bluuebunny/crossref_metadata_2025 huggingface dataset:
Minimizing the side effects of antireflux surgery
Authors: DeMeester Tom R. , Stein Hubert J.
Published: August 2005

To address the durability and long‐term side effects of the Nissen fundoplication as surgical therapy for gastroesophageal reflux disease, we evaluated 100 patients postoperatively. With careful attention to technical detail as described, the incidence of temporary postoperative dysphagia was 39% and permanent dysphagia was 3%. Effective relief of reflux symptoms over more than 10 years was achieved in 91% of the patients with minimal side effects.
Minimally invasive antireflux procedures
Authors: Stein H. J. , Feussner H. , Siewert J. R.
Published: August 2005

The advance of endoscopic and laparoscopic techniques in recent years has prompted several groups throughout the world to investigate the possibilities for a minimally invasive approach to reconstruct a defective antireflux mechanism in patients with intractable gastro‐esophgeal reflux disease. Prospective trials are needed to evaluate the long‐term durability and efficiency of these procedures.
Exploring Sequence Space through Automated Aptamer Selection
Authors: Lee Jennifer F. , Cox J. Colin , Collett James R. , Ellington Andrew D.
Published: August 2005

Theoretical studies focusing on the nature of landscapes that correlate molecular sequences to molecular function have mainly been carried out in silico due to the vast amounts of data that are needed. Automated in vitro selection is capable of producing significant amounts of data in a short time, making theoretical modeling with real experimental data attainable. A Biomek 2000 Laboratory Automation Workstation has been outfitted to carry out multiple in vitro nucleic acid selections in parallel, yielding substantial amounts of data for theoretical studies. A random sequence population of nucleic acids is initially generated by a combination of chemical synthesis and enzymatic amplification. On the workstation, this population is parsed for its ability to bind a protein, lysozyme. After each round of selection, the selected nucleic acid binding species (also known as aptamers) are amplified by a combination of reverse transcription polymerase chain reaction (PCR) and in vitro transcription. All eight pools that have undergone selection have yielded different sequences.
Single-Pot Solution Phase Synthesis Optimization Using Fully Automated Systems for Combinatorial Screening
Authors: Wendler Christian , Krüger-Sundhaus Thomas , Beller Matthias , Gördes Dirk , Thurow Kerstin
Published: August 2005

The optimization of synthesis conditions plays an important role in chemistry and life sciences. A wide variety of reaction parameters should be explored to minimize the use of educts and maximize the yields of desired products in high purity. A fully automated system for combinatorial synthesis has been developed and used for the optimization of synthesis conditions of a multicomponent single-pot reaction. In order to explore optimal reaction conditions for the synthesis of pure endo isomer of 3-(2-bromo-benzoylamino)-cyclohex-4-ene1,2-dicarboxylic acid diethyl ester, an intermediate in the synthesis route of lycorizidine analogues, several hundred experiments were carried out with varying reaction temperature, times, concentrations, and ratios of educts. In this case study, financial aspects also were considered in order to minimize synthesis costs.

The system was integrated using a Zymate XP robot as a system integrator. In addition to a GC/MS and an HPLC system, a multicomponent solid dispenser workbench and a liquid handling system are located within this fully automated system.
Bacterial genome size reduction by experimental evolution
Authors: Nilsson A. I. , Koskiniemi S. , Eriksson S. , Kugelberg E. , Hinton J. C. D. , Andersson D. I.
Published: August 2005

Bacterial evolution toward endosymbiosis with eukaryotic cells is associated with extensive bacterial genome reduction and loss of metabolic and regulatory capabilities. Here we examined the rate and process of genome reduction in the bacterium
Salmonella enterica
by a serial passage experimental evolution procedure. The initial rate of DNA loss was estimated to be 0.05 bp per chromosome per generation for a WT bacterium and ≈50-fold higher for a
mutS
mutant defective in methyl-directed DNA mismatch repair. The endpoints were identified for seven chromosomal deletions isolated during serial passage and in two separate genetic selections. Deletions ranged in size from 1 to 202 kb, and most of them were not associated with DNA repeats, indicating that they were formed via RecA-independent recombination events. These results suggest that extensive genome reduction can occur on a short evolutionary time scale and that RecA-dependent homologous recombination only plays a limited role in this process of jettisoning superfluous DNA.
Characterization of Dicer-deficient murine embryonic stem cells
Authors: Murchison Elizabeth P. , Partridge Janet F. , Tam Oliver H. , Cheloufi Sihem , Hannon Gregory J.
Published: August 2005

Dicer is an RNase III-family nuclease that initiates RNA interference (RNAi) and related phenomena by generation of the small RNAs that determine the specificity of these gene silencing pathways. We have previously shown that Dicer is essential for mammalian development, with Dicer-deficient mice dying at embryonic day 7.5 with a lack of detectable multipotent stem cells. To permit a more detailed investigation of the biological roles of Dicer, we have generated embryonic stem cell lines in which their single Dicer gene can be conditionally inactivated. As expected, Dicer loss compromises maturation of microRNAs and leads to a defect in gene silencing triggered by long dsRNAs. However, the absence of Dicer does not affect the ability of small interfering RNAs to repress gene expression. Of interest, Dicer loss does compromise the proliferation of ES cells, possibly rationalizing the phenotype previously observed in Dicer-null animals. Dicer loss also affects the abundance of transcripts from mammalian centromeres but does so without a pronounced affect on histone modification status at pericentric repeats or methylation of centromeric DNA. These studies provide a conditional model of RNAi deficiency in mammals that will permit the dissection of the biological roles of the RNAi machinery in cultured mammalian cells.
Do Xylem Fibers Affect Vessel Cavitation Resistance?
Authors: Jacobsen Anna L. , Ewers Frank W. , Pratt R. Brandon , Paddock William A. , Davis Stephen D.
Published: August 2005

