328 research outputs found
Optical Re-Injection in Cavity-Enhanced Absorption Spectroscopy: Modeling and Experiments
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219233.pdf (Publisher’s version ) (Open Access)Radboud University, 25 juni 2020Promotor : Harren, F.J.M. Co-promotor : Cristescu, S.M.193 p
Advancing the detection of molecules in gas phase with infrared lasers : further development of semiconductor Laser-based Cavity Enhanced Absorption Spectroscopy
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150239.pdf (Publisher’s version ) (Open Access)Radboud Universiteit Nijmegen, 08 mei 2015Promotor : Parker, D.H. Co-promotores : Harren, F.J.M., Cristescu, S.M.X, 163 p
Continuous-wave optical parametric oscillator for trace gas detection in life sciences
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60686.pdf (Publisher’s version ) (Open Access)RU Radboud Universiteit Nijmegen, 04 februari 2004Promotor : Parker, D.H. Co-promotores : Harren, F.J.M., Bisson, S.E.XII, 119 p
Mid-infrared frequency comb fourier transform spectroscopy for chemical analysis
No full textItem does not contain fulltextRU Radboud Universiteit, 28 oktober 2016Promotor : Parker, D.H. Co-promotores : Harren, F.J.M., Mandon, J.B.101 p
Optical parametric oscillator based real-time trace gas analysis for bio-medical applications
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100593.pdf (Publisher’s version ) (Open Access)Radboud Universiteit Nijmegen, 15 november 2012Promotor : Parker, D.H. Co-promotores : Harren, F.J.M., Cristescu, S.M.123 p
Laser-based methods for sensitive trace gas detection
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132426.pdf (Publisher’s version ) (Open Access)Radboud Universiteit Nijmegen, 26 januari 2015Promotor : Parker, D.H. Co-promotores : Harren, F.J.M., Cristescu, S.M.109 p
Proton transfer reaction-mass spectrometry, applications in life sciences
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94176.pdf (Publisher’s version ) (Open Access)Radboud Universiteit Nijmegen, 07 juni 2012Promotor : Parker, D.H. Co-promotores : Harren, F.J.M., Cristescu, S.M.152 p
Detection of respiratory infections in exhaled breath of cystic fibrosis patients
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165623.pdf (Publisher’s version ) (Open Access)Radboud University, 03 februari 2017Promotor : Wevers, R.A. Co-promotores : Cristescu, S.M., Harren, F.J.M., Merkus, P.J.F.M
Development of Proton-transfer reaction mass spectrometry techniques
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30039_deveofprr.pdf (Publisher’s version ) (Open Access)The measurement of small quantities of gases and volatiles in air is used nowadays in many different fields of science, such as chemistry, physics, biology, food science and medicine. The study of these minute quantities of gases requires highly sensitive detectors. Using such detectors to monitor the emission of molecules can provide useful insight into processes inside the emitter. However, the sources, amounts and types of volatile organic compounds can vary greatly, requiring different types of dedicated or highly versatile detectors. This thesis is about the development and application of trace gas detectors based on mass spectrometers. To be more specific, products of chemical reactions of trace gas molecules with H3O+ ions are studied. This experimental technique is called Proton-Transfer Reaction Mass Spectrometry (PTR-MS). The nature of the proton-transfer reaction enables the detection of extremely low levels (i.e. at (sub-) ppbv level; 1:1.000.000.000) of many different types of trace gases at a high time resolution. This thesis includes a description of the thermodynamics and chemistry behind the PTR-MS technique and contains a large variety of studies in different areas of application. These examples include the study of biological processes in plants and fruits and the quest for biomarkers of diseases in human breath. Besides the application of the PTR-MS technique, this thesis also contains a description of the development of a new type of PTR-MS detector, equipped with an ion trap mass spectrometer instead of the conventional quadrupole mass filter. This new system is shown to provide highly improved possibility of identification of detected volatile organic compounds.RU, Molecular and Laser Physics, 24 april 2007Promotor : Parker, D.H. Co-promotores : Harren, F.J.M., Cristescu, S.M.193 p
Detection of Trace Gases from Fermentation Processes using Photoacoustic Spectroscopy and Pronton-Transfer-Reaction Mass Spectrometry
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19620.pdf (Publisher’s version ) (Open Access)This thesis presents novel interdisciplinary Physics - Biology research work that employed Photoacoustic Spectroscopy and Proton-Transfer-Reaction Mass Spectrometry. Both techniques were used in biological studies of trace gasses emitted by crop plants and fruit under stress situations. The findings of this research bring to light essential new features in plant physiology. A line tuneable (5 - 8 ?m) infrared CO-laser based photoacoustic detector was adapted to achieve fast, non-invasive and highly sensitive on-line monitoring of biological processes. The set-up was used to study alcoholic fermentation and concomitant processes in seedlings of various crop plants, notably of rice and wheat (Chapters 2, 3, and 4). If a large number of gases are monitored by the photoacoustic method, the time resolution of the system becomes very low. In addition, there is great interest in trace gases that cannot be monitored by photoacoustics. To overcome these drawbacks, a Proton-Transfer-Reaction Mass Spectrometer (PTR-MS) was designed, constructed and optimized. In Chapter 5 this PTR-MS is described together with its use in monitoring emission of various compounds (aldehydes, alcohols, acids, esters and C-6 compounds) related to fermentation and to fruit aroma and flavour, released by four apple cultivars under short anaerobic and post-anaerobic conditions. Detection limits similar to those reported in the literature were achieved with this system. For the first time, a comparison between PTR-MS and laser photoacoustics was made in order to ensure that fragmentation processes occurring during the PTR-MS measurements do not disturb the assignment of the ion-signals to the neutral compounds of interest. Simultaneous monitoring of alcoholic fermentation products from young rice plants by both methods gave comparable results for acetaldehyde. The preliminary results show that application of PTR-MS detectors in fruit storage opens new possibilities for revealing the kinetics of metabolic processes relevant to storage conditions, fruit quality and basic physiologyNijmegen, 11 april 2005Promotores : Parker, D.H., Jackson, M.B. Co-promotor : Harren, F.J.M.126 p
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