The study of cosmological radio backgrounds with the Sunyaev-Zel'dovich effect

A thesis submitted to the Faculty of Science, University of Witwatersrand, in the ful lment of the requirements for the degree of Doctor of Philosophy Johannesburg, South Africa, 2017.According to the standard model of cosmology, the Universe has evolved from a thermal bath of elementary particles and photons towards one comprising of collapsed structures such as stars, galaxies and clusters of galaxies. The Cosmic Microwave Background (CMB) spectrum and its angular anisotropy across the sky contain information on the physical processes, matter distribution and evolution of the Universe across cosmic time. Primordial spectral distortions of the CMB and its anisotropy can be studied through the inverse comptonization process occuring in cosmic structures, known as the Sunyaev-Zel'dovich e ect (SZE). This present study demonstrates how the SZE can be used to obtain information on the 21 cm background produced between the Dark Ages (DA) and the Epoch of Reionization (EoR), on Non-Planckian (NP) modi cations of the CMB due to plasma frequency at the recombination epoch, and on the anisotropy of the CMB at cluster locations, through the study of the polarization of the SZE. To these aims, a full relativistic approach is employed, that allows us to calculate the spectra of the SZE and its polarization component with high precision, and allows to calculate it for any kind of electron population (thermal or nonthermal plasma), and for an input spectrum that can deviate from the standard black-body spectrum. The SZE-21cm, which is the comptonized spectrum of the modi ed CMB due to physical processes occuring during the DA and the EoR, is calculated for four models of the 21-cm background. A full spectral analysis of the signal is performed and the importance of relativistic e ects are highlighted. The results demonstrate that relativistic e ects are nonzero over the entire frequency spectrum and hence cannot be ignored, particularly for hot clusters. It is found that the amplitude of the SZE-21cm signal is of the order of Jy and is within the reach of the SKA instrument. Clusters with high temperature and optical depth are optimal targets to search for the SZE-21cm signal. The SKA can measure the signal in the frequency interval 75-90 MHz for clusters with temperature higher than 5 keV. Discerning the SZE-21cm from the standard SZE can be achieved using the SKA depending on the 21-cm background model for temperatures > 10 keV. Using CMB spectral data at both low and high frequencies, upper limits (206, 346 and 418 MHz at 1, 2, 3 con dence level) are placed on NP e ects associated with a non-zero plasma frequency at the recombination epoch. The SZENP is derived for a CMB spectrum modi ed due to plasma e ects using these upperlimits and a unique spectral feature is obtained. A peak occures at the plasma frequency in the SZENP independent of cluster parameters and the possibility of measuring the plasma frequency with the SKA and eVLA is shown. Plasma e ects are also investigated on the spectrum of the cosmological 21-cm background and it is found that such an e ect is important to consider when recovering the history of the Universe during these epochs. Polarization is a natural outcome of inverse Compton (IC) scattering and the anisotropy of the CMB plays a big role in the production of polarization in Comptonization process. The SZE polarization associated with the anisotropy of the CMB is derived in the full relativistic regime for any general electron distribution. The spectral shapes of the Stokes parameters induced by the IC scattering of the multipoles of the CMB for thermal and non-thermal electrons are derived, focusing mainly on the quadrupole and octupole which provide the largest possible detectable signals in cosmic structures. Our results demonstrate the implication of relativistic e ects, which become important for high temperature or non-thermal cluster environments. When relativistic e ects are accounted for, all the multipoles of the CMB are involved in the production of polarization. The octupole induced polarization spectrum reveals the existence of a cross-over frequency which is dependent on cluster parameters such as temperature, minimum momentum and spectral index. The possibilities to disentangle the quadrupole spectrum from the octupole one are discussed, which would allow the measurments of these multipoles at cluster locations. The generality of our approach allows us to calculate the SZE polarization spectra of the Bullet cluster using multifrequency SZE data in intensity and compare the results with the sensitivities of the SKA, ALMA, Millimetron and CORE++ instruments. Although the e ects that we studied here are small, however, they are still within the detection limits of the SKA, due to its very high sensitivity. Therefore, the SKA will play a big role in the study of cosmological radio backgrounds by providing high precision SZE data.LG201

Adenoid cystic carcinoma of the external auditory canal

This is a rare case of a young male with biopsy proven adenoid cystic carcinoma of the external auditory canal who underwent excision of the lesion with superficial parotidectomy sparing the facial nerve. Histopathology showed perineural invasion, which is a diagnostic hallmark of adenoid cystic carcinoma. Clinical examination, chest X-ray and CT scan showed no signs of recurrence or metastasis 2 years postoperatively

A multi-frequency study of the Sunyaev Zel'dovich effect and its polarization in cosmic structures

