Low Resolution Mode Research Articles

Development of an adiabatic calorimeter for simultaneous measurement of enthalpy and volume under high pressure

A novel adiabatic calorimeter was constructed for simultaneous measurement of enthalpy and volume under high pressure. The calorimeter works under constant pressure up to 100 MPa and in the temperature range 80–380 K. The sample is pressurized hydrostatically by using a liquid pressure transmitting medium. The sample volume is measured with a new type of dilatometer using bellows installed in the cell. The dilatometer has two resolution modes (high and low) with different scanning range. As the calibration and test experiments, the heat capacities and volumes of toluene and water were measured at 0.1 and 50.1 MPa in the temperature range between 275 and 380 K. In the low resolution mode, the accuracies of heat capacity and volume were ±0.2% and 20 ppm of total, respectively. The test of the volume measurement in the high resolution mode showed that the resolution was ±0.1 ppm of total sample volume, which is ∼ ten times better than that of the previous best dilatometer. To demonstrate the performance of the present apparatus, the enthalpy and volume changes due to the structural relaxation of glassy polystyrene were measured simultaneously.

Ultratrace analysis of Antarctic snow and ice samples using high resolution inductively coupled plasma mass spectrometry

High resolution ICP-MS was used to determine the concentrations of Al, Sc, V, Mn, Fe, Co, Pb and Bi in snow and ice from Antarctica. To overcome some potentially problematic spectral interferences, measurements were acquired in both low and medium resolution modes. Small sample volumes were analysed using a microconcentric nebuliser. After rigorous instrument cleaning and sample preparation, detection levels in the low and sub-pg g–1 range (0.3–48 pg g–1) were found for all elements. Concentration values were determined for a continental snow, sea ice snow and a representative ice core. Concentration ranges for all snow samples (n=25) were (in pg g–1): Al (30–2000), V (2–16), Mn (2–30) and Fe (30–1500), while Sc and Co were typically below detection or blank limits. The ice core sample had Al, Mn, Fe and Pb concentrations of 90, 7, 110 and 1 pg g–1, respectively, while Sc, V, Co and Bi could not be quantified (below detection or blank limits). The reliability of the analytical method for Fe was confirmed by flow injection analysis with spectrophotometric detection.

Trace element analysis of sediments by HR-ICP-MS using low and medium resolution and different acid digestions

For the multielement analysis of sediments (Li, Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Mo, Cd, Sn, Sb, Cs, Ba, lanthanides, Hf, Tl, Pb, Bi, Th, U) a dissolution with a hydrofluoric - sulfuric - nitric acid mixture, subsequent evaporation of the acids, dissolution of the residue by HCl, evaporation of the acid and redissolution of the residue by HNO3 is a useful procedure which allows the dissolution of a wide range of mineral mixtures. An ICP-MS was used for the determination of the elements. For Cr, Ni, Cu and Zn the analysis may be complicated by the interferences of sulfur or chlorine species, which remain in the solution during dissolution. The best analytical results for these elements can be achieved in the medium resolution mode of a HR-ICP-MS. In the low resolution mode (quadrupole instrument characteristics) the determination of these elements should be performed by the isotopes of 52Cr, 62Ni, 63Cu, 68Zn as it was found that interferences from remaining acids are of minor importance.

Determination of physiological palladium and platinum levels in urine using double focusing magnetic sector field ICP-MS

A new extremely sensitive method for the determination of physiological (normal) Pd and Pt levels in human urine is presented, applying UV photolysis followed by sequential determination with double focusing magnetic sector field ICP-MS. Due to the low blank values, which are a consequence of the minimal reagent addition required, UV photolysis turned out to be advantageous for the decomposition of the organic matrix. Sector field ICP-MS operating in the low resolution (LR) mode permits detection limits for Pt and Pd which are distinctly lower than in the high resolution (HR) mode or with quadrupole instruments when using a comparable sample introduction system. The practical detection limits in urine were 0.17 ng/L Pd and 0.24 ng/L Pt using standard nickel cones. Taking into account a dilution factor of 4.2, the detection limits related to the final solution were 0.04 ng/L Pd and 0.06 ng/L Pt. The use of a high-performance nickel skimmer cone did not result in any improvement of the detection limits because the signal of the analytes and the background were enhanced to a similar extent. Urinary Pd levels in 21 unexposed persons ranged from 32.7 to 219.7 ng/L (arithmetic mean (AM): 140.3 ng/L), the Pt levels were between 0.48 and 7.7 ng/L (AM: 1.8 ng/L). The relevance and severity of mass spectral interferences in the Pd and Pt determination at these concentration levels have been investigated.

