naphthenate, and the least sensitive, MMT, is 15%. Very high nebulizer efficiencies and relatively high uptake rates result in high sample transport to the flame. Absorption at a given concentration for all compounds increases in a linear fashion with the amount of sample transported to the flame up to about 3.0 ml/min. At 4.0 ml/min equivalent liquid phase volume delivered to the flame maximum absorbance occurs; absorbance diminishes rapidly thereafter. Plots of absorption vs equivalent liquid phase volume delivered to the flame passed through the origin for manganese naphthenate and manganese octoate. The same plot for MMT shows a positive intercept on the volume delivered axis, which indicates a consistent loss of absorption for MMT relative to the naphthenate and the octoate for all rates of sample delivery to the flame.
Novel bacterial molybdenum and tungsten enzymes: three-dimensional structure, spectroscopy, and reaction mechanism
Authors: Boll Matthias , Schink Bernhard , Messerschmidt Albrecht , Kroneck Peter M.H.
Published: October 2005

The molybdenum enzymes 4-hydroxybenzoyl-CoA reductase and pyrogallol-phloroglucinol transhydroxylase and the tungsten enzyme acetylene hydratase catalyze reductive dehydroxylation reactions, i.e., transhydroxylation between phenolic residues and the addition of water to a triple bond. Such activities are unusual for this class of enzymes, which carry either a mononuclear Mo or W center. Crystallization and subsequent structural analysis by high-resolution X-ray crystallography has helped to resolve the reaction centers of these enzymes to a degree that allows us to understand the interaction of the enzyme and the respective substrate(s) in detail, and to develop a concept for the respective reaction mechanism, at least in two cases.
Neuronal Basis of Covert Spatial Attention in the Frontal Eye Field
Authors: Thompson Kirk G. , Biscoe Keri L. , Sato Takashi R.
Published: October 2005

The influential “premotor theory of attention” proposes that developing oculomotor commands mediate covert visual spatial attention. A likely source of this attentional bias is the frontal eye field (FEF), an area of the frontal cortex involved in converting visual information into saccade commands. We investigated the link between FEF activity and covert spatial attention by recording from FEF visual and saccade-related neurons in monkeys performing covert visual search tasks without eye movements. Here we show that the source of attention signals in the FEF is enhanced activity of visually responsive neurons. At the time attention is allocated to the visual search target, nonvisually responsive saccade-related movement neurons are inhibited. Therefore, in the FEF, spatial attention signals are independent of explicit saccade command signals. We propose that spatially selective activity in FEF visually responsive neurons corresponds to the mental spotlight of attention via modulation of ongoing visual processing.
NMDA Receptor Activation Inhibits α-Secretase and Promotes Neuronal Amyloid-β Production
Authors: Lesné Sylvain , Ali Carine , Gabriel Cecília , Croci Nicole , MacKenzie Eric T. , Glabe Charles G. , Plotkine Michel , Marchand-Verrecchia Catherine , Vivien Denis , Buisson Alain
Published: October 2005

Acute brain injuries have been identified as a risk factor for developing Alzheimer's disease (AD). Because glutamate plays a pivotal role in these pathologies, we studied the influence of glutamate receptor activation on amyloid-β (Aβ) production in primary cultures of cortical neurons. We found that sublethal NMDA receptor activation increased the production and secretion of Aβ. This effect was preceded by an increased expression of neuronal Kunitz protease inhibitory domain (KPI) containing amyloid-β precursor protein (KPI-APP) followed by a shift from α-secretase to β-secretase-mediated APP processing. This shift is a result of the inhibition of the α-secretase candidate tumor necrosis factor-α converting enzyme (TACE) when associated with neuronal KPI-APPs. This KPI-APP/TACE interaction was also present in AD brains. Thus, our findings reveal a cellular mechanism linking NMDA receptor activation to neuronal Aβ secretion. These results suggest that even mild deregulation of the glutamatergic neurotransmission may increase Aβ production and represent a causal risk factor for developing AD.
Both Laminin and Schwann Cell Dystroglycan Are Necessary for Proper Clustering of Sodium Channels at Nodes of Ranvier
Authors: Occhi Simona , Zambroni Desirée , Del Carro Ubaldo , Amadio Stefano , Sirkowski Erich E. , Scherer Steven S. , Campbell Kevin P. , Moore Steven A. , Chen Zulin-L. , Strickland Sidney , Di Muzio Antonio , Uncini Antonino , Wrabetz Lawrence , Feltri M. Laura
Published: October 2005

