Validation and application of intravascular ultrasound in the study of percutaneous coronary intervention

Intravascular ultrasound (IVUS) is a relatively new method of imaging coronary arteries which has several advantages over contrast angiography in the accurate quantification of coronary lumen and vessel dimensions and assessment of atherosclerotic plaque. Experimentally, IVUS has so far provided detailed insights into the distribution and composition of atheroma in the coronary circulation and its behaviour when subjected, particularly, to balloon dilatation. The technique is now regarded as a useful adjunct to angiography in the routine assessment of patients with atherosclerotic coronary disease as well as in the guidance of percutaneous coronary interventional techniques such as balloon angioplasty and intracoronary stent implantation. Additionally, the concept of three-dimensional reconstruction of IVUS images has recently been realized providing the opportunity for longitudinal as well as tomographic analysisDespite the wealth of information so far provided by IVUS most in vitro studies require cautious interpretation due to well-recognised limitations of studying animal models of atherosclerosis or human coronary disease in circumstances that do not accurately reflect the clinical setting. This thesis is based upon the development of a pulsatile flow system which is capable of accurately reproducing some of the important physiological properties of in-vivo flow in normal and diseased coronary arteries. Some characteristics of in-vivo coronary blood flow cannot be met, such as the effect of blood viscosity and extrinsic compression of the vessel by the beating heart. However, the system is designed to enable the study of human coronary atherosclerotic disease by IVUS in conditions which closely resemble those seen in the clinical setting. The initial chapters provide an overview of IVUS, including methods and rationale for three-dimensional reconstruction, and describe the development and validation of the flow system. Chapters 3 and 4 assess the qualitative accuracy of IVUS in the assessment of the composition of atherosclerotic plaque and also the reproducibility of IVUS assessments of vessel and lumen dimensions in diseased coronary arteries. There follows a study of coronary balloon angioplasty designed to assess the influence of procedural factors, such as balloon calibre and inflation pressure selection, and IVUS guidance on the initial success of the procedure. In the remaining chapters two studies examine three-dimensional reconstruction of IVUS images and the influence of technical factors, which are inherent in IVUS imaging, on the accuracy of atherosclerotic plaque volume measurement and its use in assessing vascular injury following coronary balloon angioplasty. It should be emphasized that all patient donors died from causes other than cardiovascular disease such that the histopathological studies involved the use of coronary artery specimens which were not required for diagnostic purposes. The studies adhered to strict ethical standards of the day. Harvesting of specimens received ethical approval as part of the overall IVUS research programme being undertaken at the time. All specimens were retained by the Department of Pathology during the study period and disposed of appropriately following the final analysesTaken together these studies have helped to provide further insights into the quantitative and qualitative accuracy of IVUS in the assessment of coronary atherosclerosis and the technical factors which may confound these analyses. Furthermore, the value of IVUS in guiding, and assessing the outcome of, coronary balloon angioplasty is clearly demonstrated. Given the close correlation of the studies to the clinical setting the findings should be expected to influence our approach to clinical IVUS studies and utilize the technique more frequently in the guidance of percutaneous coronary intervention

Is justice deferred, justice denied? Not necessarily

At long last, the Serious Fraud Office has received a major boost in its prosecution of bribery. Serious Fraud Office v Standard Bank PLC is a landmark case because it is not only the first case where the SFO has looked to prosecute a commercial organisation for failure to prevent bribery under Bribery Act 2010, but the first occasion where it has sought to enter a Deferred Prosecution Agreement under Crime and Courts Act 2013

