A Small Family of Elements with Long Inverted Repeats is Located Near Sites of Developmentally Regulated DNA Rearrangement in \u3cem\u3eTetrahymena thermophila\u3c/em\u3e

Extensive DNA rearrangement occurs during the development of the somatic macronucleus from the germ line micronucleus in ciliated protozoans. The micronuclear junctions and the macronuclear product of a developmentally regulated DNA rearrangement in Tetrahymena thermophila, Tlr1, have been cloned. The intrachromosomal rearrangement joins sequences that are separated by more than 13 kb in the micronucleus with the elimination of moderately repeated micronucleus-specific DNA sequences. There is a long, 825-bp, inverted repeat near the micronuclear junctions. The inverted repeat contains two different 19-bp tandem repeats. The 19-bp repeats are associated with each other and with DNA rearrangements at seven locations in the micronuclear genome. Southern blot analysis is consistent with the occurrence of the 19-bp repeats within pairs of larger repeated sequences. Another family member was isolated. The 19-mers in that clone are also in close proximity to a rearrangement junction. We propose that the 19-mers define a small family of developmentally regulated DNA rearrangements having elements with long inverted repeats near the junction sites. We discuss the possibility that transposable elements evolve by capture of molecular machinery required for essential cellular functions

Thermal Studies on Rubidium Dinitramide

The present study has been carried out to investigate conflicting reports in the literature on the nature of the thermal decomposition of the energetic oxidant rubidium dinitramide in the liquid state. The techniques employed included DSC, simultaneous TG-DTA, simultaneous TG-mass spectrometry and thermomicroscopy. The measurements were supplemented by quantitative chemical analysis of the reaction products. The results showed that, following fusion at 106 °C, the overall decomposition proceeded in a single exothermic reaction stage forming a mixture of rubidium nitrate and rubidium nitrite in the molar ratio 1.2 : 1

Response and Resistance to Paradox-Breaking BRAF Inhibitor in Melanomas

FDA-approved BRAF inhibitors produce high response rates and improve overall survival in patients with BRAF V600E/K-mutant melanoma, but are linked to pathologies associated with paradoxical ERK1/2 activation in wild-type BRAF cells. To overcome this limitation, a next-generation paradox-breaking RAF inhibitor (PLX8394) has been designed. Here, we show that by using a quantitative reporter assay, PLX8394 rapidly suppressed ERK1/2 reporter activity and growth of mutant BRAF melanoma xenografts. Ex vivo treatment of xenografts and use of a patient-derived explant system (PDeX) revealed that PLX8394 suppressed ERK1/2 signaling and elicited apoptosis more effectively than the FDA-approved BRAF inhibitor, vemurafenib. Furthermore, PLX8394 was efficacious against vemurafenibresistant BRAF splice variant-expressing tumors and reduced splice variant homodimerization. Importantly, PLX8394 did not induce paradoxical activation of ERK1/2 in wild-type BRAF cell lines or PDeX. Continued in vivo dosing of xenografts with PLX8394 led to the development of acquired resistance via ERK1/2 reactivation through heterogeneous mechanisms; however, resistant cells were found to have differential sensitivity to ERK1/2 inhibitor. These findings highlight the efficacy of a paradox-breaking selective BRAF inhibitor and the use of PDeX system to test the efficacy of therapeutic agents. © 2017 American Association for Cancer Research

OVERFLOW Simulations of Space Shuttle Orbiter Reentry Based on As-Built Geometry

The Space Shuttle Orbiters Discovery and Endeavor have been digitally scanned to obtain outer mold line surfaces. Using these scans, the existing overset computational fluid dynamics (CFD) grid system will be modified by projecting the grid points to the scanned geometry. Simulations will be performed using the OVERFLOW solver and the results compared to previous OVERFLOW results on the theoretical geometry and the aerodynamic databook. The "bent airframe" term will be compared between the aerodynamic databook and the computations over a range of reentry conditions

Osteopathology and insect traces in the Australopithecus africanus skeleton StW 431

We present the first application of high-resolution micro computed tomography in an analysis of both the internal and external morphology of the lumbar region of StW 431 – a hominin skeleton recovered from Member 4 infill of the Sterkfontein Caves (South Africa) in 1987. The lumbar vertebrae of the individual present a number of proliferative and erosive bony processes, which were investigated in this study. Investigations suggest a complex history of taphonomic alteration to pre-existing spinal degenerative joint disease (SDJD) as well as post-mortem modification by an unknown insect. This study is in agreement with previous pathological diagnoses of SDJD which affected StW 431 and is the first time insect traces on this hominin are described. The results of this analysis attest to the complex series of post-mortem processes affecting the Sterkfontein site and its fossil assemblages

First direct observation of a nearly ideal graphene band structure

Angle-resolved photoemission and X-ray diffraction experiments show that multilayer epitaxial graphene grown on the SiC(000-1) surface is a new form of carbon that is composed of effectively isolated graphene sheets. The unique rotational stacking of these films cause adjacent graphene layers to electronically decouple leading to a set of nearly independent linearly dispersing bands (Dirac cones) at the graphene K-point. Each cone corresponds to an individual macro-scale graphene sheet in a multilayer stack where AB-stacked sheets can be considered as low density faults.Comment: 5 pages, 4 figure

