by Ka-wai Wong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1995. / Includes bibliographical references (leaves 106-109). / TABLE OF CONTENTS --- p.i / ABSTRACT --- p.v / LIST OF FIGURES --- p.vi / LIST OF TABLES --- p.xi / LIST OF ABBREVIATIONS --- p.x / Chapter Chapter 1 --- Research Background --- p.1 / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.2 --- The effect of solid acceptance angle --- p.2 / Chapter 1.3 --- Research goals --- p.4 / Chapter 1.3.1 --- Determination of the electron spectrometer transmission function --- p.4 / Chapter 1.3.2 --- Novel depth profiling technique by adjusting the solid acceptance angle --- p.6 / Chapter 1.3.3 --- Correction to conventional ARXPS --- p.8 / Chapter 1.4 --- Thesis Structure --- p.8 / Chapter Chapter 2 --- Fundamentals of X-ray Photoelectron Spectroscopy --- p.9 / Chapter 2.1 --- Introduction --- p.9 / Chapter 2.2 --- X-ray Photoelectron Spectroscopy (XPS) --- p.9 / Chapter 2.2.1 --- Basic principles --- p.9 / Chapter 2.2.2 --- Surface sensitivity --- p.11 / Chapter 2.2.3 --- A typical XPS spectrum --- p.13 / Chapter 2.3 --- Qualitative analysis --- p.16 / Chapter 2.3.1 --- Binding energy --- p.16 / Chapter 2.3.2 --- Chemical state information --- p.17 / Chapter 2.4 --- Quantitative analysis --- p.20 / Chapter 2.4.1 --- Factors affecting intensity --- p.20 / Chapter 2.4.2 --- Homogeneous materials --- p.22 / Chapter 2.4.3 --- Layer structure --- p.23 / Chapter Chapter 3 --- Instrumentation --- p.26 / Chapter 3.1 --- XPS spectrometer --- p.26 / Chapter 3.1.1 --- Magnetic immersion lens system --- p.26 / Chapter 3.1.2 --- Tunable iris --- p.29 / Chapter 3.1.3 --- Scan plates --- p.29 / Chapter 3.1.4 --- Input lens aperture --- p.32 / Chapter 3.2 --- Calibration of the iris --- p.32 / Chapter 3.3 --- Applications --- p.35 / Chapter 3.3.1 --- Two dimensional XPS imaging --- p.35 / Chapter 3.3.2 --- ARXPS --- p.37 / Chapter 3.4 --- Summary --- p.37 / Chapter Chapter 4 --- Determination of electron spectrometer transmission function --- p.38 / Chapter 4.1 --- Introduction --- p.38 / Chapter 4.2 --- Traditional method of determination --- p.39 / Chapter 4.3 --- Methodology of the novel approach --- p.40 / Chapter 4.4 --- Calculation Procedures and Results --- p.48 / Chapter 4.5 --- Results and Discussions --- p.50 / Chapter 4.6 --- Conclusions --- p.57 / Chapter Chapter 5 --- "Depth Profiling by Adjusting the Solid Acceptance Angle: a Starting Point to “ Three-Dimensional Imaging""" --- p.59 / Chapter 5.1 --- Introduction --- p.59 / Chapter 5.2 --- Theoretical Background --- p.60 / Chapter 5.2.1 --- Quantification of Intensity --- p.60 / Chapter 5.3 --- Experimental --- p.69 / Chapter 5.3.1 --- Operation --- p.69 / Chapter 5.3.2 --- Calibration of iris --- p.70 / Chapter 5.3.3 --- Novel depth profile by adjusting the solid acceptance angle --- p.71 / Chapter 5.4 --- Results and Discussions --- p.71 / Chapter 5.4.1 --- Depth Profiles --- p.71 / Chapter 5.4.2 --- "Concept of ""Three-Dimensional XPS Imaging""" --- p.72 / Chapter 5.5 --- Conclusions --- p.76 / Chapter Chapter 6 --- Correction to Quantitative