bluuebunny/crossref_metadata_2025 huggingface dataset:
Cardiorespiratory adjustments of homing pigeons to steady wind tunnel flight
Authors: Peters Grant W. , Steiner Dee A. , Rigoni Jason A. , Mascilli Alexia D. , Schnepp Robert W. , Thomas Steven P.
Published: August 2005

We made detailed cardiorespiratory measurements from homing pigeons during quiet rest and steady wind tunnel flight. Our pigeons satisfied their 17.4-fold increase in oxygen consumption during flight with a 7.4-fold increase in cardiac output (Q̇) and a 2.4-fold increase in blood oxygen extraction. Q̇ was increased primarily by increasing heart rate sixfold. Comparisons between our study and those from the only other detailed cardiorespiratory study on flying birds reveal a number of similarities and important differences. Although the avian allometric equations from this earlier study accurately predicted the flight Q̇ of our pigeons, this was primarily due to due to compensating discrepancies in their heart rate and stroke volume predictions. Additionally, the measured heart mass(MH)-specific Q̇(Q̇/MH) of our pigeons during wind tunnel flight was about 22% lower than the estimated value. Compared to running mammals in previous studies, the 1.65-fold Q̇ of our pigeons is consistent with their larger heart mass.
Computer simulations of high-pass filtering in zebrafish larval muscle fibres
Authors: Buckingham Steven D. , Ali Declan W.
Published: August 2005

Larval somatic muscle of the zebrafish, Danio rerio, like that of some other organisms, responds to a sustained depolarization with one, and only one, action potential. Here, we report computer simulations, using the NEURON simulation programme, of sodium and potassium currents of somatic muscle of larval Danio rerio to investigate their possible contribution to once-only firing. Our computer model incorporated simulated sodium and potassium ion channels based on steady-state and kinetic parameters derived from a recent electrophysiological study. The model responded to sustained depolarizations with a single action potential at all levels of depolarization above threshold. By varying several parameters of the sodium and potassium currents systematically, the minimum changes necessary to produce repetitive firing were found to be a positive shift in the half-inactivation and a negative shift in the half-activation potentials for the sodium current, accompanied by a slowing of the rate of inactivation to half of the experimentally observed values. This suggests that once-only spiking can be attributed to the steady-state values of activation and inactivation of the sodium current, along with a slower rate of inactivation. Mapping of the resultant firing properties against steady-state and kinetic ion channel parameters revealed a high safety factor for once-only firing and showed that the time constant of inactivation of the sodium current was the key determinant of once-only or repetitive firing. The rapidly inactivating potassium current does not influence once-only firing or the maximum rate of firing in response to periodic excitation in these simulations. Although a contribution of other currents to produce once-only firing has not been excluded, this model suggests that the properties of the sodium current are sufficient to account for once-only firing.
Design of Functional Molecular Crystals by Controlling Intermolecular Interactions
Authors: Inabe Tamotsu
Published: August 2005

In this account, two representative approaches toward the control of molecular arrangements in molecular crystals are introduced, especially for π-radicals. One is “π–π stacking structure modification of macrocyclic π-ligand complexes”, in which the interaction is modified by simply introducing axial ligands. By this method, a number of conductors with various π–π stacking structures have been obtained. The other is “design of functional crystals utilizing hydrogen bonds”, in which anions with strong self-assembling ability are used for the formation of anion networks. If the interaction between the anions is stronger than that between π-radical cations, the cations are expected to be packed in the space provided by the networks with peculiar assembly formations that differ from those inherently preferable for the cations. The arrangement of π-radicals is directly related to the electronic functionalities of the crystal, and its control is crucial for the design of the specific electronic functionalities.
Formation of α- and β-Keggin-Type [PW12O40]3− Complexes in Aqueous Media
Authors: Himeno Sadayuki , Takamoto Masayo , Ueda Tadaharu
Published: August 2005

The formation process of the α- and β-Keggin-type [PW12O40]3− complexes was investigated in an aqueous 50 mM (M = mol dm−3) W(VI)–5.0 mM P(V) system. The 31P NMR study confirmed the formation of A-α-[PW9O34]9−, A-β-[PW9O34]9−, α-[PW11O39]7−, and β1-[PW11O39]7− on acidification of an alkaline solution of WO42− and HPO42− to pH 7.5 or below. An isomeric mixture of α- and β-[PW12O40]3− was obtained on further acidification of such solutions containing both α- and β-type lacunary complexes to pH 1 or below. On the other hand, heating of the W(VI)–P(V) system caused A-α-[PW9O34]9−, A-β-[PW9O34]9−, and β1-[PW11O39]7− to disappear completely, leaving α-[PW11O39]7−. Acidification of the α-[PW11O39]7− solution produced only α-[PW12O40]3−.
Total Synthesis of Bistratamides G and H from Various Kinds of ΔAla and ΔAbu-Containing Oligopeptides
Authors: Yonezawa Yasuchika , Tani Naoki , Shin Chung-gi
Published: August 2005

