The composition of Saturn's rings

The origin and evolution of Saturn's rings is critical to understanding the Saturnian system as a whole. Here, we discuss the physical and chemical composition of the rings, as a foundation for evolutionary models described in subsequent chapters. We review the physical characteristics of the main rings, and summarize current constraints on their chemical composition. Radial trends are observed in temperature and to a limited extent in particle size distribution, with the C ring exhibiting higher temperatures and a larger population of small particles. The C ring also shows evidence for the greatest abundance of silicate material, perhaps indicative of formation from a rocky body. The C ring and Cassini Division have lower optical depths than the A and B rings, which contributes to the higher abundance of the exogenous neutral absorber in these regions. Overall, the main ring composition is strongly dominated by water ice, with minor silicate, UV absorber, and neutral absorber components. Sampling of the innermost D ring during Cassini's Grand Finale provides a new set of in situ constraints on the ring composition, and we explore ongoing work to understand the linkages between the main rings and the D ring. The D ring material is organic- and silicate-rich and water-poor relative to the main rings, with a large population of small grains. This composition may be explained in part by volatile losses in the D ring, and current constraints suggest some degree of fractionation rather than sampling of the bulk D ring material.Comment: Submitted to SSR for publication in the collection "New Vision of the Saturnian System in the Context of a Highly Dissipative Saturn

UNBOUND

Unbound showcases the graduating class from the fashion design school at Fanshawe College. Unbound describes the creative spirit and achievements of our twenty-seven emerging Canadian fashion designers. Unbound 2014 is a professional collaboration between Fanshawe College, Community and Professionals in the Fashion Industry. As you turn the pages, admire their accomplishments - the results of three years of passion, hard work, and dedication.https://first.fanshawec.ca/famd_design_fashiondesign_unbound/1003/thumbnail.jp

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Teaching : making a difference

Teaching: Making a Difference has been developed to provide the pre-service teacher with new and contemporary lenses for helping them develop as future educators. It is relevant to students in undergraduate and postgraduate teacher programs. This multi-authored volume draws on the expertise of each contributor and reflects the latest contemporary research. The text is supported by a unique multi-media package designed to meet the needs of individual learners. [Book Synopsis]Click <a href="http://research.usc.edu.au/vital/access/manager/Repository/usc:8422">here</a> to view the USC Research Bank entry for the Second Edition published in 2013

US Term Stillbirth Rates and the 39-Week Rule: A Cause for Concern?

The restriction of the use of “elective” delivery before 39 weeks 0 days of gestation, known as “the 39-week rule” or “the Rule,” was mandated in 2010 in the United States. The Rule was applicable to both labor induction and prelabor cesarean delivery, and was developed as higher rates of adverse childbirth outcomes, including infant morbidity and mortality, subsequent to deliveries that occurred before 39 weeks 0 days of gestation had been reported. However, the prospective risk of term stillbirth was known to increase as a function of increasing gestational age, and hence it was speculated that the Rule might increase the overall rate of term stillbirth. This study aimed to determine whether the term stillbirth rate increased during the 7-year period that the 39-week rule was adopted. The number of live births and the number of stillbirths that occurred within each week of gestational age at and further than 37 weeks were obtained from the state health departments for the years 2007 to 2013. The patterns of the timing of term childbirth and term stillbirth were determined as a function of calendar year and gestational age for each state and for the United States overall. The number needed to treat, which represented the number of women who would need to have an early-term delivery without an accepted indication to prevent one term stillbirth, was estimated based on the change in the proportion of deliveries that occurred before the 39th week of gestation in 2013 compared with 2007, and by the estimated change in the incidence of term stillbirth that occurred in 2013 compared with 2007

US Term Stillbirth Rates and the 39-week Rule: A Cause for Concern?

