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Nucleation of quantum dots
Kulveit, Jan ; Demo, Pavel (advisor) ; Polák, Karel (referee)
Quantum dots are increasingly important in many fields of science. Aminy other methods, quantum dots can also be formed by nucleation processes. In present work we study early stage of nucleation in NaCl and KCl crystals doped with PbCl2. Defect energies of small Pb clusters were calculated using numerical lattice methods. In NaCl-Pb system most stable small clusters have planar structure in {1; 1; 1}Na host lattice plane and intermittent planar phase nucleates. In contrast in KCl-Pb system small clusters with Suzuki phase structure are most stable and Suzuki phase nucleates. Formation of Suzuki phase hinders further transition to stable structure. These results of computer simulation are in agreemend with experimentally observed differences in KCl-Pb and NaCl-Pb systems behavior.
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Nucleation in complex systems
Kulveit, Jan ; Demo, Pavel (advisor) ; Slanina, František (referee) ; Vlček, Jaroslav (referee)
Title: Nucleation in complex systems Author: Jan Kulveit Institute: Institute of Physics of the Czech Academy of Sciences Supervisor: prof. Pavel Demo, Institute of Physics of the Czech Academy ofSciences, Department of Optical Materials Abstract: We studied nucleation in progressively more abstract contexts and systems, starting from classical nucleation theory and ending with nucleation in complex networks. The cases studied include impurity nucleation in a solid matrix on several alkali halide crystals, where we determined formation energies for clusters, treated as defects, starting from single impurity-vacancy dipole and small aggregates to possible configurations of larger clusters. In the next part, we turn to the study of heterogeneous nucleation. While in the usual treatment of heterogeneous nucleation the surface energy is assumed to be homogenous, we ask the question what happens if we consider the surface energy to be heteroge- neous.Utilizing umbrella sampling computer simulations we find the nucleation barrier can be significantly lowered in the presence of surface heterogeneity, even if the average surface energy is kept constant. In the last part we study influence of clustering coefficient on phase transitions in scale-free networks, using forward flux sampling (FFS). Keywords: nucleation,...
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Nucleation in complex systems
Kulveit, Jan ; Demo, Pavel (advisor) ; Slanina, František (referee) ; Vlček, Jaroslav (referee)
Title: Nucleation in complex systems Author: Jan Kulveit Institute: Institute of Physics of the Czech Academy of Sciences Supervisor: prof. Pavel Demo, Institute of Physics of the Czech Academy ofSciences, Department of Optical Materials Abstract: We studied nucleation in progressively more abstract contexts and systems, starting from classical nucleation theory and ending with nucleation in complex networks. The cases studied include impurity nucleation in a solid matrix on several alkali halide crystals, where we determined formation energies for clusters, treated as defects, starting from single impurity-vacancy dipole and small aggregates to possible configurations of larger clusters. In the next part, we turn to the study of heterogeneous nucleation. While in the usual treatment of heterogeneous nucleation the surface energy is assumed to be homogenous, we ask the question what happens if we consider the surface energy to be heteroge- neous.Utilizing umbrella sampling computer simulations we find the nucleation barrier can be significantly lowered in the presence of surface heterogeneity, even if the average surface energy is kept constant. In the last part we study influence of clustering coefficient on phase transitions in scale-free networks, using forward flux sampling (FFS). Keywords: nucleation,...
