993 resultados para Hubbard, Christopher
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Kirjallisuusarvostelu
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Kirjallisuusarvostelu
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Kirjallisuusarvostelu
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The leaf essential oils of Eugenia lutescens Cambess andEugenia langsdorffii O. Berg, collected in the rainy (RS) and dry seasons (DS), were extracted by hydrodistillation and then characterized by a gas chromatography-flame ionization detector and a gas chromatography-mass spectrometer. The potential acaricidal activity and oviposition deterrence of these oils were evaluated against Tetranychus urticae . The oil yields were higher in the RS for E. lutescens, while those forE. langsdorffii were higher in the DS. α-Pinene and β-pinene were determined to be the major constituents of the oils fromE. lutescens, while bicyclogermacrene, spathulenol, and β-caryophyllene predominated in E. langsdorffii . Seasonal variations in the oils were primarily related to chemical diversity, and E. lutescens was more affected than was E. langsdorffii . The E. langsdorffii oil collected in the DS was most toxic to the spider mite, while the oils of E. lutescens and E. langsdorffii collected in the RS drastically reduced its egg quantities. This study successfully determined the periods of greater oil production and acaricidal activity.
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Kirjallisuusarvostelu
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Neste trabalho avaliou-se a resistência à corrosão em solução salina das fases presentes na microestrutura de amálgamas dentários comerciais: gama1-Ag2Hg3, o eutético Ag-Cu e gama2-Sn7-8Hg, empregando-se técnicas eletroquímicas de potencial a circuito aberto com o tempo, de polarização potenciodinâmica e de espectroscopia de impedância eletroquímica. As ligas metálicas em estudo já foram caracterizadas em um trabalho prévio, por meio de microscopia eletrônica de varredura e difratometria de raios X. A resistência à corrosão se origina da formação de filmes passivos na superfície metálica e parece estar determinada pela natureza rugosa e porosa das superfícies.
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Kirjallisuusarvostelu
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Kirjallisuusarvostelu
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The etiology and epidemiology of Pythium root rot in hydroponically-grown crops are reviewed with emphasis on knowledge and concepts considered important for managing the disease in commercial greenhouses. Pythium root rot continually threatens the productivity of numerous kinds of crops in hydroponic systems around the world including cucumber, tomato, sweet pepper, spinach, lettuce, nasturtium, arugula, rose, and chrysanthemum. Principal causal agents include Pythium aphanidermatum, Pythium dissotocum, members of Pythium group F, and Pythium ultimum var. ultimum. Perspectives are given of sources of initial inoculum of Pythium spp. in hydroponic systems, of infection and colonization of roots by the pathogens, symptom development and inoculum production in host roots, and inoculum dispersal in nutrient solutions. Recent findings that a specific elicitor produced by P. aphanidermatum may trigger necrosis (browning) of the roots and the transition from biotrophic to necrotrophic infection are considered. Effects on root rot epidemics of host factors (disease susceptibility, phenological growth stage, root exudates and phenolic substances), the root environment (rooting media, concentrations of dissolved oxygen and phenolic substances in the nutrient solution, microbial communities and temperature) and human interferences (cropping practices and control measures) are reviewed. Recent findings on predisposition of roots to Pythium attack by environmental stress factors are highlighted. The commonly minor impact on epidemics of measures to disinfest nutrient solution as it recirculates outside the crop is contrasted with the impact of treatments that suppress Pythium in the roots and root zone of the crop. New discoveries that infection of roots by P. aphanidermatum markedly slows the increase in leaf area and whole-plant carbon gain without significant effect on the efficiency of photosynthesis per unit area of leaf are noted. The platform of knowledge and understanding of the etiology and epidemiology of root rot, and its effects on the physiology of the whole plant, are discussed in relation to new research directions and development of better practices to manage the disease in hydroponic crops. Focus is on methods and technologies for tracking Pythium and root rot, and on developing, integrating, and optimizing treatments to suppress the pathogen in the root zone and progress of root rot.
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Dedicated to: Carl Cronstedt, Carl Gustaf Tessin, Theodor Ankarkrona, Otto Reinhold Wrangel, Olof Sandberg, Jacob von Hökerstedt, Carl von Groot, Carl Friedrich Piper, Olof von Törne, Petter Drufwa, Johan Löwen, Swen Cederström, Johan Maurits Klinkowström, Leonhard Klinkowström, Reinholdt Berndt Hauswolff, Christopher Christopherssen, Johan Williamsson, Olof Malmer, Johan Adam Petersson, Gustaf Kierman, Anders Plomgren.
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Dedicated to: Jacobus Benzelius, Theodorus Ankarcrona, Matthias Grunerus, Olaus Thorin, Andreas Backman, Martinus Jonae Friberg, Carolus Gustavus Hallman, Andreas Sylvanus, Daniel P. Mansnerus, Daniel Lindqvist.
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Bound in: Dissertatio historica de paroecia Alandiae Lemland, eique annexa Lumparland / Daniel Ferdinandus Mallén. Aboae : typis Frenckellianis, [1792]
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P. 143-158 are misnumbered 142-157.
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Dedicated to: Pontus de la Gardie, Ephraim Otto Runeberg, Johan Billmark, Carl Joh. Bäckman, Lars Blom, Nathanael Häggström, Matths Nyman, Anders Biring, Anders Winstefn, Petter Teliin, Carl Malm.
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Dedicated to: Joanni Steuchio, Johanni Brauner, Stenoni Carolo Bielke, Maurits Wilhelm Nisbeth, Erico Klint, Gideoni Bille, Petro Bergdahl, Gudmundo Rothovio.