This research involved testing several aspects of industrial hemp (Cannabis sativa L.) production, including the impact of tillage on seed and fiber production, optimal harvest time for seed yield and quality, the response of seed yield to nitrogen fertility rates, and the potential of hemp as a forage crop. A three-year study was conducted in Blacksburg and Orange of Virginia State to assess the effects of tillage management and production systems (e.g., seed, dual, and fiber) on hemp establishment and productivity. Two cultivars, Joey (a dual-purpose variety) and EcoFibre (bred specifically for fiber), were planted into seedbeds prepared with conventional tillage and no-till management. The cultivar Joey, lower plant populations under seed production systems resulted in taller plants (P = 0.0002) compared to the dual-purpose production systems in 2020. Greater plant heights (P < 0.0001) with fiber production systems in 2021 and 2022 were due to differences between cultivars and their time of flowering. Conventional tillage resulted in greater (P ≤ 0.0161) plant populations than no-tillage for all production systems in each year, and this response was more pronounced with fiber management in 2020 (tillage × production systems interaction; P = 0.0007). Greater (P < 0.001) yields with fiber systems observed in 2021 and 2022 were largely driven by the more productive EcoFibre cultivar. Despite treatment differences in population density, biomass and seed yields varied less by tillage management and production systems. Lower plant population density was associated with greater biomass and seed yields per plant. However, for desired fiber quality and mechanical harvest feasibility, a higher plant population density is recommended. A second study aimed to determine the optimum harvest time for seed yield of two hemp cultivars. 'Joey', and 'Grandi,', were established in Blacksburg and Orange, Virginia in mid-May/early June of 2021 and 2022. The experiment was conducted as a randomized complete block design with a repeated measurement arrangement and four replicates. Plants were harvested four times at one-week intervals starting in mid-summer. Harvest date significantly affected seed yield, with the response differing by cultivar (cultivar × date interaction; P = 0.001) in 2022 at the Orange site. In Blacksburg, seed yields were similar for the two cultivars and greatest at the second harvest each season (July 22, 2021, and July 25, 2022), although they were substantially lower in 2022 due to drought (1750 vs. 480 kg ha-1; P < 0.0001). In Orange, in 2021, as planting occurred late, harvests were also deferred until August 17, and seed yields were greatest at this first harvest (1180 kg ha-1; P<0.0001). In 2022, yields at the Orange location were highest for Grandi at the first harvest (July 21; 1510 kg ha-1) and for Joey at the second harvest (July 28; 1280 kg ha-1) (Harvest Time by Cultivar interaction, P = 0.0010). Over the subsequent weeks of harvest, yields drastically declined (16 to 41% in 2021 and 27 to 47% in 2022 in Blacksburg; 52% to 91% in 2021 and 28% to 65% in 2022 in Orange, compared to the highest yield). Harvest timing is critical to achieving optimum seed yield, and it varies with cultivar, eco-physiographic location, and weather (e.g., rainfall). Fatty acids (FA) varied by cultivar, location, and harvest timing, but patterns of response were not consistent across FA. Gamma-linolenic (P ≤ 0.002) and oleic acids (P ≤ 0.023) were generally greater in Joey, with greater arachidic acid (P ≤ 0.013) concentrations in Grandi. Stearidonic acid concentrations declined with later harvest date in Orange location (P ≤ 0.0034). A third study aimed to measure hemp's response to different N rates and to determine the ability to predict plant N content and seed yield based on UAV-based multispectral imagery. Two hemp cultivars, 'Joey' and 'Grandi', were planted and five N rates (0, 60, 120, 180, 240 kg N ha-1) were tested in Blacksburg, Virginia in 2020, 2021, 2022. Aerial image acquisition occurred at three different growth stages in 2021 using dji M 300 drones mounted with multispectral sensors. Red/Blue index (R2=0.89), near-infrared (NIR) band (R2=0.84) and Enhanced vegetation index (EVI) (R2=0.81) were better predictors of N content in leaf samples than other vegetation indices that were evaluated. Green normalized difference vegetation index (GNDVI) was the better predictor of hemp seed yield (R2=0.58) than other evaluated vegetation indices. The seed yield of hemp was influenced (P ≤ 0.0177) by the N input in all three experimental years. In 2020, seed yield did not increase steadily with the increase of N rate; the highest seed yield, 1640 kg ha-1, was observed at 120 kg N ha-1. In 2021, maximum seed yield of 2500 kg ha-1 occurred at the maximum N rate (240 kg N ha-1). In 2022, a weak response to N rate was observed; maximum seed yield was 380 kg ha-1, again at 240 kg N ha-1. The overall growth of the hemp