bluuebunny/crossref_metadata_2025 huggingface dataset:
Automated Three-dimensional Volume Rendering of Helical Computed Tomographic Angiography for Aneurysms: An Advanced Application of Neuronavigation Technology
Authors: Benvenuti Lucia , Chibbaro Salvatore , Carnesecchi Stefano , Pulerà Flavio , Gagliardi Rolando
Published: July 2005

OBJECTIVE:

To introduce the possibility of volume-rendered helical computed tomographic (CT) angiographic data sets by use of Medtronic StealthStation Treon surgical navigation technology (Medtronic Surgical Navigation Technologies, Louisville, CO) and to evaluate the clinical usefulness of the method in planning and performing surgical treatment of intracranial aneurysms.

METHODS:

Between November 2002 and July 2003, we studied 15 patients with suspected intracranial aneurysms. All patients but two received conventional digital subtraction angiography, which failed to provide the requested information. Helical CT angiography was performed in all patients, and data sets were transferred to the StealthStation system across an electronic network to be automatically postprocessed by use of three-dimensional (3-D) volume rendering. The 3-D volume-rendered images were accurately analyzed to obtain more complete information about the aneurysm and to provide accurate treatment planning. In all patients, the 3-D volume-rendered model was displayed on the screen of the StealthStation system for the duration of the surgical procedure and compared with the intraoperative image.

RESULTS:

Data sets from CT angiography were automatically postprocessed by the StealthStation in seconds with excellent results, providing us, before and during surgery, with additional information not always available on traditional digital subtraction angiographic investigation. Because of the very short time necessary to complete this process (<5 min to obtain 3-D volume-rendered images), it was possible to perform emergency clipping of the aneurysms in two patients who had been admitted in very compromised neurological conditions. In 12 patients, integrated digital subtraction angiography and automated 3-D volume-rendered images allowed an accurate presurgical evaluation. Furthermore, in all patients on whom surgery was performed, aneurysms were found in the exact location and with the same anatomic features as depicted by the 3-D volume-rendered models.

CONCLUSION:

Reports in the literature indicate that information gathered by CT angiography with volume rendering shows a significant impact on aneurysm management. The StealthStation system upgraded with the adequate algorithm seems to provide a time- and cost-effective method of performing automated 3-D volume rendering of CT angiography and provides an interesting alternative to the available investigation modalities in case of emergency.
Transcranial Surgery for Pituitary Adenomas
Authors: Youssef A. Samy , Agazzi Siviero , van Loveren Harry R.
Published: July 2005

Although The Transsphenoidal approach is the preferred approach to the vast majority of pituitary tumors with or without suprasellar extension, the transcranial approach remains a vital part of the neurosurgical armamentarium for 1 to 4% of these tumors. The transcranial approach is effective when resection becomes necessary for a portion of a pituitary macroadenoma that is judged to be inaccessible from the transsphenoidal route because of isolation by a narrow waist at the diaphragma sellae, containment within the cavernous sinus lateral to the carotid artery, projection anteriorly onto the planum sphenoidale, or projection laterally into the middle fossa. The application of a transcranial approach in these circumstances may still be mitigated by response to prolactin inhibition of prolactinomas, the frequent lack of necessity to remove asymptomatic nonsecretory adenomas from the cavernous sinus, and the lack of evidence that sustained chemical cures can be reliably achieved by removal of secretory adenomas (adrenocorticotropic hormone, growth hormone) from the cavernous sinus. Cranial base surgical techniques have refined the surgical approach to pituitary adenomas but have had less effect on actual surgical indications than anticipated. Because application of the transcranial approach to pituitary adenomas is and should be rare in clinical practice, it is useful to standardize the technique to a default mode with which the surgical team is most experienced and, therefore, most comfortable. Our default mode for transcranial pituitary surgery is the frontotemporal-orbitozygomatic approach.
Monorail Snare Technique for the Recovery of Stretched Platinum Coils: Technical Case Report
Authors: Fiorella David , Albuquerque Felipe C. , Deshmukh Vivek R. , McDougall Cameron G.
Published: July 2005

OBJECTIVE AND IMPORTANCE:

Coil stretching represents a potentially hazardous technical complication not infrequently encountered during the embolization of cerebral aneurysms. Often, the stretched coil cannot be advanced into the aneurysm or withdrawn intact. The operator is then forced to attempt to retract the damaged coil, which may result in coil breakage, leaving behind a significant length of potentially thrombogenic stretched coil material within the parent vessel. To overcome this problem, we devised a technique to snare the distal, unstretched, intact portion of the platinum coil by use of the indwelling microcatheter and stretched portion of the coil as a monorail guide.

CLINICAL PRESENTATION:

We have used this technique successfully in four patients to snare coils stretched during cerebral aneurysm embolization. Three of these patients were undergoing Neuroform (Boston Scientific/Target, Fremont, CA) stent-supported coil embolization of unruptured aneurysms. In all cases, the snare was advanced easily to the targeted site for coil engagement by use of the microcatheter as a monorail guide. Once the intact distal segment of the coil was ensnared, coil removal was uneventful, with no disturbance of the remainder of the indwelling coil pack or Neuroform stent.