The total synthesis of naturally occurring bistratamides G (1) and H (2) from various kinds of dehydrooligopeptides is described. First of all, the promising building blocks of 1 and 2: N-{2-[(S)-1-(N-benzyloxycarbonyl)amino-2-methylpropyl]oxazole (4)- and N-{2-[(S)-1-(N-t-butoxycarbonyl)amino-2-methylpropyl]thiazol-4-ylcarbonyl}-l-Val-(S)NH2 (5), and methyl (S)-2-{1-[N-(3-bromo-2-oxopropanoyl)amino-2-methylpropyl]}-5-methyloxazole-4-carboxylate (6), as the left- and right-half components of the linear precursor of 1 and 2, were synthesized. Subsequent thiazolation between 4 or 5 and 6, respectively, followed by deprotection of both N- and O-protecting groups of the two formed linear trisheterocyclic peptides. By final macrocyclization using BOP as condensing agent under high-dilution conditions these peptides gave the expected 1 and 2.
Synthesis and Photoinduced Intermolecular Electronic Acceptor Ability of Pyrazolo[60]fullerenes vs Tetrathiafulvalene
Authors: Delgado Juan Luis , de la Cruz Pilar , López-Arza Vicente , Langa Fernando , Gan Zhenhai , Araki Yasuyuki , Ito Osamu
Published: August 2005

The synthesis of three novel pyrazolo[60]fullerene derivatives containing electron-withdrawing substituents has been described. High solubility in ordinary organic solvents was proved. Their electrochemical properties of pyrazolo[60]fullerenes showed better electron affinity than pristine C60 in the ground state. The nanosecond transient absorption spectra showed clear evidence for photoinduced electron transfer from TTF to the excited triplet state of the pyrazolo[60]fullerenes, in which stronger electron-withdrawing substituents accelerate the rates of the photoinduced electron-transfer, indicating a high electron-acceptor ability of the excited triplet state of pyrazolo[60]fullerenes.
Synthesis and Properties of Alkyl Phosphorylcholine Amphiphiles with a Linear and an Asymmetrically Branched Alkyl Chain
Authors: Kang Eui-Chul , Kataoka Shingo , Kato Kenji
Published: August 2005

Alkyl phosphorylcholine amphiphiles bearing one linear chain and one asymmetrically branched alkyl chain were successfully synthesized using 2-chloro-2-oxo-1,3,2-dioxaphospholane in tetrahydrofuran or ethyl acetate. 1H and 31P NMR studies revealed that the linear alkyl phosphorylcholines (Cn-PC) provide aqueous micelles in D2O and reverse micelles in CDCl3, while the branched alkyl phosphorylcholines (ISOFOLn-PC) give vesicles in D2O. The critical micelle concentrations (CMCs) of Cn-PC were measured by fluorescence dye solubilization methods: the CMCs of C12-PC, C14-PC, C16-PC, and C18-PC were 1.6, 0.38, 0.16, and 0.11 mM, respectively, in water at 25 °C. The critical association concentrations (CACs) of ISOFOL16-PC, ISOFOL20-PC, and ISOFOL24-PC were 0.068, 0.005, and 0.077 mM, respectively, in water at 25 °C. The vesicle size of ISOFOLn-PC in aqueous solution was measured by the dynamic light scattering method. The mean diameter of ISOFOLn-PC vesicles was approximately 30 nm and the size distribution was relatively monodisperse. The ISOFOLn-PC vesicles formed were colloidally stable in water over the period of several weeks.
Heteropoly Blue as a Reaction-Controlled Phase-Transfer Catalyst for the Epoxidation of Olefins
Authors: Mingqiang Li , Xigao Jian
Published: August 2005

A new reaction-controlled phase-transfer catalyst system has been designed and synthesized. In this system, heteropoly blue, [C7H7N(CH3)3]3PMo4O16, is used for the catalytic epoxidation of olefins with H2O2 as the oxidant. In this system, the catalyst not only can be recovered, like heterogeneous catalyst, but also acts as a homogeneous catalyst. The main products are epoxide of olefins and H2O; no co-product forms. The system exhibits high conversion and selectivity as well as excellent catalyst stability. 31P NMR spectra, UV–vis spectra, and infrared spectra are used to analyze the reason for the phase transfer of the catalyst, indicating that the change of structure leads to the formation of reaction-controlled phase-transfer catalyst.
Raman Spectroscopic Investigation of Isomeric and Mixed-Valence Heteropolyanions
Authors: Kasprzak Melody Starr , Leroi G. E. , Crouch S. R.
Published: August 2005

Raman spectroscopy has been used to distinguish structural differences between α-12-heteropoly anions and β-12-heteropoly anions in solution. The results are consistent with the Keggin structure for the α-isomers and a modified Keggin structure for the β-isomers. Reduced 12-molybdophosphates and molybdovanadophosphates in solution have also been characterized by Raman spectroscopy; the results are consistent with a retention of the Keggin structure.
Phase Correction in FT-IR
Authors: Chase D. B.
Published: August 2005

Two approaches to phase correction in FT-IR spectroscopy are discussed. Using synthetic data, both the Mertz method and the symmetrization-convolution method are evaluated with respect to the accurate reproduction of a single-beam spectrum. The variation in photometric accuracy with (1) the number of points used in the phase calculation, and (2) apodization in the phase calculation is examined.
ICP Emission Spectrometry: On the Selection of Analytical Lines, Line Coincidence Tables, and Wavelength Tables
Authors: Winge R. K. , Fassel V. A. , Peterson V. J. , Floyd M. A.
Published: August 2005