Possible mechanical and hydraulic costs to increased cavitation resistance were examined among six co-occurring species of chaparral shrubs in southern California. We measured cavitation resistance (xylem pressure at 50% loss of hydraulic conductivity), seasonal low pressure potential (P  min), xylem conductive efficiency (specific conductivity), mechanical strength of stems (modulus of elasticity and modulus of rupture), and xylem density. At the cellular level, we measured vessel and fiber wall thickness and lumen diameter, transverse fiber wall and total lumen area, and estimated vessel implosion resistance using (t/b)h  2, where t is the thickness of adjoining vessel walls and b is the vessel lumen diameter. Increased cavitation resistance was correlated with increased mechanical strength (r  2 = 0.74 and 0.76 for modulus of elasticity and modulus of rupture, respectively), xylem density (r  2 = 0.88), and P  min (r  2 = 0.96). In contrast, cavitation resistance and P  min were not correlated with decreased specific conductivity, suggesting no tradeoff between these traits. At the cellular level, increased cavitation resistance was correlated with increased (t/b)h  2 (r  2 = 0.95), increased transverse fiber wall area (r  2 = 0.89), and decreased fiber lumen area (r  2 = 0.76). To our knowledge, the correlation between cavitation resistance and fiber wall area has not been shown previously and suggests a mechanical role for fibers in cavitation resistance. Fiber efficacy in prevention of vessel implosion, defined as inward bending or collapse of vessels, is discussed.
Sustained hypothermia accelerates microvascular thrombus formation in mice
Authors: Lindenblatt Nicole , Menger Michael D. , Klar Ernst , Vollmar Brigitte
Published: August 2005

Cold is supposed to be associated with alterations in blood coagulation and a pronounced risk for thrombosis. We studied the effect of clinically encountered systemic hypothermia on microvascular thrombosis in vivo and in vitro. Ferric chloride-induced microvascular thrombus formation was analyzed in cremaster muscle preparations from hypothermic mice. Additionally, flow cytometry and Western blot analysis was used to evaluate the effect of hypothermia on platelet activation. To test whether preceding hypothermia predisposes for enhanced thrombosis, experiments were repeated after hypothermia and rewarming to 37°C. Control animals revealed complete occlusion of arterioles and venules after 742 ± 150 and 824 ± 172 s, respectively. Systemic hypothermia of 34°C accelerated thrombus formation in arterioles and venules (279 ± 120 and 376 ± 121 s; P < 0.05 vs. 37°C). This was further pronounced after cooling to 31°C (163 ± 57 and 281 ± 71 s; P < 0.05 vs. 37°C). Magnitude of thrombin receptor activating peptide (TRAP)-induced platelet activation increased with decreasing temperatures, as shown by 1.8- and 3.0-fold increases in mean fluorescence after PAC-1 binding to glycoprotein (GP)IIb-IIIa and 1.6- and 2.9-fold increases of fibrinogen binding on incubation at 34°C and 31°C. Additionally, tyrosine-specific protein phosphorylation in platelets was increased at hypothermic temperatures. In rewarmed animals, kinetics of thrombus formation were comparable to those in normothermic controls. Concomitantly, spontaneous and TRAP-enhanced GPIIb-IIIa activation did not differ between rewarmed platelets and those maintained continuously at 37°C. Moderate systemic hypothermia accelerates microvascular thrombosis, which might be mediated by increased GPIIb-IIIa activation on platelets but does not cause predisposition with increased risk for microvascular thrombus formation after rewarming.
Charge modification of the endothelial surface layer modulates the permeability barrier of isolated rat mesenteric small arteries
Authors: van Haaren Paul M. A. , VanBavel Ed , Vink Hans , Spaan Jos A. E.
Published: August 2005

We hypothesized that modulation of the effective charge density of the endothelial surface layer (ESL) results in altered arterial barrier properties to transport of anionic solutes. Rat mesenteric small arteries (diameter ∼190 μm) were isolated, cannulated, perfused, and superfused with MOPS-buffered physiological salt solutions. MOPS-solutions were of normal ionic strength (162 mM, MOPS), low ionic strength (81 mM, LO-MOPS), or high ionic strength (323 mM, HI-MOPS), to modulate ESL charge density (normal, high, or low ESL charge, respectively). Osmolarity of MOPS, LO-MOPS, and HI-MOPS was kept constant at 297 mosmol/l, using additional glucose when necessary. Perfusate solutions were supplemented with 1% BSA. Arteries were cannulated with a double-barreled theta-pipet on the inlet side and a regular pipet on the outlet side. After infusion of FITC-labeled dextran of 50 kDa (FITC-Δ50) and the endothelial membrane dye 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate, the dynamics of arterial dye filling were determined with confocal microscopy. ESL thickness, as determined from the initial exclusion zone for FITC-Δ50 on the luminal endothelial surface, was 6.3 ± 1.4 μm for LO-MOPS, 2.7 ± 1.0 μm for MOPS, and 1.1 ± 1.3 μm for HI-MOPS. At low ionic strength, FITC-Δ50 permeated into the ESL with a total ESL permeation time (τESL) of 26 min, and at normal ionic strength with a τESL of 20 min. No apparent exclusion of FITC-Δ50 from the ESL could be observed at high ionic strength. In conclusion, we demonstrate that the modulation of solvent ionic strength influences the thickness and barrier properties of the ESL.
Effect of mutation of amino acids 246–251 (KRKHKK) in HSP72 on protein synthesis and recovery from hypoxic injury
Authors: Voss M. R. , Gupta S. , Stice J. P. , Baumgarten G. , Lu L. , Tristan J. M. , Knowlton A. A.
Published: August 2005

