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Spectrometer
Kinds of Spectrometer Selected AbstractsOXYGEN-INHIBITED LAYER IN ADHESION DENTISTRYJOURNAL OF ESTHETIC AND RESTORATIVE DENTISTRY, Issue 5 2004Byoung I. Suh MS ABSTRACT Purpose:: Characteristics of the oxygen-inhibited layer, including bond strength, photoinitiator decomposition, and post-curing degree of conversion, were investigated. Materials and Methods: To investigate shear bond strength, BisCover (Bisco, Inc., Schaumburg, IL, USA) and D/E Resin (Bisco, Inc.) were placed on disks of Renew composite (Bisco, Inc.) and cured both with and without an oxygen-inhibited layer. Light-Bond composite (Reliance Orthodontic, Itasca, IL, USA) was placed in a gelatin capsule and light cured over the cured resin. After soaking in water for 2 hours at 37°C, specimens were sheared to failure using a universal testing machine (Model 4466, Instron Inc., Canton, MA, USA). To investigate microtensile bond strength, composite substrates prepared using Renew A2 composite were light cured either in air or under nitrogen. Light-Core (Bisco, Inc.) was placed on each substrate and light cured. The resulting specimens were sectioned into composite beams and stressed to failure using a microtensile tester (built by Bisco, Inc.). To determine camphorquinone (CQ) decomposition, an experimental CQ resin was placed between two glass plates and irradiated for different time intervals. The absorption spectrum was obtained using a Cary 50 Bio UV-Visible Spectrometer (Varian, Mulgrave, Australia). To explore the degree of conversion, polyester film strips (Mylar, DuPont, Wilmington, DE, USA) coated with the CQ resin were pre-cured in air for different time periods, and then post-cured at low intensity for 5 minutes under nitrogen. A Spectrum 1000FTIR Spectrometer (Perkin Elmer, Norwalk, CT, USA) was used to measure the degree of conversion. Results: Bond strength tests resulted in no significant difference between samples with or without an oxygen-inhibited layer. The oxygen-inhibited layer contained reduced amounts of photoinitiator. The degree of conversion of post-cured oxygen-inhibited layers was lower than that for the control. Conclusion: An oxygen-inhibited layer is not necessary for bonding with composite resin. [source] Deagglomeration of nanoparticle aggregates via rapid expansion of supercritical or high-pressure suspensionsAICHE JOURNAL, Issue 11 2009Daniel To Abstract Deagglomeration of suspensions of alumina and titania nanopowders (i.e., nanoparticle aggregates) via rapid expansion of supercritical suspensions (RESS) or high-pressure suspensions (REHPS) was studied. The size distribution of fragmented nanopowders was characterized by online Scanning Mobility Particle Spectrometer (SMPS) and Aerodynamic Particle Sizer (APS), and by offline Scanning Electron Microscopy (SEM). SMPS and SEM measurements indicate that the average agglomerate sizes were well below 1 ,m, consistent with the length scales observed in our complementary RESS/REHPS mixing experiments using alumina and silica nanopowders. The APS measurements, on the other hand, were affected by reagglomeration during sampling and yielded an agglomerate size range of 1 to 3 ,m. Analysis of the RESS/REHPS process through compressible flow models revealed that both the shear stress in the nozzle and the subsequent impact of the agglomerates with the Mach disc in the free expansion region can lead to micron or sub-micron level deagglomeration. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Probing the origin of the dark material on IapetusMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2010F. Tosi ABSTRACT Among the icy satellites of Saturn, Iapetus shows a striking dichotomy between its leading and trailing hemispheres, the former being significantly darker than the latter. Thanks to the Visual and Infrared Mapping Spectrometer (VIMS) imaging spectrometer on-board Cassini, it is now possible to investigate the spectral features of the satellites in Saturn system within a wider spectral range and with an enhanced accuracy than with previously available data. In this work, we present an application of the G-mode method to the high resolution, visible and near-infrared data of Phoebe, Iapetus and Hyperion collected by Cassini/VIMS, in order to search for compositional correlations. We also present the results of a dynamical study on the efficiency of Iapetus in capturing dust grains travelling inwards in Saturn system with the aim of evaluating the viability of the Poynting,Robertson drag as the physical mechanism transferring the dark material to the satellite. The results of spectroscopic classification are used jointly with the ones of the dynamical study to describe a plausible physical scenario for the origin of Iapetus' dichotomy. Our work shows that mass transfer from the outer Saturnian system is an efficient mechanism, particularly for the range of sizes hypothesized for the particles composing the newly discovered outer ring around Saturn. Both spectral and dynamical data indicate Phoebe as the main source of the dark material. However, due to considerations on the collisional history of the Saturnian irregular satellites and to the differences in the spectral features of Phoebe and the dark material on Iapetus in the visible and ultraviolet range, we suggest a multisource scenario where now extinct prograde satellites and the disruptive impacts that generated the putative collisional families played a significant role in supplying the original amount of dark material. [source] Upper limits on X-ray emission from two rotating radio transientsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2009D. L. Kaplan ABSTRACT X-ray emission from the enigmatic rotating radio transients (RRATs) offers a vital clue to understanding these objects and how they relate to the greater neutron star population. An X-ray counterpart to RRAT J1819,1458 is known, and its properties are similar to those of other middle-aged (0.1 Myr) neutron stars. We have searched for X-ray emission with Chandra/Advanced CCD Imaging Spectrometer at the positions of two RRATs with arcsecond (or better) localization, J0847,4316 and J1846,0257. Despite deep searches (especially for RRAT J1846,0257) we did not detect any emission with 0.3,8 keV count-rate