On the importance of nonlinear modeling in computer performance prediction

Computers are nonlinear dynamical systems that exhibit complex and sometimes even chaotic behavior. The models used in the computer systems community, however, are linear. This paper is an exploration of that disconnect: when linear models are adequate for predicting computer performance and when they are not. Specifically, we build linear and nonlinear models of the processor load of an Intel i7-based computer as it executes a range of different programs. We then use those models to predict the processor loads forward in time and compare those forecasts to the true continuations of the time seriesComment: Appeared in "Proceedings of the 12th International Symposium on Intelligent Data Analysis

Nonlinear dynamics of giant resonances in atomic nuclei

The dynamics of monopole giant resonances in nuclei is analyzed in the time-dependent relativistic mean-field model. The phase spaces of isoscalar and isovector collective oscillations are reconstructed from the time-series of dynamical variables that characterize the proton and neutron density distributions. The analysis of the resulting recurrence plots and correlation dimensions indicate regular motion for the isoscalar mode, and chaotic dynamics for the isovector oscillations. Information-theoretic functionals identify and quantify the nonlinear dynamics of giant resonances in quantum systems that have spatial as well as temporal structure.Comment: 24 pages, RevTeX, 15 PS figures, submitted Phys. Rev.

Anthropogenic Space Weather

Anthropogenic effects on the space environment started in the late 19th century and reached their peak in the 1960s when high-altitude nuclear explosions were carried out by the USA and the Soviet Union. These explosions created artificial radiation belts near Earth that resulted in major damages to several satellites. Another, unexpected impact of the high-altitude nuclear tests was the electromagnetic pulse (EMP) that can have devastating effects over a large geographic area (as large as the continental United States). Other anthropogenic impacts on the space environment include chemical release ex- periments, high-frequency wave heating of the ionosphere and the interaction of VLF waves with the radiation belts. This paper reviews the fundamental physical process behind these phenomena and discusses the observations of their impacts.Comment: 71 pages, 35 figure

An investigation of how fungal infection influences drug penetration through onychomycosis patient's nail plates

This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)The treatment of onychomycosis remains problematic even though there are several potent antifungal agents available for patient use. The aim of this investigation was to understand if the structural modifications that arise when a patient's nail become infected plates influences the permeation of drugs into the nail following topical application. It was hoped that through improving understanding of the nail barrier in the diseased state, the development of more effective topical treatments for onychomycosis could be facilitated. The permeation of three compounds with differing hydrophobicities; caffeine, terbinafine and amorolfine, (clogD at pH 7.4 of -0.55, 3.72 and 4.49 respectively), was assessed across both healthy and onychomycosis infected, full thickness, human nail plate sections. Transonychial water loss (TOWL) measurements performed on the healthy and diseased nails supported previous observations that the nail behaves like a porous barrier given the lack of correlation between TOWL values with the thicker, diseased nails. The flux of the more hydrophilic caffeine was two-fold greater across diseased in comparison to the healthy nails, whilst the hydrophobic molecules terbinafine and amorolfine showed no statistically significant change in their nail penetration rates. Caffeine flux across the nail was found to correlate with the TOWL measurements, though no correlation existed for the more hydrophobic drugs. This data supported the notion that the nail pores, opened up by the infection, facilitated the passage of hydrophilic molecules, whilst the keratin binding of hydrophobic molecules meant that their transport through the nail plate was unchanged. Therefore, in order to exploit the structural changes induced by nail fungal infection it would be beneficial to develop a small molecular weight, hydrophilic antifungal agent, which exhibits low levels of keratin binding.Peer reviewe

Salmonella Typhi Colonization Provokes Extensive Transcriptional Changes Aimed at Evading Host Mucosal Immune Defense During Early Infection of Human Intestinal Tissue

Commensal microorganisms influence a variety of host functions in the gut, including immune response, glucose homeostasis, metabolic pathways and oxidative stress, among others. This study describes how Salmonella Typhi, the pathogen responsible for typhoid fever, uses similar strategies to escape immune defense responses and survive within its human host. To elucidate the early mechanisms of typhoid fever, we performed studies using healthy human intestinal tissue samples and “mini-guts,” organoids grown from intestinal tissue taken from biopsy specimens. We analyzed gene expression changes in human intestinal specimens and bacterial cells both separately and after colonization. Our results showed mechanistic strategies that S. Typhi uses to rearrange the cellular machinery of the host cytoskeleton to successfully invade the intestinal epithelium, promote polarized cytokine release and evade immune system activation by downregulating genes involved in antigen sampling and presentation during infection. This work adds novel information regarding S. Typhi infection pathogenesis in humans, by replicating work shown in traditional cell models, and providing new data that can be applied to future vaccine development strategies

Caribou, Petroleum, and the Limits of Locality in the Canada–US Borderlands

his article discusses Karsten Heuer’s 2006 book Being Caribou in light of debates in ecocriticism and border studies about how to define the local in the context of environmental problems of vast range and uncertain temporality. It explores how Heuer’s book about following the Porcupine Caribou herd’s migration engages in multiple forms of boundary crossing—between countries, between hemispheric locations, and between species—and shows how insights from Indigenous storytelling complicate the book’s appeal to environmentalist readers by asserting a prior, transnational Indigenous presence in the transboundary landscapes of present-day Alaska and the Yukon

Grain Surface Models and Data for Astrochemistry

AbstractThe cross-disciplinary field of astrochemistry exists to understand the formation, destruction, and survival of molecules in astrophysical environments. Molecules in space are synthesized via a large variety of gas-phase reactions, and reactions on dust-grain surfaces, where the surface acts as a catalyst. A broad consensus has been reached in the astrochemistry community on how to suitably treat gas-phase processes in models, and also on how to present the necessary reaction data in databases; however, no such consensus has yet been reached for grain-surface processes. A team of ∼25 experts covering observational, laboratory and theoretical (astro)chemistry met in summer of 2014 at the Lorentz Center in Leiden with the aim to provide solutions for this problem and to review the current state-of-the-art of grain surface models, both in terms of technical implementation into models as well as the most up-to-date information available from experiments and chemical computations. This review builds on the results of this workshop and gives an outlook for future directions

Deriving Non-decoupling Effects of Heavy Fields from the Path Integral: a Heavy Higgs Field in an SU(2) Gauge Theory

We describe a method to remove non-decoupling heavy fields from a quantized field theory and to construct a low-energy one-loop effective Lagrangian by integrating out the heavy degrees of freedom in the path integral. We apply this method to the Higgs boson in a spontaneously broken SU(2) gauge theory (gauged linear sigma-model). In this context, the background-field method is generalized to the non-linear representation of the Higgs sector by applying (a generalization of) the Stueckelberg formalism. The (background) gauge-invariant renormalization is discussed. At one loop the log M_H-terms of the heavy-Higgs limit of this model coincide with the UV-divergent terms of the corresponding gauged non-linear sigma-model, but vertex functions differ in addition by finite (constant) terms in both models. These terms are also derived by our method. Diagrammatic calculations of some vertex functions are presented as consistency check.Comment: 33 Pages LaTeX, 6 figures uuencoded postscrip