Heat shock protein (HSP)72, the inducible form of HSP70, protects cells against a variety of injuries, but underlying mechanisms are poorly defined. To investigate the protective effects of HSP72, multiple clones expressing wild-type (WT) HSP72 and two mutants with defective nucleolar and nuclear localization (M45 and 985A, respectively) were made with the tet-off system in C2C12 cells. Four different parameters of cell function/injury were examined after simulated ischemia: protein synthesis, polysome formation, DNA synthesis, and lactate dehydrogenase (LDH release). Overexpression of WT HSP72 was also compared to nontransfected C2C12 cells. As expected, overexpression of HSP72 protected against simulated ischemia and reoxygenation for all parameters. In contrast, both M45 and 985A showed abnormal protein synthesis and polysome formation, both after simulated ischemia and under control conditions. Total RNA was slightly reduced in M45 and 985A at baseline, but 1 h after hypoxia, RNA levels were protected in all clones but significantly decreased in nontransfected C2C12 cells. Clones expressing 985A had nuclear retention of mRNA, suggesting that HSP72 is needed for nuclear export of RNA. All clones, both WT and mutant, had protection of DNA synthesis compared to C2C12 cells, but 985A had greater release of LDH after injury than any other group. These results support a multifactoral protective effect of HSP72, some aspects dependent on nuclear localization with stress and some not. The protection of protein synthesis and polysome formation, and abnormalities in these with the mutants, support a role for HSP72 in these processes both in the normal cell and in injury.
The role of dune morphogenetic history in the interpretation of linear dune luminescence chronologies: a review of linear dune dynamics
Authors: Munyikwa Kennedy
Published: August 2005

Contemporary knowledge on aeolian dune dynamics is reviewed to enable an appraisal of evolutionary mechanisms involved in linear dune stratigraphic sequence development. The degrees of depositional record retention in the dune structures are evaluated and the corollary applied to methods used in the interpretation of luminescence dating chronologies acquired from such sedimentary accumulations. It is demonstrated that morphogenetic aspects of dune development are an imperative element to invoke when carrying out palaeoenvironmental reconstruction using luminescence dating ages acquired from linear dune sequences. To help depict the role of dune morphogenesis, hypothetical scenarios that simulate the preservation of stratigraphical records in linear dune sequences are presented using two different theories that have been advanced to explain origin and development of linear dunes: bidirectional wind regime and helical roll vortices. It is illustrated that linear dune systems that evolve under bidirectional wind influence are intrinsically inefficient at preserving complete records of their depositional history and this places major constraints for palaeoenvironmental reconstruction using luminescence chronologies. When linear dunes develop under the influence of helical roll vortices, on the other hand, it is shown that the degree of sequence preservation would be higher. The possibility of lateral migration of linear dune structures is indicated to be an additional limitation that may encumber the interpretation of luminescence ages.
Studies on the Mutagenicity and Electron Spin Resonance Spectra of Nitrosofluorene-Lipid Adducts
Authors: Sridhar R. , Hampton M. J. , Steward J. E. , Floyd R. A.
Published: August 2005

The carcinogen 2-acetylaminofluorene undergoes metabolic activation to 2-nitrosofluorene (NOF). NOF is a powerful mutagen in the Ames assay conducted with TA 98 strain of Salmonella typhimurium in the absence of microsomal activation system. We have shown that NOF adds to unsaturated lipids in microsomes and liposomes to yield free radicals. NOF adds to methyl oleate or 2,3-dimethylbut-2-ene in an Alder-ene fashion to form a hydroxylamine derivative which undergoes oxidation to yield a fairly stable nitroxyl free radical. The second derivative electron spin resonance spectrum of the NOF-methyl oleate adduct is a triplet of a quartet with a 1:3:3:1 intensity pattern. This suggests that the free electron interacts with one nitrogen (aN = 11.5 G) and three approximately equivalent protons (a1H ≈ a2H ≈ a3H ≈ 3.5 G). The second derivative spectrum of the NOF-2,3-dimethylbut-2-ene adduct is more complex involving a triplet of 14 lines each. Both adducts were less mutagenic than NOF in the Ames assay. Membrane alterations due to NOF-lipid adduct formation may be a factor in 2-acetylaminofluorene-induced carcinogenesis.
Band Shape and Slit Width
Authors: Torkington P.
Published: August 2005

