The Experts below are selected from a list of 44805 Experts worldwide ranked by ideXlab platform
Richard D Smith - One of the best experts on this subject based on the ideXlab platform.
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orthogonal injection ion Funnel interface providing enhanced performance for selected reaction monitoring triple quadrupole mass spectrometry
Analytical Chemistry, 2015Co-Authors: Tsungchi Chen, Yehia M Ibrahim, Thomas L Fillmore, Spencer A Prost, Ronald J Moore, Richard D SmithAbstract:The electrodynamic ion Funnel facilitates efficient focusing and transfer of charged particles in the higher-pressure regions (e.g., ion source interfaces) of mass spectrometers, thus providing increased sensitivity. An “off-axis” ion Funnel design has been developed to reduce the source contamination and interferences from, e.g. ESI droplet residue and other poorly focused neutral or charged particles with very high mass-to-charge ratios. In this study, a dual ion Funnel interface consisting of an orthogonal higher pressure electrodynamic ion Funnel (HPIF) and an ion Funnel trap combined with a triple quadrupole mass spectrometer was developed and characterized. An orthogonal ion injection inlet and a repeller plate electrode was used to direct ions to an ion Funnel HPIF at a pressure of 9–10 Torr. Key factors for the HPIF performance characterized included the effects of RF amplitude, the DC gradient, and operating pressure. Compared to the triple quadrupole standard interface more than 4-fold improveme...
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development of a new ion mobility time of flight mass spectrometer
International Journal of Mass Spectrometry, 2015Co-Authors: Yehia M Ibrahim, David C Prior, Gordon A Anderson, Erin S Baker, William F Danielson, Randolph V Norheim, Mikhail E Belov, Richard D SmithAbstract:A new ion mobility spectrometer (IMS) platform was developed to improve upon the sensitivity and reproducibility of our previous platforms, and further enhance IMS-MS utility for broad ‘pan-omics’ measurements. The new platform incorporated an improved electrospray ionization source and interface for enhanced sensitivity, and providing the basis for further benefits based upon implementation of multiplexed IMS. The ion optics included electrodynamic ion Funnels at both the entrance and exit of the IMS, an ion Funnel trap for ion injection, and a design in which nearly all ion optics (e.g. drift rings, ion Funnels) were fabricated using printed circuit board technology. The IMS resolving power achieved was ~73 for singly-charged ions, very close to the predicted diffusion-limited resolving power (~75). The platform’s performance evaluation (e.g. for proteomics measurements) include LC-IMS-TOF MS datasets for 30 technical replicates for a trypsin digested human serum, and included platform performance in each dimension (LC, IMS and MS) separately.
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high sensitivity ion mobility spectrometry mass spectrometry using electrodynamic ion Funnel interfaces
Analytical Chemistry, 2005Co-Authors: Keqi Tang, Alexandre A Shvartsburg, Michael A Buschbach, David C Prior, Gordon A Anderson, Hakno Lee, Aleksey V Tolmachev, Richard D SmithAbstract:The utility of ion mobility spectrometry (IMS) for separation of mixtures and structural characterization of ions has been demonstrated extensively, including in biological and nanoscience contexts. A major attraction of IMS is its speed, several orders of magnitude greater than that of condensed-phase separations. Nonetheless, IMS combined with mass spectrometry (MS) has remained a niche technique, substantially because of limited sensitivity resulting from ion losses at the IMS-MS junction. We have developed a new electrospray ionization (ESI)-IMS-QTOF MS instrument that incorporates electrodynamic ion Funnels at both front ESI-IMS and rear IMS-QTOF interfaces. The front Funnel is of the novel “hourglass” design that efficiently accumulates ions and pulses them into the IMS drift tube. Even for drift tubes of 2-m length, ion transmission through IMS and on to QTOF is essentially lossless across the range of ion masses relevant to most applications. The rf ion focusing at the IMS terminus does not degrad...
Jianxin Zhu - One of the best experts on this subject based on the ideXlab platform.
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preparation of lead oxide nanoparticles from cathode ray tube Funnel glass by self propagating method
Journal of Hazardous Materials, 2012Co-Authors: Yu Wang, Jianxin ZhuAbstract:This paper presents a novel process of extracting lead oxide nanoparticles from cathode-ray tube (CRT) Funnel glass using self-propagating high-temperature synthesis (SHS) method. The impacts of added amount of Funnel glass on the extraction ratio of lead, the lead extraction velocity and the micromorphology, as well as particle size of extracted nanoparticles were investigated. We found that self-propagating reaction in the presence of Mg and Fe(2)O(3) could separate lead preferentially and superfine lead oxide nanoparticles were obtained from a collecting chamber. The separation ratio was related closely to the amount of Funnel glass added in the original mixture. At Funnel glass addition of no more than 40wt.%, over 90wt.% of lead was recovered from Funnel glass. High extraction yield reveals that the network structure of Funnel glass was fractured due to the dramatic energy generated during the SHS melting process. The PbO nanoparticles collected show good dispersion and morphology with a mean grain size of 40-50nm.
M J Bown - One of the best experts on this subject based on the ideXlab platform.
