Assessment of the Severity of Paravalvular Regurgitation and its Role on Survival After Transcatheter Aortic Valve Replacement

Background: To evaluate the impact of various measurements of paravalvular regurgitation (PVR) on survival after transcatheter aortic valve replacement (TAVR). PVR can be difficult to grade and both its incidence and impact on survival may be decreasing as TAVR evolves. Methods: This retrospective study included 911 patients undergoing TAVR in two institutions. PVR was graded according to the 3-grade scheme proposed by the guidelines (PVR grade), and subsequently grade 2 and 3, and grade 0 and 1 were lumped together. PVR was also graded as a composite score (PVR score), based on 6 commonly used metrics. PVR grade, PVR score and its six individual components were tested against the risk of both 1-year and longer term mortality after TAVR. Results: Patients with moderate/severe PVR had a higher Society of Thoracic Sugeons (STS) score, higher levels of serum creatinine and larger left atria compared to patients with none/mild PVR. Moderate/severe PVR was more frequent with self-expandable and larger valves. After adjusting for American College of Cardiology (ACC) TAVR risk score, neither PVR grade, PVR score nor its six components were associated with an increased risk of mortality at 1-year (severe PVR adjusted HR: 0.75, 95% Confidence Interval [CI]: 0.19, 3.01, p = 0.50). However, intervention for clinically severe PVR increased the risk of mortality by more than 7-fold (adjusted hazard ratio [HR]: 7.6, 95% CI: 2.4, 23.5, p < 0.0001). Conclusions: In the contemporary era, moderate-severe PVR is uncommon. However, re-intervention for PVR portends a poor prognosis. This highlights the crucial importance of clinical judgment over imaging alone

Analytical Models for Valence Fermions in Isotropic Traps

For isotropic confining Ioffe-Pritchard or TOP potentials, a valence fermion trapped with a closed core of other fermions can be described by an analytical effective one-particle model with a physical eigenspectrum. Related constructions exist for Paul and Penning traps. The analytical models arise from quantum-mechanical supersymmetry.Comment: accepted for publication in Physics Letters

Injury and Illness in Elite Athletics: A Prospective Cohort Study Over Three Seasons

Background: Athletics (also known as track and field) is one of the most popular sports in the world and is the centrepiece of the Summer Olympic Games. Participation in athletics training and competition involves a risk of illness and injury. Purpose: To describe injury and illness in British Olympic track and field athletes over three full training and competition seasons. Study Design: Descriptive Epidemiology Study Methods: A total of 111 athletes on the British national program were followed prospectively for three consecutive seasons between 2015-2018. Team medical personnel recorded all injuries and illnesses during this time, following current consensus-based methods. All data pertaining to these records were reviewed and analyzed for sports injury and illness epidemiological descriptive statistics. Results: The average age of the athletes was 24 years for both males and females (24 years, +/- 4). Total exposure for the three seasons was 79 205 athlete days (217 athlete years). Overuse injuries (56.4%) were more frequent than acute injuries (43.6%). The thigh was the most common injury location (0.6 per athlete year), followed by the lower leg (0.4 per athlete year) and foot (0.3 per athlete year). Muscle and tendon were the most commonly injured tissues, while strains and tears were the most common pathology type. Hamstring muscle strain was the most common diagnosis causing time loss, followed by Achilles tendinopathy and soleus muscle strain. Respiratory illness was the most common illness type (0.3 per athlete year). Conclusion: Hamstring strains, Achilles tendinopathy, and soleus strains are the most common injuries in athletics and have highest burden. Respiratory illness is the most common illness and has the highest burden. Knowledge of this injury and illness profile within athletics could be utilised for the development of targeted prevention measures within the sport at the elite level.Injury and Illness in Elite Athletics: A Prospective Cohort Study Over Three SeasonspublishedVersio

Improving Syntactic Relationships Between Language and Objects

This paper presents the integration of natural language processing and computer vision to improve the syntax of the language generated when describing objects in images. The goal was to not only understand the objects in an image, but the interactions and activities occurring between the objects. We implemented a multi-modal neural network combining convolutional and recurrent neural network architectures to create a model that can maximize the likelihood of word combinations given a training image. The outcome was an image captioning model that leveraged transfer learning techniques for architecture components. Our novelty was to quantify the effectiveness of transfer learning schemes for encoders and decoders to qualify which were the best for improving syntactic relationships. Our work found the combination of ResNet feature extraction and fine-tuned BERT word embeddings to be the best performing architecture across two datasets - a valuable discovery for those continuing this work considering the cost of compute for these complex models

Quantification of Internal Stress-Strain Fields in Human Tendon: Unraveling the Mechanisms that Underlie Regional Tendon Adaptations and Mal-Adaptations to Mechanical Loading and the Effectiveness of Therapeutic Eccentric Exercise.

