Mine roadways developed in highly stressed strata are subject to roof shear, which under severe conditions may manifest as the well known symptom of guttering, particularly at the roadway edge leading into the major horizontal stress. This roof shear can progressively reduce the effectiveness of bolt confinement of the strata within the lower roof horizon affecting stability of the immediate roof. This paper presents the results of a study to investigate the effectiveness of polymers as skin reinforcement in highly stressed coal mine roadways, as they may provide better roadway skin support than the currently used steel mesh. A large concrete block intercepted with artificial joints and reinforced with steel bolts without skin support, was loaded until significant slip occurred along the joints. Upon loading, a roof cavity resembling a gutter developed, as some of the jointed concrete parted from the free surface. In addition to bolts, subsequent models with identical fracture planes were supported with steel mesh or with glass reinforced polymer skin bonded to the free side. Loads and displacements were compared for models with and without skin reinforcement. As expected the skin support helped resist gutter formation, to various degrees, while increasing the residual strength of the concrete block. It was found that there was significantly less bedding displacements in models with the polymer skin, when compared with both steel mesh and no skin reinforcement. This suggests that there would be benefits to using a spray on polymeric skin as surface support in roofs subject to severe roof shear., Jan Nemcik, Ernest Baafi and Ian Porter., and Obsahuje bibliografii
1. The Heteroptera, principally mirids, collected in a light-trap run on a field margin at Rothamsted Experimental Station for various periods between 1933 and 2000, have been identified, and the catches analysed to show the extent of change and stability in the community.
2. Trap catch, both in terms of individuals and species, was correlated with maximum daily temperature.
3. α-diversity showed a U-shaped curve over the period. The dip may have been associated with pesticide use, although a lack of days with high maximum temperatures cannot be ruled out.
4. By the late 1990s, α-diversity had again reached a peak (Fisher's = 11), comparable to that in the 1930s.
5. However, the change in the composition of the community over the whole period (β-diversity) was significant, the index of difference being 0.66 on a scale where 0 is no change in composition or relative abundance and 1 no species in common.
6. The value of β-diversity was highest in the water bugs, which disappeared altogether. Categorising the others by host plant type, the greatest change over time was in those associated with perennial herbs. There were decreasing differences in tree-dwellers and grassland species respectively, and the least change was in the community associated with annual plants (arable weeds).
7. Changes in the abundance of Heteroptera since 1933 follow closely those of the macrolepidoptera from the same samples. However changes in diversity show very different patterns, with moth diversity continuing to decline since 1960 in contrast to the increases apparent from the Heteroptera data.
In our study we find, from the analysis of VLBI observations, small quasi-periodic fluctuations of the period and quality factor of retrograde Free Core Nutation (FCN), ranging mainly between 429.8 to 430.8 days and 17000 to 21000, respectively. To this end, we use resonant effects in several dominant forced nutation terms to calculate the period and quality factor of FCN in running 6-year intervals. We also recently demonstrated that the atmospheric and oceanic excitations are capable of exciting FCN. Both amplitude and phase of the geophysically excited motion are consistent with the values observed by VLBI, in the interval of tens of years. The geophysical excitations are now numerically integrated, using Brzeziński’s broadband Liouville equations, and removed from the observed celestial pole offsets. The remaining part is then used to derive the period and quality factor of FCN in running intervals, and to study the temporal stability of these important Earth parameters. It is demonstrated that the observed quasi-periodic variations of both parameters are probably not caused by these geophysical excitations., Jan Vondrák and Cyril Ron., and Obsahuje bibliografii
Archeologové často diskutují o pohybu obyvatel na určitém území a spolu s antropology, archeozoology a archeobotaniky uvažují o spektru rostlin a zvířat sloužících k výživě lidí v dávné minulosti. V posledních desetiletích do těmto studií proniká nová technika, a to měření kvantitativních poměrů obsahu přirozených izotopů vybraných prvků (např. uhlík, kyslík, stroncium) obsažených v tkáních, kostech a zubech. and Archaeologists very often discuss movements of inhabitants in the particular area and together with anthropologists consider the range of plants and animals used for human feeding in the past. New techniques have been applied in the relevant studies, such as the quantitative estimation of natural isotope levels in particular elements (e.g. carbon, oxygen, strontium) found in tissues, bones and teeth.
Závěrečné pokračování příspěvku představuje řadu příkladů využití stabilních izotopů při studiu výživy a migrace lidí (např. délka kojení, konzumace kukuřice v Severní Americe, původ obyvatelstva v Bavorsku, migrace v Egyptě apod.). and The final part of this contribution presents some examples of using stable isotopes in studying food and migration patterns in human populations (e.g. length of the lactation period, maize consumption in North America, Bavarian population origin, migration in Egypt, etc.).
In some species of insects, individuals with fully developed wings and capable of flying coexist with flightless individuals that lack functional wings. Their diets may differ if long-winged individuals are more mobile and therefore likely to be better at finding and utilizing high quality food resources, or if they have different food preferences or physiological requirements. Despite its potential importance, differences in the diet of dispersal phenotypes have not been unequivocally demonstrated under natural conditions. To test for dietary divergence, we compared natural abundances of carbon and nitrogen stable isotope ratios (d13C and d15N) in long- and short-winged free ranging Tetrix subulata pygmy grasshoppers collected as adults from two natural populations. Overall, this comparison of stable isotopes indicated long-term differences in the diet of the two wing morphs in both populations, but not between males and females of the same morph. We conclude that it is likely that the dietary niches of the long winged and flightless individuals differ under natural conditions. This may reduce intra-specific competition, offset the expected trade-off between flight capacity and reproduction and promote ecological speciation. Address, Einat Karpestam, Anders Forsman., and Obsahuje seznam literatury
Uroteliální karcinomy vyžadují komplexní přístup ke stagingu, jelikož jejich typickou vlastností je multifokalita - možnost lokálně agresivního chování i vzdálené diseminace. V komplexním zobrazení je možné využít MDCT, MRI i 18F-FDG-PET/CT. Při hodnocení nádorů je zásadní odlišit invazi nádoru do okolní tukové tkáně nebo do parenchymu ledviny, eventuálně do okolních orgánů. Lokální šíření je možné posoudit poměrně spolehlivě pomocí MDCT i MRI. Pro posouzení vzdálené diseminace onemocnění je optimální metodou 18F-FDG-PET/CT, která nabízí odhalení metastáz v uzlinách ve skeletu, játrech i plicním parenchymu. Při předoperačním plánování je využíváno předností trojrozměrného modelování cévního zásobení i vývodních cest močových., Urothelial carcinomas need complex approach during staging, because of they may be typically multi-focal, locally aggressive behavior and potential remote dissemination. The possibilities of complex imaging cover MDCT, MRI and 18F-FDG-PET/CT. In the assessment of the tumors, it is most important to distinguish the invasive spread of the tumor to the surrounding fatty tissue or into renal parenchyma or into neighboring organs respectively. Local invasion could be evaluated by MDCT or MRI with the relatively high accuracy. 18F-FDG-PET/CT is the optimal method able to search on the remote metastases. It offers depiction of the metastases in lymph nodes, in the skeleton, liver or lung parenchyma. The advantages of three-dimensional modeling are used in the pre-operative assessment of the renal vasculature or urotract., Jiří Ferda, Jan Kastner, Eva Ferdová, Hynek Mírka, Jan Baxa, Milan Hora, Ondřej Hes, Jindřich Fínek, Boris Kreuzberg, and Literatura 11