System for determining the angle of impact of an object on a structure

A method for determining the angle of impact of an object on a thin-walled structure which determines the angle of impact through analysis of the acoustic waves which result when an object impacts a structure is presented. Transducers are placed on and in the surface of the structure which sense the wave caused in the structure by impact. The waves are recorded and saved for analysis. For source motion normal to the surface, the antisymmetric mode has a large amplitude while that of the symmetric mode is very small. As the source angle increases with respect to the surface normal, the symmetric mode amplitude increases while the antisymmetric mode amplitude decreases. Thus, the angle of impact is determined by measuring the relative amplitudes of these two lowest order modes

Reduced heat flow in light water (H2O) due to heavy water (D2O)

The flow of heat, from top to bottom, in a column of light water can be decreased by over 1000% with the addition of heavy water. A column of light water cools from 25 C to 0 C in 11 hours, however, with the addition of heavy water it takes more than 100 hours. There is a concentration dependence where the cooling time increases as the concentration of added (D2O) increases, with a near maximum being reached with as little as 2% of (D2O) added. This phenomenon will not occur if the water is mixed after the heavy water is added.Comment: 18 pages, 22 figures, PD

Advancing the Sea Ice Hypothesis: Trophic Interactions Among Breeding Pygoscelis Penguins With Divergent Population Trends Throughout the Western Antarctic Peninsula

We evaluated annual and regional variation in the dietary niche of Pygoscelis penguins including the sea ice-obligate Adélie penguin (Pygoscelis adeliae), and sea ice-intolerant chinstrap (Pygoscelis antarcticus) and gentoo (Pygoscelis papua) penguins, three species that nest throughout the western Antarctic Peninsula (AP) to test the sea ice trophic interaction hypothesis, which posits that penguin breeding populations with divergent trends, i.e., declining or increasing, are reliant on differing food webs. Our study relies on values of naturally occurring carbon (13C/12C, δ13C) and nitrogen (15N/14N, δ15N) stable isotopes as integrated proxies of penguin food webs measuredover three years at three different breeding colonies. At Anvers Island in the north, where reductions in sea ice and changes in breeding population trends among sympatric sea ice-obligate (Adélie) and sea ice-intolerant (chinstrap and gentoo) penguins have been most notable, our analyses show that all three species of Pygoscelis penguins became more similar isotopically over the reproductive period

Advancing Biomedical Image Retrieval: Development and Analysis of a Test Collection

Objective: Develop and analyze results from an image retrieval test collection. Methods: After participating research groups obtained and assessed results from their systems in the image retrieval task of Cross-Language Evaluation Forum, we assessed the results for common themes and trends. In addition to overall performance, results were analyzed on the basis of topic categories (those most amenable to visual, textual, or mixed approaches) and run categories (those employing queries entered by automated or manual means as well as those using visual, textual, or mixed indexing and retrieval methods). We also assessed results on the different topics and compared the impact of duplicate relevance judgments. Results: A total of 13 research groups participated. Analysis was limited to the best run submitted by each group in each run category. The best results were obtained by systems that combined visual and textual methods. There was substantial variation in performance across topics. Systems employing textual methods were more resilient to visually oriented topics than those using visual methods were to textually oriented topics. The primary performance measure of mean average precision (MAP) was not necessarily associated with other measures, including those possibly more pertinent to real users, such as precision at 10 or 30 images. Conclusions: We developed a test collection amenable to assessing visual and textual methods for image retrieval. Future work must focus on how varying topic and run types affect retrieval performance. Users' studies also are necessary to determine the best measures for evaluating the efficacy of image retrieval system

Ternary Nitride Semiconductors in the Rocksalt Crystal Structure

Inorganic nitrides with wurtzite crystal structures are well-known semiconductors used in optoelectronic devices. In contrast, rocksalt-based nitrides are known for their metallic and refractory properties. Breaking this dichotomy, here we report on ternary nitride semiconductors with rocksalt crystal structures, remarkable optoelectronic properties, and the general chemical formula Mg$_{x}$TM$_{1-x}$N (TM=Ti, Zr, Hf, Nb). These compounds form over a broad metal composition range and our experiments show that Mg-rich compositions are nondegenerate semiconductors with visible-range optical absorption onsets (1.8-2.1 eV). Lattice parameters are compatible with growth on a variety of substrates, and epitaxially grown MgZrN$_{2}$ exhibits remarkable electron mobilities approaching 100 cm$^{2}$V$^{-1}$s$^{-1}$. Ab initio calculations reveal that these compounds have disorder-tunable optical properties, large dielectric constants and low carrier effective masses that are insensitive to disorder. Overall, these experimental and theoretical results highlight Mg$_{G-3}$TMN$_{G-2}$ rocksalts as a new class of semiconductor materials with promising properties for optoelectronic applications

