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Full-Text Articles in Life Sciences
Creating Virtual Wood Particulate Composites, Huaijun Wang
Creating Virtual Wood Particulate Composites, Huaijun Wang
Electronic Theses and Dissertations
Wood particulate composites are inhomogeneous, short fiber materials. The behavior of such materials depends on the properties of the constituent elements (wood particles, fibers, and adhesives) and the manner in which they are organized (the microstructure). Research on the microstructure of these composites has been carried out for several decades. However, due to the complexity of the engineered structures, most existing works are either over-simplified or lacking in general representations. While experimental approaches to improve material performance are necessary, this thesis presents another approach for better depictions of such complex systems. In this research project, digital surrogates of the composite …
Distribution And Impact Of The Oyster Parasite Bonamia Ostreae In Maine, And Its Detection Using Dna Probes, Ryan Carnegie
Distribution And Impact Of The Oyster Parasite Bonamia Ostreae In Maine, And Its Detection Using Dna Probes, Ryan Carnegie
Electronic Theses and Dissertations
Health management efforts in Maine related to the flat oyster (Ostrea edulis) parasite Bonamia ostreae are limited by a lack of knowledge of the parasite’s distribution and impact in both wild and cultured populations. This information would be more readily obtainable with improved diagnostic tools. The objectives of this dissertation were to design sensitive and specific DNA probes for detection of B. ostreae; to assess the prevalence and intensity of parasite infections in wild oyster populations in Maine; and to evaluate growth and mortality of cultured oysters in the Damariscotta River, where B. ostreae is enzootic. A polymerase …
Leaf Area, Stemwood Volume Growth, And Stand Structure In A Mixed-Species, Multi-Aged Northern Conifer Forest, Laura Kenefic
Leaf Area, Stemwood Volume Growth, And Stand Structure In A Mixed-Species, Multi-Aged Northern Conifer Forest, Laura Kenefic
Electronic Theses and Dissertations
Tree- and stand-level leaf area (LA) - stemwood volume growth relationships were explored in mixed-species, multi-aged northern conifer stands dominated by Tsuga canadensis (L.) Carr. (eastern hemlock), Abies balsameu (L.) Mill. (balsam fir), and Piceu rubens Sarg. (red spruce). A T. cunudensis LA model was developed to supplement published equations for A. bulsumeu and P. rubens. Sapwood area was an effective T. cunudensis LA surrogate, though nonsapwood-based models using stem cross-sectional area and modified live crown ratio produced results comparable to sapwood-based models. Equations for predicting tree-level stemwood volume increment (AVINC) were derived, and implied growth efficiencies (GE) were …
Factors Influencing Net Primary Production In Red Spruce, Michael Day
Factors Influencing Net Primary Production In Red Spruce, Michael Day
Electronic Theses and Dissertations
Management of forest resources, even when practiced at the scale of ecosystems, is implicitly based on managing photosynthetic acquisition of carbon by trees. This thesis examines several aspects of carbon balance at the scale of individual trees, using red spruce (Picea rubens Sarg.) as a model species. Age-related declines in net primary productivity have been described for many species, including red spruce. A potential explanation is that ontogenetic changes in meristems lead to lower photosynthetic rates, which was confirmed here for red spruce. A grafting study used scions from juvenile, 6Oy, and 120~ trees to demonstrate that age-related morphological …
Weed Population Dynamics In Potato Cropping Systems As Affected By Rotation Crop, Cultivation, And Primary Tillage, Silke Ullrich
Weed Population Dynamics In Potato Cropping Systems As Affected By Rotation Crop, Cultivation, And Primary Tillage, Silke Ullrich
Electronic Theses and Dissertations
Reduction of dependence on herbicides in potato production is important to limit environmental contamination and reduce production costs. An experiment was conducted from 1992 to 1997 in northern Maine to examine the effects of two rotation crops (a green-manure mixture of oat, pea and hairy vetch vs. barley) and two tillage practices (chisel vs. moldboard) on weed population dynamics in two-year potato rotations without the use of herbicides. Chenopodium album, Gnaphalium uliainosum, and a complex of cruciferous weeds (Brassica rapa, Brassica kaber, and Raphanus raphanistrum) were dominant. Oat-pea-vetch was more weed-suppressive than barley, however, crucifer density increased in both rotations. …
Evaluating The Durability Of Wood/Frp Bonds Through Chemical Kinetics Using A Range Of Mechanical Test Methods, Jonathan Philip Alexander
Evaluating The Durability Of Wood/Frp Bonds Through Chemical Kinetics Using A Range Of Mechanical Test Methods, Jonathan Philip Alexander
Electronic Theses and Dissertations
Hybrid composites of wood and fiber reinforced polymers (FRP) exhibit a flexibility of design properties through choices in fiber type, amount, orientation and resin type. With this flexibility comes the need to measure the durability of the composite material system, especially the bond between these two materials due to their markedly different responses to moisture. This study is two-fold; the first section examines methods for the mechanical testing and durability of wood/FRP laminations. Six mechanical tests were evaluated and a modified block shear method was identified as the most suitable due to its ability to provide representative results independent of …