TECHNIQUE:

A 2-mm Amplatz Goose Neck microsnare (Microvena Corp., White Bear Lake, MN) was placed through a Prowler-14 microcatheter (Cordis Corp., Miami, FL). The hub of the indwelling SL-10 microcatheter (Boston Scientific, Natick, MA) was then cut away with a scalpel, leaving the coil pusher wire intact, and removed. The open 2-mm snare was then advanced over the outside of the coil pusher wire and microcatheter. The snare and Prowler-14 microcatheter were then advanced into the guiding catheter (6- or 7-French) as a unit over the indwelling SL-10 microcatheter. By use of the SL-10 microcatheter and coil as a “monorail” guide, the snare was advanced over and beyond the microcatheter and the stretched portion of the coil until the snare was in position to engage the distal unstretched coil. At this point, the snare was then closed around the intact portion of the coil, and the microcatheters, snare, and coil were removed as a unit.

CONCLUSION:

The monorail snare technique represents a fast, safe, and easy method by which a stretched coil can be removed.
Supratentorial Arteriovenous Malformations
Authors: Clatterbuck Richard E. , Hsu Frank P.K. , Spetzler Robert F.
Published: July 2005

ARTERIOVENOUS MALFORMATIONS ARE a heterogeneous group of intra-axial central nervous system vascular lesions consisting of tangles of abnormal arteriovenous connections without intervening capillary beds. The heterogeneity of arteriovenous malformations is described by the Spetzler-Martin grading scale, a scale that also forms the basis for clinical decision making. The microsurgical treatment of appropriately selected supratentorial arteriovenous malformations is based on the tenets of circumferential isolation and transection of arterial feeders, preservation of vessels en passant and surrounding functional neural tissue, and skeletonization and transection of venous drainage.
A novel protein kinase C α-dependent signal to ERK1/2 activated by αVβ3 integrin in osteoclasts and in Chinese hamster ovary (CHO) cells
Authors: Rucci Nadia , DiGiacinto Claudia , Orrù Luigi , Millimaggi Danilo , Baron Roland , Teti Anna
Published: July 2005

We identified a novel protein kinase C (PKC)α-dependent signal to extracellular signal-regulated kinase (ERK)1/2 in mouse osteoclasts and Chinese hamster ovary (CHO) cells, specifically activated by the αVβ3 integrin. It involves translocation (i.e. activation) of PKCα from the cytosol to the membrane and/or the Triton X-100-insoluble subcellular fractions, with recruitment into a complex with αVβ3 integrin, growth factor receptor-bound protein (Grb2), focal adhesion kinase (FAK) in CHO cells and proline-rich tyrosine kinase (PYK2) in osteoclasts. Engagement of αvβ3 integrin triggered ERK1/2 phosphorylation, but the underlying molecular mechanism was surprisingly independent of the well known Shc/Ras/Raf-1 cascade, and of phosphorylated MAP/ERK kinase (MEK)1/2, so far the only recognized direct activator of ERK1/2. In contrast, PKCα was involved in ERK1/2 activation because inhibition of its activity prevented ERK1/2 phosphorylation. The tyrosine kinase c-Src also contributed to ERK1/2 activation, however, it did not interact with PKCα in the same molecular complex. The αVβ3/PKCα complex formation was fully dependent upon the intracellular calcium concentration ([Ca2+]i), and the use of the intracellular Ca2+ chelator 1,2-bis(o-amino-phenoxy)ethane-N,N,N′,N′-tetraaceticacidtetra (acetoxymethyl) ester (BAPTA-AM) also inhibited PKCα translocation and ERK1/2 phosphorylation. Functional studies showed that αVβ3 integrin-activated PKCα was involved in cell migration and osteoclast bone resorption, but had no effect on the ability of cells to attach to LM609, suggesting a role in events downstream of αVβ3 integrin engagement.
Imaging with Functional Group Maps Using Infrared Microspectroscopy
Authors: Harthcock M. A. , Atkin S. C.
Published: July 2005

The interface of a two-dimensional computer-controlled stepper-motor-driven microscope stage with an infrared microspectroscopy system is explained in terms of its usefulness in performing microscopic imaging. Images are obtained by reducing spatially specific infrared spectra to functional group maps. The maps are constructed at a given infrared absorption frequency and are a function of the intensity versus x and y spatial coordinates. The use of the technique is demonstrated through two examples of polymer characterization. Transmittance infrared spectra reduced to five images based on absorptions at 1735, 1241, 1016 (ester functionalities), 1892 (crystalline band), and 908 (vinyl unsaturation) cm−1 show that a polyethylene film contains an inclusion of an acetate-containing material. Reflectance infrared spectra reduced to an image based on a ratio of the absorptions at 1738 cm−1 (ester carbonyl) and 1705 cm−1 (acid carbonyl) show that the streak in a film of an ethylene-acrylic acid/ethylene-methacrylate copolymer blend on aluminum foil contains more of the ester component of the blend.
Figures of Merit for a Diffuse Reflectance Accessory Using an On-Axis Ellipsoidal Collecting Mirror
Authors: Korte E. H.
Published: July 2005

The attainable efficiency of an accessory for diffuse reflectance infrared spectroscopy where both the irradiation and detection optics are located on the same side of the sample is analyzed, the size-dependent noise level of the detector being taken into account. The resulting figures of merit are found to reach up to more than 0.3, when standard detectors of 60° field-of-view are considered.
Analytical Jet Spectroscopy of Tyrosine and its Analogs Using a Pulsed Laser Desorption Volatilization Method
Authors: Li Liang , Lubman David M.
Published: July 2005

