The photosynthetic response of 8 cotton (Gossypium hirsutum L.) genotypes to changing irradiance was investigated under field conditions during the 1998 through 2000 growing seasons. Equations developed to describe the response of net photosynthetic rate (PN) to photosynthetic photon flux density (PPFD) demonstrated that, across all irradiances, the two okra leaf-type genotypes photosynthesized at a greater rate per unit leaf area than all of the six normal leaf-type genotypes. This superior photosynthetic performance of the okra leaf-type genotypes can be partially explained by their 13 % greater leaf chlorophyll content relative to that of the normal leaf-type genotypes. The 37 % reduction in leaf size brought upon by the okra leaf trait may have concentrated the amount of photosynthetic machinery per unit leaf area. Nevertheless, the lack of sufficient canopy leaf surface area suppressed the potential yield development that could accompany the higher PN per unit leaf area.
The paper discusses Tarski’s approach to quotation. It starts from showing that it is vulnerable to semantic inconsistencies connected with what is known as Reach’s puzzle, formulated in 1938 by a Czech logician Karel Reach. This fact gives rise to serious problems concerning the relation between the metalanguage and an object language. Moreover, the paper touches upon a historic aspect, pointing out that the problem at hand is discussed in the only paper signed up as Al. Tajtelbaum, i.e. Alfred Tarski’s original name. It argues that the puzzle reveals the importance of reopening the discussion on the understanding and limitations of deriving the metalanguage from an object language.
The paper describes simulation method for the evaluation of Coulomb interactions on energy spread in electron beam in the vicinity of Schottky emission source. It presents also some preliminary results of performed Monte Carlo simulations. and Článek se zabývá problematikou výpočtu vlivu coulombovských interakcí částic na energiovou šířku emitovaného svazku v blízkosti Schottkyho katody. Popisuje model i vlastní simulaci Monte Carlo elektronového emisního zdroje a metodiku zpracování výsledků.
A general analysis is formulated for the closed loop coupled thermal and displacement viscoelastic 1-D wave problem. The proper inclusion of the highly temperature sensitive viscoelastic material properties renders the problem nonlinear, even though the displacements and material properties continue to obey linear relations. Various categories of open and closed loop temperature-displacement couplings as well as boundary conditions are fomulated and discussed. Comparisons between temperature independent and dependent material properties indicate that the nature of the latter nonlinear problem radically differs from the former steady-state temperature linear one. and Obsahuje seznam literatury
The role of Computer Aided Engineering in research as well as product development has been significantly increased during two last decades. The growing demands on the simulation address not only monodisciplinary phenomena but also phenomena from
different engineering branches. The current state-of-the-art simulation tools allow two basic approaches for meeting the demands, either coupling of various specialised simulation codes or application of multiphysical simulation tools.
This paper focuses on the simulation approaches for the multidisciplinary tasks and particularly on the connection of specialised simulation tools by interfaces. It classifies the interfaces between specialised software packages in general and gives some case studies using the coupling of specialised simulation tools. Finally, the development stages of an interface between civil and mechanical systems are presented. and Obsahuje seznam literatury
The paper deals with crack propagation through an interface between two elastic materials. The basic idea of developing stability criteria of general singular stress concentrators introduced in the first part is applied to the case of a crack with its tip at the interface between two different materials. Three different stability criteria based on different physical principles are presented and a numerical example with their mutual comparison is carried out. A procedure based on a generalized strain energy density factor is shown which makes it possible to estimate the further direction of crack propagation after the crack has passed the interface. The procedure presented is applied in the numerical examples. and Obsahuje seznam literatury
The influence of through crack in the protective surface layer on damage of coated structure is investigated. The coated structure is modeled as a particular case of a bi-material body consisting of thin surface layer on the substrate. The problem is studied under the assumptions corresponding to small scale yielding conditions and calculations are performed by the finite element method. Specific attention is devoted to the case of a through coating crack with its tip at the interface between coating and the substrate. To estimate how the coating crack with its tip at the interface influences the substrate failure the general approach described in [1, 2, 3] (Part I, II, III of this contribution) is applied. An aproximate approach based on calculations of crack mouth opening displacement for thin protective layers is suggested and developed. It is concluded that in the case of a stiffer coating on a more compliant substrate, the through coating cracks represent dangerous stress concentrators and as a consequence of elastic mismatch of both materials, the critical applied stress for substrate failure decreases. Traditional approaches may have underestimated this effect and estimations of the service life of coated structures neglecting this phenomenon could lead to non-conservative values, with unexpected failures. and Obsahuje seznam literatury
A list of plant species documented over the past 25 years to exhibit Crassulacean Acid Metabolism (CAM) is presented. The list compiles all available information on these species including their growth habits, succulent parts, carbon isotope discrimination values, CAM types, CAM inducers, and CAM modifications.
In Sedum wrightii grown in a growth chamber, detached leaves could survive for at least 120 d with a high rate of success for propagule formation. The pattern of gas exchange, associated with CAM, may be important in extending the period during which the detached leaf remains physiologically active. The added benefit for the developing propagule, still attached to the "parent" leaf, is an additional source of water and saccharide reserves over an extended period necessary for rooting. Drought survival of propagules may be determined by the amount of water-storing tissue in the detached leaf.