bluuebunny/crossref_metadata_2025 huggingface dataset:
PTEN deletion in Bergmann glia leads to premature differentiation and affects laminar organization
Authors: Yue Qing , Groszer Matthias , Gil Jose S. , Berk Arnold J. , Messing Albee , Wu Hong , Liu Xin
Published: June 2005

Development of the central nervous system is controlled by both intrinsic and extrinsic signals that guide neuronal migration to form laminae. Although defects in neuronal mobility have been well documented as a mechanism for abnormal laminar formation, the role of radial glia, which provide the environmental cues, in modulating neuronal migration is less clear. We provide evidence that loss of PTEN in Bergmann glia leads to premature differentiation of this crucial cell population and subsequently to extensive layering defects. Accordingly, severe granule neuron migration defects and abnormal laminar formation are observed. These results uncover an unexpected role for PTEN in regulating Bergmann glia differentiation, as well as the importance of time-dependent Bergmann glia differentiation during cerebellar development.
Control of body size by SMA-5, a homolog of MAP kinase BMK1/ERK5, inC. elegans
Authors: Watanabe Naoharu , Nagamatsu Yasuko , Gengyo-Ando Keiko , Mitani Shohei , Ohshima Yasumi
Published: June 2005

We have analyzed the sma-5(n678) mutant in C. elegans to elucidate mechanisms controlling body size. The sma-5 mutant is very small, grows slowly and its intestinal granules look abnormal. We found a 15 kb deletion in the mutant that includes a 226 bp deletion of the 3′ end of the W06B3.2-coding sequence. Based on this result, rescue experiments, RNAi experiments and a newly isolated deletion mutant of W06B3.2, we conclude that W06B3.2 is the sma-5 gene. The sma-5 mutant has much smaller intestine, body wall muscles and hypodermis than those of the wild type. However, the number of intestinal cells or body wall muscle cells is not changed, indicating that the sma-5 mutant has much smaller cells. In relation to the smaller cell size, the amount of total protein is drastically decreased; however, the DNA content of the intestinal nuclei is unchanged in the sma-5 mutant. The sma-5 gene is expressed in intestine,excretory cell and hypodermis, and encodes homologs of a mammalian MAP kinase BMK1/ERK5/MAPK7, which was reported to control cell cycle and cell proliferation. Expression of the sma-5 gene in hypodermis is important for body size control, and it can function both organ-autonomously and non-autonomously. We propose that the sma-5 gene functions in a MAP kinase pathway to regulate body size mainly through control of cell growth.
VEGF is crucial for the hepatic vascular development required for lipoprotein uptake
Authors: Carpenter Brian , Lin Yuankai , Stoll Stephanie , Raffai Robert L. , McCuskey Robert , Wang Rong
Published: June 2005

Hepatic lipid catabolism begins with the transport of lipoprotein remnants from the sinusoidal vasculature into hepatocytes by endocytosis via microvilli. To test the hypothesis that fenestrated sinusoidal endothelial cells (SECs) are crucial for this process, we selectively disrupted SECs by downregulating vascular endothelial growth factor (VEGF) signaling, using hepatocyte-specific, tetracycline-regulatable expression of a VEGF receptor that can sequester VEGF but cannot relay its signal. Newborn mutant livers appeared grossly normal, but displayed a dark-red color that was distinguishable from normal physiological lipid-rich pink livers. Mutant sinusoidal networks were reduced and their SECs lacked fenestrae. Hepatocellular lipid levels were profoundly reduced, as determined by Oil Red O staining and transmission electron microscopy, and fewer hepatocytic microvilli were evident, indicating impaired lipoprotein endocytosis. Levels of apolipoprotein (APO) E bound to mutant sinusoidal networks were significantly reduced, and fluorescently-labeled murine remnant lipoproteins injected into the blood stream failed to accumulate in the space of Disse and diffuse into hepatocytes, providing evidence that reduced hepatocellular lipid levels in mutant livers are due to impaired lipoprotein uptake. Temporal downregulation of VEGF signaling revealed that it is crucial at all developmental stages of hepatic vascular morphogenesis, and repression of the dominant-negative effect can rescue the phenotype. These findings provide the first genetic evidence that VEGF dynamically regulates SEC fenestration during liver organogenesis, a process that is required for lipoprotein uptake by the liver.
PLCγ1 is essential for early events in integrin signalling required for cell motility
Authors: Jones Neil P. , Peak Joanna , Brader Sharon , Eccles Suzanne A. , Katan Matilda
Published: June 2005

Cell motility is a critical event in many processes and is underlined by complex signalling interactions. Although many components have been implicated in different forms of cell migration, identification of early key mediators of these events has proved difficult. One potential signalling intermediate, PLCγ1, has previously been implicated in growth-factor-mediated chemotaxis but its position and roles in more-complex motility events remain poorly understood. This study links PLCγ1 to early, integrin-regulated changes leading to cell motility. The key role of PLCγ1 was supported by findings that specific depletion of PLCγ1 by small interfering (si)RNA, or by pharmacological inhibition, or the absence of this isoform in PLCγ1–/– cells resulted in the failure to form cell protrusions and undergo cell spreading and elongation in response to integrin engagement. This integrin-PLCγ1 pathway was shown to underlie motility processes involved in morphogenesis of endothelial cells on basement membranes and invasion of cancer cells into such three-dimensional matrices. By combining cellular and biochemical approaches, we have further characterized this signalling pathway. Upstream of PLCγ1 activity, β1 integrin and Src kinase are demonstrated to be essential for phosphorylation of PLCγ1, formation of protein complexes and accumulation of intracellular calcium. Cancer cell invasion and the early morphological changes associated with cell motility were abolished by inhibition of β1 integrin or Src. Our findings establish PLCγ1 as a key player in integrin-mediated cell motility processes and identify other critical components of the signalling pathway involved in establishing a motile phenotype. This suggests a more general role for PLCγ1 in cell motility, functioning as a mediator of both growth factor and integrin-initiated signals.
Activation of EGF receptor endocytosis and ERK1/2 signaling by BPGAP1 requires direct interaction with EEN/endophilin II and a functional RhoGAP domain
Authors: Lua Bee Leng , Low Boon Chuan
Published: June 2005