limits of 1 and 0.068 counts ks,1, respectively, at 3, confidence. Assuming thermal emission similar to that seen from RRAT J1819,1458 (a blackbody with radius ,20 km), we derive effective temperature limits of 77 and 91 eV for the nominal values of the distances and column densities to both sources, although both of those quantities are highly uncertain and correlated. If we instead fix the temperature of the emission (a blackbody with kT= 0.14 keV), we derive unabsorbed luminosity limits in the 0.3,8 keV range of 1 × 1032 and 3 × 1032 erg s,1. These limits are considerably below the luminosity of RRAT J1819,1458(4 × 1033 erg s,1), suggesting that RRATs J0847,4316 and J1846,0257 have cooled beyond the point of visibility (plausible given the differences in characteristic age). However, as we have not detected X-ray emission, it may also be that the emission from RRATs J0847,4316 and J1846,0257 has a different character from that of RRAT J1819,1458. The two non-detections may prove a counterpoint to RRAT J1819,1458, but more detections are certainly needed before we can begin to derive general X-ray emission properties for the RRAT populations. [source] Probing feedback in protogalaxies: multiphase gas in a DLA at z, 2.4MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008N. Lehner ABSTRACT We investigate the physical processes occurring in the multiphase gas of a damped Ly, absorber (DLA). We base our analysis on a high-quality Keck High-Resolution Echelle Spectrometer (HIRES) spectrum of the QSO J1211+0422 in which a DLA is detected at z, 2.377. There is little contamination of the high-ion (O vi, N v, C iv, Si iv) absorption, allowing us to explore the properties of the highly ionized gas and its connection to other gas phases. The metallicity ([Z/H]=,1.41 ± 0.08), H i column density [], full-width velocity (,vneut, 70 km s,1) and relative abundances ([Si/Fe]=+0.23 ± 0.05 and [N/Si]=,0.88 ± 0.07) of this DLA are not unusual. However, we derive the lowest C ii* cooling rate in a DLA, lc < 10,27.8 erg s,1 per H atom (3,). Using this stringent limit, we show that the neutral gas (confined at |v| < +39 km s,1) must be warm and the star formation rate is <7.1 × 10,3 M, yr,1 kpc,2. Surprisingly, the gas shows strong, complex absorption profiles from highly ionized gas whose kinematics appear connected to each other and the low ions. The total amount of highly and weakly ionized gas is very large with ,1.5. At |v| ,+39 km s,1, the gas is fully and highly ionized []. Based on ionization models, O vi and N v are generally difficult to produce by hard photons, while Si iv and C iv can be photoionized to a large extent. There is, however, no evidence of O vi -bearing gas at T, 106 K associated with this DLA. In contrast, there is some evidence for narrow O vi, N v and C iv components (unexplained by photoionization), implying too low temperatures (T < 105 K) for simple collisional ionization models to produce their observed column densities. Stellar feedback is a possible source for producing the high ions, but we cannot rule out accretion of non-pristine material on to the protogalaxy. [source] Deep spectroscopy of the FUV,optical emission lines from a sample of radio galaxies at z, 2.5: metallicity and ionization,MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008A. Humphrey ABSTRACT We present long-slit near-infrared (NIR) spectra, obtained using the Infrared Spectrometer And Array Camera (ISAAC) instrument at the Very Large Telescope, which sample the rest-frame optical emission lines from nine radio galaxies at z, 2.5. One-dimensional spectra have been extracted and, using broad-band photometry, have been cross-calibrated with spectra from the literature to produce line spectra spanning a rest wavelength of ,1200,7000 Å. The resulting line spectra have a spectral coverage that is unprecedented for radio galaxies at any redshift. We have also produced a composite of the rest-frame ultraviolet (UV),optical line fluxes of powerful, z, 2.5 radio galaxies. We have investigated the relative strengths of Ly,, H,, H,, He ii,1640 and He ii,4687, and we find that Av can vary significantly from object to object. In addition, we have identified new line ratios to calculate electron temperature: [Ne v],1575/[Ne v],3426, [Ne iv],1602/[Ne iv],2423, O iii],1663/[O iii],5008 and [O ii],2471/[O ii],3728. We calculate an average O iii temperature of 14100+1000,600 K. We have modelled the rich emission line spectra, and we conclude that they are best explained by active galactic nucleus (AGN) photoionization with the ionization parameter U varying between objects. For shock models (with or without the precursor) to provide a satisfactory explanation for the data, an additional source of ionizing photons is required , presumably the ionizing radiation field of the AGN. Single slab photoionization models are unable to reproduce the high- and the low-ionization lines simultaneously: the higher ionization lines imply higher U than do the lower ionization lines. This problem may be alleviated either by combining two or more single slab photoionization models with different U, or by using mixed-medium models such as those of Binette, Wilson & Storchi-Bergmann. In either case, U must vary from object to object. On the basis of N v/N iv] and N iv]/C iv we argue that, while photoionization is the dominant ionization mechanism in the extended emission line regions (EELR), shocks make a fractional contribution (,10 per cent) to its ionization. The N v/N iv] and N iv]/C iv ratios in the broad-line region (BLR) of some quasars suggest that shock ionization may be important in the BLR also. We find that in the EELR of z, 2 radio galaxies the N/H abundance ratio is close to its solar value. We conclude that N/H and metallicity do not vary by more than a factor of 2 in our sample. These results are consistent with the idea that the massive ellipticals which become the hosts to powerful AGN are assembled very early in the history of the universe, and then evolve relatively passively up to the present day. [source] Near-infrared polarimetry and modelling of the dusty young planetary nebula IRAS 19306+1407MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2007K. T. E. Lowe ABSTRACT We present near-infrared polarimetric images of the dusty circumstellar envelope (CSE) of IRAS 19306+1407, acquired at the United Kingdom Infrared Telescope (UKIRT) using the UKIRT 1,5 ,m Imager Spectrometer (UIST) in conjunction with the half-waveplate module IRPOL2. We present additional 450- and 850-,m photometry data obtained with the Submillimetre Common-User Bolometer Array (SCUBA) at the James Clerk Maxwell Telescope (JCMT), as well as archived Hubble Space Telescope (HST) F606W - and F814W -filter images. The CSE structure in polarized flux at J and K bands shows an elongation north of north-east and south of south-west with two bright scattering shoulders north-west and south-east. These features are not perpendicular to each other and could signify a recent ,twist' in the outflow axis. We model the CSE using an axisymmetric light scattering (als) code to investigate the polarization produced by the CSE, and an axisymmetric radiation transport (dart) code to fit the spectral energy distribution. A good fit was achieved with the als and dart models using silicate grains, 0.1,0.4 ,m with a power-law size distribution of a,3.5, and an axisymmetric shell geometry with an equator-to-pole ratio of 7:1. The spectral type of the central star is determined to be B1i supporting previous suggestions that the object is an early planetary nebula. We have constrained the CSE and interstellar extinction as 2.0 and 4.2 mag, respectively, and have estimated a distance of 2.7 kpc. At this distance, the stellar luminosity is ,4500 L, and the mass of the CSE is ,0.2 M,. We also determine that the mass loss lasted for ,5300 yr with a mass-loss rate of ,3.4 × 10,5 M, yr,1. [source] Constraints on the initial mass function of the first starsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2006Raffaella Schneider ABSTRACT Motivated by theoretical predictions that the first stars were predominantly very massive, we investigate the physics of the transition from an early epoch dominated by massive Pop III stars to a later epoch dominated by familiar low-mass Pop II/I stars by means of a numerically generated catalogue of dark matter haloes coupled with a self-consistent treatment of chemical and radiative feedback. Depending on the strength of the chemical feedback, Pop III stars can contribute a substantial fraction (several per cent) of the cosmic star formation activity even at moderate redshifts, z, 5. We find that the three z, 10 sources tentatively detected in Near Infrared Camera and Multi-Object Spectrometer (NICMOS) Ultra Deep Fields (UDFs) should be powered by Pop III stars, if these are massive; however, this scenario fails to reproduce the derived Wilkinson Microwave Anisotropy Probe (WMAP) electron scattering optical depth. Instead, both the UDFs and WMAP constraints can be fulfilled if stars at any time form with a more standard, slightly top-heavy, Larson initial mass function. [source] Analysis of sesquiterpene lactones in Eupatorium lindleyanum by HPLC-PDA-ESI-MS/MSPHYTOCHEMICAL ANALYSIS, Issue 2 2010Nian Yun Yang Abstract Introduction , The aerial part Eupatorium lindleyanum is commonly used as an antipyretic and detoxicant clinically in traditional Chinese medicine. Our previous research showed that germacrane sesquiterpene lactones were its main active constituents, so the development of rapid and accurate methods for the identification of the sesquiterpene lactones is of great significance. Objective , To develop an HPLC-PDA-ESI-MS/MS method capable for simple and rapid analysis of germacrane sesquiterpene lactones in the aerial part E. lindleyanum. Methodology , High-performance liquid chromatography-photodiode array detection-electrospray ionization-tandem mass spectrometry was used to analyze germacrane sesquiterpene lactones of Eupatorium lindleyanum. The fragmentation behavior of germacrane sesquiterpene lactones in a Micromass Q/TOF Mass Spectrometer was discussed, and 9 germacrane sesquiterpene lactones were identified by comparison of their characteristic data of HPLC and MS analyses with those obtained from reference compounds. Results , The investigated germacrane sesquiterpene lactones were identified as eupalinolides C (1), 3,-acetoxy-8,-(4,-hydroxy-tigloyloxy)-14-hydroxy-costunolide (2), eupalinolides A (3), eupalinolides B (4), eupalinolides E (5), 3,-acetoxy-8,-(4,-oxo-tigloyloxy)-14-hydroxy-heliangolide (6), 3,-acetoxy-8,-(4,-oxo- tigloyloxy)-14-hydroxy-costunolide (7), hiyodorilactone B (8), and 3,-acetoxy-8,-(4,-hydroxy-tigloyloxy)- costunolide (9). Compounds 6, 7 and 9 were reported for the first time. Conclusion , HPLC-PDA-ESI-MS/MS provides a new powerful approach to identify germacrane sesquiterpene lactones in E. lindleyanum rapidly and accurately. Copyright © 2009 John Wiley & Sons, Ltd. [source] The effect of overlying absorbing aerosol layers on remote sensing retrievals of cloud effective radius and cloud optical depthTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 598 2004Jim M. Haywood Abstract Two types of partially absorbing aerosol are included in calculations that are based on intensive aircraft observations: biomass burning aerosol characterized during the Southern AFricAn Regional science Initiative (SAFARI 2000) and mineral dust aerosol characterized during the SaHAran Dust Experiment (SHADE). Measurements during SAFARI 2000 reveal that the biomass burning aerosol layer is advected over the South Atlantic ocean at elevated altitudes above the marine boundary layer which is capped by semi-permanent stratocumulus cloud sheets. Similarly, the mineral dust is measured at elevated altitudes during SHADE resulting in transport above cloud for distances of several thousands of kilometres. We perform theoretical calculations of the effect of these partially absorbing aerosol layers on satellite retrievals of cloud effective radius and cloud optical depth, and show that, in these cases, retrievals of cloud optical depth or liquid water path are likely to be subject to systematic low biases. The theoretical calculations suggest that the cloud effective radius may be subject to a significant low bias for Moderate resolution Imaging Spectrometer (MODIS) retrievals that rely on the 0.86 and 1.63 µm radiance pair for an overlying aerosol layer of either biomass burning aerosol or mineral dust. Conversely, the cloud effective radius may be subject to a significant high bias