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Taborelli, Mauro. "Magnetism of epitaxial thin films and single-crystal surfaces studied with spin-polarized secondary electrons /." [S.l.] : [s.n.], 1988. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=8545.
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Skladaný, Roman. "Návrh detektoru sekundárních elektronů pro ultravakuový elektronový mikroskop." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-402574.
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In this master’s thesis, a mechanical design of an in-column secondary electrons (SE) detector is presented. It is an ultravacuum compatible fibre-scintillation detector designed for use in an ultrahigh vacuum scanning electron microscope (UHV SEM). The designed in-column SE detector was manufactured and tested upon overcoming R&D challenges. The first section of this thesis deals with theoretical basis needed for understanding of functional principles of UHV SEM system and means of SE’s detection. In the second section, mechanical design of the in-column SE detector is described. The last section describes functionality of the designed detector. Effectiveness of light shielding of the detector was tested and the detective quantum efficiency was measured. Finally, images created by the designed in-column detector and an in-chamber SE detector were evaluated and compared.
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Cai, Zhongli. "DNA damage induced by secondary electrons and x-rays." Thèse, Université de Sherbrooke, 2005. http://savoirs.usherbrooke.ca/handle/11143/4204.
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X-rays are widely used in medical diagnosis and radiotherapy. The effects of X-rays on cells are dominated by their actions on the cellular DNA. The interaction of X-rays with DNA produces photoelectrons, Auger electrons, Compton electrons and large quantities of secondary electrons (SE), the majority of which have energies lower than 70 eV. This thesis aims to compare the DNA damage induced by SE and X-rays. A dosimetry method to measure the absorbed dose of Al[subscript k alpha] X-rays (1.5 keV) in ultrahigh vacuum chamber (UHV) using radiochromatic dosimetry films and a color scanner was developed. This provided the value for the absorbed dose in dry biological samples irradiated under UHV, allowing direct comparison of DNA damage induced by Al[subscript k alpha] X-rays and SE. The induction of covalent interduplex DNA crosslinks (CL) by X-rays was detected using restriction enzyme digestion and alkaline agarose gel electrophoresis. The G value for CL induction in DNA in UHV by Al[subscript k alpha] X-rays is 16 « 4 nmol J[superscript -1], 2.8 fold that of double strand breaks (DSB). G(CL) in air by soft X-rays (14.8 keV) is 3 « 1([gamma] [approximate] 6, [gamma] is defined as the number of water molecules per nucleotide,) and 3.2 « 0.4 ([gamma] [approximate] 21) nmol J[superscript -1], 61 and 89% of those for DSB. These results suggest that CL is an important type of DNA damage, possibly as important as DSB in radiobiology. A new method of studying SE-induced DNA damage in comparison to Al[subscript k alpha] X-rays under identical experimental conditions was developed, using thin and thick films of DNA deposited on tantalum. X-ray induced SE emission from the tantalum serves as a source of SE in UHV. The lower limits of G values for DNA SSB and DSB induced by SE were derived to be: 86 « 2 and 8 « 2 nmol J[superscript -1], respectively. These values are 1.5 and 1.6 times larger than those obtained with 1.5 keV photons. The enhanced DNA damage by SE emission from tantalum exposed to soft X-rays (14.8 keV) in air was studied as a function of DNA hydration levels. The enhancement factor for SSB, DSB and CL induced by SE vs X-rays were derived to be: 5.0 « 0.8, 3.6 « 1.0 and 9 « 4 at [gamma] [approximate] 6, and 8 « 1, 9 « 2 and 5.0 « 1.4 at [gamma] [approximate] 21, respectively. This study provides a molecular basis for understanding the enhanced interface biological effects during X-ray diagnostic examination and radiotherapy. A self-assembled monolayer (SAM) of a 5'-32 P-labelled 3'-thiolated oligonucleotide chemisorbed on gold was bombarded by low energy electrons (LEE) of 8 to 68 eV."--Résumé abrégé par UMI.
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Zheng, Yi. "Damage to simple DNA components induced by secondary electrons." Thèse, Université de Sherbrooke, 2005. http://savoirs.usherbrooke.ca/handle/11143/4218.
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A major objective of our research group is to understand the mechanism of DNA damage induced by secondary electrons and its relationship to radiosensitization. My project focuses on simple systems, in which small DNA components, nucleosides (dThd), nucleotides (dTp), oligonucleotides (GCAT and CGTA) and modified oligonucleotides, are exposed to low energy electrons, and the subsequent reactions are studied by chemical analysis of the products. A new low-energy electron irradiation system was constructed in which a relatively large area of target compounds can be irradiated. Thus, this system provides sufficient amount of damage products for further chemical analysis by HPLC, GC/MS and LC/MS. Our systematic studies revealed two main types of LEE-induced fragmentation reactions in DNA: (1) cleavage of the N-glycosidic and (2) cleavage of the phosphodiester bond. The results show that phosphodiester bond cleavage by 4-15 eV electrons involves cleavage of the C-O bond rather than the P-O bond. Below 14 eV, the yield of LEE-induced damage products in DNA is dominated by the formation of transient anions located around 6 and 10 eV. Beyond 14 eV, direct LEE impact is believed to contribute substantially to damage. Our studies suggest that electron transfer occurs from the base moiety to the sugarphosphate backbone in DNA, but the inverse does not occur, in agreement with theoretical studies. The present study provides a chemical basis for the formation of strand breaks by the reaction of LEE with DNA. The capture of non-thermalized electrons with 4-10 eV of energy by DNA bases may be an important factor in DNA damage in living cells.
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Elliott, Sarah Louise. "Dopant profiling with the scanning electron microscope." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270885.
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Cai, Linghui, and 蔡凌辉. "Monte Carlo simulation of positron induced secondary electrons in thincarbon foils." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B45460863.
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Aebi, Philippe. "Experimental and theoretical study of scattering state fine structures observed in secondary electron spectroscopy from solid surfaces /." [S.l.] : [s.n.], 1989. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=8994.
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Pintao, Carlos Alberto Fonzar. "Novo arranjo para determinar os coeficientes de emissão e a distribuição de energia dos elétrons secundários emitidos por sólidos." Universidade de São Paulo, 1996. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-14112007-091415/.
