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29802. Speciální optická vlákna - srdce thuliových vláknových laserů a zesilovačů
- Creator:
- Kašík, Ivan, Honzátko, Pavel, Peterka, Pavel, Mrázek, Jan, Podrazký, Ondřej, Aubrecht, Jan, Proboštová, Jana, Cajzl, Jakub, and Todorov, Filip
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- optics, optical fibers, optika, optická vlákna, vláknové lasery, vláknové zesilovače, thulium, holmium, širokopásmové zdroje zesílené spontánní emise, and ASE
- Language:
- Czech
- Description:
- Fiber lasers and amplifiers have been developed as magnificent alternative to traditional solid-state or gas lasers. They are effectively employed for low-power applications, e.g. in metrology or in medicine, as well as for high-power applications like industrial splicing, cutting, or welding. Special optical fibers based on silica or soft optical glasses are heart of the fiber lasers. This paper deals with special silica-based optical fibers doped with thulium and/or holmium ions for amplified spontaneous emission (ASE) sources operating around 2 μm. Pretty versatile method of fiber preparation was elaborated making ones possible fabrication of single-mode or double-clad fibers with core modified with Al2 O3 or P2 O5 up to 14 mol % and doped with rare-earth ions (Tm3+, Ho3+, Er3+, Eu3+, Dy3+, Yb3+, Sm3+) in the range of 102 ppm - 104 ppm. This method is suitable also for doping the fiber core with nanoparticles. Such fibers can be employed for preparation of high-power fiber lasers and/or stable ASE sources in infrared region. This kind of sources was demonstated in generator of extremely wide emission within 1540 m - 2340 nm suitable for spectroscopy characterization of optical components. and Vláknové lasery a zesilovače jsou rozvíjeny jako úspěšná alternativa ke klasickým pevnolátkovým nebo plynovým laserům, která má své významné přednosti při uplatnění od aplikací nízkovýkonových, např. v metrologii či medicíně, až po aplikace vysokovýkonové, např. průmyslové svařování, řezání, navařování apod. Srdcem vláknových laserů jsou optická vlákna z křemenného skla, případně z měkkých optických skel. Článek se zabývá speciálními křemennými optickými vlákny pro thuliem a holmiem dopované zdroje zesílené spontánní emise (ASE) pracující v oblasti okolo 2 μm. Byla vypracována poměrně univerzální metoda, která umožňuje přípravu speciálních jednovidových optických vláken s obsahem Al2 O3 nebo P2 O5 až do 14 mol % v jádře dopovaném dále ionty prvků vzácných zemin (Tm3+, Ho3+, Er3+, Eu3+, Dy3+, Yb3+, Sm3+) v rozsahu 102 ppm - 104 ppm. Metoda umožňuje i dopování optického jádra nanočásticemi. Tato optická vlákna lze úspěšně využít pro přípravu dvouplášťových vláken pro vysokovýkonové vláknové lasery nebo stabilních širokopásmových zdrojů infračerveného záření. Takové zdroje, vykazující řadu předností, byly s úspěchem demonstrovány v generátoru s rekordně širokou emisí v rozmezí od 1540 nm až do 2340 nm, vhodném pro spektroskopické charakterizace optických komponent.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
29803. Species of Strigea (Digenea: Strigeidae), parasites of the savanna hawk Buteogallus meridionalis (Aves: Accipitridae) from Argentina, with the description of a new species
- Creator:
- Lunaschi, Lía I. and Drago, Fabiana B.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- Strigeidae, Strigea meridionalis, Strigea elliptica, Strigea microbursa, Buteogallus meridionalis, Accipitridae, and Argentina
- Language:
- English
- Description:
- A new strigeid digenean, Strigea meridionalis sp. n., is described from the small intestine of the savanna hawk, Buteogallus meridionalis (Latham) (Aves: Accipitridae), from Formosa Province, Argentina. This species is characterised by the absence of a neck region in the hindbody, the presence of entire testes, a copulatory bursa with a membranous fold originated from the muscular ring (Ringnapf) and by the arrangement of vitelline follicles in the forebody. Other two strigeid species collected from the savanna hawk, Strigea elliptica (Brandes, 1888) and Strigea microbursa Pearson et Dubois, 1985, are described and illustrated. Strigea microbursa is reported for the first time from the Neotropical Region and B. meridionalis represents a new host record for S. elliptica. These findings allow us to increase the knowledge of these species, adding new metric and morphological data. A key to the species of the Neotropical Strigea Abildgaard, 1790 is presented including data on their geographical distribution.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
29804. Species richness of vertebrates in the Czech Republic
- Creator:
- Krojerová-Prokešová, Jarmila, Barančeková, Miroslava, Šímová, Petra, Šálek, Miroslav, Anděra, Miloš, Bejček, Vladimír, Hanák, Vladimír, Hanel, Lubomír, Lusk, Stanislav, Mikátová, Blanka, Moravec, Jiří, Šťastný, Karel, and Zima, Jan
