Dissertations / Theses on the topic 'Ion chamber'
To see the other types of publications on this topic, follow the link: Ion chamber.
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 'Ion chamber.'
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
Mahalingam, Sudhakar. "Particle Based Plasma Simulation for an Ion Engine Discharge Chamber." Wright State University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=wright1198181910.
Full text
2
Hobeila, Fadi. "Monte Carlo study of ion chamber response in low energy photon beams." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=78378.
Full textAbstract:
192Ir is one of the most popular radiation sources used for brachytherapy treatments. However, 192Ir emits a wide photon spectrum (10 keV to 900 keV) which impedes the creation of an 192Ir primary standard. The 192Ir air kerma calibration factor is derived by interpolating between 60Co, 137Cs and hard orthovoltage air kerma calibration factors obtained from a standards laboratory. The EGSnrc Monte Carlo package was used to calculate the response in low energy photon beams of a commercial parallel-plate chamber to assess useability as a 192Ir and kilovoltage photon beam calibration tool. XCOM photoeffect cross-sections were implemented in EGSnrc to improve kerma calculation agreement at low energies. The response calculations were compared to experimental data from PTB (Germany). Overall, agreement between calculations and measurement is good and represents an improvement to results from the literature. However, discrepancies exist at the lowest energies which may be caused by differences in the measurement and calculation geometries.
3
Camp, Paul W. "Design and installation of a field ionization test chamber for ion thrusters." Monterey, California. Naval Postgraduate School, 2011. http://hdl.handle.net/10945/10574.
Full textAbstract:
The utilization of carbon nanotube arrays for field ionization in ion thrusters allows for a substantial reduction in thruster size and weight. The availability of miniature ion thrusters may enable the development of a suitable propulsion system for nano- and picosatellites, and can realize substantial weight, volume, and cost savings in existing satellite platforms. This research focuses on the design of a field ionization test chamber that can be used to determine a comprehensive performance metric for the carbon nanotube field ionization micro-ion thruster (CNTFIMIT). Using the knowledge gathered from two previously employed test chamber designs, a third generation apparatus with higher precision and improved capabilities is constructed. This new design incorporates a mass flow controller for propellant flow rate measurements, a high-voltage source-measure unit for ionization current measurements, and a linear shift with position feedback for adjusting the distance between the carbon nanotubes and the counter electrode during field-ionization. The design emphasizes user-friendly operation by simplifying the sample exchange and by reducing the chamber volume under vacuum for a faster turn-around time between experiments. The proposed design is highly modular, allowing for easy installation of additional analytic capabilities and other future upgrades.
4
Dhar, Saurav. "Ionospheric Simulator (IonSim): Simulating Ionospheric conditions in a vacuum chamber." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/23931.
Full textAbstract:
Understanding and improving ionospheric models is important for both military and civilian purposes. This understanding improves prediction of radio propagation used for communication and GPS navigation. Various space-borne instruments, such as retarding potential analyzers (RPAs) and ion traps are routinely flown in low earth orbit (LEO) to provide data for seeding/improve ionospheric models. This thesis describes and characterizes a new ion source that can be used to test and calibrate these space-borne instruments inside a laboratory vacuum chamber. Hot filaments are used to thermionically emit electrons inside the source. These electrons collisionally ionize neutral particles inside the source. Guided by ion-optics simulations, the ion and the electron trajectories inside the source are controlled to provide the required ion beams. A detailed description of the control electronics and the embedded controller for electron emission is discussed within. Using the custom made electronics, the source is able to provide an ion beam with current densities and mean energy comparable to the conditions in LEO.Master of Science
5
Tran, Binh Phuoc. "Modeling of Ion Thruster Discharge Chamber Using 3D Particle-In-Cell Monte-Carlo-Collision Method." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/33510.
Full textAbstract:
This thesis is aimed toward developing a method to simulate ion thruster discharge chambers in a full three dimensional environment and to study the effect of discharge chamber size on ion thruster performance. The study focuses solely on ring-cusped thrusters that make use of Xenon for propellant and discharge cathode assembly for mean of propellant ionization. Commercial software is used in both the setup and analysis phases. Numerical simulation is handled by 3D Particle-In-Cell Monte-Carlo-Collision method. Simulation results are analyzed and compared with other works. It is concluded that the simulation methodology is validated and can be used to simulate different cases. Therefore, different simulation cases of varying chamber sizes are done and the results are used to develop a performance curve. This plot suggests that the most efficient case is the 30 cm thruster. The result further validates the simulation process since the operating parameters used for all of the cases are taken from a 30 cm thruster experiment. One of the obvious applications for such a simulation process is to determine a set of the most efficient operating parameters for a certain size thruster before actual fabrication and laboratory testing.Master of Science
6
Gruber, J. R. "A study of erosion due to low-energy sputtering in the discharge chamber of the Kaufman ion thruster." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249396.
Full text
7
Andersson, Jonas. "Ion recombination in liquid ionization chambers : development of an experimental method to quantify general recombination." Doctoral thesis, Umeå universitet, Radiofysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-68942.
Full textAbstract:
An experimental method (the two-dose-rate method) for the correction of general recombination losses in liquid ionization chambers has been developed and employed in experiments with different liquids and radiation qualities. The method is based on a disassociation of initial and general recombination, since an ionized liquid is simultaneously affected by both of these processes. The two-dose-rate method has been compared to an existing method for general recombination correction for liquid ionization chambers, and has been found to be the most robust method presently available. The soundness of modelling general recombination in liquids on existing theory for gases has been evaluated, and experiments indicate that the process of general recombination is similar in a gas and a liquid. It is thus reasonable to employ theory for gases in the two-dose-rate method to achieve experimental corrections for general recombination in liquids. There are uncertainties in the disassociation of initial and general recombination in the two-dose-rate method for low applied voltages, where initial recombination has been found to cause deviating results for different liquids and radiation qualities. Sensitivity to ambient electric fields has been identified in the microLion liquid ionization chamber (PTW, Germany). Experimental data may thus be perturbed if measurements are conducted in the presence of ambient electric fields, and the sensitivity has been found to increase with an increase in the applied voltage. This can prove to be experimentally limiting since general recombination may be too severe for accurate corrections if the applied voltage is low.
8
Sánchez, Parcerisa Daniel [Verfasser], and Katia [Akademischer Betreuer] Parodi. "Experimental and computational investigation of water-to-air stopping power ratio for ion chamber dosimetry in carbon ion radiotherapy / Daniel Sánchez Parcerisa ; Betreuer: Katia Parodi." Heidelberg : Universitätsbibliothek Heidelberg, 2012. http://d-nb.info/1179785762/34.
Full text
9
Chan, Kin Wa (Karl), University of Western Sydney, of Science Technology and Environment College, and School of Computing and Information Technology. "Lateral electron disequilibrium in radiation therapy." THESIS_CSTE_CIT_Chan_K.xml, 2002. http://handle.uws.edu.au:8081/1959.7/538.
Full textAbstract:
The radiation dose in radiation therapy is mainly measured by ion chamber. The ion chamber measurement will not be accurate if there is not enough phantom material surrounding the ion chamber to provide the electron equilibrium condition. The lack of electron equilibrium will cause a reduction of dose. This may introduce problems in treatment planning. Because some planning algorithms cannot predict the reduction, they over estimate the dose in the region. Electron disequilibrium will happen when the radiation field size is too small or the density of irradiated material is too low to provide sufficient electrons going into the dose volume. The amount of tissue required to provide electron equilibrium in a 6MV photon beam by three methods: direct calculation from Klein-Nisina equation, measurement in low density material phantom and a Monte Carlo simulation is done to compare with the measurement, an indirect method from a planning algorithm which does not provide an accurate result under lateral electron disequilibrium. When the error starts to happen in such planning algorithm, we know that the electron equilibrium conditions does not exist. Only the 6MV photon beam is investigated. This is because in most cases, a 6MV small fields are used for head and neck (larynx cavity) and 6MV fields are commonly used for lung to minimise uncertainity due to lateral electron at higher energies.Master of Science (Hons)
10
Kabir, Md Latiful. "A MEASUREMENT OF THE PARITY VIOLATING ASYMMETRY IN THE NEUTRON CAPTURE ON 3He AT SNS." UKnowledge, 2017. http://uknowledge.uky.edu/physastron_etds/45.
