Error Threshold for Color Codes and Random 3-Body Ising Models

We study the error threshold of color codes, a class of topological quantum codes that allow a direct implementation of quantum Clifford gates suitable for entanglement distillation, teleportation and fault-tolerant quantum computation. We map the error-correction process onto a statistical mechanical random 3-body Ising model and study its phase diagram via Monte Carlo simulations. The obtained error threshold of p_c = 0.109(2) is very close to that of Kitaev's toric code, showing that enhanced computational capabilities does not necessarily imply lower resistance to noise.Comment: 4 pages, 3 figures, 1 tabl

Meso-scale turbulence in living fluids

Turbulence is ubiquitous, from oceanic currents to small-scale biological and quantum systems. Self-sustained turbulent motion in microbial suspensions presents an intriguing example of collective dynamical behavior amongst the simplest forms of life, and is important for fluid mixing and molecular transport on the microscale. The mathematical characterization of turbulence phenomena in active non-equilibrium fluids proves even more difficult than for conventional liquids or gases. It is not known which features of turbulent phases in living matter are universal or system-specific, or which generalizations of the Navier-Stokes equations are able to describe them adequately. Here, we combine experiments, particle simulations, and continuum theory to identify the statistical properties of self-sustained meso-scale turbulence in active systems. To study how dimensionality and boundary conditions affect collective bacterial dynamics, we measured energy spectra and structure functions in dense Bacillus subtilis suspensions in quasi-2D and 3D geometries. Our experimental results for the bacterial flow statistics agree well with predictions from a minimal model for self-propelled rods, suggesting that at high concentrations the collective motion of the bacteria is dominated by short-range interactions. To provide a basis for future theoretical studies, we propose a minimal continuum model for incompressible bacterial flow. A detailed numerical analysis of the 2D case shows that this theory can reproduce many of the experimentally observed features of self-sustained active turbulence.Comment: accepted PNAS version, 6 pages, click doi for Supplementary Informatio

Knowing too much: knowledge of energy content prevents liking change through flavour-nutrient associations

Associations between flavours and the consequences of ingestion can lead to changes in flavour liking depending on nutrient content, an example of flavour-nutrient learning. Expectations about the consequences of ingestion can be modified by information at the point of ingestion, such as nutritional labelling. What is unknown is the extent to which these label-based expectations modify flavour-nutrient learning. Since nutrient information can alter expectations about how filling a product would be, we hypothesised that labels predicting higher energy (HE) content would enhance satiety and so promote more rapid flavour learning. To test this, participants consumed either a lower (LE: 164kcal) or HE (330kcal) yoghurt breakfast on four separate days, either with no product label or with labels displaying either the actual energy content (Congruent label) or inaccurate energy (Incongruent label). Participants rated liking on all four days: on days one and four they could also consume as much as they liked, but consumed a fixed amount (300g) on days two and three. Both liking and intake increased with exposure in the HE, and decreased in the LE, condition when unlabelled in line with flavour-nutrient learning. In contrast, no significant changes were seen in either the Congruent or Incongruent label conditions. Contrary to predictions, these data suggest that flavour-nutrient learning occurs when there is an absence of explicit expectations of actual nutrient content, with both accurate and inaccurate information on nutrient content disrupting learning

Quantitative Analysis of the Publishing Landscape in High-Energy Physics

World-wide collaboration in high-energy physics (HEP) is a tradition which dates back several decades, with scientific publications mostly coauthored by scientists from different countries. This coauthorship phenomenon makes it difficult to identify precisely the ``share'' of each country in HEP scientific production. One year's worth of HEP scientific articles published in peer-reviewed journals is analysed and their authors are uniquely assigned to countries. This method allows the first correct estimation on a ``pro rata'' basis of the share of HEP scientific publishing among several countries and institutions. The results provide an interesting insight into the geographical collaborative patterns of the HEP community. The HEP publishing landscape is further analysed to provide information on the journals favoured by the HEP community and on the geographical variation of their author bases. These results provide quantitative input to the ongoing debate on the possible transition of HEP publishing to an Open Access model.Comment: For a better on-screen viewing experience this paper can also be obtained at: http://doc.cern.ch/archive/electronic/cern/preprints/open/open-2006-065.pd

