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Analysis of the gas glow
Hladká, K. ; Maxa, J. ; Neděla, Vilém ; Vyroubal, P. ; Vaculík, S. ; Hlavatá, P.
In order to optimize the shape of the Differentially pumped chamber in the area of the Primary Electron Beam passage for the current concept of the location of the foci of the Primary Electron Beam, it was necessary to adapt to the size and shape of the limitations of the existing structure. On fig. 1a is the total cross sectional view of the Differentially pumped chamber. Three variants were examined: Current concept with an easily machined shape of the passage of the primary beam, semi-closed concept with a conical shape, cone concept with a wider cone.
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Use systems for the analysis of gas flow
Maxa, J. ; Neděla, Vilém ; Hladká, K. ; Vyroubal, P. ; Vaculík, S. ; Hlavatá, P.
Environmental scanning electron microscope is explaining withdrawing of two differentially pumped chambers in a drawing area. To solve this problem is used finite volume method. This method includes several steps: - With using of mesh the area is dividing into discrete volume. - Discretization and balancing of the unknown quantities in each finite volume - Numerical solution of discretized equations.
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Physical and biocatalytic properties of polyvinyl alcohol lens-shaped particles versus spherical polyelectrolyte complex microcapsules
Schenkmayerová, A. ; Bučko, M. ; Gemeiner, P. ; Treľová, D. ; Lacík, I. ; Chorvát Jr., D. ; Ačai, P. ; Polakovič, M. ; Lipták, L. ; Rebroš, M. ; Rosenberg, M. ; Štefuca, V. ; Neděla, Vilém ; Tihlaříková, Eva
Direct comparison of key physical and chemical-engineering properties of two representative matrices for multipurpose immobilisations was performed for the first time. Polyvinyl alcohol lens-shaped particles LentiKats and polyelectrolyte complex microcapsules were characterised by advanced techniques with respect to the size distribution of the particles, their inner morphology as revealed by fluorescent probe staining, mechanical resistance, size-exclusion properties, determination of effective diffusion coefficient and environmental scanning electron microscope imaging. Recombinant cells E. coli overexpressing enzyme cyclopentanone monooxygenase were immobilised in polyelectrolyte complex microcapsules and LentiKats for comparison of their operational stability using model Baeyer-Villiger oxidation of (±)-cis-bicyclo[3.2.0]hept-2-en-6-one to regioisomeric lactones as important chiral synthons for potential pharmaceuticals.
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Progress in imaging techniques for characterization of polyelectrolyte complex microcapsules as encapsulation matrice for biocatalysts
Bučko, M. ; Gemeiner, P. ; Vikartovská, A. ; Schenkmayerová, A. ; Bertóková, A. ; Lacík, I. ; Chorvát Jr., D. ; Neděla, Vilém
Polyelectrolyte complex microcapsules showed to be an univerzal encapsulation matrice for wide range of biocatalysts including viable, native and recombinant bacterial cells, non-viable bacterial cells as well as enzymes. Developed continuous encapsulation protocol based on the polyelectrolyte complexation of oppositely charged polymers enabled production of uniform microcapsules with a controlled shape, size, membrane thickness, permeability and mechanical resistance. The characterisation and control of the microcapsule properties including the inner structure and surface properties was inevitable to determine their proper function and predictability in important applications such as the stabilisation and reuse of encapsulated biocatalysts for more efficient production of valuable compounds. Recent utilisation of unique environmental scanning electron microscope enabled an innovative observation and characterization of capsule morphology in native and fully hydrated state. Achieved results and comparison with previously used conventional microscopic techniques will be presented.
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Ice and its impurities from the perspectives of photochemistry and electron microscopy
Heger, D. ; Krausko, J. ; Klán, P. ; Runštuk, Jiří ; Neděla, Vilém
Ice as a solid phase of water is an interesting but still not well understood medium. Our photochemical group utilized chemical and spectroscopic tools to acquire information relevant to the environmental and applied science. In the introduction I would like to stress some important facts on ice and frozen aqueous solutions stemmed from our work. Still opened question, that we are trying to answer by the ESEM, is where and at what forms are the impurities located after the freezing. The recently published results from the pilot collaboration with Dr. Neděla’s group will be detailed.
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The study of the different percentage performance of nanoparticles on the properties of epoxy resin
Hudec, Jiří ; Neděla, Vilém ; Polsterová, H.
