Studies of visual attention in physics problem solving

Doctor of PhilosophyDepartment of PhysicsN. Sanjay RebelloThe work described here represents an effort to understand and influence visual attention while solving physics problems containing a diagram. Our visual system is guided by two types of processes -- top-down and bottom-up. The top-down processes are internal and determined by ones prior knowledge and goals. The bottom-up processes are external and determined by features of the visual stimuli such as color, and luminance contrast. When solving physics problems both top-down and bottom-up processes are active, but to varying degrees. The existence of two types of processes opens several interesting questions for physics education. For example, how do bottom-up processes influence problem solvers in physics? Can we leverage these processes to draw attention to relevant diagram areas and improve problem-solving? In this dissertation we discuss three studies that investigate these open questions and rely on eye movements as a primary data source. We assume that eye movements reflect a person’s moment-to-moment cognitive processes, providing a window into one’s thinking. In our first study, we compared the way correct and incorrect solvers viewed relevant and novice-like elements in a physics problem diagram. We found correct solvers spent more time attending to relevant areas while incorrect solvers spent more time looking at novice-like areas. In our second study, we overlaid these problems with dynamic visual cues to help students’ redirect their attention. We found that in some cases these visual cues improved problem-solving performance and influenced visual attention. To determine more precisely how the perceptual salience of diagram elements influenced solvers’ attention, we conducted a third study where we manipulated the perceptual salience of the diagram elements via changes in luminance contrast. These changes did not influence participants’ answers or visual attention. Instead, similar to our first study, the time spent looking in various areas of the diagram was related to the correctness of an answer. These results suggest that top-down processes dominate while solving physics problems. In sum, the study of visual attention and visual cueing in particular shows that attention is an important component of physics problem-solving and can potentially be leveraged to improve student performance

Role of the Neutral Amino Acid Transporter SLC7A10 in Adipocyte Lipid Storage, Obesity and Insulin Resistance

Elucidation of mechanisms that govern lipid storage, oxidative stress, and insulin resistance may lead to improved therapeutic options for type 2 diabetes and other obesity-related diseases. Here, we find that adipose expression of the small neutral amino acid transporter SLC7A10, also known as alanine-serine-cysteine transporter-1 (ASC-1), shows strong inverse correlates with visceral adiposity, insulin resistance, and adipocyte hypertrophy across multiple cohorts. Concordantly, loss of Slc7a10 function in zebrafish in vivo accelerates diet-induced body weight gain and adipocyte enlargement. Mechanistically, SLC7A10 inhibition in human and murine adipocytes decreases adipocyte serine uptake and total glutathione levels and promotes reactive oxygen species (ROS) generation. Conversely, SLC7A10 overexpression decreases ROS generation and increases mitochondrial respiratory capacity. RNA sequencing revealed consistent changes in gene expression between human adipocytes and zebrafish visceral adipose tissue following loss of SLC7A10, e.g., upregulation of SCD (lipid storage) and downregulation of CPT1A (lipid oxidation). Interestingly, ROS scavenger reduced lipid accumulation and attenuated the lipid-storing effect of SLC7A10 inhibition. These data uncover adipocyte SLC7A10 as a novel important regulator of adipocyte resilience to nutrient and oxidative stress, in part by enhancing glutathione levels and mitochondrial respiration, conducive to decreased ROS generation, lipid accumulation, adipocyte hypertrophy, insulin resistance, and type 2 diabetes.acceptedVersio

Apoptotic cell-based therapies against transplant rejection: role of recipient’s dendritic cells

One of the ultimate goals in transplantation is to develop novel therapeutic methods for induction of donor-specific tolerance to reduce the side effects caused by the generalized immunosuppression associated to the currently used pharmacologic regimens. Interaction or phagocytosis of cells in early apoptosis exerts potent anti-inflammatory and immunosuppressive effects on antigen (Ag)-presenting cells (APC) like dendritic cells (DC) and macrophages. This observation led to the idea that apoptotic cell-based therapies could be employed to deliver donor-Ag in combination with regulatory signals to recipient’s APC as therapeutic approach to restrain the anti-donor response. This review describes the multiple mechanisms by which apoptotic cells down-modulate the immuno-stimulatory and pro-inflammatory functions of DC and macrophages, and the role of the interaction between apoptotic cells and APC in self-tolerance and in apoptotic cell-based therapies to prevent/treat allograft rejection and graft-versus-host disease in murine experimental systems and in humans. It also explores the role that in vivo-generated apoptotic cells could have in the beneficial effects of extracorporeal photopheresis, donor-specific transfusion, and tolerogenic DC-based therapies in transplantation

A 'snip' in time: what is the best age to circumcise?

<p>Abstract</p> <p>Background</p> <p>Circumcision is a common procedure, but regional and societal attitudes differ on whether there is a need for a male to be circumcised and, if so, at what age. This is an important issue for many parents, but also pediatricians, other doctors, policy makers, public health authorities, medical bodies, and males themselves.</p> <p>Discussion</p> <p>We show here that infancy is an optimal time for clinical circumcision because an infant's low mobility facilitates the use of local anesthesia, sutures are not required, healing is quick, cosmetic outcome is usually excellent, costs are minimal, and complications are uncommon. The benefits of infant circumcision include prevention of urinary tract infections (a cause of renal scarring), reduction in risk of inflammatory foreskin conditions such as balanoposthitis, foreskin injuries, phimosis and paraphimosis. When the boy later becomes sexually active he has substantial protection against risk of HIV and other viral sexually transmitted infections such as genital herpes and oncogenic human papillomavirus, as well as penile cancer. The risk of cervical cancer in his female partner(s) is also reduced. Circumcision in adolescence or adulthood may evoke a fear of pain, penile damage or reduced sexual pleasure, even though unfounded. Time off work or school will be needed, cost is much greater, as are risks of complications, healing is slower, and stitches or tissue glue must be used.</p> <p>Summary</p> <p>Infant circumcision is safe, simple, convenient and cost-effective. The available evidence strongly supports infancy as the optimal time for circumcision.</p