A compendium of NASA Aerobee sounding rocket launchings for 1966

Compendium of Aerobee sounding rocket launchings for 196

Force dependent fragility in RNA hairpins

We apply Kramers theory to investigate the dissociation of multiple bonds under mechanical force and interpret experimental results for the unfolding/refolding force distributions of an RNA hairpin pulled at different loading rates using laser tweezers. We identify two different kinetic regimes depending on the range of forces explored during the unfolding and refolding process. The present approach extends the range of validity of the two-states approximation by providing a theoretical framework to reconstruct free-energy landscapes and identify force-induced structural changes in molecular transition states using single molecule pulling experiments. The method should be applicable to RNA hairpins with multiple kinetic barriers.Comment: Latex file, 4 pages+3 figure

Snowier Winters Extend Autumn Availability of High-quality Forage for Caribou in Arctic Alaska

Caribou (Rangifer tarandus) rely on the short Arctic growing season to restore body condition, support the demands of lactation, and prepare for the long arctic winter, making them susceptible to even small changes in forage availability or quality. Body condition in the summer and autumn is linked to winter survival rates and fecundity in cows, critical factors in the productivity of caribou populations. Climate change predictions of warmer and wetter northern winters suggest increased snowfall over Alaska’s North Slope, which has recently been verified between 1995 and 2017. However, a comprehensive analysis of how deeper snow will affect caribou forage quality is absent across Alaska. In this study, we quantify how snow depth alters the quality and seasonality of caribou forage using a long-term (24 yr) International Tundra Experiment snow depth manipulation to evaluate how winter climate change scenarios may affect tussock tundra systems in northern Alaska. Deeper snow in prior winters leads to increases in growing season leaf N and digestible protein (DP) in deciduous shrubs (and Betula spp.) and graminoids (Carex spp. and Eriophorum spp.), but not evergreen dwarf shrubs (Rhododendron spp. and Vaccinium spp.). Dry matter digestibility varied among species with small differences (\u3c5%) associated with snow depth. Most striking was the discovery that deeper snow in the prior winter increased the duration of DP levels above the minimum threshold for protein gain in caribou by as much as 25 d in Salix pulchra and 6–9 d in Betula nana and Carex bigelowii in late summer and early autumn. Consequently, deeper winter snow may provide an extended window of opportunity for foraging and the accumulation of lean body mass and fat reserves which promote winter survival and successful calving the following spring and potentially improve the productivity of caribou in northern Alaska

Reaction-diffusion systems and nonlinear waves

The authors investigate the solution of a nonlinear reaction-diffusion equation connected with nonlinear waves. The equation discussed is more general than the one discussed recently by Manne, Hurd, and Kenkre (2000). The results are presented in a compact and elegant form in terms of Mittag-Leffler functions and generalized Mittag-Leffler functions, which are suitable for numerical computation. The importance of the derived results lies in the fact that numerous results on fractional reaction, fractional diffusion, anomalous diffusion problems, and fractional telegraph equations scattered in the literature can be derived, as special cases, of the results investigated in this article.Comment: LaTeX, 16 pages, corrected typo

Superfast solution of linear convolutional Volterra equations using QTT approximation

NOTICE: this is the author’s version of a work that was accepted for publication in Journal of Computational and Applied Mathematics. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of Applied and Computational Mathematics, 260, 2014, doi: 10.1016/j.cam.2013.10.025This article address a linear fractional differential equation and develop effective solution methods using algorithms for the inversion of triangular Toeplitz matrices and the recently proposed QTT format. The inverses of such matrices can be computed by the divide and conquer and modified Bini’s algorithms, for which we present the versions with the QTT approximation. We also present an efficient formula for the shift of vectors given in QTT format, which is used in the divide and conquer algorithm. As a result, we reduce the complexity of inversion from the fast Fourier level O(nlogn) to the speed of superfast Fourier transform, i.e., O(log^2n). The results of the paper are illustrated by numerical examples.During this work D. V. Savostyanov and E. E. Tyrtyshnikov were supported by the Leverhulme Trust to visit, stay and work at the University of Chester, as the Visiting Research Fellow and the Visiting Professor, respectively. Their work was also supported in part by RFBR grants 11-01-00549, 12-01-91333-nnio-a, 13-01-12061, and Russian Federation Government Contracts 14.740.11.0345, 14.740.11.1067, 16.740.12.0727

Visual Psychophysics and Physiological Optics Development of Refractive Error in Individual Children With Regressed Retinopathy of Prematurity

PURPOSE. We investigated longitudinally the refraction development in children with regressed retinopathy of prematurity (ROP), including those with and those without a history of peripheral retinal laser photocoagulation. METHODS. Longitudinal (0-7 years) cycloplegic refraction data were collected prospectively for two groups of preterm children: severe ROP group included those with regressed ROP following bilateral panretinal laser photocoagulation (n ¼ 37; median gestational age [GA] ¼ 25.2; range, 22.7-27.9 weeks) and mild/no ROP group included those with spontaneously regressed ROP or no ROP (n ¼ 27; median GA ¼ 27.1; range, 23.1-32.0 weeks). Analyses were based on spherical equivalent (SEQ), anisometropia, astigmatism, and age (corrected for gestation). RESULTS. The prevalence, magnitude, and rate of myopic progression all were significantly higher in the severe ROP group than in the mild/no ROP group. Longitudinal SEQ in the severe ROP group were best fit with a bilinear model. Before 1.3 years old, the rate of myopic shift was À4.7 diopters (D)/y; after 1.3 years, the rate slowed to À0.15 D/y. Longitudinal SEQ in the mild/no ROP group was best fit with a linear model, with a rate of À0.004 D/y. Anisometropia in the severe ROP group increased approximately three times faster than in the mild/no ROP group. In the severe ROP group, with-the-rule astigmatism increased significantly with age. CONCLUSIONS. The severe ROP group progressed rapidly toward myopia, particularly during the first 1.3 years; anisometropia and astigmatism also increased with age. The mild/no ROP group showed little change in refraction. Infants treated with laser photocoagulation for severe ROP should be monitored with periodic cycloplegic refractions and provided with early optical correction. Keywords: myopia, refractive error development, retinopathy of prematurity, laser photocoagulation R etinopathy of prematurity (ROP) is one of the leading causes of childhood visual impairment and blindness in the United States. The prevalence of myopia has been reported to vary with severity of ROP, ranging from 0% to 16% for preterm infants with no ROP 1-3 to 21% to 100% for children whose severe ROP was laser-treated. 1-4 The prevalence of myopia in children with severe ROP is astonishingly high, especially in those who received peripheral laser-photocoagulation. 7,8 A longitudinal study of 62 preterm children with mild/no ROP reported that 24% had myopia during early childhood and only 11% had high myopia. 9 This study will focus on comparing longitudinal changes in refractive error of individual preterm children who had severe ROP (treated with laser-photocoagulation) and those with mild/no ROP. To our knowledge, previous studies have not offered a model to predict an individual's development of refractive error because they did not track individual myopic progression. As a result, gaps remain in our understanding of refractive error development in individual children with ROP. Furthermore, it is well-known that there is a high prevalence (6-fold higher tha