A thorough knowledge of the spectral emission characteristics of the inductively coupled plasma is a prerequisite for its maximum utilization in atomic emission spectroscopy. Toward this end an Atlas of Spectral Information for Inductively Coupled Plasma, Atomic Emission Spectroscopy has been assembled to provide the analyst with the basic information concerning the analytical capabilities and the potential spectral interferences of the prominent spectral lines of 70 elements. The Atlas contains 232 wavelength scans of 70 elements covering the range of 189 to 517 nm (189 to 597 nm for sodium and the reference blank). The Atlas also contains a listing of 973 prominent lines with estimated detection limits and a detailed collection of coincidence profiles for 281 of the most prominent lines, each with profiles of ten of the most prevalent concomitant elements superimposed. This paper contains a survey of the spectral information contained in the Atlas.
Raman Excitation Profiles of Purine and Pyrimidine Nucleic Acid Bases
Authors: Samanta Swadesh R. , Lytle Fred E.
Published: August 2005

Raman excitation profiles for the monophosphates of guanosine, cytidine, and thymidine have been obtained experimentally using tunable ultraviolet radiation. These data were then fit to a single state, preresonance enhancement equation in order to determine the effective absorption wavelength. In all cases these band origins agreed quite well with the electronic spectral maxima. For two of the bases these studies were performed at drastically varying pH's. A neutral-to-alkaline change produced only minor differences in the spectral data for guanosine, whereas a neutral-to-acidic change had a marked effect on both the spectrum and band origin for cytidine.
Precision in Condensed Phase Vibrational Spectroscopy
Authors: Cameron David G. , Kauppinen Jyrki K. , Moffatt Douglas J. , Mantsch Henry H.
Published: August 2005

Algorithms for the computation of bandwidths, and center of gravity and least-squares frequencies are developed. The sources of error are discussed, and it is shown that the above parameters can be determined with maximum uncertainties of hundredths or thousandths of a wave number.
Vibrational Spectra and Normal Coordinate Calculations of Chlorophosphazene Compounds. III. Polydichlorophosphazene
Authors: Coleman M. M. , Zarian J. , Painter P. C.
Published: August 2005

Vibrational spectra and normal coordinate calculations of polydichlorophosphazene (PDP) are presented. The valence force field derived previously from the two conformers of octachlorocyclotetraphosphazene was directly transferred to a distorted “cis-plan” helical model of PDP without refinement. A reasonable agreement between the observed and calculated frequencies was obtained and the assignment of the normal modes of PDP is discussed.
Simplified Procedure for Optical Emission Analysis of Nitrogen 15 and Carbon 13
Authors: Johansen H. Saaby , Middelboe V.
Published: August 2005

In an endeavor to facilitate the use of stable isotopes in biological tracer research, we have developed a simple, real time procedure for reasonably accurate optical emission analysis of 15N and 13C in ammonium salts and bicarbonates, respectively. The amount of sample required for each analysis is in the range 10 to 100 μmol. In the procedure proposed, complicated chemical techniques have been avoided through (1) decomposition of the sample by heating; (2) removal of unwanted compounds, and regulation of pressure, by cooling; and (3) production of N2 and CO+ from NH3 and CO2, respectively, by electrodeless microwave interaction. These three steps are followed by (4) measurement of relevant peak heights in the N2 and CO+ spectra obtained.
Deconvolution of the Lorentzian Linewidth and Determination of Fraction Lorentzian Character from the Observed Profile of a Raman Line by a Comparison Technique
Authors: Asthana B. P. , Kiefer W.
Published: August 2005

We report on a simple method to derive the Lorentzian linewidth of a Raman line as well as its fraction Lorentzian character. The method is based on the experimental determination of the bandwidths at half maximum obtained from recorded Raman and plasma lines with same spectrometer slit settings. From the ratio of the two half bandwidths, the Lorentzian Raman linewidth can be easily derived from the given table. This table was compiled by explicit calculations of Voigt profiles. The fraction Lorentzian character, needed for instance for Raman difference spectroscopy, can be obtained directly from this table to a good accuracy.
Influence of the Generator Frequency on the Spectral Characteristics of Inductively Coupled Plasma
Authors: Capelle B. , Mermet J. M. , Robin J.
Published: August 2005

Different high-frequency generators have been studied in the 5 to 56 MHz range in order to observe the influence of frequency on spectral characteristics of inductively coupled plasmas used in emission spectroscopy. Higher frequencies tended to yield decreased excitation temperatures and electron number densities and therefore decreased line and background continuum intensities. Signal-to-noise ratios were improved ranging from 1 to 8 MHz going from 27 to 56 MHz with similar improvements in detection limits. Precision, working curve linearity, chemical interferences, and the ability to atomize high salt concentration samples were unaffected by frequency.
Vibrational Spectral Studies of Solutions at Elevated Temperatures and Pressures. III. A Furnace Assembly for Raman Spectral Studies to 300°C and 15 MPa
Authors: Irish D. E. , Jarv T. , Ratcliffe C. I.
Published: August 2005

The design of a furnace assembly for maintaining aqueous solutions at temperatures up to 300°C and controlled pressures of up to 15 MPa is described. The apparatus is being used to monitor the chemical processes taking place in high-temperature aqueous solutions. Spectra of the Zn(NO3)2/H2O system and the HCl/H2O system are presented as examples.
Phase Dependence of Saturation Transfer EPR Signals and Estimated Rotational Correlation Times
Authors: Watanabe Tokuko , Sasaki Takayoshi , Fujiwara Shizuo
Published: August 2005