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Neste trabalho estudou-se um novo arranjo de medida para se obter a distribuição de energia dos elétrons secundários emitidos e os coeficientes de emissão por um sólido. Pelo fato deste arranjo permitir a medida direta do potencial de superfície no caso dos polímeros e da ddp de contato no caso dos metais, foi possível aplicar e descrever teoricamente o método de medida empregado para determinar o espectro energético dos secundários para a platina, Teflon-FEP, Mylar, PVDF- α, PVDF- β e polimero condutor. As cargas acumuladas durante a irradiação dos polímeros foram compensadas através do próprio feixe eletrônico. Este procedimento não é muito usual em relação aqueles aplicados na literatura e mostrou-se bastante eficaz. Pela primeira vez empregou-se o método dinâmico para determinar o coeficiente de emissão total em função da energia dos elétrons incidentes nos metais e verificou-se que estes resultados são idênticos aqueles obtidos pelo método do pulso. Um desdobramento natural ao aplicar o método dinâmico aos metais foram as medidas realizadas para camadas de ouro com espessura de 50 nm, 10 nm e 2,5 nm depositada sobre o Teflon-FEP, que deram origem ao modelo das duas camadas na interpretação dos resultados experimentais.A new arrangement of measure was developed in this study, in order to obtain the energy distribution from the emitted secondaries and the emission yields by a solid. Because this arrangement allowed the direct measurement of the surface potential, in the case of metals, it was possible to apply and describe theoretically the mensuration method employed, to determine the energy distribution of the secondaries to platinum, Teflon-FEP. Mylar, PVDF α, PVDF- β and thie conducting polymer. The charges accumulated during the polymers irradiation were compensated through the electronic beam itself. This proceeding is not very usual, as referring to the ones applied in literature, and it proved to be very efficacious. The dynamic method was employed for the first time to metals in order to determine the total emission yield in function of the energy of the inciding electrons and it was found out that these results were identical to the ones obtained through the pulse method. As a natural development, by applying the dynamic method to metals, the measurements achieved were also applied to golden layers 50 nm, 10 nm and 2,5 nm wide deposited on Teflon-FEP, and they gave birth to the two layers, in the interpretation of the experimental results.
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Porter, Troy Anthony. "Signatures of the propagation of primary and secondary cosmic ray electrons and positrons in the galaxy." Title page, table of contents and abstract only, 1999. http://web4.library.adelaide.edu.au/theses/09PH/09php848.pdf.
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Includes bibliographical references (8 p.) Examines some of the consequences of the acceleration and production, and propagation, of high energy electrons and positrons in the Galaxy. In particular, predictions are made of the diffuse photon signals arising from the interactions of electrons and positrons with gas, low energy photons, and the galactic magnetic field during their transport in the Galaxy.
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Kay, Gillian. "Science practical work: what types of knowledge do secondary science teachers use?" Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/13355.
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Includes bibliographical references.The prominence of practical work in science curricula today infers that these activities offer unique learning experiences for achieving specific goals. Yet, but for a few exceptions, practical work in school science is often neglected and has not been effective in achieving the goals normally associated with it. The rationale behind this study was that an understanding of the bases for decisions made as teachers plan, enact and assess practical work in Grade 8 and 9 natural sciences, may reveal the nature of the knowledge base required for effective practical work. It was thought that such insight might also shed light on some of the reasons for the apparent lack of effective practical work in South African schools. Furthermore it could inform the design of those aspects of pre - service and in - service teacher professional learning programmes aimed at developing the knowledge and skills required for effective practical work. There is a paucity of research on the knowledge base required for science practical work and no instruments designed to measure, capture or describe such a knowledge base, were found. The aim of this study was firstly to develop a valid and reliable instrument to facilitate the analysis of what teacher s say and do with respect to practical work, and secondly to get a feel for using this instrument for the purpose it was intended. Informed by literature, and using Shulman’s notion of pedagogical content knowledge (PCK) as the theoretical lens, the analytical instrument, called the practical work PCK table (PPCK T able), consisting of different categories and sub - categories of knowledge, was developed. A number of strategies were used to improve the validity and reliability of the instrument. These strategies included: i) using the instrument to analyse interviews and lessons of three natural sciences teachers working in three different educational settings, ii) soliciting the input from experts in the field of PCK, and iii) determining the inter - rater agreement in the interpretation of the categories or sub - categories among four raters by calculating the percentage agreement and the Fleiss’ kappa statistic. Addressing the shortcomings revealed by these measures culminated in the final version of the instrument, the practical work knowledge table (PracK Table) and its accompanying codebook. The second aim was addressed by conducting a pilot case study to explore the usefulness of the PracK Table as a heuristic device. A series of eight Grade 9 lessons taught by one teacher were observed. Data sources included lesson observations, teacher and learner interviews, worksheets and samples of learners’ work. The PracK Table was used to identify and describe the knowledge the teacher drew on when he engaged his learners in practical work. This study has shown the construct, ‘PCK for practical work’, to be invalid. It also revealed that a useful, valid and reliable instrument could be developed, if it is informed by authoritative literature, and if its validity and reliability are empirically tested in real contexts. In the case study the strengths and weaknesses in a teacher’s knowledge and practice could readily be identified using PracK Table as the analytical tool. The findings of the case study indicate that a broad knowledge base and access to laboratory resources, although necessary, does not always translate into effective practical work. Furthermore, it suggests that for well - qualified, experienced natural sciences teachers, teaching in fairly well - resourced schools, it is their theories about teaching and learning in general that is the main factor that determines the effectiveness of the practical work they engage in. These findings could have significant implications for the development of teacher professional learning programmes.
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Gretak, Alyssa P. "The Relationship of Primary and Secondary Psychopathy to Different Types of Empathetic Deficits." University of Dayton / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1446738444.
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Primeau, Jessica M. "WHAT TYPES OF READ-ALOUD PRACTICES DO SECONDARY TEACHERS ENGAGE IN? WHAT ARE THE STUDENTS' PERCEPTIONS OF THE SECONDARY READ-ALOUD PRACTICE?" Bowling Green, Ohio : Bowling Green State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=bgsu1174664271.
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Zhang, Pengchong. "Comparing different types of EFL vocabulary instruction for Chinese senior secondary school learners of English." Thesis, University of Reading, 2018. http://centaur.reading.ac.uk/77933/.