- Type:
- article and TEXT
- Subject:
- mapping squares, species numbers, environmental variables, and PCA
- Language:
- English
- Description:
- The species richness of free-living vertebrates was analysed using mapping of occurrence within individual grid squares (12 x 11.1 km) over the territory of the Czech Republic. The data on species distribution were derived from recent distributional atlases published in the last 15 years, and the records originated mostly in the last 20 years. Altogether, 384 species of cyclostomes, bony fishes, amphibians, reptiles, birds and mammals were included in this study and their presence or absence was recorded in 678 grid squares. The species numbers ascertained in the 523 grid squares situated completely within the Czech Republic varied from 92 to 259 species, with a median of 182 species. The first two principal components explained 44.9 % of the total variance and separated two main habitat gradients based on values of different environmental, topographic, and demographic variables in particular squares. The PC1 represents a gradient from urban habitats at lower altitudes to more homogenous habitats with dominant coniferous forests and meadows situated at higher altitudes. The importance of natural habitats (represented by broad-leaved and mixed forests, as well as by protected areas) and landscape heterogeneity increases along the PC2. Generalized Linear Modelling for each group of vertebrates was fitted using the number of species of individual vertebrate groups as a response variable and the first two principal components as explanatory variables. The species richness of all vertebrate groups except for reptiles is highly dependent on the PC1. The number of fish, amphibian, and bird species in squares decreases with increasing value of the PC1, i.e. it is higher in urban areas at lower altitudes. By contrast, the number of mammal species is higher in uninhabited areas at higher altitudes. The gradient represented by the PC2 is highly significant for species richness of reptiles and mammals, and the number of species of both groups increases with increasing importance of natural habitats.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/
29805. Species specific diurnal changes in chlorophyll fluorescence in tropical deciduous and evergreen plants growing in the field during summer
- Creator:
- Joshi, S.C.
- Format:
- Type:
- model:internalpart and TEXT
- Subject:
- Acer, Aesculus, Bauhinia, Boehmeria, Celtis, Dalbergia, Eugenia, Ficus, Grewia, and Sapium
- Language:
- Multiple languages
- Description:
- Diumal changes in chlorophyll (Chl) a fluorescence characteristics of sun-exposed and shade leaves of some tropical and temperate tree species growing under fíeld conditions on sunny and cloudy days during summer were recorded. Significant reduction in photochemical efficiency of photosystem (PS) 2 measured as ratio during periods of maximum irradiance was observed in sun-exposed leaves of some plants. The extent of this reduction was probably a function of the plant species. Among the tropical species tested, Boehmeria rugulosa, Celíis ausíralis, Dalbergia sissoo, Eugenia jambolana and Grewia optiva showed maximum reduction (15-22 %), whereas species like Ficus racemosa and Sapium sebiferum showed least dechne (< 7 %) in the F^/F^ ratio. On the other hand, no significant reduction in this ratio was observed in Bauhinia purpurea. Temperate species, v/z. Acer oblongum and Aesculus indica, were most susceptible to high irradiances. Prolonged exposure of these plants to high irradiances resulted in lesion development in their leaves characterized by reduction in pigment contents and Fy/F^, ratio. Plant species with considerable midday dechne in Fy/Fn, ratio showed (7) slight but significant rise in initial fluorescence (Fq), (2) pronounced decrease in F^ value, and (3) significant reduction in area over the curve between Fq and Fj„ indicating the pool size of electron acceptors on the reducing side of PS2. The depression in Fy/F^ ratio though reversible could not be alleviated even after watering the plants at hourly intervals. No reduction in Fy/F^, was observed in shade leaves of the same plants and/or when measurements were taken on cloudy days. Hence high solar radiation and high atmospheric evaporative demand existing during summer period could probably be the major contributoiy factors for this reduction.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
29806. Specific and general human capital in an endogenous growth model
- Creator:
- Vourvachaki, Evangelia, Jerbashian, Vahagn, Slobodyan, Sergey, Univerzita Karlova. Centrum pro ekonomický výzkum a doktorské studium, and Národohospodářský ústav (Akademie věd ČR)
- Publisher:
- CERGE-EI
- Format:
- electronic and 44 s. : il.
