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30152. Století kosmického záření
- Creator:
- Grygar, Jiří
- Format:
- Type:
- model:article and TEXT
- Subject:
- fyzika, vesmír, physics, universe, 6, and 53
- Language:
- Czech and English
- Description:
- Cesta k objevu a následnému zkoumání vlastností kosmického zářeni byla a je stejně klikatá jako dráhy nabitých částic tohoto záření v propastech vesmíru. Ohlédnutí za prehistorií i historií výzkumu kosmických paprsků by mohlo být podnětem k vyřešení záhad, které se ani po stoletém úsilí mnoha badatelů nepodařilo rozluštit., The path to the discovery and subsequent study of the properties of the rather mysterious cosmic rays was, and still is as tortuous as the trajectories of charged particles in the depths of the universe. Looking back to the prehistory and history of cosmic-ray research might therefore serve as a stimulus for deciphering the puzzles that resist to be solved in spite of a hundred-year effort by many brilliant scientists., Jiří Grygar., and Obsahuje seznam literatury
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
30153. Století kosmologické konstanty
- Creator:
- Slaný, Petr and Stuchlík, Zdeněk
- Format:
- print, bez média, and svazek
- Type:
- model:article and TEXT
- Subject:
- kosmologická konstanta, teorie relativity, vesmír, cosmological constant, relativity theory, universe, 6, and 53
- Language:
- Czech and English
- Description:
- In 2017, 100 years elapsed since the introduction of the cosmological constant into the equations of general theory of relativity. In this paper we show which role the cosmological constant played in the beginning, what its status is today, and when it became a commonly accepted part of the physical description of reality as a suitable representative of the vacuum energy or, more generally, the so-called dark energy responsible for the current accelerated expansion of our universe. Finally, we discuss possible astrophysical manifestations of the cosmological constant., V roce 2017 uplynulo 100 let od zavedení kosmologické konstanty do rovnic obecné teorie relativity. V referátu ukazujeme, jakou roli hrála kosmologická konstanta na počátku a jaký je její status dnes, kdy se stala běžně přijímanou součástí fyzikálního popisu reality jako vhodný představitel energie vakua či obecně tzv. temné energie zodpovědné za současnou urychlovanou expanzi našeho vesmíru. Na závěr diskutujeme možné astrofyzikální projevy kosmologické konstanty., Petr Slaný, Zdeněk Stuchlík., and Obsahuje bibliografii
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
30154. Století proměn v pohřbívání: Od církevního uložení do země ke zpopelnění bez obřadu
- Creator:
- Nešporová, Olga
- Type:
- article, model:article, and TEXT
- Subject:
- last rites, funerals, cremation, Czech Republic, and 20th century
- Language:
- Czech
- Description:
- The changes in funeral practices in Czech society which occured during the 20th century were more significant than those that took place during the whole of the second millenium. Traditional Roman Catholic Christian funerals which were performed at the turn of the 19th and 20th centuries are described as a starting point from which the focus moves to a study of the major changes which took place from then onwards.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
30155. Stomatal and mesophyll limitations to photosynthesis in one evergreen and one deciduous Mediterranean oak species
- Creator:
- Mediavilla, S., Santiago, H., and Escudero, A.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- field gas exchange, leaf mass per unit area, leaf nitrogen content, leaf water potential, photosynthetic capacity, Quercus faginea, Quercus rotundifolia, and vapour pressure deficit
- Language:
- Multiple languages
- Description:
- In the evergreen Quercus rotundifolia and the co-existing deciduous Q. faginea we studied the diurnal variations in photosynthetic capacity (Pmax), measured as the rate of O2 evolution at photon and CO2 saturation, and in the rate of net CO2 assimilation (PN) in the field during the period of maximum photosynthetic activity. Our aim was to check the contribution of stomatal and non-stomatal limitations to the diurnal variation in photosynthesis, and to study the differences between both species. Q. faginea leaves displayed lower mass per unit area and higher nitrogen content than Q. rotundifolia leaves. The maximum stomatal conductance and PN in the field were higher in Q. faginea than in Q rotundifolia. Also Pmax of Q. faginea was higher than that of Q. rotundifolia. Both species attained in the field a high percentage of the Pmax (around 82 % for Q. faginea and 73 % for Q. rotundifolia). This indicates reduced stomatal limitation of photosynthesis under favourable conditions, especially in Q. faginea. PN underwent a sharp decrease towards mid-day in association with increase in the atmospheric vapour pressure deficit and decrease in the leaf water potential. Pmax was also reduced during mid-day. This demonstrated the contribution of mesophyll limitations to the PN in the two species under stress. The mesophyll limitation of photosynthesis seemed to be similar for both species, independently from the differences in leaf traits between them. and S. Mediavilla, H. Santiago, A. Escudero.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
30156. Stomatal and nonstomatal limítations to photosynthesís in two wheat cultivars subjected to water stress
- Creator:
- Kicheva, M.I., Tsonev, T.D., and Popova, L.P.
