The hypothesis for this study was that phenanthrene degrading bacterial inoculants, in combination with grass species able to tolerate petroleum hydrocarbon contamination, will result in increased degradation, as compared to natural rates of hydrocarbon degradation, or to rates of degradation attributed to bacteria or plants alone. Three experiments were performed to examine this hypothesis: i) assessment of the effect of phenanthrene degrading bacteria (<i>Sphingomonas yanoikuyae</i>, <i>Rahnella aquatilis</i>, and <i>Arthrobacter globiformis</i>) on seed germination, location of attachment on seeds and roots, and inoculant survival on selected grass species, ii) determination of the inoculant survival in contaminated soil in the absence of plants and the ability to degrade target compounds, and iii) degradation potential and survival of selected grass species and bacterial inoculants in soil. In general, all applied inoculants were able to effectively colonize the seeds and had a neutral or positive effect on seed germination and seedling growth. Possible plant and bacteria pairs were chosen based on positive influence of the inoculant and are as follows: perennial ryegrass (<i>Lolium perenne</i>) or creeping red fescue (<i>Festuca rubra</i>) with <i>A. globiformis</i> or <i>S. yanoikuyae</i>, or slender wheatgrass (<i>Elymus trachycaulus</i>) with <i>A. globiformis</i> or <i>R. aquatilis</i>. Soil-based assessment of the survival and degradation of hydrocarbons by the selected inoculants was examined with or without a manure nutrient amendment. The addition of the inoculants had a positive impact on the efficacy of hydrocarbon removal in the soil. The manure-amended soil, or <i>A. globiformis</i> inoculated non-amended soil treatments reduced total petroleum hydrocarbon concentration by ~45%, whereas the non-amended control only resulted in a ~20% reduction. When soils were amended with manure and inoculated with any of the phenanthrene degrading bacteria, contaminant concentration decreased in soil by ~33%. <i>Sphingomonas yanoikuyae</i> survived the longest in soil in the absence of plants. A growth chamber experiment was conducted to determine the efficacy of plant and bacteria pairs for hydrocarbon removal in recalcitrant contamination found in soil from Bruderheim, Alberta. Additional replicates containing this soil were spiked with hexadecane, phenanthrene, and pyrene so the effectiveness of the plant and bacteria pairs at higher levels of fresh contamination could be assessed. In the spiked treatment, inoculation with <i>S. yanoikuyae</i> increased creeping red fescue root biomass. In the non-spiked treatment, <i>S. yanoikuyae</i> application increased creeping red fescue root and shoot biomass. Perennial ryegrass root and shoot biomass did not increase when inoculated with <i>S. yanoikuyae</i>, although root biomass values were observably higher in non-spiked soils. Creeping red fescue inoculated with <i>S. yanoikuyae</i> resulted in the greatest decrease in hydrocarbon concentration as compared to other treatments (~61%). The perennial ryegrass treatment, when inoculated with <i>S. yanoikuyae</i> increased percent hydrocarbon removal (~10%) above that obtained with perennial ryegrass alone. The addition of plants and <i>S. yanoikuyae</i> increased hydrocarbon degradation relative to control soils, although the addition of vegetation alone had a comparable effect. A critical benefit of inoculation was the increase in creeping red fescue root biomass at higher concentrations of contamination. This is important because the larger the root biomass the larger the volume of soil that can be remediated. The results indicate that the use of specific plant-bacterial inoculants can enhance remediation of hydrocarbon contaminated soils.

This thesis reports on an experimental study of slow viscoelastic flow through models of fibrous porous media. The models were square arrays of parallel cylinders, with solid volume fractions or ‘solidities’ of 2.5%, 5.0%, and 10%. An initial study using a Newtonian fluid provided a baseline for comparison with results for two Boger fluids, so that the effects of fluid elasticity could be determined. Boger fluids are elastic fluids that have near constant viscosities and can be used in experiments without having to account for shear-thinning effects. The experimental approach involved measurements of pressure loss through the three arrays and interior velocity measurements using particle image velocimetry (PIV). For the Newtonian flows, pressure loss measurements were in good agreement with the analytical predictions of Sangani and Acrivos (1982). PIV measurements showed velocity profiles which were symmetrical and independent of flow rate. Pressure loss measurements for the Boger fluid flows revealed that the onset of elastic effects occurred at a Deborah number of approximately 0.5, for both fluids and the three arrays. Flow resistance data collapsed for the two Boger fluids, and increased with solidity. For all three models, the flow resistance increased monotonically with Deborah number, reaching values up to four times the Newtonian resistance for the 10% model. PIV measurements showed that the transverse velocity profiles for the Newtonian and Boger fluids were the same at Deborah numbers below the elastic onset. Above onset, the profiles became skewed. The skewness, like the flow resistance, was observed to increase with both Deborah number and solidity. In the wake regions between cylinders in a column, periodic flow structures formed in the spanwise direction. The structures were staggered from column to column, consistent with the skewing. As either Deborah number or solidity increased, the flow structures became increasingly three-dimensional, and the stagger became more symmetric. An analysis of fluid stresses reveals that the elastic flow resistance is attributed to additional normal stresses caused by shearing, and not by extension.