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Verification of the use of pva based nanofiber textiles as a rehabilitation for the structures attack by wood decaying fungi
Rácová, Z. ; Ryparová, Pavla ; Wasserbauer, R. ; Nežerka, V. ; Tesárek, Pavel ; Demo, Pavel
The presented paper is focused on the investigation of antifungal properties of nanofiber PVA-based textiles with incorporated copper and silver ions. In particular, the ability to prevent the growth of Dry rot fungus (Serpula lacrymans) was studied in laboratory conditions. For that purpose, the Petri dishes with malt agar were inoculated with square cut-outs of seed stocks, consequently covered by the nanofiber textiles and kept in an incubator at 28 degrees C. The fungal growth had been monitored and recorded at regular intervals for 28 days. The comparison of the individual treatments (PVA, PVA + Ag, PVA + Cu, PVA + Ag + Cu) is finally discussed.\n
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Algicidal properties nanofibrous fabrics doped by metals
Ryparová, Pavla ; Wasserbauer, R. ; Rácová, Z. ; Demo, Pavel ; Tesárek, Pavel
The paper presents a novel protection against algae by nanofiber fabrics doped with metal ions. Nanofiber textiles were prepared by electrospinning on the Nanospider LB 500 device, equipped with cylindrical electrodes of a length 600 mm and electrode distance about 140 mm. The produced nanofiber textiles had a specific weight between 2 and 4 g/m2. The entire surface was covered with algae commonly accompanied by bacteria. The sample had placed in the middle of circular dishes having the diameter 20 mm. The cultivation took place at light environment in common laboratory conditions. Algicidal effect was evaluated as the resulting halo size and quality around the sample. The PVA treated sample had not produce any halo effect, unlike the samples with the addition of metal salts (AgNO3, CuSO4 center dot 5H(2)O) that exhibited the halo effect dependent on the concentration the salts, usually ranging from 0.3-2 mm, giving the evidence about their algicidal properties.\n
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A laparoscopic approach to the prevention of complications in female endometrial cancer
Demo, Pavel ; Kučera, Eduard (advisor)
In this thesis I present a retrospective analytical study , which evaluates the results laparoscopically assisted vaginal hysterectomy (LAVH ) in the treatment of endometrial cancer and compare them with the results of similar studies in the professional press . This work will also basis for extensive retrospective study that will compare laparoscopically assisted vaginal hysterectomy and abdominal open surgical technique in the treatment of endometrial cancer . The aim of the thesis is to verify : Whether the laparoscopic approach yields fewer complications than the abdominal approach . What is the length of hospitalization using laparoscopic techniques . Compare the length of laparoscopic surgery of the file with a length of operations other workplaces. At the beginning of the thesis is devoted to the issue of endometrial cancer laparoscopic operations generally focus on a laparoscopically assisted vaginal hysterectomy (LAVH ) and its use in the treatment of endometrial cancer . Information for creating a group of patients who underwent LAVH in the diagnosis endometrial cancer , I have gained from operating books of the year 2001 - 2005 from the Institute for Mother and Child in Prague - Podolí. I also used a computerized database archive , also courtesy of Institute for the Care of Mother and Child...
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Nucleation of quantum dots
Kulveit, Jan ; Polák, Karel (referee) ; Demo, Pavel (advisor)
Quantum dots are increasingly important in many fields of science. Aminy other methods, quantum dots can also be formed by nucleation processes. In present work we study early stage of nucleation in NaCl and KCl crystals doped with PbCl2. Defect energies of small Pb clusters were calculated using numerical lattice methods. In NaCl-Pb system most stable small clusters have planar structure in {1; 1; 1}Na host lattice plane and intermittent planar phase nucleates. In contrast in KCl-Pb system small clusters with Suzuki phase structure are most stable and Suzuki phase nucleates. Formation of Suzuki phase hinders further transition to stable structure. These results of computer simulation are in agreemend with experimentally observed differences in KCl-Pb and NaCl-Pb systems behavior.
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Applications of self-assembled 2D polystyrene nanosphere arrays
Domonkos, Mária ; Ižák, Tibor ; Demo, Pavel ; Kromka, Alexander
In this study nanosphere lithography (NSL) is demonstrated to be a low-cost, parallel and material independent fabrication process for creating periodic arrays of nanostructures using self-assembled nanospheres as templates. SA is the most feasible way to fabricate 2D or 3D colloidal crystals on large areas. After the mask preparation NSL uses different steps of plasma etching and deposition processes. The resulting patterned nanostructures have a wide range of applications in many important areas such as photonics, antireflection, surface wetting, biological and chemical sensing, solar cells, etc. This study focuses on an overview of applications of 2D colloidal crystals. First, structuring of substrate surfaces and the creation of various nano-objects (nanotips, nanopillars, nanocones) is shown. Next, direct growth of patterned structures (graphene nanomesh and diamond structures) is pointed out.
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