- Format:
- Type:
- model:internalpart and TEXT
- Language:
- Multiple languages
- Description:
- Two wheat {Triticum aestivum L.) cultivars, Trakia (drought-sensitive, DS) and Slavianka 196 (drought-tolerant, DT), were subjected to water stress induced by polyethyleneglycol (PEG) 6000; 15 % PEG for 6 h (mild stress); 25 % PEG for 6 h and 15 % PEG for 24 h (severe stress). Exposure of plants to water stress led to a noticeable decrease in both the initial slope of net photosynthetic rate to intercellular CO2 concentration {Pfilc^ curves and the maximum P-^. Ribulose 1,5-bisphosphate carboxylase (RuBPC) activity was almost unchanged under mild stress while under severe stress it was reduced by about 26-27 %. The ratio of variable to maximal chlorophyll fluorescence did not change which implied that there was little effect of examined stress conditions on the photosystem 2 electron transport. The relative magnitude of stomatal and nonstomatal factors in limitation of photosynthesis depended on stress severity.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
30157. Stomatal conductance in Amazonian tree saplings in response to variations in the physical environment
- Creator:
- Marenco, R. A., Nascimento, H. C. S., and Magalhães, N. S.
- Format:
- print, bez média, and svazek
- Type:
- model:article and TEXT
- Subject:
- fotosyntéza, photosynthesis, Amazonský deštný prales, atmospheric variables, red to far-red ratio, sunflecks, understory CO2, 2, and 581
- Language:
- Multiple languages
- Description:
- In juvenile trees growing at the rainforest understory, light is the most limiting factor for growth. It has been assumed that stomata quickly respond to light irrespective of the physical conditions prevailing before leaf illumination. Nevertheless, so far this issue has not been addressed for saplings of Amazonian tree species. The aim of this study was to determine how stomatal conductance (gs) and photosynthetic parameters of Amazonian saplings respond to diurnal variation in the physical environment and to rainfall seasonality. Light-saturated net photosynthetic rate (PNmax) and gs at light saturation (gsmax) were measured in the dry (August) and rainy (January) season of 2008 in saplings of 10 Amazonian tree species (Minquartia guianensis, Myrcia paivae, Protium apiculatum, Guatteria olivacea, Unonopsis duckei, Rinorea guianensis, Dicypellium manausense, Eschweilera bracteosa, Gustavia elliptica, and Tapura amazonica). At the forest understory, variables of the physical environment were measured. Rainfall seasonality did not affect PNmax and gsmax, nor was the effect of species on PNmax and gsmax significant (p>0.05). The gs and PNmax increased as the forest understory became brighter and warmer; as a result, PNmax and gsmax were higher at midday than early in the morning or in the afternoon. However, contrary to expectations, neither changes in air vapor pressure deficit nor air CO2 concentration at the forest understory affected stomatal opening. More investigation is needed to elucidate the role of environmental factors in modulating stomatal movements in juvenile trees growing beneath the dense canopy of tropical rainforests., R. A. Marenco, H. C. S. Nascimento, N. S. Magalhães., and Obsahuje bibliografii
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
30158. Stomatal development and associated photosynthetic performance of capsicum in response to differential light availabilities
- Creator:
- Fu, Q. S., Zhao, B., Wang, Y. J., Ren, S., and Guo, Y. D.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- botanika, botany, capsicum, chloroplast, low light, photosynthesis, Rubisco, and stomata
- Language:
- Multiple languages
- Description:
- The mechanisms of capsicum growth in response to differential light availabilities are still not well elucidated. Hereby, we analyzed differential light availabilities on the relationship between stomatal characters and leaf growth, as well as photosynthetic performance. We used either 450-500 µmol m-2 s-1 as high light (HL) or 80-100 µmol m-2 s-1 as low light (LL) as treatments for two different cultivars. Our results showed that the stomatal density (SD) and stomatal index (SI) increased along with the leaf area expansion until the peak of the correlation curve, and then decreased. SD and SI were lower under the LL condition after three days of leaf expansion. For both cultivars, downregulation of