1,437 research outputs found
Non-proportional loading for 3-D stress situations in sequentially linear analysis
No full textThis article presents a new non-proportional loading strategy for Sequentially Linear Analysis (SLA), which is a robust secant stiffness based procedure for nonlinear finite element analysis of quasi-brittle materials, like concrete and masonry. The strategy is based on finding the principal planes for a total strain based fixed cracking model, by searching for the critical plane where the normal stresses due to the scaled combination of two non-proportional loads is equal to the allowable strength. For a plane stress situation (2D), the scaling factor λ is ex-pressed as a function of θ, the inclination of an arbitrary plane to the reference coordinate system, and a one dimensional (θ) optimization of λ is done to determine the principal plane and the resulting fixed crack coordinate system. This approach has been illustrated to match up to the closed form solution, obtained previously based on the principal stress theory, using single element tests and a quasi-static test pushover test on a masonry shear wall. Finally, the concept for the 3-D stress situation is presented, where the optimization problem becomes two-dimensional, with respect to l and m (two-directional cosines).Applied MechanicsStructural Design & Mechanic
Coordination-dependence of hyperfine interactions at impurities on fcc metal surfaces. II. Magnetic hyperfine field
No full textWe present a comparison between ab initio calculations and a high-quality experimental data set (1990–2002) of magnetic hyperfine fields of Cd at different sites on Ni surfaces. The experimentally observed parabolic coordination number dependence of this hyperfine field is verified as a general trend, but we demonstrate that individual cases can significantly deviate from it. It is shown that the hyperfine fields of other 5sp impurities at Ni surfaces have their own, typical coordination number dependence. A microscopic explanation for the different dependencies is given in terms of the details of the s-DOS near the Fermi level
Coordination dependence of hyperfine interactions at impurities on fcc metal surfaces. I. Electric-field gradient
No full textWe present a comparison between accurate ab initio calculations and a high-quality experimental data set (1986-2002) of electric-field gradients of Cd at different sites on Ni, Cu, Pd, and Ag surfaces. Experiments found a systematic rule to assign surface sites on (100) and (111) surfaces based on the main component of the electric-field gradient, a rule that does not work for (110) surfaces. Our calculations show that this particular rule is a manifestation of a more general underlying systematic behavior. When looked upon from this point of view, (100), (111) and (110) surfaces behave in precisely the same way. The physical mechanism behind the systematics of the EFG for other 5sp impurities (Cd-Ba) at different fcc surfaces sites is revealed, showing in a natural way why the first half of the 5p elements shows a coordination dependence that is opposite with respect to the second half
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The Etiology and Control of Root and Stem Rots of Peas in Washington
No full textTopics include: Introduction; Nature and importance of root and stem rots of peas; Cause of root and stem rots of peas; Control experiments; Discussion; Summary; Literature cite
Effect of short hypobaric treatments on postharvest rots of sweet cherries, strawberries and table grapes
No full textThe effectiveness of short hypobaric treatments against postharvest rots was investigated by exposing sweet cherries, strawberries and table grapes to sub-atmospheric pressures (0.25, 0.50, and 0.75 atm) for different times (from 1 to 24 h). Postharvest rots of sweet cherries and strawberries arose from natural infections, whereas small table grape bunches and artificially wounded single berries were inoculated with Botrytis cinerea after hypobaric treatment. Sweet cherries exposed to 0.50 atm for 4 h had the lowest incidence of gray mould, brown rot and total rots, while a 1 h treatment was not effective. On strawberries, the greatest reductions of gray mould and Rhizopus rot were observed on fruits treated for 4 h at 0.25 and 0.50 atm, respectively. On table grape bunches treatment with 0.25 atm applied for 24 h significantly reduced the incidence of gray mould. In experiments performed with artificially wounded single table grape berries exposed to 0.50 atm for 24 h and then inoculated, the percentage of infected fruits and the diameter of the lesions were significantly reduced, in comparison with the controls. As a sub-atmospheric pressure of 0.25 atm did not affect radial growth of B. cinerea and Monilinia laxa, induced resistance was likely to be responsible for the observed reduction in decay. (C) 2001 Elsevier Science B.V. All rights reserved
The contribution of stone tool residues in reconstructing Late Pleistocene hominin stone tool behaviour at Grotta di Fumane, Italy
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Reduction of gray mold development in table grapes by preharvest sprays with ethanol and calcium chloride.