Pulsed laser desorption is used as a means of volatilizing nonvolatile and thermally labile molecules for entrainment into a supersonic jet expansion. The jet expansion provides ultracold molecules whose sharp spectral features are probed by resonant two-photon ionization spectroscopy in a time-of-flight mass spectrometer. Such jet-cooled spectra are demonstrated for tyrosine and related structural analogs. Despite the similarity between these tyrosine-based compounds, electronic spectroscopy is shown to be a sensitive probe of small structural changes in these related biological compounds.
Resonant Two-Photon Ionization of CBZ-Derivatized Nonaromatic Peptides Using Pulsed Laser Desorption in Supersonic Beam Mass Spectrometry
Authors: Li Liang , Lubman David M.
Published: July 2005

Resonant two-photon ionization (R2PI) of nonaromatic peptides is studied with the use of CBZ-derivatization as a means of providing an absorbing aromatic center in the near-UV region at 266 nm. The peptides are then vaporized with a pulsed laser-induced desorption method, with subsequent entrainment of the desorbed neutral species into a supersonic expansion. The CBZ-derivatized peptides are then ionized and mass analyzed in a time-of-flight mass spectrometer. The resulting R2PI/MPI-induced fragmentation-ionization patterns generally yield the molecular ion as well as fragments due to specific bond cleavages which are characteristic of the structure of the peptide. Thus, the resulting mass spectra can be used for identification and structural analysis of these small peptides. Most significantly, the laser-induced fragmentation can be used to distinguish between isomeric peptides containing Ile, Leu, or Nle.
Remote Near-IR Spectroscopy over an Optical Fiber with a Modified FT Spectrometer
Authors: Archibald D. D. , Lin L. T. , Honigs D. E.
Published: July 2005

A Fourier transform (FT) spectrometer was configured to measure near-infrared (near-IR) transmission spectra using 80 meters of a 206-μm optical fiber. The single-beam signal-to-noise ratio (S/N) was evaluated for the remote-sensing spectrometer for both Ge and InSb detectors. The instrumental performance was compared with that of the conventional FT spectrometer. The optical attenuation of several different fibers was measured and their possible use as transmission sensors was evaluated. Some advantages and implications of combining an FT spectrometer with optical-fiber sensor measurements are discussed.
Preliminary Studies of Laser-Induced Thermal Emission Spectroscopy of Condensed Phases
Authors: Lin L. T. , Archibald D. D. , Honigs D. E.
Published: July 2005

Laser-Induced Thermal Emission (LITE) spectroscopy is introduced as an analytical technique for condensed-phase specimens. In this technique, a laser beam is used to locally heat the specimen, and the mid-infrared thermal emission is observed. Two different materials and different thicknesses of each material were examined with LITE. The equilibrium temperature attained during a LITE measurement was estimated to be about 50°C. The advantages of LITE over conventional thermal emission are noted. The multiple dimensions of information present and some of the potential analytical applications of LITE are discussed.
Design of a Transmission IR Cell for the High-Temperature Study of Transient Adsorption and Reaction in a Flow System
Authors: Prokopowicz R. A. , Silveston P. L. , Baudais F. L. , Irish D. E. , Hudgins R. R.
Published: July 2005

Acquisition of adsorbate spectra under transient conditions at moderate temperatures and pressures with catalytic solids which adsorb strongly at IR wavelengths requires a carefully conceived cell design. A temperature-controlled, heated block cell with a built-in preheating coil, designed to permit in situ pressing of the catalyst wafers, was designed and built to meet these requirements. Measurements of CO oxidation on a CuO/silica catalyst employing step changes of O2 and CO partial pressures were conducted with the cell mounted in a Bomem FT-IR spectrophotometer, Model DA3.02. A time resolution of about 10 s was achieved with the use of a wafer of millimeter dimension, atmospheric pressure, and temperatures up to 260°C. Significant quantities of unreactive CO were found on the CuO surface.
The Effect of Temperature on the Infrared Spectra of a Polyimide
Authors: Snyder Randy W. , Sheen C. Wade , Painter Paul C.
Published: July 2005

The effect of high temperature on the infrared spectra of fully cured PMDA/ODA polyimide is discussed. Changes in some bands can be explained by Boltzmann effects on the distribution of excited states. Other bands, in particular the 1780-cm−1 band that is often used for cure measurements, change in ways that cannot be related to Boltzmann's equation. These band position and intensity changes are explained as configurational changes occurring during heating. Determination of correction factors for integrated peak areas from spectra taken at elevated temperature are discussed.
Aqueous Infrared Pharmaceutical Analysis of Two Choline Compounds by Flow Injection Analysis Using the CIRCLE Cell
Authors: Miller Blair E. , Danielson Neil D. , Katon J. E.
Published: July 2005

The advent of the cylindrical internal reflectance (CIRCLE) cell has solved the difficult problem of quantitation of solutes in aqueous solutions by infrared spectroscopy. By a combination of flow injection analysis (FIA) and Fourier transform infrared (FT-IR) spectroscopy with the CIRCLE cell, a fast, reproducible technique suited for the determination of two choline compounds of pharmaceutical interest—succinylcholine chloride and bethanechol chloride—was developed. Quantitation was carried out with the use of either the ester band at 1075 cm−1 for bethanechol or the trimethyl quaternary ammonium band at 953 cm−1 for succinylcholine. Linearity of standard solutions was achieved from about 0.5 to at least 50 ppt for both compounds, and detection limits of 0.02% w/v were possible. A sample throughput of 60 samples/h was estimated. Analysis of pharmaceutical preparations was performed after minor sample clean-up, which was necessary only in the case of the bethanechol chloride tablets.
The Effect of Propane on Atomic Spectrometric Signals in the Direct-Current Plasma
Authors: McCreary Terry W. , Long Gary L.
Published: July 2005

