Dissertations / Theses on the topic 'Field spectrometry'
To see the other types of publications on this topic, follow the link: Field spectrometry.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Field spectrometry.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Brown, Lauren J. "Field asymmetric waveform ion mobility spectrometry-mass spectrometry studies of peptides and proteins." Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/12001.
Full textAbstract:
Field asymmetric waveform ion mobility spectrometry (FAIMS) is a gas phase atmospheric pressure separation technique that exploits the difference in the mobility of ions in alternating low and high electric fields as they are carried between two electrodes. In this thesis, a miniaturised FAIMS separation step has been applied to increase selectivity, enhance sensitivity and improve the quality of mass spectral data for rapid, high-throughput protein and peptide analysis. In Chapter 2, charge state separations were used to generate pseudo-peptide mass fingerprint data by FAIMS-MS, permitting confident protein identification using ESI sample introduction as an alternative to MALDI-TOF-MS methods. In addition, pre-cursor ions were targeted prior to MS/MS analysis. Chapter 3 describes the analysis of intact proteins by miniaturised FAIMS-MS. Multiple charge states of intact proteins were separated on the basis of differences in differential mobility. Higher charge states were found to be transmitted at similar CVs suggesting that the miniaturised FAIMS device was separating ions on the basis of 3D structure. In addition, multiple species could be observed at the same m/z suggesting the presence of different protein conformers. In Chapter 4, miniaturised FAIMS was used to select ions on the basis of differential mobility prior to in-source collision-induced dissociation CID, LC and ToF-MS analysis for qualitative and quantitative analysis of peptides mixtures. This was applied to the analysis of co-eluting model peptides and tryptic peptides derived from human plasma proteins, allowing precursor ion selection and CID to yield product ion data suitable for peptide identification via database searching.
2
Bozec, Laurent. "Near-field photothermal Fourier-transform infrared micro-spectrometry." Thesis, Lancaster University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.418454.
Full text
3
Syed, Sarfaraz Uddin. "Quadrupole mass spectrometry under the influence of magnetic field." Thesis, University of Liverpool, 2012. http://livrepository.liverpool.ac.uk/5533/.
Full textAbstract:
A Quadrupole Mass Spectrometer (QMS) is an instrument for measuring concentrations of atoms and molecules by separating atomic and molecular ions according to their mass-to-charge ratios (m/z). It consists primarily of an ion source, quadrupole mass filter (QMF) and detector. Generally, QMF resolution can be improved by increasing the number of rf cycles of the alternating electric field the ion experiences when passing through the mass filter. In order to improve the resolution, the dimensions of the QMF or the operating parameters are to be changed. However geometric modifications to improve performance increase the manufacturing cost and usually the size of the instrument. A low cost method to increase the resolution of a given QMS is the application of magnetic field to the mass filter. The work is mainly concerned with the performance of a QMS under the influence of magnetic field. Significant improvement in QMS performance was obtained under certain magnetic field conditions, and these have been explained in terms of our theoretical model developed in the University of Liverpool. The theoretical approach assumed in the model is that the QMF contains hyperbolic rods as electrodes and that the magnetic field acts over the full length of the mass filter assembly. This model is capable of accurate simulation of spectra allowing the user to specify different values of mass spectrometer dimensions and applied input signals. The model has been upgraded for better sensitivity, and to simulate the QMF at very high number of rf cycles. Simulation and experimental results were presented for different conditions. This work also demonstrates the modeling of mass spectra of gases using the theoretical model for stability zones 1 and 3. The performance of QMF operating in stability zones 1 and 3 has been derived and a relationship between maximum obtainable resolution and scan line is obtained.
4
Thomas, Benjamin. "Tandem time-of-flight mass spectrometry incorporating quadratic-field technology." Thesis, University of Warwick, 2000. http://wrap.warwick.ac.uk/66998/.
Full textAbstract:
The study involved the desig~ constructio~ optimisation and utilisation of a novel tandem time-of-flight (TOF-TOF) instrument. The instrument was designed to use a laser ion source capable of laser desorption or matrix-assisted laser desorption/ionisation. The instrument used a twin ion mirror geometry in which the first ion mirror was a single-stage ion mirror, while the second ion mirror was a quadratic-field ion mirror. The instrument was designed for highenergy (>10keV) collision-induced dissociation (CID). The initial design criteria of a tandem time-of-flight spectrometer are discussed. The design and construction of the vacuum chamber and pumping system are discussed. The design and construction of the laser ion source are covered in detail. Computer simulations of typical ion trajectories were calculated using the SIMION program. The design and construction of the steering optics, single-stage ion mirror and pulsed mass gate are discussed. Computer simulations of ion trajectories were used to characterise the ion optical properties of the system. Experiments to characterise the energy focusing properties and transmission of the single-stage ion mirror were conducted. The mass resolving power of the single-stage ion mirror were characterised. The single-stage ion mirror achieved a resolution of2000 full-width half-maximum (FWHM). The design and construction of the differentially pumped collision-cell and the quadratic-field ion mirror are outlined. Experiments to demonstrate the transmission of the collision-cell and quadratic-field ion mirror are discussed. Experiments to characterise the energy focusing properties of the quadratic-field ion mirror were conducted. The full instrument achieved precursor mass resolving powers of approximately 7000 (FWHM) for laser desorbed species and 3500 (FWHM) for MALDI generated peptide species. Initial CID results are presented. The study thoroughly discusses the problems with the current instrument configuration and goes on to propose solutions to the problems encountered.
5
Smith, Robert W. "An evaluation of miniaturised field asymmetric waveform ion mobility spectrometry hyphenated with time-of-flight mass spectrometry." Thesis, Loughborough University, 2014. https://dspace.lboro.ac.uk/2134/17837.
Full textAbstract:
In this thesis, the performance of a miniaturised field asymmetric waveform ion mobility spectrometry (FAIMS) device hyphenated with time-of-flight mass spectrometry is studied and evaluated for analysis of a variety of compounds in different sample matrices. FAIMS is a selective spectrometer which is highly orthogonal to mass spectrometry and has the potential for enhancing sensitivity and improve selectivity of rapid analyses. In Chapter 2, the performance of the miniaturised FAIMS device is tested for stability and transmission under a wide range of ion source conditions. An investigation of three different systems, including pairs of isobaric, isomeric and near-mass ions shows that miniaturised FAIMS has the ability to distinguish between analytes that are challenging to separate by mass spectrometry. Chapter 3 explores the effect of changing the composition of the carrier gas by observing the effect of adding gas modifiers on the FAIMS spectra of small molecules, peptides and proteins. Chapter 4 investigates the advantages of combining a fast FAIMS separation with mass spectrometry in the analysis of nitrogen-containing pharmaceutical impurities, where FAIMS is found to offer additional selectivity. In Chapter 5, the development of a UHPLC-FAIMS-MS method for the quantitative determination of a drug metabolite in urine is reported. UHPLC-FAIMS-MS shows improvements in signal-to noise and linear dynamic range as well as a reduction in chemical noise, demonstrating the potential of combining FAIMS with mass spectrometry.
6
Holmes, Colette Gail. "Field sampling and microcolumn preconcentration techniques in inductively coupled plasma spectrometry." Thesis, Sheffield Hallam University, 1996. http://shura.shu.ac.uk/19820/.
Full textAbstract:
This thesis is concerned with analytical studies on the trace analytes barium, cadmium, cobalt, chromium, copper, iron, manganese, nickel, lead, vanadium and zinc, present in high purity and highly complex matrices. The technique utilises activated alumina microcolumns in a flow injection (FI) system, to perform analyte enrichment and matrix removal. The analytes, after retention on the microcolumn are subsequently eluted and quantified by inductively coupled plasma-emission spectrometry (ICP-ES).Initial studies focus on trace analytes in caesium iodide, however a selection of the alkali metal salts, lithium nitrate, potassium bromide, sodium fluoride and sodium chloride, are investigated. New methodology for the ultratrace determination of high purity alkali metal salts is thus provided. The microcolumn enrichment technique with ICP-ES detection is robust, utilises limited sample handling and simultaneously preconcentrates and separates the analytes from matrix components. Hence possible matrix interferences are eliminated and limits of detection are significantly improved, in comparison to conventional ICP-ES analysis. A technique for the determination of the total content of eleven trace analytes present in natural waters (mineral, reservoir), using microcolumns of activated alumina in a FI-ICP-ES is investigated. The use of the complexing agent tartaric acid is shown to be effective in improving analyte retention. The procedure is successfully applied to determination of these analytes in a certified river water reference material (SLRS-1). Due to low retention and elution efficiencies, the total content of the analytes Fe and V present in Buxton, Redmires and Langsett samples could not be accurately determined by this technique. Activated alumina microcolumns are utilised as a new field sampling tools. Samples are collected in the field and processed through the alumina microcolumns for the effective retention of desired analytes. Hence, an alumina microcolumn sampling stage to effect concentration and isolation prior to analytical measurement is at the core of the investigation. The overall aim is to extend the application of alumina microcolumns, and in particular to provide a new multi-element field sampling device, which gives high sample integrity and preconcentration.
7
McGill, Colin Adam. "Studies of low-field nuclear magnetic resonance and Raman spectrometries for process analytical chemistry." Thesis, University of Strathclyde, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248282.
Full text
8
Murray, Jacolin Ann. "High Flow Air Sampling for Field Detection Using Gas Chromatography-Mass Spectrometry." BYU ScholarsArchive, 2010. https://scholarsarchive.byu.edu/etd/2414.
Full textAbstract:
The ability to rapidly detect and identify hazardous analytes in the field has become increasingly important. One of the most important analytical detection methods in the field is gas chromatography-mass spectrometry (GC-MS). In this work, a hand-portable GC-MS system is described that contains a miniature toroidal ion trap mass analyzer and a low thermal mass GC. The system is self-contained within the dimensions of 47 x 36 x 18 cm and weighs less than 13 kg. Because the instrument has a small footprint, it was used as the detector for an automated near-real-time permeation testing system. In permeation testing, materials that are used to make individual protective equipment such as gloves, masks, boots, and suits are exposed to hazardous analytes to determine how long the equipment can be worn safely. The system described herein could test five samples simultaneously. A multi-position valve rotated among the various sample streams and delivered time aliquots into the MS for quantitation. Current field air sampling techniques suffer from long desorption times, high pressure drops, artifact formation and water retention. These disadvantages can be avoided by concentrating the analytes in short open tubular traps containing thick films. There are several advantages to using polymer coated capillaries as traps, including fast desorption, inertness and low flow restriction. An air sampling trap was constructed utilizing open tubular traps for the concentration of semi-volatile organic compounds. The system consisted of multiple capillary traps bundled together, providing high sample flow rates. The analytes were desorbed from the multi-capillary bundle and refocused in a secondary trap. The simultaneous focusing and separation effect of a trap subjected to a negative temperature gradient was also explored. In this configuration, analytes were focused because the front of the peak was at a lower temperature than the rear of the peak and, hence, moved slower. In addition to the focusing effect, analytes with different volatilities focused at different temperatures within the gradient, allowing for separation.