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The primary aim of the study was to explore the teaching and learning of vocabulary through listening among 137 senior secondary school EFL learners in China. A quasiexperimental, mixed method design was adopted comparing incidental vocabulary learning through listening (Control Group) with different types of Lexical Focus-on-Form delivered to three treatment groups: post-listening vocabulary explanations in the L2; codeswitched explanations; and explanations providing additional cross-linguistic information (contrastive Focus-on-Form, CFoF). The second aim of the study was to investigate whether learners’ listening comprehension developed alongside their vocabulary. Finally, the study explored what strategies were used by learners in response to the vocabulary instruction in each of the three experimental conditions. The data collection procedure, involving a classroom intervention, lasted three months. Learners completed aural vocabulary tests at pre, post and delayed post-test and listening assessments at pre and post-test. The three treatment groups also completed an additional final vocabulary delayed post-test. Stimulated recall interviews were conducted finally with twelve learners from the three treatment groups. The findings first indicate that for short and long-term vocabulary acquisition, the three treatment groups significantly outperformed the Control group. Gains for the CFoF group were significantly greater than for the L2 and codeswitching groups. Additionally, the codeswitching group significantly outperformed the L2 group for short-term but not for long-term acquisition. Regarding whether the vocabulary learning varied according to learners’ general English language proficiency, findings reveal that compared with lower-level learners, higher-level learners benefited more from the L2-only and the CFoF vocabulary explanations for shortterm vocabulary learning. Additionally, analysing the learning by word classes and for collocations, results on the one hand indicate that collocations and nouns tended to be better acquired than verbs and adjectives, on the other hand suggest that the learning of collocations and single words by the learners who received CFoF vocabulary explanations was significantly better than those from the L2 and codeswitching group. Furthermore, regarding the impact of different repetitions on vocabulary retention, findings confirm that target lexical items receiving nine repetitions were significantly better retained than those receiving seven, five or three repetitions. Looking at the impact of vocabulary intervention on learners’ listening comprehension, findings indicate that the L2, codeswitching and Control group showed significant pre to post-test improvement in listening comprehension, with most progress for the Control group. However, the CFoF group did not make significant progress and their performance was significantly worse than the Control group’s at post-test. Finally, the qualitative analysis regarding the strategies used in response to the vocabulary instruction suggest that learners used L2 listening comprehension strategies to understand the listening input as well as employing vocabulary learning strategies to guess the meaning of the unfamiliar lexical items and to further remember these items. In addition, in general, higher proficiency level learners tended to use more different strategies than low proficiency level learners. Moreover, although certain patterns of strategy use were shared by both higher and lower proficiency level learners within each treatment condition, higher proficiency level learners tended to use these strategy patterns in a more active way, compared with lower proficiency level learners who employed the strategies in a passive manner. The thesis concludes by discussing these findings in relation to theories of vocabulary acquisition and listening comprehension, as well as their implications for pedagogy, the limitations of the study and areas for future research.
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Chan, Chun-ping, and 陳俊平. "The impact of different types of feedback on learning." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B37208901.
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Brown, Paula Diane MacGregor Cynthia J. "A comparison of learning cultures in different size and types of high schools." Diss., Columbia, Mo. : University of Missouri--Columbia, 2009. http://hdl.handle.net/10355/6876.
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Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 24, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dissertation advisor: Dr. Cynthia MacGregor. Includes bibliographical references.
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Wong, Kuk-ying Esther, and 王菊英. "Learner preferences of task types: a case study in a Chinese-medium secondary school in Hong Kong." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31945211.
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Wong, Kuk-ying Esther. "Learner preferences of task types : a case study in a Chinese-medium secondary school in Hong Kong /." Hong Kong : University of Hong Kong, 2001. http://sunzi.lib.hku.hk:8888/cgi-bin/hkuto%5Ftoc%5Fpdf?B23425209.
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Ng, Mei Han May. "Learner preferences of activity types : a case study in a Chinese-medium secondary school in Hong Kong." HKBU Institutional Repository, 2003. http://repository.hkbu.edu.hk/etd_ra/496.
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Travia, Anderson Dingfelder Michael. "Interaction cross sections needed for simulation of secondary electron emission spectra from thin metal foils after fast proton impact." [Greenville, N.C.] : East Carolina University, 2009. http://hdl.handle.net/10342/1906.
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Thesis (M.S.)--East Carolina University, 2009.Presented to the faculty of the Department of Physics. Advisor: Michael Dingfelder. Title from PDF t.p. (viewed Apr. 23, 2010). Includes bibliographical references.
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Taylor, Cassidy S. "Examining Personality Across College Institution Types." Wittenberg University Honors Theses / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=wuhonors1617969300425738.
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Flídr, Karel. "Vliv tvaru sacích kanálů na čerpání u scintilačního detektoru." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2015. http://www.nusl.cz/ntk/nusl-221082.
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The thesis is concerned with the design of the shape of suction canals used for pumping in the scintillation detector. The goal is to perform analysis of the model of the detector according to the current conception and then perform an optimalisation of the suction canals as per demands to their function. In the beginning of the thesis the history of the microscope and electron microscopy is described. The next chapter is focused on a more detailed description of ESEM. The following charter is dedicated to describing the scintillation detector.The thesis recounts the kinds of liquid flow. In conclusion the programs SolidWorks and Ansys Fleunt are described. Next part of this thesis describes in detail parameters‘ settings of simulation calculation. Following chapter introduces designed changes of suction channels shape and its results are shown and described.
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Čudek, Pavel. "Scintilační detektor sekundárních elektronů pro ESEM." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2016. http://www.nusl.cz/ntk/nusl-234652.
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The thesis deals with the scintillation secondary electron detector for environmental scanning electron microscope, its design and construction. The starting point was numerical simulation of electrostatic fields and electron trajectories in the electrode system of the detector and simulation of pressure distribution and flow of gases in different parts of the detector. On the basis of modeling and simulation, construction changes of the detector were gradually implemented. Detection efficiency of each version of the detector was determined by the method described in the work. This method enables to evaluate signal level from the captured images of the specimen, quality of images was stated from signal to noise ratio. The thesis describes the whole process of the detector improvement from initial state, when the detector operated with lower efficiency in the pressure range from 300 to 900 Pa, to final version that enables usage of the detector in the range from vacuum up to 1000 Pa of water vapors in the specimen chamber of the microscope.
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Petit, Valentine. "Conditioning of surfaces in particle accelerators." Thesis, Toulouse, ISAE, 2020. http://www.theses.fr/2020ESAE0002.