The addition of small amounts of propane to the direct-current plasma (DCP) affects the emission signal of analyte species in the plasma. In the normal analytical region of the plasma, a reduction in emission is seen; this reduction can be accounted for by a decrease in excitation temperature caused by the propane in this region of the plasma. Above the analytical region, an enhancement in atomic emission is seen. The excitation temperature in this region of the plasma was found to remain unchanged when propane was added. The mechanism for the enhancement is thought to be the reduction of metal oxides to the corresponding free metal by carbon. Evidence for the mechanism is provided by recognition of the fact that a large reservoir of atomic carbon exists in this region of the plasma and by examination of the behavior of slurries of the metal oxides, introduced into the plasma via a Babington nebulizer.
Characterization of Thin-Film Negative Resist via Photo-FT-IR
Authors: Sommer A. J. , Fuerniss S. J. , Appelt B. K.
Published: July 2005

Negative thin-film photoresists are used extensively in the circuitization of metalized substrates. Frequently questions regarding resist performance and reproducibility arise which require extensive functional evaluation. The analysis of the exposure (intensity, dose, and wavelength) and temperature effects typically requires the incremental analysis of a large matrix of samples. Photoreactions occurring in these resists can be conveniently monitored by FT-IR and correlated with functional performance. We have developed hardware and software accessories for an FT-IR spectrometer which allows spectroscopic analysis of photoresists during exposure to UV light. The utility of the Photo-FT-IR is demonstrated by a report of the photoresponse of two typical negative photoresists as a function of intensity and wavelength. We also report on the thermal stability of these two resist systems.
Polarized FT-IR Spectra of Transition Metal Carbonyl Complexes Oriented in Nematic Liquid Crystal Solvents
Authors: Butler Ian S. , Sedman Jacqueline
Published: July 2005

The polarized FT-IR spectra of Mn2(CO)10, M(CO)6 (M = Cr, W), and CpM′(CO)3 (Cp = η5-C5H5; M′ = Mn, Re) dissolved in a nematic liquid crystal solvent (Merck 1132 TNC) have been recorded at room temperature. Definitive vibrational assignments have been made for the CO stretching modes of the complexes on the basis of their observed polarization behavior. For Mn2(CO)10, assignments are also proposed for MnCO bending modes. The group VIB metal hexacarbonyls are shown to be tetragonally distorted in Merck 1132 TNC. Dichroic spectra were obtained for the CO stretching modes of the CpM′(CO)3 complexes with the use of both Merck 1132 TNC and Kodak X11643 liquid crystal solvents. The complexes orient perpendicularly to the long axes of the components of the Merck liquid crystal and parallel to those of the Kodak one. The dichroic spectra show that the known distortions of the Cp′ rings in these complexes are apparently accompanied by deformation of the M′(CO)3 moieties.
Application of Legendre Polynomials to the Elimination of Baseline Variation in Biological FT-IR Spectra
Authors: Lipkus Alan H.
Published: July 2005

A method for eliminating baseline variation is proposed for use on biological FT-IR spectra. This method is motivated by the fact that baselines are often assumed to be low-degree polynomials. Spectra are expanded in terms of a set of orthonormal polynomials derived from the Legendre polynomials, and leading terms of the expansion, which contain most of the baseline variation, are removed. An application of this method to protein spectra is presented and discussed.
A Detector for Liquid Chromatography and Flow Injection Analysis Using Surface-Enhanced Raman Spectroscopy
Authors: Freeman R. D. , Hammaker R. M. , Meloan C. E. , Fateley W. G.
Published: July 2005

A successful interface between a high-performance liquid chromatograph and a Raman spectrometer is described. Surface-enhanced techniques are utilized to overcome the sensitivity problem inherent to conventional Raman spectrometry by adding a Ag sol to the chromatographic effluent in a post-column mixing coil. The system is designed so that Raman spectra may be obtained from chromatographic effluent or from flow injection analysis effluent. A common organic dye (pararosaniline hydrochloride) is used to evaluate the reproducibility, dynamic range, and analytical capabilities of the system. The SERS instrument is found to be a viable detector for HPLC and FIA, capable of providing structural information with a sensitivity comparable to that of other commonly used HPLC detectors.
An Analysis of the Vibrational Characteristics of Zeolites Using Factor Group Methods
Authors: Maroni V. A.
Published: July 2005

The complete group theoretical representations for the normal modes of twelve high-symmetry zeolite crystal structures (including sodalite, offretite, and zeolite rho, as well as A, X, Y, and L-type zeolites) have been determined by factor group analysis. Comparisons of the predicted number of Raman and infrared active vibrations were made with existing experimental data in cases where such data were available. The prospects for conducting detailed analyses of the vibrational dynamics of zeolite framework structures based on the factor-group-derived representations were also examined. Much of the accepted intuitive understanding of zeolite vibrational spectra is confirmed by the findings of this work: e.g., that the number of predicted Raman and infrared frquencies (1) is consistently far greater than the number actually observed and (2) depends more on the level of symmetry of the zeolite crystal than on the number of atoms in the Bravais unit cell. Tight overlapping of frequencies, particularly those that are primarily bond stretching in nature, is to be expected.
The Design of a Versatile Nanosecond Transient and Time-Resolved Raman Spectrometer
Authors: Findsen E. W. , Ondrias M. R.
Published: July 2005

