Radiacni poruchy v polovodicich.

A project of the MESA, MESA Planar detectors production and their study are the target of this doctor thesis. The detectors of MESA, MESA Planar and SINTEF were produced as a part of cooperation RD48 coordinated in CERN. The increase of the radiation hardness of the original silicon material was attended. The detector was irradiated by different doses of protons with the energy of 24GeV/c. A set of measurements of these detectors were provided to determine the charge collection efficiency. The spectroscopy using heavy charged particles (alpha's, protons) was used. A measurement of theirs electric parameters was provided. The DLTS for measurements of the deep levels in band gap was used. The second part is devoted to the effort of increasing the radiation hardness of the silicon material using impurities. The standard silicon material was doped with several elements (O_2, N, C). The detectors produced by standard and doped silicon were irradiated by several doses. The comparing measurement of detectors produced by standard silicon and non-standard silicon was provided.Available from STL Prague, CZ / NTK - National Technical LibrarySIGLECZCzech Republi

Tyčovité nanočástice maghemitu potažené silikou: Syntéza přes akaganeit, charakterizace a biologické vlastnosti

A multistep procedure, employing akaganeite FeO(OH,Cl) as a precursor, was developed for the preparation of rod-like maghemite particles for medical applications. At first, akaganeite rods with length of several hundred nm and width of approximate to 85 nm were prepared under hydrothermal conditions and were subsequently coated with mesoporous silica. Such coating enabled to maintain the shape of rods during the following steps that involved structural transformation of akaganeite to maghemite, i.e. gamma-Fe2O3. Then the original protective coating was removed by alkaline leaching, bare maghemite rods were isolated, and their structure and ferrimagnetic order were characterized by X-ray diffraction, TEM inspection, Mossbauer spectroscopy and SQUID magnetometry. The magnetization of the bare maghemite rods, that were formed by elongated clusters of approximate to 10-20 nm crystallites, made 47.0 and 41.7 Am-2/kg in magnetic field of 3 T at 5 K and 300 K, respectively. The hysteresis loops of both the bare and coated products at 300 K and ZFC/FC studies showed that the maghemite particles were largely blocked at room temperature in spite of the small size of crystallites. Finally, the particles were equipped with standard silica coating for biological studies. An evaluation of cytotoxicity of this silica-coated product was performed on two cell lines, namely A549 and MCF-7. The viability of cells incubated with particles at the concentration of 0.10, 0.21 and 0.42 mmol(Fe)/L was determined after 24 h and 48 h of incubation, and the values normalized to the viability of negative control were generally higher than 95%. Moreover, the real-time monitoring of cell adhesion, proliferation, and cytotoxicity by an xCELLigence system during 72 h of the incubation with particles revealed only some decrease of the cell index for the MCF-7 cells at the high concentration.Pro přípravu tyčovitých maghemitových částic pro lékařské aplikace byl vyvinut vícestupňový postup využívající akaganeit FeO (OH, Cl) jako prekurzor. Nejprve byly za hydrotermálních podmínek připraveny akaganeitové tyče s délkou několika stovek nm a šířkou přibližně 85 nm a následně byly potaženy mesoporézním oxidem křemičitým. Takový povlak umožnil udržet tvar tyčinek v následujících krocích, které zahrnovaly strukturální přeměnu akaganeitu na maghemit, tj. gama-Fe203. Poté byl původní ochranný povlak odstraněn alkalickým vyluhováním, byly izolovány holé maghemitové tyčinky a jejich struktura a ferrimagnetické uspořádání byly charakterizovány rentgenovou difrakcí, TEM kontrolou, Mossbauerovou spektroskopií a SQUID magnetometrií. Magnetizace holých maghemitových tyčí, které byly vytvořeny protáhlými shluky přibližně 10 až 20 nm krystalů, vytvořila 47,0 a 41,7 Am-2 / kg v magnetickém poli 3 T při 5 K a 300 K. Hysterezní smyčky holých i potažených produktů při 300 K a ZFC / FC studie ukázaly, že částice maghemitu byly z velké části blokovány při pokojové teplotě navzdory malé velikosti krystalů. Nakonec byly částice potaženy silikou pro účely biologických testů. Vyhodnocení cytotoxicity bylo provedeno na dvou buněčných liniích, konkrétně A549 a MCF-7. Viabilita buněk inkubovaných s částicemi v koncentraci 0,10, 0,21 a 0,42 mmol (Fe) / l byla stanovena po 24 hodinách a 48 hodinách a hodnoty byly vztaženy k viabilitě negativní kontroly. Viabilita byla vyšší než 95%. Kromě toho, monitorování buněčné adheze, proliferace a cytotoxicity v reálném čase pomocí systému xCELLigence po dobu 72 hodin, ukázalo pouze nepatrné snížení buněčného indexu u buněčné linie MCF-7 při vysoké koncentraci částic

