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24152. Variační počet, přirozený aparát fyziky

Creator:
Musilová, Jana and Musilová, Pavla
Format:
print, bez média, and svazek
Type:
model:article and TEXT
Subject:
variační počet, variační metody, physics, calculus of variations, variational methods, matematická estetika, variační matematika, variační fyzika, 6, and 53
Language:
Czech and English
Description:
Říká se, že jedním ze znaků správné fyzikální teorie je její krása. Máme-li na mysli estetičnost matematickou, patří variační počet k matematickým metodám, které naplňují tento požadavek vrchovatě. Je také pravda, že správné (zkušeností a experimentem prověřené) fyzikální teorie bývají variační, tj. odvoditelné z variačního principu: Klasická mechanika, relativistická mechanika, kvantová mechanika, klasická elektrodynamika... Na zcela elementární úrovni předkládáme základní myšlenku a klasické postupy variačního počtu, s ukázkami použití v geometrii a fyzice. Zaměříme se pouze na variační princip prvního řádu, s důrazem na mechaniku, kde na rozdíl od teorie pole závisí řešené úlohy pouze na jedné nezávisle proměnné, ve fyzice obvykle na čase., It is said that one of the characteristic features of physical theories is their beauty. Having in mind the "mathematical aesthetic appearance" one can say that the calculus of variations highly fulfils this requirement! It is also well known that correct physical theories (those verified experimentally), are often variational, i.e. based on a variational principle: classical mechanics, relativistic mechanics, quantum mechanics, classical electrodynamics, etc. We present, at a very basic level, the fundamental ideas and classical approaches of the calculus of variations, including examples of their use in geometry and physics. We focus on the first order variational principle, emphasizing mechanics, because contrary to field theories, the variational problems in mechanics depend on one independent variable only (usually time in physics)., Jana Musilová, Pavla Musilová., and Obsahuje bibliografii
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

24154. Variation in carbonic anhydrase activity and its relationship with photosynthesis and dry mass of mustard

Creator:
Khan, N.A.
Format:
print
Type:
model:internalpart and TEXT
Language:
Multiple languages
Description:
Carbonic anhydrase (CA) activity and net photosynthetic rate (/’N) in the leaves, and plant dry mass (DM) in twelve cultivars of mustard (Brassica juncea L.) were measured 50, 70 and 90 d after sowing. At different sampling stages CA was strongly associated with PN and DM.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

24155. Variation in parameters affecting risk of human disease due to TBE virus

Creator:
Korenberg, E. I. and Kovalevskii, Yu V.
Format:
print
Type:
model:internalpart and TEXT
Subject:
tick-borne encephalitis, Ixodes persulcatus, and risk of infection
Language:
English
Description:
To rank variables affecting risk of human disease due to tick-borne encephalitis (TBE) virus in the Russian Far East, we compared annual changes in ( 1 ) frequency of human contact with vector ticks, (2) prevalence of infection in the tick population and (3) quantity of virus present infected ticks. Sites were sampled uniformly over a 4-year period in a forested region where Ixodes persulcatus serves as the principle vector. The questing density of ticks on vegetation remained relatively constant during the course of this study. The frequency of contacts of the local human population with ticks carrying different doses of the TBE virus was changeable. The rate of TBE infection of humans in the study site corresponded to that of human contacts with highly infected ticks. The density of highly infected ticks represents the principal parameter for determining potential epidemiological significance of a natural TBE focus.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

24156. Variation in the morphology of the wings of the endangered grass-feeding butterfly Coenonympha oedippus (Lepidoptera: Nymphalidae) in response to contrasting habitats

