Mechanics of CPR Performed with the Patient on a Soft Bed Versus a Hard Surface

Objective: To study the effects of underlying bed softness versus stiffness on the effectiveness of chest compressions in CPR. Methods: For a wide range of bed stiffness constants, mathematical models describing compression of the human chest supported by a hospital bed were created for an adult thorax experiencing either a sinusoidal compressive force or a sinusoidal sternal displacement. Results: With 5 cm peak displacement, sternum-to-spine compression fell from 4.3 to 1.0 cm, and peak power fell from 59 to 23 Watts, as bed stiffness decreased from 50,000 to 5,000 N/m. Less than 35% of maximal chest compression occurred at a typical bed stiffness of 10,000 N/m. With 400 N peak force, sternum-to-spine compression decreased from 5.0 to 2.0 cm, and peak power increased from 82 to 226 Watts, as bed stiffness decreased from 50,000 to 5,000 N/m. However, greater than 85% of maximal chest compression was obtained at a typical bed stiffness of 10,000 N/m. Conclusion: The deterioration of chest compression performed on soft beds is technique dependent. If necessary, CPR can be performed effectively on a softer surface using a constant peak force technique. However, a firm surface is most desirable

Complex Dynamics and Multistability in a Damped Harmonic Oscillator with Delayed Negative Feedback

A center manifold reduction and numerical calculations are used to demonstrate the presence of limit cycles, two-tori, and multistability in the damped harmonic oscillator with delayed negative feedback. This model is the prototype of a mechanical system operating with delayed feedback. Complex dynamics are thus seen to arise in very plausible and commonly occurring mechanical and neuromechanical feedback systems

The genetic basis for panicle trait variation in switchgrass (Panicum virgatum)

Key message: We investigate the genetic basis of panicle architecture in switchgrass in two mapping populations across a latitudinal gradient, and find many stable, repeatable genetic effects and limited genetic interactions with the environment. Abstract: Grass species exhibit large diversity in panicle architecture influenced by genes, the environment, and their interaction. The genetic study of panicle architecture in perennial grasses is limited. In this study, we evaluate the genetic basis of panicle architecture including panicle length, primary branching number, and secondary branching number in an outcrossed switchgrass QTL population grown across ten field sites in the central USA through multi-environment mixed QTL analysis. We also evaluate genetic effects in a diversity panel of switchgrass grown at three of the ten field sites using genome-wide association (GWAS) and multivariate adaptive shrinkage. Furthermore, we search for candidate genes underlying panicle traits in both of these independent mapping populations. Overall, 18 QTL were detected in the QTL mapping population for the three panicle traits, and 146 unlinked genomic regions in the diversity panel affected one or more panicle trait. Twelve of the QTL exhibited consistent effects (i.e., no QTL by environment interactions or no QTL × E), and most (four of six) of the effects with QTL × E exhibited site-specific effects. Most (59.3%) significant partially linked diversity panel SNPs had significant effects in all panicle traits and all field sites and showed pervasive pleiotropy and limited environment interactions. Panicle QTL co-localized with significant SNPs found using GWAS, providing additional power to distinguish between true and false associations in the diversity panel

A generalist–specialist trade-off between switchgrass cytotypes impacts climate adaptation and geographic range

Polyploidy results from whole-genome duplication and is a unique form of heritable variation with pronounced evolutionary implications. Different ploidy levels, or cytotypes, can exist within a single species, and such systems provide an opportunity to assess how ploidy variation alters phenotypic novelty, adaptability, and fitness, which can, in turn, drive the development of unique ecological niches that promote the coexistence of multiple cytotypes. Switchgrass, Panicum virgatum, is a widespread, perennial C4 grass in North America with multiple naturally occurring cytotypes, primarily tetraploids (4×) and octoploids (8×). Using a combination of genomic, quantitative genetic, landscape, and niche modeling approaches, we detect divergent levels of genetic admixture, evidence of niche differentiation, and differential environmental sensitivity between switchgrass cytotypes. Taken together, these findings support a generalist (8×)–specialist (4×) trade-off. Our results indicate that the 8× represent a unique combination of genetic variation that has allowed the expansion of switchgrass’ ecological niche and thus putatively represents a valuable breeding resource

Night lights in economics: Sources and uses

Night lights, as detected by satellites, are increasingly used by economists, typically as a proxy for economic activity. The growing popularity of these data reflects either the absence, or the presumed inaccuracy, of more conventional economic statistics, like national or regional GDP. Further growth in use of night lights is likely, as they have been included in the AidData geo-query tool for providing sub-national data, and in geographic data that the Demographic and Health Survey links to anonymised survey enumeration areas. Yet this ease of obtaining night lights data may lead to inappropriate use, if users fail to recognize that most of the satellites providing these data were not designed to assist economists, and have features that may threaten validity of analyses based on these data, especially for temporal comparisons, and for small and rural areas. In this paper we review sources of satellite data on night lights, discuss issues with these data, and survey some of their uses in economics

The Extended Fetal Cardiac Examination

The aims of this study were to demonstrate the feasibility of obtaining additional cardiac views as proposed on an extended fetal cardiac examination and to see if there was any variation in individual components of that examination stratified by sonographer training, patient body habitus, or equipment. We retrospectively reviewed 200 consecutive detailed second-trimester high-risk fetal obstetric sonograms that included additional extended cardiac views. We analyzed the percentage of the time individual views were obtained, with variation based on (1) a sonographer with greater than 3 years of training compared with a group with 6 to 12 months of training, (2) 2 different ultrasound units, and (3) different body mass indices. Overall, the highest rate of visualization was achieved with the 4-chamber view (98.2%), whereas the 3-vessel tracheal view had the lowest percentage of visualization (40.2%), among the less experienced sonographers. Differences in successful completion of the extended cardiac views were not statistically different between the sonographer with a level of training greater than 3 years as compared with those with 6 to 12 months' training except for the 3-vessel tracheal view (P < 0.001). There is no statistically significant difference in our ultrasound equipment, when considering only inexperienced sonographers. Increasing body mass index had an inverse relationship with obtaining the components of the detailed cardiac examination. Using state-of-the-art ultrasound equipment and with focused additional training of obstetric sonographers, the majority of extended cardiac views can be obtained. There are exceptions