No full textPreharvest applications of a 16% ethanol (EtOH) solution, containing 1 % of calcium chloride (CaCl2), reduced gray mold development in ‘Chasselas’ table grapes picked at a late harvest date, the losses due to rotten clusters dropped from 15% in controls to 5% in grapes treated with EtOH+CaCl2. Then over a 6-week cold storage, the losses due to gray mold rots were reduced by 50% when storing EtOH+CaCl2 treated clusters, compared to untreated controls. Preliminary experiments had shown that a 2% EtOH solution was already inducing significant drop of gray mold growth. A range of concentrations up to 50% ethanol had been tested in preliminary trials without observing damages to the vines and clusters. The treatments did not induce significant changes to the fruit quality assessed by sensory analyses on healthy berries
Scraping hide in the early Upper Paleolithic: insights into the life and function of the Protoaurignacian endscrapers at Fumane cave
No full textEndscrapers are specialized tools that are usually recovered in great quantities in every Upper Paleolithic site in Europe. Although they make their first ephemeral appearance in the Middle – late Middle Paleolithic transitional technocomplexes, endscrapers commonly appear in tool-kits from initial and early Upper Paleolithic traditions onwards. Nevertheless, endscrapers and, in general, domestic tools have attracted relatively little attention in debates revolving around the significance of technological change, tool-function and tool-specialization after the end of the Middle Paleolithic. With the aim to overcome this paucity of information, here, we present the results of a techno-functional study performed on the large endscraper assemblage recovered from the early and late Protoaurignacian layers at Fumane Cave in northeastern Italy. We analyzed these artefacts using technological, morpho-metrical, typological and functional approaches. Despite the large morphological variability, use-wear traces reveal functional consistency and high levels of specialization for these tools. Almost all the use-wear traces we recorded developed from hide working with transverse motion. Moreover, we find no evidence that endscrapers were involved in the production of bone and antler tools during the late Protoaurignacian. Macroscopic and microscopic wear on the lateral edges of tools point to a considerable number of hafted endscrapers, which implies systematic time investment and planning depth. Comparison with the few endscrapers from transitional industries that have been analyzed highlights marked differences in the production, morphology and use of these tools and reinforces our view of the Aurignacian as a complex not directly related with preceding European traditions
Control of peanut root and pod rots diseases using certain bioagents
No full textTo evaluate the potential of certain bacterial and fungal bioagents against Macrophomina phasolina, Rhizoctonia solani and Fusarium oxysporum which causing peanut root and pod rots diseases. Thirty three fungal isolates obtained from infected plants showing typical symptoms of peanut root and pod rot, collected from different localities in Assiut, Sohag and Minia governorates, Egypt were identified as R. solani, M. phaseolina, F. solani, Aspergillus niger, A. flavus, F. moniliforme, F. equesti and F. semitectum. Pathogenicity tests showed that M. phaseolina No. 4 recorded was the most pathogenic as incited root-rot and pod rot on the tested peanut cultivars NC followed by R. solani No. 6 and F. solani No. 7. Under laboratory conditions, twelve isolates of bacterial bioagents i.e Bacillus subtilis (BS1 and BS2), Bacillus megaterium (BM1 and BM2), Penibacillus polymyxa BP, Pseudomonas fluorescens (PF1 and PF2) and Azotobacter spp. (AZ1, AZ2, AZ3, AZ4 and AZ5), as well as, six isolates of Trichoderma spp. (T5, T7, T8, T9, T10 and T34) were tested to study their effects against the mycelial growth of the causal pathogens isolates i.e. M. phaseolina No. 4, R. solani No. 6 and F. solani No. 7. In vitro, our results showed that seven bacterial isolates (B. subtilis BS1, B. megaterium BM2, B. polymyxa BP, P. fluorescense (PF1 and PF2), Azotobacter spp. (AZ2 and AZ5)) and three isolates of Trichoderma spp. (T7, T10 and T34) gave the highest significant antagonistic effects against the test pathogens. The ten bioagents isolates which exhibited the best inhibition to the pathogenic fungi in vitro were tested in vivo during 2019 and 2020 growing seasons and the results revealed that Trichoderma spp. T34, B. subtilis BS1, P. polymyxa BP, Azotobacter spp. AZ2, B. megaterium BM2 and Trichoderma spp. T10, which tested against M. phaseolina, R. solani and F. solani, gave the highest reduction of both peanut root and pod rots diseases
Projectile points vs tools for dental treatment? From the impact fracture analysis to a new perspective of research: the case of Riparo Villabruna (Belluno – Italy)
No full textRiparo Villabruna (Sovramonte – Belluno – Italy) is a small shelter with Final Epigravettian lithic industry at 500m asl, located in the Dolomites of Veneto region and excavated in the 1988-89. The archaeological site is famous for the discovering of a burial, found during roadworks. The buried individual was an adult male of 25 years old and 170cm tall, recognized as a hunter-gatherer for the presence of funerary goods (a bone point, a backed knife, a flint blade and a core, a siltstone pebble and a lump of unidentified material). Direct radiocarbon dates in addition to dated charcoals found in the burial pit place the burial in the interval 14,400 – 13,800 cal yr BP. The dentition of this individual also documents the earliest evidence of dental caries intervention on a Late Upper Paleolithic modern human specimen. Using SEM, striations were observed that were interpreted as deriving from the manipulation of a large occlusal carious cavity of the lower right third molar, which also was confirmed experimentally. Those striations appear to have been produced ante-mortem with pointed flint tools during scratching and levering activities.
The results will be presented of a macro-fracture analysis that has been performed on part of the assemblage focused on an evaluation of the presence of impact-related fractures and the potential presence of projectile points in order to understand the function of the archaeological site. Some backed points proved to show a differing wear pattern and it was questioned whether these traces could correspond to dental caries intervention. In order to test this hypothesis, experiments were performed in combination with use-wear analysis to evaluate whether the observed damage patterns could indeed be caused by scratching enamel and dentine in view of dental treatment
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