The Cross-Wavelet Transform and Analysis of Quasiperiodic Behavior in the Pearson-Readhead VLBI Survey Sources

We introduce an algorithm for applying a cross-wavelet transform to analysis of quasiperiodic variations in a time-series, and introduce significance tests for the technique. We apply a continuous wavelet transform and the cross-wavelet algorithm to the Pearson-Readhead VLBI survey sources using data obtained from the University of Michigan 26-m parabloid at observing frequencies of 14.5, 8.0, and 4.8 GHz. Thirty of the sixty-two sources were chosen to have sufficient data for analysis, having at least 100 data points for a given time-series. Of these thirty sources, a little more than half exhibited evidence for quasiperiodic behavior in at least one observing frequency, with a mean characteristic period of 2.4 yr and standard deviation of 1.3 yr. We find that out of the thirty sources, there were about four time scales for every ten time series, and about half of those sources showing quasiperiodic behavior repeated the behavior in at least one other observing frequency.Comment: Revised version, accepted by ApJ. 17 pages, 13 figures, color figures included as gifs, seperate from the text. The addition of statistical significance tests has resulted in modifying the technique and results, but the broad conclusion remain the same. A high resolution version may be found at http://www.astro.lsa.umich.edu/obs/radiotel/prcwdata.htm

The Influence of Student Enrollment in Pre-College Engineering Courses on Their Interest in Engineering Careers

Pre-college student enrollment in engineering courses increases every year in the United States, yet little is known about the relationship between taking these courses and subsequent science, technology, engineering, and mathematics (STEM) career interest. Through multinomial logistic regressions, and while controlling for student background variables and prior STEM career interest, this study addresses two research questions: (1) Does completing a pre-college engineering course increase the likelihood of an engineering career interest at the end of high school? (2) Does completing a pre-college engineering course have a different influence on career interest in engineering than on career interest in other STEM fields (namely science, technology, and mathematics)? The study uses data from the Outreach Programs and Science Career Intentions survey (N 5 15,847), a large U.S. sample of college students enrolled in mandatory English courses. Our analysis reveals that the relationship between completing a pre-college engineering course and interest in a STEM career appears to be field-specific. Students completing a pre-college engineering course were two times more likely to want to pursue an engineering career than those without such a course, after controlling for a host of other relevant variables. By contrast, taking a pre-college engineering course was not associated with heightened interest in other science, technology, or mathematics careers. These findings suggest that high schools should offer engineering courses as an effective way to foster students’ career interest in engineering. This effect appears to apply similarly to all students, independent of gender, race/ethnicity, and other background variables

The Impact on the Ohio River Watershed by the United States Federal Government

poster abstractThis interactive timeline, which currently covers 1775 through the first quarter of 2014, takes accounts of water-related actions of the federal government and places them alongside water-related environmental events. Research drew together water use information within Acts of Congress, legal cases argued before the Supreme Court, actions undertaken by agencies within the Executive Department, and reports of pollution or flood incidents. This data was then charted using Tiki-Toki software into separate bands along the timeline with descriptions, images, and links to add depth of explanation. This juxtaposition reveals a story tracing human interaction along the Ohio River watershed since the American Revolution. In addition, the Tiki-Toki software makes the information available in multiple views through which different patterns emerge allowing future researchers to manipulate the timeline to more easily see connections with their own projects. Because of the data’s inclusiveness and ease of use, this timeline can provide a platform for comparison with the companion site of the Rivers of the Anthropocene study, the River Tyne. However, since the primary region of study in the United States is the Ohio River and its tributaries, only data applicable to this region specifically or all water in the United States generally was utilized. Because of the exclusiveness of the data, frequent gaps in events may risk being misinterpreted as a period of inactivity on the part of the federal government, though this is likely not the case; even apparent inactivity along the Ohio reveals much about human impact on the waterway systems

Rivers of the Anthropocene, Phase 1: A Comparative Study of the Ohio and Tyne River Systems

poster abstractRivers of the Anthropocene” addresses a fundamental problem facing scholars and policy makers alike: despite important advances in our understanding of the earth as a system — one in which humans and human systems have become recognized as prime agents in effecting changes to the earth — we have yet to create an approach that brings together scholars of earth systems with scholars of human systems. This is to the detriment of our overall understanding of global ecological change and limits our ability to respond to escalating crises. Without integrating methods from the earth sciences, social sciences, and humanities, scholars of the environment lose important tools in tackling some of the biggest issues facing humanity in the 21st century. As humans continue to play an increasingly significant role in altering their planet, it is incumbent upon environmental scholars to understand the human-environment interface in all its complexities. It is not enough that scientists measure what humans have done or what they can do to shift environmental systems; it is necessary that they work hand-in-hand with specialists in human systems to understand the limits and feedback mechanisms that beliefs, practices, ideologies, social structures, and cultural norms impose on human action. A comparative study of international river systems is a good place to begin building more meaningful bridges across the science-humanities divide, and it addresses the pressing issue of global water insecurity, which 80% of the earth’s population faces. The first stage of “Rivers of the Anthropocene” will create a flexible, interdisciplinary methodological and conceptual framework for examining the human-environment interface, one in which specialists in the earth sciences can learn from the approaches of the humanities and human sciences and vice versa

