Injected Power Fluctuations in 1D Dissipative Systems

Using fermionic techniques, we compute exactly the large deviation function (ldf) of the time-integrated injected power in several one-dimensional dissipative systems of classical spins. The dynamics are T=0 Glauber dynamics supplemented by an injection mechanism, which is taken as a Poissonian flipping of one particular spin. We discuss the physical content of the results, specifically the influence of the rate of the Poisson process on the properties of the ldf.Comment: 18 pages, 8 figure

Magnetic Fluctuations and Correlations in MnSi - Evidence for a Skyrmion Spin Liquid Phase

We present a comprehensive analysis of high resolution neutron scattering data involving Neutron Spin Echo spectroscopy and Spherical Polarimetry which confirm the first order nature of the helical transition and reveal the existence of a new spin liquid skyrmion phase. Similar to the blue phases of liquid crystals this phase appears in a very narrow temperature range between the low temperature helical and the high temperature paramagnetic phases.Comment: 11 pages, 16 figure

Membrane fluctuations near a plane rigid surface

We use analytical calculations and Monte Carlo simulations to determine the thermal fluctuation spectrum of a membrane patch of a few tens of nanometer in size, whose corners are located at a fixed distance $d$ above a plane rigid surface. Our analysis shows that the surface influence on the bilayer fluctuations can be effectively described in terms of a uniform confining potential that grows quadratically with the height of the membrane $h$ relative to the surface: $V=(1/2)\gamma h^2$. The strength $\gamma$ of the harmonic confining potential vanishes when the corners of the membrane patch are placed directly on the surface ($d=0$), and achieves its maximum value when $d$ is of the order of a few nanometers. However, even at maximum strength the confinement effect is quite small and has noticeable impact only on the amplitude of the largest bending mode.Comment: Accepted for publication in Phys. Rev.

Goal pursuit during the three stages of the migration process

Migration poses a strong contextual change for individuals and it necessitates the adjustment of goals and aspirations. Although goal-related processes seem highly relevant to migration success (e.g., migrant well-being and adjustment), existing research in the area is scattered and lacks an overarching theoretical framework. By systematically analyzing the current literature on goal pursuit in the migration context, we aim to give an overview of the current state of the field, identify areas that need further research attention, and recommend alternative methodological approaches for future studies. This systematic literature review uses the different stages of the migration process (pre-migration, during migration, and potential repatriation or onward migration) and the three different goal facets (goal structure, goal process, and goal content) as an organizing framework. Our discussion focuses on the theoretical and methodological implications of our findings. The article demonstrates the need for further research in the field of goal pursuit in the migration context

Lipid Bilayers and Membrane Dynamics: Insight into Thickness Fluctuations

Thickness fluctuations have long been predicted in biological membranes but never directly observed experimentally. Here, we utilize neutron spin echo spectroscopy to experimentally reveal such fluctuations in a pure, fully saturated, phosphocholine lipid bilayer system. These fluctuations appear as an excess in the dynamics of undulation fluctuations. Like the bending rigidity, the thickness fluctuations change dramatically as the lipid transition temperature is crossed, appearing to be completely suppressed below the transition. Above the transition, the relaxation rate is on the order of 100 ns and is independent of temperature. The amplitude of the thickness fluctuations is $3.7 \AA ±0.7 \AA$, which agrees well with theoretical calculations and molecular dynamics simulations. The dependence of the fluctuations on lipid tail lengths is also investigated and determined to be minimal in the range of 14 to 18 carbon tails

Experimental study of work fluctuations in a harmonic oscillator

The work fluctuations of a harmonic oscillator in contact with a thermostat and driven out of equilibrium by an external force are studied experimentally. For the work both the transient and stationary state fluctuation theorems hold. The finite time corrections are very different from those of a first order Langevin equation. The heat and work fluctuations are studied when a periodic forcing is applied to the oscillator. The importance of the choice of the ''good work'' to compute the free energy from the Jarzinsky equality is discussed

Different faces of the phantom

The SNe type Ia data admit that the Universe today may be dominated by some exotic matter with negative pressure violating all energy conditions. Such exotic matter is called {\it phantom matter} due to the anomalies connected with violation of the energy conditions. If a phantom matter dominates the matter content of the universe, it can develop a singularity in a finite future proper time. Here we show that, under certain conditions, the evolution of perturbations of this matter may lead to avoidance of this future singularity (the Big Rip). At the same time, we show that local concentrations of a phantom field may form, among other regular configurations, black holes with asymptotically flat static regions, separated by an event horizon from an expanding, singularity-free, asymptotically de Sitter universe.Comment: 6 pages, presented at IRGAC 2006, Barcelona, 11-15 July 200

Molecular observation of contour-length fluctuations limiting topological confinement in polymer melts

In order to study the mechanisms limiting the topological chain confinement in polymer melts, we have performed neutron-spin-echo investigations of the single-chain dynamic-structure factor from polyethylene melts over a large range of chain lengths. While at high molecular weight the reptation model is corroborated, a systematic loosening of the confinement with decreasing chain length is found. The dynamic-structure factors are quantitatively described by the effect of contour-length fluctuations on the confining tube, establishing this mechanism on a molecular level in space and time

Características físico-químicas de meis produzidos por espécies de meliponíneos.

Além da abelhas Africanizadas (Apis mellifera L.), as abelhas indígenas sem ferrão ou meliponíneos (Meliponinae) são potenciais produtoras de mel. Esse produto apresenta carcterísticas distintas do mel produzido pelas abelhas do gênero Apis, sendo muito apreciado pelos consumidores. Entretanto, são escassos os dados científicos a respeito da composição desse mel na literatura nacional e internacional. A proposta deste trabalho é avaliar as características físico-químicas do mel produzido por meliponíneos. As análises físico-químico foram realizadas de acordo com as técnicas descritas pela AOAC (Association of Official Analytical Chemists), e pela European Honey Comission, conforme recomendado pela CAC (Codex Alimentarius Comission). Os resultados obtidos reforçam a necessidade do desenvolvimento de um padrão próprio para os méis de abelhas sem ferrão, incluindo critérios microbiológicos.Disponível também em: Cadernos de Agroecologia, V. 5, n.1, 2010