Dissertations / Theses on the topic 'Two-components'

In previous work on the slotted flow meter, repeatibility and reproducibility were studied under different flow conditions and different configurations. In accordance with previous work, the effects of the distance between the slotted plate were identified as an area requring further investigation. The preset 5D distance is expanded to the 10D distance. The flow coefficient KY, the pressure drop, and the uncertainty analysis is conducted. There were definite deference in the results between the 5D distance and the 10D distance in many aspects. As a base line, the flow coefficient KY showed 0.8% ~ 2% difference between the 5D and the 10D distance case. Depending upon the upstream flow conditions, the reproducibility of the slotted flow meter was affected. The pressure drop increased as the upstream Reynolds number increased. The result from the analysis of the water cut meter showed that there are definite relationships between the parameteres of the water cut meter and the parameters of the flow.

Thesis (Ed.D.)--Wichita State University, College of Education, Dept. of Educational Leadership.
"May 2007." Title from PDF title page (viewed on December 14, 2007). Thesis adviser: Randall Turk. Includes bibliographic references (leaves 210-228).

The relationship between social skill deficits and emotional and behavioural problems has led researchers to examine the cognitive and behavioural elements of social skill acquisition in childhood. This research aimed to compare the effectiveness of two components of the Aussie Optimism program for enhancing social behaviour in late childhood. One hundred and twenty-eight children (68 boys and 60 girls) aged between 9 and 12 years from two schools participated in the study: (a) 34 students received the social life skills program; (b) 49 students received the optimistic thinking skills program; and (c) 45 students were assigned to a no-treatment control group. Children were assessed with self-report and teacher-report measures of social skills, adjustment and explanatory style at pretest, posttest and three months follow-up. In addition, the relationship between these variables at pretest and health-related variables measured throughout the intervention was examined. The results indicated that the social skills program improved the social skills of participating children at posttest. No intervention effects were found for explanatory style. No intervention effects were found for teacher-rated measures of behaviour or adjustment, although in general students improved on these measures over time. Eating breakfast was associated with increased social skills, and better teacher-rated academic performance and adaptive functioning at pretest. Stressful life events were negatively correlated with academic performance and teacher-rated happiness at pretest, and higher exercise levels were associated with less teacher-rated social problems at pretest. This research indicates that the social life skills intervention program improves the social skills of participating children in the short-term. Limitations and implications of the present findings are discussed. Further research is needed to clarify the impact of health-related variables on intervention outcomes for children.

The relationship between social skill deficits and emotional and behavioural problems has led researchers to examine the cognitive and behavioural elements of social skill acquisition in childhood. This research aimed to compare the effectiveness of two components of the Aussie Optimism program for enhancing social behaviour in late childhood. One hundred and twenty-eight children (68 boys and 60 girls) aged between 9 and 12 years from two schools participated in the study: (a) 34 students received the social life skills program; (b) 49 students received the optimistic thinking skills program; and (c) 45 students were assigned to a no-treatment control group. Children were assessed with self-report and teacher-report measures of social skills, adjustment and explanatory style at pretest, posttest and three months follow-up. In addition, the relationship between these variables at pretest and health-related variables measured throughout the intervention was examined. The results indicated that the social skills program improved the social skills of participating children at posttest. No intervention effects were found for explanatory style. No intervention effects were found for teacher-rated measures of behaviour or adjustment, although in general students improved on these measures over time. Eating breakfast was associated with increased social skills, and better teacher-rated academic performance and adaptive functioning at pretest. Stressful life events were negatively correlated with academic performance and teacher-rated happiness at pretest, and higher exercise levels were associated with less teacher-rated social problems at pretest. This research indicates that the social life skills intervention program improves the social skills of participating children in the short-term. Limitations and implications of the present findings are discussed. Further research is needed to clarify the impact of health-related variables on intervention outcomes for children.

To achieve passive vibration control, an adaptive flywheel design is proposed and fabricated from two different materials. The corresponding mathematical models for the adaptive flywheels are developed. A two-terminal hydraulic device and a two-terminal inverse screw device are introduced to analyze the two adaptive flywheels. Experiments are carried out to identify key parameters for both the two-terminal hydraulic system and the inverse screw system. The performance of three different suspension systems are evaluated; these are the traditional suspension system, the suspension system consisting of an ideal two-terminal device with constant flywheel and the suspension system consisting of an ideal two-terminal device with an adaptive flywheel (AFW suspension system). Results show that the AFW suspension system can outperform the other two suspension systems under certain conditions. The performance of a suspension system with the adaptive flywheel under different changing ratio is evaluated, and an optimal changing ratio is identified under certain circumstances. To obtain the steady-state response of the two-terminal device with adaptive flywheel, three different methods have been applied in this thesis. These methods are the single harmonic balance method, the multi-harmonic balance method and the scanning iterative multi-harmonic balance method, respectively. Compared to the single harmonic balance method, the multi-harmonic balance method provides a much more accurate system response. However, the proposed scanning iterative multi-harmonic balance method provides more accurate system response than the single harmonic balance method with much less computational effort.

I used a field experiment to measure total competition intensity and its above- and below-ground components in two wetlands that represent extremes in habitat productivity: an infertile sandy shoreline and a fertile bay. Transplants of Lythrum salicaria and Carex crinita were grown with no neighbours, with roots of neighbours only and with all neighbours; their growth rates were used to estimate competition intensity. The experiment was carried out to answer the following main questions: (1) Is there a difference in total, above- and below-ground competition intensity in two wetlands that differ in standing crop? (2) Is there an effect of standing crop on total, above- and below-ground competition intensity when the data from the two wetlands are combined? Both total and above-ground competition intensity were found to be greater in the high standing crop wetland but below-ground competition did not differ between wetlands (CI$\rm\sb{TOTAL}$: p 0.00001, CI$\rm\sb{ABOVE}$: p = 0.0013 CI$\rm\sb{BELOW}$: p = 0.58). Mean total competition increased from 0.16 to 0.43, the above-ground component increased from $-$0.063 to 0.21 and the below-ground component was close to 0.20 in both wetlands. Total and above-ground competition intensity was significantly affected by standing crop in the wetlands studied but below-ground competition intensity was not (CI$\rm\sb{TOTAL}$: p = 0.0001, CI$\rm\sb{ABOVE}$: p = 0.0001, CI$\rm\sb{BELOW}$: p =0.89). The result that competition was predominantly below-ground in the low standing crop wetland supports previous work in agricultural pot experiments (Wilson 1988) and terrestrial field studies (Wilson and Tilman 1991, Putz and Canham 1992, Wilson and Tilman 1993, Wilson in press). The result that root and shoot competition were roughly equal in the high standing crop wetland is not typical of past studies. (Abstract shortened by UMI.)

Pseudomonas aeruginosa is an opportunistic pathogen that express a plethora of virulence components controlled through two-component regulatory systems that allow for sensing and responding to environmental stimuli. This study was aimed at identifying transcription regulators of algZ that encodes the histidine sensor kinase (AlgZ) of the AlgZR two-component regulatory system. To understand how the algZ gene is transcriptionally controlled, transposon mutagenesis was used to create a mutant library with varying algZ expression based on their b-Galactosidase activity. The gene PA3327 was identified as a potential regulator of algZ expression using arbitrary PCR. This gene encodes a probable non-ribosomal peptide synthetase responsible for the biosynthesis of secondary metabolites such as antibiotics. Further experiments are required to understand how PA3327 transcriptionally regulates algZ expression and its physiological role in the organism. Because the AlgZ/R system regulates virulence, it is possible to attenuate virulence by targeting the expression of algZ gene.

Thesis (D.M.A.)--University of North Texas, 2006.
System requirements: Adobe Acrobat Reader. Accompanied by 4 recitals, recorded June 28, 1999, Jan. 24, 2000, Jan. 29, 2001, and Apr. 10, 2006. Includes bibliographical references and discography (p. 66-70).

Thesis (M.Sc. (Plant Production)) -- University of Limpopo, 2014
Wild medlar (Vangueria infausta subsp. infausta) is a popular indigenous fruit available and consumed by rural communities in Limpopo Province, South Africa. Inadequate post-harvest practices in indigenous fruit plants including V. infausta fruit forms major constrains in expanding their production. There is scanty information documented on neither objective nor subjective harvesting indices of indigenous fruit plants consumed by locals in sub-Saharan Africa. Thus, the objective of this study was to determine the effect of harvesting time on physico-chemical properties and selected nutritional composition of V. infausta fruit. Fruits were harvested twice, where two harvesting times were regarded as treatments and each tree as replication. The reduction for fruit weight, sugar content and sugar/acid ratio was highly significant (P ≤ 0.05), whereas for average fruit diameter, seed weight, acid ratio and pH content this may imply that the listed parameters are treatment which was non-significant (P ≤ 0.05). The treatment reduced P, K, Mn and Fe by 33%, 18%, 3% and 7%, respectively. On the other hand, treatments had no effect on N and Ca. The reduction of phosphorus was highly significant (P ≤ 0.05), whereas for N, K, Ca, Mn and Fe treatment impact was non-significant (P ≤ 0.05). Similarly, the treatment consistently reduced moisture content and increased dry matter and crude protein of V. infausta by 76%, 300% and 7%, respectively. The reduction of moisture content, increase in dry matter was highly significant (P ≤ 0.05), whereas crude protein treatment impact was non-significant (P ≤ 0.05). The data indicated that the best time to harvest V. infausta fruit was during January when fruits were cosmetically appealing and not wrinkled. This study demonstrated that there was less variation in some measured objective harvesting indices of V. infausta fruit harvested at two harvesting time. More work would be required to do physico-chemical properties and selected mineral elements analysis from wide growth habitat for conclusive recommendations.