The second harmonic absorption out-of-phase signal (V2′ mode) is usually observed in saturation transfer electron paramagnetic resonance spectroscopy to determine slow rotational correlation times. It is known that adjustment of 90° out-of-phase is critically important to detect accurate ST-EPR spectra. The digitized ST-EPR spectrometer using the Fourier transformation method developed by the authors has enabled determination of the phase dependence of ST-EPR signals simply by calculating V2′ signals under the condition of various phase deviations from exactly 90° out-of-phase. The overall 90° out-of-phase accuracy of the present system was confirmed to be within 0.3°. Phase dependence of both the ST-EPR parameters and the correlation times estimated from them was quantitatively discussed. Conclusively, accuracy of phase-adjustment is required to be within ±0.5° for less than 10%, and ±2° or 3° for less than approximately 30% errors on the correlation times. For determination of correlation times the parameter L″/L provides better accuracy than the parameter C′/C, even if 90° out-of-phase is set with some phase deviation.
Practical Determination of Flame Species via Laser Saturation Fluorescence Spectroscopy
Authors: Ahn B. T. , Bastiaans G. J. , Albahadily F.
Published: August 2005

The observation of molecular fluorescence caused by high-power pulsed laser excitation has been found to be an accurate technique for the determination of relative OH radical concentrations on a spatially resolved basis in a circular air-acetylene flame. It was found that the high power of radiational excitation used allowed fluorescence saturation to be approached. Theory then predicts fluorescence intensities to be independent of temperature and collisional quenching effects. However accurate estimates of relative concentrations can not be obtained unless corrections are made for incomplete saturation and postfilter effects. Procedures for conveniently applying such corrections are reported.
Determination of Atomic and Molecular Excited-State Lifetimes Using an Optoelectronic Cross-Correlation Method
Authors: Russo R. E. , Hieftje G. M.
Published: August 2005

A new optoelectronic cross-correlation technique has been used to measure excited-state lifetimes of several organic fluorophores in solution and of sodium atoms in both air-acetylene and methane-air flames. Capable of time resolution in the picosecond range, the new method was validated by the excellent agreement between measured and literature values for fluorescence lifetimes of the organic species. Lifetime values for Na atoms in flames are among the most precise ever reported and agree closely with values calculated from the known flame gas composition, temperature, and the quenching cross-sections of the two dominant quenching species in the flame, N2 and CO2. From the Na excited-state lifetimes (0.72 ± 0.07 ns for air-acetylene and 0.48 ± 0.08 ns for methane-air flames), quantum efficiencies for atomic fluorescence were calculated.
Frequency Analysis of Pulsed Optoacoustic Signals and the Application to Chemical Analysis
Authors: Fisher M. R. , Fasano D. M. , Nogar N. S.
Published: August 2005

The optoacoustic signal generated via pulsed laser excitation-transducer detection is frequency analyzed via a discrete Fourier transform. The frequency spectrum is found to exhibit a pronounced maximum at the transducer resonant frequency. Use of this maximum as a measure of the optoacoustic signal strength allows for discrimination against window absorption and various electrical and mechanical noise sources.
Thermal Lensing Colorimetry of Nitrite Ion with Single-Laser System
Authors: Fujiwara Kitao , Uchiki Hisao , Shimokoshi Fumio , Tsunoda Kin-Ichi , Fuwa Keiichiro , Kobayashi Takayoshi
Published: August 2005

Thermal lensing colorimetry has been applied to the determination of nitrite ion. Color development was based on the diazo-coupling reaction among NO2−, N-(naphthyl)-ethylenediamine dihydrochloride, and sulfanylamide. The source was the chopped output of an Ar+ laser operated at 514.5 nm. The beam intensity was measured with a silicon photocell of 1 mm2 surface area and the resultant electrical signal was processed with a microcomputer system. The minimal detectable amount of nitrite ion using a cell of 1 cm path length is 0.2 n M. This is more than 200 times smaller than the detection limit of ordinary spectrophotometry using a commercial spectrophotometer.
Criteria for Presentation of Spectra from Computerized IR Instruments
Authors: Grasselli Jeanette G. , Griffiths Peter R. , Hannah Robert W.
Published: August 2005

With the development of sophisticated data systems for dispersive and Fourier transform infrared spectrophotometers, users of these instruments have capabilities at their fingertips which were not available to infrared spectroscopists a few years ago. Although computers permit more advanced experiments to be performed using an infrared spectrometer, they also increase the need for detailed communication of exactly how spectra were measured and subsequently manipulated. Using a computerized infrared spectrophotometer, a competent spectroscopist can obtain an enormous quantity of information on his sample through such operations as spectral subtraction, but these new capabilities can also occasionally lead to the generation of unexpected artifacts in computer-manipulated spectra. In an attempt to guard against problems of this type and to allow better interlaboratory reproducibility, a subcommittee of the Coblentz Society was set up to recommend the type of information which should be included with published spectra.
Compression of an Infrared Spectral Library by Karhunen-Loeve Transformation
Authors: Hangac G. , Wieboldt R. C. , Lam R. B. , Isenhour T. L.
Published: August 2005

