The Use of the 129Xe MRI Ventilatory ADC Approach for the Evaluation of Emphysema Progression

Hyperpolarized gas pulmonary MRI provides the identification of biomarkers of various obstructive lung diseases such as emphysema. However, emphysema progression is able to cause increasing unventilated lung areas which likely excludes the estimates of the largest apparent diffusion coefficient (ADC). As such, longitudinal observation of the emphysema progression using hyperpolarized gas MRI-based ADC can be problematic, masking the severity of emphysema. The ventilatory ADC (vADC) method, which is the combination of static-ventilation (SV) and ADC measurements, adapted for 129Xe MRI should aid to provide an accurate assessment of the emphysema-progression. Moreover, the SV measurements providing the gas-distribution should remain to portray an increase in the ventilation defects reflecting the progression of emphysema. The objective of this project is to show that the progression of emphysema can be accurately quantified using the vADC approach by utilizing pulmonary static-ventilation and diffusion-weighted images of 129Xe

A system dynamics analysis of the growth in Virginia\u27s residential electricity consumption trends, 1980-2010.

Residential electricity consumption in the Commonwealth of Virginia has more than doubled in three decades, between 1980 and 2010. Per capita and per household consumption rates have grown faster than many other states including New York and California. The following dissertation applies systems dynamics methodology to explore the causes of growth in Virginia’s per capita and per household residential electricity consumption rates in relative contrast to New York and California over the past several decades. Major databases used in the study were accessed from the United States Energy Information Administration and the Census Bureau. Qualitative modelling applying system dynamics principles is used to understand the general dynamics that drive residential electricity consumption across U.S households. The extent to which these dynamics prevail in Virginia is then analyzed using the state’s historical data. Further comparative analysis with benchmark states of New York and California helps identify if those dynamics uniquely prevail in Virginia or are common across the benchmark states too. The study finds that a combination of economic and lifestyle factors among Virginia’s residents, compounded by a low-cost high-volume ‘business as usual’ strategy by the state’s power utility sector with negligible investments in demand side management efforts, have worked relentlessly to cause per capita and per household residential electricity consumption rates to rise in the Commonwealth during the three decades. The results of this study are intended to support in better management of residential electricity consumption rates in the Commonwealth of Virginia. Public educational programs, Government tax credits and rebates, and stronger utility demands side management are key recommendations in the interest of addressing the issue. A successful future reduction in consumption rates will help lessen pressures on the state’s economy as well as the environment

Light quark jet quenching and the Gauge/Gravity duality

In this dissertation, the gauge/gravity duality is used to study light quark jet quenching in the context of strongly coupled non-Abelian plasmas. In particular, we focus on using the so-called finite end point momentum strings to probe such plasmas. First, the Sakai-Sugimoto model is investigated using these strings. The stopping distance of thermalised light quarks and their rate of energy loss are computed. This stopping distance is then used to compute the transverse momentum broadening parameter $\hat{q}$. The Sakai-Sugimoto model shows less jet quenching than $\mathcal{N} = 4$ super Yang-Mills plasma. Both the super Yang-Mills and Sakai-Sugimoto cases over predict the jet quenching parameter relative to phenomenological models that extract $\hat{q}$ from experimental data. Next, the impact of non-zero chemical potentials within the plasma has on light probe quenching is investigated. The two cases of interest are the finite $R$-charged case and the finite baryon chemical potential. It is found that the baryon or flavour chemical potential has very little effect on the jet quenching relative to the $R$-charged case. Finally, small anisotropy is added to the plasma and it is found that for fixed temperature, the anisotropy increases jet quenching for motion in all directions. The longitudinal direction increases the jet quenching parameter the most. However, the parameter decreases in the transverse direction for fixed entropy density

