It is evident that the origin of EGRB is not well established. In this thesis I examine the unresolved discrete origin of EGRB. The contribution from normal galaxies, starburst galaxies and AGNs to the EGRB is examined. The second chapter includes the methodology used to find the contributions from different source classes. In the third chapter the contribution from normal and starburst galaxies is discussed. A methodology is developed to derive the contribution from normal and starburst galaxies to the EGRB considering all the major γ-ray production processes in these galaxies. The calculations in this thesis consider the detailed γ-ray measurements of our galaxy(Hunter etal.1997) to derive suitable scaling relations to extend the analysis beyond the Milky Way. It is assumed that all normal and starburst galaxies also have similar γ-ray spectra. A relationship is derived between the γ-ray luminosity and SFR of a normal galaxy. Infrared luminosity of a normal galaxy is used as a tracer of SFR of that galaxy (Kewley et al.2002). For starburst galaxies, the contribution depends on the relative ratio(β)of cosmic-ray enhancement per SFR w.r.t the Milky Way. To find the proportionality constants between cosmic-ray production rate and SFR of starburst galaxies, M82 has been taken as a standard. Contribution from FSRQs and BL Lacs to the EGRB is discussed in the fourth chapter. FSRQs and BL Lacs are considered as separate source classes, and their luminosity functions are constructed separately from the recent identifications of EGRET sources(Sowards-Emmerd,Romani&Michelson2003 and Sowards-Emmerd et al.2004) which almost doubled the blazers count than that used by Chiang & Mukher-jee(1998). Radio-loud AGNs with all possible jet to line-of-sight angle (SSRQs, FR IIs, FR Is) are termed here off-axis AGNs. It is considered that SSRQs and FSRQs and FR IIs are from one parent population, BL Lacs and FR Is are from another parent population. The scenario considered includes an AGN jet which slows down as it moves away from the central source. The contributions from these AGNs (relative to the FSRQs and BL Lacs contribution) are discussed in chapter five. Chapter six briefly summarised the findings from the thesis.

Immunohistological (IHC) stained images occupy a fundamental role in the pathologist¿s diagnosis and monitoring of cancer development. The manual process of monitoring such images is a subjective, time consuming process that typically relies on the visual ability and experience level of the pathologist. A novel and comprehensive system for the automated quantification of antibody inside stained cell nuclei in immunohistochemistry images is proposed and demonstrated in this research. The system is based on a cellular level approach, where each nucleus is individually analyzed to observe the effects of protein antibodies inside the nuclei. The system provides three main quantitative descriptions of stained nuclei. The first quantitative measurement automatically generates the total number of cell nuclei in an image. The second measure classifies the positive and negative stained nuclei based on the nuclei colour, morphological and textural features. Such features are extracted directly from each nucleus to provide discriminative characteristics of different stained nuclei. The output generated from the first and second quantitative measures are used collectively to calculate the percentage of positive nuclei (PS). The third measure proposes a novel automated method for determining the staining intensity level of positive nuclei or what is known as the intensity score (IS). The minor intensity features are observed and used to classify low, intermediate and high stained positive nuclei. Statistical methods were applied throughout the research to validate the system results against the ground truth pathology data. Experimental results demonstrate the effectiveness of the proposed approach and provide high accuracy when compared to the ground truth pathology data.

No description available.

Thesis (PhD)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Please refer to full text. / AFRIKAANSE OPSOMMING: Sien asb volteks vir opsomming