X-ray Photoelectron Spectroscopy with Consideration of the Solid Acceptance Angle --- p.79 / Chapter 6.1 --- Introduction --- p.79 / Chapter 6.2 --- The effect of the solid acceptance angle --- p.80 / Chapter 6.3 --- Theoretical Background --- p.83 / Chapter 6.4 --- Results and Discussions --- p.87 / Chapter 6.4.1 --- Homogeneous Sample --- p.87 / Chapter 6.4.2 --- Layer structure --- p.90 / Chapter 6.4.3 --- Simulation plots and further investigation --- p.92 / Chapter 6.5 --- Conclusions --- p.101 / Chapter Chapter 7 --- Conclusion --- p.103 / Acknowledgment --- p.105 / References --- p.106

by Poon Mei Yu. / Thesis submitted in: Dec. 1997. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (leaves 127-132). / Abstract also in Chinese. / Declaration --- p.i / Acknowledgement --- p.ii / Table of Contents --- p.iii / Abbreviations --- p.xi / List of Figures --- p.xiv / List of Tables --- p.xvii / Abstract --- p.xxi / Introduction --- p.1 / Chapter Chapter 1: --- Obesity & related abnormalities --- p.2 / Chapter Chapter 2: --- Measurement of body fat --- p.11 / Objective --- p.18 / Chapter Chapter 3: --- Purpose of study --- p.19 / Method --- p.24 / Chapter Chapter 4: --- Technical considerations on CT technique --- p.25 / Chapter Chapter 5: --- Data Collection --- p.32 / Chapter Chapter 6: --- Data Analysis --- p.44 / Results --- p.49 / Chapter Chapter 7: --- Amount of adipose tissue --- p.50 / Chapter Chapter 8: --- "Adipose tissue distribution, VSR & VTR" --- p.81 / Discussion --- p.105 / Chapter Chapter 9: --- Discussion --- p.106 / Conclusions --- p.122 / Chapter Chapter 10: --- Conclusions --- p.123 / References --- p.127 / Appendix I --- p.133 / Appendix II --- p.136 / Appendix III --- p.139 / DECLARATION --- p.i / ACKNOWLEDGEMENT --- p.ii / TABLE OF CONTENTS --- p.iii / Brief Contents --- p.iii / Detailed Contents --- p.v / ABBREVIATIONS --- p.xi / LIST OF FIGURES --- p.xiv / LIST OF TABLES --- p.xvii / ABSTRACT --- p.xxi / INTRODUCTION --- p.1 / Chapter Chapter 1: --- OBESITY & RELATED ABNORMALITIES --- p.2 / Chapter 1.1 --- Adipose Tissue --- p.2 / Chapter 1.2 --- Classification of Adiposity --- p.3 / Chapter 1.3 --- Obesity --- p.5 / Chapter Chapter 2: --- MEASUREMENT OF BODY FAT --- p.11 / Chapter 2.1 --- Methods of Measuring Body Fat --- p.11 / Chapter 2.1.1 --- Non-imaging Methods --- p.12 / Chapter 2.1.2 --- Imaging Methods --- p.13 / Chapter 2.1.2.1 --- Plain radiograph --- p.13 / Chapter 2.1.2.2 --- Ultrasound --- p.13 / Chapter 2.1.2.3 --- Computed tomography --- p.14 / Chapter 2.1.2.4 --- Magnetic resonance imaging --- p.16 / OBJECTIVE --- p.18 / Chapter Chapter 3: --- PURPOSE OF STUDY --- p.19 / Chapter 3.1 --- Objectives --- p.19 / Chapter 3.2 --- Explanation --- p.20 / Chapter 3.2.1 --- Best level of AT area measurement --- p.21 / Chapter 3.2.2 --- Linear AT dimension --- p.22 / Chapter 3.2.3 --- Sex and age differences --- p.22 / Chapter 3.2.4 --- Difference in attenuation interval of fat --- p.23 / METHOD --- p.24 / Chapter Chapter 4: --- TECHNICAL CONSIDERATIONS ON CT TECHNIQUE --- p.25 / Chapter 4.1 --- Defining Anatomy --- p.25 / Chapter 