Renormalization Group Theory for a Perturbed KdV Equation

We show that renormalization group(RG) theory can be used to give an analytic description of the evolution of a perturbed KdV equation. The equations describing the deformation of its shape as the effect of perturbation are RG equations. The RG approach may be simpler than inverse scattering theory(IST) and another approaches, because it dose not rely on any knowledge of IST and it is very concise and easy to understand. To the best of our knowledge, this is the first time that RG has been used in this way for the perturbed soliton dynamics.Comment: 4 pages, no figure, revte

Chemistry of a Protoplanetary Disk with Grain Settling and Ly_ Radiation

We present results from a model of the chemical evolution of protoplanetary disks. In our models, we directly calculate the changing propagation and penetration of a high energy radiation field with Ly_ radiation included. We also explore the effect on our models of including dust grain settling. We find that, in agreement with earlier studies, the evolution of dust grains plays a large role in determining how deep the UV radiation penetrates into the disk. Significant grain settling at the midplane leads to much smaller freeze-out regions and a correspondingly larger molecular layer, which leads to an increase in column density for molecular species such as CO, CN, and SO. The inclusion of Ly_ radiation impacts the disk chemistry through specific species that have large photodissociation cross sections at 1216 Å. These include HCN, NH 3 , and CH 4 , for which the column densities are decreased by an order of magnitude or more due to the presence of Ly_ radiation in the UV spectrum. A few species, such as CO 2 and SO, are enhanced by the presence of Ly_ radiation, but rarely by more than a factor of a few.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90767/1/0004-637X_726_1_29.pd

Detecting human impacts on the flora, fauna, and summer monsoon of Pleistocene Australia

International audienceAll of Australia's largest mammalian vertebrates became extinct 50 to 45 ka (thousand years ago), shortly after human colonization. Between 60 and 40 ka Australian climate was similar to present and not changing rapidly. Consequently, attention has turned toward plausible human mechanisms for the extinction, with proponents for over-hunting, ecosystem change, and introduced disease. To differentiate between these options we utilize isotopic tracers of diet preserved in eggshells of two large, flightless birds to track the status of ecosystems before and after human colonization. ?13C preserved in their eggshells monitor a bird's dietary intake in the weeks to months before egg-laying. More than 500 dated eggshells from central Australia of the Australian emu (Dromaius novaehollandiae), an opportunistic, dominantly herbivorous feeder, provide a continuous 140 kyr dietary ? 13C reconstruction. More than 350 dated eggshells from the same region of the heavier, extinct, giant bird Genyornis newtoni define its dietary intake from 140 ka until its extinction about 50 ka. Additional dietary records for both species were developed from two distant regions. Dromaius eggshell dietary ?13C reveals an unprecedented reduction in the bird's food resources about 50 ka, coeval in all three regions, suggesting conversion at that time of a tree/shrub savannah with occasionally rich grasslands to the modern desert scrub. We speculate that ecosystem collapse across the arid and semi-arid zones is a consequence of systematic burning by early humans. Genyornis diet everywhere is more restricted than in co-existing Dromaius, implying a more specialized feeding strategy. These data suggest that generalist feeders, such as Dromaius, were able to adapt to a changed vegetation regime, whereas more specialized feeders, such as Genyornis, became extinct. The altered vegetation may have also impacted Australian climate. Changes in the strength of climate feedbacks linked to vegetation and soil type (moisture recycling, surface roughness, albedo) may have weakened the penetration of monsoon moisture into the continental interior under the new ecosystem. Climate modeling suggests such a shift may have reduced monsoon rain in the interior by as much as 50%

Towards hardware acceleration of neuroevolution for multimedia processing applications on mobile devices

This paper addresses the problem of accelerating large artificial neural networks (ANN), whose topology and weights can evolve via the use of a genetic algorithm. The proposed digital hardware architecture is capable of processing any evolved network topology, whilst at the same time providing a good trade off between throughput, area and power consumption. The latter is vital for a longer battery life on mobile devices. The architecture uses multiple parallel arithmetic units in each processing element (PE). Memory partitioning and data caching are used to minimise the effects of PE pipeline stalling. A first order minimax polynomial approximation scheme, tuned via a genetic algorithm, is used for the activation function generator. Efficient arithmetic circuitry, which leverages modified Booth recoding, column compressors and carry save adders, is adopted throughout the design

Strain-induced partially flat band, helical snake states, and interface superconductivity in topological crystalline insulators

Topological crystalline insulators in IV-VI compounds host novel topological surface states consisting of multi-valley massless Dirac fermions at low energy. Here we show that strain generically acts as an effective gauge field on these Dirac fermions and creates pseudo-Landau orbitals without breaking time-reversal symmetry. We predict the realization of this phenomenon in IV-VI semiconductor heterostructures, due to a naturally occurring misfit dislocation array at the interface that produces a periodically varying strain field. Remarkably, the zero-energy Landau orbitals form a flat band in the vicinity of the Dirac point, and coexist with a network of snake states at higher energy. We propose that the high density of states of this flat band gives rise to interface superconductivity observed in IV-VI semiconductor multilayers at unusually high temperatures, with non-BCS behavior. Our work demonstrates a new route to altering macroscopic electronic properties to achieve a partially flat band, and paves the way for realizing novel correlated states of matter.Comment: Accepted by Nature Physic

