James C. Squire

Stent and Artery Geometry Determine Intimal Thickening Independent of Arterial Injury

BACKGROUND Clinical trials show that larger immediate postdeployment stent diameters provide greater ultimate luminal size, whereas animal data show that arterial injury and stent design determine late neointimal thickening. At deployment, a stent stretches a vessel, imposing a cross-sectional polygonal luminal shape that depends on the stent design, with each strut serving as a vertex. We asked whether this design-dependent postdeployment luminal geometry affects late neointimal thickening independently of the extent of strut-induced injury. METHODS AND RESULTS Stainless steel stents of 3 different configurations were implanted in rabbit iliac arteries for 3 or 28 days. Stents designed with 12 struts per cross section had 50% to 60% less mural thrombus and 2-fold less neointimal area than identical stents with only 8 struts per cross section. Sequential histological sectioning of individual stents showed that immediate postdeployment luminal geometry and subsequent neointimal area varied along the course of each stent subunit. Mathematical modeling of the shape imposed by the stent on the artery predicted late neointimal area, based on the re-creation of a circular vessel lumen within the confines of the initial stent-imposed polygonal luminal shape. CONCLUSIONS Immediate postdeployment luminal geometry, dictated by stent design, determines neointimal thickness independently of arterial injury and may be useful for predicting patterns of intimal growth for novel stent designs.

Endothelial Cell Electrical Impedance Parameter Artifacts Produced by a Gold Electrode and Phase Sensitive Detection

Frequency dependent cellular micro-impedance estimates obtained from a gold two-electrode configuration using phase sensitive detection have become increasingly used to evaluate cellular barrier model parameters. The results of this study show that cellular barrier function parameter estimates optimized using measurements obtained from this biosensor are highly susceptible to both time dependent and systematic instrumental artifacts. Based on a power spectral analysis of experimentally measured microelectrode voltages, synchronous, 60 Hz, and white Gaussian noise were identified as the most significant time dependent instrumental artifacts. The reduction of these artifacts using digital filtering produced a corresponding reduction in the optimized model parameter fluctuations. Using a series of instrumental circuit models, this study also shows that electrode impedance voltage divider effects and circuit capacitances can produce systematic deviations in cellular barrier function parameter estimates. Although the implementation of an active current source reduced the voltage divider effects, artifacts produced by coaxial cable and other circuit capacitive elements at frequencies exceeding 1 kHz still remained. Reducing time dependent instrumental fluctuations and systematic errors produced a significant reduction in cellular model barrier parameter errors and improved the model fit to experimental data

Measuring arterial strain induced by endovascular stents.

Endovascular stents are expandable, fenestrated tubes that are threaded in their collapsed state through an artery to a site of occlusion, plastically enlarged and left as permanent implants to scaffold the artery open. The stent induces largescale vascular strains that are difficult to measure in vivo and yet can be critical determinants of stent-vessel biology. A method is developed to measure the strain tensor developed on the surface of an artery as a stent is expanded in vivo. Arterial sections are marked with reference points and imaged as the stent is expanded. An axially symmetric parametric model of the artery is determined for each expansion timepoint, and these reference points are backprojected onto this surface. The backprojected reference points are grouped and analysed to determine the circum-ferential, axial and torsional strain tensor components in each arterial subsection. The method is characterised in vitro using bovine artery segments and a latex phantom, and is then tested on rabbits to demonstrate its feasibility in vivo. In vitro experiments on stented bovine arteries show typical post-stenting strains of 0.60, −0.26, and 0.08 mm mm−1 in the circumferential, axial and torsional directions, respectively, sampled every 1 mm along the length of the stented region. Phantom experiments characterise the RMS error of system measurements as 0.1 mm mm−1. The system is shown capable of measuring strains of straight, accessible vessels in the presence of respiratory/cardiac motion and visual glare in vivo.