Large-Scale Vented Deflagration Tests

PresentationThis paper presents results from a test program carried out to determine the peak deflagration pressure achieved within a congested enclosure vented through one wall of the enclosure. The industry standard in the United States for predicting the peak pressure developed in a vented deflagration is the National Fire Protection Association's Standard on Explosion Protection by Deflagration Venting (NFPA 68). The NFPA 68 (2013 edition) vent area correlation accounts for varying degrees of congestion if the ratio of the obstacle surface area (Aobs) to that of the enclosure (As) is greater than 0.4 (i.e., Ar = Aobs/As > 0.4). The tests described in this paper were performed using an obstacle array with an Ar ratio of less than 0.4. These tests were conducted in a rig with a 48-foot width, 24-foot depth, and 12-foot height. The rig was enclosed with solid walls, roof, and floor, allowing for venting through one of the long walls (i.e., 48-foot by 12-foot). The venting face of the rig was sealed with a 6 mil (0.15 mm) thick plastic vapor barrier to allow for the formation of a near-stoichiometric propane-air mixture. The flammable gas cloud was ignited near the center of the rear wall. Steel vent panels (20-gauge, 2 lbm/ft2 ) were installed over the plastic vapor barrier using explosion relief fasteners. The vent panels were configured to release at 0.3 psig; vent panel restraint devices were not utilized. The congestion inside the rig was provided by a regular array of vertical cylinders (2-inch schedule 40 pipe and 2-inch outer diameter cylinders) giving area and volume blockage ratios (ABR and VBR) of 4.9% and 2.2%, respectively, within the congestion array. The obstacle to enclosure surface area ratio (Ar) for this obstacle array pattern is 0.3 with the array extended throughout the rig, which is less than the critical value to account for congestion in the NFPA 68 correlation. Four series of tests were conducted with varying vent parameters, flammable gas cloud sizes, and congestion levels. Baseline tests were performed with the congestion array and flammable gas cloud extending throughout the rig without vent panels present (i.e., vapor barrier only). The second test series included the addition of vent panels for the same congestion pattern as that employed for the baseline tests. The third test series utilized a flammable gas cloud which filled only the back half of the rig. For the fourth test series, the congestion array only occupied 1⁄4 of the rig. The peak pressures and impulses for each test series are provided, along with pressure histories internal and external to the rig for selected tests. The steel vent panel throw distance is also provided as a function of internal peak pressure. The test data were compared with the predictions of the vent area correlations provided in NFPA 68. For all but the fourth test series (i.e., congestion array occupying 1⁄4 of the rig), the average internal peak pressures were approximately a factor of 2 larger than those predicted by NFPA 68

The Weng’an Biota (Doushantuo Formation):an Ediacaran window on soft bodied and multicellular microorganisms

The Weng’an Biota is a fossil Konservat-Lagerstätte in South China that is approximately 570-600 million years old and provides an unparalleled snapshot of marine life during the interval in which molecular clocks estimate that animal clades were diversifying. It yields specimens that are three-dimensionally preserved in calcium phosphate with cellular and sometimes subcellular fidelity. The biota includes candidates for the oldest animals in the fossil record, including embryonic, larval and adult forms. We argue that, while the Weng’an Biota includes forms that could be animals, none can currently be assigned to this group with confidence. Nonetheless, the biota offers a rare and valuable window on the evolution of multicellular and soft-bodied organisms in the prelude to the Cambrian radiation

Cost efficient narrow linewidth laser transmitter for coherent detection

Authors present a cost efficient narrow linewidth laser transmitter for future coherent detection systems. The spectral purity of the laser allows the phase modulation of data signals at bit rates as low as 155 Mb/s

Sex Differences in the Subjective Effects of Oral Δ\u3csup\u3e9\u3c/sup\u3e-THC in Cannabis Users

Previous studies suggest that there are sex differences in endocannabinoid function and the response to exogenous cannabinoids, though data from clinical studies comparing acute cannabinoid effects in men and women under controlled laboratory conditions are limited. To further explore these potential differences, data from 30 cannabis users (N=18 M, 12 F) who completed previous Δ9-tetrahydrocannabinol (Δ9-THC) discrimination studies were combined for this retrospective analysis. In each study, subjects learned to discriminate between oral Δ9-THC and placebo and then received a range of Δ9-THC doses (0, 5, 15 and a “high” dose of either 25 or 30 mg). Responses on a drug-discrimination task, subjective effects questionnaire, psychomotor performance tasks, and physiological measures were assessed. Δ9-THC dose-dependently increased drug-appropriate responding, ratings on “positive” visual analog scale (VAS) items (e.g., Good Effects, Like Drug, Take Again), and items related to intoxication (e.g., High, Stoned). Δ9-THC also dose-dependently impaired performance on psychomotor tasks and elevated heart rate. Sex differences on VAS items emerged as a function of dose. Women exhibited significantly greater subjective responses to oral drug administration than men at the 5 mg Δ9-THC dose, whereas men were more sensitive to the subjective effects of the 15 mg dose of Δ9-THC than women. These results demonstrate dose-dependent separation in the subjective response to oral Δ9-THC administration by sex, which might contribute to the differential development of problematic cannabis use