Дисертації з теми "Spatial redistribution"

100 keV 10 B+ ions were implanted into poly-(di-n-hexyl silane) in different directions at a fluence of 1x1014 cm-2, and their depth distribution was determined by means of the neutron depth profiling technique. In no case the projectile ions are found to come to rest according to their predicted range profiles. Instead, they are always found to undergo considerable long-range migration. During the irradiation process this motion appears to be radiation-enhanced, and during the subsequent annealing steps one appears to deal with regular thermal diffusion. The implant redistribution is always found to be governed strongly by the self-created damage, insofar as both electronic and nuclear defects in the polymer act as trapping centers. Their population ratio is modified by thermal annealing. The as-implanted redistribution shows a pronounced directional dependence, which essentially is a consequence of the spatial distributions of the electronic and nuclear damage. The changes of the nuclear defect distribution during thermal annealing are studied by a specially developed tomographic method. It is found that boron is preferentially trapped along the irradiation direction, exhibiting quite pronounced prolate (i.e. cigar-like) distributions. This shape is hardly affected by thermal annealing.

100 keV 10 B+ ions were implanted into poly-(di-n-hexyl silane) in different directions at a fluence of 1x1014 cm-2, and their depth distribution was determined by means of the neutron depth profiling technique. In no case the projectile ions are found to come to rest according to their predicted range profiles. Instead, they are always found to undergo considerable long-range migration. During the irradiation process this motion appears to be radiation-enhanced, and during the subsequent annealing steps one appears to deal with regular thermal diffusion. The implant redistribution is always found to be governed strongly by the self-created damage, insofar as both electronic and nuclear defects in the polymer act as trapping centers. Their population ratio is modified by thermal annealing. The as-implanted redistribution shows a pronounced directional dependence, which essentially is a consequence of the spatial distributions of the electronic and nuclear damage. The changes of the nuclear defect distribution during thermal annealing are studied by a specially developed tomographic method. It is found that boron is preferentially trapped along the irradiation direction, exhibiting quite pronounced prolate (i.e. cigar-like) distributions. This shape is hardly affected by thermal annealing.

Geology
M.S.
Many grasslands in arid and semi-arid regions are undergoing rapid changes in vegetation, including encroachment of woody plants and invasive grasses, which can alter the rates and patterns of fire and sediment transport in these landscapes. We investigated the spatial distribution of sediments at the scale of vegetated microsites for three years following a prescribed fire using a multiple rare earth element (REE) tracer-based approach in a shrub-grass transition zone in the northern Chihuahuan desert (New Mexico, USA). To this end, we applied REE tracers – holmium, europium, and ytterbium on shrub, grass, and bare microsites, respectively in March 2016. Soil samples were collected from both burned and control (not burned) sites before (March) and after (June) the annual windy season, from 2016 through 2018. Results indicate that although the horizontal mass flux (HMF) of wind-borne sediment increased approximately threefold in the first windy season following the fire, and the HMF of both plots were not significantly different after three windy seasons. Comparing REE concentrations in sediments from both plots over the three years and three annual windy seasons, we observed a post-fire shift in source and sink dynamics of sediments. The tracer analysis of wind-borne sediments indicated that the source of the HMF in the burned site was mostly derived from shrub microsites following the fire, whereas the bare microsites were the major contributors for aeolian sediment in control areas. The shift in sources and sinks, and the spatial homogenization of REEs indicate that the removal of shrub vegetation resulted in sediment redistribution to the bare microsites even three years after the prescribed fire. The findings of this study will improve our understanding of post-fire geomorphic processes at a microsite scale in a grassland ecosystem undergoing land degradation induced by shrub encroachment.
Temple University--Theses

Thesis (doctoral)--Swedish University of Agricultural Sciences, 2003.
Thesis documentation sheet inserted. Includes appendix of four papers and manuscripts, two co-authored with Barbara Ekbom. Includes bibliographical references. Also partially issued electronically via World Wide Web in PDF format; online version lacks appendix of papers.

A thorough investigation of legislation involved in the land reform programme was conducted. This includes the Constitution of South Africa, as well as the legal frameworks that manage the land reform process. Many of the unintended results are because of misunderstandings. This study sought to clarify those misunderstandings and confusing language. The South African land reform process was excellently planned. The process is managed in three phases, namely land restitution, land redistribution and land tenure. There are some successes and failures due to the way those programmes were implemented. In order to implement and manage the land reform programmes and spatial planning on national, provincial and district level, the following plans were introduced: National Level: Pro-active Land Acquisition Strategy (PLAS) & Area-based Planning Provincial Level: Limpopo Growth and Development Strategy (LGDS) District Level: Mopani Integrated Development Plan Local Level: Greater Tzaneen Municipality Integrated Development Plan & Spatial Development Framework The study area, the Tzaneen Local Municipality, was chosen because it is home to some of the first land reform projects in South Africa, it is the district with some of the highest intensity of land claims and it offers a complete menu of land reform programmes in an advanced state on a small area. The impact that land reform has had on the spatial development in the Tzaneen Local Municipality has been studied in more detail. As the study progressed, it was realised that the impact not only stops at spatial development. The influence was much bigger than that. The local economy was affected, as were job opportunities, tourism, food security, the retail industry and even the mining industry. Such an impact is also not restricted to the Tzaneen Local Municipality. In order to control the land reform process, the government should involve the private sector in the land reform process. The moment this happens, the skills and experience locked in the private sector are transferred to the government for the benefit of all people involved in and influenced by the land reform process. An Integrated Land Reform Action Forum (ILRAF) must be established that manages the land reform process on national, provincial and local level. This ILRAF has to fulfil much the same purpose as the former Joint Monitoring Committees (JMCs) accomplished. The ILRAF must consist of all role-players within the land reform process. These include, national, provincial and local government officials, commercial farmers, key role-players from the private sector, farm worker representatives, Agri-SA, professionals such as town and regional planners and transfer attorneys, farmers? associations, commercial banks and the media to ensure transparency. In order to correct past mistakes and to ensure that the next five years of the land reform process goes off without a hitch, it is important to involve all role-players and ensure transparency throughout all decision-making processes. Key Terms: Land Reform; Agri-village; Area Based Planning; Land Restitution; Land Redistribution; Land Tenure Reform; Greater Tzaneen Municipality; Willing buyer-willing seller; Spatial Development Framework; Integrated Development Plan.
Thesis (M.Art. et Scien. (Town and Regional Planning))--North-West University, Potchefstroom Campus, 2010.