Nodes of Ranvier are specialized axonal domains, at which voltage-gated sodium channels cluster. How axons cluster molecules in discrete domains is mostly unknown. Both axons and glia probably provide constraining mechanisms that contribute to domain formation. Proper sodium channel clustering in peripheral nerves depends on contact from Schwann cell microvilli, where at least one molecule, gliomedin, binds the sodium channel complex and induces its clustering. Furthermore, mice lacking Schwann cell dystroglycan have aberrant microvilli and poorly clustered sodium channels. Dystroglycan could interact at the basal lamina or at the axonglial surface. Because dystroglycan is a laminin receptor, and laminin 2 mutations [merosin-deficient congenital muscular dystrophy (MDC1A)] cause reduced nerve conduction velocity, we asked whether laminins are involved. Here, we show that the composition of both laminins and the dystroglycan complex at nodes differs from that of internodes. Mice defective in laminin 2 have poorly formed microvilli and abnormal sodium clusters. These abnormalities are similar, albeit less severe, than those of mice lacking dystroglycan. However, mice lacking all Schwann cell laminins show severe nodal abnormalities, suggesting that other laminins compensate for the lack of laminin 2. Thus, although laminins are located at a distance from the axoglial junction, they are required for proper clustering of sodium channels. Laminins, through their specific nodal receptors and cytoskeletal linkages, may participate in the formation of mechanisms that constrain clusters at nodes. Finally, abnormal sodium channel clusters are present in a patient with MDC1A, providing a molecular basis for the reduced nerve conduction velocity in this disorder.
Pattern-Specific Associative Long-Term Potentiation Induced by a Sleep Spindle-Related Spike Train
Authors: Rosanova Mario , Ulrich Daniel
Published: October 2005

Spindles are non-rapid eye movement (non-REM) sleep EEG rhythms (7-14 Hz) that occur independently or in association with slow oscillations (0.6-0.8 Hz). Despite their proposed function in learning and memory, their role in synaptic plasticity is essentially unknown. We studied the ability of a neuronal firing pattern underlying spindlesin vivoto induce synaptic plasticity in neocortical pyramidal cellsin vitro. A spindle stimulation pattern (SSP) was extracted from a slow oscillation upstate that was recorded in a cat anesthetized with ketamine-xylazine, which is known to induce a sleep-like state. To mimic the recurrence of spindles grouped by the slow oscillation, the SSP was repeated every 1.5 s (0.6 Hz). Whole-cell patch-clamp recordings were obtained from layer V pyramidal cells of rat somatosensory cortex with infrared videomicroscopy, and composite EPSPs were evoked within layers II-III. Trains of EPSPs and action potentials simultaneously triggered by the SSP induced an NMDA receptor-dependent short-term potentiation (STP) and an L-type Ca2+channel-dependent long-term potentiation (LTP). The number of spindle sequences affected the amount of STP-LTP. In contrast, spindle trains of EPSPs alone led to long-term depression. LTP was not consistently induced by a regular firing pattern, a mirrored SSP, or a randomized SSP; however, a synthetic spindle pattern consisting of repetitive spike bursts at 10 Hz reliably induced STP-LTP. Our results show that spindle-associated spike discharges are efficient in modifying excitatory neocortical synapses according to a Hebbian rule. This is in support of a role for sleep spindles in memory consolidation.
Formation of a Motor Memory by Action Observation
Authors: Stefan Katja , Cohen Leonardo G. , Duque Julie , Mazzocchio Riccardo , Celnik Pablo , Sawaki Lumy , Ungerleider Leslie , Classen Joseph
Published: October 2005