There are some conflicting arguments for the categorization of different variables considered to be important democratic components. On the one side there are those who are advocates for a distinction of a political order and a democratic political order where components such as rule of law resides in the political order. The other side argues that the substantive side has such a large effect on democracy that especially the variable of rule of law should be counted as a democratic political variable. The theoretical idea is that a primary political order is separate and enables the establishment of a democratic political order. What this study seeks to do is to analyze the effects of the two distinctions to determine if a separation of the two is the best option or if they should be merged into one singular distinction or dimension. The primary method for conducting the study is statistical analysis with quantitative data and the aim is to make a generalizable result and conclusion.

An algorithm, called the WSF algorithm, was developed which could predict the dyers‟ attributes of colour difference (depth, ΔD, brightness, ΔB, and hue, ΔH*) from the reflectance values of a pair of dyeings, enabling the dyer to take full advantage of colorimetric analysis. The algorithm was based on extensive experimental work to map surfaces of constant visual depth throughout the colour space and the thesis describes the methodology and the necessary calculations to determine the ΔD, ΔB and ΔH values of a pair of dyed samples. This algorithm was compared to other existing algorithms (the DBH and the Sato models) using two data sets with 49 dyed pairs for data set 1 and 117 dyed pairs for data set 2 respectively. The correlation of the values of ΔD, ΔB and ΔH determined using the WSF algorithm with the DBH and the Sato models showed an excellent relationship between these three algorithms for both the data sets. Qualitative comparison of the visual assessments of data set 2 with the WSF algorithm was encouraging but the quantitative comparison of the visual assessment for data set 1 was disappointing. The pre-requisite of the WSF algorithm is the six equi-depth surfaces which have been defined numerically in the CIELAB colour space and previously reported as WSI depth surfaces. The first stage of this algorithm was to generate, using the WSI algorithm, the equi-depth line in the L* C* plane that passes through the L* C* coordinates of the standard. The K/S values of the batch were then iterated, until its depth became equal to that of the standard. At this point, the precise location of the batch on the equi-depth surface might be different from that of the standard. The linear distances between the batch and the standard, gave the differences in depth and brightness between the standard and the batch. A new approach was investigated for the hue correction of dyed pairs, where the hue of the batch was different from that of the standard. Real data of highest possible chroma values from Munsell colour atlas were used to create maximum chroma boundaries which were found necessary for the hue correction of the batch. It was noted that the DBH and the Sato models also incorporated hue correction of the batch. The WSF algorithm described in Chapter 4 contained an iterative stage which created an additional complexity in programming. Therefore an alternative version of the WSF algorithm was developed, called the linear WSF model, which avoided the need for iteration and yielded the same results. This linear WSF algorithm strongly correlated with the WSF (iterative) model and also to other empirical models as well.

Les glycoprotéines et les protéoglycanes sont impliqués dans de nombreux phénomènes biologiques qui peuvent être régulés par les carbohydratzs attachés à la chaîne protéique après traduction. La structure et la dynamique de ces modifications post-traductionnelle dépendent des interactions avec d'autres molécules présentes dans le même milieu. L'effet de ces interactions sur la structure est souvent négligé et les molécules sont souvent étudiées à l'état isolé. L'influence de ces interactions a été étudié au travers des deux exemples : l'héparine et les ancres GPI. L'influence de ces interactions a été étudié au travers de deux exemples : l'héparine et les ancres GPI. L'influence du patron de sulfatation de l'héparine sur l'interaction avec des contre ions ainsi que l'ancrage d'un GPI dans une micelle ont été étudiées par RMN et Modelling
Glycoproteins and proteoglycans are involved in various phenomena which could be regulated by the carbohydrates chains linked after translation to the core protein. Structure and dynamics of these modifications depend on the interactions with take place with others molecules present in the same milieu. Their effect on the structure is sometimes neglected and molecules are often studied as isolated and pure. The influence of these interactions has been put under focus through two different examples : heparin and GPI anchor. The influence of the sulphation pattern of heparin on their interaction with counter ions and the anchorage of a GPI into a micelle have been studied by NMR spectroscopy and Modelling

The Skoenmakers River (located in the semi-arid Karoo region of the Eastern Cape) is being used as a transfer route for water transferred by the Orange-Fish-Sundays River Interbasin Transfer Scheme. The change in the hydrological regime of this once ephemeral stream to a much bigger perennial river led to dramatic changes to both the physical structure and riparian vegetation structure of the river system. These changes differ for each of the three river sections, the upper,middle and lower reaches. Qualitative, descriptive geomorphological data was gathered by means of field observations and this was then compared to the quantitative data collected by means of surveyed cross-sectional profiles at selected sites along the length of both the regulated Skoenmakers River and a nonregulated tributary of equivalent size, the Volkers River. Riparian vegetation data was gathered by means of plot sampling along belt transects at each site. A qualitative assessment of the vegetation conditions was also made at each site and then added to the quantitative data from the plot sampling. At each site the different morphological units were identified along the cross-section and changes in the vegetation and sediment composition were recorded. Aerial photographs were used as additional sources of data and observations made from these were compared to data gathered in the field. The pre-IBT channel in this river section was formed by low frequency flood flows but the hydrological regime has now been converted to base flows much higher than normal flood flows. Severe incision, erosion and degradation of both the channel bed and banks occurred. In the lower reaches, post-IBT base flows are lower than pre-IBT flood flows and, due to the increased catchment area, the impact of the IBT was better ‘absorbed’ by the river system. Aggradation and deposition increased for the regulated river in comparison to the non-regulated river due to more sediment introduced The IBT had the greatest impact in the upper reaches of the regulated river due to more sediment introduced at the top of the system.

Les systèmes de transduction du signal et les transporteurs ABC contribuent de façon conjointe à la réponse adaptative des bactéries aux changements d’environnement. Trois modules, associant un phosphorelais et un transporteur ABC, ont été répertoriés chez B. subtilis et sont impliqués dans la réponse à différents antibiotiques: BceRSAB, PsdRSAB et YxdJKLM. Ils sont caractérisés par une histidine kinase possédant une boucle extracytoplasmique courte et appartenant à la famille des Intramembrane Sensing - Histidine Kinase (IM-HK) et par un transporteur ABC possédant une Membrane Spanning Domain (MSD) à boucle extracytoplasmique exceptionnellement longue. En utilisant une approche phylogénomique, il a été établi que ce type de modules était restreint aux Firmicutes, où ils sont apparus et se sont largement répandus. De plus, cette analyse met en lumière une histoire évolutive très dynamique impliquant de nombreux transferts horizontaux, duplications et pertes de gènes, conduisant à un répertoire de modules Bce-like très varié chez ce phylum. Grâce à une analyse phylogénétique fine, il a été proposé une classification de ces modules en six sous-familles bien définies.Des études fonctionnelles ont été réalisées sur des membres de la sous-famille IV comprenant le module de résistance à la bacitracine BceRSAB de B. subtilis, dont l’expression des gènes codant pour le transporteur requiert, en présence de l’antibiotique, le système de transduction du signal aussi bien que le transporteur lui-même. Les résultats de ces études montrent que d’autres membres de la sous-famille IV, YtsCD de B. licheniformis et BceAB de B. halodurans, sont également impliqués dans la résistance à la bacitracine. Ils suggèrent aussi que dans ces modules le transporteur ABC est le premier senseur de la présence de l’antibiotique et qu'il active le système de transduction une interaction entre une sous unité du transporteur et la kinase du module. De plus, en présence de bacitracine, l’expression des gènes codant pour le transporteur BceAB ainsi que la résistance à cet antibiotique requièrent la présence de la boucle de la MSD BceB ce qui démontre l'importance de cette boucle aussi bien au niveau fonctionnel que structural.Par ailleurs, l’étude que nous avons réalisée suggère que le mécanisme original de régulation des gènes du transporteur BceAB de B. subtilis pourrait être généralisé à tous les modules équivalents présents chez les Firmicutes. Ces modules constitueraient ainsi un mécanisme important de résistance aux antibiotiques peptidiques chez les bactéries de ce phylum qui comprend de nombreux pathogènes
Signal transduction systems and ABC transporters often contribute jointly to adaptive bacterial responses to environmental changes. In Bacillus subtilis, three such pairs, thereafter called modules, are involved in responses to antibiotics: BceRSAB, PsdRSAB and YxdJKLM. They are characterized by a histidine kinase belonging to the Intramembrane Sensing – Histine Kinase family (IM-HK) and by a Membrane Spanning Domain (MSD) possessing an unusually large extracytoplasmic loop. Using a phylogenomic approach we were able to demonstrate that such modules, associating a phosphorelay and an ABC transporter, are specific but widespread in Firmicutes where they originated. This analyse highlight a highly dynamic evolutionary history involving numerous horizontal gene transfers, duplications and lost events, leading to a great variety of Bce-like module repertories in members of this bacterial phylum. Based on fine phylogenetic analyses, the Bce-like modules were divided into six well-defined subfamilies. Functional studies were performed on some members of subfamily IV comprising the bacitracin resistance module BceRSAB of B. subtilis, the expression of which being found to require, in the presence of bacitracin, the signal transduction system as well as the ABC transporter itself. The present results indicate that two other members of subfamily IV, YtsCD of B. licheniformis and BceAB of B. halodurans, were also found to participate in bacitracin resistance processes. The results also suggest that in these modules the ABC transporter works as the first sensor of the antibiotic and that it then activates the signal transduction system through an interaction between one of the two ABC transporter domains and the module kinase.Bacitracin dependent expression of bceAB and bacitracin resistance processes were shown to require the presence of the BceB translocator loop suggesting a crucial role for this loop as well at a functional level, as at a structural level.This study suggests that the original BceRSAB module regulatory mechanism might be generalised to other modules and would constitute an important common antibiotic resistance mechanism in Firmicutes which comprise many human pathogens

