Relativistic surfatron process for Landau resonant electrons in radiation belts

Recent theoretical studies of the nonlinear wave-particle interactions for relativistic particles have shown that Landau resonant orbits could be efficiently accelerated along the mean background magnetic field for propagation angles $\theta$ in close proximity to a critical propagation $\theta_\textrm{c}$ associated with a Hopf--Hopf bifurcation condition. In this report, we extend previous studies to reach greater modeling capacities for the study of electrons in radiation belts by including longitudinal wave effects and inhomogeneous magnetic fields. We find that even though both effects can limit the surfatron acceleration of electrons in radiation belts, gains in energy of the order of 100 keV, taking place on the order of ten milliseconds, are sufficiently strong for the mechanism to be relevant to radiation belt dynamics.Comment: Published in Nonlinear Processes of Geophysics but available in here without some random typos introduced by publishe

Breaking the PPSZ Barrier for Unique 3-SAT

The PPSZ algorithm by Paturi, Pudl\'ak, Saks, and Zane (FOCS 1998) is the fastest known algorithm for (Promise) Unique k-SAT. We give an improved algorithm with exponentially faster bounds for Unique 3-SAT. For uniquely satisfiable 3-CNF formulas, we do the following case distinction: We call a clause critical if exactly one literal is satisfied by the unique satisfying assignment. If a formula has many critical clauses, we observe that PPSZ by itself is already faster. If there are only few clauses allover, we use an algorithm by Wahlstr\"om (ESA 2005) that is faster than PPSZ in this case. Otherwise we have a formula with few critical and many non-critical clauses. Non-critical clauses have at least two literals satisfied; we show how to exploit this to improve PPSZ.Comment: 13 pages; major revision with simplified algorithm but slightly worse constant

Germination of primed seed under NaCl stress in wheat.

Copyright © 2012 Michael P. Fuller et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Soil salinity affects a large and increasing amount of arable land worldwide, and genetic and agronomic solutions to increasing salt tolerance are urgently needed. Experiments were conducted to improve wheat seed performance under salinity stress conditions after priming. An experiment was conducted using a completely randomized design of four replications for germination indices in wheat (Triticum aestivum L. cv. Caxton). Normal and primed seed with PEG6000 at −1MPa and five concentrations of NaCl (0, 50, 100, 150, and 200mM) were tested. Results indicate that priming seed significantly (P < 0.05) increased germination percentage at first count and final count, coefficient of velocity of germination, germination rate index, and mean germination time, while increasing of NaCl concentration significantly reduced it. Priming seed improved germination attributes at all NaCl concentration levels. The priming appeared to be able to overcome the effect of salt stress at 50 to 100mMand reduce the effect of NaCl at higher concentrations up to 200 mM. The primed seed gave both faster germination and led to higher germination when under salt stress. We conclude that using priming techniques can effectively enhance the germination seed under saline condition

An Empirical Investigation of Code Smell ‘Deception’ and Research Contextualisation through Paul’s Criteria

Code smells represent code decay and as such should be eradicated from a system to prevent future maintenance problems. A range of twenty smells described by Fowler and Beck each require varying numbers and combinations of refactorings in order to be eradicated — but exactly how many are needed when we consider related, nested refactorings is unclear. In this paper, we enumerate these refactorings when categorised according to Mantyla’s smell taxonomy. We then show how, ironically, the ‘smelliest’ of smells (and hence most difficult to eradicate) are actually those best understood by developers. So, code smells are not only unpleasant to have around, but are deceptive in their nature and make-up. The study is thus a warning against attempting to eradicate what are seemingly easily eradicated smells — these are often the smells the developer needs to be most wary of. Finally, we incorporate the answers to six questions suggested by Paul for ‘How to write a paper properly’ to position the paper in a reflective way

Exploring the eradication of code smells: An empirical and theoretical perspective

This article has been made available through the Brunel Open Access Publishing Fund - Copyright @ 2010 Hindawi Publishing CorporationCode smells reflect code decay, and, as such, developers should seek to eradicate such smells through application of “deodorant” in the form of one or more refactorings. However, a relative lack of studies exploring code smells either theoretically or empirically when compared with literature on refactoring suggests that there are reasons why smell eradication is neither being applied in anger, nor the subject of significant research. In this paper, we present three studies as supporting evidence for this stance. The first is an analysis of a set of five, open-source Java systems in which we show very little tendency for smells to be eradicated by developers; the second is an empirical study of a subsystem of a proprietary, C# web-based application where practical problems arise in smell identification and the third, a theoretical enumeration of smell-related refactorings to suggest why smells may be left alone from an effort perspective. Key findings of the study were that first, smells requiring application of simple refactorings were eradicated in favour of smells requiring more complex refactorings; second, a wide range of conflicts and anomalies soon emerged when trying to identify smelly code; an interesting result with respect to comment lines was also observed. Finally, perceived (estimated) effort to eradicate a smell may be a key factor in explaining why smell eradication is avoided by developers. The study thus highlights the need for a clearer research strategy on the issue of code smells and all aspects of their identification and measurement.The research in this paper was supported by a grant from the UK Engineering and Physical Sciences Research Council (EPSRC) (Grant no: EP/G031126/1

On the Digital Holographic Interferometry of Fibrous Material, I. Optical Properties of Polymer and Optical Fibers

The digital holographic interferometry (DHI) was utilized for investigating the optical properties of polymer and optical fibers. The samples investigated here were polyvinylidene fluoride (PVDF) polymer fiber and graded-index (GRIN) optical fiber. The phase shifting Mach-Zehnder interferometer was used to obtain five phase-shifted holograms, in which the phase difference between two successive holograms is pi/2, for each fiber sample. These holograms were recorded using a CCD camera and were combined to gain a complex wavefield, which was numerically reconstructed using the convolution approach into amplitude and phase distributions. The reconstructed phase distribution was used to determine the refractive index, birefringence and refractive index profile of the studied samples. The mean refractive index has been measured with accuracy up to 4 {\times} 10-4. The main advantage of DHI is to overcome the manual focusing limitations by means of the numerical focusing. The results showed accurate measurements of the optical properties of fibers.Comment: abstract, reference