plants was affected by limited rainfall and weed pressures in 2022, leading to a significant reduction in seed yield. Response to N rate will vary depending on other factors such as available soil moisture during the growing season, weed pressure, and growing period. A fourth study examined the yield and nutritive value of three hemp cultivars, 'Grandi', 'Joey', and 'EcoFibre' as potential forage crops when harvested at weekly intervals in Blacksburg, VA. The greatest biomass and TDN yields across cultivars were 3.17 Mg ha-1 and 2.08 Mg ha-1 respectively, at two months after establishment in 2021. In the dry 2022 season, biomass and TDN yield were 1.9 Mg ha-1 and 1.03 Mg ha 1, respectively, two months after establishment. Hemp nutritive value measures varied by cultivar and harvest time (P < 0.05). Depending on the cultivar and harvest time, hemp plant biomass contained 13 to 32% CP, 22 to 45% NDF, 20 to 38% ADF, 4 to 9% lignin, and 52 to 80% TDN (cultivar × time interaction; P < 0.05). Hemp CP and TDN decreased gradually with maturation while ADF, NDF, and lignin increased (P<0.0001); however, this decline with maturity did not appear as severe as occurs with many other forages. These preliminary results suggest that hemp has the potential to be used as a forage crop. More research is needed to address hemp management and utilization, including field establishment and production, harvest timing for optimum tonnage and forage quality, and animal intake and performance studies. These findings provide new insights into industrial hemp production in the mid-Atlantic region of the United States. Optimal tillage practices, precise harvest timing, appropriate N fertility rates, and proper management techniques all are crucial for maximizing hemp seed and fiber production and quality. Furthermore, hemp shows promise as a forage crop with its adaptability and favorable nutritional properties. Further research is warranted to refine cultivation techniques, improve crop quality, and explore the full potential of hemp in various industries. / Doctor of Philosophy / Industrial hemp (Cannabis sativa L.) is a versatile crop with numerous applications in various industries, but much work must be done to understand crop responses to management practices and improve its potential as a crop for greater sustainability. In this study, we explored different aspects of hemp agronomic management. Hemp traditionally has been planted into tilled fields, which increases the chance for soil erosion. We examined whether hemp could be established without tillage and found that although tilled fields generally had great populations of taller plants; total biomass and seed yields were not as influenced by tillage. Our research suggests that with some tweaking, hemp can be successfully established without soil tillage. Next, we investigated the optimal time to harvest hemp for maximum seed yield. Harvesting at the right moment is crucial, as seeds ripen unevenly, resulting in varying quality and yield. By carefully timing the harvest, we can maximize seed yield and ensure high-quality seeds. Our cultivars were best harvested in a late July to early August time frame. Under favorable weather conditions, we observed seed yields ranging from 1,180 to 2,510 kilograms per hectare, depending on the hemp cultivar and location. Additionally, we studied the response of hemp seed yield to nitrogen fertilization rates. Nitrogen is an essential nutrient for plant growth, and we found that nitrogen significantly influenced seed yield, although the pattern of response varied by growing conditions. Over three years, seed yields ranged from 380 to 2,510 kilograms per hectare. Yields generally increased with nitrogen inputs but were highly affected by available moisture. Fertility studies help farmers determine the ideal nitrogen levels for their hemp crops, promoting healthy growth, maximizing yield, and minimizing environmental contamination. Within this study, we also evaluated aerial imagery technologies to monitor plant nitrogen status and we observed that remote sensing technologies are promising for building predictive nutrient management tools. Lastly, we explored the potential of hemp as a forage crop. Hemp plants have unique nutritional properties (e.g., protein, fatty acids) and can be used as feed for livestock. We investigated the best time to harvest hemp for maximum biomass and nutrient content, important factors for animal nutrition. Hemp plants grow rapidly and within two months after establishment they yielded up to 3.17 metric tons of biomass per hectare, with relatively high nutritional value. Overall, these studies provide valuable insights into hemp production, including the importance of tillage practices, optimal harvest timing, and appropriate nutrient management. By applying these findings, farmers can enhance their hemp cultivation techniques, resulting in higher yields, improved crop quality, and better environmental outcomes.