Full textAbstract:
Weak nucleon nucleon couplings are largely unknown because of the involved theoretical and experimental challenges. Theoretically the topic is difficult due to the non-perturbative nature of the strong interaction, which makes calculations of the couplings challenging. Experimentally, the topic is difficult given that 1) the observables are determined by ratios between strong couplings and weak couplings which differ in size by seven orders of magnitude, and 2) theoretically clean and predictable measurements are almost always restricted to simple systems that do not allow for effects that enhance the size of the asymmetry. However parity violation (PV) can be used to separate out the weak part and thus studies of PV in hadronic systems could offer a unique probe of nucleon structure. The n-3He experiment at the Spallation Neutron Source was performed to measure the parity violating asymmetry of the recoil proton momentum kp with respect to the neutron spin in the reaction n + 3He ---> p + T + 764 keV. This asymmetry is sensitive to the isospin-conserving and isospin-changing (∆I = 0, 1, 2) parts of the Hadronic Weak Interaction (HWI), and is expected to be small (~10-7). The goal of this experiment was to determine this PV asymmetry with a statistical sensitivity of 2x10-8. We also measured the parity even nuclear asymmetry proportional to kp · σn x kn for the first time for verification of nuclear theory and for confirmation of the sensitivity of our experiment to the parity violating asymmetry.
11
Deisting, Alexander [Verfasser], and Silvia [Akademischer Betreuer] Masciocchi. "Measurements of ion mobility and GEM discharge studies for the upgrade of the ALICE time projection chamber / Alexander Deisting ; Betreuer: Silvia Masciocchi." Heidelberg : Universitätsbibliothek Heidelberg, 2018. http://d-nb.info/1177384647/34.
Full text
12
Penkal, Bryan James. "Steps in the Development of a Full Particle-in-Cell, Monte Carlo Simulation of the Plasma in the Discharge Chamber of an Ion Engine." Wright State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=wright1367586856.
Full text
13
Togno, Michele Verfasser], Jan [Akademischer Betreuer] [Wilkens, and Franz [Gutachter] Pfeiffer. "A novel ion chamber technology for quality assurance in external beam radiotherapy / Michele Togno ; Gutachter: Jan J. Wilkens, Franz Pfeiffer ; Betreuer: Jan J. Wilkens." München : Universitätsbibliothek der TU München, 2017. http://nbn-resolving.de/urn:nbn:de:bvb:91-diss-20170717-1356924-1-1.
Full text
14
Togno, Michele [Verfasser], Jan J. [Akademischer Betreuer] [Gutachter] Wilkens, and Franz [Gutachter] Pfeiffer. "A novel ion chamber technology for quality assurance in external beam radiotherapy / Michele Togno ; Gutachter: Jan J. Wilkens, Franz Pfeiffer ; Betreuer: Jan J. Wilkens." München : Universitätsbibliothek der TU München, 2017. http://d-nb.info/1141296071/34.
Full text
15
Fortune, Eugene C. IV. "Gamma and neutron dose profiles near a Cf-252 brachytherapy source." Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34781.
Full textAbstract:
A new generation of medical grade Cf-252 sources was developed in 2002 at the Oak Ridge National Laboratory (ORNL). The combination of small size and large activity of these Cf-252 sources makes them suitable to be used with the conventional high-dose-rate (HDR) remote afterloading systems for interstitial brachytherapy. A recent in-water calibration experiment showed that the measured gamma dose rates near the new source are slightly greater than the neutron dose rates; contradicting the well established neutron-to-gamma dose ratio of approximately 2:1 at locations near a Cf-252 brachytherapy source. Specifically, the MCNP-predicted gamma dose rate is a factor of two higher than the measured gamma dose rate at the distance of 1 cm, and the differences between the two results gradually diminish at distances farther away from the source. To resolve this discrepancy, we updated the source gamma spectrum by including in the ORIGEN-S data library the experimentally measured Cf-252 prompt gamma spectrum as well as the true Cf-252 spontaneous fission yield data to explicitly model delayed gamma emissions from fission products. We also investigated the bremsstrahlung x-rays produced by the beta particles emitted from fission-product decays. The results show that the discrepancy of gamma dose rates is mainly caused by the omission of the bremsstrahlung x-rays in the MCNP runs. By including the bremsstrahlung x-rays, the MCNP results show that the gamma dose rates near a new Cf-252 source agree well with the measured results and that the gamma dose rates are indeed greater than the neutron dose rates.
The calibration experiment also showed discrepancies between the experimental and computational neutron dose profiles obtained. Specifically the MCNP-predicted neutron dose rates were ~25% higher than the measured neutron dose rates at all distances. In attempting to resolve this discrepancy the neutron emission rate was verified by the National Institute of Standards and Technology (NIST) and an experiment was performed to explore the effects of bias voltage on ion chamber charge collection. So far the discrepancies between the computational and experimental neutron dose profiles have not been resolved. Further study is needed to completely resolve this issue and some suggestions on how to move forward are given.
16
Jang, Si Young. "Advanced neutron irradiation system using Texas A&M University Nuclear Science Center Reactor." Texas A&M University, 2004. http://hdl.handle.net/1969.1/2788.
Full textAbstract:
A heavily filtered fast neutron irradiation system (FNIS) was developed for a variety of applications, including the study of long-term health effects of fast neutrons by evaluating the biological mechanisms of damage in cultured cells and living animals such as rats or mice. This irradiation system includes an exposure cave made with a lead-bismuth alloy, a cave positioning system, a gamma and neutron monitoring system, a sample transfer system, and interchangeable filters. This system was installed in the irradiation cell of the Texas A&M University Nuclear Science Center Reactor (NSCR).
By increasing the thickness of the lead-bismuth alloy, the neutron spectra were shifted into lower energies by the scattering interactions of fast neutrons with the alloy. It is possible, therefore, by changing the alloy thickness, to produce distinctly different dose weighted neutron spectra inside the exposure cave of the FNIS. The calculated neutron spectra showed close agreement with the results of activation foil measurements, unfolded by SAND-II close to the cell window. However, there was a considerable less agreement for locations far away from the cell window. Even though the magnitude of values such as neutron flux and tissue kerma rates in air differed, the weighted average neutron energies showed close agreement between the MCNP and SAND-II since the normalized neutron spectra were in a good agreement each other.
A paired ion chamber system was constructed, one with a tissue equivalent plastic (A-150) and propane gas for total dose monitoring, and another with graphite and argon for photon dose monitoring. Using the pair of detectors, the neutron to gamma ratio can be inferred. With the 20 cm-thick FNIS, the absorbed dose rates of neutrons measured with the paired ion chamber method and calculated with the SAND-II results were 13.7 ?? 0.02 Gy/min and 15.5 Gy/min, respectively. The absorbed dose rate of photons and the gamma contribution to total dose were 6.7??10-1 ?? 1.3??10-1 Gy/min and 4.7%, respectively. However, the estimated gamma contribution to total dose varied between 3.6 % to 6.6 % as the assumed neutron sensitivity to the graphite detector was changed from 0.01 to 0.03.
17
Motloung, Setumo Victor. "Intense pulsed neutron generation based on the principle of Plasma Immersion Ion Implantation (PI3) technique." Thesis, University of the Western Cape, 2006. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_9599_1182748458.
Full textAbstract:
The development of a deuterium-deuterium/ tritium-deuterium (D-D/ D-T) pulsed neutron generator based on the principle of the Plasma Immersion Ion Implantation (PI3) technique is presented, in terms of investigating development of a compact system to generate an ultra short burst of mono-energetic neutrons (of order 1010 per second) during a short period of time (<
20&mu
s) at repetition rates up to 1 kHz. The system will facilitate neutron detection techniques, such as neutron back-scattering, neutron radiography and time-of-flight activation analysis.
Aspects addressed in developing the system includes (a) characterizing the neutron spectra generated as a function of the target configuration/ design to ensure a sustained intense neutron flux for long periods of time, (b) the system was also characterised as a function of power supply operating conditions such as voltage, current, gas pressure and plasma density.
18
Lokits, Kirk Edward. "Interfacing Conventional and Capillary Flow to Argon Plasma: Elemental Detection for Bio-Analytical Applications." Cincinnati, Ohio : University of Cincinnati, 2008. http://rave.ohiolink.edu/etdc/view.cgi?acc_num=ucin1227049009.
Full textAbstract:
Thesis (Ph. D.)--University of Cincinnati, 2008.Advisor: Joseph Caruso PhD (Advisor), Patrick Limbach PhD (Committee Member), James Mack PhD (Committee Member). Title from electronic thesis title page (viewed Feb. 8, 2009). Keywords: ICPMS; phosphorothioates; antisense oligonucleotides; speciation; ion-paring reverse phase; microflow capillary nebulizer; total consumption spray chamber. Includes abstract. Includes bibliographical references.