This thesis reports on an experimental study of slow viscoelastic flow through models of fibrous porous media. The models were square arrays of parallel cylinders, with solid volume fractions or ‘solidities’ of 2.5%, 5.0%, and 10%. An initial study using a Newtonian fluid provided a baseline for comparison with results for two Boger fluids, so that the effects of fluid elasticity could be determined. Boger fluids are elastic fluids that have near constant viscosities and can be used in experiments without having to account for shear-thinning effects. The experimental approach involved measurements of pressure loss through the three arrays and interior velocity measurements using particle image velocimetry (PIV). For the Newtonian flows, pressure loss measurements were in good agreement with the analytical predictions of Sangani and Acrivos (1982). PIV measurements showed velocity profiles which were symmetrical and independent of flow rate. Pressure loss measurements for the Boger fluid flows revealed that the onset of elastic effects occurred at a Deborah number of approximately 0.5, for both fluids and the three arrays. Flow resistance data collapsed for the two Boger fluids, and increased with solidity. For all three models, the flow resistance increased monotonically with Deborah number, reaching values up to four times the Newtonian resistance for the 10% model. PIV measurements showed that the transverse velocity profiles for the Newtonian and Boger fluids were the same at Deborah numbers below the elastic onset. Above onset, the profiles became skewed. The skewness, like the flow resistance, was observed to increase with both Deborah number and solidity. In the wake regions between cylinders in a column, periodic flow structures formed in the spanwise direction. The structures were staggered from column to column, consistent with the skewing. As either Deborah number or solidity increased, the flow structures became increasingly three-dimensional, and the stagger became more symmetric. An analysis of fluid stresses reveals that the elastic flow resistance is attributed to additional normal stresses caused by shearing, and not by extension.

The hypothesis for this study was that phenanthrene degrading bacterial inoculants, in combination with grass species able to tolerate petroleum hydrocarbon contamination, will result in increased degradation, as compared to natural rates of hydrocarbon degradation, or to rates of degradation attributed to bacteria or plants alone. Three experiments were performed to examine this hypothesis: i) assessment of the effect of phenanthrene degrading bacteria (<i>Sphingomonas yanoikuyae</i>, <i>Rahnella aquatilis</i>, and <i>Arthrobacter globiformis</i>) on seed germination, location of attachment on seeds and roots, and inoculant survival on selected grass species, ii) determination of the inoculant survival in contaminated soil in the absence of plants and the ability to degrade target compounds, and iii) degradation potential and survival of selected grass species and bacterial inoculants in soil. In general, all applied inoculants were able to effectively colonize the seeds and had a neutral or positive effect on seed germination and seedling growth. Possible plant and bacteria pairs were chosen based on positive influence of the inoculant and are as follows: perennial ryegrass (<i>Lolium perenne</i>) or creeping red fescue (<i>Festuca rubra</i>) with <i>A. globiformis</i> or <i>S. yanoikuyae</i>, or slender wheatgrass (<i>Elymus trachycaulus</i>) with <i>A. globiformis</i> or <i>R. aquatilis</i>. Soil-based assessment of the survival and degradation of hydrocarbons by the selected inoculants was examined with or without a manure nutrient amendment. The addition of the inoculants had a positive impact on the efficacy of hydrocarbon removal in the soil. The manure-amended soil, or <i>A. globiformis</i> inoculated non-amended soil treatments reduced total petroleum hydrocarbon concentration by ~45%, whereas the non-amended control only resulted in a ~20% reduction. When soils were amended with manure and inoculated with any of the phenanthrene degrading bacteria, contaminant concentration decreased in soil by ~33%. <i>Sphingomonas yanoikuyae</i> survived the longest in soil in the absence of plants. A growth chamber experiment was conducted to determine the efficacy of plant and bacteria pairs for hydrocarbon removal in recalcitrant contamination found in soil from Bruderheim, Alberta. Additional