The theoretical dependence of band contour on effective slit width is examined with the object of obtaining a simple method of representation. With an initial Lorentzian the contour can be expressed to a good approximation as a sum of Lorentzian and Gaussian components, and the variation of the function with slit width is studied. How the results can be applied to resolution enhancement is also shown. Two other functions are compared to the sum. The contour arising from distribution of pure forms about a center is briefly investigated.
A High Resolution Vacuum Fourier Transform Far Infrared Spectrometer
Authors: Covey J. P. , Mead D. G. , Mattson D. R.
Published: August 2005

A vacuum infrared interferometric system for use to 5 cm−1 is outlined. Examples given include high resolution vibrational spectra of some gases.
The Determination of Trace Amounts of Selenium by Hydride Generation-Nondispersive Flame Atomic Fluorescence Spectrometry
Authors: Nakahara Taketoshi , Kobayashi Syoji , Wakisaka Tatsushi , Musha Sôichirô
Published: August 2005

A method has been developed for the determination of trace selenium by generation of its gaseous hydride using either metallic zinc or sodium borohydride as a reductant and followed by the introduction of the hydride into a premixed argon (entrained air)-hydrogen flame where all atomic fluorescence lines of selenium are simultaneously detected by use of a nondispersive system. The comparison of the zinc and the sodium borohydride reduction methods is discussed in terms of detection limit, precision, and interference. The best attainable detection limits for selenium are 0.3 ng (15 pg/ml) and 0.4 ng (20 pg/ml) with the zinc and sodium borohydride methods, respectively. Analytical calibration curves obtained by measuring peak heights and integrated peak areas of the fluorescence signals are linear over the range of approximately 4 orders of magnitude from the detection limits. Most mineral acids examined in the range up to 2.0 M do not interfere; however, the nitric acid is an exception which gives a depressing interference. The interference was found to be much more severe in the zinc method than in the sodium borohydride technique. The presence of several elements including other hydride-forming elements in 1000-fold ratio to selenium causes a depressing interference, whereas an enhancing interference from tellurium is observed only in the zinc reduction method. The present method has been successfully applied to the determination of selenium in wastewaters and foods.
The Anisotropy Factor in Dense Scattering Media
Authors: Hecht Harry G.
Published: August 2005

It has been found that the Pitts-Giovanelli formula gives a good account of diffuse reflectance over a large concentration range in model systems containing a soluble absorber in a dispersion of nonabsorbing particles. However, a very anisotropic scattering phase function is required. The concentration and wavelength dependence of the anisotropy factor are explored in the present work and are found to follow trends which are reminiscent of those predicted on the basis of the Mie theory of single scatter. This lends further support to the applicability of the Pitts-Giovanelli method to model systems of this type.
Functional Group Analysis of Interferometric Data from Gas Chromatography Fourier Transform Infrared Spectroscopy
Authors: Wieboldt R. C. , Hohne B. A. , Isenhour T. L.
Published: August 2005

A method is presented for the direct analysis of interferometric data from gas chromatography Fourier transform infrared spectroscopy (GC/FTIR). A synthetic interferogram is initially produced which represents the characteristic absorption features of a particular functional group or compound class. A zero displacement correlation is performed between this test interferogram and each sample interferogram from the GC data. The presence of the desired functionality in the GC effluent is indicated by a small value of the resulting cumulative sum. A “correlogram” which emulates the response from a chemically specific GC detector is obtained by plotting the cumulative sum from each sample correlation. Synthetic interferograms representing infrared absorption bands which are truly specific for a particular functionality yield the best results.
Characterization of an Interelement Enhancement Effect in a dc Plasma Atomic Emission Spectrometry System
Authors: Johnson G. W. , Taylor H. E. , Skogerboe R. K.
Published: August 2005

The enhancement of atomic and ionic emission in a dc plasma due to the addition of easily ionized elements has been studied. The results show that the addition of the concomitants: (1) causes enhancements in both atomic and ionic emission, (2) does not cause significant changes in the electron temperature or the electron population of the plasma excitation zone, (3) results in a downward shift in the rotational temperature of that zone, and (4) does not cause significant changes in the efficiency with which analytical species are delivered to the plasma. These observations indicate that the enhancement effect cannot be readily explained based on plasma temperature increases or the classical ionization repression mechanism. As an alternative, it is suggested that the enhancement may result from increases in the population of metastable argon with coincident increases in excitation via collision with this species. This mechanism is circumstantially supported by the present results but must be regarded as tentative.
The Particle Track Method of Measuring Flame Rise Velocity Tested Experimentally in CO-Air Flames
Authors: Borgers A. J. , Jongerius M. J. , Hollander Tj.
Published: August 2005

The rise velocity of premixed, laminar flame gases flowing in one (vertical) direction is usually measured using the particle track method. Our investigations in CO-air flames of about 2000 K with uniform rise velocities of about 15 m s−1 showed that the most suitable substance for velocity measurements was powdered molybdenite (MoS2). Under our experimental conditions the velocity of the solid particles increased with the height of measurement in the flame due to relaxation effects. The flame rise velocities we have determined experimentally could be reconciled, with allowance for the effects of gravity and relaxation, with those we have calculated from flame data.
The Measurement of the Optical Constants of Thin Solid Films in the Infrared
Authors: Ribbegård G. K. , Jones R. N.
Published: August 2005