19
Larsson, Isak. "Utläsning av jonkammardata." Thesis, Umeå universitet, Institutionen för tillämpad fysik och elektronik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-176136.
Full textAbstract:
Tracercenter på Norrlands Universitetssjukhus producerar radiotracers. För att mäta aktiviteten hos de radioaktiva isotoperna används idag en jonkammare tillsammans med mjukvara byggt på Windows XP. Målet med det här examensarbetet är att bygga ny mjukvara som är kompatibelt med Windows 10. Mjukvaran ska tillhandahålla kalibreringsmöjligheter för isotoperna F-18, C-11 och Cs-137 samt kunna överföra uppmätt värde till datahanteringssystemet PETra.Med användandet av kodspråket Python och biblioteket TkInter har ett användargränsnitt och bakomliggande funktionskod utvecklats. Mjukvaran kommunicerar med både jonkammare och PETra seriellt via COM-Port. Linjäritetstester har gjorts för jonkammaren som påvisat god linjäritet. Detta resultat bekräftar mjukvarans tillförlitlighet med en liten felmarginal. Ytterligare tester behövs för att fastställa magnituden av felmarginalen.Tracercenter at Norrlands University Hospital is a producer of radiotracers. To measure the activity of the radioactive isotopes an Ion Chamber combined with software built on Windows XP is used. The purpose of this thesis is to develop new software for the ion chamber compatible with Windows 10. The software has to provide a calibration function for the isotopes F-18, C-11 and Cs-137 aswell as be able to transfer measured activity to the laboratory information management system PETra.A graphical user interface together with backend code has been developed with Python and the library TkInter. The software communicates with both the ion chamber and PETra with a serial connection via COM-Port. Linearity tests have been made for the ion chamber which has shown that the output of the ion chamber itself is linear. This result confirms the software’s reliability with a slight margin of error. Further tests is needed to determine the magnitude of the margin of error.
20
Kelm, Robert S. "In-water neutron and gamma dose determination for a new Cf-252 brachytherapy source." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28121.
Full text
21
Osuagwu, Chiemeriwo Godday. "Investigation of volatile organic compounds from diesel engine emissions using H3O+ chemical ionisation mass spectrometry (H3O+-CIMS)." Thesis, Queensland University of Technology, 2020. https://eprints.qut.edu.au/205507/1/Chiemeriwo_Osuagwu_Thesis.pdf.
Full textAbstract:
Volatile organic compounds (VOCs) are organic compounds which exist in the gas phase at room temperature and atmospheric pressure. The lifespan of VOCs in the Earth's atmosphere ranges from a few minutes to months. Many VOCs are dangerous to human health and can undergo oxidation mediated aggregation to form secondary organic aerosols which are equally detrimental to human health. VOCs come from biogenic and anthropogenic sources, however, in cities, anthropogenic sources are dominant. A significant portion of these anthropogenic VOCs are coming from diesel vehicle emissions. Chemical composition of VOCs from diesel exhaust is complex and varies with the engine technology, driving conditions and fuel used.
Previously, VOCs have been measured using offline methods which required sample collection over a period (making it difficult to capture their temporal variability) and sample preparation (making the whole process time-consuming). The development of online mass spectrometrybased measurement techniques enabled monitoring VOCs in real time. Real time measurement of VOCs from the atmosphere is based on chemical ionisation mass spectrometry with hydronium ions as reagent ions. This was because hydronium ion allows the instrument to detect compounds that have proton affinity (PA) higher than that of water. Normal air components like N2 and O2 all have PA lower than water, however most of the saturated and unsaturated volatile organic compounds emitted from diesel exhaust have PA higher than water. The most commonly used instruments for atmospheric VOC measurement are Proton Transfer Reaction-Mass Spectrometer (quadrupole and Time of Flight), Selective Ion Flow Tube-Mass Spectrometer. The Aerodyne Chemical Ionisation Mass Spectrometer (CIMS) is a more recent instrument that allows the use of different reagent ions including hydronium ion H3O+. While both PTR-MS and SIFT-MS ionise samples at relatively low pressure (1-2 mbar) and their ionisation chambers been extensively studied, ion-Molecule Reaction (IMR) chamber in H3O+-CIMS operates at substantially higher pressure (~100 mbar) and, therefore, reagent ion distribution and ionisation chemistry are likely to be significantly different from the ones in PTR-MS and SIFT-MS. However, performance of the H3O+-CIMS has not been characterised in detail yet nor has this instrument been applied to investigate VOCs coming from diesel exhaust. This study is, therefore, aimed at characterising the performance of Aerodyne TOF-CIMS with H3O+ as reagent ions, herein referred to as H3O+-CIMS and later using the same for characterisation of diesel exhaust VOCs.
In characterising the H3O+-CIMS, the influence of the pressure inside the IMR chamber and SSQ (small sequential quadrupole) chamber on the intensity of reagent ions was explored. It was found that the optimum pressures for IMR and SSQ were ≥ 160 mbar and ≥ 2.3 mbar respectively. Exploration of radio frequency (RF) voltages of quadrupole ion guides inside the atmospheric pressure interface showed that 200V for the SSQ and 350V for the big sequential quadrupole (BSQ) are the optimum RF voltages for obtaining a maximum reagent ion signal intensity. The sensitivity of the instrument towards some common VOCs was determined using a custom-made VOC mixture. It was found that H3O+-CIMS was more sensitive to oxygenated VOCs compared to non-oxygenated VOCs. The sensitivity to oxygenated VOCs was comparable to PTR-MS and SIFT-MS while it was lower for non-oxygenated VOCs. It was also observed that relative humidity of the incoming air influences VOCs signal intensity with different compounds showing different RH dependence. Hydrate formation was explored as PTR-MS and SIFT-MS have both shown the formation of hydrate with increase in humidity.
In dry conditions with RH of 5%, hydrates were not formed for both non-oxygenated and oxygenated VOCs (NO-VOCs and O-VOCs respectively) except for acetonitrile with hydrate composition of ~7 – 25%. However, as RH increased to ~90%, hydrate composition was 10% 60% for NO-VOCs and ~ 3% to 4% for oxygenated VOCs. The instrument was tuned using 2 different tuning approaches - one aimed at maximising m/z 19 signal (H3O+) relative to the m/z 37 signal (H5O2 +) which maximises ion declustering and the other aimed at maximising m/z 37 signal (H5O2 +) relative to m/z 19 signal (H3O+) which minimises ion declustering. It was found that reagent ions and VOC signals were the highest with m/z 19 tuning approach.
After characterisation, the H3O+-CIMS was used to investigate VOCs from diesel exhaust. A total of 256 peaks were identified within a m/z range 15Th – 200Th, could not go beyond m/z 200 because peak resolution becomes very difficult beyond this point. 179 VOCs remained after the background had been subtracted, 44 of these VOCs were non-oxygenated hydrocarbon species, 79 were oxygenated species, 50 were nitrogen containing species and 9 were sulphur containing species.
VOC emissions from 3 diesel engines (Perkins, Kubota and Cummins) running on neat diesel fuel were compared. Cummins engine was found to emit the least number of VOCs in m/z 15 – 200 range which might be because it uses a common rail injection system unlike the other two engines, which utilise direct injection. When VOC emissions from neat diesel (D100) were compared with neat biodiesel (B100) using 3 diesel engines, benzene, toluene and xylene emissions were higher in B100 compared to D100 in all the engines. Similar trend was observed for CH5O+, C2H5O+, C4H5O+ and C5H9O+. This may be due to higher oxygen content in biodiesel compared to diesel fuel. However, a set of measurements was conducted where oxygen content of the fuel was varied by the use of biodiesel blends and it was shown that increasing the oxygen content of the fuel does not necessarily translate to increase in emissions of oxygenated VOCs. The role of oxygen content in the fuel was found to be compound dependent instead. It was also found that benzene, toluene and xylene emissions generally decreased with increase in oxygen content.
The contribution of this study to knowledge is that H3O+ -CIMS with IMR inlet is a useful tool in analysing VOCs emitted from diesel exhaust. This study is among the few studies that have identified hydrogen cyanide to be among the VOCs emitted from diesel exhaust. It also showed that neat biodiesel had the highest number of oxygenated VOCs peaks despite the diesel engine used. Lastly, it was shown that increasing the oxygen content of the fuel does not necessarily mean that oxygenated VOC emissions will increase.