replicates containing this soil were spiked with hexadecane, phenanthrene, and pyrene so the effectiveness of the plant and bacteria pairs at higher levels of fresh contamination could be assessed. In the spiked treatment, inoculation with <i>S. yanoikuyae</i> increased creeping red fescue root biomass. In the non-spiked treatment, <i>S. yanoikuyae</i> application increased creeping red fescue root and shoot biomass. Perennial ryegrass root and shoot biomass did not increase when inoculated with <i>S. yanoikuyae</i>, although root biomass values were observably higher in non-spiked soils. Creeping red fescue inoculated with <i>S. yanoikuyae</i> resulted in the greatest decrease in hydrocarbon concentration as compared to other treatments (~61%). The perennial ryegrass treatment, when inoculated with <i>S. yanoikuyae</i> increased percent hydrocarbon removal (~10%) above that obtained with perennial ryegrass alone. The addition of plants and <i>S. yanoikuyae</i> increased hydrocarbon degradation relative to control soils, although the addition of vegetation alone had a comparable effect. A critical benefit of inoculation was the increase in creeping red fescue root biomass at higher concentrations of contamination. This is important because the larger the root biomass the larger the volume of soil that can be remediated. The results indicate that the use of specific plant-bacterial inoculants can enhance remediation of hydrocarbon contaminated soils.

Ce travail porte sur la caractérisation physico-chimique de l'huile de Jatropha Curcas et sa capacité à remplacer l'huile minérale dans les transformateurs de puissance. Ce produit présente plusieurs avantages sur les autres huiles végétales comme l'huile de palme ou l'huile de colza, qui recommandent sa production et son utilisation. En effet, la plante de Jatropha Curcas peut être cultivée sur des sols pauvres à faibles précipitations, évitant ainsi d'utiliser des sols plus fertiles pour sa culture permettant ainsi aux petits exploitants de réserver leurs terres aux cultures de base. Cette plante peut pousser facilement dans des zones où les niveaux de précipitations annuelles sont nettement inférieures à celles requises par d'autres espèces telles que le colza, le tournesol, le soja, le maïs, le palmier à huile et d'autres. Elle peut être cultivée sur tous les types de sol en Indonésie, même sur des terres arides, dans de nombreuses régions de l'Indonésie orientale, inexploitées en raison des difficultés à planter d'autres cultures. En outre, l'huile de Jatropha Curcas est un produit non alimentaire. En faisant subir à l’huile de Jatropha Curcas brute une estérification à base alcaline avec de l'hydroxyde de potassium (KOH), on obtient de l’huile de méthylester de Jatropha Curcas (JMEO) dont la viscosité et l’acidité sont acceptables pour les équipements à haute tension en particulier pour les transformateurs de puissance. Les propriétés physico-chimiques et électriques de JMEO ont été mesurées ainsi que celles de l'huile minérale (MO) pour la comparaison. Pour les propriétés physico-chimiques, il s’agit de la densité relative, la teneur en eau, la viscosité, l'acidité, l'indice d'iode, la corrosivité, le point d'éclair, le point d'écoulement, la couleur, l'examen visuel, et la teneur en ester méthylique. Quant aux propriétés électriques, elles concernent la rigidité diélectrique sous différentes formes de tension (alternative, continu et choc de foudre), les phénomènes de pré-claquage et de claquage sous choc de foudre, les décharges glissantes sur les surfaces de carton comprimé, immergé dans JMEO et MO. Les résultats obtenus montrent que les tensions de claquage moyennes en continu et en choc de foudre des huiles JMEO et MO sont très proches ; la tension de claquage moyenne de JMEO est même plus élevée que celle de l'huile minérale (de type naphténique). La mesure des tensions de claquage des mélanges d'huiles «80% JMEO + 20% MO» et «50% JMEO et 50% MO» montrent que la tension de claquage du mélange «80% JMEO + 20% MO» est toujours supérieure à celle de l'huile minérale sous tensions alternative et continue. Cela indique que le mélange d'huile minérale et de JMEO avec un rapport de 20:80 ne dégrade pas ses performances. Le mélange d'huiles peut se produire lors du remplacement de l'huile minérale par JMEO dans les transformateurs installés et en exploitation. L'analyse des caractéristiques des streamers (la forme, le temps d'arrêt, le courant associé et la charge électrique) se