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Le nuage d'électrons se développant dans les chambres à vide du LHC lors de l'opérationdes faisceaux de protons engendre une charge thermique sur le système cryogénique deses aimants supraconducteurs. La valeur de cette charge thermique présente une fortedispersion entre les différents arcs du LHC, pourtant identiques par design, dont certainssont actuellement proches de la limite de la capacité cryogénique. Sous l'effet du nuaged'électrons, le conditionnement de la surface de cuivre des chambres à vide du LHCa lieu, réduisant son rendement d'électrons secondaires. Un tel processus est supposédécroitre l'activité du nuage vers un niveau acceptable pour l'opération du LHC et sembledonc localement mis en défaut. Ce travail a analysé les phénomènes de conditionnementdu cuivre ayant lieu dans le LHC afin d'expliquer les différences d'activités du nuageélectronique observées dans l'accélérateur. L'étude des mécanismes de conditionnementdu cuivre en laboratoire, à température ambiante, en remplaçant le nuage par un canon àélectrons, a mis en évidence le rôle crucial du carbone dans la décroissance du rendementd'électrons secondaires. L'étude du déconditionnement, ayant lieu à la remise à l'air d'unesurface irradiée (étape nécessaire à l'extraction de tubes faisceau du LHC) a permisd'établir une procédure limitant l'effacement de l'état de conditionnement in-situ de cescomposants en vue de l'analyse de leur surface en laboratoire. Des analyses réaliséessur des tubes faisceau extraits d'un aimant à faible charge thermique montrent que cessurfaces présentent des caractéristiques similaires à celles conditionnées en laboratoire.En revanche, les tubes faisceau extraits d'un aimant à forte charge thermique présententdu CuO ainsi qu'un taux de carbone surfacique extrêmement faible. Il est prouvé que cesmodifications résultent de l'opération du LHC et conduisent à un conditionnement altéréde ces surfaces. Ces modifications sont actuellement le meilleur candidat pour expliquerl'origine des différences de charge thermique observées dans le LHCThe electron cloud developing in the vacuum chambers of the LHC during the protonbeam operation is responsible for heat load on the cryogenic system of the superconductingmagnets. The observed heat load exhibits a strong dispersion between the differentLHC arcs, although identical by design. Some of them are currently close to the limitof the cryoplant capacity. Under the effect of the cloud itself, conditioning of the coppersurface of the LHC beam pipes is expected, decreasing thus the secondary electronyield of the surface and leading to a decrease of the cloud intensity down to operationcompatiblelevels. Such a process seems therefore to be hindered in some parts of theLHC ring. This work aims to understand the copper conditioning processes occurringin the LHC, to unravel the origin of the heat load dispersion observed along the ring.Copper conditioning mechanisms were studied in the laboratory at room temperature bymimicking the electron cloud by an electron gun. The fundamental role of carbon, amongthe surface chemical components, in the reduction of the secondary electron yield duringconditioning was evidenced. Studying the deconditioning, occurring while exposing aconditioned surface to air (necessary step to extract beam pipes from the LHC) allowedestablishing a procedure to limit the erasing of the in-situ conditioning state of suchcomponents before the analysis of their surface in the laboratory. The surface of beampipes extracted from a low heat load magnet were found to have similar characteristicsas the ones conditioned in the laboratory. However, beam pipes extracted from a highheat load magnet exhibit cupric oxide CuO and a very low amount of surface carbon. Itis demonstrated that these modifications are induced by the LHC operation and lead toa slower conditioning of these surfaces. Therefore, these modifications are currently thebest candidate to explain the heat load dispersion observed in the LHC
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Tihlaříková, Eva. "Scintilační detektor SE pro EREM." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-217869.
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This project deals with the theme of environmental scanning electron microscopy (EREM). This method allows the examination of insulators and wet specimens without pretreatment and modification like drying and metallization. The principle of this method consists in using higher pressure in a specimen chamber. The pressure is within the range of 100 – 200 Pa. However, the pressure in the specimen chamber restricts the signal detection interference. The objective of the work is to explore the possibility of interference in secondary electron route detection by way of electrostatic field. The electrostatic field was realized with the system consisting of four electrodes located in front of the scintillation detector. It should have interfered the secondary electron´s trajectory to the detector chamber. The optimization of voltage on the electrodes was made by simulation program called SIMION. The simulation results were experimentally verified with laboratory EREM.
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Vale, Pamela. "Describing the relationship between the cognitive and linguistic complexity of a mathematical literacy examination and types of student errors." Thesis, Rhodes University, 2013. http://hdl.handle.net/10962/d1001774.
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Much prior research has shown that if students have a poor command of the language in which they are taught and assessed, they experience a complex and deep learning disadvantage (Barton & Neville-Barton, 2003). Abedi (2006) mentions, in particular, that unnecessary linguistic complexity can threaten the validity of examination items and thus compromises the fairness of the assessment for English language learners. In Clarkson’s (1991, p. 31) research it was found that for the English language learners in the study “comprehension errors [made] up a high proportion of the errors made when…students attempt[ed] to solve mathematical word problems”. In an attempt to explore whether this was the case for a group of National Certificate (Vocational) [NC(V)] students at an FET college, the research conducted in this study focused on describing the cognitive and linguistic complexity of Level 4 Mathematical Literacy examination items as well as the types of responses from a sample of students. A mixed-methods case study design was selected. Student errors were classified as either due to mathematical literacy-related sources, or language-related sources and the question was asked as to how the cognitive and linguistic complexity of items might be related to the types of errors made. Statistically significant correlations were found between the linguistic complexity of items and language-related errors, and between the cognitive complexity of items and all types of errors. It was also possible to identify which language features, in particular, were statistically significantly correlated with linguistic complexity, namely: prepositional phrases; words of 7 letters or more and complex/compound sentences. As was expected, the majority of errors were categorised as mathematical literacy-related. However, as many as 19.22% of all errors made were identified as language-related. While the scope of the study prevents any generalisations from being made, the results indicate a need for a larger-scale study of this nature to determine if the complex and deep learning disadvantage mentioned by Barton and Neville-Barton (2003) does exist with regard to the assessment of Mathematical Literacy for NC(V) students who are English language learners (Barton & Neville-Barton, 2003).
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Wong, Shun-wan, and 黃信雲. "How different types of discussion tasks in HKCEE affect students' performance." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B31962002.
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Foret, Zdeněk. "Návrh koncepce a vývoj jednoúčelového rastrovacího elektronového mikroskopu." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-233919.
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Electron microscopy has become an essential component in many scientific fields, in which it contributes to new discoveries. The microscopy itself is continually being developed and the limits, which seemed to be insurmountable, have been overcome. The instruments have become user friendlier and their mobility enables flexible practical use in the field. The subject of this work is the design of a scanning electron microscope, the calculation of a magnetic curcuit of an immersion objective combined with standard lens, the theoretical calculation of a microscope resolution and the design solution of the mechanical parts of the microscope with a sample manipulator. The thesis includes a description of the electron microscopy development summarizing it briefly from the very beginning up to now. It also deals with electron sources, especially the Shottky cathode, which is to be the main object observed by the proposed device. The work also contains a description of the calculation of the microscope resolution as a function of the current density distribution. Another interesting issue included in the theoretical part is the signal detection, a description of several types of detectors and possible signal processing. The solution of the thesis includes a description of the concept of the scanning electron microscope with an explanation of the distribution of combined lens functions. The optical diagram shows the arrangement of the electron optics system and the distibution of pressure in the chamber of the microscope. The theoretical calculation is devoted to the magnetic curcuit design of the objective and to the resolution of the microscope for a given extent of working distances. Two modifications of the lens were designed – a standard simple objective and a combination of the standard objective with the immersion magnetic one. The results of both modifications are given for the parameters to be compared. The combined objective was designed with the possibility of use in two modes, as a standard and immersion lens. The deflection system is also divided into two modes, as a single deflection for the standard lens and as a two-dimension deflection for the immersion lens. Detectors for secondary electrons (SE) and detectors for back scattered electrons (BSE) will be used for the signal detection. The design of the microscope is another large part, which gives details on the most significant components of the microscope. The content of the technical solution is a three-dimensional computer model, created in Autodesk Inventor, which also includes a sample manipulator driven by piezoelectric actuators.