Foodborne outbreaks have continued to be associated with produce contamination originating from on-farm sources, such as soil or agricultural water. Additionally, the heterogeneity of the pre-harvest environment complicates the development of universal strategies for managing produce safety risks. Understanding the ecology and epidemiology of foodborne pathogens and fecal indicator bacteria (FIB) by growing regions, sample types, scale of analysis, and detection method is essential for developing targeted mitigation strategies. This dissertation utilized quantitative research methods and statistical modeling to examine the impact of sampling method, spatial, temporal, meteorological, and physicochemical factors on pathogen prevalence and FIB levels. Key findings highlight that the drivers of prevalence differ between pathogens and were influenced by sample type, scale, and region.. The variations in associations emphasize that risk varies by space and time. Therefore, results support regional and scale-dependent food safety standards and guidance documents for controlling hazards to minimize risk. Additionally, the method used for pathogen detection influences prevalence highlighting the need for standard methods since methodological differences confound comparisons across studies. Furthermore, since agricultural water quality is an important food safety priority, this dissertation aimed to determine the efficacy of chemical antimicrobial sanitizers against Salmonella in pre-harvest agricultural water. Results demonstrated that certain sanitizer treatments and conditions can significantly reduce Salmonella populations in preharvest agricultural water sources and thus may serve as a risk reduction option when used correctly. / Doctor of Philosophy / Fresh fruits and vegetables are continually implicated in foodborne outbreaks. Additionally, the source of the pathogen that causes illness in these outbreaks is often due to contact with contaminated soil or water on the farm. Since the environment is extremely diverse, the risk of foodborne pathogens is not uniform across a farm and between farms. Therefore, the development of a one-size-fits-all plan to reduce the risk of foodborne pathogens from contaminating produce on a farm is difficult. Understanding the incidence and distribution of foodborne pathogens and fecal bacteria and how these microorganisms interact with the environment is important to develop strategies to manage risk. Additionally, understanding how the prevalence of bacteria varies by state, medium (water vs soil), and farm is needed to develop targeted mitigation plans. This dissertation utilized laboratory and field-based experiments to understand how space, time, weather, and physical properties impact the occurrence of foodborne pathogens and fecal bacteria. The primary results show factors that impact prevalence are different between pathogens (Salmonella vs Listeria vs E. coli). Furthermore, the occurrence differed by sampling method (molecular vs culture), sample type (water vs soil), scale (within a farm vs between multiple farms), and region emphasizing that the risk from foodborne pathogens varies over space and time. Overall, this dissertation's results suggest that both regional and scale-specific guidelines are needed to reduce foodborne pathogen risks in the farm environment. Lastly, since the quality of the water used in growing fresh produce is an important food safety priority, the effectiveness of chemical antimicrobial sanitizers against Salmonella in agricultural water was evaluated. Results demonstrated that certain sanitizer treatments and conditions (sanitizer concentrations, water temperatures) can significantly reduce Salmonella populations in pre-harvest water sources and may serve as a risk reduction option when sanitizers are used correctly.