Confinement of knotted polymers in a slit

We investigate the effect of knot type on the properties of a ring polymer confined to a slit. For relatively wide slits, the more complex the knot, the more the force exerted by the polymer on the walls is decreased compared to an unknotted polymer of the same length. For more narrow slits the opposite is true. The crossover between these two regimes is, to first order, at smaller slit width for more complex knots. However, knot topology can affect these trends in subtle ways. Besides the force exerted by the polymers, we also study other quantities such as the monomer-density distribution across the slit and the anisotropic radius of gyration.Comment: 9 pages, 6 figures, submitted for publicatio

Roughness gradient induced spontaneous motion of droplets on hydrophobic surfaces: A lattice Boltzmann study

The effect of a step wise change in the pillar density on the dynamics of droplets is investigated via three-dimensional lattice Boltzmann simulations. For the same pillar density gradient but different pillar arrangements, both motion over the gradient zone as well as complete arrest are observed. In the moving case, the droplet velocity scales approximately linearly with the texture gradient. A simple model is provided reproducing the observed linear behavior. The model also predicts a linear dependence of droplet velocity on surface tension. This prediction is clearly confirmed via our computer simulations for a wide range of surface tensions.Comment: 6 pages, 8 figure

Incidence de certains facteurs sur l’issue d’une psychothérapie dans un essai clinique randomisé auprès de patients avec trouble de personnalité limite (TPL)

Au Personality Disorders Institute, nous avons étudié l’efficacité de la psychothérapie focalisée sur le transfert (PFT), une psychothérapie psychodynamique manualisée qui se déroule deux fois par semaine à l’intention de personnes souffrant de troubles de personnalité limite (TPL). Nous avons comparé la PFT à la thérapie dialectique comportementale (TDC) et à la psychothérapie psychodynamique de soutien (PPS) dans un essai clinique randomisé auprès de 90 patients ayant un TPL. Dans un premier temps, nous présentons certains fondements à l’origine du développement des TPL, suivis d’une discussion des bases théoriques de la PFT. Nous abordons ensuite les caractéristiques des patients qui influent sur les résultats du traitement. Nous présentons des données à la fois cliniques et empiriques dans une discussion de cas individuels représentatifs de l’échantillon de patients borderline traités en PFT.At the Personality Disorders Institute we have been investigating the efficacy of Transference-Focused Psychotherapy (TFP), a twice weekly manualized psychodynamic psychotherapy for borderline personality disorder compared to Dialectical Behavior Therapy (DBT) and Supportive Psychotherapy (SP) in a randomized clinical trial of 90 borderline patients. We will first present some developmental foundations of BPD, followed by a discussion of the theoretical foundations of TFP. We will then discuss patient characteristics that have an impact on outcome. We will present both clinical and empirical data in a discussion of individual cases that were representative of a sample of borderline patients treated in Transference-Focused Psychotherapy (TFP).En el Personality Disorders Institute estudiamos la eficacia de la psicoterapia focalizada en la transferencia (PFT), una psicoterapia psicodinámica hecha manual, que se lleva a cabo dos veces por semana para las personas que sufren de trastornos de personalidad límite (TPL). Comparamos la PFT con la terapia dialéctica comportamental (TDC) y la psicoterapia psicodinámica de apoyo (PPS) en una prueba clínica aleatoria en 90 pacientes con TPL. En un primer momento, presentamos ciertos fundamentos al origen del desarrollo de las TPL, seguidos de una discusión de las bases teóricas de la PFT. Enseguida abordamos las características de los pacientes que influyen en los resultados del tratamiento. Presentamos los datos, a la vez clínicos y empíricos, en una discusión de casos individuales representativos de la muestra de pacientes límite tratados por medio de PFT.No Personality Disorders Institute, estudamos a eficácia da psicoterapia focalizada na transferência (PFT), uma psicoterapia psicodinâmica manualizada que é realizada duas vezes por semana com pessoas que sofrem de transtornos de personalidade borderline (TPB). Comparamos a PFT com a terapia comportamental dialética (TCD) e com a psicoterapia psicodinâmica de apoio (PPA) em um teste clínico randomizado junto a 90 pacientes que sofrem de um TPB. Primeiramente, apresentamos alguns fundamentos originários do desenvolvimento dos TPB, seguidos de uma discussão sobre as bases teóricas da PFT. Abordamos, em seguida, as características dos pacientes que influenciam os resultados do tratamento. Apresentamos dados, ao mesmo tempo clínicos e empíricos em uma discussão de casos individuais representativos da amostragem de pacientes borderline tratados em PFT