9
Kuzema, P. O., M. Ya Dovzhyk, and O. S. Kuzema. "Main Stages of Development and Recent Advances of Mass Spectrometry." Thesis, Sumy State University, 2015. http://essuir.sumdu.edu.ua/handle/123456789/42625.
Full textAbstract:
It has been presented the review and analysis of the main evolution stages of one of the most efficient methods for investigation of composition and properties of substances – mass spectrometry. The advantages and application area of the method were described, as well as physical and technical peculiarities of the devices for its realization were considered.
10
Taylor, M. J. "Field desorption mass spectrometry applied to polymers and compounds relevant to their synthesis." Thesis, Swansea University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.639167.
Full textAbstract:
Early chapters contain (i) a comprehensive survey of the techniques conception, development and reported applications of relevance, (ii) classical and the most recent theoretical treatment of the complex behaviour manifest in the FD mass spectrum, and (iii) a thorough description of the sophisticated instrumentation and experimental procedures which were used in these studies and facilitated a renaissance in the utility of FDMS. The versatility and utility of FDMS was rigorously tested, using an intimidating array of often novel compound classes covering a wide range of molecular weights and chemical functionality. Compounds studied included; organophosphazenes, alkyphenol-formaldehyde resins, liquid crystal monomers, phthalocyanines, various aliphatic and aromatic polymers and polymer additives. Comparisons have been made throughout the studies with other ionisation techniques to establish the most appropriate ionisation method for successful structural characterisation. The ability of FDMS to yield abundant molecular weight information has been explored in depth and the concomitant advantages and disadvantages of this behaviour have been assessed in context. Where necessary complementary spectroscopic and mass spectrometric information was obtained, used to assist in structural characterisation and demonstrated the benefits of adopting a multi-technique approach. The influence of compound class upon the inherent technical features of the technique, which include: ionisation efficiency; reproducibility; ionisation mechanisms; fragmentation; sample preparation; and experimental adaptations are presented and extended to tandem mass spectrometry. Collision-induced dissociation (CID) offered the means to obtain structural detail generally precluded by the low internal energy of the so-called field desorbed ions. These investigations have established that from being considered a somewhat esoteric analytical method, FDMS is a sophisticated yet routine analytical tool when used with the power of the modern mass spectrometer. Its utility is not confined to the mass spectrometric fraternity but extends to a much wider industrial community including a variety of research chemists and affiliated spectroscopic groups.
11
Zhao, Hongyan. "Development and application of high-field asymmetric waveform ion mobility spectrometry and mass spectrometry for the investigation of fibroblast growth factor signalling." Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/7022/.
Full textAbstract:
The deregulation of FGF signalling is closely linked to many human diseases, including cancer. Through phosphorylation and dephosphorylation processes, FGF signalling is finely controlled. The thesis presented focuses on applying mass spectrometry tools to investigate FGF signalling using the breast carcinoma SUM52 cell line. High-Field Asymmetric Waveform Ion Mobility Spectrometry (FAlMS) is a technique that separates and focuses ions at atmospheric pressure. It has been demonstrated the application of LC-FAIMS-MS/MS results in increased signal-to-noise ratios and improved dynamic range in analysis of complex proteomics samples. The LC-FAIMS-MS /MS method for large-scale quantitative analysis was optimized and the performance of LC-MS/MS and LC-FAIMS-MS/MS was compared. Results showed the two techniques shared good complementarity. The incorporation of FAIMS resulted in an increase of novel phosphosites and multiply-phosphorylated peptides. Next, a modified FAlMS interface was evaluated for proteomic analyses. This novel FA IMS device exhibited potential in enhancing proteomic analysis showing an increase in peak capacity and proteome coverage and a lower level of redundancy. Next, SRM was applied for accurate quantitation of75 phosphopeptides in a time-resolved way. The data revealed that these phosphorylation sites showed different associations with FGFJ stimulation. Expression patterns were clustered into early, mid- and late stage response.
12
Bolton, David Robert. "Circuits and systems for CW and pulsed high-field electron spin resonance." Thesis, University of St Andrews, 2006. http://hdl.handle.net/10023/7104.
Full textAbstract:
This thesis is concerned with the design and realisation of components for a new state of the art 94GHz Electron Spin Resonance (ESR) spectrometer capable of operating in both pulsed and CW modes. The complete spectrometer is designed to provide phase coherent 1kW peak power sub-nanosecond π/2 pulses having variable duration and repetition rate. The mm-wave response of a paramagnetic sample to these pulses is detected with a superheterodyne detector. Such a system would offer a step change in performance, promising unprecedented resolution and sensitivity. These aims should be compared with the performance of commercial (Bruker) instruments capable of delivering 200mW 30ns π/2 pulses. For this type of system, both the long term (thermal) and short term (phase) stability of oscillators and sources employed are extremely important. Consideration of phase noise, frequency, tunability and power output shows that multiplied sources offer substantial benefits compared to fundamental sources. A delay line discriminator method of phase noise measurement, suitable for use with the low frequency oscillators is described and implemented. This is extended to 94GHz using a down convertor with a quasi-optically stabilised Gunn oscillator. These tools are used to select an optimum oscillator-multiplier combination to produce a low noise 94GHz source. Anew method of pulse generation, which has produced +23dBm peak power 250ps rectangular and 115ps Gaussian envelope phase coherent pulses, is described. These are believed to be the shortest phase coherent pulses at 94GHz available. This system will be used to provide ns pulses suitable for amplification to 1kW using a Klystron amplifier. A heterodyne detector has been constructed which employs the same oscillator/multiplier techniques identified above to produce the required local oscillator signal. It is demonstrated that by careful consideration of multiplication factors a system employing one variable and one fixed oscillator allows all the signals required in the spectrometer to maintain phase coherence. It is demonstrated that the complete demodulator responds to pulses on a ns time scale and has a noise temperature of 737K.
13
Bekker, Dmitriy L. "Hardware and software optimization of Fourier transform infrared spectrometry on hybrid-FPGAs /." Online version of thesis, 2007. http://hdl.handle.net/1850/4805.
Full text
14
Wu, Alex Ching-Hong. "Fundamentals and applications of high-field asymmetric waveform ion mobility spectrometry for the analysis of explosives." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0024838.
Full text
15
Gagnon, Joel Edward. "Genesis of hydrothermal high field strength element mineral deposits : evidence from laser ablation--inductively coupled plasma mass spectrometry." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=100367.
Full textAbstract:
High field strength elements (HFSE) are geologically and economically important. These elements were once thought to be immobile during metasomatic processes, however, a growing body of empirical evidence indicates that HFSE can be mobilized under certain conditions. Despite this evidence, little is known about the factors controlling solubility, transport and deposition of HFSE by aqueous fluids, apart from some theoretical estimates and rare experimental studies. Therefore, the study of natural systems (e.g., HFSE ore deposits) provides an excellent opportunity to evaluate HFSE mobility by aqueous fluids. Five localities where evidence of hydrothermal transport of HFSE has been previously documented were included in this study: Gallinas Mountains, New Mexico; South Platte, Colorado; Rock Canyon Creek, British Columbia; St. Lawrence, Newfoundland; and Strange Lake, Quebec/Labrador. Minerals and, in the case of South Platte, fluid inclusions from these localities were analyzed using petrography and laser ablation inductively-coupled plasma mass spectrometry (LA-ICPMS) to evaluate the source of the HFSE and the hydrothermal fluids responsible for HFSE transport, and factors controlling HFSE and gangue mineral (e.g., fluorite, quartz) precipitation. Analysis of some of the important gangue minerals, which are also the primary host of fluid inclusions in many of these deposits (e.g., fluorite), is difficult using 266 nm Nd:YAG-based LA-ICPMS. Furthermore, complex mineral intergrowths and the desire to quantify the chemical composition of unknown minerals required the development of analytical and data reduction protocols for LA-ICPMS. Methods for conducting traversed opening of fluid inclusions, removing the host mineral contribution to fluid inclusion signals by calculating count rate ratios, and quantifying the composition of minerals without using an internal standard are presented. In general, hydrothermal enrichment of HFSE in these deposits appears to have resulted from interaction of an HFSE- and F-bearing magmatic fluid with another, Ca-bearing fluid or with Ca-bearing wall rocks or preexisting minerals. In most cases, HFSE appear to be derived locally, within the associated igneous intrusion.
16
McCulloch, Ross David. "Development and characterization of a next generation, field-free atmospheric pressure photoionization (APPI) source for liquid chromatography-mass spectrometry." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44441.
Full text
17
Zhai, Lailiang. "Gas Chromatography: Mass Spectrometry of Chemical Agents and Related Interferents." Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1266.pdf.
Full text
18
Conner, Laura. "Evaluation of field sampling and analysis methods for fire investigation including electronic noses and adsorption sampling/gas chromatography mass spectrometry." FIU Digital Commons, 2005. http://digitalcommons.fiu.edu/etd/2422.
Full textAbstract:
This study evaluates the use of commercially available instruments for locating and collecting accelerants in the field. Electronic noses can be used to scan a fire scene for the possible presence of an accelerant. The TLV Sniffer® was found to be able to detect accelerants at low levels but did alert to some burned matrix alone. When subjected to a proficiency test designed for canines, the TLV Sniffer® was able to locate accelerants in two of the three tests. The tpi®Pocket was found not to be sensitive or selective enough to be useful in locating accelerants. Once the location of possible accelerants has been determined, they can be collected by dynamic headspace sampling in the field with the Portable Arson Sampler (PAS). The PAS was found to be able to collect a broad range of compounds from ignitable liquids and had comparable efficiency to a conventional method.
19
Bohinski, Timothy Blaise. "STRONG FIELD MOLECULAR IONIZATION: CONTROLLED DISSOCIATION IN RADICAL CATIONS WITH DYNAMIC RESONANCES AND ADIABATICALLY PREPARED LAUNCH STATES." Diss., Temple University Libraries, 2015. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/310686.