Rho GTPases are important regulators for cell dynamics. They are activated by guanine nucleotide exchange factors and inactivated by GTPase-activating proteins (GAPs). We recently identified a novel RhoGAP, BPGAP1, that uses the BNIP-2 and Cdc42GAP homology (BCH) domain, RhoGAP domain and proline-rich region to regulate cell morphology and migration. To further explore its roles in intracellular signaling, we employed protein precipitations and matrix-assisted laser desorption/ionization mass-spectrometry and identified EEN/endophilin II as a novel partner of BPGAP1. EEN is a member of the endocytic endophilin family but its function in regulating endocytosis remains unclear. Pull-down and co-immunoprecipitation studies with deletion mutants confirmed that EEN interacted directly with BPGAP1 via its Src homology 3 (SH3) domain binding to the proline-rich region 182-PPPRPPLP-189 of BPGAP1, with prolines 184 and 186 being indispensable for this interaction. Overexpression of EEN or BPGAP1 alone induced EGF-stimulated receptor endocytosis and ERK1/2 phosphorylation. These processes were further enhanced when EEN was present together with the wildtype but not with the non-interactive proline mutant of BPGAP1. However, EEN lacking the SH3 domain served as a dominant negative mutant that completely inhibited these effects. Furthermore, BPGAP1 with a catalytically inactive GAP domain also blocked the effect of EEN and/or BPGAP1 in EGF receptor endocytosis and concomitantly reduced their level of augmentation for ERK1/2 phosphorylation. Our findings reveal a concomitant activation of endocytosis and ERK signaling by BPGAP1 via the coupling of its proline-rich region, which targets EEN and its functional GAP domain. BPGAP1 could therefore provide an important link between cytoskeletal network, endocytic trafficking and Ras/MAPK signaling.
Health advisor workload
Authors: Kellock D J , Bingwa E , Carlton S , Carlin E
Published: June 2005

Health advisors (HAs) are an integral part of the multidisciplinary team within genitourinary (GU) medicine clinics, with a pivotal role in the National Sexual Health Strategy by enhancing liaison between community sexual health provision and GU medicine services. Greater clarity is needed about HAs' current activities and workload in order to enable benchmarking and ensure accurate workforce planning. We describe a tool for assessing HA workload and activity and evaluating its use in real clinic environments through a prospective time and motion model.

Ten centres (63% of those invited to participate) within a single region did so. Median HA working times were calculated at almost 15 min/patient consultation and approximately 10 min/telephone call.

Although there were strong positive correlations between HA availability and some markers of clinical activity, these were weaker than similar correlations applied to medical staff, raising the possibility of suboptimal HA workforce planning.
Chronic vulval ulceration — another immune reconstitution inflammatory syndrome?
Authors: Reddy V , Luzzi G A
Published: June 2005

We describe a patient who developed intractable chronic vulval ulceration that we believe was related to immune reconstitution following treatment of HIV infection with highly active antiretroviral treatment (HAART). Immune reconstitution inflammatory syndrome should be considered in the differential diagnosis of unexplained vulval ulceration that arises after starting HAART.
HIV in couples in South India; implications for prevention
Authors: Rogers M Chatterjee , Gopalakrishnan G , Kumarasamy N , Flanigan T P , Carpenter C C J , Mayer K H , Solomon S
Published: June 2005

We studied HIV prevalence in couples in Chennai, India. In 56% both partners were infected. Among discordant couples, 35 men and seven women were infected. Heterosexual intercourse is the primary risk factor. Concordance was related to sex with commercial sex workers for men and to genital ulcer disease for women. Median CD4 count was 97 cells/mm3 among concordant men, 222 cells/mm3 among discordant men. Condom use increased, and frequency of sexual intercourse decreased, among all couples after HIV diagnosis.
Severe Hyperglycemia During Renally Adjusted Gatifloxacin Therapy
Authors: Blommel Amy L , Lutes Ronald A
Published: June 2005

OBJECTIVE

To report a case of severe hyperglycemia in a nondiabetic patient receiving gatifloxacin that was properly dosed based on renal function.

CASE SUMMARY

A 65-year-old nondiabetic female with progressive renal dysfunction was admitted for severe hyperglycemia. The patient had received 9 days of a 10-day course of renally adjusted therapy with gatifloxacin 200 mg/day for bronchitis. Her blood glucose level on admission was 1121 mg/dL, at which point the gatifloxacin was discontinued. After several days of intensive insulin therapy, the blood glucose levels returned to normal, and the patient was subsequently discharged.

