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Experimental Acquisition and Characterisation of Large-Scale Flow Structures in Turbulent Mixed ConvectionSchmeling, Daniel 02 July 2014 (has links)
No description available.
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Promene nuklearnih spektara pod dejstvom kosmičkog zračenja / Changes of nuclear spectra under the influence of cosmic radiationBikit Kristina 13 June 2015 (has links)
<p>U ovoj disertaciji su prikazani rezultati kompleksnih istraživanja uticaja<br />kosmičkog zračenja na nuklearne spektre na nivou mora.<br />Utvrđivanje specifičnih vremenskih intervala u vremenskom spektru,<br />kojima odgovaraju tačno određene grupe događaja indukovane<br />kosmičkim mionima, omogućava adekvatno odbacivanje ometajućih<br />događaja u željenim energetskim oblastima detektovanih spektara, pri<br />antikoincidentnom režimu rada ultraniskofonskih sistema. U prvom<br />eksperimentu prikazanom u ovoj disertaciji, istraživana je mogućnost<br />vremenskog razlaganja detektovanih događaja, pomoću koincidentnog<br />sistema u čijem sklopu se nalazi HPGe detektor i plastični scintilator, u<br />površinskoj laboratoriji. Ustanovljeno je da se promptni i zakasneli<br />koincidentni događaji između plastičnog “veto” detektora i<br />germanijumskog detektora mogu jasno razdvojiti u dve grupe, za oko<br />100 ns. Dodatno, zakočno zračenje i anihilacioni događaji mogu se<br />razdvojiti u vremenu od (n,n’) događaja, iako svi ovi događaji pripadaju<br />grupi zakasnelih događaja. Takođe, registrovani su i značajno zakasneli<br />anihilacioni događaji, koji nastaju usled raspada zaustavljenih pozitivnih<br />miona.<br />Drugi eksperiment prikazan u ovoj disertaciji baziran je na ultra-niskofonskom HPGe spektrometru relativne efikasnosti 100%.<br />Dodatkom dva plastična scintilatora i brzo-sporog koincidentnog kola,<br />istraživani su koincidentni događaji između plastičnih scintilatora i<br />HPGe spektrometra. Ovaj spektrometarski sistem MIREDO <em>(Muon<br />Induced Rare Event Dynamic Observatory</em>) prvenstveno je namenjen<br />proučavanju procesa indukovanih kosmičkim mionima u različitim<br />materijalima. Analiza ovakvih interakcija može biti od značaja za ultra-niskofonske eksperimente. Rezultati dobijeni za tri ispitivana materijala,<br />pakovana u<em> Marinelli</em> sud, prezentovani su i diskutovani.<br />U trećem eksperimentu prikazanom u ovoj disertaciji ispitan je<br />potencijalni uticaj solarnih neutrina na izmerenu brzinu radioaktivnog<br />raspada, merenjem varijacija u brzini brojanja<br /><sup>3</sup>H metodom tečnog scintilacionog brojanja. Korišćenjem sofisticiranog tečnog scintilacionog spektrometra <em> Quantulus</em> ustanovljeno je da na merenje<br />visokoenergetskog dela <sup>3</sup>H spektra može značajno uticati nestabilnost<br />instrumenta. Oscilatorni karakter izmerenog visokoenergetskog dela<br /><sup>3</sup>H spektra je registrovan, ali sa veoma malom amplitudom (manjom od<br />0.5%), koja se ne može jednostavno objasniti samo nestabilnošću<br />instrumenta. Kada je meren ukupan <sup>3</sup>H spektar, nisu nađene značajne<br />varijacije u brzini brojanja.<br />Već duže vreme je poznato da je niskoenergetsko gama zračenje<br />kontinualne distribucije prisutno na otvorenom prostoru, u vazduhu na<br />površini Zemlje. U prethodnim istraživanjima pretpostavljano je da ovo<br />zračenje potiče skoro isključivo od gama fotona koji su emitovani usled<br />prirodne radioaktivnosti i potom rasejani u nazad od strane vazduha<br />iznad zemlje. U četvrtom eksperimentu prikazanom u ovoj disertaciji<br />pokazano je da je ovo zračenje (u energetskom regionu 30 keV-300<br />keV), sa maksimumom na oko 90 keV, u značajnoj meri proizvedeno<br />kosmičkim zračenjem, sa fluksom fotona od oko 3000 m<sup>-2</sup>s<sup>-1</sup>. Takođe,<br />ustanovljeno je da dozama opšte populacije doprinosi ovo sveprisutno<br />niskoenergetsko gama zračenja kosmičkog porekla, zajedno sa<br />odgovarajućim fluksom niskoenergetskih elektrona i da ove komponente<br />ukupnih doza indukovanih kosmičkim zračenjem na nivou mora nisu<br />zanemarljive.</p> / <p>In this dissertation results of complex research on cosmic-ray impact on nuclear spectra at sea level are shown. The appropriate selection of coincidence time interval in low-background experiments that are based on the rejection of anticoincidence background events is very important for reducing the influence of cosmic-ray muons on acquired spectral data. In the first experiment presented in this dissertation, performed by the coincidence system of an HPGe detector and a plastic detect or in a surface laboratory, the time resolution of the detected events is explored. It is found that the prompt and delayed coincidence events between a plastic veto detector and a Ge detector can be sharply divided for approximately 100 ns in two groups. In addition, the bremsstrahlung and annihilation events can be time-resolved from the (n,n’) events, although all of these events belong to the group of delayed events. Also, substantially delayed annihilation events, which are caused by the <br />decays of stopped positive muons, were detected.