22
Schmitt, Romain. "S-nitrosoglutathion et perméabilité intestinale : de la mise en place d’un modèle de chambre de Ussing à l’étude de l’impact de ce donneur de monoxyde d’azote sur la barrière intestinale Involved factors in the maintenance of intestinal barrier homeostasis: a review How to guarantee results from ex vivo studies based on Ussing chamber system for studying intestinal barrier integrity and function Comparison between two derivatization methods of nitrite ion labeled with 15N applied to liquid chromatography-tandem mass spectrometry Influence of S-nitrosoglutathione metabolism on its intestinal permeability Luminal S-nitrosoglutathione effects on intestinal barrier in an ex vivo model of Ussing chamber." Thesis, Université de Lorraine, 2019. http://www.theses.fr/2019LORR0342.
Full textAbstract:
Le monoxyde d’azote (NO) est connu pour ses nombreuses actions afin de maintenir l’homéostasie de la barrière intestinale, régulant la sécrétion de mucus, le stress oxydant, le système immunitaire… Le S-nitrosoglutathion (GSNO), donneur de NO naturellement produit par l’organisme, a montré une action bénéfique sur le renforcement de la barrière intestinale. L’enjeu est aujourd’hui de comprendre les mécanismes inhérents à cette observation. Pour ce faire une étude en Chambre de Ussing a été menée. Une fois le modèle d’étude validé par le suivi de marqueurs de perméabilité, les études histologiques et d’expression des protéines de jonctions cellulaires, le métabolisme du GSNO administré dans la lumière de l’intestin ont été explorés. Également, l’effet du GSNO sur la perméabilité de la barrière intestinale a été étudié. Les résultats permettent aujourd’hui d’envisager le GSNO comme une piste thérapeutique intéressante et prometteuse aux multiples applications possibles : intestinales, cardiovasculaires ou encore cérébralesNitric oxide is known for its many actions to maintain intestinal barrier homeostasis, regulating mucus secretion, oxidative stress, immune system… S-nitrosoglutathione (GSNO), a nitric oxide donor naturally produced by the organism, has shown a beneficial effect on the intestinal barrier reinforcement. Nowadays, challenge is to understand the mechanisms inherent to this observation. For that, a Ussing chamber study was performed. After the model validation, by following permeability markers, histological studies, and cell junction proteins expression study, the GSNO metabolism administered in the intestinal lumen was explored. Also, GSNO effect on the intestinal barrier permeability was evaluated. Results allow today to consider GSNO as an interesting and promising drug candidate, in the context of intestinal, cardiovascular or cerebral pathologies
23
Wallman, Andrew. "Safety and Visual Outcomes of Novel Abexterno Akreos® Single Pass Method of Transscleral Sutured Posterior Chamber IOL Implantation for Scleral Fixation of IOL." Thesis, The University of Arizona, 2016. http://hdl.handle.net/10150/606216.
Full textAbstract:
A Thesis submitted to The University of Arizona College of Medicine - Phoenix in partial fulfillment of the requirements for the Degree of Doctor of Medicine.We present the safety and efficacy of a novel transscleral sutured posterior chamber intraocular lens (TSSPCIOL) implantation approach utilizing 25 gauge vitrectomy and a foldable posterior chamber intraocular lens implant (AKREOS AO60, Bausch & Lomb). 80 consecutive eyes that underwent single surgeon TSSPCIOL implantation between October 2008 and July 2012 at a referral‐based retina institution were analyzed for best spectacle‐corrected visual acuity (BCVA) and safety indicators. Postoperative complications included retinal detachment in 2 eyes (2.5%), Irvine‐Gass cystoid macular edema in 3 eyes (3.75%), with 2 of those cases occurring late, persistent postoperative corneal edema in 1 eye (1.25%), hyphema in 2 eyes (2.5%) and 1 case of postoperative vitreous hemorrhage with spontaneous clearing. The modified external approach with AKREOS® TSSPCIOL placement with 25 gauge vitrectomy has relatively few complications, improves visual acuity in patients requiring TSSPCIOL, and offers several advantages over traditional anterior chamber or conventional scleral sutured techniques.
24
Troup, Daniel James, and Daniel James Troup. "Impact of Passive Air Treatment on Microbial Contamination in a Controlled Chamber Environment." Thesis, The University of Arizona, 2017. http://hdl.handle.net/10150/625694.
Full textAbstract:
Microbial pathogens commonly transmitted through the aerosol route to surfaces, equipment, and hands in the clinical setting leads to costly and life threatening hospital-acquired infections (HAIs). Even with improved hand hygiene and surface disinfection, HAIs continue to persist in healthcare environments, warranting consideration of novel interventions to reduce the transmission risk of HAIs. This study quantitated the efficacy of ion generating passive air treatment (PAT) against viruses (MS2), bacteria (Escherichia coli), and bacterial spores (Bacillus thuringiensis) in a controlled environmental setting.
Microorganisms were seeded into a 2.72 m3 chamber using a positive pressure nebulizing device to generate aerosolized droplets. The PAT unit was then turned on and seeded organisms were collected at various time points using impingers to concentrate the organisms into sterile aqueous solution. The microorganisms were enumerated using approved standard protocols developed in the Environment, Exposure Science, and Risk Assessment Center's laboratory at The University of Arizona.
Three experiments were conducted to challenge the PAT unit. Experiment one evaluated the efficacy of the PAT unit over a single 10-minute period on microbial inactivation from the airborne environment following a single seeding; additionally, experiment one aimed to determine the efficacy of the PAT unit against viruses, bacteria, and bacterial spores on environmental surfaces; experiment two evaluated the efficacy of the PAT unit running continuously over a period of 6 hours following a single seeding; and experiment three evaluated the efficacy of the PAT unit running two continuously over a period of 5.25 hours following two seeding events. Bacterial spores from pre- and post-treatment with the PAT unit were collected and analyzed by scanning electron microscopy to assess structural differences.
After a single seeding and 10 minutes of continuous treatment of the PAT unit, normalized average microbial log10 reductions of post-treatment compared to pre-treatment air concentrations were 1.67, 0.59, and 1.04 for MS2, B. thuringiensis spores, and E. coli, respectively. Differences in average log10 reductions between the control unit and the PAT unit were statistically significant for MS2 (p=0.009) and B. thuringiensis (p=0.0455), but not for E. coli (p=0.0565). The geometric mean log10 surface concentrations of MS2, B. thuringiensis, and E. coli after a single seeding and 10 minutes of continuous treatment of the PAT unit were 7.30 PFU/100 cm2, 5.90 CFU/100 cm2, and 2.74 CFU/100 cm2, respectively, compared to exposure of the control unit, 8.59 PFU/100 cm2, 6.03 CFU/100 cm2, and 4.96 CFU/100 cm2, respectively. There was a statistically significant difference between the mean log10 surface concentrations following 10 minutes of treatment with the control unit compared to the PAT unit for E. coli (p=0.002), but not for MS2 (p=0.3358) or B. thuringiensis (p=0.0866).
After a single seeding and 6-hours of continuous treatment of the PAT unit, normalized average microbial log10 reductions of MS2 and B. thuringiensis were 1.43 and 1.32, respectively. The difference in average log10 reduction of all post-treatment samples between the control unit and the PAT unit was statistically significant for B. thuringiensis (p=0.0008) but not for MS2 (p=0.2568).
After two seedings and 5.25 hours of continuous treatment of the PAT unit, normalized average microbial log10 reductions of MS2 and B. thuringiensis were 1.59 and 1.26, respectively. There was a statistically significant difference in the average log10 reductions between the control unit and the PAT unit for MS2 (p=0.002) and B. thuringiensis (p=0.0003).
Scanning electron microscopy analysis identified visual modification to B. thuringiensis spores following treatment with the PAT unit. In this study, the tested ion generating PAT unit was effectively able to reduce airborne microbial concentrations between 1-2 log10 in a controlled chamber environment within 10 minutes and up to 6 hours of treatment. The implications of this study suggest that ion producing PAT systems may represent a beneficial supplement to cleaning and disinfection practices in the reduction of pathogen contamination from the airborne and fomite-airborne routes.
25
Lippmann, Christian. "Detector physics of resistive plate chambers." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=968973019.
Full text
26
SOUZA, EDSON A. de. "Medidas de fluxo de neutrons termicos utilizando ceramicas piroeletricas do tipo PZT com conversores de boro." reponame:Repositório Institucional do IPEN, 1995. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10425.
Full textAbstract:
Made available in DSpace on 2014-10-09T12:38:33Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:05:29Z (GMT). No. of bitstreams: 1 06050.pdf: 2669277 bytes, checksum: d5c09b330819048bd8379029a5eabfe4 (MD5)
Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
27
SAMPA, MARIA H. de O. "Desenvolvimento do processo de deposicao eletroforetica de boro em substratos de aluminio destinados a construcao de detectores de neutrons." reponame:Repositório Institucional do IPEN, 1988. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9892.