DISCUSSION

Gatifloxacin-induced hyperglycemia has been reported in the literature, but based on a MEDLINE search (1966–December 2004), no such cases were found in a nondiabetic patient receiving the proper gatifloxacin dose, adjusted for degree of renal insufficiency. The available case reports seem to suggest the increase in blood glucose concentrations could have been precipitated by high drug concentrations in patients not receiving the renally adjusted dose or in those with preexisting, undiagnosed diabetes. A definite mechanism of action for gatifloxacin-induced hyperglycemia is not known. The Naranjo probability scale revealed a probable adverse reaction of hyperglycemia associated with gatifloxacin therapy.

CONCLUSIONS

Healthcare professionals should be more aware of the possible development of hyperglycemia in all patients taking gatifloxacin, including those who are not diabetic and those receiving appropriately reduced doses for renal dysfunction.
Venous Thromboembolism Prevention in Acutely Ill Nonsurgical Patients
Authors: Brophy Donald F , Dougherty John A , Garrelts James C , Parish Roy C , Rivey Michael P , Stumpf Janice L , Taylor Charles T , Mathis A Scott
Published: June 2005

OBJECTIVE

To review recent advances in the prevention of venous thromboembolism (VTE) in acutely ill nonsurgical inpatients.

DATA SOURCES

A MEDLINE search (1966–March 2005) was done to identify relevant articles relating to prevention of VTE in acutely ill nonsurgical inpatients.

STUDY SELECTION AND DATA EXTRACTION

Four major prophylaxis trials, one registry, one guideline, and supporting articles representative of the subject matter from the last few years were included.

DATA SYNTHESIS

Enoxaparin, dalteparin, fondaparinux, and unfractionated heparin 5000 units every 8 hours are effective in reducing the risk of VTE in acutely ill medical patients, but such prophylaxis is currently underused. Barriers to be overcome include recognition of the importance of VTE in this population, definition of the optimal strategy to assess risks, optimal timing of the risk assessment, optimal prophylactic regimen for a given level of risk or disease state, and optimal duration of prophylaxis. We recommend that acutely ill medical inpatients should be risk-stratified early in their hospitalization. At this time, the specific risk-assessment protocol should be derived from the trial(s) of the available formulary agent(s). Decisions about providing prophylaxis must also be made considering anticoagulant contraindications and renal function. Mechanical methods of prophylaxis should be considered as monotherapy only if an anticoagulant contraindication exists. The optimal duration of prophylaxis is not known, but 14 days was used in recent studies.

CONCLUSIONS

Prophylaxis of VTE in acutely ill medical inpatients is underused. Data provide some guidance for increasing awareness and optimizing patient care.
Evaluation of the Effect of Wavelength Positioning Errors on Kalman Filtering Results in Inductively Coupled Plasma Atomic Emission Spectrometry
Authors: Yang Jingfu , Piao Zhexiu , Zeng Xianjin
Published: June 2005

This work evaluates the effect of wavelength positioning errors in spectral scans on analytical results when the Kalman filtering technique is used for the correction of line interferences in inductively coupled plasma atomic emission spectrometry (ICP-AES). The results show that a positioning accuracy of 0.1 pm is required in order to obtain accurate and precise estimates for analyte concentrations. The positioning error in sample scans is more crucial than that in model scans. The relative bias in measured analyte concentration originating from a positioning error in a sample scan increases linearly with an increase in the magnitude of the error and the peak distance of the overlapping lines, but is inversely proportional to the signal-to-background ratio. By the use of an optimization procedure for the positions of scans with the innovations number as the criterion, the wavelength positioning error can be reduced and, correspondingly, the accuracy and precision of analytical results improved.
Calibration of Chromium Tanning Solution with Different Regression Methods
Authors: Marjoniemi M.
Published: June 2005

This paper presents a model of a chromium-tanning solution used in leather processing. Chromium(III)sulfate is used in leather processes as a tanning agent. This model provides a quick and easy way of determining Cr(III) content in a tanning process having high chromium concentrations. Shifts of absorption peaks and changes in the intensity of absorption—due to different ligands of the chromium complex, aging, or differences in pH and temperature—all create difficulties in the modeling of a chromium-tanning solution. Different multilinear and factor-based regression methods were applied, and the results were compared. The influence of the derivatives in the calibration of chromium-tanning solutions was also studied.
Fluorometric Data Processing Strategies Using Nanosecond Waveform Digitizers
Authors: Campos Teresa L. , Lytle Fred E.
Published: June 2005

Developments in commercially available digitization technology have made practical the software processing of nanosecond fluorometric data. The data are digitized and transferred to a microcomputer after each excitation pulse, then processed by a software module simulating either analog or photon counting detection. Software anode current processing provides display of the decay and integration of its area in the same operation, offers a multiplex advantage to improve decay collection rate, and allows the definition of a nearly rectangular gating function with sharp 1-ns edges. Application of the photon counting method to fluorometric instruments based on low-repetition-rate lasers is achieved with a multistop, multilevel discrimination algorithm to increase the usable detection rate. The ability to achieve photon counting detection permits a more rigorous statistical treatment of the data and can provide transit time-spread limited resolution.
Optical Comparison of Thin Ag Films on Glass and Formvar
Authors: Roark Shane E. , Rowlen Kathy L.
Published: June 2005