4.1.1 --- Abdominal visceral cavity --- p.26 / Chapter 4.1.1.1 --- Diaphragm --- p.26 / Chapter 4.1.1.2 --- Pelvis --- p.26 / Chapter 4.1.1.3 --- Boundary at mid-potion --- p.27 / Chapter 4.1.2 --- Intra- and retro- peritoneal compartments --- p.28 / Chapter 4.2 --- Attenuation interval of fat --- p.29 / Chapter 4.2.1 --- Distinctive pixel value vs. attenuation interval --- p.30 / Chapter 4.2.2 --- Choice of interval --- p.30 / Chapter Chapter 5: --- DATA COLLECTION --- p.32 / Chapter 5.1 --- Subjects --- p.32 / Chapter 5.2 --- Acquisition --- p.33 / Chapter 5.3 --- Measurement --- p.34 / Chapter 5.3.1 --- AT area measurement --- p.35 / Chapter 5.3.2 --- Linear AT measurement --- p.38 / Chapter 5.3.2.1 --- Subcutaneous AT thickness --- p.38 / Chapter 5.3.2.2 --- Visceral AT thickness --- p.39 / Chapter Chapter 6: --- DATA ANALYSIS --- p.44 / Chapter 6.1 --- Tools --- p.44 / Chapter 6.2 --- Mathematical Assumptions --- p.45 / RESULTS --- p.49 / Chapter Chapter 7: --- AMOUNT OF ADIPOSE TISSUE --- p.50 / Chapter 7.1 --- AT Volumes --- p.50 / Chapter 7.1.1 --- In male and female subgroups --- p.50 / Chapter 7.1.2 --- VAT and SAT increase with TAT --- p.52 / Chapter 7.1.3 --- A VAT volume vs. VAT volume --- p.54 / Chapter 7.2 --- AT Areas at Various Anatomical Levels --- p.55 / Chapter 7.2.1 --- In male and female subgroups --- p.56 / Chapter 7.2.2 --- Correlation between AT volumes and areas --- p.62 / Chapter 7.2.3 --- Prediction of abdominal AT volumes from AT areas --- p.63 / Chapter 7.3 --- Linear AT Dimensions --- p.66 / Chapter 7.3.1 --- Linear SAT dimensions correlated to AT volumes --- p.66 / Chapter 7.3.2 --- Linear VAT dimensions correlated to AT volumes --- p.68 / Chapter 7.3.3 --- Prediction of abdominal SAT volume --- p.70 / Chapter 7.3.4 --- Prediction of abdominal A VAT volume --- p.71 / Chapter 7.3.5 --- Prediction of abdominal TAT volume --- p.72 / Chapter 7.4 --- "AT Measurements, Sex and Age" --- p.73 / Chapter 7.4.1 --- In whole study population --- p.73 / Chapter 7.4.2 --- In male and female subgroups --- p.75 / Chapter 7.5 --- Difference in Attenuation Interval --- p.79 / Chapter Chapter 8: --- DISTRIBUTION OF ADIPOSE TISSUE: VSR & VTR --- p.81 / Chapter 8.1 --- VSR --- p.81 / Chapter 8.1.1 --- Correlation --- p.82 / Chapter 8.1.2 --- Prediction --- p.83 / Chapter 8.1.3 --- Effect of attenuation interval --- p.84 / Chapter 8.1.3.1 --- On VSR value --- p.84 / Chapter 8.1.3.2 --- On correlation and prediction results --- p.86 / Chapter 8.2 --- VTR --- p.88 / Chapter 8.2.1 --- Correlation --- p.88 / Chapter 8.2.2 --- Prediction --- p.89 / Chapter 8.2.3 --- Effect of attenuation interval --- p.91 / Chapter 8.2.3.1 --- On VTR value --- p.91 / Chapter 8.2.3.2 --- On correlation and prediction results --- p.93 / Chapter 8.3 --- VSR vs. VTR --- p.95 / Chapter 8.4 --- "VSR, VTR, Sex and Age" --- p.96 / Chapter 8.4.1 --- Correlation --- p.99 / Chapter 8.4.2 --- Prediction --- p.100 / Chapter 8.4.3 --- VSR and VTR increase with age --- p.101 / DISCUSSION --- p.105 / Chapter Chapter 9: --- DISCUSSION --- p.106 / Chapter 9.1 --- Absolute AT Content (Amount) --- p.106 / Chapter 9.1.1 --- AT areas of various anatomical levels --- p.106 / Chapter 9.1.1.1 --- Correlated to AT volume --- p.107 / Chapter 9.1.1.2 --- Prediction of abdominal A T volume: best level --- p.107 / Chapter 9.1.2 --- Linear AT dimensions --- p.109 / Chapter 9.1.2.1 --- Correlated to AT volume --- p.109 / Chapter 9.1.2.2 --- Prediction of abdominal AT volume --- p.111 / Chapter 9.2 --- AT Distribution Indices: VSR and VTR --- p.112 / Chapter 9.2.1 --- The best level --- p.114 / Chapter 9.3 --- Sex and Age Difference --- p.114 / Chapter 9.3.1 --- absolute AT content --- p.114 / Chapter 9.3.2 --- VSR and VTR --- p.116 / Chapter 9.4 --- Difference in Attenuation Interval --- p.118 / Chapter 9.4.1 --- Absolute AT content --- p.118 / Chapter 9.4.2 --- VSR and VTR --- p.119 / Chapter 9.5 --- Limitations --- p.120 / Chapter 9.5.1 --- Study population --- p.120 / Chapter 9.5.2 --- Differentiation of compartments --- p.121 / CONCLUSIONS --- p.122 / Chapter Chapter 10: --- CONCLUSIONS --- p.123 / Chapter 10.1 --- Absolute AT Content in Abdomen --- p.123 / Chapter 10.2 --- Abdominal AT Distribution --- p.125 / Chapter 10.3 --- Effect of Attenuation Interval --- p.126 / REFERENCES --- p.127 / APPENDIX I: Comparison of study populations & scanning techniques --- p.133 / APPENDIX II: Comparison of definitions of attenuation interval of fat and anatomical compartments --- p.136 / APPENDIX III: Statistical summary of the adipose tissue measurements in this study --- p.139

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Biology, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Vita. / Includes bibliographical references. / by Thomas Clifford Alber. / Ph.D.

Este trabalho visou a análise estrutural de três compostos orgânicos: [A] : (2SR, 8SR)-2-(8-O-borinil-8-fenil)etil piperidina (C17H28NOB), [B] : (1SR, 2SR)-1-p-Bromoanilina-1-fenil-2-metil-3-pentanona -(C18H20NOBr) e [C] : um triterpeno-(C30O3H46) por difração de raio-X e por mecânica molecular. As estruturas no estado sólido foram primeiramente obtidas por difração de raios-x por monocristais, e posteriormente analisadas por mecânica molecular. [A]: monoclínico, grupo espacial C2/c, a=15.259(3)&#197, b=12.574(2)&#197, c=17.413(5)&#197, &#946=94.44&#176, Z=8, Dx=1.089 g/cm3, V=3331.45޵ as estruturas cristalográficas e por mecânica molecular não apresentam grandes desvios. [B]: triclínico, grupo espacial P1&#175, a=8.467(7)&#197, b=8.7361(3)&#197, c=12.468(9)&#197, &#945=82.401(5)&#176, &#946=83.096(6)&#176, &#978=69.026(5)&#176, Z=2, Dx=1.430 g/cm3, V=850.95޵ a principal diferença entre as duas estruturas cristalográfica e por mecânica molecular está no ângulo de torsão C(2)-C(1)-N-C(8) de 59.8&#176. Entre as moléculas relacionadas pelo centro de inversão existe duas pontes de hidrogênio entre os átomos O-N. [C]: ortorrômbico, grupo espacial P212121, a=7.314(7)&#197, b=12.807(3)&#197, c=26.812(5)&#197, Z=4, Dx=1.197 g/cm3, V=2511.49&#1973. Não existem grandes diferenças entre as estruturas cristalográficas e por mecânica molecular. As moléculas estão dimerizadas por uma ponte de hidrogênio entre os