Full textAbstract:
Made available in DSpace on 2014-10-09T12:32:32Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:09:09Z (GMT). No. of bitstreams: 1 03259.pdf: 2834364 bytes, checksum: fcbdf9e370a39ffdb27be573e65f253c (MD5)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
28
Lamotte, Maxime. "Etude du signal optique des chambres à fission et évaluation de son exploitation pour un système de mesure neutronique d'un réacteur de génération IV Development and first use of an experimental device for fission-induced spectrometry applied to neutron flux monitoring SCENA: A simulation tool for radiation-induced gas scintillation Simulation of heavy-ion slowing-down tracks with the SCENA code Design and irradiation test of an innovative optical ionization chamber technology Pulse-reactor core monitoring with an innovative optical neutron detector." Thesis, Université Grenoble Alpes, 2021. http://www.theses.fr/2021GRALI023.
Full textAbstract:
Cette thèse de doctorat expose l'étude la luminescence induite dans des capteurs à gaz de type chambre à fission, afin d'évaluer son utilisation pour le suivi de puissance des réacteurs nucléaires de quatrième génération comme ASTRID.Le dépôt d'énergie dans un gaz par des ions lourds produits lors de fissions nucléaires dans une chambre à fission est d'ordinaire exploité pour sa capacité à produire des charges libres, qui peuvent être détectées avec des électrodes. Cette méthode, utilisée depuis le début de l'ère atomique, n'est pas sans inconvénients, et des axes d'amélioration ont été clairement identifiés.En estimant la production d'états excités du gaz d'une chambre à fission classique, on déduit que de la lumière peut être émise en son sein, et être détectée par un photo-détecteur. L'utilisation du signal optique plutôt qu'électrique apporte une robustesse accrue aux systèmes de mesures neutroniques, insensibles au bruit électromagnétique.L'étude spectroscopique d'un plasma d'origine nucléaire dans un dispositif analytique dimensionné et conçu par nos soins permet d'enregistrer des spectres de raies d'émission caractéristiques de la scintillation du gaz. L'analyse de ses raies permet d'affirmer la supériorité de la détection optique de neutrons, car la pression et la composition du gaz de remplissage peuvent alors être estimées en ligne.Parallèlement à nos activités expérimentales, un code de simulation de la dynamique de peuplement des niveaux des plasmas froids excités par ions-lourds est développé afin d'optimiser de futurs détecteurs basés sur ce principe. Les temps caractéristiques nécessaires à la génération d'états radiatifs et la position des excitations autour d'une trace d'ionisation ont été estimés.Plusieurs prototype de capteurs de neutrons fonctionnant uniquement sur un principe optique sont exploités dans des faisceaux de neutrons froids du réacteur Orphée afin de vérifier la preuve de concept d'un tel système de mesure neutronique. Des essais dans le réacteur Cabri permettent quant à eux de quantifier la limite de détection, la linéarité et la dynamique du système.Les très bons résultats apportés par ces trois volets valident la preuve de concept de la détection passive et en ligne de neutrons, capable d'auto-diagnostic, pour des applications exigeantes en milieu difficileThis PhD thesis details the study of luminescence produced in gaseous detectors as fission chambers, to evaluate its use in 4th generation nuclear reactor power monitoring, as ASTRID.Energy deposition in the gas, from heavy-ions produced during nuclear fission in a fission chamber is usually used for its charge generation ability, that can be detected with electrodes. Such method has been used since the beginning of atomic era present disadvantages, and necessary improvements have been assessed.By estimating fission chamber gas excited states production, one can deduce intrinsic light emission, and its detection by appropriate photo-detectors. Use of an optical signal against an electric one improves dependability of a neutron flux monitoring system, immune to electromagnetic noise.Spectroscopic studies of a nuclear plasma in a self-designed analytical device allows observation of typical gas scintillation emission lines. Analysis of emission lines reinforce optical detection attraction, as pressure and gas composition can be monitored online.Alongside our experiments, a simulation code dedicated to heavy-ions induced cold-plasma excited levels population has been produced to optimise future detectors relying on optical emission. Typical times encountered for excited states generation and their position around an ionization track have been estimated.Several neutron detector prototypes based on the sole gas scintillation principle have been assessed in cold neutron beam lines of the Orphée reactor, to validate a proof of concept for neutron monitoring. Experiments on the Cabri reactor allowed quantification of detection limit, linearity and dynamic range of our system.The positive outcomes provided by these 3 lines of work validate the proof of concept of passive, on-line, and self-diagnosed neutron detection with high dependability in harsh environments
29
Ahmed, Syed Naeem. "Quantum fluctuations in a segmented ionization chamber for beam monitoring of synchrotron radiation." [S.l. : s.n.], 1998. http://deposit.ddb.de/cgi-bin/dokserv?idn=957510330.
Full text
30
Münnich, Astrid. "Simulation studies for a high resolution time projection chamber at the international linear collider." [S.l.] : [s.n.], 2007. http://deposit.ddb.de/cgi-bin/dokserv?idn=984635068.
Full text
31
Sans, Merce Marta. "Development of drift chambers and physics simulations for the COMPASS experiment." Diss., [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=96444139X.
Full text
32
Rabeony, Haveloma Manese. "Phenomenes de nucleation en phase vapeur : condensation a basse temperature et en presence d'ions." Université Louis Pasteur (Strasbourg) (1971-2008), 1986. http://www.theses.fr/1986STR13012.
Full textAbstract:
Etude experimentale de la germination homogene de vapeurs organiques a basse temperature a l'aide d'une chambre a diffusion thermique en vue de tester sur le plus grand intervalle possible de temperature la theorie classique de la germination homogene et de confronter les resultats obtenus avec ceux d'autres techniques experimentales. Etude theorique et experimentale de la germination heterogene en presence d'ions : l'etude theorique permet de verifier l'aptitude des differentes theories a prevoir correctement l'influence de l'ion central, puis les predictions sont confrontees aux resultats experimentaux obtenus a l'aide de la chambre a diffusion thermique
33
Jenkins, Helen L. "Polyembryony, brood chamber development and gender specialisation in cyclostome bryozoans." Thesis, Bangor University, 2013. https://research.bangor.ac.uk/portal/en/theses/polyembryony-brood-chamber-development-and-gender-specialisation-in-cyclostome-bryozoans(1ae0346f-b932-4a2f-8169-a81b6e8bde4b).html.
Full textAbstract:
Investigations were conducted into aspects of the reproductive biology of the Cyclostomata, a relatively understudied ancient order of bryozoans. Evidence for polyembryony (cloning of sexually produced embryos) in all three major cyclostome clades was obtained using a molecular genetic approach (Chapter 2) confirming historical inferences based on microscopy and supporting the widely held view that this apparently paradoxical reproductive mode characterises the order. The paradoxical nature of polyembryony in the case of cyclostomes was investigated. Genotyping provided evidence for the prolonged production of genetically identical larvae from a single brood in Filicrisia geniculata and the presence of genetic diversity between broods within the same colony (Chapter 5). By cloning multiple progeny genotypes at a given time and testing each against varying environmental conditions over a substantial period, polyembryony may be less paradoxical in this group than first assumed. Variation in gender roles among colonies of Filicrisia geniculata was investigated using cultured material (Chapter 4). Two distinct categories of colony were discovered. Sperm were produced exclusively by 'male' colonies, composed solely of autozooids. 'Female' colonies comprised regular autozooids and gonozooids. These observations are consistent with at least very pronounced gender specialisation, apparently amounting to outright gonochorism, at the colony level. This is the first properly documented example of separate sexes in bryozoans. Mating trials investigating the effect of exposure to conspecific allosperm on brood chamber development revealed variation in reproductive traits between the two cyclostome species studied (Chapter 3). Tubulipora plumosa demonstrated greater production of gonozooids and larvae in the presence of conspecific allosperm, but with evidence of some selfing when in reproductive isolation. Similar investigations with Filicrisia geniculata revealed that, in female colonies, completion of gonozooid development and brooding occurred exclusively in the presence of allosperm.
34
Schreiner, Alexander. "Aging studies of drift chambers of the HERA-B outer tracker using CF4 -based gases." [S.l. : s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=964245442.
Full text
35
Mahmoud, Tariq. "Development of the readout chamber of the ALICE transition radiation detector and evaluation of its physics performance in the quarkonium sector." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972387382.
Full text
36
MAIA, ANA F. "Padronização de feixes e metodologia dosimétrica em tomografia computadorizada." reponame:Repositório Institucional do IPEN, 2005. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11291.