<br />The second experiment shown in this dissertation is based on the 100% relative efficiency ultra-low-background HPGe spectrometer. With the addition of two plastic scintillators and a fast-slow coincidence circuit, the coincidence events between the plastic detectors and the HPGe spectrometer have been investigated. This MIREDO (Muon Induced Rare Event Dynamic Observatory) spectrometer system is primarily <br />developed for the study of cosmic muon induced processes in different materials. Exploration of such interactions can be important for ultra-low background experiments. Results derived for three samples, placed in a Marinelli beaker, are presented and discussed.<br />In third experiment shown in this dissertation, the potential influence of solar neutrinos on measured decay rate is investigated by the liquid scintillation measurement of the count rate variations of <sup>3</sup>H. Making use of the sophisticated Quantulus liquid scintillation spectrometer, it is found that the measurement of the high-energy tail of <sup>3</sup>H spectrum may be significantly influenced by instrumental instability. The oscillatory behavior of measured high-energy tail of <sup>3</sup>H spectrum is registered, but with very small amplitude (less than 0.5%), which cannot be easily <br />explained only by instrumental instability. When the total <sup>3</sup>H spectrum was measured, no significant variations in the count rate were found. <br />For a long time, it has been known that low-energy continuous gamma radiation is present in open air at the Earth’s surface. In previous investigations it was assumed that this radiation is produced almost exclusively by gamma photons emitted due to the natural radioactivity, which are backscattered by air above ground. In the fourth experiment presented in this dissertation, it is shown that significant amount of this <br />radiation (related to energy region 30 keV-300 keV) that peaks at about 90 keV, is produced by cosmic-rays, with the photon flux of about 3000 m<sup>-2</sup>s<sup>-1</sup>. Also, it is found that the contribution of this omnipresent low energy gamma radiation of cosmic-ray origin, including the corresponding low-energy electron flux, to the doses of general <br />population are non-negligible components of overall doses induced by cosmic rays near sea level.</p>
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Thrombin inhibitors grafting on polyester membranes for the preparation of blood-compatible materialsSalvagnini, Claudio 28 November 2005 (has links)
The design of biomaterials, historically initiated and developed by physicians and engineers, in the last decades has slowly shifted toward a more biochemical based approach. For the replacement, repair and regeneration of tissues scientists are now focusing on materials that stimulate specific biological response at the molecular level. These biomaterials have already shown interesting applications in cell proliferation, differentiation, and extracellular matrix production and organization when the material modifications are designed to elicit specific interactions with cell integrins. In the present work we propose the application of this strategy for the development of blood-compatible materials. We first identified, in the coagulation cascade a key enzyme that constitute a valuable biological target for the development of anti-thrombogenic compounds. Piperazinyl-amide derivatives of N-alfa-(3-trifluoromethyl-benzenesulfonyl)-L-arginine were synthesized as graftable thrombin inhibitors. These inhibitors provided a spacer arm for surface grafting and a fluorine tag for XPS (X-ray photoelectron spectroscopy) detection. The possible disturbance of biological activity due to a variable spacer-arm fixed on the N-4 piperazinyl position was evaluated in vitro against human alfa-thrombin, in silico by molecular modelling and via X-ray diffraction study. Selected inhibitors, having inhibition potency in the mM range, were grafted on polyesters surface via wet chemistry and photochemical activation treatments. Wet chemistry surface grafting was performed by specific hydroxyl chain-ends activation and resulted in bioactive molecules fixation of 20-300pmol/cm2. The photochemical grafting was performed using a molecular clip providing an aromatic azide, for nitrene insertion into a polymer, and an activated ester for grafting of tag compounds. This grafting technique resulted in a dramatic increase in fixed bioactive signals (up to nmol/cm2). The material blood-compatibilization induced by the surface fixation of the inhibitors, was measured by a static blood clot weight measurement test. The wet chemistry grafting technique resulted in moderate blood-compatibilization while by the photochemical grafting method important decrease in surface blood clot formation was observed. In the latter case, the blood response to material contact was found to be strongly affected by the polyester surface photo-degradation induced by the activation treatment.