A data compression technique using factor analysis and the Karhunen-Loeve transformation has been applied to a library of vapor phase infrared spectra. Application of the compression algorithm results in a fivefold reduction in storage requirements for the spectral library and a corresponding reduction in search time. A search system based on the compression data has been evaluated and found to compare favorably with a search using the entire spectrum.
Applications of ESR to Carbonaceous Materials
Authors: Singer L. S. , Lewis I. C.
Published: August 2005

The applications of electron spin resonance (ESR) to carbonaceous materials are reviewed. The stable paramagnetic species observed in the products of low-temperature pyrolysis are odd-alternate neutral free radicals, whereas the unpaired spins of higher temperature carbons and graphites are primarily conduction electrons. The variety of ESR properties and phenomena requires special attention to techniques of measurement and interpretations of results. The relevance to the carbonization process of the free radicals observed by ESR is also discussed.
Quantitative Trace Analysis by X-ray Fluorescence Using the Computer Program NRLXRF
Authors: Keenan J. A. , Holmes D.
Published: August 2005

The computer program NRLXRF has been applied to the determination of minor and trace constituents in aluminum alloys and several National Bureau of Standards certified standard reference materials. Limitations arising from energy dispersive x-ray analysis and the fundamental-parameter method used by NRLXRF are illustrated.
Capillary Discharge Lamp for the Direct Determination of Iodine by Flame Atomic Absorption Spectroscopy
Authors: Lowe M. D. , Sutton M. M. , Clinton O. E.
Published: August 2005

A simple and inexpensive iodine capillary discharge lamp has been developed. The spectrum of iodine was produced by maintaining a current-limited alternating current discharge in a helium-iodine vapor mixture flowing through a quartz capillary discharge tube. The performance of this spectral lamp as a source of resonance radiation for atomic absorption spectroscopy was evaluated using both unshielded and argon-shielded air-acetylene and nitrous oxide-acetylene flames. Sensitivities and detection limits for iodine obtained using the reported spectral source were found to compare favorably with data reported by other workers who used an electrodeless discharge lamp and a modified hollow cathode lamp.
Layered Synthetic Microstructures as Dispersing Devices in X-ray Spectrometers
Authors: Gilfrich J. V. , Nagel D. J. , Barbee T. W.
Published: August 2005

Layered synthetic microstructures (LSM's) are useful dispersing devices for x-ray spectroscopy. They can be produced with virtually any layer spacing ( d) greater than approximately 10 Å and they have high diffraction efficiency. Integral reflection coefficients for such structures made up of alternating layers of a transition metal and carbon are 3 to 10 times greater than values for other dispersing elements used in the moderate to long wavelength region of the x-ray spectrum. Resolving power of the LSMs is somewhat poorer than crystals at this time but is sufficient to permit significant applications.
Spectrophotometry and Spectrofluorometry with the Self-Scanned Photodiode Array
Authors: Talmi Yair
Published: August 2005

A state-of-the-art self-scanned photodiode array, utilized as a spectrometric multichannel detector, was studied for its applicability to molecular absorption and molecular fluorescence spectrometry. Molecular absorption spectrophotometry requires detectors with high UV to near IR response, high dynamic range, linear response, low noise, and temporal as well as thermal stability. Molecular fluorescence spectrometry requires, in addition, sensitivity to low-light level signals. These requirements were satisfied by the systems under study. Other parameters that govern the overall performance of diode array-based spectrophotometers and spectrofluorometers include: photometric range, stray energy radiation and its effect on photometric accuracy, photometric precision, spectral resolution sensitivity, and signal-to-noise considerations. Various readout methods for the array detectors were examined including: real time, in-memory signal integration, on-target signal integration, variable integration time (VIT), diode grouping, and diode fast access (a pseudorandom access readout). Performance demonstrations of these multichannel spectrometers were made with a few typical chemical systems. The spectrophotometric performance of the diode array system was excellent, practically equal to that of conventional single-channel systems. Exceptions were higher amenability to the adverse effects of stray radiation energy and a dependency of the geometric (wavelength) accuracy on spatial fluctuations (wander) in the light source. Potential long-term UV degradation of diode arrays may present an inherent problem, but was not discussed here because data accumulated up-to-date was considered inconsequential. As a spectrofluorometer multichannel detector, the diode array showed an “unexpected” signal-to-noise (detectability) performance, closely matching that of conventional high gain detectors. However, this performance was achieved only if sufficiently long signal integration times (20 to 160 s) were feasible. Overall performance of the diode array has demonstrated that theoretical multiplex advantages are achievable, resulting in either a considerable improvement in signal-to-noise or a corresponding shortening in observation time.
Calculation of Discharge Current Waveforms in High Voltage Spark Sources. II. Extensions and Limitations of Closed-Form Solution
Authors: Scheeline Alexander , Tran T. V.
Published: August 2005

Simulation of gap breakdown and dynamic impedance effects in high voltage spark sources is performed using an algebraically exact solution to an approximate model of source behavior. The importance of diode shunt capacitance in determining gap breakdown behavior is shown. Limitations in generality and implicit use of numerical methods in dynamic situations lead naturally to consideration of numerical integration methods. Comparisons to hardware sources are made.
Effect of Spectrometer Resolution on Absorption Spectra
Authors: Arora A. K. , Kesavamoorthy R.
Published: August 2005