Full textAbstract:
Made available in DSpace on 2014-10-09T12:50:22Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T13:58:51Z (GMT). No. of bitstreams: 1 10890.pdf: 10562798 bytes, checksum: 063bd7e321751780a6d96cafecfe45bc (MD5)
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
FAPESP:01/06837-2
37
Abu, Shgair Khaleel. "New possibilities for building high-vacuum chambers using glued aluminum plates and application to sputtered nanocomposite coatings." [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=966505174.
Full text
38
Burgei, Rémi. "Une chambre à plaques parallèles à avalanche pour la localisation d'ions lourds relativistes." Paris 11, 1989. http://www.theses.fr/1989PA112289.
Full textAbstract:
Afin de localiser le point d'impact des ions lourds relativistes sur la cible de Diogène, nous avons réalisé et mis au point un détecteur X-Y à avalanche à basse pression d'isobutane comportant trois feuilles minces métallisées. Une étude préliminaire montre que c'est le seul détecteur répondant à notre cahier des charges : efficacité, précision de localisation, faible masse totale de matière (1,9 mg/cm2) répartie uniformément dans le faisceau de particules. La réalisation fait largement appel à une électronique fiable qui procure une grande souplesse de réglage et garantit une excellente stabilité de fonctionnement. La localisation basée sur une mesure du temps de transit des signaux dans une ligne à retard représente la meilleure solution associant faible coût et bonnes performances. Les mesures du gain, de l'efficacité et de la précision de localisation s'effectuent en laboratoire à l'aide d'une source de particules alpha. L'association de deux de nos détecteurs installés au Laboratoire National Saturne permet de reconstruire parmi un million de particules par seconde la trajectoire des 10 à 100 qui sont désignées par le déclencheur de Diogène. Les premiers résultats expérimentaux avec un faisceau d'ions argon à 400 MeV par nucléon donnent une incertitude de localisation sur la cible de 0,54 mm (écart type) et, pour notre détecteur, de 0,31 mm avec une efficacité de 94 %. Les résultats de l'ensemble expérimental Diogène, destiné à l'étude des collisions centrales entre ions lourds relativistes, gagnent en précision et en rapidité de dépouillement grâce à notre réalisation qui est opérationnelleIn order to determine the interaction point of relativistic heavy ions in the Diogene target, we have built and tested an X-Y low pressure parallel plate avalanche chamber. It uses three thin metallized foils and is filled with isobutane. A preliminary study shows that it is the only detector with the required specifications: efficiency, accurate position determination and a small uniform amount of material (1. 9 mg/cm²) for the particle beam to go through. The electronics system is designed for reliability, easy adjustments and high stability. The interaction point is given on delay-line read-out. This represents the optimum compromise between low price and good performance. Laboratory measurements of gain, efficiency and position accuracy are done with an alpha-particle source. Two of these detectors are working at the Saturne National Laboratory. They allow the trajectory of several tens of particles (among a million per second) to be reconstructed. With an argon beam at 400 MeV per nucleon, the position uncertainty in the target has been measured to be 0. 5 mm (standard deviation). This uncertainty is 0. 3 mm for each detector, with an efficiency of 94 per cent. Our set-up, which is now operational, improves the accuracy of the results and speed of analysis of Diogene experiments devoted to the study of central collisions between heavy ions
39
Kosmata, Marcel. "Elastische Rückstoßatomspektrometrie leichter Elemente mit Subnanometer-Tiefenauflösung." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-84041.
Full textAbstract:
In der vorliegenden Arbeit wird erstmals das QQDS-Magnetspektrometer für die höchstauflösende Ionenstrahlanalytik leichter Elemente am Helmholtz-Zentrum Dresden-Rossendorf umfassend vorgestellt. Zusätzlich werden sowohl alle auf die Analytik Einfluss nehmenden Parameter untersucht als auch Methoden und Modelle vorgestellt, wie deren Einfluss vermieden oder rechnerisch kompensiert werden kann. Die Schwerpunkte dieser Arbeit gliedern sich in fünf Bereiche. Der Erste ist der Aufbau und die Inbetriebnahme des QQDS-Magnetspektrometers, der zugehörige Streukammer mit allen Peripheriegeräten und des eigens für die höchstauflösende elastische Rückstoßanalyse entwickelten Detektors. Sowohl das umgebaute Spektrometer als auch der im Rahmen dieser Arbeit gebaute Detektor wurden speziell an experimentelle Bedingungen für die höchstauflösende Ionenstrahlanalytik leichter Elemente angepasst und erstmalig auf einen routinemäßigen Einsatz hin getestet. Der Detektor besteht aus zwei Komponenten. Zum einen befindet sich am hinteren Ende des Detektors eine Bragg-Ionisationskammer, die zur Teilchenidentifikation genutzt wird. Zum anderen dient ein Proportionalzähler, der eine Hochwiderstandsanode besitzt und direkt hinter dem Eintrittsfenster montiert ist, zur Teilchenpositionsbestimmung im Detektor. Die folgenden zwei Schwerpunkte beinhalten grundlegende Untersuchungen zur Ionen-Festkörper-Wechselwirkung. Durch die Verwendung eines Magnetspektrometers ist die Messung der Ladungszustandsverteilung der herausgestreuten Teilchen direkt nach einem binären Stoß sowohl möglich als auch für die Analyse notwendig. Aus diesem Grund werden zum einen die Ladungszustände gemessen und zum anderen mit existierenden Modellen verglichen. Außerdem wird ein eigens entwickeltes Modell vorgestellt und erstmals im Rahmen dieser Arbeit angewendet, welches den ladungszustandsabhängigen Energieverlust bei der Tiefenprofilierung berücksichtigt. Es wird gezeigt, dass ohne die Anwendung dieses Modells die Tiefenprofile nicht mit den quantitativen Messungen mittels konventioneller Ionenstrahlanalytikmethoden und mit der Dickenmessung mittels Transmissionselektronenmikroskopie übereinstimmen, und damit falsche Werte liefern würden. Der zweite für die Thematik wesentliche Aspekt der Ionen-Festkörper-Wechselwirkung, sind die Probenschäden und -modifikationen, die während einer Schwerionen-bestrahlung auftreten. Dabei wird gezeigt, dass bei den hier verwendeten Energien sowohl elektronisches Sputtern als auch elektronisch verursachtes Grenzflächendurchmischen eintreten. Das elektronische Sputtern kann durch geeignete Strahlparameter für die meisten Proben ausreichend minimiert werden. Dagegen ist der Einfluss der Grenzflächendurchmischung meist signifikant, so dass dieser analysiert und in der Auswertung berücksichtigt werden muss. Schlussfolgernd aus diesen Untersuchungen ergibt sich für die höchstauflösende Ionenstrahlanalytik leichter Elemente am Rossendorfer 5-MV Tandembeschleuniger, dass die geeignetsten Primärionen Chlor mit einer Energie von 20 MeV sind. In Einzelfällen, wie zum Beispiel der Analyse von Bor, muss die Energie jedoch auf 6,5 MeV reduziert werden, um das elektronische Sputtern bei der notwendigen Fluenz unterhalb der Nachweisgrenze zu halten. Der vierte Schwerpunkt ist die Untersuchung von sowohl qualitativen als auch quantitativen Einflüssen bestimmter Probeneigenschaften, wie beispielsweise Oberflächenrauheit, auf die Form des gemessenen Energiespektrums beziehungsweise auf das analysierte Tiefenprofil. Die Kenntnis der Rauheit einer Probe an der Oberfläche und an den Grenzflächen ist für die Analytik unabdingbar. Als Resultat der genannten Betrachtungen werden die Einflüsse von Probeneigenschaften und Ionen-Festkörper-Wechselwirkungen auf die Energie- beziehungsweise Tiefenauflösung des Gesamtsystems beschrieben, berechnet und mit der konventionellen Ionenstrahlanalytik verglichen. Die Möglichkeiten der höchstauflösenden Ionenstrahlanalytik werden zudem mit den von anderen Gruppen veröffentlichten Komplementärmethoden gegenübergestellt. Der fünfte und letzte Schwerpunkt ist die Analytik leichter Elemente in ultradünnen Schichten unter Berücksichtigung aller in dieser Arbeit vorgestellten Modelle, wie die Reduzierung des Einflusses von Strahlschäden oder die Quantifizierung der Elemente im dynamischen Ladungszustandsnichtgleichgewicht. Es wird die Tiefenprofilierung von Mehrschichtsystemen, bestehend aus SiO2-Si3N4Ox-SiO2 auf Silizium, von Ultra-Shallow-Junction Bor-Implantationsprofilen und von ultradünnen Oxidschichten, wie zum Beispiel High-k-Materialien, demonstriertIn this thesis the QQDS magnetic spectrometer that is used for high resolution ion beam analysis (IBA) of light elements at the Helmholtz-Zentrum Dresden-Rossendorf is presented for the first time. In addition all parameters are investigated that influence the analysis. Methods and models are presented with which the effects can be minimised or calculated. There are five focal points of this thesis. The first point is the construction and commissioning of the QQDS magnetic spectrometer, the corresponding scattering chamber with all the peripherals and the detector, which is