National Repository of Grey Literature 7 records found  Search took 0.00 seconds. 
Transmission of very slow electrons as a diagnostic tool
Frank, Luděk ; Nebesářová, Jana ; Vancová, Marie ; Paták, Aleš ; Mikmeková, Eliška ; Müllerová, Ilona
The penetration of electrons through solids is retarded by sequences of their interactions with the matter in which the electron changes its direction of motion and loses its energy. Inelastic collisions, the intensity of which reaches a maximum at around 50 electronvolts (eV) and drops steeply on both sides of this fuzzy threshold, are decisive for the penetration of electrons. Transmission microscopy (TEM or STEM) observes thin samples of tens to hundreds of nanometres in thickness by passing electrons of energies of tens to hundreds of kiloelectronvolts through them. The range below 50 eV has recently been utilized in the examination of surfaces with reflected electrons, where high image resolution is achieved thanks to the retardation of electrons close to the sample surface in the ´cathode lens´ . In this lens, the role of the cathode is played by the sample itself, biased to a high negative potential. This principle can also be utilized in the transmission mode with samples of a thickness at and below 10 nm. This method has recently been implemented and verified on graphene samples prepared by various methods. The results have made it possible to diagnose the continuity and quality of the graphene flakes. Furthermore, series of experiments have been performed involving the observation of ultrathin tissue sections with electrons decelerated to about 500 eV and less, where they provide an image contrast of the cell ultrastructure much higher than that provided by traditional microscopic modes.
Child accelerated in premathematics literacy
Vancová, Marie ; Kaslová, Michaela (advisor) ; Vondráková, Eva (referee)
The bachelor thesis discusses accelerated children in the field of premathematics literacy. It concentrates on characteristic signs of accelerated children in preschool age, methods of early identification, forms of education, development of accelerated individuals, and last but not least addresses premathematical education in pre-school. This work is divided into two parts, which coincide with the two main goals. The goal is: map the level of care for accelerated children in a selected pre-school and design work sheets for their development in premathematics literacy, which will support the preparation for school mathematics respecting individual needs of preschool children. This work offers 23 adapted and modified work sheets considering the specifications of the given group. Suitability has been verified on 13 children from 5 to 7, 2 years of age, identified officially as accelerated. The author assumes that this work will help to improve the care for accelerated children.
Very low energy STEM for biology
Frank, Luděk ; Nebesářová, Jana ; Vancová, Marie ; Paták, Aleš ; Müllerová, Ilona
Examination of tissue sections with transmitted electrons has been performed at energies of hundreds and tens of eV with thicknesses of sections of 10 nm or less. This was possible by employing the cathode lens principle working without lowest energy limitations with the help of biasing the sample to a high negative potential. The reflected and transmitted electrons were attracted with the same electric field to earthed detectors situated above and below the sample. Very high image contrasts have been obtained even for samples free of any heavy metal salts for contrast enhancement.
Observation of biological material in low voltage transmission electron microscope
Vancová, Marie ; Nebesářová, Jana
Different methods of specimen preparation for low voltage transmission electron microscopy (LVEM) were evaluated. The contrast of the image in LVEM, contrary to high voltage TEM, is strongly influenced by the thickness of the specimen. The resin embedding media used and the process of sectioning employed contributed to image quality and resolution.
Comparison of the cell structure of tissues prepared by different methods for transmission electron microscopy
Vancová, Marie ; Nebesářová, Jana
The aim of this work is to show how methods which are able to retain antigenicity of tissues can influence the structural appearance of the specimen. We compared the ultrastructure of tissues conventionally embedded in hydrophobic epoxides, with tissues embedded in hydrophilic acrylic resins (polymerized by heat or UV light) and cryo-sections.
The first experience with the specimen preparation for low-voltage transmission electron microscope
Nebesářová, Jana ; Vancová, Marie
The low-voltage transmission electron microscope, working in the TEM mode, requires ultrathin sections with a thickness 20-30nm. This demand brings problems with a section cohesion caused by insufficient resin infiltration and with a chatter caused by unequal thickness of the section. The contrast of unstained biological specimens in LV TEM is comparable with the contrast obtained in HV TEM of stained specimens.

See also: similar author names
4 VANCOVÁ, Marie
1 Vančová, Martina
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