Comment on "Regularizing capacity of metabolic networks"

In a recent paper, Marr, Muller-Linow and Hutt [Phys. Rev. E 75, 041917 (2007)] investigate an artificial dynamic system on metabolic networks. They find a less complex time evolution of this dynamic system in real networks, compared to networks of reference models. The authors argue that this suggests that metabolic network structure is a major factor behind the stability of biochemical steady states. We reanalyze the same kind of data using a dynamic system modeling actual reaction kinetics. The conclusions about stability, from our analysis, are inconsistent with those of Marr et al. We argue that this issue calls for a more detailed type of modeling

The formative years of relativity : the history and meaning of Einstein's Princeton Lectures

TABLE OF CONTENTS: Foreword Diana Kormos Buchwald ix Preface xiii I Preliminaries 1 1 Introduction 3 2 Einstein's First Trip to America 11 3 Structure and Contents of The Meaning of Relativity 17 II The Emerging World of General Relativity 23 1 Physics and Geometry 25 2 The Principles of General Relativity 34 3 The First Solutions and the Challenge of Their Interpretation 46 4 Einstein and the Astronomers 52 5 The Genesis of Relativistic Cosmology 69 6 The Controversy over Gravitational Waves 94 7 Philosophical Debates on General Relativity 106 8 The Quest for a Unified Field Theory 122 9 Early Monographs on Relativity 140 10 Beyond the Formative Years 155 III Einstein's Book with the Appendixes 159 1 Space and Time in Pre-relativity Physics 161 2 The Theory of Special Relativity 184 3 The General Theory of Relativity 215 4 The General Theory of Relativity (Continued) 239 5 Appendix for the Second Edition: On the "Cosmologic Problem" 269 6 Appendix II (PUP 4th edition, 1953): Generalization of Gravitation Theory 293 7 Appendix II (PUP 5th edition, 1956): Relativistic Theory of the Non-symmetric Field 326 IV The Popular Lectures 361 1 Introductory Remarks 363 2 Einstein's Lectures 366 V Biographical Notes on the Protagonists of the Formative Years 387 Index 40

Interface-induced d-wave pairing

We discuss a scenario for interface-induced superconductivity involving pairing by dipolar excitations proximate to a two-dimensional electron system controlled by a transverse electric field. If the interface consists of transition metal oxide materials, the repulsive on-site Coulomb interaction is typically strong and a superconducting state is formed via exchange of non-local dipolar excitations in the d-wave channel. Perspectives to enhance the superconducting transition temperature are discussed.Comment: 4 pages, 3 figure

The ATPase mechanism of myosin and actomyosin

Myosins are a large family of molecular motors that use the common P-loop, Switch 1 and Switch 2 nucleotide binding motifs to recognize ATP, to create a catalytic site than can efficiently hydrolyze ATP and to communicate the state of the nucleotide pocket to other allosteric binding sites on myosin. The energy of ATP hydrolysis is used to do work against an external load. In this short review I will outline current thinking on the mechanism of ATP hydrolysis and how the energy of ATP hydrolysis is coupled to a series of protein conformational changes that allow a myosin, with the cytoskeleton track actin, to operate as a molecular motor of distinct types; fast movers, processive motors or strain sensors. This article is protected by copyright. All rights reserved

Solid Surface Structure Affects Liquid Order at the Polystyrene/SAM Interface

We present a combined x-ray and neutron reflectivity study characterizing the interface between polystyrene (PS) and silanized surfaces. Motivated by the large difference in slip velocity of PS on top of dodecyl-trichlorosilane (DTS) and octadecyl-trichlorosilane (OTS) found in previous studies, these two systems were chosen for the present investigation. The results reveal the molecular conformation of PS on silanized silicon. Differences in the molecular tilt of OTS and DTS are replicated by the adjacent phenyl rings of the PS. We discuss our findings in terms of a potential link between the microscopic interfacial structure and dynamic properties of polymeric liquids at interfaces

Transition from regular to complex behaviour in a discrete deterministic asymmetric neural network model

We study the long time behaviour of the transient before the collapse on the periodic attractors of a discrete deterministic asymmetric neural networks model. The system has a finite number of possible states so it is not possible to use the term chaos in the usual sense of sensitive dependence on the initial condition. Nevertheless, at varying the asymmetry parameter, $k$, one observes a transition from ordered motion (i.e. short transients and short periods on the attractors) to a ``complex'' temporal behaviour. This transition takes place for the same value $k_{\rm c}$ at which one has a change for the mean transient length from a power law in the size of the system ($N$) to an exponential law in $N$. The ``complex'' behaviour during the transient shows strong analogies with the chaotic behaviour: decay of temporal correlations, positive Shannon entropy, non-constant Renyi entropies of different orders. Moreover the transition is very similar to that one for the intermittent transition in chaotic systems: scaling law for the Shannon entropy and strong fluctuations of the ``effective Shannon entropy'' along the transient, for $k > k_{\rm c}$.Comment: 18 pages + 6 figures, TeX dialect: Plain TeX + IOP macros (included