Protective coatings are widely used to improve the lifetime of some machine parts exposed to a repeated dynamical stress. An analysis technique called dynamical impact test is applied to determine a fatigue, wear resistance and possibility of protective coating optimisation as well. This technique and the unique dynamical impact tester employed at the Institute of Scientific Instruments of the Czech Academy of Sciences, v.v.i. are described. Some of the impact test results important to indicate the protective coatings behaviour under repeated dynamical load are noticed in the last part of this paper. and Ochranné vrstvy jsou často užívány ke zvýšení životnosti součástí přístrojů vystavených opakovanému dynamickému namáhání. Pro určení životnosti, otěruvzdornosti a následné optimalizaci ochranných vrstev je používána analýza pomocí tzv. dynamického impaktního testu. V textu je popsán princip této metody, přiblížen je i unikátní přístroj využívaný k impaktnímu testování na Ústavu přístrojové techniky AV ČR, v.v.i. V závěru jsou popsány některé výsledky testu důležité pro určení chování ochranných vrstev pod opakovanou dynamickou zátěží.
Dynamical behavior of a boundary layer separation is studied using both theoretical analysis and experimental approach. The dynamical nature of the phenomenon is demonstrated on a simple case of a boundary layer in adverse pressure gradient studied experimentally. The Time-Resolved PIV technique was used to study instantaneous structure of the separation region and its time development. Distinctive coherent structures and their dynamical behavior were identified using the BOD method. and Obsahuje seznam literatury
To specify the role of individual cytokines in the immune response to pyrogens, isolated and cultivated human peripheral blood mononuclear cells (PBMC) were used for the experiments. Different pyrogens (lipopolysaccharide from Escherichia coli - LPS and live Borrelia afzelii) were applied and the time course of changes in concentrations of different cytokines in the medium was followed using the ELISA method. It was found that nonstimulated human PBMC proliferate under in vitro conditions and produce IL-6, TNF-a, IL-10 and finally also IL-1b. Productions of IL-12 and INF-g are not changed. Proliferation of PBMC is potentiated after incubation with LPS or live Borrelia. PBMC stimulated by LPS increase the net production (stimulated minus unstimulated) of IL-1b and TNF-a significantly, while production of IL-6 was smaller. A delayed increase in the production of IL-10 was also observed. Productions of IL-12 and INF-g were not influenced. In contrast to LPS, stimulation of PBMC with live Borrelia, increases also the production of IL-12 and IFN-g, besides IL-1b, TNF-a, IL-6 and IL-10. Productions of IL-1b, IL-6 and TNFa increased immediately after incubation with both LPS and Borrelia, while productions of IL-12 and INF-g begin to increase 8 hours and production of IL-10 12 hours after stimulation. Data indicate that stimulation with different pyrogens may activate the cells of the immune cascade in a different way. Stimulation of BPMC by LPS seems to activate the initial steps of the immune response (macrophages and granulocytes) only, while infection with live Borrelia also stimulates the later phase of the immune response, probably due to effect of initially produced cytokines., L. Janský, P. Reymanová, J. Kopecký., and Obsahuje bibliografii
To specify the role of individual cytokines in the immune response to pyrogens, isolated and cultivated human peripheral blood mononuclear cells (PBMC) were used for the experiments. Different pyrogens (lipopolysaccharide from Escherichia coli - LPS and live Borrelia afzelii) were applied and the time course of changes in concentrations of different cytokines in the medium was followed using the ELISA method. It was found that nonstimulated human PBMC proliferate under in vitro conditions and produce IL-6, TNF-a, IL-10 and finally also IL-1b. Productions of IL-12 and INF-g are not changed. Proliferation of PBMC is potentiated after incubation with LPS or live Borrelia. PBMC stimulated by LPS increase the net production (stimulated minus unstimulated) of IL-1b and TNF-a significantly, while production of IL-6 was smaller. A delayed increase in the production of IL-10 was also observed. Productions of IL-12 and INF-g were not influenced. In contrast to LPS, stimulation of PBMC with live Borrelia, increases also the production of IL-12 and IFN-g, besides IL-1b, TNF-a, IL-6 and IL-10. Productions of IL-1b, IL-6 and TNFa increased immediately after incubation with both LPS and Borrelia, while productions of IL-12 and INF-g begin to increase 8 hours and production of IL-10 12 hours after stimulation. Data indicate that stimulation with different pyrogens may activate the cells of the immune cascade in a different way. Stimulation of BPMC by LPS seems to activate the initial steps of the immune response (macrophages and granulocytes) only, while infection with live Borrelia also stimulates the later phase of the immune response, probably due to effect of initially produced cytokines., L. Janský, P. Reymanová, J. Kopecký., and Obsahuje bibliografii
