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Syed A. M. Tofail - One of the best experts on this subject based on the ideXlab platform.
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Polarisation changes in guided infrared thermography using silver halide poly-crystalline mid-infrared fibre bundle
Journal of Thermal Analysis and Calorimetry, 2020Co-Authors: Sarah K. Markham, Aladin Mani, Elena A. Korsakova, Aleksandr S. Korsakov, Liya V. Zhukova, Joanna Bauer, Christophe Silien, Syed A. M. TofailAbstract:Broadband mid-infrared (B-MIR) thermography using fibre optic waveguides can be critical in real-time imaging in harsh environments such as additive manufacturing, personalised medical diagnosis and therapy. We investigate the polarisation effect on thermal measurements through poly-crystalline fibre bundle employing a simple broadband cross-polarisation configuration experimental set-up. Silver halide poly-crystalline fibres AgCl_1−xBr_x (0 ≤ x ≤1) (AgClBr-PolyC) have very wide transmission bandwidth spanning over the spectral range from 1 µm up to 31 µm FWHM. Moreover, they are non-toxic, non-hygroscopic, with relatively good flexibility, which make them very adequate for spectroscopic and thermal measurements in medical and clinical fields. In this study, we used a fibre bundle composed of seven single AgClBr-PolyC fibres, each with a core diameter of about 300 µm, inserted between two broadband MIR polarisers. A silicon carbide Filament Source was placed at the entrance of the fibre bundle, while a FLIR thermal camera with a close-up lens was employed to measure the spatial temperature distribution over the fibre-bundle end. Indeed, polarisation dependence of temperature measurements has been clearly observed in which the orientation of temperature extrema (minima and maxima) vary from one fibre to another within the bundle. Moreover, these observations have enabled the classification of AgClBr-PolyC fibres following their polarisation sensitivities by which some fibres are relatively highly sensitive to polarisation with polarisation temperature difference (PTD) that can reach 22.1 ± 2.8 °C, whereas some others show very low PTD values down to 3.1 ± 2.8 °C. Many applications can readily be found based on the advantages of both extreme cases.
Sarah K. Markham - One of the best experts on this subject based on the ideXlab platform.
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Polarisation changes in guided infrared thermography using silver halide poly-crystalline mid-infrared fibre bundle
Journal of Thermal Analysis and Calorimetry, 2020Co-Authors: Sarah K. Markham, Aladin Mani, Elena A. Korsakova, Aleksandr S. Korsakov, Liya V. Zhukova, Joanna Bauer, Christophe Silien, Syed A. M. TofailAbstract:Broadband mid-infrared (B-MIR) thermography using fibre optic waveguides can be critical in real-time imaging in harsh environments such as additive manufacturing, personalised medical diagnosis and therapy. We investigate the polarisation effect on thermal measurements through poly-crystalline fibre bundle employing a simple broadband cross-polarisation configuration experimental set-up. Silver halide poly-crystalline fibres AgCl_1−xBr_x (0 ≤ x ≤1) (AgClBr-PolyC) have very wide transmission bandwidth spanning over the spectral range from 1 µm up to 31 µm FWHM. Moreover, they are non-toxic, non-hygroscopic, with relatively good flexibility, which make them very adequate for spectroscopic and thermal measurements in medical and clinical fields. In this study, we used a fibre bundle composed of seven single AgClBr-PolyC fibres, each with a core diameter of about 300 µm, inserted between two broadband MIR polarisers. A silicon carbide Filament Source was placed at the entrance of the fibre bundle, while a FLIR thermal camera with a close-up lens was employed to measure the spatial temperature distribution over the fibre-bundle end. Indeed, polarisation dependence of temperature measurements has been clearly observed in which the orientation of temperature extrema (minima and maxima) vary from one fibre to another within the bundle. Moreover, these observations have enabled the classification of AgClBr-PolyC fibres following their polarisation sensitivities by which some fibres are relatively highly sensitive to polarisation with polarisation temperature difference (PTD) that can reach 22.1 ± 2.8 °C, whereas some others show very low PTD values down to 3.1 ± 2.8 °C. Many applications can readily be found based on the advantages of both extreme cases.
Fred W Mclafferty - One of the best experts on this subject based on the ideXlab platform.
