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AB INITIO STUDY OF SILVER NANOPARTICLES, GRAIN BOUNDARIES AND THEIR \nQUADRUPLE JUNCTIONS
Polsterová, Svatava ; Všianská, Monika ; Friák, Martin ; Pizúrová, Naděžda ; Sokovnin, S. ; Šob, Mojmír
Motivated by our experimental research related to silver nanoparticles with various morphologies, we have employed quantum-mechanical calculations to provide our experiments with theoretical insight. We have computed properties of a 181-atom decahedral silver nanoparticle and two types of internal extended defects, -5(210) grain boundaries (GBs) and quadruple junctions (QJs) of these GBs. We have employed a supercell approach with periodic boundary conditions. Regarding the thermodynamic stability of the decahedral nanoparticle, its energy is higher than that of a defect-free face-centered cubic (fcc) Ag by 0.34 eV/atom. As far as the -5(210) GB is concerned, its energy amounts to 0.7 J/m2 and we predict that the studied GBs would locally expand the volume of the lattice. Importantly, the system with GBs is found rather close to the limit of mechanical stability. In particular, the computed value of the shear-related elastic constant C66 is as low as 9.4 GPa with the zero/negative value representing a mechanically unstable system. We thus predict that the -5(210) GBs may be prone to failure due to specific shearing deformation modes. The studied GBs have also the value of Poisson’s ratio for some loading directions close to zero. Next, we compare our results related solely to -5(210) GBs with those of a system where multiple intersecting -5(210) GBs form a network of quadruple junctions. The value of the critical elastic constant C66 is higher in this case, 13 GPa, and the mechanical stability is, therefore, better in the system with QJs.
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Rezistence dřepčíků rodu Phyllotreta a Psylliodes k vybraným účinným látkám insekticidů
Janáčová, Erika
Diploma thesis “The resistance of the flea beetles of the genus Phyllotreta and Psylliodes to active substances of insecticides“ is followed of NAZV QJ 1230077 Testing the sensitivity of selected insect pests of Brassicaceae crops to insecticides solved in 2012-2016. In the diploma thesis the sensibility of the flea beetles of genus Phyllotreta and Psylliodes to active substances of pyrethroid insecticides (tau-fluvalinate and lambda-cyhalothrin) and neonicotinoids (thiacloprid) was evaluate. The research was realized in 2017 on the 21 locations in the Czech Republic. The beetles were collected from commercial oil rapeseed?s (Brassica napus L. var. napus) and mustard?s (Sinapis alba) fields. The testing was conducted by laboratory methods of IRAC number 011 and 021, the adult-vital test was used for testing. These methods are known for monitoring pollen beetles (Meligethes spp.), but they are suitable for testing another species of pest of oil rapeseed. The results showed a decrease in the sensitivity to some insecticides.
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Electrochemical determinations of biologically active organic substances
Fischer, Jan
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Methodology of testing wheat resistance to brown leaf spot diseases under field conditions
Šíp, Václav ; Chrpová, Jana ; Palicová, Jana ; Hanzalová, Alena ; Čejka, Lubomír
This handbook brings new conclusions and recommendations concerning mainly the field resistance tests - the choice of fungal isolates, design of experiments, inoculum preparation and inoculation technique, as well as evaluation of disease symptoms and tolerance to the disease. Attention was paid to the pathogens Mycosphaerella graminicola anam. Septoria tritici, Pyrenophora tritici – repentis anam. Drechslera tritici-repentis and Phaeosphaeria nodorum anam. Stagonospora nodorum that showed frequent occurrence in the examined territory. The presented findings are based on experience gained from the ring tests of disease resistance performed in the period 2002-2014, available literature and special experiments with Septoria tritici performed within the research project QJ QJ 1210189 This methodology is mainly aimed at increasing precision of tests of resistance to these diseases which will favourably impact on resistance breeding, variety testing, as well as on adequacy of plant protection measures taken in agricultural practice.
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