Relationship of thromboxane generation to the aggregation of platelets from humans: Effects of eicosapentaenoic acid

A non-linear relationship between the percent aggregation of human platelets and the amount of TXB2 generated requires investigators to use caution when using the data to assess antiplatelet regimens. The relationship approximates a hyperbola with a roughly linear relationship from 0 to 70% aggregation and 0 to 50 ng TXB2 per ml of platelet-rich plasma. Above these values, the amount of TXB2 produced may increase up to 500 ng per ml of platelet-rich plasma with no clear relationship to the observed platelet function of aggregation. Also, appreciable inhibition of TXB2 formation can occur at high TXB2 levels with no detectable decrease in aggregation. Thus, assessment of antiplatelet regimens using TXB2 formation alone are unlikely to be interpretable without reference to this non-linear property of platelet function. We applied this concept when evaluating a study of forty subjects with dietary supplements of 1.8 g or 2.7 g of ethyl eicosapentaenoate (20:5n-3) for four weeks. There was a moderate,but statistically significant decrease in average values for the percent aggregation (60+/-15 to 45+/-30) and thromboxane production (51+/-30 to 33+/-31 ng/ml) the differences in mean values were slight relative to the overall standard deviations, reductions of platelet function were clearly evident in 31 of 40 subjects when paired results were examined relative to the recognized hyperbolic relationship.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25520/1/0000061.pd

Are Thiel-embalmed Cadavers Effective Tools in Educating Medical Students to Perform Knee Arthrocentesis?

INTRODUCTION: The purposes of this study are to determine whether Thiel-embalmed cadavers are an effective educational tool in teaching medical students to perform knee arthrocentesis, to compare the use of Thiel-embalmed cadavers to formalin-embalmed cadavers in arthrocentesis education, and to determine whether the use of Thiel-embalmed cadavers is potentially generalizable to the instruction of other orthopedic procedures. METHODS: Sixty-eight third-year medical students participated in the study. The participants first completed a pre-survey to assess their prior experience with arthrocentesis procedures and Thiel-embalmed cadavers. Participants then attended an instructional session where the knee arthrocentesis procedure was demonstrated on a Thiel-embalmed cadaver. Participants then individually performed the simulated knee arthrocentesis procedure twice: once on a Thiel-embalmed cadaver and once on a formalin-embalmed cadaver. Success of each attempt was determined through the visualization of aspirated joint fluid. Following the laboratory session, each participant completed a post-survey to determine whether the session improved their perceived confidence in performing knee arthrocentesis, if they preferred the use of Thiel-embalmed cadavers or formalin-embalmed cadavers as a teaching tool, and if they believed simulated practice using Thiel-embalmed cadavers would be effective for learning other orthopedic procedural skills. RESULTS: Sixty-eight students participated in the laboratory session and successfully completed both pre- and post-course surveys. 96% of participants reported that they felt confident performing knee arthrocentesis under physician supervision following their participation in the laboratory session (versus 15% of participants in the pre-survey). 96% of participants reported that the Thiel-embalmed cadavers provided a more realistic teaching model than formalin-embalmed cadavers for learning knee arthrocentesis. 100% of participants believed the incorporation of simulated practice using Thiel-embalmed cadavers is an effective method in teaching students to perform knee arthrocentesis. 100% of participants reported that they would participate in future sessions using Thiel-embalmed cadavers to learn and practice other orthopedic procedural techniques. DISCUSSION: This study used a moderate sample size of third-year medical students to provide data regarding the suitability of using Thiel cadavers in arthrocentesis education. Results indicate that Thiel cadavers are effective tools in teaching medical students to perform knee arthrocentesis, that students preferred the Thiel cadavers to the formalin cadavers, and that the use of Thiel cadavers is a safe, engaging, and high-quality teaching modality for demonstrating proper arthrocentesis procedural technique to medical students. Since this study looked specifically at teaching knee arthrocentesis to medical students, it is uncertain whether the benefits of Thiel cadavers are generalizable to the education of other orthopedic procedures and subject groups such as residents, fellows, and practicing physicians. Further studies should be performed to assess whether Thiel cadavers are beneficial in teaching other orthopaedic procedures and if these benefits extend to other subject groups