Mirror neurons discharge with both action observation and action execution. It has been proposed that the mirror neuron system is instrumental in motor learning. The human primary motor cortex (M1) displays mirror activity in response to movement observation, is capable of forming motor memories, and is involved in motor learning. However, it is not known whether movement observation can lead directly to the formation of motor memories in the M1, which is considered a likely physiological step in motor learning. Here, we used transcranial magnetic stimulation (TMS) to show that observation of another individual performing simple repetitive thumb movements gives rise to a kinematically specific memory trace of the observed motions in M1. An extended period of observation of thumb movements that were oriented oppositely to the previously determined habitual directional bias increased the probability of TMS-evoked thumb movements to fall within the observed direction. Furthermore, the acceleration of TMS-evoked thumb movements along the principal movement axis and the balance of excitability of muscle representations active in the observed movements were altered in favor of the observed movement direction. These findings support a role for the mirror neuron system in memory formation and possibly human motor learning.
Age-Dependent and Selective Impairment of Long-Term Potentiation in the Anterior Piriform Cortex of Mice Lacking the Fragile X Mental Retardation Protein
Authors: Larson John , Jessen Ruth E. , Kim Daniel , Fine Ananda-Kriiya S. , du Hoffmann Johann
Published: October 2005

Synaptic function and plasticity were studied in mice lacking the fragile X mental retardation protein (FMRP), a model for the fragile X mental retardation syndrome. Associational connections were studied in slices of anterior piriform (olfactory) cortex, and Schaffer-commissural synapses were studied in slices of hippocampus. Knock-out (KO) mice lacking FMRP were compared with congenic C57BL/6J wild-type (WT) controls. Input-output curves and paired-pulse plasticity were not significantly altered in KO compared with WT mice in either the olfactory cortex or hippocampus. Long-term potentiation (LTP) induced by theta burst stimulation in the anterior piriform cortex was normal in KO mice aged <6 months but was impaired in KO mice aged > 6 months. The deficit in LTP was significant in mice aged 6-12 months and more pronounced in mice aged 12-18 months. Similar differences between WT and KO mice were seen whether LTP was induced in the presence or absence of a GABAAreceptor blocker. Postsynaptic responses to patterned burst stimulation in KO mice showing impaired LTP were not significantly different from those in WT mice, suggesting that the LTP deficit was not caused by alterations in circuit properties. No differences in hippocampal LTP were observed in WT and KO mice at any ages. The results indicate that FMRP deficiency is associated with an age-dependent and region-selective impairment in long-term synaptic plasticity.
Processing Efficiency of Divided Spatial Attention Mechanisms in Human Visual Cortex
Authors: McMains Stephanie A. , Somers David C.
Published: October 2005

Many visual tasks require deployment of attention to multiple objects or locations. We used functional magnetic resonance imaging and behavioral experiments to investigate the relative processing efficiency of two putative attentional mechanisms for performing such tasks: the “zoom lens” and “multiple spotlights.” Two key questions were investigated: (1) does splitting the spotlight into multiple foci incur an overhead cost that diminishes the efficacy of attention compared with the zoom lens, and (2) does splitting the spotlight provide a benefit relative to the zoom lens by conserving attention resources that otherwise would be directed to task irrelevant stimuli? For both mechanisms, attending to multiple object locations decreased processing efficiency at a single location, resulting in both decreased behavioral performance and decreased blood oxygenation level-dependent (BOLD) signal attentional modulation. When the two mechanisms attended to multiple objects across the same spatial extent, the multiple spotlight mechanism, which ignores intervening stimuli, yielded better performance and higher BOLD signal. When the two mechanisms processed the same number of stimuli, splitting the spotlight neither impaired performance nor diminished BOLD signal in occipital cortex. The surprising efficiency of the multiple spotlight mechanism supports the emerging view that spatial attention is easily deployed in a diverse range of spatial configurations.