Thesis (MSc (Physics))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Highly exotic nuclei can be studied in rare reactions using stable beams, with macroscopic intensities, and thick targets. Exotic nuclei are interesting for a number of reasons e.g. for testing nuclear models under conditions of high isospins. In the case of very neutron-deficient nuclei, two-proton decay is the most recently discovered nuclear decay mode and the subject of many theoretical investigations involving cluster and shell models. This thesis presents a feasibility study of investigating light exotic nuclei near the proton drip line with the K600 magnetic spectrometer. The 27Al(3He,8He)22Al five-neutron pick-up reaction was investigated at a spectrometer angle of θlab = 8◦ with a beam energy of Elab = 220 MeV. This reaction can be used to populate highly neutron-deficient nuclei. Should the study of this reaction prove to be feasible, then a number of nuclei on the proton drip line or beyond could be investigated. A new data acquisition system, with VME electronics and MIDAS software, was used along with one new drift chamber, which consists of both an X wire plane and a U wire plane. The particles 1,2,3H and 3,4He were all identified as outgoing particles from the collision of 3He with 27Al. Cross section calculations were performed for these observed reactions. Discrete spectra for the (3He,6He) and (3He,8He) reactions could not be identified. The mass calculation of A ∼ 20 nuclei on the proton drip line depends on the determination of the Coulomb energy, which differs a lot between mirror nuclei. Mass calculations were performed for known nuclei in the mass region A ≤ 50, using the Isobaric Multiplet Mass Equation. Agreement with experimental data was found to be far better in odd nuclei than in even nuclei. Hence mass predictions were performed for odd nuclei along the proton drip line. / AFRIKAANSE OPSOMMING: Hoogs eksotiese kerne kan bestudeer word in seldsame reaksies deur middel van stabiele bundels, met makroskopiese intensiteite, en dik teikens. Eksotiese kerne is interessant om verskeie redes, onder andere om kernfisiese modelle te toets onder omstandighede van ho¨e isospin. In die geval van baie neutron-arm kerne is twee-proton verval die nuutste ontdekte tipe van kernverval. Dit is ook die onderwerp van vele teoretiese studies met betrekking tot bondel en skilmodelle. Hierdie tesis beskryf ‘n uitvoerbaarheidstudie vir die ondersoek van ligte eksotiese kerne naby die proton drup lyn met behulp van die K600 magnetiese spektrometer. Die 27Al(3He,8He)22Al vyf-neutron kaapreaksie is ondersoek by ‘n spektrometer hoek van θlab = 8◦ met ‘n bundel energie van Elab = 220 MeV. Sou die uitvoerbaarheidstudie van hierdie reaksie slaag, dan kan verskeie kerne op of anderkant die proton drup lyn ondersoek word. ‘n Nuwe data verkrygingssisteem, met VME elektronika en MIDAS sagteware, is gebruik saam met een nuwe dryfkamer, wat bestaan uit beide ‘n X draadvlak en ‘n U draadvlak. Die partikels 1,2,3H en 3,4He is almal geidentifiseer as uitgaande partikels van die botsing van 3He met 27Al. Kansvlak-berekeninge is uitgevoer vir alle waargenome reaksies. Diskrete spektra kon nie gevind word vir die (3He,6He) of (3He,8He) reaksies nie. Die massa berekening van A ∼ 20 kerne op die proton drup lyn is afhanklik van die bepaling van die Coulomb energie, wat baie verskil tussen spie¨elkerne. Massa berekeninge is uitgevoer vir bekende kerne in die massa gebied A ≤ 50, deur die gebruik van die Isobariese Multiplet Massa Vergelyking. Die ooreenstemming met eksperimentele data was baie beter in die geval van onewe kerne as met ewe kerne. Daarom was die massa voorspellings uitgevoer vir slegs onewe kerne naby die proton drup lyn.