The effect of spectrometer resolution on the parameters of an absorption spectrum is studied by numerical convolution. The dependencies of observed full width at half maximum (FWHM) and peak absorption on spectrometer resolution, true FWHM and peak absorption of the absorption band is obtained. The observed dependencies are explained qualitatively. Over the useful range of parameters, coupled empirical relations are obtained which estimate the parameters of the true spectrum from the parameters of the observed spectrum within 1.5%. The usefulness of the coupled empirical relations is demonstrated by applying them to C—H stretching mode of CHCl3.
An Objective Function for Optimization Techniques in Simultaneous Multiple-Element Analysis by Inductively Coupled Plasma Spectrometry
Authors: Leary J. J. , Brookes A. E. , Dorrzapf A. F. , Golightly D. W.
Published: August 2005

This work considers several composite objective functions and uses the sequential simplex optimization technique to evaluate the performance of a proposed objective function in locating optimal instrumental operating conditions for simultaneous multiple-element determinations by inductively coupled plasma spectrometry. The proposed objective function, combined with a generalized approach to optimization, can be applied to any group of analysis elements and is of value in routine optimization procedures for simultaneous multiple-element methods of analysis.
Computer Control of Basic and Applied Experiments in Spark Emission Spectroscopy
Authors: Mathews Samuel E. , Ekimoff David , Walters John P.
Published: August 2005

A hardware system is described which provides for software-independent timing of events necessary for the smooth operation of an adjustable waveform spark source. Illustrative cases are given showing the extension of this system into a single-channel spectrometer and a complex schlieren photography experiment. Software outlines are also provided. The use of an optical coupler and a fiber optic are shown to improve system performance greatly in high radio frequency interference environments.
Electron Number Density Measurements in Ar and Ar-N2 Inductively Coupled Plasmas
Authors: Montaser Akbar , Fassel Velmer A.
Published: August 2005

The emission spectrum of the series limit of Al was used to estimate the electron number densities ( n e) in inductively coupled Ar or Ar-N2 plasmas (ICP). The spectra of the series limit were recorded either with a silicon-intensified target vidicon detector or by a computer-controlled, scanning spectrometer. Background stripping was performed on the spectra recorded by both instruments to enhance signal recovery. Under comparable experimental conditions, the n e values in the Ar-supported ICP were higher than those observed in Ar-N2 plasma, when pure N2 was used in the outer flow. However, the n e value of the Ar ICP under the conditions commonly used in analytical laboratories (15 mm observation height and 1200 W forward power) was comparable to that found in pure N2 outer flow, Ar-N2 plasmas operated under conditions (5 mm observation height and 3000 W forward power) suitable for exciting spectral lines of high excitation energies. Whereas the use of higher, carrier gas flows tended to reduce the n e values of the Ar ICP substantially, this trend was not observed for the pure N2 outer flow Ar-N2 plasma.
Characterization of Carlin-Type Gold Ore by Photoacoustic, Raman, and EPR Spectroscopy
Authors: Nelson John H. , Macdougall J. Jeffrey , Baglin Frank G. , Freeman Dean W. , Nadler Mel , Hendrix James L.
Published: August 2005

Low-grade carbonaceous gold ore (0.01 to 1.8 oz/ton of gold) from the Carlin mine in Elko county, Nevada, has been characterized by a variety of analytical and spectroscopic techniques with emphasis on vibrational spectroscopy. A particular concern was determining the nature of the carbon-containing material in the ore. It was found that in addition to the anticipated carbonate, finely disseminated elemental carbon is present in amounts ranging from 0.062 to 0.43 wt. %. Contrary to previous reports, no detectable amounts of humic acid materials or organic hydrocarbons are present in any of the samples investigated.
Analysis of Oxalic Acid Leachates of Geologic Materials by Inductively Coupled Plasma-Atomic Emission Spectroscopy
Authors: Motooka J. M. , Sutley S. J.
Published: August 2005

The introduction of induction coupled plasma-atomic emission spectroscopy (ICP-AES) has satisfied, to a large degree, the requirement for a higher quality data-generating technique. The methods used in exploration geochemistry include many partial or selective digestion techniques that can readily be adapted to ICP-AES analysis. Extensive and highly significant new information cannot only be added to a mineral's evaluation by providing associated trace metals previously overlooked or unobtainable because of detection limits, but also suggests a degree of differentiation of mineral fractions and their ability to scavenge trace metals from other sources. Oxalic acid leaching of soils and stream sediments has long been recognized as a method for dissolving secondary Fe and Mn oxides. Modifications in the digestive procedure to produce solutions compatible with ICP-AES instrumentation have not only significantly reduced analytical time and increased precision over previously used instrumental methods, but have also provided a technique that allows for greater geochemical interpretation.
Anomalous Bands in Infrared Difference Spectra Due to Frequency Shifts
Authors: Brown Chris W. , Lynch Patricia F. , Obremski Robert J.
Published: August 2005

Artifacts appearing in infrared difference spectra can be caused by the lack of wavelength reproducibility and/or molecular interactions such as solvent effects. These artifacts appear as derivatives in difference spectra. Experimental spectra containing a number of bands with a variety of bandwidths were shifted over a range of frequencies and subtracted from the original spectra to intentionally produce anomalous bands. Models based on both Lorentzian and Gaussian band shapes were used to fit the observed data, and it was found that either band shape could be used to adequately predict the observed results within the experimental error of the measurements. Moreover, the models can be used to determine the values of the frequency shifts from the peak-to-peak differences of artifacts.
An Evaluation of the Rasberry-Heinrich Model for the Analysis of Silicate Rocks
Authors: Lindsay James R. , Rose Harry J. , Larson Richard R.
Published: August 2005

