Advocating for our patients using clinical research

This reflection is about experiences trying to relate medical research evidence to actual patient care. This piece talks about shared decision-making about screening mammography

A Study of Improving the Parallel Performance of VASP.

This thesis involves a case study in the use of parallelism to improve the performance of an application for computational research on molecules. The application, VASP, was migrated from a machine with 4 nodes and 16 single-threaded processors to a machine with 60 nodes and 120 dual-threaded processors. When initially migrated, VASP\u27s performance deteriorated after about 17 processing elements (PEs), due to network contention. Subsequent modifications that restrict communication amongst VASP processes, together with additional support for threading, allowed VASP to scale up to 112 PEs, the maximum number that was tested. Other performance-enhancing optimizations that were attempted included replacing old libraries, which produced improvements of about 10%, and prefetching, which degraded, rather than enhanced, VASP performance

Doctor of Philosophy

dissertationThree-dimensional (3D) models of industrial plant primitives are used extensively in modern asset design, management, and visualization systems. Such systems allow users to efficiently perform tasks in Computer Aided Design (CAD), life-cycle management, construction progress monitoring, virtual reality training, marketing walk-throughs, or other visualization. Thus, capturing industrial plant models has correspondingly become a rapidly growing industry. The purpose of this research was to demonstrate an efficient way to ascertain physical model parameters of reflectance properties of industrial plant primitives for use in CAD and 3D modeling visualization systems. The first part of this research outlines the sources of error corresponding to 3D models created from Light Detection and Ranging (LiDAR) point clouds. Fourier analysis exposes the error due to a LiDAR system's finite sampling rate. Taylor expansion illustrates the errors associated with linearization due to flat polygonal surfaces. Finally, a statistical analysis of the error associated with LiDar scanner hardware is presented. The second part of this research demonstrates a method for determining Phong specular and Oren-Nayar diffuse reflectance parameters for modeling and rendering pipes, the most ubiquitous form of industrial plant primitives. For specular reflectance, the Phong model is used. Estimates of specular and diffuse parameters of two ideal cylinders and one measured cylinder using brightness data acquired from a LiDAR scanner are presented. The estimated reflectance model of the measured cylinder has a mean relative error of 2.88% and a standard deviation of relative error of 4.0%. The final part of this research describes a method for determining specular, diffuse and color material properties and applies the method to seven pipes from an industrial plant. The colorless specular and diffuse properties were estimated by numerically inverting LiDAR brightness data. The color ambient and diffuse properties are estimated using k-means clustering. The colorless properties yielded estimated brightness values that are within an RMS of 3.4% with a maximum of 7.0% and a minimum of 1.6%. The estimated color properties effected an RMS residual of 13.2% with a maximum of 20.3% and a minimum of 9.1%

Satellite-Based Correlation Studies of Mesospheric O2 and OH Infrared Emissions

The Mesosphere and Lower Thermosphere/Ionosphere (MLTI) plays an important role in the energy balance of the Earth-Sun planetary system. The SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) instrument on NASAs TIMED (Thermosphere Ionosphere Mesosphere Energetics and Dynamics) satellite is a spatially scanning 10-channel infrared radiometer. To aid in the modeling of the photo-chemical dynamics that take place in the MLTI region, a series of correlations concerning three radiometric airglow bands of SABER are explored. The three bands of interest are O2(14g), OH(9-7;8-6) and OH(5-3), centered at wavelengths of 1.27, 2.06 and 1.64 μm, respectively. It was found that both the O2(14g) and OH(4v = 2) nighttime airglow volume emission rates have consistently brighter values and lower altitudes at near equatorial latitudes compared with values at midlatitudes. Two correlations are presented herein: (1) latitudinal and (2) global. The correlations performed showed consistent results. The more reliable results come from the global correlation using a binning technique that allowed for more data. The binning technique also made it possible to view the correlations over the entire globe. The dual OH airglow bands exhibited a strong correlation (0.85 to 1.0). The O2 1.27 μm airglow band showed a strong correlation (0.8 to 1.0) with the OH 2.06 μm airglow band. The O2 1.27 μm airglow band is less correlated (0.6 to 0.8) with the OH 1.64 μm airglow band

