Elementary Teacher Candidates’ Flexibility with Comparing Fractions

The teaching and learning of fractions have been persistent challenges, and data on national assessments continue to show students’ difficulties with fractions. The Common Core State Standards have provided a new lens for the study of fractions, and with it a need to update teacher candidates’ mathematical knowledge for teaching. Fractions are a challenge for mathematics teacher educators working with teacher candidates. Exploring instructional approaches to building teacher candidate understanding is important. Technology could play an important role in building robust teacher candidates’ conceptual understanding of fractions. Whitacre & Nickerson’s (2016) framework provides background knowledge for exploring whether technology can promote flexible strategies for comparing fractions. In this study, we examine the impact on teacher candidates’ flexibility with solving fraction comparison problems through the use of a sequenced set of interactive dynamic technology-based learning experiences modeling the approach advocated in the Common Core Standards. Keywords: fractions, technology, elementary teacher DOI: 10.7176/JEP/11-9-01 Publication date:March 31st 2020

Stabilisation strategies in primary commodity exporting countries: A case study of Chile

A number of recent studies have shown that the short term level of economic activity and employment in primary commodity exporting countries is particularly vulnerable to price fluctuations in world commodity markets. The authorities in such countries, in seeking to maintain output and employment stability, must invoke compensatory macroeconomic adjustment strategies to accommodate both favourable and unfavourable movements in the foreign terms of trade. Chile provides a case in point. Chile has traditionally been heavily reliant on raw materials exports, particularly copper, for its foreign exchange earnings. Copper exports averaged around 70 per cent of total export earnings for the period 1960-19 76. They currently represent about one half of total foreign exchange earnings

The Short-Run Impact of fluctuating primary commodity prices on three developing economies: Colombia, Ivory Coast and Kenya

Computable general equilibrium models are used to study the short-run impact of fluctuating primary commodity prices on the economies of Colombia, Ivory Coast and Kenya. The results indicate that these economies are destabilized by primary commodity price fluctuations unless governments act to hold real domestic absorption constant. To achieve this, however, would require foreign exchange reserves in excess of the level normally available to these governments for the purpose of stabilising, domestic economic activity

Developmental Considerations of Sperm Protein 17 Gene Expression in Rheumatoid Arthritis Synoviocytes

Rheumatoid arthritis (RA) is an autoimmune disease characterized by proliferative synovial tissue. We used mRNA differential display and library subtraction to compare mRNA expression in RA and osteoarthritis (OA) synoviocytes. We initially compared the mRNA expression patterns in 1 female RA and 1 OA synovia and found a differentially expressed 350 bp transcript in the RA synoviocytes which was, by sequence analysis, 100% homologous to sperm protein 17 (Sp17). Moreover, the Sp17 transcript was found differentially expressed in a RA synovial library that was subtracted with an OA synovial library. Using specific primers for full length Sp17, a 1.1 kb transcript was amplified from the synoviocytes of 7 additional female RA patients, sequenced and found to 100% homologous to Sp17. Thus, we found the unexpected expression of Sp17, a thought to be gamete-specific protein, in the synoviocytes of 8/8 female RA patients in contrast to control OA synoviocytes. Interestingly, Sp17's structural relationship with cell-binding and recognition proteins, suggests that Sp17 may function in cell-cell recognition and signaling in the RA synoviocyte. Further, Sp17 could have a significant regulatory role in RA synoviocyte gene transcription and/or signal transduction. Thus, Sp17 could have an important role in RA synoviocyte proliferation or defective apoptosis. Finally, the presence of Sp17 in synoviocytes has interesting developmental considerations

Computational Naval Ship Hydrodynamics

The primary purpose of our research efforts is to improve naval design and detection capabilities. Our current research efforts leverage high performance computing (HPC) resources to perform high-resolution numerical simulations with hundreds-of-millions to billions of unknowns to study wave breaking behind a transom stern, wave-impact loading, the generation of spray by high-speed planing craft, air entrainment by plunging breaking waves, forced-motion, and storm seas. This paper focuses on the air entrainment and free-surface turbulence in the flow behind a transom-stern and wave-impact loading on marine platforms. Two codes, Numerical Flow Analysis (NFA) and Boundary Data Immersion Method (BDIM), are used in this study. Both codes are Cartesian-based Large-Eddy Simulation (LES) formulations, and use either Volume-of-Fluid (VOF) (NFA) or conservative Volume-of-Fluid (cVOF) BDIM treatments to track the free-surface interface. The first project area discussed is the flow behind the transom stern. BDIM simulations are used to study the volume of entrained air behind the stern. The application of a Lagrangian bubble-extraction algorithm elucidates the location of air cavities in the wake and the bubble-size distribution for a flow that has over 10 percent void fraction. NFA simulations of the transom-stern flow are validated by comparing the numerical simulations to experiments performed at the Naval Surface Warfare Center, Carderock Division (NSWCCD), where good agreement between simulations and experiments is obtained for mean elevations and regions of white water in the wake. The second project area discussed is wave impact loading, a topic driven by recent structural failures of high-speed planing vessels and other advanced vehicles, as well as the devastation caused by Tsunamis impacting low-lying coastal areas. NFA simulations of wave breaking events are compared to the NSWCCD cube impact experiments and the Oregon State University, O.H. Hinsdale Wave Research Laboratories Tsunami experiments, and it is shown that NFA is able to accurately simulate the propagation of waves over long distances after which it also accurately predicts highly-energetic impact events. © 2011 IEEE.United States. Office of Naval Research (N00014-07-C-0184)United States. Office of Naval Research (N00014-01-1-0124