Electron Holography of Electromagnetic Fields

Electron holography can lend crucial insights to understanding the subtle manifestations of electro-magnetism in a wide range of materials. Whereas conventional microscopy is sensitive only to the intensity, holography reveals the phase changes in coherent electron wavefronts making it a unique tool to probe electric and magnetic fields on the nanometer scale. We have employed electron holography to characterize materials for mean inner potential measurements and also their electric and magnetic properties.Electron holograms were acquired in a 300 kV FE-TEM under two optical conditions: the standard high resolution mode was employed for mean inner potential measurements; to examine the intrinsic electromagnetic states, a lower resolution mode was used whereby the objective lens is turned off and the diffraction lens images the specimen. Digitally acquired holograms were reconstructed with the HolograFREE software package.Nanophase TiO2 particles generated in a flame burner system were found to have unusual central features. The rutile particles appear to contain faceted voids, raising the question whether the feature is truly a void or a secondary amorphous phase.

Factorial optimization of data acquisition factors for lead isotope ratio determination by inductively coupled plasma mass spectrometry

A factorial optimization of data acquisition factors was performed to minimize non-random instrumental noise on an inductively coupled plasma mass spectrometer. Results have identified instrumental and analytical operating conditions under which lead isotope ratios can be measured precisely and accurately in natural samples. Precision was checked periodically over weeks and ranged 0.10–0.30, 0.15–0.35, 0.15–0.35, 0.10–0.30 and 0.10–0.20 (%) for 206/204, 207/204, 208/204, 206/207 and 208/206 ratios respectively. Mass bias was minimized and the correction factors were typically of 0.6% for 206/204, 1.5% for 207/204, 1.8% for 208/204, 0.8% for 206/207 and 1.2% for 208/206. These results were performed with a dwell time of 20 ms, 40 sweeps per replicate, 8 replicates by analysis, a time factor of 15 applied on mass 204 and three points per peak in the low resolution mode. The total duration time of an analysis was 10:50 min and it was found that optimum concentration of lead in solution was 50 ng ml −1 on our instrument.

Analysis of ruthenium carbonyl–porphyrin complexes: a comparison of matrix-assisted laser desorption/ionisation time-of-flight, fast-atom bombardment and field desorption mass spectrometry

The mass spectrometric characterisation of ruthenium carbonyl‐porphyrin complexes and the corresponding porphyrins is described. Matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF-MS), fast-atom bombardment mass spectrometry (FAB-MS), in both low-resolution (LR) and high-resolution (HR) modes, and field desorption mass spectrometry (FD-MS) have been used and compared in detail. MALDI-TOF-MS turned out to be ideal for rapid screening of potential synthetic pathways. FAB-MS proved to be especially useful in establishing elemental compositions by HR measurement. Whereas the porphyrins gave very good molecular ion intensities, the ruthenium carbonyl complexes exhibited abundant carbon monoxide (CO) loss in MALDI-TOF-MS and still a measurable CO loss in FAB-MS. Only FD-MS yielded the molecular ion as the base peak of the spectrum in all cases. Optimised FD emitter heating conditions allow the remaining portion of the thermally-induced CO loss to be significantly reduced.

Mass spectral interferences in the determination of trace levels of precious metals in human blood using quadrupole magnetic sector field and inductively coupled plasma mass spectrometry

The results of the determination of physiological levels of precious metals in blood with a new type of magnetic sector field high resolution (HR)-ICP-MS instrument are presented. Palladium levels, for example, ranged between 32 and 102.5 ng l–1. HR-ICP-MS operating in the low resolution mode is advantageous for such ultratrace analyses as it is about 100 times more sensitive than in the HR mode or conventional quadrupole (Q)-ICP-MS. It is also shown that the determination of Rh and Pd in the ng l–1 range is impaired by spectral interferences originating from Cd+, Pb2+, SrO+, RbO+, CuAr+ and ZnAr+. Using standard instrumental operating conditions on a Q-ICP-MS instrument, Pb2+:Pb+ and SrO+ :Sr+ ratios were found to be about 0.1%, which results in a severe impairment of the determination of physiological Rh and Pd concentrations in body fluids. The resolution of the HR instrument used (m/Δm= 7500) was not sufficient to separate Rh and Pd from all spectral overlaps. These remaining spectral interferences can only be overcome by an appropriate sample preparation step.