- Type:
- model:monograph and TEXT
- Subject:
- Ekonomie, lidský kapitál, ekonomický růst, vzdělávací politika, ekonomické aspekty, human capital, economic development, educational policy, economic aspects, 331.108.23, 330.35, 37.014.5, 33, (048.8), and 4
- Language:
- English and Czech
- Description:
- Evangelia Vourvachaki, Vahagn Jerbashian, Sergey Slobodyan., Obsahuje bibliografii a bibliografické odkazy., Anglické a české resumé, and born digital
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
29807. Specific degradation of D1 protein during exposure of thylakoid membranes to high temperature in the dark
- Creator:
- Singh, A. K. and Singhal, G. S.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- antibody, polyacrylamide gel electrophoresis, protease, Triticum aestivum, and wheat
- Language:
- Multiple languages
- Description:
- Exposure of thylakoid membranes to high temperature in dark leads to the degradation of D1 protein. Maximum degradation of D1 protein occurred at 45 °C. Using N-terminal specific D1 antibody, a 23 kDa fragment of D1 protein was detected. The degradation of D1 protein could be prevented both by radical scavengers and inhibitors of serine protease and metallo-protease. These results suggest that degradation of D1 protein during exposure of thylakoid membranes to high temperature in dark is catalyzed by protease. and A. K. Singh, G. S. Singhal.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
29808. Specific features of water infiltration into soil with different management in winter and early spring period
- Creator:
- Hejduk, Stanislav and Kasprzak, Klaudius
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- infiltration, cryopedosphere, surface runoff, thawing and freezing, soil tillage, grassland, infiltrace, kryopedosféra, povrchový odtok, tání a mrznutí, obdělávání půdy, and travní porost
- Language:
- Slovak
- Description:
- The paper deals with the effects of agricultural soils management on surface runoff in winter and early spring period. Cryogenic processes that take place in soils can cause temporary reduction of infiltration capacity of soil. In the periods of snow-thawing and rain these phenomena induce conditions promoting the occurrence of surface runoff and floods. Effects of agricultural soils management on surface runoffs were studied at the research station in BrnoKníničky, Czech Republic, from 1965 to 2002. The aim of this research was to find out the differences between the winter surface runoff from experimental plots under winter wheat crop sown after plowing and under perennial forage crops without tillage. On soils without plowing, the decrease of soil infiltration rate occurred faster and was more intensive than on loose soils. During ten winter periods the average surface runoff from perennial forages was significantly higher (2.05 times) than from wheat crop (runoff coefficients 0.239 vs. 0.489). and Příspěvek se zabývá hodnocením vlivu kultivace zemědělských půd na povrchové odtoky v zimním a předjarním období. Kryogenní procesy v půdách mohou způsobovat dočasnou redukci jejich infiltrační rychlosti. V obdobích tání sněhu a dešťů vytváří podmínky pro výskyt povrchového odtoku a povodní. V letech 1965-2002 byl sledován na výzkumné stanici v Brně-Kníničkách vliv kultivace zemědělských půd na povrchové odtoky. Cílem tohoto výzkumu bylo najít rozdíly mezi zimními povrchovými odtoky z pokusných ploch s ozimou pšenicí vysetou po orbě a s víceletými pícninami bez zpracovaní půdy. Na půdách bez orby došlo k redukci infiltrační rychlosti rychleji a tato redukce byla intenzivnější než na kyprých půdách po orbě. Během deseti hodnocených zimních období byl povrchový odtok z víceletých pícnin průkazně vyšší (2,05 krát) než z pšenice. Průměrný koeficient povrchového odtoku u ozimé pšenice dosáhl hodnoty 0,239 a u víceletých pícnin 0,489.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
29809. Specific leaf area variations drive acclimation of Cistus salvifolius in different light environments
- Creator:
- Puglielli, G., Varone, L., Gratani, L., and Catoni, R.