Coccydynia

Coccydynia is a term that refers to pain in the region of the coccyx. Most cases are associated with abnormal mobility of the coccyx which may trigger a chronic inflammatory process leading to degeneration of this structure. In some patients this instability may be detected on dynamic radiographs. Nonsurgical management remains the gold standard treatment for coccydynia, consisting of decreased sitting, seat cushioning, coccygeal massage, stretching, manipulation, local injection of steroids or anesthetics, and postural adjustments. Those patients who fail these conservative modalities may potentially benefit from coccygectomy. However, surgical intervention is typically reserved for patients with evidence of advanced coccygeal instability (e.g., subluxation or hypermobility) or spicule formation, as this population appears to exhibit the greatest improvement postoperatively

Computational models for inferring biochemical networks

Biochemical networks are of great practical importance. The interaction of biological compounds in cells has been enforced to a proper understanding by the numerous bioinformatics projects, which contributed to a vast amount of biological information. The construction of biochemical systems (systems of chemical reactions), which include both topology and kinetic constants of the chemical reactions, is NP-hard and is a well-studied system biology problem. In this paper, we propose a hybrid architecture, which combines genetic programming and simulated annealing in order to generate and optimize both the topology (the network) and the reaction rates of a biochemical system. Simulations and analysis of an artificial model and three real models (two models and the noisy version of one of them) show promising results for the proposed method.The Romanian National Authority for Scientific Research, CNDI–UEFISCDI, Project No. PN-II-PT-PCCA-2011-3.2-0917

Disk Imaging Survey of Chemistry with SMA (DISCS): I. Taurus Protoplanetary Disk Data

Chemistry plays an important role in the structure and evolution of protoplanetary disks, with implications for the composition of comets and planets. This is the first of a series of papers based on data from DISCS, a Submillimeter Array survey of the chemical composition of protoplanetary disks. The six Taurus sources in the program (DM Tau, AA Tau, LkCa 15, GM Aur, CQ Tau and MWC 480) range in stellar spectral type from M1 to A4 and offer an opportunity to test the effects of stellar luminosity on the disk chemistry. The disks were observed in 10 different lines at ~3" resolution and an rms of ~100 mJy beam-1 at ~0.5 km s-1. The four brightest lines are CO 2-1, HCO+ 3-2, CN 2_3-1_2 and HCN 3-2 and these are detected toward all sources (except for HCN toward CQ Tau). The weaker lines of CN 2_2-1_1, DCO+ 3-2, N2H+ 3-2, H2CO 3_03-2_02 and 4_14-3_13 are detected toward two to three disks each, and DCN 3-2 only toward LkCa 15. CH3OH 4_21-3_12 and c-C3H2 are not detected. There is no obvious difference between the T Tauri and Herbig Ae sources with regard to CN and HCN intensities. In contrast, DCO+, DCN, N2H+ and H2CO are detected only toward the T Tauri stars, suggesting that the disks around Herbig Ae stars lack cold regions for long enough timescales to allow for efficient deuterium chemistry, CO freeze-out, and grain chemistry.Comment: 29 pages, 4 figures, accepted for publication in Ap

Modeling mycorrhizal fungi dispersal by the mycophagous swamp wallaby (Wallabia bicolor)

Despite the importance of mammal-fungal interactions, tools to estimate the mammal-assisted dispersal distances of fungi are lacking. Many mammals actively consume fungal fruiting bodies, the spores of which remain viable after passage through their digestive tract. Many of these fungi form symbiotic relationships with trees and provide an array of other key ecosystem functions. We present a flexible, general model to predict the distance a mycophagous mammal would disperse fungal spores. We modelled the probability of spore dispersal by combining animal movement data from GPS-telemetry with data on spore gut-retention time. We test this model using an exemplar generalist mycophagist, the swamp wallaby (Wallabia bicolor). We show that swamp wallabies disperse fungal spores hundreds of metres—and occasionally up to 1265 m—from the point of consumption, distances that are ecologically significant for many mycorrhizal fungi. In addition to highlighting the ecological importance of swamp wallabies as dispersers of mycorrhizal fungi in eastern Australia, our simple modelling approach provides a novel and effective way of empirically describing spore dispersal by a mycophagous animal. This approach is applicable to the study of other animal-fungi interactions in other ecosystems.Funding provided by: Hermon Slade FoundationCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100001109Award Number: HSF08-6Funding provided by: Australian Research CouncilCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100000923Award Number: DP0557022Methods are described in the published article