développant dans les huiles JMEO et MO sous tension impulsionnelle de foudre, montre une grande similitude. Aussi, la longueur finale (Lf) et la densité des branches des décharges surfaciques se propageant sur le carton comprimé immergé dans l'huile de Jatropha Curcas de méthylester (JMEO) et de l'huile minérale (MO), sous tensions de choc de foudre positif et négatif (1,2/50 μs), pour deux configurations d'électrodes divergentes (électrode pointe haute tension perpendiculaire et tangente au carton, respectivement), sont fortement influencées par l'épaisseur du carton comprimé. Pour une épaisseur donnée, Lf augmente avec la tension et décroît lorsque l'épaisseur augmente. Lf est plus long lorsque la pointe est positive que lorsque la pointe est négative. Pour une tension et une épaisseur du carton comprimé donnée, les valeurs de Lf dans l’huile minérale et l’huile JMEO sont très proches. [...] / This work is aimed at the investigation of the physicochemical characterization of Jatropha Curcas seeds oil and its capacity to be an alternative option to replace mineral oil in power transformers. This product presents several advantages that recommend both its production and usage over those of other vegetable oils as crude palm oil and rapeseeds oil. Indeed, it may be grown on marginal or degraded soils avoiding thus the need to utilize those more fertile soils currently being used by smallholders to grow their staple crops; and it will readily grow in areas where annual rainfall levels are significantly lower than those required by other species such as palm oil, rape-seeds oil, sunflower oil, soybeans oil, corn oil and others. For instance, these plants can grow on all soil types in Indonesia, even on barren soil. The barren soil types can be found in many parts of eastern Indonesia that remain untapped because of the difficulty planted with other crops. Moreover, jatropha curcas oil is nonfood crops. Jatropha Curcas oil was processed by alkali base catalyzed esterification process using potassium hydroxide (KOH) to produce Jatropha Curcas methyl ester oil (JMEO) has a viscosity and a acidity that are acceptable for high voltage equipment especially in power transformer. The physicochemical and electrical properties of JMEO were measured as well as those of mineral oil (MO) for comparison. The physicochemical properties cover relative density, water content, viscosity, acidity, iodine number, corrosivity, flash point, pour point, color, visual examination, and methyl ester content. Meanwhile the electrical properties cover dielectric strength under AC, DC and lightning impulse voltages, pre-breakdown / streamers under lightning impulse voltage, creeping discharge over pressboard immersed in JMEO and MO. The obtained results show that the average DC and lightning impulse breakdown voltages of JMEO and MO are too close, even the average AC breakdown voltage of JMEO are higher than that of mineral oil (napthenic type). The measurement of breakdown voltages of two oil mixtures namely “80% JMEO + 20% MO” and “50% JMEO and 50% MO” shows that the breakdown voltage of the first mixture (i.e., “80%JMEO+20%MO”) is always higher than that of mineral oil under both AC and DC voltages. This indicates that mixing 20:80 mineral oil to JMEO ratio does not degrade its performance. The mixing of oils can occur when replacing mineral oil by JMEO in installed transformers. The analysis of the streamers characteristics (namely; shape, stopping length, associated current and electrical charge) developing in JMEO and MO under lightning impulse voltages, shows that these are too close (similar). It is also shown that the stopping (final) length Lf and the density of branches of creeping discharges propagating over pressboard immersed in Jatropha Curcas methyl ester oil (JMEO) and mineral oil (MO), under positive and negative lightning impulse voltages (1.2/50 μs), using two divergent electrode configurations (electrode point perpendicular and tangential to pressboard), are significantly influenced by the thickness of pressboard. For a given thickness, Lf increases with the voltage and decreases when the thickness increases. Lf is longer when the point is positive than with a negative point. For a given voltage and thickness of pressboard, the values of Lf in mineral oil and JMEO are very close. It appears from this work that JMEO could constitute a potential substitute for mineral oil for electrical insulation and especially in high voltage power transformers.

