The induced unsteady flow due to a stretching porous surface in a rotating fluid, where the unsteadiness is caused by the suddenly stretched surface is studied in this paper. After a similarity tranformation, the unsteady Navier-Stokes equations have been solved numerically using the Adams Predictor Corrector Method. It is found that there is a smooth transition from the small time solution to the large time or steady state solution. and Obsahuje seznam literatury a názvosloví
The unsteady Hartmann flow of a conducting incompressible non-Newtonian viscoelastic fluid between two parallel horizontal insulating porous plates is studied with heat transfer. A uniform pressure gradient which decays exponentially is imposed in the axial direction. An external uniform magnetic field and uniform suction and injection through the surface of the plates are applied in the vertical direction. The two plates are kept at different but constant temperatures while the Joule and viscous dissipations are considered in the energy equation. Numerical solutions for the governing momentum and energy equations are obtained using finite differences. The effect of the magnetic field, the parameter describing the non-Newtonian behavior, and the velocity of suction and injection on both the velocity and temperature distributions is investigated. and Obsahuje seznam literatury
In modern society, many people keep working hours different from the standard (9 hours, 5 days a week during conventional time of the day), a regimen leading to sleep deprivation and/or circadian desynchronization, and, consequently, to sleepiness, fatigue, impaired efficiency and ultimately to psychic and somatic complaints. Fortunately, sleepiness-related health and occupational hazards can be kept under control using scientifically tested precautions designed to help maintain wakefulness. Suitable work and rest scheduling and observance of the principles of sleep hygiene are of major importance there. In situations which interfere with sleep, it is possible to use hypnotics or behavioral techniques and melatonin for circadian regimen optimization. In situations when sleep loss is temporarily inevitable, options to be taken into account include work shift shortening, breaks for rest, naps of short duration or administration of vigilance enhancing drugs. In the future, risks associated with sleepiness could be mitigated by means of currently developed technologies for real-time detection of sleepiness.
The corpora cardiaca (CC) of the two grasshopper species Zonocerus elegans (Pyrgomorphidae) and Lamarckiana sparrmani (Pamphagidae) contain (a) substance(s) that cause(s) hyperlipaemia in the migratory locust and hypertrehalosaemia in the American cockroach. Isolation of neuropeptides belonging to the adipokinetic hormone (AKH) family was achieved by single-step reversed-phase high performance liquid chromatography of CC extracts from both species and monitoring tryptophan fluorescence. The material of both species showed three distinct fluorescence peaks with adipokinetic activity in the migratory locust. The peptides were identifid by at least two of the following methods: (1) sequencing by Edman degradation, (2) sequencing by tandem fast atom bombardment mass spectrometry, (3) mass determination by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry and (4) co-elution of the native and synthetic peptides. Both species were found to have three AKH peptides stored in the CC, but unlike in other grasshoppers, none of those peptides were decapeptides. In Z. elegans the following three octapeptides occur: Schgr-AKH-II (pELNFSTGWamide), Peram-CAH-II (pELTFTPNWamide) and Phymo-AKH-III (pEINFTPWWamide), whereas L. sparrmani contains the octapeptides Grybi-AKH (pEVNFSTGWamide), Pyrap-AKH (pELNFTPNWamide) and also Phymo-AKH-III. Conspecific bioassays show no adipokinetic and only a weak (not significant) hypertrehalosaemic effect (in the pamphagid grasshopper). Some explanations are offered on the possible role of these peptides in the species investigated by interpreting their life style.
Research on the diet of barn owls on some of the lesser Pityusic Islands (Formentera, s’Espalmador and s’Espartar) reveals a previously undescribed opportunistic trophic behaviour based on regular foraging in patches of territory separated by relatively broad sea channels. Individually, small islets with reduced human influence do not usually provide enough food for the barn owl. Consequently, the species expands its home range to include multiple islands or islets. This study is the first to document the regular
crossing of broad sea channels (one of which exceeds 4.5 km) by barn owls in order to hunt. The islets provide the barn owls with prey otherwise considered as marginal (such as Oryctolagus cuniculus and Hydrobates pelagicus).
Hoplitis pici (Friese, 1899) is a rare species of bee occurring in southeast Europe, Turkey and the Near East. The females are equipped with conspicuous hooked bristles on the galeae of the proboscis. Microscopical analysis of both pollen contained in the abdominal scopa and sticking to the bodies of females indicates a distinct preference of H. pici for the flowers of Muscari Miller (Hyacinthaceae), which are characterized by having the anthers completely hidden within an urn-shaped corolla. Field observations showed that the specialized bristles serve to scrape pollen out of the Muscari flowers. Specialized bristles aiding female bees to extract pollen from narrow flower tubes must have independently evolved at least eight times in osmiine bees. H. pici is the only osmiine species known to use its pollen-harvesting bristles to exploit host plants other than narrow-tubed Boraginaceae.