TickBot: A novel robotic device for controlling tick populations in the natural environment

A semi-autonomous 4-wheeled robot (TickBot) was fitted with a denim cloth treated with an acaricide (permethrin™) and tested for its ability to control ticks in a tick-infested natural environment in Portsmouth, Virginia. The robots sensors detect a magnetic field signal from a guide wire encased in 80m polyethylene tubing, enabling the robot to follow the trails, open areas and other terrain where the tubing was located. To attract ticks to the treated area, CO2 was distributed through the same tubing, fitted with evenly spaced pores and flow control valves, which permitted uniform CO2 distribution. Tests were done to determine the optimum frequency for TickBot to traverse the wire-guided treatment site as well as the duration of operation that could be accomplished on a single battery charge. Prior to treatment, dragging was done to determine the natural abundance of ticks in the test site. Controls were done without CO2 and without permethrin. TickBot proved highly effective in reducing the overall tick densities to nearly zero with the treatment that included both carbon dioxide pretreatment and the permethrin treated cloth. Following a 60min traverse of the treatment areas, adult tick numbers, almost entirely Amblyomma americanum, was reduced to zero within 1h and remained at or near zero for 24h. Treatments without CO2 also showed reduction of ticks to near zero within 1h, but the populations were no different than the control sections at 4h. This study demonstrates the efficacy of TickBot as a tick control device to significantly reduce the risk of tick bites and disease transmission to humans and companion animals visiting a previously tick-infested natural environment. Continued deployment of TickBot for additional days or weeks can assure a relatively tick-safe environment for enjoyment by the public.

Robo-Tic: Development of a Tick-Eliminating Robot

Tick bites are a calculated risk of enjoying outdoor activities; yet in certain geographic regions, deer ticks are more likely than not infected with Lyme disease even to the extent that some medical journals recommend physicians automatically begin antibiotic treatment following bites in high-risk areas regardless of a patients symptoms. There exists no Lyme vaccine approved for use in humans, and annual reported cases in people are rising with the spread of infected ticks across the northeast United States.Undergraduate electrical and mechanical engineering students from the Virginia Military Institute (VMI) have developed a tick-control robot that uses biomimicry to encourage ticks to attach to a pesticide-infused fabric patch. A prototype was found to remove 45 ± 4 out of 50 ticks seeded in a small and noncontrolled study by Woulfe et al. A ruggedized prototype was next developed by engineering students from both VMI and Washington & Lee University capable of withstanding a multiweek controlled study by an independent environmental testing laboratory while students from Wake Forest University examined how to commercialize the device.

Random Selection of Petit Jurors on the Virginia Frontier, 1746-55

Abstract. Eighteenth-century English common-law courts used petit juries in civil litigation to try issues of fact or find damages after defendants defaulted. In colonial Virginia, county sheriffs impaneled potential jurors for trials of the issue; before trial, litigants selected a 12-man jury during voir dire. By contrast, juries on writs of inquiry to ascertain damages were selected solely by sheriffs and reached verdicts under the sheriffs supervision. Scholarly consensus holds juror selection to have been prejudiced, but pure probability predictions generated with hypergeometric distributions indicate that on writs of inquiry sheriffs often picked jurors in a functionally random manner. This article presents a new test for identifying bias in jury selection by identifying improbable numbers of magistrates, constables, and grand jurors.

Cellular electrical micro-impedance parameter artifacts produced by passive and active current regulation.

This study analyzes the cellular microelectrode voltage measurement errors produced by active and passive current regulation, and the propagation of these errors into cellular barrier function parameter estimates. The propagation of random and systematic errors into these parameters is accounted for within a Riemannian manifold framework consistent with information geometry. As a result, the full non-linearity of the model parameter state dependence, the instrumental noise distribution, and the systematic errors associated with the voltage to impedance conversion, are accounted for. Specifically, cellular model parameters are treated as the coordinates of a model space manifold that inherits a Riemannian metric from the data space. The model space metric is defined in terms of the pull back of an instrumental noise-dependent Fisher information metric. Additional noise sources produced by the evaluation of the cell-covered electrode model that is a function of a naked electrode random variable are also included in the analysis. Based on a circular cellular micro-impedance model in widespread use, this study shows that cellular barrier function parameter estimates are highly model state dependent. Systematic errors produced by coaxial lead capacitances and circuit loading can also lead to significant and model state-dependent parameter errors and should, therefore, be either reduced or corrected for analytically.