Improved Commuter Rail Workstation Table through Crash Energy Management

Workstation tables in commuter rail trains have been identified as an area for improving passenger safety during train collisions. The goal of this senior project was to create such a table using a composite sandwich structure designed to safely absorb energy. Testing of previous table designs was used to establish engineering specifications for the static loading, work surface durability, and impact performance requirements of the new table. Analytical and finite element models were used to analyze new concepts until a design was achieved that could meet all specifications. The tabletop developed consists of a crushable aluminum honeycomb core with fiberglass laminates on top and bottom. This sandwich structure uses a combination of E‐glass cloth and S‐glass unidirectional tape in a unique layup that lowers impact forces inflicted on the passenger while maintaining overall table strength during normal loading conditions. Four tables were built during the senior project. These tables were fabricated using a combination of fiberglass layup, metal working, welding, and adhesive bonding. Using these tables, four validation tests were conducted to evaluate the performance of the new design: work surface indent testing, vertical and horizontal static loading, quasi-static crush testing, and dynamic impact testing. The results of these tests showed that the new table met all of the engineering specifications outlined at the beginning of the project. The work surface was stronger than expected, showing deformation at a load of 175lbs; well above the requirement of 65lbs or more. The table easily withstood the 225lb vertical and 337lb horizontal static loading requirements at all critical locations. Quasi-static testing showed that a 1500‐2000lb edge load is needed to initiate crushing of the table. Although the desired goal of 800‐1000lb was not achieved, the facesheets did begin buckling in the unbounded sections as designed at about 1000lbs; only 100lbs from the 900lb buckling load predicted by FEA. Unfortunately, the tables continue to support load after initial buckling up to the witnessed 1500‐2000lbs. In dynamic impact testing, the table produced some of the lowest peak acceleration levels of any design to date. The peak acceleration levels recorded were 14g and 20g for the two impacting masses; well below the specification of 30g for any time period over 3ms. The tabletop structure also crushed evenly and the facesheets remained bonded and contained under the aluminum edging. The overall metal structure of the table also held its form, suggesting that the passenger would remain safe during such an impact. The new table costs about $475 and weighs 37lbs

Shifting Centers of Production: The Amphorae Assemblages at Mons Porphyrites and Bir Umm Fawakhir

Mons Porphyrites and Bir Umm Fawakhir in the Eastern Desert of Egypt were two sites of resource extraction during the Roman and subsequent Byzantine occupation of Egypt. Mons Porphyrites was quarried for its vibrant purple stone featured in building projects such as the Pantheon. Bir Umm Fawakhir was a gold mine which was worked intermittently from the twentieth dynasty of the Egyptian pharaohs through the Ptolemies and into the Byzantine period. In this paper, I examine the amphorae evidence from both sites to trace the patterns over time in the distribution of goods including centers of production, routes of transportation, and the larger networks of supplying the labor forces at these zones of extraction. The end result is that the provisioning of the quarries and the mines took place in a complex system of trade which functioned alongside local lines of supply.Master of Art

Using a browser extension to provide a natural environment

Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (page 59).People are spending ever increasing amounts of time online. As a result, companies are investing greater amounts of money into online advertising in an effort to influence their behavior. The impact and effectiveness of these ads is still an open question. One possible method of analyzing the effectiveness is through the analysis of clickstream data. However, this data may be difficult to obtain and does not measure behavioral change. Behavioral change is a change in consideration or preference. Surrogate sites can be used to study behavioral change but are difficult and time-consuming to create and do a poor job of mimicking certain classes of sites. This is particularly true of social media sites where the amount of content is impossible to fully reproduce and yet this content is the defining component of the web site. In this thesis, I present a Chrome extension that can be used for conducting high fidelity web site market research. The framework provides the opportunity to measure behavioral change and provide a natural environment almost identical to the actual sites. I detail the implementation of the extension and its use in a web-based media experiment with a sample size of 13,000. Preliminary results and learnings are discussed. Results suggest that use of the extension is feasible and is capable of producing significant changes in consumer consideration.by Brandon H. Baker.M. Eng

Spinal compression fractures: no additional pain relief with use of back braces

A critical appraisal and clinical application of Li M, Law SW, Cheng J, Kee HM, Wong MS. A comparison study on the efficacy of SpinoMed® and soft lumbar orthosis for osteoporotic vertebral fracture. J. Prosthet. Orthot. Int. 2015;39(4):270-276. doi: 10.1177/030936461452820