ECSEL/MIT Engineering Education Workshop '99: A Report with Recommendations

In May, 1999, the NSF funded, Engineering Coalition of Schools for Excellence in Education and Leadership, (ECSEL) sponsored a workshop at MIT to: (i) describe and disseminate the principal results of the coalition's efforts over the past decade, (ii) bring together faculty, department chairs and deans from a wide variety of engineering schools to explore how the most significant barriers to reform of engineering education might be overcome, and (iii) to promote the development of effective policies for the future. Panel sessions and roundtables addressed many of the critical issues facing faculty and administrators seeking to renovate undergraduate engineering education. A wide range of experiences were described and proposals advanced. The authors summarize these discussions and put forward a set of recommendations founded upon the essential points made over the course of the two‐day workshop.     

Comparison of two barium suspensions for dedicated small-bowel series

OBJECTIVE: The in vivo radiographic features of two commercially available formulations of barium used as contrast media in dedicated small-bowel series were compared. SUBJECTS AND METHODS: Fifty-six consecutive outpatients referred for a dedicated small-bowel series were randomly administered either E-Z-Paque or Entrobar. Representative survey radiographs from each examination were randomized and reviewed by six gastrointestinal radiologists from three institutions. Each observer assigned a numeric score (1 = poor, 2 = fair, 3 = good, and 4 = excellent) that rated the quality of the radiograph with respect to these characteristics: definition of fold pattern, translucency, distention, and integrity of the barium column. Statistical analysis was performed for each characteristic using Wilcoxon's two-sample rank sum test. RESULTS: All six observers found a statistically significant difference between the two barium formulations for mean scores for definition of fold pattern and translucency. Mean scores for fold pattern were 3.3, 3.0, 3.2, 3.6, 3.3, and 3.4 for Entrobar and 2.1, 2.3, 2.4, 3.2, 2.6, and 2.7 for E-Z-Paque. Mean scores for translucency were 2.5, 2.7, 2.8, 3.1, 2.7, and 3.3 for Entrobar and 1.6, 1.7, 2.1, 2.3, 1.9, and 2.7 for E-Z-Paque. No statistically significant difference was found for mean score for distention or integrity of the barium column. CONCLUSION: On radiographs, Entrobar was found to have superior characteristics for visualization of fold pattern and translucency but offered no advantages for distention or integrity of the barium column. Improved translucency and definition of fold pattern may translate into improved sensitivity and confidence in diagnosing small-bowel abnormality.     

Prospective memory and aging: Forgetting intentions over short delays.

Retrieved intentions often cannot be performed immediately and must be maintained until there is an opportunity to perform them. In 3 experiments, on seeing a target event, younger and older participants were to withhold an action until they encountered the appropriate phase of the experiment. When initial retrieval was made facile by the use of a salient retrieval cue, the age-related decrements were often dramatic, even over unfilled delay intervals as brief as 10 s (Experiments 1 and 2). When initial retrieval was difficult, older adults showed no forgetting over the retention interval (Experiment 3). Several theoretical perspectives were offered as explanations for the age differences observed with salient retrieval cues, including those that focus on age differences in metamemory, the degree to which plans are reformulated, and the ability to nonstrategically maintain current concerns in working memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Metal-molecule interface fluctuations

We have created self-assembled circular chains of C60 laterally bound to a layer of Ag atoms as a model system for characterizing fluctuations at a metal-molecule interface. STM measurements show that the Ag and C60 sides of the interface fluctuate independently, with frequency-dependent amplitudes of magnitude 0.1 nm at approximately 1 Hz for the Ag edge and approximately 0.01 Hz for the C60 ring. The measured frequency spectra of the metal and molecule fluctuation amplitudes will contribute characteristic signatures to transport measurements involving such interfaces.     

Do two-dimensional "noble gas atoms" produce molecular honeycombs at a metal surface?

Anthraquinone self-assembles on Cu(111) into a giant honeycomb network with exactly three molecules on each side. Here we propose that the exceptional degree of order achieved in this system can be explained as a consequence of the confinement of substrate electrons in the pores, with the pore size tailored so that the confined electrons can adopt a noble-gas-like two-dimensional quasi-atom configuration with two filled shells. Formation of identical pores in a related adsorption system (at different overall periodicity due to the different molecule size) corroborates this concept. A combination of photoemission spectroscopy with density functional theory computations (including van der Waals interactions) of adsorbate-substrate interactions allows quantum mechanical modeling of the spectra of the resultant quasi-atoms and their energetics.     

Fracture coalescence in rock-type materials under uniaxial and biaxial compression

Fracture coalescence, which plays an important role in the behavior of brittle materials, is investigated by loading pre-fractured specimens of gypsum, used as a rock model material, in uniaxial and biaxial compression. Several new phenomena and their dependence on geometry and other conditions are observed. The specimens have two pre-existing fractures or flaws that are arranged in different geometries, and that can be either open or closed. Two different test series are performed with these flaw geometries, one under uniaxial loading and one with biaxial loading in which confining stresses of 2.5, 5.0, 7.5 and 10 MPa are applied. As the vertical (axial) load is increased, new cracks emanate from the flaws and eventually coalesce. Flaw slippage, wing crack initiation, secondary crack initiation, crack coalescence, and failure are observed. Two types of cracks occur: wing cracks, which are tensile cracks, and secondary cracks which initiate as shear cracks in a plane roughly co-planar with the flaw. The secondary cracks usually propagate as shear cracks in the same plane but, depending on the geometry, they also propagate out of plane as either tensile or shear cracks. The wing cracks initiate at the flaw tips for uniaxial or low confinement biaxial conditions but move to the middle of the flaw and disappear completely for higher confining stresses. Three types of coalescence, which depend on the geometry of the flaws and to some extent on stress conditions, occur; they can be distinguished by different combinations of wing cracks and secondary cracks. For closed flaw specimens, at least partial debonding and slippage of the flaws is required prior to initiation of a crack. In uniaxial compression coalescence and failure occur simultaneously, while failure in biaxial compression occurs after coalescence.     

Estimating the intensity of rock discontinuities

This paper presents an approach for estimating the intensity of discontinuities and formulating intensity and orientation as a fracture tensor. Specifically the size distribution and the number of discontinuities are estimated first, from which the fracture tensor is then derived. Discontinuity size distribution is inferred from the trace data sampled in circular windows by using a general stereological relationship between the true trace length distribution and the discontinuity diameter distribution assuming circular shaped discontinuities. Because the measured trace lengths are biased, a method is proposed to estimate the true trace length distribution for circular window sampling. Circular window sampling has the advantage of automatically eliminating the orientation bias when estimating the true trace lengths. A method is then presented with which the total number of discontinuities in an objective volume can be estimated from the number of discontinuities observed in normal-size boreholes and using the inferred discontinuity diameter from the circular window sampling on the rock surface. With the derived size distribution and number of discontinuities, the intensity of discontinuities, which is the total surface area of discontinuities per unit volume, can then be calculated and included in a new definition of a fracture tensor. An application of the approach to analyze simulated discontinuities produces satisfactory results.