for Advanced Very High Resolution Radiometer or MODIS retrievals that rely on the 0.63 and 3.7 µm radiance pair for an overlying aerosol layer of mineral dust. Analysis of 1 km resolution MODIS data for the SAFARI 2000 period suggests that the effective radius derived from the 0.86 and 1.63 µm radiance pair is, indeed, subject to a low bias in the presence of overlying biomass burning aerosol. These results show the difficulties associated with remote sensing retrievals, which must be kept in mind when attempting to assess any potential indirect effect. © Crown copyright 2004. [source] Review of Hinode resultsASTRONOMISCHE NACHRICHTEN, Issue 6 2010Y. Suematsu Abstract Hinode is an observatory-style satellite, carrying three advanced instruments being designed and built to work together to explore the physical coupling between the photosphere and the upper layers for understanding the mechanism of dynam- ics and heating. The three instruments aboard are the Solar Optical Telescope (SOT), which can provide high-precision photometric and polarimetric data of the lower atmosphere in the visible light (388,668 nm) with a spatial resolution of 0.2,0.3 arcseconds, the X-Ray Telescope (XRT) which takes a wide field of full sun coverage X-ray images being capable of diagnosing the physical condition of coronal plasmas, and the EUV Imaging Spectrometer (EIS) which observes the upper transition region and coronal emission lines in the wavelength ranges of 17,21 nm and 25,29 nm. Since first-light observations in the end of October 2006, Hinode has been continuously providing unprecedented high-quality solar data. We will present some new findings of the sun with Hinode, focusing on those from SOT (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Radial velocities, dynamics of stars and nebulosities with GAIA and VLT-GIRAFFEASTRONOMISCHE NACHRICHTEN, Issue 9-10 2008C. Martayan Abstract This document is divided in two parts. The first part deals with the radial velocities (RV) distributions for B-type stars and nebulosities observed with the VLT-GIRAFFE in the Large and Small Magellanic Clouds towards the open clusters NGC2004 and NGC330. Thanks to the resolution of GIRAFFE spectra, we found that the RV distribution for the nebulosities in the LMC is bi-modal. This bi-modality can be interpreted, in term of dynamics, by the expansion of the LMC4 super-bubble. The second part deals with the GAIA space mission and the determination of the radial velocities by using Radial Velocity Spectrometer (RVS) spectra. The methods to determine the radial velocities are presented as well as preliminary results on simulated RVS spectra. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Mid-Infrared Imaging and Spectroscopic Observations of the Galactic Center with Subaru/COMICSASTRONOMISCHE NACHRICHTEN, Issue S1 2003Y. Okada Abstract We report the results of mid-infrared (7.8,m,13.2 ,m) high-spatial resolution imaging and spectroscopic observations of the Galactic center region with the Cooled Mid-Infrared Camera and Spectrometer (COMICS) on the Subaru telescope. The images clearly show bright infrared sources and small structures in the diffuse emission. The spectra of all the observed positions show the 9.7 ,m silicate absorption feature. After corrected for the empirically-derived extinction, the intrinsic spectra of the infrared sources show either strong silicate emission or absorption, while the intrinsic diffuse emission has a power-law type spectrum. This difference indicates a possibility of dust processing due to the interaction between the infrared sources and their surrounding medium or a different origin of the dust grains surrounding the sources from those in the diffuse region. [source] An HPLC-MS method for simultaneous estimation of ,,, -arteether and its metabolite dihydroartemisinin, in rat plasma for application to pharmacokinetic studyBIOMEDICAL CHROMATOGRAPHY, Issue 7 2003M. Rajanikanth Abstract This manuscript reports, the development and validation of a sensitive and selective assay method for simultaneous determination of ,,, -arteether and its metabolite dihydroartemisinin (DHA) in rat plasma by liquid chromatography,mass spectrometry. Chromatographic separations were achieved by gradient elution of the analytes with an initial composition of methanol,potassium acetate buffer (pH 4; 73:27, v/v) to 100% methanol in 3 min and maintained for 5 min on a Spheri-10, RP18 (100 × 4.6 mm i.d.) column following an RP18 (30 × 4.6 mm i.d.) guard column. The total ef,uent from the column was split so that one-tenth was injected into the electrospray LC/MS interface. ESI-MS analysis was performed using a Micromass Quattro II Triple Quadrupole Mass Spectrometer equipped with an electrospray source. The MS analysis was carried out at cone voltage of 22 V with a scan range of 200,500 Da. The analytes were quanti,ed from the [M+ K]+ ion chromatograms of ,,, -arteether at m/z 352, DHA at m/z 323, artemisinin at m/z 321 and propyl ether analogue of arteether at m/z 365. Liquid,liquid extractions with a combination of n -hexane and hexane,ethyl acetate (8:2) were used to isolate ,,, -arteether and DHA from rat plasma. The method was validated and gave good accuracy and precision for the studied domain. Linearity in serum was observed over the range 4.375,70 ng/mL for a -arteether and 10,160 ng/mL for , -arteether and DHA. Percentage bias (accuracy) and within- and between-assay precision were well within the acceptable range. This method was applied to study the pharmacokinetics following oral administration of ,,, -arteether (30 mg/kg) in rats. Copyright © 2003 John Wiley & Sons, Ltd. [source] Dynamic range expansion of receiver by using optimized gain adjustment for high-field MRICONCEPTS IN MAGNETIC RESONANCE, Issue 4 2010C.H. Oh Abstract In high-field magnetic resonance imaging (MRI) system, the signal-to-noise ratio of MR signal is so high that the receiver frequently cannot cover the full dynamic range of the MR signal. Although this problem can be overcome by using a compander (compressor and expander) composed of logarithmic amplifiers and a ROM table to retrieve the nonlinearity of the logarithmic amplifiers or by simply increasing the number of bits of analog-to-digital converter, the methods can be costly and complex or even impossible