Cette étude concerne l’étude des écoulements diphasiques dans le cadre du refroidissement des composants électroniques en systèmes embarqués. L’étude bibliographique a permis de sélectionner le refroidissement par spray comme technique prometteuse pour dissiper des flux de chaleur au-delà de 100 W/cm2. Une étude hydraulique, utilisant de l’eau et du HFE7100 comme fluides de refroidissement, nous a permis de valider des modèles permettant de déterminer la taille et la vitesse de gouttes provenant d’une sélection de buses de spray. Pour la partie thermique, nous avons conçu une section d’essais (évaporateur) permettant de pulvériser en spray afin d’étudier le refroidissement avec une boucle fermée diphasique.Vu la complexité du système de spray influencé par plusieurs paramètres et phénomènes physiques, nous avons isolé le phénomène d’ébullition nucléée dans une configuration en ébullition nucléée avec un élément chauffant identique à celui employé avec le refroidissement par spray. Pour améliorer les échanges thermiques, 6 surfaces avec différentes structurations (macroscopiques, microscopiques et hybrides) ont été sélectionnées. Les résultats de tests avec ces surfaces ont été comparés avec une surface lisse tant pour le refroidissement par spray que pour le refroidissement en vase.D’une part, avec un refroidissement par spray, les surfaces macrostructurées nous ont permis de dissiper des puissances thermiques de l’ordre de 140 W/cm2 avec d’importants coefficients de transfert thermique. D’autre part, avec un système de refroidissement par immersion, une des surfaces hybrides a montré être la plus performante.Les résultats reportés dans cette thèse ont permis d’approfondir la compréhension des mécanismes de transfert de chaleur en refroidissement par spray. De même, ils ouvrent la voie à l’étude des améliorations et optimisations du système permettant de l’employer en systèmes embarqués
This dissertation concerns the study of two-phase flow cooling of electronic components in embedded systems. From a literature review, Spray Cooling was selected as a promising technique for dissipating heat fluxes above 100 W/cm2. A hydraulic study, using water and HFE7100 as coolants, has validate models for determining the size and speed of drops from a selection of spray nozzles. Regarding the thermal study, we have designed a test section (evaporator) to study cooling in a two-phase closed loop system.Given the complexity of Spray Cooling systems, which are influenced by several parameters and involve several physical phenomena, the nucleate boiling phenomenon has been isolated in a Pool Boling system with an identical heating element as Spray Cooling experiment. To improve heat exchange, 6 surfaces with different structures (macroscopic, microscopic and hybrid) were selected. The boiling test results with these surfaces have been compared with a smooth surface for both Spray Cooling and Pool Boiling.On one hand, in Spray Cooling tests, the macrostructured surfaces dissipated heat flux up to 140 W/cm2 with significant heat transfer coefficients. On the other hand, in the Pool Boling system, one of the hybrid surfaces has shown to be the most efficient.The results reported in this dissertation contributes on the understanding of the boiling mechanisms of heat transfer in Spray Cooling. Likewise, they open the way to the study of improvements and optimizations of the system for its use in embedded systems