Beyond expectations: the physiological basis of sensory-enhancement of satiety

Background/Objectives: Consumption of high-energy beverages has been implicated as a risk factor for weight gain, yet why nutrients ingested as beverages fail to generate adequate satiety remains unclear. In general consumers do not expect drinks to be satiating, but drinks generate greater satiety when their sensory characteristics imply they may be filling. These findings challenge traditional bottom-up models of how gut-based satiety signals modify behavior to suggest that beliefs at the point of ingestion modify gut-based satiety signaling. Subjects/Methods: Healthy volunteers (n = 23) consumed four different beverages, combining an overt sensory manipulation (thin, Low Sensory, LS, or thicker and more creamy, Enhanced Sensory, ES) and covert nutrient manipulation (low energy, LE, 78kcal; high energy, HE, 267 kcal) on different days. Effects on satiety were assessed through rated appetite and levels of glucose, insulin, pancreatic polypeptide (PP) and cholesystokinin (CCK) recorded periodically over 90 minutes, and through intake at an ad libitum test lunch. Results: Intake at the test lunch and rated appetite were both altered by both the sensory and nutrient manipulations, with lowest intake and greatest suppression of hunger post-drink in the ESHE condition. Insulin increased more after HE than LE drinks, and after ES than LS drinks, while PP levels were higher after ES than LS versions. CCK levels only increased after the ESHE drink. Conclusions: These data confirm acute sensitivity of satiety after consuming a drink both to the sensory characteristics and nutrient content of the drink, and suggest that this may be at least in part due to top-down modulation of release of satiety-related gut hormones

Destruction of first-order phase transition in a random-field Ising model

The phase transitions that occur in an infinite-range-interaction Ising ferromagnet in the presence of a double-Gaussian random magnetic field are analyzed. Such random fields are defined as a superposition of two Gaussian distributions, presenting the same width $\sigma$. Is is argued that this distribution is more appropriate for a theoretical description of real systems than its simpler particular cases, i.e., the bimodal ($\sigma=0$) and the single Gaussian distributions. It is shown that a low-temperature first-order phase transition may be destructed for increasing values of $\sigma$, similarly to what happens in the compound $Fe_{x}Mg_{1-x}Cl_{2}$, whose finite-temperature first-order phase transition is presumably destructed by an increase in the field randomness.Comment: 13 pages, 3 figure

Magnetic properties and critical behavior of disordered Fe_{1-x}Ru_x alloys: a Monte Carlo approach

We study the critical behavior of a quenched random-exchange Ising model with competing interactions on a bcc lattice. This model was introduced in the study of the magnetic behavior of Fe_{1-x}Ru_x alloys for ruthenium concentrations x=0%, x=4%, x=6%, and x=8%. Our study is carried out within a Monte Carlo approach, with the aid of a re-weighting multiple histogram technique. By means of a finite-size scaling analysis of several thermodynamic quantities, taking into account up to the leading irrelevant scaling field term, we find estimates of the critical exponents \alpha, \beta, \gamma, and \nu, and of the critical temperatures of the model. Our results for x=0% are in excellent agreement with those for the three-dimensional pure Ising model in the literature. We also show that our critical exponent estimates for the disordered cases are consistent with those reported for the transition line between paramagnetic and ferromagnetic phases of both randomly dilute and $\pm J$ Ising models. We compare the behavior of the magnetization as a function of temperature with that obtained by Paduani and Branco (2008), qualitatively confirming the mean-field result. However, the comparison of the critical temperatures obtained in this work with experimental measurements suggest that the model (initially obtained in a mean-field approach) needs to be modified