Shear behaviour of bond lines in glued laminated timber beams at high temperatures     

Andrea?FrangiEmail author  Mario?Fontana  Adrian?Mischler 《Wood Science and Technology》2004,38(2):119-126

A comprehensive research project has been carried out at the Swiss Federal Institute of Technology (ETH) on the fire behaviour of timber-concrete composite slabs (Frangi and Fontana 2000). The glued laminated timber beams used for the fire tests were bonded with a one-component polyurethane (1-K-PUR) adhesive. As one fire test on a slab showed an unexpected shear failure of a glued laminated timber beam, a series of tests was carried out to study the shear behaviour of different types of adhesives at high temperatures. The first part of the paper describes the results of the shear tests at elevated temperatures, in the second part the shear test results are compared to the fire test on a slab.  相似文献   

Growth and nut production of black walnut in relation to site, tree type and stand conditions in south-central United States     

Adrian Ares  David Brauer 《Agroforestry Systems》2004,63(1):83-90

Black walnut (Juglans nigra) is a prime tree species for agroforestry practices in the United States providing highly prized wood and nuts for human consumption and wildlife. In 54 black walnut stands in south central United States, the site index (i.e., mean dominant height [DH], at age 25 years) ranged between 5.2 and 21.4 m, and was independent of stand density. There were no differences in height and stem diameter (DBH) growth rates between stands with improved varieties and native stock. Most stands were in a “free growth” stage because of either early age or wide spacing. Mean annual increments in DBH and height were positively related both for improved varieties and native stock. Understory competition had a substantial detrimental effect on DH. In a 26 year-old stand, trees growing within Kentucky blue grass (Poa pratensis) had a site index 5 m greater than trees growing within tall fescue (Festuca arundinacea). Predicted nut yields in 2002 varied between 0 and 1370 kg of hulled nuts per ha. Improved varieties had, in general, higher nut yields than predicted from a nut yield-DBH equation developed for individual trees. Nut yields were highly variable both within and among stands, and were related to DBH in native stock but not in improved varieties.  相似文献   

Television food advertising to children: the extent and nature of exposure     

Kelly B  Smith B  King L  Flood V  Bauman A 《Public health nutrition》2007,10(11):1234-1240

OBJECTIVE: To describe the pattern and prevalence of food and drink advertisements to children on commercial television in Sydney, Australia, and compare these with advertising regulations set out in the Children's Television Standards and results from a similar study in 2002. DESIGN: Data were collected by recording television from 06.00 hours until 23.00 hours on all three commercial channels from Sunday 14 May 2006 to Saturday 20 May 2006 (357 h). The study analysed advertisements in two children's viewing periods, one as defined in the 2002 study and the other according to current standards. Food advertisements were coded using 18 food categories and were analysed by time period and popular children's programmes. RESULTS: Food advertisements occurred in similar proportions during children's viewing hours and adult's viewing hours (25.5 vs. 26.9% of all advertisements, respectively), although there was a higher rate of high-fat/high-sugar food advertisements during children's viewing hours (49 vs. 39% of all food advertisements, P < 0.001). There were even more advertisements for high-fat/high-sugar foods during popular children's programmes, contributing to 65.9% of all food advertisements. Estimates of exposure indicate that children aged 5-12 years were exposed to 96 food advertisements, including 63 high-fat/high-sugar advertisements per week. Since 2002, there has been a reduction in overall food and high-fat/high-sugar food advertisements.CONCLUSION: Despite reductions in overall levels of food advertising, children continue to experience high levels of exposure to food advertisements, which remain skewed towards unhealthy foods. Further food advertising regulation should be required to curtail the current levels of advertising of high-fat/high-sugar foods to children, to make them commensurate with recommended levels of consumption.  相似文献   

Mast cells can enhance resistance to snake and honeybee venoms     

Metz M  Piliponsky AM  Chen CC  Lammel V  Abrink M  Pejler G  Tsai M  Galli SJ 《Science (New York, N.Y.)》2006,313(5786):526-530

Snake or honeybee envenomation can cause substantial morbidity and mortality, and it has been proposed that the activation of mast cells by snake or insect venoms can contribute to these effects. We show, in contrast, that mast cells can significantly reduce snake-venom-induced pathology in mice, at least in part by releasing carboxypeptidase A and possibly other proteases, which can degrade venom components. Mast cells also significantly reduced the morbidity and mortality induced by honeybee venom. These findings identify a new biological function for mast cells in enhancing resistance to the morbidity and mortality induced by animal venoms.  相似文献   

Physics. High-temperature superconductors feel the vibe after all     

Cho A 《Science (New York, N.Y.)》2006,313(5787):602

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Nanotechnology. Pretty as you please, curling films turn themselves into nanodevices     

Cho A 《Science (New York, N.Y.)》2006,313(5784):164-165

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High-energy physics. A quiet leader unites researchers in drive for the next big machine     

Cho A 《Science (New York, N.Y.)》2006,312(5777):1128-1129

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Nuclear physics. Scheme for boiling nuclear matter gathers steam at accelerator lab     

Cho A 《Science (New York, N.Y.)》2006,312(5771):190-191

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Structural basis for double-stranded RNA processing by Dicer     

Macrae IJ  Zhou K  Li F  Repic A  Brooks AN  Cande WZ  Adams PD  Doudna JA 《Science (New York, N.Y.)》2006,311(5758):195-198

The specialized ribonuclease Dicer initiates RNA interference by cleaving double-stranded RNA (dsRNA) substrates into small fragments about 25 nucleotides in length. In the crystal structure of an intact Dicer enzyme, the PAZ domain, a module that binds the end of dsRNA, is separated from the two catalytic ribonuclease III (RNase III) domains by a flat, positively charged surface. The 65 angstrom distance between the PAZ and RNase III domains matches the length spanned by 25 base pairs of RNA. Thus, Dicer itself is a molecular ruler that recognizes dsRNA and cleaves a specified distance from the helical end.  相似文献   

Preclinical dilated cardiomyopathy in the dobermann     

Summerfield N  Dukes-McEwan J  Swift S  Patteson M  Wotton P  Martin M  Johnson M  Boswood A  Fuentes VL  French A  Culshaw G  Little C  Smith P  Smith S  Willis R 《The Veterinary record》2006,158(21):742-743

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