The optical characteristics of vapor-deposited Ag films were investigated as a function of Ag thickness on both glass and Formvar-coated glass substrates. The optical density and the wavelength at maximum optical density were found to depend on the nature of the substrate.
Multispectral Analysis for Quantitative Measurements of Myoglobin Oxygen Fractional Saturation in the Presence of Hemoglobin Interference
Authors: Arakaki Lorilee S. L. , Burns David H.
Published: June 2005

Quantitative values for myoglobin oxygen fractional saturation were extracted from visible absorption spectra of myoglobin and hemoglobin solutions by analysis with three algorithms: classical least-squares, partial least-squares, and stagewise multiple linear regression. In an effort to mimic in vivo conditions, oxygen tensions and concentrations of myoglobin and hemoglobin solutions in separate cuvettes were varied independently. Transmission measurements were made through both cuvettes so that spectra contained contributions from both myoglobin and hemoglobin. Oxygen tensions in the myoglobin solutions spanned the rapidly varying region of the myoglobin oxygen saturation curve with pO2 ranging from 0 to 4.79 Torr, corresponding to fractional saturation values between 0 and 0.903. A range of hemoglobin oxygenations from fully oxygenated to fully deoxygenated was used. Estimation of myoglobin fractional saturation by the classical least-squares algorithm had a standard error (SEest) of 0.094, while the partial least-squares method resulted in an SEest of 0.070. Partial least-squares estimations resulted in an SEest of 0.041 when a limited wavelength range was used. The stagewise multiple linear regression method had an SEest of 0.052. Results indicate that stagewise regression and partial least-squares yielded estimates of myoglobin fractional saturation that were more accurate than those obtained from classical least-squares.
Structure of Ice Layers on Electrical Transmission Cables with Raman Microprobe Spectroscopy
Authors: Sonwalkar Nishikant , Sunder S. Shyam , Sharma S. K.
Published: June 2005

An icing chamber employing a closed-cycle helium cryostat has been fabricated for Raman microprobe spectroscopy of the icing on electrical transmission cable samples. A thick layer of ice deposited on a cable sample at low temperature (30 K) evaporates gradually under vacuum by increasing the temperature at intervals of 10 K up to 180 K. The Raman spectra of the gradually thinning ice layer obtained in the O-H stretching region reveals the layer-by-layer structure of ice. The study suggests that the structure of the initial ice changes from low-density amorphous ice at low temperatures to high-defect-density polycrystalline ice at higher temperatures. This observation, made for the first time on electrical transmission cable samples, is consistent with the observed phase diagram of bulk amorphous ice.
Computer Simulation of the Operation of a Three-Dimensional Quadrupole Ion Trap
Authors: Ma Ce , Lee Heewon , Lubman David M.
Published: June 2005

A computer simulation of the motion of ions in a three-dimensional (3-D) quadrupole ion trap has been performed with a Gateway 386 PC/AT computer. The SIMION program was used as the main program to calculate the potential array of the ion trap space. Several user-written programs were interfaced to the SIMION program to simulate the effects of changing various operating conditions, such as the radio-frequency (rf) potential, the collisional buffer gas, external ion injection, dc ejection from the trap, and resonance ejection. With the use of this simulation, the total storage mass range could be obtained as a function of rf voltage and frequency. The simulations show, as expected, that the collisional buffer gas plays an important role in both stabilizing the trajectory of high-kinetic-energy ions (hot ions) inside the ion trap and trapping ions injected from an external source. Several different buffer gases were studied for their effects upon the trapping motion. In addition, both the total mass ejection that results from applying a dc pulse on the output end-cap electrode and the ion ejection that results from applying an rf frequency to the end cap to produce resonance ejection were also studied with this simulation program. It is demonstrated that a simple PC computer using a modified SIMION program provides results very similar to those expected from theory or from previous work.
Sulfur Hexafluoride: Optimal Use as a Gas-Phase, Infrared Sensitizer
Authors: Stanley A. E. , Ludwick L. M. , White D. , Andrews D. E. , Godbey S. E.
Published: June 2005

Investigations into the use of sulfur hexafluoride, SF6, as a gas-phase, infrared photochemical sensitizer have revealed several interesting phenomena. The expedient use of SF6 can produce an optimal quantity of nitrated product in the gas-phase, laser-induced nitration of cyclopen-tane. The optimal utilization of sulfur hexafluoride required critical optimization of both frequency and quantity. The results are described herein.
Aluminum Determination Using Resonance Ionization Spectrometry
Authors: Zilliacus R. , Likonen J.
Published: June 2005

In the present study, the determination of aluminum using resonance ionization spectroscopy has been investigated. The atomization of the sample was achieved with the use of electrothermal heating in pyrolytically coated graphite in a vacuum. The atoms were excited in two resonant steps to the Rydberg state and ionized with an electric field pulse. The influence of the sample matrix on the aluminum signal and the use of matrix modifier were studied. The detection limit for aluminum determined in this work was 4 pg. Analytical results for some reference samples are presented.
A Novel Idea for Practical UV Resonance Raman Measurement with a Double Monochromator and its Application to Protein Structural Studies
Authors: Kaminaka Shoji , Kitagawa Teizo
Published: June 2005

