877 research outputs found
Functional food consumption in Germany: A lifestyle segmentation study
Due to increasing health consciousness among consumers, there is an ever‐growing demand for food and beverages with health‐improving components. Not only ‘light’ and low fat products are in demand, but increasingly so‐called well‐being products and food which can prevent certain diseases. The German market for functional food is still growing. But who are the German functional food consumers? In an online‐survey referring to the Food‐ Related Lifestyle by BRUNSØ and GRUNERT (1995) we tried to identify different groups of functional food buyers in Germany and to answer the following questions: If there are different consumer groups, how do they vary in their functional food consumption, their buying motives for functional food and their lifestyles? In conclusion, we have identified two different groups of functional food consumers in Germany: The “Health oriented functional food buyers” and the “Convenient functional food buyers” and give recommendations for marketing strategies. --functional food, cluster analysis, Food-Related Lifestyle
A Fast Algorithm for Computing Prefix Probabilities
Multiple algorithms are known for efficiently calculating the prefix
probability of a string under a probabilistic context-free grammar (PCFG). Good
algorithms for the problem have a runtime cubic in the length of the input
string. However, some proposed algorithms are suboptimal with respect to the
size of the grammar. This paper proposes a novel speed-up of Jelinek and
Lafferty's (1991) algorithm, which runs in , where is the input length and is the
number of non-terminals in the grammar. In contrast, our speed-up runs in
.Comment: To be published in the Proceedings of ACL 202
Slow nonequilibrium dynamics: parallels between classical and quantum glasses and gently driven systems
We review an scenario for the non-equilibrium dynamics of glassy systems that
has been motivated by the exact solution of simple models. This approach allows
one to set on firmer grounds well-known phenomenological theories. The old
ideas of entropy crisis, fictive temperatures, free-volume... have clear
definitions within these models. Aging effects in the glass phase are also
captured. One of the salient features of the analytic solution, the breakdown
of the fluctuation-dissipation relations, provides a definition of a bonafide
{\it effective temperature} that is measurable by a thermometer, controls heat
flows, partial equilibrations, and the reaction to the external injection of
heat. The effective temperature is an extremely robust concept that appears in
non-equilibrium systems in the limit of small entropy production as, for
instance, sheared fluids, glasses at low temperatures when quantum fluctuations
are relevant, tapped or vibrated granular matter, etc. The emerging scenario is
one of partial equilibrations, in which glassy systems arrange their internal
degrees of freedom so that the slow ones select their own effective
temperatures. It has been proven to be consistent within any perturbative
resummation scheme (mode coupling, etc) and it can be challenged by
experimental and numerical tests, some of which it has already passed.Comment: 15 pages, 8 figure
Glassy dynamics in granular compaction: sand on random graphs
We discuss the use of a ferromagnetic spin model on a random graph to model
granular compaction. A multi-spin interaction is used to capture the
competition between local and global satisfaction of constraints characteristic
for geometric frustration. We define an athermal dynamics designed to model
repeated taps of a given strength. Amplitude cycling and the effect of
permanently constraining a subset of the spins at a given amplitude is
discussed. Finally we check the validity of Edwards' hypothesis for the
athermal tapping dynamics.Comment: 13 pages Revtex, minor changes, to appear in PR
Solving Optimization Problems by the Public Goods Game
This document is the Accepted Manuscript version of the following article: Marco Alberto Javarone, ‘Solving optimization problems by the public goods game’, The European Physical Journal B, 90:17, September 2017. Under embargo. Embargo end date: 18 September 2018. The final, published version is available online at doi: https://doi.org/10.1140/epjb/e2017-80346-6. Published by Springer Berlin Heidelberg.We introduce a method based on the Public Goods Game for solving optimization tasks. In particular, we focus on the Traveling Salesman Problem, i.e. a NP-hard problem whose search space exponentially grows increasing the number of cities. The proposed method considers a population whose agents are provided with a random solution to the given problem. In doing so, agents interact by playing the Public Goods Game using the fitness of their solution as currency of the game. Notably, agents with better solutions provide higher contributions, while those with lower ones tend to imitate the solution of richer agents for increasing their fitness. Numerical simulations show that the proposed method allows to compute exact solutions, and suboptimal ones, in the considered search spaces. As result, beyond to propose a new heuristic for combinatorial optimization problems, our work aims to highlight the potentiality of evolutionary game theory beyond its current horizons.Peer reviewedFinal Accepted Versio
Aharonov-Bohm scattering of charged particles and neutral atoms: the role of absorption
The Aharonov-Bohm scattering of charged particles by the magnetic field of an
infinitely long and infinitely thin solenoid (magnetic string) in an absorbing
medium is studied. We discuss the partial-wave approach to this problem and
show that standard partial-wave method can be adjusted to this case. The effect
of absorption leads to oscillations of the AB cross section.