A technique previously described for the measurement of the optical constants of thin liquid films in the infrared has been extended to free-standing films of polymers. It is established that the computational procedure can cope effectively with the more severe dispersion distortion generated by the large refractive index changes at the solid-air interfaces. The method is illustrated by simulation studies on bands having a damped harmonic oscillator profile and on films of three commercial polymers (Lexan, Trogamid-T, and Saran).
The Calculation of Absolute Intensities Observed Due to Magneto-Optic Rotation in Atomic Vapors
Authors: Kankare J. , Stephens R.
Published: August 2005

The optical systems required to observe the Faraday or Voigt effects in atomic vapors are described in terms of the corresponding Jones matrices. The solution of the matrix equations reveals separate, additive dichroic and dispersive contributions to the transmitted intensity. The two contributions are combined by use of the Kronig-Kramers relations to give a final expression for the intensity due to magneto-optical rotation. This appears as the product of the intensity transmitted through the atomic vapor, the square of the zero field absorbance within the vapor, and the inverse square of a “Zeeman factor” z. Empirical data for the latter two parameters are currently available. Thus, the final formulae permit estimates of magneto-optic signal magnitudes to be made on the basis of presently existing information.
Improved Sensitivity of Infrared Spectroscopy by the Application of Least Squares Methods
Authors: Haaland David M. , Easterling Robert G.
Published: August 2005

Improved sensitivity and precision in the quantitative analysis of trace gases by Fourier transform infrared spectroscopy have been achieved by the application of new spectral least squares methods. By relating all of the spectral information present in the reference spectrum of a trace gas to that of the unknown sample and by appropriately fitting the baseline, detections of trace gases can be obtained even though the individual spectral features may lie well below the noise level. Four least squares methods incorporating different baseline assumptions were investigated and compared using calibrated gases of CO, N2O, and CO2 in dry air. These methods include: (I) baseline known, (II) baseline linear over the spectral region of interest, (III) baseline linear over each spectral peak, and (IV) negligible baseline shift between successive data points. Methods III and IV were found to be most reliable for the gases studied. When method III is applied to the spectra of these trace gases, detection limits improved by factors of 5 to 7 over conventional methods applied to the same data. “Three sigma” detection limits are equal to 0.6, 0.2, and 0.08 ppm for CO, N2O, and CO2, respectively, when a 10-cm pathlength at a total pressure of 640 Torr is used with a ∼35 min measurement time at 0.06 cm−1 resolution.
A Babington-Type Nebulizer for Use in the Analysis of Natural Water Samples by Inductively Coupled Plasma Spectrometry
Authors: Garbarino J. R. , Taylor H. E.
Published: August 2005

The construction and evaluation of a Babington-type pneumatic nebulizer for use in the inductively coupled plasma, emission spectrometric analysis of natural water samples is described. The performance of the nebulizer is relatively insensitive to suspended particulate matter, and detection limits for a wide variety of elements are equivalent to or better than those achieved with other pneumatic nebulizers. An accuracy comparison with a conventional crossflow pneumatic nebulizer shows essentially no analysis bias.
Atmospheric Pressure Active Nitrogen (APAN)—A New Source for Analytical Spectroscopy
Authors: D'Silva A. P. , Rice G. W. , Fassel V. A.
Published: August 2005

An atmospheric pressure “active nitrogen” (APAN) afterglow was generated in pure flowing nitrogen (<10 ppm O2) excited in an electrodeless ozonizer discharge. The afterglow, which contains several metastable species, has been observed to be an efficient source for the excitation of atomic emission, through energy transfer. The application of the APAN afterglow for the detection and determination of ultratrace levels of Hg and the volatile hydride forming elements, As, Bi, Ge, Pb, Sb, Se, Sn, and Te is documented.
Infrared Microsampling by Diffuse Reflectance Fourier Transform Spectrometry
Authors: Fuller Michael P. , Griffiths Peter R.
Published: August 2005

It is shown that diffuse reflectance techniques enable increased sensitivity to be obtained for infrared microsampling compared with the use of KBr micropellets. When nonabsorbing matrices, such as KCl, are used, detection limits of less than 10 ng of samples are observed. Samples absorbed on graphitized substrates, which have a fairly strong general absorption but few intense absorption bands, may also be studied but at somewhat reduced sensitivity. Diffuse reflectance infrared Fourier transform spectrometry does not appear to be particularly useful for studying adsorbates on silica gel, which is not only a strong infrared absorber but also has a surface which is so active that small changes in the surface structure can change the spectrum significantly. Extraction of sample spots from thin layer chromatography plates followed by deposition onto KCl yields much better results than in situ measurements.
Production of DF* from Polytetrafluoroethylene and Deuterium Plasma as Observed in the Mid-Infrared by Fourier Transform Infrared Spectroscopy
Authors: Gallaher T. N. , DeVore T. C. , Carter R. O. , Anderson C.
Published: August 2005

The reaction of a deuterium plasma and polytetrafluoroethylene has been investigated. Vibrationally excited DF* (up to v′ = 3) has been observed in emission via Fourier transform infrared spectroscopy. The vibrational and rotational temperatures suggest that a mechanism similar to that found previously for the reaction between H atoms and the fluoroethylenes is responsible for the production of the DF.
Solution Conformation of Peptides through 1H Nuclear Magnetic Double Resonance Measurement of Amide Hydrogen Exchange Rates: Study of the Active Pentapeptide Fragment of Thymopoietin
Authors: Krishna N. Rama , Huang D. H. , Goldstein Gideon
Published: August 2005