The instrumental details of a nanosecond to millisecond transient and time-resolved Raman spectrometer are presented. This instrument allows for a variety of sample handling protocols and provides time-resolution appropriate for the investigation of most biological kinetic processes and solution photochemistry involving long-lived excited states. Two specific examples of its application are presented.
An Emission-Based Feedback System for Stabilizing an Inductively Coupled Plasma
Authors: Marks M. A. , Hieftje G. M.
Published: July 2005

An emission-controlled feedback system for stabilizing an ICP has been investigated. Unlike previous stabilization methods which monitor only the power being sent to the plasma, the present one uses an emission signal from either argon or an internal reference element as a stability indicator. Using a previously constructed power-modulation circuit for rf power control, the feedback network adjusts the plasma power to compensate for changes in the emission level of the reference element. It is shown to be particularly useful for reducing or eliminating the drift that occurs when the plasma is warming up. A key point for successful operation of the feedback arrangement is that both the feedback-signal and the analysis photometric systems must receive light from exactly the same region of the plasma. Also, the excitation energy and ionization characteristics of the reference element should be comparable to those of the desired analyte. Results with several combinations of argon, barium, calcium, iron, manganese, sodium, and strontium lines are presented.
Improved Fluorescence Rejection in Measurements of Raman Spectra of Fluorescent Compounds
Authors: Kamogawa Keiji , Fujii Takashi , Kitagawa Teizo
Published: July 2005

Practical ways to achieve fluorescence rejection were developed by using the technique of Raman difference spectroscopy and a gated diode-array detector. In order to improve the signal-to-noise ratio, we had to circumvent the problem presented by the fact that the sensitivities of each element of the diode-array detector are not always uniform and linear—a problem which results in an apparent noise in the observed spectra. Therefore, in this study we tried to separately observe a Raman-plus-fluorescence spectrum ( ST) and a pure fluorescence spectrum ( SF), with a high S/N ratio, and to obtain a Raman spectrum ( SR) as their difference. With a cw Ar+ laser, ST and SF were excited at different wavelengths but recorded in the same wavelength region. This procedure was easy and quite successful for compounds, such as methyl orange and methylene blue, that have a Raman-to-fluorescence intensity ratio ( IR/ IF) of greater than 0.01. With a mode-locked and Q-switched Nd:YAG laser, ST and SF were obtained from different timings of the detector gate (6 ns), i.e., −6 to 0 ns for ST and 3 to 9 ns for SF. The temporal discrimination between Raman and fluorescence photons combined with the Raman difference technique significantly improved the 532-nm excited Raman spectrum of the tetraphenylporphyrin solution. This method is applicable to compounds with an IK/ IF of smaller than 0.01. The time-correlated single photon counting method with a time-to-amplitude converter was improved, to enable it to work with a high repetition rate, and was applied to a Rhodamine 6G solution, which was also examined by the gated Raman difference technique. Advantages and problems associated with each technique and appropriate methods for a given sample will be discussed.
Beating the Nyquist Limit by Means of Interleaved Alternated Delay Sampling: Extension of Lower Mass Limit in Direct-Mode Fourier Transform Ion Cyclotron Resonance Mass Spectrometry
Authors: Verdun Francis R. , Ricca Tom L. , Marshall Alan G.
Published: July 2005

According to the Nyquist theorem, the highest signal frequency which can be represented without foldover (aliasing) in a Fourier transform frequency-domain discrete spectrum is one-half of the time-domain sampling frequency. For example, since ion cyclotron resonance (ICR) frequency is inversely related to ionic mass-to-charge ratio, m/z, the highest ICR frequency (corresponding to the lowest correctly represented m/z) in direct-mode Fourier transform ICR mass spectrometry is restricted to one-half of the maximum sampling frequency, or about m/z ≥ 18 at 3.058 tesla (T) for a maximum sampling frequency of about 5.2 MHz. In this paper, we show that interleaved addition of two digitized time-domain transient signals, one of which is delayed by one-half of one sampling period (i.e., half of one cycle of the time-domain sampling frequency) with respect to the other, generates a time-domain discrete waveform which is indistinguishable from a single waveform produced by sampling at twice the original sampling rate. Thus, provided that the two transients have (or have been normalized to) the same magnitude, one can double the Nyquist-limited frequency range. If the sampling period is divided into three or more equal parts, with interleaved addition of three or more correspondingly delayed transients, the same method can further increase the upper frequency limit. The method is applied to the experimental doubling or quadrupling of FT/ICR direct-mode frequency range, as for example in the extension of the lower mass limit to below m/z = 12 at 3.058 T with a sampling rate of only 4.0 MHz.
Multicomponent Analysis Using Fourier Transform Infrared and UV Spectra
Authors: Donahue Steven M. , Brown Chris W. , Obremski Robert J.
Published: July 2005

