12 research outputs found

    Considering Duty in Take-Home Asbestos Exposure Cases

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    Comparison of the Hygrothermal Properties of Mechanically Fastened and Adhesive Bonded Wood-Fiber Insulated Panels

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    This study aimed to characterize the hygrothermal and material, i.e., physical and mechanical, properties of wood fiber insulation (WFI) that can be an alternative to fossil-based building insulation, targeting structural insulated panels, retrofit insulated panels, and a novel all wood structural insulated panel. The hygrothermal properties of rigid WFI boards with varying densities, 110, 140, and 180 kg/m3, and one 140 kg/m3 without paraffin wax treatment were evaluated following relevant ASTM standards. The hygrothermal properties measured were, porosity, water vapor transmission, liquid water absorption, and thermal conductivity at varying temperatures. Additionally, the Tensile strength and block shear strength of WFI bonded to lumber, OSB, and WFI was evaluated using three different structural adhesives to select one adhesive for further prototyping. The porosity of the WFI varied from 85-92% and is primarily impacted by density and not the presence of wax in the composite. The permeability of the WFI ranged from 65 ng·s-1m-1Pa-1 to 90 ng·s-1m-1Pa-1 depending on the samples’ density. Liquid water absorption on a % volume basis ranged from 2.5 – 20%, both wax and density were impactful to the results. Thermal conductivity coefficient (λ), ranged from .038 - .055 W/(m·K) depending on moisture content, average temperature, and density. 140 kg/m3 WFI with wax was selected as a representative material for the mechanical property testing of WFI laminated to other substrates. The tensile-perpendicular to grain bond strength was 10-16 kPa with substrate being more impactful than adhesive type. The shear strength was 60-90 kPa again with substrate being more impactful than adhesive type. For all tests the primary failure occurred within the insulation substrate illustrating the strength of the composite was not controlled by the adhesive layer but instead the insulation lamina itself. The results of this body of work establish that all wood structural insulated panels have the potential to succeed when used properly as a component of novel bio-based buildings based on their competitive hygrothermal properties and no immediate issue presented in using construction adhesives to manufacture the panels. However, the work also shows that bio-based materials are variable and complex in their composition and interaction with the environment. Rigorous testing will be required to fully predict how WFI will perform in-situ in various climates and in more complex assemblies. The built environment is one of the leading contributors to global CO2 emissions and this margin is projected to grow. The materials that are used to construct a building are a major component of the associated carbon of a building. They represent the majority of embodied carbon and contribute to the rate at which operational carbon is generated. High performance, renewable, and carbon sequestering materials will be critical as the world continues to develop and demand more housing. This study reports the continuation of the development of a wood fiber-insulated panel (WIP) that offers a high-performance envelope without requiring hydro-carbon materials, by utilizing an all-wood design constructed with adhesives as opposed to mechanical fasteners. This design eliminates the cost and thermal reduction associated with the fasteners while retaining thermal performance. To this end, a WIP prototype was developed and manufactured along with two control wall assemblies: a similar wall assembly to the WIP with fasteners instead of adhesive (to laminate the WIP components), and an assembly made with polystyrene insulation. These assemblies were then evaluated in a simulated winter environment in climate zone 6A for hygrothermal performance. Temperature, relative humidity, and moisture content data were collected throughout the panels, and heat flux measurements were used to evaluate the impact of the fastener penetrations on thermal bridging. The WIP panels were found to perform as well or better than the control panels when evaluated for moisture interactions and insulative performance. Primarily, the use of structural adhesives within the assembly did not create a location where moisture accumulated. The mechanically fastened wood insulated panels performed well and managed bulk moisture very effectively. The polystyrene insulated panels performed well thermally but had high moisture levels between layers of insulation. Through these results it can be seen that a prefabricated all-wood panel could be successfully implemented as a high performance and environmentally friendly solution to growing housing demands and the requirements for more efficient buildings. Further analysis of the life cycle of these panels and complex hygrothermal simulations to investigate other potential designs and climate zones will be necessary to further develop this product

    Bonding Performance of the Ten Species in the Spruce-Pine-Fir (South) Lumber Grouping for Cross-laminated Timber