Pattern classification via unsupervised learners

We consider classification problems in a variant of the Probably Approximately Correct (PAC)-learning framework, in which an unsupervised learner creates a discriminant function over each class and observations are labeled by the learner returning the highest value associated with that observation. Consideration is given to whether this approach gains significant advantage over traditional discriminant techniques. It is shown that PAC-learning distributions over class labels under Ll distance or KL-divergence implies PAC classification in this framework. We give bounds on the regret associated with the resulting classifier, taking into account the possibility of variable misclassification penalties. We demonstrate the advantage of estimating the a posteriori probability distributions over class labels in the setting of Optical Character Recognition. We show that unsupervised learners can be used to learn a class of probabilistic concepts (stochastic rules denoting the probability that an observation has a positive label in a 2-class setting). This demonstrates a situation where unsupervised learners can be used even when it is hard to learn distributions over class labels - in this case the discriminant functions do not estimate the class probability densities. We use a standard state-merging technique to PAC-learn a class of probabilistic automata and show that by learning the distribution over outputs under the weaker L1 distance rather than KL-divergence we are able to learn without knowledge of the expected length of an output. It is also shown that for a restricted class of these automata learning under L1 distance is equivalent to learning under KL-divergence

ACL RUPTURE IN COLLEGIATE WRESTLER

Objective: To educate others on unique Anterior Cruciate Ligament tears and percentage of usage of the ACL in normal daily function. Background: Patient is an eighteen year old male participating in wrestling and football at the time of the injury. Patient now only participates in wrestling. No previous knee or chronic injuries were reported prior to this injury. Patient was playing football during the time of injury. The patient stated that he planted his foot down and was tackled at the same time when the injury occurred. The patient felt his knee twist and buckle. Patient complained of clicking inside the knee and had minimal swelling. He also complained of it being difficult to bear weight at the time. The patient did not seek further treatment until two months after the injury occurred when he received an MRI. His MRI showed a positive finding for an Anterior Cruciate Ligament rupture. His previous Athletic Trainer could not find a positive diagnosis for the patient prior to the MRI. Differential Diagnosis: Possible meniscal or ACL injury. Treatment: Doctors officially diagnosed the injury as a complete rupture of the ACL. The patient did not receive surgery immediately. Doctors have stated that he only uses about 50% of his ACL on a daily basis compared to a normal person who uses about 95% of their ACL daily. Because of this, the patient played on his rupture for seven months before receiving surgery. He played a whole season of high school football and a whole season of wrestling his senior year with the ACL ruptured. The patient only used a brace for better comfort during the seven months. The patient then received reconstructive surgery to repair the rupture. A hamstring tendon graft was used to repair the ruptured ACL. Because a tendon was taken from the hamstring, patient experienced a tight ACL and hamstring of the left leg post-surgery. The patient participated in Physical Therapy for five months to strengthen and stretch the new ACL and hamstring. After completing five months of physical therapy, the patient joined a college wrestling team in August 2013. The athletic training staff at the university started him on a quadriceps and hamstring strengthening rehabilitation program for about one month. The staff also worked on continuous flexion and extension of the knee to where the patient could feel comfortable with doing activities with his knee. The patient continues to participate in daily stretching and strengthening protocols for his quadriceps and hamstring bilaterally. Deviation from the Expected/Uniqueness: The patient still participated on a fully ruptured ACL for seven months with just complaining of minimal pain and discomfort. The athlete chose to complete two seasons of activities instead of receiving surgery immediately. The ratio of people who rupture their ACL is about 5 in every 100,000 people. It is interesting that the high school clinician could not diagnose the injury until the patient received an MRI two months post-injury. The patient was also told by doctors that he only uses about 50% of his ACL on a daily basis compared to anyone else who uses their ACL about 95%. The patient felt comfortable with the ACL ruptured and changed any discomfort by just wearing a brace. Conclusions: Not many people can play on a ruptured ACL for seven months before receiving any surgical repairs. We need to keep this in mind as Athletic Trainers so we are not sending our athletes back on the field and possibly causing them more damage. The athlete continues stretching protocols daily. Key Words: rupture, ACL, Anterior Cruciate Ligamen

