This paper focuses on the impact of changes in temperature on one bay of St Vitus’ Cathedral in Prague Castle. The objective of the study is to simulate as correctly as possible the distribution of temperatures in the structure, and then to compute the thermal dilatation movements. Theoretical simulation of dilatation movements involves simulating the temperatures in the structure and then computing the displacements. Insolation and changes in air temperature around the structure are included in the temperature simulation. The computed temperature fields are used as a loading for computing the forces and deformations of one bay of St Vitus’ Cathedral. The theoretical deformation values obtained by means of the 3-D finite element model were compared with the measurements. The computed surface temperatures were also confronted with the surface temperatures measured in the interior and on the exterior of the cathedral. The results obtained from the simulations correspond well with the measured surface temperatures and deformations., Pavel Beran, Jiří Máca and Petr Fajman., and Obsahuje bibliografii
The aim of this study was to determine the potential development of water sorptivity of soil aggregates by heating. Soil aggregates were sampled from arable layer of 5 Polish soils: Haplic Luvisol 1 from Czesławice, Haplic Luvisol 2 from Wierzchucinek, Haplic Cambisol from Felin, Gleyic Mollic Cambisol from Chylice, and Haplic Phaeozem from Grabiec. Three aggregates of each soil type with minimum diameter between 4 and 10 mm were heated in the oven for at least 3 hours at temperatures 20, 100, 200, 250, and 360ºC. After each temperature treatment the soil aggregates were conditioned at the room temperature for 16 hours. Laboratory measurements of water sorptivity of soil aggregates were performed under a negative tension h0 = -2 cm using tension infiltrometer. It was found that the exposure to temperatures between 100 and 200°C tends to decrease water sorptivity of aggregates from all the studied soils but one (Haplic Luvisol 1), followed by about two- to four-fold increase in water sorptivity for exposure to temperatures of 250°C (in Haplic Luvisol 1, Haplic Luvisol 2, and Haplic Phaeozem) or 360°C (in Haplic Cambisol and Gleyic Mollic Cambisol).
The seasonal variation in photosynthetic rate of grass swards is partly the result of changes in the environment and partly the result of changes in the photosynthetic capacity of the sward itself. We evaluated two types of photosynthesis equations regarding their capacity to analyse seasonal and short-term temperature effects on photosynthesis of ryegrass (Lolium perenne L.). Intact cores of a field-grown ryegrass sward were taken to the laboratory 10 d after cutting for measurement of photosynthesis under controlled conditions. This was done during two four-week periods, in summer and autumn. Net photosynthetic rate (PN) of the sward was lower in autumn than in summer. Both a simple negatively exponential photosynthesis irradiance-response curve and the Farquhar equations for photosynthesis were applied to the in vivo canopy measurements. Application of the irradiance-response curve showed that irradiance-saturated gross photosynthetic rate increased linearly with increasing temperature and was higher in summer than in autumn. The initial radiation use efficiency did not differ between the seasons but decreased with the temperature rise. This explains the observation that total canopy photosynthetic rate decreased after short-term temperature increases in both seasons. The parameters in Farquhar equations that represent the temperature sensitivity of the maximum electron transport rate and of the Michaelis-Menten constants for CO2 and O2 fixation could not be quantified satisfactorily. Parameterisation of the Farquhar equations was hampered by a lack of robust information on many biochemical parameters, and the use of simple empirical response-functions may be preferable in the case of in vivo canopy measurements on grass swards. and B. O. M. Dirks ... [et al.].
The kinetic component (39 ps) for the energy transfer from a phycobilisome (PBS) to the photosystems was temperature-dependent while the components related to the kinetic processes within PBS, photosystem 2 (PS2) or PS1 were temperature-independent. The 39 ps component possessed the amplitude maximum at 647 nm but the minimum at 715 nm (room temperature) or 685 nm (0 °C), suggesting a direct energy transfer from C-phycocyanin to PS1 at room temperature but to PS2 at 0 °C. The temperature-induced kinetic change originated from a position shift of PBS along the thylakoid membrane. and Y. Li ... [et al.].
The effects of varying leaf temperature (T1) on some ecophysiological characteristics of photosynthesis for Quercus liaotungensis Koiz. under ambient radiation stress around midday on clear summer days were investigated using an IRGA equipped with a temperature-controlled cuvette. Net photosynthetic rate (PN) decreased as T1 increased from 30 to 35 °C as a result of stomatal closure, whereas non-stomatal limitation led to decreased PN in the T1 range of 35-45 °C. Decreased transpiration rate (E) and stomatal conductance (gs) at leaf temperatures above 30 °C were interpreted as a combined 'feedward' effect as a result of enhanced leaf-air vapour pressure deficit (VPD) and stomatal closure. Changes in E from T1 30 to 20 °C depended on VPD when gs was maintained constant. Water use efficiency (WUE) varied inversely with T1 by following a hyperbola. A decrease in intercellular CO2 concentration (Ci) occurred as a result of stomatal closure and a relatively high carboxylation capacity, whereas inactivation of mesophyll carboxylation in combination with photorespiration might be associated with the observed increase in Ci in the T1 range of 40 to 45 °C. and Shouren Zhang ... [et al.].
Glochidia are the larval stage of freshwater unionid mussels that parasitize the fins and gill apparatus of fish. A total of 22 fish species were examined for the presence of glochidia whose distribution on individual hosts was studied on three common fish species, the roach Rutilus rutilus (L.), perch Perca fluviatilis L. and bitterling Rhodeus sericeus (Pallas). Between 1997 and 1999, the fish were obtained from the rivers Morava and Kyjovka and surrounding water pools in the Czech Republic. The glochidia of two genera, Unio and Anodonta, were found. Anodonta glochidia were observed on 10 fish species, Unio glochidia on 17 fish species. There was a difference in spatial distribution of glochidia on the body of the host fish. Unio glochidia were predominantly located on the gills, whereas most Anodonta glochidia were found on the fins, with the highest numbers of glochidia were observed on the margin of the pectoral fins. For the gill apparatus, Unio glochidia were found predominantly on the second and third arch. Anodonta glochidia were predominantly found during winter and spring (November-May), whereas Unio glochidia were more abundant during May and June. The number of glochidia was positively correlated with fish length in perch highly infected by Anodonta glochidia and perch infected by Unio glochidia. Of the three fish species, the highest occurrence of parasites was found on perch with fewer observed on roach. In spite of the close relationship between bitterling and unionid mussels, glochidiosis was rare on this fish species.
A simple chlorophyll fluorescence (CF) measuring system has been implemented to study temporal characteristics of chlorophyll fluorescence induction (CFI) in dark-adapted freshwater algal cultures of Chlorella emersonii. There were two different decay time constants describing the CF quenching: τ0 (the faster) and τ1 (the slower) with amplitudes A0 and A1, respectively. The relative amplitude of the faster quenching component decreased once the sample was subject to deprivation from dissolved oxygen (DO). The DO concentration of samples was monitored to validate the effects of deprivation from air contact for up to 7 d and to the effect of adding DCMU to the culture (herbicide for blocking electron transport of photosystem 2). CFI analysis and DO measurements showed that the relative amplitude of A0 to (A0 + A1) and the DO concentration can be used as an indication of relative photosynthetic activity, thus allowing for the possibility to classify the physiological state of algal blooms into active and inactive states. and N. E. El Khachia, E. O'Mongain, A. Collins.