Efficient Algorithms for Robust Estimation

One of the most commonly encountered tasks in computer vision is the estimation of model parameters from image measurements. This scenario arises in a variety of applications -- for instance, in the estimation of geometric entities, such as camera pose parameters, from feature matches between images. The main challenge in this task is to handle the problem of outliers -- in other words, data points that do not conform to the model being estimated. It is well known that if these outliers are not properly accounted for, even a single outlier in the data can result in arbitrarily bad model estimates. Due to the widespread prevalence of problems of this nature, the field of robust estimation has been well studied over the years, both in the statistics community as well as in computer vision, leading to the development of popular algorithms like Random Sample Consensus (RANSAC). While recent years have seen exciting advances in this area, a number of important issues still remain open. In this dissertation, we aim to address some of these challenges. The main goal of this dissertation is to advance the state of the art in robust estimation techniques by developing algorithms capable of efficiently and accurately delivering model parameter estimates in the face of noise and outliers. To this end, the first contribution of this work is in the development of a coherent framework for the analysis of RANSAC-based robust estimators, which consolidates various improvements made over the years. In turn, this analysis leads naturally to the development of new techniques that combine the strengths of existing methods, and yields high-performance robust estimation algorithms, including for real-time applications. A second contribution of this dissertation is the development of an algorithm that explicitly characterizes the effects of estimation uncertainty in RANSAC. This uncertainty arises from small-scale measurement noise that affects the data points, and consequently, impacts the accuracy of model parameters. We show that knowledge of this measurement noise can be leveraged to develop an inlier classification scheme that is dependent on the model uncertainty, as opposed to a fixed inlier threshold, as in RANSAC. This has the advantage that, given a model with associated uncertainty, we can immediately identify a set of points that support this solution, which in turn leads to an improvement in computational efficiency. Finally, we have also developed an approach to addresses the issue of the inlier threshold, which is a user-supplied parameter that can vary depending on the estimation problem and the data being processed. Our technique is based on the intuition that the residual errors for good models are in some way consistent with each other, while bad models do not exhibit this consistency. In other words, looking at the relationship between \\subsets of models can reveal useful information about the validity of the models themselves. We show that it is possible to efficiently identify this consistent behaviour by exploiting residual ordering information coupled with simple non-parametric statistical tests, which leads to an effective algorithm for threshold-free robust estimation.Doctor of Philosoph

Prospective Randomized Controlled Study Comparing Conventional Surgery and Ultrasound guided Foam Sclerotherapy for the Treatment of Primary Superficial Venous Insufficiency of Lower limbs

INTRODUCTION: The problem of varicose veins and venous ulcer has plagued mankind since prehistoric times. It is one of the many prices he had to pay for gaining an erect posture. Though we have achieved cure for various diseases, till now no permanent cure has been found for venous insufficiency. Surgery has been the gold standard for treating chronic venous insufficiency. The challenge for the surgeon dealing with varicose veins has always been balancing a cosmetically acceptable result with a low incidence of recurrence and complications. Increasingly well-informed patients who pressure the treating surgeon for cosmetically acceptable results in conjunction with expansion of minimally invasive techniques have made the treatment of superficial venous reflux and varicose veins a rapidly evolving field. New, minimally invasive techniques for the treatment of varicose veins including Radio frequency ablation (RFA), Endovenous laser therapy (EVLT), and Transilluminated power phlebectomy (TIPP) represent effective and possibly superior alternatives to traditional saphenous vein stripping and stab avulsion of varicose veins. Sclerotherapy can improve the cosmetic appearance of aberrant blood vessels and greatly benefit symptomatic veins by decreasing pain, burning, and cramps that many patients describe. Resolution of larger varicosities can improve the risk of further venous disease sequelae. Sclerotherapy continues to be the gold standard in the treatment of lower extremity small vessel disease. The results of using liquid sclerosant for large veins were poor. After the use of foam sclerotherapy for large veins, the recurrence rates have come down. The availability of a simple method to create foam, proposed by Tessari, has made foam sclerotherapy popular. The safety of foam sclerotherapy has been proven in large scale studies. The recurrence rates following foam sclerotherapy has been comparable to surgery. So far no randomised controlled trial has compared ultrasound guided sclerotherapy with surgery. Therefore this study was carried out to compare the efficacy of foam sclerotherapy when compared to surgery. AIMS AND OBJECTIVES: 1. To assess the obliteration of superficial venous system following conventional surgery and ultrasound guided foam sclerotherapy at the end of 3 months. 2. To compare the clinical outcome following conventional surgery and ultrasound guided foam sclerotherapy at the end of 3 months. 3. To compare the cost of the conventional surgery and ultrasound guided foam sclerotherapy for the treatment of chronic venous insufficiency. MATERIALS AND METHODS: Sample size and randomisation: Since there were no previous similar studies, it was planned to arbitrarily include 60 patients and randomly allocate 30 patients each to surgery and foam sclerotherapy group. Inclusion criteria: All patients with symptomatic primary venous insufficiency of lower limbs, who were willing for definitive management with surgery and foam sclerotherapy, were included. Exclusion criteria: 1. Patients with a history or duplex finding of deep venous thrombosis. 2. Patients who had already undergone surgery for superficial venous Insufficiency. 3. Patients not willing for randomization. METHODOLOGY: All patients presenting with features of venous insufficiency underwent clinical examination and venous duplex examination. Patients who were willing for definitive management were randomized into two groups – one for surgery and another for foam sclerotherapy. Statistical Analysis: The results were tabulated on a spread sheet and statistical analysis was done using SPSS software with the help of bio-statistician. CONCLUSIONS: 1. Obliteration of superficial venous system in short term (3 months) is similar in surgery and foam sclerotherapy. 2. Clinical improvement as measured by CEAP class and venous severity score are similar in both groups. 3. Complications in both the groups are minor and relatively less frequent. 4. Foam sclerotherapy is less time consuming and less morbid than surgery. 5. Patients undergoing foam sclerotherapy returned to work earlier. 6. Foam sclerotherapy is significantly cheaper than surgery

