Urychlovače slouží k získávání intenzivních svazků iontů nebo částic s vysokou rychlostí a energií. Kinetické energie dodávané současnými urychlovači jsou v rozsahu od několika stovek keV do několika TeV (1 eV = 1.6 x 10(19) J). V makrosvětě tyto energie nikoho neohromí, ale v mikrosvětě je vše jinak: rychlost protonu s kinetickou energií 200 keV činí 2 % rychlosti světla, u elektronu se stejnou kinetickou eneregií je to dokonce 70 %. Ve světě vysokých energií se slovo urychlovač stává trochu nesmyslným, neboť rychlost částic už skoro neroste (blíží se rychlosti světla), ale roste jejich energie a tudíž i relativistická hmotnost., Zdeněk Doležal., and Obsahuje bibliografii
Using ^^C02, ^^02 and H2O gas exchange as weU as metabolite analysis, net CO2 uptake (P]4) and transpiration rate (£) were measured in the water-stressed plants of Digitalis lanata EHRH. The leaf conductance (gcch). the gross CO2 uptake (Pq), Úie photorespiration (Rp) and reassíinilation (RA) rates were calculated from measuied parameters. The pulse modulated fluorescence was measured duiing the steady statě photosynthesis. After withholding iirigation, the leaf water potential decreased to -2.S MPa, but leaves remained turgid and fully exposed to iiradiance even at a severe water stress. Due to the stress-induced reduction of gcch. and E were drastically reduced, whereas Pq and Rp were less affected. Water use efficiency (WUE), which was higher in 1 000 than 350 cm3(C02) increased as the water stress developed. The stomatal closure induced an increase in the reassimilation (RA) of internally liberated CO2 (Rp). The increased CO2 recycling in relation to the water stress was high in 350 cm^(C02) m-^ and still substantial in 1 000 cm3(C02) and consumed a substantial amount of radiant energy in the form of ATP and reduction equivalents. Consequently, the metabolic demand for radiant energy was reduced by less than 40 %, whereas was diminished by more than 70 % in severely stressed plants at 350 cm3(C02) m*3. Additionally, the quantum efiBciency of photosystem 2 as a measure for the flux of photosynthetically generated electrons was reduced upon the stress. This (and possibly other mechanisms) enabled the stressed plants to avoid overreduction of the photosynthetic electron transport chain.
Computed tomography (CT) is an effective diagnostic modality for three-dimensional imaging of bone structures, including the geometry of their defects. The aim of the study was to create and optimize 3D geometrical and real plastic models of the distal femoral component of the knee with joint surface defects. Input data included CT images of stifle joints in twenty miniature pigs with iatrogenic osteochondrosis-like lesions in medial femoral condyle of the left knee. The animals were examined eight and sixteen weeks after surgery. Philips MX 8000 MX and View workstation were used for scanning parallel plane cross section slices and Cartesian discrete volume creation. On the average, 100 slices were performed in each stifle joint. Slice matrices size was 512 x 512 with slice thickness of 1 mm. Pixel (voxel) size in the slice plane was 0.5 mm (with average accuracy of ± 0.5 mm and typical volume size 512 × 512 × 100 voxels). Three-dimensional processing of CT data and 3D geometrical modelling, using interactive computer graphic system MediTools formerly developed here, consisted of tissue segmentation (raster based method combination and 5 % of manual correction), vectorization by the marching-cubes method, smoothing and decimation. Stifle- joint CT images of three individuals of different body size (small, medium and large) were selected to make the real plastic models of their distal femurs from plaster composite using rapid prototyping technology of Zcorporation. Accuracy of the modeling was ± 0.5 mm. The real plastic models of distal femurs can be used as a template for developing custom made press and fit scaffold implants seeded with mesenchymal stem cells that might be subsequently implanted into iatrogenic joint surface defects for articular cartilage-repair enhancement., P. Krupa, P. Kršek, M. Javorník, O. Dostál, R. Srnec, D. Usvald, P. Proks, H. Kecová, E. Amler, J. Jančář, P. Gál, L. Plánka, A. Nečas., and Obsahuje bibliografii
In three separate experiments, the effectiveness of a SPAD-502 portable chlorophyll (Chl) meter was evaluated for estimating Chl content in leaves of Eugenia uniflora seedlings in different light environments and subjected to soil flooding. In the first experiment, plants were grown in partial or full sunlight. In the second experiment plants were grown in full sunlight for six months and then transferred to partial sunlight or kept in full sunlight. In the third experiment plants were grown in a shade house (40% of full sunlight) for six months and then transferred to partial shade (25-30% of full sunlight) or full sunlight. In each experiment, plants in each light environment were either flooded or not flooded. Non-linear regression models were used to relate SPAD values to leaf Chl content using a combination of the data obtained from all three experiments. There were no significant effects of flooding treatments or interactions between light and flooding treatments on any variable analyzed. Light environment significantly affected SPAD values, chlorophyll a (Chl a), chlorophyll b (Chl b), and total chlorophyll [Chl (a+b)] contents in Experiment I (p≤0.01) and Experiment III (p≤0.05). The relationships between SPAD values and Chl contents were very similar among the three experiments and did not appear to be influenced by light or flooding treatments. There were high positive exponential relationships between SPAD values and Chl (a+b), Chl a, and Chl b contents. and M. S. Mielke, B. Schaffer, C. Li.