A practical system for UV resonance Raman (RR) measurements based on the combined use of the first-/second-order dispersions of two gratings in an ordinary double monochromator is proposed. This system rejects visible stray light completely and gives four times larger throughput than the combination of the normal second-order dispersion of two gratings and a visible-cut filter. Newly designed f/1.1 Cassegrainian mirror optics and a sensitive spinning cell using an ESR sample tube are combined with this spectrometer and applied to measurements of UV RR spectra of hen egg white lysozyme. The continuous-wave 244-nm excited spectra of lysozyme yielded Raman bands of tryptophan (Trp) and deprotonated tyrosine (Tyr−) residues in 10 min with high signal-to-noise ratios, and there was no sample degradation. It is demonstrated that the intensity of the Tyr− v8 a band in the 244-nm excited spectrum can be used to quantify the number of deprotonated Tyr residues in the stepwise ionization of a protein.
Pure Component Analysis of Chain Length Distributions from Solid-State Polymerization of Formaldehyde
Authors: Mansueto Edward S. , Wight Charles A.
Published: June 2005

Infrared spectra of oligomers formed during solid-state polymerization of formaldehyde at 77 K and subsequent warm-up to 150 K have been analyzed with the use of Simple Interactive Self-Modeling Multivariate Analysis (SIMPLISMA). Two pure spectral components, corresponding roughly to “short”- and “long”-chain oligomers, were extracted from the data along with their associated infrared spectra. The cutoff length that separates the two types of oligomers has been determined to be about 20 monomer units. This value is calculated within the context of a statistical model of solid-state polymerization in which chain length distributions are governed largely by spatial and orientational disorder of molecules in lattice sites adjacent to the growing end of each polymer chain. The cutoff length is observed to be essentially constant during thermal annealing cycles in which chain growth takes place, lending support to the validity of the model.
Quantitative Diffuse Reflectance and Transmittance Infrared Spectroscopy of Nondiluted Powders
Authors: Boroumand Farnaz , Moser Jacques E. , Van Den Bergh Hubert
Published: June 2005

An adaptation of Kubelka's general model of diffuse reflectance and diffuse transmittance of light to nonideal scattering samples is proposed. It is applied to quantitative Fourier transform infrared spectrometry of nondiluted surface-derivatized silica powders. Corrections of the measurements are introduced in order to take into account common problems that often prevent a truly quantitative application of the DRIFTS analytical method. Effects on the measured data due to the background absorption of the sample and to the specular reflection on its surface are discussed and quantitatively corrected for. The possible existence of gradients of the optical properties of the powder medium is taken into account by a numerical adaptation of the model to inhomogeneities of the phenomenological absorption and scattering coefficients K and S. Model systems constituted of two types of silica powders of very different morphology are prepared. Known concentrations of molecules carrying a cyano functional group as chromophore were covalently anchored on the powder surface. Application of the adapted model gives a quite good description of the measured diffuse reflectance and diffuse transmittance in these cases where the simple Kubelka-Munk function fails.
Concurrent Determination of Optical Constants and the Kramers-Kronig Integration Constant (Anchor Point) Using Variable-Angle ATR/FT-IR Spectroscopy
Authors: Tickanen Lane D. , Tejedor-Tejedor M. Isabel , Anderson Marc A.
Published: June 2005

Attenuated total reflection Fourier transform infrared (ATR/FT-IR) spectroscopy has been used to determine optical constants in the infrared region of the spectrum for a variety of materials. Usually, the Kramers-Kronig transform is used to obtain optical constants from spectra, given that the baseline refractive index (anchor point) is known or can be determined. This determination often involves performing a separate experiment in which the refractive index of the sample is measured in a nonabsorbing region of the visible part of the spectrum, and the result extrapolated to the infrared. However, this is not feasible for opaque samples or for ones that contain domains large enough to scatter visible light. In this paper, we present a method for concurrently determining the anchor point and the optical constants using only variable-angle ATR/FT-IR spectroscopy and the subtractive form of the Kramers–Kronig transform. The method for determining the anchor point involves ratioing pATR (the negative log of the intensity of the ATR spectrum) values from weak absorption bands from spectra recorded at different angles of incidence. The anchor point can then be determined by computer. The only requirements are that the ATR system use unpolarized radiation and that the sample be thicker than the sampling depth of the IR radiation.
Near-IR Spectroscopic Determination of NaCl in Aqueous Solution
Authors: Lin Jie , Brown Chris W.
Published: June 2005

The concentrations of NaCl in aqueous solutions have been determined with the use of near-IR spectra between 1100 and 1900 nm. Models expressing the concentration of NaCl are developed with linear and nonlinear regression with the use of the absorbances at selected wavelengths and with principal component regression (PCR) using entire spectra. Temperature perturbations on water bands interfere with the measurement of NaCl but can be removed by linear or nonlinear regressions using the absorbances at the wavelengths where the temperature effects are zero, or they can be accounted for by PCR. Standard errors of 5 mM and a detection limit of IS mM are obtained for NaCl. This technique can be applied for quantitative analysis of NaCl in the laboratory or can be readily adapted for continuous monitoring in process control.
Optical Measurements on Heavily Reduced Bismuth Iron Molybdate: Evidence for Vacancy-Induced Phase Transitions
Authors: Sears W. M. , Keeler W. J.
Published: June 2005