Objective of Research The interest in crop modelling started since the introduction and popularisation of computer technology, which facilitated the dynamic simulation of complex natural systems. In particular, crop growth and soil water balance models for irrigation scheduling are popular at locations where water is a limiting factor for crop production. In a Water Research Commission project, the soil water balance model (SWB) for irrigation scheduling under full and deficit irrigation was made available. The SWB model is a relatively simple generic crop growth model based on sound physical and physiological principles, (i.e. mechanistic) using daily climatic inputs for daily time-step calculations of the soil-plant-atmosphere water balance to estimate plant growth water use. The SWB model was primarily developed for predicting real-time soil water deficit of field crops with a one-dimensional canopy light interception and water redistribution procedure. Hedgerow tree crops are planted in widely spaced rows to allow access between trees to carry out necessary management practices (e.g. pest control and harvesting). Distribution of energy is not uniform in widely spaced crops. In addition, localised under tree irrigation is often used for tree crops to reduce system installation costs. This irrigation (micro- or drip) only wets a limited area under the canopy of the trees so that evaporation from the soil surface is also not uniform. One can expect root density to vary with depth as well as with distance between the rows so water uptake for transpiration will also vary in two dimensions. It is also essential to take into account the limited volume of soil wetted under micro-irrigation. If this is not done, the soil capacity will be incorrectly estimated with a standard one-dimensional approach, leading to undesirable over-irrigation in the wetted zone, as well as possible crop stress resulting from a too long an irrigation interval. In order to accurately estimate canopy growth, water balance and yield, it is therefore essential to model canopy radiant interception and soil water balance of hedgerow tree crops in two dimensions and on an hourly time step, based on sound physical principles. Lack of suitable user-friendly tools to mechanistically describe the two-dimensional energy and soil water balance of tree crops was identified. Due to the importance of fruit crops, on the export as well as local markets, as well as the encouraging results from the initial SWB model, it was decided to improve the SWB model by incorporating a two-dimensional system for use in hedgerow plantings. This thesis reports on the methodology developed to monitor the energy and soil moisture differences within various hedgerows through 24 hour cycles and the results obtained, as well as the subsequent use of the results to evaluate the 2-dimensional water balance model. This research was an integral, but independent, part of a larger research thrust, i.e. the development of a two-dimensional fruit tree water balance model that can account for the unique fractional interception of solar radiation associated with hedgerow orchards as opposed to the horizontal planar interception encountered in agronomic crops. The primary objective of this thesis is not the actual programming and mathematical manipulations of the relevant algorithms but to create a reliable data base and then evaluate the model. The primary objective of this thesis was to evaluate the model for deciduous fruit trees using peaches as an example and evaluate the model for evergreen fruit trees using citrus as an example. Model description In the overall research thrust two types of model, both predicting crop water requirements on a daily time step, were developed for hedgerow tree crops and included in SWB: i) A mechanistic two-dimensional energy interception and finite difference, Richards’ equation based soil water balance model; and ii) An FAO-based crop factor model, with a quasi-2D cascading soil water balance model. For the sake of clarity and completeness, the principles of the models are presented in the thesis and are briefly described in this subsection. The first model calculates the two-dimensional energy interception for hedgerow fruit trees, based on solar and row orientation, tree size and shape, as well as leaf area density. The two-dimensional soil water redistribution is calculated with a finite difference solution. The two-dimensional energy interception model assumes leaves to be uniformly distributed within an ellipsoid truncated at its base, and radiation penetrating the canopy is attenuated according to Beer’s law. This geometry is very versatile as many different shapes can be generated. In order to determine the spatial distribution of soil irradiance across the tree row, the canopy path length through which the radiation must travel to reach a certain point on the soil surface is calculated. Radiation can penetrate neighbouring rows, so two rows on either side of the simulated row are considered. Beam or direct radiation and diffuse radiation for the PAR (photosynthetically active radiation) and NIR (near-infrared radiation) wavebands are calculated separately, as they interact differently with the canopy. The ratio of actual measured to potential radiation is used to estimate the proportion of direct and diffuse radiation in these two spectral bands. The attenuation of beam radiation by the canopy is strongly dependent on zenith angle, and, for crops planted in rows, azimuth angle and row orientation will also be crucial. Elevation and azimuth angles are calculated from latitude, solar declination that depends on day of year, and time of day. Before the length of canopy through which radiation penetrates can be calculated, azimuth angle needs to be adjusted to take row orientation into account. Input data required to run the two-dimensional canopy interception model are: day of year (DOY), latitude, standard meridian, longitude, daily solar radiation, row width and orientation, canopy height and width, bare stem height and distance from the ground to the bottom of the canopy, extinction coefficient, absorptivity and leaf area density. In order to simulate two-dimensional water movement in the soil, a grid of nodes were established. This divides the soil up into a number of elements. The distances between nodes are selected so that model output can easily be compared to field measured values. Each element has its own physical properties, so this scheme allows variation in soil properties in two dimensions. Symmetry planes are assumed to occur mid-way between two rows on either side of the hedgerow and no water flux is allowed across these planes. The model redistributes water in the soil in two-dimensions using a finite difference solution to Richards’ continuity equation for water flow. The aim is to find the matric potentials, which will cause the mass balance error to be negligible. This is done using the Newton-Raphson procedure. Two lower boundary conditions can be chosen in the model: i) gravity drainage for well-drained soils, and ii) zero-flux lower boundary to simulate an impermeable layer. A precipitation or irrigation in mm is converted to a flux in kg m-1 s-1 by dividing the time step and multiplying by the horizontal distance over which the water is distributed. The infiltration does not have to be uniform over the surface. Non-uniform infiltration is especially important in very coarse soils where lateral redistribution is likely to be limited, or in the case of micro-irrigation. As with the infiltration flux, evaporation is multiplied by the horizontal distance over which it occurs in order to get an evaporative flux in kg m-1 s-1. Potential vapotranspiration (PET) is calculated from weather data using the Penman-Monteith equation and the maximum crop factor after rainfall occurs. PET is then partitioned at the soil surface into potential evaporation and potential transpiration depending on solar orientation, row direction and canopy size, shape and leaf area density. Crop water uptake (transpiration) can either be limited by atmospheric demand or soil-root water supply. Root densities at different soil depths are accounted for in the calculation of root water uptake. The user can specify root depth and the fraction of roots in the wetted volume of soil. Required inputs for the two-dimensional soil water balance model are: starting and planting dates, altitude, rainfall and irrigation water amounts, as well as maximum and minimum daily temperature. Two points on the water retention function (usually field capacity and permanent wilting point), initial volumetric soil water content and bulk density are required for each soil layer. Soil saturated hydraulic conductivity can also be entered as input for each soil layer, or calculated by the model using the water retention curve. Row distance, wetted diameter of micro-jets or drippers, fraction of roots in the wetted volume of soil as well as distance of the nodes from the tree row are also required as input. The second, simpler model, based on the FAO crop factor approach, was developed to enable users to predict crop water requirements with limited input data. This model includes a semi-empirical approach for partitioning of aboveground energy, a cascading soil water redistribution that separates the wetted and non-wetted portion of the ground, as well as prediction of crop yields. The FAO-based crop factor procedure was combined with the mechanistic SWB model, thereby still allowing evaporation and transpiration to be modelled separately as supply and demand limited processes. The crop factor model does not grow the canopy mechanistically and therefore the effect of water stress on canopy size is not simulated. The simpler crop factor model should, however, still perform satisfactorily if the estimated canopy cover closely resembles that found in the field. The following input parameters are required to run the FAO-type crop factor model: planting date, latitude, altitude, maximum and minimum daily air temperatures, FAO crop factors and duration of crop stages. The input data required to run the two-dimensional cascading model are rainfall and irrigation amounts, volumetric soil water content at field capacity and permanent wilting point, as well as initial volumetric soil water content for each soil layer. Row spacing, wetted diameter, distance between micro-irrigators or drippers and the fraction of roots in the wetted volume of soil are also required. Required input data for yield prediction with the FAO model are FAO stress factors for growing stages and potential yield. Field Trial Evaluation of the model was carried out for a wide range of conditions (row orientation, period of the year and canopy density). For this purpose, two field trials were set up. The first trial was established in a peach (Prunus persica cv Transvaalia) orchard on the lysimeter facilities at Hatfield (Pretoria University experimental farm). This provided a site where detailed observations could be easily recorded to evaluate the SWB model for deciduous trees. The second trial was established in a citrus clementine (Citrus reticulate cv. Nules Clementine) orchard at the Syferkuil experimental farm of the University of the North. This was the site where measured data were collected to evaluate the SWB model for evergreen trees. In both field trials, the following field measurements were carried out and used to evaluate the two-dimensional energy interception and soil water balance model: i) Weather measurements (temperature and relative humidity, wind speed, solar radiation and rainfall). ii) Soil texture, bulk density, penetrometer resistance. iii) Volumetric soil water content with neutron water meter and time domain reflectometry (TDR). iv) Soil matrix potential with heat dissipation sensors. v) Root distribution by taking soil core samples and washing out roots to determine root length. vi) Soil irradiance at different distances from the tree row with tube solarimeters. v) Leaf area index and density with a LAI-2000 plant canopy analyser. vi) Canopy size and row orientation. In addition, load cell lysimeters were used in the peach orchard at Hatfield in order to measure crop water use. An additional field trial was carried out at the Hatfield experimental station on Leuceaena (Leucaena leucocephela) trees in order to test the two-dimensional radiant interception model for different environmental conditions (tree size and shape as well as row orientation). For the same purpose, two other trials were carried out on two commercial orchards at Brits in Empress Mandarin (Citrus reticulate cv. Empress) and Delta Valencia (Citrus sinensis [L.] cv. Osbeck) orchards. In these field trials, weather data were recorded, soil irradiance across the row was measured with tube solarimeters, as well as leaf area index and density, canopy size and row orientation. Results The simple, quasi two-dimensional, cascading soil water balance model was calibrated using data from the peach trial at the Hatfield experimental station. In the process, FAO basal crop coefficients (Kcb) were determined for first and second leaf peach trees. The daily crop factor (Kc) was calculated using evapotranspiration measurements from the lysimeters and the grass reference evapotranspiration calculated from weather data. The Kcb values for the various growth stages were determined by fitting an appropriate line through the lower values of Kc, which were taken to reflect the condition where the soil surface was dry (negligible evaporation), subsoil drainage was negligible and there was sufficient water not to restrict transpiration. There was good agreement between predicted and measured daily soil water deficit for water stressed and non-stressed treatments. This was expected since the calibration data came from the trial. Field measurements in Hatfield also indicated that in hedgerow plantings the whole area across the row must be borne in mind when assessing soil water content. The practice of using single or restricted locality measurements, as utilised in agronomic crops, can be misleading in orchards. The reason for this is the effect of the irrigation distribution and rain interception by the canopy, the variation in radiation interception by the canopy across the row, the irradiance reaching the soil surface as the season progresses, the presence of a grass sod or bare soil in the inter-row region and the root density across the row. In both field trials at Hatfield and Syferkuil, it was found that there are significant amounts of roots in the inter-row region and thus this portion of the rooting volume must not be disregarded when assessing the water balance. The two-dimensional energy interception and soil evaporation components were evaluated separately. The crucial interactions between the model components were integrated in the validation of the two-dimensional soil water balance model, which uses the energy interception and soil evaporation sub-models to split evaporation and transpiration. The radiant interception model predictions and the tube solarimeter measured soil irradiance generally gave very good agreement at different distances from the tree row and in different orchards. However, some discrepancies between measurements and model predictions occurred. This was attributed to the presence of trunks and branches shading the tube solarimeters at low leaf area densities, irregularities in the shape of the hedgerow, and nonuniform distribution of leaves within the canopy. In one case the canopy shape differed drastically from that used in the model. The output obtained with the two-dimensional soil water balance model was compared to independent field measurements in order to evaluate the full SWB two-dimensional model. Volumetric soil water content data collected with the TDR system in the peach and citrus orchards were compared to SWB simulations. Results of model simulations done during drying cycles showed that the surface layer predictions were generally very good. However, in certain situations discrepancies between measurements and simulations were observed, in particular, for deeper soil layers. This could have been due to spatial variability of soil properties, as well as soil disturbance during the installation of TDR probes. It is clear that TDR probes can be used in irrigation scheduling to determine crop water use over certain periods. Caution should, however, be exercised in the interpretation of absolute values of volumetric soil water content obtained from the probes. Scenario modelling and sensitivity analyses were carried out by varying some input parameters and observing variations in certain output variables. The aim was to show an application of this tool to identify the most suitable management practice in order to maximise water use efficiency. Two case studies were considered for two “virtual” orchards located at different latitudes and in different climates (Kakamas in the Northern Cape and Stellenbosch in the Western Cape). The results of the scenario simulations indicated that, based on the inputs used, the orchards should be planted in a N-S row orientation, a wetted diameter of 0.5 m should be applied when the canopy width is 2 m, in order to minimize water losses through evaporation. As the canopy width increased to 3 m, so the wetted diameter should be increased to 1.5 m. If the wetted diameter is too small, transpiration and thus yield will be reduced. A sensitivity analysis was also carried out for both case studies varying the fraction of roots in the wetted volume of soil, and observing variations in the output results of evaporation and transpiration. The contribution to crop water uptake from the inter-row volume of soil can be high, in particular under high atmospheric evaporative demand, and this needs to be accounted for in irrigation management in order to maximise rainfall use efficiency in areas of higher summer rainfall. Conclusions and recommendations The methodologies developed to measure the temporal and spatial variation in solar radiation and thus the energy distribution within Hedgerow orchards worked well. The methods used to measure the temporal and spatial variation of the soil water balance also worked well. Thus a very good data set was generated that enabled the sound evaluation of the 2-D SWB model. Thus one can conclude that the two-dimensional energy interception and soil water balance model that was developed in the overall research thrust and included in the Soil Water Balance irrigation scheduling model worked well. The simpler model, based on the FAO crop factor approach and a cascading soil water balance, that was also developed to enable users to predict crop water requirements with a limited set of input data, also gave very satisfactory results. The FAO-based model and the cascading soil water balance were calibrated for first leaf and second leaf peaches at Hatfield. The two-dimensional model was fully evaluated for deciduous orchards using data obtained in field trials on peaches and Leucaena (Hatfield). For model validation in evergreen citrus orchards, data obtained in field trials set up at the Syferkuil experimental station (University of the North) and on two commercial farms in Brits were used. Irregular trunks and branches could cause inaccuracies in predictions of the energy balance. At low leaf area densities, the shade from trunks and branches is not accounted for in the SWB model. The relative importance of non-symmetric canopy shape as opposed to nonuniform leaf distribution did have an effect but indications where that this was not critical. The major difficulties encountered in the evaluation of the soil water balance were due to spatial variability of soil properties and disturbance of the soil when the water status monitoring sensors were installed. Careful installation is therefore recommended when using sensors that give localised measurements like those used in this study (heat dissipation sensors and TDR probes). The successful evaluation of the two-dimensional energy interception and soil water balance model opens the opportunity to develop a useful yield predictor and productivity efficiency measure if one knows the canopy to fruit ratio. This information could also be useful for fruit colour and internal quality research. As demonstrated with data from the peach trial at Hatfield, soil or cover crops between rows can also have a large effect on the efficient use of rainfall, and this could be further investigated. The biggest contribution of this model is likely to be the quantification of the contribution that rainfall can make to crop water use by taking the non-irrigated inter-row soil reservoir into account. It is recommended to accurately estimate the root fraction in the wetted and nonwetted volume of soil by digging a trench across the row, taking core soil samples and determining root densities. The two-dimensional energy interception and finite difference soil water balance model is expected to be more accurate than the cascading soil water balance, due to the sound physical principles on which it is based. The mechanistic detailed approach could give guidance with respect to the magnitude of errors made by using simpler, more empirical approaches. However, the two-dimensional model will also require more input parameters compared to the simpler cascading model. In particular, the most difficult parameters to determine will be the leaf area density for the radiation energy interception part due to the cost of the instrumentation, and the hydraulic conductivity for the soil part due to the specialised knowledge and scientific equipment required. On the other hand, the cascading model requires calibrated FAO crop factors in order to reasonably partition evaporation and transpiration. It would be interesting to compare the cascading and the two-dimensional soil water balance models against field measurements in order to determine the level of accuracy in predictions. The two-dimensional energy and soil water balance model is primarily meant to be a realtime, irrigation scheduling tool for commercial orchards. Results from this study should guide irrigation scheduling consultants, extension officers and farmers to more efficiently use scarce water resources on high value tree crops. The two-dimensional model, however, can also be used for planning purposes as demonstrated in the scenario simulations. The mechanistic canopy radiation interception routine which has been shown to be very accurate will make it possible to evaluate the effect of row orientation and spacing as well as the effect of wetted diameter and pruning practices on water use. This model also holds tremendous potential as a teaching aid to allow students to do “whatif?” scenario analyses and thus study cause and effect interactions of various orchard designs and practices.
Thesis (PhD (Agriculturae: Plant Production))--University of Pretoria, 2007.
Plant Production and Soil Science
unrestricted