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. Johannesburg, 24 May 2014.The Sunyaev-Zel'dovich e ect (hereafter SZE), i.e. the distortion of the cosmic microwave background (CMB) spectrum due to inverse Compton scattering of CMB photons o energetic electrons in cosmic structures, is a relevant inves- tigation tool for astrophysical and cosmological studies. Since the SZE is an interaction between photons and electrons, polarization arises as a natural out- come and then provides the SZE with an important complementary component as an astrophysical and cosmological probe. This thesis is an extensive study on the SZE in non-relativistic and relativistic regime including polarization. We rst perform a study on a set of galaxy clusters hosting radio halos where we constrain the non-thermal pressure present in these structures using multifre- quency data such as SZE, radio and X-ray. We found that the average ratio between non-thermal to thermal pressure is 0:5. We then derive, in the full relativistic regime, a general formulation of the properties of the SZE, and we further derive the Stokes parameters, Q and U, of the polarized SZE. This is done in a general case by solving the polarized Boltzmann collisional integral in the Thomson limit that allows us to extract the Stokes parameters for arbitrary electron distribution functions. We further discuss the spectral features of the SZE polarization as produced by other additional e ects occurring in the clus- ter atmospheres, like nite optical depth e ects and transverse plasma motions. We nally apply the results of our study to di erent cosmic structures (e.g. galaxy clusters and radio galaxies) and we discuss the relevance of SZE polar- ization in the study of extragalactic astrophysical plasmas and for cosmological applications

Induced Myopia Secondary to Blunt Trauma

A 28-year-old young man presented with sudden and severe visual loss in the left eye, starting three days ago following blunt head trauma from a closed fist. Vision was not improved to better than 0.4 in the left eye. Slit lamp examinations revealed asymmetric anterior chamber depth (ACD) with shallow ACD in the left eye. The key learning in this report is the use of anterior segment optical coherence tomography (AS-OCT) to better document the anterior segment changes following the blunt trauma. AS-OCT was used to visualize the forward displacement of the iris-crystalline lens diaphragm secondary to ciliary body anterior rotation and ciliochoroidal effusion. There was a temporary myopic shift about 7.00D which resolved after 15 days

Predicting postoperative cardio-pulmonary complications by a test of stair climbing

OBJECTIVE: To assess whether a test of stair climbing ability could be used to predict the risk of developing postoperative cardiopulmonary complications in patients undergoing general anesthesia. DESIGN: Cohort study. PLACE AND DURATION OF STUDY: The Aga Khan University Hospital, Karachi. The duration of the study was from December 2003 to December 2004. PATIENTS AND METHODS: This study was carried out on consecutive, adult patients presenting for elective thoracic or abdominal surgery under general anesthesia. Pre-operatively, patients were asked to climb a standard staircase. Number of steps climbed was recorded. Those unable to climb stairs due to debilitating cardiac, pulmonary or rheumatologic disease were categorized as 0 stairs climbed. Outcome variables were postoperative cardiopulmonary complications or mortality. Period of follow-up was until hospital discharge. RESULTS: Seventy-eight patients were enrolled, 59 (75.6%) climbed 1 flight of stairs, 19 (24.3%) climbed \u3c 1 flight. All-cause cardiopulmonary complications rate was 26 %. The most frequent complication was lobar atelectasis, followed by bronchospasm and acute MI. The complication rate was 22.8% in those able to climb 1 flight and 40% in those patients who climbed \u3c 1 flight. The group that climbed \u3c 1 flight tended to have complications associated with poor reserves of the cardiopulmonary systems, i.e. pulmonary edema, exacerbation of underlying lung disease. The relative risk of developing complications, if unable to climb at least 1 flight of stairs, was calculated to be 1.8 (95% CI 0.7 - 4.6). CONCLUSION: Stair climbing can be a useful pre-operative tool to predict the risk of postoperative cardiopulmonary complication

Market orientation and SME performance : Moderating role of IoT and mediating role of creativity

Peer reviewe

Effectiveness of Vitamin D in Prevention of Dengue Haemorrhagic Fever and Dengue Shock Syndrome

Background: To compare the risk and severity of development of Dengue Hemorrhagic Fever (DHF) and Dengue Shock Syndrome(DSS) in patients receiving Vitamin D supplement compared to those not receiving it.Methods: Diagnosed patients of DF (n=124) were enrolled in this comparative study. Patients were randomized into two groups having 62 participants in each group. Group A received single dose of 200,000 IU Vitamin D and Group B received no intervention. Both groups were followed for development of DHF or DSS. Chi square was applied to compare the groups.Results: One patient (1.6%) in Group A developed DHF. Seventeen (27%) patients in Group B progressed to DHF. The relationship between Vitamin D and progression to DHF was significant, X2 (2, N=170) =16.43, p= 0.000). The calculated relative risk was 0.0588 (95% confidence interval, .0081 to .4285; p for trend = 0.0588).Conclusion: Vitamin D decreases the risk of DHF and may have a role in management of dengue fever

Global Chaos Synchronization of Two different Chaotic Systems Using Nonlinear Control

Synchronization between two chaotic systems occurs when the trajectory of one of the system asymptotically follows the trajectory of another system due to coupling or due to forcing. In this research paper, the synchronization problem between two identical Li and identical Lorenz systems and nonidentical Li and Lorenz Chaotic Systems have been addressed. In this study, the synchronization is performed through a nonlinear controller based on Lyapuonov Stability Theory to stabilize the error dynamics. It has been shown that the proposed strategies have excellent transient performances using less control effort with fast transient speed and has shown analytically as well as graphically that synchronization is asymptotically globally stable