131 research outputs found
How Does the Past of a Soccer Match Influence Its Future? Concepts and Statistical Analysis
Scoring goals in a soccer match can be interpreted as a stochastic process. In the most simple description of a soccer match one assumes that scoring goals follows from independent rate processes of both teams. This would imply simple Poissonian and Markovian behavior. Deviations from this behavior would imply that the previous course of the match has an impact on the present match behavior. Here a general framework for the identification of deviations from this behavior is presented. For this endeavor it is essential to formulate an a priori estimate of the expected number of goals per team in a specific match. This can be done based on our previous work on the estimation of team strengths. Furthermore, the well-known general increase of the number of the goals in the course of a soccer match has to be removed by appropriate normalization. In general, three different types of deviations from a simple rate process can exist. First, the goal rate may depend on the exact time of the previous goals. Second, it may be influenced by the time passed since the previous goal and, third, it may reflect the present score. We show that the Poissonian scenario is fulfilled quite well for the German Bundesliga. However, a detailed analysis reveals significant deviations for the second and third aspect. Dramatic effects are observed if the away team leads by one or two goals in the final part of the match. This analysis allows one to identify generic features about soccer matches and to learn about the hidden complexities behind scoring goals. Among others the reason for the fact that the number of draws is larger than statistically expected can be identified.
Contributions to the mixed-alkali effect in molecular dynamics simulations of alkali silicate glasses
The mixed-alkali effect on the cation dynamics in silicate glasses is
analyzed via molecular dynamics simulations. Observations suggest a description
of the dynamics in terms of stable sites mostly specific to one ionic species.
As main contributions to the mixed--alkali slowdown longer residence times and
an increased probability of correlated backjumps are identified. The slowdown
is related to the limited accessibility of foreign sites. The mismatch
experienced in a foreign site is stronger and more retarding for the larger
ions, the smaller ions can be temporarily accommodated. Also correlations
between unlike as well as like cations are demonstrated that support
cooperative behavior.Comment: 10 pages, 12 figures, 1 table, revtex4, submitted to Phys. Rev.
Tunneling dynamics of side chains and defects in proteins, polymer glasses, and OH-doped network glasses
Simulations on a Lennard-Jones computer glass are performed to study effects
arising from defects in glasses at low temperatures. The numerical analysis
reveals that already a low concentration of defects may dramatically change the
low temperature properties by giving rise to extrinsic double-well potentials
(DWP's). The main characteristics of these extrinsic DWP's are (i) high barrier
heights, (ii) high probability that a defect is indeed connected with an
extrinsic DWP, (iii) highly localized dynamics around this defect, and (iv)
smaller deformation potential coupling to phonons. Designing an extension of
the Standard Tunneling Model (STM) which parametrizes this picture and
comparing with ultrasound experiments on the wet network glass -BO
shows that effects of OH-impurities are accurately accounted for. This model is
then applied to organic polymer glasses and proteins. It is suggested that side
groups may act similarly like doped impurities inasmuch as extrinsic DWP's are
induced, which possess a distribution of barriers peaked around a high barrier
height. This compares with the structurlessly distributed barrier heights of
the intrinsic DWP's, which are associated with the backbone dynamics. It is
shown that this picture is consistent with elastic measurements on polymers,
and can explain anomalous nonlogarithmic line broadening recently observed in
hole burning experiments in PMMA.Comment: 34 pages, Revtex, 9 eps-figures, accepted for publication in J. Chem.
Phy
Dynamic effects on the loss of control in template-directed nucleation
Full nucleation control for deposited functional molecules on pre-patterned
surfaces is of major technological relevance. To understand the nucleation
behavior we combine the numerical solution for the evolution of the adatom
concentration with standard nucleation theory. From the qualitative change in
nucleation behavior upon variation of the pattern spacing and coverage we show
why the quality of nucleation control can vary significantly in different
parameter regimes. In some limits analytical expressions can be formulated for
the nucleation control. Our analysis provides a theoretical explanation for
previous experimental observations [Wang et al, PRL 98, 225504 (2007)]
Memory effects in the relaxation of the Gaussian trap model
We investigate the memory effect in a simple model for glassy relaxation, a
trap model with a Gaussian density of states. In this model thermal equilibrium
is reached at all finite temperatures and therefore we can consider jumps from
low to high temperatures in addition to the quenches usually considered in
aging studies. We show that the evolution of the energy following the
Kovacs-protocol can approximately be expressed as a difference of two
monotonously decaying functions and thus show the existence of a so-called
Kovacs hump whenever these functions are not single exponentials. It is well
established that the Kovacs effect also occurs in the linear response regime
and we show that most of the gross features do not change dramatically when
large temperature jumps are considered. However, there is one distinguishing
feature that only exists beyond the linear regime which we discuss in detail.