átomos (O1) e (O2) das moléculas relacionadas por simetria. / This work aimed the structural analysis of three organic compounds: [A] : (2SR, 8SR)-2-(8-O-borinyl-8-phenyl)ethyl piperidine (C17H28NOB), [B] : (1SR, 2SR)-1-p-Bromoaniline-1-phenyl-2-methyl-3-pentanone -(C18H20NOBr) e [C] : um triterpene-(C30O3H46) using X-ray diffraction and molecular mechanics. The solid state structures were firstly obtained by X-ray diffraction of single crystals, and further analyzes by molecular mechanics. [A]: monoclinic, space group, C2/c, a=15.259(3)&#197, b=12.574(2)&#197, c=17.413(5)&#197, &#946=94.44&#176, Z=8, Dx=1.089 g/cm3, V=3331.45޵ the crystallographic and molecular mechanics structures dont show large differences. [B]: triclinic, space group P1&#175, a=8.467(7)&#197, b=8.7361(3)&#197, c=12.468(9)&#197, &#945=82.401(5)&#176, &#946=83.096(6)&#176, &#978=69.026(5)&#176, Z=2, Dx=1.430 g/cm3, V=850.95޵ the main difference between the crystallographic and the molecular mechanics structures is in the dihedral angle C(2)-C(1)-N-C(8) de 59.8&#176. There are between the molecules related by inversion center two hydrogen bonds between the atoms O-N. [C]: orthorhombic, space group, P212121, a=7.314(7)&#197, b=12.807(3)&#197, c=26.812(5)&#197, Z=4, Dx=1.197 g/cm3, V=2511.49&#1973. There are not large differences between the crystallographic and the molecular mechanics structures. The molecules are dimerized by a hydrogen bond between the atoms (O1) and (O2) from molecules symmetrically related.

No description available.

Semi-solid deformation mechanisms are important in a range of manufacturing and natural phenomena, which range from squeeze casting to magma flows. In this thesis, using high speed synchrotron X-ray tomography and a bespoke precision thermo-mechanical rig, a four dimensional (3D plus time) quantitative investigation was performed to study the mechanical / rheological behavior of semi-solid Al-Cu alloys. Various deformation techniques, namely, isothermal semi-solid compression, extrusion and indentation were used. The time-resolved dynamic 3D images were analyzed with the help of novel image quantification techniques including digital volume correlation and image-based simulations of fluid flow. The quantified dynamics at a microstructural scale was then linked with macroscopic mechanical properties. The qualitative and quantitative analyses revealed a range of important semi-solid micromechanical mechanisms including the occurrence and effects of dilatancy, associated liquid flow through the equiaxed microstructure, intra-dendritic deformation, and strain localization during semi-solid deformation, not only shedding new insights into the mechanisms of deformation-induced solidification defect formation (solute segregation, porosity and hot tearing) of semi-solid alloys at both a macroscopic and microscopic level, but also providing benchmark cases for semi-solid deformation models and theories. The experimental methodology, techniques and analysis procedures developed in this thesis are generic in nature and can be applied to a wide range of research fields.