Court-day crowds in colonial Virginia

ABSTRACT For a generation, legal historians investigating colonial Virginia have emphasized the dramaturgy of court day. According to the dramaturgical school of interpretation, administrative and judicial activities of county court officials amounted to theatrical performances that simultaneously enforced economic order and stabilized traditional social relationships. Such interpretations assume a large audience routinely attended county courts to observe legal dramas. Often, however, only a small number of persons can be documented as present during court day. The independence theorem from probability theory suggests that the number of documentable attendees is a useful and easily calculated estimate for actual total crowd size. If so, some Virginia court sessions were attended by hundreds of people, while others drew only a few participants. A variety of factors apparently inhibited court attendance in older Virginia counties. By contrast, in newer frontier counties, mid-eighteenth-century revisions of court calendars produced heavy attendance at court day. Regardless of the number of people in attendance, any Virginia county court could still effectively enforce credit contracts.

Modeling Stent Expansion Dynamics And Blood Flow Patterns In A Stenotic Artery

restenosis remains a significant problem in coronary intervention. although stent migrations, collapses, and positioning difficulties remain serious issues, it is the problem of restenosis which is the most common long term problem in treating atherosclerotic coronary arteries with stents. although much attention has focused on biocompatibility, thrombosis and neointimal pathology, less attention has been given to matching stents to the inflation balloon, artery and occlusion size. balloons are typically sized 1–2 mm longer than endovascular stents, yet the effects of the degree of balloon overhang are unknown. In this study, a computational model capable of predicting balloon/stent/artery interactions and their effects on arterial stresses was developed to assess the effects of length mismatch on stent expansion characteristics and arterial stresses. results from this study indicate that maximum arterial stress at balloon contact is approximately proportional to the degree of balloon overhang. a 100% increase in balloon overhang results in a 4% increase in maximum endflare and a 39% change in the peak arterial stress. However, at the end of expansion, which is of the most clinical importance, the increase in maximum endflare is 2% and the increase in maximum arterial stress is 93% at the balloon point of contact and 45% at the point of contact with the far proximal and distal ends of the stent. When comparing the results of calcified and cellular plaque, a maximum endflare of about 55% was observed for both the calcified and cellular plaque cases during expansion. at the end of expansion the increase in maximum endflare was 10% for the cellular plaque and 40% of the calcified plaque. The peak equivalent stress seen by the artery was about 100% larger in the cellular case than in the calcified plaque case.

Work in progress - relationship of demonstration construction quality on pedagogic effectiveness

Scientific studies have established the importance of engineering demonstrations, yet comparatively little is known about what makes some demonstrations more effective than others. In this study we investigate the pedagogic effect of demonstration construction quality. This study considers two build qualities: “raw” and “polished”. Raw demonstrations use prototype-quality construction techniques such as exposed solderless breadboards, and polished demonstrations use production-quality construction techniques designed to emulate typical consumer electronics. The impact of the demonstrations on student interest were assessed by constructing paired sets of demonstrations of raw and polished quality. These were used in lectures to 119 students and student interest and comprehension were assessed by post-lecture surveys. Initial data using only a single demonstration in both raw and polished versions show students in both technical and nontechnical majors score higher in objective testing and report higher interest in the material using raw construction techniques (two-tailed p=0.051 and ≪0.01 respectively). Further data using other demonstrations will be obtained in 2009 to determine if these findings can be generalized.