for most commercial systems. In addition, the spectrometer has to be specifically designed to operate in those modes. In this article, we developed a simple dynamic range improvement method using a receiver with optimized variable gain control in which function can be implemented without any hardware modification to the spectrometer, if the spectrometer can do gain control during a scan. Simulations as well as experiments for the brain and resolution phantom have been performed, and the results demonstrate the utility of the proposed method. © 2010 Wiley Periodicals, Inc. Concepts Magn Reson Part A 36A: 243,254, 2010. [source] A pulse programmer for nuclear magnetic resonance spectrometersCONCEPTS IN MAGNETIC RESONANCE, Issue 2 2007C.C. Odebrecht Abstract A pulse programmer (PP) designed to control a nuclear magnetic resonance (NMR) spectrometer is reported on. The heart of the PP is a computer programmable logic device (CPDL) that provides flexibility to the design and, at the same time, reduces the number of electronics components needed and the dimensions of the printed circuit board. The PP works as follow: first, a pulse sequence defined by a set of instructions is loaded into the RAM memory of the PP. Then, when the process is started, the instructions are, one by one, read, decoded, and executed. Four types of instructions (functions) were defined: PRINT A, PRINT B, WAIT, and STOP. PRINT A and PRINT B change the status of the output channels A and B, respectively, WAIT generates a time delay, and STOP terminates the sequence. The output ports A and B have 14 channels each, and the shortest pulse and resolution are both 200 ns. The design of the PP is versatile, and new functions can be added through software without modifying the printed circuit board. To control the PP from a personal computer, a program named PulseJr was developed. It contains a graphical user interface (GUI) and pulse sequences can be drawn on the monitor screen with the mouse of the computer. Once the pulse sequence is sketched, clicking a button the program compiles the pulse sequence, generates the set of instructions, loads them into the RAM memory of the PP, and starts the pulse sequence. © 2007 Wiley Periodicals, Inc. Concepts Magn Reson Part A 30A: 127,131, 2007. [source] Design and implementation of a high-performance CCA event service,CONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 9 2009Ian Gorton Abstract Event services based on publish,subscribe architectures are well-established components of distributed computing applications. Recently, an event service has been proposed as part of the common component architecture (CCA) for high-performance computing (HPC) applications. In this paper we describe our implementation, experimental evaluation, and initial experience with a high-performance CCA event service that exploits efficient communications mechanisms commonly used on HPC platforms. We describe the CCA event service model and briefly discuss the possible implementation strategies of the model. We then present the design and implementation of the event service using the aggregate remote memory copy interface as an underlying communication layer for this mechanism. Two alternative implementations are presented and evaluated on a Cray XD-1 platform. The performance results demonstrate that event delivery latencies are low and that the event service is able to achieve high-throughput levels. Finally, we describe the use of the event service in an application for high-speed processing of data from a mass spectrometer and conclude by discussing some possible extensions to the event service for other HPC applications. Published in 2009 by John Wiley & Sons, Ltd. [source] Parallel processing of remotely sensed hyperspectral imagery: full-pixel versus mixed-pixel classificationCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 13 2008Antonio J. Plaza Abstract The rapid development of space and computer technologies allows for the possibility to store huge amounts of remotely sensed image data, collected using airborne and satellite instruments. In particular, NASA is continuously gathering high-dimensional image data with Earth observing hyperspectral sensors such as the Jet Propulsion Laboratory's airborne visible,infrared imaging spectrometer (AVIRIS), which measures reflected radiation in hundreds of narrow spectral bands at different wavelength channels for the same area on the surface of the Earth. The development of fast techniques for transforming massive amounts of hyperspectral data into scientific understanding is critical for space-based Earth science and planetary exploration. Despite the growing interest in hyperspectral imaging research, only a few efforts have been devoted to the design of parallel implementations in the literature, and detailed comparisons of standardized parallel hyperspectral algorithms are currently unavailable. This paper compares several existing and new parallel processing techniques for pure and mixed-pixel classification in hyperspectral imagery. The distinction of pure versus mixed-pixel analysis is linked to the considered application domain, and results from the very rich spectral information available from hyperspectral instruments. In some cases, such information allows image analysts to overcome the constraints imposed by limited spatial resolution. In most cases, however, the spectral bands collected by hyperspectral instruments have high statistical correlation, and efficient parallel techniques are required to reduce the dimensionality of the data while retaining the spectral information that allows for the separation of the classes. In order to address this issue, this paper also develops a new parallel feature extraction algorithm that integrates the spatial and spectral information. The proposed technique is evaluated (from the viewpoint of both classification accuracy and parallel performance) and compared with other parallel techniques for dimensionality reduction and classification in the context of three representative application case studies: urban characterization, land-cover classification in agriculture, and mapping of geological features, using AVIRIS data sets with detailed ground-truth. Parallel performance is assessed using Thunderhead, a massively parallel Beowulf cluster