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electron capture dissociation of multiply charged protein cations a nonergodic process
Journal of the American Chemical Society, 1998Co-Authors: Roman A Zubarev, Neil L Kelleher, Fred W MclaffertyAbstract:Neutralization-reionization mass spectrometry (MS)1 is of unique value for preparing and characterizing highly reactive and unstable neutral species, such as the intermediate in the dissociative-recombination reaction H3O + ef H2O + H + 6.4 eV.2 Following an earlier suggestion,3 using neutralization accompanying surface-induced dissociation (SID)4 to form an unstable site did not yield new cleavage reactions5 in multiply charged protein cations from electrospray ionization (ESI) with Fourier transform (FT) MS.6 Serendipitously, we now find that one or more charges on such protein cations can be neutralized with low-energy electrons to cause specific cleavage of the amine bond to form c, z products,7 in contrast to the amide cleavage b, y products formed by collisionally activated dissociation (CAD),8 infrared multiphoton (IRMPD)9 and UV10 photodissociation, 70 eV electron impact excitation,11 and SID.5 The b, y products are formed by the lowest energy backbone cleavage of ESI protein ions.6-9 An attempt to cleave stronger bonds using high-energy (6.4 eV) 193 nm photons gave mainly b, y products for 2 kDa protein ions,10 but for 2.8 and 8.6 kDa protein ions12 gave small yields of c, z amine bond cleavage products not previously observed. In this further investigation, extra electrodes were placed outside the ion cell electrodes that trap the positively charged ions. With the outside electrodes at +9 V,13 extensive 193 nm laser irradiation of SWIFT-selected14 (M + 11H)11+ ubiquitin ions (8.6 kDa) only produces b, y, not c, z, ions. However, with the outside electrodes at -1 V, the c, z products are formed along with 10+ molecular ions; unexpectedly, these are mainly (M + 11H)10+• ions (Figure 1d), 1 Da heavier than the (M + 10H)10+ ions formed by ESI (Figure 1c). The 4+ mellitin ion spectrum measured under the same conditions (Figure 1b) similarly contains (M + 4H)3+•, consistent with capture of secondary electrons formed by the 193 nm photons impinging on metal surfaces and trapped by the -1 V electrodes: (M + 4H)4+ + ef (M + 4H)3+•.15 Electrons were produced instead (no laser) by a conventional heated Filament Source outside the FTMS magnet opposite the ESI Source.11 With a 10-5 Torr Ar pulse for ecooling (energy < 0.2 eV; an SF6 pulse lowered the efficiency), the 11+ ions of ubiquitin gave a spectrum that showed c, z cleavage of 50 out of 75 backbone positions; CAD8/IRMPD9 gave b, y cleavage of eight of these positions plus seven others. Cooled electrons plus the 15+ ions of FeIII equine cytochrome c16 produced (Figure 2) c, z fragment ions from cleavages at all but 40 of the 103 possible backbone sites (e.g., N-terminal side of Pro, none; of Ile, Leu, Val, few); CAD produces b, y cleavages (total 19) at eight additional sites. The 21+ apomyoglobin ions (17 kDa) yielded 33 c, z cleavages, but the 34+ ions of bovine carbonic anhydrase (29 kDa) as yet has given only 33+, 32+, and 31+ molecular ions. Electron capture dissociation (ECD)1-3 rationalizes these results. The capture cross section should be proportional to the ionic charge squared, consistent with the minimal secondary fragmentations to produce internal ions and the predominance of cleavages in the central∼70% of the protein chain. Charge values and masses17 of the complementary product ions are consistent with dissociation after ecapture, such as c39/z37 from the 76-residue ubiquitin 11+ ions and c69/z35 from the 104residue cytochrome c 15+ ions. The most favored protonation sites are the side chains of Lys, Arg, and His;18 neutralization to form hypervalent species1-3 at Lys and Arg would account for ions (Figure 2) representing losses of 17, 44, and 59 Da from (M + nH)(n-x)+ (eq 1; neutralization of protonated His gives a more stable radical site).
Han Bin Oh - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of the internal temperatures of an 8.6 kDa protein cation exposed to a hot dispenser cathode employed in electron capture dissociation mass spectrometry
Rapid communications in mass spectrometry : RCM, 2006Co-Authors: Yong-hyeon Yim, Byungjoo Kim, Seonghee Ahn, Sunyoung Lee, Han Bin OhAbstract:The ‘effective’ internal temperature of an 8.6 kDa ubiquitin cation was estimated under electron capture dissociation (ECD) conditions, in which a dispenser cathode electron Source was mounted just outside an ion cyclotron resonance (ICR) cell, i.e., axially displaced at a distance less than 1 cm from the rear trap plate of the ICR cell. In this ECD configuration, thermal activation of the molecular ions stored in the ICR cell was anticipated since the heated dispenser cathode (Tcathode surface > 1000°C) emitted a large amount of (both visible and infrared) radiation as well as electrons. An evaluation of the internal temperature of ubiquitin 6+ and 7+ cations was made by comparing our ECD fragmentation patterns with those obtained by McLafferty et al. (J. Am. Chem. Soc. 2002; 124: 6407) as a function of the ion temperature. In McLafferty's configuration, the heating (or thermal activation) effect of their Filament Source was minimal since the Filament was displaced by a distance as far as 70 cm from their ICR cell. A careful comparison reveals that the fragmentation patterns obtained in this work are very similar to those previously measured at T ∼ 125°C. In terms of sequence coverage, our ECD configuration provides better results, and in particular without the aid of any other simultaneous activation method, such as thermal heating, infrared multiphoton irradiation, or collisional activation, except for the visible and infrared radiation from the heated cathode. Copyright © 2006 John Wiley & Sons, Ltd.
Robert J. Cotter - One of the best experts on this subject based on the ideXlab platform.
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Carbon nanotube electron ionization Source for portable mass spectrometry
Analytical Chemistry, 2011Co-Authors: Theresa Evans-nguyen, Christina Hammock, Andrew H. Monica, Elena Adams, Luann Becker, Charles B. Parker, Jeffrey T. Glass, Robert J. CotterAbstract:Cold cathode carbon nanotubes (CNTs) are used in a low-voltage quadrupole ion trap mass spectrometer and shown to be a viable low-power alternative to Filament Sources for portable mass spectrometry instrumentation. No heating is necessary, and the power consumption depends only on the switching characteristics of the electronics. The CNT electron Sources are mounted directly in the ring electrode, and their performance is compared directly with a Filament Source also mounted in the ring electron. Up to a 5 × 10–4 Torr CO2 environment, reflecting conditions expected during operation in a Mars atmosphere, the CNT emitters may provide up to 1 μA of current over more than 200 h.