Harvest weed seed controls (HWSC) destroy weed seeds that are retained by the plant at crop harvest, which would typically be spread by the harvester along with other field residues. HWSC exploits coincidental maturity between crops and weeds, so an experiment was designed to collect weed seeds as they shatter throughout the growing season and through a simulated harvest delay. This experiment monitored four economically important broadleaf species and two grass species in a soybean (Glycine max (L.) Merr.) field. Results indicated that broadleaf species shattered seed at rates accelerating through the growing season, while grass species shattered more seed early in the growing season. Field experiments in organic and conventional winter wheat (Triticum aestivum L.) fields infested with Italian ryegrass (Lolium perenne L. ssp. multiflorum (Lam.) Husnot) compared two HWSC techniques to grower-standard weed management programs in each system, including both no-till and full-till standard treatments in the conventional system. Italian ryegrass populations were monitored, and wheat yield was measured both before and after HWSC application. In both organic and conventional cropping systems, HWSC treatments did not provide better Italian ryegrass control than the grower-standard treatments. The conventional program including tillage boosted Italian ryegrass populations. These results suggest that HWSC treatments did not enhance Italian ryegrass control compared to grower-standard practices in either the organic or conventional systems. Additionally, broadleaf weeds may retain enough seeds to be viable targets for HWSC. Incorporating best practices, such as a timely crop harvest, is key for understanding and optimizing HWSC. / Master of Science / Harvest weed seed controls (HWSC) destroy weed seeds that the weed plant retains at the time of crop harvest. On a typical farm, these weed seeds pass through the crop harvester and get spread across the field along with other plant materials. HWSC directly targets weed seeds, differentiating itself from normal weed management practices, such as herbicides, that kill emerging or emerged weed plants. With HWSC, weed seeds never enter the soil seed bank, thus depleting weed populations over time. HWSC works through mechanical means, such as crushing, burning, or removal. For conventional farmers battling herbicide resistant weeds, HWSC can provide effective weed management by diversifying weed management programs. HWSC also has promise as a new chemical-free weed management for organic farmers. HWSC relies on crops and weeds having coincidental maturity; seeds released from the plant (shattered) before crop harvest cannot be targeted by HWSC. An experiment was designed to collect weed seeds weekly as they shatter throughout the growing season, continuing until three weeks after the ideal date to harvest crops, thereby simulating a situation where weather or logistical factors prevented a timely crop harvest. This experiment monitored four broadleaf species and two grass species that infest soybean fields. Broadleaf species shattered seeds at increasing rates throughout the soybean growing season, with each species shattering over 50% of captured seed during the simulated harvest delay. Compared to broadleaf weeds, grass species shattered relatively more seed early in the growing season. This experiment indicates that broadleaf weeds may be more suited to control by HWSC. HWSC was also used in organic and conventional winter wheat fields infested with Italian ryegrass. These experiments compared two HWSC techniques, windrow burning of field residue and residue removal to standard weed management programs in each system. Windrow burning incinerates field residues, eliminating weed seeds within. Residue removal takes all field residues off the field for disposal elsewhere. While the standard organic weed management program involved tillage by default, the conventional cropping system featured both no-till and full-till standard weed management programs. Italian ryegrass populations were monitored through population counts, biomass collections, and counting of seed remaining at harvest. Wheat yield was also recorded. These measurements were taken both before HWSC application and after the first year of HWSC, to compare year-to-year changes. In the organic cropping system, Italian ryegrass populations grew and wheat yield decreased at similar rates for both HWSC treatments and the standard weed management program. In the conventional cropping system, Italian ryegrass populations declined and wheat yield increased for HWSC and the no-till standard treatments. Tillage, however, boosted Italian ryegrass populations, keeping them at similar levels to the previous growing season. These results suggest that HWSC treatments did not enhance Italian ryegrass control compared to standard practices in either the organic or no-till conventional systems. Though these results indicate that broadleaf weeds may retain enough seeds to be viable targets for HWSC, more research is needed to optimize HWSC for Italian ryegrass control, especially for organic growers. Incorporating best agricultural practices, such as a timely crop harvest, is key for improving HWSC’s efficacy. Commercial implementation of HWSC depends on further understanding of how specific HWSC practices, such as windrow burning, interact with the agricultural landscape, including effects on landscape aesthetics and soil nutrition. HWSC holds promise for diversifying weed management and limiting reliance on herbicides, but its true potential is yet to be revealed.

