Aggregation Behaviour of Polysaccharides in Aqueous Solutions

Tato práce je zaměřena na agregační chování nativního a hydrofobně modifikovaného hyaluronanu, v různých molekulových hmotnostech a stupních substituce, ve vodném prostředí. Pro studium bylo vybráno šest fluorescenčních sond s různými vlastnostmi (Pyren; Nilská červeň; Perylen; Akridinová oranž; 6-(p-Toluidino)-2-nafthalenesulfonová kyselina; PRODAN). a výsledky získané pomocí těchto sond byly porovnány s jednoduchým anionaktivním tenzidem (Dodecylsíran sodný). U všech použité sond byly testovány jejich spektrální vlastnosti v závislosti na polaritě okolí a/nebo na koncentraci. Pro stanovení vlastností nepolárního jádra hyaluronového agregátu byly vybrány dvě sondy (Pyren, Nilská červeň). U domén byly sledovány polarita a viskozita vnitřního prostředí a jejich závislost na iontové síle a teplotě. Pro modifikované hyaluronany bylo stanoveno, že jejich kritická agregační koncentrace klesá s rostoucí molekulovou hmotností a stupněm substituce. Pro vlastní doménu platí, že její kompaktnost roste s rostoucí iontovou silou, ale klesá s rostoucí teplotou.his thesis is focused on aggregation properties of native and hydrophobized hyaluronan, in different molecular weights and degree of substitution, in aqueous solutions. These samples were studied using six different fluorescence probes (Pyrene; Nile red; Perylene; Acridine orange; 6-(p-Toluidino)-2-naphthalenesulfonic acid; PRODAN) and results were compared with simple anionic surfactant (Sodium dodecyl sulfate). All used probes were tested for their spectral properties in dependence on polarity and/or concentration. Two of them (Pyrene, Nile red) were selected to determine apolar core properties of novel hydrophobicaly modified hyaluronan. Domains were tested for polarity and viscosity and dependencies of these two parameters on ionic strength and temperature. For modified hyaluronans were found that critical aggregation concentration decreasing with increasing degree of substitution and molecular weight. Domain qualities show their compactness increasing with increasing ionic strength and decreasing with increasing temperature.

Fluorescence study of freeze-drying as a method for support the interactions between hyaluronan and hydrophobic species

A freeze-drying method enabling solubilization of hydrophobic species in aqueous solutions of native hyaluronan is described. The method is based on opening the access to supposed hydrophobic patches on hyaluronan by disturbing its massive hydration shell. Hydrophobic and/or polarity-sensitive fluorescence probes were used as hydrophobic models or indicators of interactions with hydrophobic patches. Fluorescence parameters specific to individual probes confirmed the efficiency of the freeze-drying method. This work is the first step in developing biocompatible and biodegradable carriers for hydrophobic drugs with targeted distribution of the active compound from native, chemically non-modified hyaluronan

Digitalized two parametric system for gamma/neutron spectrometry

Many types of detectors like stilbene, NE-213 etc. in conjunction with photomultiplier loaded with low working resistance produce pulses of approximately 100 ns length and contain information about deposited particle in the trailing edge. Using fast analog to digital converters (ADC) and field-programmable gate array (FPGA) it is possible to create a spectrometric system working in mixed gamma and neutron fields which is not loaded dead time. The count rate of processed pulses can reach more than one million per second. Such a high count rate of processed pulses can be achieved due to the pulse processing is implemented in FPGA. The output of this pulse processing is amplitude which describes the energy of deposited particle and discrimination parameter whereby it is possible to discriminate photons and neutrons. To increase the dynamic range of energy of detectable particle the signal from photomultiplier is separated into two branches with different amplification. Each branch is digitalized by separate ADC. Components from which the system is composed are so light that the spectrometer can be easily transported. Its weight is less than 3 kilograms. Spectrometer was tested in the research reactor LR-0 in Rez near Prague (Czech Republic). The measured data was processed using deconvolution into a neutron flux density and compared with nowadays used analog spectrometer and simulation result. Measured neutron spectrum of Cf-252 is included.Článek popisuje spektrometr pro měření ve směsných polích gama/neutrony. Analogový signál z detektoru je vzorkován AD převodníky pracujícími na frekvenci 1 GHz. Předzpracování signálu probíhá v FPGA a tím je zajištěna vysoká propustnost systému bez mrtvé doby. Spektrometr byl testován v Centru výzkumu Řež na reaktoru LR-0.Many types of detectors like stilbene, NE-213 etc. in conjunction with photomultiplier loaded with low working resistance produce pulses of approximately 100 ns length and contain information about deposited particle in the trailing edge. Using fast analog to digital converters (ADC) and field-programmable gate array (FPGA) it is possible to create a spectrometric system working in mixed gamma and neutron fields which is not loaded dead time. The count rate of processed pulses can reach more than one million per second. Such a high count rate of processed pulses can be achieved due to the pulse processing is implemented in FPGA. The output of this pulse processing is amplitude which describes the energy of deposited particle and discrimination parameter whereby it is possible to discriminate photons and neutrons. To increase the dynamic range of energy of detectable particle the signal from photomultiplier is separated into two branches with different amplification. Each branch is digitalized by separate ADC. Components from which the system is composed are so light that the spectrometer can be easily transported. Its weight is less than 3 kilograms. Spectrometer was tested in the research reactor LR-0 in Rez near Prague (Czech Republic). The measured data was processed using deconvolution into a neutron flux density and compared with nowadays used analog spectrometer and simulation result. Measured neutron spectrum of Cf-252 is included