In arid and semiarid ecosystems, plant interspaces are frequently covered by communities of cyanobacteria, algae, lichens and mosses, known as biocrusts. These crusts often act as runoff sources and are involved in soil stabilization and fertility, as they prevent erosion by water and wind, fix atmospheric C and N and contribute large amounts of C to soil. Their contribution to the C balance as photosynthetically active surfaces in arid and semiarid regions is receiving growing attention. However, very few studies have explicitly evaluated their contribution to organic carbon (OC) lost from runoff and erosion, which is necessary to ascertain the role of biocrusts in the ecosystem C balance. Furthermore, biocrusts are not resilient to physical disturbances, which generally cause the loss of the biocrust and thus, an increase in runoff and erosion, dust emissions, and sediment and nutrient losses. The aim of this study was to find out the influence of biocrusts and their removal on dissolved and sediment organic carbon losses. One-hour extreme rainfall simulations (50 mm h-1) were performed on small plots set up on physical soil crusts and three types of biocrusts, representing a development gradient, and also on plots where these crusts were removed from. Runoff and erosion rates, dissolved organic carbon (DOC) and organic carbon bonded to sediments (SdOC) were measured during the simulated rain. Our results showed different SdOC and DOC for the different biocrusts and also that the presence of biocrusts substantially decreased total organic carbon (TOC) (average 1.80±1.86 g m-2) compared to physical soil crusts (7.83±3.27 g m-2). Within biocrusts, TOC losses decreased as biocrusts developed, and erosion rates were lower. Thus, erosion drove TOC losses while no significant direct relationships were found between TOC losses and runoff. In both physical crusts and biocrusts, DOC and SdOC concentrations were higher during the first minutes after runoff began and decreased over time as nutrient-enriched fine particles were washed away by runoff water. Crust removal caused a strong increase in water erosion and TOC losses. The strongest impacts on TOC losses after crust removal occurred on the lichen plots, due to the increased erosion when they were removed. DOC concentration was higher in biocrust-removed soils than in intact biocrusts, probably because OC is more strongly retained by BSC structures, but easily blown away in soils devoid of them. However, SdOC concentration was higher in intact than removed biocrusts associated with greater OC content in the top crust than in the soil once the crust is scraped off. and Consequently, the loss of biocrusts leads to OC impoverishment of nutrient-limited interplant spaces in arid and semiarid areas and the reduction of soil OC heterogeneity, essential for vegetation productivity and functioning of this type of ecosystems.
Based on the biological significance of the ubiquitin-proteasome pathway (UPP) and its potential role during sepsis, burns and ischemia-reperfusion injury, we hypothesized that the systemic response to traumatic shock (TS) is accompanied by tissue-specific UPP alterations. Therefore, we studied tissue ubiquitin pools, chymotryptic- and tryptic-like proteasome peptidase activities and ubiquitin-protein ligation (UbPL) rates in skeletal muscle, heart, lung, liver, spleen and kidney using a clinically relevant porcine model (bilateral femur fracture/hemorrhage followed by fluid resuscitation). TS induced a systemic reduction of tissue- specific high molecular mass ubiquitin-protein conjugates (>50 kDa). Free ubiquitin was unaffected. The dynamic organ patterns of ubiquitin pools paralleled the typical physiological response to TS and resuscitation. Reduction of ubiquitin-protein conjugates was most pronounced in heart and lung (p<0.05 vs. control) and accompanied by significant increases in proteasome peptidase and UbPL activities in these organs. Unlike all other tissues, spleen proteasome peptidase and UbPL activities were significantly reduced 10 h after TS. These findings support the concept that the UPP could play an important role in regulation of cell functions during the early whole-body response to TS. The UPP might be a therapeutic target to improve the metabolic care after TS, particularly in the heart, lung, and spleen., M. B. Patel, S. A. Earle, M. Majetschak., and Obsahuje bibliografii a bibliografické odkazy
The article covers the topic of women's migration from poorer countries to the so called First World to provide domestic work and care giving. On the one hand, their movement is caused by the demand for domestic labour in rich countries where double career couples resolve the dilemma of reconciliation of public and private spheres by externalization of domestic work. On the other hand, the supply is significant. Migration and provision of domestic service is often the only survival strategy available to women from developing countries due to high unemployment and few working opportunities. The practice of hiring a migrant as domestic worker creates global care chains (Hochschild, 2001) that connect women engaged in care giving - those who are postponing it and those who are providing it. Migrant women hold an unequal position in these chains. They comprise a cheap labour in the informal private sector and so are vulnerable to abusive treatment. To tackle such discrimination, the patriarchal system stereotyping both women's and men's roles has to be challenged on the both sides of the care chain: in the developed as well developing countries.
[Zprávy Československé společnosti pro dějiny věd a techniky při ČSAV 9-10, 29-66 (1968)] and I. Bernard Cohen ; úvod redakce společný i pro předchozí článek je uveden na straně 220.