at NASA's Goddard Space Flight Center. The detailed cross-validation of parallel algorithms conducted in this work may specifically help image analysts in selection of parallel algorithms for specific applications. Copyright © 2008 John Wiley & Sons, Ltd. [source] Spectroscopic Diagnostics of Pulsed arc Plasmas for Particle GenerationCONTRIBUTIONS TO PLASMA PHYSICS, Issue 8 2008K. Behringer Abstract Pulsed arc plasmas were diagnosed by means of emission spectroscopy. A capacitor was discharged through argon and hydrogen leading to a few cycles of damped current oscillation with ,120 ,s period and 5-12 kA maximum current. Spectroscopic measurements in the visible range were carried out in order to characterise the electron temperature and density in the arc channel as well as electron and gas temperatures in the afterglow plasmas. Spectra were integrated over 10 ,s time windows and shifted in time from pulse to pulse. The plasmas also contained substantial fractions of electrode material (brass), namely copper and zinc. The electron density was measured in the conventional way from the broadening of H, or from the Ar I Stark width. In the arc channel, it ranged from about 3 · 1022 to 2 · 1023 m,3. The broadening of Zn II lines could also be used. Ratios of Ar I to Ar II and of Zn I to Zn II line intensities were analysed for the electron temperature. Line pairs were found which lay conveniently close in one frame of the spectrometer allowing automatic on-line analysis without relying on reproducibility. Atomic physics models including opacity were developed for Ar II and Zn II in order to check the existence of a Boltzmann distribution of their excited states. These calculations showed that the observed levels were in fact close to thermodynamic equilibrium, in particular, if the resonance lines were optically thick. Electron temperature measurements yielded values between 14000 K and 21000 K. The gas temperature in the afterglow, where particles should have formed, was derived from the rotational and vibrational temperatures of C2 molecular bands. Ratios between Cu I line intensities yielded the electron temperatures. Both were found to be a few 1000 K. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Synthesis and properties of ,-Fe2O3 nanorodsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 9 2010R. Ramesh Abstract We report synthesis of ,-Fe2O3 (hematite) nanorods by reverse micelles method using cetyltrimethyl ammonium bromide (CTAB) as surfactant and calcined at 300 °C. The calcined ,-Fe2O3 nanorods were characterized by X-ray diffraction (XRD), high-resolution scanning electron microscopy (HRSEM), transmission electron microscopy (TEM), energy dispersive spectrometer (EDS), fourier transform infrared spectroscopy (FTIR) and vibrating sample magnetometer (VSM). The result showed that the ,-Fe2O3 nanorods were hexagonal structure. The nanorods have diameter of 30-50 nm and length of 120-150 nm. The weak ferromagnetic behavior was observed with saturation magnetization = 0.6 emu/g, coercive force = 25 Oe and remanant magnetization = 0.03 emu/g. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Transmission spectra of crystals at elevated temperatures for the calculation of internal radiant heat transport during crystal growth , Part 1: The spectrometer and its performanceCRYSTAL RESEARCH AND TECHNOLOGY, Issue 10 2003D. Schwabe Abstract We report the construction, operation and performance of a transmission spectrometer for the visible to the IR (up to 3.5 ,m wavelength) to measure crystals up to a temperature of 1400 °C. The spectral resolution is almost comparable to that of a commercial spectrometer. The performance of the spectrometer and some problems are demonstrated by spectra of YAG : Nd at different temperatures. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Screening for the calstabin-ryanodine receptor complex stabilizers JTV-519 and S-107 in doping control analysisDRUG TESTING AND ANALYSIS, Issue 1 2009Mario Thevis Abstract Recent studies outlined the influence of exercise on the stability of the skeletal muscle calstabin1-ryanodine receptor1-complex, which represents a major Ca2+ release channel. The progressive modification of the type-1 skeletal muscle ryanodine receptor (RyR1) combined with reduced levels of calstabin1 and phosphodiesterase PDE4D3 resulted in a Ca2+ leak that has been a suggested cause of muscle damage and impaired exercise capacity. The use of 1,4-benzothiazepine derivatives such as the drug candidates JTV-519 and S-107 enhanced rebinding of calstabin1 to RyR1 and resulted in significantly improved skeletal muscle function and exercise performance in rodents. Due to the fact that the mechanism of RyR1 remodelling under exercise conditions were proven to be similar in mice and humans, a comparable effect of JTV-519 and S-107 on trained athletes is expected, making the compounds relevant for doping controls. After synthesis of JTV-519, S-107, and a putative desmethylated metabolite of S-107, target compounds were characterized using nuclear magnetic resonance spectroscopy and electrospray ionization (ESI),high-resolution/high-accuracy Orbitrap mass spectrometry. Collision-induced dissociation pathways were suggested based on the determination of elemental compositions of product ions and H/D-exchange experiments. The most diagnostic product ion of JTV-519 was found at m/z 188 (representing the 4-benzyl-1-methyl piperidine residue), and S-107 as well as its desmethylated analog yielded characteristic fragments at m/z 153 and 138 (accounting for 1-methoxy-4-methylsulfanyl-benzene and 4-methoxy-benzenethiol residues, respectively). The analytes were implemented in existing doping control screening procedures based on liquid chromatography, multiple reaction monitoring and simultaneous precursor ion scanning modes using a triple quadrupole mass spectrometer. Validation items such as specificity, recovery (68,92%), lower limit of detection (0.1,0.2 ng/mL), intraday (5.2,18.5%) and interday (8.7,18.8%) precision as well as ion suppression/enhancement effects were determined. Copyright © 2009 John Wiley & Sons, Ltd. [source] Zinc Oxide/Zinc Hexacyanoferrate Hybrid Film-Modified Electrodes for Guanine DetectionELECTROANALYSIS, Issue 18 2007Hung-Wei Chu Abstract An electroactive polynuclear