Browsing Doctoral Dissertations by Title
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Kovačević, Jovana (Beograd , 2015)[more][less]
Abstract: Proteins represent the most important groups of biomoleculs. Di erent functions that they carry out in each organism are unique and irreplaceable, including versatile cellular processes, structural role of proteins, catalytic function, a number of metabolic functions and so on. Knowing and under- standing protein function is therefore essential in investigation of any biolo- gical process, especially of human diseases since a lot of them are caused by functional mutations. In this paper, we represent investigation of protein function domain through two di erent approaches. In the rst one, protein function is represented by GO ontologies with the structure of a directed acyclic graph. There are three GO ontologies: one for functions regarding biological processes, one for functions regarding cellular components and one for molecular functions. Each ontology contains several thousands of nodes, where every node deter- mines more speci c function than his ascendants. The task of this part of research was to develop a software for predicting protein function from its primary sequence based on structural support vector machines method which represents generalization of well-known support vector machines method on structural output. Structure-function paradigm is one of basic concepts in molecular biology, stating that 3D proten structure is closely connected to its role in organism. It has been detected that disordered proteins (the ones that lack 3D struc- ture) and disordered regions of proteins are related with severe contemporary illnesses, which contributed to their popularity in modern research. In an- other aspect, we investigated the relationship between proteins' functional categories and their disorder, as well ad with other physico-chemical char- acteristics of proteins. Here, protein function has been observed through 25 elementary functions grouped in 4 functional groups. In this work, we present results of thorough analysis over large protein dataset where dis- order has been determined computationally, using publicly available tools. URI: http://hdl.handle.net/123456789/4451 Files in this item: 1
DoktoratJK2015.pdf ( 1.116Mb ) -
Stamenković, Blagoje (Belgrade)[more][less]
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Gjergji, Rexhep (Priština)[more][less]
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Martinović, Mihailo (, 2016)[more][less]
Abstract: The quasi-thermal noise spectroscopy is an accurate method of determination of density and temperature in space plasmas. When an electric antenna is immersed into a plasma, it is able to measure electrostatic uctuations caused by the thermal motion of plasma particles. These uctuations are detected as the power spectral density at the antenna terminals, observing a spectrum at frequencies comparable to the electron plasma frequency for both electrons and protons, since the proton signal is strongly Doppler-shifted towards higher frequencies due to the solar wind drift velocity. Beside inducing the uctuating electric eld, some of the electrons are impacting the antenna surface, causing disturbances of the antenna electric potential. The signal caused by this population is directly proportional to the ux of plasma electrons impacting the antenna and is dominant if the antenna has a large surface area. In this work, we use the orbit limited theory to calculate the incoming particle ux for a non-thermal plasma described by velocity distribution function, commonly measured in the solar wind. The increase in the particle collection by cylindrical and spherical objects is quanti ed and presented as a function of the surface electrostatic potential and the fraction of supra-thermal particles. Including these results into the theory has turned out to be absolutely necessary for accurate measurements of the plasma parameters whenever the shot noise is the dominant component in the power spectrum. This is the case for STEREO because the impact noise is overwhelming on this probe, due to the presence of short and thick antennas. The comprehensive study of data on this mission is motivated by the fact that the electron analyzers are malfunctioning since launch and no information on thermal electrons is available. Results obtained are veri ed by comparing with the results from Wind, showing a good match between the values measured by the two spacecraft. Uncertainties of the measurements are determined by the uncertainties of the instruments used and are estimated to be around 40%. The nal outcome of this work will be establishing a database of the electron moments in both STEREO A and B that will be covering the entire duration of the mission. In the second part of the thesis, we use the kinetic approach to expand the theory of the quasi-thermal noise to plasmas where electron-neutral collisions play a dominant role. This technique is able to measure the electron density, temperature and the collision frequency as independent parameters using the wide frequency range both below and above the plasma frequency, if the ratio of the collisional to plasma frequency is not smaller than 0.1. The results presented here have can be potentially applied in laboratory plasmas and unmagnetized ionospheres, while at the ionosphere of Earth their use is limited to low frequencies due to the presence of the magnetic field. URI: http://hdl.handle.net/123456789/4476 Files in this item: 1
MMartinovic_Thesis.pdf ( 16.42Mb ) -
Petrović, Mihailo (Paris)[more][less]
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Adamović, Dušan (Belgrade , 1965)[more][less]
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Gajić, Ljiljana (Novi Sad , 1982)[more][less]
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Laković, Bosiljka (Titograd , 1979)[more][less]
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Laković, Bosiljka (Belgrade)[more][less]
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Jablan, Slavik (Belgrade , 1984)[more][less]
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Spasić, Slađana (Belgrade)[more][less]
