Supernova Remnants as Clues to Their Progenitors

Supernovae shape the interstellar medium, chemically enrich their host galaxies, and generate powerful interstellar shocks that drive future generations of star formation. The shock produced by a supernova event acts as a type of time machine, probing the mass loss history of the progenitor system back to ages of $\sim$ 10 000 years before the explosion, whereas supernova remnants probe a much earlier stage of stellar evolution, interacting with material expelled during the progenitor's much earlier evolution. In this chapter we will review how observations of supernova remnants allow us to infer fundamental properties of the progenitor system. We will provide detailed examples of how bulk characteristics of a remnant, such as its chemical composition and dynamics, allow us to infer properties of the progenitor evolution. In the latter half of this chapter, we will show how this exercise may be extended from individual objects to SNR as classes of objects, and how there are clear bifurcations in the dynamics and spectral characteristics of core collapse and thermonuclear supernova remnants. We will finish the chapter by touching on recent advances in the modeling of massive stars, and the implications for observable properties of supernovae and their remnants.Comment: A chapter in "Handbook of Supernovae" edited by Athem W. Alsabti and Paul Murdin (18 pages, 6 figures

Modeling the Hubble Space Telescope ultraviolet and optical spectrum of spot 1 on the circumstellar ring of SN 1987A

We report and interpret Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) long-slit observations of the optical and ultraviolet (1150-10270 Å) emission line spectra of the rapidly brightening spot 1 on the equatorial ring of SN 1987A between 1997 September and 1999 October (days 3869-4606 after outburst). The emission is caused by radiative shocks created where the supernova blast wave strikes dense gas protruding inward from the equatorial ring. We measure and tabulate line identifications, fluxes, and, in some cases, line widths and shifts. We compute flux correction factors to account for substantial interstellar line absorption of several emission lines. Nebular analysis shows that optical emission lines come from a region of cool (T e ≈ 10 4 K) and dense (n e ≈ 10 6 cm -3) gas in the compressed photoionized layer behind the radiative shock. The observed line widths indicate that only shocks with shock velocities V s < 250 km s -1 have become radiative, while line ratios indicate that much of the emission must have come from yet slower (V s ≲ 135 km s -1) shocks. Such slow shocks can be present only if the protrusion has atomic density n ≳ 3 × 10 4 cm -3, somewhat higher than that of the circumstellar ring. We are able to fit the UV fluxes with an idealized radiative shock model consisting of two shocks (V s = 135 and 250 km s -1). The observed UV flux increase with time can be explained by the increase in shock surface areas as the blast wave overtakes more of the protrusion. The observed flux ratios of optical to highly ionized UV lines are greater by a factor of ∼2-3 than predictions from the radiative shock models, and we discuss the possible causes. We also present models for the observed Ha line widths and profiles, which suggest that a chaotic flow exists in the photoionized regions of these shocks. We discuss what can be learned with future observations of all the spots present on the equatorial ring.published_or_final_versio

A survey of health professions students for knowledge, attitudes, and confidence about tuberculosis, 2005

<p>Abstract</p> <p>Background</p> <p>In 2003 the NIH perceived a need to strengthen teaching about tuberculosis (TB) to health professions students. The National Tuberculosis Curriculum Consortium (NTCC) was funded to meet this need. The purpose of this study was to survey students enrolled in NTCC schools prior to NTCC-developed educational materials being made available to faculty.</p> <p>Methods</p> <p>A self-administered survey for students in NTCC schools to establish a baseline level of knowledge, attitudes, and confidence about tuberculosis.</p> <p>Results</p> <p>1480/2965 (50%) students in 28 programs in 20 NTCC schools completed the survey. If public health students are eliminated from totals (only 61 respondents of 765 public health students), the overall response proportion for the seven clinically-related disciplines was 64.5%. The majority (74%) were in schools of medicine (MD/DO), undergraduate nursing (BSN), and pharmacy (PharmD); others were in programs for physician assistants (PA), advanced practice nursing (NP/APN), respiratory therapy (RT), clinical laboratory sciences (MT/CLS), and public health (MPH). Almost 90% had attended at least one lecture about TB. Although 91.4% knew TB was transmitted via aerosols, about one-third did not know the method for administering tuberculin, or that Bacillus Calmette-Guerin (BCG) vaccine was not a contraindication to TB skin testing. Fewer than two-thirds knew that about 10% of people in the U.S.A. who have latent tuberculosis infection (LTBI) and a normal immune system will develop TB disease, or that BCG is not part of the routine vaccination program in the U.S.A. because it complicates surveillance for new TB infection.</p> <p>Conclusion</p> <p>There is room for improvement in knowledge, attitudes, and confidence about TB by health professions students surveyed. The NTCC-developed educational products may be used by faculty to improve student performance to be assessed with future surveys.</p

Timing of antenatal care for adolescent and adult pregnant women in south-eastern Tanzania