Full textAbstract:
ChemistryPh.D.
This dissertation investigates the electronic spectroscopy of a series of alkyl phenyl ketone radical cations and the dynamics of selective launch states in the strong field regime with tunable near infrared ultrashort laser pulses from 790 nm - 1550 nm coupled to mass spectrometric detection. Our method relies on tunable strong field laser pulses in the range from 1150 nm - 1550 nm to adiabatically ioinized gas phase molecules and prepare ions in the ground ionic state that serve as a launch state for future excitation and control. Adiabatic ionization is capable of transferring little energy to the molecule and producing a majority of a parent molecular ion in comparison to nonadiabatic ionization wherein multiple ionic states can be populated with an accompanying high degree of molecular fragmentation. We measure a dynamic resonance in the low lying electronic states of the acetopheone radical cation via preparation of a launch state with adiabatic ionization followed by a one photon transition within a single pulse duration which facilitates bond dissociation to produce the benzoyl ion. Experiments on acetophenone homologues and derivatives elucidate the structural dependence of the electronic resonance and supporting ab initio calculations identify the dynamic resonance along the molecular torsional coordinate between the ground ionic state, D0, and second excited state, D2. Post ionization excitation within the pulse duration transfers the ground state wavepacket to the D2 surface where the wavepacket encounters a three state conical intersection that facilitates the preferred bond dissociation. Time resolved photodissociation experiments measure the dynamics of the launch state, large amplitude oscillations and extended coherence times support the notion that adiabatic ionization populates a majority of the ground ionic surface. Control of the dissociation products is initiated from the launch state by varying the pump wavelength and probe intensity. Elimination of the D0 wavepacket with a 1370 nm reveals additional secondary dynamics that are attributed to wavepacket motion on the D2 surface. Finally, the effect of para substitution on the acetophenone radical cation is explored as a strategy to control the launch state wavepacket dynamics. Suppresion of the wavepacket dynamics are observed with the addition of alkoxy groups whereas extended coherence of the launch state dynamics approaching ~5 ps is observed upon trifluoromethyl substitution. A possible mechanism for the extended coherenece based on coupled torsional rotors is proposed.
Temple University--Theses
20
Alberti, James Joseph. "Fatty Acid Biomarker Detection for Breast Cancer Using Differential Mobility Spectrometry with Non-Radioactive Ion Source." Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/6611.
Full textAbstract:
Differential Mobility Spectrometry (DMS) using a non-radioactive ion source (NRIS) is investigated as a possible medical diagnostic instrument for near real-time detection of breast cancer biomarkers. In previous clinical studies, concentrations of Linoleic, Palmitic and Stearic fatty acids have been observed at different levels in women with carcinoma breast cancer versus women with benign tumors or healthy women showing no signs of breast cancer. Present diagnostic methods require a biopsy of the suspect tissue and a microscopic lab analysis performed to determine its disease state. This process can take hours or days before the patient and doctor are informed of the results. Controlled volumetric samples of each fatty acid listed above were introduced into a DMS instrument, using a NRIS, to determine detectability of each acid. The results provide proof-of-concept that Linoleic, Palmitic and Stearic fatty acids can be uniquely identified by varying the sample temperature and scanning the ionized fatty acid molecules in both the negative and positive ion mode of the DMS instrument. Detection response times range from 2 to 6 seconds for initial detection up to 35 seconds for peak detection. The Limit of Detection for the DMS instrument is estimated in the low parts per billion.
21
Reid, Joy Emily. "The development and geological application of a whole rock-LA-ICP-MS technique for the determination of high field strength elements." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0004/MQ42434.pdf.
Full text
22
Ghalaieny, Mohamed. "Lab and field studies of the kinetics and composition of atmospheric reactive nitrogen and volatile organic compounds." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/lab-and-field-studies-of-the-kinetics-and-composition-of-atmospheric-reactive-nitrogen-and-volatile-organic-compounds(14561aed-da23-44e8-8819-c752f0f9613d).html.
Full textAbstract:
Accurate measurements of ammonia, nitric acid and formic acid are important for achieving a complete understanding of their atmospheric role. Models and measurements of formic acid in the atmosphere continue to show disagreements. Also, the contributions of NMHCs and reactive nitrogen (HNO3 and NH3) to organic and inorganic aerosol formation are important to quantify as gaps in the knowledge of atmospheric aerosols are a source of uncertainty in climate science. In this thesis, concentrations of ammonia were measured in the atmosphere and the production of formic acid from the ozonolysis of isoprene was measured in the EXTRA (EXTreme RAnge) chamber. Both gases were studied using chemical ionisation mass spectrometry (CIMS). The kinetics of the reactions of sesquiterpenes and terminal alkenes with ozone were studied in theEXTRA chamber using the relative rates technique and GC-FID. The ozonolysis rate coefficients of a homologous series of terminal alkenes were measured at elevated temperatures and found to be invariant with the carbon number. This led to the conclusion that previous measurements of these rate coefficients were subject to experimental artefacts. The elevated temperature protocol was employed to study the ozonolysis of sesquiterpenes, leading to revisions in ko3 for β-caryophyllene and α-humulene of 3 orders of magnitude. It was thus concluded that ozonolysis only accounts for 9-15% of sesquiterpeneoxidation in the atmosphere. A field intercomparison of CIMS for measuring ammonia was conducted wherein CIMS was found to perform well alongside instruments of comparable time response and limits of detection. This thesis also characterised inlet materials used in atmospheric measurements in the first systematic study on the uptake onto inlet walls in a flow tube system coupled to CIMS. It was found that PFA is the preferable material for atmospheric measurements, both for its kinetic qualities and its ready availability and ease of use. Finally, CIMS was used to measure the yield of formic acid from isoprene ozonolysis as a function of relative humidity. Formic acid yield was found to increase between 0-40% RH to a maximum of 0.18. Using the measured formic acid yields in a global chemistry model leads to an estimate that formic acid production from isoprene ozonolysis is ~9.5 Tg yr-1.
23
Peterson, Zlatuse Durda. "Analysis of Clinically Important Compounds Using Electrophoretic Separation Techniques Coupled to Time-of-Flight Mass Spectrometry." BYU ScholarsArchive, 2004. https://scholarsarchive.byu.edu/etd/23.
Full textAbstract:
Capillary electrophoretic (CE) separations were successfully coupled to time-of-flight mass spectrometric (TOFMS) detection for the analysis of three families of biological compounds that act as mediators and/or indicators of disease, namely, catecholamines (dopamine, epinephrine, norepinephrine) and their O-methoxylated metabolites (3-methoxytyramine, norepinephrine, and normetanephrine), indolamines (serotonin, tryptophan, and 5-hydroxytryptophan), and angiotensin peptides. While electrophoretic separation techniques provided high separation efficiency, mass spectrometric detection afforded specificity unsurpassed by other types of detectors. Both catecholamines and indolamines are present in body fluids at concentrations that make it possible for them to be determined by capillary zone electrophoresis coupled to TOFMS without employing any preconcentration scheme beyond sample work up by solid phase extraction (SPE). Using this hyphenated approach, submicromolar levels of catecholamines and metanephrines in normal human urine and indolamines in human plasma were detected after the removal of the analytes from their biological matrices and after preconcentration by SPE on mixed mode cation-exchange sorbents. The CE-TOFMS and SPE methods were individualized for each group of compounds. While catecholamines and metanephrines in urine samples were quantitated using 3,4-dihydroxybenzylamine as an internal standard, deuterated isotopes, considered ideal internal standards, were used for the quantitation of indolamines. Because the angiotensin peptides are present in biological fluids at much lower concentrations than the previous two families of analytes, their analysis required the application of additional preconcentration techniques. In this work, the coupling of either of two types of electrophoretic preconcentration methods - field amplified injection (FAI) and isotachophoresis (ITP) - to capillary zone electrophoresis with both UV and MS detection was evaluated. Using FAI-CE-UV, angiotensins were detected at ~1 nM concentrations. Using similar conditions but TOFMS detection, the detection limits were below 10 nM. ITP was evaluated in both single-column and two-column comprehensive arrangements. The detection limits achieved for the ITP-based techniques were approximately one order of magnitude higher than for the FAI-based preconcentration. While the potential usefulness of these techniques was demonstrated using angiotensins standards, substantial additional research would be required to allow these approaches to be applied to plasma as part of clinical assays.
24
Parrish, Douglas K. "Application of solid phase microextraction with gas chromatography-mass spectrometry as a rapid, reliable, and safe method for field sampling and analysis of chemical warfare agent precursors /." Download the dissertation in PDF, 2005. http://www.lrc.usuhs.mil/dissertations/pdf/Parrish2005.pdf.
Full text
25
Paudel, Liladhar. "High Field 1H Nuclear Magnetic Resonance (NMR) Spectroscopy Based Metabolomics and Complex Mixture Analysis by Multidimensional NMR and Liquid Chromatography-Mass Spectrometry (LC-MS)." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1343403647.
Full text
26
McDonald, Shannon Scott. "Characterization and optimization of a high surface area-solid phase microextraction sampler for the collection of trace level volatile organic compounds in the field /." Download the thesis in PDF, 2006. http://www.lrc.usuhs.mil/dissertations/pdf/McDonald2006.pdf.
Full text
27
Sales, Martínez Carlos. "Development of advanced analytical methodologies based on gas chromatography coupled to mass spectometry for the determination of pops and vocs in the food and environmental field." Doctoral thesis, Universitat Jaume I, 2019. http://hdl.handle.net/10803/668939.
Full textAbstract:
The work in this thesis has been clearly divided into three parts:
In the first part, efforts were directed to obtaining a trace level quantification method for halogenated flame retardants using high-volume injections and gas chromatography coupled to GC-MS/MS tandem mass spectrometry.
In the second part, the potential of the GC-MS / MS technique was evaluated together with the new atmospheric pressure chemical ionization source (APCI) for the quantification of PBDEs, NBFRs (including hexabromocyclododecane (HBCD)) and DL-PCBs at trace levels in food and environmental samples.