Com o objetivo de estudar a eficiência de herbicidas dessecantes, o momento ideal de aplicação, a viabilidade da antecipação da colheita e seus efeitos sobre o rendimento e as qualidades fisiológica e sanitária de sementes de feijão, foi instalada uma pesquisa em Área Experimental e no Laboratório de Análise de Sementes do Departamento de Produção Vegetal da Escola Superior de Agricultura "Luiz de Queiroz" em Piracicaba - SP. Para tanto, utilizou-se o cultivar Pérola, o qual foi semeado na safra da "seca", na população aproximada de 200.000 plantas/ha. O delineamento experimental foi o de blocos casualizados com quatro repetições em esquema fatorial 5 x 5, sendo cinco herbicidas, combinados com as cinco épocas de aplicação (28, 32, 36, 40 e 44 dias após o florescimento) e uma testemunha (sem aplicação de herbicida dessecante). A análise dos dados e a interpretação dos resultados obtidos permitiram as seguintes conclusões: os herbicidas dessecantes Paraquat e Paraquat associado a Diuron proporcionaram antecipação da colheita em onze dias, sem causar danos ao rendimento e a qualidade das sementes, enquanto para Glifosate e Glifosate + uréia a antecipação foi de seis dias; os herbicidas dessecantes Paraquat e Paraquat associado a Diuron não afetaram nem o rendimento, nem a qualidade das sementes produzidas, independemente da época de aplicação; os herbicidas Glifosate e Glifosate mais uréia somente quando aplicados aos 44 dias após florescimento não afetaram a qualidade das sementes e o herbicida dessecante Glufosinato de Amônio, independentemente da época de aplicação, afetou negativamente a qualidade das sementes produzidas. / Viewing to study the efficiency of desiccant herbicides, the ideal moment for their application, the feasibility of anticipating the harvest and their effects on yield and the physiological and sanitary quality of common bean seeds, an experiment was conducted at the College of Agriculture "Luiz de Queiroz", in Piracicaba, state of São Paulo, Brazil. Seeds of the cultivar 'Pérola' were sown during the dry season so as to result in a population of 200,000 plants/hectare. The experimental design was a randomized complete block with four replications in a 5 X 5 factorial arrangement - 5 herbicides in combination with 5 moments of application (28, 32, 36, 40, and 44 days after flowering) and a control treatment (no desiccant was applied). The statistical analyses of the data and the interpretation of the results allowed the following conclusions: Paraquat and Paraquat plus Diuron permited an 11 days anticipation in the harvest with no harm to seed quality or reduction in yield. For Glyphosate and Glyphosate plus Urea the anticipation was of 6 days. Paraquat and Paraquat plus Diuron were not harmful to seed quality or caused yield reduction in none of the moments of application. Glyphosate and Glyphosate plus Urea were not harmful only when applied 44 days after flowering. Ammonium Gluphosinate was always harmful to seed quality independently on the moment of application.