By virtue of their anatomical location between muscles and bones, tendons make it possible to transform contractile force to joint rotation and locomotion. However, tendons do not behave as rigid links, but exhibit viscoelastic tensile properties, thereby affecting the length and contractile force in the in-series muscle, but also storing and releasing elastic stain energy as some tendons are stretched and recoiled in a cyclic manner during locomotion. In the late 90s, advancements were made in the application of ultrasound scanning that allowed quantifying the tensile deformability and mechanical properties of human tendons in vivo. Since then, the main principles of the ultrasound-based method have been applied by numerous research groups throughout the world and showed that tendons increase their tensile stiffness in response to exercise training and chronic mechanical loading, in general, by increasing their size and improving their intrinsic material. It is often assumed that these changes occur homogenously, in the entire body of the tendon, but recent findings indicate that the adaptations may in fact take place in some but not all tendon regions. The present review focuses on these regional adaptability features and highlights two paradigms where they are particularly evident: (a) Chronic mechanical loading in healthy tendons, and (b) tendinopathy. In the former loading paradigm, local tendon adaptations indicate that certain regions may "see," and therefore adapt to, increased levels of stress. In the latter paradigm, local pathological features indicate that certain tendon regions may be "stress-shielded" and degenerate over time. Eccentric exercise protocols have successfully been used in the management of tendinopathy, without much sound understanding of the mechanisms underpinning their effectiveness. For insertional tendinopathy, in particular, it is possible that the effectiveness of a loading/rehabilitation protocol depends on the topography of the stress created by the exercise and is not only reliant upon the type of muscle contraction performed. To better understand the micromechanical behavior and regional adaptability/mal-adaptability of tendon tissue it is important to estimate its internal stress-strain fields. Recent relevant advancements in numerical techniques related to tendon loading are discussed

Metabolic Factors Limiting Performance in Marathon Runners

Each year in the past three decades has seen hundreds of thousands of runners register to run a major marathon. Of those who attempt to race over the marathon distance of 26 miles and 385 yards (42.195 kilometers), more than two-fifths experience severe and performance-limiting depletion of physiologic carbohydrate reserves (a phenomenon known as ‘hitting the wall’), and thousands drop out before reaching the finish lines (approximately 1–2% of those who start). Analyses of endurance physiology have often either used coarse approximations to suggest that human glycogen reserves are insufficient to fuel a marathon (making ‘hitting the wall’ seem inevitable), or implied that maximal glycogen loading is required in order to complete a marathon without ‘hitting the wall.’ The present computational study demonstrates that the energetic constraints on endurance runners are more subtle, and depend on several physiologic variables including the muscle mass distribution, liver and muscle glycogen densities, and running speed (exercise intensity as a fraction of aerobic capacity) of individual runners, in personalized but nevertheless quantifiable and predictable ways. The analytic approach presented here is used to estimate the distance at which runners will exhaust their glycogen stores as a function of running intensity. In so doing it also provides a basis for guidelines ensuring the safety and optimizing the performance of endurance runners, both by setting personally appropriate paces and by prescribing midrace fueling requirements for avoiding ‘the wall.’ The present analysis also sheds physiologically principled light on important standards in marathon running that until now have remained empirically defined: The qualifying times for the Boston Marathon

Characterizing and monitoring student discomfort in upper-division quantum mechanics

We investigate student comfort with the material in an upper-division spins-first quantum mechanics course. Pre-lecture surveys probing students' comfort were administered weekly, in which students assigned themselves a "discomfort level" on a scale of 0--10 and provided a written explanation for their choice. The weekly class-wide average discomfort level was effectively constant over the semester, suggesting that the class found no single unit especially jarring nor especially easy. Student written responses were coded according to their reported source of discomfort---math, math-physics connection, physics, and notation. The relative prevalence of these categories varied significantly over the semester, indicating that students find that different units present different challenges, and also that some of these challenges fade in importance as the semester progresses. Semi-structured interviews with students in a similar quantum mechanics course at a different institution provided additional context and insight into these results.Comment: 4 pages, 3 figures, to be published in 2020 Physics Education Research Conference Proceeding

Assessing the Accuracy of Ancestral Protein Reconstruction Methods

The phylogenetic inference of ancestral protein sequences is a powerful technique for the study of molecular evolution, but any conclusions drawn from such studies are only as good as the accuracy of the reconstruction method. Every inference method leads to errors in the ancestral protein sequence, resulting in potentially misleading estimates of the ancestral protein's properties. To assess the accuracy of ancestral protein reconstruction methods, we performed computational population evolution simulations featuring near-neutral evolution under purifying selection, speciation, and divergence using an off-lattice protein model where fitness depends on the ability to be stable in a specified target structure. We were thus able to compare the thermodynamic properties of the true ancestral sequences with the properties of “ancestral sequences” inferred by maximum parsimony, maximum likelihood, and Bayesian methods. Surprisingly, we found that methods such as maximum parsimony and maximum likelihood that reconstruct a “best guess” amino acid at each position overestimate thermostability, while a Bayesian method that sometimes chooses less-probable residues from the posterior probability distribution does not. Maximum likelihood and maximum parsimony apparently tend to eliminate variants at a position that are slightly detrimental to structural stability simply because such detrimental variants are less frequent. Other properties of ancestral proteins might be similarly overestimated. This suggests that ancestral reconstruction studies require greater care to come to credible conclusions regarding functional evolution. Inferred functional patterns that mimic reconstruction bias should be reevaluated