In the third part, two untargeted analytical methodologies by GC-MS were developed as complementary tools to the PANEL TEST for the classification of olive oil samples according to their quality.El trabajo en la presente tesis se ha dividido claramente en tres partes: En la primera parte, los esfuerzos se dirigieron a la obtención de un método de cuantificación a nivel de trazas para retardantes de llama halogenados utilizando inyecciones de gran volumen y cromatografía de gases acoplada a espectrometría de masas en tándem GC-MS/MS. En la segunda parte, se evaluó el potencial de la técnica GC-MS/MS junto con la nueva fuente de ionización química a presión atmosférica (APCI) para la cuantificación de PBDEs, NBFRs (incluido el hexabromociclododecano (HBCD)) y DL-PCBs a niveles de traza en alimentos y muestras ambientales. En la tercera parte, se desarrollaron dos metodologías de análisis no dirigido por GC-MS como herramientas complementarias de la PRUEBA DE PANEL para la clasificación del aceite de oliva de acuerdo a su calidad.
28
Chau, Thoi-Dai. "Réactions chimiques sur surfaces de platine et d'or à l'échelle atomique: approche théorique et expérimentale." Doctoral thesis, Universite Libre de Bruxelles, 2004. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/211119.
Full textAbstract:
Dans ce travail nous avons étudié des réactions chimiques sur la surface de deux métaux :le platine et l'or, en utilisant la microscopie ionique à effet de champ électrique (FIM) et la spectrométrie de masse de désorption par champ pulsé (PFDMS). En complément de ces données expérimentales, nous apportons des résultats obtenus par la théorie de la fonctionnelle de la densité (DFT). La taille et la morphologie de nos échantillons font qu’ils sont de bons modèles de grains de phase active dans un catalyseur réel.\
Doctorat en sciences, Spécialisation chimie
info:eu-repo/semantics/nonPublished
29
Al, Manasfi Rayana. "Uptake of organic micropollutants by vegetable crops irrigated by reclaimed wastewater : Analytical developments to conduct field studies." Thesis, Montpellier, 2020. http://www.theses.fr/2020MONTG037.
Full textAbstract:
L'utilisation des eaux usées dans l’agriculture à des fins d'irrigation et de fertilisation n'est pas une pratique récente. Cependant, au cours de ces deux dernières décennies, cette pratique a suscité un intérêt croissant au regard des risques potentiels qu’elle représente pour la santé humaine. Outre les nutriments utiles et la matière organique que ces eaux introduisent dans les terres agricoles, des produits pharmaceutiques (PhACs) et d’autres micropolluants organiques sont également co-introduits, conduisant à la présence de composés chimiques indésirables dans les agroécosystèmes, plus remarquablement dans les cultures destinées à la consommation humaine. Des efforts incroyables ont été faits au cours des deux dernières décennies pour analyser ces contaminants dans des échantillons environnementaux, mais il y a encore un manque de méthodes analytiques robustes pour l'extraction et la quantification des multiples micropolluants organiques présents dans des matrices complexes comme les sols et les végétaux, et un manque de connaissances concernant leur devenir dans les agroécosystèmes. Dans ce contexte, le premier objectif de cette thèse est de développer des méthodologies analytiques robustes pour analyser de nombreux micropolluants organiques présents dans les eaux usées, particulièrement les PhACs et leurs métabolites dans le sol et les racines/feuilles de laitue et poireau. Ces méthodes sont basées sur QuEChERS suivies d'une détection par LC-HRMS-QTOF. Des bons taux de récupérations ont été obtenus pour les 48 composés étudiés dans toutes les matrices (en général entre 80 et 120% pour la plupart des composés). La comparaison des deux modes d'acquisition récemment développés, high-resolution multiple reaction monitoring et Sequential Window Acquisition of All Theoretical Fragment-Ion Spectra ont donné des résultats similaires, bien que la MRMHR ait donné des résultats plus cohérents pour la plupart des composés. Enfin, des limites de détection et de quantification satisfaisantes ont été obtenues pour les 3 matrices (par exemple, 0,01 à 0,12 ng/g et 0,04 à 0,38 ng/g poids sec ont été obtenus par les feuilles de laitue, respectivement)L'objectif suivant consiste à appliquer ces méthodologies analytiques pour suivre le comportement et devenir de certains micropolluants sur un champ agricole irrigué avec des eaux usées domestiques traitées. Le deuxième objectif nous a donc permis de comprendre leur distribution dans le sol et les cultures en calculant des facteurs de bioconcentration, en discriminant leur dégradation dans le sol à celle dans les plantes, ceci afin d'évaluer le risque potentiel pour la consommation humaine de végétaux irrigués avec des eaux usées traitées. Deux années successives de culture de laitue et poireau sous serre ont été mises en œuvre, et irrigués goutte à goutte avec différents types d'eau, principalement les eaux usées domestiques traitées. Une faible accumulation dans le sol et les végétaux a été constatée, ce qui s'explique par leur dégradation intensive dans le sol et la plante. Quelques métabolites ont été détectés dans les feuilles de laitue, en particulier la carbamazépine-époxyde issue du métabolisme de la carbamazépine par la plante. Enfin, cette étude a révélé un risque minimum pour la santé humaine lié à la consommation de légumes crus irrigués avec des eaux usées traitées. Le dernier objectif est d'étudier le devenir de certains contaminants introduits dans le sol par l'irrigation des eaux usées, lorsqu'ils sont exposés aux champignons filamenteux du genre Trichoderma omniprésents dans le sol. Des expériences mises en œuvre en milieu liquide ont révélé pour la première fois une capacité importante des espèces de Trichoderma (T. harzanium et T. asperellum) à dégrader deux antibiotiques (ciprofloxacine et ofloxacine) et un fongicide (climazole). Tout aussi important, de nouveaux métabolites de l'ofloxacine et du climbazole ont été identifiés pour la première foisThe use of wastewater in agricultural sector for irrigation and fertilization purposes is not a recent practice. However, until the past couple decades this practice has been of increasing interest regarding the global safety, particularly human health. Besides to the useful nutrients and organic matter that wastewater introduces to the agricultural lands, pharmaceutical active compounds (PhACs) and other organic micropollutants are also co-introduced leading to the presence of undesired chemicals in agroecosystems, most remarkably in crops intended for human consumption. Incredible effort has been made in last couple decades to analyze such contaminants in environmental samples, yet there is still a lack of robust analytical methods for the extraction and quantification of a large number of PhACs and other wastewater pollutants, and a lack of knowledge regarding their fate and behavior in the entire agroecosystem including soil and crops.In this context, the first objective of this thesis was to develop robust and sensitive analytical methodologies specific to soil and crops matrices (e.g., root and leave) to analyze a large number of wastewater organic contaminants mainly PhACs and their metabolites. QuEChERS-based methods followed by detection and quantification on high-resolution mass spectrometry were successfully developed for soil, lettuce/leek root and lettuce/leek leaves. Good recoveries were obtained for the 48 studied compounds in all matrices (in general between 80 and 120 % for most of the compounds). Detection and quantification of compounds was performed on a high-resolution mass spectrometry on quadrupole-time of flight (Q-TOF) coupled to liquid chromatography provided from SCIEX technology. Comparing the two recently developed acquisition modes high-resolution multiple reaction monitoring (MRMHR) and Sequential Window Acquisition of All Theoretical Fragment-Ion Spectra (SWATH) gave similar results, though MRMHR gave more consistent results for most of the compounds. Finally, satisfying detection and quantification limits were obtained for all 3 matrices, for instance lettuce leaves matrix in MRMHR acquisition gave detection limits ranging from 0.01 to 0.12 ng/g and quantification limits ranging from 0.04 to 0.38 ng/g dry weight (d.w).Later, the following objective was to apply these methodologies on real agricultural field irrigated with local treated domestic wastewater. The second objective allowed us to understand the distribution of selected contaminants in soil and crops and calculate their bioconcentration factors, to discriminate their degradation in soil and crops, and finally to assess the potential risk for human consumption of wastewater irrigated crops. Two years of successive growth cycles of lettuce and leek under greenhouse field conditions were successfully implemented. Different kinds of water were used for irrigation mainly domestic treated wastewater, following real drip irrigation conditions. Little accumulation in soil and crops was found, which was explained by the intensive degradation of contaminants in soil and metabolism in crops. A few metabolites were detected in lettuce leaves, particularly carbamazepine-epoxide which was produced by the lettuce metabolism. Finally, this study revealed a de minimis human health risk related to the consumption of raw vegetable irrigated with treated wastewater.The last objective was to study the fate of selected contaminants introduced in soil by wastewater irrigation, when they are exposed to the ubiquitous filamentous soil fungi Trichoderma. Implemented experiments in liquid medium revealed for the first time an important ability of Trichoderma species, namely T. harzanium and T. asperellum to degrade two fluoroquinolones antibiotics (ciprofloxacin and ofloxacin), and one fungicide (climbazole). Equally important, new metabolites of ofloxacin and climbazole were tentatively identified in this study for the first time
30
Green, P., Ngozi G. Anyakoha, I. Gispan-Herman, G. Yadid, and Anna Nicolaou. "Arachidonic acid-containing phosphatidylcholine species are increased in selected brain regions of a depressive animal model: implications for pathophysiology." Elsevier, 2009. http://hdl.handle.net/10454/4584.
Full textAbstract:
noThe Flinders Sensitive Line (FSL) rat is a genetic animal model of depression. Following recent findings that the brain fatty acid composition of FSL is characterised by increased arachidonic acid (AA), we used electrospray tandem mass spectrometry and 1H-NMR to examine lipid species in different brain areas. Cholesterol and sphingolipids were increased in the hypothalamus of the FSL rats. Furthermore, arachidonic acid-containing phosphatidylcholine species (AA-PC) were elevated with PC16:0/20:4, PC18:1/20:4 and PC18:0/20:4 (p<0.003) increased in the hypothalamus and striatum. In contrast, there was a decrease in some docosahexaenoic acid (DHA)-containing species, specifically PC18:1/22:6 (p<0.003) in the striatum and PE18:1/22:6 (p<0.004) in the prefrontal cortex. Since no significant differences were observed in the erythrocyte fatty acid concentrations, dietary or environmental causes for these observations are unlikely. The increase in AA-PC species which in this animal model may be associated with altered neuropathy target esterase activity, an enzyme involved in membrane PC homeostasis, may contribute to the depressive phenotype of the FSL rats.
31
Le, Galudec Joël. "lmagerie hyperspectrale infrarouge pour l'identification sans marquage de pathogènes sur milieu gélosé." Thesis, Université Grenoble Alpes, 2022. http://www.theses.fr/2022GRALS006.