Adaptive computation of gravitational waves from black hole interactions

We construct a class of linear partial differential equations describing general perturbations of non-rotating black holes in 3D Cartesian coordinates. In contrast to the usual approach, a single equation treats all radiative $\ell -m$ modes simultaneously, allowing the study of wave perturbations of black holes with arbitrary 3D structure, as would be present when studying the full set of nonlinear Einstein equations describing a perturbed black hole. This class of equations forms an excellent testbed to explore the computational issues of simulating black spacetimes using a three dimensional adaptive mesh refinement code. Using this code, we present results from the first fully resolved 3D solution of the equations describing perturbed black holes. We discuss both fixed and adaptive mesh refinement, refinement criteria, and the computational savings provided by adaptive techniques in 3D for such model problems of distorted black holes.Comment: 16 Pages, RevTeX, 13 figure

Work in Progress: Rigorously Assessing the Anecdotal Evidence of Increased Student Persistence in an Active, Blended, and Collaborative Mechanical Engineering Environment

This work in progress describes an ongoing study of an active, blended, and collaborative (ABC) course environment used in a core mechanical engineering course. This course has built on the growing body of literature citing active learning (Freeman et al., 2014), blended structures (Bowen & Ithaka, 2012), and collaborative engagement (Jeong & Chi, 2007) as positive influences on college and university science, technology, engineering, and math (STEM) outcomes. For the last six years, “Dynamics”, a core mechanical engineering course at a large public university, has utilized in-class activities, frequently-watched problem-solving videos, and a collaborative blog space to realize an ABC environment. On one key metric of course success, the rate of students who drop, fail, or withdraw from (DFW), the course has experienced near-constant improvements since the ABC structures were introduced. In this study, the authors utilize rigorous longitudinal methods to determine whether this drop in DFW rates can be directly attributed to increased implementation of ABC features. The authors hypothesize that as instructors become accustomed to the ABC environment and increase the level of in-class activity, use of blended resources, and collaboration, the likelihood of DFW in each subsequent year would drop. However, in the same time period, each subsequent class entered with higher levels of performance on proxy measures for prior knowledge. We therefore build a logistic regression model to predict individual-level DFW and determine whether the anecdotal drops in DFW that we observe can be attributed to the expansion of the ABC environment. More specifically, we predict likelihood of DFW based on students’ prior knowledge (grade in the preceding course, SAT math score), key demographics (gender, race/ethnicity), the semester and year they took Dynamics, their instructor, their year in school, and their major. We test for year fixed effects {year_t, t = 1, 2, ..., 7} to determine whether odds ratios for DFW consistently and significantly decrease over time. We also test for instructor effects, in particular for differences between the instructors who were involved in the design and development of the ABC environment and more independent instructors who only partially implemented the ABC course components. We anticipate results that will provide more rigorous, less biased, and efficient estimates for the individual- and class-level components that explain variance in DFW rates. These results would provide immediate implications for the next phase of our work, as we assess the next on-term implementation of the course in 2016. Our findings would also have long-term significance for other classes in mechanical engineering and related disciplines and for classes at other institutions that are considering implementing a comprehensive ABC learning environment

Transforming a Dynamics Course to an Active, Blended, and Collaborative Format: Focus on the Faculty

Mechanical engineering programs are increasingly applying educational research by transforming courses to be more interactive and to use a blend of online and face-to-face materials. However, the process of an existing course adopting these new practices is not well studied, and even less is understood about the faculty experience from on-boarding to delivery of a new curriculum or pedagogy. In this study, we follow the translation of an active, blended, and collaborative (ABC) curriculum for a core dynamics course from a large public university (where the ABC curriculum was developed) to a small private university. We use interpretive phenomenology to focus on the lived experience of the instructor newly implementing these course materials, format, and pedagogical approach. Specifically, we address the following research questions: (1) What is the lived experience of a mechanical engineering instructor at a different institution as she adopts and adapts the provided materials and format? (2) How does the experience of this instructor evolve throughout the semester? We use rich qualitative data to understand the experience of the instructor, who taught this course in its prior format and, in Fall 2015, taught the “off-term” core dynamics course via the new ABC structure. Through weekly reflection prompts, pre- and post-semester interviews, and supplementary process data (e.g., notes of weekly meetings between the new implementer and ABC team at the large public university), we describe and characterize the multi-faceted instructor experience. This includes her experience learning about the curriculum and online tools, implementing the class and adjusting her teaching practices, and assessing her students’ engagement with the course and understanding of dynamics concepts. Our findings suggest further areas of inquiry for studies of faculty practices around curriculum adoption, including probing opportunities for cross-institutional collaborations to share materials and transform courses, interrogating variation in mechanical engineering department and student cultures, and studying sources of faculty development and support throughout the course transformation process