La tuberculosi, la malaltia infecciosa causada per Mycobacterium tuberculosis, es un problema de salut global que provoca aproximadament 2 milions de morts anuals. Un terç de la població mundial es troba crònicament infectada amb Mycobacterium tuberculosis però no mostra símptomes clínics encara que té un risc d’un 10% de desenvolupar la malaltia, la qual cosa representa un reservori incontrolable de tuberculosi. En aquesta condició asimptomàtica, coneguda com a tuberculosi latent, Mycobacterium tuberculosis es localitza en lesions granulomatoses a l’hoste i és resistent als medicaments antimicobacterians existents en l’actualitat. En bacteris, els sistemes reguladors de dos components son un conjunt de proteïnes implicades en l’adaptació a canvis en l’entorn del microorganisme. Un sistema de dos components típic consta d’una histidina quinasa unida a membrana que té un paper essencial com a sensor dels canvis ambientals i un regulador transcripcional citosòlic que exerceix la seva funció controlant l’expressió de gens diana. Aquest parell de proteïnes funciona com un interruptor molecular que controla diferents respostes adaptatives a canvis a l’ambient cel•lular. Mycobacterium tuberculosis té 11 sistemes de dos components complets. El sistema DosRST, composat per un regulador transcripcional, DosR, i dues histidines quinases, DosS i DosT, té un paper estel•lar en l’adaptació de Mycobacterium tuberculosis a la tuberculosi latent. DosS i DosT s’autofosforilen en residus conservats d’histidina i ambdues proteïnes transfereixen aquesta un unitat de fosfat al residu d’àcid aspàrtic en posició 54 del regulador DosR. La fosforilació d’Asp54 és un interruptor que activa DosR i incrementa la seva afinitat per als promotors dels gens que regula. Les treonines 198 i 205 de DosR tenen un paper crucial en la dimerització de DosR i en la seva unió al DNA. Les dinàmiques moleculars realitzades amb la proteïna salvatge DosR i amb versions mutants mostren diferències notables en la formació del dímer actiu. També mostren una reducció o abolició completa de les interaccions proteïna-DNA a causa de les repulsions generades pels residus mutants carregats negativament. Encara més, les substitucions en Thr198 i Thr205 tenen un important efecte en la fosforilació química i enzimàtica de DosR així com també en la seva defosforilació catalitzada per DosS. El sistema de dos components DosRST és una bona diana per al desenvolupament de nous compostos amb activitat antimicobacteriana contra formes dorments de Mycobacterium tuberculosis. S’ha iniciat un programa de recerca dirigit al desenvolupament d’inhibidors específics de la proteïna reguladors DosR, usant com a punt de partida compostos comercials estructuralment relacionats amb un derivat fenilcumarínic que ha estat descrit com a molècula que interfereix en la interacció DosR-DNA.
La tuberculosis, la enfermedad infecciosa causada por Mycobacterium tuberculosis, es un problema de salud global que provoca aproximadamente 2 millones de muertes anuales. Un tercio de la población mundial se encuentra crónicamente infectada con Mycobacterium tuberculosis pero no muestra síntomas clínicos aunque tiene un riesgo de un 10% de desarrollar la enfermedad, lo que representa un reservorio incontrolable de tuberculosis. En esta condición asintomática, conocida como tuberculosis latente, Mycobacterium tuberculosis se localiza en lesiones granulomatosas en el huésped y es resistente a los medicamentos antimicobacterianos existentes en la actualidad. En bacterias, los sistemas regulatorios de dos componentes son un conjunto de proteínas implicadas en la adaptación a cambios en el entorno del microorganismo. Un sistema de dos componentes típico consta de una histidina quinasa unida a membrana que tiene un papel esencial como sensor de los cambios ambientales y un regulador transcripcional citosólico que ejerce su función controlando la expresión de genes diana. Este par de proteínas funciona como un interruptor molecular que controla distintas respuestas adaptativas a cambios en el ambiente celular. Mycobacterium tuberculosis tiene 11 sistemas de dos componentes completos. El sistema DosRST, compuesto por un regulador transcripcional, DosR, y dos histidinas quinasas, DosS y DosT, juega un papel estelar en la adaptación de Mycobacterium tuberculosis a la tuberculosis latente. DosS y DosT se autofosforilan en residuos conservados de histidina y ambas proteínas transfieren esta unidad de fosfato al residuo de ácido aspártico en posición 54 del regulador DosR. La fosforilación de Asp54 es un interruptor que activa a DosR e incrementa su afinidad por los promotores de los genes que regula. Las treoninas 198 y 205 de DosR juegan un papel crucial en la dimerización de DosR y en su unión al DNA. Las dinámicas moleculares realizadas con la proteína salvaje DosR y con versiones mutantes muestran diferencias notables en la formación del dímero activo. También muestran una reducción o abolición completa de las interacciones proteína-DNA a causa de las repulsiones generadas por los residuos mutantes cargados negativamente. Más aún, las sustituciones en Thr198 y Thr205 tienen un importante efecto en la fosforilación química y enzimática de DosR así como también en su defosforilaición catalizada por DosS. El sistema de dos componentes DosRST es una buena diana para el desarrollo de nuevos compuestos con actividad antimicobacteriana contra formas durmientes de Mycobacterium tuberculosis. Se ha iniciado un programa de investigación dirigido al desarrollo de inhibidores específicos de la proteína reguladora DosR, usando como punto de partida compuestos comerciales estructuralmente relacionados con un derivado fenilcumarínico que ha sido descrito como molécula que interfiere en la interacción DosR-DNA.
Tuberculosis, the infectious disease caused by Mycobacterium tuberculosis, is a global health problem with approximately two million deaths annually. One-third of the world population is chronically infected with Mycobacterium tuberculosis but do not show clinical symptoms although there is a 10% risk to development active disease, representing an uncontrollable reservoir of tuberculosis. In this asymptomatic condition, referred to as latent tuberculosis, Mycobacterium tuberculosis is located within granulomatous lesions in the host and is resistant to currently available antimycobacterial drugs. Two-component regulatory systems in bacteria are a major class of signal transduction proteins involved in adaptation to environmental changes. Typical system contains a membrane-bound histidine kinase that plays a crucial role in sensing environmental stimuli, and a cytosolic response regulator. This pair of proteins functions as a molecular switch that controls diverse adaptive environmental responses. Mycobacterium tuberculosis has eleven complete two-component systems. The DosRST system, composed of a response regulator, DosR, and two histidine kinases, DosS and DosT, plays a key role in Mycobacterium tuberculosis adaptation to latent tuberculosis. DosS and DosT autophosphorylate at conserved histidine residues and both proteins transfer this phosphor moiety to aspartic acid residue 54 of DosR. The phosphorylation of Asp54 serves as a switch to activate DosR and to increase the affinity for its cognate DNA promoters. Threonines 198 and 205 of DosR play a crucial role in DosR dimerization and DNA binding. The molecular dynamics with wild type and mutant version of DosR show different stability in the formation of the active DosR dimer. They also show the reduction or the abolishment of protein-DNA interactions because of the repulsions generated by negatively charged mutated residues. Moreover, substitutions in threonines 198 and 205 of DosR have a relevant effect on the chemical and enzymatic phosphorylation of DosR and on its DosS-catalysed dephosphorylation. The DosRST two-component system is a good target for the development of novel antimycobacterial drugs against dormant forms of M. tuberculosis. A structure-based discovery programme of inhibitors of DosR response regulator has been initiated with commercially available compounds showing a certain degree of similarity with a phenylcoumarin derivative previously described as DosR-DNA interfering molecule.