The Rasberry-Heinrich model for correcting for absorption and secondary fluorescence effects is evaluated in the analysis of silicate rocks. The interelement effect of binary mixtures of the oxides of Na, Mg, Al, Si, K, Ca, Ti, Fe, and Mn is studied in a 1:11 fusion mixture with Li2B4O7. Two binary systems are expected to exhibit secondary fluorescence effects and are reported in detail. The combination Fe2O3/TiO2 shows a small secondary fluorescence, whereas the Al2O3/SiO2 binary shows an absorption effect. The latter effect is attributed to the large absorption effect due to oxygen. The secondary fluorescence of its Fe2O3/TiO2 system in a diluted matrix of Li2B4O7 acts like a negative absorption rather than secondary fluorescence as described by the Rasberry-Heinrich model.
The Emergence and Exploration of Vibrational Optical Activity
Authors: Nafie Laurence A.
Published: August 2005

Vibrational optical activity is a new field of molecular spectroscopy which combines the methods of circular differential polarization measurement with the infrared and Raman forms of vibrational spectroscopy. These new spectroscopies, known as infrared vibrational circular dichroism and Raman optical activity, have evolved over the past decade and are presently beginning to make meaningful contributions to the understanding of vibrational force fields and the redistribution of electronic charge in vibrating chiral molecules. In this article some of the early events which led to the author to pursue the development of vibrational optical activity will be described followed by a sampling of recent results of the measurement and calculation of vibrational circular dichroism intensities.
A Modular-Type Spectrophotometer System Characterized by Distributed Multiprocessor Configuration
Authors: Susaki Hironori , Minami Shigeo
Published: August 2005

The advent of the microprocessor has made it possible to provide a variety of intelligent instruments for the analytical laboratory. This trend eventually suggested the introduction of the distributed function multiprocessor concept, one of the recent system approaches in computer technology, to accommodate the growing intricacy of laboratory automation systems. To demonstrate an example of unconventional design schemes for intelligent instruments, a distributed function multiprocessor network is implemented in a small spectrophotometer. The total function is divided into basic spectrophotometric measurement, data processing, and data display, and each of them is allocated to an individual microprocessor integrated module which can communicate with others through the IEEE-488 standard interface bus. The notable feature of the system is simplicity of expansion by combining the independent functional modules along the standard interface bus. The details of the system structure and operational procedures are presented together with typical performance data.
A Study of Measurement Interference in the Optoacoustic Detection of NO2 by Argon-Ion Laser Excitation
Authors: Fried Alan
Published: August 2005

Optoacoustic measurements of NO2 excited by an Ar+ laser were performed in the presence of NO, N2, H2O, and O2 matrix gases. Identical sensitivities were measured in all matrix gases except O2 where energy transfer from NO2 to the metastable O2(1Δg) state resulted in a dramatic decrease in sensitivity.
Polarization Demodulation: A New Approach to the Reduction of Polarization Artifacts from Vibrational Circular Dichroism Spectra
Authors: Lipp Elmer D. , Zimba Carl G. , Nafie Laurence A. , Vidrine D. Warren
Published: August 2005

In vibrational circular dichroism (VCD) measurements and other polarization modulation techniques, artifact signals often arise due to polarization sensitivity of the optical components located subsequent to the sample. In this paper, we describe a method for demodulating the light beam after passage through the sample in such a manner that only one linearly polarized state is allowed to reach the detector, thus eliminating these artifacts. The method is a beam reversal technique in which the light subsequent to the sample is redirected through the photoelastic modulator in such a way that the retardation produced on the first traversal through the modulator is removed. The light is returned to its original state of linear polarization prior to detection. The method is applicable to Fourier transform as well as to dispersive spectrometers since demodulation is effected for all wavelengths simultaneously. The results of preliminary demodulation experiments are presented and found to be more than 90% efficient in removing circular dichroism intensity of a birefringent origin.
Librational Modes of Water in Zinc Formate Dihydrate
Authors: Tewari G. D. , Tayal V. P. , Khandelwal D. P. , Bist H. D.
Published: August 2005

The infrared spectra of zinc formate dihydrate are presented for the region 1000 to 400 cm−1 along with the laser-excited Raman spectra. With the use of the corresponding IR and Raman spectra for the deuterated and anhydrous samples and their temperature dependence (between 300 to 90 K), two sets of bands for the in-plane bending mode of formate ion and all the three librations of water have been identified corresponding to two types of formate and water in the unit cell. The large shift of the formate ν3 mode in going from the hydrate to the deuterate has been attributed to a dynamic interaction of this mode with the close-lying H2O rocking mode.
A Model for the Interpretation of CARS Experimental Profiles
Authors: Kotlar Anthony J. , Vanderhoff John A.
Published: August 2005