Determination of physiological platinum levels in human urine using magnetic sector field inductively coupled plasma mass spectrometry in combination with ultraviolet photolysis

An extremely sensitive and reliable procedure for the determination of physiological (normal) Pt levels in human urine is described based on UV photolysis of the sample followed by the determination of Pt with magnetic sector field ICP-MS. Owing to the low blank values, which are a consequence of the minimal reagent addition required, UV photolysis was used to decompose the organic matrix components. Magnetic sector field ICP-MS operated in the low resolution mode afforded detection limits that were 100 times lower than those obtained in the high resolution mode or with conventional quadrupole ICP-MS and was found to be advantageous for the ultratrace determination of non-interfered isotopes. The detection limit in urine samples was 0.24 ng l–1 using standard nickel cones. The use of a high performance nickel skimmer cone did not result in an improvement in the detection limit, because the analyte and background signals were enhanced to a similar extent. The urinary Pt levels in 16 non-exposed persons ranged between 0.48 and 7.65 ng l–1(arithmetic mean: 1.72 ng l–1).

A FIBER-FED ECHELLE SPECTROGRAPH FOR THE HALE 5-M TELESCOPE

ABSTRACT We describe a new fiber-fed echelle spectrograph which is now in operation on the Hale 5-meter telescope at Palomar Observatory. The instrument is optimized for high spectral stability, necessary for asteroseismology measurements of small periodic variations in stellar radial velocities. It features a 7-element all-spherical 610-mm focal length f/3.0 lens system and prism cross-disperser in a compact double-pass quasi-Littrow configuration. Light enters the system at prime focus, and is channeled to the spectrograph by a fiber optic cable. The instrument rests on a fixed-orientation optical bench inside the telescope's East Arm. It can be operated in a low-resolution mode, with resolution R=20,000 and overal efficiency (including atmospheric seeing) e~5 percent at 550 nm, or a high-resolution mode, with R=40,000 and e~1.5 percent at 550 nm; both modes have Rpixel=100,000. With large-format CCD detector (2048X2048 with 27-micron pixels), the entire visible spectrum from 400-1000 nm can be recorded in two exposures, with no gaps. We have also incorporated a novel imaging system to produce a circularly symmetric guide image of the input fiber tip. Using a fiber-optic double scrambler, the instrument produces radial-velocity measurements which are stable at the ~1 m/sec level over short (<~ 30 minute) time periods.

High resolution ICP-MS ? a new concept for elemental mass spectrometry

Interfering molecular species are of major concern to the analyst currently using quadrupole based ICP-MS instrumentation. The recognized advantage and convenience offered by atmospheric plasma ionisation to multielement trace analysis can be significantly deteriorated by the limited resolving power of these analyzers. The result is poor sensitivity and lack of selectivity. With respect to sensitivity and resolution significant enhancement can be achieved by using magnetic sector based high resolution analyzers instead of quadrupoles. Unfortunately, up to now, commercially available HR-ICP-MS systems have been derived from complex instruments originally designed to meet the requirements of organic mass applications. Consequently, operation and performance of those systems expose the compromise which had to be made between an atmospheric plasma atomic ion source at high potential and an analyzer technology dedicated to molecular mass spectroscopy of organic compounds. At Finnigan MAT the first purpose designed high resolution ICP-MS has now been developed, which can be operated in high and low resolution mode at enhanced sensitivity. An innovative electric and magnetic field scanning strategy (SynchroScan) results in high on-peak duty cycles. Improved magnet technology offers high speed quadrupole style survey scans covering the full elemental mass range at nominal mass resolution. By extremely rapid peak switching, for example, all barium isotopes can be monitored in less than 100 ms with more than 90% on-peak detection efficiency. Examples are shown for computer controlled high and low resolution scan modes demonstrating the analytical performance of the new instrument concept. A comparison of detection limits achieved in low and high resolution mode is given.