photosynthesis and electron transport components was observed in LL-grown plants as indicated by lower light- and CO2-saturated photosynthetic rate (Pmax and RuBPmax), quantum efficiency of photosystem II (PSII) photochemistry (ΦPSII), electron transport rate (ETR) and photochemical quenching of fluorescence (qp). The observed inhibition of the photosynthesis could be explained by the decrease of SD, SI, Rubisco content and by the changes of the chloroplast. The low light resulted in lower total biomass, root/shoot ratio, and the thickness of the leaf decreased. However, the specific leaf area (SLA) and the content of leaf pigments were higher in LL-treatment. Variations in the photosynthetic characteristics of capsicum grown under different light conditions reflected the physiological adaptations to the changing light environments. and Q. S. Fu ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
30159. Stomatal responses of bean (Phaseolus vulgaris L.) leaves to changing irradiance, air humidity, and water potential of root medium
- Creator:
- Maleszewski, S., Burchacka, E., Rakus, M., and Kozłowska-Szerenos, B.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- blue radiation, guard cells, leaf conductance, and red radiation
- Language:
- Multiple languages
- Description:
- Stomatal responses of attached bean (Phaseolus vulgaris L.) leaves to changing spectral composition ("white" - WL., blue - BL, or red - RL radiation), air humidity (100 % or about 4 % RH), and water potential of the root medium (close to 0 or -1.2 MPa) were determined by air flow porometer. Opening of stomata always increased under BL and decreased under RL. In response to decline in air humidity, leaf conductance showed transient increase before it reached lowered steady state. BL enhanced and RL diminished this response. and S. Maleszewski ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
30160. Stomatocystis goerresi, a new species of gregarine parasite (Apicomplexa, Monocystidae) from the invasive Japanese earthworm Amynthas tokioensis (Megascolecidae), with a description of the parasite's life cycle
- Creator:
- Schall, Joseph J.
- Format:
- počítač and online zdroj
- Type:
- model:article and TEXT
- Subject:
- protist, standardised diagnostic morphology, introduced species, and host specificity
- Language:
- English
- Description:
- Stomatocystis goerresi sp. n., a gregarine (phylum Apicomplexa, Monocystidae) parasite of an important invasive earthworm in North America, Amynthas tokioensis (Beddard), is described. This is the second species placed into the genus, and details of its morphology and life cycle support Stomatocystis Bandyopadhyay, Mitra et Göçmen, 2006 as a valid taxon. The new species is described using standard nomenclature, measurements, shape descriptors, and photographs of living cells. The parasite was found only in A. tokioensis, and absent in sympatric earthworm species, suggesting it arrived when the earthworms were introduced from their origin from Japan. The species is distinctive from the type species in the genus, S. indica Bandyopadhyay, Mitra et Göçmen, 2006, in being substantially larger in all stages, found in only the host's seminal vesicles, and found in a different host species from East Asia. The distinctive trophozoites/gamonts develop a large funnel structure ringed with a collar of pronounced ridges, and the funnel appears even in the smallest cells. This funnel varies greatly in relative size (to the cell body) and shape, sometimes forming a large fan. The life cycle of S. goerresi is described including distinctive syzygy in which the funnels fuse and then produce a large cell with local centres of isogamete production (thus sex without gender). Gametes are large ( ~5 μm) spheres with complex tips. Oocyst production is large, > 1,000 per mature gametocyst. The genus Stomatocystis is placed into the Monocystidae, but the life cycle of the new species differs from those of other monocystid taxa, which may mean the Monocystidae are not monophyletic or life cycles are variable within the family. Prevalence of S. goerresi at the type locality was high (~ 90%). The parasites destroy the earthworm's organ of sperm self-storage thus eliminating the male function in the hermaphroditic host which may influence the ability of the earthworm to invade and be successful at new sites
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public