A simple formalism is presented for interpreting the influence of experimental design parameters on CARS profiles. An explanation for the observed CARS signal is given in terms of idealized limiting cases for both narrow band and broadband applications, with the role of the detector slit function emphasized in interpreting experimental results. Expressions are derived that reduce the calculation of the CARS signal to a single numerical integration for Gaussian laser profiles and both Gaussian and triangular slit functions. These expressions explicitly contain the experimental design parameters. For flexibility, the form of the susceptibility is unspecified except for a single frequency dependence.
Analytical Applications of Matrix Isolation Fourier Transform Infrared Spectroscopy
Authors: Mamantov G. , Garrison A. A. , Wehry E. L.
Published: August 2005

A review of analytical applications of matrix isolation Fourier transform infrared spectroscopy is presented. The characteristics of matrix isolation spectroscopy are discussed along with practical techniques for obtaining analytically useful results. A few studies relating to matrix isolation used in conjunction with Raman and conventional IR spectroscopy are reviewed. The majority of analytical applications of matrix isolation vibrational spectroscopy has entailed the use of FT-IR techniques. Qualitative and quantitative results from a number of sample types are presented. The coupling of matrix isolation vibrational spectroscopy with chromatographic separations is reviewed.
Application of Raman Spectroscopy to the Study of Adsorption Effects at Liquid-Solid Interfaces
Authors: Witke Klaus
Published: August 2005

A sample cell for investigating suspensions or emulsions by Raman spectroscopy in the optically favorable 90° scattering arrangement is described. The Raman spectra of pyridine in a suspension of Aerosil 200 in carbon tetrachloride are recorded. The adsorption isotherm of pyridine is determined from the intensities of the Raman lines at 1008 and 990 cm−1. Over a long range of coverage a linear relationship exists between reciprocal concentrations of chemisorbed and dissolved molecules. The minimal surface area that is occupied by a chemisorbed molecule is determined to be approximately 0.75 nm2.
Atomic Emission Spectrometry with a Skimmed Inductively Coupled AR Plasma
Authors: Montaser Akbar , Fassel V. A.
Published: August 2005

A skimmer located below the usual observation height of an inductively coupled plasma (ICP) allows the axial channel region of the ICP to flow through the central hole of the skimmer while the outer Ar flow is deflected. Signal-to-background (S/B) ratios and the estimated detection limits measured immediately above the skimmer were generally 5 to 20 times superior to the best results obtained by the conventional ICP system. The highest S/B lines possessed wavelengths greater than 300 nm. Matrix effect studies on the Ca-PO4 and the Ca-Al systems revealed that the skimmed plasma was as free of vaporization-atomization interference as the conventional plasma, but easily ionizable elements produced a greater level of suppression/enhancement effects. Electron number densities, as determined via the series limit line merging technique, were lower in the skimmed plasmas as compared with the conventional ICP's.
A Double-Modulation Fourier Transform Infrared Approach to Studying Adsorbates on Metal Surfaces
Authors: Dowrey A. E. , Marcott Curtis
Published: August 2005

Polarization modulation has been combined with Fourier transform infrared (FT-IR) spectroscopy to yield a sensitive method for obtaining infrared reflection-absorption spectra of monolayer films adsorbed on low-area metal surfaces. A 10-Å film of cellulose acetate adsorbed on a polished copper coupon was examined and the results compared with spectra obtained on the same instrument without polarization modulation. The signal-to-noise ratio is significantly better with the polarization modulation approach. The new method has the additional advantage of being sensitive only to molecules adsorbed on the surface. IR absorption by background gases is not detected.
Spatial Distribution of Interference Effects in ICP Emission Analysis
Authors: Roederer J. E. , Bastiaans G. J. , Fernandez M. A. , Fredeen K. J.
Published: August 2005

The spatial dependence of spectral and matrix interference effects known to affect ICP emission spectrometry has been studied. The emissions of atoms, ions, and molecules were resolved on both a vertical and radial basis. Interference and sample volatility effects were found to be limited to specific spatial regions. Molecular background emission was dominated by the entrainment of air and was limited primarily to the outer radial regions of the plasma. In contrast, the radial displacement of analyte molecular emission from more slowly atomized samples varied with height. In the case of the easily ionized element interference on Ca atomic/ionic emission, evidence was found indicating at least two different mechanisms of interaction. The ability to attain radial resolution was instrumental in assigning causes to interference effects.
Standard Addition Technique for Quantitative Trace Gas Analysis Using Derivative Infrared Diode Laser Spectroscopy
Authors: Mucha John A.
Published: August 2005

The method of standard additions has been applied to the determination of moisture in flowing gases using a derivative diode laser spectrometer to monitor infrared absorption. The suitability of derivative spectroscopy for standard addition analysis is discussed in terms of stability of the blank and linearity of response. It is shown that by using the method of standard additions in spectroscopic determinations, line-broadening effects due to the components of the bulk gas are automatically compensated and do not influence analytical accuracy. Simple experimental procedures are outlined for making additions and the use of standards several orders of magnitude more concentrated than the unknown is validated experimentally.
A Scanning Algorithm for Condensed-Phase CARS and Folded Boxcars
Authors: Carreira L. A. , Nelson R. , Horovitz M. L. , Azarraga L.
Published: August 2005

A scanning algorithm for condensed-phase CARS and folded BOXCARS along with the necessary optical alignment hardware for folded BOXCARS have been developed. Due to the unique geometry of the folded BOXCARS beams, the CARS signal is sufficiently isolated from the pump and Stokes beams such that extended spectra with a lower frequency limit of 70 cm−1 have been obtained.