Using the tracer caesium-137 (137Cs) and experimental approaches this study quantified soil redistribution induced spatial variation of nutrients and soil organic carbon (SOC), net C flux between soil and atmosphere and soil respiration rate at various landscapes positions (eroding to deposition) within agricultural fields from the foot hills of Indian Himalaya. The depth distributions of 137Cs and the spatial patterns of 137Cs inventories were consistent with previous applications of the approach in that low inventories were associated with low concentrations in the cultivation layer and high inventories were reflected in deeper 137Cs profiles indicative of accumulation of labelled soil. This supports the contention that 137Cs is a suitable tracer for use in this environment. The study found that soil redistribution within fields altered the spatial variation of nutrients and SOC; with significantly lower concentrations of nutrients in the most eroded part of fields (upslope) and significantly higher concentrations of nutrients and SOC in the depositional part of field (downslope). The spatial pattern of nutrients and SOC is reflected in differences in depth distributions between eroded and depositional areas. The 137Cs and SOC inventory and depth distribution data were used to derive retrospective assessments of net C exchange between soil and atmosphere. The C flux quantification model was used to estimate lateral and vertical soil and SOC redistribution under an assumption of equilibrium conditions and the net exchange of C between soil and atmosphere was derived from the difference between measured and ‘equilibrium’ SOC inventories. Fluxes were derived for each landscape position within the agricultural fields studies and calculated at field and site scale. High rates of soil loss were measured and the results showed that the majority of eroded sediment and SOC was exported from field with only a small fraction redeposited within the field. The effect of soil and SOC redistribution was to create disequilibrium in SOC dynamics at eroding and deposition positions and this supported the formation of a field scale C sink. The sink strength is highest in the most eroded parts of the fields due to dynamic replacement of eroded C. This is assumed to be due to the high rate of incorporation of SOC-poor subsoil, with a large C-unsaturated surface area, into the cultivation layer. The C sink is smaller that those reported from high nutrient-input mechanised farm lands. Irrespective of the fate of exported SOC, the SOC stocks in the fields appear to be in dynamic equilibrium and, therefore, there is no evidence of a C source to the atmosphere due to erosion. Also the rate of SOC export from the fields is very high, especially when compared with mechanised fields and, if it is assumed that some portion of exported C is stored in some part of low lying area, the C sink strength would be comparable to mechanised farm lands. The soil redistribution and C flux study confirmed the existence of spatial variation in C flux at various landscapes position and was consistent with an important role for vertical mixing of soil and SOC in determining net C exchange with the atmosphere. This informed the design of the final element of the research that examined soil respiration differences in soil from shallow and deep layers in eroding and aggrading landscapes position. Respiration was measured over a one year period in samples derived from separate depth layers and in mixtures of soil from different depths at each landscape position. No significant difference was found in C release rate (per unit mass of C) from topsoil of eroding and deposition position but the subsoil of eroding pits exhibited significantly higher C release than the subsoil from deposition positions. This result suggests that topsoil in both locations has almost equal and similar C origin. The relatively high rate of respiration in sub soils from eroding pits may be due to the presence of a larger proportion of SOC formed from recently incorporated plant material (crop roots) at these locations. In buried and deposition locations the reduced mineralisation is consistent with the proposition that burial of top soil can contribute to formation of a C sink. In the samples containing mixed topsoil and subsoil, evidence for priming was seen where the respiration rate in the mixed sample was significantly higher than the expected rate based on the respiration rate seen in the separate depth samples. No priming was evident in mixed soils from eroding locations, suggesting that mixing of subsoil and surface soil does not accelerate loss of old SOC from the subsoil. In contrast, significant priming action was evident in mixed soils from aggrading locations suggesting that buried SOC at depositional locations may be subject to accelerated respiration as long as it is exposed to fresh plant input (as found in surface soils). In conclusion, despite the low input and low productivity of the farmlands in the Indian Himalaya region studied here, there is consistent evidence that high rates of soil erosion and soil redistribution have induced spatial variation of nutrients and SOC, net C flux and soil respiration rates that combine to create a pattern of SOC stocks that are close to equilibrium and, if some of the exported C is sequestered, to create a net C sink. This result again confirms that erosion induced redistribution of C does not directly cause a net release of C to the atmosphere. The consistency of these results with previous studies suggests that there is both scope and need for soil erosion induced carbon fluxes to be incorporated into carbon budgets, research frameworks, land management and climate change mitigation strategies at policy-relevant scales.