Les études présentées dans cette thèse font l’objet d’un travail innovant concernant la conception des antennes pour les réseaux de type BAN et la modélisation des canaux associés. L’ouvrage de thèse est réparti en quatre chapitres. Deux chapitres sont consacrés à la modélisation de la propagation le long du corps où l’on montre que les formulations analytiques d’ondes de surface et d’ondes rampantes sont applicables dans ce contexte. L’effet des tissus adipeux est également pris en compte par le biais d’un modèle à trois couches (peau, graisse et muscle) et renseigne sur la variabilité du bilan de liaison suivant les personnes. Ce type de modélisation est le premier à inclure les formes du corps, les caractéristiques électriques des tissus biologiques et les caractéristiques de rayonnement des antennes. Une méthode basée sur l’autocorrélation du canal est également présentée afin de connaître les temps de cohérences des évanouissements lents et rapides. Par la suite, il est montré comment les évanouissements lents sont extraits par le biais d’un filtrage FFT fonction du temps de cohérence associé. L’étude des canaux se termine sur une série de mesures en chambre anéchoïde qui a permis de vérifier la validité des modèles analytiques. Des mesures en milieu indoor ont abouti à la proposition de plusieurs modèles statistiques basés sur une loi de Nakagami-m fonction de la distance sur le corps. Deux autres chapitres sont consacrés à la conception d’antennes à proximité de tissus biologiques et devant être intégrées dans des biocapteurs ou des vêtements. Pour cela, nous nous sommes particulièrement intéressés aux structures en F-inversé comme les IFA imprimées et les PIFA. Nous avons également réalisé des monopôles courts ayant un comportement de type magnétique. Nous montrons par le biais de simulations et de mesures sur un fantôme que seules les antennes du type monopôle et PIFA permettent une bonne excitation des ondes de surface. On montre par la suite l’influence du facteur de qualité d’une antenne sur son rendement et l’on en conclue qu’une antenne doit présenter un facteur de qualité faible pour avoir un bon rendement. La désensibilisation d’une antenne face au corps est également présentée. L’emploi de feuilles de ferrites aide à concentrer le champ réactif et limite ainsi les inévitables désadaptations dues au corps. Le coefficient de qualité joue également un rôle important dans le comportement de l’antenne face aux variabilités des tissus biologiques. L’estimation du rendement est un autre point difficile à réaliser lorsque les antennes sont sur le corps. Malgré tout nous proposons une nouvelle méthode que nous vérifions par simulation. Finalement, une structure à diversité est également proposée. Cette dernière tient compte des connaissances acquises au long de ce travail de recherche. Une sélection des meilleurs types d’antennes du point de vu canal et rendement est réalisée. La structure choisie est composée d’une PIFA et d’un monopôle court découplés par le biais de fentes λ/4. Des mesures in situ en milieu indoor donnent un gain en diversité maximum de 8.1 dB pour un schéma de type sélection / BAN antennas conception and channel modelling

No description available.

No description available.

Annual bluegrass (Poa annua L.) and roughstalk bluegrass (Poa trivialis L.) are among the most troublesome grass weeds on golf courses throughout the United States. Herbicides for selective control of these weeds in cool-season fairways are limited and ineffective. Methiozolin is a new isoxazoline herbicide that controls annual bluegrass on putting greens and shows promise for possible weed control in fairways. Kentucky bluegrass (Poa pratensis L.) is among the most common turfgrass species used for golf fairways in the Northern United States and its response to methiozolin has scarcely been tested. A 2.5-yr field study was conducted at four Virginia locations to evaluate methiozolin efficacy for selective annual bluegrass and roughstalk bluegrass control in creeping bentgrass (Agrostis stolonifera L.) or Kentucky bluegrass fairways. Another study evaluated the response of 110 Kentucky bluegrass varieties to three rates of methiozolin. Annual bluegrass has long been presumed to impact putting green trueness, or the ability of the greens canopy to provide a smooth and directionally-consistent ball roll. Although much research has evaluated the impact of greens management on ball roll distance, no peer-reviewed research has evaluated how canopy surface factors, such as weedy annual bluegrass, will influence ball roll direction. Laboratory and field research was conducted to elucidate and overcome experimental errors that may be limiting assessment of ball directional imprecision caused by greens canopy anomalies. Techniques to minimize experimental error were employed in field studies at two Virginia golf courses to determine the influence of annual bluegrass on ball directional imprecision, bounce, and acceleration. Study results suggest that annual bluegrass patches in a creeping bentgrass putting surface