Includes bibliographical references.
Impairment in classical eyeblink conditioning (EBC) has previously been reported in children with fetal alcohol spectrum disorders (FASD) (Jacobson et al., 2008). The deep cerebellar nuclei and cerebellar cortex are critical elements of the cerebellar-brainstem circuitry that mediates EBC (Green et al., 2002a; Yeo and Hardiman, 1992; Perret et al., 1993). In this study, we used magnetic resonance spectroscopy (MRS) and functional MRI (fMRI) to assess the effects of prenatal alcohol exposure on brain metabolism in the cerebellar deep nuclei and brain function in the cerebellar cortex, respectively. We found that higher levels of prenatal alcohol exposure were associated with lower levels of both N-Acetylaspartate (NAA) and choline-containing metabolites, and with higher levels of glutamate plus glutamine (Glx), suggesting a disruption of the glutamate-glutamine cycling involved in glutamatergic excitatory neurotransmission. Since the interpositus nucleus is one of the most crucial structures in the acquisition of the EBC response, abnormal metabolism in this region could be responsible for altered synaptic plasticity in children with FASD. Of the four cerebellar regions that were identified as being activated more by control children during rhythmic vs. non-rhythmic finger tapping, smaller differences in BOLD (blood oxygenation level dependent) activation were observed in children with FASD in two, namely vermis IV-V and right Crus I. Increasing levels of prenatal alcohol exposure were, however, associated with smaller differences in activation in all four regions, all of which have previously been linked to timed responses. In the paced/unpaced finger tapping fMRI study, we found four regions where increased BOLD activation during unpaced tapping compared to rest was associated with improved ability to maintain rhythm as evidenced by lower intertapping variability - right VIIIa and b, left VIIIa and right VI. These regions have previously been implicated in motor control with additional evidence of timing in lobule VI. In three of the regions, all except right VIIIa, increasing alcohol exposure was related to smaller increases in activation during unpaced tapping, with the strongest relations seen in the dosage dependent variable. Interestingly, the location of the activation in right VI is similar to a region that has been implicated in studies of EBC (Blaxton et al., 1996; Cheng et al., 2008). Our results point to altered metabolic levels in the deep nuclei and reduced functioning of several cerebellar cortical regions in children with FASD, highlighting the extensive damage caused by prenatal alcohol exposure. Although we did not find associations of EBC performance with either metabolite levels or activity in these regions, suggesting that damage to these areas are not primarily responsible for the observed EBC deficit, the extent of this damage could play a role in the impaired EBC performance seen in these children.

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As árvores do gênero Copaifera (Leguminosae), conhecidas popularmente como copaibeiras, exsudam um óleo-resina extensamente utilizado na medicina popular e por indústrias farmacêuticas e de cosméticos, devido às suas atividades cicatrizante e anti-inflamatória. Quimicamente, esses óleos se caracterizam pela presença de hidrocarbonetos sesquiterpênicos, sesquiterpenos oxigenados e ácidos diterpênicos. No entanto, a composição química desses óleos-resina é variável e ainda não se tem conhecimento dos fatores que as determinam, embora vários fatores bióticos e abióticos sejam considerados fontes dessa variação. Essa variação dificulta a padronização da composição química desses óleos, comprometendo seu controle de qualidade e consequentemente a qualidade dos produtos a que darão origem, fato que tem causado um grande entrave à sua maior aplicação e comercialização. Essa variabilidade em sua composição química já é bastante conhecida e relatada na literatura, mas a maioria dos estudos realizados têm se restringido a caracterizar quimicamente o óleo-resina e poucos tem se preocupado em estudar as causas dessas variações. O objetivo deste trabalho foi padronizar a composição química dos óleos de copaíba por meio de técnicas de cromatografia em fase gasosa acoplada à detectores de ionização de chama (CG-DIC) e espectrometria de massas (CG-EM) e cromatografia em fase gasosa bidimensional abrangente (CGXCG); analisar estatisticamente a influência de fatores abióticos como sazonalidade, tipo de solo e diâmetro à altura do peito (DAP), além da infestação por cupins, sobre a composição química desses óleos. Além disso, foram comparados 5 métodos de esterificação dos ácidos diterpênicos presentes nos óleos de copaíba envolvendo catálise ácida, que utilizam BF3/MeOH, H2SO4/MeOH e HCl/MeOH, levando-se em consideração suas eficiências e frequências analíticas, além do consumo e toxicidade dos reagentes utilizados, relação custo benefício e, principalmente, a possibilidade de alteração/degradação da estrutura dos constituintes quando aplicados em óleos de copaíba. Para isso foram obtidos óleos de copaíba de 3 coletas: em novembro de 2004 e novembro de 2005 (épocas consideradas secas) e em maio de 2005 (época considerada chuvosa). No total, 43 amostras de óleo-resina de copaíba foram coletadas na Reserva Ducke (Manaus-AM), de 33 espécimes diferentes, que possuíam diferentes DAP s e se encontravam em diferentes tipos de solo. As análises por CG-DIC e CG-EM permitiram a identificação de 35 constituintes: sendo 22 hidrocarbonetos sesquiterpênicos, 9 sesquiterpenos oxigenados e 4 ácidos diterpênicos. Enquanto a análise por CGxCG permitiu a identificação de outros 13 sesquiterpenos, além de 7 monoterpenos, inéditos em óleos-resina de copaíba. O β-cariofileno e seu óxido foram os constituintes majoritários em 29 e 11 amostras, respectivamente. As análises hierárquica por agrupamento (HCA) e de componentes principais (PCA) evidenciaram a existência de dois grupos distintos com diferentes perfis cromatográficos, em que foi comprovada apenas a influência do tipo de solo, sobre a composição química desses óleos. Outros fatores analisados como sazonalidade, DAP e infestação por cupins, não tiveram influência sobre a composição química dos óleos-resina de copaíba. Quanto aos métodos de esterificação, as análises das 5 metodologias testadas, apesar de terem sido reprodutíveis, não se mostraram eficientes, ao passo que não permitiram a identificação dos constituintes formados e levaram à formação de artefatos.