Successful management of hydrocarbon reservoirs, geothermal energy extraction sites, radioactive waste and CO2 storage sites depends on a detailed knowledge of fluid transport properties, porosity and permeability. Amongst deformation processes, fluid-rock interaction plays an important role in controlling the petrophysical properties of a rock. The presence of fluids in the rocks induce chemical and physical changes in compositions and texture, affecting porosity and permeability, hence influencing dynamic transport properties and fluid flow. Fluid-rock interaction processes have been deeply investigated in nature and in numerous experimental and numerical modelling studies. However, these studies lack a spatio-temporal characterization of the dynamic evolution of porosity and reaction microfabrics. There is no clear understanding of the spatio-temporal evolution of these properties in three dimensions, and how this evolution affects fluid percolation in the rock. Computed X-ray micro-Tomography (μCT) was applied to investigate these processes in three dimensions and observe their evolution in time (4DμCT). The combination of μCT with 2D analytical techniques (e.g. scanning electron microscope, SEM, electron microcrobe, EMPA, electron backscatter diffraction, EBSD) furthermore enables the extrapolation of the information gained from 2D analyses to the 3rd an 4th dimension (4D μCT). The thesis investigates two different categories of fluid-rock interaction processes, by using 4DμCT to monitor the evolution of mineral reactions (in the first case) and porosity (second case) in relation to strain and time. In the first case study, natural rock samples were analysed. The samples show a compositional change along a strain gradient from olivinic metagabbros to omphacite-garnet bearing eclogites in a ductile shear zone. Synchroton-based x-ray microtomography (sμCT) was applied to document the 3D evolution of garnets along the strain gradient (which represent the 4th dimension). The 3D spatial arrangement of garnet microfabrics can help determine the deformation history and the extent of fluid-rock interaction active during deformation. Results from the sμCT show that in the low strain domain, garnets form a large and well interconnected cluster that develops throughout the entire sample and garnet coronas never completely encapsulate olivine grains. In the most highly deformed eclogites, the oblate shapes of garnets reflect a deformational origin of the microfabrics. EBSD analyses reveal that garnets do not show evidence for crystal plasticity, but rather they highlight evidence for minor fracturing, neo-nucleation and overgrowth, which points to a mechanical disintegration of the garnet coronas during strain localisation. In the second case study, pressure-solution processes were investigated using NaCl as rock-analogue, to monitor the evolution of porosity and pore connectivity in four dimensions, providing a time-resolved characterization of the processes. NaCl samples were uniaxially compacted and μCT scans were taken at regular interval times to characterize the evolution of grain morphologies, pore space and macro-connectivity of the samples. Different uniaxial loads, as well as different bulk sample compositions (phyllosilicates and/or glass beads) were used to investigate their effect on the process. Greater uniaxial loads, and the presence of phyllosilicates within the deforming NaCl columns were found to enhance pressure-solution processes. The pore space becomes highly disconnected in the presence of phyllosilicates, with important implications for fluid percolation and dynamic transport properties. Mean strain rates, calculated from volumetric Digital Image Correlation (3D-DIC) analyses, were found to be higher where phyllosilicates were located. The combination of μCT with volumetric DIC and SEM imaging proved to be an efficient analytical method for investigating the dynamic behaviour of porosity and permeability during ongoing pressure-solution processes. The results showed that fluid-rock interaction critically modifies the rocks at the pore/grain scale, with important consequences on dynamic fluid transport properties. The combination of μCT with classical 2D techniques provided a better understanding on the dynamic evolution of transport properties and fluid percolation during fluid-rock interaction processes, allowing the characterization in three dimensions of reaction microfabrics and porosity.

No description available.

