This study made it possible to show, using the example of Bohemia, that agrarian areas which have thus far been viewed as the “traditional” regions of emigration, also feature significant numbers of immigrants. Migration from agrarian regions not only moved in the direction of towns and urban centres. Commonly it was the case that each region was connected with other regions along multidirectional channels of exchange. In addition, in the rural environment there is clear evidence of the existence of an important system of seasonal migration. Intensive research of migration flows in the Central European rural environment, a task that still awaits international historiography, will certainly bring to light many more, thus far unknown, migration systems.
Biofilms are communities of microorganisms irreversibly attached to various substrates which are embedded in the matrix of extracellular polymeric substances. Biofilms are present in both natural and human environments, which may cause serious problems. In this article, we deal with the basic characteristics, origin, development and functions of biofilms. and Martin Rulík, Veronika Holá.
The function of biofilms in natural waters is driven primarily by mutual interactions between algae, bacteria and their grazers. In turn, the grazers together with a hydraulic regime of the environment may control the biomass and the thickness of the biofilms and affect their ability to intake and retain nutrients and toxic pollutants. Thus biofilms represent the hot spots of metabolic activity which contribute substantially to water self-purification and serve as food for invertebrate organisms. However, biofilms may also show adverse effects on the surfaces they colonize. and Martin Rulík.
Biofilm, as a form of microbial existence, is very important from the medical point of view. Both our native microflora and pathogenic bacteria live in the biofilm form. Microbes growing in the biofilm show higher resistance to externall conditions and to the action of antimicrobials, which is considered to be very important virulence factor common to all biofilm-positive bacteria. The article deals with both biofilmformed native microflora and biofilm infections. and Veronika Holá.
Gravimetrie jako geofyzikální metoda je založena na měření tíhového pole na zemském povrchu. K danému účelu slouží gravimetry, určující hodnotu tíhového zrychlení. Tyto přístroje mají jednoduchý princip, ale vyspělou technologii, která umožňuje registrovat tuto veličinu v řádu 10-8 m.s-2. Této hodnotě se říká mikroGal a je běžně používanou jednotkou při velmi přesných měřeních. Tíhové zrychlení na povrchu Země se pohybuje v rozmezí 978 000 000 až 983 000 000 mikroGal, zatímco mikrogravimetrický průzkum se zabývá anomáliemi 10 až 100 mikroGal. Chyba měření se pohybuje okolo 3-5 mikroGal. S ohledem na fakt, že tíhové zrychlení závisí na zeměpisné šířce (vliv zploštění a rotace Země) a nadmořské výšce (vzdálenost od těžiště Země), zavádějí se příslušné korekce. Rovněž tak je nutno redukovat data a slapové efekty Měsíce a Slunce, vliv morfologie terénu a drift přístroje, závisející na mechanických vlastnostech měřícího systému, environmentálních faktorech (teplota, atmosférický tlak), transportních podmínkách apod., Jan Mrlina., and Obsahuje seznam literatury