The text is divided into two parts. In the first part, the author describes the eternalists’ and presentists’ positions as the two basic possible statements of the ontology of time (there exists only what is present - presentism - and there also actually exists both what is past and what is future). The eternalist position and the emphasis it puts on the actual existence of past and future events (expressed usually by the use of present tense or of some tenseless form of the verb) are thoroughlly analysed in order to show that in fact, they end up making strings of symbols that are not correct statements. It is therefore necessary to step beyond these clumsy statements and try to understand more exactly the eternalist intuitions on a deeper, metaphysical level. That is the main concern of the second part of the text, in which the metaphysical implications of both positions are compared. At the end of the linguistical analysis in the first part, we got to a point where it may seem that presentism and eternalism are only different attempts at expressing what is in fact the same understanding of the nature of time, but in the metaphysical analysis that follows, it will turn out that they are not. Presentism and eternalism are shown to be two different ontological approaches of time in relation to space (time as a basically homogenous fourth dimension and time as something essentially different from space). The author then focuses on the consequences these two positions have especially on the concept of the present and of its flow through time. In the end, presentism and eternalism turn out to be completely different positions that - in parallel with the famous McTaggart’s argument - claim a very strong reality of time on the one hand (presentism) or, on the other hand, its utter unreality (eternalism)., Text je rozdělen do dvou částí. V první části autor popisuje postoje eternalistů a presentistů jako dvě základní možná prohlášení ontologie času (existuje pouze to, co je přítomno - presentismus - a tam také skutečně existuje to, co je minulost a co je budoucnost) . Postavení eternalistů a důraz, který kladou na skutečnou existenci minulých a budoucích událostí (vyjádřených obvykle pomocí přítomného času nebo nějaké napjaté podoby slovesa), jsou důkladně analyzovány, aby se ukázalo, že ve skutečnosti končí řetězců symbolů, které nejsou správné. Je proto nutné překonat tyto neohrabané výroky a snažit se přesněji pochopit eternalistické intuice na hlubší, metafyzické úrovni. To je hlavním zájmem druhé části textu, ve kterých jsou porovnány metafyzické důsledky obou pozic. Na konci lingvistické analýzy v první části jsme se dostali do bodu, kdy se může zdát, že presentismus a eternalismus jsou pouze různými pokusy o vyjádření toho, co je vlastně stejné chápání podstaty času, ale v metafyzické analýze, že následuje, ukáže se, že nejsou. Současnost a věčnost jsou ukázány jako dva rozdílné ontologické přístupy času ve vztahu k prostoru (čas jako v podstatě homogenní čtvrtá dimenze a čas jako něco, co je v podstatě odlišné od prostoru). Autor se pak zaměřuje na důsledky, které tyto dvě pozice mají zejména na koncepci přítomnosti a jejího toku v čase.Současnost a eternismus se nakonec ukázaly jako zcela odlišné pozice, které - paralelně s proslulým argumentem McTaggarta - tvrdí na jedné straně velmi silnou realitu času (presentismus) nebo na druhé straně její naprostou neskutečnost (eternalismus)., and Jacques Joseph
In this essay the author argues that an ontological problem of a work of art, one of the long-standing problems of the philosophy of art, is merely an apparent one. The author argues that it in fact comprises two particular, different problems. The first is the question of how the thing being described in aesthetic terms exists, whether the aesthetic and physical description of a thing are so different, indeed disparate, that they cannot – as some philosophers of art assume – relate to the same thing. The second problem is the question of how a work of a multiple art (for example, of music or literature) can exist, whether we can identify it with the individual act of performing or using this work (for example, the performance of music or a reading of a book). The first problem, argues the author, stems from the erroneous assumption that the disparateness of the aesthetic and physical description of a thing leads to the conclusion that the object of aesthetic description must exist differently from the way a physical description exists. The second problem emerges from a lack of understanding of how we use the term “work of art,” when we use it for a work of multiple art. The author also criticizes simultaneous attempts by Arthur Danto and Joseph Margolis, two leading philosophers of art, to solve the ontological problem of the work of art.