Dans le contexte du changement climatique mondial et la nécessité d'étudier les conséquences de l'ampleur de la fonte des glaces continentales sur le niveau des mers ainsi que sur la répartition des masses fluides à l'échelle du globe, notre travail de thèse s'intéresse aux phénomènes à très grande échelle qui modifient la forme de la Terre, son champ de gravité et l'équilibre de sa rotation. Il se focalise sur la stratégie à mettre en place pour observer et modéliser des variations très fines sur des termes géodynamiques (coefficients de bas degrés) qui sont encore aujourd'hui mal connus, et pourtant déterminants dans l'établissement des références terrestres fondamentales. La première partie de la thèse concerne l'observation du mouvement du géocentre par différentes techniques de mesures géodésiques. Ces travaux débouchent, par une meilleure maîtrise des sources d'erreurs, sur une explication des écarts entre les séries de mesures laser du mouvement du géocentre obtenues sur les satellites LAGEOS (référence actuelle pour l'origine du repère international, ITRF) et celles obtenues indépendamment sur le satellite altimétrique Jason-2 à partir d'observations DORIS/laser/GPS. La deuxième partie de la thèse s'intéresse à la détermination cohérente des coefficients de degrés 0 (coefficient gravitationnel GM), 1 (géocentre), et 2 (inertie/orientation) du champ de pesanteur terrestre. Nous utilisons pour cela les mesures de télémétrie laser disponibles depuis les années 1970 (par exemple, Starlette lancé en précurseur par le CNES dès 1975), car ce sont les seules mesures à caractère absolu qui donnent accès à ces trois premiers degrés. Nos analyses menées sur près de 35 ans aboutissent à une nouvelle valeur de la constante gravitationnelle géocentrique et la détection d'une réponse viscoélastique du manteau de notre planète aux échelles de temps décennales, par combinaison des termes de degré 2 et paramètres d'orientation de la Terre avec les équations d'Euler-Liouville
In the context of the overall climate change and the need to analyze the implications of the record ice-sheet melting for the sea level and global fluid mass redistribution budgets, our PhD work focuses on large-scale phenomena impacting the shape of the Earth, its gravity field, and the stability of its rotation pole. We explore strategies for the observation and modeling of subtle variations in geodynamic parameters (lowermost degree coefficients), which are still poorly constrained, despite their importance in determining fundamental terrestrial references. The first part of this PhD is dedicated to the observation of the geocenter motion, using different geodetic technics. The outcomes of this work provided explanations, through a correct handling of the dominant error sources, for the discrepancies between the reference laser-based LAGEOS geocenter time series (defining the origin of the international frame, ITRF) and independent solutions using DORIS/laser/GPS observations from the Jason-2 altimeter satellite. The second part of this PhD presents a self-consistent determination of the degrees 0 (gravitational coefficient GM), 1 (geocenter motion), and 2 (Earth's figure axis orientation) of the geopotential. To this end, we use the available laser data since the 1970s (e.g., the first geodetic satellite Starlette launched by CNES in 1975), as they are the only absolute measurements making possible the monitoring of the first three degree terms. Based on 35 years of satellite laser tracking, an updated value of the geocentric gravitational coefficient was obtained, and a viscoelastic behavior of the Earth's mantle manifesting at decadal time scales was exhibited, combining the derived figure axis variations of the Earth and polar motion observations with the Euler-Liouville equations

La caractérisation et la surveillance des systèmes d'eau souterraine sont fondamentales pour la conservation et la gestion des ressources en eau souterraine. Dans cette intention, l'hydrogéophysique fournit une série de méthodes non invasives pour étudier l'environnement souterrain peu profond et les processus qui s'y déroulent sur plusieurs échelles. Les applications hydrogéophysiques à méthode dites time-lapse sont notamment utiles pour surveiller la dynamique de l'eau et suivre les variations temporelles de la teneur en eau. Largement dominées par des méthodes électriques et électromagnétiques, ces applications sont de plus en plus explorées avec des méthodes sismiques. Le signal sismique dépend des propriétés mécaniques du milieu qui sont à leur tour affectées par les changements de teneur en eau. Par conséquent, les réponses sismiques sont également influencées par les propriétés et variables hydrologiques. Néanmoins, les complexités liées à la description du comportement mécanique de matériaux peu profonds et partiellement saturés limitent la caractérisation quantitative de la subsurface et la dynamique de l'eau associée par les méthodes sismiques. Dans ce travail, nous étudions l'évolution temporelle des réponses sismiques en fonction des variations de teneur en eau par la méthode de time-lapse acquise sur le terrain. Nous analysons à la fois les données et les paramètres inversés et nous comparons ensuite les tendances résultantes avec des relations pétrophysiques établies. De cette façon, nous montrons que les inversions sismiques en time-lapse des données de réfraction de l'onde P et les changements correspondant à la vitesse de propagation des ondes permettent la reconnaissance des chemins d'écoulement préférentiels de l'eau dans la subsurface, mettant ainsi en évidence le potentiel des méthodes sismiques pour surveiller les processus hydrologiques et les écoulements non saturés. De manière générale, on observe un fossé d'observations entre les estimations quantitatives de la teneur en eau obtenue par les paramètres sismiques inversés et les corrélations qualitatives, jusqu'à présent dominantes, reliant la vitesse sismique aux relations pétrophysiques théoriques. Cet écart d'observation pourra être comblé par de nouvelles études sismiques en time-lapse sur le terrain. À la suite des progrès récents d'équipement et techniques sismiques, les relations pétrophysiques à l'échelle du terrain joueront un rôle important dans le développement de méthodes sismiques pour des applications hydrologiques
The characterization and monitoring of subsurface water systems are fundamental to groundwater resources conservation and management. To this end, hydrogeophysics provides a suite of non-invasive methods to study the shallow subsurface environment and the processes occurring therein over multiple scales. Time-lapse hydrogeophysical applications are notably useful to monitor water dynamics and follow temporal variations in water content. Largely dominated by electrical and electromagnetic methods, these applications are being increasingly explored with seismic methods. The seismic signal is dependent on the mechanical properties of the medium which are in turn affected by changes in water content. Consequently, seismic responses are also influenced by hydrological properties and state variables. Nonetheless, complexities in describing the mechanical behavior of partially saturated shallow materials have limited the quantitative characterization of the subsurface and associated water dynamics by means of seismic methods. Here we investigate the evolution of seismic responses with varying water content in time-lapse field contexts, analyzing both data and inverted parameters, and compare the resulting trends with established petrophysical relationships. We show that seismic time-lapse inversions of P-wave refraction data and corresponding changes in wave propagation velocity enable the recognition of preferential water flow paths in the subsurface, highlighting the potential of seismic methods to monitor hydrological processes and unsaturated flow. Overall, qualitative agreements between seismic velocity trends and theoretical petrophysical relationships still eclipse accurate quantitative estimations of water content from inverted seismic parameters. We anticipate further time-lapse seismic field studies to help bridge the gap between qualitative and quantitative observations. In the wake of the recent advancements in seismic equipment and techniques, appropriate field-scale petrophysical relationships will play an important role in the development of seismic methods for hydrological applications