Full textAbstract:
L’industrie et le domaine de la santé sont demandeurs de moyens rapides et peu couteux pour l’identification de microorganismes. Des avantages pratiques et un coût réduit font de la culture en boite de Petri un outil omniprésent en microbiologie, mais l’observation des colonies microbiennes n’offre pas de diagnostic fiable sans validation par une analyse secondaire. Ces analyses, qu’il s’agisse de réactions chimiques, d’une PCR ou de spectrométrie de masse, demandent une préparation d’échantillon spécifique impliquant des coûts et des délais supplémentaires. C’est pourquoi plusieurs systèmes d’imagerie de boite ont déjà été expérimentés pour automatiser l’observation des cultures et proposer une identification directement sur la boite de Petri. Toutefois, ceux-ci se cantonnent jusqu’à présent au domaine du visible et du proche infrarouge (400 – 1000 nm), ce qui n’apporte des informations que sur le morphotype des colonies de micro-organismes et limite la précision d’identification.Cette thèse est consacrée à l’exploration d’un système d’imagerie multispectrale dans l’infrarouge moyen. Cette gamme de longueurs d’onde apporte des informations à la fois sur le morphotype et sur la composition chimique des colonies observées. Cette imagerie non destructive et sans marquage pourrait fournir une identification à l’espèce des colonies cultivées sur agar, tout en ouvrant la voie à de nouvelles applications. Un système expérimental, combinant des lasers à cascade quantique comme source lumineuse et une matrice de microbolomètres comme imageur, a permis l’acquisition d’images de colonies à neuf longueurs d’ondes comprises entre 5 et 8 µm. 2253 colonies appartenant à huit espèces de microorganismes communs ont ainsi été imagées. Pour l’une des espèces, Staphylococcus epidermidis, trois souches différentes ont été analysées pour tester la capacité du système en matière de typage.Après acquisition, plusieurs méthodes de classification d’image ont été testées pour aboutir à un taux d’identification correct moyen de 94.4 %Industry and health care are demanding rapid and inexpensive means for microbial identification. Thanks to its low cost and practical advantages, Petri dish culture is a ubiquitous tool in microbiology, but the sole observation of microbial colonies does not offer a reliable diagnosis. Identification in itself depends on secondary analysis, such as chemical reactions, PCR or mass spectrometry, which require specific sample preparation, which involves additional costs and delays. That is why several dish imaging systems have already been tested to automate the observation of cultures and to propose an identification directly on the Petri dish. However, these systems are generally limited to the visible and near infrared range (400 - 1000 nm), which only provides information on the morphotype of the microorganism colonies and therefore limits the identification accuracy.This thesis focuses on the development of a multispectral imaging system in the mid-infrared. In this wavelength range, images provide information on both the morphotype and the chemical composition of the observed colonies. This non-destructive and label-free imaging could provide species identification of colonies grown on agar, while opening the way to new applications. An experimental system, combining quantum cascade lasers as a light source and a microbolometers array as an imager, allowed the acquisition of images of colonies at nine wavelengths between 5 and 8 µm. 2253 colonies belonging to eight species of common microorganisms were imaged. For one of the species, Staphylococcus epidermidis, three different strains were analyzed to test the typing capabilities of the system.After acquisition, several image classification methods were tested to obtain an average correct identification rate of 94.4%
32
Le, Breton Michael Robert. "Airborne measurements of trace gases using a Chemical Ionisation Mass Spectrometer (CIMS) onboard the FAAM BAe-146 research aircraft." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/airborne-measurements-of-trace-gases-using-a-chemical-ionisation-mass-spectrometer-cims-onboard-the-faam-bae146-research-aircraft(84308915-6dae-46d8-acb6-f189683e3e6d).html.
Full textAbstract:
A chemical ionisation mass spectrometer (CIMS) was developed and utilised for measurements onboard the Facility for Atmospheric Airborne Measurements (FAAM) BAe-146 aircraft. The I- ionisation scheme was implemented to detect nitric acid (HNO3), formic acid (HC(O)OH), hydrogen cyanide (HCN) and dinitrogen pentoxide (N2O5) simultaneously at a sampling frequency of 1 Hz. Sensitivities ranged from 35±6 ion counts pptv-1 s-1 for HC(O)OH to 4±0.9 ion counts pptv-1 s-1 for HCN and limits of detection from 37 ppt for HNO3 and 5 ppt for HCN. Trace gas concentrations of species such as HC(O)OH are currently under predicted in global models. In order to understand their role in controlling air quality, it is crucial that their production pathways and abundance are accurately measured and constrained. To date, airborne measurements of these trace gases have been difficult as a result of instrumental limitations on an aircraft such as limit of detection and sampling frequency. The first UK airborne measurements of HC(O)OH and HNO3 confirmed that HC(O)OH is under predicted by up to a factor of 2 in a trajectory model that implements the full Master Chemical Mechanism (MCM) and Common Representative Intermediate Scheme (CRI). The inclusion of a primary vehicle source enabled the model to reproduce the concentrations observed; verifying that direct sources are under represented. Secondary formation of HC(O)OH was observed through its correlation with HNO3 and ozone (O3), indicating a strong photochemical production source. Hydroxyl (OH) concentrations were estimated for the first time in a flight around the UK using the HC(O)OH and HNO3 measurements. A biomass burning (BB) plume identification technique is applied to data obtained from Canadian biomass fires using HCN as a marker. A 6 sigma above background approach to defining a plume resulted in a higher R2 correlating value for the normalised excess mixing ratio (NEMR) to carbon monoxide (CO) when compared to current methods in the literature. The NEMR obtained from this work; 3.76±0.02 pptv ppbv-1, lies within the range found in the literature. This NEMR is then used to calculate a global emission total for HCN of 0.92 Tg (N) yr-1 when incorporated into the global tropospheric model STOCHEM CRI. The first direct N2O5 airborne measurements on an aircraft at night are compared to indirect measurements taken by a broadband cavity enhancement absorption spectrometer. An average R2 correlation coefficient of 0.87 observed over 8 flights for 1 Hz measurements indicates the selectiveness of the I- ionisation scheme to detect N2O5 directly, without nitrate (NO3) interference.
33
Rösch, Tobias [Verfasser]. "Filling the gap in environmental analysis : enrichment of ionizable micropollutants by electromembrane extraction or field-step electrophoresis and their analysis by capillary electrophoresis and liquid chromatography mass spectrometry for (non-)target screening / Tobias Rösch." Tübingen : Universitätsbibliothek Tübingen, 2022. http://d-nb.info/1240673264/34.
Full text
34
Brenac, Ariel. "Développements instrumentaux pour la photoémission inverse." Grenoble 1, 1987. http://www.theses.fr/1987GRE10010.
Full textAbstract:
Canon a electron fournissant un faisceau dans la gamme 5 ev-50 ev: resolution en vecteur d'onde de 0,2 a**(-1), courant maximal de 25 microamperes a 20 ev. Les spectres de photoemission inverse resolue angulairement presentent des effets angulaires a 30 ev. A 10 ev les effets angulaires devraient etre plus marques mais de faible rendement du spectrometre a cette energie rend les experiences difficiles. Caracterisation de nouvelles sources d'electrons: electrons emis par effet du champ par une cathode comprenant un grand nombre de micropointes. Ces cathodes fonctionnent a basse temperature. Description du spectrometre uv du vide et de la multidetection des photons
35
Agbonkonkon, Nosa. "Counter-flow Ion Mobility Analysis: Design, Instrumentation, and Characterization." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd2136.pdf.
Full text
36
Manea, Vladimir. "Penning-trap mass measurements of exotic rubidium and gold isotopes for a mean-field study of pairing and quadrupole correlations." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112246/document.
Full textAbstract:
Les noyaux les plus complexes sont situés entre les nombres magiques et les médianes des espaces de valence, dans des régions connues pour les changements abrupts des observables nucléaires. Dans ces régions appelées de transition de forme, le paradigme nucléaire change entre la goutte liquide vibrationnelle et le rotor statique. Sauf quelques exceptions, les noyaux de ces régions sont radioactifs, avec des demi-vies qui chutent dans les millisecondes. Complémentaires aux propriétés des états excités à basse énergie, les énergies de liaison et les rayons de charge nucléaires sont parmi les observables les plus sensibles à ces changements de structure nucléaire. Dans ce travail, une étude du phénomène de transition de forme est effectuée, par des mesures de nucléides radioactifs produits dans le laboratoire ISOLDE au CERN. Les masses des isotopes de rubidium riches en neutrons 98-100Rb et des isotopes d’or riches en protons 180,185,188,190,191Au sont mesurées avec le spectromètre de masse de type Penning ISOLTRAP. La masse de 100Rb est déterminée pour la première fois. Des déviations significatives par rapport à la littérature sont trouvées pour les isotopes 188,190Au. Une nouvelle méthode expérimentale est présentée, utilisant un spectromètre de masse à multi-réflexion comme analyseur de faisceau pour la spectroscopie laser d’ionisation résonante. La nouvelle méthode donne la possibilité d’effectuer des études de structure hyperfine atomique avec ISOLTRAP, dont on peut extraire les rayons de charge et les moments électromagnétiques nucléairesThe most complex nuclei are situated between the magic and the mid-shell ones, in regions known for sudden changes of the trends of nuclear observables. These are the so-called shape-transition regions, where the nuclear paradigm changes from the vibrational liquid drop to the static rotor. With few exceptions, nuclei in these regions are radioactive, with half-lives dropping into the millisecond range.Complementing the information obtained from the low-lying excitation spectrum, nuclear binding energies and mean-square charge radii are among the observables most sensitive to these changes of nuclear structure. In the present work, a study of the shape-transition phenomenon is performed by measurements of radioactive nuclides produced by the ISOLDE facility at CERN. The masses of the neutron-rich rubidium isotopes 98−100Rb and of the neutron-deficient gold isotopes 180,185,188,190,191Au are determined using the Penning-trap mass spectrometer ISOLTRAP. The mass of 100Rb is determined for the first time. Significant deviations from the literature values are found for the isotopes 188,190Au. A new experimental method is presented, using a recently developed multi-reflection time-of-flight mass spectrometer as a beam-analysis tool for resonance-ionization laser spectroscopy. The new method opens the path to measurements of atomic hyperfine spectra with ISOLTRAP, from which charge radii and electromagnetic moments of radioactive nuclides can be extracted. The properties of the studied nuclides map the borders of two prominent regions of quadrupole deformation, which constrain the fine balance between pairing and quadrupole correlations in the nuclear ground states. This balance is studied by the Hartree-Fock- Bogoliubov (HFB) approach. The sensitivity of the shape-transition phenomenon to the strength of pairing correlations is demonstrated. In particular, the strong odd-even staggering of charge radii in the mercury isotopic chain is shown to result in the HFB approach from the fine interplay between pairing, quadrupole correlations and quasi-particle blocking
37
Døhlen, Kjetil. "Design of an interferometric spectrometer for environmental surveillance." Thesis, Imperial College London, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283824.