It is known that the conductance of a bismuth iron molybdate pellet is greatly affected by the stoichiometry (number of oxygen vacancies) of the compound. The number of these vacancies is determined by the amount of reducing vapor (such as ethanol), which tends to increase their number and the amount of oxygen, which tends to decrease it, in the atmosphere. For this reason the compound can be used as a chemical sensor. Earlier measurements of the conductance in a highly reducing methanol vapor atmosphere, determined by measuring the current passing between two gold wires embedded in a pressed pellet, have shown three well-defined stages in the conductance, which are related to solid-state phase transitions occurring on the surface of the pellet granules. In this paper we further examine the nature of these transitions using infrared, Raman, and photoluminescence spectroscopy to follow the structural changes that occur as greater amounts of oxygen are removed. These changes are seen as shifts in relative scattering intensity as well as frequency.
Infrared Photoacoustic Spectra of the Solid Manganese(I) Carbonyl Halides, Mn(CO)5X and [Mn(CO)4X]2 (X = Cl, Br, I)
Authors: Li Hongqi , Butler Ian S.
Published: June 2005

Mid- and near-IR photoacoustic (PA) spectra have been measured at room temperature for two series of crystalline manganese(I) carbonyl halides: Mn(CO)5 X and [Mn(CO)4 X]2 ( X = Cl, Br, I). Vibrational assignments are proposed for many of the observed bands. The PA spectra in the near-IR region (4200-3800 cm−1), where the binvary v(CO) overtones and combinations absorb, are useful spectral fingerprints for these organomanganese(I) complexes.
Determination of Carbon Monoxide and Carbon Dioxide Concentrations at Temperatures between 295 and 1250 K Using Fourier Transform Infrared Absorption Spectroscopy
Authors: Medvecz Patrick J. , Nichols Kenneth M.
Published: June 2005

Fourier transform infrared absorption spectroscopy has been used for the determination of CO and CO2 gas concentrations in a high-temperature cell. The gas mixtures analyzed consisted of CO, CO2, and nitrogen; among the samples, the concentration of CO was varied between 0.5 and 4.7% and the CO2 ranged between 0.7 and 4.9%. The temperature of the gas cell was varied between 295 and 1250 K, while the pressure was maintained at atmospheric. Throughout this temperature range, 123 absorption spectra were recorded in the gas cell at a nominal instrument resolution of 0.25 cm−1. The absorption lines used for the concentration analysis consisted of 22 P-branch CO vibrational-rotational lines from the fundamental absorption band, and 19 R-branch CO2 vibrational-rotational lines from the v3 fundamental absorption band. All of the peak heights used for the concentration calculations were first numerically corrected for photometric errors resulting from the finite resolution of the FT-IR instrument. The corrected peak heights were assumed to follow the Bouguer-Lambert law at a constant furnace temperature. Fifty-one of the spectra were used to determine the temperature dependence of the line strength for each of the 41 lines. The experimentally obtained line strengths were then used to determine the gas concentrations of all 123 spectra. The calculated concentrations were compared to NDIR instrument measurements of the gas composition exiting the flow-through high-temperature gas cell. Comparison of the NDIR measured gas concentrations with the calculated concentrations from absorption spectra yielded an average accuracy of 3.6% for the CO spectra and 4.9% for the CO2 spectra.
Sampling, Excitation, and Ionization Characteristics of a Planar Magnetron Glow-Discharge Device
Authors: McCaig Lori , Shi Zhan , Woodrum Teresa Holbrook , Brewer Stephen , Sacks Richard
Published: June 2005

Measurements of mass loss during sputtering, atomic emission intensities, and ionization characteristics are described for a coaxial magnetron glow-discharge device. By the use of the magnetic field from a coaxial magnet pair placed behind the cathode, stable plasma operation is achieved for all pressures from 0.0004 Torr (0.05 Pa) to over 2.5 Torr (330 Pa). Mass loss measurement values from pellets of Al, Cu, brass, Zn, and Au located in the region of greatest sputtering show much larger values at pressures which are lower than those usually used with glow-discharge excitation and ionization sources. Emission line ratio measurements at the lower pressures indicate that populations of low-energy electronic states are greater than equilibrium values. This observation suggests that the plasma is dominated by ionization processes rather than by recombination processes. Emission line ratio and mass spectrometric measurements also indicate that ionization is increased at the lower pressures.
Comparison of Different Calibration Methods Suited for Calibration Problems with Many Variables
Authors: Holst Helle
Published: June 2005

This paper describes and compares different kinds of statistical methods proposed in the literature as suited for solving calibration problems with many variables. These are: principal component regression, partial least-squares, and ridge regression. The statistical techniques themselves do not provide robust results in the spirit of calibration equations which can last for long periods. A way of obtaining this property is by smoothing and differentiating the data. These techniques are considered, and it is shown how they fit into the treated description.
Diode Laser-Based Concentration Gradient Detector for Detection of Capillary Isoelectric Focusing
Authors: Wu Jiaqi , Frank Peter , Pawliszyn Janusz
Published: June 2005

A diode laser-based concentration gradient detector was used in a compact capillary isoelectric focusing (CIEF) instrument which also includes a short piece of 20- μm-i.d. capillary. The diode laser was mounted with a focusing lens and driving circuit in an 8-cm-long, 2-cm-diameter aluminium barrel, and was powered by a 9-V battery. The size of the whole instrument is about 25 cm × 15 cm—much smaller than that of any other capillary electrophoresis (CE) instrument. In order to focus the laser beam into the narrow capillary, optical geometry of the detector was optimized. This diode laser-based detector is the first one which has been applied to CE with capillaries narrower than 50 μm. The detection limit in concentration for ovalbumin reaches 2.0 × 10−7 M, which corresponds to a 7.0 fmol on-column detection limit for the protein. This on-column detection limit of the universal detector is within the same order of magnitude as that of a diode laser-based fluorescence CE detector. The resolution of the instrument is about 0.02 pH units, and small amounts of protein samples in a wide isoelectric point range can be separated and detected by the compact instrument without derivatization in less than 12 minutes.
ICP Sample Matrix Identification by Acoustic Signature
Authors: Webb Douglas P. , Power Joan F. , Salin Eric D.
Published: June 2005

