Candido Cabo

Dynamics of propagation of premature impulses in structurally remodeled infarcted myocardium: a computational analysis

Initiation of cardiac arrhythmias typically follows one or more premature impulses either occurring spontaneously or applied externally. In this study, we characterize the dynamics of propagation of single (S2) and double premature impulses (S3), and the mechanisms of block of premature impulses at structural heterogeneities caused by remodeling of gap junctional conductance (Gj) in infarcted myocardium. Using a sub-cellular computer model of infarcted tissue, we found that |INa,max|, prematurity (coupling interval with the previous impulse), and conduction velocity (CV) of premature impulses change dynamically as they propagate away from the site of initiation. There are fundamental differences between the dynamics of propagation of S2 and S3 premature impulses: for S2 impulses |INa,max| recovers fast, prematurity decreases and CV increases as propagation proceeds; for S3 impulses low values of |INa,max| persist, prematurity could increase, and CV could decrease as impulses propagate away from the site of initiation. As a consequence it is more likely that S3 impulses block at sites of structural heterogeneities causing source/sink mismatch than S2 impulses block. Whether premature impulses block at Gj heterogeneities or not is also determined by the values of Gj (and the space constant λ) in the regions proximal and distal to the heterogeneity: when λ in the direction of propagation increases >40%, premature impulses could block. The maximum slope of CV restitution curves for S2 impulses is larger than for S3 impulses. In conclusion: (1) The dynamics of propagation of premature impulses make more likely that S3 impulses block at sites of structural heterogeneities than S2 impulses block; (2) Structural heterogeneities causing an increase in λ (or CV) of >40% could result in block of premature impulses; (3) A decrease in the maximum slope of CV restitution curves of propagating premature impulses is indicative of an increased potential for block at structural heterogeneities.

Alice's Adventures in Programming Narratives

This chapter describes our innovative approach to the teaching of computer programming and writing; professors worked with students across classes united by a theme of narrative. A year-long study examined if using Alice, a three-dimensional microworld programming software that allows users to create interactive narratives, was more effective than Visual Basic (VB) in developing problem-solving abilities in first-year college students in introductory computer programming courses. Results revealed that although both the Alice and VB group showed a statistically significant (p<0.05) increase in performance for problem-solving questions related to computer programming, only the Alice group showed a significant increase in problem-solving abilities not directly related to computer programming, and an increase in student retention.

Synergies between writing stories and writing programs in problem-solving courses

First-year problem-solving and computer programming courses are gateway courses with low passing rates, resulting in student attrition and transfers out of computer science degrees. Our urban institution serves mostly under-represented minority students, typically an at-risk population given their minimal previous programming experience and weak mathematical background. We offer a computer problem-solving course (PS) to prepare students in computing and engineering majors for a rigorous first programming course (CSI). Given a change in programming learning context from a programming language to the 3D programming environment Alice, the pass rate increased by 8% points (from 70% to 78%). The higher pass rate in the Alice PS course does not result in a weaker preparation of students for the subsequent CSI course. Moreover, teaching the Alice PS course as part of an interdisciplinary learning community linked to a first course in English composition with strong narrative components further increases student performance and retention. This intentional interdisciplinary approach to problem solving allows students to purposefully connect and integrate knowledge and skills from across the disciplines, developing synergies between writing stories and writing computer programs.

Making Connections: Writing Stories and Writing Code

Interdisciplinary competence should be an integral part of undergraduate education. The development of interdisciplinary skills expands students’ perspectives and blurs differences between general education and major courses, preparing them to be better problem-solvers in an increasingly complex and connected world. This chapter describes the design, development, and teaching of an interdisciplinary course linking creative writing and computational thinking for non-computer majors. In this interdisciplinary course, students develop original stories which they then implement as a video game prototype using computer programming. Via interdisciplinary connections between writing stories and writing computer code, even non-computer majors acquire computational thinking concepts and skills.