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    Cross-laminated timber (CLT) is an engineered wood product made of three or more orthogonally bonded layers of lumber that are glued together with structural adhesives to form a panel intended for roofs, floors, or walls. Currently, there are no CLT manufacturers in the Northeastern U.S. despite the region having vast forestlands of commercial softwood timber. Sitting atop one of the planet’s largest population centers, Maine is the region’s primary wood basket, the most heavily forested state in the nation (as a percentage of land area) containing over 27 billion cubic feet of wood, i.e., live trees, on its forest land (USDA Forest Service, 2002). For CLT manufacturing in the Northeast, spruce-pine-fir-south (SPF-S) is the target grouping, with five major sawmills in the region producing 500 MMBF of dimensional lumber each year

    Rapid whole genome optical mapping of Plasmodium falciparum

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    <p>Abstract</p> <p>Background</p> <p>Immune evasion and drug resistance in malaria have been linked to chromosomal recombination and gene copy number variation (CNV). These events are ideally studied using comparative genomic analyses; however in malaria these analyses are not as common or thorough as in other infectious diseases, partly due to the difficulty in sequencing and assembling complete genome drafts. Recently, whole genome optical mapping has gained wide use in support of genomic sequence assembly and comparison. Here, a rapid technique for producing whole genome optical maps of <it>Plasmodium falciparum </it>is described and the results of mapping four genomes are presented.</p> <p>Methods</p> <p>Four laboratory strains of <it>P. falciparum </it>were analysed using the Argus™ optical mapping system to produce ordered restriction fragment maps of all 14 chromosomes in each genome. <it>Plasmodium falciparum </it>DNA was isolated directly from blood culture, visualized using the Argus™ system and assembled in a manner analogous to next generation sequence assembly into maps (AssemblyViewer™, OpGen Inc.<sup>®</sup>). Full coverage maps were generated for <it>P. falciparum </it>strains 3D7, FVO, D6 and C235. A reference <it>P. falciparum in silico </it>map was created by the digestion of the genomic sequence of <it>P. falciparum </it>with the restriction enzyme AflII, for comparisons to genomic optical maps. Maps were then compared using the MapSolver™ software.</p> <p>Results</p> <p>Genomic variation was observed among the mapped strains, as well as between the map of the reference strain and the map derived from the putative sequence of that same strain. Duplications, deletions, insertions, inversions and misassemblies of sizes ranging from 3,500 base pairs up to 78,000 base pairs were observed. Many genomic events occurred in areas of known repetitive sequence or high copy number genes, including <it>var </it>gene clusters and <it>rifin </it>complexes.</p> <p>Conclusions</p> <p>This technique for optical mapping of multiple malaria genomes allows for whole genome comparison of multiple strains and can assist in identifying genetic variation and sequence contig assembly. New protocols and technology allowed us to produce high quality contigs spanning four <it>P. falciparum </it>genomes in six weeks for less than $1,000.00 per genome. This relatively low cost and quick turnaround makes the technique valuable compared to other genomic sequencing technologies for studying genetic variation in malaria.</p

    Quorum-Sensing Control of Antibiotic Synthesis in Burkholderia thailandensisâ–ż

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    The genome of Burkholderia thailandensis codes for several LuxR-LuxI quorum-sensing systems. We used B. thailandensis quorum-sensing deletion mutants and recombinant Escherichia coli to determine the nature of the signals produced by one of the systems, BtaR2-BtaI2, and to show that this system controls genes required for the synthesis of an antibiotic. BtaI2 is an acyl-homoserine lactone (acyl-HSL) synthase that produces two hydroxylated acyl-HSLs, N-3-hydroxy-decanoyl-HSL (3OHC10-HSL) and N-3-hydroxy-octanoyl-HSL (3OHC8-HSL). The btaI2 gene is positively regulated by BtaR2 in response to either 3OHC10-HSL or 3OHC8-HSL. The btaR2-btaI2 genes are located within clusters of genes with annotations that suggest they are involved in the synthesis of polyketide or peptide antibiotics. Stationary-phase cultures of wild-type B. thailandensis, but not a btaR2 mutant or a strain deficient in acyl-HSL synthesis, produced an antibiotic effective against gram-positive bacteria. Two of the putative antibiotic synthesis gene clusters require BtaR2 and either 3OHC10-HSL or 3OHC8-HSL for activation. This represents another example where antibiotic synthesis is controlled by quorum sensing, and it has implications for the evolutionary divergence of B. thailandensis and its close relatives Burkholderia pseudomallei and Burkholderia mallei
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