hybrid films of zinc oxide and zinc hexacyanoferrate (ZnO/ZnHCF) have been deposited on electrode surfaces from H2SO4 solution containing Zn(NO3)2 and K3[Fe(CN)6] by repetitive potential cycling method. Simultaneous cyclic voltammetry and electrochemical quartz crystal microbalance (EQCM) measurements demonstrate the steady growth of hybrid film. There are two redox couples present in the voltammograms of hybrid film and it is obvious in the case of pH,2. Surface morphology of hybrid film was investigated using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Energy dispersive spectrometer (EDS) data confirm existence of zinc oxide in the hybrid film. The effect of type of monovalent cations on the redox behavior of resulting film was investigated. In pure supporting electrolyte, electrochemical responses of modified electrode resemble with that of a surface immobilized redox couple. The electrocatalytic activity of ZnO/ZnHCF hybrid film was investigated towards guanine using cyclic voltammetry and rotating disc electrode (RDE) techniques. Finally, feasibility of using ZnO/ZnHCF hybrid film-coated electrodes for guanine estimation in flow injection analysis (FIA) was also investigated. [source] Voltammetry as an Alternative Tool for Trace Metal Detection in Peloid Marine SedimentsELECTROANALYSIS, Issue 13 2007Irena Ciglene Abstract Here was demonstrated for the first time a possible application of abrasive stripping voltammetry in the direct measurement of trace metals in anoxic, sulfidic marine sediments (peloid mud) from a small and shallow (0.2,1,m) marine lagoon in Central Dalmatia, Croatia. Trace amounts of sample compounds are transferred to the graphite electrode surface and electrochemical reduction or oxidation processes are followed by the cyclic voltammetry in seawater or 0.55,M NaCl as electrolyte. After a preelectrolysis at potentials ranging from ,1.0 to ,1.5,V (vs. SCE) a well-defined anodic stripping peak corresponding to the oxidation of metal deposits generated at deposition potentials is obtained around ,0.74,V (vs. SCE). The same samples were studied by anodic stripping voltammetry at the Hg electrode and inductively coupled plasma-mass spectrometer (ICP-MS). ICP-MS showed higher concentrations of trace metals such as Al, Fe, Mo, Mn. A relatively high concentration of reduced sulfur species (RSS) (10,3 M) is determined electrochemically in porewater of the peloid mud, indicating that the magnitude of metal enrichment in the sediments is probably controlled by precipitation with sulfide. [source] CEC-ESI ion trap MS of multiple drugs of abuseELECTROPHORESIS, Issue 7 2010Zeineb Aturki Abstract This article describes a method for the separation and determination of nine drugs of abuse in human urine, including amphetamines, cocaine, codeine, heroin and morphine. This method was based on SPE on a strong cation exchange cartridge followed by CEC-MS. The CEC experiments were performed in fused silica capillaries (100,,m×30,cm) packed with a 3,,m cyano derivatized silica stationary phase. A laboratory-made liquid junction interface was used for CEC-MS coupling. The outlet capillary column was connected with an emitter tip that was positioned in front of the MS orifice. A stable electrospray was produced at nanoliter per minute flow rates applying a hydrostatic pressure (few kPa) to the interface. The coupling of packed CEC columns with mass spectrometer as detector, using a liquid junction interface, provided several advantages such as better sensitivity, low dead volume and independent control of the conditions used for CEC separation and ESI analysis. For this purpose, preliminary experiments were carried out in CEC-UV to optimize the proper mobile phase for CEC analysis. Good separation efficiency was achieved for almost all compounds, using a mixture containing ACN and 25,mM ammonium formate buffer at pH 3 (30:70, v/v), as mobile phase and applying a voltage of 12,kV. ESI ion-trap MS detection was performed in the positive ionization mode. A spray liquid, composed by methanol,water (80:20, v/v) and 1% formic acid, was delivered at a nano-flow rate of ,200,nL/min. Under optimized CEC-ESI-MS conditions, separation of the investigated drugs was performed within 13,min. CEC-MS and CEC-MS2 spectra were obtained by providing the unambiguous confirmation of these drugs in urine samples. Method precision was determined with RSDs values ,3.3% for retention times and ,16.3% for peak areas in both intra-day and day-to-day experiments. LODs were established between 0.78 and 3.12,ng/mL for all compounds. Linearity was satisfactory in the concentration range of interest for all compounds (r2,0.995). The developed CEC-MS method was then applied to the analysis of drugs of abuse in spiked urine samples, obtaining recovery data in the range 80,95%. [source] CE-LIF-MSn profiling of oligosaccharides in human milk and feces of breast-fed babiesELECTROPHORESIS, Issue 7 2010Simone Albrecht Abstract Mixtures of the complex human milk oligosaccharides (HMOs) are difficult to analyze and gastrointestinal bioconversion products of HMOs may complicate analysis even more. Their analysis, therefore, requires the combination of a sensitive and high-resolution separation technique with a mass identification tool. This study introduces for the first time the hyphenation of CE with an electrospray mass spectrometer, capable to perform multiple MS analysis (ESI-MSn) for the separation and characterization of HMOs in breast milk and feces of breast-fed babies. LIF was used for on- and off-line detections. From the overall 47 peaks detected in off-line CE-LIF electropherograms, 21 peaks could be unambiguously and 11 peaks could be tentatively assigned. The detailed structural characterization of a novel lacto- N -neo-tetraose isomer and a novel lacto- N -fucopentaose isomer was established in baby feces and pointed to gastrointestinal hydrolysis of higher-Mw HMOs. CE-LIF-ESI-MSn presents, therefore, a useful tool which contributes to an advanced understanding on the fate of individual HMOs during their gastrointestinal passage. [source] A novel methodology for the analysis of membrane and cytosolic sub-proteomes of erythrocytes by 2-DEELECTROPHORESIS, Issue 23 2009Gloria Alvarez-Llamas Abstract With the aim of studying a wide cohort of erythrocyte