X-Means Clustering Implementing the Gap Statistic for Multiple Positron Emission Particle Tracking

The most efficient and accurate method for clustering Coincidence Lines (CL) for Positron Emission Particle Tracking (PEPT) is undetermined. A number of methods have been created to perform this task. A novel clustering method featuring x-means is presented using an automated k-value estimator for k-means clustering. Gap statistic is used to select the best k-value. Geant4 Application for Tomographic Emission is used to simulate particles of 50 µCi and the detection and electronic chain associated with the Siemens Inveon Pre-Clinical Scanner. The simulation produces an array of coincident lines (CL) in a format consistent with scanner output. The CL are used to reconstruct particle positions every 100 ms. The position reconstruction is compared to earlier methods

Potential Impact of Nuclear Power on Water Resources in the Southeast United States

Water stress threatens to impact electricity production from thermoelectric plants in the Southeast United States (SE). This is concerning because 97.4% of electricity in the region is produced from thermoelectric sources. These coal, nuclear, and natural gas plants require water for waste heat rejection (WHR), comprising the majority of the SE’s water consumption (58.9%). Increasing nuclear power has been proposed as a way to reduce carbon emissions while being an efficient utilization of land resources compared to wind or solar. However, the impact of an increased reliance on water resources should be examined. To do this, it is necessary to characterize the SE’s electricity mix, water utilization, and determine how these resources are used. In 2010, nuclear plants produced 22.5% of the electricity in the SE, yet comprised 36.8% of the thermoelectric water withdrawal. Thermoelectric plants withdrew the majority of water in the region (58.9%). Only a fraction of withdrawals are consumed by evaporation, but warmer water is returned to streams, which can have harmful effects on aquatic ecosystems. Nuclear plants have larger water withdrawals per GWh because of their lower thermal efficiencies. As more nuclear plants are added to the region, the thermoelectric water demand will grow. To reduce the amount of water needed for WHR, it is advantageous to build cooling towers in waterstressed areas because of their low water withdrawals and to slowly phase out once-through WHR except in areas where environmental impact is negligible. Technologies that could better utilize water resources such as dry heat rejection, waste heat recovery for desalination, and high-temperature reactors with higher thermal efficiencies, like salt-cooled reactors and supercritical CO2 systems, should be considered

Development of Monte Carlo models for the optimisation of positron emission particle tracking experiments

Positron emission particle tracking (PEPT) is a non-invasive technique used to measure the three-dimensional position of positron-emitting tracers. PEPT is useful for studying myriad industrial and/or scientific systems which often are optically inaccessible. However, when running an experiment, often little attention is paid to optimising the tracers, detectors, algorithms, and experimental procedures. As a result, trajectories can be degraded leading to inefficient use of resources. To address this opportunity, Monte Carlo simulations are employed to model experiments and predict the tracer activity, detector geometry, and algorithm parameters that will produce the best trajectory resolution possible and even determine whether an experiment is feasible or how long the experiment should be conducted to reduce uncertainty to an acceptable degree. Importantly, this simulated work can be conducted prior to experiments. In this thesis, a general procedure for simulating PEPT experiments is described which can be applied to any PEPT experiment. The results of this work demonstrate that not only is this method able to produce realistic synthetic PEPT data, but allows, for the first time, a quantitative comparison of PEPT algorithms, the ability to optimise experiments, and to develop new PEPT methodologies using information difficult or impossible to extract from real experiments

Sex differences in the cardiovascular effects of GnRH analogues

The integral role of the hypothalamic–pituitary–gonadal axis in reproductive processes makes it a prime therapeutic target. By inhibiting sex steroid synthesis, gonadotropin-releasing hormone (GnRH) analogues are used in the management of cancers, benign neoplasms, infertility and gender dysphoria. However, the wide application of these therapeutics raises concerns regarding the unintended effects upon the cardiovascular system. In males with prostate cancer, GnRH analogues when used as an androgen deprivation therapy appear to increase the risk of cardiovascular disease, which is the leading cause of death in this population. Therefore, due to the utilisation of GnRH analogues across the lifespan and gender spectrum, this relationship merits discussion. Existing data suggest an association between GnRH analogues and major adverse cardiovascular events in males. Conversely, females receiving GnRH analogues for breast cancer treatment appear to be at an increased risk of developing hypertension. In this narrative review, we describe the uses of GnRH analogues in adults, adolescents and children. We discuss whether sex plays a role in the cardiovascular effects of GnRH analogues and explore the significance of sex hormone receptors in the vasculature. We also consider confounding factors such as malignancy, advanced age and infertility