specially developed for high resolution elastic recoil detection. Both the reconstructed spectrometer and the detector were adapted to the specific experimental conditions needed for high-resolution Ion beam analysis of light elements and tested for routine practice. The detector consists of two compo-nents. At the back end of the detector a Bragg ionization chamber is mounted, which is used for the particle identification. At the front end, directly behind the entrance window a proportional counter is mounted. This proportional counter includes a high-resistance anode. Thus, the position of the particles is determined in the detector. The following two points concern fundamental studies of ion-solid interaction. By using a magnetic spectrometer the charge state distribution of the particles scattered from the sample after a binary collision is both possible and necessary for the analysis. For this reason the charge states are measured and compared with existing models. In addition, a model is developed that takes into account the charge state dependent energy loss. It is shown that without the application of this model the depth profiles do not correspond with the quantitative measurements by conventional IBA methods and with the thickness obtained by transmission electron microscopy. The second fundamental ion-solid interaction is the damage and the modification of the sample that occurs during heavy ion irradiation. It is shown that the used energies occur both electronic sputtering and electronically induced interface mixing. Electronic sputtering is minimised by using optimised beam parameters. For most samples the effect is below the detection limit for a fluence sufficient for the analysis. However, the influence of interface mixing is so strong that it has to be included in the analysis of the layers of the depth profiles. It is concluded from these studies that at the Rossendorf 5 MV tandem accelerator chlorine ions with an energy of 20 MeV deliver the best results. In some cases, such as the analysis of boron, the energy must be reduced to 6.5 MeV in order to retain the electronic sputtering below the detection limit. The fourth focus is the study of the influence of specific sample properties, such as surface roughness, on the shape of a measured energy spectra and respectively on the analysed depth profile. It is shown that knowledge of the roughness of a sample at the surface and at the interfaces for the analysis is needed. In addition, the contribution parameters limiting the depth resolution are calculated and compared with the conventional ion beam analysis. Finally, a comparison is made between the high-resolution ion beam analysis and complementary methods published by other research groups. The fifth and last focus is the analysis of light elements in ultra thin layers. All models presented in this thesis to reduce the influence of beam damage are taken into account. The dynamic non-equilibrium charge state is also included for the quantification of elements. Depth profiling of multilayer systems is demonstrated for systems consisting of SiO2-Si3N4Ox-SiO2 on silicon, boron implantation profiles for ultra shallow junctions and ultra thin oxide layers, such as used as high-k materials
40
Bashford, Christina Margaret. "Public chamber-music concerts in London, 1825-50 : aspects of history, repertory and reception." Thesis, King's College London (University of London), 1996. https://kclpure.kcl.ac.uk/portal/en/theses/public-chambermusic-concerts-in-london-182550--aspects-of-history-repertory-and-reception(49fd20fc-be12-4495-b0e9-6cb82deb2914).html.
Full text
41
Nowack, Andreas. "Investigations of a pre-series of micro strip gas chambers with gas electron multipliers for high rate environments." [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=965272036.
Full text
42
Osinga-Blättermann, Julia-Maria [Verfasser], and Wolfgang [Akademischer Betreuer] Schlegel. "Determination of absorbed dose to water in a clinical carbon ion beam by means of fluorescent nuclear track detectors, ionization chambers, and water calorimetry / Julia-Maria Osinga-Blättermann ; Betreuer: Wolfgang Schlegel." Heidelberg : Universitätsbibliothek Heidelberg, 2017. http://d-nb.info/1180738578/34.
Full text
43
Vazquez, Numez Bernardo. "An experimental and numerical study of forced convection in ventilated chambers." Thesis, King's College London (University of London), 1997. https://kclpure.kcl.ac.uk/portal/en/theses/an-experimental-and-numerical-study-of-forced-convection-in-ventilated-chambers(5525a851-2a87-4a65-9669-d7098efd28ac).html.
Full text
44
Jacquens, Julien. "Stabilité, réactivité et performances de conducteurs par ions oxyde de la famille LAMOX comme éléments de cœur de pile à combustible SOFC mono-chambre." Le Mans, 2010. http://cyberdoc.univ-lemans.fr/theses/2010/2010LEMA1020.pdf.
Full textAbstract:
Les composés de la famille LAMOX, dérivés de La2Mo2O9, sont de bons conducteurs ioniques par ions oxyde sous air mais peuvent être réduits sous atmosphère pauvre en oxygène. Mes travaux ont consisté à démontrer la faisabilité de leur utilisation en tant qu’électrolyte de pile à combustible à oxydes solides (SOFC) en configuration monochambre (moins réductrice). La première partie des résultats traite de la stabilité et des propriétés catalytiques des matériaux LAMOX et d’électrodes sous atmosphère propane:air (proche des conditions de pile monochambre). La stabilité des poudres LAMOX a été démontrée après 72h à 600°C. La2Mo2O9 (LM) peut en outre présenter une activité catalytique oxydative intéressante en vue d’une utilisation sous forme de cermet Ni:LM. Sous atmosphère plus pauvre en oxygène (dihydrogène dilué), des mesures électriques ont montré que la réduction des composés LAMOX semble être optimisable afin de réaliser des électrodes conductrices mixtes ioniques/électroniques (MIEC). Une deuxième partie traite de la compatibilité des interfaces électrolyte/électrodes. Des tests de compatibilité, chimique et mécanique, nous ont conduit à privilégier l’utilisation de nouveaux matériaux de cathode, La0,85Ca0,15FeO3-δ et La0,75Ca0,25Co0,8Fe0,2O3-δ/Ce0,9Gd0,1O1,95 qui n’avaient jamais été testés en conditions réelles de pile. L’anode Ni:La2Mo1,5W0,5O9 (LMW0,5) quant à elle n’a pas présenté de problèmes d’incompatibilité avec l’électrolyte LMW0,5. Enfin, dans une troisième partie, des tests de piles montrent que l’utilisation de cet électrolyte semble possible en conditions réelles de pile monochambre à 600°C. Les performances de piles obtenues sont toutefois inférieures de deux ordres de grandeur à celles de la littérature, en raison de la faiblesse de l’activité électrochimique des cathodes pour la réduction du dioxygène, vérifiée par tests de cellules symétriques. La teneur en nickel de l’anode et ses dimensions se sont par ailleurs avérées déterminantes pour l’orientation du choix des conditions opératoires et la stabilité des performances de pileThe compounds of the LAMOX family, based on La2Mo2O9, are pure fast oxide ionic conductors in air. However, they could be reduced in atmosphere with low oxygen partial pressure. The aim of this work has been to probe the feasibility of their use as electrolyte of Solid Oxide Fuel Cell, with inglechamber geometry (less reducing). The first part of results is dedicated to the stability and catalytical properties of LAMOX compounds and electrode materials under propane:air mixture (similar to single chamber conditions). The stability of LAMOX powder has been probed after 72h at 600°C. Moreover La2Mo2O9 (LM) seems to be a good oxidation catalyst, which might be useful as anode composite Ni:LM. Under more reducing atmosphere (diluted hydrogen), electrical measurements have shown that the reduction of LAMOX compounds could be optimised in order to form mixed ionic/electronic conducting anodes. In the second part, interest is given to solid/solid compatibility between different components. Chemical and mechanical compatibility tests have guided our choice on two new cathode materials, La0. 85Ca0. 15FeO3-δ and La0. 75Ca0. 25Co0. 8Fe0. 2O3-δ/Ce0. 9Gd0. 1O1. 95 which had never been tested in real operating conditions of fuel cell. Concerning the anode Ni:La2Mo1. 5W0. 5O9 (LMW0,5), no problem of incompatibility has been observed with the electrolyte LMW0. 5. Finally, in a third part, fuel cell tests have shown that the use of this electrolyte seems to be possible under propane:air mixture at 600°C. However, the power of cell is lower with two levels of magnitude to that reported in litterature, because of poor electrochemical activity of the cathodes for oxygen reduction, checked by symmetric cell measurements. The nickel content of the anode and its dimensions have also proved crucial for the choice of operating conditions and the stability of fuel cell performances
45
Monnet, François. "Système de détection à large acceptance angulaire et grande dynamique en énergie destiné à la physique des ions lourds aux énergies intermédiaires : détecteur M.E.Ω [oméga]." Paris 11, 1985. http://www.theses.fr/1985PA112156.