Two- and three-component mixtures of methylated benzenes were analyzed with the use of both infrared and UV spectra. The spectra of known mixtures were Fourier transformed and coefficients from the transforms selected to form coordinates of vectors. The resulting vectors were subjected to factor analysis to obtain representations for multicomponent analysis. A total of eight data sets were analyzed by factor analysis after preprocessing by taking the Fourier transforms of the spectra. The eight data sets were also analyzed by the P-matrix method (inverse Beer's law) in the spectral domain after preprocessing of the data to allow selection of the optimum analytical wavenumbers. This spectral method was compared to the Fourier transform method using cross-validation, in which one sample at a time was left out of the standards and treated as an unknown. The Standard Error of Prediction (SEP) was calculated for the two methods for all possible numbers of vectors and numbers of wavenumbers, starting with the number equal to the number of components and increasing up to a total number of standards or some reasonable cut-off value. Processing in the Fourier domain clearly produced the best results for seven of the data sets and equal results for the other set.
Subsurface Image Reconstruction by Near-Infrared Reflectance Analysis
Authors: Lodder Robert A. , Hieftje Gary M.
Published: July 2005

A method is described for reconstructing decorative images concealed by layers of overcoatings. The method employs a nonparametric multivariate algorithm and a cellular-automaton construct to convert the near-infrared spectrum of a surface into digital images of the surface layers. The technique is potentially applicable to the restoration of historic buildings where aging, previous restoration attempts, and even political considerations have resulted in the alteration of the original historic surfaces.
Phase Correction of Vibrational Circular Dichroic Features
Authors: McCoy Colleen A. , De Haseth James A.
Published: July 2005

Several sources of phase-correction-induced spectral anomalies in FT-IR vibrational circular dichroism (VCD) spectra have been investigated. Misidentification of the zero-phase retardation position in dichroic interferograms that exhibit no optical or electronic bias can produce spectral errors. Production of such errors is from the introduction of linear phase error into the phase curve. When the zero-phase retardation position is correctly identified, other spectral anomalies, such as “reflected peaks,” can appear in VCD spectra. These peaks are readily observed in quarterwave plate reference spectra. The anomalies are directly correlated to the arctangent function used to define the phase curve and result only from the nature of the VCD signal. VCD spectra can exhibit negative, as well as positive, peaks; consequently the phase correction must be designed to accommodate negative features. Both Mertz and Forman phase-correction algorithms have been modified to correct the phase of VCD interferograms without error. Such corrections are not necessary, or even desirable, for normal absorption spectrometry.
Application of Waveguide Raman Spectroscopy to High-Index Dielectric Films
Authors: Tallant David R. , Higgins Karen L. , Stewart Alan F.
Published: July 2005

Waveguide Raman spectroscopy has been applied to the analysis of single-layer, refractory-oxide, thin-film coatings on fused silica. With the use of the film as a waveguide, the interaction of the laser probe beam with the film is maximized, and interference from the silica substrate is minimized. An amorphous film of Ta2O5 was found to be an excellent waveguide, yielding an intense Raman spectrum. Even though polycrystalline films of Y2O3, ZrO2, HfO2, and ThO2 were found to be poor waveguides, they still yielded Raman spectra containing useful structural information. Such Raman spectra showed that the ThO2 film was initially in an unusual structural form, which spontaneously transformed into cubic ThO2. Even for films yielding relatively weak Raman bands, substrate Raman scattering was not a serious interference. Representative spectra are presented, along with a brief discussion of the requirements for coupling optical beams into films with large refractive indices.
Raman Cross Sections of Chemical Agents and Simulants
Authors: Christesen Steven D.
Published: July 2005

The differential Raman scattering cross sections of the chemical agents GA, GB, HD, and VX, and the chemical agent simulants DMMP and DIMP have been measured with visible and UV wavelength excitation. These compounds proved to be weak Raman scatterers with cross sections for the strongest lines on the order of 6 to 10 × 10−30 cm2/sr/molecule with 514.5-nm excitation. Excitation at 363.8 nm yielded only a slight preresonance enhancement of the Raman cross sections. Because of the small cross sections and the lack of enhancement, remote Raman detection of chemical agents appears doubtful.
Low-Frequency Photoacoustic Spectroscopy of Solids
Authors: Donini J. C. , Michaelian K. H.
Published: July 2005

Research-quality far-infrared photoacoustic (PA) spectra are obtainable with a Fourier transform infrared spectrometer, the only changes with respect to conventional mid-infrared PA spectroscopy being the use of (1) a caesium iodide or polyethylene window on the PA cell, and (2) a mylar beamsplitter. Far-infrared PA spectra of several solids (bentonite, Fe+3-bentonite, and asbestos), in addition to the PA reference carbon black, have been recorded in this way. In order to improve signal-to-noise ratios in one of the spectra, we recorded ten interferograms under identical conditions; it was found that the average of the ten individually calculated spectra displays less noise and fewer spurious features than the spectrum obtained by first averaging the interferograms and then calculating a single spectrum. The results of this investigation demonstrate the feasibility of far-infrared PA spectroscopy, and illustrate that both experimental and computational procedures should be optimized in order to obtain the most satisfactory spectra.
Characterization of Torch-Deposited Silica for Light-Guide Preforms
Authors: Wood D. L. , Potkay E. , Clark H. R. , Kometani T. Y.
Published: July 2005