Full text
38
Kopelvski, Maycon Max. "Sistema de caracterização elétrica de dispositivos emissores de campo." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/3/3142/tde-28032008-174207/.
Full textAbstract:
Neste trabalho é apresentado o desenvolvimento de um sistema de ensaios elétricos de dispositivos de emissão de campo para que, a partir desses ensaios, possam ser extraídas as características elétricas desses dispositivos. O sistema é composto por hardware e software dedicados e pode ser controlado local ou remotamente. O hardware inclui uma fonte de alta tensão gerenciada por um sistema microcontrolado. Para programação do microcontrolador, foi utilizado um ambiente de programação disponibilizado pelo próprio fabricante do microcontrolador. Nesse desenvolvimento foram empregados periféricos de entrada e saída do microcontrolador, tais como: leitura de teclado, manipulação de USART, ajuste do nível de saída da fonte e conversores analógicos digitais. No microcontrolador foram implantadas rotinas de configuração, personalização e varredura do display, além de envio e recebimento de informações com um computador. Para o computador foi elaborado um programa dedicado para a manipulação do sistema de ensaio utilizando o conceito de instrumentação virtual, que permite escolher o tipo de ensaio elétrico, armazenar as leituras dos ensaios e a visualização \"on-line\" do andamento do ensaio através de diversos gráficos disponíveis no programa, inclusive o gráfico de Fowler-Nordheim, adequado para o estudo de dispositivos de emissão de campo.At this work is presented the development of a field emission devices trial system to render possible to obtain the electrical characteristics of the field emission devices. Here are shown some results taken from some trials. During the development of the trial system, it was used at the programming microcontroller stage, the environment of programming supplied by the manufacturer of the microcontroller. At this development, peripheral of input and output from the microcontroller, like, keyboard reading, USART manipulation, SPI manipulation and analogic to digital converters were used. At the microcontroller were implanted routines of configuration, customing and display sweeping, besides the transmission and the receiving of instructions came from the computer. For computer, a program was elaborated dedicated for manipulation of the trials system applying the virtual instrumentation concept, storing readings of the trials as well as the visualization \"on-line\" of the course of the trial through available graphs in the program. As an important result of this work has the establishment of a system for trial of field emission devices controlled on place or remotely, system that is composed by hardware and software in which were made several trials with acquisition and data manipulation and the presentation of received information.
39
Mitri, Georges Habib. "An investigation in the use of advanced remote sensing and geographic information system techniques for post-fire impact assessment on vegetation." Doctoral thesis, Università degli studi di Trieste, 2008. http://hdl.handle.net/10077/2662.
Full textAbstract:
2006/2007Gli incendi boschivi rappresentano uno dei maggiori problemi ambientali nella regione Mediterranea con vaste superfici colpite ogni estate. Una stima dell’impatto ambientale degli incendi (a breve e a lungo termine) richiede la raccolta di informazioni accurate post-incendio relative al tipo di incendio, all’intensità, alla rigenerazione forestale ed al ripristino della vegetazione. L’utilizzo di tecniche avanzate di telerilevamento può fornire un valido strumento per lo studio di questi fenomeni. L’importanza di queste ricerche è stata più volte sottolineata dalla Commissione Europea che si è concentrata sullo studio degli incendi boschivi ed il loro effetto sulla vegetazione attraverso lo sviluppo di adeguati metodi di stima dell’impatto e di mitigazione. Scopo di questo lavoro è la stima dell’impatto post-incendio sulla vegetazione in ambiente Mediterraneo per mezzo di immagini satellitari ad alta risoluzione, di rilievi a terra e mediante tecniche avanzate di analisi dei dati. Il lavoro ha riguardato lo sviluppo di un sistema per l’integrazione di dati telerilevati ad altissima risoluzione spaziale e spettrale. Per la stima dell’impatto a breve termine, un modello di classificazione ad oggetti è stato sviluppato utilizzando immagini Ikonos ad altissima risoluzione spaziale per cartografare il tipo di incendio, differenziando l’incendio radente dall’incendio di chioma. I risultati mostrano che la classificazione ad oggetti potrebbe essere utilizzata per distinguere con elevata accuratezza (87% di accuratezza complessiva) le due tipologie di incendio, in particolare nei boschi Mediterranei aperti. È stata inoltre valutata la capacità della classificazione ad oggetti di distinguere e cartografare tre livelli di intensità del fuoco utilizzando le immagini Ikonos e l’accuratezza del risultato è stimata all’ 83%. Per la stima dell’impatto a lungo termine, la mappatura della rigenerazione post-incendio (pino) e la ripresa della vegetazione arbustiva sono state valutate mediante tre approcci: 1) la classificazione ad oggetti di immagini ad altissima risoluzione QuickBird che ha permesso di mappare la ripresa della vegetazione e l’impatto sulla copertura a seguito dell’incendio distinguendo due livelli di intensità dell’incendio (accuratezza della classificazione 86%). 2) l’analisi statistica di dati iperspettrali rilevati in campo che ha permesso una riduzione del 97% del volume di dati e la selezione delle migliori 14 bande per discriminare l’età e le specie di pino e le 18 migliori bande per la caratterizzazione delle specie arbustive. Successivamente, i dati iperspettrali Hyperion sono stati utlizzati per mappare la rigenerazione forestale e la ripresa della vegetazione. L’accuratezza complessiva della classificazione è stata del 75.1% considerando due diverse specie di pino ed altre specie vegetali. 3) una classificazione ad oggetti che ha combinato l’analisi dei dati QuickBird ed Hyperion. Si è registrato un aumento dell’accuratezza della classificazione pari all’8.06% rispetto all’utilizzo dei soli dati Hyperion. Complessivamente, si osserva che strumenti avanzati di telerilevamento consentono di raccogliere le informazioni relative alle aree incendiate, la rigenerazione forestale e la ripresa della vegetazione in modo accurato e vantaggioso in termini di costi e tempi.
Forest fires are a major environmental problem in the Mediterranean region, where large areas are affected each summer. An assessment of the environmental impact of forest fires (in the short-term and in the long-term) requires the collection of accurate and detailed post-fire information related to fire type, fire severity, forest regeneration and vegetation recovery. Advanced tools in remote sensing provide a powerful tool for the study of this phenomenon. The importance of this work was often emphasized by the European Commission, which focused on the studying of forest fires and their effect on vegetation through the development of appropriate impact assessment and mitigation methods. The aim of this study was to assess the post-fire impact on vegetation in a Mediterranean environment by employing high quality satellite and field data and by using advanced data processing techniques. The work entailed the development of a whole system integrating very high spatial and spectral resolution remotely sensed data. For short-term impact assessment, an object-oriented model was developed using very high spatial resolution Ikonos imagery to map the type of fire, namely, canopy fire and surface fire. The results showed that object-oriented classification could be used to accurately distinguish and map areas of surface and crown fire spread (overall accuracy of 87%), especially that occurring in open Mediterranean forests. Also, the performance of object-based classification in mapping three levels of fire severity by employing high spatial resolution Ikonos imagery was evaluated, and accuracy of the obtained results was estimated to be 83%. As for long-term impact assessment, the mapping of post-fire forest regeneration (pine) and vegetation recovery (shrub) was performed by following three different approaches. First, the developed object-based classification of QuickBird (very high spatial resolution) allowed post-fire vegetation recovery and survival mapping of canopy within two different fire severity levels (86% of classification accuracy). The main effect of fire has been to create a more homogeneous landscape. Second, statistical analysis of field hyperspectral data allowed a 97% reduction in data volume and recommended 14 best narrowbands to discriminate among pine trees (age and species) and 18 bands that best characterize the different shrub species. Then, hyperspectral Hyperion was employed for mapping post-fire forest regeneration and vegetation recovery. The overall classification accuracy was found to be 75.81% when mapping two different regenerated pine species and other species of vegetation recovery. Third, an object-oriented combined analysis of QuickBird and Hyperion was investigated for the same objective. An improvement in classification accuracy of 8.06% was recorded when combining both Hyperion and QuickBird imageries than by using only the Hyperion image. Overall, it was observed that advanced tools in remote sensing provided the necessary means for gathering information about the burned areas, the regenerated forests and the recovered vegetations in a successful and a timely/cost effective manner.
XX Ciclo
1977
40
Bertin, Gwladys. "Etude différentielle des protéines membranaires exprimées à la surface de l'hématie infectée par Plasmodium falciparum, en fonction de la symptomatologie." Thesis, Paris 5, 2013. http://www.theses.fr/2013PA05P635/document.