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Idrus, Faizah. "The construction of shared Malaysian identity in the upper secondary English literature classroom." Thesis, University of Nottingham, 2012. http://eprints.nottingham.ac.uk/12429/.
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In Malaysia, ethnic and cultural tension and conflicts have escalated in the past 5 years bringing undesirable impacts on the nation’s economy and, most importantly, on inter-ethnic relationships. In line with the government’s 1Malaysia effort to produce a more integrated society, this study proposes the need to construct a shared Malaysian identity, starting from the classroom, which is facilitated by teachers through the use of Malaysian short stories. This proposition, amidst the differences in cultural, religious and beliefs systems, aims to close the ethnic and cultural divide and cultivate widespread inter and intra cultural awareness. The study is grounded in the notion of hybridity in the Third Space espoused by Bhabha (1994) and ameliorated and geared towards the classroom context by the works of Gutiérrez (1999, 2004, 2008). The inquiry was designed using primarily qualitative research instruments employing non-participant classroom observations, semi-structured interviews with 7 English Language teachers, and group interviews with 6 groups of students from 4 different schools in Kuala Lumpur. A one-day workshop was also conducted with the 7 teachers to introduce new Malaysian short stories and also for the purpose of sharing experiences in teaching literature in English. This data source was then supported by secondary quantitative data derived from self-completion questionnaires administered to the students of the teachers involved in this study. The findings from the analyses of the results show various attitudes, beliefs and teaching and practices in the English language classroom in response to the notion of constructing a shared identity in the Third Space. The notion of the hidden curriculum is also investigated to determine how it can be usefully theorized towards identity construction in the classroom. On the one hand, students mainly accepted the shared identity concept as a basis for classroom practice, whilst teachers had a range of views about this idea. In the conclusion, the thesis explores the implications of the classroom practices adopted by the teachers in this study as part of the process of constructing a shared Malaysian identity. It also examines the plausibility of and barriers to creating an awareness of the Third Space through the use of narratives produced by local writers, both as a medium for developing the skills to access the Third Space and also as the container of messages about Malaysian society and identity. Finally, this study suggests the way forward for realizing the country’s aspiration of a unified society and becoming a full-fledged developed country, which can possibly start in the classrooms.
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Rugbeer, Hemduth. "Communicating by ordering electrons : the development of electronic communication as part of a secondary school Communication Science curriculum in the Language, Literacy and Communication learning area." Thesis, University of Zululand, 2001. http://hdl.handle.net/10530/314.
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A thesis submitted in fulfilment of the requirements for the Degree of MA in Communication Science, University of Zululand, 2001.In this thesis I focus on the introduction of Electronic Cornmunication as part of an envisaged Communication Science curriculum in the Language, Literacy and Communication Learning area of the Further Education and Training band. In the course of my thesis I will show that the requisite elements of verbal and written cornmunication are dispersed throughout the Language, Literacy and Communication learning area in the General Education and Training band, and that they can be utilised as basis for formally introducing Communication Science, as a subject in the Language, literacy and Communication learning area in the Further Education and Train¬ing band. I also show that electronic communication will form a crucial area of study in such a Communication Science curriculum. I argue that due to the diversity of cultures in South Africa, cross-cultural cornmunication is required in such a curriculum. I also argue that by the very na¬ture of Outcomes-Based Education it is necessary to have a subject into our school curriculum that will form an interface with conceptual learning and experiential learning, that will contextu-alise language study within the more comprehensive scope of forms of human communication, and that will form an interface between the humanities and science to prevent the humanities from becoming soft options in Further Education and Training band learning programmes. To this effect I focus on the crucial role of Constructivism as integrating theory to account for vari¬ous approaches to motivational learning, the primary form of learning required in Outcomes-Based Education. I examine the principles of curriculum construction in OBE and its associated culture of learn¬ing against the backdrop of the theory of Situated Cognition. This presents a platform to argue the case for Electronic Communication as part of Communication Science in the Further Edu¬cation and Training band curricula in South African schools.
National Research Foundation
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Neděla, Vilém. "Detekce signálních elektronů v prostředí vysokého tlaku plynů environmentálního rastrovacího elektronového mikroskopu." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2008. http://www.nusl.cz/ntk/nusl-233420.
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The thesis deals with the study of properties of a new system for detection of true secondary and backscattered electrons in high pressure conditions of the specimen chamber of a newly built environmental scanning electron microscope AQUASEM II. Detection system contains three detectors. For the first time is introduced and analyzed the working principle of ionisation detector with electrostatic separator, which is in many experiments compared with ionisation detector of secondary electrons. Experimentally demonstrated are unique properties of this detection system, especially the ability of energy separation of detected signal electrons. For the various working conditions are also analyzed signal levels detected by the BSE YAG detector, which is designed as a part of the new detection system and which worked together with both ionisation detectors.
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Aberegg, David T. "Types of hardware and software in use and problems associated with their use in secondary agricultural education programs in West Virginia." Morgantown, W. Va. : [West Virginia University Libraries], 2004. https://etd.wvu.edu/etd/controller.jsp?moduleName=documentdata&jsp%5FetdId=3333.
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Thesis (M.S.)--West Virginia University, 2004.Title from document title page. Document formatted into pages; contains vii, 45 p. Vita. Includes abstract. Includes bibliographical references (p. 30-32).
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Yau, Kiu-chun, and 丘僑春. "An analysis of Hong Kong textbooks: a focus on problem types and ICT in geometry strand." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B48369342.
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This is an analysis on textbooks for elementary secondary levels in Hong Kong, focusing on the type of problem solving and the use of information and communication technology (ICT) in geometry strand. Textbooks can provide different learning opportunities for students. Usage of textbooks is widespread in secondary schools and most mathematics teachers are used to rely on textbooks in classrooms. As such, the differences of textbooks would affect what happens in the lessons. Problems in the textbooks are significant elements of the approach, as they are of any educational process, because problems focus on energy and attention, and conduct the students in the integration, application, and extension of knowledge.