Germanium-doped silica soot particles from the Vapor-phase Axial Deposition (VAD) process were taken from unconsolidated light-guide preform boules and characterized by infrared spectroscopy, light scattering, x-ray diffraction, ICP elemental analysis, and TEM examination. The results show that while GeO2 concentration decreases with increasing radius as required for the light-guiding refractive index profile, the fraction of the GeO2 in the crystalline form increases with increasing radial position in the boule. Infrared spectra are consistent with most of the soot particles containing separate phases of partially crystalline GeO2 and amorphous SiO2 as opposed to a compound glass. The light scattering by particles suspended in media of various refractive indices is that expected from inhomogeneous particles, as required for the two-phase model. Water solubility experiments followed by infrared or ICP analyses confirm this model and further support a detailed structure for the particles in which the separate GeO2 phase is present as a shell or coating on a predominantly silica core. Particles have sizes ranging from 10 to more than 125 nm, and they are mostly spherical in shape. Near the center of the boule, however, where substrate temperatures are higher for longer times, partially fused chains of spherical particles are found, and the sizes and shapes of the particles in both regions are consistent with growth by Brownian coagulation.
Theoretical and Experimental Investigation of the Relationship between Aperture Dimension and Signal-to-Noise Optimization in Thermal Lens Spectroscopy
Authors: Erskine Steven R. , Bobbitt Donald R.
Published: July 2005

The effect of three types of experimental laser noise on conventional thermal lens spectroscopy are considered. Theoretical calculations of noise and signal-to-noise ratio as a function of aperture size are included to determine ideal aperture dimensions for systems limited by laser pointing instabilities, flicker noise, and/or shot noise. Experimentally determined noise curves are also presented and discussed in the context of the theoretical results. The results show that for most thermal lens configurations based on lock-in detection, optimum S/N is obtained at an aperture-to-beam-size ratio of 0.6.
Searching a UV-Visible Spectral Library
Authors: Brown Chris W. , Donahue Steven M.
Published: July 2005

A UV-visible spectral library has been generated after the spectra have been preprocessed with a Fourier analysis. Both the library and unknown spectra are Fourier transformed and are represented by a window of coefficients from the transforms. In order that the optimum window for the coefficients could be determined, synthetic spectra were generated and used to test the effects of band shifts, high-frequency noise, and background fluctuations. Spectra of 24 compounds, many of which were very similar, were measured and processed from 200 to 712 nm. Eight of the samples were treated as unknowns and their spectra remeasured. The arc-cosine of the dot product was used as the similarity metric. All eight of the unknowns were correctly identified with the use of as few as 16 coefficients to represent the spectra. Since many of the spectra were very similar, the success of the algorithm is due to the fact that it incorporates wavelengths and band shapes, widths, and heights into the comparison process.
Angular Dependence of Diffuse Reflectance Infrared Spectra. Part III: Linearity of Kubelka-Munk Plots
Authors: Brimmer Paul J. , Griffiths Peter R.
Published: July 2005

The linearity of plots of the Kubelka-Munk function against concentration is investigated for weak and strong absorption bands in the spectrum of a typical organic analyte, caffeine. The linear region is extended when measurements are made with an off-axis optical geometry, in comparison to an in-line configuration. For the latter configuration, the linearity is improved when crossed polarizers are placed before and after the sample.
Room-Temperature Phosphorimetry to Study Petroleum Product Permeation through Protective Clothing Materials
Authors: White D. A. , Vo-Dinh T.
Published: July 2005

In this study a simple analytical tool based on room-temperature phosphorimetry (RTP) is developed and used for evaluating the effectiveness of protective clothing materials against permeation of organic substances containing compounds such as the polycyclic aromatic compounds. A special permeation cell is designed, which allows direct RTP measurements of the permeated products after exposure, without requiring any sample extraction procedure. Results for a variety of petroleum product-protective material combinations illustrate the usefulness of the technique.
A Spectrometer for Measuring Time-Resolved Infrared Linear Dichroism Induced by a Small-Amplitude Oscillatory Strain
Authors: Noda Isao , Dowrey A. E. , Marcott Curtis
Published: July 2005

A spectrometer for detecting dynamic infrared linear dichroism (DIRLD) induced by a small-amplitude oscillatory strain is described. The strain-induced dynamic variations of absorbance and linear dichroism, as well as the normal static absorbance and dichroism, are measured simultaneously as functions of IR wavenumber, temperature, and strain frequency. The phase (temporal) relationships between the dynamic optical signals and the applied strain are also obtained. The instrument is sensitive enough to detect dynamic optical signals on the order of 10−4 absorbance units with a time resolution of about 14 μs. The dynamic dichroism signals arise from the strain-induced temporary reorientation of dipole-transition moments associated with the molecular vibrations of chemical functional groups. Both the rate and extent of reorientations are strongly influenced by the local molecular environment of the functional groups. Because of the specificity of IR absorbance bands to the individual submolecular structures, DIRLD spectroscopy is especially suited for the study of the intra- and intermolecular interactions and the detection of subtle changes in the local molecular environment. Example DIRLD spectra of atactic polystyrene are presented to demonstrate the potential utility of this spectroscopic technique.
Partial Least-Squares Quantitative Analysis of Infrared Spectroscopic Data. Part II: Application to Detergent Analysis
Authors: Fuller M. P. , Ritter G. L. , Draper C. S.
Published: July 2005

An implementation of the PLS (partial least-squares) statistical approach to quantitative analysis was applied to a set of mid-infrared spectra obtained from a series of commercial detergent samples. The components analyzed included the base detergent, sodium benzoate, 2-propanol, 1,2-propanediol, polypropylene glycol, and glycerol. The samples were analyzed with the use of a horizontal attenuated total reflectance (ATR) accessory equipped with a zinc selenide crystal. The PLS model created in the calibration was found to provide excellent results for a set of validation samples.
Metal Ion Binding Properties of Perfluorosulfonate Membranes by Laser Excitation Spectroscopy
Authors: Wong E. K. L. , Richmond G. L.
Published: July 2005

