Correlated interaction fluctuations in photosynthetic complexes

The functioning and efficiency of natural photosynthetic complexes is strongly influenced by their embedding in a noisy protein environment, which can even serve to enhance the transport efficiency. Interactions with the environment induce fluctuations of the transition energies of and interactions between the chlorophyll molecules, and due to the fact that different fluctuations will partially be caused by the same environmental factors, correlations between the various fluctuations will occur. We argue that fluctuations of the interactions should in general not be neglected, as these have a considerable impact on population transfer rates, decoherence rates and the efficiency of photosynthetic complexes. Furthermore, while correlations between transition energy fluctuations have been studied, we provide the first quantitative study of the effect of correlations between interaction fluctuations and transition energy fluctuations, and of correlations between the various interaction fluctuations. It is shown that these additional correlations typically lead to changes in interchromophore transfer rates, population oscillations and can lead to a limited enhancement of the light harvesting efficiency

Evolutionary Dynamics of Populations with Conflicting Interactions: Classification and Analytical Treatment Considering Asymmetry and Power

Evolutionary game theory has been successfully used to investigate the dynamics of systems, in which many entities have competitive interactions. From a physics point of view, it is interesting to study conditions under which a coordination or cooperation of interacting entities will occur, be it spins, particles, bacteria, animals, or humans. Here, we analyze the case, where the entities are heterogeneous, particularly the case of two populations with conflicting interactions and two possible states. For such systems, explicit mathematical formulas will be determined for the stationary solutions and the associated eigenvalues, which determine their stability. In this way, four different types of system dynamics can be classified, and the various kinds of phase transitions between them will be discussed. While these results are interesting from a physics point of view, they are also relevant for social, economic, and biological systems, as they allow one to understand conditions for (1) the breakdown of cooperation, (2) the coexistence of different behaviors ("subcultures"), (2) the evolution of commonly shared behaviors ("norms"), and (4) the occurrence of polarization or conflict. We point out that norms have a similar function in social systems that forces have in physics

JAIL: a structure-based interface library for macromolecules

The increasing number of solved macromolecules provides a solid number of 3D interfaces, if all types of molecular contacts are being considered. JAIL annotates three different kinds of macromolecular interfaces, those between interacting protein domains, interfaces of different protein chains and interfaces between proteins and nucleic acids. This results in a total number of about 184 000 database entries. All the interfaces can easily be identified by a detailed search form or by a hierarchical tree that describes the protein domain architectures classified by the SCOP database. Visual inspection of the interfaces is possible via an interactive protein viewer. Furthermore, large scale analyses are supported by an implemented sequential and by a structural clustering. Similar interfaces as well as non-redundant interfaces can be easily picked out. Additionally, the sequential conservation of binding sites was also included in the database and is retrievable via Jmol. A comprehensive download section allows the composition of representative data sets with user defined parameters. The huge data set in combination with various search options allow a comprehensive view on all interfaces between macromolecules included in the Protein Data Bank (PDB). The download of the data sets supports numerous further investigations in macromolecular recognition. JAIL is publicly available at http://bioinformatics.charite.de/jail

Numerical Evolution of General Relativistic Voids

In this paper, we study the evolution of a relativistic, superhorizon-sized void embedded in a Friedmann-Robertson-Walker universe. We numerically solve the spherically symmetric general relativistic equations in comoving, synchronous coordinates. Initially, the fluid inside the void is taken to be homogeneous and nonexpanding. In a radiation- dominated universe, we find that radiation diffuses into the void at approximately the speed of light as a strong shock---the void collapses. We also find the surprising result that the cosmic collapse time (the $1^{\rm st}$-crossing time) is much smaller than previously thought, because it depends not only on the radius of the void, but also on the ratio of the temperature inside the void to that outside. If the ratio of the initial void radius to the outside Hubble radius is less than the ratio of the outside temperature to that inside, then the collapse occurs in less than the outside Hubble time. Thus, superhorizon-sized relativistic void may thermalize and homogenize relatively quickly. These new simulations revise the current picture of superhorizon-sized void evolution after first-order inflation.Comment: 37 pages plus 12 figures (upon request-- [email protected]) LaTeX, FNAL-PUB-93/005-