Nanotechnology offers a great potential do design fertilizers with unique properties capable to boost the plant productivity. However, the nanoparticles environmental fate and their toxic responses still need to be deeply investigated to their safe use. This study aims to investigate the effect of copper oxide (nCuO) and magnetite nanoparticles (nFe3O4) on the germination and seedling development of Phaseolus vulgaris L. Seeds were treated in nanoparticles dispersions in a wide range of concentrations (1, 10, 100 and 1 000 mg L-1) and incubated in a germination chamber during 5 days. Different sized nCuO (25, 40 and <80 nm) and polyethylene glycol (PEG) coated nFe3O4 were evaluated. Although both nCuO and nFe3O4 treatments did not affected the germination rate, seedling weight gain was promoted by 40 nm CuO at 100 mg Cu L-1 and inhibited by 1 000 mg Cu L-1 of 25 nm CuO and positive control (CuSO4). Among the tested nCuO, the higher chemical reactivity was found for the 25 nm CuO, and this may partially explain the observed deleterious effects. Seeds treated in nFe3O4-PEG at 1 000 mg Fe L-1 increased radicle elongation compared to the negative control (water), while Fe2+/Fe3+ (aq) (positive control) and bare nFe3O4 at 1 000 mg Fe L-1 treatments reduced the radicle of the seedlings. The growth promoted by the PEG-coated nanoparticles can be justified by the higher water uptake induced by the PEG, and also by its lower chemical reactivity compared to the bare nanoparticles. This was reinforced by enzymatic assays since nFe3O4-PEG treatment was also the least harmful to the alpha-amylase activity. X-ray fluorescence spectroscopy (XRF) showed that most of the Cu and Fe incorporated by the seeds remained in the seed coat, specially in the hilum region, and X-ray tomography indicated that Fe3O4-PEG penetrated in this structure. X-ray absorption spectroscopy (XAS) unraveled that the Cu and Fe chemical environment of the nCuO and nFe3O4-PEG treated seeds persisted mostly in its primitive form. These results contribute to the understanding of how nCuO, nFe3O4 and nFe3O4-PEG interact with common bean seeds and seedlings and highlights its potential use in seed priming / A nanotecnologia oferece um grande potencial para o desenvolvimento de fertilizantes com propriedades únicas, capazes de impulsionar a produtividade das plantas. Contudo, o destino ambiental e os efeitos tóxicos das nanopartículas ainda necessitam ser profundamente investigados para o seu uso seguro. Este estudo visa investigar o efeito das nanopartículas de óxido de cobre (nCuO) e magnetita (nFe3O4) na germinação e desenvolvimento das plântulas de Phaseolus vulgaris L. As sementes foram tratadas em dispersões de nanopartículas em diversas concentrações (1, 10, 100 and 1 000 mg L-1) e incubadas em uma câmara de germinação durante 5 dias. Diferentes tamanhos de nCuO (25, 40 e <80 nm) e nFe3O4 recoberta com polietileno glicol (PEG) e foram avaliados. Embora ambos tratamentos de nCuO e nFe3O4 não afetaram a taxa de germinação, o ganho de massa das plântulas foi promovido pela nCuO de 40 nm à 100 mg Cu L-1 e inibido pelos tratamentos de nCuO de 25 nm e controle positivo (CuSO4) à 1 000 mg Cu L-1. Dentre as nCuO testadas, a maior reatividade química foi encontrada para a nCuO de 25 nm, e isso pode explicar parcialmente os efeitos deletérios desta nanopartícula. Sementes tratadas com nFe3O4-PEG à 1 000 mg Fe L-1 aumentaram o alongamento das radículas em comparação ao controle negativo (água), enquanto que os tratamentos Fe2+/Fe3+ (aq) (controle positivo) e nFe3O4 sem recobrimento à 1 000 mg Fe L-1 reduziram as radículas das plântulas. O crescimento promovido pelas nanopartículas recobertas com PEG pode ser justificado pela maior absorção de água induzido pelo PEG, e também pela sua baixa reatividade química comparada às nanopartículas sem recobrimento. Isso foi reforçado por ensaios enzimáticos uma vez que o tratamento de nFe3O4-PEG foi também o menos prejudicial à atividade da alfa-amilase. A espectroscopia de fluorescência de raios-X (XRF) mostrou que a maior parte do Cu e do Fe incorporados pelas sementes permaneceu no tegumento, especialmente na região do hilo, e a tomografia de raios-X indicou que nFe3O4-PEG penetrou nesta estrutura. A espectroscopia de absorção de raios-X (XAS) revelou que o ambiente químico do Cu e do Fe das sementes tratadas com nCuO e nFe3O4-PEG persistiram majoritariamente em sua forma primitiva. Estes resultados contribuem para o entendimento de como nCuO, nFe3O4 e nFe3O4-PEG interagem com sementes de feijão e destaca seu potencial uso no tratamento de sementes