For the memory experiment with 'inverted' temperatures, i.e. jumping up and
then down again, we find a very similar behavior apart from an opposite sign of
the hump.Comment: 16 pages, 13 figure
Finite-Size Effects in a Supercooled Liquid
We study the influence of the system size on various static and dynamic
properties of a supercooled binary Lennard-Jones liquid via computer
simulations. In this way, we demonstrate that the treatment of systems as small
as N=65 particles yields relevant results for the understanding of bulk
properties. Especially, we find that a system of N=130 particles behaves
basically as two non-interacting systems of half the size.Comment: Proceedings of the III Workshop on Non Equilibrium Phenomena in
Supercooled Fluids, Glasses and Amorphous Materials, Sep 2002, Pis
The potential energy landscape of a model glass former: thermodynamics, anharmonicities, and finite size effects
It is possible to formulate the thermodynamics of a glass forming system in
terms of the properties of inherent structures, which correspond to the minima
of the potential energy and build up the potential energy landscape in the
high-dimensional configuration space. In this work we quantitatively apply this
general approach to a simulated model glass-forming system. We systematically
vary the system size between N=20 and N=160. This analysis enables us to
determine for which temperature range the properties of the glass former are
governed by the regions of the configuration space, close to the inherent
structures. Furthermore, we obtain detailed information about the nature of
anharmonic contributions. Moreover, we can explain the presence of finite size
effects in terms of specific properties of the energy landscape. Finally,
determination of the total number of inherent structures for very small systems
enables us to estimate the Kauzmann temperature
Astrocyte dysfunction and neuronal network hyperactivity in a CRISPR engineered pluripotent stem cell model of frontotemporal dementia
Frontotemporal dementia (FTD) is the second most prevalent type of early-onset dementia and up to 40% of cases are familial forms. One of the genes mutated in patients is CHMP2B, which encodes a protein found in a complex important for maturation of late endosomes, an essential process for recycling membrane proteins through the endolysosomal system. Here, we have generated a CHMP2B-mutated human embryonic stem cell line using genome editing with the purpose to create a human in vitro FTD disease model. To date, most studies have focused on neuronal alterations; however, we present a new co-culture system in which neurons and astrocytes are independently generated from human embryonic stem cells and combined in co-cultures. With this approach, we have identified alterations in the endolysosomal system of FTD astrocytes, a higher capacity of astrocytes to uptake and respond to glutamate, and a neuronal network hyperactivity as well as excessive synchronization. Overall, our data indicates that astrocyte alterations precede neuronal impairments and could potentially trigger neuronal network changes, indicating the important and specific role of astrocytes in disease development
Bose-Einstein Correlations of Three Charged Pions in Hadronic Z^0 Decays
Bose-Einstein Correlations (BEC) of three identical charged pions were
studied in 4 x 10^6 hadronic Z^0 decays recorded with the OPAL detector at LEP.
The genuine three-pion correlations, corrected for the Coulomb effect, were
separated from the known two-pion correlations by a new subtraction procedure.
A significant genuine three-pion BEC enhancement near threshold was observed
having an emitter source radius of r_3 = 0.580 +/- 0.004 (stat.) +/- 0.029
(syst.) fm and a strength of \lambda_3 = 0.504 +/- 0.010 (stat.) +/- 0.041
(syst.). The Coulomb correction was found to increase the \lambda_3 value by
\~9% and to reduce r_3 by ~6%. The measured \lambda_3 corresponds to a value of
0.707 +/- 0.014 (stat.) +/- 0.078 (syst.) when one takes into account the
three-pion sample purity. A relation between the two-pion and the three-pion
source parameters is discussed.Comment: 19 pages, LaTeX, 5 eps figures included, accepted by Eur. Phys. J.
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