Reduction of some selected spectral interferences in inductively coupled plasma mass spectrometry

The reduction of spectral interferences has been investigated and both aerosol desolvation and the utilization of high mass resolution have been applied in order to improve detection limits for V, Cr, Ga, Ge and As, which are subject to interferences by polyatomic ions in solutions containing Cl. Experiments with a laboratory-made quadrupole ICP-MS have been performed in order to optimize the desolvation parameters. Ion signals corresponding to CIO+ and CIOH+ are reduced by more than one order of magnitude if appropriate heating and cooling temperatures are chosen. A reduction in polyatomic ions like CIO2+, CI2+ and ArCI+ by using desolvation was also observed. With the prototype of a new double-focusing ICP-MS system from Finnigan MAT, Bremen, Germany, operated in the low resolution mode, the detection limits with desolvation have been determined and were found to be up to 2 orders of magnitude lower compared with measurements without desolvation. The detection limit (3s) for V in 0.4 mol l–1 HCl was reduced from 25 to 1 ng ml–1. High mass resolution improved the detection limits for V, Cr and Ga in HCl by up to 4 orders of magnitude compared with measurements in the low resolution mode (2 pg ml–1 for V in 0.4 mol 1–1 HCl), and lowest detection limits have been obtained with the combination of desolvation and high mass resolution (0.6 pg ml–1 for V in 0.4 mol l–1 HCl).

Performance characteristics of inductively coupled plasma mass spectrometry with high mass resolution

A laboratory prototype is described of a new ICP-MS system with high mass resolution, based on a double focusing magnetic field analyser, which has been especially designed for application in elemental analysis. The performance characteristics of this instrument are summarized comparing operation in a low resolution mode (R= 300) and a high resolution mode (R= 3000) with reference to common quadrupole instruments with (nearly) unit resolution. Most of the typical spectral interferences can be resolved. Detection limits were achieved of one order of magnitude and more below those obtained with quadrupole instruments. Several operational features of the instrument are described.

Diagnostic efficacy of digitized images vs plain films: a study of the joints of the fingers.

Four hundred fifteen finger joints from 30 patients were evaluated for the presence of joint-space erosion, narrowing, and degenerative spurring on plain films, low-resolution digitized images (1024 x 840 bytes x 12 bit matrix), and high-resolution digitized images (2048 x 1680 bytes x 12 bit matrix). Three hundred four joints were abnormal. Low- and high-resolution digital images were displayed on a 1K x 1K monitor with the ability to change level, window, orientation, and brightness. Five radiologists interpreted images. The presence or absence of each abnormality was determined by consensus of two skeletal radiologists who did not otherwise participate in the study. Receiver-operating-characteristic analysis was used to obtain an area and a true-positive rate at a 0.10 false-positive rate for each interpreter. Randomized block analysis of variance with interpreters as blocks was used to compare areas and true-positive rates among imaging techniques for each type of abnormality; no statistically significant differences were found. In conclusion, the efficacy of display of digitized images on high- and low-resolution modes is not significantly different from that of plain films in the detection of erosions, joint-space narrowing, or degenerative spurring in small joints of the hands.

Mass Spectrometry in Forensic Chemistry: 1. Pigment Identification by Direct Mixture Analysis in a Case of Bank Note Falsification

Abstract A rapid mass spectrometry procedure, based on direct mixture analysis using conventional electron ionization in both the low and high resolution modes, was used to match pigments present on a counterfeit $100 United States bank note with pigments contained in two inks suspected of having been used. The results demonstrated that the pigments present on the false bank note and those contained in the inks were the same.

A spectrophotometric atlas of white dwarfs compiled from the IUE archives

Ultraviolet spectrophotometric data are presented for 182 subluminous stars, mostly white dwarfs, that have been observed with the low-resolution mode of the IUE satellite since 1978 and for which archived data became available on April 1, 1989. Tables of 20 A binned data are given for all stars. Of these, 133 cover the entire wavelength range of the IUE, while the remainder have partial coverage. Plots of the original unbinned spectra are given. Many targets had multiple spectra combined, and the older spectra were reprocessed and corrected for reduction procedure changes made over the past 10 years.