Full textAbstract:
Destiné à la physique des ions lourds aux énergies intermédiaire, le détecteur M. E. Ω fait appel à des techniques de détection très variées (chambre d’ionisation, plaques parallèles, plastiques scintillants), et complémentaires. Elles permettent la mesure de la vitesse et de l’énergie de noyaux, donc de leur masse et de leur charge, pour de grandes dynamiques. De l’étude théorique approfondie de chacune de ces techniques, on en déduit les limitations et les sources de perturbations. On explique les méthodes utilisées pour l’optimisation du compteur et les résultats obtenus. La sectorisation interne du détecteur, qui permet un ajustement des taux de comptage et des réglages électroniques en fonction de l’angle, s’est révélée bien adaptée à la physique des ions lourds aux énergies intermédiaires. On commente enfin la première expérience, réalisée avec M. E. Ω, sur le système Ar (35 MeV/u) + AgBuilt for intermediate energy heavy ions nuclear physics, the M. E. Ω detector uses various and complementary detection methods: ionization chamber, parallel plate avalanche counter, plastic scintillators. With these techniques, velocity, energy, mass and charge of nuclei were measured over wide range. From the detailed theoretical study of each method, limitations and perturbation causes are deduced. The solutions used for optimizing the detector, and the main results are exposed. The internal sectorisation of the detector, which permits a modulation in counting rate and electronical adjustments, has been revealed to be very suitable for heavy ions intermediate energy physics. Results of the first experiment realized with M. E. Ω (Ar + Ag at 35 MeV/u) are commented
46
Csigi, Péter János. "Shades of identity : an iconographic approach to the early Christian burial chambers in Sopianae (Pannonia)." Thesis, King's College London (University of London), 2018. https://kclpure.kcl.ac.uk/portal/en/theses/shades-of-identity-an-iconographic-approach-to-the-early-christian-burial-chambers-in-sopianae-pannonia(cb986e5d-ec77-47ef-b676-cf7cf582c271).html.
Full textAbstract:
There are several burial chambers in the Late Antique cemetery of the Roman town of Sopianae in Pannonia province (modern Hungary) decorated with wall paintings resembling Roman catacomb art. These underground chambers from the second half of the fourth century contain both specifically Christian images as well as gen-eral motifs in Roman funerary art. Via the iconographic analysis of the decorations in the SS Peter and Paul Burial Chamber and the Burial Chamber with the Jar, the identity of the commissioners can be assumed. The various iconographic elements and the compositions as a whole were used in the different levels of contempora-neous communication, which will be interpreted through the concept of ‘language games’ according to Ludwig Wittgenstein’s epistemology. Six hypotheses explaining the repertoire of biblical scenes in early Christian artefacts are investigated and evaluated. The question of the presence of martyr relics (especially that of the Sancti Quattro Coronati) in this cemetery is considered and relevant hypotheses evaluated. The iconographic parallels of the key motifs in the SS Peter and Paul Bur-ial Chamber, such as the Christogram and the images of Peter and Paul, are pre-sented and compared to examples in art from Rome and the Balkans and inter-preted as showing ‘family resemblances’ also in the Wittgensteinian sense. The identification of an ambiguous wall painting in the same chamber is attempted by proposing a hypothesis of an intentionally ambiguous image combining the Three Youths in the Fiery Furnace and the Adoration of the Magi in a single picture. The religious identification of the Burial Chamber with the Jar is studied by questioning the validity of the concept of ‘neutrality’ in Late Antique art. Late Antiquity is inter-preted in the framework of mutually enriching interactions between different reli-gious groups via the notion of ‘lived religion’.
47
Eason, Christina. "Their Lordships divided? : the representation of women in the transitional House of Lords 1999-2009." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/their-lordships-divided-the-representation-of-women-in-the-transitional-house-of-lords-19992009(77d08d32-d7e2-4b77-afc8-dedd1987d4b7).html.
Full textAbstract:
This thesis set out to discern how women's representation, as a multi-faceted concept and process, plays out in the context of the House of Lords. The primary motivation of this inquiry concerned the reality that women are persistently under-represented in political chambers worldwide. Beyond this, scholarship has overlooked the site of the House of Lords despite significant advances made in women's presence that facilitate closer analysis. This is also compounded by the status of the chamber itself: in its 'transitional' phase post the passing of the House of Lords Act 1999 the chamber is suggested to act with greater legitimacy and effectiveness. Finally concentration upon the representation of women in the transitional House of Lords is pertinent as the chamber remains in a state of flux and there is an opportunity to prioritise women's representation as a key plank of the reform agenda. Normative feminist interpretations of representation are the primary frameworks of analysis. Methodologically, this research inquiry synthesised and triangulated the use of quantitative and qualitative research techniques in order to unpack the processes and influences upon all dimensions of women's political representation in the House of Lords. This helped to present a sufficiently nuanced analysis. There have been obvious attempts to numerically feminise the chamber, although there are systemic de facto and de jure reserved seats for men in the chamber which guard against radical improvements in women's descriptive presence. Women peers undertake important roles and the House of Lords maintains a culture and institutional norms that are befitting for women and feminised styles of politics which is positive for the symbolic representation of women. Finally, women peers actively seek to represent women through the agenda-setting features of the Lords, although the way this is manifested is mediated by political affiliation. The opportunities to substantively represent women through the legislative features of the House of Lords are narrower, although both male and female peers have successfully influenced legislative output to act for women.
48
Rider, C. M. "Our city and Chamber of London : the relationship between the City of London and the Crown in the reigns of Edward VI and Mary." Thesis, Bangor University, 1992. https://research.bangor.ac.uk/portal/en/theses/our-city-and-chamber-of-london--the-relationship-between-the-city-of-london-and-the-crown-in-the-reigns-of-edward-vi-and-mary(e2a28ab4-2afa-45b4-902f-4eb7368abaee).html.
Full textAbstract:
This study of the relationship between the City of London and the Crown in the reigns of Edward VI and Mary brings together the results of original research, based principally on the records of the City Corporation, the City livery companies and the central government, and the work of other historians of sixteenth century London, in particular G D Ramsay, S Rappaport, S Brigden, and I Archer. It examines the interaction between the central and civic governments in a number of areas of mutual concern: finance, overseas and internal trade, taxation, war and rebellion, high politics, patronage and pageantry. In the course of the study an attempt is made to trace the development of the City as a financial centre, to explore its role in relation to the royal debt and to analyse the reasons for the withdrawal and the subsequent restoration of Hanseatic privileges in England. Other issues used to illustrate the liaison between the state and the capital in the mid-sixteenth century include the chantry legislation of 1548, the rebellions of 1549 and 1554, the coups d'etat of 1549 and 1553, and the pageantry provided by the City for Edward VI, Mary and Philip II. The conclusion reached is that, although the Crown had particular need of the capital at this period, both financially, in relation to taxation and to the royal debt, and politically, to validate its regime and to enforce its policies, the relationship was not one-sided. The City establishment continued to require central government support to legitimise its rule, to further the trade of its merchants, to ensure adequate supplies of commodities in the capital and, most importantly, to retain its liberties and privileges.
49
Matysiak-Budnik, Tamara. "Helicobacter pylori et modifications de la perméabilité épithéliale gastrique." Bordeaux 2, 2000. http://www.theses.fr/2000BOR28767.
Full text
50
Shaddad, Amna. "The classification and dynamics of the momentum polytopes of the SU(3) action on points in the complex projective plane with an application to point vortices." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/the-classification-and-dynamics-of-the-momentum-polytopes-of-the-su3-action-on-points-in-the-complex-projective-plane-with-an-application-to-point-vortices(456a7a49-ef1b-4660-a8e6-8d4cd0791d9d).html.
Full textAbstract:
We have fully classified the momentum polytopes of the SU(3) action on CP(2)xCP(2) and CP(2)xCP(2) xCP(2), both actions with weighted symplectic forms, and their corresponding transition momentum polytopes. For CP(2)xCP(2) the momentum polytopes are distinct line segments. The action on CP(2)xCP(2) xCP(2), has 9 different momentum polytopes. The vertices of the momentum polytopes of the SU(3) action on CP(2)xCP(2) xCP(2), fall into two categories: definite and indefinite vertices. The reduced space corresponding to momentum map image values at definite vertices is isomorphic to the 2-sphere. We show that these results can be applied to assess the dynamics by introducing and computing the space of allowed velocity vectors for the different configurations of two-vortex systems.