Twenty-five genotypes of early CIMMYT hexaploid wheat were screened for salt tolerance in a glasshouse experiment using photosynthetic capacity and water relation parameters as selection criteria. Under salt stress (150 mM NaCl) the genotypes Frontana, Norin-10, Mayo-54, Noreste-66, and Yaktana-54 excelled all other lines in shoot dry mass, and Na(20)TPP, Penjamo-62, Inia-66, Frontana, Siete Cerros, and Jaral-66 in grain yield per plant in both absolute and relative (percent of control) terms. Although net photosynthetic rate (PN) declined in all genotypes due to salt stress, it was not helpful in discriminating among genotypes according to salt tolerance. Similarly, no positive relationships of salt tolerance of the genotypes with stomatal conductance, leaf water potential, or turgor pressure were found. Every genotype used its own specific mechanism to tolerate salt stress. However, a large amount of variation in salt tolerance observed in 25 early CIMMYT wheat genotypes can be of considerable practical value for improving salt tolerance in the existing commercial hexaploid wheats. and M. Ashraf, M. Shahbaz.
The paper presents the experimental results of turbulent flow over hydraulically smooth and rough beds. Experiments were conducted in a rectangular flume under the aspect ratio b/h = 2 (b = width of the channel 0.5 m, and h = flow depth 0.25 m) for both the bed conditions. For the hydraulically rough bed, the roughness was created by using 3/8″ commercially available angular crushed stone chips; whereas sand of a median diameter d50 = 1.9 mm was used as the bed material for hydraulically smooth bed. The three-dimensional velocity components were captured by using a Vectrino (an acoustic Doppler velocimeter). The study focuses mainly on the turbulent characteristics within the dip that were observed towards the sidewall (corner) of the channel where the maximum velocity occurs below the free-surface. It was also observed that the nondimensional Reynolds shear stress changes its sign from positive to negative within the dip. The quadrant plots for the turbulent bursting shows that the signs of all the bursting events change within the dip. Below the dip, the probability of the occurrence of sweeps and ejections are more than that of inward and outward interactions. On the other hand, within the dip, the probability of the occurrence of the outward and inward interactions is more than that of sweeps and ejections.
Akustická emise se často používá ke studiu procesů probíhajících v materiálech podrobených mechanickému a/nebo tepelnému zatěžování. Proti jiným metodám má měření akustické emise přednost, že se jedná o nedestruktivní metodu a že je ji možné použít v průběhu studia procesů, tj. jedná se o metodu in situ. V tomto článku chceme poukázat na to, jaké informace je možné získat při studiu vlivu teplotního cyklování hořčíkových kompozitů při použití metody akustické emise. Kompozity byly teplotně cyklovány mezi pokojovou teplotou a nějakou vyšší teplotou, až do 400 °C. V průběhu cyklování byla průběžně registrována změna délky vzorku a monitorována akustická emise. Získané experimentální výsledky nasvědčují, že v matrici se vytváří vnitřní termická napětí, jejichž velikost je závislá na změně teploty, na rozdílu koeficientů teplotní roztažnosti matrice a zpevňující fáze, na elastických vlastnostech obou složek kompozitu a na plastických vlastnostech matrice., Pavel Lukáč, František Chmelík., and Obsahuje seznam literatury