Pulse separation charakteristic based on their approximation

This article discusses the design of models for approximation of the electrical impulses shape which are generated in the detector of nuclear radiation. Scintillation detector reacts diferently on interact with two kinds of particles. The electrical impulses of the two reactions differ in the order of nanoseconds. Mathematical models of the responses to the interaction of particles with scintillation detector make it easy to distinguish the type of detected particles. The article describes four separation methods and their effectiveness is evaluated.Tento článek pojednává o návrhu modelů pro aproximaci tvaru elektrických impulsů vznikajících v detektoru jaderného záření. Scintilační detektor reaguje odlišně na interakci se dvěma druhy částic. Elektrické impulsy obou reakcí se liší v řádu nanosekund. Matematické modely odezev na interakce jednotlivých částic se scintilačním detektorem umožňují snadno rozlišit typ detekované částice. V článku jsou popsány čtyři separační metody a je hodnocena jejich účinnost.This article discusses the design of models for approximation of the electrical impulses shape which are generated in the detector of nuclear radiation. Scintillation detector reacts diferently on interact with two kinds of particles. The electrical impulses of the two reactions differ in the order of nanoseconds. Mathematical models of the responses to the interaction of particles with scintillation detector make it easy to distinguish the type of detected particles. The article describes four separation methods and their effectiveness is evaluated

Quick algorithms for real-time discrimination of neutrons and gamma rays

Several new methods for the digital discrimination of neutrons and gamma-rays in a mixed radiation field are presented. The methods introduced discriminate neutrons and gamma rays successfully in the digital domain. They are mathematically simple and exploit samples during the life time of the pulse, hence appropriate for field measurements. All these methods are applied to a set of mixed neutron and photon signals from a stilbene scintillator and their discrimination qualities are compared.V článku je prezentováno několik nových metod pro digitální diskriminace neutronů a gama záření ve směsném radiačním poli. Klasické metody diskriminace neutronů a gama záření pracují úspěšně v digitální doméně. Jsou matematicky jednoduché a využívat vzorků během doby trvání impulsu (odezvy) a jsou tedy vhodné pro měření v terénu. Všechny tyto metody jsou aplikovány na řadu odezev smíšených polí neutronového a fotonového záření ze scintilátoru typu stilben a jejich separační vlastnosti jsou porovnány.Several new methods for the digital discrimination of neutrons and gamma-rays in a mixed radiation field are presented. The methods introduced discriminate neutrons and gamma rays successfully in the digital domain. They are mathematically simple and exploit samples during the life time of the pulse, hence appropriate for field measurements. All these methods are applied to a set of mixed neutron and photon signals from a stilbene scintillator and their discrimination qualities are compared

N,N,N-Trimethyl chitosan as a permeation enhancer for inhalation drug delivery: interaction with a model pulmonary surfactant

N,N,N-Trimethyl chitosan (TMC), a biocompatible and biodegradable derivative of chitosan, is currently used as a permeation enhancer to increase the translocation of drugs to the bloodstream in the lungs. This article discusses the effect of TMC on a mimetic pulmonary surfactant, Curosurf, a low-viscosity lipid formulation administered to preterm infants with acute respiratory distress syndrome. Curosurf exhibits a strong interaction with TMC, resulting in the formation of aggregates at electrostatic charge stoichiometry. At nanoscale, Curosurf undergoes a profound reorganization of its lipid vesicles in terms of size and lamellarity. The initial micron-sized vesicles (average size 4.8 microns) give way to a froth-like network of unilamellar vesicles about 300 nm in size. Under such conditions, neutralization of the cationic charges by pulmonary surfactant may inhibit TMC permeation enhancer capacity, especially as electrostatic charge complexation is found at low TMC content. The permeation properties of pulmonary surfactant-neutralized TMC should then be evaluated for its applicability as a permeation enhancer for inhalation in the alveolar region.Comment: 20 pages, 7 figure

Protokol o testování plastického detektoru v poli radionuklidu Cf-252

Získané výsledky ukazují na schopnost plastického scintilátoru oddělovat fotonovou a neutronovou složku záření. Spodní hranice diskriminace je pod 1 MeV a v porovnání se zkušenostmi se scintilátorem stilben lze předpokládat, že dekonvoluce energetického spektra bude možná v energetickém intervalu nad 2 MeV.Získané výsledky ukazují na schopnost plastického scintilátoru oddělovat fotonovou a neutronovou složku záření. Spodní hranice diskriminace je pod 1 MeV a v porovnání se zkušenostmi se scintilátorem stilben lze předpokládat, že dekonvoluce energetického spektra bude možná v energetickém intervalu nad 2 MeV.The results indicate the ability of the plastic scintillator separate neutron and photon radiation component. The lower boundary of discrimination is below 1 MeV and compared with experience with stilbene scintillator can be assumed that the energy spectrum deconvolution will be possible in the energy range above 2 MeV

Benchmarking of stainless steel cube neutron leakage in Research Center Rez

The integral experiments covering the neutron leakage from geometrically simple assemblies with a 252Cf source inside are very valuable tools usable in validation of transport cross section data, since geometric uncertainties play a much smaller role in simple geometric assemblies than in complex assemblies as for example reactor pressure vessel geometry. Since 252Cf(s.f.) is standard neutron source, the uncertainties connected with the source neutron spectrum can be even neglected. The paper refers on validation efforts of neutron leakage from stainless steel block ~50 x 50 x50 cm in Research Center Rez. Both the neutron leakage flux at a distance of 1 m from the center of the cubical assembly using stilbene spectrometry and the activation rates at different positions of the assembly were evaluated. In addition to experiments, main sources of uncertainty were identified and evaluated. The results of the stilbene measurements are consistent with the activation measurements results