La question des disparités territoriales, pourtant ancienne, se pose aujourd'hui de manière accrue et renouvelée avec l'ouverture européenne et la globalisation qui induisent une concurrence des territoires toujours plus forte. Or, si celle-ci n'est pas maîtrisée, les conséquences peuvent se révéler importantes en termes de cohésion spatiale. Ainsi, une réflexion approfondie sur les outils de traitement de la question sensible des disparités territoriales s'avère tout à la fois pertinente et nécessaire. Nous retenons ici deux types d'intervention publique qui peuvent apparaître aujourd'hui comme les outils les plus significatifs de réduction des disparités territoriales et que nous étudions dans un contexte de mobilité interrégionale. La thèse est donc organisée autour de deux parties bien distinctes, mais complémentaires quant au fond. La Partie I traite de la péréquation financière comme outil de réduction des disparités territoriales. Le Chapitre 1 a pour vocation d'offrir une revue approfondie et raisonnée de la littérature sur la péréquation financière dans un contexte de mobilité des agents économiques et par conséquent dans une perspective d'efficacité économique. Le Chapitre 2 s'inscrit dans la suite du premier et étudie la capacité d'un système transparent de péréquation financière à restaurer l'efficacité économique. La Partie II de la thèse s'intéresse quant à elle à un second instrument de réduction des disparités territoriales, la coopération intercommunale et à son implication sur la pression fiscale. Le Chapitre 3 évalue cette question d'un point de vue théorique tandis que le Chapitre 4 consiste en une analyse empirique appliquée au cas Français
The question of territorial disparities, although not a new one, appears to be a very topical issue with European opening and globalization. If the higher competition between territories that arises in this context is not controlled, the consequences can be extremely important in terms of social cohesion. Thereby, a detailed analysis about the instruments used to deal with the sensitive issue of territorial disparities is both relevant and necessary. We then focus on two types of public intervention that appear as the most important instruments used in the reduction of territorial disparities and that we analyze in a context of mobility. The thesis is then organized in two parts that are distinct but complement each other. The Part I is interested in the issue of fiscal equalization as a device to reduce fiscal disparities. The Chapter 1 provides a detailed survey of literature on equalization payments in a context of economic agents' mobility and therefore in an economic efficiency perspective. The Chapter 2 is in line with the first one and analyses the ability of a transparent equalization scheme to be efficiency enhancing. The Part II of the thesis studies a second instrument reduction of territorial disparities, inter-municipal cooperation, and its impact on fiscal pressure. The Chapter 3 look at this issue from a theoretical point of view, while the Chapter 4 is an empirical analysis applied to the French case