A novel technique for rapidly determining properties of the sample matrix of nebulized samples in inductively coupled plasma spectrometry via acoustic signature is discussed. Properties such as surface tension and high dissolved salts can be determined by analyzing the acoustic signal produced by the sample nebulization process. With digital signal processing equipment, determination of the presence of organic matrices or high-salt matrices should be possible before the plasma or the nebulizer is adversely affected.
Surface-Enhanced Raman Analysis of p-Nitroaniline on Vacuum Evaporation and Chemically Deposited Silver-Coated Alumina Substrates
Authors: Li Ying-Sing , Vo-Dinh Tuan , Stokes David L. , Wang Yu
Published: June 2005

In this study we investigated the surface-enhanced Raman scattering (SERS) properties of p-nitroaniline, which is a potential chemical for use in optical disk coating(s) and also an important compound used as an intermediate or precursor in the manufacture of chemical agents, pesticides, pharmaceuticals, dyes, and antioxidants. The SERS spectra of p-nitroanaline ( p-NA), adsorbed on or near the surface of either vacuum thermally evaporated or chemically prepared silver-coated alumina substrates, have been recorded in the frequency region from 200 to 1800 cm−1. The performances of these substrates to enhance the Raman scattering signals were not possible to compare with each other because of different experimental conditions. The infrared (IR) (500–1800 cm−1) and Raman (200–1800 cm−1) spectra have been recorded for the solution of p-NA. Vibrational assignments were made for the molecule in the frequency region. The Raman enhancement factor was estimated to be on the order of 106, and the absolute limit of optical detection was determined to be 30 femtograms.
A Simple, Lensless Interface of an RF Glow Discharge Device to an FT-ICR (FTMS)
Authors: Marcus R. Kenneth , Cable Paula R. , Duckworth Douglas C. , Buchanan Michelle V. , Pochkowski Joseph M. , Weller Robert R.
Published: June 2005

High mass resolving powers ( m/Δ m = 39,000) are achieved by coupling an rf-powered glow discharge device to an FT/ICR mass spectrometer (FTMS). Introduction of the ions from the externally mounted ion source into the ICR analyzer cell is accomplished without the use of ion optics, relying simply on the ions' kinetic energy in the z (magnetic axis) direction. Magnetic focusing is believed to facilitate efficient ion transport. Basic improvements in the instrument design are expected to yield resolving powers of > 100,000—sufficient to overcome almost any isobaric interference encountered in plasma source mass spectrometry.
On the Use of Fast Hadamard Transforms for Spectrum Recovery in Hadamard Transform Spectroscopy
Authors: Harms B. K. , Park J. B. , Dyer S. A.
Published: June 2005

The spectrum-recovery step in Hadamard transform spectroscopy is commonly implemented with a fast Hadamard transform (FHT). When the Hadamard or simplex matrix corresponding to the mask does not have the same ordering as the Hadamard matrix corresponding to the FHT, a modification is required. When the two Hadamard matrices are in the same equivalence class, this modification can be implemented as a permutation scheme. This paper investigates permutation schemes for this application. The investigation clarifies inaccurate claims about the applicability of existing methods; reveals a new, more efficient method; and leads to an extension that allows a permutation scheme to be applied to any Hadamard or simplex matrix in the appropriate equivalence class.
The Electronic Absorption Edge of Petroleum
Authors: Mullins Oliver C. , Mitra-Kirtley Sudipa , Zhu Yifu
Published: June 2005

The electronic absorption spectra of more than 20 crude oils and asphaltenes are examined. The spectral location of the electronic absorption edge varies over a wide range, from the near-infrared for heavy oils and asphaltenes to the near-UV for gas condensates. The functional form of the electronic absorption edge for all crude oils (measured) is characteristic of the “Urbach tail,” a phenomenology which describes electronic absorption edges in wide-ranging materials. The crude oils all show similar Urbach widths, which are significantly larger than those generally found for various materials but are similar to those previously reported for asphaltenes. Monotonically increasing absorption at higher photon energy continues for all crude oils until the spectral region is reached where single-ring aromatics dominate absorption. However, the rate of increasing absorption at higher energies moderates, thereby deviating from the Urbach behavior. Fluorescence emission spectra exhibit small red shifts from the excitation wavelength and small fluorescence peak widths in the Urbach regions of different crude oils, but show large red shifts and large peak widths in spectral regions which deviate from the Urbach behavior. This observation implies that the Urbach spectral region is dominated by lowest-energy electronic absorption of corresponding chromophores. Thus, the Urbach tail gives a direct measure of the population distribution of chromophores in crude oils. Implied population distributions are consistent with thermally activated growth of large chromophores from small ones.
Two Test Methods for Determining the Relative Background Emission from a Hollow Cathode Lamp
Authors: Fleming Paddy
Published: June 2005