Foram realizadas medidas das seçõesde choque de produção de raios X L, L e L bem como medidas das seções de choque de ionização das subcamadas L1, L2 e L3 para os elementos Au e Ta com o Acelerador de elétrons Microtron de São Paulo, do Instituto de Física da Universidade de São Paulo. Os alvos foram produzidos no Laboratório de Alvos do Pelletron por evaporação desses elementos sobre substratos finos de carbono. Eles foram posicionados no centro da câmara de irradiação, de modo que o feixe incidia perpendicularmente à sua superfície. Os raios X decorrentes da ionização do alvo de tântalo foram observados com um detetor de Si(Li), enquanto que para o alvo de ouro usou-se um detetor HPGe, ambos posicionados a 120 graus em relação ao feixe. As curvas de eficiência de ambos os detetores foram levantadas usando as fontes de calibração e ajustando os pontos obtidos com um modelo analítico. Para cada energia de feixe, a seção de choque foi determinada a partir das áreas dos picos dos raios X característicos, da corrente incidente no alvo, da eficiência de deteção no pico e da espessura do alvo. As áreas dos picos foram determinadas pelo ajuste de uma forma gaussiana, a corrente incidente no alvo foi medida com um copo de Faraday e corrigida para a dispersão dos elétrons ao passarem pelo alvo, e as medidas de espessura dos alvos foram realizadas pelo método de retro-espalhamento de Rutherford (RBS). Os resultados experimentais obtidos ficaram acima do calculado com a aproximação de Born de ondas distorcidas para as medidas de seção de choque de produção de raios X L, L do Au e para os multipletos L e L do Ta. Para o grupo L do Au e do Ta as medidas foram consistentes com o modelo teórico. Os dados encontrados na literatura para ambos os elementos referem-se todos a energias próximas do limiar de ionização da camada L e nessa faixa são consistentes com o modelo teórico, embora em alguns casos afetados por incertezas superiores a 20%. Este trabalho traz as primeiras medidas para a seção de choque de produção de raios X L do Ta para energias superiores a 50 keV. / Measurements were made of the L, L and L x-rays production cross section and also of the ionization cross section of subshell L1 , L_2 and L3 for the elements Au and Ta in the electron accelerator Microtron of São Paulo, located at the Institute of Physics of the University of São Paulo. The targets used were produced in the Pelletron Targets Laboratory and consisted of fine targets evaporated on thin carbon substrates. These targets were positioned in the center of the Microtrons irradiation chamber, so that the focused beam perpendicular to the surface. The x-ray originated from the ionization of the Ta target were obtained with a Si(Li), for the Au target it was used a HPGe detector, both positioned at 120 degrees relative to the electrons beam. The efficiency curve for both detectors was made by using calibration sources and by adjusting the points with a analytical model. For every beam energy the x-rays production cross section were obtained by an accurate knowledge of the peak areas, of the current incident on the target, of the absolute efficiency, and of the thickness of the target. The peak areas were determined by fitting a Gaussian shape, the measurements of the current were made with a Faraday cup and it were corrected for the electrons\' dispersion when they pass through the target, and the measurements of the thickness were performed with the method of Rutherford Back Scattering (RBS). The experimental results were above the Born approximation of distorted waves for measurements of L and L x-rays production cross sections of Au and for the multiplets L and L and of Ta. The measurements of L group of Au and Ta were consistent with the theoretical model. The data founded in literature for both elements are all near to the region of the threshold ionization energy of the shell L, on that energy range they are consistent with the theoretical model, although in some instances they are affected by uncertainties greater than 20%. This work presents the first measurements of Ta L x-rays production cross section to energies above 50 keV.