Роботу виконано та захищено в Інституті фізики НАН України.
Кохтич Л. M. Закономірності формування об'ємних періодичних структур полімер-наночастинки голографічним методом. - На правах рукопису. Дисертація на здобуття наукового ступеня кандидата фізико-математичних наук за спеціальністю 01.04.05 - оптика, лазерна фізика. - Інститут фізики НАЛ України, Київ, 2014. У дисертації представлено результати дослідження об'ємних періодичних структур полімер - НЧ різної природи, отриманих голографічним методом. В роботі вперше показана можливість отримання стабільних об'ємних структур з НЧ металу шляхом синтезу НЧ з прекурсору металу, попередньо розподіленого в полімерній матриці. Розроблені та оптимізовані органо-неорганічні нанокомпозити, чутливі в діапазоні 400-520 нм, основані на комерційних доступних акрилових мономерах, які забезпечують ефективний дифузний перерозподіл НЧ різної природи та прекурсору НЧ в полімерній матриці. Досліджені голографічні властивості отриманих нанокомпозитів та механізми впорядкування НЧ. З використанням НЧ різної природи (TiO2, SiO2, ZrO2, LaPO4, CdSe/ZnS, прекурсору НЧ Ag) отримані стабільні об'ємні структури (ґратки пропускаючого типу) з періодом 0.3 - 3 мкм і амплітудою модуляції показника заломлення 0.005 - 0.026, що в деяких випадках на порядок перевищує раніше досягнуті величини. Досліджено дифракційні, люмінесцентні та лазерні властивості періодичних структур з НЧ різних типів.
Kokhtych L.M. Regularities in formation of volume periodic structures polymer – nanoparticles by the holographic method. – Used only as a manuscript. This thesis is for obtaining the scientific degree candidate of sciences (physics and mathematics) by the specialty 01.04.05 – optics, laser physics. – Institute for Physics, NAS of Ukraine, – Kyiv, 2014. The results of study of volume periodic structures polymer – nanoparticles (NP) of different kinds fabricated by holographic method are introduced in this thesis. For the first time it was shown the possibility to obtain the stable volume structures polymer – metal NP by using the synthesis of NP from the metal precursor preliminary distributed in a polymer matrix. Based on commercially available acryl monomers organic-inorganic nanocomposites light-sensitive within the range 400 – 520 nm have been developed and optimized. These materials provide efficient diffusion redistribution of NP and NP precursor in polymer matrix. Holographic properties of the obtained nanocomposites as well as the mechanism of NP ordering have been investigated. Using of NP of various nature (TiO2, SiO2, ZrO2, LaPO4, CdSe/ZnS, precursor of Ag NP), we have obtained stable volume transmission gratings with the period 0.3 - 3 µm and the amplitude of refractive index modulation from 0.005 up to 0.026, that sometimes exceeds by one order the values reached earlier. Diffraction, luminescent and laser properties of the obtained structures were also investigated.
Кохтич Л. М. Закономерности формирования объемных периодических структур полимер-наночастицы голографическим методом. - На правах рукописи. Диссертация на соискание ученой степени кандидата физико-математических наук по специальности 01.04.05 – оптика, лазерная физика. – Институт физики НАН Украины, Киев, 2014. В диссертации представлены результаты исследования особенностей формирования периодических структур полимер – НЧ различной природы: SiO2, LaPO4:Ce,Tb, CdSe/ZnS, TiO2, ZrO2 и Ag голографическим методом. Для достижения поставленных задач, в отличие от известных двухкомпонентных систем, включающих мономер и НЧ, была реализованная идея использования трьохкомпонентной системы, базирующейся на двух акриловых мономерах с разным количеством двойных связей (CH=CH2)m и разной реакционной способностью. Установлено, что оптимальной мономерной составляющей является смесь поли- и однофункционального мономеров. Первый должен иметь высокую скорость полимеризации и формировать трехмерную полимерную сетку, второй, с низкой скоростью полимеризации, – образовывать линейные полимерные цепи и иметь низкое термодинамическое сродство к полимерной сетке, что способствует вытеснению низкореакционного мономера и НЧ из максимумов светового поля в минимумы поля. Показано, что наиболее универсальным вариантом является мономерная смесь, которая состоит с SR444 (m=3) и IBA (m=1). Она обеспечивает эффективное пространственное перераспределение компонент для всех исследуемых НЧ. Использование других комбинаций может обеспечивать дополнительные свойства структур. Для получения высокого контраста структуры, нанокомпозит должен включать не менее 10об.% НЧ. Детально исследован механизм формирования периодических структур полимер - НЧ и усовершенствована его полимеризационно-дифузная модель. Определено влияние фазового разделения, вязкости среды, концентрации мономеров и НЧ на степень их пространственного перераспределения и, соответственно, эффективность структуры. Упорядочение НЧ в полимерной матрице происходит вследствие неоднородной полимеризации и диффузионного перераспределения компонент композита в пространственно периодическом поле. Относительная модуляция объемной концентрации НЧ достигается при концентрационном соотношении SR444:IBA 30:70вес.% составляет 85-99%. В результате, формируется объемная структура, эффективность которой определяется различием показателей преломления в облученных и необлученных областях решетки и степенью пространственного перераспределения компонент. Амплитуда модуляции показателя преломления n1 определяется также соотношением характерных времен полимеризации и диффузионного массопереноса на расстояние порядка периода поля. Максимальное n1 достигается в случае, когда диффузионный массоперенос происходит быстрее, чем формирование полимерной сетки, что определяется условиями голографической экспозиции: интенсивностью и периодом поля, которые составляют I=0.8÷9мВт/см2, Λ= 0.8÷1.2 мкм, соответственно. С использованием НЧ различной природы получены объемные периодические структуры с периодом 0.4 – 2 мкм и величиной n1 0.005 – 0.026, что существенно превышает величины, достигнутые для тех же НЧ в композитах, включающих один мономер. В работе впервые показана возможность получения стабильных объемных структур полимер - НЧ металла с высоким содержанием НЧ и низким уровнем дефектности. Формирование структур происходит в результате синтеза НЧ из металлического прекурсора, периодически распределенного в полимерной матрице. На первом этапе при фотополимеризации в интерференционном поле формируется стабильная периодическая структура (объемная решетка) полимер – металлический прекурсор. Образование НЧ металла происходит, главным образом, после голографической записи вследствие термической обработки. Фотостабильность решеток обеспечивается необратимым диффузионным разделением компонент в процессе записи. В зависимости от условий записи и используемого инициатора средний диаметр НЧ составляет 5 и 3 нм. Образование НЧ серебра подтверждено электронно-микроскопическими и спектральными исследованиями. Исследовано механизмы фото- и термостимулированного синтеза НЧ в полимерных слоях. Для структур с периодом 0.3 – 3 мкм показано, что термоиндуцированный синтез НЧ Ag обеспечивает максимальное значение n1 = 0.02, что в два раза превышает величину, полученную при фотоиндуцированном восстановлении. Предложена наиболее вероятная схема восстановления Ag+ и образования НЧ серебра в периодических структурах. Исследованы дифракционные, люминесцентные и лазерные свойства периодических структур с НЧ различных типов. На базе разработанных материалов изготовлены голографические оптические элементы 1D-2D размерности и РЗЗ-структуры. Стабильность параметров структур сохраняется не менее 8 лет. Дифракционная эффективность одномерных структур на длинах волн 440-650 нм составляет 80-99%, двумерных – 65-70%.

