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Extension of instrumental capabilities in cryomagnetic laboratory
Proschek, Petr ; Prokleška, Jan (advisor) ; Javorský, Pavel (referee)
Measurement of elastic properties (thermal expansion and magnetostriction) under (multi)extreme conditions is a difficult task. In the vicinity of the room temperature or above it an abundance of methods is available, with decreasing temperature and adding magnetic field and/or hydrostatic pressure their number is limited. Dilatometric cells (either planparaller or tilted plate design) provide superior sensitivity in low temperatures and applied magnetic fields, however, cannot be used in hydrostatic cell. Common choice for the measurement of thermal expansion under hydrostatic pressure are methods based on strain-gauges, with mediocre sensitivity and more importantly a difficult or even impossible usage at very low temperatures (T ≲ 3 K). Measurement of magnetic properties (especially magnetization) under (multi)extreme conditions is also a difficult task. In the vicinity of temperature 2 K and above it an abundance of methods is available, with decreasing temperature and adding magnetic field and/or hydrostatic pressure their number is limited. VSM system provides great sensitivity, but can not be used under 2 K and hydrostatic pressure. MPMS aparature provides pressure up to 9 GPa (diamond pressure cell), but still we can not apply lower temperatures than 2 K. Our aim is to develop a simple yet sensitive...
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Studium magnetismu ve sloučeninách CeTX3
Moudřík, Jan ; Prokleška, Jan (advisor) ; Javorský, Pavel (referee)
Solid solutions of BaNiSn3 type CeTX3 (T and X denote a transition met- al and Si/Ge, respectively) compounds were studied. Polycrystalline samples of solid solutions CeCoxRh1−xSi3 (x = 0.5, x = 0.8, x = 0.9 and x = 1.0) and CeIr(SixGe1−x)3 (x = 0.1, x = 0.4, x = 0.6 and x = 0.8) were successfully grown. A superconducting transition at 0.7-0.9 K was exhibited by all four compositions of the solution CeCoxRh1−xSi3. Based on measurements of specific heat, we con- clude that the superconductivity is probably caused by impurity phases. We have determined crystallographic, thermodynamic and magnetic properties of the solu- tion CeIr(SixGe1−x)3. Magnetic phase transition temperatures were established, the character of the transitions changed significantly in all four compositions, the temperatures themselves did not. 1
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Embryonic and postembryonic development of marbled crayfish in different temperatures
FOJT, Martin
The aim of this bachelor thesis was to characterise the life cycle by parthenogenetic reproduction of marbled crayfishProcambarus fallax f. virginalis and to focus on the effects of its life cycle at different temperatures. The theoretical part of this thesis is focused on the reproductive biology of crayfish, with emphasis on embryonic and postembryonic development of marbled crayfish. It also acquaints us with the reproduction of indigenous crayfish and introduced crayfish species occurring in the territory of the Czech Republic. The practical part acquaints us with the conditions that need to be adhered during the experiment, changes in embryo development and assessing embryo development at different temperatures. Our experiment confirmed that the postembryonic stages of marbled crayfish were able to survive at low temperature (10 °C). Individuals were able to undergo the first postembryonic stadium at the lower temperature, but they developed slowly. Individuals develop without problems at 15 °C. The duration of postembryonic development was a little bit longer than in warmer temperature. There were expectations that the highest survival rate would be at higher temperatures, but our experiment showed that our predictions were false. Temperature of 20 °C was shown as the lowest survival rate, but we suspect that this poor result wasn't caused by the effect of water temperature, but rather by other physical-chemical water parameters which were not controlled. The highest survival rate of embryos in our experiment was at 15 °C. This thesis deals with the prediction of survival rates of marbled crayfish in the Czech Republic as written in the scientific literature and the obtained results refer to the ability in hatched individuals of marbled crayfish to tolerate the natural conditions of low temperatures in the Czech Republic.
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Assembling and testing of low temperature STM microscope
Sojka, Antonín ; Páleníček, Michal (referee) ; Pavera, Michal (advisor)
This bachelor thesis addresses the problem of assebling the low temperature STM working in ultrahigh vacuum. The thesis deals with connecting the microscope and electronics. The desing of temperature stabilizers for fixing the low temperatures is described along with a construction of expanding the vacuum chamber to test STM in low temperatures. The thesis describes the construction of sample and tip holders to insert samples and tips into the STM. At the end there are brief instructions to use GXSM software and testing the microscope in atmospheric pressure.
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