- Format:
- print, bez média, and svazek
- Type:
- model:article and TEXT
- Subject:
- karotenoidy, carotenoids, aklimatizace, acclimatization, fluorescence chlorofylu, výměna plynu, absorptance listu, Cistus salvifolius, list, chlorophyll fluorescence, gas exchange, leaf absorptance, leaf nitrogen partitioning, leaf, 2, and 581
- Language:
- Multiple languages
- Description:
- Cistus salvifolius L. is the most widely spread Cistus species around the Mediterranean basin. It colonizes a wide range of habitats growing from sea level to 1,800 m a.s.l., on silicolous and calcicolous soils, in sun areas as well as in the understory of wooded areas. Nevertheless, this species has been mainly investigated in term of its responsiveness to drought. Our aim was to understand which leaf traits allow C. salvifolius to cope with low-light environments. We questioned if biochemical and physiological leaf trait variations in response to a reduced photosynthetic photon flux density were related to leaf morphological plasticity, expressed by variations of specific leaf area (SLA) and its anatomical components (leaf tissue density and thickness). C. salvifolius shrubs growing along the Latium coast (41°43'N,12°18'E, 14 m a.s.l., Italy) in the open and in the understory of a Pinus pinea forest, were selected and the relationships between anatomical, gas exchange, chlorophyll (Chl) fluorescence, and biochemical parameters with SLA and PPFD variations were tested. The obtained results suggested long-term acclimation of the selected shrubs to contrasting light environments. In high-light conditions, leaf nitrogen and Chl contents per leaf area unit, leaf thickness, and Chl a/b ratio increased, thus maximizing net photosynthesis, while in shade photosynthesis, it was downregulated by a significant reduction in the electron transport rate. Nevertheless, the increased pigment-protein complexes and the decreased Chl a/b in shade drove to an increased light-harvesting capacity (i.e. higher actual quantum efficiency of PSII). Moreover, the measured vitality index highlighted the photosynthetic acclimation of C. salvifolius to contrasting light environments. Overall, our results demonstrated the morphological, anatomical, and physiological acclimation of C. salvifolius to a reduced light environment., G. Puglielli, L. Varone, L. Gratani, R. Catoni., and Obsahuje bibliografii
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
29810. Specific leaf area, leaf nitrogen content, and photosynthetic acclimation of Trifolium repens L. seedlings grown at different irradiances and nitrogen concentrations
- Creator:
- An, H. and Shangguan, Z.-P.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- actual photochemical efficiency of photosystem 2, chlorophyll content and fluorescence, clover, photosynthetic acclimation, irradiance, photosynthetic nitrogen use efficiency, and specific leaf area
- Language:
- Multiple languages
- Description:
- Clover seedlings were grown at different nitrogen concentrations (5, 10, 15, 20, 25 mM NO3 -, i.e. N5 to N25) and two irradiances, I (200 and 400 µmol m-2 s-1 of photon flux density, i.e. I 200 and I 400). Net photosynthetic rate (PN), photosynthetic nitrogen use efficiency (PNUE), leaf chlorophyll (Chl) content, maximum photochemical efficiency (Fv/Fm), and actual photochemical efficiency of photosystem 2 (PS2) (ΦPS2) increased from N5 to N15 and decreased with N15 to N25. P N, PNUE, and ΦPS2 were higher at I 400 than at I 200, but Fv/Fm and leaf Chl contents at I 400 were lower than at I 200. The effects of the N and I on specific leaf area (SLA) and N contents per unit dry mass (Nm) were similar, the SLA and Nm increased from N5 to N25 and they were higher at I 200 than at I 400. The nitrogen contents per unit area (Na) increased from N5 to N20, but decreased from N20 to N25. The Na was higher at I 200 than at I 400 when Trifolium repens grew at N5 and N10, but it was higher at I 400 than at I 200 at N15 to N25. and H. An, Z. P. Shangguan.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public