This thesis consists of four self-contained empirical essays. In the first essays "Markets for Risk and Openness to Trade: How are They Related?" (with Helena Svaleryd), we ask if there is an empirical relationship between financial development and openness to trade. Numerous theoretical papers have noted that trade policies can be used as an insurance against shocks from international markets. It follows that the development of markets for risk should reduce the incentives to rely on trade policy for insurance purposes. Feeney and Hillman (2001) explicitly demonstrate how asset-market incompleteness can affect trade policy in a model where trade policy is determined by the lobbying of interest groups. If risk can be fully diversified, special-interest groups have no incentive to lobby for protection, and free trade will prevail. Likewise, trade liberalization might increase the demand for financial services, thereby spurring the development of financial markets. Using several indicators of both openness to trade and financial development, we find an economically significant relation between the two. In particular, the relation holds when using the well known, although criticized (Rodriguez and Rodrik 1999), Sachs-Warner index, and structurally adjusted trade, as indicators of openness. For tariff levels and non-tariff barriers, the results hold only for relatively rich countries. Causality seems to be running both from openness to financial development and the other way around, depending on which indicator and methodology are used. Due to underlying technological differences, industries differ in their need for external financing (Rajan and Zingales, 1998). Since services provided by the financial sector are largely immobile across countries (Pagano et al., 2001), the pattern of specialization should be influenced by the degree of financial development. In the second essay, "Financial Markets, the Pattern of Specialization, and Comparative Advantage: Evidence from OECD Countries" (with Helena Svaleryd), we find this effect to be strong. In fact, the financial sector has an even greater impact on the pattern of specialization among OECD countries than differences in human- and physical capital. Further, the financial sector gives rise to comparative advantage in a way consistent with the Hecksher-Ohlin-Vanek model. Large and active stock markets, as well as the degree of concentration in the banking sector, produce the strongest and most consistent effects. The results also support the view that the quality accounting standards and the legal protection of creditors affect the pattern of industry specialization, while the depth of the financial system (measured by the amount of liquidity in an economy) is a source of comparative advantage. The third essay, "Who Wants Political Integration? Evidence from the Swedish EU-Membership Referendum" looks directly at the determinants of political attitudes towards regional integration and separation. More precisely, the regional voting pattern of the 1994 Swedish EU-membership referendum is analyzed. To explain this variation, an empirical investigation based on the extensive theoretical literature analyzing the determinants of regional economic and political integration is undertaken. Since enhanced possibilities of inter-regional risk sharing is one of the main gains from integration discussed in the literature (e.g Persson and Tabellini, 1996), special attention is given to this issue. The empirical results show that individuals living in labor markets exposed to a high degree of risk were more negative towards EU-membership than those living in safe ones. It is also shown that inhabitants of high-income labor markets, with a high level of schooling and small receipts of central government transfers were relatively positive towards the EU-membership. Given the restrictive regulations limiting discretionary policies within the EU, these results suggest that inhabitants of safe and rich regions voted in favor of secession from the Swedish transfer system, rather than in favor of European integration. In the final essay, "Does Labor Market Risk Increase the Size of the Public Sector? Evidence From Swedish Municipalities", I study if a high degree of private labor-market risk is related to a larger public sector in Swedish municipalities. The theoretical hypothesis is based on Rodrik (1998), who argues (and shows empirically) that countries exposed to a high degree of external risk also tend to have larger governments. The safe public sector is expanded at the expense of risky sectors and hence provides insurance against income volatility. Several problems related to data availability and comparability that apply to cross-country studies are circumvented by using data on Swedish municipalities. Further, there is no need to aggregate the public sector across different levels of governance: local risk is directly related to the size of the local public sector. The paper is not a complete parallel to Rodrik’s study, however. Several alternative insurance mechanisms that do not exist between countries are available between municipalities. For example, the central government provides insurance against individual-specific risk such as unemployment and illness, private capital markets are better integrated within than between countries, and the central government can hand out grants to municipalities. Despite these mitigating factors, local labor-market risk is found to have a substantial impact on municipal public employment. It is also found that shocks increasing the size of the public sector across all municipalities tend to generate a larger increase in risky locations. For municipal public spending and taxation the results are, however, much weaker. Hence, labor-market risk affects the labor intensity of the municipal public sector, rather than its size.

Diss. Stockholm : Handelshögskolan, 2002

Par le feu de prelevements operes sur certains agents economiques, et l'affectation des ressources ainsi collectees a la fourniture de services publics qui ne beneficient pas forcement aux memes agents, un budget public local constitue un important vecteur potentiel de redistribution du revenu entre les individus et les espaces. Au moment ou, en france, les lois de decentralisation venaient de confier aux regions des responsabilites accrues dans l'amenagement de leur territoire, il est apparu opportun de developper une methodologie appropriee a l'evaluation des phenomenes de redistribution spatiale induits par la mise en oeuvre du budget regional, en l'appliquant au cas de la region ile-de-france. L'etude de l'incidence des budgets 1983-1985 de cette region sur les huits departements qui la composent, fait apparaitre des effets qui vont dans le sens de l'affaiblissement des desequilibres spatiaux constates en ile-de-france: la distribution departementale des benefices retires du budget augmente avec la distance au centre de l'agglomeration, et avantage les departements de l'est par rapport a ceux de l'ouest
The combined effects of the incidence of local public revenues and of public expenditures for the provision of local services are apt to produce important redistributions between individuals and areas. The decentralization process has given french regions new responsibilities regarding regional and local development, and we found particularly relevant to try and answer the question of the spatial impacts of the regional budget. The chosen case study for the method we propose is the region ile-de-france, and the results are given for fiscal years 1983 to 1985. The overall impact of these budgets on the eight departements which constitute ile-de-france clearly tends to reduce spatial inequalities in the area: the regional budget favors the poorer departements of the east vs. The west, and the less well-to-do suburbs vs. Well-off paris