Katalyzátory na bázi kobaltu nanesené na alkáliemi aktivovaných zeolitických pěnách pro N2O rozklad

In this work, we studied the effect of alkali-activated zeolite foams modifications on properties and catalytic activity of cobalt phases in the process of catalytic decomposition of N2O. The zeolite foam supports were prepared by alkali activation of natural zeolite followed by acid leaching and ion exchange. The cobalt catalysts were synthesised by a different deposition technique (direct ion exchange (DIE) and incipient wetness impregnation (IWI) method of cobalt on zeolite foams. For comparison, catalysts on selected supports were prepared and the properties of all were compared in catalytic tests in the pellet form and as crushed catalysts to determine the effect of internal diffusion. The catalysts and supports were in detail characterized by a variety of techniques. The catalyst activity strongly depended on the structure of support and synthesis procedure of a cobalt catalyst. Ion exchange method provided active phase with higher surface areas and sites with better reducibility, both of these factors contributed to higher N2O conversions of more than 80% at 450 degrees C. A large influence can also be attributed to the presence of alkali metals, in particular, potassium, which resulted in a modification of electronic and acid base properties of the cobalt oxide phase on the catalyst surface. The promotional effect of potassium is better reducibility of cobalt species.Byl studován efekt alkalicky aktivovaných zeolitických pěn na vlastnosti a katalytickou aktivitu kobaltové fáze v procesu katalytického rozkladu N2O

Mn-Zn feritové nanočástice obalené silikou a titanem: syntéza, transverzální relaxivita a cytotoxicita

Mn-Zn ferrite nanoparticles of composition Mn0.61Zn0.42Fe1.97O4 and mean size of crystallites d(XRD) = 11 nm are synthesized under hydrothermal conditions as a single-phase product. Subsequently, two coated samples are prepared by encapsulation of the ferrite particles into silica and titania. Transmission electron microscopy confirms the core-shell structure of the products and shows that the cores are actually formed by small clusters of ferrite crystallites. Powder X-ray diffraction, combined with experimental hydrothermal treatment of the titania-coated product, demonstrates that the titania coating is amorphous but can easily be transformed into anatase. The colloidal stability of nanoparticles in water is evidenced by dynamic light scattering, and the respective hydrodynamic sizes are d(Z) = 87 and 157 nm for the silica-coated and titania-coated particles. The colloidal behavior is confirmed based on the measurements of zeta potential, whose negative values lead to strong Coulombic repulsion among coated particles. Magnetic measurements on bare and coated particles show high magnetization of Mn0.61Zn0.42Fe1.97O4 cores and superparamagnetic state at room temperature. The relaxometric study on aqueous suspensions in magnetic fields of 0.5 and 11.75 T reveals high transverse relaxivity of the samples and two distinct forms of its temperature dependence, which are analyzed with respect to the role of temperature-dependent parameters, that is, the diffusion of water and the magnetization of ferrite cores. Finally, careful evaluation of cytotoxicity of coated particles is carried out by using two different methods, namely, the determination of viability and proliferation of Jurkat cells and the real-time monitoring of attachment and proliferation of A549 cells. In the studied range of concentrations, the viability and proliferation of suspension cells are not affected, and only negligible effects are detected in the cell index of adherent cells.Mn-Zn feritové nanočástice o složení Mn0.61Zn0.42Fe1.97O4 a průměrné velikosti krystalů d(XRD) = 11 nm) byly připraveny hydrotermální syntézou. Nakonec byla podrobně vyhodnocena cytotoxicita obalených nanočástic pomocí dvou odlišných metod: pomocí stanovení viability a proliferace buněčné linie Jurkat a pomocí analýzy adheze a proliferace buněčné linie A549 v reálném čase. V rámci hodnoceného koncentračního rozsahu, nebyla ovlivněna viabilita a proliferace suspenzních buněk a pouze zanedbatelný vliv na buněčný index byl pozorován u adherentních buněk

RD50 Status Report 2008 - Radiation hard semiconductor devices for very high luminosity colliders

The objective of the CERN RD50 Collaboration is the development of radiation hard semiconductor detectors for very high luminosity colliders, particularly to face the requirements of a possible upgrade scenario of the LHC.This document reports the status of research and main results obtained after the sixth year of activity of the collaboration