can cause subtle increases in ball directional imprecision and bounce but several sources of error must be controlled before these effects can be measured. By using a mechanical putter to avoid directional errors associated with simulated-putt devices, selecting golf balls with balanced centers of gravity, eliminating legacy or "tracking" effects of repeated ball rolls via canopy brushing, and scoring ball direction 30 cm prior to terminal acceleration, we were able to detect an increase in ball directional imprecision of 8 mm m⁻¹ when balls rolled over a single patch of annual bluegrass compared to adjacent rolls on visually-pure creeping bentgrass. In herbicide efficacy studies, methiozolin-only treatments did not significantly injure creeping bentgrass or Kentucky bluegrass, reduce quality, or reduce normalized difference vegetative index regardless of application timings and rates. In general, fall applications of methiozolin reduced roughstalk bluegrass and annual bluegrass cover more than the spring-only treatments. At 1 year after the last treatment, methiozolin at 1500 g ha⁻¹ applied four times in fall at 2-wk intervals for two consecutive years controlled roughstalk bluegrass and annual bluegrass ≥85% and more consistently than other herbicides or treatment regimes. Spanning 110 Kentucky bluegrass varieties, a commercially-acceptable threshold of 30% Kentucky bluegrass injury required between 3.4 to more than 10 times the methiozolin rate needed for annual bluegrass control. Results indicate that annual bluegrass increases directional imprecision and bounce of golf balls rolling across a greens canopy. Methiozolin could be a viable herbicide for managing annual and roughstalk bluegrass in Kentucky bluegrass and creeping bentgrass fairways but weed control efficacy may be dependent on application timing. By measuring small differences in ball directional imprecision as influenced by greens canopy factors, future research efforts will aim to help turf managers choose appropriate greens management techniques. / Ph. D. / Annual bluegrass and roughstalk bluegrass are among the most troublesome grass weeds on golf courses throughout the United States. Both these weedy bluegrass species reduces the aesthetics and playability of golf turf, including fairways, tees, and putting greens. Since both annual bluegrass and roughstalk bluegrass favors growing conditions very similar to that of desirable cool-season grasses, especially Kentucky bluegrass and creeping bentgrass – the most prominent cool-season grasses on golf courses throughout the Northern USA, selective removal of these weedy bluegrass species from the desirable turf sward is very difficult. Moreover, genetic similarity of annual bluegrass and roughstalk bluegrass to Kentucky bluegrass accentuates the difficulty in selective control even more. Commercially-available herbicides for selective control of these weedy bluegrass species in cool-season golf fairways are limited and often ineffective for long-term control. Methiozolin (PoaCure®) is a new herbicide that has been extensively studied and shown to control annual bluegrass on golf putting greens and shows promise for possible weed control in fairways. However, PoaCure® has scarcely been tested to selectively and safely control annual bluegrass and roughstalk bluegrass in cool-season golf fairways. Therefore, field research was conducted at four Virginia locations to evaluate PoaCure® efficacy for selective, long-term annual bluegrass and roughstalk bluegrass control in creeping bentgrass or Kentucky bluegrass fairways. To assess the weed-control potential of PoaCure® on a broader spectrum of Kentucky bluegrass varieties grown here in VA and other cool-season grass growing parts of the nation, another field research was conducted to evaluate the response of 110 Kentucky bluegrass varieties to three different field application rates of PoaCure®. In PoaCure® weed control efficacy studies, PoaCure® by itself did not injure or reduced quality of creeping bentgrass or Kentucky bluegrass regardless of application timings and rates. In general, fall applications of PoaCure® reduced roughstalk bluegrass and annual bluegrass green cover more than the spring-only treatments. At trial completion, which was 2.5 years after trial initiation and 1 year after the last herbicidal treatment, PoaCure® at 82 fl oz/A applied four times in fall at 2-wk intervals for two consecutive years provided ≥85% control of annual bluegrass and roughstalk bluegrass and did so more consistently than other herbicides or treatment regimes in the study. In the tolerance study of 110 Kentucky bluegrass varieties, a commercially-acceptable threshold of 30% injury required between 3.4 to more than 10 times the PoaCure® rate needed for annual bluegrass control. Results from herbicide efficacy and tolerance studies indicate that PoaCure® could be a viable herbicide for managing annual and roughstalk bluegrass in Kentucky bluegrass and creeping bentgrass fairways but weed control efficacy may be dependent on application timing. In