Miniaturized Ultraviolet Imager High Voltage Power Supply

Sending satellites into orbit becomes exponentially more expensive with weight and size, so designing high-voltage DC-DC converters that can achieve kilovolt level outputs in a small form factor is crucial to reducing costs. The Miniaturized Ultraviolet Imager (MUVI) aims to monitor Earth’s ionosphere and report weather patterns to climate scientists within a 2U cube satellite footprint. The imaging equipment consists of a microchannel plate and phosphor screen that require 2.5kV and 5.5kV respectively at microamp level currents. This report explains the implementation of a high voltage boost cascaded flyback converter to meet all of the MUVI satellite output voltage requirements. The small mechanical footprint of a cube satellite severely limits board size and component heights. This design further expands the power electronics field and provides inspiration for future space-rated voltage converters in small form factors. The results from circuit simulations validated the design as a viable solution for MUVI’s imaging equipment. A boost-flyback converter can achieve the required high voltage DC output while remaining within the 7ppm ripple specification. This report summarizes all of the circuit simulation results for both the power stage and analog circuitry that monitor and control the output voltage. The analog circuitry was hardware tested and validated for the monitoring and control signals. The power stage testing is scheduled for the Summer of 2021 so those results are not included in this report

University Energy Demand Forecasting using Machine Learning: A Comparative Study

Undergraduate Applie

Association of plasma uric acid with ischaemic heart disease and blood pressure: mendelian randomisation analysis of two large cohorts

Objectives: To assess the associations between both uric acid levels and hyperuricaemia, with ischaemic heart disease and blood pressure, and to explore the potentially confounding role of body mass index. Design: Mendelian randomisation analysis, using variation at specific genes (SLC2A9 (rs7442295) as an instrument for uric acid; and FTO (rs9939609), MC4R (rs17782313), and TMEM18 (rs6548238) for body mass index). Setting: Two large, prospective cohort studies in Denmark. Participants: We measured levels of uric acid and related covariables in 58 072 participants from the Copenhagen General Population Study and 10 602 from the Copenhagen City Heart Study, comprising 4890 and 2282 cases of ischaemic heart disease, respectively. Main outcome: Blood pressure and prospectively assessed ischaemic heart disease. Results: Estimates confirmed known observational associations between plasma uric acid and hyperuricaemia with risk of ischaemic heart disease and diastolic and systolic blood pressure. However, when using genotypic instruments for uric acid and hyperuricaemia, we saw no evidence for causal associations between uric acid, ischaemic heart disease, and blood pressure. We used genetic instruments to investigate body mass index as a potentially confounding factor in observational associations, and saw a causal effect on uric acid levels. Every four unit increase of body mass index saw a rise in uric acid of 0.03 mmol/L (95% confidence interval 0.02 to 0.04), and an increase in risk of hyperuricaemia of 7.5% (3.9% to 11.1%). Conclusion: By contrast with observational findings, there is no strong evidence for causal associations between uric acid and ischaemic heart disease or blood pressure. However, evidence supports a causal effect between body mass index and uric acid level and hyperuricaemia. This finding strongly suggests body mass index as a confounder in observational associations, and suggests a role for elevated body mass index or obesity in the development of uric acid related conditions

Pattern classification via unsupervised learners

We consider classification problems in a variant of the Probably Approximately Correct (PAC)-learning framework, in which an unsupervised learner creates a discriminant function over each class and observations are labeled by the learner returning the highest value associated with that observation. Consideration is given to whether this approach gains significant advantage over traditional discriminant techniques. It is shown that PAC-learning distributions over class labels under Ll distance or KL-divergence implies PAC classification in this framework. We give bounds on the regret associated with the resulting classifier, taking into account the possibility of variable misclassification penalties. We demonstrate the advantage of estimating the a posteriori probability distributions over class labels in the setting of Optical Character Recognition. We show that unsupervised learners can be used to learn a class of probabilistic concepts (stochastic rules denoting the probability that an observation has a positive label in a 2-class setting). This demonstrates a situation where unsupervised learners can be used even when it is hard to learn distributions over class labels - in this case the discriminant functions do not estimate the class probability densities. We use a standard state-merging technique to PAC-learn a class of probabilistic automata and show that by learning the distribution over outputs under the weaker L1 distance rather than KL-divergence we are able to learn without knowledge of the expected length of an output. It is also shown that for a restricted class of these automata learning under L1 distance is equivalent to learning under KL-divergence.EThOS - Electronic Theses Online ServiceEngineering and Physical Sciences Research Council (Great Britain) (EPSRC) (GR/R86188/01)GBUnited Kingdo