The amide hydrogen exchange rates of peptides (and other biomolecules) can be related to their secondary and tertiary structures. The exchange rates in the range ∼0.1 to ∼100 s−1 can be conveniently measured in H2O by a double resonance technique involving a combination of two separate 1H NMR experiments: (1) the transfer of solvent saturation and (2) the selective saturation recovery of the labile hydrogen. When a peptide exists in a dynamic equilibrium among several conformations, the interpretation of the above two experiments in terms of intrinsic exchange rates is not straightforward in general. The effect of a multistate conformational averaging is considered in the interpretation of the above two experiments, and analytical expressions have been presented for a few limiting cases of conformational and chemical equilibria. The amide hydrogen exchange rates of the pentapeptide Arg-Lys-Asp-Val-Tyr, the active fragment of the thymic hormone thymopoietin, have been measured in H2O through the transfer of solvent saturation and saturation recovery experiments. The results suggest that this fragment exists in a highly motile dynamic equilibrium among several conformations. In some of these, the Val4 NH hydrogen is shielded significantly from the solvent.
Practical Aspects of Rapid Scanning Fourier Transform Time-Resolved Infrared Spectroscopy
Authors: Garrison Arlene A. , Crocombe R. A. , Mamantov Gleb , de Haseth James A.
Published: August 2005

The results of experiments designed to study the infrared spectra of transient species produced by ultraviolet photolysis of acetaldehyde are reported and analyzed. Spectra obtained in similar work [A. W. Mantz, Appl. Opt. 17, 1347 (1978)] are critically reinterpreted. The evidence presented demonstrates that insufficient attention has been given to the necessary stringent control of experimental conditions. The consequences of poor control are described and a qualitative explanation is offered. This paper discusses, in particular, the production of spectral artifacts consisting of displaced (not folded) bands and their previous erroneous assignments. Other practical aspects of time resolved Fourier transform spectroscopy with a rapid scanning Michelson interferometer are outlined.
Analysis of a Polarizing Michelson Interferometer for Dual Beam Fourier Transform Infrared, Circular Dichroism Infrared, and Reflectance Ellipsometric Infrared Spectroscopies
Authors: Dignam M. J. , Baker M. D.
Published: August 2005

The properties of a Fourier transform infrared (FT-IR) spectrometer designed around a polarizing Michelson interferometer (PMI) are analyzed with respect to applications in both conventional absorption as well as polarization spectroscopies. The PMI design is that of Martin and Puplett and consists of a metal grid polarizing beam splitter combined with rooftop retromirrors set to rotate the polarization direction in each beam by 90°. If used in conjunction with additional grid polarizers, positioned according to application, the result is an FT-IR instrument that can function both as a dual beam absorption spectrometer and as a polarization spectrometer. Operating in the former mode, the instrument is predicted to achieve speeds comparable to those achievable using a nonpolarizing dual beam Michelson interferometer but to cover a much wider spectral range due to the achromatic nature of metal grid polarizing beam splitters. In the latter mode, it is predicted to give at least double the effective throughput achievable with conventional instruments equipped with external polarization modulating optics, and again to cover a much wider spectral range. It would extend the capability of determining circular dichroism spectra into the far IR (down to ∼3 cm−1) for the first time. With the development of a process for forming a metal grid polarizer of fine spacing (∼0.1 μm) on a KBr substrate, the instrument would be capable of covering the spectral range 25 000 to 3 cm−1 or lower using only two beam splitters, i.e., in two ranges: 25 000 to 450 cm−1 using a KBr-supported metal grid, and 600 to 3 cm−1 or less using an unsupported wire grid.
Removal of Redundant Coordinates from the Vibrational Problem
Authors: Eysel H. H. , Bussian B. M.
Published: August 2005

A numerical technique for the removal of redundant vibrational coordinates has been developed. This method is based on matrix calculations and is applicable to any choice of coordinates or molecules. First the exact zero coordinates are calculated using the transformation ( B matrix) from internal coordinates to cartesian displacements. Second a full set of independent coordinates—preferably symmetry adapted—is constructed by an orthogonalization procedure. Retaining the character of group motions like rocking, wagging, twisting can be taken care of. A description of the method is supplemented by a numerical appendix for an easy (CH2O) and a complicated (C6H12) example.
Second Derivative Infrared Spectroscopy
Authors: Whitbeck Michael R.
Published: August 2005

The analysis of trace gases by infrared spectroscopy is enhanced by computing the second derivative of the spectrum. The peak maxima are increased for sharp bands while contributions from broad, structureless, continua are reduced. For weak absorbers the peak maxima are linear in concentration. The advantages of second derivative infrared spectroscopy in trace gas analysis are illustrated, and an algorithm is described for numerical differentiation of a digitized infrared spectrum.
Stimulated Raman Gain Spectroscopy Utilizing Counter-Propagating Pulsed Dye Lasers
Authors: Nestor James R.
Published: August 2005

A simplified experimental arrangement, in which the laser beams are counter-propagating, has allowed the acquisition of Raman gain spectra without the aid of optically dispersive devices. The method allows high spectral resolution with the spatial rejection of fluorescence typical of coherent Raman techniques. Access to the low-frequency spectral region has revealed stimulated gain involving mechanical waves of the bulk medium. Quasi-continuous scans of the entire vibrational region have been made using only two laser dyes.
Measurements of Rotational Temperatures in the Hollow Cathode Discharge
Authors: Dobrosavljević J. S. , Pešić D. S.
Published: August 2005

