Dust Formation and Survival in Supernova Ejecta

The presence of dust at high redshift requires efficient condensation of grains in SN ejecta, in accordance with current theoretical models. Yet, observations of the few well studied SNe and SN remnants imply condensation efficiencies which are about two orders of magnitude smaller. Motivated by this tension, we have (i) revisited the model of Todini & Ferrara (2001) for dust formation in the ejecta of core collapse SNe and (ii) followed, for the first time, the evolution of newly condensed grains from the time of formation to their survival - through the passage of the reverse shock - in the SN remnant. We find that 0.1 - 0.6 M_sun of dust form in the ejecta of 12 - 40 M_sun stellar progenitors. Depending on the density of the surrounding ISM, between 2-20% of the initial dust mass survives the passage of the reverse shock, on time-scales of about 4-8 x 10^4 yr from the stellar explosion. Sputtering by the hot gas induces a shift of the dust size distribution towards smaller grains. The resulting dust extinction curve shows a good agreement with that derived by observations of a reddened QSO at z =6.2. Stochastic heating of small grains leads to a wide distribution of dust temperatures. This supports the idea that large amounts (~ 0.1 M_sun) of cold dust (T ~ 40K) can be present in SN remnants, without being in conflict with the observed IR emission.Comment: MNRAS accepte

Secondary analysis of teaching methods in introductory physics: A 50 k-student study

Citation: Von Korff, J., Archibeque, B., Gomez, K. A., Heckendorf, T., McKagan, S. B., Sayre, E. C., . . . Sorell, L. (2016). Secondary analysis of teaching methods in introductory physics: A 50 k-student study. American Journal of Physics, 84(12), 969-974. doi:10.1119/1.4964354Physics education researchers have developed many evidence-based instructional strategies to enhance conceptual learning of students in introductory physics courses. These strategies have historically been tested using assessments such as the Force Concept Inventory (FCI) and the Force and Motion Conceptual Evaluation (FMCE). We have performed a review and analysis of FCI and FMCE data published between 1995 and 2014. We confirm previous findings that interactive engagement teaching techniques are significantly more likely to produce high student learning gains than traditional lecture-based instruction. We also establish that interactive engagement instruction works in many settings, including those with students having a high and low level of prior knowledge, at liberal arts and research universities, and enrolled in both small and large classes. (C) 2016 Author(s)

The Underbelly of Entrepreneurship: A Multilevel Perspective of Destructive Entrepreneurship

Destructive entrepreneurship is an important research topic because it challenges the frequent implicit assumption that all entrepreneurship is “good.” Recent scholarly interest has been directed toward destructive entrepreneurship from various perspectives, including economics, psychology, and business ethics. This article offers a comprehensive review of the destructive entrepreneurship literature. We begin with a definition of destructive entrepreneurship, distinguishing it from seemingly similar constructs, such as unproductive entrepreneurship. We organize the fragmented studies into a multilevel model highlighting what we know about destructive entrepreneurship. This study also reveals potential holes in this framework that future research can fill

Tobacco industry globalization and global health governance: : towards an interdisciplinary research agenda

Shifting patterns of tobacco production and consumption, and the resultant disease burden worldwide since the late twentieth century prompted efforts to strengthen global health governance through adoption of the Framework Convention on Tobacco Control. While the treaty is rightfully considered an important achievement, to address a neglected public health issue through collective action, evidence suggests that tobacco industry globalization continues apace. In this article we provide a systematic review of the public health literature and reveal definitional and measurement imprecision, ahistorical timeframes, transnational tobacco companies and the state as the primary units and levels of analysis, and a strong emphasis on agency as opposed to structural power. Drawing on the study of globalization in international political economy and business studies, we identify opportunities to expand analysis along each of these dimensions. We conclude that this expanded and interdisciplinary research agenda provides the potential for fuller understanding of the dual and dynamic relationship between the tobacco industry and globalization. Deeper analysis of how the industry has adapted to globalization over time, as well as how the industry has influenced the nature and trajectory of globalization, is essential for building effective global governance responses

Indacenodibenzothiophenes: Synthesis, Optoelectronic Properties and Materials Applications of Molecules with Strong Antiaromatic Character

