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[en] The fundamental processes of biological development are governed by multiple signaling molecules that create non-uniform concentration profiles known as morphogen gradients. It is widely believed that the establishment of morphogen gradients is a result of complex processes that involve diffusion and degradation of locally produced signaling molecules. We developed a multi-dimensional discrete-state stochastic approach for investigating the corresponding reaction-diffusion models. It provided a full analytical description for stationary profiles and for important dynamic properties such as local accumulation times, variances, and mean first-passage times. The role of discreteness in developing of morphogen gradients is analyzed by comparing with available continuum descriptions. It is found that the continuum models prediction about multiple time scales near the source region in two-dimensional and three-dimensional systems is not supported in our analysis. Using ideas that view the degradation process as an effective potential, the effect of dimensionality on establishment of morphogen gradients is also discussed. In addition, we investigated how these reaction-diffusion processes are modified with changing the size of the source region
[en] Conclusions: A new phase of mastering the FR and CNFC technologies began in Russia with a challenging scientific goal to develop innovative technologies appropriate for large-scale NP development in future. Meanwhile it is proposed for industry to use demonstrated BN and MOX technologies in addressing present day burning issue of VVER SNF accumulation. The proposed option would provide possibility to: • dispose timely all VVER SNF and by this would minimize time for SNF storage, Am inventory and improve public perception; • export VVER with SNF take-back policy; • preserve accumulated in VVER Pu for future; • stabilize Pu inventory in future in case of NP stagnation
[en] Antibiotic residues pose a threat to the health of aquatic organisms. The effects and accumulation of antibiotic ciprofloxacin (CIP) in a floating macrophyte (Eichhornia crassipes) under hydroponic conditions were investigated. It was found that E. crassipes exposure to CIP (< 1000 μg L−1) could maintain a stable photosynthesis efficiency. In response to CIP stress, catalase and peroxidase activities of leaves were 7.24–37.51 nmol min−1 g−1 and 98.46–173.16 U g−1, respectively. The presence of CIP did not inhibit the growth of the plant. After 14 days of exposure, tender leaves became white and withered, ascribed to the decline of chlorophyll content and chlorophyll fluorescence parameters. The CIP concentrations, absorbed by E. crassipes, were highest in the roots, followed by white aerial parts and green aerial parts at CIP concentrations of 100 and 1000 μg L−1. These findings demonstrated that E. crassipes could absorb and tolerate CIP in a limited time-scale and imply an alternative solution for phytoremediation in water bodies contaminated with antibiotics.
[en] Three general reasons for undertaking statistical studies of occupational exposure to radiation are identified. Some important points to be considered in such analyses are given and some interesting questions for future research are identified. (author)
[en] The aim of this work was to perform a critical evaluation of this mechanism of metal accumulation in selected strains of bacteria. A ''Citrobacter freundii'' and some other strains of bacteria isolated from soil polluted by heavy metals were used. All these strains exhibited an enhanced activity of an acid-type phosphatase with a pH optimum at pH 5 typical of microorganisms. Time course of accumulation of uranium (in the form of 0.1 mM uranyl nitrate) by these bacteria was followed in a substrate-less system and at increasing concentrations (from 1 to 16 mM) of glycerol-2-phosphate as a substrate for the phosphatase. It was found that at low glycerol-2-phosphate concentrations (1.0 mM) the bacteria accumulated about 30% uranium more than in a substrate-less system. At higher glycerol-2-phosphate concentrations less metal was accumulated. Electron microscopic observation of ultra thin sections of cells revealed that metal was located mainly at the surface as a dense precipitate. It was presumed that an observed inhibition of uranium accumulation could be connected with a formation of soluble uranyl compounds with glycerol-2-phosphate within a pH of 5 to 6. Such a presumption was confirmed by revealing a 60 to 80% uranium recovery from the loaded cells in 10 mM glycerol-2-phosphate solution. (author). 13 refs, 10 figs, 1 tab
[en] Variations in cadmium accumulation and translocation among 40 Chinese cabbage cultivars were studied to identify and screen out Cd-safe cultivars (CSCs), i.e. cultivars with low enough accumulation of Cd in their edible parts even when grown in contaminated soils. It was observed in the pot-culture experiment that there was a significant difference (p < 0.05) in shoot Cd concentrations under three Cd treatments (1.0, 2.5 and 5.0 mg/kg), with corresponding average values 0.88, 4.45 and 7.76 mg/kg, respectively. Shoot Cd concentrations in 16 cabbage cultivars were lower than 0.50 mg/kg. The translocation factors (TFs) and the extraction factors (EFs) in five cabbage cultivars were lower than 1.0 in the pot-culture experiment. The field-culture experiment further validated that New Beijing 3 and Fengyuanxin 3 could be considered as CSCs. In particular, the two cultivars can be cultivated in low to moderate Cd-contaminated soils (Cd concentration <1.25 mg/kg) to minimize the Cd accumulation in the food.
[en] Ultrasound stimulated microbubbles have been shown to be capable of breaking up blood clots through micro-scale interactions occurring near the clot surface. However, only a small fraction of bubbles circulating in the bloodstream will be in close proximity to such boundaries, where they must be to elicit therapeutic effects. Here, the accumulation and subsequent behavior of microbubbles displaced from an overlying flow channel to a boundary under radiation forces were examined. Experimental data were acquired using a novel high speed microscopy configuration and simulations were conducted to provide insight into the accumulation process. There was broad agreement between experiments and simulations, both indicating that the size distribution and number of bubbles arriving at the boundary depended on channel flow rate, applied pressure, and bubble concentration. For example, higher flow rates and lower pressures favored the accumulation of larger bubbles relative to the native agent distribution. Moreover, bubble dynamics were dependent on the surface type, exhibiting rapid translation along agarose gel surfaces whereas on fibrin surfaces, they accumulated in localized regions inducing repetitive strain cycles. The results indicate that the process of bringing bubbles from within a vessel to a boundary is complex and should be an important consideration in the development of therapeutic applications such as sonothrombolysis. (paper)
[en] The article Cellular distribution of cadmium in two amaranth (Amaranthus mangostanus L.) cultivars differing in cadmium accumulation, written by Keyu Chi, Rong Zou, Li Wang, Wenmin Huo and Hongli Fan, was originally published electronically on the publisher’s internet portal (currently SpringerLink)
[en] The glycogen-binding domain of the AMP-activated kinase β subunit has been crystallized in the presence of β-cyclodextrin. The structure has been determined by single isomorphous replacement and threefold averaging using in-house X-ray data collected from selenomethionine-substituted protein. AMP-activated protein kinase (AMPK) is an intracellular energy sensor that regulates metabolism in response to energy demand and supply by adjusting the ATP-generating and ATP-consuming pathways. AMPK potentially plays a critical role in diabetes and obesity as it is known to be activated by metforin and rosiglitazone, drugs used for the treatment of type II diabetes. AMPK is a heterotrimer composed of a catalytic α subunit and two regulatory subunits, β and γ. Mutations in the γ subunit are known to cause glycogen accumulation, leading to cardiac arrhythmias. Recently, a functional glycogen-binding domain (GBD) has been identified in the β subunit. Here, the crystallization of GBD in the presence of β-cyclodextrin is reported together with preliminary X-ray data analysis allowing the determination of the structure by single isomorphous replacement and threefold averaging using in-house X-ray data collected from a selenomethionine-substituted protein