Full textAbstract:
La virulence de Plasmodium falciparum est fonction de sa capacité à séquestrer les érythrocytes infectés (iEs) dans les organes profonds de l’hôte. Elle est liée à la mise en place d’un trafic protéique conséquent au niveau membranaire et sub-membranaire de l’iE. Cet adressage protéique aboutit à l’expression d’antigènes variant de surface, dont P. falciparum Erythrocyte Membrane Protein-1, PfEMP-1. Cet adhésine présente une affinité pour divers récepteurs de l'hôte impliqués dans la physiopathologie des formes graves, telles que le paludisme associé à la grossesse (PAM) et le paludisme cérébral (CM). La diversité de liaison de PfEMP-1 est associée à la variabilité de séquence de son domaine extracellulaire. Ce domaine est constitué d’une succession de domaines DBL et CIDR en nombre variable. PfEMP-1 est codée par les gènes var classifiés en groupes Ups A, B, C, E et B/A, B/C. Des régions de PfEMP-1 constituées d’une succession établie de 2 à 4 domaines, nommées Domain Cassette, « DC » sont retrouvées dans différents isolats. L’obtention de données exhaustives par LC-MS/MS a permis d’établir un comparatif du protéome membranaire et hypothétique à partir des échantillons PAM et CM en comparaison à des accès simples de paludisme (UM). L’identification protéique des PfEMP-1 a montré la singularité de l’expression d’une PfEMP-1 particulière, VAR2CSA chez les PAM. Ces résultats corroborent les analyses des transcrits du gène var2csa comme surexprimé chez les PAM, transcrit qu’on retrouve également dans les infections de début et de fin de grossesse. Les PfEMP-1 identifiés au sein des CM étaient significativement associés aux groupes Ups A et B/A et la plupart des peptides identifiés étaient associés à la cassette DC8 dont le transcrit était également surexprimé. L’analyse de filter-based feature selection a permis d’identifier un sous ensemble de 13 et 14 protéines assignées comme protéines membranaires ou hypothétiques, prédictives des formes de paludisme PAM et CM, respectivement. Parmi ces protéines surexprimées chez les PAM, la présence de VAR2CSA valide l’approche d’analyse. PFI1785w a été identifiée et associée au PAM, quatre autres protéines apparaissent prédictives de cette forme clinique PFB0115w, PFF0325c, PFA_0410w et PF14_0018. Pour les CM, on distingue les protéines PfEMP-2 et antigen-332 comme spécifiques de cette forme clinique. Les autres protéines qui émergent de ce groupe sont des protéines de fonction inconnue, dont trois sont assignées comme des protéines exportées. L’obtention et l’analyse en LC-MS/MS d’extraits protéiques issus d’isolats de terrain font l’originalité de ce travail et permettent la corrélation entre les données cliniques et biologiques. Cette étude confirme les données de transcrits sur la famille des gènes var et suggère de nouvelles intéractions protéiques dans le cadre du paludisme associé à la grossesse et cérébralPlasmodium falciparum is responsible for severe malaria (cerebral malaria, CM and pregnancy associated malaria, PAM). During the intra-erythrocytic maturation of P. falciparum, parasite-derived proteins are expressed, exported and presented at the surface of the infected erythrocyte (iE) membrane. These include Plasmodium falciparum erythrocyte membrane protein-1 (PfEMP-1). PfEMP-1 is a highly polymorphic adherence receptor, variants of which have been assigned to four groups (A-E) based on their sequence homology. Semi-conserved types, defined by tandem runs of specific domains (“domain cassettes” (DC)), are also recognized. The PfEMP-1 type expressed determines the iE adherence phenotype, and is associated with the clinical outcome of infection. Parasite isolates from Beninese children or women presenting with, respectively, CM or PAM were collected along with samples from patients with uncomplicated malaria (UM). We assessed the transcript level of var genes by RT-qPCR and the expression of membrane and hypothetical proteins of Plasmodium by LC-MS/MS. Obtaining LC-MS/MS data enabled a comparison of hypothetical and membrane proteome samples from PAM and CM for comparison with UM samples. The proteomics-based identification of PfEMP-1 showed the expression of a particular PfEMP-1, VAR2CSA, in PAM isolates. These results corroborate the analysis of gene transcripts showing that var2csa is overexpressed in PAM, with transcripts found in isolates from infections both early and late in pregnancy. The PfEMP-1 variants identified in CM samples were predominantly from the Ups groups A and B/A, and most of the peptides identified by LC-MS/MS were associated with the DC8 cassette for which the transcripts were also overexpressed. Analysis using filter-based feature selection identified subsets of 13 and 14 proteins, assigned either as hypothetical or membrane proteins that were predictive of PAM and CM syndromes respectively. The presence of VAR2CSA amongst the proteins overexpressed in PAM samples validates the analytical approach. PFI1785w has previously been identified and associated with the PAM, whilst four other proteins, PFB0115w, PFF0325c, PFA_0410w and PF14_0018, appear to be also predictive of the syndrome. PfEMP-2 protein and antigen-332 were found to be specifically expressed in CM samples. Three other proteins, assigned as ‘exported’ but with unknown function, were also associated with CM samples. Obtaining and analyzing LC-MS/MS-derived data from protein extracts of field isolates represents the originality of this work and it allowed the identification of correlations between clinical and biological data. This study confirms the transcriptional data relating to the var gene family and provides evidence of new protein interactions in the context both of malaria associated with pregnancy and of cerebral malaria
41
Rouleau, Gary. "An electron spectrometer using adiabatic motion in a magnetic field /." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65933.
Full text
42
Anyakoha, Ngozi Gloria. "Fatty acid and lipid profiles in models of neuroinflammation and mood disorders : application of high field NMR, gas chromotography and liquid chromotography-tandem mass spectrometry to investigate the effects of atorvaststin in brain and liver lipids and explore brain lipid changes in the FSL model of depression." Thesis, University of Bradford, 2009. http://hdl.handle.net/10454/4328.
Full textAbstract:
Lipids are important for the structural and physiological functions of neuronal cell membranes. Alterations in their lipid composition may result in membrane dysfunction and subsequent neuronal deficits that characterise various disorders. This study focused on profiling lipids of aged and LPS-treated rat brain and liver tissue with a view to explore the effect of atorvastatin in neuroinflammation, and examining lipid changes in different areas of rat brain of the Flinders Sensitive Line (FSL) rats, a genetic model of depression. Lipids and other analytes extracted from tissue samples were analysed with proton nuclear magnetic resonance spectroscopy (1H-NMR), gas chromatography (GC) and liquid chromatography-tandem mass spectroscopy (LC/ESI-MS/MS). Changes in the lipid profiles suggested that brain and liver responded differently to ageing and LPS-induced neuroinflammation. In the aged animals, n-3 PUFA were reduced in the brain but were increased in the liver. However, following treatment with LPS, these effects were not observed. Nevertheless, in both models, brain concentration of monounsaturated fatty acids was increased while the liver was able to maintain its monounsaturated fatty acid concentration. Atorvastatin reversed the reduction in n-3 PUFA in the aged brain without reducing brain and liver concentration of cholesterol. These findings further highlight alterations in lipid metabolism in agerelated neuroinflammation and show that the anti-inflammatory actions of atorvastatin may include a modulation of fatty acid metabolism. When studying the FSL model, there were differences in the lipid profile of different brain areas of FSL rats compared to Sprague-Dawley controls. In all brain areas, arachidonic acid was increased in the FSL rats. Docosahexaenoic acid and ether lipids were reduced, while cholesterol and sphingolipids were increased in the hypothalamus of the FSL rats. Furthermore, total diacylglycerophospholipids were reduced in the prefrontal cortex and hypothalamus of the FSL rats. These results show differences in the lipid metabolism of the FSL rat brain and may be suggestive of changes occurring in the brain tissue in depression.
43
Anyakoha, Ngozi G. "Fatty acid and lipid profiles in models of neuroinflammation and mood disorders. Application of high field NMR, gas chromotography and liquid chromotography-tandem mass spectrometry to investigate the effects of atorvaststin in brain and liver lipids and explore brain lipid changes in the FSL model of depression." Thesis, University of Bradford, 2009. http://hdl.handle.net/10454/4328.
Full textAbstract:
Lipids are important for the structural and physiological functions of neuronal cell
membranes. Alterations in their lipid composition may result in membrane dysfunction
and subsequent neuronal deficits that characterise various disorders. This study
focused on profiling lipids of aged and LPS-treated rat brain and liver tissue with a view
to explore the effect of atorvastatin in neuroinflammation, and examining lipid changes
in different areas of rat brain of the Flinders Sensitive Line (FSL) rats, a genetic model
of depression.
Lipids and other analytes extracted from tissue samples were analysed with proton
nuclear magnetic resonance spectroscopy (1H-NMR), gas chromatography (GC) and
liquid chromatography-tandem mass spectroscopy (LC/ESI-MS/MS).
Changes in the lipid profiles suggested that brain and liver responded differently to
ageing and LPS-induced neuroinflammation. In the aged animals, n-3 PUFA were
reduced in the brain but were increased in the liver. However, following treatment with
LPS, these effects were not observed. Nevertheless, in both models, brain
concentration of monounsaturated fatty acids was increased while the liver was able to
maintain its monounsaturated fatty acid concentration. Atorvastatin reversed the
reduction in n-3 PUFA in the aged brain without reducing brain and liver concentration
of cholesterol. These findings further highlight alterations in lipid metabolism in agerelated
neuroinflammation and show that the anti-inflammatory actions of atorvastatin
may include a modulation of fatty acid metabolism.
When studying the FSL model, there were differences in the lipid profile of different
brain areas of FSL rats compared to Sprague-Dawley controls. In all brain areas,
arachidonic acid was increased in the FSL rats. Docosahexaenoic acid and ether lipids
were reduced, while cholesterol and sphingolipids were increased in the hypothalamus
of the FSL rats. Furthermore, total diacylglycerophospholipids were reduced in the
prefrontal cortex and hypothalamus of the FSL rats. These results show differences in
the lipid metabolism of the FSL rat brain and may be suggestive of changes occurring
in the brain tissue in depression.
44
Ren, Deqing. "New techniques of multiple integral field spectroscopy." Thesis, Durham University, 2001. http://etheses.dur.ac.uk/3800/.
Full textAbstract:
The work of this thesis is to investigate new techniques for Integral Field Spectroscopy (IPS) to make the most efficient use of modem large telescopes. Most of the work described is aimed at the FMOS for the SUBARU 8m telescope. Although this is primarily a system for Multiple Object Spectroscopy (MOS) employing single fibres, there is an option to include a multiple-IFS (MIPS) system. Much of this thesis is therefore aimed at the design and prototyping of critical systems for both the IPS and MOS modes of this instrument. The basic theory of IFU design is discussed first. Some particular problems are described and their soludons presented. The design of the MIPS system is described together with the construction and testing of a prototype deployable IFU. The assembly of the pickoff/fore-optics, microlens array and fibre bundle and their testing are described in detail. The estimated performance of the complete module is presented together with suggestions for improving the system efficiency which is currently limited by the performance of the microlens array. The prototyping of the MIPS system is supported by an extensive programme of testing of candidate microlens arrays. Another critical aspect of the instrument is the ability to disconnect the (IPS and MOS) fibre input which is installed on a removable prime focus top-end ring from the spectrographs which are mounted elsewhere on the telescope. This requires high-performance multiple fibre connectors. The designs of connectors for the MOS and IPS modes are described. Results from the testing of a prototype for the MOS mode are presented. This work is supported by a mathematical model of the coupling efficiency which takes into account optical aberrations and alignment errors. The final critical aspect of FMOS which has been investigated is the design of the spectrographs. The baseline system operates in the near-infrared (NIR) but an additional visible channel is an option. Efficient designs for both the visible and NIR systems are presented. The design of the NIR spectrograph presents challenges in the choice of materials for the doublet and triplet lenses employed. The choice of material and the combinations in which they can be used are described. This thesis shows that all these critical aspects of FMOS have good solutions that will result in good performance of the whole instrument. For the multiple IFU system, the prototype demonstrates acceptable performance which can be made excellent by the use of a better microlens array. The multiple fibre connector prototype already indicates excellent performance. Finally, the spectrograph designs presented should result in high efficiency and good image quality.