Rotational temperatures in the uncooled hollow cathode discharge (HCD) have been measured. Using rotational lines of the OH (0,0) band, the temperatures were measured in a helium fill gas pressure range from 266 to 2130 Pa and in the discharge current between 0.1 and 0.3 A. A comparative study of these temperatures with gas and excitation temperatures in HCD is presented.
Single-Atom Detection
Authors: Alkemade C. Th. J.
Published: August 2005

An overview is presented of the principles and achievements of various laser-assisted detection techniques that have been developed to observe a single or a small number of neutral atoms in the gaseous state. Possible applications of these single-atom detection (SAD) techniques and their significance for the improvement of analytical detection limits are mentioned. Section I describes the general implications of SAD techniques and contains statistical expressions for the mean and the fluctuation of the signal. An intrinsic limit of detection is defined that relates to the statistical fluctuation of the number of registered atoms in the observation volume. Section II gives a classification and a more detailed description of reported techniques. Experimental detection limits are compared with the intrinsic limits predicted by theory. In Section III, conclusions are drawn about the state-of-the-art and suggestions are made for further improvements, including the lowering of the analytical detection limit.
A Fourier Transform Infrared Study of Mineral Matter in Coal: The Application of a Least Squares Curve-Fitting Program
Authors: Painter Paul C. , Rimmer Susan M. , Snyder Randy W. , Davis Alan
Published: August 2005

The application of Fourier transform infrared spectroscopy to the quantitative determination of mineral matter in coal is discussed. The use of a least squares curve-fitting program allows a choice between standards to be made. The results of an analysis of mineral mixtures and a coal low temperature ash are presented. The results are in good agreement with known concentrations and those obtained by other methods of analysis.
In Situ FT-IR Spectroscopy of the Adsorption of CO on Methanol Catalysts
Authors: Edwards J. F. , Schrader G. L.
Published: August 2005

Fourier transform infrared spectroscopy was used to identify surface species on zinc oxide and a zinc-copper mixed oxide at CO pressures up to 50 atm and a temperature of 200°C. In situ spectra were recorded in a high-pressure cell having a short path length. Spectra of adsorbed species on both oxides indicated the presence of carbonate, carboxylate, hydride, hydroxide, and formate surface species. The spectrum of the mixed oxide at 50 atm had additional bands which were assigned to a methoxide surface species.
Deviation from Beer's Law Caused by Spectral Interference
Authors: Elsirafy A. A.
Published: August 2005

A cause of deviation from Beer's Law is discovered. It is the presence of excess indicator in the standard solutions of the calibration curve when the indicator absorbs. The deviation is negative with either solvent or blank-reference. Theoretical and experimental evidences are given.
Laser-Induced Fluorometric Determination of Aluminium by the Lumogallion Complex
Authors: Haugen G. R. , Steinmetz L. L. , Hirschfeld T. B. , Klainer S. M.
Published: August 2005

Laser-induced fluorescence of aluminium-ion lumogallion complex was studied and the limit of detection was determined by the reagent blank. The blank fluorescence was equivalent to 0.7 ± 0.2 μg Al+3/l. At concentrations less than 6 μg Al+3/l, the stoichiometry of the complex changes, yielding higher sensitivities but poorer precision.
Simple and Inexpensive Design for an Isolated Droplet Generator Useful in Studies of Atomization in Flames
Authors: Russo R. E. , Withnell R. , Hieftje G. M.
Published: August 2005

A new design is presented for a droplet generator useful in studies of atomization processes in analytical flames. Based in part on medium-scale integrated circuitry, the design is superior in performance to earlier models and is far simpler to construct. Fabrication details are provided and the performance of the new device is assessed.
Spectroscopic Studies of —2-OxO-2,3 Dihydrobenzimidazol and Some N-Monosubstituted or N,N′-Disubstituted Derivatives
Authors: Guiliano M. , Mille G. , Chouteau J. , Kister J. , Metzger J.
Published: August 2005

Infrared, Raman and ultraviolet spectroscopic data for —2-oxo-2,3 dihydrobenzimidazol and 23 N-monosubstituted or N,N′-disubstituted derivatives have been correlated. Attributions of the principal infrared and Raman bands and ultraviolet absorptions are given.
Axial Distributions of Spectral Line Intensities in the Arc under the Influence of External Rotating Magnetic Field
Authors: Pavlović B. V. , Mihailidi T. A.
Published: August 2005

The influence of external rotating magnetic field (RMF) on the electric arc plasma, and therefore the axial distributions of the spectral line intensities and the atomic concentrations of the investigated elements in the plasma, was studied. The axial distribution of the spectral line intensities has, in all of the investigated cases, such a shape that the intensity has a maximum close to the cathode in the case of a cathode excitation as well as in the case of an anode excitation. At that, there is a very significant influence of the RMF on the axial distributions of spectral line intensities of the investigated elements. The effect of the RMF on the arc, in the case of anode excitation, leads to an outstanding increase of spectral line intensities in the zones close to the cathode, whereas in the case of a cathode excitation, it leads to an expanding of the zones close to the cathode with relatively higher spectral line intensities. Determining the particle concentrations has shown that the shape of particle concentration axial distribution curves and spectral line intensity axial distribution curves of the same element is very similar. Thus, a conclusion is drawn about a great influence of the particle concentration axial distribution on the spectral line intensity axial distribution of the considered elements.
Mass Spectrometric Evidence for Suprathermal Ionization in an Inductively Coupled Argon Plasma
Authors: Houk Robert S. , Svec Harry J. , Fassel Velmer A.
Published: August 2005