Indeno[1,2-b]fluorenes (IFs), while containing 4n π-electrons, are best described as two aromatic benzene rings fused to a weakly paratropic s-indacene core. In this study, we find that replacement of the outer benzene rings of an IF with benzothiophenes allows the antiaromaticity of the central s-indacene to strongly reassert itself. Herein we report a combined synthetic, computational, structural, and materials study of anti- and syn-indacenodibenzothiophenes (IDBTs). We have developed an efficient and scalable synthesis for preparation of a series of aryl- and ethynyl-substituted IDBTs. NICS-XY scans and ACID calculations reveal an increasingly antiaromatic core from [1,2-b]IF to anti-IDBT, with syn-IDBT being nearly as antiaromatic as the parent s-indacene. As an initial evaluation, the intermolecular electronic couplings and electronic band structure of a diethynyl anti-IDBT derivative reveal the potential for hole and/or electron transport. OFETs constructed using this molecule show the highest hole mobilities yet achieved for a fully conjugated IF derivative

Slope instabilities at an active continental margin: large-scale polyphase submarine slides along the northern Peruvian margin, between 5 °S and 6 °S

A mega-submarine slide was evidenced along the Peruvian margin during a Seabeam survey of the R/V Charcot (Bourgois et al., 1986). The debris-slide was initially interpreted as the result of the slope failure occurring along a seaward curved scarp, and extending from east to west, along the line of maximum slope. Complementary bathymetrie data obtained from the R/V Sonne survey conducted to the north and to the south of the previous surveyed area has resulted in the identification of large-scale polyphase submarine slides involving a total surface of about 1000 km2, between latitudes 5 °15′S and 6 °05′S. Using Seabeam and Hydrosweep multibeam echosounder data in combination with deep-sea submersible observations, three distinct slope-failure types related to three main stages have been revealed. The three sliding phases occurred roughly along the same trend, orientated N230 °, and are therefore mainly controlled by the N80 ° orientation of the subducting Nazca plate. (1) The first phase of slope failure is documented by a debris-avalanche deposit, which extends from the lower slope down to 5 km within the trench floor. The deposit originates from the northern wall of a wide valley located along the upper slope. (2) The second phase of slope failure is characterized by a debris-avalanche, with a crescent-shaped scar, located along the middle slope and a hummocky deposit covering the lower slope and extending up to 10 km across the trench. The volume of rock involved in this event is estimated to some 250 km3. The slope failure is assumed to be related to an oversteepening of the middle slope induced by a rollover deformation. (3) The third phase of slope failure corresponds to a translational sliding block and a toppling block with volumes of 6 km3 and 13 km3, respectively. The seismic energy produced during the seismic cycle has greatly increased facturation and fluids buildup along the area previously weakened by a rollover fold. A restricted N-S folding is observed in the vicinity of the trench, to the north of the two debris-avalanche deposits. It may have formed in relation to the local compression limited to the subduction of the Nazca plate. Sliding and folding thus document the paradox between the compressive regime in the lower plate and the extensional regime in the upper part of the upper plate

An integrated cell atlas of the lung in health and disease

Single-cell technologies have transformed our understanding of human tissues. Yet, studies typically capture only a limited number of donors and disagree on cell type definitions. Integrating many single-cell datasets can address these limitations of individual studies and capture the variability present in the population. Here we present the integrated Human Lung Cell Atlas (HLCA), combining 49 datasets of the human respiratory system into a single atlas spanning over 2.4 million cells from 486 individuals. The HLCA presents a consensus cell type re-annotation with matching marker genes, including annotations of rare and previously undescribed cell types. Leveraging the number and diversity of individuals in the HLCA, we identify gene modules that are associated with demographic covariates such as age, sex and body mass index, as well as gene modules changing expression along the proximal-to-distal axis of the bronchial tree. Mapping new data to the HLCA enables rapid data annotation and interpretation. Using the HLCA as a reference for the study of disease, we identify shared cell states across multiple lung diseases, including SPP1+ profibrotic monocyte-derived macrophages in COVID-19, pulmonary fibrosis and lung carcinoma. Overall, the HLCA serves as an example for the development and use of large-scale, cross-dataset organ atlases within the Human Cell Atlas

An integrated cell atlas of the lung in health and disease

Single-cell technologies have transformed our understanding of human tissues. Yet, studies typically capture only a limited number of donors and disagree on cell type definitions. Integrating many single-cell datasets can address these limitations of individual studies and capture the variability present in the population. Here we present the integrated Human Lung Cell Atlas (HLCA), combining 49 datasets of the human respiratory system into a single atlas spanning over 2.4 million cells from 486 individuals. The HLCA presents a consensus cell type re-annotation with matching marker genes, including annotations of rare and previously undescribed cell types. Leveraging the number and diversity of individuals in the HLCA, we identify gene modules that are associated with demographic covariates such as age, sex and body mass index, as well as gene modules changing expression along the proximal-to-distal axis of the bronchial tree. Mapping new data to the HLCA enables rapid data annotation and interpretation. Using the HLCA as a reference for the study of disease, we identify shared cell states across multiple lung diseases, including SPP