This paper describes two test methods, based respectively on direct transmittance spectrometry and transmittance ratio spectrometry, to determine the relative background emission from the hollow cathode lamps used in atomic absorption spectrophotometry.
Excitation versus Emission Spectra as a Means to Examine Selective Fluorescence Quenching Agents
Authors: Tucker Sheryl A. , Acree William E.
Published: June 2005

To ascertain whether fluorescence quenching is best studied with the use of excitation or emission spectra, and to expand our existing PAH spectral data file, we have recorded excitation spectra of benzo[b]perylene, dibenzo[hi,wx]heptacene, tetrabenzo[de,hi,mn,qr]naphthacene, perylene, benzo[a]fluoranthene, benzo[def]indeno[1,2,3hi]chrysene, naphtho[2,1a]fluoranthene, naphtho[2,3b]fluoranthene, benzo[k]fluoranthene, 2-azapyrene, naphtho[8,1,2hij]pyreno[9,10,1def]phthalazine, indeno[1,-2,3ij]isoquinoline, benzo(lmn][3,8]phenanthroline, and 7-methyldibenzo(b,def]chrysene at various nitromethane concentrations. Results of these measurements verify our earlier observations concerning the nitromethane selective quenching rule and further illustrate the importance of considering inner-filtering artifacts in quenching studies.
Characterization of Conversion-Coated Aluminum Using Fourier Transform Infrared and Raman Spectroscopies
Authors: Ahern Angela M. , Schwartz Paul R. , Shaffer Lori A.
Published: June 2005

Fourier transform infrared and Raman spectroscopies have been employed to define the molecular composition of chromium phosphate conversion coatings on aluminum. Attenuated total reflectance at 55° can be employed to probe the structure of conversion coatings present on aluminum at relatively high coating weights (≥23 mg Cr/m2). Both reflection-absorption infrared and surface-enhanced Raman spectroscopic techniques can discern the presence of conversion coatings at coverages as low as 9 mg Cr/m2. On the basis of the vibrational spectra from these techniques, we have determined that hydrated chromium phosphate is the major component in these conversion coatings on aluminum. Reflection-absorption infrared and surface-enhanced Raman spectroscopies also provide a means to determine the molecular structure of the nascent oxide layer on aluminum as a function of processing conditions. Specular reflection, attenuated total reflectance at 35°, diffuse reflectance, and Raman spectroscopic methods, in general, lack the surface sensitivity necessary to probe thin (≤23 mg/m2) inorganic films on aluminum.
Luminescence Linewidth Broadening and Nonradiative Energy Transfer Studies of Solid UO2+2-Datura
Authors: Ke Huei-Yang D. , Rayson Gary D.
Published: June 2005

The emission spectra and fluorescence decay curves of solid UO2+2- Datura at liquid nitrogen temperature have been measured. The linewidth of the emission peaks of UO2+2 ions in UO2+2- Datura decreases with the UO2+2 concentration. This linewidth broadening phenomenon can be explained by the existence of resonance interactions between adjacent UO2+2- Datura species. The analysis of the emission peak position of the bound ions has been used to provide a measure of the electronic factors contributing to the interaction between the uranyl ion and phosphoryl and dicarboxyl moieties on the cell wall material. An observed blue shift of the uranyl fluorescence spectrum as a function of solution pH has been ascribed to a distortion of the normally linear O-U-O bond. An inter- and intra-molecular nonradiative energy transfer model has been successfully used to interpret the measured lifetime data of UO2+2- Datura.
Calculation of Carbonaceous Overlayer Thickness in XPS to Yield Substrate Stoichiometries
Authors: Griffiths Lee , Bradley Les
Published: June 2005

A method has been developed which calculates the thickness of the hydrocarbon overlayer from x-ray photoemission spectroscopy (XPS) spectra. The method is specific to each sample and utilizes the relative intensity of the C 1 s peak and all other peaks. Attenuations calculated with this overlayer thickness yield more accurate substrate stoichiometries. A rough-sample model is also developed which not only explains previous anomalies in the thickness of hydrocarbon overlayer calculated but is capable of yielding further accuracy in substrate stoichiometries.
Absorbance Measurements in Optically Inhomogeneous Samples Using Phase-Conjugate Thermal Lens Spectroscopy
Authors: Plumb D. M. , Harris J. M.
Published: June 2005

The optical phase conjugation properties of a BaTiO3 crystal are employed in a thermal lens experiment to measure small absorbance values of optically inhomogeneous samples. The sensitivity of the thermal lens, together with the beam reconstruction capabilities of phase conjugation, allows measurement of absorbances as low as 1.2 × 10−5 in the presence of large-amplitude spatial noise. A model which describes the behavior of an ordinary thermal lens could be used to evaluate the behavior of the phase-conjugate thermal lens response. Controlled phase-front perturbations generated by the thermal lens are used to characterize the influence of optical path distortions on phase-conjugate reflectivity.
Application of Laser-Enhanced Ionization: Atomization Efficiency Determination
Authors: Su King-Dow , Lin King-Chuen , Luh Wei-Tzou
Published: June 2005

We have demonstrated that the laser-enhanced ionization (LEI) technique can be used to determine the efficiency of atomization of metal elements in an atmospheric acetylene/air flame. We have derived a useful relation between the time-integrated LEI signal and the total free atom number density in a flame. We determine the efficiency of atomization of ∼0.13–0.37 for the lithium element and of ∼1.0 for the sodium element. Our results agree well with AA measurements reported previously.