O presente trabalho trata do estudo do fatiamento de cristais de quartzo quanto as suas características e influências na fabricação de micro sistemas eletromecânicos (MEMS). A metodologia é iniciada pelo projeto estruturado de um MEMS, convergindo para um gerador energia elétrica do tipo energy harvest, capaz de gerar energia limpa, renovável, de escala reduzida (micro componente), de baixa potência e com vistas para aplicação comercial. Geração de energia tem se tornado um tema cada vez mais frequente, em especial energia para sistemas autônomos (wireless) aonde o uso de baterias é restritivo ou até mesmo inviável devido às dimensões e dificuldade de manutenção. A fabricação de MEMS é a etapa de maior investimento financeiro e por consequência, maior estudo. No caso do gerador de energia, a ênfase recai sobre os processos de corte, que consomem a maior parte do processo fabril. O objetivo do presente trabalho é avaliar o processo de corte abrasivo do quartzo e a influência dos defeitos impregnados pelo processo, sobre o desempenho de geradores de energia piezelétricos baseados em quartzo sintético e natural. Os processos de corte com uso de fita abrasiva (band saw) e disco abrasivo (dicing saw) se destacaram devido aos bons resultados, disponibilidade, produtividade e baixo custo. Procedimentos de corte também foram realizados em outros materiais - Alumina Policristalina 99,8% e Silício (111) - como estudo comparativo das características do mecanismo de remoção de material aplicado aos processos de corte abrasivos. Os parâmetros de corte foram trabalhados em busca de melhor qualidade, que significa redução da impregnação de falhas (principalmente, o chipping e backside chipping) e melhor acabamento das superfícies geradas pelo corte final. Foram obtidas peças nos planos AT, X, Y e Z, com espessuras a partir de 0,5 mm, segmentadas em larguras de 1 a 7 mm. / This work is a study of characteristics and influences of cutting process in manufacturing of microelectromechanical systems (MEMS) based on quartz single crystal. The methodology starts by the structured design of a MEMS device, converging to an electric power generator device, type energy harvest that generates clean energy, renewable, with small dimensions (micro component) and low power. Power generating has become a frequent topic, especially the power generation for wireless devices systems, which use of batteries can be restrictive or even impracticable because of dimensions and difficult of maintenance. The base of the study is the process manufacturing of MEMS, which is the major investment and because of this, the most studied stage. In the case of a power generator, the emphasis is on the cutting process that consumes most part of the work flow. The objective of this work is evaluate the abrasive cutting process of quartz and the influence of defects generated by the cutting process applied to the performance of piezoelectric power generators based on synthetic and natural quartz crystal. The abrasive cutting process of band saw and dicing saw were featured due availability and high productivity with low cost. Procedures of cutting were also applied in other materials - Alumina Polycrystalline 99,8% and Silicon (111) - as comparison for material removal mechanism in cutting process. The process parameters were optimized to reach better cutting quality, which means reduction in faults (mainly, chipping and backside chippings) and better surface finishing from cutting process. It was obtained pieces from AT, X, Y and Z cutting plans, with thickness starting from 0,5 mm and widths from 1 to 7 mm.

Com o objetivo de estudar a eficiência de herbicidas dessecantes, o momento ideal de aplicação, a viabilidade da antecipação da colheita e seus efeitos sobre o rendimento e as qualidades fisiológica e sanitária de sementes de feijão, foi instalada uma pesquisa em Área Experimental e no Laboratório de Análise de Sementes do Departamento de Produção Vegetal da Escola Superior de Agricultura "Luiz de Queiroz" em Piracicaba - SP. Para tanto, utilizou-se o cultivar Pérola, o qual foi semeado na safra da "seca", na população aproximada de 200.000 plantas/ha. O delineamento experimental foi o de blocos casualizados com quatro repetições em esquema fatorial 5 x 5, sendo cinco herbicidas, combinados com as cinco épocas de aplicação (28, 32, 36, 40 e 44 dias após o florescimento) e uma testemunha (sem aplicação de herbicida dessecante). A análise dos dados e a interpretação dos resultados obtidos permitiram as seguintes conclusões: os herbicidas dessecantes Paraquat e Paraquat associado a Diuron proporcionaram antecipação da colheita em onze dias, sem causar danos ao rendimento e a qualidade das sementes, enquanto para Glifosate e Glifosate + uréia a antecipação foi de seis dias; os herbicidas dessecantes Paraquat e Paraquat associado a Diuron não afetaram nem o rendimento, nem a qualidade das sementes produzidas, independemente da época de aplicação; os herbicidas Glifosate e Glifosate mais uréia somente quando aplicados aos 44 dias após florescimento não afetaram a qualidade das sementes e o herbicida dessecante Glufosinato de Amônio, independentemente da