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Alexandria, VA, United States

Pindzola M.S.,Auburn University | Colgan J.,Los Alamos National Laboratory | Robicheaux F.,Purdue University | Lee T.G.,University Research Park | And 4 more authors.
Advances in Atomic, Molecular and Optical Physics | Year: 2016

We review the application of the time-dependent close-coupling method to the study of ion-impact ionization of atoms and molecules. Ionization cross sections are presented for bare ion, antiproton, and neutron collisions with light atoms and molecules. © 2016 Elsevier Inc. Source


Habicht S.C.,Purdue University | Habicht S.C.,Center for Naval Analysis | Amundson L.M.,Purdue University | Duan P.,Purdue University | And 3 more authors.
Analytical Chemistry | Year: 2010

In recent years, laser-induced acoustic desorption (LIAD) coupled with a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer has been demonstrated to provide a valuable technique for the analysis of a wide variety of nonvolatile, thermally labile compounds, including analytes that could not previously be analyzed by mass spectrometry. Although FT-ICR instruments are very powerful, they are also large and expensive and, hence, mainly used as research instruments. In contrast, linear quadrupole ion trap (LQIT) mass spectrometers are common due to several qualities that make these instruments attractive for both academic and industrial settings, such as high sensitivity, large dynamic range, and experimental versatility. Further, the relatively small size of the instruments, comparatively low cost, and the lack of a magnetic field provide some distinct advantages over FT-ICR instruments. Hence, we have coupled the LIAD technique with a commercial LQIT, the Thermo Fischer Scientific LTQ mass spectrometer. The LQIT was modified for a LIAD probe by outfitting the removable back plate of the instrument with a 6 in. ConFlat flange (CFF) port, gate valve, and sample lock. Reagent ions were created using the LQIT's atmospheric pressure ionization source and trapped in the mass analyzer for up to 10 s to allow chemical ionization reactions with the neutral molecules desorbed via LIAD. These initial experiments focused on demonstrating the feasibility of performing LIAD in the LQIT. Hence, the results are compared to those obtained using an FT-ICR mass spectrometer. Despite the lower efficiency in the transfer of desorbed neutral molecules into the ion trap, and the smaller maximum number of available laser pulses, the intrinsically higher sensitivity of the LQIT resulted in a higher sensitivity relative to the FT-ICR. © 2010 American Chemical Society. Source


Amundson L.M.,Purdue University | Gallardo V.A.,Purdue University | Vinueza N.R.,Purdue University | Owen B.C.,Purdue University | And 8 more authors.
Energy and Fuels | Year: 2012

A tandem mass spectrometric method using a commercial linear quadrupole ion trap (LQIT) mass spectrometer and another LQIT coupled with a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer is described for the identification and counting of different oxygen-containing functionalities and alkyl groups in unknown aromatic analytes. A total of 64 aromatic model compounds were evaporated and ionized via positive-mode atmospheric pressure chemical ionization (APCI). Ionization of the model compounds primarily results in the formation of protonated molecules, [M + H] +. In some cases, the molecular radical cation, [M] +•, and/or a fragment ion, [M - H] +, are formed instead. Only in one case, no ions were observed near the m/z value of the molecular ion, and the ion with the greatest m/z value is a fragment ion, [M + H - H 2O] +. Once ionized, the ions were subjected to multiple isolation and collision-activated dissociation (CAD) events until no more fragmentation was observed (up to MS 5). In most cases, all functionalities were sequentially cleaved, one or more at a time, by the CAD events. The type of neutral molecule cleaved and the number of times that it was cleaved facilitate the identification and counting of the functionalities. The method was successfully used in concert with high-performance liquid chromatography (HPLC). The HPLC retention times offer further structural information for the analytes. This methodology benefits the chemical, pharmaceutical, and biofuels industries by facilitating the identification of previously unknown compounds directly in complex mixtures, such as crude products of chemical processes, drug metabolites, and lignin degradation products. © 2012 American Chemical Society. Source


Habicht S.C.,Purdue University | Habicht S.C.,Center for Naval Analysis | Vinueza N.R.,Purdue University | Amundson L.M.,Purdue University | Kenttamaa H.I.,Purdue University
Journal of the American Society for Mass Spectrometry | Year: 2011

We report here a comparison of the use of diagnostic ion-molecule reactions for the identification of oxygen-containing functional groups in Fourier-transform ion cyclotron resonance (FTICR) and linear quadrupole ion trap (LQIT) mass spectrometers. The ultimate goal of this research is to be able to identify functionalities in previously unknown analytes by using many different types of mass spectrometers. Previous work has focused on the reactions of various boron reagents with protonated oxygen-containing analytes in FTICR mass spectrometers. By using a LQIT modified to allow the introduction of neutral reagents into the helium buffer gas, this methodology has been successfully implemented to this type of an ion trap instrument. The products obtained from the reactions of trimethyl borate (TMB) with various protonated analytes are compared for the two instruments. Finally, the ability to integrate these reactions into LC-MS experiments on the LQIT is demonstrated. © American Society for Mass Spectrometry,2011. Source


Adamatzky A.,University of the West of England | Akl S.,Queens University | Alonso-Sanz R.,Technical University of Madrid | Van Dessel W.,Scientific Institute of Public Health | And 11 more authors.
International Journal of Parallel, Emergent and Distributed Systems | Year: 2013

We analyse the results of our experimental laboratory approximation of motorway networks with slime mould Physarum polycephalum. Motorway networks of 14 geographical areas are considered: Australia, Africa, Belgium, Brazil, Canada, China, Germany, Iberia, Italy, Malaysia, Mexico, the Netherlands, UK and USA. For each geographical entity, we represented major urban areas by oat flakes and inoculated the slime mould in a capital. After slime mould spanned all urban areas with a network of its protoplasmic tubes, we extracted a generalised Physarum graph from the network and compared the graphs with an abstract motorway graph using most common measures. The measures employed are the number of independent cycles, cohesion, shortest paths lengths, diameter, the Harary index and the Randić index. We obtained a series of intriguing results, and found that the slime mould approximates best of all the motorway graphs of Belgium, Canada and China, and that for all entities studied the best match between Physarum and motorway graphs is detected by the Randić index (molecular branching index). © 2013 Copyright Taylor and Francis Group, LLC. Source

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