|
|
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.
|
|
|
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.
|
|
|
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.
|
|
|
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.
|
|
|
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.
|
|
|
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.
|
|
|
The Different Percentage Performance of Nanoparticles and their Effect on the Properties of Exposy Resin
Hudec, Jiří ; Neděla, Vilém ; Polsterová, H.
The study deals with 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 tgδ, permittivity εr and resistivity ρv by measuring. We are able to prepare samples with better electrical properties. Unfortunately, despite the advanced procedure of samples production, our main problem is the inhomogeneity of distribution of nanoparticles in the sample manifested by the formation of lumps. Scanning electron microscope REM Jeol JSM 6700F was used to detect lumps of nanoparticles. The lowest permittivity was encountered in the samples with the 2% filling of Al2O3 and SiO2, in the case of TiO2 it was 1%. In the samples containing Al2O3 a SiO2 the impact of the nanoparticles on the intrinsic resistivity is evident in the full temperature range. The highest intrinsic resistivity is in the sample with the 0.5% content of SiO2, apart from the sample with 0.5% of Al2O3 which has a lower resistivity than pure epoxide. The most pronounced improvement in electrical properties of the resulting nanocomposite was achieved by adding Al2O3 and SiO2. The influence of TiO2 was less obvious, and adding the nanoparticles of WO3 caused no change in any of the measured parameters.
|
|
|
Computations in Charged Particle Optics
Oral, Martin ; Radlička, Tomáš
The design of modern electron microscopes could not be possible without appropriate software tools. With the sub-nanometer resolution in SEM, and the sub-ångström resolution in TEM, one can see that the simulations involved in designing the instruments need to be tremendously accurate. A simulation starts with the computation of the electric and magnetic fields generated by various optical elements. That is followed by determinig the paraxial properties, aberrations and accurate particle trajectories (ray tracing). The distributions of the fields are mostly detemined with the Finite Element Method (FEM), the Boundary Element Method (BEM) or the Finite Difference Method (FDM). As the field data are at the input of all the subsequent calculations, they need to be very accurate, especially in the region close to the optical axis. Current expertise includes a set of rules that need to be applied in generating a FEM or BEM mesh. Advanced field interpolation techniques are necessary for accurate aberration analysis and particle tracing with high-order integration methods. Specialized software has been developped for the use in charged particle optics which aids the user in getting meaningful and accurate results. For instance, the EOD (Electron Optical Design) is a comprehensive package for particle optical sumulations. Field data produced by SIMION and Comsol need a specialized post-processing before their use in accurate ray tracing. Presented will be different methods of computing the optical aberrations, intensity distribution and probe size (resolution) on basic as well as more advanced examples (electron and ion optical columns, deflection systems, ToF spectrometers etc.) that were solved in the EOD and using custom programs.
|
|
|
Environmental Scanning Electron Microscopy and its Application Possibilites in ISI ASCR
Neděla, Vilém
The first commercially available environmental scanning electron microscope (ESEM) was introduced in 1988 by Dr. G.D. Danilat and his company Electro Scan. Prof. Autrata and Doc. Jirák of the Institute of Scientific Instruments of the Academy of Science of the Czech Republic, public research institution, and the Brno University of Technology launched a laboratory operation with the first purely Czech ESEM AQUASEM in 1995. The Team of Environmental Electron Microscopy (EEM), headed by Dr. Vilém Neděla, a former student of Professor Autrata, has continued the nearly twenty-year tradition of ESEM progress in the Czech Republic. The team has studied interactions of electrons with high-pressure gas environments, designed, developed and simulated detection systems for SEM and ESEM and performed simulations of gas flows in ESEM. In interdisciplinary cooperation with various partners the team has developed and tested methods of observation of sensitive, native or live specimen studied under conditions of dynamic in-situ experiments using the today already obsolete ESEM AQUASEM II with directly heated tungsten cathode converted by Dr. Neděla at the Institute of Scientific Instruments of the Academy of Science of the Czech Republic still in his student years. In near future the institute plans purchase of a new ESEM with high resolution and a unique configuration of accessory analytical and other equipment. Thus a new laboratory of environmental electron microscopy with state-of-the-art equipment will be established at the ISI ASCR in Brno. The new laboratory will allow for specimen study with electron beam in combination with optional micro handling, dynamic in-situ experiments with specimen temperature variation from -25°C to 1000°C, or local gas and liquid injecting directly onto the sample.
|
|
|
History of Electron Microscopy at the Institute of Scientific Instruments
Müllerová, Ilona
The development of the first transmission electron microscope (EM) at the Institute of Scientific Instruments (ISI) was completed in 1951. In 1954 a functional model of a desktop EM (the Tesla BS 242) was built and it won the Gold Medal at EXPO 1958. Over 1000 of these instruments were produced over a period of 20 years and exported to 20 countries. Unique transmission, emission and scanning EMs were developed and built during the 1960s. At the same time, the issues with high voltage sources, vacuum (and subsequently ultrahigh vacuum) and with the analysis of residual gases were resolved. In 1962, the first electron interference experiments in the world were carried out at ISI. Non-conventional forms of EM were also developed in the 1970s, e.g. interference shadow EM, Lorentz and tunneling EM, emission microscopy, as well as low energy electron diffraction [1]. Since 1973 the finite element method has been exploited for the computation of electrostatic and magnetic lenses. The ultrahigh vacuum scanning EM with cold field emission gun and an Auger spectrometer was fully developed and built at ISI in 1976, and the electron beam writer with a shaped beam and field emission gun in 1985. The development of new scintillation and cathodoluminescent screens began in the 1970s and our single crystal Yttrium Aluminium Garnet detector significantly improved detection systems all over the world. Low- and very-low-energy scanning EM was introduced to the world in 1990 as a unique technique. Today, it can achieve resolution as low as 4.5 nm at the incident electron energy of 20 eV.
|
guest ::