This thesis tackles issues of particular interest regarding analysis and design of passive components at the mm-wave and Terahertz (THz) bands. Innovative analysis techniques and modeling of complex structures, design procedures, and practical implementation of advanced passive devices are presented. The first part of the thesis is dedicated to THz passive components. These days, THz technology suffers from the lack of suitable waveguiding structures since both, metals and dielectric, are lossy at THz frequencies. This implies that neither conventional closed metallic structures used at microwave frequencies, nor dielectric waveguides used in the optical regime, are adequate solutions. Among a variety of new proposals, the Single Wire Waveguide (SWW) stands out due to its low attenuation and dispersion. However, this surface waveguide presents difficult excitation and strong radiation on bends. A Dielectric-Coated Single Wire Waveguide (DCSWW) can be used to alleviate these problems, but advantages of the SWW are lost and new problems arise. Until now, literature has not given proper solution to radiation on bends and, on the other hand, rigorous characterization of these waveguides lacks these days. This thesis provides, for the first time, a complete modal analysis of both waveguides, appropriated for THz frequencies. This analysis is later applied to solve the problem of radiation on bends. Several structures and design procedures to alleviate radiation losses are presented and experimentally validated. The second part of the thesis is dedicated to mm-wave passive components. These days, when implementing passive components to operate at such small, millimetric wavelengths, to ensure proper metallic contact and alignment between parts results challenging. In addition, dielectric absorption becomes significant at mm-wave frequencies. Consequently, conventional hollow metallic waveguides and planar transmission lines present high attenuation so that new topologies are being considered. Gap Waveguides (GWs), based on a periodic structure introducing an Electromagnetic Bandgap effect, result very suitable since they do not require metallic contacts and avoid dielectric losses. However, although GWs have great potential, several issues prevent GW technology from becoming consolidated and universally used. On the one hand, the topological complexity of GWs difficulties the design process since full-wave simulations are time-costly and there is a lack of appropriate analysis methods and suitable synthesis procedures. On the other hand, benefits of using GWs instead of conventional structures are required to be more clearly evidenced with high-performance GW components and proper comparatives with conventional structures. This thesis introduces several efficient analysis methods, models, and synthesis techniques that will allow engineers without significant background in GWs to straightforwardly implement GW devices. In addition, several high-performance narrow-band filters operating at Ka-band and V-band, as well as a rigorous comparative with rectangular waveguide topology, are presented.
Esta tesis aborda problemas actuales en el análisis y diseño de componentes pasivos en las bandas de onda milimétrica y Terahercios (THz). Se presentan nuevas técnicas de análisis y modelado de estructuras complejas, procedimientos de diseño, e implementación práctica de dispositivos pasivos avanzados. La primera parte de la tesis se dedica a componentes pasivos de THz. Actualmente no se disponen de guías de onda adecuadas a THz debido a que ambos, metales y dieléctricos, introducen grandes pérdidas. En consecuencia, no es adecuado escalar las estructuras metálicas cerradas usadas en microondas, ni las guías dieléctricas usadas a frecuencias ópticas. Entre un gran número de recientes propuestas, la Single Wire Waveguide (SWW) destaca por su baja atenuación y casi nula dispersión. No obstante, como guía superficial, la SWW presenta difícil excitación y radiación en curvas. El uso de un recubrimiento dieléctrico, creando la Dielecric-Coated Single Wire Waveguide (DCSWW), alivia estos inconvenientes, pero las ventajas anteriores se pierden y nuevos problemas aparecen. Hasta la fecha, no se han encontrado soluciones adecuadas para la radiación en curvas de la SWW. Además, se echa en falta una caracterización rigurosa de ambas guías. Esta tesis presenta, por primera vez, un análisis modal completo de SWW y DCSWW, adecuado a la banda de THz. Este análisis es aplicado posteriormente para evitar el problema de la radiación en curvas. Se presentan y validan experimentalmente diversas estructuras y procedimientos de diseño. La segunda parte de la tesis abarca componentes pasivos de ondas milimétricas. Actualmente, estos componentes sufren una importante degradación de su respuesta debido a que resulta difícil asegurar contacto metálico y alineamiento adecuados para la operación a longitudes de onda tan pequeñas. Además, la absorción dieléctrica incrementa notablemente a estas frecuencias. En consecuencia, tanto guías metálicas huecas como líneas de transmisión planares convencionales presentan gran atenuación, siendo necesario considerar topologías alternativas. Las Gap Waveguides (GWs), basadas en una estructura periódica que introduce un efecto de Electromagnetic Bandgap, resultan muy adecuadas puesto que no requieren contacto entre partes metálicas y evitan las pérdidas en dieléctricos. No obstante, a pesar del potencial de las GWs, varias barreras impiden la consolidación y uso universal de esta tecnología. Por una parte, la compleja topología de las GWs dificulta el proceso de diseño dado que las simulaciones de onda completa consumen mucho tiempo y no existen actualmente métodos de análisis y diseño apropiados. Por otra parte, es necesario evidenciar el beneficio de usar GWs mediante dispositivos GW de altas prestaciones y comparativas adecuadas con estructuras convencionales. Esta tesis presenta diversos métodos de análisis eficientes, modelos, y técnicas de diseño que permitirán la síntesis de dispositivos GW sin necesidad de un conocimiento profundo de esta tecnología. Asimismo, se presentan varios filtros de banda estrecha operando en las bandas Ka y V con altas prestaciones, así como una comparativa rigurosa con la guía rectangular.
Aquesta tesi aborda problemes actuals en relació a l'anàlisi i disseny de components passius en les bandes d'ona mil·limètrica i Terahercis. Es presenten noves tècniques d'anàlisi i modelatge d'estructures complexes, procediments de disseny, i implementació pràctica de dispositius passius avançats. La primera part de la tesi es focalitza en components passius de THz. Actualment no es disposen de guies d'ona adequades a THz causa que tots dos, metalls i dielèctrics, introdueixen grans pèrdues. En conseqüència, no és adequat escalar les estructures metál·liques tancades usades en microones, ni les guies dielèctriques usades a freqüències òptiques. Entre un gran nombre de propostes recents, la Single Wire Waveguide (SWW) destaca per la seua baixa atenuació i quasi nul·la dispersió. No obstant això, com a guia superficial, la SWW presenta difícil excitació i radiació en corbes. L'ús d'un recobriment dielèctric, creant la Dielecric-Coated Single Wire Waveguide (DCSWW), alleuja aquests inconvenients, però els avantatges anteriors es perden i nous problemes apareixen. Fins a la data, no s'han trobat solucions adequades per a la radiació en corbes de la SWW. A més, es troba a faltar una caracterització rigorosa d'ambdues guies. Aquesta tesi presenta, per primera vegada, un anàlisi modal complet de SWW i DCSWW, adequat a la banda de THz. Aquest anàlisi és aplicat posteriorment per evitar el problema de la radiació en corbes. Es presenten i validen experimentalment diverses estructures i procediments de disseny. La segona part de la tesi es centra en components passius d'ones mil·limètriques. Actualment, aquests components pateixen una important degradació de la seua resposta a causa de que resulta difícil assegurar contacte metàl·lic i alineament adequats per a l'operació a longituds d'ona tan menudes. A més, l'absorció dielèctrica incrementa notablement a aquestes freqüències. En conseqüència, tant guies metàl·liques buides com línies de transmissió planars convencionals presenten gran atenuació, sent necessari considerar topologies alternatives. Les Gap Waveguides (GWs), basades en una estructura periòdica que introdueix un efecte de Electromagnetic Bandgap, resulten molt adequades ja que no requereixen contacte entre parts metàl·liques i eviten les pèrdues en dielèctrics. No obstant, tot i el potencial de les GWs, diverses barreres impedixen la consolidació i ús universal d'aquesta tecnologia. D'una banda, la complexa topologia de les GWs dificulta el procés de disseny atés que les simulacions d'ona completa consumeixen molt de temps i no existeixen actualment mètodes d'anàlisi i disseny apropiats. D'altra banda, és necessari evidenciar el benefici d'utilitzar GWs mitjançant dispositius GW d'altes prestacions i comparatives adequades amb estructures convencionals. Aquesta tesi presenta diversos mètodes d'anàlisi eficients, models, i tècniques de disseny que permetran la síntesi de dispositius GW sense necessitat d'un coneixement profund d'aquesta tecnologia. Així mateix, es presenten diversos filtres de banda estreta operant en les bandes Ka i V amb altes prestacions, així com una comparativa rigorosa amb la guia rectangular.
Berenguer Verdú, AJ. (2017). Analysis and design of efficient passive components for the millimeter-wave and THz bands [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/84004
TESIS

This case study sought to examine constructs of two fourth-grade elementary writing programs in Volusia County, Florida. With only the Sunshine State Standards as a guide, each district, school, or teacher must design a writing curriculum that addresses those standards, develops writers, and provides accountability. Fourth-grade classrooms were selected because students at that grade level are required to participate in the FCAT Writing +, a two-day state assessemnt that requires students to compose an essay on a designated topic within a 45-minute period. A second part of the assessment consists of multiple-choice items covering editing and revising, graphic organizers, and letter writing. Both sections of this assessment measure student progress relative to the Sunshine State Standards' benchmarks for writing. Data was collected through multiple sources. An observation instrument, based in part on Karen Bromley's Key Components of Sound Writing Instruction, was constructed. Survey, focus group, and interview questions were derived in part from a survey Dr. Roger Brindley and Dr. Jenifer Jasinski Schneider created to study fourth-grade teachers' perspectives on teaching writing. Writing artifacts were also collected. Karen Bromley suggested five elements to address both process and product that are necessary for a balanced approach to writing. They are; Standards and Assessment, Large Blocks of Time, Direct Instruction, Choice and Authenticity, and Writing Across the Curriculum. Findings revealed that although both schools subscribed to different methods and materials for writing instruction, similarities were revealed with consideration to these components. Current test scores validated these practices. Implications for further study and investigation based on these findings ensures the advancement of the body of knowledge about writing instruction.
Ed.D.
Department of Teaching and Learning Principles
Education
Curriculum and Instruction