A content analysis has been taken in this study, by comparing the distribution patterns of the quantities of problems representing various kinds of applications in the selected textbooks. The framework is the conceptual framework used by Fan and Zhu (2006) which concerns with the definition of the task from the perspective of textbook analysis. According to the quantitative patterns, it hints the frequencies with students exposed to different kinds of the problems and, therefore, has critical influence on student’s learning. The coding results of the study indicated that the majority of the three types of problems were traditional, closed-end, non-application and problems with sufficient data provided. Most of the to-be-solved problems and worked problems were routine ones while half of the problems with use of ICT were of that type.published_or_final_version
Education
Master
Master of Education
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Burnham, Shawn David. "Improved understanding and control of Mg-doped GaN by plasma assisted molecular beam epitaxy." Diss., Available online, Georgia Institute of Technology, 2007, 2007. http://etd.gatech.edu/theses/available/etd-06122007-133821/.
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Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008.Doolittle, W. Alan, Committee Chair ; Ferguson, Ian T., Committee Member ; Cressler, John D., Committee Member ; Dorsey, John F., Committee Member ; Carter, W. Brent, Committee Member.
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Pokluda, Tomáš. "Ionizační detektor pro ESEM." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2013. http://www.nusl.cz/ntk/nusl-220106.
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This thesis is focused on the environmental scanning electron microscopes including a description of the basic physical mechanisms. It describes the design and realization of the electrode ionization detector system suitable for the detection of signal electrons with a greater proportion of secondary electrons. It also deals with simulations of trajectories of electrons in the electrostatic field of the detector, and with verification of the functionality of the detector in the environment of water vapors in the specimen chamber of the electron microscope.
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Zhang, Yu, and 張毓. "Investigation of the lifetime spectrum of monoenergetic positrons in silicon involving secondary electrons emission from a carbon foil as start signal, and positron annihilation spectroscopy studies of strontium titante." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/197507.
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A proposed design of the variable energy positron annihilation spectroscopy (VEPALS) system based on secondary electron (SE) emission from a thin carbon foil has been investigated practically. The SE yield and the positron transmission coefficient were investigated as a function of the positron beam energy, the annular electrode potentials, and the column lengths of the annular electrode. The positron lifetime spectra of single crystal p-type silicon(Si) sample under different annular electrode potentials were analyzed. The result gives a supposed annular electrode potential of 1.5 kV. In view of this, the positron lifetime spectra were measured under different positron beam energy by fixing the annular electrode potential. It can be seen that all the spectra have the main p-type Si bulk lifetime component of 234 ps occupying more than 60% intensities. The intensity of the 234 ps component reaches up to 84.5 ±1.3 % when the positron beam energy is 15 keV. Further, the origin of the satellite peaks in the positron lifetime spectra are also investigated. It has been shown that the satellite peaks is attributed to the overflowing positrons on the MCP detector.
The single crystal strontium titanate (STO) substrates after vacuum annealing treatment have been investigated in detail by several experimental techniques. The crystallization changes induced by the vacuum annealing were investigated by X-ray diffraction(XRD). Secondary phases were occurred after annealing treatment. The measured X-ray photoelectron spectroscopy (XPS) at O1s and C1s core levels were analyzed. The additional peaks after annealing are attributed to hydroxyl species, C-OH compounds, and carbonates. The variable energy Doppler broadening spectroscopy (VEDBS) and the traditional coincidence positron annihilation lifetime spectroscopy (PALS) were used to probe defects in STO samples. For long annealing time samples, the S parameters decrease below the reference level. The S-Wplot suggests that almost the same type of vacancy defects were induced during the annealing treatment. The positron lifetime results suggest that the main defects in annealed samples are oxygen monovacancies or divacancies and Sr-O vacancy complexes. The sample with annealing time of 110h has minimum positron effective diffusion length and maximum average lifetime, which is attributed to the increase of the vacancy-type defects during the long annealing treatment.published_or_final_version
Physics
Master
Master of Philosophy
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Keller, Brenda J. (Brenda Jo) 1942. "Effect of Three Different Types of High School Class Schedules (Traditional, Rotating Block, and Accelerated Block) on High School Biology Achievement and on Differences in Science Learning Environments." Thesis, University of North Texas, 1997. https://digital.library.unt.edu/ark:/67531/metadc278645/.
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This study analyzes the effect of three different high school scheduling options on the delivery of biology instruction, on student achievement, and on student perceptions of their instructional activities. Participants were biology students and teachers from twelve high schools in a north Texas urban school district of 76,000. Block classes had 11 to 18 percent less instructional time than traditional classes. Texas Biology I End-of-Course Examination achievement results for 3,195 students along with student and teacher surveys provided information on instructional activities, attitudes, and individualization. Using an analysis of variance at a j i< .01 the following results were found; student achievement was significantly different for each of the scheduled comparisons groups, test score means were not statistically significant between the scheduled comparison groups for different ethnic groups, economically disadvantaged students, and magnet students. No significant differences were found between the science learning activity index for each of the scheduled groups. Student response data when disaggregrated and reaggregrated into program groups found a statistically significant higher index of science activity at a p. < .01 for magnet students when compared to both the regular and honor students. Regular program students had a significantly higher index of individualization than honors program students. Accelerated and rotating block classes were found to hold a significantly more positive attitude about their science learning conditions than did the traditional students. These data suggest that during the first two years of block scheduling, the initial impact of block scheduling, where total time for science is reduced, results in lower student achievement scores when compared to traditionally scheduled classes. Yet, block scheduled student attitudes and perceptions about science learning are significantly more positive than the traditionally scheduled students.
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Shapange, Ismael. "An investigation into the types of classroom tasks senior secondary school (grade 11 and 12) mathematics teachers give to their learners : a case study." Thesis, Rhodes University, 2015. http://hdl.handle.net/10962/d1017356.
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This interpretive case study was undertaken to investigate the nature of classroom tasks that teachers give to their learners and to gain insights into how they choose these tasks. It was carried out at two secondary schools in the Okahao circuit of the Omusati region in Namibia. The schools range from Grade 8 to Grade 12. This study focused mainly on teachers who teach Mathematics at senior secondary phase (Grade 11 and 12). The research participants were of four mathematics teachers – two from each school. The study was designed around two phases. Phase one consisted of video-recording of lessons, and phase two consisted of interviewing the teachers. The main purpose of the study was to ascertain the types and nature of tasks that teachers give to their learners and to gain insights into how they chose these tasks. The research adopted a combination of both qualitative and quantitative approaches. The study revealed that the participating teachers provided a near equal amount of lower level cognitive tasks and higher level cognitive tasks. It further revealed several factors that influence teachers when selecting the types of tasks they give to their learners. These factors include curriculum requirements, types of learners and their experiences, and learners’ contexts.