época de aplicação, afetou negativamente a qualidade das sementes produzidas. / Viewing to study the efficiency of desiccant herbicides, the ideal moment for their application, the feasibility of anticipating the harvest and their effects on yield and the physiological and sanitary quality of common bean seeds, an experiment was conducted at the College of Agriculture "Luiz de Queiroz", in Piracicaba, state of São Paulo, Brazil. Seeds of the cultivar 'Pérola' were sown during the dry season so as to result in a population of 200,000 plants/hectare. The experimental design was a randomized complete block with four replications in a 5 X 5 factorial arrangement - 5 herbicides in combination with 5 moments of application (28, 32, 36, 40, and 44 days after flowering) and a control treatment (no desiccant was applied). The statistical analyses of the data and the interpretation of the results allowed the following conclusions: Paraquat and Paraquat plus Diuron permited an 11 days anticipation in the harvest with no harm to seed quality or reduction in yield. For Glyphosate and Glyphosate plus Urea the anticipation was of 6 days. Paraquat and Paraquat plus Diuron were not harmful to seed quality or caused yield reduction in none of the moments of application. Glyphosate and Glyphosate plus Urea were not harmful only when applied 44 days after flowering. Ammonium Gluphosinate was always harmful to seed quality independently on the moment of application.

No description available.

A decline in the size of fish within a population is concerning. Large-sized fish are ecologically important and valued for social and economic reasons. Following widespread collapses from angling overharvest, the densities of Walleyes Sander vitreus in Albertas lakes increased rapidly with large-minimum-size limits. Anglers were unhappy, however, as catch rates increased (>1 Walleyes*hour-1) but fish remained small and did not exceed the minimum size limit. The two alternate explanations for the small, yet old Walleyes were either compensatory growth because of high density (stunting) or size-selective mortality (overfishing). Size-selective mortality has evolutionary consequences. Paradoxically, the management solutions for these problems are in opposition (more harvest versus less harvest), and a wrong diagnosis could exacerbate the problem. I used nested hypotheses, and implemented active adaptive management at several Alberta lakes, to diagnose the causal mechanism creating the small fish problem. For inferences on the source of the mortality, I analysed backcalculated growth rates from pelvic fins. Walleyes that had fast-growth to an early maturity, and then subsequent slow-growth, had greater survival. This hockey stick-shaped growth allows for successful reproduction while the Walleyes remain below the minimum size limit, avoiding harvest. Using changes to sport fishing regulations, I then modified angler effort and harvest at four different Alberta lakes to increase or decrease size-selective harvest and Walleye densities. I found that size-selective mortality from angling rapidly truncated the population-size structure. With concerns of evolutionary consequences because of evidence of size selective harvest, I used an age- and size-structured, single-species model, parameterized with data from Albertas Walleye fisheries, to evaluate the selectiveness of various management regulations. I found that the 50-cm minimum size limit used to recover Albertas Walleye populations did indeed select for the hockey stick life history, although this regulation allowed for sustainable populations (>5 Walleyes*hectare-1) and angler effort up to 16 angler-hours*ha-1*year-1. The optimal regulation to reduce life history selection and allow for population sustainability was a 40-50 cm harvest-tag regulation. This regulation reversed the selection for the hockey stick life history, yet produced sustainable fish densities and allowed angler effort up to 30 angler-hours*ha-1*year-1. However, increasing angler-noncompliance reduced the sustainability of this regulation. / Wildlife Ecology and Management

Kangaroo paw inflorescences stored dry at 0 to 1 Degrees Celsius for 14 days have been found previously to have substantially reduced post-storage vase life. In this project, experiments were conducted to quantify the vase life of dry, stored Kangaroo paw flowers following storage at either 0, 7.5 or 13 Degrees Celsius for up to four weeks. the aim of these experiments was to determine a dry storage temperature suitable for commercial use. experiments were carried out using two cultivars of Kangaroo paw, 'Bush Dawn' and 'Big Red'. For each cultivar, vase life was assessed by (1) determining the time taken for each flower to lose 20% of its initial fresh weight and (2) determining the time taken for 10% of the inflorescence to become to discoloured. Vase life studies were carried out a 22 Degrees Celsius prior to and following removal from low temperature storage and flowers were weighed, inflorescence colour determined and chlorophyll fluorescence parameters Fo, minimal fluorescence emission, and Fm, maximum fluorescence emission were determined.