Background More than a decade ago an obstetric directive called “the 39-week rule” sought to limit “elective” delivery, via labor induction or cesarean delivery, before 39 weeks 0 days of gestation. In 2010 the 39-week rule became a formal quality measure in the United States. The progressive adherence to the 39-week rule throughout the United States has caused a well-documented, progressive reduction in the proportion of term deliveries occurring during the early-term period. Because of the known association between increasing gestational age during the term period and increasing cumulative risk of stillbirth, however, there have been published concerns that the 39-week rule—by increasing the gestational age of delivery for a substantial number of pregnancies—might increase the rate of term stillbirth within the United States. Although adherence to the 39-week rule is assumed to be beneficial, its actual impact on the US rate of term stillbirth in the years since 2010 is unknown. Objective To determine whether the adoption of the 39-week rule was associated with an increased rate of term stillbirth in the United States. Study Design Sequential ecological study, based on state data, of US term deliveries that occurred during a 7-year period bounded by 2007 and 2013. The patterns of the timing of both term childbirth and term stillbirth were determined for each state and for the United States as a whole. Results A total of 46 usable datasets were obtained (45 states and the District of Columbia). During the 7-year period, there was a continuous reduction in all geographic entities in the proportion of term deliveries that occurred before 39 weeks of gestation. The overall rate of term stillbirth, when we compared 2007−2009 with 2011−2013, increased significantly (1.103/1000 vs 1.177/1000, RR 1.067, 95% confidence interval 1.038−1.096). Furthermore, during the 7-year period, the increase in the rate of US term stillbirth appeared to be continuous (estimated slope: 0.0186/1000/year, 95% confidence interval 0.002−0.035). Assuming 3.5 million term US births per year, and given 6 yearly “intervals” with this rate increase, it is possible that more than 335 additional term stillbirths occurred in the United States in 2013 as compared with 2007. In addition, during the 7-year period, there was a progressive shift in the timing of delivery from the 40th week to the 39th week. Absent this confounding factor, the magnitude of association between the adoption of the 39-week rule and the increase in rate of term stillbirth might have been greater. Conclusions Between 2007 and 2013 in the United States, the adoption of the 39-week rule caused a progressive reduction in the proportion of term births occurring before the 39th week of gestation. During the same interval the United States experienced a significant increase in its rate of term stillbirth. This study raises the possibility that the 39-week rule may be causing unintended harm. Additional studies of the actual impact of the adoption of the 39-week rule on major childbirth outcomes are urgently needed. Pressures to enforce the 39-week rule should be reconsidered pending the findings of such studies

US Term Stillbirth Rates and the 39-week Rule: A Cause for Concern?

Background More than a decade ago an obstetric directive called “the 39-week rule” sought to limit “elective” delivery, via labor induction or cesarean delivery, before 39 weeks 0 days of gestation. In 2010 the 39-week rule became a formal quality measure in the United States. The progressive adherence to the 39-week rule throughout the United States has caused a well-documented, progressive reduction in the proportion of term deliveries occurring during the early-term period. Because of the known association between increasing gestational age during the term period and increasing cumulative risk of stillbirth, however, there have been published concerns that the 39-week rule—by increasing the gestational age of delivery for a substantial number of pregnancies—might increase the rate of term stillbirth within the United States. Although adherence to the 39-week rule is assumed to be beneficial, its actual impact on the US rate of term stillbirth in the years since 2010 is unknown. Objective To determine whether the adoption of the 39-week rule was associated with an increased rate of term stillbirth in the United States. Study Design Sequential ecological study, based on state data, of US term deliveries that occurred during a 7-year period bounded by 2007 and 2013. The patterns of the timing of both term childbirth and term stillbirth were determined for each state and for the United States as a whole. Results A total of 46 usable datasets were obtained (45 states and the District of Columbia). During the 7-year period, there was a continuous reduction in all geographic entities in the proportion of term deliveries that occurred before 39 weeks of gestation. The overall rate of term stillbirth, when we compared 2007−2009 with 2011−2013, increased significantly (1.103/1000 vs 1.177/1000, RR 1.067, 95% confidence interval 1.038−1.096). Furthermore, during the 7-year period, the increase in the rate of US term stillbirth appeared to be continuous (estimated slope: 0.0186/1000/year, 95% confidence interval 0.002−0.035). Assuming 3.5 million term US births per year, and given 6 yearly “intervals” with this rate increase, it is possible that more than 335 additional term stillbirths occurred in the United States in 2013 as compared with 2007. In addition, during the 7-year period, there was a progressive shift in the timing of delivery from the 40th week to the 39th week. Absent this confounding factor, the magnitude of association between the adoption of the 39-week rule and the increase in rate of term stillbirth might have been greater. Conclusions Between 2007 and 2013 in the United States, the adoption of the 39-week rule caused a progressive reduction in the proportion of term births occurring before the 39th week of gestation. During the same interval the United States experienced a significant increase in its rate of term stillbirth. This study raises the possibility that the 39-week rule may be causing unintended harm. Additional studies of the actual impact of the adoption of the 39-week rule on major childbirth outcomes are urgently needed. Pressures to enforce the 39-week rule should be reconsidered pending the findings of such studies