167 research outputs found
Novel instrumentation and method development for a quadrupole ion trap mass spectrometer
No full textPart of the work described in this dissertation has involved development of instrumentation for the analysis of aerosol compounds. A quadrupole ion trap mass spectrometer (QITMS) is modified to sample particles via an aerodynamic lens inlet. The instrument has a unique capability for volatilization and chemical ionization within the heated ion trap that reduces fragmentation compared to other methods. Compounds in particles are detected in real time at low concentrations, over a broad concentration range, and in complex mixtures. Unlike most mass spectrometry systems used for aerosol detection, the aerosol QITMS is able to perform tandem mass spectrometry (MS/MS) to identify analyte ions. The performance of the instrument is demonstrated by monitoring the ozonolysis reaction of a volatile organic compound producing aerosol particles. The aerosol QITMS is presented as an effective design for detection and analysis of aerosol compounds. This work also describes the development of more efficient and informative MS/MS methods using infrared multiphoton photodissociation (IRMPD). IRMPD experiments are made practical for the QITMS by focusing the laser irradiation to increase photon flux on trapped ions. Efficient performance is used to increase sensitivity to product ions. Trapped ion clouds are profiled with higher resolution than previously obtained to characterize the effects of trapping parameters. IRMPD is also made selective by controlling the spatial distribution of ions relative to the laser pathway. More informative MS/MS spectra can be acquired without empirical determination of irradiation time, as is necessary for conventional IRMPD. The methods described use the fundamentals of ion trapping to design more effective photodissociation MS/MS experiments
SPME-DART Interface and Multi-slot Syringe for Arrow Fiber
No full text1. eMachineShop CAD files for four components of a desorption and sampling system for joining a DART probe, Vapur interface, and SPME Arrow fiber syringe in a Restek injection guide
2. Assembly instructions in a readme document
3. eMachineShop CAD file for a replacement Arrow syringe with: multiple slots on one side for discrete DART desorption; multiple slots on the opposite side for manual sampling to the same positions on the fiber; and a channel to rotate the plunger set screw between sides</p
Family Assessment- Author Index
No full textAuthor Index (12 pages)
A-Z
A
Abbott, D.: 263 Abery, B.: 242 Abidin, R: 81, 265 Abramovitch, R: 134, 135, 136, 137, 139,142,143,144,145,146 Abril, s.: 118 Achenbach, T. M.: 12,47, 118, 223, 265 Acock, A. c.: 206 Adams, G. R: 205 Adams, S. J.: 226 Al-Khayyal, M.: 74 Alexander, J. F.: 75 Allisson, P. D.: 185 Alwin, D. F.: 182,191,194 Amato, P. R: 205- 231, 206, 207, 210, 213,215,216, 219, 221, 222, 224, 227,230 Ammerman, R : 263 Amoloza, T. 0 .: 170, 171,172,176, 179, 187, 188 Anastasi, A.: 265 Anderson, B. J.: 85 Anderson, c.: 117 Anderson, P. P.: 104 Anderson, S. A.: 79, 168, 177 Anthony, J.: 117 Apley, J.: 84 Aponte, H. J.: 117 Appelbaum, M.: 263 Arrington, A.: 11 Asher, S.: 82 Asterita, M. F. : 92 Attneave, c.: 121 Auslander, W. F: 85
Z
Zane, N .: 107, 119 Zetlin, A.: 263 Zill, N.: 83 Zuo, J.: 171, 180, 18
Intentions And Information In Discourse
No full textThis paper is about the flow of inference between communicative intentions, discourse structure and the domain during discourse processing. We augment a theory of discourse interpretation with a theory of distinct mental attitudes and reasoning about them, in order to provide an account of how the attitudes interact with reasoning about discourse structure. INTRODUCTION The flow of inference between communicative intentions and domain information is often essential to discourse processing. It is well reflected in this discourse from Moore and Pollack (1992): (1)a. George Bush supports big business. b. He's sure to veto House Bill 1711. There are at least three different interpretations. Consider Context 1: in this context the interpreter I believes that the author A wants to convince him that (1b) is true. For example, the context is one in which I has already uttered Bush won't veto any more bills. I reasons that A's linguistic behavior was intentional, and therefore that A believ..