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in meta analyses of proportion studies Funnel plots were found to be an inaccurate method of assessing publication bias
Journal of Clinical Epidemiology, 2014Co-Authors: James P Hunter, Alex J. Sutton, Athanasios Saratzis, Rebecca H Boucher, Robert D Sayers, M J BownAbstract:Abstract Objective To assess the utility of Funnel plots in assessing publication bias (PB) in meta-analyses of proportion studies. Study Design and Setting Meta-analysis simulation study and meta-analysis of published literature reporting peri-operative mortality after abdominal aortic aneurysm (AAA) repair. Data for the simulation study were stochastically generated. A literature search of Medline and Embase was performed to identify studies for inclusion in the published literature meta-analyses. Results The simulation study demonstrated that conventionally constructed Funnel plots (log odds vs. 1/standard error [1/SE]) for extreme proportional outcomes were asymmetric despite no PB. Alternative Funnel plots constructed using study size rather than 1/SE showed no asymmetry for extreme proportional outcomes. When used in meta-analyses of the mortality of AAA repair, these alternative Funnel plots highlighted the possibility for conventional Funnel plots to demonstrate asymmetry when there was no evidence of PB. Conclusion Conventional Funnel plots used to assess for potential PB in meta-analyses are inaccurate for meta-analyses of proportion studies with low proportion outcomes. Funnel plots of study size against log odds may be a more accurate way of assessing for PB in these studies.
C Olson J Reichhardt - One of the best experts on this subject based on the ideXlab platform.
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commensurability jamming and dynamics for vortices in Funnel geometries
Physical Review B, 2010Co-Authors: C Olson J ReichhardtAbstract:With advances in fabrication technologies it is now possible to create precisely controlled geometries and pinning landscapes for vortex matter in type-II superconductors. Here we use numerical simulations to examine vortex states and dynamics in periodic Funnel geometries where a drive is applied in the easy-flow direction. We show that this system exhibits a number of different commensurability effects when the vortex configurations match to both the periodicity of the array and the geometry of the Funnels. The vortex configurations in this system are generally different from those observed for single isolated triangular superconducting samples due to the coupling of vortices in adjacent Funnels. At certain matching fields, peaks in the critical current are absent due to the particular vortex configurations that occur at these fields. We find that the overall depinning force increases with increasing vortex density as a result of the enhanced vortex-vortex interactions caused by a crowding effect at the Funnel tips. When a system becomes less mobile as a result of increased particle interactions, it is said to exhibit a jamming behavior. Under an applied drive we observe a series of elastic and plastic vortex flow phases which produce pronounced features such as jumps or dips in the transport curves. In all of the flow phases, only one vortex can pass through the Funnel tip at a time due to the vortex-vortex repulsion forces. As a consequence of this constraint, we observe the remarkable result that the sum of the vortex velocities at a fixed drive remains nearly constant with increasing magnetic field $B$ rather than increasing linearly. This result is similar to the behavior of sand in an hourglass. We also show how noise fluctuations can be used to distinguish the different flow phases. Our results should be readily generalizable to other systems of particles flowing in periodic Funnel geometries, such as colloids or Wigner crystals.
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commensurability jamming and dynamics for vortices in Funnel geometries
arXiv: Superconductivity, 2010Co-Authors: C Olson J ReichhardtAbstract:We use numerical simulations to examine vortex states and dynamics in periodic Funnel geometries where a drive is applied in the easy flow direction. We show that this system exhibits a number of different commensurability effects when the vortex configurations match to both the periodicity of the array and the geometry of the Funnels. The vortex configurations in this system are generally different from those observed for single isolated triangular superconducting samples due to the coupling of vortices in adjacent Funnels. At certain matching fields, peaks in the critical current are absent due to the particular vortex configurations that occur at these fields. We find that the overall depinning force increases with increasing vortex density as a result of the enhanced vortex-vortex interactions caused by a crowding effect at the Funnel tips. When a system becomes less mobile as a result of increased particle interactions, it is said to exhibit a jamming behavior. Under an applied drive we observe a series of elastic and plastic vortex flow phases which produce pronounced features such as jumps or dips in the transport curves. In all of the flow phases, only one vortex can pass through the Funnel tip at a time due to the vortex-vortex repulsion forces. As a consequence of this constraint, we observe the remarkable result that the sum of the vortex velocities at a fixed drive remains nearly constant with increasing magnetic field B rather than increasing linearly. This result is similar to the behavior of sand in an hourglass. We also show how noise fluctuations can be used to distinguish the different flow phases. Our results should be readily generalizable to other systems of particles flowing in periodic Funnel geometries, such as colloids or Wigner crystals.
Yu Wang - One of the best experts on this subject based on the ideXlab platform.
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preparation of lead oxide nanoparticles from cathode ray tube Funnel glass by self propagating method
Journal of Hazardous Materials, 2012Co-Authors: Yu Wang, Jianxin ZhuAbstract:This paper presents a novel process of extracting lead oxide nanoparticles from cathode-ray tube (CRT) Funnel glass using self-propagating high-temperature synthesis (SHS) method. The impacts of added amount of Funnel glass on the extraction ratio of lead, the lead extraction velocity and the micromorphology, as well as particle size of extracted nanoparticles were investigated. We found that self-propagating reaction in the presence of Mg and Fe(2)O(3) could separate lead preferentially and superfine lead oxide nanoparticles were obtained from a collecting chamber. The separation ratio was related closely to the amount of Funnel glass added in the original mixture. At Funnel glass addition of no more than 40wt.%, over 90wt.% of lead was recovered from Funnel glass. High extraction yield reveals that the network structure of Funnel glass was fractured due to the dramatic energy generated during the SHS melting process. The PbO nanoparticles collected show good dispersion and morphology with a mean grain size of 40-50nm.
