SAWdoubler: a program for counting self-avoiding walks

This article presents SAWdoubler, a package for counting the total number Z(N) of self-avoiding walks (SAWs) on a regular lattice by the length-doubling method, of which the basic concept has been published previously by us. We discuss an algorithm for the creation of all SAWs of length N, efficient storage of these SAWs in a tree data structure, and an algorithm for the computation of correction terms to the count Z(2N) for SAWs of double length, removing all combinations of two intersecting single-length SAWs. We present an efficient numbering of the lattice sites that enables exploitation of symmetry and leads to a smaller tree data structure; this numbering is by increasing Euclidean distance from the origin of the lattice. Furthermore, we show how the computation can be parallelised by distributing the iterations of the main loop of the algorithm over the cores of a multicore architecture. Experimental results on the 3D cubic lattice demonstrate that Z(28) can be computed on a dual-core PC in only 1 hour and 40 minutes, with a speedup of 1.56 compared to the single-core computation and with a gain by using symmetry of a factor of 26. We present results for memory use and show how the computation is made to fit in 4 Gbyte RAM. It is easy to extend the SAWdoubler software to other lattices; it is publicly available under the GNU LGPL license.Comment: 29 pages, 3 figure

Memory erasure in small systems

We consider an overdamped nanoparticle in a driven double-well potential as a generic model of an erasable one-bit memory. We study in detail the statistics of the heat dissipated during an erasure process and show that full erasure may be achieved by dissipating less heat than the Landauer bound. We quantify the occurrence of such events and propose a single-particle experiment to verify our predictions. Our results show that Landauer's principle has to be generalized at the nanoscale to accommodate heat fluctuations.Comment: 4 pages, 4 figure

Essai de mise au point d'une méthode d'expérimentation adaptée aux conditions de la cacaoyère camerounaise traditionnelle

L'inefficacité des schémas expérimentaux classiques lorsqu'ils sont mis en oeuvre dans la cacaoyère camerounaise traditionnelle a conduit les auteurs à analyser, à partir d'observations minutieuses effectuées pendant trois années consécutives sur près de 10.000 arbres, la production des cacaoyers et ses variations dans le temps. Les auteurs attribuent les échecs constatés, tant au Cameroun que dans les autres pays producteurs de cacao: aux facteurs d'hétérogénéité génétique, pédologique et microclimatique qui caractérisent généralement les plantations de cacaoyers et que les schémas expérimentaux classiques ne sont pas en mesure d'éliminer; au fait que les caractéristiques de la production des cacaoyers ne sont pas en accord avec les hypothèses implicitement admises lors de la mise en pratique d'un essai agricole. Les auteurs ont tenté de donner une expression analytique des variations dans le temps et dans l'espace de la production des cacaoyers, ce qui les amène à proposer un dispositif expérimental original dans lequel les facteurs d'hétérogénéité sont pris en considération grâce aux observations faites au cours d'une année témoin, et dont les principes d'analyse des résultats tiennent compte des lois de variation mises en évidence. Des tableaux, qui indiquent la taille des essais à prévoir pour mettre en évidence une augmentation relative minimum donnée, ont été dressé

social media s impact on the consumer mindset when to use which sentiment extraction tool

Abstract User-generated content provides many opportunities for managers and researchers, but insights are hindered by a lack of consensus on how to extract brand-relevant valence and volume. Marketing studies use different sentiment extraction tools (SETs) based on social media volume, top-down language dictionaries and bottom-up machine learning approaches. This paper compares the explanatory and forecasting power of these methods over several years for daily customer mindset metrics obtained from survey data. For 48 brands in diverse industries, vector autoregressive models show that volume metrics explain the most for brand awareness and purchase intent, while bottom-up SETs excel at explaining brand impression, satisfaction and recommendation. Systematic differences yield contingent advice: the most nuanced version of bottom-up SETs (SVM with Neutral) performs best for the search goods for all consumer mind-set metrics but Purchase Intent for which Volume metrics work best. For experienced goods, Volume outperforms SVM with neutral. As processing time and costs increase when moving from volume to top-down to bottom-up sentiment extraction tools, these conditional findings can help managers decide when more detailed analytics are worth the investment

Localized In‐Band Rotational Phonons in Mixed Molecular Crystals: Electronic Spectra of Naphthalene Doped Biphenyl and Durene

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70064/2/JCPSA6-56-7-3716-1.pd

Slipping friction of an optically and magnetically manipulated microsphere rolling at a glass-water interface

The motion of submerged magnetic microspheres rolling at a glass-water interface has been studied using magnetic rotation and optical tweezers combined with bright-field microscopy particle tracking techniques. Individual microspheres of varying surface roughness were magnetically rotated both in and out of an optical trap to induce rolling, along either plain glass cover slides or glass cover slides functionalized with polyethylene glycol. It has been observed that the manipulated microspheres exhibited nonlinear dynamic rolling-while-slipping motion characterized by two motional regimes: At low rotational frequencies, the speed of microspheres free-rolling along the surface increased proportionately with magnetic rotation rate; however, a further increase in the rotation frequency beyond a certain threshold revealed a sharp transition to a motion in which the microspheres slipped with respect to the external magnetic field resulting in decreased rolling speeds. The effects of surface-microsphere interactions on the position of this threshold frequency are posed and investigated. Similar experiments with microspheres rolling while slipping in an optical trap showed congruent results.Comment: submitted to Journal of Applied Physics, 11 figure