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Černoch, Pavel. "Detekce signálu segmentovým ionizačním detektorem v environmentálním SEM." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2008. http://www.nusl.cz/ntk/nusl-233435.
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The dissertation thesis deals with signal detection by an ionization detector in the environmental scanning electron microscope and utilization of this detector to gain required information in a specimen image. Main interest is focused on the detector containing several electrodes with a varied geometry arrangement and voltages on these electrodes. The detector was named segmental ionization detector. Detection capabilities of the segmental ionization detector were studied through computer simulations and experiments in the microscope utilizing knowledge from a technical literature background. On the base of the accomplished experiments, the segmental ionization detector has been optimized for the secondary electron detection improvement and at another configuration optimized for a high material contrast acquisition of the specimen image. Consideration of benefits of the examined segmental ionization detectors is included in the work.
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Yu, Yiting. "The Influence of Types of Homework on Opportunity to Learn and Students' Mathematics Achievement: Examples from the University of Chicago School Mathematics Project." Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/5808.
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ABSTRACT
Public views on assigning students mathematics homework have been controversial. Although homework is designed for students to complete during non-school hours (Cooper, 1989), many see homework as excessive pressure on students. Most research placed their focus on the influence of the time spent on homework or the amount of homework on student achievement. Few studies have addressed the impact of types of mathematics homework. The purpose of this study is to examine the role of homework types in influencing opportunity to learn (OTL) on student achievement.
This quantitative study used subsets of a large existing dataset collected by University of Chicago School Mathematics Project (UCSMP) in Pre-Transition Mathematics, Transition Mathematics, and Algebra. The findings showed that OTL measured by lesson coverage and by teachers’ reported posttest OTL have significant impact. Each type of homework as a mediator might have significant, positive or negative mediating effects or no mediating effects at all. The findings from having OTL measured by lesson coverage as the independent variable were more consistent with each mathematics course. The differences of the mediating effects of types of homework on the impact of OTL measured by lesson coverage on student mathematics achievement and on the impact of teachers’ reported posttest OTL on students’ mathematics achievement may be explained through the nature of the types of homework as well as through limitations of the study. Recommendations for future research and implications of the study were presented in the discussion part of the study.
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Garforth, Graham. "School control of information, advice and guidance during transition : a two year study into post-16 student decision-making." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/35625/.
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The majority of research into choice, transition and decision-making took place in the 1990s-2000s. Since this time the context in which post-16 transition takes place has been changing due to increased competition between institutions and the extended length of time students are required to remain in education or training through raising the participation age. Additionally, in 2012 the government made schools responsible for Information, Advice and Guidance. This thesis explores choice and decision-making during the transition to post-16 education and training. It provides new research evidence to contribute to the existing literature in light of the changes in context since the body of literature was formed. In particular, it explores the impact of the changes to Information, Advice and Guidance provision and the role of schools in influencing students' transition. The study uses evidence from three schools with sixth forms, drawn from two contrasting counties of England during the first year of research. The second year of research draws evidence from a range of post-16 institutions which the students progressed onto. Overall, the data from staff, students and documentary evidence explores student transition from the final year of secondary schooling to post-16 education or training. The study finds that competition between post-16 institutions has implications for the way that post-16 Information, Advice and Guidance is provided by schools. The practical strategies schools use to influence transition include practical prevention of access to alternative IAG, control of the application process and active student selection. The most powerful strategies involve the social construction of unique selling points and the management of culture and trust. The implications of these strategies for students' transition is assessed taking into account how students make their post-16 transition decisions in a loosely coupled manner and the common belief that their position is of their own making. Overall, a continuum of schools' influence on transition is presented. The study concludes that the competitive post-16 environment coupled with school control of guidance may lead to imperfect transition for students and reproduction of the structural status quo rather than social change. For school leaders implications exist in being able to mitigate competition through collaboration and specialisation. However, the complexity of achieving this in the competitive post-16 marketplace produces implications for guidance providers in equipping students with decision-making skills and empowering them with an understanding of their position which is more likely to lead to students being able to challenge influencing structures and make effective post-16 transitions.
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Dicus, Christina Marie. "Relationship between pore geometry, measured by petrographic image analysis, and pore-throat geometry, calculated from capillary pressure, as a means to predict reservoir performance in secondary recovery programs for carbonate reservoirs." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-2076.
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Westerholm, Sylvia. ""Du pratar som dom i Sommarpratarna" : Om gymnasieelevers respons på argumenterande tal och attityder till respons." Thesis, Linnéuniversitetet, Institutionen för svenska språket (SV), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-38706.
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The aim of this study is to investigate oral peer review on argumentative speech and to study the attitudes towards this peer review. The investigation was performed in an up-per secondary school class, and it focused on the different types of oral responses students give each other. In addition, the study investigated in what way the students experience this type of peer review. The results show that students reflect on form and performance as well as content, but they place more emphasis on form and performance than content. Students are positive about peer review and its importance for their progress. The investigation shows that peer review is needed, but the methods need to be developed further as response should mirror all parts of a work process, peer review can be used in other situations such as work life as well as in the teaching of other subjects.
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Kozák, Josef. "Scintilační detektor sekundárních elektronů s řízeným prouděním plynů pro EREM." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-217926.
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This master’s thesis deals with a design and optimization of an experimental scintillation secondary electron detector for the environmental scanning electron microscope and with a description of a detector operation principle. The experiment is founded on simulations of a gas flow in detector inner sections and on simulations of secondary electron trajectories in electrostatic fields of the detector. On the basis of the simulations, new solutions of the detector designs are proposed. For these designs, same simulations as previous are performed and designs that seem to be feasible for the secondary electron detection in environmental scanning electron microscope are selected.
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Liljedahl, Christina. "Elevers skrivande på engelska på fritiden." Thesis, Malmö högskola, Lärarutbildningen (LUT), 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-30835.
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The purpose of this degree project is to investigate in what types of situations and to what extent some upper secondary students write in English in their spare time, what reasons they have for doing so and what text types and genres are represented in their writing. Qualitative interviews were carried out with a group of six students in year two in an upper secondary school in the southern part of Sweden, three with MVG as a final grade and three with VG as a final grade in English A.The results show that all of the students write in English each day in instant text messages on MSN messenger. However, they mostly use English in the form of abbreviations, single words, phrases and sentences. Longer pieces of text, like poems and other literary pieces, written in English were created only by the three students with MVG.
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Monart, Brigitte. "Etude experimentale del'emission secondaire (ions atomiques et moleculaires, agregats, electrons) induite par bombardement de surface par des ions lourds energetiques ( equiv. A mev/u) : effets de l'etat de charge des projectiles." Paris 7, 1988. http://www.theses.fr/1988PA077121.