The nearly Newtonian regime in Non-Linear Theories of Gravity

The present paper reconsiders the Newtonian limit of models of modified gravity including higher order terms in the scalar curvature in the gravitational action. This was studied using the Palatini variational principle in [Meng X. and Wang P.: Gen. Rel. Grav. {\bf 36}, 1947 (2004)] and [Dom\'inguez A. E. and Barraco D. E.: Phys. Rev. D {\bf 70}, 043505 (2004)] with contradicting results. Here a different approach is used, and problems in the previous attempts are pointed out. It is shown that models with negative powers of the scalar curvature, like the ones used to explain the present accelerated expansion, as well as their generalization which include positive powers, can give the correct Newtonian limit, as long as the coefficients of these powers are reasonably small. Some consequences of the performed analysis seem to raise doubts for the way the Newtonian limit was derived in the purely metric approach of fourth order gravity [Dick R.: Gen. Rel. Grav. {\bf 36}, 217 (2004)]. Finally, we comment on a recent paper [Olmo G. J.: Phys. Rev. D {\bf 72}, 083505 (2005)] in which the problem of the Newtonian limit of both the purely metric and the Palatini formalism is discussed, using the equivalent Brans--Dicke theory, and with which our results partly disagree.Comment: typos corrected, replaced to match published versio

Descriptive Epidemiology of Collegiate Women's Ice Hockey Injuries: National Collegiate Athletic Association Injury Surveillance System, 2000–2001 Through 2003–2004

Objective: To review 4 years of National Collegiate Athletic Association (NCAA) injury surveillance data for women’s ice hockey and to identify potential areas for injury prevention initiatives. Background: The NCAA ISS prospectively collects data on injuries sustained during collegiate participation. Women’s NCAA ice hockey began participation in the ISS during the 2000–2001 season. On average, over the 4 years, 15.6% of the eligible schools elected to send their injury data. Main Results: Over the 4 years of study, the rate of injury in games was more than 5 times higher than the injury rate in practices (12.6 versus 2.5 injuries per 1000 athlete-exposures, rate ratio = 5.0, 95% confidence interval = 4.2, 6.1, P < .01). Preseason practice injury rates were almost twice as high as in-season practice rates (4.2 versus 2.3 injuries per 1000 athlete- exposures, rate ratio = 1.8, 95% confidence interval = 1.7, 2.0, P < .01). Concussions were the most common injury in both games (21.6%) and practices (13.2%). The rate of concussions in games appeared to be trending upward over the study period. The greatest number of game injuries (approximately 50%) resulted from player contact, whereas practice injuries were from either contact with another object or noncontact mechanisms. Recommendations: Women’s ice hockey is an evolving NCAA sport. Only 4 years of ISS data are available and, therefore, data should be interpreted with caution. Women’s ice hockey does not allow for formal body checking; however, approximately 50% of all game injuries were reported to result from contact with another player. Future researchers need to evaluate the effectiveness of the no-checking rule. Additional years of data collection will be required to allow the data to become more stable, and to increase attention to mechanism of- injury issues. We anticipate that the hypothesized inconsistencies in skill level across and within the various women’s teams also will be reduced as more consistently skilled players develop, allowing for more stability in the injury scenario

Long range transport of ultra cold atoms in a far-detuned 1D optical lattice

We present a novel method to transport ultra cold atoms in a focused optical lattice over macroscopic distances of many Rayleigh ranges. With this method ultra cold atoms were transported over 5 cm in 250 ms without significant atom loss or heating. By translating the interference pattern together with the beam geometry the trap parameters are maintained over the full transport range. Thus, the presented method is well suited for tightly focused optical lattices that have sufficient trap depth only close to the focus. Tight focusing is usually required for far-detuned optical traps or traps that require high laser intensity for other reasons. The transport time is short and thus compatible with the operation of an optical lattice clock in which atoms are probed in a well designed environment spatially separated from the preparation and detection region.Comment: 14 pages, 6 figure