L'objectif était de quantifier les modifications de la contractilité cardiaque au cours d’un bedrest de 21 jours (HDBR) par la methode speckle tracking 4D et de déterminer si la contre-mesure « exercice » était capable de préserver cette contractilité cardiaque. Les méthodes traditionnelles 2D ne mesurent qu'une variation de la taille du ventricule de la systole à la diastole et ne suivent pas la cinetique des mouvements de contractilité à l’interieur de la paroi. De plus l’echographie 2D ne permet d’acceder qu’a la contractilite longitudinale globale par la mesure de la distance Apex-Valve mitrale. Le suivi des mouvements des speckles (points singuliers a l’interieur du myocarde) en 4D montre que la contractilité radiale diminuée signifcativement pendant le HDTBR chez les sujets témoins alors qu’elle est conservée dans le groupe exercice. Par contre la contractilité longitudinale n’est pas affectée dans aucun des 2 groupes. Bien sûr, l'IRM pourrait fournir des données similaires, mais il n’est pas possible à ce jour d’imaginer avoir une IRM a bord de l’ISS dans un futur proche. A la suite de ces resultats nous avons mis au point un algorithme de traitement des video cardiaque qui permet d’acceder a la contractilite radiale et longitudinale en vol (prog Vasc-Aging en cours) .L’objectif de l’experimentation était de montrer que quatre jours en immersion seche suffisaient pour realiser un transfert liquidien important vers les régions céphaliques comparable à celui observé en vol spatial. Notre protocole consistait donc a mesurer les volume veineux au niveau cervical cerebral et porte au debut de la periode en immersion (a 2h) puis a 4 jours d’immersion. Compte tenu des problemes engendrés par ce transfert liquidien en vol nous avions proposé de tester la capacité des brassarts de cuisse a reduire l’amplitude du transfert veineux. Les résultats montrent que l’immersion provoque un transfert de sang veineux au niveau cervical maximal à 2H et que les Brassarts de cuisse reduisent signifcativement ce transfert dans cette phase precoce. Par contre a 4 jours d’immersion l’amplitude du transfert sanguin est considerablement diminuée (bien que toujours presente) et les brassarts de cuisse n’ont pas d’effet visible à ce moment-là. En fait le volume plasmatique decroit significativement à la fin du premier jour (env 20%) des lors la masse de sang deplacées vers la tete par l’immersion est insuffisante pour generer une stase importante au niveau cervical comme à 2h d’immersion. Pour cette meme raison la vitesse dans les veines cerebrales n’est pas augmentée à 4 jours d’immersion contrairement à ce qu’on avait observé à 2h d’immersion lors d’une precedente etude. Donc le modele immersion seche est un modele pour etudier les transferts liquidiens en microgravité mais seulement en debut de phase d’immersion. Sur cette période de temps, les Brassarts de cuisse ont bien un effet protecteur pour les organes de la zone cephalique
Objective: to evaluate functional myocardial contractility after 21 days of head-down bed rest (HDTBR) in sedentary control (CON) or with a resistive vibration exercise (RVE) countermeasure (CM) applied, by using 4D echocardiographic (4D Echo) imaging and speckle tracking strain quantification.Methods: Twelve volunteers were enrolled in a crossover HDTBR design, and 4D Echo was performed in supine position (REST) at BDC-2 and at R+2, and in -6° HDTBR (on day 18), and also during the first and the last minute of the 80° head-up step of Standard Measures tilt test, performed at both BDC-2 and R+2. Radial (Rad-Str), longitudinal (Lg-Str) and twist (Tw-Str) strain were measured by 4D speckle tracking, as well as left ventricle diastolic volume (LVDV) and mass (LVmass).Results: On day 18: in the CON group, LVDV and LVmass were reduced (p<0.05), the Rad-Str decreased (p<0.05) and Tw-Str showed a tendency to increase (p< 0.11), with no changes in Lg-Str. In RVE group, LVDV and LV mass, as well as all the strain parameters remained unchanged.On R+2: in the CON group, LVDV and LVmass were not recovered in all subjects compared to pre-HDTBR (p<0.08), Rad-Str was still decreased (p<0.05), while Tw-Str tended to increase (p<0.09). These parameters remained unchanged in the RVE group.Tilt 80°: Rad-Str and Lg-Str values at 80° tilt were similar post HDT in both groups.Conclusion: 4D Echo and speckle tracking analysis showed that in the CON group, Rad-Str decreased concomitant with LVmass and LVDV with HDTBR, but this observation did not support the hypothesis that this HDTBR induced remodelling or a muscle atrophy. RVE acted to preserve both LVmass, LVDV and contractility during HDTBR, thus proving its effectiveness to this aim. Nevertheless, the significant HDTBR-induced changes observed in the CON group had only a limited effect on the cardiac contractile response as observed during post HDTBR tilt test. The level of contractility at 80° Tilt position was not affected neither by HDTBR nor by RVE CM.Purpose: The objective was to quantify the venous redistribution during a 4-day dry immersion (DI) and evaluate the effect of thigh cuffs.Methods: The study included 9 control (Co) and 9 subjects wearing thigh cuffs during daytime hours (CU). Ultrasound images were collected Pre DI, on the fourth day in the morning (D4 AM) and on the fourth day in the afternoon (D4 PM), to assess the following outcome variables: left ventricle dimension, stroke volume, and ejection fraction (LVD, SV, EF), jugular vein volume (JV), portal vein dimension (PV), middle cerebral vein velocity (MCVv). An additional measure of JV dimension was performed on the first day after having worn the cuffs for two hours (D1 2H).Results: The JV volume increased significantly from Pre to D1 2H in both groups, but increased more in the Co compare to the CU subjects (Co: 0,27+/0.15cm3 to 0.94+/-0;22 cm3;P<0.01 CU: 0,32+/-0.13 cm3 to 0.64+/-0.32 cm3 P<0.042).At D4 AM no difference was found between the two treatment groups for any of the parameters listed above.Stroke volume and EF decreased from Pre (SV:111+/-23cm3 to 93+/-24 cm3 p<0.05; EF:0.66+/-0.07 to 0.62+/-0.07 p<0.05). JV volume was slightly, but significantly increased (Co: 0.47+/-0.22cm3 CU:0.35+/-014cm3 P<0.05), while MCVv and PV remained unchanged from Pre DI. From D4 AM to PM these parameters did not show any significant change.Conclusion: The results confirm that DI induces, during the first 2-3 h, a significant cephalic fluid shift as observed in spaceflight. During this early phase the thigh cuffs reduced the amplitude of the fluid shift towards the head, but after 4 days in DI there was only a slight memory (residual) effect of DI on the jugular volume and no residual effect of thigh cuffs

L'effet du réseau bocager sur l'organisation des sols à l'échelle d'un paysage reste mal connu, car la majorité des études ont été menées en deux dimensions, en se limitant souvent à des contextes de talus perpendiculaires à la ligne de plus grande pente. L'extrapolation des résultats ainsi obtenus à l'ensemble du paysage, est de ce fait difficile et conduit à une mésestimation de l'impact du bocage sur les sols.
Les objectifs de ce travail étaient de comprendre et de quantifier à l'échelle d'un paysage bocager, l'effet du système talus/haie sur l'organisation des sols et sur les stocks de carbone organique associés, ainsi que de décrire la dynamique des processus spatiaux qui ont conduit aux organisations observées.
Pour y parvenir, la démarche adoptée a combiné trois approches complémentaires. Tout d'abord, nous avons conduit une étude de terrain dans un paysage bocager historiquement documenté et offrant des conditions topo-paysagères contrastées avec pour but une caractérisation spatiale de l'effet du réseau bocager qui prenne en compte l'action de l'homme et la nature tridimensionnelle de la couverture pédologique à l'échelle du paysage.
Ensuite, nous avons couplé des approches de datation relative (analyse de documents historiques et géométrie des horizons) et absolue (carbone-14, césium-137), complémentaires des approches spatiales, pour dater les sols et analyser la dynamique des processus à l'origine des modifications de leur
organisation spatiale.
Cette prise en compte de la dimension temporelle était nécessaire pour améliorer notre compréhension des processus de redistribution en sol et nous permettre d'engager une modélisation spatiale et temporelle simulant des évolutions du paysage bocager en fonction de différents scénarii d'occupation des sols.