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Etude de l'emission secondaire en fonction de la vitesse en projectile, de l'angle d'incidence du faisceau par rapport a la cible (minerale ou organique) et surtout de l'etat de charge au projectile, par spectrometrie de masse a temps de vol principalement: cette emission depend fortement de la charge du projectile et aussi du changement d'etat de charge a l'interieur du materiau. Interpretation des resultats a l'aide du modele de maynard et al. , en supposant l'existence d'une profondeur d'interaction ion primaire-materiau qui depend du type d'ions secondaires et de la charge de l'ion incident
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Mubatanhema, Wellington. "Incidence, geographical distribution and taxonomy of Fusarium species of the section (Leseola and Reink) and related species on Zimbabwean corn (Zea mays) : the application of mating types and secondary metabolite production to their identification." Thesis, University of Surrey, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240010.
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Báborský, Tomáš. "Charakterizace automobilových vysokopevnostních ocelí pomocí elektronového mikroskopu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-400477.
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The diploma thesis deals with the determination of the structure of AHSS steels and offers solutions in the form of new observation methods with the aid of a scanning electron microscope using filtration of slow secondary electrons. The thesis describes electron filtration in order to display secondary electrons in a certain energy range which carry a surface information that is not normally visible. The advantages and benefits of such observation are clearly demonstrated.
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Vídeňský, Ondřej. "Analýza bateriových hmot metodami EDS." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2019. http://www.nusl.cz/ntk/nusl-399522.
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This master thesis deals with analysis of battery mass using x-ray spectral microanalysis. For the measurement two scanning electron microscopes equipped with energy dispersive x-ray spectroscopes were used. Appropriate examples were prepaired by standard method. Then elemental analysis was performed with changing conditions of measurement. Two programs were used for spectrums evaluation and in the end the size of errors was observed for every conditions.
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Fréneau, Amélie. "Étude comparative des effets moléculaires et cellulaires induits par des rayonnements X de différentes énergies." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS350/document.
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Lors d’un examen ou radiologique, des rayonnements X de basse énergie sont utilisés (<100 keV). Pour certains traitements radiologiques, l’énergie utilisée est de plusieurs MeV. La publication 103 de la CIPR considère actuellement que les photons, indépendamment de leur énergie, ont le même facteur de pondération. Cependant, il existe des différences topologiques à l'échelle nanométrique du dépôt d'énergie des rayonnements X en fonction de leur spectre énergétique. En effet, à mesure que l’énergie des photons décroit, la nature de leurs interactions avec la matière vivante se modifie. Pour étudier ces différences, nous avons caractérisé nos conditions d'irradiation en termes d'énergies initiales des photons, mais surtout en termes de spectres d'énergie des électrons secondaires au niveau du volume cellulaire, en utilisant des simulations de Monte Carlo. Nous nous sommes intéressés à la signalisation des dommages de l'ADN en analysant un grand nombre de foyers γH2A.X après exposition de cellules endothéliales humaines synchronisées en phase G0/G1 à des doses allant de 0,25 à 5 Gy à 40 kV, 220 kV et 4 MV. Le nombre et la distribution spatiale des foyers γH2A.X ont été explorés. Aussi, nous avons étudié la fréquence de division et de mort cellulaire. Nous avons également étudié le taux d’anomalies de ségrégation après la division cellulaire. Nous avons mis en évidence un nombre plus élevé de cassures double-brin de l'ADN signalisées par γH2A.X pour 40 kVp et/ou 220 kVp, comparé à 4 MVp pour les plus fortes doses testées de 2 et 5 Gy. Entre 40 et 220 kVp, aucune différence biologique n’a été observée. Ce manque de différence pourrait s’expliquer par la grande similarité des spectres énergétiques des électrons secondaires, au niveau du volume cellulaire.Le spectre d'énergie des électrons secondaires semble être plus étroitement lié au niveau de dommage à l'ADN mesuré par γH2A.X que le spectre initial des paramètres d'énergie ou de tension des photons. Nos résultats indiquent qu'à mesure que le spectre d'énergie des électrons secondaires augmente, les dommages à l'ADN signalés par γH2A.X diminuent et cet effet est observable au-delà de 220 kVpIn a radiological examination, low-energy X-radiation is used (<100 keV). For other radiological procedures, the energy used is several MeV. ICRP in publication 103 has currently considered that photons irrespective of their energy have the same radiation weighting factor. Nevertheless, there are topological differences at the nanoscale of X-ray energy deposition as a function of its energy spectrum, meaning that the different interactions with living matter could vary in biological efficacy. To study these differences, we characterized our irradiation conditions in terms of initial photon energies, but especially in terms of energy spectra of secondary electrons at the cell nucleus level, using Monte Carlo simulations. We evaluated signaling of DNA damage by monitoring a large number of γH2A.X foci after exposure of G0/G1-phase synchronized human primary endothelial cells at a dose from 0.25 to 5 Gy at 40 kV, 220 kV and 4 MV X-rays. Number and spatial distribution of γH2A.X foci were explored. In parallel, we investigated cell behavior through cell death and ability of a mother cell to produce two daughter cells. We also studied the missegregation rate after cell division. We report a higher number of DNA double-strand breaks signaled by γH2A.X for 40 kVp and/or 220 kVp compared to 4 MVp for the highest tested doses of 2 and 5 Gy. We observed no difference between the biological endpoint studies with 40 kVp and 220 kVp X-ray spectra. This lack of difference could be explained by the relative similarity of the calculated energy spectra of secondary electrons at the cell monolayer. The energy spectrum of secondary electrons seems to be more closely related to the level of DNA damage measured by γH2A.X than the initial spectrum of photon energy or voltage settings. Our results indicate that as the energy spectrum of secondary electrons increases, the DNA damage signaled by γH2A.X decreases and this effect is observable beyond 220 kVp
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Uhlář, Vít. "Víceelektrodový systém ionizačního detektoru pro environmentální rastrovací elektronový mikroskop." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2015. http://www.nusl.cz/ntk/nusl-221175.
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Thesis deals with environmental scanning electron microscopy and with detection of signal electrons by using ionization detector. First part talks about the principle of environmental scanning electron microscope. Second part describes signals generated by interaction of primary electron beam with sample. Third section explains the principle of impact ionization and ionization detector. Experimental part deals with usage of segmental ionization detector and with measuring of signal amplification from copper and platinum. Thesis also examines arrangement of electrodes of ionisation detector on material contrast and examines also on influence of voltage contrast on base - emitter junction of an NPN bipolar transistor. All experiments were carried out in dependency on saturated water vapour pressure in sample chamber.