Early and frequent antenatal care attendance during pregnancy is important to identify and mitigate risk factors in pregnancy and to encourage women to have a skilled attendant at childbirth. However, many pregnant women in sub-Saharan Africa start antenatal care attendance late, particularly adolescent pregnant women. Therefore they do not fully benefit from its preventive and curative services. This study assesses the timing of adult and adolescent pregnant women's first antenatal care visit and identifies factors influencing early and late attendance.\ud The study was conducted in the Ulanga and Kilombero rural Demographic Surveillance area in south-eastern Tanzania in 2008. Qualitative exploratory studies informed the design of a structured questionnaire. A total of 440 women who attended antenatal care participated in exit interviews. Socio-demographic, social, perception- and service related factors were analysed for associations with timing of antenatal care initiation using regression analysis. The majority of pregnant women initiated antenatal care attendance with an average of 5 gestational months. Belonging to the Sukuma ethnic group compared to other ethnic groups such as the Pogoro, Mhehe, Mgindo and others, perceived poor quality of care, late recognition of pregnancy and not being supported by the husband or partner were identified as factors associated with a later antenatal care enrolment (p < 0.05). Primiparity and previous experience of a miscarriage or stillbirth were associated with an earlier antenatal care attendance (p < 0.05). Adolescent pregnant women started antenatal care no later than adult pregnant women despite being more likely to be single. Factors including poor quality of care, lack of awareness about the health benefit of antenatal care, late recognition of pregnancy, and social and economic factors may influence timing of antenatal care. Community-based interventions are needed that involve men, and need to be combined with interventions that target improving the quality, content and outreach of antenatal care services to enhance early antenatal care enrolment among pregnant women

Effects of a mechanical engineering design course on students’ motivational features

Diverse learning opportunities and deep engagement are needed to support development of engineering competencies and expertise. Deep engagement evolves from productive and high-quality motivation that derives from both internal and external sources. Motivation to learn is lacking in many fields, like engineering, because it is too often assumed or ignored, rather than explicitly built into course instruction. While the lack of motivation in engineering education is clear in data-like attrition, there is little relevant research that informs the necessary changes for the field. The purpose of this study is to present a systematic approach that explicitly considers motivational elements in engineering courses. First a comprehensive set of motivational characteristics and the interrelationships for productive motivation of mechanical engineering students are identified. Students’ motivational characteristics and profiles of change over time are assessed using a multipoint predictive correlational design. This information is then used to strategically redesign motivational elements of a senior-level mechanical engineering design course. The SUCCESS framework has been used to redesign motivational features of the existing course. This paper reports results of the study, including implications for redesign of other engineering courses. Analysis of the data demonstrates the complexity of motivation in the engineering classroom, which includes addressing implicit and explicit, intrinsic and extrinsic, individual and team interaction and instruction. These elements extend not only to direct communication and interactions of instructor with students but into the full scope of the learning environment, peer-to-peer interactions, grading, (a)synchronous activities, face to face, and virtual communications. Key features of engineering students’ productive (learning and engagement-related) motivational profiles consisted of clusters of perceptual and experiential variables that were strongly correlated with motivational and learning outcomes. Tracking these factors demonstrated that they changed over time. These changes corresponded to perceptions of instructor and peer interactions, which were amenable to instructional intervention and responsive to social modeling. This study also revealed links among engineering students’ perceptions of their field of study, their own development of self-efficacy, and success expectations in both the design course and for their careers. This work revealed important distinctions between engineering students’ self-efficacy for, and engagement in, the course generally and for group tasks more specifically. These newly revealed relationships offer the opportunity to improve engineering instruction and the design of dynamic learning environments that support adaptive skill development.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline

Supernova remnants: the X-ray perspective

Supernova remnants are beautiful astronomical objects that are also of high scientific interest, because they provide insights into supernova explosion mechanisms, and because they are the likely sources of Galactic cosmic rays. X-ray observations are an important means to study these objects.And in particular the advances made in X-ray imaging spectroscopy over the last two decades has greatly increased our knowledge about supernova remnants. It has made it possible to map the products of fresh nucleosynthesis, and resulted in the identification of regions near shock fronts that emit X-ray synchrotron radiation. In this text all the relevant aspects of X-ray emission from supernova remnants are reviewed and put into the context of supernova explosion properties and the physics and evolution of supernova remnants. The first half of this review has a more tutorial style and discusses the basics of supernova remnant physics and thermal and non-thermal X-ray emission. The second half offers a review of the recent advances.The topics addressed there are core collapse and thermonuclear supernova remnants, SN 1987A, mature supernova remnants, mixed-morphology remnants, including a discussion of the recent finding of overionization in some of them, and finally X-ray synchrotron radiation and its consequences for particle acceleration and magnetic fields.Comment: Published in Astronomy and Astrophysics Reviews. This version has 2 column-layout. 78 pages, 42 figures. This replaced version has some minor language edits and several references have been correcte