Les disparités socio-spatiales sont à la fois une cause et une conséquence des inégalités sociales. Cette thèse interroge le rôle des inégalités sociales dans la formation et la correction des disparités socio-spatiales. Elle est composée de trois essais, qui éclairent différentes facettes de ce questionnement, faisant intervenir les migrations résidentielles et les politiques publiques. Le premier essai analyse la pertinence des orientations stratégiques nationales de la politique de développement rural à l'aune du débat philosophique sur la justice sociale. Il met en évidence le rôle que joue et que devrait jouer l'objectif de réduction des inégalités sociales dans la définition d'une politique agissant sur les disparités socio-spatiales. Les deux essais suivants montrent comment les inégalités sociales génèrent des disparités socio-spatiales par le biais des mobilités résidentielles de longues et de courtes distances. Le second essai étudie les effets du sentiment d'aversion à l'inégalité locale et de la politique de redistribution du revenu sur les mobilités et les disparités interrégionales, dans le cadre théorique de la Nouvelle Economie Géographique. Le dernier essai examine comment les inégalités sociales conditionnent les choix résidentiels et induisent une ségrégation socio-spatiale au sein des aires urbaines françaises, à l'aide de modèles économétriques de choix discrets

L'analyse des systèmes de distribution "sociale" de l'eau et des systèmes de "redistribution" aboutit à une nouvelle approche de la planification et de la conception des réseaux de distribution prenant en compte les limites des premiers et les potentialités des seconds. Les méthodes de prévision de la demande ont d'abord été questionnées. A peu près fiables dans le cas de la desserte par branchements individuels d'une zone à l'urbanisation contrôlée et maîtrisée, elles semblent donner des résultats beaucoup plus incertains lorsque la desserte collective ou semi-collective devient prépondérante. Après avoir analysé chacune des variables explicatives de la demande, notamment les revenus, les tarifs et la distance au point d'eau -les principales en cause pour les systèmes redistributifs-, nous mettons en évidence les difficultés inhérentes aux méthodes d'ajustement statistique de la demande à des variables telles que la population et ses nombreux paramètres descriptifs. Ces méthodes viennent souvent ôter toute signification aux modèles de prévision. En revanche, les outils de l'analyse économique spatiale permettent de jeter les bases d'une modélisation nouvelle de la demande. L'optimisation économique des réseaux de distribution implique non seulement le choix d'un niveau de desserte et d'un tarif optimaux - ce que les modèles précédents peuvent aider à atteindre -, mais aussi de planifier les investissements d'expansion du réseau. La question se pose en effet de savoir si l'on doit construire directement un réseau calibré pour les besoins à satisfaire à l'horizon de planification, ou bien en plusieurs étapes de capacité réduite. Le phasage optimal est celui qui minimise le coût total actualisé des investissements. Grâce au recours à des modèles de réseaux arborescents simples, nous élaborons un modèle d'optimisation du phasage des réseaux ramifiés. Ce modèle aboutit au choix des alternatives (1 ou plusieurs phases) et des dates optimales d'extension ou de densification des réseaux en fonction de la loi attendue de progression de la demande, du retard initial de l'offre sur la demande et du taux d'actualisation.

Many authors and practitioners involved in rural or local development agree that co-operation and the integration of efforts by the delivery agents is crucial for sustainable development programmes. The delivery of Land Reform as initiated by the new government in South Africa (SA) is one programme that has been faced by a number of challenges including the slow pace of delivery, lack of support and co-operation from the key stakeholders, negligible impact on the improvement in the lives of its beneficiaries and many others. Many Land Reform participants including the government argue that among the challenges facing this programme is a lack of co-operation between the key stakeholders including the different spheres of government involved or impacted upon by the delivery of the Land Reform programme. The Department of Land Affairs (DLA) which is responsible for Land Reform delivery is facing challenges in integrating Land Reform with the rural or local level development which is facilitated by the local and district municipalities through the Integrated Development Planning (IDP) process. This thesis seeks to look at how the Land Reform planning process and the internal spatial data systems within the DLA can be used to integrate Land Reform delivery with the municipal IDP processes to attain integrated rural development. There is a growing realization of the fact that the development of an integrated spatial data is critical for sustainable development in SA. A number of initiatives have been embarked upon by various organizations to establish the spatial data infrastructure. However these efforts have been reported to be often fragmented and isolated in the areas of operation and focus. Thus, the challenge is to develop a strategy to develop an integrated spatial data infrastructure that would be used to support sustainable development programmes such as the Land Reform programme. This thesis therefore proposes to look at the various data sources particularly within the DLA and from other organs of state involved in Land Reform and local development with a view to highlight the limitation and shortcomings that can be addressed in integrated spatial data infrastructure. To assess the current status of the spatial data sources and usage for Land Reform implementation, an analysis of the spatial data sources within the DLA was conducted to determine its suitability for the development of an integrated spatial data infrastructure. Different sections of the DLA responsible for acquiring and providing spatial data were assessed to ascertain whether their data can be shared, transferred or integrated to support the Land Reform implementation. An integrated spatial data infrastructure is then proposed as a solution to forge co-operation and collaboration among all users involved in Land Reform implementation.
Thesis (M.Sc.) - University of KwaZulu-Natal, Pietermaritzburg, 2006.