The construction of dams is a significant environmental issue due to its impacts on native fish populations and riparian animals and habitats. The response of otters Lutra lutra Linnaeus, 1758 to such disturbances was evaluated using the Aguieira reservoir (Central Portugal) and its associated tributaries as a model. Visiting rates suggested the presence of resident otters, both in the reservoir and in two of the tributaries. There was a significant negative influence of water level and precipitation in the number of spraints found around the reservoir. Nevertheless, marking behaviour was positively related to substrate and negatively related to vegetation cover, though these variables explained only a small amount of variation in otter signs. In the tributaries, although precipitation also negatively affected the number of otter signs found, the availability of rocks in the riverbed and the presence of refuge had a positive influence in marking behaviour. Prey composition and abundance differed between reservoir and tributaries, but the main otter prey in both systems was the pumpkinseed, which is very abundant in the reservoir. Results demonstrate that otters regularly use the Aguieira reservoir, which provides a good prey base, and the associated tributaries, which provide shelter.
This study appears from an experiment previously carried out in New Zealand white rabbits. Allogenic mesenchymal stem cells (MSCs) were transplanted into an iatrogenically-created defect in the lateral section of the distal physis of the left femur in 10 miniature pigs. The right femur with the same defect served as a control. To transfer MSCs, a freshly prepared porous scaffold was used, based on collagen and chitosan, constituting a compact tube into which MSCs were implanted. The pigs were euthanized four months after the transplantation. On average, the left femur with transplanted MSCs grew more in length (0.56±0.14 cm) compared with right femurs with physeal defect without transplanted MSCs (0.14 ± 0.3 cm). The average angular (valgus) deformity of the left femur had an angle point of 0.78°, following measurement and X-ray examination, whereas in the right femur without transplantation it was 3.7°. The initial results indicate that preventive transplantation of MSCs into a physeal defect may prevent valgus deformity formation and probably also reduce disorders of the longitudinal bone growth. This part of our experiment is significant in the effort to advance MSCs application in human medicine by using pig as a model, which is the next step after experimenting on rabbits., L. Plánka ... [et al.]., and Obsahuje seznam literatury
Reports of wood mouse arboreality are rather scarce outside Britain. I reviewed and analysed 267 visits and 16,456 checks of glirids artificial nest-boxes mounted on trees, in twelve sample areas of Meso- and Supra-Mediterranean woodlands (Sicily, 1995–2005). The wood mouse was recorded only 65 times (0.395%) using the artificial nest-boxes in nine sample areas, and based on this low frequency, the wood mouse can be considered as an occasional dweller of artificial nest-boxes. The resource selection index allowed checking the use respect to the availability of nest-boxes placed at different heights. These were likely reached by climbing the dense understorey and low tree branches up to 5 m, but nest-boxes in the two lower classes (0.5–1.0 and 1.1–1.5 m) were used more than those in the two higher classes (1.6–2.0 and 2.1–5.0 m). ANOVA results suggested that the box use was not related to any particular habitat or sample area feature, and it was slightly more pronounced from March to May. Regardless of their age and sex, individuals mostly exploited nest-boxes placed near the ground (0.5–1.5 m) and generally for 2–3 months. Nonetheless, cases of consecutive use for longer periods and instances of reproduction inside nest-boxes showed that some individuals extended their home range also to the vertical dimension.
To estimate the size of fish taken as prey by piscivorous predators, linear or non-linear relationships between bone measures (pharyngeal, opercula, cleithra, anal and dorsal spine bones, otoliths) and body length were elaborated for eleven Eurasian cyprinid fish species captured in three lakes of Turkey: rudd Scardinius erythrophthalmus, Baltic vimba Vimba vimba, Danube bleak Chalcalburnus chalcoides, gibel carp Carassius gibelio, roach Rutilus rutilus, silver bream Blicca bjoerkna, common carp Cyprinus carpio, chub Leuciscus cephalus, Dnieper chub Petroleuciscus borysthenicus, tench Tinca tinca and tarek Alburnus tarichi (endemic species for Lake Van). All calculated regressions were highly significant, with coefficients of determination >81% in most of cases. The results suggest that the biometric relationships between fish length and some bones (pharyngeal, opercula, cleithra) are well suited for use in prey-predator studies of all the studied species, but otoliths and the dorsal and anal spines can be used for some fish species only (rudd, Baltic vimba, roach, silver bream, gibel carp).
A comparison of the effects of ultrasound produced by low- and high-frequency ultrasonic apparatuses upon biological systems is one of the basic problems when studying ultrasound cavitation effects. One possibility for how to compare these effects is the indirect method which uses well-known physical quantities characterizing the interaction of ionizing radiation with matter and which also converts these quantities to one common physical quantity. The comparison was performed with two methods applied to the chemical dosimetry of ionizing radiation. The first method employed a twocomponent dosimeter which is composed of 50 % chloroform and 50 % re-distilled water (i.e. Taplin dosimeter). The other method used a modified iodide dosimeter prepared from a 0.5 M potassium iodide solution. After irradiation or ultrasound exposure, measurable chemical changes occurred in both dosimeters. The longer the exposure, the greater the chemical changes. These effects are described by the relationship of these changes versus the exposure times in both dosimeters. The UZD 21 ultrasonic disintegrator (with a frequency of 20 kHz, 50 % power output) was used as a lowfrequency ultrasound source, and the BTL-07 therapeutic instrument (with a frequency of 1 MHz and intensity of 2 W/cm2) was used as a high-frequency cavitation ultrasound source. For comparison, a 60Co gamma source was applied (60Co, gamma energies of 1.17 and 1.33 MeV, activity of 14 PBq). Results of this study have demonstrated that the sonochemical products are generated during exposure in the exposed samples of both dosimeters for all apparatuses used. The amount of these products depends linearly upon the exposure time. The resulting cavitation effects were recalculated to a gray-equivalent dose (the proposed unit is cavitation gray [cavitGy]) based on the sonochemical effects compared to the effects of ionizing radiation from the 60Co source., B. Kratochvíl, V. Mornstein., and Obsahuje bibliografii