45
Líšková, Ivana. "Stanovení geotechnických vlastností zemin s využitím metody Elektrické impedanční spektrometrie." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2017. http://www.nusl.cz/ntk/nusl-265699.
Full textAbstract:
This diploma thesis deals with determination of geotechnical properties of soils with using method of electrical impedance spectrometry (EIS). For measurement was used device Z-meter of 3rd generation, which was developed with projects of international program of applied research EUREKA. Experiment was realized in Laboratory of soil mechanics in GEOtest a.s. in Brno.
46
García, Fusté María José. "Neutron spectrometry in complex n - y fields: Application to LINAC and PET facilities." Doctoral thesis, Universitat Autònoma de Barcelona, 2010. http://hdl.handle.net/10803/3427.
Full textAbstract:
El presente trabajo responde a la necesidad de caracterizar experimentalmente los campos de neutrones generados en instalaciones médicas tipo LINAC y PET. Estos campos pueden ser pulsados, intensos y venir acompañados de una componente predominante de fotones de alta energía tal que los instrumentos activos pueden experimentar algunas limitaciones, como la aparición del fenómeno de pile‐up, tiempos muertos grandes y interferencias de radiofrecuencia. Para superar estas dificultades, se ha desarrollado recientemente en el laboratorio del Grup de Física de les Radiacions de la UAB, un espectrómetro pasivo de esferas Bonner (BSS), utilizando láminas de oro puro como detector central. Este espectrómetro debe tolerar exposiciones en condiciones ambientales extremas de temperatura y humedad, y debe ser capaz de medir los espectros de neutrones en estos entornos independientemente de su dirección de incidencia y en un amplio rango de energías (de 1 MeV a 20 MeV). El manuscrito describe el diseño, caracterización y aplicación del nuevo espectrómetro pasivo de esferas Bonner para neutrones de la UAB. La matriz de respuesta en energía del espectrómetro se ha simulado con técnicas de Monte‐Carlo y se ha validado experimentalmente con irradiaciones en campos neutrónicos de referencia. Se ha establecido un procedimiento para estimar el límite de detección de la tasa de fluencia neutrónica. El BSS pasivo de la UAB se ha utilizado para medir los espectros de neutrones alrededor de 7 aceleradores LINAC diferentes. A partir de los resultados obtenidos se han estudiado los efectos de la utilización de diferentes técnicas de irradiación, de diferentes energías nominales del haz de fotones y de diferentes geometrías de las salas de irradiación. El espectrómetro también se ha utilizado para determinar los espectros de neutrones alrededor de 2 ciclotrones PET, uno de ellos una máquina sin blindaje, el otro un ciclotrón auto‐blindado.
The present work deals with the need of characterising experimentally the neutron fields generated in LINAC and PET medical facilities. These fields may be pulsed, intense and mixed with high energy predominant photon component, where active instruments may experiment some limitations such as pulse pile‐up, dead‐time and radiofrequency interferences. To overcome these difficulties, a passive Bonner sphere spectrometer (BSS), using pure gold foils as central detectors, has been recently developed in the laboratory of the Grup de Física de les Radiacions at the UAB. This spectrometer should tolerate exposures in extreme environment conditions of temperature and humidity, and should be able to measure neutron spectra in such environments independently on their direction of incidence and over a wide energy range (from 1meV up to 20 MeV).
The manuscript describes the design, characterisation and application of the new UAB neutron passive Bonner sphere spectrometer. The energy response matrix of the spectrometer has been simulated with Monte‐Carlo techniques and experimentally validated with irradiations in reference neutron fields. A procedure to estimate the neutron fluence rate detection limit has also been established. The UAB passive BSS has been used to measure the neutron spectra around 7 different LINAC accelerators to study the effects of using different irradiation techniques, nominal beam energies and room geometries. The spectrometer has also been used to determine the neutron spectra around 2 PET cyclotrons, one of them an un‐shielded machine, the other one a self‐shielded one.
47
Fuchs, Martin R. "A high field, high frequency electron paramagnetic resonance spectrometer (360 GHz, 14 T)." [S.l. : s.n.], 1999. http://www.diss.fu-berlin.de/2000/7/index.html.
Full text
48
Gouilleux, Boris. "Gradient-based methodson a benchtop spectrometer : new perspectives for low-field NMR spectroscopy." Thesis, Nantes, 2017. http://www.theses.fr/2017NANT4036/document.
Full textAbstract:
La RMN à haut champ, basée sur des aimants supraconducteurs, est caractérisée par une instrumentation onéreuse et encombrante qui limite son utilisation dans les environnements de production. Le récent renouveau des aimants permanents a engendré des spectromètres RMN de paillasse qui permettent la réalisation d’expériences RMN directement sous la hotte du chimiste. L’objectif de cette thèse est d’améliorer la performance analytique de ces nouveaux spectromètres à bas champ. Dans cette optique, nous avons implémenté pour la première fois la RMN 2D Ultrarapide (UF) ainsi que des méthodes modernes de suppression du signal du solvant sur un spectromètre de paillasse opérant à 43 MHz équipé d’une bobine de gradient de champ magnétique. Suite à plusieurs optimisations, la RMN 2D UF à bas champ délivre des spectres 2D en un temps fortement réduit de qualité tout à fait intéressante. En parallèle, le développement des méthodes de suppressions permet dorénavant d’appréhender l’utilisation de solvant non-deutérés sur des échantillons statiques ou en flux. Ces travaux ont débouché sur de nouvelles opportunités pour la RMN à bas champ. Plusieurs suivis de réactions, réalisés en ligne et en temps réel, ont été menés à bien sur diverses réactions comme le couplage de Heck-Matsuda, la neutralisation de mimes de gaz moutardes ou encore la synthèse d’un composé naturel par chimie en flux. Par ailleurs, la RMN 2D UF à bas champ a été appliquée avec succès pour discriminer des huiles alimentaires en fonction de leurs origines botaniques. Cette méthodologie 2D, compatible avec des analyses à haut débit, démontre une amélioration notable par rapport à la RMN 1DHigh-field NMR based on superconducting magnets involves an expensive and bulky equipment, which has hampered the use of NMR in harsh environments. A new generation of benchtop NMR spectrometers, compact and cryogen free, has brought NMR spectroscopy under the chemist’s fume-hood and as close as possible to production sites. The driving force of this PhD project is to improve the analytical performance of these benchtop NMR systems. We report here the first implementation of Ultrafast (UF) 2D NMR- a method yielding 2D NMR spectra in a single scan- as well as modern gradient-based solvent suppression methods on a 43 MHz benchtop spectrometer, including a B0-gradient coil. Substantial optimizations have led to UF experiments at low-field (LF) with a reasonable performance while the acquisition duration is reduced by one order of magnitude. Then, the presence of non-deuterated solvents –commonly used in LF NMR– has been tackled by the development of suppression methods both in static and flowing conditions. This methodological effort has opened new opportunities for benchtop NMR applications. Several on- and in-line real-time monitorings have been performed on different types of chemical reactions: Heck-Matsuda coupling reaction, oxidative neutralization of mustard-gas simulants or even the synthesis of a natural product in flow-chemistry. Besides applications to process monitoring, UF 2D NMR at 43 MHz has been successfully applied to discriminate the botanical origins of a panel of edible oils. This fast 2D approach has provided a better classification than standard 1D experiments while remaining compatible with high-throughput analysis
49
Dreyfus, Matthew A. "Laboratory and field measurements of organic aerosols with the photoionization aerosol mass spectrometer." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 166 p, 2008. http://proquest.umi.com/pqdweb?did=1654492141&sid=6&Fmt=2&clientId=8331&RQT=309&VName=PQD.
Full text
50
Bostrom, Gregory Alan. "Modifications to a Cavity Ringdown Spectrometer to Improve Data Acquisition Rates." PDXScholar, 2015. https://pdxscholar.library.pdx.edu/open_access_etds/2208.
Full textAbstract:
Cavity ringdown spectroscopy (CRDS) makes use of light retention in an optical cavity to enhance the sensitivity to absorption or extinction of light from a sample inside the cavity. When light entering the cavity is stopped, the output is an exponential decay with a decay constant that can be used to determine the quantity of the analyte if the extinction or absorption coefficient is known. The precision of the CRDS is dependent on the rate at which the system it acquires and processes ringdowns, assuming randomly distributed errors. We have demonstrated a CRDS system with a ringdown acquisition rate of 1.5 kHz, extendable to a maximum of 3.5 kHz, using new techniques that significantly changed the way in which the ringdowns are both initiated and processed. On the initiation side, we combined a custom high-resolution laser controller with a linear optical feedback configuration and a novel optical technique for initiating a ringdown. Our optical injection "unlock" method switches the laser off-resonance, while allowing the laser to immediately return to resonance, after terminating the unlock, to allow for another ringdown (on the same cavity resonance mode). This part of the system had a demonstrated ringdown initiation rate of 3.5 kHz. To take advantage of this rate, we developed an optimized cost-effective FGPA-based data acquisition and processing system for CRDS, capable of determining decay constants at a maximum rate of 4.4 kHz, by modifying a commercial ADC-FPGA evaluation board and programming it to apply a discrete Fourier transform-based algorithm for determining decay constants. The entire system shows promise with a demonstrated ability to determine gas concentrations for H2O with a measured concentration accuracy of ±3.3%. The system achieved an absorption coefficient precision of 0.1% (95% confidence interval). It also exhibited a linear response for varying H2O concentrations, a 2.2% variation (1σ) for repeated measurements at the same H2O concentration, and a corresponding precision of 0.6% (standard error of the mean). The absorption coefficient limit of detection was determined to be 1.6 x 10-8 cm-1 (root mean square of the baseline residual). Proposed modifications to our prototype system offer the promise of more substantial gains in both precision and limit of detection. The system components developed here for faster ringdown acquisition and processing have broader applications for CRDS in atmospheric science and other fields that need fast response systems operating at high-precision.