Mortality and pulmonary complications in patients undergoing surgery with perioperative SARS-CoV-2 infection: an international cohort study

Background: The impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on postoperative recovery needs to be understood to inform clinical decision making during and after the COVID-19 pandemic. This study reports 30-day mortality and pulmonary complication rates in patients with perioperative SARS-CoV-2 infection. Methods: This international, multicentre, cohort study at 235 hospitals in 24 countries included all patients undergoing surgery who had SARS-CoV-2 infection confirmed within 7 days before or 30 days after surgery. The primary outcome measure was 30-day postoperative mortality and was assessed in all enrolled patients. The main secondary outcome measure was pulmonary complications, defined as pneumonia, acute respiratory distress syndrome, or unexpected postoperative ventilation. Findings: This analysis includes 1128 patients who had surgery between Jan 1 and March 31, 2020, of whom 835 (74·0%) had emergency surgery and 280 (24·8%) had elective surgery. SARS-CoV-2 infection was confirmed preoperatively in 294 (26·1%) patients. 30-day mortality was 23·8% (268 of 1128). Pulmonary complications occurred in 577 (51·2%) of 1128 patients; 30-day mortality in these patients was 38·0% (219 of 577), accounting for 81·7% (219 of 268) of all deaths. In adjusted analyses, 30-day mortality was associated with male sex (odds ratio 1·75 [95% CI 1·28–2·40], p\textless0·0001), age 70 years or older versus younger than 70 years (2·30 [1·65–3·22], p\textless0·0001), American Society of Anesthesiologists grades 3–5 versus grades 1–2 (2·35 [1·57–3·53], p\textless0·0001), malignant versus benign or obstetric diagnosis (1·55 [1·01–2·39], p=0·046), emergency versus elective surgery (1·67 [1·06–2·63], p=0·026), and major versus minor surgery (1·52 [1·01–2·31], p=0·047). Interpretation: Postoperative pulmonary complications occur in half of patients with perioperative SARS-CoV-2 infection and are associated with high mortality. Thresholds for surgery during the COVID-19 pandemic should be higher than during normal practice, particularly in men aged 70 years and older. Consideration should be given for postponing non-urgent procedures and promoting non-operative treatment to delay or avoid the need for surgery. Funding: National Institute for Health Research (NIHR), Association of Coloproctology of Great Britain and Ireland, Bowel and Cancer Research, Bowel Disease Research Foundation, Association of Upper Gastrointestinal Surgeons, British Association of Surgical Oncology, British Gynaecological Cancer Society, European Society of Coloproctology, NIHR Academy, Sarcoma UK, Vascular Society for Great Britain and Ireland, and Yorkshire Cancer Research

GATE Simulations for Benchmarking PEPT Algorithms

A series of tests for Position Emission Particle Tracking (PEPT) algorithms are simulated using the Geant4 Application for Tomographic Emission (GATE). In these simulations, a positron-emitting source is prescribed to known locations. The Lines-of-Response (LoR) detected in a planar and ring geometry are recorded. The objective of this work is to provide a basis for comparing the performance of PEPT algorithms on identical data with ground-truth positions to compare against

GATE Simulations for Benchmarking PEPT Algorithms

A series of tests for Position Emission Particle Tracking (PEPT) algorithms are simulated using the Geant4 Application for Tomographic Emission (GATE). In these simulations, a positron-emitting source is prescribed to known locations. The Lines-of-Response (LoR) detected in a planar and ring geometry are recorded. The objective of this work is to provide a basis for comparing the performance of PEPT algorithms on identical data with ground-truth positions to compare against