addition to being difficult to control and aesthetically unpleasing to view, annual bluegrass has also long been blamed for missed golf putts. Some researchers have surmised that a golf ball's direction may be altered when the ball traverses an anomaly in the greens surface, such as annual bluegrass, but no scientific studies have tested this assumption. Laboratory and field research was conducted to elucidate and overcome experimental errors that may be limiting assessment of ball directional imprecision caused by greens canopy anomalies. Study results suggest that an isolated patch of annual bluegrass increases ball directional imprecision by 8 mm m^-1 compared to visibly-pure creeping bentgrass and that tools and methodology currently reported in scientific literature are not precise enough to discern these subtle changes in direction. At Virginia Tech, we devised a new methodology to discern subtle changes in ball roll directional precision and bounce as influenced by an isolated patch of annual bluegrass in an otherwise visually-pure creeping bentgrass canopy. We used a mechanical putter to minimize directional errors associated with commercially-available simulated putt-devices, selected balanced golf balls, eliminated legacy of repeated ball rolls by brushing putting green surface canopy between ball rolls, scored ball direction prior to terminal acceleration with pressuresensitive paper, and used high-speed video and motion tracking software to measure ball wobble and bounce. Results indicate that annual bluegrass increases directional imprecision and bounce of golf balls rolling across a greens canopy.

Inscrite dans la dialectique changement-permanence, la stabilité juridique ne saurait s'opposer au changement normatif. Si rien ne changeait, il n'y aurait nul besoin de parler de stabilité, mais tout simplement d'intangibilité, d'immutabilité ou même d'éternité du droit. Par la stabilité, on cherche donc à garantir deux valeurs juridiques importantes : l'évolution du droit et la sécurité juridique. Tout produit juridique aspire à la stabilité. Sur le terrain du droit objectif, la stabilité est protégée afin d'éviter des situations d'inflation normative, de désordre dans la production normative, et de faciliter l'application des produits juridiques dans le temps. Sur le terrain des droits subjectifs, elle est souvent protégée afin d'assurer le maintien des situations juridiques individuelles malgré l'écoulement du temps. Ces aspects transparaissent dans le droit international des investissements à travers l'attente légitime de stabilité juridique. Cela étant, pour qu'une telle attente de stabilité juridique présente un caractère légitime, il faut qu'existe un engagement explicite ou implicite de l'État en ce sens et que les investisseurs se comportent d'une façon diligente et de bonne foi. Sur le plan substantiel, l’investisseur ne doit également pas s’attendre à ce que le droit ne change pas, car le droit est évolutif par nature. En revanche, il peut légitimement s’attendre à ce que les changements normatifs soient introduits de façon prévisible et non arbitraire. La violation de la stabilité juridique de la part de l'État engage sa responsabilité internationale. Au-delà de toutes ces considérations, la stabilité juridique fait face aujourd'hui à de nombreux bouleversements, le plus important semblant être son émergence en tant que principe coutumier de droit international. / Discussions of legal stability involve the notions of change and permanence; therefore, legal stability cannot oppose legal change. If nothing changed, there would be no need to talk of stability, and one would simply speak of intangibility, immutability or even of the eternity of the law. Through stability we seek to ensure two important legal values: the development of law and the principle of legal security. Stability is a central aspiration of every law. In the field of objective law, stability is protected in order to prevent a surfeit of laws, disorder in the legislative process and to facilitate the application of laws over time. In the field of subjective rights, it often exists in order to maintain certain specific legal situations and rights in spite of the passage of time. These aspects are reflected in international investment law through the legitimate expectation of legal stability. This being the case, so that such an expectation of legal stability be considered legitimate, there must be an explicit or implicit commitment by the State in this direction and investors must act diligently and in good faith. On the substantive side, it is also necessary that the investor does not expect the law not to change given that law evolves with time. Nevertheless, the investor can legitimately expect that regulatory changes be introduced in a predictable and non-arbitrary manner. Violation of legal stability by the State incurs international liability. Beyond these considerations, today legal stability faces a lot of challenges; the most important of which seems to be its emergence as a customary principle of international law.