Study of Prevalence of Coronary Atherosclerosis in Bodies Subjected to Autopsy belonging to Age Group 21-40 Years in Local Population

BACKGROUND: Atherosclerotic plaques in the coronary arteries can protrude into the lumen and obstruct the blood flow to myocardium. Depending on the severity of the occlusion it may produce sudden death if the degree of occlusion is very severe. Therefore it is needed to assess the prevalence of coronary atherosclerosis in general population. AIM OF THE STUDY: To find out the prevalence of coronary atherosclerosis in bodies subjected to autopsy belonging to age group 21 – 40 years so as to determine their prevalence. METHODS: It was a prospective study with a sample size of 100 cases belonging to age groups 21 – 40 years including both males and females from January 2017 to June 2018. The heart of the cases were examined and degree of coronary atherosclerosis related narrowing of the right and coronary arteries is studied. RESULTS: Overall the prevalence of coronary atherosclerosis in age group 21-40 years is found to be 37% had varying degree of atherosclerotic plaque occlusion in their right and left coronary artery and 63% of cases were normal. Males had overall prevalence of 41% and females 28% CONCLUSION: The prevalence of coronary atherosclerosis in age group 21 – 40 years is significantly high with 37 % of cases showing some degree of atherosclerosis. Most common lesion in Right coronary artery is grade 2 in both males and females and Most common lesion in left coronary artery is grade 2 & grade 3 & showed equal prevalence in males and grade 2 in females

Prevalence of HIV ocular manifestations in relation to CD4 count at ART Centre, SMCH, Chennai