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Cvetković, Ljiljana (Novi Sad)[more][less]
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Janikijevik, Ljiljana (Skopje , 1973)[more][less]
URI: http://hdl.handle.net/123456789/157 Files in this item: 1
phdLjiljanaJanikijevik.pdf ( 4.625Mb ) -
Teorija onfinitezimalnih transformacija i njihova primena na integraljenje diferencijalnih jednačinaOkiljević, Blažo (Belgrade , 1986)[more][less]
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Jarić, Jovo (Belgrade , 1973)[more][less]
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Đaja, Časlav (Belgrade , 1967)[more][less]
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Onić, Dušan (Beograd , 2013)[more][less]
Abstract: The evolution of supernova remnants is linked to the propagation of a collisionless shock wave, formed during the initial expansion of high-velocity supernova ejecta through the interstellar environment. Theoretical studies of shock waves are very important for the analysis of supernova remnants, as well as processes in the interstellar medium in general. In this doctoral dissertation, some theoretical results based on the magnetohydrodynamical theory of shock waves are presented, with special emphasis on ideal radiative magnetohydrodynamics for the optically thick case. Particularly, solutions for the case when jump in adiabatic index and/or ratio of gas to total pressure is allowed, are discussed. The main hypothesis of this dissertation is that thermal bremsstrahlung radiation at radio continuum frequencies can provide a signi cant contribution in the case of several Galactic supernova remnants. This hypothesis can give a natural explanation for nearly concave up radio continuum spectra of several Galactic supernova remnants that are expanding in the environment with higher than average density. In this context, it is important to identify the existence of the possible indicators of ensemble of thermal electrons at su ciently low temperatures and su ciently high densities so that the thermal bremsstrahlung radiation linked to a particular remnant could be observed at radio continuum frequencies (vicinity, interaction or expansion through the molecular cloud, presence of the cooled thermal X-ray electrons during the post Sedov-Taylor phases, detection of low-frequency turnovers associated with thermal absorption linked to the remnant, detection in H , identi cation of radio recombination lines linked to the remnant, etc). The signi cant presence of thermal component could theoretically explain radiospectral indices less than 0.5 measured for several evolutionary older supernova remnants, (mainly of mixed-morphology class) that expand in the high density region. Actually, these smaller radio-spectral indices, under the assumption of simple power law, would represent a natural manifestation of a signi cant fraction of thermal emission at radio continuum frequencies. However, present knowledge of the radio continuum spectra of Galactic supernova remnants is still not determined precisely enough for any de nite conclusions to be made about the inherent thermal radio-emission from supernova remnants. A thorough analysis is only possible in the case of three Galactic supernova remnants (3C396, IC443, 3C391) for which the thermal contribution is determined despite high associated uncertainties. New observations in the near future will lay the groundwork for making rmer conclusions about the existence of the so-called radio thermally active supernova remnants. This dissertation highlights the importance of observations of supernova remnants in X and -rays, and multiwavelength analysis is general. Besides, it suggests a possible detection of -rays from supernova remnant 3C434.1 based on the observations made by Fermi. URI: http://hdl.handle.net/123456789/3051 Files in this item: 1
Onic_Dusan_disertacija.pdf ( 10.67Mb ) -
Kuzmanović, Dragoslav (Beograd , 1986)[more][less]
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Golubović, Zoran (Belgrade , 1984)[more][less]
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Cuparić, Marija (Beograd , 2021)[more][less]
Abstract: The goal of this dissertation is the construction of new goodness-of-fit tests,analysis of their properties, as well as to obtain new theoretical findings regarding the limitingdistributions of weakly degeneratedV−statistics with estimated parameters. New goodness-of-fit tests are based on equidistributional type characterizations of two sample functions.Test statistics are formed asL2distances betweenV−empirical distribution functions ofstatistics from characterization, and also asL2andL∞distances betweenV−empiricalLaplace transformations of those statistics. In the latter case, resulting test statistics can beobserved asV−statistics with an estimated parameter or as functions of those statistics.Until now, limiting results were known for non-degenerateV−statistics with estimatedparameters, as well as for weakly degenerateV−statistics of degree two with estimatedparameters. Limiting results for the appropriate class of weakly degenerateV−statistics withan estimated parameter of degreem, wheremis even number, are derived in this dissertation.Owing to these results, asymptotic properties for presented tests are determined. To assessthe quality of these tests, empirical powers were determined using Monte Carlo simulations, aswell as approximate Bahadur efficiency. New results are presented regarding the approximateBahadur efficiency in case of close alternatives, which is applicable also when the limitingdistribution of statistics under the null hypothesis is not normal. In this sense, the comparisonbetween many tests is performed, both classical tests and recently developed tests.All previously mentioned results were obtained for complete samples. Additional, modifi-cation of previously introduced tests for randomly censored data was also proposed. In sucha case, the new theoretically justified bootstrap method is proposed for the approximation ofp−value. URI: http://hdl.handle.net/123456789/5212 Files in this item: 1
marijacuparicdr.pdf ( 1.771Mb )