Creator:
Jugovic, Jure, Zupan, Sara, Bužan, Elena, and Čelik, Tatjana
Format:
print, počítač, and online zdroj
Type:
model:article and TEXT
Subject:
motýli, babočkovití, křídla (zoologie), adaptace (biologie), butterflies, Nymphalidae, wings (zoology), adaptation (biology), Lepidoptera, Coenonympha oedippus, False Ringlet, classical morphometrics, geometric morphometrics, environmental heterogeneity, 2, and 59
Language:
English
Description:
At the southern limit of its range the endangered butterfly Coenonympha oedippus inhabits grasslands (wet, dry) that differ significantly in the abundance of its larval hostplants (wet > dry) and mean annual air temperature (wet < dry). We determined the difference in the wing morphology of individuals in the two contrasting habitats to test whether and how traits associated with wing size, shape and eye like spots vary in the sexes and two ecotypes. We show that sexual dimorphism follows the same (wing size and shape, number of eyespots on forewing) or different (relative area of eyespots on hindwings) patterns in the two contrasting habitats. Irrespective of ecotype, females had larger, longer and narrower wings, and more forewing eyespots than males. Sexual dimorphism in the relative area of eyespots on hindwing was female-biased in the wet, but male-biased in the dry ecotype. Ecotype dimorphism in wing size and the relative area of eyespots on the hindwing is best explained by mean annual air temperature and abundance of host-plants. While ecotype dimorphism in wing size did not differ between sexes, neither in direction (wet > dry) or in degree, in the two sexes the relative area of eyespots on hindwing had opposite patterns (males: dry > wet; females: wet > dry) and was more pronounced in males than in females. The differences in wing shape between ecotypes were detected only in the hindwings of males, with more rounded apex in the dry than in the wet ecotype. We discuss the life-history traits, behavioural strategies and selection mechanisms, which largely account for the sex- and ecotype-specific variation in wing morphology., Jure Jugovic, Sara Zupan, Elena Bužan, Tatjana Čelik., and Obsahuje bibliografii
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public

24157. Variation of photosynthetic characteristics and yield in wild and cultivated species of yams (Dioscorea spp.) from Koraput, India

Creator:
Padhan, B. and Panda, D.
Format:
print, bez média, and svazek
Type:
model:article and TEXT
Subject:
fotosyntéza, photosynthesis, chlorophyll fluorescence, gas exchange, tuber yield, 2, and 581
Language:
Multiple languages
Description:
Variations in leaf gas-exchange characteristics, PSII activity, leaf pigments, and tuber yield were investigated in seven wild and one cultivated species of Dioscorea from Koraput, India, in order to find out their overall adaptability to the environment. The leaf photosynthetic rate, transpiration, stomatal conductance, water-use efficiency, carboxylation efficiency, and photosynthetic pigments were significantly higher in some wild species compared to the cultivated species. In addition, some wild species showed better photochemical efficiency of PSII, photochemical quenching, and electron transport rate in comparison to cultivated one. Furthermore, leaf dry matter accumulation and tuber yield was also higher in some wild species compared to the cultivated species. Taken together, the wild species, such as D. oppositifolia, D. hamiltonii, and D. pubera, showed the superior photosynthetic efficiency compared to the cultivated D. alata and they could be used for future crop improvement programs., B. Padhan, D. Panda., and Obsahuje bibliografii
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

24158. Variation of thorax flight temperature among twenty Australian butterflies (Lepidoptera: Papilionidae, Nymphalidae, Pieridae, Hesperiidae, Lycaenidae)

Creator:
Nève, Gabriel and Hall, Casey
Format:
print, počítač, and online zdroj
Type:
article, články, journal articles, model:article, and TEXT
Subject:
Zoologie, otakárkovití, babočkovití, běláskovití, motýli, Papilionidae, Nymphalidae, Pieridae, butterflies, Lepidoptera, Hesperiidae, Lycaenidae, thorax flight temperature, wing loading, infra red thermometer, warming-up rate, physical constraint, allometry, 2, and 59
Language:
English
Description:
Thermal requirements for flight in butterflies is determined by a combination of external factors, behaviour and physical constraints. Thorax temperature of 152 butterflies was monitored with an infra-red thermometer in controlled laboratory conditions. The temperature at take-off varied from 13.4°C, for a female Heteronympha merope to 46.3°C, for a female Junonia villida. Heteronympha merope, an understorey species, had the lowest recorded take-off temperatures, with females flying at a much lower thorax temperatures than males. Among the tested butterfly species, warming-up rate was positively correlated with take-off temperature and negatively with body mass. Wing loading is a major variable in determining the thorax flight temperature. Butterflies with the highest wing-loadings experienced the highest thorax temperatures at take-off. A notable exception to this rule is Trapezites symmomus, the only Hesperiidae of our data set, which had thorax flight temperatures of 31.5°C and 34.5°C, well within the range of the observed butterflies, despite a wing load ca. five times higher. The high thorax temperature recorded in J. villida is probably linked to its high flight speed. The results highlight the importance of physical constraints such as body size on the thermal requirements for flight across a range of butterfly species., Gabriel Nève, Casey Hall., and Obsahuje bibliografii
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

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