The metal ion binding properties of the perfluorosulfonate membrane Nafion® have been investigated in this study. The experiments involve laser-induced fluorescence measurements of europium (III) ions which are bound to the membrane. By the exploitation of the hypersensitivity of the D → F transitions of europium (III) to the ligand binding environment, the properties of the metal binding sites have been analyzed as a function of various experimental parameters. The spectra and fluorescence lifetime measurements provide evidence for distinct metal binding sites within the polymer, each of which is sensitive to the conditions of the membrane preparation.
Identification of Dust Particles by Molecular Microspectroscopy
Authors: Lang Patricia L. , Katon J. E. , Bonanno Anthony S.
Published: July 2005

Frequently dust contamination is found on materials to be analyzed by molecular microspectroscopy. The presence of these contaminants often makes it difficult to ascertain the legitimate reason for a product defect or failure. A microspectroscopic study of dust in an office/lab environment has been carried out to identify the types and possible sources of dust contaminants. Various types of natural and synthetic polymeric materials were identified. It appears that paper products and proteinaceous materials are the major sources of dust contamination in the environments studied.
HPLC Separation and FT-IR Isomer Differentiation of the 1,2,4,7/1,2,4,8-Tetrachlorodibenzodioxin Isomer Pair—A Theoretical/Empirical Approach to Dibenzodioxin Isomer Assignment
Authors: Grainger James , Barnhart Elizabeth , Patterson Donald G. , Presser David
Published: July 2005

The 1,2,4,7- and 1,2,4,8-tetrachlorodibenzodioxin (TCDD) isomers were separated by reversed-phase high-performance liquid chromatography (HPLC) with the use of a pyrene column. Fourier transform infrared (FT-IR) matrix isolation and vapor-phase spectra of the individual isomers were recorded. The spectra of the HPLC-separated isomers correlate well with spectral subtraction results and were found to be distinct in three spectral regions—one of which allows for isomer structural assignment. Ambiguities and differences in published TCDD isomer FT-IR assignments are discussed in terms of a qualitative valence-bond approach and empirically derived estimates of ether linkage asymmetric stretching frequencies.
FT-IR Analysis of High-Temperature Solid-Phase Reactions Using GC-IR Software
Authors: Snyder Randy W. , Sheen C. Wade
Published: July 2005

A method for following chemical reactions in polymers, using the GC-IR software on an FT-IR spectrometer and a high-temperature thermal cell, is discussed. The method reduces disk access time between the collection of each spectrum, allowing many more data points for kinetic experiments to be collected. The imidization reaction of polyimides above 200°C is given as an example.
Double Lightpipe System for Analytical GC/FT-IR and Spectral Libraries
Authors: Kalasinsky V.F. , Whitehead K. G. , Kenton R. C. , Kalasinsky K. S.
Published: July 2005

A GC/FT-IR accessory has been configured with two lightpipes in order to allow flexibility in chromatographic separations. A capillary column is connected to a 15-cm lightpipe (1.5-mm bore) and is used for analytical GC/FT-IR. The second lightpipe (42-cm, 3-mm bore) is connected to a packed column and is configured with valves to provide a stopped-flow capability. This lightpipe is used when the sample size is not limited or when signal-averaging and high resolution are necessary. Broad-band MCT detectors are generally used because they are not adversely affected by unmodulated blackbody radiation from the heated lightpipe. In those instances when a narrow-band MCT detector is needed, an aperture and one additional mirror are used to discriminate against the unmodulated radiation. Applications of both systems are discussed.
Application of Emission and Absorption Spectroscopy for Characterization of a Copper Converting Process
Authors: Wendt Wilhelm , Aldén Marcus , Persson Willy
Published: July 2005

The emission and absorption spectra of a copper converter flame have been investigated. It was found that the emission spectra consisted of Planck radiation and superimposed discrete structures. The band structure was dominated by PbS in the slag-making stage and by PbO in the copper-making stage. Towards the end of the slag-making stage the ratio of the PbO and PbS band intensities (PbO/PbS) changed, in good agreement with thermodynamical calculations. Absorption measurements were performed during the copper-making stage, where the absorption edge of SO2 at about 380 nm was the dominating feature. The implications of these measurements for process steering and control are discussed.
Application of Optogalvanic Spectroscopy to the Measurement of Pressure Broadening and Shift in the Negative Glow Region of an Ar Hollow Cathode Discharge
Authors: Masaki Takashi , Adachi Yukio , Hirose Chiaki
Published: July 2005

Optogalvanic spectroscopy has been applied to the measurement of the pressure broadening and frequency shift of the Ar 7 d[5/2]3–4 p[3/2]2 transition in the negative glow region of a hollow cathode discharge at gas pressures from 1 to 6 Torr and discharge currents from 12 to 20 mA. The neutral atoms have been found to be the dominant collision partners to the argon atoms in the excited state, and the values of β = (3.9 ± 0.2) × 10−3 cm−1 Torr and δ = –(3.9 ± 0.2) × 10−3 cm−1/Torr have been derived as the coefficients of the pressure broadening and shift, respectively.