La membrane bactérienne a fait l'objet de nombreuses études de localisation de protéines et de phospholipides. Par fusion d’une protéine fluorescente (GFP) aux gènes d’intérêt, il est alors possible d‘observer la localisation des protéines associées par microscopie. La plupart de ces observations ont été réalisées à l’aide de microscopes dits à épifluorescence. Afin d’obtenir une qualité d’image suffisante, il était nécessaire de surexprimer la protéine observée, insérée à un locus ectopique non naturel. Ce travail de thèse a permis d’utiliser une nouvelle technologie acquise dans notre laboratoire, le microscope à fluorescence par réflexion totale interne (TIRFM), plus puissant que le microscope à épifluorescence utilisé précédemment. Cette technologie a permis une caractérisation plus détaillée de la localisation de protéines d’intérêt, placées sous contrôle de leur promoteur naturel. Il a également été possible de caractériser la dynamique des foci observés. Nous avons concentré notre étude sur 3 protéines: (i) SecA pour l’étude de la translocation des protéines du cytoplasme vers la membrane, (ii) YidC pour l’insertion des protéines dans la membrane, (iii) PgsA pour la synthèse des phospholipids. Les foci se déplacent dynamiquement et s’associent de manière transitoire dans la membrane. L’observation sur la durée de ces foci, et l’analyse de leur intensité moyenne au cours des observations, montre que SecA se déplace sur l’ensemble de la membrane de manière uniforme. L’analyse du déplacement des foci montre une relation quadratique entre la distance moyenne parcourue par les foci en fonction du temps. Ce résultat est en accord avec l’hypothèse d’un mouvement brownien des foci. Les foci sont observés dans les différentes phases de croissance des cellules, et le nombre de foci présents dans une cellule de la longueur de celle-ci. SecA-GFP a été testés dans un certain nombre de contextes génétiques. La localisation a été perturbée lors de la déplétion de pgsA. Cependant, comme PgsA est une protéine essentielle, il ne peut être exclu que ce changement de localisation apparaît des cellules qui sont mortes ou mourantes. Dans une souche mutante ΔclsA, on n’observe aucune différence dans la localisation de SecA en phase exponentielle, mais on aperçoit une relocalisation aux poles en phase stationnaire de croissance. La voie Tat est responsable du transport des protéines devant être exportées dans un état structuré, par exemple dans le cas de l’incorporation d’un co-facteur. À ce jour, la régulation du système Tat est peu connues, de même que les interactions entre les différentes sous-unités du système Tat et d'autres protéines dans le cytoplasme, dans la membrane ou dans la paroi cellulaire. Des fusions de les gènes de la voie Tat ont été co-exprimées deux à deux dans des cellules de levure, et leur capacité à interagir in vivo a été testée par la méthode dite du double hybride chez la levure. Nous avons généré un réseau d’interaction autour des cinq composants de système Tat. Pour déterminer les implications fonctionnelles des composants du réseau, nous avons travaillé en collaboration avec le laboratoire de Jan-Maarten van Dijl. Nous avons utilisé une collection de souches mutantes pour lesquels certains composants individuels du réseau ont été retires. Trois a été observe d’etre nécessaires pour la sécrétion Tat-dépendante. Nous avons étudié la localisation des fusions GFP avec ces proteins. On a observé une localisation double de HemAT selon l’état physiologique de la cellule. En phase exponentielle, les cellules de B. subtilis sont généralement présentes sous forme de chaînes dans lesquelles le septum de division a déjà été formé, mais la séparation cellulaire n'a pas encore eu lieu. Une fusion de la GFP à CsbC apparaît de façon homogène dans la membrane
In the years since the cloning of GFP, the field of bacterial cell biology has characterized a variety of specific protein localization patterns in the bacterial membrane. The vast majority of early subcellular localization studies made use of inducible GFP fusions, which generally required the presence of high concentrations of inducer, and can therefore be considered to be overexpressed. An outstanding question remains over the organization of natively expressed proteins in the membrane. Here, we have investigated the localization of functional GFP fusions to proteins catalyzing important membrane processes; the secretion motor protein SecA, the membrane insertase YidC1, and the essential phospholipid synthase PgsA using total internal reflection fluorescence microscopy (TIRFM). This allowed natively expressed proteins to be localized with temporal resolution that can capture their dynamics. We characterized dynamic complexes dispersed throughout the membrane displaying diffusive movement with no preferred trajectories. Further characterization focused upon identifying conditions in which the localization pattern was disturbed. A polar mislocalization was identified in a cardiolipin mutant strain. The yeast two-hybrid (Y2H) approach is a robust approach to detect binary interactions on a proteome-scale. We performed genome-wide Y2H screens as well as targeted Y2H analyses for specific interactions involving components of the Sec and Tat secretion machineries of B. subtilis, revealing an intricate protein-protein interaction network involving 71 proteins. Furthermore, three proteins identified in the Tat network, WprA, CsbC and HemAT, were shown to be important for effective protein secretion via the B. subtilis Tat system, indicating that our yeast two hybrid assays reveal biologically significant interactions involving membrane proteins. The studies provide a novel proteomic view on the interaction network of the secretion systems of B. subtilis

Thesis (M.A.)--West Virginia University, 2002.
Title from document title page. Document formatted into pages; contains ix, 61 p. : col. ill., col. maps. Includes abstract. Includes bibliographical references (p. 40-42).

La transformation génétique naturelle contribue au maintien et à l'évolution des génomes bactériens, elle constitue pour les bactéries un mécanisme clé pour s'adapter à l'environnement. Elle permet l'intégration d'ADN exogène au sein du chromosome bactérien par recombinaison homologue lors d'un état physiologique particulier de la bactérie appelé compétence. Mon travail de thèse a porté sur la régulation de la compétence chez S. pneumoniae (ComD, ComE) et sur les interactions entre les protéines impliquées dans la prise en charge, le traitement et la recombinaison de l'ADN transformant (DprA, RecA). Chez cette bactérie, l'entrée en compétence est sous le contrôle du système à deux composantes ComD-ComE qui induit la transcription des gènes cibles. DprA est l'une des protéines surexprimée lors de la compétence, elle est très conservée dans le monde bactérien, et participe à la fermeture de la compétence via une interaction directe avec ComE. DprA est également une protéine centrale de la transformation impliquée dans la protection de l'ADN entrant contre les nucléases, et dans le recrutement de la recombinase RecA. L'analyse par SAXS du complexe ComD-ComE, la résolution de la structure cristallographique des domaines REC de ComE, et l'étude des interaction entre ComE et ses régions promotrices ont permis de mieux comprendre la chorégraphie de l'entrée en compétence de S. pneumoniae. En parallèle, nous avons étudié les interactions de SpDprA avec l'ADN et avec RecA. Ces données nous ont permis de proposer un modèle d'interaction entre DprA et RecA chez S. pneumoniae et de proposer un mécanisme de chargement de RecA sur l'ADNsb par DprA. Je me suis également intéressée à DprA de H. pylori en participant à la résolution de la structure 3D de son domaine C-terminal par RMN et en étudiant son interaction avec l'ADNdb
The natural genetic transformation contributes to the maintenance and the evolution of the genomes in bacteria; it is a key mechanism to adapt to their environment. It allows the integration of exogenous DNA into the bacterial chromosome by homologous recombination during a particular state called competence.My thesis focused on the regulation of the competence state in S. pneumoniae (ComD, ComE), and on the interactions between the proteins involved in the uptake, the processing and recombination of exogenous DNA (DprA, RecA). In this bacterium, the opening of the competence is under the control of the two-component system ComD-ComE, who induces the transcription of target genes. DprA is one of the protein induced during the competence state, it is very conserved into the bacterial kingdom, and is involved in the closure of competence via direct interaction with ComE. DprA is also a key transformation protein involved in processing the incoming DNA, protection against nucleases, and recruitment of the RecA recombinase. SAXS analysis of the ComD-ComE, resolution of the crystallographic structure of ComE REC domain study of the interactions between ComE and its promoter regions allowed us to understand the choreography of competence opening in S. pneumoniae. Meanwhile, we studied spDprA interactions with DNA and with RecA. These data allowed us to propose an interaction model between DprA and RecA in S. pneumoniae and to propose a mechanism for RecA's loading on the ssDNA by DprA. I focused too on H. pylori DprA participating on the resolution of the 3D structure of the C-terminal domain by NMR and studying its interaction with the dsDNA

The increased use of the diesel engine in the passenger car, truck and bus market is due to high efficiency and lower fuel costs. This growing market share has brought with it several environmental issues for instance soot particle emission. Different technologies to remove the soot have been developed and are normally based on some kind of soot trap. In particular for automobiles the use of diesel particulate traps or filters (DPF:s) based on ceramic monolithic honeycombs are becoming a standard. This new exhaust system component will affect the acoustics and also work as a muffler. To properly design exhaust systems acoustic models for diesel particulate traps are needed. The first part of this thesis considers the modelling of sound transmission and attenuation for traps that consist of narrow channels separated by porous walls. This work has resulted in two new models an approximate 1-D model and a more complete model based on the governing equations for a visco-thermal fluid. Both models are expressed as acoustic 2-ports which makes them suitable for implementation in acoustic software for exhaust systems analysis. The models have been validated by experiments on clean filters at room temperature with flow and the agreement is good. In addition the developed filter models have been used to set up a model for a complete After Treatment Device (ATD) for a passenger car. The unit consisted of a chamber which contained both a diesel trap and a Catalytic Converter (CC). This complete model was also validated by experiments at room temperature. The second part of the thesis focuses on experimental techniques for plane wave decomposition in ducts with flow. Measurements in ducts with flow are difficult since flow noise (turbulence) can strongly influence the data. The difficulties are also evident from the lack of good published in-duct measurement data, e.g., muffler transmission loss data, for Mach-numbers above 0.1-0.2. The first paper in this part of the thesis investigates the effect of different microphone mountings and signal processing techniques for suppressing flow noise. The second paper investigates in particular flow noise suppression techniques in connection with the measurement of acoustic 2-ports. Finally, the third paper suggests a general wave decomposition procedure using microphone arrays and over-determination. This procedure can be used to determine the full plane wave data, e.g., the wave amplitudes and complex wave numbers k+ and k-. The new procedure has been applied to accurately measure the sound radiation from an unflanged pipe with flow. This problem is of interest for correctly determining the radiated power from an engine exhaust outlet. The measured data for the reflection coefficient and end correction have been compared with the theory of Munt [33] and the agreement is excellent. The measurements also produced data for the damping value (imaginary part of the wavenumber) which were compared to a model suggested by Howe [13]. The agreement is good for a normalized boundary layer thickness less than 30-40