This paper deals with the study of impact of different percentage filling of nanoparticles on the electrical properties of epoxy resin, which has very good mechanical and electrical properties. The sample is the blended mixture which is evacuated, subjected to ultrasound and then cured. It is expected that the formation of lumps should be minimised due to the influence of microwaves. Nanoparticles should be equally distributed in epoxide volume for this case. Unfortunately, this assumption was not proven. The mixture contains an epoxy resin CY228, hardener HY918, softener DY045 and accelerator DY062. Nanoparticles of alumina (Al2O3), sulfur dioxide (SiO2), titanium dioxide (TiO2) and tungsten oxide (WO3) from Sigma Aldrich Company were used as a filler. There were made samples for each filler with 0.25, 0.5, 1, 2 weight percent for our experiment and were determined values of the dissipation factor tg.delta., permittivity .epsilon.r and resistivity .rho.v by measuring.
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Using environmental scanning electron microscopy (ESEM) as a non-invasive method to studying fixed parasites
Mašová, Šárka ; Neděla, Vilém ; Tihlaříková, Eva
Scanning electron microscopy (SEM) is popular and for taxonomy of parasites very important and not substituted method in many times. However sometimes taxonomists have only one specimen and cannot use classical SEM, because their sample (poor conductor) have to be fixed, dehydrated and coated before it can be observed. This method condemns samples for destroying and do not allow other using of it, e.g. for molecular study or depositing as type material in museum. Moreover, the specimen preparation is often long and slow. Environmental scanning electron microscopy (ESEM) brings two main advantages: elimination of speed of sample preparation and non-invasivity.
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The Study of Ice Impurities Using the Environmental Scanning Electron Microscopy at Higher Pressures and Temperatures
Neděla, Vilém ; Runštuk, Jiří ; Klán, P. ; Heger, D.
Natural ice and snow accumulate and concentrate significant amounts of impurities that can be stored or chemically transformed, and eventually released to the environment. The location of impurities and their interactions with the water molecules of ice have not yet been sufficiently clarified. The aim of this work is to observe an uranyl-salt brine layer on the ice surface using a back scattered electron detection and the ice surface morphology using a secondary electron detection under equilibrium conditions in a specimen chamber of environmental scanning electron microscope (ESEM). Our specially modified ESEM AQUASEM II equipped with the YAG:Ce3+ backscattered electron detector, an ionization detector of secondary electrons, a special hydration system and a Peltier cooled stage was used. The pressures between 400-700 Pa, 50% water-vapor saturation, and the temperatures above 250 K were utilized in our experiments. At these conditions, the phenomena of etching and subsequent stripping of impurities are largely suppressed.
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Electron Microscopy as Unreplaceable Method in Parasitology: SEM and ESEM Utilization
Mašová, Šárka ; Foitová, I. ; Tihlaříková, Eva ; Neděla, Vilém
Systematic parasitology studies diversity and its origin. It includes mainly collection, naming, classification and describing of different species of parasites as well as a reconstruction of their evolutionary history. SEM is very important method in study and describing new species or redescribing insufficiently described species of parasites, because it empower opportunities for more detailed studies of their outer morphology. This method was applied in our research mainly for study of several species of parasitic roundworm (Nematoda) and one species of spiny headed worm (Acanthocephala). Our second topic concerning with SEM in parasitology is orangutan self-medication by plants with mechanical influence. However this method condemns parasite samples for destroying and do not allow other using of it. In case of specimens deficiency, environmental scanning electron microscopy (ESEM) is helpful. It would speed up a preparation of sample and is not invasive so valuable specimens can be used for other types of taxonomical studies. Non-invasivity of this method is shown in. Two species of already fixed roundworms (Multicaecum heterotis, Contracaecum osculatum) and one species of spiny headed worm (Corynosoma pseudohamanni) were documented also by ESEM. The samples were examined on a non-commercial ESEM AQUASEM II, they were placed to the Peltier specimen holder with silicon surface, into a drop of water. Observation conditions were: beam accelerating voltage 20 kV, probe current 50 pA, sample temperature 2°C, water vapour pressure 680 Pa. ESEM seems to be good alternative to classical SEM, in a case of lack of samples or need to use samples for molecular study or depositing them as type material in museum.
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