Mass spectra have been obtained of species in the axial channel of an inductively coupled argon plasma by extracting ions from the inductively coupled plasma into a vacuum system housing a quadrupole mass spectrometer. Ionization temperatures ( Tion) are obtained from relative count rates of m/z-resolved ions according to two general types of ionization equilibrium considerations: (a) the ratio of doubly/singly charged ions of the same element, and (b) the ratio of singly charged ions from two elements of different ionization energy. The Tion values derived from measurement of Ar+2/Ar+, Ba+2/Ba+, Sr+2/Sr+, and Cd+/I+ are all greater than those expected from excitation temperatures measured by other workers. The latter three values for Tion are in reasonable agreement with values obtained by optical spectrometry for a variety of argon inductively coupled plasmas.
Microwave-Supported Discharges
Authors: Zander A. T. , Hieftje G. M.
Published: August 2005

A review is presented on the historical, fundamental, and practical aspects of microwave-induced plasmas (MIP) and their application to spectrochemical analysis. In particular, the mechanism of formation and stabilization of a microwave discharge is explored and possible excitation processes involving analyte atoms are described. Conditions under which a MIP can be operated are delineated and instrumentation necessary for MIP spectroscopy is described in detail. Methods for sample introduction into a MIP are reviewed and evaluated critically and the performance of MIP sources in real sample determinations is evaluated. Overall, the MIP appears to be a highly promising and under-utilized source in atomic spectrometry.
Electron Number Densities in Analytical Inductively Coupled Plasmas as Determined via Series Limit Line Merging
Authors: Montaser Akbar , Fassel V. A. , Larsen G.
Published: August 2005

A convenient and a rapid technique is introduced to estimate the electron number densities, ne, in inductively coupled plasmas. The method is based on previously reported observations that the principal quantum number of the last discernible line in a series limit depends on ne. The spatially integrated ne values, as determined from the spectra of H, Li, Mg, Al, Ca, and K emitted in a pure Ar plasma ranged between ∼4 × 1014 and ∼3 × 1015 cm−3 for various forward powers and observation heights. These results agreed with ne values derived from other methodologies such as the Stark broadening and absolute continuum intensity.
Photodiode Array Studies of near Infrared and Red Atomic Emissions of C, H, N, and O in the Argon Inductively Coupled Plasma
Authors: Hughes Steven K. , Brown Robert M. , Fry Robert C.
Published: August 2005

Preliminary qualitative multielemental inductively coupled plasma atomic spectra of C, H, N, and O are presented using a low dispersion, near infrared and red photodiode array spectrometer. Simple spectra of reasonable intensity are obtained with short (4 ms) integration times. Sensitivity and dispersion considerations are sharply contrasted with those conventionally associated with ultraviolet photodiode array spectra of metals in the inductively coupled plasma.
Quantitative Analysis of Binary Mixtures. I. General Method
Authors: Diem Hugh E. , Krimm Samuel
Published: August 2005

A general spectroscopic method for the analysis of binary mixtures which does not require external calibration has been developed. Spectra of the original mixture and of the mixture following some fractionation procedure are obtained. The method is based on the scaling factors required to null the components, one at a time, in successive absorbance subtractions of the two spectra. The accuracy is improved by a factor of approximately ten more than that of an earlier method. The effect of errors in the scaling factors on the analytical results is considered.
The Use of a High Temperature Hollow Cathode Lamp for the Determination of Trace Elements in Steels, Nickel-Base Alloys, and Ferroalloys by Emission Spectrometry
Authors: Thelin Bo
Published: August 2005

A high temperature hollow cathode lamp from Applied Research Laboratories, Luton, was used for multielement determination of trace elements in steels, nickel-base alloys and ferroalloys. A 10-mg sample (chips) was placed inside a hollow graphite electrode in the lamp, which was filled with helium. It was possible to raise the power through the lamp linearly and automatically, so that the combined thermal and sputtering effect in the lamp atomized the different elements one after another according to their boiling points. This selective volatilization improved the precision and the limits of detection for the elements determined. Analysis results for Pb, Bi, Zn, Ag, Sb, and Ca in the concentration range 0.05 to 100 μg g−1 are discussed. Because of the effective atomization in the lamp, no matrix effects were observed for these elements. One of the main purposes of this investigation was to study the time dependence of the intensity for the different elements during the volatilization phase. This procedure gave very clean spectra. In this investigation a new computerized image dissector echelle spectrometer, was used as the registration system.
Vibrational Manifold Considerations for the Metal Indicator Dye 2-(2-Pyridylazo)-1-Naphthol
Authors: Long M. E. , Trotter P. J.
Published: August 2005

Metallized pyridyl azonaphthol dyes show a well-resolved vibronic manifold in the absorption spectra of their main hue band. The vibrations and groups causing this vibronic activity were investigated by resonance Raman spectroscopy, absorption spectroscopy, and molecular orbital calculations. Resonance Raman intensity enhancements of up to 5 × 104 were observed, and all of the major group vibrations were strongly enhanced. Consequently, we have concluded that the resolvable vibronic manifold has its origin in several group vibrations.