Based on this we investigate the scattering of neutral atoms with induced
electric dipole moments by a charge wire of finite radius which is placed in an
uniform magnetic field. The physical realistic and practically important case
that all atoms which collide with the wire are totally absorbed at its surface,
is studied in detail. The dominating terms of the scattering amplitude are
evaluated analytically for different physical constellations. The rest terms
are written in a form suitable for a numerical computation. We show that if the
magnetic field is absent, the absorbing charged wire causes oscillations of the
cross section. In the presence of the magnetic field the cross section
increases and the dominating Aharonov--Bohm peak appears in the forward
direction, suppressing the oscillations.Comment: 15 pages, LaTeXfile, 2 figure
Different reactions to adverse neighborhoods in games of cooperation
In social dilemmas, cooperation among randomly interacting individuals is
often difficult to achieve. The situation changes if interactions take place in
a network where the network structure jointly evolves with the behavioral
strategies of the interacting individuals. In particular, cooperation can be
stabilized if individuals tend to cut interaction links when facing adverse
neighborhoods. Here we consider two different types of reaction to adverse
neighborhoods, and all possible mixtures between these reactions. When faced
with a gloomy outlook, players can either choose to cut and rewire some of
their links to other individuals, or they can migrate to another location and
establish new links in the new local neighborhood. We find that in general
local rewiring is more favorable for the evolution of cooperation than
emigration from adverse neighborhoods. Rewiring helps to maintain the diversity
in the degree distribution of players and favors the spontaneous emergence of
cooperative clusters. Both properties are known to favor the evolution of
cooperation on networks. Interestingly, a mixture of migration and rewiring is
even more favorable for the evolution of cooperation than rewiring on its own.
While most models only consider a single type of reaction to adverse
neighborhoods, the coexistence of several such reactions may actually be an
optimal setting for the evolution of cooperation.Comment: 12 pages, 5 figures; accepted for publication in PLoS ON
The effects of grain shape and frustration in a granular column near jamming
We investigate the full phase diagram of a column of grains near jamming, as
a function of varying levels of frustration. Frustration is modelled by the
effect of two opposing fields on a grain, due respectively to grains above and
below it. The resulting four dynamical regimes (ballistic, logarithmic,
activated and glassy) are characterised by means of the jamming time of
zero-temperature dynamics, and of the statistics of attractors reached by the
latter. Shape effects are most pronounced in the cases of strong and weak
frustration, and essentially disappear around a mean-field point.Comment: 17 pages, 19 figure
Thermodynamics and statistical mechanics of frozen systems in inherent states
We discuss a Statistical Mechanics approach in the manner of Edwards to the
``inherent states'' (defined as the stable configurations in the potential
energy landscape) of glassy systems and granular materials. We show that at
stationarity the inherent states are distributed according a generalized Gibbs
measure obtained assuming the validity of the principle of maximum entropy,
under suitable constraints. In particular we consider three lattice models (a
diluted Spin Glass, a monodisperse hard-sphere system under gravity and a
hard-sphere binary mixture under gravity) undergoing a schematic ``tap
dynamics'', showing via Monte Carlo calculations that the time average of
macroscopic quantities over the tap dynamics and over such a generalized
distribution coincide. We also discuss about the general validity of this
approach to non thermal systems.Comment: 10 pages, 16 figure
Mutation-Selection Balance: Ancestry, Load, and Maximum Principle
We show how concepts from statistical physics, such as order parameter,
thermodynamic limit, and quantum phase transition, translate into biological
concepts in mutation-selection models for sequence evolution and can be used
there. The article takes a biological point of view within a population
genetics framework, but contains an appendix for physicists, which makes this
correspondence clear. We analyze the equilibrium behavior of deterministic
haploid mutation-selection models. Both the forward and the time-reversed
evolution processes are considered. The stationary state of the latter is
called the ancestral distribution, which turns out as a key for the study of
mutation-selection balance. We find that it determines the sensitivity of the
equilibrium mean fitness to changes in the fitness values and discuss
implications for the evolution of mutational robustness. We further show that
the difference between the ancestral and the population mean fitness, termed
mutational loss, provides a measure for the sensitivity of the equilibrium mean
fitness to changes in the mutation rate. For a class of models in which the
number of mutations in an individual is taken as the trait value, and fitness
is a function of the trait, we use the ancestor formulation to derive a simple
maximum principle, from which the mean and variance of fitness and the trait
may be derived; the results are exact for a number of limiting cases, and
otherwise yield approximations which are accurate for a wide range of
parameters. These results are applied to (error) threshold phenomena caused by
the interplay of selection and mutation. They lead to a clarification of
concepts, as well as criteria for the existence of thresholds.Comment: 54 pages, 15 figures; to appear in Theor. Pop. Biol. 61 or 62 (2002
- …