Revisited Mass-Loss Rates of Planetary Nebula Nuclei Observed with IUE

The first order moment of P Cygni line profiles has been computed for the case of resonance doublet and subordinate line transitions, using realistic velocity and opacity distributions. This improved method has allowed us to rederive mass-loss rates for a sample of 17 PNN observed in the low resolution mode with IUE. The average value of our mass-loss rates amounts to 10−7 M⊙/yr.

Inmarsat to assist developing countries

Long-term observations of surface elevation change of the Greenland ice sheet (GrIS) is of utmost importance when assessing the state of the ice sheet. Satellite radar altimetry offers a long time series of data over the GrIS, starting with ERS-1 in 1991. ESA's Cryosat-2 mission, launched in 2010, provides an invaluable radar altimetry dataset for monitoring the current changes of the ice sheets due to its dense spatial and temporal coverage of these areas. Here, we investigate the effects of including different parameters which describe the shape of the return radar waveform (waveform parameters) in the elevation change algorithm, to correct for temporal changes in the ratio between surface- and volume-scatter in Cryosat-2 observations. We present elevation and volume changes for the Greenland ice sheet in the period from 2010 until 2014. The waveform parameters considered here are the backscatter coefficient, and the leading edge width, which are both available in the ESA Cryosat-2 Level-2i data product. Investigations into relocation of radar reflection points are also included.Inter-comparison of the Cryosat-2 derived elevation changes with those derived from Operation IceBridge laser data suggests waveform parameters to be applicable for correcting for changes in volume scattering. The best results in the Synthetic Aperture Radar Interferometric mode area of the GrIS are found when applying only the backscatter correction, whereas the best result in the Low Resolution Mode area is obtained by only applying a leading edge width correction. Using this approach to correct for the scattering properties, a volume loss of −292±38 km3 yr −1 is found for the GrIS for the time span November 2010 until November 2014. The inclusion of waveform parameter corrections and improved relocation for the GrIS, helps to reconcile the satellite-derived elevation changes with those observed by Operation IceBridge. However, the bias of temporal changes in the scattering horizons of Cryosat-2 is not entirely removed and suggests that future improvements could be made by including climate data and/or additional waveform parameters to make additional corrections in the Cryosat-2 radar altimetry.

Stellar winds in the Small Magellanic Cloud

According to the predictions of line-driven stellar wind theory, the mass loss from luminous stars should be proportional to some power of the metallicity, yet previous studies have not shown this effect clearly. The authors have observed 22 main-sequence and giant O-type stars n the SMC with the low-resolution mode of the IUE in order to study the stellar winds in a particularly metal-poor galaxy. These stars are compared with carefully selected Galactic counterparts for wind terminal velocities and line strengths of C IV and N v. While the wind velocities in the SMC stars are confirmed to be systematically lower than in Galactic stars, as theory predicts, the mass-loss rates which are inferred from these data are comparable to those in the Galactic stars. The possible reasons for this result are discussed, including systematic effects in the data, assumed metal abundance, different ionization structure, and different physical parameters for the SMC stars.

Hydrogen-tritium exchange survey of allosteric effects in hemoglobin.

The oxy and deoxy forms of hemoglobin display major differences in H-exchange behavior. Hydrogen-tritium exchange experiments on hemoglobin were performed in the low-resolution mode to observe the dependence of these differences on pH (Bohr effect), organic phosphates, and salt. Unlike a prior report, increasing pH was found to decrease the oxy-deoxy difference monotonically, in general accordance with the alkaline Bohr effect. A prior report that the H-exchange difference between oxy- and deoxyhemoglobin vanishes at pH 9, and thus appears to reflect the Bohr effect alone, was found to be due to the borate buffer used, which at high pH tends to abolish the oxy-deoxy difference in a limited region of the H-exchange curve. Effects on hemoglobin H exchange due to organic phosphates parallel the differential binding of these agents (inositol hexaphosphate more than diphosphoglycerate, deoxy more than oxy, at low pH more than at high pH). Added salt slows H exchange of deoxyhemoglobin and has no effect on the oxy form. These results display the sensitivity of simple H-exchange measurements for finding and characterizing effects on structure and dynamics that may occur anywhere in the protein and help to define conditions for higher resolution approaches that can localize the changes observed.