'I-I' and 'I-me' : Transposing Buber's interpersonal attitudes to the intrapersonal plane

Hermans' polyphonic model of the self proposes that dialogical relationships can be established between multiple I-positions1 (e.g., Hermans, 2001a). There have been few attempts, however, to explicitly characterize the forms that these intrapersonal relationships may take. Drawing on Buber's (1958) distinction between the 'I-Thou' and 'I-It' attitude, it is proposed that intrapersonal relationships can take one of two forms: an 'I-I' form, in which one I-position encounters and confirms another I-position in its uniqueness and wholeness; and an 'I-Me' form, in which one I-position experiences another I-position in a detached and objectifying way. This article argues that this I-Me form of intrapersonal relating is associated with psychological distress, and that this is so for a number of reasons: Most notably, because an individual who objectifies and subjugates certain I-position cannot reconnect with more central I-positions when dominance reversal (Hermans, 2001a) takes place. On this basis, it is suggested that a key role of the therapeutic process is to help clients become more able to experience moments of I-I intrapersonal encounter, and it is argued that this requires the therapist to confirm the client both as a whole and in terms of each of his or her different voices

A Common Endocrine Signature Marks the Convergent Evolution of an Elaborate Dance Display in Frogs

Unrelated species often evolve similar phenotypic solutions to the same environmental problem, a phenomenon known as convergent evolution. But how do these common traits arise? We address this question from a physiological perspective by assessing how convergence of an elaborate gestural display in frogs (foot-flagging) is linked to changes in the androgenic hormone systems that underlie it. We show that the emergence of this rare display in unrelated anuran taxa is marked by a robust increase in the expression of androgen receptor (AR) messenger RNA in the musculature that actuates leg and foot movements, but we find no evidence of changes in the abundance of AR expression in these frogs’ central nervous systems. Meanwhile, the magnitude of the evolutionary change in muscular AR and its association with the origin of foot-flagging differ among clades, suggesting that these variables evolve together in a mosaic fashion. Finally, while gestural displays do differ between species, variation in the complexity of a foot-flagging routine does not predict differences in muscular AR. Altogether, these findings suggest that androgen-muscle interactions provide a conduit for convergence in sexual display behavior, potentially providing a path of least resistance for the evolution of motor performance

Structural Brain Changes Related to Disease Duration in Patients with Asthma

Dyspnea is the impairing, cardinal symptom patients with asthma repeatedly experience over the course of the disease. However, its accurate perception is also crucial for timely initiation of treatment. Reduced perception of dyspnea is associated with negative treatment outcome, but the underlying brain mechanisms of perceived dyspnea in patients with asthma remain poorly understood. We examined whether increasing disease duration in fourteen patients with mild-to-moderate asthma is related to structural brain changes in the insular cortex and brainstem periaqueductal grey (PAG). In addition, the association between structural brain changes and perceived dyspnea were studied. By using magnetic resonance imaging in combination with voxel-based morphometry, gray matter volumes of the insular cortex and the PAG were analysed and correlated with asthma duration and perceived affective unpleasantness of resistive load induced dyspnea. Whereas no associations were observed for the insular cortex, longer duration of asthma was associated with increased gray matter volume in the PAG. Moreover, increased PAG gray matter volume was related to reduced ratings of dyspnea unpleasantness. Our results demonstrate that increasing disease duration is associated with increased gray matter volume in the brainstem PAG in patients with mild-to-moderate asthma. This structural brain change might contribute to the reduced perception of dyspnea in some patients with asthma and negatively impact the treatment outcome

Cosmological Solutions in Bimetric Gravity and their Observational Tests

We obtain the general cosmological evolution equations for a classically consistent theory of bimetric gravity. Their analytic solutions are demonstrated to generically allow for a cosmic evolution starting out from a matter dominated FLRW universe while relaxing towards a de Sitter (anti-de Sitter) phase at late cosmic time. In particular, we examine a subclass of models which contain solutions that are able to reproduce the expansion history of the cosmic concordance model inspite of the nonlinear couplings of the two metrics. This is demonstrated explicitly by fitting these models to observational data from Type Ia supernovae, Cosmic Microwave Background and Baryon Acoustic Oscillations.Comment: Latex, 26 pages. References added and minor revision of introduction and appendix