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Thrombin inhibitors grafting on polyester membranes for the preparation of blood-compatible materialsSalvagnini, Claudio 28 November 2005 (has links)
The design of biomaterials, historically initiated and developed by physicians and engineers, in the last decades has slowly shifted toward a more biochemical based approach. For the replacement, repair and regeneration of tissues scientists are now focusing on materials that stimulate specific biological response at the molecular level. These biomaterials have already shown interesting applications in cell proliferation, differentiation, and extracellular matrix production and organization when the material modifications are designed to elicit specific interactions with cell integrins. In the present work we propose the application of this strategy for the development of blood-compatible materials. We first identified, in the coagulation cascade a key enzyme that constitute a valuable biological target for the development of anti-thrombogenic compounds. Piperazinyl-amide derivatives of N-alfa-(3-trifluoromethyl-benzenesulfonyl)-L-arginine were synthesized as graftable thrombin inhibitors. These inhibitors provided a spacer arm for surface grafting and a fluorine tag for XPS (X-ray photoelectron spectroscopy) detection. The possible disturbance of biological activity due to a variable spacer-arm fixed on the N-4 piperazinyl position was evaluated in vitro against human alfa-thrombin, in silico by molecular modelling and via X-ray diffraction study. Selected inhibitors, having inhibition potency in the mM range, were grafted on polyesters surface via wet chemistry and photochemical activation treatments. Wet chemistry surface grafting was performed by specific hydroxyl chain-ends activation and resulted in bioactive molecules fixation of 20-300pmol/cm2. The photochemical grafting was performed using a molecular clip providing an aromatic azide, for nitrene insertion into a polymer, and an activated ester for grafting of tag compounds. This grafting technique resulted in a dramatic increase in fixed bioactive signals (up to nmol/cm2). The material blood-compatibilization induced by the surface fixation of the inhibitors, was measured by a static blood clot weight measurement test. The wet chemistry grafting technique resulted in moderate blood-compatibilization while by the photochemical grafting method important decrease in surface blood clot formation was observed. In the latter case, the blood response to material contact was found to be strongly affected by the polyester surface photo-degradation induced by the activation treatment.
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Využití simulace pro predikci vad a hodnocení vlastností u tlakově litých odlitků z Al slitin / Using simulation to predict defects in and evaluate properties of die-cast Al-alloy castingsMorávková, Jitka January 2011 (has links)
The purpose of this diploma thesis is comparing the quantity of porosity in die-cast aluminium casting with using simulation. The cast engine blocks were made by high pressure die-casting and a local squeeze casting (LSC) technology. There was also examined the relationship between porosity and mechanical properties of castings. There were evaluated and compared the results of my own measurements with data from previous students theses at the Faculty of Mechanical Engineering BUT. All data were tested by statistical tests. The comparison of simulation results and experimentally measured values was found a good programme-ability to simulate and estimate porosity.
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Les oncogènes NUP98-PHF23 et NUP98-HOXD13 confèrent un potentiel aberrant d’auto-renouvellement aux progéniteurs thymiquesTardif, Magalie 09 1900 (has links)
No description available.
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