INTRODUCTION: HIV;bane of new era has been a serious health issue since its discovery in the early 70’s. Although with the current fall in the incidence globally and India; as per UN 2012 reports ;India is still the third largest nation with HIV population. HIV manifests indirectly and it does so by decreasing the immunity especially CD4 cells,thereby leading to secondary infections. It affects all systems alike ;eye and its adnexa is no exception. HIV ocular complications include minor opportunistic infection,tumor, inflammation, vasculopathy and retinopathy. It is important that these manifestations are detected irrespective of symptoms or history and treated at the earliest possible. This study is done in order to find the prevalence of the various ocular manifestation of HIV, its correlation to CD4 count and the role of HAART. AIM: To evaluate the prevalence of ocular manifestations in HIV seropositive patients, attending the ART centre, Stanley Medical College and Hospital. To evaluate how the manifestations correlate to the CD4 count. To evaluate the impact of HAART on ocular HIV manifestations. METHODS AND MATERIALS: STUDY DESIGN: Cross sectional study was undertaken on 100 HIV seropositive patient attending the ART centre with known CD4 count was included in the study.The study period was from February 2013 till completion of hundred patients. INCLUSION CRITERIA HIV seropositve consented patients attending ART centre irrespective of ocular complaints, irrespective of treatment status. Any age group CD4 count obtained at the time of examination. EXCLUSION CRITERIA Severely ill patients. CD4 count could not be obtained. Pre-existing systemic illnesses. The importance of ocular examination in them was thoroughly explained in patients own language.Consent in patients own language was obtained from all those who were willing to take part in study.Any photographic records of the lesions were taken only if the patient consented for the same.Upon completion of data collection, statistical analysis was applied. STATISTICAL ANALYSIS: Chi square test was done for statistical analysis of the obtained data. ROUTINE OCULAR EXAMINATION WAS DONE AS FOLLOWS: • Ocular history. • Ocular examination included: • Best corrected visual acuity. ( Snellen’s chart ) • Slit lamp evaluation – Adnexa and Anterior segment • Dilated fundus evaluation (0.8 % tropicamide with 5% phenylephirine) – 90 D and 20 D • Neuro ophthalmological examination • Orbit • Tonometry for IOP evaluation • Schirmer’s for dry eye evaluation • Patient with suspected lesions were referred for complete systemic and laboratory work up. • Serological investigations included TORCH titre, PCR assay for HZV, VZ. • Other investigations were done as per clinical indication included CT brain/ MRI brain. OBSERVATION AND DISCUSSION: The mean age of patients in our study was 38.14 +/- 11.84 which fell in line with mean age of the comparative studies.Majority of the patient prevalence in our study fell under the reproductive age group of 20-40 years. This pattern was similarly noticed in Biswas et al , Gururaj et al and Lamichhane G et al study. However our prevalence rate of 58 % was closely comparable to the Gururaj et al study which had 54 %.Also comparable with the Gururaj et al study was the decrease in prevalence with increase in age.Of special mention is the similarity in the prevalence of patients in the age group < 20 years. Our study shows a higher male prevalence in comparison to females. The age gender distribution in our study was not significant, p= 0.3. This was also the finding in Lamichhane G et all study. Sexual route was the most common mode of disease transmission, and this was observed in study by Biswas et al and Gururaj et al. Gururaj et al had 1 homosexual route of exposure.P value of 0.1274 signifies that the route of exposure has no impact the prevalence of the ocular manifestations.Majority of the patients in our study were observed in clinical stage I and II. The findings were similar in the Gururaj et al and Amare et al study. It was observed in our study that all patients those who fell under the Clinical category III /IV had ocular HIV manifestation, and mostly of the opportunistic type. This was equally observed in the studies to which we compared to in the above table.With p value of 0.003 we can conclude that prevalence of ocular manifestation increases with the clinical staging of disease. And this is probably due to the increase in the opportunistic infection in these stages. This was observed both in Gururaj et al and the Amare et al study as well.We observed an increased prevalence of ocular manifestations in the CD4 range of 200 – 500 cells/mm3. This was comparable to the Ethiopian study by Amare et al.P value in our study was 0.0235, which was significant. This significance was observed in all the above mentioned studies.Hence ocular manifestations is seen to increase significantly with decrease in CD4 count, especially in levels < 200 cells/mm3. Blepharitis and conjunctival microvasculopathy was the commonest anterior segment findings observed in this study. The prevalence of both of which were significantly higher in comparison to the studies mentioned above.Kaposi sarcoma and conjunctival squamous cell carcinoma were nil, and were comparable to the two Indian studies mentioned above. These findings were present in the African studies. And this has been implicated due to the homosexual practises.we see differences in most of the anterior segment presentations in comparison to other Indian studies. This can be attributed to the geographical change in location of the study.The prevalence of HIV retinopathy, toxoplasmosis acute retinal necrosis and uveitis in our study was comparable to the prevalence in Biswas et al study.The same finding was not so with CMV retinitis. This limitation was observed probably due to the sample size in our study. Ocular TB and syphilis were not recorded in our study. CONCLUSION: HIV infection is a problematic communicable disease present in our population, affecting commonly the reproductive age group. HIV manifests in the eye either directly in the form of viral load or causes low immunity thereby increasing chances for opportunistic infections.With the introduction of HAART, the life expectancy of the patients have significantly increased. However the ocular manifestations continue to present in innumerable forms.Not all patients with early HIV opportunistic infection present to us with ocular symptoms until unless the manifestation is severely blinding and irreversible.Most of the symptomatic patients are the ones with blepharitis and conjunctivitis, a non-blinding yet troublesome form of disease manifestations.The ART centres in India at present practice just the referral of patients for ophthalmological examination only when the patient develops ocular complaints.With the number of ocular findings observed, our study highlights the need for a routine ophthalmological screening of all HIV seropositive patients. We recommend a routine screening of HIV seropositive patients upon diagnosis, prior to starting ART therapy to obtain a baseline ocular status. Once the patient is started on HAART , he/she must undergo at-least a half yearly ocular examination. This is important for two reasons; one to look out for immune reconstitution syndromes, two to identify the ocular side effects of HAART.CD4 counts have to be strictly considered while monitoring these patients. It serves both as a risk factor as well as an indicator of opportunistic manifestations.A very important observation we made was the patients non-consenting to any detailed examination outside of the ART centre. This was due to the stigma attached to the disease and the fear of being publically recognised as HIV seropositive.All this indicates a need for provision of ophthalmic setup in the ART centre.This can be made possible with adequate resources and trained ophthalmic personnel