published_or_final_version / abstract / Physics / Master / Master of Philosophy

Halo nuclei are among the strangest nuclear structures. They are viewed as a core containing most of the nucleons surrounded by one or two loosely bound nucleons. These have a high probability of presence at a large distance from the core. Therefore, they constitute a sort of halo surrounding the other nucleons. The core, remaining almost unperturbed by the presence of the halo is seen as a usual nucleus. <P> The Coulomb breakup reaction is one of the most useful tools to study these nuclei. It corresponds to the dissociation of the halo from the core during a collision with a heavy (high <I>Z</I>) target. In order to correctly extract information about the structure of these nuclei from experimental cross sections, an accurate theoretical description of this mechanism is necessary. <P> In this work, we present a theoretical method for studying the Coulomb breakup of one-nucleon halo nuclei. This method is based on a semiclassical approximation in which the projectile is assumed to follow a classical trajectory. In this approximation, the projectile is seen as evolving in a time-varying potential simulating its interaction with the target. This leads to the resolution of a time-dependent Schrödinger equation for the projectile wave function. <P> In our method, the halo nucleus is described with a two-body structure: a pointlike nucleon linked to a pointlike core. In the present state of our model, the interaction between the two clusters is modelled by a local potential. <P> The main idea of our method is to expand the projectile wave function on a three-dimensional spherical mesh. With this mesh, the representation of the time-dependent potential is fully diagonal. Furthermore, it leads to a simple representation of the Hamiltonian modelling the halo nucleus. This expansion is used to derive an accurate evolution algorithm. <P> With this method, we study the Coulomb breakup of three nuclei: ¹¹Be, ¹⁵C and ⁸B. ¹¹Be is the best known one-neutron halo nucleus. Its Coulomb breakup has been extensively studied both experimentally and theoretically. Nevertheless, some uncertainty remains about its structure. The good agreement between our calculations and recent experimental data suggests that it can be seen as a <I>s1/2</I> neutron loosely bound to a ¹⁰Be core in its 0⁺ ground state. However, the extraction of the corresponding spectroscopic factor have to wait for the publication of these data. <P> ¹⁵C is a candidate one-neutron halo nucleus whose Coulomb breakup has just been studied experimentally. The results of our model are in good agreement with the preliminary experimental data. It seems therefore that ¹⁵C can be seen as a ¹⁴C core in its 0⁺ ground state surrounded by a <I>s1/2</I> neutron. Our analysis suggests that the spectroscopic factor corresponding to this configuration should be slightly lower than unity. <P> We have also used our method to study the Coulomb breakup of the candidate one-proton halo nucleus ⁸B. Unfortunately, no quantitative agreement could be obtained between our results and the experimental data. This is mainly due to an inaccuracy in the treatment of the results of our calculations. Accordingly, no conclusion can be drawn about the pertinence of the two-body model of ⁸B before an accurate reanalysis of these results. <P> In the future, we plan to improve our method in two ways. The first concerns the modelling of the halo nuclei. It would be indeed of particular interest to test other models of halo nuclei than the simple two-body structure used up to now. The second is the extension of this semiclassical model to two-neutron halo nuclei. However, this cannot be achieved without improving significantly the time-evolution algorithm so as to reach affordable computational times.

Seven very luminous galaxies were examined to determine the contribution of active nuclei to their luminosity, the nature of their stellar population, and the validity of previous measurements of their H₂ content. Spectra of the 2.3 μm bands of CO were used to measure the stellar velocity dispersion, and hence the mass in the central regions. The bolometric luminosity, ionizing continuum luminosity, CO index, and 2.2 μm luminosity were also determined. Models of young stellar populations were compared to the observed properties of the galaxies. It was found that four of the seven galaxies have properties which are inconsistent with those of stellar populations. The active nuclei of these four galaxies produce more than half the total light of the galaxies, but less than one-third of the 2.2 μm light. The galaxies containing AGN also have young stellar populations. There is no evidence for the existence of active nuclei in the other three galaxies. The stellar populations that dominate the starlight in the galaxies have a wide range of properties. Stellar populations range in age from 10 to 65 Myr. The timescale for star formation ranges from 5 Myr to 100 Myr. The local initial mass function is ruled out for one of the four galaxies for which stellar population analysis could be done. The molecular gas masses for some very luminous galaxies determined from the ¹²CO J = 1 → 0 line are in error. The previously determined molecular gas masses are larger than the dynamical masses. The I(CO)/M(H₂) conversion factor found for Milky Way giant molecular clouds is evidently not correct for some very luminous infrared galaxies.

No description available.

No description available.