Family Assessment- Author Index
No full textAuthor Index (12 pages)
A-Z
A
Abbott, D.: 263 Abery, B.: 242 Abidin, R: 81, 265 Abramovitch, R: 134, 135, 136, 137, 139,142,143,144,145,146 Abril, s.: 118 Achenbach, T. M.: 12,47, 118, 223, 265 Acock, A. c.: 206 Adams, G. R: 205 Adams, S. J.: 226 Al-Khayyal, M.: 74 Alexander, J. F.: 75 Allisson, P. D.: 185 Alwin, D. F.: 182,191,194 Amato, P. R: 205- 231, 206, 207, 210, 213,215,216, 219, 221, 222, 224, 227,230 Ammerman, R : 263 Amoloza, T. 0 .: 170, 171,172,176, 179, 187, 188 Anastasi, A.: 265 Anderson, B. J.: 85 Anderson, c.: 117 Anderson, P. P.: 104 Anderson, S. A.: 79, 168, 177 Anthony, J.: 117 Apley, J.: 84 Aponte, H. J.: 117 Appelbaum, M.: 263 Arrington, A.: 11 Asher, S.: 82 Asterita, M. F. : 92 Attneave, c.: 121 Auslander, W. F: 85
Z
Zane, N .: 107, 119 Zetlin, A.: 263 Zill, N.: 83 Zuo, J.: 171, 180, 18
Lessons for Asian Countries from Pension Reforms in Chile
No full textChile's 1981 reform revolutionized pension design and created a system that was lauded and emulated widely. The main feature of the system was the creation of state-mandated, privately managed individual pension capitalization accounts based on contributions of employees. After nearly three decades of experience, there is a reassessment of the extent to which the pension system has achieved its objectives, particularly with respect to coverage and adequacy. In March 2006, the newly elected President Bachelet set up a Presidential Advisory Council on Pension Reform under the chairmanship of Mario Marcel to evaluate the existing pension system. This paper examines the rationale and the nature of the recommendations made by the Council. The analysis focuses on the structure of the proposed new pension system and risk-sharing implications of different pillars of the system, the accessibility of the existing pension system in terms of coverage, particularly for women and self-employed persons, the impact of reform on transaction costs; investment policies and management and their implications for rates of return and financial market development. The implications of the new system on pension design and policy debate in Asian countries are addressed. The paper suggests that must imbibe lessons from countries such as Chile and urgently undertake the task of constructing sustainable, robust and adequate pension systems and social safety nets.Chile, Asia, Pension Reform
In-Line Dopant Generation for Atmospheric Pressure Ionization Mass Spectrometry
No full textA concentric
trace gas permeation tube that diffuses chemical reagents
to a central carrier gas stream is used to drive chemical reaction
pathways and influence gas-phase chemistry for a variety of atmospheric
pressure ionization sources for mass spectrometry. Tunable permeation
through the reservoir-jacketed polymer membrane is triggered by the
heated gas moving through the tube, evaporating the dopant into a
sheath dry gas or into a sample stream in room air without diluting
the analyte concentration. The permeator is used to add dopants to
an electrospray plume for analyte ion charge reduction and to perform
hydrogen–deuterium exchange on biomolecules in different spray
conditions. Dopants are also added to atmospheric pressure chemical
ionization to favor the ionization of select components of diesel
fuel. Atmospheric pressure photoionization is performed with the permeation
tube in line with tubing transporting sample headspace to an enclosed
discharge lamp. Toluene dopant from the permeator increases the proton
transfer and charge exchange signal from clove oil and mothballs many
times without exposing the laboratory to reagent fumes. Water permeation
is also used to humidify the sample gas stream
Improving IRMPD in a Quadrupole Ion Trap
No full textA focused laser is used to make infrared multiphoton photodissociation (IRMPD) more efficient in a quadrupole ion trap mass spectrometer. Efficient (up to 100%) dissociation at the standard operating pressure of 1 × 10−3 Torr can be achieved without any supplemental ion activation and with shorter irradiation times. The axial amplitudes of trapped ion clouds are measured using laser tomography. Laser flux on the ion cloud is increased six times by focusing the laser so that the beam waist approximates the ion cloud size. Unmodified peptide ions from 200 Da to 3 kDa are completely dissociated in 2.5–10 ms at a bath gas pressure of 3.3 × 10−4 Torr and in 3–25 ms at 1.0 × 10−3 Torr. Sequential dissociation of product ions is increased by focusing the laser and by operating at an increased bath gas pressure to minimize the size of the ion cloud
Interface for Reproducible, Multishot Direct Analysis of Solid-Phase Microextraction Samples
No full textAn enclosed interface that joins
a direct analysis in real time
(DART) probe, solid-phase microextraction (SPME) fiber, and the inlet
of a high-resolution mass spectrometer is described. Unlike other
systems to couple SPME sampling to ambient mass spectrometry, the
interface is able to perform discrete analyses on different areas
of a single SPME fiber device for up to three technical replicate
measurements of one sampling event. Inlet flow speed and desorption
temperature are optimized, and reproducibility is demonstrated between
replicate analyses on the same derivatized SPME fiber and with sequential
fiber sampling events, yielding analyte measurement center of variance
(CV) from 3 to 6%. Conditioning is also performed with the enclosed
DART. The interface is a straightforward addition to commercially
available technologies, and machine diagrams for custom components
operated with SPME/DART/MS equipment are included
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