Ca2+ has been considered as a necessary ion for alleviation of stress-induced damages in plants. We investigated effects of exogenous Ca2+ on waterlogging-induced damage to pepper and its underlying mechanisms. Pepper seedlings under stress were treated by spraying of 10 mM CaCl2. Applying exogenous Ca2+ increased the biomass of pepper leaves and roots, improved photosynthetic characteristics, membrane permeability, root activity, osmotic substance contents, antioxidant enzyme and alcohol dehydrogenase activities, while it reduced lactate dehydrogenase activity. It maintained hydroxide radical contents and activities of malate dehydrogenase and succinate dehydrogenase relatively high. Our results suggested that applying exogenous Ca2+ could regulate osmotic substance contents, antioxidant system activity, root respiration, and metabolism, and subsequently alleviate waterlogging-induced damages to pepper plants., B. Z. Yang, Z. B. Liu, S. D. Zhou, L. J. Ou, X. Z. Dai, Y. Q. Ma, Z. Q. Zhang, W. C. Chen, X. F. Li, C. L. Liang, S. Yang, X. X. Zou., and Obsahuje bibliografii
The hypothesis that application of exogenous glycine betaine (GBEX) may attenuate the effects of mild water deficit in leaf gas exchange and lipid peroxidation in Carapa guianensis was examined. For this reason, 110-d old plants were sprayed with 0, 25, and 50 mM GBEX and then subjected to two watering regimes. In the first, irrigation was continuously performed to maintain the soil near to field capacity (watered plants). In the second, irrigation was withheld and water deficit resulted from progressive evapotranspiration (water-stressed plants). Treatment comparisons were assessed when predawn leaflet water potential (Ψpd) of stressed plants reached -1.28 ± 0.34 MPa. Regardless of the watering regime, significant (P<0.05) increases in foliar glycine betaine (GBLeaf) concentration were observed in response to increasing GBEX; however, such increases were more expressive in stressed plants. The net photosynthetic rate, stomatal conductance to water vapor, and intercellular to ambient CO2 concentration ratio were significantly lower in water-stressed plants independently of GBEX concentration sprayed on leaves. The application of 25 and 50 mM GBEX caused significant (P<0.05) increases in ascorbate peroxidase (APX) activity in stressed plants, while significant (P<0.05) increases in catalase activity was observed just in the stressed plants treated with 50 mM GBEX. Malondialdehyde concentrations did not differ between watered and stressed plants regardless of GBEX concentration. In conclusion, C. guianensis was able to incorporate GBEX through their leaves and the resulting increases in GBLeaf attenuated lipid peroxidation in stressed plants through positive modulation of APX and CAT activities., F. J. R. Cruz ...[et al.]., and Obsahuje bibliografii
Cyanobacteria Spirulina platensis and Nostoc linckia were grown in the presence of 5 mM and 50 mM glucose or 5 mM mannose, non-metabolisable glucose analogue that effectively triggers the repression of photosynthesis. Glucose evoked active cyanobacterial growth but chlorophyll (Chl) content decreased to some extent and porphyrins were excreted. The content of monogalactosyldiacylglycerol decreased in glucose-grown cyanobacteria and that of phosphatidylglycerol increased substantially. Mannose inhibited cyanobacteria growth as well as Chl synthesis, however, phosphatidylglycerol contents were higher than in respective control samples. In cyanobacterial cells glucose may not only inhibit photosynthetic processes, but also cause structural transformations of membranes which may be necessary for the activity of respiratory electron transport chain components under heterotrophic conditions. and N. F. Mykhaylenko ... [et al.].
Melatonin mediates many physiological processes in animals and plants. To examine the potential roles of melatonin in salinity tolerance, we investigated the effects of exogenous melatonin on growth and antioxidant system in cucumber under 200 mM NaCl stress conditions. The results showed that the melatonin-treated plants significantly increased growth mass and antioxidant protection. Under salinity stress, the addition of melatonin effectively alleviated the decrease in the net photosynthetic rate, the maximum quantum efficiency of PSII, and the total chlorophyll content. Our data also suggested that melatonin and the resistance of plants exhibited a concentration effect. The application of 50-150 μM melatonin significantly improved the photosynthetic capacity. Additionally, the pretreatment with melatonin reduced the oxidative damage under salinity stress by scavenging directly H2O2 or enhancing activity of antioxidant enzymes (including superoxide dismutase, peroxidase, catalase, ascorbate peroxidase) and concentrations of antioxidants (ascorbic acid and glutathione). Therefore, the melatonin-treated plants could effectively enhance their salinity tolerance., L. Y. Wang, J. L. Liu, W. X. Wang, Y. Sun., and Obsahuje seznam literatury
This year‘s Nobel Prize in Physics was awarded to three astrophysicists, Jim Peebles, Michel Mayor and Didier Queloz. Peebles was awarded half of the prize for cosmology and Mayor and Queloz were awarded a quarter each for the discovery of the first exoplanet orbiting a Sun-like star 51 Pegasi. Their discovery was reported almost 25 years ago and started a new era of exoplanetary research. This article presents the steps leading to the discovery of planet 51 Pegasi b and the following efforts to detect and characterise exoplanets. The future of the exoplanetary research field is also discussed in this article. and Petr Kabáth.
In this paper we investigate the expected terminal utility maximization approach for a dynamic stochastic portfolio optimization problem. We solve it numerically by solving an evolutionary Hamilton-Jacobi-Bellman equation which is transformed by means of the Riccati transformation. We examine the dependence of the results on the shape of a chosen utility function in regard to the associated risk aversion level. We define the Conditional value-at-risk deviation (CVaRD) based Sharpe ratio for measuring risk-adjusted performance of a dynamic portfolio. We compute optimal strategies for a portfolio investment problem motivated by the German DAX 30 Index and we evaluate and analyze the dependence of the CVaRD-based Sharpe ratio on the utility function and the associated risk aversion level.