Strength and Stiffness of Laminated Douglas-Fir Blocks in Perpendicular-To-Glueline Tension

Blocks of commercial glued-laminated Douglas-fir were tested to failure in tension perpendicular-to-gluelines. The results of a two-level factorial experiment indicated that blocks 22 inches in length were weaker in strength than blocks 7 inches in length and that blocks of 5- X 5-inch cross section were weaker than blocks 3 X 3 inches. Additional longer specimens were tested to provide better estimates of their ultimate strength.The average modulus of elasticity of 3- X 3-inch blocks was about 70,000 psi. Undetected ring shake caused early failure of some specimens, indicating that this natural characteristic might be responsible for unexplained failures of beams in service.According to Weibull, specimen size affects material strength. To confirm application of his work to these tests, additional blocks of three other configurations were tested for strength. An assumption of a log-log relation as hypothesized by Weibull is acceptable. Test results of other researchers found from similar specimens show no noticeable deviation from the relationship

Strength and Deformation of Pitched-Tapered Douglas-Fir Glued-Laminated Beams

Strength tests were conducted on 12 pitched-tapered beams. Four of these beams failed in radial tension, the estimated maximum stress levels ranging from 176 to 286 psi. The other beams failed in bending at the extreme fiber. In all cases, the load-deflection and load-strain responses were linear to failure under short-term loading conditions. The radial strengths were marginally acceptable at the allowable unit stress level currently assigned in Canada for tension perpendicular-to-the-grain. Other studies on size effect suggest that working stress levels should be governed by the volume of wood subjected to perpendicular-to-glueline tensile stress

Large coronary arteries in humans are responsive to changing blood flow: An endothelium-dependent mechanism that fails in patients with atherosclerosis

AbstractChanges in blood flow can alter vasomotion of conduit arteries. This study examined vasomotor responses to incremental blood flow induced by papaverine in the epicardial arteries of 10 patients with angiographically normal coronary arteries (group 1) and in 14 patients with arterial irregularities (group 2) using quantitative angiography and Doppler ultrasound flow velocity measurements. An increase in coronary blood flow of 384.3 ± 32.8% (p < 0.001) in group 1 patients was associated with dilation of the proximal coronary artery segment and a 23.2 ± 4.6% increase in cross-sectional area (p < 0.001). In contrast, in group 2 patients a similar increase in coronary blood flow of 339.3 ± 18.7% (p < 0.001) was associated with mixed responses and a Modest net constriction in cross-sectional area of -7.4 ± 2.8% (p < 0.05). The dilation response to nitroglycerin was intact in group 1 (31.7 ± 4.2%, p < 0.001) and in group 2 (26.4 ± 3.2%, p < 0.001).In five patients from group 1 acetylcholine, an endothelium-dependent dilator, produced an increase in cross-sectional area of 20.7 ± 4.6% (p < 0.05) that paralleled the response to an increase in flow in the same segment (a 24.3 ± 6.1% increase in cross-sectional area, p < 0.05). Five group 21 patients demonstrated a vasoconstrictor response to acetylcholine (a − 22.8 ± 3.4% decrease in cross-sectional area, p < 0.05) together with an impaired dilation response to incremental flow (a − 6.4 ± 3.2% decrease in cross-sectional area). Thus, the normal flow-mediated dilation of coronary arteries is lost in atherosclerosis and this impairment may be due to endothelial cell vasodilator dysfunction

Inhibition of electrogenic anion entry into rat liver mitochondria by N,N'-dicyclohexylcarbodiimide

AbstractThe carboxyl group reagent dicyclohexylcarbodiimide inhibits the electrogenic entry of Cl− and NO3− into rat liver mitochondria at alkaline pH. The inhibition is time dependent and 50% inhibition is obtained by the addition of 3–4 nmol DCCD/mg protein. The blockage of the pH-dependent anion-conducting pore appears to be unrelated to the other known actions of DCCD on rat liver mitochondria but seems similar to its effect on the uncoupling protein of brown adipose tissue

Global value chains and human development: a class-relational framework

Global Value Chain proponents argue that regional and human development can be achieved through ‘strategic coupling’ with transnational corporations. This argument is misleading for two reasons. First, GVC abstracts firm-firm and firm-state relations from their class-relational basis, obscuring fundamental developmental processes. Second, much GVC analysis promotes linear conceptions of development. This article provides a class-relational framework for GVC analysis. The formation and functioning of GVCs and the developmental effects associated with them are products of histories of evolving and often conflictive, class relations. A study of export horticulture in North East Brazil provides empirical support for these arguments

Encoded

ENCODED is an immersive aerial dance performance and installation that uses the latest interactive technologies to build a projected digital environment that responds to the movements of the performers

Deglacial grounding-line retreat in the Ross Embayment, Antarctica, controlled by ocean and atmosphere forcing

Modern observations appear to link warming oceanic conditions with Antarctic ice sheet grounding-line retreat. Yet, interpretations of past ice sheet retreat over the last deglaciation in the Ross Embayment, Antarctica’s largest catchment, differ considerably and imply either extremely high or very low sensitivity to environmental forcing. To investigate this, we perform regional ice sheet simulations using a wide range of atmosphere and ocean forcings. Constrained by marine and terrestrial geological data, these models predict earliest retreat in the central embayment and rapid terrestrial ice sheet thinning during the Early Holocene. We find that atmospheric conditions early in the deglacial period can enhance or diminish ice sheet sensitivity to rising ocean temperatures, thereby controlling the initial timing and spatial pattern of grounding-line retreat. Through the Holocene, however, grounding-line position is much more sensitive to subshelf melt rates, implicating ocean thermal forcing as the key driver of past ice sheet retreat