samples in a clinical setting, we propose here a novel approach that allows the analysis of both human cytosolic and membrane sub-proteomes. Despite their simple structure, the high content of hemoglobin present in the red blood cells (RBCs) makes their proteome analysis enormously difficult. We investigate here different strategies for isolation of the membrane and cytosolic fractions from erythrocytes and their influence on proteome profiling by 2-DE, paying particular attention to hemoglobin removal. A simple, quick and satisfactory approach for hemoglobin depletion based on HemogloBindÔ reagent was satisfactorily applied to erythrocyte cells, allowing the analysis of the cytosolic sub-proteome by 2-DE without major interference. For membrane proteome, a novel combined strategy based on hypotonic lysis isolation and further purification on minicolumns is described here, allowing detection of high molecular weight proteins (i.e. spectrin, ankyrin) and well-resolved 2-DE patterns. An aliquot of the membrane fraction was also in solution digested and analyzed by nano-LC coupled to an LTQ-Orbitrap mass spectrometer. A total of 188 unique proteins were identified by this approach. This study sets the basis for future clinical studies where the erythrocyte cell may be implicated. [source] Analyses of gibberellins in coconut (Cocos nucifera L.) water by partial filling-micellar electrokinetic chromatography-mass spectrometry with reversal of electroosmotic flowELECTROPHORESIS, Issue 10 2008Liya Ge Abstract In this paper, we present the results of simultaneous screening of eight gibberellins (GAs) in coconut (Cocos nucifera L.) water by MEKC directly coupled to ESI-MS detection. During the development of MEKC-MS, partial filling (PF) was used to prevent the micelles from reaching the mass spectrometer as this is detrimental to the MS signal, and a cationic surfactant, cetyltrimethylammonium hydroxide, was added to the electrolyte to reverse the EOF. On the basis of the resolution of the neighboring peaks, different parameters (i.e., the pH and concentration of buffer, surfactant concentrations, length of the injected micellar plug, organic modifier, and applied separation voltage) were optimized to achieve a satisfactory PF-MEKC separation of eight GA standards. Under optimum conditions, a baseline separation of GA standards, including GA1, GA3, GA5, GA6, GA7, GA9, GA12, and GA13, was accomplished within 25,min. Satisfactory results were obtained in terms of precision (RSD of migration time below 0.9%), sensitivity (LODs in the range of 0.8,1.9,,M) and linearity (R2 between 0.981 and 0.997). MS/MS with multiple reaction monitoring (MRM) detection was carried out to obtain sufficient selectivity. PF-MEKC-MS/MS allowed the direct identification and confirmation of the GAs presented in coconut water (CW) sample after SPE, while, the quantitative analysis of GAs was performed by PF-MEKC-MS approach. GA1 and GA3 were successfully detected and quantified in CW. It is anticipated that the current PF-MEKC-MS method can be applicable to analyze GAs in a wide range of biological samples. [source] Rapid capillary electrophoresis time-of-flight mass spectrometry separations of peptides and proteins using a monoquaternarized piperazine compound (M7C4I) for capillary coatingsELECTROPHORESIS, Issue 8 2008Anisa Elhamili Abstract A monoquaternarized piperazine, 1-(4-iodobutyl) 4-aza-1-azoniabicyclo[2,2,2] octane iodide (M7C4I), has been evaluated as a surface derivatization reagent for CE in combination with TOF MS for the analysis of proteins, peptides, and protein digests. The M7C4I piperazine, at alkaline pH, forms a covalent bond via alkylation of the ionized silanols producing a cationic surface with a highly stable and reversed EOF. The obtained surface yields rapid separations (less than 5,min) of peptides and proteins at acidic pH with high separation efficiencies (up to 1.1×106 plates/m for peptides and up to 1.8×106 plates/m for proteins) and no observed bleeding of the coating reagent into the mass spectrometer. The simplicity of the coating procedure also enables fast (2,min) regeneration of the surface, if necessary. This is useful in the analysis of complex samples in order to prevent possible memory effects. The potential of using M7C4I-coated capillaries for MS analysis of complex samples is demonstrated by the separation of peptides, proteins, and protein digests. Even more, the spectacular thing in which large intact proteins with molecular masses over 0.5,MDa could be separated. The coating showed good ability to handle these large proteins with high efficiency and retained peak shape as demonstrated by separation of IgG1 (150,kDa) and thyroglobulin (669,kDa). [source] A novel approach for analysis of oligonucleotide,cisplatin interactions by continuous elution gel electrophoresis coupled to isotope dilution inductively coupled plasma mass spectrometry and matrix-assisted laser desorption/ionization mass spectrometryELECTROPHORESIS, Issue 7 2008Wolfram Brüchert Abstract In this work we present a novel approach for in vitro studies of cisplatin interactions with 8-mer oligonucleotides. The approach is based on the recently developed coupling of continuous elution gel electrophoresis (GE) to an inductively coupled plasma-sector field mass spectrometer (ICP-SFMS) with the aim of monitoring the interaction process between this cytostatic drug and the nucleotides. In contrast to existing methods, the electrophoretic separation conditions used here allow both the determination of the reaction kinetics in more detail as well as the observation of dominant intermediates. Two different nucleotides sequences have been investigated for comparison purposes, one containing two adjacent guanines (5,-TCCGGTCC-3,) and one with a combination of thymine and guanine (5,-TCCTGTCC-3,), respectively. In order to gain further structural information, MALDI-TOF MS measurements have been performed after fraction collection. This allows for identification of the intermediates and the final products and confirms the stepwise coordination of cisplatin via monoadduct to bisadduct formation. Furthermore, the ICP-MS results were quantitatively evaluated in order to calculate the kinetics of the entire process. [source] | ||||||||||||||||||||||||||||||||||||||||||||||