O presente trabalho trata do estudo do fatiamento de cristais de quartzo quanto as suas características e influências na fabricação de micro sistemas eletromecânicos (MEMS). A metodologia é iniciada pelo projeto estruturado de um MEMS, convergindo para um gerador energia elétrica do tipo energy harvest, capaz de gerar energia limpa, renovável, de escala reduzida (micro componente), de baixa potência e com vistas para aplicação comercial. Geração de energia tem se tornado um tema cada vez mais frequente, em especial energia para sistemas autônomos (wireless) aonde o uso de baterias é restritivo ou até mesmo inviável devido às dimensões e dificuldade de manutenção. A fabricação de MEMS é a etapa de maior investimento financeiro e por consequência, maior estudo. No caso do gerador de energia, a ênfase recai sobre os processos de corte, que consomem a maior parte do processo fabril. O objetivo do presente trabalho é avaliar o processo de corte abrasivo do quartzo e a influência dos defeitos impregnados pelo processo, sobre o desempenho de geradores de energia piezelétricos baseados em quartzo sintético e natural. Os processos de corte com uso de fita abrasiva (band saw) e disco abrasivo (dicing saw) se destacaram devido aos bons resultados, disponibilidade, produtividade e baixo custo. Procedimentos de corte também foram realizados em outros materiais - Alumina Policristalina 99,8% e Silício (111) - como estudo comparativo das características do mecanismo de remoção de material aplicado aos processos de corte abrasivos. Os parâmetros de corte foram trabalhados em busca de melhor qualidade, que significa redução da impregnação de falhas (principalmente, o chipping e backside chipping) e melhor acabamento das superfícies geradas pelo corte final. Foram obtidas peças nos planos AT, X, Y e Z, com espessuras a partir de 0,5 mm, segmentadas em larguras de 1 a 7 mm. / This work is a study of characteristics and influences of cutting process in manufacturing of microelectromechanical systems (MEMS) based on quartz single crystal. The methodology starts by the structured design of a MEMS device, converging to an electric power generator device, type energy harvest that generates clean energy, renewable, with small dimensions (micro component) and low power. Power generating has become a frequent topic, especially the power generation for wireless devices systems, which use of batteries can be restrictive or even impracticable because of dimensions and difficult of maintenance. The base of the study is the process manufacturing of MEMS, which is the major investment and because of this, the most studied stage. In the case of a power generator, the emphasis is on the cutting process that consumes most part of the work flow. The objective of this work is evaluate the abrasive cutting process of quartz and the influence of defects generated by the cutting process applied to the performance of piezoelectric power generators based on synthetic and natural quartz crystal. The abrasive cutting process of band saw and dicing saw were featured due availability and high productivity with low cost. Procedures of cutting were also applied in other materials - Alumina Polycrystalline 99,8% and Silicon (111) - as comparison for material removal mechanism in cutting process. The process parameters were optimized to reach better cutting quality, which means reduction in faults (mainly, chipping and backside chippings) and better surface finishing from cutting process. It was obtained pieces from AT, X, Y and Z cutting plans, with thickness starting from 0,5 mm and widths from 1 to 7 mm.